Science.gov

Sample records for nuclei echo spinowe

  1. Echo Mapping of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Peterson, B. M.; Horne, K.

    2004-01-01

    Echo mapping makes use of the intrinsic variability of the continuum source in active galactic nuclei to map out the distribution and kinematics of line-emitting gas from its light travel time-delayed response to continuum changes. Echo mapping experiments have yielded sizes for the broad line-emitting region in about three dozen AGNs. The dynamics of the line-emitting gas seem to be dominated by the gravity of the central black hole, enabling measurement of the black-hole masses in AGNs. We discuss requirements for future echo-mapping experiments that will yield the high quality velocity-delay maps of the broad-line region that are needed to determine its physical nature.

  2. Echo

    NASA Technical Reports Server (NTRS)

    1961-01-01

    'William J. O'Sullivan, the father of the Echo balloon, was also the father of five children. ... The NASA public affairs office distributed copies of this family portrait to the news media along with stories about O'Sullivan's ingenious invention of the Echo balloon.' 'O'Sullivan became one of NASA's most highly publicized scientists. In December 1960, the U.S. Post Office Department issued a commemorative 4-cent stamp in honor of his beloved Echo balloon. For his concept of the inflatable space vehicle, NASA would award him one of its distinguished service medals, in addition to $5000 cash. In 1962, O'Sullivan would appear as a guest on the popular TV game show 'What's My Line?'; all four of the celebrity panelists correctly picked him from the lineup as the father of the Echo satelloons.'

  3. Electron spin echo envelope modulation of molecular motions of deuterium nuclei

    NASA Astrophysics Data System (ADS)

    Syryamina, V. N.; Maryasov, A. G.; Bowman, M. K.; Dzuba, S. A.

    2015-12-01

    Electron Spin Echo Envelope Modulation (ESEEM) spectroscopy is a powerful technique for the study of hyperfine interactions between an unpaired electron and nearby nuclei in solids, and is employed in quantitative structural studies. Here, we describe the use of ESEEM to study the slow motion of deuterium nuclei using their nuclear quadrupole resonance (NQR) line shapes. Two ESEEM techniques were employed: the conventional three-pulse ESEEM experiment, π/2 - τ - π/2 - T- π/2 - τ - echo, and the four-pulse ESEEM, π/2 - τ - π/2 - T/2 - π - T/2 - π/2 - τ - echo, with the time variable T scanned in both cases. The nitroxide free radical 4-tert-butyliminomethyl-2,2,5,5-tetramethyl(d12)-3-imidazoline-1-oxyl with four deuterated methyl groups was investigated in a glassy ortho-terphenyl matrix over a wide temperature range. It was shown that four-pulse ESEEM allowed measurement of the nearly pure 2H NQR line shape. Between 90 K and 120 K, the ESEEM spectra change drastically. At low temperatures, four-pulse ESEEM spectra show a Pake-like pattern, which evolves into a single line at higher temperatures, which is typical for NQR of rotating methyl CD3 groups. Comparison with literature data on NQR allows estimation of the reorientation rate, k. At ∼100 K, where the spectral changes are most pronounced, k was found to be ∼105 s-1. The spectral linewidths for the three-pulse ESEEM were found to decrease similarly with increasing temperature; so the three-pulse technique is also capable to detect motion of this type. The ESEEM approach, along with site-directed spin labeling, may be useful for detection of motional transitions near the spin labels in biological systems, when information on motion is required in a wide temperature range.

  4. Electron spin echo envelope modulation of molecular motions of deuterium nuclei.

    PubMed

    Syryamina, V N; Maryasov, A G; Bowman, M K; Dzuba, S A

    2015-12-01

    Electron Spin Echo Envelope Modulation (ESEEM) spectroscopy is a powerful technique for the study of hyperfine interactions between an unpaired electron and nearby nuclei in solids, and is employed in quantitative structural studies. Here, we describe the use of ESEEM to study the slow motion of deuterium nuclei using their nuclear quadrupole resonance (NQR) line shapes. Two ESEEM techniques were employed: the conventional three-pulse ESEEM experiment, π/2 - τ - π/2 - T- π/2 - τ - echo, and the four-pulse ESEEM, π/2 - τ - π/2 - T/2 - π - T/2 - π/2 - τ - echo, with the time variable T scanned in both cases. The nitroxide free radical 4-tert-butyliminomethyl-2,2,5,5-tetramethyl(d12)-3-imidazoline-1-oxyl with four deuterated methyl groups was investigated in a glassy ortho-terphenyl matrix over a wide temperature range. It was shown that four-pulse ESEEM allowed measurement of the nearly pure (2)H NQR line shape. Between 90K and 120K, the ESEEM spectra change drastically. At low temperatures, four-pulse ESEEM spectra show a Pake-like pattern, which evolves into a single line at higher temperatures, which is typical for NQR of rotating methyl CD3 groups. Comparison with literature data on NQR allows estimation of the reorientation rate, k. At ∼100K, where the spectral changes are most pronounced, k was found to be ∼10(5)s(-1). The spectral linewidths for the three-pulse ESEEM were found to decrease similarly with increasing temperature; so the three-pulse technique is also capable to detect motion of this type. The ESEEM approach, along with site-directed spin labeling, may be useful for detection of motional transitions near the spin labels in biological systems, when information on motion is required in a wide temperature range. PMID:26583529

  5. Echo mapping of active galactic nuclei broad-line regions: Fundamental algorithms

    NASA Technical Reports Server (NTRS)

    Vio, Roberto; Horne, Keith; Wamsteker, Willem

    1994-01-01

    We formulate and test a series of algorithms for echo mapping the emission-line regions near active galactic nuclei from measurements of correlated variability in their line and continuum light curves. The linear regularization method (LRM) employs a direct inversion of evenly spaced light-curve data, with a regularization parameter that can be used to control the trade-off between noise and resolution. Matrix formulas express the formal solution as well as its variance and covariance in terms of uncertainties in the measurements. Unlike the maximum-entropy method (MEM), LRM applies to kernels with both positive and negative values, but the results are somewhat limited by ringing effects. A positivity constraint proves effective in controlling the ringing. MEM combines regularization and positivity in a natural way, but similar results are also found using positivity constraints with nonentropic regularization functions. Direct inversions of unevenly sampled light curves require interpolating the noisy data. In this case better results are found by solving for both the continuum light curve and kernel function in a simultaneous fit to the data. Our conclusion is that while echo mapping currently gives ambiguous results, the algorithms are not the limiting factor. Progress depends on efforts to increase the accuracy and completeness of sampling of the observed light curves.

  6. ECHO virus

    MedlinePlus

    ... page: //medlineplus.gov/ency/article/001340.htm ECHO virus To use the sharing features on this page, please enable JavaScript. Enteric cytopathic human orphan (ECHO) viruses are a group of viruses that lead to ...

  7. Echo's Legacy

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The Echo 1 Satellite is simply a very large balloon, the diameter of a 10 story building. Metallized Products, Inc. developed a special material for NASA used for the balloons's skin. For "bouncing signals," material had to be reflective, lightweight, and thin enough to be folded into a beach ball size canister for delivery into orbit, where it would automatically inflate. Material selected was mylar polyester, with a reflective layer of tiny aluminum particles so fine that Echo's skin had a thickness half that of cellophane on a cigarette package.

  8. ECHO virus

    MedlinePlus

    Enteric cytopathic human orphan (ECHO) viruses are a group of viruses that lead to gastrointestinal infection and skin rashes. ... Echovirus is one of several families of viruses that affect the ... are common. In the United States, they are most common in ...

  9. Nuclear quadrupole resonance single-pulse echoes.

    PubMed

    Prescott, David W; Miller, Joel B; Tourigny, Chris; Sauer, Karen L

    2008-09-01

    We report the first detection of a spin echo after excitation of a powder sample by a single pulse at the resonance frequency during nuclear quadrupole resonance (NQR). These echoes can occur in samples that have an inhomogeneously broadened line, in this case due to the distribution of electric field gradients. The echoes are easily detectable when the Rabi frequency approaches the linewidth and the average effective tipping angle is close to 270 degrees. When limited by a weak radio-frequency field, the single-pulse echo can be used to increase the signal to noise ratio over conventional techniques. These effects can be used to optimize the NQR detection of contraband containing quadrupole nuclei and they are demonstrated with glycine hemihydrochloride and hexhydro-1,3,5-trinitro-1,3,5-triazine (RDX). PMID:18571445

  10. Orientation and Alignment Echoes

    NASA Astrophysics Data System (ADS)

    Karras, G.; Hertz, E.; Billard, F.; Lavorel, B.; Hartmann, J.-M.; Faucher, O.; Gershnabel, Erez; Prior, Yehiam; Averbukh, Ilya Sh.

    2015-04-01

    We present one of the simplest classical systems featuring the echo phenomenon—a collection of randomly oriented free rotors with dispersed rotational velocities. Following excitation by a pair of time-delayed impulsive kicks, the mean orientation or alignment of the ensemble exhibits multiple echoes and fractional echoes. We elucidate the mechanism of the echo formation by the kick-induced filamentation of phase space, and provide the first experimental demonstration of classical alignment echoes in a thermal gas of CO2 molecules excited by a pair of femtosecond laser pulses.

  11. Project Echo Task Group

    NASA Technical Reports Server (NTRS)

    1964-01-01

    'A technician assigned to the Project Echo Task Group separates the two hemispheres of the Echo 1 container for inspection. The charge that freed the balloon was placed inside of a ring encircling the canister at its equator.' Published in James R. Hansen, Spaceflight Revolution: NASA Langley Research Center From Sputnik to Apollo, NASA SP-4308, p. 181.

  12. Light echoes - Novae

    NASA Technical Reports Server (NTRS)

    Schaefer, Bradley E.

    1988-01-01

    The sudden brilliance of a nova eruption will be reflected on surrounding dust grains to create a phantom nebula. Previous searches for these light echoes have used relatively short exposures with photograhic detectors. This paper reports on a search around eight recent novae with long exposures using a CCD camera. Despite an increase of sensitivity by over an order of magnitude, no light echoes were detected. It is found that the average grain density must be less than about 10 to the -9th per cu cm for distances from 0.1 pc to 1000 pc from the novae. The light echo around Nova Persei 1901 was caused by reflection off clouds with grain densities of several times 10 to the -9th per cu cm which are at distances between 0.1 pc and 10 pc. Echoes from dust in a circumstellar shell or ejected during a previous eruption will be effectively unobservable.

  13. ECHO Status for International Partners

    NASA Technical Reports Server (NTRS)

    Weinstein, Beth; Lubelczyk, Jeff

    2006-01-01

    The EOS Clearinghouse (ECHO) is a clearinghouse of spatial and temporal metadata, inclusive of NASA's Distributed Active Archive Center (DAAC) data holdings, that enables the science community to more easily exchange NASA data and information. Currently, ECHO has metadata descriptors for over 55 million individual data granules and 13 million browse images. The majority of ECHO's holdings come directly from data held in the NASA DAACs. The science disciplines and domains represented in ECHO are diverse and include metadata for all of NASA's Science Focus Area data. As middleware for a service-oriented enterprise, ECHO offers access to its capabilities through a set of publicly available Application Program Interfaces (APIs). More information about ECHO is available at http://eos.nasa.gov.echo. The presentation will discuss the status of the ECHO Partners, holdings, and activities, including the transition from the EOS Data Gateway to the Warehouse Inventory Search Tool (WIST)

  14. Echo Boom Impact

    ERIC Educational Resources Information Center

    Dordai, Phillipe; Rizzo, Joseph

    2006-01-01

    Like their baby-boomer parents, the echo-boom generation is reshaping the college and university landscape. At 80 million strong, this group of children and young adults born between 1980 and 1995 now is flooding the college and university system, spurring a college building boom. According to Campus Space Crunch, a Hillier Architecture survey of…

  15. Single Echo MRI

    PubMed Central

    Galiana, Gigi; Constable, R. Todd

    2014-01-01

    Purpose Previous nonlinear gradient research has focused on trajectories that reconstruct images with a minimum number of echoes. Here we describe sequences where the nonlinear gradients vary in time to acquire the image in a single readout. The readout is designed to be very smooth so that it can be compressed to minimal time without violating peripheral nerve stimulation limits, yielding an image from a single 4 ms echo. Theory and Methods This sequence was inspired by considering the code of each voxel, i.e. the phase accumulation that a voxel follows through the readout, an approach connected to traditional encoding theory. We present simulations for the initial sequence, a low slew rate analog, and higher resolution reconstructions. Results Extremely fast acquisitions are achievable, though as one would expect, SNR is reduced relative to the slower Cartesian sampling schemes because of the high gradient strengths. Conclusions The prospect that nonlinear gradients can acquire images in a single <10 ms echo makes this a novel and interesting approach to image encoding. PMID:24465837

  16. Light Echoes of Historic Transients

    NASA Astrophysics Data System (ADS)

    Rest, Armin; Sinnott, B.; Welch, D. L.; Prieto, J. L.; Bianco, F.

    2014-01-01

    Light echoes, light from a variable source scattered off dust, have been observed for over a century. The recent discovery of light echoes around centuries-old supernovae in the Milky Way and the Large Magellanic Cloud have allowed the spectroscopic characterization of these events, even without contemporaneous photometry and spectroscopy using modern instrumentation. Here we review the recent scientific advances using light echoes of ancient and historic transients, and focus on our latest work on SN 1987A's and Eta Carinae's light echoes.

  17. TRANSVERSE ECHO MEASUREMENTS IN RHIC.

    SciTech Connect

    FISCHER, W.

    2005-09-18

    Diffusion counteracts cooling and the knowledge of diffusion rates is important for the calculation of cooling times and equilibrium beam sizes. Echo measurements are a potentially sensitive method to determine diffusion rates, and longitudinal measurements were done in a number of machines. We report on transverse echo measurements in RHIC and the observed dependence of echo amplitudes on a number of parameters for beams of gold and copper ions, and protons. In particular they examine the echo amplitudes of gold and copper ion bunches of varying intensity, which exhibit different diffusion rates from intrabeam scattering.

  18. Transverse Echo Measurements in RHIC

    SciTech Connect

    Fischer, Wolfram

    2006-03-20

    Diffusion counteracts cooling and the knowledge of diffusion rates is important for the calculation of cooling times and equilibrium beam sizes. Echo measurements are a potentially sensitive method to determine diffusion rates, and longitudinal measurements were done in a number of machines. We report on transverse echo measurements in RHIC and the observed dependence of echo amplitudes on a number of parameters for beams of gold and copper ions, and protons. In particular we examine the echo amplitudes of gold and copper ion bunches of varying intensity, which exhibit different diffusion rates from intrabeam scattering.

  19. Echo 1 container

    NASA Technical Reports Server (NTRS)

    1964-01-01

    Echo 1 container: The design of this container was one of the most difficult technical tasks. Hansen writes: 'After several weeks of examining potential solutions to this problem, the Langley engineers narrowed the field of ideas to five. They then built working models of these five container designs, and 12-foot-diameter models of the satellite for simulation studies. With help from Langley's Engineering Service and Mechanical Service divisions, the Echo group built a special 41-foot-diameter spherical vacuum chamber equipped with pressure-proof windows. There the dynamics of opening the container and inflating the satelloon could be studies as the satelloon fell to the bottom of the tank.' 'The container-opening mechanism that eventually resulted from these vacuum tests was surely one of the oddest explosive devices ever contrived. The container was a sphere that opened at its equator into top and bottom hemispheres. the top half fit on the bottom half much like a lid fits snugly atop a kitchen pot. The joint between the two hemispheres, therefore, formed a sliding valve. The halves had to move apart an inch or two before the canister was actually open. It was in this joint between the hemispheres that the charge was placed.' The whole whole system was laced together with fishing line which resulted in many disdainful comments from visiting scientists and engineers but the system worked. Published in James R. Hansen, Spaceflight Revolution: NASA Langley Research Center From Sputnik to Apollo, (Washington: NASA, 1995), p. 180.

  20. Simple Echoes and Subtle Reverberations

    ERIC Educational Resources Information Center

    Keeports, David

    2010-01-01

    Reverberation within an enclosed space can be viewed as a superposition of a large number of simple echoes. The echoes that make up the sound of reverberation fall neatly into two categories, relatively loud and sparse early reflections, and relatively soft and dense late reflections. Ways in which readily available music production software can…

  1. Neutron phase spin echo

    NASA Astrophysics Data System (ADS)

    Piegsa, Florian M.; Hautle, Patrick; Schanzer, Christian

    2016-04-01

    A novel neutron spin resonance technique is presented based on the well-known neutron spin echo method. In a first proof-of-principle measurement using a monochromatic neutron beam, it is demonstrated that relative velocity changes of down to a precision of 4 ×10-7 can be resolved, corresponding to an energy resolution of better than 3 neV. Currently, the sensitivity is only limited by counting statistics and not by systematic effects. An improvement by another two orders of magnitude can be achieved with a dedicated setup, allowing energy resolutions in the 10 peV regime. The new technique is ideally suited for investigations in the field of precision fundamental neutron physics, but will also be beneficial in scattering applications.

  2. Balanced echo state networks.

    PubMed

    Koryakin, Danil; Lohmann, Johannes; Butz, Martin V

    2012-12-01

    This paper investigates the interaction between the driving output feedback and the internal reservoir dynamics in echo state networks (ESNs). The interplay is studied experimentally on the multiple superimposed oscillators (MSOs) benchmark. The experimental data reveals a dual effect of the output feedback strength on the network dynamics: it drives the dynamic reservoir but it can also block suitable reservoir dynamics. Moreover, the data shows that the reservoir size crucially co-determines the likelihood of generating an effective ESN. We show that dependent on the complexity of the MSO dynamics somewhat smaller networks can yield better performance. Optimizing the output feedback weight range and the network size is thus crucial for generating an effective ESN. With proper parameter choices, we show that it is possible to generate ESNs that approximate MSOs with several orders of magnitude smaller errors than those previously reported. We conclude that there appears to be still much more potential in ESNs than previously thought and sketch-out some promising future research directions. PMID:23037774

  3. Simple echoes and subtle reverberations

    NASA Astrophysics Data System (ADS)

    Keeports, David

    2010-03-01

    Reverberation within an enclosed space can be viewed as a superposition of a large number of simple echoes. The echoes that make up the sound of reverberation fall neatly into two categories, relatively loud and sparse early reflections, and relatively soft and dense late reflections. Ways in which readily available music production software can be used for the study of reverberation are suggested. Additionally, methods of adding reverberation to recorded sound are discussed.

  4. X-ray Echo Spectroscopy.

    PubMed

    Shvyd'ko, Yuri

    2016-02-26

    X-ray echo spectroscopy, a counterpart of neutron spin echo, is being introduced here to overcome limitations in spectral resolution and weak signals of the traditional inelastic x-ray scattering (IXS) probes. An image of a pointlike x-ray source is defocused by a dispersing system comprised of asymmetrically cut specially arranged Bragg diffracting crystals. The defocused image is refocused into a point (echo) in a time-reversal dispersing system. If the defocused beam is inelastically scattered from a sample, the echo signal acquires a spatial distribution, which is a map of the inelastic scattering spectrum. The spectral resolution of the echo spectroscopy does not rely on the monochromaticity of the x rays, ensuring strong signals along with a very high spectral resolution. Particular schemes of x-ray echo spectrometers for 0.1-0.02 meV ultrahigh-resolution IXS applications (resolving power >10^{8}) with broadband ≃5-13  meV dispersing systems are introduced featuring more than 10^{3} signal enhancement. The technique is general, applicable in different photon frequency domains. PMID:26967404

  5. Rapid Gradient-Echo Imaging

    PubMed Central

    Hargreaves, Brian

    2012-01-01

    Gradient echo sequences are widely used in magnetic resonance imaging (MRI) for numerous applications ranging from angiography to perfusion to functional MRI. Compared with spin-echo techniques, the very short repetition times of gradient-echo methods enable very rapid 2D and 3D imaging, but also lead to complicated “steady states.” Signal and contrast behavior can be described graphically and mathematically, and depends strongly on the type of spoiling: fully balanced (no spoiling), gradient spoiling, or RF-spoiling. These spoiling options trade off between high signal and pure T1 contrast while the flip angle also affects image contrast in all cases, both of which can be demonstrated theoretically and in image examples. As with spin-echo sequences, magnetization preparation can be added to gradient-echo sequences to alter image contrast. Gradient echo sequences are widely used for numerous applications such as 3D perfusion imaging, functional MRI, cardiac imaging and MR angiography. PMID:23097185

  6. X-ray Echo Spectroscopy

    NASA Astrophysics Data System (ADS)

    Shvyd'ko, Yuri

    2016-02-01

    X-ray echo spectroscopy, a counterpart of neutron spin echo, is being introduced here to overcome limitations in spectral resolution and weak signals of the traditional inelastic x-ray scattering (IXS) probes. An image of a pointlike x-ray source is defocused by a dispersing system comprised of asymmetrically cut specially arranged Bragg diffracting crystals. The defocused image is refocused into a point (echo) in a time-reversal dispersing system. If the defocused beam is inelastically scattered from a sample, the echo signal acquires a spatial distribution, which is a map of the inelastic scattering spectrum. The spectral resolution of the echo spectroscopy does not rely on the monochromaticity of the x rays, ensuring strong signals along with a very high spectral resolution. Particular schemes of x-ray echo spectrometers for 0.1-0.02 meV ultrahigh-resolution IXS applications (resolving power >108 ) with broadband ≃5 - 13 meV dispersing systems are introduced featuring more than 103 signal enhancement. The technique is general, applicable in different photon frequency domains.

  7. Frequency selective detection of nuclear quadrupole resonance (NQR) spin echoes

    NASA Astrophysics Data System (ADS)

    Somasundaram, Samuel D.; Jakobsson, Andreas; Smith, John A. S.; Althoefer, Kaspar A.

    2006-05-01

    Nuclear Quadrupole Resonance (NQR) is a radio frequency (RF) technique that can be used to detect the presence of quadrupolar nuclei, such as the 14N nucleus prevalent in many explosives and narcotics. The technique has been hampered by low signal-to-noise ratios and is further aggravated by the presence of RF interference (RFI). To ensure accurate detection, proposed detectors should exploit the rich form of the NQR signal. Furthermore, the detectors should also be robust to any remaining residual interference, left after suitable RFI mitigation has been employed. In this paper, we propose a new NQR data model, particularly for the realistic case where multiple pulse sequences are used to generate trains of spin echoes. Furthermore, we refine two recently proposed approximative maximum likelihood (AML) detectors, enabling the algorithm to optimally exploit the data model of the entire echo train and also incorporate knowledge of the temperature dependent spin-echo decay time. The AML-based detectors ensure accurate detection and robustness against residual RFI, even when the temperature of the sample is not precisely known, by exploiting the dependencies of the NQR resonant lines on temperature. Further robustness against residual interference is gained as the proposed detector is frequency selective; exploiting only those regions of the spectrum where the NQR signal is expected. Extensive numerical evaluations based on both simulated and measured NQR data indicate that the proposed Frequency selective Echo Train AML (FETAML) detector offers a significant improvement as compared to other existing detectors.

  8. Echo particle image velocimetry.

    PubMed

    DeMarchi, Nicholas; White, Christopher

    2012-01-01

    The transport of mass, momentum, and energy in fluid flows is ultimately determined by spatiotemporal distributions of the fluid velocity field.(1) Consequently, a prerequisite for understanding, predicting, and controlling fluid flows is the capability to measure the velocity field with adequate spatial and temporal resolution.(2) For velocity measurements in optically opaque fluids or through optically opaque geometries, echo particle image velocimetry (EPIV) is an attractive diagnostic technique to generate "instantaneous" two-dimensional fields of velocity.(3,4,5,6) In this paper, the operating protocol for an EPIV system built by integrating a commercial medical ultrasound machine(7) with a PC running commercial particle image velocimetry (PIV) software(8) is described, and validation measurements in Hagen-Poiseuille (i.e., laminar pipe) flow are reported. For the EPIV measurements, a phased array probe connected to the medical ultrasound machine is used to generate a two-dimensional ultrasound image by pulsing the piezoelectric probe elements at different times. Each probe element transmits an ultrasound pulse into the fluid, and tracer particles in the fluid (either naturally occurring or seeded) reflect ultrasound echoes back to the probe where they are recorded. The amplitude of the reflected ultrasound waves and their time delay relative to transmission are used to create what is known as B-mode (brightness mode) two-dimensional ultrasound images. Specifically, the time delay is used to determine the position of the scatterer in the fluid and the amplitude is used to assign intensity to the scatterer. The time required to obtain a single B-mode image, t, is determined by the time it take to pulse all the elements of the phased array probe. For acquiring multiple B-mode images, the frame rate of the system in frames per second (fps) = 1/δt. (See 9 for a review of ultrasound imaging.) For a typical EPIV experiment, the frame rate is between 20-60 fps

  9. Cosmogenic nuclei

    NASA Technical Reports Server (NTRS)

    Raisbeck, G. M.

    1986-01-01

    Cosmogenic nuclei, nuclides formed by nuclear interactions of galactic and solar cosmic rays with extraterrestrial or terrestrial matter are discussed. Long lived radioactive cosmogenic isotopes are focused upon. Their uses in dating, as tracers of the interactions of cosmic rays with matter, and in obtaining information on the variation of primary cosmic ray flux in the past are discussed.

  10. Commissioning the Echo-Seeding Experiment Echo-7 at SLAC

    SciTech Connect

    Weathersby, S.a E.Colby; Dunning, M.; Gilevich, S.; Hast, C.; Jobe, K.; McCormick, D.; Nelson, J.; Raubenheimer, T.O.; Soong, K.; Stupakov, G.; Szalata, Z.; Walz, D.; Woodley, M.; Xiang, D.; Pernet, P-L.; /Ecole Polytechnique, Lausanne

    2011-06-02

    ECHO-7 is a proof-of-principle echo-enabled harmonic generation (EEHG) FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment is intended to test the EEHG principle at low electron beam energy, 120 MeV, and determine the sensitivities and limitations to understand the expected performance at the higher energy scales and harmonic numbers required for x-ray FELs. In this paper we present the experimental results from the commissioning run of the completed experimental setup which started in April 2010.

  11. Fluid echoes in a pure electron plasma.

    PubMed

    Yu, J H; O'Neil, T M; Driscoll, C F

    2005-01-21

    Experimental observations of diocotron wave echoes on a magnetized electron column are reported, representing Kelvin wave echoes on a rotating near-ideal fluid. The echoes occur by reversal of an inviscid wave damping process, and the phase-space mixing and unmixing are directly imaged. The basic echo characteristics agree with a simple nonlinear ballistic theory. At late times, the echo is degraded, and the maximal observed echo times agree with a theory of electron-electron collisions acting on separately evolving velocity classes. PMID:15698185

  12. Decorrelation in interferometric radar echoes

    NASA Technical Reports Server (NTRS)

    Zebker, Howard A.; Villasensor, John

    1992-01-01

    A radar interferometric technique for topographic mapping of surfaces promises a high resolution, globally consistent approach to generation of digital elevation models. One implementation approach, that of utilizing a single SAR system in a nearly repeating orbit, is attractive not only for cost and complexity reasons but also in that it permits inference of changes in the surface over the orbit repeat cycle from the correlation properties of the radar echoes. The various sources contributing to the echo correlation statistics are characterized, and the term which most closely describes surficial change is isolated. There is decorrelation increasing with time, but digital terrain model generation remains feasible.

  13. Acoustic echoes reveal room shape.

    PubMed

    Dokmanic, Ivan; Parhizkar, Reza; Walther, Andreas; Lu, Yue M; Vetterli, Martin

    2013-07-23

    Imagine that you are blindfolded inside an unknown room. You snap your fingers and listen to the room's response. Can you hear the shape of the room? Some people can do it naturally, but can we design computer algorithms that hear rooms? We show how to compute the shape of a convex polyhedral room from its response to a known sound, recorded by a few microphones. Geometric relationships between the arrival times of echoes enable us to "blindfoldedly" estimate the room geometry. This is achieved by exploiting the properties of Euclidean distance matrices. Furthermore, we show that under mild conditions, first-order echoes provide a unique description of convex polyhedral rooms. Our algorithm starts from the recorded impulse responses and proceeds by learning the correct assignment of echoes to walls. In contrast to earlier methods, the proposed algorithm reconstructs the full 3D geometry of the room from a single sound emission, and with an arbitrary geometry of the microphone array. As long as the microphones can hear the echoes, we can position them as we want. Besides answering a basic question about the inverse problem of room acoustics, our results find applications in areas such as architectural acoustics, indoor localization, virtual reality, and audio forensics. PMID:23776236

  14. Exotic Nuclei

    SciTech Connect

    Galindo-Uribarri, Alfredo {nmn}

    2010-01-01

    Current experimental developments on the study of exotic nuclei far from the valley of stability are discussed. I start with general aspects related to the production of radioactive beams followed by the description of some of the experimental tools and specialized techniques for studies in reaction spectroscopy, nuclear structure research and nuclear applications with examples from selected topical areas with which I have been involved. I discuss some of the common challenges faced in Accelerator Mass Spectrometry (AMS) and Radioactive Ion Beam (RIB) science.

  15. Echo-Enabled Harmonic Generation

    SciTech Connect

    Stupakov, Gennady; /SLAC

    2012-06-28

    A recently proposed concept of the Echo-Enabled Harmonic Generation (EEHG) FEL uses two laser modulators in combination with two dispersion sections to generate a high-harmonic density modulation in a relativistic beam. This seeding technique holds promise of a one-stage soft x-ray FEL that radiates not only transversely but also longitudinally coherent pulses. Currently, an experimental verification of the concept is being conducted at the SLAC National Accelerator Laboratory aimed at the demonstration of the EEHG.

  16. Dance of the Light Echoes

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Click on image for larger poster version

    This composite image from NASA's Spitzer Space Telescope shows the remnant of a star that exploded, called Cassiopeia A (center) and its surrounding 'light echoes' -- dances of light through dusty clouds, created when stars blast apart. The light echoes are colored and the surrounding clouds of dust are gray.

    In figure 1, dramatic changes are highlighted in phenomena referred to as light echoes (colored areas) around the Cassiopeia A supernova remnant (center). Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died.

    A light echo occurs when a star explodes, acting like a cosmic flashbulb. The light from this explosion zips through nearby dust clumps, illuminating and heating them up slightly. This brief period of warming causes them to glow in infrared, like a chain of Christmas bulbs lighting up one by one. The result is an optical illusion, in which the dust appears to be flying outward at the speed of light. In figure 1, this apparent motion can be seen here by the shift in colored dust clumps

    Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died. This remnant is located 11,000 light-years away in the northern constellation Cassiopeia.

    This composite consists of six processed images taken over a time span of three years. Dust features that have not changed over time appear gray, while those that have changed are colored blue or orange. Bluer colors represent an earlier time and redder ones, a later time. The progression of the light echo through the dust can be seen here by the shift in colored dust clumps.

    This

  17. Echo characteristics of two salmon species

    NASA Astrophysics Data System (ADS)

    Nealson, Patrick A.; Horne, John K.; Burwen, Debby L.

    2005-04-01

    The Alaska Department of Fish and Game relies on split-beam hydroacoustic techniques to estimate Chinook salmon (Oncorhynchus tshawytscha) returns to the Kenai River. Chinook counts are periodically confounded by large numbers of smaller sockeye salmon (O. nerka). Echo target-strength has been used to distinguish fish length classes, but was too variable to separate Kenai River chinook and sockeye distributions. To evaluate the efficacy of alternate echo metrics, controlled acoustic measurements of tethered chinook and sockeye salmon were collected at 200 kHz. Echo returns were digitally sampled at 48 kHz. A suite of descriptive metrics were collected from a series of 1,000 echoes per fish. Measurements of echo width were least variable at the -3 dB power point. Initial results show echo elongation and ping-to-ping variability in echo envelope width were significantly greater for chinook than for sockeye salmon. Chinook were also observed to return multiple discrete peaks from a single broadcast echo. These characteristics were attributed to the physical width of chinook exceeding half of the broadcast echo pulse width at certain orientations. Echo phase variability, correlation coefficient and fractal dimension distributions did not demonstrate significant discriminatory power between the two species. [Work supported by ADF&G, ONR.

  18. A radar-echo model for Mars

    NASA Technical Reports Server (NTRS)

    Thompson, T. W.; Moore, H. J.

    1990-01-01

    Researchers developed a radar-echo model for Mars based on 12.6 cm continuous wave radio transmissions backscattered from the planet. The model broadly matches the variations in depolarized and polarized total radar cross sections with longitude observed by Goldstone in 1986 along 7 degrees S. and yields echo spectra that are generally similiar to the observed spectra. Radar map units in the model include an extensive cratered uplands unit with weak depolarized echo cross sections, average thermal inertias, moderate normal refelectivities, and moderate rms slopes; the volcanic units of Tharsis, Elysium, and Amazonis regions with strong depolarized echo cross sections, low thermal inertia, low normal reflectivities, and large rms slopes; and the northern planes units with moderate to strong depolarized echo cross sections, moderate to very high thermal inertias, moderate to large normal reflectivities, and moderate rms slopes. The relevance of the model to the interpretation of radar echoes from Mars is discussed.

  19. The acoustics of the echo cornet

    NASA Astrophysics Data System (ADS)

    Pyle, Robert W., Jr.; Klaus, Sabine K.

    2002-11-01

    The echo cornet was an instrument produced by a number of makers in several countries from about the middle of the nineteenth to the early twentieth centuries. It consists of an ordinary three-valve cornet to which a fourth valve has been added, downstream of the three normal valves. The extra valve diverts the airstream from the normal bell to an ''echo'' bell that gives a muted tone quality. Although the air column through the echo bell is typically 15 cm longer than the path through the normal bell, there is no appreciable change of playing pitch when the echo bell is in use. Acoustic input impedance and impulse response measurements and consideration of the standing-wave pattern within the echo bell show how this can be so. Acoustically, the echo bell is more closely related to hand-stopping on the French horn than to the mutes commonly used on the trumpet and cornet.

  20. The Echoes of Earth Science

    NASA Technical Reports Server (NTRS)

    2006-01-01

    NASA s Earth Observing System Data and Information System (EOSDIS) acquires, archives, and manages data from all of NASA s Earth science satellites, for the benefit of the Space Agency and for the benefit of others, including local governments, first responders, the commercial remote sensing industry, teachers, museums, and the general public. EOSDIS is currently handling an extraordinary amount of NASA scientific data. To give an idea of the volume of information it receives, NASA s Terra Earth-observing satellite, just one of many NASA satellites sending down data, sends it hundreds of gigabytes a day, almost as much data as the Hubble Space Telescope acquires in an entire year, or about equal to the amount of information that could be found in hundreds of pickup trucks filled with books. To make EOSDIS data completely accessible to the Earth science community, NASA teamed up with private industry in 2000 to develop an Earth science "marketplace" registry that lets public users quickly drill down to the exact information they need. It also enables them to publish their research and resources alongside of NASA s research and resources. This registry is known as the Earth Observing System ClearingHOuse, or ECHO. The charter for this project focused on having an infrastructure completely independent from EOSDIS that would allow for more contributors and open up additional data access options. Accordingly, it is only fitting that the term ECHO is more than just an acronym; it represents the functionality of the system in that it can echo out and create interoperability among other systems, all while maturing with time as industry technologies and standards change and improve.

  1. Loschmidt echo for quantum metrology

    NASA Astrophysics Data System (ADS)

    Macrı, Tommaso; Smerzi, Augusto; Pezzè, Luca

    2016-07-01

    We propose a versatile Loschmidt echo protocol to detect and quantify multiparticle entanglement. It allows us to extract the quantum Fisher information for arbitrary pure states, and finds direct application in quantum metrology. In particular, the protocol applies to states that are generally difficult to characterize, as non-Gaussian states, and states that are not symmetric under particle exchange. We focus on atomic systems, including trapped ions, polar molecules, and Rydberg atoms, where entanglement is generated dynamically via long-range interaction, and show that the protocol is stable against experimental detection errors.

  2. Light echoes - Type II supernovae

    NASA Technical Reports Server (NTRS)

    Schaefer, Bradley E.

    1987-01-01

    Type II supernovae (SNs) light curves show a remarkable range of shapes. Data have been collected for the 12 Type II SNs that have light curve information for more than four months past maximum. Contrary to previous reports, it is found that (1) the decay rate after 100 days past maximum varies by almost an order of magnitude and (2) the light curve shapes are not bimodally distributed, but actually form a continuum. In addition, it is found that the extinctions to the SNs are related to the light curve shapes. This implies that the absorbing dust is local to the SNs. The dust is likely to be part of a circumstellar shell emitted by the SN progenitor that Dwek (1983) has used to explain infrared echoes. The optical depth of the shell can get quite large. In such cases, it is found that the photons scattered and delayed by reflection off dust grains will dominate the light curve several months after peak brightness. This 'light echo' offers a straightforward explanation of the diversity of Type II SN light curves.

  3. Ultrasound echoes as biometric navigators.

    PubMed

    Schwartz, Benjamin M; McDannold, Nathan J

    2013-04-01

    We demonstrate a new method of using ultrasound data to achieve prospective motion compensation in MRI, especially for respiratory motion during interventional MRI procedures in moving organs such as the liver. The method relies on fingerprint-like biometrically distinct ultrasound echo patterns produced by different locations in tissue, which are collated with geometrical information from MRI during a training stage to form a mapping table that relates ultrasound measurements to positions. During prospective correction, the system makes frequent ultrasound measurements and uses the map to determine the corresponding position. Results in motorized linear motion phantoms and freely breathing animals indicate that the system performs well. Apparent motion is reduced by up to 97.8%, and motion artifacts are reduced or eliminated in two-dimensional spoiled gradient-echo images. The motion compensation is sufficient to permit MRI thermometry of focused ultrasound heating during respiratory-like motion, with results similar to those obtained in the absence of motion. This new technique may have applications for MRI thermometry and other dynamic imaging in the abdomen during free breathing. PMID:22648783

  4. Minimum complexity echo state network.

    PubMed

    Rodan, Ali; Tino, Peter

    2011-01-01

    Reservoir computing (RC) refers to a new class of state-space models with a fixed state transition structure (the reservoir) and an adaptable readout form the state space. The reservoir is supposed to be sufficiently complex so as to capture a large number of features of the input stream that can be exploited by the reservoir-to-output readout mapping. The field of RC has been growing rapidly with many successful applications. However, RC has been criticized for not being principled enough. Reservoir construction is largely driven by a series of randomized model-building stages, with both researchers and practitioners having to rely on a series of trials and errors. To initialize a systematic study of the field, we concentrate on one of the most popular classes of RC methods, namely echo state network, and ask: What is the minimal complexity of reservoir construction for obtaining competitive models and what is the memory capacity (MC) of such simplified reservoirs? On a number of widely used time series benchmarks of different origin and characteristics, as well as by conducting a theoretical analysis we show that a simple deterministically constructed cycle reservoir is comparable to the standard echo state network methodology. The (short-term) MC of linear cyclic reservoirs can be made arbitrarily close to the proved optimal value. PMID:21075721

  5. Solar Sail Model Validation from Echo Trajectories

    NASA Technical Reports Server (NTRS)

    Heaton, Andrew F.; Brickerhoff, Adam T.

    2007-01-01

    The NASA In-Space Propulsion program has been engaged in a project to increase the technology readiness of solar sails. Recently, these efforts came to fruition in the form of several software tools to model solar sail guidance, navigation and control. Furthermore, solar sails are one of five technologies competing for the New Millennium Program Space Technology 9 flight demonstration mission. The historic Echo 1 and Echo 2 balloons were comprised of aluminized Mylar, which is the near-term material of choice for solar sails. Both spacecraft, but particularly Echo 2, were in low Earth orbits with characteristics similar to the proposed Space Technology 9 orbit. Therefore, the Echo balloons are excellent test cases for solar sail model validation. We present the results of studies of Echo trajectories that validate solar sail models of optics, solar radiation pressure, shape and low-thrust orbital dynamics.

  6. Nonlinear Echoes from Encapsulated Antibubbles

    NASA Astrophysics Data System (ADS)

    Johansen, Kristoffer; Kotopoulis, Spiros; Poortinga, Albert T.; Postema, Michiel

    An antibubble consists of a liquid droplet, surrounded by a gas, often with an encapsulating shell. Antibubbles of microscopic sizes suspended in fluids are acoustically active in the ultrasonic range. Antibubbles have applications in food processing and guided drug delivery. We study the sound generated from antibubbles, with droplet core sizes in the range of 0-90% of the equilibrium antibubble inner radius. The antibubble resonance frequency, the phase difference of the echo with respect to the incident acoustic pulse, and the presence of higher harmonics are strongly dependent of the core droplet size. Antibubbles oscillate highly nonlinearly around resonance size. This may allow for using antibubbles in clinical diagnostic imaging and targeted drug delivery.

  7. Diffusion weighted vertical gradient and spin echo.

    PubMed

    Engström, Mathias; Bammer, Roland; Skare, Stefan

    2012-12-01

    In this work, diffusion weighting and parallel imaging is combined with a vertical gradient and spin echo data readout. This sequence was implemented and evaluated on healthy volunteers using a 1.5 and a 3 T whole-body MR system. As the vertical gradient and spin echo trajectory enables a higher k-space velocity in the phase-encoding direction than single-shot echo planar imaging, the geometrical distortions are reduced. When combined with parallel imaging such as generalized autocalibrating partially parallel acquisition, the geometric distortions are reduced even further, while also keeping the minimum echo time reasonably low. However, this combination of a diffusion preparation and multiple refocusing pulses during the vertical gradient and spin echo readout, generally violates the Carr-Purcell-Meiboom-Gill condition, which leads to interferences between echo pathways. To suppress the stimulated echo pathway, refocusing pulses with a sharper slice profiles and an odd/even crusher variation scheme were implemented and evaluated. Being a single-shot acquisition technique, the reconstructed images are robust to rigid-body head motion and spatially varying brain motion, both of which are common sources of artifacts in diffusion MRI. PMID:23008151

  8. A simple method for MR elastography: a gradient-echo type multi-echo sequence.

    PubMed

    Numano, Tomokazu; Mizuhara, Kazuyuki; Hata, Junichi; Washio, Toshikatsu; Homma, Kazuhiro

    2015-01-01

    To demonstrate the feasibility of a novel MR elastography (MRE) technique based on a conventional gradient-echo type multi-echo MR sequence which does not need additional bipolar magnetic field gradients (motion encoding gradient: MEG), yet is sensitive to vibration. In a gradient-echo type multi-echo MR sequence, several images are produced from each echo of the train with different echo times (TEs). If these echoes are synchronized with the vibration, each readout's gradient lobes achieve a MEG-like effect, and the later generated echo causes a greater MEG-like effect. The sequence was tested for the tissue-mimicking agarose gel phantoms and the psoas major muscles of healthy volunteers. It was confirmed that the readout gradient lobes caused an MEG-like effect and the later TE images had higher sensitivity to vibrations. The magnitude image of later generated echo suffered the T2 decay and the susceptibility artifacts, but the wave image and elastogram of later generated echo were unaffected by these effects. In in vivo experiments, this method was able to measure the mean shear modulus of the psoas major muscle. From the results of phantom experiments and volunteer studies, it was shown that this method has clinical application potential. PMID:25311570

  9. CRITICAL CARE ECHO ROUNDS: Echo in cardiac arrest

    PubMed Central

    Asrress, Kaleab; Redwood, Simon; Gillon, Stuart; Walker, David

    2014-01-01

    Management of medical cardiac arrest is challenging. The internationally agreed approach is highly protocolised with therapy and diagnosis occurring in parallel. Early identification of the precipitating cause increases the likelihood of favourable outcome. Echocardiography provides an invaluable diagnostic tool in this context. Acquisition of echo images can be challenging in cardiac arrest and should occur in a way that minimises disruption to cardiopulmonary resuscitation (CPR). In this article, the reversible causes of cardiac arrest are reviewed with associated echocardiography findings. Case A 71-year-old patient underwent right upper lobectomy for lung adenocarcinoma. On the 2nd post-operative day, he developed respiratory failure with rising oxygen requirement and right middle and lower lobe collapse and consolidation on chest X-ray. He was commenced on high-flow oxygen therapy and antibiotics. His condition continued to deteriorate and on the 3rd post-operative day he was intubated and mechanically ventilated. Six hours after intubation, he became suddenly hypotensive with a blood pressure of 50 systolic and then lost cardiac output. ECG monitoring showed pulseless electrical activity. CPR was commenced and return of circulation occurred after injection of 1 mg of adrenaline. Focused echocardiography was performed, which demonstrated signs of massive pulmonary embolism. Thrombolytic therapy with tissue plasminogen activator was given and his condition stabilised. PMID:26693304

  10. Discrepancies between decoherence and the Loschmidt echo

    NASA Astrophysics Data System (ADS)

    Casabone, B.; García-Mata, I.; Wisniacki, D. A.

    2010-03-01

    The Loschmidt echo and the purity are two quantities that can provide invaluable information about the evolution of a quantum system. While the Loschmidt echo characterizes instability and sensitivity to perturbations, purity measures the loss of coherence produced by an environment coupled to the system. For classically chaotic systems both quantities display a number of —supposedly universal— regimes that can lead to think of them as equivalent quantities. We study the decay of the Loschmidt echo and the purity for systems with finite-dimensional Hilbert space and present numerical evidence of some fundamental differences between them.

  11. Photon Echoes from Retinal Proteins

    NASA Astrophysics Data System (ADS)

    Johnson, Philip James Maddigan

    This thesis focuses on the ultrafast isomerization reaction of retinal in both rhodopsin and bacteriorhodopsin, examples of sensory and energy transduction proteins that exploit the same photoactive chromophore for two very different functions. In bacteriorhodopsin, retinal isomerizes from an all-trans to 13-cis conformation as the primary event in light- driven proton pumping. In the visual pigment rhodopsin, the retinal chromophore isomerizes from an 11-cis to all-trans geometry as the primary step leading to our sense of vision. This diversity of function for nominally identical systems raises the question as to just how optimized are these proteins to arrive at such drastically different functions? Previous work has employed transient absorption spectroscopy to probe retinal protein photochemistry, but many of the relevant electronic and nuclear dynamics of isomerization are masked by inhomogeneous broadening effects and strong spectral overlap between reactant and photoproduct states. This work exploits the unique properties of two-dimensional photon echo spectroscopy to deconvolve inhomogeneous broadening and spectral overlap effects and fully reveal the dynamics that direct retinal isomerization in proteins. In bacteriorhodopsin, vibrational coupling to the reaction coordinate results in a surface crossing event prior to the conventional conical intersection associated with isomerization to the J intermediate. In rhodopsin, however, a similarly early vibrationally-mediated barrier crossing event is observed, resulting in spectral signals consistent with the known photoproduct state appearing an order of magnitude faster than determined from conventional transient absorption measurements. The competing overlapping spectral signals that obscured the initial dynamics when probed with transient absorption spectroscopy are now clearly resolved with two-dimensional photon echo spectroscopy. These experiments illustrate the critical role of the protein in directing

  12. Echoes in correlated neural systems

    NASA Astrophysics Data System (ADS)

    Helias, M.; Tetzlaff, T.; Diesmann, M.

    2013-02-01

    Correlations are employed in modern physics to explain microscopic and macroscopic phenomena, like the fractional quantum Hall effect and the Mott insulator state in high temperature superconductors and ultracold atoms. Simultaneously probed neurons in the intact brain reveal correlations between their activity, an important measure to study information processing in the brain that also influences the macroscopic signals of neural activity, like the electroencephalogram (EEG). Networks of spiking neurons differ from most physical systems: the interaction between elements is directed, time delayed, mediated by short pulses and each neuron receives events from thousands of neurons. Even the stationary state of the network cannot be described by equilibrium statistical mechanics. Here we develop a quantitative theory of pairwise correlations in finite-sized random networks of spiking neurons. We derive explicit analytic expressions for the population-averaged cross correlation functions. Our theory explains why the intuitive mean field description fails, how the echo of single action potentials causes an apparent lag of inhibition with respect to excitation and how the size of the network can be scaled while maintaining its dynamical state. Finally, we derive a new criterion for the emergence of collective oscillations from the spectrum of the time-evolution propagator.

  13. MEASUREMENT OF TRANSVERSE ECHOES IN RHIC.

    SciTech Connect

    FISCHER, W.; SATOGATA, T.; TOMAS. R.

    2005-05-16

    Beam echoes are a very sensitive method to measure diffusion, and longitudinal echo measurements were performed in a number of machines. In RHIC, for the first time, a transverse beam echo was observed after applying a dipole kick followed by a quadrupole .kick. After application of the dipole kick, the dipole moment decohered completely due to lattice nonlinearities. When a quadrupole kick is applied at time {tau} after the dipole kick, the beam re-cohered at time 2{tau} thus showing an echo response. We describe the experimental setup and measurement results. In the measurements the dipole and quadrupole kick amplitudes, amplitude dependent tune shift, and the time between dipole and quadrupole kick were varied. In addition, measurements were taken with gold bunches of different intensities. These should exhibit different transverse diffusion rates due to intra-beam scattering.

  14. Analysis and representation of sonar echo returns

    NASA Astrophysics Data System (ADS)

    Hackman, Roger H.; Abatzoglou, Theagenis J.; Arnold, Hal B.; Reagan, John T.

    1993-10-01

    Active acoustic classification of underwater targets is an important problem of current interest. The echo return of such objects has components related to such distinct dynamical elements as the specular (geometric) return, reradiation of elastic resonances, diffracted (or Franz) waves, etc. The arrival times and spectral content of these components will generally give information about the structure and geometry of the scatterer. This information is reflected to the time- frequency structure of the echo return. In this paper, a comparative study is presented of the time-frequency analysis capability of a number of tools in applications to the echo structure of finite elastic cylinders. The time-frequency tools considered include the Wigner-Ville distribution, the Choi-Williams distribution, the Gabor transform, and the continuous wavelet transforms. The comparison is based on echo returns that have been synthesized from numerical T-matrix solutions to the associated free-field scattering problems.

  15. Geometric spin echo under zero field

    PubMed Central

    Sekiguchi, Yuhei; Komura, Yusuke; Mishima, Shota; Tanaka, Touta; Niikura, Naeko; Kosaka, Hideo

    2016-01-01

    Spin echo is a fundamental tool for quantum registers and biomedical imaging. It is believed that a strong magnetic field is needed for the spin echo to provide long memory and high resolution, since a degenerate spin cannot be controlled or addressed under a zero magnetic field. While a degenerate spin is never subject to dynamic control, it is still subject to geometric control. Here we show the spin echo of a degenerate spin subsystem, which is geometrically controlled via a mediating state split by the crystal field, in a nitrogen vacancy centre in diamond. The demonstration reveals that the degenerate spin is protected by inherent symmetry breaking called zero-field splitting. The geometric spin echo under zero field provides an ideal way to maintain the coherence without any dynamics, thus opening the way to pseudo-static quantum random access memory and non-invasive biosensors. PMID:27193936

  16. Geometric spin echo under zero field.

    PubMed

    Sekiguchi, Yuhei; Komura, Yusuke; Mishima, Shota; Tanaka, Touta; Niikura, Naeko; Kosaka, Hideo

    2016-01-01

    Spin echo is a fundamental tool for quantum registers and biomedical imaging. It is believed that a strong magnetic field is needed for the spin echo to provide long memory and high resolution, since a degenerate spin cannot be controlled or addressed under a zero magnetic field. While a degenerate spin is never subject to dynamic control, it is still subject to geometric control. Here we show the spin echo of a degenerate spin subsystem, which is geometrically controlled via a mediating state split by the crystal field, in a nitrogen vacancy centre in diamond. The demonstration reveals that the degenerate spin is protected by inherent symmetry breaking called zero-field splitting. The geometric spin echo under zero field provides an ideal way to maintain the coherence without any dynamics, thus opening the way to pseudo-static quantum random access memory and non-invasive biosensors. PMID:27193936

  17. EuroEcho-Imaging 2015: highlights.

    PubMed

    Magne, Julien; Popescu, Bogdan A; Cosyns, Bernard; Donal, Erwan; Miller, Owen; Neglia, Danilo; Plein, Sven; Lancellotti, Patrizio; Habib, Gilbert

    2016-06-01

    The annual meeting of the European Association of Cardiovascular Imaging, EuroEcho-Imaging, was held in Seville, Spain, in December 2015. In the present paper, we present a summary of the 'Highlights' session. PMID:27099280

  18. Data processing of records of meteoric echoes

    NASA Astrophysics Data System (ADS)

    Dolinský, P.

    2016-01-01

    The data obtained in the period from 4 November 2014 to 31 July 2014 by our receiving and recording system was statistically processed. The system records meteoric echoes from the TV transmitter Lviv 49.739583 MHz (N49.8480° E24.0369°, Ukraine) using a 4-element Yagi antenna with horizontal polarization (elevation of 0° and azimuth of 60°), receiver ICOM R-75 in the CW mode, and a computer with a recording using HROFFT v1.0.0f. The main goal was to identify weak showers in these data. Mayor or strong showers are visible without processing (referred at IMC2015, Mistelbach). To find or to identify weaker showers is more difficult. Not all echoes are meteoric echoes, but also ionospheric echoes or lightning disturbances are present.

  19. Geometric spin echo under zero field

    NASA Astrophysics Data System (ADS)

    Sekiguchi, Yuhei; Komura, Yusuke; Mishima, Shota; Tanaka, Touta; Niikura, Naeko; Kosaka, Hideo

    2016-05-01

    Spin echo is a fundamental tool for quantum registers and biomedical imaging. It is believed that a strong magnetic field is needed for the spin echo to provide long memory and high resolution, since a degenerate spin cannot be controlled or addressed under a zero magnetic field. While a degenerate spin is never subject to dynamic control, it is still subject to geometric control. Here we show the spin echo of a degenerate spin subsystem, which is geometrically controlled via a mediating state split by the crystal field, in a nitrogen vacancy centre in diamond. The demonstration reveals that the degenerate spin is protected by inherent symmetry breaking called zero-field splitting. The geometric spin echo under zero field provides an ideal way to maintain the coherence without any dynamics, thus opening the way to pseudo-static quantum random access memory and non-invasive biosensors.

  20. Estimation of Characteristics of Echo Envelope Using RF Echo Signal from the Liver

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Tadashi; Hachiya, Hiroyuki; Kamiyama, Naohisa; Ikeda, Kazuki; Moriyasu, Norifumi

    2001-05-01

    To realize quantitative diagnosis of liver cirrhosis, we have been analyzing the probability density function (PDF) of echo amplitude using B-mode images. However, the B-mode image is affected by the various signal and image processing techniques used in the diagnosis equipment, so a detailed and quantitative analysis is very difficult. In this paper, we analyze the PDF of echo amplitude using RF echo signal and B-mode images of normal and cirrhotic livers, and compare both results to examine the validity of the RF echo signal.

  1. Re-visiting the echo state property.

    PubMed

    Yildiz, Izzet B; Jaeger, Herbert; Kiebel, Stefan J

    2012-11-01

    An echo state network (ESN) consists of a large, randomly connected neural network, the reservoir, which is driven by an input signal and projects to output units. During training, only the connections from the reservoir to these output units are learned. A key requisite for output-only training is the echo state property (ESP), which means that the effect of initial conditions should vanish as time passes. In this paper, we use analytical examples to show that a widely used criterion for the ESP, the spectral radius of the weight matrix being smaller than unity, is not sufficient to satisfy the echo state property. We obtain these examples by investigating local bifurcation properties of the standard ESNs. Moreover, we provide new sufficient conditions for the echo state property of standard sigmoid and leaky integrator ESNs. We furthermore suggest an improved technical definition of the echo state property, and discuss what practicians should (and should not) observe when they optimize their reservoirs for specific tasks. PMID:22885243

  2. Light Echoes of Galactic Explosions and Eruptions

    NASA Astrophysics Data System (ADS)

    Rest, Armin; Bianco, Federica; Chornock, Ryan; Foley, Ryan; Matheson, Thomas; Olsen, Knut; Prieto, Jose Luis; Sinnott, Brendan; Smith, Chris; Smith, Nathan; Welch, Doug

    2013-02-01

    We propose to continue our search for the first light echoes (LEs) associated with historical Galactic supernovae and LBV outbursts: SN 1006, Kepler's SN, RCW 86, Crab Nebula, and P Cygni. In previously granted NOAO time, we have discovered light echoes of three ancient SNe in the LMC as well as from the historic SN events of Cas A and Tycho [2, 3], which allowed their spectroscopic classification [6, 7, 10] and 3D spectroscopy [8, 9]. Most recently, we discovered light echoes of the mid-19th-century Great Eruption of eta Carinae using CTIO 4m Mosaic images [11]. Subsequent spectroscopic follow-up of Eta Carinae revealed that its outburst spectral type was most similar to those of G-type supergiants, rather than reported LBV outburst spectral types of F-type (or earlier) [11]. We propose to continue our search for light echoes of the remaining historical events. With DECam, we have a 10-15 fold improvement in efficiency over the retired Mosaic camera, which allows us to cover the bigger search areas of most of the remaining targets. The study of scattered-light echoes from these Galactic supernovae and eruptions will give us the opportunity to directly compare the original outburst and its current remnant, and in favorable cases (like Eta Carinae), it provides a three-dimensional view of the event and/or a spectral time series.

  3. Echolocation versus echo suppression in humans

    PubMed Central

    Wallmeier, Ludwig; Geßele, Nikodemus; Wiegrebe, Lutz

    2013-01-01

    Several studies have shown that blind humans can gather spatial information through echolocation. However, when localizing sound sources, the precedence effect suppresses spatial information of echoes, and thereby conflicts with effective echolocation. This study investigates the interaction of echolocation and echo suppression in terms of discrimination suppression in virtual acoustic space. In the ‘Listening’ experiment, sighted subjects discriminated between positions of a single sound source, the leading or the lagging of two sources, respectively. In the ‘Echolocation’ experiment, the sources were replaced by reflectors. Here, the same subjects evaluated echoes generated in real time from self-produced vocalizations and thereby discriminated between positions of a single reflector, the leading or the lagging of two reflectors, respectively. Two key results were observed. First, sighted subjects can learn to discriminate positions of reflective surfaces echo-acoustically with accuracy comparable to sound source discrimination. Second, in the Listening experiment, the presence of the leading source affected discrimination of lagging sources much more than vice versa. In the Echolocation experiment, however, the presence of both the lead and the lag strongly affected discrimination. These data show that the classically described asymmetry in the perception of leading and lagging sounds is strongly diminished in an echolocation task. Additional control experiments showed that the effect is owing to both the direct sound of the vocalization that precedes the echoes and owing to the fact that the subjects actively vocalize in the echolocation task. PMID:23986105

  4. Active galactic nuclei

    PubMed Central

    Fabian, Andrew C.

    1999-01-01

    Active galactic nuclei are the most powerful, long-lived objects in the Universe. Recent data confirm the theoretical idea that the power source is accretion into a massive black hole. The common occurrence of obscuration and outflows probably means that the contribution of active galactic nuclei to the power density of the Universe has been generally underestimated. PMID:10220363

  5. Transient Loschmidt echo in quenched Ising chains

    NASA Astrophysics Data System (ADS)

    Lupo, Carla; Schiró, Marco

    2016-07-01

    We study the response to sudden local perturbations of highly excited quantum Ising spin chains. The key quantity encoding this response is the overlap between time-dependent wave functions, which we write as a transient Loschmidt Echo. Its asymptotics at long time differences contain crucial information about the structure of the highly excited nonequilibrium environment induced by the quench. We compute the echo perturbatively for a weak local quench but for arbitrarily large global quench, using a cumulant expansion. Our perturbative results suggest that the echo decays exponentially, rather than power law as in the low-energy orthogonality catastrophe, a further example of quench-induced decoherence already found in the case of quenched Luttinger liquids. The emerging decoherence scale is set by the strength of the local potential and the bulk excitation energy.

  6. fMRI of the brainstem using dual-echo EPI.

    PubMed

    Beissner, Florian; Deichmann, Ralf; Baudrexel, Simon

    2011-04-15

    The brainstem is the part of the human brain that plays a pivotal role in the maintenance of many critical body functions. Due to the elevated level of cardiogenic noise, few fMRI studies have investigated the brainstem so far. Cardiac-gated echo-planar imaging with acquisition of two echoes per excitation (dual-echo EPI) is one method that significantly reduces cardiogenic noise and, thus, allows for fMRI measurements of the brainstem. As information on optimal preprocessing approaches for brainstem-fMRI data is still scarce, the goal of this study was to compare different combinations of normalization and smoothing procedures as implemented in standard fMRI software packages and to identify the combinations yielding optimal results for dual-echo EPI. 21 healthy subjects were measured while executing a simple motor paradigm to activate the facial and trigeminal motor nucleus in the brainstem. After motion correction and calculation of T(2)*-maps the data were preprocessed with 24 combinations of standard normalization (SPM classic, SPM unified, FSL, ABC) and smoothing procedures (pre-/post-smoothing with 3mm-, 4.5mm- and 6mm-kernel) before undergoing first- and second-level statistical analysis. Activation results were compared for first-level and second-level statistics using two anatomically defined regions of interest. Five methods were found to be sensitive for activation of both nuclei. These included FSL normalization with 3mm and 4.5mm pre-smoothing as well as 3mm post-smoothing, SPM unified normalization with 3mm pre-smoothing and ABC normalization with 4.5mm pre-smoothing. All these methods can be recommended for normalization and smoothing when analyzing fMRI data of the brainstem acquired by cardiac-gated dual-echo EPI. PMID:21256220

  7. Evolution of entanglement under echo dynamics

    SciTech Connect

    Prosen, Tomaz; Znidaric, Marko; Seligman, Thomas H.

    2003-04-01

    Echo dynamics and fidelity are often used to discuss stability in quantum-information processing and quantum chaos. Yet fidelity yields no information about entanglement, the characteristic property of quantum mechanics. We study the evolution of entanglement in echo dynamics. We find qualitatively different behavior between integrable and chaotic systems on one hand and between random and coherent initial states for integrable systems on the other. For the latter the evolution of entanglement is given by a classical time scale. Analytic results are illustrated numerically in a Jaynes-Cummings model.

  8. Research of laser echo signal simulator

    NASA Astrophysics Data System (ADS)

    Xu, Rui; Shi, Rui; Wang, Xin; Li, Zhou

    2015-11-01

    Laser echo signal simulator is one of the most significant components of hardware-in-the-loop (HWIL) simulation systems for LADAR. System model and time series model of laser echo signal simulator are established. Some influential factors which could induce fixed error and random error on the simulated return signals are analyzed, and then these system insertion errors are analyzed quantitatively. Using this theoretical model, the simulation system is investigated experimentally. The results corrected by subtracting fixed error indicate that the range error of the simulated laser return signal is less than 0.25m, and the distance range that the system can simulate is from 50m to 20km.

  9. Nanosecond image processing using stimulated photon echoes.

    PubMed

    Xu, E Y; Kröll, S; Huestis, D L; Kachru, R; Kim, M K

    1990-05-15

    Processing of two-dimensional images on a nanosecond time scale is demonstrated using the stimulated photon echoes in a rare-earth-doped crystal (0.1 at. % Pr(3+):LaF(3)). Two spatially encoded laser pulses (pictures) resonant with the (3)P(0)-(3)H(4) transition of Pr(3+) were stored by focusing the image pulses sequentially into the Pr(3+):LaF(3) crystal. The stored information is retrieved and processed by a third read pulse, generating the echo that is the spatial convolution or correlation of the input images. Application of this scheme to high-speed pattern recognition is discussed. PMID:19768008

  10. Relationship between tornadoes and hook echoes on April 3, 1974

    NASA Technical Reports Server (NTRS)

    Forbes, G. S.

    1975-01-01

    Radar observations of tornado families occurring on April 3, 1974 are discussed. Of the 93 tornadoes included in the sample, 81% were associated with hook-like echoes with appendages at least 40 deg to the south of the echo movement. At least one tornado was associated with 62% of the hook-like echoes observed. All of the tornadoes with intensities of F 4 and F 5 were produced by hook-like echoes; the mean intensity of all tornadoes associated with this type of echo was F 3, while the mean intensity of the remaining tornadoes was F1. The tornadic hook-like echoes moved to the right of the non-tornadic echoes forming a tornado line in advance of the squall line. Some tornadoes were associated with 'spiral' echoes.

  11. On the reliability of hook echoes as tornado indicators

    NASA Technical Reports Server (NTRS)

    Forbes, G. S.

    1981-01-01

    A study of radar echoes associated with the tornadoes of the 3 April 1974 outbreak was performed to evaluate the usefulness of echo shape as an indicator of tornadic thunderstorms. The hook shape was usually successful in characterizing an echo as tornadic, with a false alarm rate of 16%. Because hook echoes were relatively rare, however, a less restrictive shape called distinctive was more successful at detecting tornadic thunderstorms, identifying 65% of the tornadic echoes. An echo had a distinctive shape if it possessed a marked appendage on its right rear flank or was in the shape of a spiral, comma or line echo wave pattern (LEWP). Characteristics of the distinctive echo are given.

  12. Asymmetric radar echo patterns from insects

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Radar echoes from insects, birds, and bats in the atmosphere exhibit both symmetry and asymmetry in polarimetric patterns. Symmetry refers to similar magnitudes of polarimetric variables at opposite azimuths, and asymmetry relegates to differences in these magnitudes. Asymmetry can be due to diffe...

  13. Light Echoes of Galactic Explosions and Eruptions

    NASA Astrophysics Data System (ADS)

    Rest, Armin; Bianco, Federica; Chornock, Ryan; Foley, Ryan; Matheson, Thomas; Narayan, Gautham; Olsen, Knut; Prieto, Jose Luis; Smith, Chris; Smith, Nathan; Suntzeff, Nick; Welch, Doug; Zenteno, Alfredo

    2014-02-01

    We propose to continue our search for the first light echoes (LEs) associated with historical Galactic supernovae and LBV outbursts: SN 1006, Kepler's SN, RCW 86, Crab Nebula, and P Cygni. In previously granted NOAO time, we have discovered LEs of three ancient SNe in the LMC as well as from the historic SN events of Cas A and Tycho [2, 3], which allowed their spectroscopic classification [6, 7, 10] and 3D spectroscopy [8, 9]. Most recently, we discovered light echoes of the mid-19th-century Great Eruption of η Carinae using CTIO 4m Mosaic images [11]. Subsequent spectroscopic follow-up of Eta Carinae revealed that its outburst spectral type was most similar to those of G-type supergiants, rather than reported LBV outburst spectral types of F-type (or earlier) [11]. We propose to continue our search for light echoes of the remaining historical events. With DECam, we have a 10-15 fold improvement in efficiency over the retired CTIO-Mosaic camera, which allows us to cover the bigger search areas of most of the remaining targets. With the KPNO 4-m, we will observe fields too far north for CTIO/DECam. The study of scattered-light echoes from these Galactic supernovae and eruptions will give us the opportunity to directly compare the original outburst and its current remnant, and in favorable cases (like Eta Carinae), it provides a three-dimensional view of the event and/or a spectral time series.

  14. AN ECHO OF SUPERNOVA 2008bk

    SciTech Connect

    Van Dyk, Schuyler D.

    2013-08-01

    I have discovered a prominent light echo around the low-luminosity Type II-plateau supernova (SN) 2008bk in NGC 7793, seen in archival images obtained with the Wide Field Channel of the Advanced Camera for Surveys on board the Hubble Space Telescope (HST). The echo is a partial ring, brighter to the north and east than to the south and west. The analysis of the echo I present suggests that it is due to the SN light pulse scattered by a sheet, or sheets, of dust located Almost-Equal-To 15 pc from the SN. The composition of the dust is assumed to be of standard Galactic diffuse interstellar grains. The visual extinction of the dust responsible for the echo is A{sub V} Almost-Equal-To 0.05 mag in addition to the extinction due to the Galactic foreground toward the host galaxy. That the SN experienced much less overall extinction implies that it is seen through a less dense portion of the interstellar medium in its environment. The late-time HST photometry of SN 2008bk also clearly demonstrates that the progenitor star has vanished.

  15. Preliminary Results of the Echo-Seeding Experiment ECHO-7 at SLAC

    SciTech Connect

    Xiang, D.; Colby, E.; Ding, Y.; Dunning, M.; Frederico, J.; Gilevich, S.; Hast, C.; Jobe, K.; McCormick, D.; Nelson, J.; Raubenheimer, T.O.; Soong, K.; Stupakov, G.; Szalata, Z.; Walz, D.; Weathersby, S.; Woodley, M.; Corlett, J.; Qiang, J.; Penn, G.; Prestemon, S.; /LBL, Berkeley /LPHE, Lausanne

    2010-06-15

    ECHO-7 is a proof-of-principle echo-enabled harmonic generation FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment aims to generate coherent radiation at 318 nm and 227 nm, which are the 5th and 7th harmonic of the infrared seed laser. In this paper we present the preliminary results from the commissioning run of the completed experimental setup which started in April 2010.

  16. Exotic Light Nuclei

    ERIC Educational Resources Information Center

    Cerny, Joseph; Poskanzer, Arthur M.

    1978-01-01

    Among the light elements, nuclei with unequal numbers of protons and neutrons are highly unstable. Some survive just long enough to be detected and exhibit unusual regimes of radioactive decay. ( Autor/MA)

  17. Robust Frequency Domain Acoustic Echo Cancellation Filter Employing Normalized Residual Echo Enhancement

    NASA Astrophysics Data System (ADS)

    Shimauchi, Suehiro; Haneda, Yoichi; Kataoka, Akitoshi

    We propose a new robust frequency domain acoustic echo cancellation filter that employs a normalized residual echo enhancement. By interpreting the conventional robust step-size control approaches as a statistical-model-based residual echo enhancement problem, the optimal step-size introduced in the most of conventional approaches is regarded as optimal only on the assumption that both the residual echo and the outlier in the error output signal are described by Gaussian distributions. However, the Gaussian-Gaussian mixture assumption does not always hold well, especially when both the residual echo and the outlier are speech signals (known as a double-talk situation). The proposed filtering scheme is based on the Gaussian-Laplacian mixture assumption for the signals normalized by the reference input signal amplitude. By comparing the performances of the proposed and conventional approaches through the simulations, we show that the Gaussian-Laplacian mixture assumption for the normalized signals can provide a better control scheme for the acoustic echo cancellation.

  18. Intensity-Corrected Dual-Echo Echo-Planar Imaging (DE-EPI) for Improved Pediatric Brain Diffusion Imaging

    PubMed Central

    Straka, Matus; Iv, Michael; Moseley, Michael E.; Barnes, Patrick D.; Skare, Stefan

    2015-01-01

    Here we investigate the utility of a dual-echo Echo-Planar Imaging (DE-EPI) Diffusion Weighted Imaging (DWI) approach to improve lesion conspicuity in pediatric imaging. This method delivers two ‘echo images’ for one diffusion-preparation period. We also demonstrate how the echoes can be utilized to remove transmit/receive coil-induced and static magnetic field intensity modulations on both echo images, which often mimic pathology and thereby pose diagnostic challenges. DE-EPI DWI data were acquired in 18 pediatric patients with abnormal diffusion lesions, and 46 pediatric patient controls at 3T. Echo1 [TE = 45ms] and Echo2 [TE = 86ms] were corrected for signal intensity variation across the images by exploiting the images equivalent coil-sensitivity and susceptibility-induced modulations. Two neuroradiologists independently reviewed Echo1 and Echo2 and their intensity-corrected variants (cEcho1 and cEcho2) on a 7-point Likert scale, with grading on lesion conspicuity diagnostic confidence. The apparent diffusion coefficient (ADC) map from Echo1 was used to validate presence of true pathology. Echo2 was unanimously favored over Echo1 for its sensitivity for detecting acute brain injury, with a mean respective lesion conspicuity of 5.7/4.4 (p < 0.005) and diagnostic confidence of 5.1/4.3 (p = 0.025). cEcho2 was rated higher than cEcho1, with a mean respective lesion conspicuity of 5.5/4.3 (p < 0.005) and diagnostic confidence of 5.4/4.4 (p < 0.005). cEcho2 was favored over all echoes for its diagnostic reliability, particularly in regions close to the head coil. This work concludes that DE-EPI DWI is a useful alternative to conventional single-echo EPI DWI, whereby Echo2 and cEcho2 allows for improved lesion detection and overall higher diagnostic confidence. PMID:26069959

  19. Stark echo modulation for quantum memories

    NASA Astrophysics Data System (ADS)

    Arcangeli, A.; Ferrier, A.; Goldner, Ph.

    2016-06-01

    Quantum memories for optical and microwave photons provide key functionalities in quantum processing and communications. Here we propose a protocol well adapted to solid-state ensemble-based memories coupled to cavities. It is called Stark echo modulation memory (SEMM) and allows large storage bandwidths and low noise. This is achieved in an echo-like sequence combined with phase shifts induced by small electric fields through the linear Stark effect. We investigated the protocol for rare-earth nuclear spins and found a high suppression of unwanted collective emissions that is compatible with single-photon-level operation. Broadband storage together with high fidelity for the Stark retrieval process is also demonstrated. SEMM could be used to store optical or microwave photons in ions and/or spins. This includes nitrogen-vacancy centers in diamond and rare-earth-doped crystals, which are among the most promising solid-state quantum memories.

  20. Faraday rotation echo spectroscopy of phase transitions

    NASA Astrophysics Data System (ADS)

    Chen, Shaowen; Liu, Renbao

    2013-03-01

    Faraday rotation is widely used to study magnetic dynamics. We designed a scheme of Faraday rotation echo spectroscopy (FRES) that can be used to study spin noise dynamics in transparent materials by measuring the fluctuation of Faraday rotation angle. The FRES suppresses the static part of the noise and reveal the quantum fluctuations at relatively high temperature, which shares the same idea of the spin echo technique in nuclear magnetic resonance (NMR). We tested our theory on a rare-earth compound LiHoF4. The quantum fluctuations obtained by FRES give an enhanced feature at the phase boundary. The FRES can be straightforwardly generalized to more complicated configurations that correspond to more complex dynamical decoupling sequences in NMR and electron spin resonance, which may give us more extensive information on the structural and dynamical properties of magnetic materials. This work was supported by Hong Kong RGC 402410 and CUHK FIS.

  1. Ultrasonic unipolar pulse/echo instrument

    DOEpatents

    Hughes, M.J.; Hsu, D.K.; Thompson, D.O.; Wormley, S.J.

    1993-04-06

    An ultrasonic unipolar pulse/echo instrument uses active switches and a timing and drive circuitry to control electrical energy to a transducer, the discharging of the transducer, and the opening of an electrical pathway to the receiving circuitry for the returning echoes. The active switches utilize MOSFET devices along with decoupling circuitry to insure the preservation of the unipolar nature of the pulses, insure fast transition times, and maintain broad band width and time resolution. A housing contains the various circuitry and switches and allows connection to a power supply and a movable ultrasonic transducer. The circuitry maintains low impedance input to the transducer during transmitting cycles, and high impedance between the transducer and the receiving circuit during receive cycles to maintain the unipolar pulse shape. A unipolar pulse is valuable for nondestructive evaluation, a prime use for the present instrument.

  2. Ultrasonic unipolar pulse/echo instrument

    DOEpatents

    Hughes, Michael S.; Hsu, David K.; Thompson, Donald O.; Wormley, Samuel J.

    1993-01-01

    An ultrasonic unipolar pulse/echo instrument uses active switches and a timing and drive circuitry to control electrical energy to a transducer, the discharging of the transducer, and the opening of an electrical pathway to the receiving circuitry for the returning echoes. The active switches utilize MOSFET devices along with decoupling circuitry to insure the preservation of the unipolar nature of the pulses, insure fast transition times, and maintain broad band width and time resolution. A housing contains the various circuitry and switches and allows connection to a power supply and a movable ultrasonic transducer. The circuitry maintains low impedance input to the transducer during transmitting cycles, and high impedance between the transducer and the receiving circuit during receive cycles to maintain the unipolar pulse shape. A unipolar pulse is valuable for nondestructive evaluation, a prime use for the present instrument.

  3. Light Echo From Star V838 Monocerotis

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This photo, captured by the NASA Hubble Space Telescope's (HST) Advanced Camera for Surveys, is Hubble's latest view of an expanding halo of light around the distant star V838 Monocerotis, or V Mon, caused by an unusual stellar outburst that occurred back in January 2002. A burst of light from the bizarre star is spreading into space and reflecting off of surrounding circumstellar dust. As different parts are sequentially illuminated, the appearance of the dust changes. This effect is referred to as a 'light echo'. Located about 20,000 light-years away in the winter constellation Monoceros (the Unicorn), the star brightened to more than 600,000 times our Sun's luminosity. The light echo gives the illusion of contracting, until it finally disappears by the end of the decade.

  4. Light-echo spectroscopy of historic Supernovae

    NASA Astrophysics Data System (ADS)

    Krause, Oliver

    Young Galactic supernova remnants are unique laboratories for supernova physics. Due to their proximity they provide us with the most detailed view of the outcome of a supernova. However, the exact spectroscopic types of their original explosions have been undetermined so far -hindering to link the wealth of multi-wavelength knowledge about their remnants with the diverse population of supernovae. Light echoes, reflektions of the brilliant supernova burst of light by interstellar dust, provide a unique opportunity to reobserve today -with powerful scientific instruments of the 21st century -historic supernova exlosions even after hundreds of years and to conclude on their nature. We report on optical light-echo spectroscopy of two famous Galactic supernovae: Tycho Brahe's SN 1572 and the supernova that created the Cassiopeia A remnant around the year 1680. These observations finally recovered the missing spectroscopic classifications and provide new constraints on explosion models for future studies.

  5. Project Echo: Satellite-Tracking Radar

    NASA Technical Reports Server (NTRS)

    DeLange, O. E.

    1961-01-01

    The radar employed at the Bell Telephone Laboratories' Holmdel, New Jersey site for tracking the Echo I satellite was originally designed for the sole purpose of antenna pointing. Recently, however, it has also been employed to measure earth-balloon-earth path loss at regular intervals of time in order to ascertain the balloon's condition. The performance of the system and some of the data obtained are discussed.

  6. Radiations from hot nuclei

    NASA Technical Reports Server (NTRS)

    Malik, F. Bary

    1993-01-01

    The investigation indicates that nuclei with excitation energy of a few hundred MeV to BeV are more likely to radiate hot nuclear clusters than neutrons. These daughter clusters could, furthermore, de-excite emitting other hot nuclei, and the chain continues until these nuclei cool off sufficiently to evaporate primarily neutrons. A few GeV excited nuclei could radiate elementary particles preferentially over neutrons. Impact of space radiation with materials (for example, spacecraft) produces highly excited nuclei which cool down emitting electromagnetic and particle radiations. At a few MeV excitation energy, neutron emission becomes more dominant than gamma-ray emission and one often attributes the cooling to take place by successive neutron decay. However, a recent experiment studying the cooling process of 396 MeV excited Hg-190 casts some doubt on this thinking, and the purpose of this investigation is to explore the possibility of other types of nuclear emission which might out-compete with neutron evaporation.

  7. Physics of Unstable Nuclei

    NASA Astrophysics Data System (ADS)

    Khoa, Dao Tien; Egelhof, Peter; Gales, Sydney; Giai, Nguyen Van; Motobayashi, Tohru

    2008-04-01

    Studies at the RIKEN RI beam factory / T. Motobayashi -- Dilute nuclear states / M. Freer -- Studies of exotic systems using transfer reactions at GANIL / D. Beaumel et al. -- First results from the Magnex large-acceptance spectrometer / A. Cunsolo et al. -- The ICHOR project and spin-isospin physics with unstable beams / H. Sakai -- Structure and low-lying states of the [symbol]He exotic nucleus via direct reactions on proton / V. Lapoux et al. -- Shell gap below [symbol]Sn based on the excited states in [symbol]Cd and [symbol]In / M. Górska -- Heavy neutron-rich nuclei produced in the fragmentation of a [symbol]Pb beam / Zs. Podolyák et al. -- Breakup and incomplete fusion in reactions of weakly-bound nuclei / D.J. Hinde et al. -- Excited states of [symbol]B and [symbol]He and their cluster aspect / Y. Kanada-En'yo et al. -- Nuclear reactions with weakly-bound systems: the treatment of the continuum / C. H. Dasso, A. Vitturi -- Dynamic evolution of three-body decaying resonances / A. S. Jensen et al. -- Prerainbow oscillations in [symbol]He scattering from the Hoyle state of [symbol]C and alpha particle condensation / S. Ohkubo, Y. Hirabayashi -- Angular dispersion behavior in heavy ion elastic scattering / Q. Wang et al. -- Microscopic optical potential in relativistic approach / Z.Yu. Ma et al. -- Exotic nuclei studied in direct reactions at low momentum transfer - recent results and future perspectives at fair / P. Egelhof -- Isotopic temperatures and symmetry energy in spectator fragmentation / M. De Napoli et al. -- Multi-channel algebraic scattering theory and the structure of exotic compound nuclei / K. Amos et al. -- Results for the first feasibility study for the EXL project at the experimental storage ring at GSI / N. Kalantar-Nayestanaki et al. -- Coulomb excitation of ISOLDE neutron-rich beams along the Z = 28 chain / P. Van Duppen -- The gamma decay of the pygmy resonance far from stability and the GDR at finite temperature / G. Benzoni et al

  8. Light Echoes of Galactic Explosions and Eruptions

    NASA Astrophysics Data System (ADS)

    Rest, Armin; Bianco, Federica; Chornock, Ryan; Foley, Ryan; Kunder, Andrea; Matheson, Thomas; Olsen, Knut; Prieto, Jose Luis; Sinnott, Brendan; Smith, Chris; Smith, Nathan; Welch, Doug

    2013-08-01

    We propose to search for light echoes (LEs) from the historical brightening of the Luminous Blue Variable (LBV) P Cygni using the KPNO 4m Mosaic 1.1 imager. We also propose to conclude our search - so far unsuccessful - for LEs from the the Crab supernova SN 1054 by surveying one remaining region of the LE ellipsoid behind the plane of the supernova remnant on the sky. In addition, we continue to monitor the LEs from the Cas A and Tycho supernovae in order to identify suitable LE candidates for 3D-spectroscopy and spectral time series. In previously granted NOAO time, we have discovered light echoes of three ancient SNe in the LMC as well as from the historic SN events of Cas A and Tycho [2, 3], which allowed their spectroscopic classification [6, 7, 10] and 3D spectroscopy [8, 9]. Most recently, we discovered light echoes of the mid-19th-century Great Eruption of η Carinae using CTIO 4m Mosaic images [11]. Subsequent spectroscopic follow-up of Eta Carinae revealed that its outburst spectral type was most similar to those of G-type supergiants, rather than reported LBV outburst spectral types of F-type (or earlier) [11]. Our extension of LE techniques to LBV outbursts promises to extend our ability to record outburst activity hundreds of years into the past - a timescale which is likely a significant fraction of the brief final phases of these probable core- collapse supernova precursors.

  9. Light Echoes of Galactic Explosions and Eruptions

    NASA Astrophysics Data System (ADS)

    Rest, Armin; Bianco, Federica; Chornock, Ryan; Clocchiatti, Alejandro; Foley, Ryan; James, David; Matheson, Thomas; Narayan, Gautham; Olsen, Knut; Points, Sean; Prieto, Jose Luis; Smith, Chris; Smith, Nathan; Suntzeff, Nick; Welch, Doug; Zenteno, Alfredo

    2014-08-01

    We propose to search for light echoes (LEs) from the historical brightening of the Luminous Blue Variable (LBV) P Cygni using the KPNO 4m Mosaic 1.1 imager. We also propose to us DECam to continue our search for LEs from the the Crab supernova SN 1054. In addition, we continue to monitor the LEs from the Cas A and Tycho supernovae in order to identify suitable LE candidates for 3D-spectroscopy and spectral time series. In previously granted NOAO time, we have discovered light echoes of three ancient SNe in the LMC as well as from the historic SN events of Cas A and Tycho [2, 3], which allowed their spectroscopic classification [6, 7, 10] and 3D spectroscopy [8, 9]. Most recently, we discovered light echoes of the mid-19th-century Great Eruption of η Carinae using CTIO 4m Mosaic images [11]. Subsequent spectroscopic follow-up of Eta Carinae revealed that its outburst spectral type was most similar to those of G-type supergiants, rather than reported LBV outburst spectral types of F-type (or earlier) [11]. Our extension of LE techniques to LBV outbursts promises to extend our ability to record outburst activity hundreds of years into the past - a timescale which is likely a significant fraction of the brief final phases of these probable core- collapse supernova precursors.

  10. Heterodyne-Detected Dispersed Vibrational Echo Spectroscopy

    NASA Astrophysics Data System (ADS)

    Jones, Kevin C.; Ganim, Ziad; Tokmakoff, Andrei

    2009-11-01

    We develop heterodyned dispersed vibrational echo spectroscopy (HDVE) and demonstrate the new capabilities in biophysical applications. HDVE is a robust ultrafast technique that provides a characterization of the real and imaginary components of third-order nonlinear signals with high sensitivity and single-laser-shot capability and can be used to extract dispersed pump-probe and dispersed vibrational echo spectra. Four methods for acquiring HDVE phase and amplitude spectra were compared: Fourier transform spectral interferometry, a new phase modulation spectral interferometry technique, and combination schemes. These extraction techniques were demonstrated in the context of protein amide I spectroscopy. Experimental HDVE and heterodyned free induction decay amide I spectra were explicitly compared to conventional dispersed pump-probe, dispersed vibrational echo, and absorption spectra. The new capabilities of HDVE were demonstrated by acquiring single-shot spectra and melting curves of ubiquitin and concentration-dependent spectra of insulin suitable for extracting the binding constant for dimerization. The introduced techniques will prove particularly useful in transient experiments, studying irreversible reactions, and micromolar concentration studies of small proteins.

  11. Perception of echo delay is disrupted by small temporal misalignment of echo harmonics in bat sonar

    PubMed Central

    Bates, Mary E.; Simmons, James A.

    2011-01-01

    Echolocating big brown bats emit ultrasonic frequency-modulated (FM) biosonar sounds containing two prominent downward-sweeping harmonics (FM1 and FM2) and perceive target distance from echo delay. In naturally occurring echoes, FM1 and FM2 are delayed by the same amount. Even though echoes from targets located off-axis or far away are lowpass filtered, which weakens FM2 relative to FM1, their delays remain the same. We show here that misalignment of FM2 with FM1 by only 2.6 μs is sufficient to significantly disrupt acuity, which then persists for larger misalignments up to 300 μs. However, when FM2 is eliminated entirely rather than just misaligned, acuity is effectively restored. For naturally occurring, lowpass-filtered echoes, neuronal responses to weakened FM2 are retarded relative to FM1 because of amplitude-latency trading, which misaligns the harmonics in the bat's internal auditory representations. Electronically delaying FM2 relative to FM1 mimics the retarded neuronal responses for FM2 relative to FM1 caused by amplitude-latency trading. Echoes with either electronically or physiologically misaligned harmonics are not perceived as having a clearly defined delay. This virtual collapse of delay acuity may suppress interference from off-axis or distant clutter through degradation of delay images for clutter in contrast to sharp images for nearer, frontal targets. PMID:21228198

  12. Echo amplitude sensitivity of bat auditory neurons improves with decreasing pulse-echo gap.

    PubMed

    Jen, Philip H-S; Wu, Chung Hsin

    2015-01-01

    During hunting, insectivorous bats systematically vary the parameters of emitted pulses and analyze the returning echoes to extract prey features. As such, the duration of the pulse (P) and echo (E), the P-E gap, and the P-E amplitude difference progressively decrease throughout the prey-approach sequence. Our previous studies have shown that most inferior collicular neurons of bats discharge maximally to a best duration, and they have the sharpest echo frequency and amplitude sensitivity when stimulated with P-E pairs with duration the same as the best duration. Furthermore, their echo duration and frequency sensitivity improves with decreasing P-E duration and P-E gap. The present study shows that this is also true in the amplitude domain. Thus, all these data indicate that bats can better extract multiple parameters of expected rather than unexpected echo after pulse emission. They also support the hypothesis that a bat's inferior collicular neurons improve the response sensitivity in multiple parametric domains as the prey is approached to increase the success of hunting. PMID:25426829

  13. Perception of echo delay is disrupted by small temporal misalignment of echo harmonics in bat sonar.

    PubMed

    Bates, Mary E; Simmons, James A

    2011-02-01

    Echolocating big brown bats emit ultrasonic frequency-modulated (FM) biosonar sounds containing two prominent downward-sweeping harmonics (FM1 and FM2) and perceive target distance from echo delay. In naturally occurring echoes, FM1 and FM2 are delayed by the same amount. Even though echoes from targets located off-axis or far away are lowpass filtered, which weakens FM2 relative to FM1, their delays remain the same. We show here that misalignment of FM2 with FM1 by only 2.6 μs is sufficient to significantly disrupt acuity, which then persists for larger misalignments up to 300 μs. However, when FM2 is eliminated entirely rather than just misaligned, acuity is effectively restored. For naturally occurring, lowpass-filtered echoes, neuronal responses to weakened FM2 are retarded relative to FM1 because of amplitude-latency trading, which misaligns the harmonics in the bat's internal auditory representations. Electronically delaying FM2 relative to FM1 mimics the retarded neuronal responses for FM2 relative to FM1 caused by amplitude-latency trading. Echoes with either electronically or physiologically misaligned harmonics are not perceived as having a clearly defined delay. This virtual collapse of delay acuity may suppress interference from off-axis or distant clutter through degradation of delay images for clutter in contrast to sharp images for nearer, frontal targets. PMID:21228198

  14. Scattering Of Light Nuclei

    SciTech Connect

    Quaglioni, S; Navratil, P; Roth, R

    2009-12-15

    The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. Above all nuclear scattering and reactions, which require the solution of the many-body quantum-mechanical problem in the continuum, represent an extraordinary theoretical as well as computational challenge for ab initio approaches.We present a new ab initio many-body approach which derives from the combination of the ab initio no-core shell model with the resonating-group method [4]. By complementing a microscopic cluster technique with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters, this approach is capable of describing simultaneously both bound and scattering states in light nuclei. We will discuss applications to neutron and proton scattering on sand light p-shell nuclei using realistic nucleon-nucleon potentials, and outline the progress toward the treatment of more complex reactions.

  15. Response of hot nuclei

    SciTech Connect

    Broglia, R.A.

    1986-01-01

    The dipole giant resonance is reviewed, as it is the only vibration which has been experimentally identified in the decay of hot nuclei. The mechanism of exciting the resonance and the mode of the resonance are described. The methods used to calculate the vibrations from the shell model are discussed, including the Hartree-Fock approximation and random phase approximation. Nuclei formed by compound nuclear reactions, which possess high excitation energy and angular momentum, are considered. It is argued that the stability of the dipole may be used to advantage in the study of other properties of nuclei at high excitation. It is also considered possible that the discussion of the dipole giant resonance may be extended to the gamma decay of the isovector quadrupole vibration. 26 refs., 18 figs. (LEW)

  16. Super-heavy nuclei

    NASA Astrophysics Data System (ADS)

    Hofmann, Sigurd

    2015-11-01

    Scientifically based searches for elements beyond uranium started after the discovery of the neutron. Neutrons captured by uranium nuclei and subsequent {β }- decay, similarly as most of the elements were produced in nature, was the successful method applied. However, as a first result, Hahn and Strassmann discovered nuclear fission indicating a limit for the existence of nuclei at an increasing number of protons. Eventually, the nuclear shell model allowed for a more accurate calculation of binding energies, half-lives and decay modes of the heaviest nuclei. Theoreticians predicted a region of increased stability at proton number Z = 126, later shifted to 114, and neutron number N = 184. These nuclei receive their stability from closed shells for the protons and neutrons. Later, increased stability was also predicted for deformed nuclei at Z = 108 and N = 162. In this review I will report on experimental work performed on research to produce and identify these super-heavy nuclei (SHN). Intensive heavy ion beams, sophisticated target technology, efficient electromagnetic ion separators, and sensitive detector arrays were the prerequisites for discovery of 12 new elements during the last 40 years. The results are described and compared with theoretical predictions and interpretations. An outlook is given on further improvement of experimental facilities which will be needed for exploration of the extension and structure of the island of SHN, in particular for searching for isotopes with longer half-lives predicted to be located in the south east of the island, for new elements, and last not least, for surprises which, naturally, emerge unexpectedly.

  17. The EChO science case

    NASA Astrophysics Data System (ADS)

    Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul; Hartogh, Paul; Isaak, Kate; Linder, Martin; Lovis, Christophe; Micela, Giusi; Ollivier, Marc; Puig, Ludovic; Ribas, Ignasi; Snellen, Ignas; Swinyard, Bruce; Allard, France; Barstow, Joanna; Cho, James; Coustenis, Athena; Cockell, Charles; Correia, Alexandre; Decin, Leen; de Kok, Remco; Deroo, Pieter; Encrenaz, Therese; Forget, Francois; Glasse, Alistair; Griffith, Caitlin; Guillot, Tristan; Koskinen, Tommi; Lammer, Helmut; Leconte, Jeremy; Maxted, Pierre; Mueller-Wodarg, Ingo; Nelson, Richard; North, Chris; Pallé, Enric; Pagano, Isabella; Piccioni, Guseppe; Pinfield, David; Selsis, Franck; Sozzetti, Alessandro; Stixrude, Lars; Tennyson, Jonathan; Turrini, Diego; Zapatero-Osorio, Mariarosa; Beaulieu, Jean-Philippe; Grodent, Denis; Guedel, Manuel; Luz, David; Nørgaard-Nielsen, Hans Ulrik; Ray, Tom; Rickman, Hans; Selig, Avri; Swain, Mark; Banaszkiewicz, Marek; Barlow, Mike; Bowles, Neil; Branduardi-Raymont, Graziella; du Foresto, Vincent Coudé; Gerard, Jean-Claude; Gizon, Laurent; Hornstrup, Allan; Jarchow, Christopher; Kerschbaum, Franz; Kovacs, Géza; Lagage, Pierre-Olivier; Lim, Tanya; Lopez-Morales, Mercedes; Malaguti, Giuseppe; Pace, Emanuele; Pascale, Enzo; Vandenbussche, Bart; Wright, Gillian; Ramos Zapata, Gonzalo; Adriani, Alberto; Azzollini, Ruymán; Balado, Ana; Bryson, Ian; Burston, Raymond; Colomé, Josep; Crook, Martin; Di Giorgio, Anna; Griffin, Matt; Hoogeveen, Ruud; Ottensamer, Roland; Irshad, Ranah; Middleton, Kevin; Morgante, Gianluca; Pinsard, Frederic; Rataj, Mirek; Reess, Jean-Michel; Savini, Giorgio; Schrader, Jan-Rutger; Stamper, Richard; Winter, Berend; Abe, L.; Abreu, M.; Achilleos, N.; Ade, P.; Adybekian, V.; Affer, L.; Agnor, C.; Agundez, M.; Alard, C.; Alcala, J.; Allende Prieto, C.; Alonso Floriano, F. J.; Altieri, F.; Alvarez Iglesias, C. A.; Amado, P.; Andersen, A.; Aylward, A.; Baffa, C.; Bakos, G.; Ballerini, P.; Banaszkiewicz, M.; Barber, R. J.; Barrado, D.; Barton, E. J.; Batista, V.; Bellucci, G.; Belmonte Avilés, J. A.; Berry, D.; Bézard, B.; Biondi, D.; Błęcka, M.; Boisse, I.; Bonfond, B.; Bordé, P.; Börner, P.; Bouy, H.; Brown, L.; Buchhave, L.; Budaj, J.; Bulgarelli, A.; Burleigh, M.; Cabral, A.; Capria, M. T.; Cassan, A.; Cavarroc, C.; Cecchi-Pestellini, C.; Cerulli, R.; Chadney, J.; Chamberlain, S.; Charnoz, S.; Christian Jessen, N.; Ciaravella, A.; Claret, A.; Claudi, R.; Coates, A.; Cole, R.; Collura, A.; Cordier, D.; Covino, E.; Danielski, C.; Damasso, M.; Deeg, H. J.; Delgado-Mena, E.; Del Vecchio, C.; Demangeon, O.; De Sio, A.; De Wit, J.; Dobrijévic, M.; Doel, P.; Dominic, C.; Dorfi, E.; Eales, S.; Eiroa, C.; Espinoza Contreras, M.; Esposito, M.; Eymet, V.; Fabrizio, N.; Fernández, M.; Femenía Castella, B.; Figueira, P.; Filacchione, G.; Fletcher, L.; Focardi, M.; Fossey, S.; Fouqué, P.; Frith, J.; Galand, M.; Gambicorti, L.; Gaulme, P.; García López, R. J.; Garcia-Piquer, A.; Gear, W.; Gerard, J.-C.; Gesa, L.; Giani, E.; Gianotti, F.; Gillon, M.; Giro, E.; Giuranna, M.; Gomez, H.; Gomez-Leal, I.; Gonzalez Hernandez, J.; González Merino, B.; Graczyk, R.; Grassi, D.; Guardia, J.; Guio, P.; Gustin, J.; Hargrave, P.; Haigh, J.; Hébrard, E.; Heiter, U.; Heredero, R. L.; Herrero, E.; Hersant, F.; Heyrovsky, D.; Hollis, M.; Hubert, B.; Hueso, R.; Israelian, G.; Iro, N.; Irwin, P.; Jacquemoud, S.; Jones, G.; Jones, H.; Justtanont, K.; Kehoe, T.; Kerschbaum, F.; Kerins, E.; Kervella, P.; Kipping, D.; Koskinen, T.; Krupp, N.; Lahav, O.; Laken, B.; Lanza, N.; Lellouch, E.; Leto, G.; Licandro Goldaracena, J.; Lithgow-Bertelloni, C.; Liu, S. J.; Lo Cicero, U.; Lodieu, N.; Lognonné, P.; Lopez-Puertas, M.; Lopez-Valverde, M. A.; Lundgaard Rasmussen, I.; Luntzer, A.; Machado, P.; MacTavish, C.; Maggio, A.; Maillard, J.-P.; Magnes, W.; Maldonado, J.; Mall, U.; Marquette, J.-B.; Mauskopf, P.; Massi, F.; Maurin, A.-S.; Medvedev, A.; Michaut, C.; Miles-Paez, P.; Montalto, M.; Montañés Rodríguez, P.; Monteiro, M.; Montes, D.; Morais, H.; Morales, J. C.; Morales-Calderón, M.; Morello, G.; Moro Martín, A.; Moses, J.; Moya Bedon, A.; Murgas Alcaino, F.; Oliva, E.; Orton, G.; Palla, F.; Pancrazzi, M.; Pantin, E.; Parmentier, V.; Parviainen, H.; Peña Ramírez, K. Y.; Peralta, J.; Perez-Hoyos, S.; Petrov, R.; Pezzuto, S.; Pietrzak, R.; Pilat-Lohinger, E.; Piskunov, N.; Prinja, R.; Prisinzano, L.; Polichtchouk, I.; Poretti, E.; Radioti, A.; Ramos, A. A.; Rank-Lüftinger, T.; Read, P.; Readorn, K.; Rebolo López, R.; Rebordão, J.; Rengel, M.; Rezac, L.; Rocchetto, M.; Rodler, F.; Sánchez Béjar, V. J.; Sanchez Lavega, A.; Sanromá, E.; Santos, N.; Sanz Forcada, J.; Scandariato, G.; Schmider, F.-X.; Scholz, A.; Scuderi, S.; Sethenadh, J.; Shore, S.; Showman, A.; Sicardy, B.; Sitek, P.; Smith, A.; Soret, L.; Sousa, S.; Stiepen, A.; Stolarski, M.; Strazzulla, G.; Tabernero, H. M.; Tanga, P.; Tecsa, M.; Temple, J.; Terenzi, L.; Tessenyi, M.; Testi, L.; Thompson, S.; Thrastarson, H.; Tingley, B. W.; Trifoglio, M.; Martín Torres, J.; Tozzi, A.; Turrini, D.; Varley, R.; Vakili, F.; de Val-Borro, M.; Valdivieso, M. L.; Venot, O.; Villaver, E.; Vinatier, S.; Viti, S.; Waldmann, I.; Waltham, D.; Ward-Thompson, D.; Waters, R.; Watkins, C.; Watson, D.; Wawer, P.; Wawrzaszk, A.; White, G.; Widemann, T.; Winek, W.; Wiśniowski, T.; Yelle, R.; Yung, Y.; Yurchenko, S. N.

    2015-12-01

    The discovery of almost two thousand exoplanets has revealed an unexpectedly diverse planet population. We see gas giants in few-day orbits, whole multi-planet systems within the orbit of Mercury, and new populations of planets with masses between that of the Earth and Neptune—all unknown in the Solar System. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? How do planetary systems work and what causes the exceptional diversity observed as compared to the Solar System? The EChO (Exoplanet Characterisation Observatory) space mission was conceived to take up the challenge to explain this diversity in terms of formation, evolution, internal structure and planet and atmospheric composition. This requires in-depth spectroscopic knowledge of the atmospheres of a large and well-defined planet sample for which precise physical, chemical and dynamical information can be obtained. In order to fulfil this ambitious scientific program, EChO was designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large, diverse and well-defined planet sample within its 4-year mission lifetime. The transit and eclipse spectroscopy method, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allows us to measure atmospheric signals from the planet at levels of at least 10-4 relative to the star. This can only be achieved in conjunction with a carefully designed stable payload and satellite platform. It is also necessary to provide broad instantaneous wavelength coverage to detect as many molecular species as possible, to probe the thermal structure of the planetary atmospheres and to correct for the contaminating effects of the stellar photosphere. This requires wavelength

  18. Superdeformed oblate superheavy nuclei

    SciTech Connect

    Jachimowicz, P.; Kowal, M.; Skalski, J.

    2011-05-15

    We study stability of superdeformed oblate (SDO) superheavy Z{>=}120 nuclei predicted by systematic microscopic-macroscopic calculations in 12D deformation space and confirmed by the Hartree-Fock calculations with the SLy6 force. We include into consideration high-K isomers that very likely form at the SDO shape. Although half-lives T{sub 1/2} < or approx. 10{sup -5} s are calculated or estimated for even-even spin-zero systems, decay hindrances known for high-K isomers suggest that some SDO superheavy nuclei may be detectable by the present experimental technique.

  19. Hadrons in Nuclei

    SciTech Connect

    Mosel, Ulrich

    2004-08-30

    Changes of hadronic properties in dense nuclear matter as predicted by theory have usually been investigated by means of relativistic heavy-ion reactions. In this talk I show that observable consequences of such changes can also be seen in more elementary reactions on nuclei. Particular emphasis is put on a discussion of photonuclear reactions; examples are the dilepton production at {approx_equal} 1 GeV and the hadron production in nuclei at 10-20 GeV photon energies. The observable effects are expected to be as large as in relativistic heavy-ion collisions and can be more directly related to the underlying hadronic changes.

  20. EChO. Exoplanet characterisation observatory

    NASA Astrophysics Data System (ADS)

    Tinetti, G.; Beaulieu, J. P.; Henning, T.; Meyer, M.; Micela, G.; Ribas, I.; Stam, D.; Swain, M.; Krause, O.; Ollivier, M.; Pace, E.; Swinyard, B.; Aylward, A.; van Boekel, R.; Coradini, A.; Encrenaz, T.; Snellen, I.; Zapatero-Osorio, M. R.; Bouwman, J.; Cho, J. Y.-K.; Coudé de Foresto, V.; Guillot, T.; Lopez-Morales, M.; Mueller-Wodarg, I.; Palle, E.; Selsis, F.; Sozzetti, A.; Ade, P. A. R.; Achilleos, N.; Adriani, A.; Agnor, C. B.; Afonso, C.; Allende Prieto, C.; Bakos, G.; Barber, R. J.; Barlow, M.; Batista, V.; Bernath, P.; Bézard, B.; Bordé, P.; Brown, L. R.; Cassan, A.; Cavarroc, C.; Ciaravella, A.; Cockell, C.; Coustenis, A.; Danielski, C.; Decin, L.; De Kok, R.; Demangeon, O.; Deroo, P.; Doel, P.; Drossart, P.; Fletcher, L. N.; Focardi, M.; Forget, F.; Fossey, S.; Fouqué, P.; Frith, J.; Galand, M.; Gaulme, P.; Hernández, J. I. González; Grasset, O.; Grassi, D.; Grenfell, J. L.; Griffin, M. J.; Griffith, C. A.; Grözinger, U.; Guedel, M.; Guio, P.; Hainaut, O.; Hargreaves, R.; Hauschildt, P. H.; Heng, K.; Heyrovsky, D.; Hueso, R.; Irwin, P.; Kaltenegger, L.; Kervella, P.; Kipping, D.; Koskinen, T. T.; Kovács, G.; La Barbera, A.; Lammer, H.; Lellouch, E.; Leto, G.; Lopez Morales, M.; Lopez Valverde, M. A.; Lopez-Puertas, M.; Lovis, C.; Maggio, A.; Maillard, J. P.; Maldonado Prado, J.; Marquette, J. B.; Martin-Torres, F. J.; Maxted, P.; Miller, S.; Molinari, S.; Montes, D.; Moro-Martin, A.; Moses, J. I.; Mousis, O.; Nguyen Tuong, N.; Nelson, R.; Orton, G. S.; Pantin, E.; Pascale, E.; Pezzuto, S.; Pinfield, D.; Poretti, E.; Prinja, R.; Prisinzano, L.; Rees, J. M.; Reiners, A.; Samuel, B.; Sánchez-Lavega, A.; Forcada, J. Sanz; Sasselov, D.; Savini, G.; Sicardy, B.; Smith, A.; Stixrude, L.; Strazzulla, G.; Tennyson, J.; Tessenyi, M.; Vasisht, G.; Vinatier, S.; Viti, S.; Waldmann, I.; White, G. J.; Widemann, T.; Wordsworth, R.; Yelle, R.; Yung, Y.; Yurchenko, S. N.

    2012-10-01

    A dedicated mission to investigate exoplanetary atmospheres represents a major milestone in our quest to understand our place in the universe by placing our Solar System in context and by addressing the suitability of planets for the presence of life. EChO—the Exoplanet Characterisation Observatory—is a mission concept specifically geared for this purpose. EChO will provide simultaneous, multi-wavelength spectroscopic observations on a stable platform that will allow very long exposures. The use of passive cooling, few moving parts and well established technology gives a low-risk and potentially long-lived mission. EChO will build on observations by Hubble, Spitzer and ground-based telescopes, which discovered the first molecules and atoms in exoplanetary atmospheres. However, EChO's configuration and specifications are designed to study a number of systems in a consistent manner that will eliminate the ambiguities affecting prior observations. EChO will simultaneously observe a broad enough spectral region—from the visible to the mid-infrared—to constrain from one single spectrum the temperature structure of the atmosphere, the abundances of the major carbon and oxygen bearing species, the expected photochemically-produced species and magnetospheric signatures. The spectral range and resolution are tailored to separate bands belonging to up to 30 molecules and retrieve the composition and temperature structure of planetary atmospheres. The target list for EChO includes planets ranging from Jupiter-sized with equilibrium temperatures T eq up to 2,000 K, to those of a few Earth masses, with T eq u223c 300 K. The list will include planets with no Solar System analog, such as the recently discovered planets GJ1214b, whose density lies between that of terrestrial and gaseous planets, or the rocky-iron planet 55 Cnc e, with day-side temperature close to 3,000 K. As the number of detected exoplanets is growing rapidly each year, and the mass and radius of those

  1. Quark structure of nuclei

    SciTech Connect

    Blankenbecler, R.

    1981-01-01

    A brief review is given of selected topics involved in the relativistic quark structure of nuclei such as the infinite momentum variables, scaling variables, counting rules, forward-backward variables, thermodynamic-like limit, QCD effects, higher quark bags, confinement, and many unanswered questions.

  2. Transfer involving deformed nuclei

    SciTech Connect

    Rasmussen, J.O.; Guidry, M.W.; Canto, L.F.

    1985-03-01

    Results are reviewed of 1- and 2-neutron transfer reactions at near-barrier energies for deformed nuclei. Rotational angular momentum and excitation patterns are examined. A strong tendency to populating high spin states within a few MeV of the yrast line is noted, and it is interpreted as preferential transfer to rotation-aligned states. 16 refs., 12 figs.

  3. Physics with Polarized Nuclei.

    ERIC Educational Resources Information Center

    Thompson, William J.; Clegg, Thomas B.

    1979-01-01

    Discusses recent advances in polarization techniques, specifically those dealing with polarization of atomic nuclei, and how polarized beams and targets are produced. These techniques have greatly increased the scope of possible studies, and provided the tools for testing fundamental symmetries and the spin dependence of nuclear forces. (GA)

  4. Octupole collectivity in nuclei

    NASA Astrophysics Data System (ADS)

    Butler, P. A.

    2016-07-01

    The experimental and theoretical evidence for octupole collectivity in nuclei is reviewed. Recent theoretical advances, covering a wide spectrum from mean-field theory to algebraic and cluster approaches, are discussed. The status of experimental data on the behaviour of energy levels and electric dipole and electric octupole transition moments is reviewed. Finally, an outlook is given on future prospects for this field.

  5. The decay of hot nuclei

    SciTech Connect

    Moretto, L.G.; Wozniak, G.J.

    1988-11-01

    The formation of hot compound nuclei in intermediate-energy heavy ion reactions is discussed. The statistical decay of such compound nuclei is responsible for the abundant emission of complex fragments and high energy gamma rays. 43 refs., 23 figs.

  6. Echo tracker/range finder for radars and sonars

    NASA Technical Reports Server (NTRS)

    Constantinides, N. J. (Inventor)

    1982-01-01

    An echo tracker/range finder or altimeter is described. The pulse repetition frequency (PFR) of a predetermined plurality of transmitted pulses is adjusted so that echo pulses received from a reflecting object are positioned between transmitted pulses and divided their interpulse time interval into two time intervals having a predetermined ratio with respect to each other. The invention described provides a means whereby the arrival time of a plurality of echo pulses is defined as the time at which a composite echo pulse formed of a sum of the individual echo pulses has the highest amplitude. The invention is applicable to radar systems, sonar systems, or any other kind of system in which pulses are transmitted and echoes received therefrom.

  7. Synthesized Bistatic Echo Imaging Using Phased Arrays

    NASA Astrophysics Data System (ADS)

    Soumekh, Mehrdad

    1990-01-01

    An object illuminated by a source produces a scattered signal; this signal depends upon both the source and the physical properties of the object. The problem of deducing coordinates, shape and/or certain physical properties of the object from the measurements of the returned signal is an inverse problem called echo imaging. The problem of echo imaging arises in medical imaging, remote sensing (radar; sonar; geophysical exploration), and non-destructive testing. In this paper, we address the problem of imaging an object form its returned signals using a phased array. Our approach is to exploit the array's various radiation patterns and the recordable portion of the returned signal's spectrum to generate the data base for this echo imaging system. Rapid steering of a phased array's radiation patterns can be achieved electronically. These steered waves can be utilized to synthesize waves with varying angles of propagation. In this case, the recorded returned signal for each direction of propagation can be viewed as data obtained by a bistatic array configuration. We first formulate the imaging problem for a plane wave source in a bistatic configuration. We utilize the two-way propagation time and amplitude of the returned signal to relate the object's properties, reflectivity function and coordinates, to the measured data (system modeling). This relationship is the basis for deducing the object's reflectivity function from the recorded data (inverse problem). We then extend these results for an arbitrary radiation pattern and synthesized radiation patterns generated by an array capable of beam steering in cross-range. We show that the recorded returned signals can be related to the spatial frequency contents of the reflectivity function. We also show that these array processing principles can be utilized to formulate a system model and inversion for synthetic aperture radar (SAR) imaging that incorporates wavefront curvature.

  8. Probing localization in absorbing systems via Loschmidt echos.

    PubMed

    Bodyfelt, Joshua D; Zheng, Mei C; Kottos, Tsampikos; Kuhl, Ulrich; Stöckmann, Hans-Jürgen

    2009-06-26

    We measure Anderson localization in quasi-one-dimensional waveguides in the presence of absorption by analyzing the echo dynamics due to small perturbations. We specifically show that the inverse participation number of localized modes dictates the decay of the Loschmidt echo, differing from the Gaussian decay expected for diffusive or chaotic systems. Our theory, based on a random matrix modeling, agrees perfectly with scattering echo measurements on a quasi-one-dimensional microwave cavity filled with randomly distributed scatterers. PMID:19659075

  9. From Echo 1 to entertainment plus

    NASA Astrophysics Data System (ADS)

    Frohbieter, J. A.

    This paper traces the history of the space communications industry from the early days of the NASA sponsored SCORE talking Atlas missile, through the Echo balloon passive reflector, to the dawn of active satellites, first at low orbit and then at geosynchronous. It further traces the economics which led to the broad based operational systems of today, like RCA Satcom, and postulates some of the future economics which are leading to the development of Direct Broadcast Satellite Systems for the 1980's and into the 1990's.

  10. Energetic Nuclei, Superdensity and Biomedicine

    ERIC Educational Resources Information Center

    Baldin, A. M.

    1977-01-01

    High-energy, relativistic nuclei were first observed in cosmic rays. Studing these nuclei has provided an opportunity for analyzing the composition of cosmic rays and for experimentally verifying principles governing the behavior of nuclear matter at high and super-high temperatures. Medical research using accelerated nuclei is suggested.…

  11. Optimal Gain Filter Design for Perceptual Acoustic Echo Suppressor

    NASA Astrophysics Data System (ADS)

    Kim, Kihyeon; Ko, Hanseok

    This Letter proposes an optimal gain filter for the perceptual acoustic echo suppressor. We designed an optimally-modified log-spectral amplitude estimation algorithm for the gain filter in order to achieve robust suppression of echo and noise. A new parameter including information about interferences (echo and noise) of single-talk duration is statistically analyzed, and then the speech absence probability and the a posteriori SNR are judiciously estimated to determine the optimal solution. The experiments show that the proposed gain filter attains a significantly improved reduction of echo and noise with less speech distortion.

  12. Measurement of ice accretion using ultrasonic pulse echo techniques

    NASA Technical Reports Server (NTRS)

    Hansman, R. John, Jr.; Kirby, Mark S.

    1987-01-01

    Many figures are given to illustrate the measurement of ice deposition using ultrasonic pulse echo techniques. The basic concept is to measure the thickness of the ice by relating the pulse echo time to the speed of sound. The measurements are made in an icing research tunnel (IRT), where echo patterns are videotaped during icing exposures under a variety of conditions. Typical echo patterns for different types of ice are illustrated. A table summarizing the icing rates measured in the IRT, along with the presence or absence of surface water is also given.

  13. Temporal signal processing of dolphin biosonar echoes from salmon prey.

    PubMed

    Au, Whitlow W L; Ou, Hui Helen

    2014-08-01

    Killer whales project short broadband biosonar clicks. The broadband nature of the clicks provides good temporal resolution of echo highlights and allows for the discriminations of salmon prey. The echoes contain many highlights as the signals reflect off different surfaces and parts of the fish body and swim bladder. The temporal characteristics of echoes from salmon are highly aspect dependent and six temporal parameters were used in a support vector machine to discriminate between species. Results suggest that killer whales can classify salmon based on their echoes and provide some insight as to which features might enable the classification. PMID:25096148

  14. Fast REDOR with CPMG multiple-echo acquisition

    NASA Astrophysics Data System (ADS)

    Hung, Ivan; Gan, Zhehong

    2014-01-01

    Rotational-Echo Double Resonance (REDOR) is a widely used experiment for distance measurements in solids. The conventional REDOR experiment measures the signal dephasing from hetero-nuclear recoupling under magic-angle spinning (MAS) in a point by point manner. A modified Carr-Purcell Meiboom-Gill (CPMG) multiple-echo scheme is introduced for fast REDOR measurement. REDOR curves are measured from the CPMG echo amplitude modulation under dipolar recoupling. The real time CPMG-REDOR experiment can speed up the measurement by an order of magnitude. The effects from hetero-nuclear recoupling, the Bloch-Siegert shift and echo truncation to the signal acquisition are discussed and demonstrated.

  15. Neutron spin echo scattering angle measurement (SESAME)

    SciTech Connect

    Pynn, R.; Fitzsimmons, M.R.; Fritzsche, H.; Gierlings, M.; Major, J.; Jason, A.

    2005-05-15

    We describe experiments in which the neutron spin echo technique is used to measure neutron scattering angles. We have implemented the technique, dubbed spin echo scattering angle measurement (SESAME), using thin films of Permalloy electrodeposited on silicon wafers as sources of the magnetic fields within which neutron spins precess. With 30-{mu}m-thick films we resolve neutron scattering angles to about 0.02 deg. with neutrons of 4.66 A wavelength. This allows us to probe correlation lengths up to 200 nm in an application to small angle neutron scattering. We also demonstrate that SESAME can be used to separate specular and diffuse neutron reflection from surfaces at grazing incidence. In both of these cases, SESAME can make measurements at higher neutron intensity than is available with conventional methods because the angular resolution achieved is independent of the divergence of the neutron beam. Finally, we discuss the conditions under which SESAME might be used to probe in-plane structure in thin films and show that the method has advantages for incident neutron angles close to the critical angle because multiple scattering is automatically accounted for.

  16. Project Echo: 960-Megacycle, 10-Kilowatt Transmitter

    NASA Technical Reports Server (NTRS)

    Schafer, J. P.; Brandt, R. H.

    1961-01-01

    A 10-kw transmitter operating at 960 to 961 Mc was used at the eastern terminus of the Project Echo communications experiment. This transmitter is located on Crawford's Hill near Holmdel, New Jersey. The 10-kw output feeds into a waveguide line leading to a 60-foot dish antenna. Exciter-driver units are available to drive the power amplifier with various modulations, such as wide-deviation FM, low-index phase modulation, single-sideband or double-sideband modulation with or without carrier, 960.05 or 961.05 Mc constant-frequency CW, and radar on-off pulses at 961.05 Mc. The main output amplifier consists primarily of a four-stage, externally-tuned-cavity, water-cooled klystron, operating at a beam voltage of 16 to 18 kv. The transmitter has been operated during many Moonbounce, tropospheric scatter, and Echo I tests with very satisfactory results. This paper describes its use before March 1, 1961.

  17. Light Echo From Star V838 Monocerotis

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This series of photos, captured by the NASA Hubble Space Telescope's (HST) Advanced Camera for Surveys from May to December 2002, dramatically demonstrates the reverberation of light through space caused by an unusual stellar outburst in January 2002. A burst of light from the bizarre star is spreading into space and reflecting off of surrounding circumstellar dust. As different parts are sequentially illuminated, the appearance of the dust changes. This effect is referred to as a 'light echo'. The red star at the center of the eyeball like feature is the unusual erupting super giant called V838 Monocerotis, or V Mon, located about 20,000 light-years away in the winter constellation Monoceros (the Unicorn). During its outburst, the star brightened to more than 600,000 times our Sun's luminosity. The circular feature has now expanded to slightly larger than the angular size of Jupiter on the sky, and will continue to expand for several more years until the light from the back side of the nebula begins to arrive. The light echo will then give the illusion of contracting, until it finally disappears by the end of the decade.

  18. Light Echoes of Transients and Variables

    NASA Astrophysics Data System (ADS)

    Rest, Armin

    2012-04-01

    abstract-type="normal">SummaryTycho Brahe's observations of a supernova in 1572 challenged the contemporaneous European view of the cosmos that the celestial realm was unchanging. 439 years later we have once again seen the light that Tycho saw, as some of the light from the 1572 supernova is reflected off dust and is only now reaching Earth. These light echoes, as well as ones detected from other transients and variables, give us a very rare opportunity in astronomy: direct observation of the cause (the supernova explosion) and the effect (the supernova remnant) of the same astronomical event. Furthermore, in some cases we can compare light echoes at different angles around a supernova remnant, and thus investigate possible asymmetry in the supernova explosion. In addition, in cases where the scattering dust is favorably positioned, the geometric distance to the SN remnant can be determined using polarization measurements. These techniques have been successfully applied to various transients in the last decade, and the talk gave an overview of the scientific results and techniques, with a particular focus on the challenges we will face in the current and upcoming wide-field time-domain surveys.

  19. Space Shuttle ice nuclei

    NASA Technical Reports Server (NTRS)

    Turco, R. P.; Toon, O. B.; Whitten, R. C.; Cicerone, R. J.

    1982-01-01

    Estimates are made showing that, as a consequence of rocket activity in the earth's upper atmosphere in the Shuttle era, average ice nuclei concentrations in the upper atmosphere could increase by a factor of two, and that an aluminum dust layer weighing up to 1000 tons might eventually form in the lower atmosphere. The concentrations of Space Shuttle ice nuclei (SSIN) in the upper troposphere and lower stratosphere were estimated by taking into account the composition of the particles, the extent of surface poisoning, and the size of the particles. Calculated stratospheric size distributions at 20 km with Space Shuttle particulate injection, calculated SSIN concentrations at 10 and 20 km altitude corresponding to different water vapor/ice supersaturations, and predicted SSIN concentrations in the lower stratosphere and upper troposphere are shown.

  20. Nuclei in Astrophysics

    NASA Astrophysics Data System (ADS)

    Penionzhkevich, Yu. E.

    2016-06-01

    This work is an attempt to present some problems on the evolution of the Universe: the nucleosynthesis and cosmochronology from the standpoint of physics of particles and nuclei, in particular with the use of the latest results, obtained by means of radioactive nuclear beams. The comparison is made between the processes taking place in the Universe and the mechanisms of formation and decay of nuclei, as well as of their interaction at different energies. Examples are given to show the capabilities of nuclearphysics methods for studying cosmic objects and properties of the Universe. The results of investigations in nuclear reactions, induced by radioactive nuclear beams, make it possible to analyze the nucleosynthesis scenario in the region of light elements in a new manner.

  1. Exotic phenomena in nuclei

    NASA Astrophysics Data System (ADS)

    Neff, Thomas; Feldmeier, Hans; Roth, Robert

    2006-10-01

    In the Fermionic Molecular Dynamics (FMD) model the nuclear many-body system is described using Slater determinants with Gaussian wave-packets as single-particle states. The flexibility of the FMD wave functions allows for a consistent description of shell model like structures, deformed states, cluster structures as well as halos. An effective interaction derived from the realistic Argonne V18 interaction using the Unitary Correlation Operator Method is used for all nuclei. Results for nuclei in the p-shell will be presented. Halo features are present in the Helium isotopes, cluster structures are studied in Beryllium and Carbon isotopes. The interplay between shell structure and cluster structures in the ground and the Hoyle state in ^12C will be discussed.

  2. Rapid and accurate measurement of transverse relaxation times using a single shot multi-echo echo-planar imaging sequence.

    PubMed

    Tyler, Damian J; Moore, Rachel J; Marciani, Luca; Gowland, Penny A

    2004-09-01

    Methods for making rapid and accurate measurements and maps of the transverse relaxation time from a single free induction decay (FID) are proposed. The methods use a multi-echo sequence in combination with B1 insensitive (hyperbolic secant or BIREF2b) refocusing pulses and rapid echo-planar imaging techniques. The results were calibrated against a single spin echo echo-planar imaging sequence using a phantom containing a range of CuSO4 concentrations. The mean percentage absolute difference between the multi-echo and single-echo results was 3% for the multi-echo sequence using the hyperbolic secant refocusing pulse, and 7% for the multi-echo sequence using the BIREF2b refocusing pulse, compared to 13% for a multi-echo sequence using a nonselective sinc refocusing pulse. The use of the sequences in vivo has been demonstrated in studies of gastric function, i.e., the measurement of gastric dilution and monitoring of formation of a raft of alginate polysaccharide within the stomach. PMID:15288145

  3. The Future of ECHO: Evaluating Open Source Possibilities

    NASA Astrophysics Data System (ADS)

    Pilone, D.; Gilman, J.; Baynes, K.; Mitchell, A. E.

    2012-12-01

    NASA's Earth Observing System ClearingHOuse (ECHO) is a format agnostic metadata repository supporting over 3000 collections and 100M science granules. ECHO exposes FTP and RESTful Data Ingest APIs in addition to both SOAP and RESTful search and order capabilities. Built on top of ECHO is a human facing search and order web application named Reverb. ECHO processes hundreds of orders, tens of thousands of searches, and 1-2M ingest actions each week. As ECHO's holdings, metadata format support, and visibility have increased, the ECHO team has received requests by non-NASA entities for copies of ECHO that can be run locally against their data holdings. ESDIS and the ECHO Team have begun investigations into various deployment and Open Sourcing models that can balance the real constraints faced by the ECHO project with the benefits of providing ECHO capabilities to a broader set of users and providers. This talk will discuss several release and Open Source models being investigated by the ECHO team along with the impacts those models are expected to have on the project. We discuss: - Addressing complex deployment or setup issues for potential users - Models of vetting code contributions - Balancing external (public) user requests versus our primary partners - Preparing project code for public release, including navigating licensing issues related to leveraged libraries - Dealing with non-free project dependencies such as commercial databases - Dealing with sensitive aspects of project code such as database passwords, authentication approaches, security through obscurity, etc. - Ongoing support for the released code including increased testing demands, bug fixes, security fixes, and new features.

  4. Pairing forces in nuclei

    SciTech Connect

    Chasman, R.R.

    1996-12-31

    In this contribution, the author mentions some features of pairing forces that are unique to nuclei and cover some areas of major interest in nuclear structure research, that involve pairing. At the level of most nuclear structure studies, nuclei are treated as consisting of two kinds of fermions (protons and neutrons) in a valence space with rather few levels. These features give rise to unique aspects of pairing forces in nuclei: (1) n-p pairing in T = 0 as well as the usual T = 1 pairing that is characteristic of like fermions; (2) a need to correct pairing calculations for the (1/N) effects that can typically be neglected in superconducting solids. An issue of current concern is the nature of the pairing interaction: several recent studies suggest a need for a density dependent form of the pairing interaction. There is a good deal of feedback between the questions of accurate calculations of pairing interactions and the form and magnitude of the pairing interaction. Finally, the authors discuss some many-body wave functions that are a generalization of the BCS wave function form, and apply them to a calculation of energy level spacings in superdeformed rotational bands.

  5. Electron spin dephasing by hyperfine interaction with nuclei in quantum dots

    NASA Astrophysics Data System (ADS)

    Cywinski, Lukasz

    2010-03-01

    The problem of the dynamics of an electron spin coupled by hyperfine (hf) interaction to nuclear spins has been a focus of large theoretical attention, since the interaction with the nuclear bath is the most limiting decoherence mechanism in spin qubits based on quantum dots made of III-V materials. I will present a theory of pure dephasing decoherence which gives predictions for electron dynamics in narrowed state free induction decay, spin echo, and under higher order dynamical decoupling sequences [1,2]. In this theory we take advantage of the long-range character of hf-mediated interactions (which couple remote nuclei via virtual flip-flops with the electron spin), and we resum the leading terms in 1/N expansion of the decoherence time-evolution function (N being the large number of nuclei interacting appreciably with the electron spin). For the case of a thermal uncorrelated bath this approach is applicable as long as the electron Zeeman splitting is larger than the typical Overhauser shift of the electron energy (i.e. magnetic field must be larger than a few mT in a large GaAs dot). For the spin echo evolution we show that the dominant decoherence process at low fields is due to interactions between nuclei having different Zeeman energies (i.e. nuclei of As and two isotopes of Ga in GaAs). The robustness of this theory is verified by comparison with a numerical simulation of spin echo in a system with N = 20 nuclei. I will also discuss the application of our approach to singlet-triplet qubit in a double quantum dot. [4pt] [1] L. Cywinski, W.M. Witzel, and S. Das Sarma, Phys. Rev. Lett. 102, 057601 (2009). [0pt] [2] L. Cywinski, W.M. Witzel, and S. Das Sarma, Phys. Rev. B 79, 245314 (2009).

  6. Temporal characteristics of NMR signals from spin 3/2 nuclei of incompletely disordered systems.

    PubMed

    Woessner, D E; Bansal, N

    1998-07-01

    Anisotropic nuclear quadrupole interactions can produce residual quadrupole splitting in the NMR spectra of rapidly moving quadrupolar nuclei in incompletely disordered aqueous heterogeneous systems. Such systems may include hydrated sodium nuclei in biological tissue and biopolymer gels. To describe the NMR signals from such samples, we use a domain model in which each domain is characterized by a quadrupole frequency and a residence time of the nucleus. We show that the signals from each domain after one pulse, the quadrupole echo sequence, and the various multiple quantum filters (MQFs) can be expressed as a linear combination of five different phase coherences. To simulate the effect of various distributions (Pake powder pattern, Gaussian, etc.) of quadrupole frequencies for different domains on the NMR signal, we have written the computer program CORVUS. CORVUS also includes the effects of exchange between different domains using diffusion and random jump models. The results of computer simulations show that the Gaussian and Pake powder pattern quadrupole frequency distributions produce very different phase coherences and observable NMR signals when the exchange rate (1/taue) between different domains is slow. When 1/taue is similar to the root mean square quadrupole frequency (final sigma), the signals from the two distributions are similar. When 1/taue is an order of magnitude greater than final sigma, there is no apparent evidence of quadrupole splitting in the shape of the signal following one pulse, but the residual effects of the quadrupole splitting make a significant contribution to the fast transverse relaxation rate. Therefore, in this case, it is inappropriate to use the observed biexponential relaxation rates to obtain a single correlation time. The quadrupole echo and the various MQF signals contain an echo from the satellite transitions in the presence of quadrupole splitting. The peak of this echo is very sensitive to 1/taue. The time domain

  7. The EChO science case

    NASA Astrophysics Data System (ADS)

    Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul; Hartogh, Paul; Isaak, Kate; Linder, Martin; Lovis, Christophe; Micela, Giusi; Ollivier, Marc; Puig, Ludovic; Ribas, Ignasi; Snellen, Ignas; Swinyard, Bruce; Allard, France; Barstow, Joanna; Cho, James; Coustenis, Athena; Cockell, Charles; Correia, Alexandre; Decin, Leen; de Kok, Remco; Deroo, Pieter; Encrenaz, Therese; Forget, Francois; Glasse, Alistair; Griffith, Caitlin; Guillot, Tristan; Koskinen, Tommi; Lammer, Helmut; Leconte, Jeremy; Maxted, Pierre; Mueller-Wodarg, Ingo; Nelson, Richard; North, Chris; Pallé, Enric; Pagano, Isabella; Piccioni, Guseppe; Pinfield, David; Selsis, Franck; Sozzetti, Alessandro; Stixrude, Lars; Tennyson, Jonathan; Turrini, Diego; Zapatero-Osorio, Mariarosa; Beaulieu, Jean-Philippe; Grodent, Denis; Guedel, Manuel; Luz, David; Nørgaard-Nielsen, Hans Ulrik; Ray, Tom; Rickman, Hans; Selig, Avri; Swain, Mark; Banaszkiewicz, Marek; Barlow, Mike; Bowles, Neil; Branduardi-Raymont, Graziella; du Foresto, Vincent Coudé; Gerard, Jean-Claude; Gizon, Laurent; Hornstrup, Allan; Jarchow, Christopher; Kerschbaum, Franz; Kovacs, Géza; Lagage, Pierre-Olivier; Lim, Tanya; Lopez-Morales, Mercedes; Malaguti, Giuseppe; Pace, Emanuele; Pascale, Enzo; Vandenbussche, Bart; Wright, Gillian; Ramos Zapata, Gonzalo; Adriani, Alberto; Azzollini, Ruymán; Balado, Ana; Bryson, Ian; Burston, Raymond; Colomé, Josep; Crook, Martin; Di Giorgio, Anna; Griffin, Matt; Hoogeveen, Ruud; Ottensamer, Roland; Irshad, Ranah; Middleton, Kevin; Morgante, Gianluca; Pinsard, Frederic; Rataj, Mirek; Reess, Jean-Michel; Savini, Giorgio; Schrader, Jan-Rutger; Stamper, Richard; Winter, Berend; Abe, L.; Abreu, M.; Achilleos, N.; Ade, P.; Adybekian, V.; Affer, L.; Agnor, C.; Agundez, M.; Alard, C.; Alcala, J.; Allende Prieto, C.; Alonso Floriano, F. J.; Altieri, F.; Alvarez Iglesias, C. A.; Amado, P.; Andersen, A.; Aylward, A.; Baffa, C.; Bakos, G.; Ballerini, P.; Banaszkiewicz, M.; Barber, R. J.; Barrado, D.; Barton, E. J.; Batista, V.; Bellucci, G.; Belmonte Avilés, J. A.; Berry, D.; Bézard, B.; Biondi, D.; Błęcka, M.; Boisse, I.; Bonfond, B.; Bordé, P.; Börner, P.; Bouy, H.; Brown, L.; Buchhave, L.; Budaj, J.; Bulgarelli, A.; Burleigh, M.; Cabral, A.; Capria, M. T.; Cassan, A.; Cavarroc, C.; Cecchi-Pestellini, C.; Cerulli, R.; Chadney, J.; Chamberlain, S.; Charnoz, S.; Christian Jessen, N.; Ciaravella, A.; Claret, A.; Claudi, R.; Coates, A.; Cole, R.; Collura, A.; Cordier, D.; Covino, E.; Danielski, C.; Damasso, M.; Deeg, H. J.; Delgado-Mena, E.; Del Vecchio, C.; Demangeon, O.; De Sio, A.; De Wit, J.; Dobrijévic, M.; Doel, P.; Dominic, C.; Dorfi, E.; Eales, S.; Eiroa, C.; Espinoza Contreras, M.; Esposito, M.; Eymet, V.; Fabrizio, N.; Fernández, M.; Femenía Castella, B.; Figueira, P.; Filacchione, G.; Fletcher, L.; Focardi, M.; Fossey, S.; Fouqué, P.; Frith, J.; Galand, M.; Gambicorti, L.; Gaulme, P.; García López, R. J.; Garcia-Piquer, A.; Gear, W.; Gerard, J.-C.; Gesa, L.; Giani, E.; Gianotti, F.; Gillon, M.; Giro, E.; Giuranna, M.; Gomez, H.; Gomez-Leal, I.; Gonzalez Hernandez, J.; González Merino, B.; Graczyk, R.; Grassi, D.; Guardia, J.; Guio, P.; Gustin, J.; Hargrave, P.; Haigh, J.; Hébrard, E.; Heiter, U.; Heredero, R. L.; Herrero, E.; Hersant, F.; Heyrovsky, D.; Hollis, M.; Hubert, B.; Hueso, R.; Israelian, G.; Iro, N.; Irwin, P.; Jacquemoud, S.; Jones, G.; Jones, H.; Justtanont, K.; Kehoe, T.; Kerschbaum, F.; Kerins, E.; Kervella, P.; Kipping, D.; Koskinen, T.; Krupp, N.; Lahav, O.; Laken, B.; Lanza, N.; Lellouch, E.; Leto, G.; Licandro Goldaracena, J.; Lithgow-Bertelloni, C.; Liu, S. J.; Lo Cicero, U.; Lodieu, N.; Lognonné, P.; Lopez-Puertas, M.; Lopez-Valverde, M. A.; Lundgaard Rasmussen, I.; Luntzer, A.; Machado, P.; MacTavish, C.; Maggio, A.; Maillard, J.-P.; Magnes, W.; Maldonado, J.; Mall, U.; Marquette, J.-B.; Mauskopf, P.; Massi, F.; Maurin, A.-S.; Medvedev, A.; Michaut, C.; Miles-Paez, P.; Montalto, M.; Montañés Rodríguez, P.; Monteiro, M.; Montes, D.; Morais, H.; Morales, J. C.; Morales-Calderón, M.; Morello, G.; Moro Martín, A.; Moses, J.; Moya Bedon, A.; Murgas Alcaino, F.; Oliva, E.; Orton, G.; Palla, F.; Pancrazzi, M.; Pantin, E.; Parmentier, V.; Parviainen, H.; Peña Ramírez, K. Y.; Peralta, J.; Perez-Hoyos, S.; Petrov, R.; Pezzuto, S.; Pietrzak, R.; Pilat-Lohinger, E.; Piskunov, N.; Prinja, R.; Prisinzano, L.; Polichtchouk, I.; Poretti, E.; Radioti, A.; Ramos, A. A.; Rank-Lüftinger, T.; Read, P.; Readorn, K.; Rebolo López, R.; Rebordão, J.; Rengel, M.; Rezac, L.; Rocchetto, M.; Rodler, F.; Sánchez Béjar, V. J.; Sanchez Lavega, A.; Sanromá, E.; Santos, N.; Sanz Forcada, J.; Scandariato, G.; Schmider, F.-X.; Scholz, A.; Scuderi, S.

    2015-12-01

    The discovery of almost two thousand exoplanets has revealed an unexpectedly diverse planet population. We see gas giants in few-day orbits, whole multi-planet systems within the orbit of Mercury, and new populations of planets with masses between that of the Earth and Neptune—all unknown in the Solar System. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? How do planetary systems work and what causes the exceptional diversity observed as compared to the Solar System? The EChO (Exoplanet Characterisation Observatory) space mission was conceived to take up the challenge to explain this diversity in terms of formation, evolution, internal structure and planet and atmospheric composition. This requires in-depth spectroscopic knowledge of the atmospheres of a large and well-defined planet sample for which precise physical, chemical and dynamical information can be obtained. In order to fulfil this ambitious scientific program, EChO was designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large, diverse and well-defined planet sample within its 4-year mission lifetime. The transit and eclipse spectroscopy method, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allows us to measure atmospheric signals from the planet at levels of at least 10-4 relative to the star. This can only be achieved in conjunction with a carefully designed stable payload and satellite platform. It is also necessary to provide broad instantaneous wavelength coverage to detect as many molecular species as possible, to probe the thermal structure of the planetary atmospheres and to correct for the contaminating effects of the stellar photosphere. This requires wavelength

  8. Coherent Optical Information Processing Using a Stimulated Echo Hologram

    NASA Astrophysics Data System (ADS)

    Garnaeva, G. I.; Nefediev, L. A.; Sahbieva, A. R.

    2016-01-01

    We consider information recording and reconstruction using a reversed stimulated echo hologram, when the recording medium is exposed to pulses of nonresonant electromagnetic standing waves. We show that the spatial intensity distribution in the stimulated echo hologram response depends on the strength of the electric fields in the nonresonant standing waves, which makes it possible to control the reconstructed image.

  9. ECHOS: Early Childhood Hands-On Science Efficacy Study

    ERIC Educational Resources Information Center

    Brown, Judy A.; Greenfield, Daryl B.; Bell, Elizabeth; Juárez, Cheryl Lani; Myers, Ted; Nayfeld, Irena

    2013-01-01

    "ECHOS: Early Childhood Hands-On Science" was developed at the Miami Science Museum as a comprehensive set of science lessons sequenced to lead children toward a deeper understanding of science content and the use of science process skills. The purpose of the research is to determine whether use of the "ECHOS" model will…

  10. 21 CFR 892.1560 - Ultrasonic pulsed echo imaging system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ultrasonic pulsed echo imaging system. 892.1560 Section 892.1560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1560 Ultrasonic pulsed echo...

  11. In vivo thermal ablation monitoring using ultrasound echo decorrelation imaging.

    PubMed

    Subramanian, Swetha; Rudich, Steven M; Alqadah, Amel; Karunakaran, Chandra Priya; Rao, Marepalli B; Mast, T Douglas

    2014-01-01

    Previous work indicated that ultrasound echo decorrelation imaging can track and quantify changes in echo signals to predict thermal damage during in vitro radiofrequency ablation (RFA). In the in vivo studies reported here, the feasibility of using echo decorrelation imaging as a treatment monitoring tool was assessed. RFA was performed on normal swine liver (N = 5), and ultrasound ablation using image-ablate arrays was performed on rabbit liver implanted with VX2 tumors (N = 2). Echo decorrelation and integrated backscatter were computed from Hilbert transformed pulse-echo data acquired during RFA and ultrasound ablation treatments. Receiver operating characteristic (ROC) curves were employed to assess the ability of echo decorrelation imaging and integrated backscatter to predict ablation. Area under the ROC curves (AUROC) was determined for RFA and ultrasound ablation using echo decorrelation imaging. Ablation was predicted more accurately using echo decorrelation imaging (AUROC = 0.832 and 0.776 for RFA and ultrasound ablation, respectively) than using integrated backscatter (AUROC = 0.734 and 0.494). PMID:24239361

  12. Psychoacoustic influences of the echoing environments of prehistoric art

    NASA Astrophysics Data System (ADS)

    Waller, Steven J.

    2002-11-01

    Cave paintings and ancient petroglyphs around the world are typically found in echo rich locations such as caves, canyons, and rocky cliff faces. Analysis of field data shows that echo decibel levels at a large number of prehistoric art sites are higher than those at nondecorated locations. The selection of these echoing environments by the artists appears not to be a mere coincidence. This paper considers the perception of an echoed sound as a psychoacoustic event that would have been inexplicable to ancient humans. A variety of ancient legends from cultures on several continents attribute the phenomenon of echoes to supernatural beings. These legends, together with the quantitative data, strongly implicate echoing as relevant to the artists of the past. The notion that the echoes were caused by spirits within the rock would explain not only the unusual locations of prehistoric art, but also the perplexing subject matter. For example, the common theme of hoofed animal imagery could have been inspired by echoes of percussion noises perceived as hoof beats. Further systematic acoustical studies of prehistoric art sites is warranted. Conservation of the natural acoustic properties of rock art environments--a previously unrecognized need--is urged.

  13. Measurement of Heteronuclear Dipolar Coupling by Transferred-Echo Double-Resonance NMR

    NASA Astrophysics Data System (ADS)

    Hing, A. W.; Vega, S.; Schaefer, J.

    A magic-angle spinning experiment called transferred-echo double resonance (TEDOR) has been introduced recently to measure the I-S dipolar coupling of heteronuclear I-S pairs of spin- {1}/{2} nuclei while eliminating unwanted background signals from uncoupled I and S spins via a coherence-transfer process. In this paper, a quantitative description of the TEDOR experiment is given in terms of the evolution of the density matrix for a pair of heteronuclear spins. The resulting equations provide a theoretical basis for evaluating the selectivity and sensitivity of TEDOR and suggest strategies for determining dipolar coupling constants directly from TEDOR data. Experimental examples illustrating these aspects of TEDOR are provided by studies performed on a range of 13C- 15N dipolar couplings found in double-labeled asparagine, alanine, glycine, and the linear peptide antibiotic, gramicidin.

  14. Diurnal variation of overdense meteor echo duration and ozone

    NASA Technical Reports Server (NTRS)

    Simek, Milos

    1992-01-01

    The diurnal variation of the median duration of overdense sporadic radar meteor echoes is examined. The meteors recorded in August, December, and January by the Ondrejov meteor radar during the period 1958-1990 were used for the analysis. A maximum median echo duration 1-3 hours after the time of local sunrise in the meteor region confirms the already known sunrise effect. Minimum echo duration occurring at the time of sunset seems to be the most important point of diurnal variation of the echo duration, when ozone is no longer dissociated by solar UV radiation. The effect of diurnal changes of the echo duration should be considered when the mass distribution of meteor showers is analyzed.

  15. Echoes from Ancient supernovae in the Large Magellanic Cloud

    SciTech Connect

    Rest, A; Suntzeff, N B; Olsen, K; Prieto, J L; Smith, R C; Welch, D L; Becker, A; Bergmann, M; Clocchiatti, A; Cook, K; Garg, A; Huber, M; Miknaitis, G; Minniti, D; Nikolaev, S; Stubbs, C

    2005-06-15

    In principle, historical supernovae could still be visible as scattered-light echoes even centuries later [1, 2]. Searches for surface brightness variations using photographic plates have not recovered any echoes in the regions of historical Galactic supernovae [3]. Using differenced images, our SuperMACHO collaboration has discovered three faint new variable surface brightness complexes with high apparent proper motion pointing back to well-defined positions in the Large Magellanic Cloud (LMC). These correspond to three of the six smallest (and likely youngest) supernova remnants believed to be due to thermonuclear (Type Ia) supernovae [4]. A lower limit to the age of these remnants and echoes is 200 years given the lack of any reported LMC supernovae until 1987. The discovery of historical supernova echoes in the LMC suggests that similar echoes for Galactic supernovae such as Tycho, Kepler, Cas A, or SN1006 could be visible using standard image differencing techniques.

  16. Echoes from anharmonic normal modes in model glasses.

    PubMed

    Burton, Justin C; Nagel, Sidney R

    2016-03-01

    Glasses display a wide array of nonlinear acoustic phenomena at temperatures T ≲ 1 K. This behavior has traditionally been explained by an ensemble of weakly coupled, two-level tunneling states, a theory that is also used to describe the thermodynamic properties of glasses at low temperatures. One of the most striking acoustic signatures in this regime is the existence of phonon echoes, a feature that has been associated with two-level systems with the same formalism as spin echoes in NMR. Here we report the existence of a distinctly different type of acoustic echo in classical models of glassy materials. Our simulations consist of finite-ranged, repulsive spheres and also particles with attractive forces using Lennard-Jones interactions. We show that these echoes are due to anharmonic, weakly coupled vibrational modes and perhaps provide an alternative explanation for the phonon echoes observed in glasses at low temperatures. PMID:27078434

  17. Echo power analysis and simulation of low altitude radio fuze

    NASA Astrophysics Data System (ADS)

    Chen, Xiaolu; Chen, Biao; Xu, Tao; Xu, Suqin

    2013-01-01

    The echo power from the earth gound which was received by fuze plays an important role in aerial defense missile, especially when the fuze is working in the look down mode. It is necessary to analyze and even simulate the echo power signals to enhance the missile's anti-jamming ability. In this paper, the quantity of echo power from the earth ground of low altitude radio fuze was analyzed in detail. Three boundary equations of area irradiated by electromagnetic beams were presented, which include two equidistant curve equations and one equal-Doppler curve equation. The relationship between the working mode and the critical height was analyzed. The calculating formula of echo power waveform was derived. And based on the derived formula, the correlation between the maximal echo power and the incident height was given and simulated, which would be helpful for the further researches of low altitude radio fuze.

  18. Light echoes from ancient supernovae in the Large Magellanic Cloud.

    PubMed

    Rest, Armin; Suntzeff, Nicholas B; Olsen, Knut; Prieto, Jose Luis; Smith, R Chris; Welch, Douglas L; Becker, Andrew; Bergmann, Marcel; Clocchiatti, Alejandro; Cook, Kem; Garg, Arti; Huber, Mark; Miknaitis, Gajus; Minniti, Dante; Nikolaev, Sergei; Stubbs, Christopher

    2005-12-22

    The light from historical supernovae could in principle still be visible as scattered-light echoes centuries after the explosion. The detection of light echoes could allow us to pinpoint the supernova event both in position and age and, most importantly, permit the acquisition of spectra to determine the 'type' of the supernova centuries after the direct light from the explosion first reached Earth. Although echoes have been discovered around some nearby extragalactic supernovae, targeted searches have not found any echoes in the regions of historical Galactic supernovae. Here we report three faint variable-surface-brightness complexes with high apparent proper motions pointing back to three of the six smallest (and probably youngest) previously catalogued supernova remnants in the Large Magellanic Cloud, which are believed to have been thermonuclear (type Ia) supernovae. Using the distance and apparent proper motions of these echo arcs, we estimate ages of 610 and 410 years for two of them. PMID:16372003

  19. Dual-rail optical gradient echo memory

    NASA Astrophysics Data System (ADS)

    Higginbottom, D. B.; Geng, J.; Campbell, G. T.; Hosseini, M.; Cao, M. T.; Sparkes, B. M.; Bernu, J.; Robins, N. P.; Lam, P. K.; Buchler, B. C.

    2015-09-01

    We introduce a scheme for the parallel storage of frequency separated signals in an optical memory and demonstrate that this dual-rail storage is a suitable memory for high fidelity frequency qubits. The two signals are stored simultaneously in the Zeeman-split Raman absorption lines of a cold atom ensemble using gradient echo memory techniques. Analysis of the split-Zeeman storage shows that the memory can be configured to preserve the relative amplitude and phase of the frequency separated signals. In an experimental demonstration dual-frequency pulses are recalled with 35% efficiency, 82% interference fringe visibility, and 6 degrees phase stability. The fidelity of the frequency-qubit memory is limited by frequency-dependent polarisation rotation and ambient magnetic field fluctuations, our analysis describes how these can be addressed in an alternative configuration.

  20. Dual-rail optical gradient echo memory.

    PubMed

    Higginbottom, D B; Geng, J; Campbell, G T; Hosseini, M; Cao, M T; Sparkes, B M; Bernu, J; Robins, N P; Lam, P K; Buchler, B C

    2015-09-21

    We introduce a scheme for the parallel storage of frequency separated signals in an optical memory and demonstrate that this dual-rail storage is a suitable memory for high fidelity frequency qubits. The two signals are stored simultaneously in the Zeeman-split Raman absorption lines of a cold atom ensemble using gradient echo memory techniques. Analysis of the split-Zeeman storage shows that the memory can be configured to preserve the relative amplitude and phase of the frequency separated signals. In an experimental demonstration dual-frequency pulses are recalled with 35% efficiency, 82% interference fringe visibility, and 6° phase stability. The fidelity of the frequency-qubit memory is limited by frequency-dependent polarisation rotation and ambient magnetic field fluctuations, our analysis describes how these can be addressed in an alternative configuration. PMID:26406693

  1. Sea echo in tropospheric ducting environments

    NASA Astrophysics Data System (ADS)

    Pappert, R. A.; Paulus, R. A.; Tappert, F. D.

    1992-04-01

    Path loss formulas for sea surface backscatter are developed for horizontally stratified tropospheric ducting environments. First-order Bragg backscatter results coupled with ray and waveguide formalism serve as the basis for the development. Two features of composite model formalism, namely shadowing and tilting of the surface normal in the plane of incidence, are included in the development. Though developed for hh polarization, conventional composite model modifications for vertical polarization and depolarization can be incorporated into the echo models. Comparisons are made with previously generated parabolic equation results and with empirical model results generated by Engineers Refractive Effects Prediction System. These comparisons are for a frequency of 9.6 GHz for the standard atmosphere and for 14- and 28-m evaporation ducts. Results apply to wind speeds of 10, 20, 30, and 40 knots (about 5, 10, 15, and 20 m/s).

  2. Gene transfection by echo contrast agent microbubbles

    NASA Astrophysics Data System (ADS)

    Tachibana, Katsuro

    2002-11-01

    In vitro and in vivo experiments have demonstrated that various echo contrast agent microbubbles can be intentionally ruptured by diagnostic and therapeutic ultrasound. Violent microstreaming are produced during microbubble collapse. Researchers have hypothesized that these microjets or microstreaming could be applied to promote diffusion of drugs into various tissues and lesions. The most exciting application of this method is probably delivery of genes into cells. As various genes are currently under investigation for the purpose of treating diseases, ultrasound and microbubbles may be used as a modality to promote better outcome for gene therapy. Recent studies have shown that different gases contained within the bubbles greatly influence the degree of gene transfection. Also, the outer layer of the microbubbles can be custom-made for binding to target tissue. Recent advance on this topic will be discussed.

  3. Acoustooptic pulse-echo transducer system

    NASA Technical Reports Server (NTRS)

    Claus, R. O.; Wade, J. C.

    1983-01-01

    A pulse-echo transducer system which uses an ultrasonic generating element and an optical detection technique is described. The transmitting transducer consists of a concentric ring electrode pattern deposited on a circular, X-cut quartz substrate with a circular hole in the center. The rings are independently pulsed with a sequence high voltage signals phased in such a way that the ultrasonic waves generated by the separate rings superimpose to produce a composite field which is focused at a controllable distance below the surface of the specimen. The amplitude of the field reflected from this focus position is determined by the local reflection coefficient of the medium at the effective focal point. By processing the signals received for a range of ultrasonic transducer array focal lengths, the system can be used to locate and size anomalies within solids and liquids. Applications in both nondestructive evaluation and biomedical scanning are suggested.

  4. Spin Echo and Interference in Synchrotrons

    SciTech Connect

    Chao, Alex; /SLAC

    2006-11-30

    Spin dynamics in crossing a single depolarization resonance is a well-studied subject. One well-known example is that of Froissart and Stora in 1960. More is needed to complete the understanding, particularly of the transient effects, when crossing a single resonance, but question arises what happens if we cross two resonances or cross a single resonance twice. When a resonance is crossed twice, the particle's spin dynamics encounters two additional phenomena. First, the two crossings will interfere with each other, leading to an interference effect. Second, there will be a spin echo effect. We discuss these two effects in this report. Two proposals to test these effects experimentally are made at the end.

  5. Parallel electric fields detected via conjugate electron echoes during the Echo 7 sounding rocket flight

    NASA Technical Reports Server (NTRS)

    Nemzek, R. J.; Winckler, J. R.

    1991-01-01

    Electron detectors on the Echo 7 active sounding rocket experiment measured 'conjugate echoes' resulting from artificial electron beam injections. Analysis of the drift motion of the electrons after a complete bounce leads to measurements of the magnetospheric convection electric field mapped to ionospheric altitudes. The magnetospheric field was highly variable, changing by tens of mV/m on time scales of as little as hundreds of millisec. While the smallest-scale magnetospheric field irregularities were mapped out by ionospheric conductivity, larger-scale features were enhanced by up to 50 mV/m in the ionosphere. The mismatch between magnetospheric and ionspheric convection fields indicates a violation of the equipotential field line condition. The parallel fields occurred in regions roughly 10 km across and probably supported a total potential drop of 10-100 V.

  6. Recent Results for the ECHo Experiment

    NASA Astrophysics Data System (ADS)

    Hassel, C.; Blaum, K.; Goodacre, T. Day; Dorrer, H.; Düllmann, Ch. E.; Eberhardt, K.; Eliseev, S.; Enss, C.; Filianin, P.; Fäßler, A.; Fleischmann, A.; Gastaldo, L.; Goncharov, M.; Hengstler, D.; Jochum, J.; Johnston, K.; Keller, M.; Kempf, S.; Kieck, T.; Köster, U.; Krantz, M.; Marsh, B.; Mokry, C.; Novikov, Yu. N.; Ranitzsch, P. C. O.; Rothe, S.; Rischka, A.; Runke, J.; Saenz, A.; Schneider, F.; Scholl, S.; Schüssler, R. X.; Simkovic, F.; Stora, T.; Thörle-Pospiech, P.; Türler, A.; Veinhard, M.; Wegner, M.; Wendt, K.; Zuber, K.

    2016-02-01

    The Electron Capture in ^{163} Ho experiment, ECHo, is designed to investigate the electron neutrino mass in the sub-eV range by means of the analysis of the calorimetrically measured spectrum following the electron capture (EC) in ^{163} Ho. Arrays of low-temperature metallic magnetic calorimeters (MMCs), read-out by microwave SQUID multiplexing, will be used in this experiment. With a first MMC prototype having the ^{163} Ho source ion-implanted into the absorber, we performed the first high energy resolution measurement of the EC spectrum, which demonstrated the feasibility of such an experiment. In addition to the technological challenges for the development of MMC arrays, which preserve the single pixel performance in terms of energy resolution and bandwidth, the success of the experiment relies on the availability of large ultra-pure ^{163} Ho samples, on the precise description of the expected spectrum, and on the identification and reduction of background. We present preliminary results obtained with standard MMCs developed for soft X-ray spectroscopy, maXs-20, where the ^{163} Ho ion-implantation was performed using a high-purity ^{163} Ho source produced by advanced chemical and mass separation. With these measurements, we aim at determining an upper limit for the background level due to source contamination and provide a refined description of the calorimetrically measured spectrum. We discuss the plan for a medium scale experiment, ECHo-1k, in which about 1000 Bq of high-purity ^{163} Ho will be ion-implanted into detector arrays. With one year of measuring time, we will be able to achieve a sensitivity on the electron neutrino mass below 20 eV/c^2 (90 % C.L.), improving the present limit by more than one order of magnitude. This experiment will guide the necessary developments to reach the sub-eV sensitivity.

  7. Recent Results for the ECHo Experiment

    NASA Astrophysics Data System (ADS)

    Hassel, C.; Blaum, K.; Goodacre, T. Day; Dorrer, H.; Düllmann, Ch. E.; Eberhardt, K.; Eliseev, S.; Enss, C.; Filianin, P.; Fäßler, A.; Fleischmann, A.; Gastaldo, L.; Goncharov, M.; Hengstler, D.; Jochum, J.; Johnston, K.; Keller, M.; Kempf, S.; Kieck, T.; Köster, U.; Krantz, M.; Marsh, B.; Mokry, C.; Novikov, Yu. N.; Ranitzsch, P. C. O.; Rothe, S.; Rischka, A.; Runke, J.; Saenz, A.; Schneider, F.; Scholl, S.; Schüssler, R. X.; Simkovic, F.; Stora, T.; Thörle-Pospiech, P.; Türler, A.; Veinhard, M.; Wegner, M.; Wendt, K.; Zuber, K.

    2016-08-01

    The Electron Capture in ^{163}Ho experiment, ECHo, is designed to investigate the electron neutrino mass in the sub-eV range by means of the analysis of the calorimetrically measured spectrum following the electron capture (EC) in ^{163}Ho. Arrays of low-temperature metallic magnetic calorimeters (MMCs), read-out by microwave SQUID multiplexing, will be used in this experiment. With a first MMC prototype having the ^{163}Ho source ion-implanted into the absorber, we performed the first high energy resolution measurement of the EC spectrum, which demonstrated the feasibility of such an experiment. In addition to the technological challenges for the development of MMC arrays, which preserve the single pixel performance in terms of energy resolution and bandwidth, the success of the experiment relies on the availability of large ultra-pure ^{163}Ho samples, on the precise description of the expected spectrum, and on the identification and reduction of background. We present preliminary results obtained with standard MMCs developed for soft X-ray spectroscopy, maXs-20, where the ^{163}Ho ion-implantation was performed using a high-purity ^{163}Ho source produced by advanced chemical and mass separation. With these measurements, we aim at determining an upper limit for the background level due to source contamination and provide a refined description of the calorimetrically measured spectrum. We discuss the plan for a medium scale experiment, ECHo-1k, in which about 1000 mathrm {Bq} of high-purity ^{163}Ho will be ion-implanted into detector arrays. With one year of measuring time, we will be able to achieve a sensitivity on the electron neutrino mass below 20 eV/c^2 (90 % C.L.), improving the present limit by more than one order of magnitude. This experiment will guide the necessary developments to reach the sub-eV sensitivity.

  8. Properties of Cometary Nuclei

    NASA Technical Reports Server (NTRS)

    Rahe, J.; Vanysek, V.; Weissman, P. R.

    1994-01-01

    Active long- and short-period comets contribute about 20 to 30 % of the major impactors on the Earth. Cometary nuclei are irregular bodies, typically a few to ten kilometers in diameter, with masses in the range 10(sup 15) to 10(sup 18) g. The nuclei are composed of an intimate mixture of volatile ices, mostly water ice and hydrocarbon and silicate grains. The composition is the closest to solar composition of any known bodies in the solar system. The nuclei appear to be weakly bonded agglomerations of smaller icy planetesimals, and material strengths estimated from observed tidal disruption events are fairly low, typically 10(sup 2) to 10(sup 4) N m(sup -2). Density estimates range between 0.2 and 1.2 g cm(sup -3) but are very poorly determined, if at all. As comets age they develop nonvolitile crusts on their surfaces which eventually render them inactive, similar in appearance to carbonaceous asteroids. However, dormant comets may continue to show sporadic activity and outbursts for some time before they become truly extinct. The source of the long-period comets is the Oort cloud, a vast spherical cloud of perhaps 10(sup 12) to 10(sup 13) comets surrounding the solar system and extending to interstellar distances. The likely source for short-period comets is the Kuiper belt. a ring of perhaps 10(sup 8) to 10(sup 10) remnant icy planetesimals beyond the orbit of Neptune, though some short-period comets may also be long-period comets from the Oort cloud which have been perturbed into short-period orbits.

  9. Resting state BOLD functional connectivity at 3T: spin echo versus gradient echo EPI.

    PubMed

    Chiacchiaretta, Piero; Ferretti, Antonio

    2015-01-01

    Previous evidence showed that, due to refocusing of static dephasing effects around large vessels, spin-echo (SE) BOLD signals offer an increased linearity and promptness with respect to gradient-echo (GE) acquisition, even at low field. These characteristics suggest that, despite the reduced sensitivity, SE fMRI might also provide a potential benefit when investigating spontaneous fluctuations of brain activity. However, there are no reports on the application of spin-echo fMRI for connectivity studies at low field. In this study we compared resting state functional connectivity as measured with GE and SE EPI sequences at 3T. Main results showed that, within subject, the GE sensitivity is overall larger with respect to that of SE, but to a less extent than previously reported for activation studies. Noteworthy, the reduced sensitivity of SE was counterbalanced by a reduced inter-subject variability, resulting in comparable group statistical connectivity maps for the two sequences. Furthermore, the SE method performed better in the ventral portion of the default mode network, a region affected by signal dropout in standard GE acquisition. Future studies should clarify if these features of the SE BOLD signal can be beneficial to distinguish subtle variations of functional connectivity across different populations and/or treatments when vascular confounds or regions affected by signal dropout can be a critical issue. PMID:25749359

  10. Fast T(2) relaxometry with an accelerated multi-echo spin-echo sequence.

    PubMed

    Sénégas, Julien; Liu, Wei; Dahnke, Hannes; Song, Hotaek; Jordan, E Kay; Frank, Joseph A

    2010-10-01

    A new method has been developed to reduce the number of phase-encoding steps in a multi-echo spin-echo imaging sequence allowing fast T(2) mapping without loss of spatial resolution. In the proposed approach, the k-space data at each echo time were undersampled and a reconstruction algorithm that exploited the temporal correlation of the MR signal in k-space was used to reconstruct alias-free images. A specific application of this algorithm with multiple-receiver acquisition, offering an alternative to existing parallel imaging methods, has also been introduced. The fast T(2) mapping method has been validated in human brain T(2) measurements in a group of nine volunteers with acceleration factors up to 3.4. The results demonstrated that the proposed method exhibited excellent linear correlation with the regular T(2) mapping with full sampling and achieved better image reconstruction and T(2) mapping with respect to SNR and reconstruction artifacts than the selected reference acceleration techniques. The new method has also been applied for quantitative tracking of injected magnetically labeled breast cancer cells in the rat brain with acceleration factors of 1.8 and 3.0. The proposed technique can provide an effective approach for accelerated T(2) quantification, especially for experiments with single-channel coil when parallel imaging is not applicable. PMID:20878973

  11. Electroproduction of Strange Nuclei

    SciTech Connect

    E.V. Hungerford

    2002-06-01

    The advent of high-energy, CW-beams of electrons now allows electro-production and precision studies of nuclei containing hyperons. Previously, the injection of strangeness into a nucleus was accomplished using secondary beams of mesons, where beam quality and target thickness limited the missing mass resolution. We review here the theoretical description of the (e, e'K+) reaction mechanism, and discuss the first experiment demonstrating that this reaction can be used to precisely study the spectra of light hypernuclei. Future experiments based on similar techniques, are expected to attain even better resolutions and rates.

  12. Total photoabsorption in nuclei

    SciTech Connect

    Bianchi, N.

    1992-06-01

    The Frascati-Genova collaboration proposes to measure the total photonuclear cross section on a wide range of nuclei between 500 MeV and 2 GeV, to obtain informations on the interaction of baryon resonances with nucleons and on the onset of the shadowing effect. The experiment could be performed in the Hall B as soon as the tagging facility will be ready and before the end of the installation of the CLAS spectrometer. The requirements for the photon beam, like maximum energy, intensity and beam definition, are not so strong so that the experiment would also be a good first test of the tagged photon facility.

  13. Quark distributions in nuclei

    SciTech Connect

    Catara, F.; Sambataro, M. Italy Dipartimento di Fisica dell'Universita, 95129 Catania )

    1992-08-01

    By making use of a mapping procedure recently proposed, we construct the nucleon image of the one-body quark density operator in the framework of the nonrelativistic quark model of the nucleons. We evaluate the expectation value of this operator in the ground state of the doubly magic nuclei {sup 4}He, {sup 16}O, and {sup 40}Ca described within the nuclear shell model. We analyze the role of quark exchanges between nucleons. We also investigate the effect on the quark density of short-range correlations in the nuclear wave functions as well as of variations in the nucleon size.

  14. View angle tilting echo planar imaging for distortion correction.

    PubMed

    Ahn, Sinyeob; Hu, Xiaoping P

    2012-10-01

    Geometric distortion caused by field inhomogeneity along the phase-encode direction is one of the most prominent artifacts due to a relatively low effective bandwidth along that direction in magnetic resonance echo planar imaging. This work describes a method for correcting in-plane image distortion along the phase-encode direction using a view angle tilting imaging technique in spin-echo echo planar imaging. Spin-echo echo planar imaging with view angle tilting uses the addition of gradient blips along the slice-select direction, concurrently applied with the phase-encode gradient blips, producing an additional phase. This phase effectively offsets an unwanted phase accumulation caused by field inhomogeneity, resulting in the removal of image distortion along the phase-encode direction. The proposed method is simple and straightforward both in implementation and application with no scan time penalty. Therefore, it is readily applicable on commercial scanners without having any customized postprocessing. The efficacy of the spin-echo echo planar imaging with view angle tilting technique in the correction of image distortion is demonstrated in phantom and in vivo brain imaging. PMID:22213567

  15. Kinematics of illumination patterns and light echoes from flashes.

    PubMed

    Zhong, Qi

    2016-09-01

    Flash-induced light echoes-the observation of light reflected from a burst-have been observed in astronomical settings for more than a century and have been observed in the laboratory recently. Because of the flight time of light, perceived light echoes are different from real light illumination patterns on a scattering plane, neglecting interreflections and non-opaque scattering effects. The shape and motion of real illumination patterns are studied from a spherical flash. Then, ellipsoids of constant time delay for a specifically chosen coordinate system are applied. Generally, perceived light echoes are elliptical annular rings and the center of a light echo will not start at the flash, which leads to light echoes moving angularly toward the flash instead of away from it, a phenomenon actually recorded by other groups. The brightness of perceived light echoes was studied, and maximum brightness occurred close to the flash's projective point on the scattering plane. Two specific examples are given and a magnification effect between perceived echoes and real illumination patterns is proposed. PMID:27607505

  16. No Counterpart of Visual Perceptual Echoes in the Auditory System

    PubMed Central

    İlhan, Barkın; VanRullen, Rufin

    2012-01-01

    It has been previously demonstrated by our group that a visual stimulus made of dynamically changing luminance evokes an echo or reverberation at ∼10 Hz, lasting up to a second. In this study we aimed to reveal whether similar echoes also exist in the auditory modality. A dynamically changing auditory stimulus equivalent to the visual stimulus was designed and employed in two separate series of experiments, and the presence of reverberations was analyzed based on reverse correlations between stimulus sequences and EEG epochs. The first experiment directly compared visual and auditory stimuli: while previous findings of ∼10 Hz visual echoes were verified, no similar echo was found in the auditory modality regardless of frequency. In the second experiment, we tested if auditory sequences would influence the visual echoes when they were congruent or incongruent with the visual sequences. However, the results in that case similarly did not reveal any auditory echoes, nor any change in the characteristics of visual echoes as a function of audio-visual congruence. The negative findings from these experiments suggest that brain oscillations do not equivalently affect early sensory processes in the visual and auditory modalities, and that alpha (8–13 Hz) oscillations play a special role in vision. PMID:23145143

  17. Light Echoes from Supernova 2014J in M82

    NASA Astrophysics Data System (ADS)

    Crotts, Arlin P. S.

    2015-05-01

    Type Ia SN 2014J exploded in the nearby starburst galaxy M82 = NGC 3032 and was discovered at Earth about seven days later on 2014 January 21, reaching maximum light in V around 2014 February 5. SN 2014J is the closest SN Ia in at least four decades and probably many more. Recent Hubble Space Telescope/WFC3 imaging (2014 September 5 and 2015 February 2) of M82 in the vicinity of SN 2014J reveals a light echo at radii of about 0.6 arcsec from the supernova (SN; corresponding to about 12 pc at the distance of M82). Likely additional light echoes reside at a smaller radii of about 0.4 arcsec The major echo signal corresponds to echoing material about 330 pc in the foreground of SN 2014J and tends to be bright where pre-existing nebular structure in M82 is also bright. The second, likely echo corresponds to foreground distances of 80 pc in front of the SN. Even one year after maximum light, there are indications of further echo structures appearing at smaller radii, and future observations may show how extinction in these affect detected echo farther from the SN, which will affect interpretation of details of the three-dimensional structure of this gas and dust. Given enough data, we might even use these considerations to constrain the near-SN material’s shadowing on distant echoing clouds, even without directly observing the foreground structure. This is in addition to echoes in the near future that might also reveal circumstellar structure around SN 2014J’s progenitor star from direct imaging observations and other techniques.

  18. Application of fast BLMS algorithm in acoustic echo cancellation

    NASA Astrophysics Data System (ADS)

    Zhao, Yue; Li, Nian Q.

    2013-03-01

    The acoustic echo path is usually very long and ranges from several hundreds to few thousands of taps. Frequency domain adaptive filter provides a solution to acoustic echo cancellation by means of resulting a significant reduction in the computational burden. In this paper, fast BLMS (Block Least-Mean-Square) algorithm in frequency domain is realized by using fast FFT technology. The adaptation of filter parameters is actually performed in the frequency domain. The proposed algorithm can ensure convergence with high speed and reduce computational complexity. Simulation results indicate that the algorithm demonstrates good performance for acoustic echo cancellation in communication systems.

  19. Exotic nuclei in astrophysics

    NASA Astrophysics Data System (ADS)

    Penionzhkevich, Yu. E.

    2012-07-01

    Recently the academic community has marked several anniversaries connected with discoveries that played a significant role in the development of astrophysical investigations. The year 2009 was proclaimed by the United Nations the International Year of Astronomy. This was associated with the 400th anniversary of Galileo Galilei's discovery of the optical telescope, which marked the beginning of regular research in the field of astronomy. An important contribution to not only the development of physics of the microcosm, but also to the understanding of processes occurring in the Universe, was the discovery of the atomic nucleus made by E. Rutherford 100 years ago. Since then the investigations in the fields of physics of particles and atomic nuclei have helped to understand many processes in the microcosm. Exactly 80 years ago, K. Yanski used a radio-telescope in order to receive the radiation from cosmic objects for the first time, and at the present time this research area of physics is the most efficient method for studying the properties of the Universe. Finally, the April 12, 1961 (50 years ago) launching of the first sputnik into space with a human being onboard, the Russian cosmonaut Yuri Gagarin, marked the beginning of exploration of the Universe with the direct participation of man. All these achievements considerably extended our ideas about the Universe. This work is an attempt to present some problems on the evolution of the Universe: the nucleosynthesis and cosmochronology from the standpoint of physics of particles and nuclei, in particular with the use of the latest results, obtained by means of radioactive nuclear beams. The comparison is made between the processes taking place in the Universe and the mechanisms of formation and decay of nuclei, as well as of their interaction at different energies. Examples are given to show the capabilities of nuclear-physics methods for studying cosmic objects and properties of the Universe. The results of

  20. IBA in deformed nuclei

    SciTech Connect

    Casten, R.F.; Warner, D.D.

    1982-01-01

    The structure and characteristic properties and predictions of the IBA in deformed nuclei are reviewed, and compared with experiment, in particular for /sup 168/Er. Overall, excellent agreement, with a minimum of free parameters (in effect, two, neglecting scale factors on energy differences), was obtained. A particularly surprising, and unavoidable, prediction is that of strong ..beta.. ..-->.. ..gamma.. transitions, a feature characteristically absent in the geometrical model, but manifest empirically. Some discrepancies were also noted, principally for the K=4 excitation, and the detailed magnitudes of some specific B(E2) values. Considerable attention is paid to analyzing the structure of the IBA states and their relation to geometric models. The bandmixing formalism was studied to interpret both the aforementioned discrepancies and the origin of the ..beta.. ..-->.. ..gamma.. transitions. The IBA states, extremely complex in the usual SU(5) basis, are transformed to the SU(3) basis, as is the interaction Hamiltonian. The IBA wave functions appear with much simplified structure in this way as does the structure of the associated B(E2) values. The nature of the symmetry breaking of SU(3) for actual deformed nuclei is seen to be predominantly ..delta..K=0 mixing. A modified, and more consistent, formalism for the IBA-1 is introduced which is simpler, has fewer free parameters (in effect, one, neglecting scale factors on energy differences), is in at least as good agreement with experiment as the earlier formalism, contains a special case of the 0(6) limit which corresponds to that known empirically, and appears to have a close relationship to the IBA-2. The new formalism facilitates the construction of contour plots of various observables (e.g., energy or B(E2) ratios) as functions of N and chi/sub Q/ which allow the parameter-free discussion of qualitative trajectories or systematics.

  1. Quaternion-valued echo state networks.

    PubMed

    Xia, Yili; Jahanchahi, Cyrus; Mandic, Danilo P

    2015-04-01

    Quaternion-valued echo state networks (QESNs) are introduced to cater for 3-D and 4-D processes, such as those observed in the context of renewable energy (3-D wind modeling) and human centered computing (3-D inertial body sensors). The introduction of QESNs is made possible by the recent emergence of quaternion nonlinear activation functions with local analytic properties, required by nonlinear gradient descent training algorithms. To make QENSs second-order optimal for the generality of quaternion signals (both circular and noncircular), we employ augmented quaternion statistics to introduce widely linear QESNs. To that end, the standard widely linear model is modified so as to suit the properties of dynamical reservoir, typically realized by recurrent neural networks. This allows for a full exploitation of second-order information in the data, contained both in the covariance and pseudocovariances, and a rigorous account of second-order noncircularity (improperness), and the corresponding power mismatch and coupling between the data components. Simulations in the prediction setting on both benchmark circular and noncircular signals and on noncircular real-world 3-D body motion data support the analysis. PMID:25794374

  2. Light Echoes of Galactic Explosions and Eruptions

    NASA Astrophysics Data System (ADS)

    Rest, Armin; Bianco, Federica; Chornock, Ryan; Foley, Ryan; Huber, Mark E.; Matheson, Thomas; McDonald, Brittany; Olsen, Knut; Prieto, Jose Luis; Sinnott, Brendan; Smith, Nathan; Welch, Doug

    2012-08-01

    We propose to search for light echoes (LEs) from the historical brightening of the Luminous Blue Variable (LBV) P Cygni using the KPNO 4m Mosaic 1.1 imager. We also propose to conclude our search - so far unsuccessful - for LEs from the the Crab supernova SN 1054 by surveying one remaining region of the LE ellipsoid behind the plane of the supernova remnant on the sky. In addition, we continue to monitor the LEs from the Cas A and Tycho supernovae in order to identify suitable LE candidates for 3D-spectroscopy and spectral time series. Recently, we discovered LEs of the mid-19th-century Great Eruption of η Carinae using CTIO 4m Mosaic images. Subsequent spectroscopic follow-up revealed that its outburst spectral type was most similar to those of G-type supergiants, rather than the reported LBV outburst spectral types (F-type or earlier) teRest12_eta. The application of the LE studies to LBVs promises to extend our ability to record outburst activity hundreds of years into the past - a timescale which is likely a significant fraction of the brief final phases of these probable core-collapse supernova precursors.

  3. First radar echoes from cumulus clouds

    NASA Technical Reports Server (NTRS)

    Knight, Charles A.; Miller, L. J.

    1993-01-01

    In attempting to use centimeter-wavelength radars to investigate the early stage of precipitation formation in clouds, 'mantle echoes' are rediscovered and shown to come mostly from scattering by small-scale variations in refractive index, a Bragg kind of scattering mechanism. This limits the usefulness of single-wavelength radar for studies of hydrometeor growth, according to data on summer cumulus clouds in North Dakota, Hawaii, and Florida, to values of reflectivity factor above about 10 dBZe with 10-cm radar, 0 dBZe with 5-cm radar, and -10 dBZe with 3-cm radar. These are limits at or above which the backscattered radar signal from the kinds of clouds observed can be assumed to be almost entirely from hydrometeors or (rarely) other particulate material such as insects. Dual-wavelength radar data can provide the desired information about hydrometeors at very low reflectivity levels if assumptions can be made about the inhomogeneities responsible for the Bragg scattering. The Bragg scattering signal itself probably will be a useful way to probe inhomogeneities one-half the radar wavelength in scale for studying cloud entrainment and mixing processes. However, this use is possible only before scattering from hydrometeors dominates the radar return.

  4. Isolation of nuclei from yeast.

    PubMed

    Bhargava, M M; Halvorson, H O

    1971-05-01

    A method for isolation of nuclei from Saccharomyces cervisiae in high yield is described. The DNA/protein ratio of the isolated nuclei is 10 times higher than that of whole cells. Examination of these nuclei in phase and electron microscopes has shown them to be round bodies having a double membrane, microtubules, and a dark crescent at one end. The optimum conditions for extraction and resolution of histones of these nuclei on acrylamide gels have been investigated. The nuclei have an active RNA polymerase (E.C. 2.7.7.6) and are able to synthesize RNA in vitro. They are also readily stainable with Giemsa's, Feulgen's, and acridine orange methods. PMID:19866769

  5. Quarks in Few Body Nuclei

    NASA Astrophysics Data System (ADS)

    Holt, Roy J.

    2016-03-01

    Electron scattering at very high Bjorken x from hadrons provides an excellent test of models, has an important role in high energy physics, and from nuclei, provides a window into short range correlations. Light nuclei have a key role because of the relatively well-known nuclear structure. The development of a novel tritium target for Jefferson Lab has led to renewed interest in the mass three system. For example, deep inelastic scattering experiments in the light nuclei provide a powerful means to determine the neutron structure function. The isospin dependence of electron scattering from mass-3 nuclei provide information on short range correlations in nuclei. The program using the new tritium target will be presented along with a summary of other experiments aimed at revealing the large-x structure of the nucleon.

  6. Loschmidt echo and time reversal in complex systems.

    PubMed

    Goussev, Arseni; Jalabert, Rodolfo A; Pastawski, Horacio M; Wisniacki, Diego A

    2016-06-13

    Echoes are ubiquitous phenomena in several branches of physics, ranging from acoustics, optics, condensed matter and cold atoms to geophysics. They are at the base of a number of very useful experimental techniques, such as nuclear magnetic resonance, photon echo and time-reversal mirrors. Particularly interesting physical effects are obtained when the echo studies are performed on complex systems, either classically chaotic, disordered or many-body. Consequently, the term Loschmidt echo has been coined to designate and quantify the revival occurring when an imperfect time-reversal procedure is applied to a complex quantum system, or equivalently to characterize the stability of quantum evolution in the presence of perturbations. Here, we present the articles which discuss the work that has shaped the field in the past few years. PMID:27140977

  7. Light echoes and transient luminescence near SN 1987A

    NASA Technical Reports Server (NTRS)

    Crotts, Arlin P. S.; Kunkel, William E.; Mccarthy, Patrick J.

    1989-01-01

    The discovery of two new light echoes from sheets of material behind supernova 1987A and present images of the progenitor's circumstellar shell are reported, indicating diffuse echoes from the star's red giant wind. The echo sheets' geometry explains well the behavior of SN 1987's 10-micron flux, but the circumstellar shell appears to be 70 percent larger than the prediction from the analysis of narrow UV emission lines. The sheets' recombination time show them relatively thin and dense. The data also constrain the existence of any fourth star in the Sanduleak -69 deg 202 system and show that the feature reported 8 arcsecs from the supernova is probably not an echo from a thin sheet in SN 1987A's foreground.

  8. Loschmidt echo and time reversal in complex systems

    PubMed Central

    Goussev, Arseni; Jalabert, Rodolfo A.; Pastawski, Horacio M.; Wisniacki, Diego A.

    2016-01-01

    Echoes are ubiquitous phenomena in several branches of physics, ranging from acoustics, optics, condensed matter and cold atoms to geophysics. They are at the base of a number of very useful experimental techniques, such as nuclear magnetic resonance, photon echo and time-reversal mirrors. Particularly interesting physical effects are obtained when the echo studies are performed on complex systems, either classically chaotic, disordered or many-body. Consequently, the term Loschmidt echo has been coined to designate and quantify the revival occurring when an imperfect time-reversal procedure is applied to a complex quantum system, or equivalently to characterize the stability of quantum evolution in the presence of perturbations. Here, we present the articles which discuss the work that has shaped the field in the past few years. PMID:27140977

  9. Polarization properties of long-lived stimulated photon echo

    NASA Astrophysics Data System (ADS)

    Reshetov, V. A.; Popov, E. N.

    2015-01-01

    The polarization properties of the long-lived stimulated photon echo formed on the transition ja → jb with the atomic levels degenerate in the projections of the angular momenta are studied theoretically. The two particular transitions ja = 1 → jb = 0 and ja = 1 → jb = 1 with degenerate ground state ja = 1 are discussed. For the transitions ja = 1 → jb = 1 the polarizations and areas of the first (‘write’) and the third (‘read’) excitation pulses are found when the echo polarization faithfully reproduces the arbitrary polarization of the weak (single-photon) second (‘information’) pulse, so that this echo scheme may implement the quantum memory for a single-photon polarization qubit, while for the transitions ja = 1 → jb = 0 it is shown, that the echo polarization differs from that of the second pulse at any conditions.

  10. Beam Echo Effect for Generation of Short-Wavelength Radiation

    SciTech Connect

    Stupakov, G.; /SLAC

    2009-12-09

    The Echo-Enabled Harmonic Generation (EEHG) FEL uses two modulators in combination with two dispersion sections to generate a high-harmonic density modulation starting with a relatively small initial energy modulation of the beam. After presenting the concept of the EEHG, we address several practically important issues, such as the effect of coherent and incoherent synchrotron radiation in the dispersion sections. Using a representative realistic set of beam parameters, we show how the EEHG scheme enhances the FEL performance and allows one to generate a fully (both longitudinally and transversely) coherent radiation. We then discuss application of the echo modulation for generation of attosecond pulses of radiation, and also using echo for generation of terahertz radiation. We present main parameters of a proof-of-principle experiment currently being planned at SLAC for demonstration of the echo modulation mechanism.

  11. Fast REDOR with CPMG multiple-echo acquisition.

    PubMed

    Hung, Ivan; Gan, Zhehong

    2014-01-01

    Rotational-Echo Double Resonance (REDOR) is a widely used experiment for distance measurements in solids. The conventional REDOR experiment measures the signal dephasing from hetero-nuclear recoupling under magic-angle spinning (MAS) in a point by point manner. A modified Carr-Purcell Meiboom-Gill (CPMG) multiple-echo scheme is introduced for fast REDOR measurement. REDOR curves are measured from the CPMG echo amplitude modulation under dipolar recoupling. The real time CPMG-REDOR experiment can speed up the measurement by an order of magnitude. The effects from hetero-nuclear recoupling, the Bloch-Siegert shift and echo truncation to the signal acquisition are discussed and demonstrated. PMID:24316818

  12. Free-electron lasers: Echoes of photons past

    NASA Astrophysics Data System (ADS)

    Campbell, Lawrence T.; McNeil, Brian W. J.

    2016-08-01

    High-harmonic generation is an established method to significantly upshift laser photon energies. Now, researchers at the SLAC National Accelerator Laboratory have used echo concepts to generate coherent high-harmonic output from an electron-beam light source.

  13. Rotary echos for the preservation of quantum memories

    NASA Astrophysics Data System (ADS)

    Uys, Hermann; de Clerq, Ludwig; Green, Todd; Biercuk, Michael; Bollinger, John

    2011-05-01

    Dynamical decoupling is a promising technique for fighting the unwanted effects of decoherence in the context of quantum information. Decoupling techniques span two extremes from pulsed spin-echo sequences to optimized, continuous amplitude and phase modulation allowing arbitrary rotations on the Bloch sphere. On the one hand spin-echo techniques have the advantage of simplicity, while on the other optimized continuous modulation is expected to achieve better performance results at the cost complexity. That complexity exists both in the implementation and the modulation design, which either requires intimate knowledge of the relevant noise environment for numerical optimization or experimental optimization through feedback. Rotary echos represent an intermediate approach which have the advantage of continuous averaging of dephasing noise and pulsed compensation of fluctuations in the control field amplitude. Here we consider a classical dephasing noise environment and compare the performance of rotary echos to both pulsed and optimized continuous control decoupling techniques.

  14. A SAMPLE OF SEYFERT-2 GALAXIES WITH ULTRALUMINOUS GALAXY-WIDE NARROW-LINE REGIONS: QUASAR LIGHT ECHOES?

    SciTech Connect

    Schirmer, M.; Diaz, R.; Levenson, N. A.; Winge, C.; Holhjem, K.

    2013-01-20

    We report the discovery of Seyfert-2 galaxies in SDSS-DR8 with galaxy-wide, ultraluminous narrow-line regions (NLRs) at redshifts z = 0.2-0.6. With a space density of 4.4 Gpc{sup -3} at z {approx} 0.3, these 'green beans' (GBs) are amongst the rarest objects in the universe. We are witnessing an exceptional and/or short-lived phenomenon in the life cycle of active galactic nuclei (AGNs). The main focus of this paper is on a detailed analysis of the GB prototype galaxy J2240-0927 (z = 0.326). Its NLR extends over 26 Multiplication-Sign 44 kpc and is surrounded by an extended NLR. With a total [O III] {lambda}5008 luminosity of (5.7 {+-} 0.9) Multiplication-Sign 10{sup 43} erg s{sup -1}, this is one of the most luminous NLRs known around any type-2 galaxy. Using VLT/XSHOOTER, we show that the NLR is powered by an AGN, and we derive resolved extinction, density, and ionization maps. Gas kinematics is disturbed on a global scale, and high-velocity outflows are absent or faint. This NLR is unlike any other NLR or extended emission line region known. Spectroscopy with Gemini/GMOS reveals extended, high-luminosity [O III] emission also in other GBs. WISE 24 {mu}m luminosities are 5-50 times lower than predicted by the [O III] fluxes, suggesting that the NLRs reflect earlier, very active quasar states that have strongly subsided in less than a galaxy's light-crossing time. These light echoes, or ionization echoes, are about 100 times more luminous than any other such echo known to date. X-ray data are needed for photoionization modeling and to verify the light echoes.

  15. ECHO Services: Foundational Middleware for a Science Cyberinfrastructure

    NASA Technical Reports Server (NTRS)

    Burnett, Michael

    2005-01-01

    This viewgraph presentation describes ECHO, an interoperability middleware solution. It uses open, XML-based APIs, and supports net-centric architectures and solutions. ECHO has a set of interoperable registries for both data (metadata) and services, and provides user accounts and a common infrastructure for the registries. It is built upon a layered architecture with extensible infrastructure for supporting community unique protocols. It has been operational since November, 2002 and it available as open source.

  16. Preliminary results of the echo-seeding experiment at SLAC

    SciTech Connect

    Xiang, D.; Colby, E.; Ding, Y.; Dunning, M.; Frederico, J.; Gilevich, S.; Hast, C.; Jobe, K.; McCormick, D.; Nelson, J.; Raubenheimer, T.O.; Soong, K.; Stupakov, G.; Szalata, Z.; Walz, D.; Weathersby, S.; Woodley, M.; Corlett, J.; Qiang, J.; Penn, G.; Prestemon, S.; Schlueter, R.; Venturini, M.; Wan, W.; Pernet, P-L.

    2010-05-23

    ECHO-7 is a proof-of-principle echo-enabled harmonic generation FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment aims to generate coherent radiation at 318 nm and 227 nm, which are the 5th and 7th harmonic of the infrared seed laser. In this paper we present the preliminary results from the commissioning run of the completed experimental setup which started in April 2010.

  17. The architecture of dynamic reservoir in the echo state network

    NASA Astrophysics Data System (ADS)

    Cui, Hongyan; Liu, Xiang; Li, Lixiang

    2012-09-01

    Echo state network (ESN) has recently attracted increasing interests because of its superior capability in modeling nonlinear dynamic systems. In the conventional echo state network model, its dynamic reservoir (DR) has a random and sparse topology, which is far from the real biological neural networks from both structural and functional perspectives. We hereby propose three novel types of echo state networks with new dynamic reservoir topologies based on complex network theory, i.e., with a small-world topology, a scale-free topology, and a mixture of small-world and scale-free topologies, respectively. We then analyze the relationship between the dynamic reservoir structure and its prediction capability. We utilize two commonly used time series to evaluate the prediction performance of the three proposed echo state networks and compare them to the conventional model. We also use independent and identically distributed time series to analyze the short-term memory and prediction precision of these echo state networks. Furthermore, we study the ratio of scale-free topology and the small-world topology in the mixed-topology network, and examine its influence on the performance of the echo state networks. Our simulation results show that the proposed echo state network models have better prediction capabilities, a wider spectral radius, but retain almost the same short-term memory capacity as compared to the conventional echo state network model. We also find that the smaller the ratio of the scale-free topology over the small-world topology, the better the memory capacities.

  18. Neural time course of visually enhanced echo suppression.

    PubMed

    Bishop, Christopher W; London, Sam; Miller, Lee M

    2012-10-01

    Auditory spatial perception plays a critical role in day-to-day communication. For instance, listeners utilize acoustic spatial information to segregate individual talkers into distinct auditory "streams" to improve speech intelligibility. However, spatial localization is an exceedingly difficult task in everyday listening environments with numerous distracting echoes from nearby surfaces, such as walls. Listeners' brains overcome this unique challenge by relying on acoustic timing and, quite surprisingly, visual spatial information to suppress short-latency (1-10 ms) echoes through a process known as "the precedence effect" or "echo suppression." In the present study, we employed electroencephalography (EEG) to investigate the neural time course of echo suppression both with and without the aid of coincident visual stimulation in human listeners. We find that echo suppression is a multistage process initialized during the auditory N1 (70-100 ms) and followed by space-specific suppression mechanisms from 150 to 250 ms. Additionally, we find a robust correlate of listeners' spatial perception (i.e., suppressing or not suppressing the echo) over central electrode sites from 300 to 500 ms. Contrary to our hypothesis, vision's powerful contribution to echo suppression occurs late in processing (250-400 ms), suggesting that vision contributes primarily during late sensory or decision making processes. Together, our findings support growing evidence that echo suppression is a slow, progressive mechanism modifiable by visual influences during late sensory and decision making stages. Furthermore, our findings suggest that audiovisual interactions are not limited to early, sensory-level modulations but extend well into late stages of cortical processing. PMID:22786953

  19. The architecture of dynamic reservoir in the echo state network.

    PubMed

    Cui, Hongyan; Liu, Xiang; Li, Lixiang

    2012-09-01

    Echo state network (ESN) has recently attracted increasing interests because of its superior capability in modeling nonlinear dynamic systems. In the conventional echo state network model, its dynamic reservoir (DR) has a random and sparse topology, which is far from the real biological neural networks from both structural and functional perspectives. We hereby propose three novel types of echo state networks with new dynamic reservoir topologies based on complex network theory, i.e., with a small-world topology, a scale-free topology, and a mixture of small-world and scale-free topologies, respectively. We then analyze the relationship between the dynamic reservoir structure and its prediction capability. We utilize two commonly used time series to evaluate the prediction performance of the three proposed echo state networks and compare them to the conventional model. We also use independent and identically distributed time series to analyze the short-term memory and prediction precision of these echo state networks. Furthermore, we study the ratio of scale-free topology and the small-world topology in the mixed-topology network, and examine its influence on the performance of the echo state networks. Our simulation results show that the proposed echo state network models have better prediction capabilities, a wider spectral radius, but retain almost the same short-term memory capacity as compared to the conventional echo state network model. We also find that the smaller the ratio of the scale-free topology over the small-world topology, the better the memory capacities. PMID:23020466

  20. Multi-Echo Acquisition of O-Space Data

    PubMed Central

    Galiana, Gigi; Peters, Dana; Tam, Leo; Constable, R. Todd

    2014-01-01

    Purpose Nonlinear gradient encoding methods, such as O-Space imaging, have been shown to provide good images from very few echoes. Acquiring data in a train of spin or gradient echoes is a very flexible way to further speed acquisition time. However, combining these strategies presents significant challenges, both in terms of the contrast and artifacts. We present strategies in both pulse sequence design and image processing to mitigate these effects. Theory and Methods The three strategies include a new echo ordering that takes into account the unique way that O-Space samples the k-space of the image; a new post-processing filter that allows tuning of T2-weighting by emphasizing the contribution of low frequency spatial information at selectable points in space and time; and an offset between linear and nonlinear gradients that makes the central point of each echo unique. Results Simulations indicate that these strategies mitigate artifacts introduced by T2 (or T2*) decay and produce contrast that reflects relaxation at a given TE. Conclusion Turbo spin echo O-Space is theoretically feasible, and the greater undersampling should make it possible to use shorter echo trains for a given scan time. PMID:24459076

  1. Comparison of Twice Refocused Spin Echo versus Stimulated Echo Diffusion Tensor Imaging for Tracking Muscle Fibers

    PubMed Central

    Noehren, Brian; Andersen, Anders; Feiweier, Thorsten; Damon, Bruce; Hardy, Peter

    2014-01-01

    Purpose To compare the precision of measuring the pennation angle and fiber length in the Vastus Lateralis (VL) using two distinctly different diffusion tensor imaging sequences. Materials and Methods We imaged the thigh of ten normal subjects on a 3T MR imager with twice refocused spin echo (TRSE) and stimulated echo (STEAM) DTI-MRI techniques. Both techniques took the same total acquisition time, employed the same diffusion weighting and gradient directions. Using the diffusion tensor images produced by each sequence muscle fiber bundles were tracked from the aponeurosis by following the first eigenvector of the diffusion tensor. From these tracks we calculated the pennation angle and fiber length. Results The STEAM acquisition resulted in significantly higher SNR, lower ADC, higher FA values and longer fibers than the TRSE. Although no difference in the pennation angle between the two acquisitions was found, the TRSE sequence had a significantly greater within subject dispersion in the pennation angle of tracked fibers which may indicate a reduction in the coherence of fiber bundles. Conclusion Diffusion tensor imaging of muscle using a STEAM acquisition resulted in significant improvements in the SNR and FA, resulting in tracking a larger number of muscle fiber bundles over longer distances and with less within subject dispersion. PMID:24554376

  2. Extended Locus of Regular Nuclei

    SciTech Connect

    Amon, L.; Casten, R. F.

    2007-04-23

    A new family of IBM Hamiltonians, characterized by certain parameter values, was found about 15 years ago by Alhassid and Whelan to display almost regular dynamics, and yet these solutions to the IBM do not belong to any of the known dynamical symmetry limits (vibrational, rotational and {gamma} - unstable). Rather, they comprise an 'Arc of Regularity' cutting through the interior of the symmetry triangle from U(5) to SU(3) where suddenly there is a decrease in chaoticity and a significant increase in regularity. A few years ago, the first set of nuclei lying along this arc was discovered. The purpose of the present work is to search more broadly in the nuclear chart at all nuclei from Z = 40 - 100 for other examples of such 'regular' nuclei. Using a unique signature for such nuclei involving energy differences of certain excited states, we have identified an additional set of 12 nuclei lying near or along the arc. Some of these nuclei are known to have low-lying intruder states and therefore care must be taken, however, in judging their structure. The regularity exhibited by nuclei near the arc presumably reflects the validity or partial validity of some new, as yet unknown, quantum number describing these systems and giving the regularity found for them.

  3. Shape coexistence in atomic nuclei

    SciTech Connect

    Heyde, Kris; Wood, John L.

    2011-10-01

    Shape coexistence in nuclei appears to be unique in the realm of finite many-body quantum systems. It differs from the various geometrical arrangements that sometimes occur in a molecule in that in a molecule the various arrangements are of the widely separated atomic nuclei. In nuclei the various ''arrangements'' of nucleons involve (sets of) energy eigenstates with different electric quadrupole properties such as moments and transition rates, and different distributions of proton pairs and neutron pairs with respect to their Fermi energies. Sometimes two such structures will ''invert'' as a function of the nucleon number, resulting in a sudden and dramatic change in ground-state properties in neighboring isotopes and isotones. In the first part of this review the theoretical status of coexistence in nuclei is summarized. Two approaches, namely, microscopic shell-model descriptions and mean-field descriptions, are emphasized. The second part of this review presents systematic data, for both even- and odd-mass nuclei, selected to illustrate the various ways in which coexistence is observed in nuclei. The last part of this review looks to future developments and the issue of the universality of coexistence in nuclei. Surprises continue to be discovered. With the major advances in reaching to extremes of proton-neutron number, and the anticipated new ''rare isotope beam'' facilities, guidelines for search and discovery are discussed.

  4. Single echo acquisition MRI using RF encoding.

    PubMed

    Wright, Steven M; McDougall, Mary Preston

    2009-11-01

    Encoding of spatial information in magnetic resonance imaging is conventionally accomplished by using magnetic field gradients. During gradient encoding, the position in k-space is determined by a time-integral of the gradient field, resulting in a limitation in imaging speed due to either gradient power or secondary effects such as peripheral nerve stimulation. Partial encoding of spatial information through the sensitivity patterns of an array of coils, known as parallel imaging, is widely used to accelerate the imaging, and is complementary to gradient encoding. This paper describes the one-dimensional limit of parallel imaging in which all spatial localization in one dimension is performed through encoding by the radiofrequency (RF) coil. Using a one-dimensional array of long and narrow parallel elements to localize the image information in one direction, an entire image is obtained from a single line of k-space, avoiding rapid or repeated manipulation of gradients. The technique, called single echo acquisition (SEA) imaging, is described, along with the need for a phase compensation gradient pulse to counteract the phase variation contained in the RF coil pattern which would otherwise cause signal cancellation in each imaging voxel. Image reconstruction and resolution enhancement methods compatible with the speed of the technique are discussed. MR movies at frame rates of 125 frames per second are demonstrated, illustrating the ability to monitor the evolution of transverse magnetization to steady state during an MR experiment as well as demonstrating the ability to image rapid motion. Because this technique, like all RF encoding approaches, relies on the inherent spatially varying pattern of the coil and is not a time-integral, it should enable new applications for MRI that were previously inaccessible due to speed constraints, and should be of interest as an approach to extending the limits of detection in MR imaging. PMID:19441080

  5. Exoplanetary Characterisation Observatory (EChO)

    NASA Astrophysics Data System (ADS)

    Waldmann, Ingo; Tinetti, Giovanna

    2013-04-01

    The science of extrasolar planets is one of the most rapidly changing areas of astrophysics and since 1995 the number of planets known has increased by almost two orders of magnitude. A combination of ground-based surveys and dedicated space missions has resulted in 800-plus planets being detected, and over 2000 that await confirmation. NASA's Kepler mission has opened up the possibility of discovering Earth-like planets in the habitable zone around some of the 100,000 stars it is surveying during its 3 to 4-year lifetime. The new ESA's Gaia mission is expected to discover thousands of new planets around stars within 200 parsecs of the Sun. The key challenge now is moving on from discovery, important though that remains, to characterisation: what are these planets actually like, and why are they as they are? The Exoplanet Characterisation Observatory (EChO) is a space mission dedicated to undertaking spectroscopy of transiting exoplanets over the widest range possible and is currently being studied by ESA in the context of a medium class mission within the Cosmic Vision programme for launch post 2020. The mission is based around a highly stable space platform with a 1.2 m class telescope at L2, hosting a suit of spectrographs providing continuous spectral coverage from 0.5 to 16 microns. Such a broad and simultaneous wavelength coverage allows the unique insight into the atmospheric make up of these foreign worlds and allows us to study their planetary and atmospheric compositions and evolutions.

  6. Hematopoietic bone marrow in the adult knee: spin-echo and opposed-phase gradient-echo MR imaging.

    PubMed

    Lang, P; Fritz, R; Majumdar, S; Vahlensieck, M; Peterfy, C; Genant, H K

    1993-01-01

    Hematopoietic bone marrow in the distal femur of the adult may be mistaken for a pathologic marrow process in magnetic resonance imaging of the knee. We investigated the incidence of hematopoietic marrow in the distal femur in a series of 51 adult patients and compared spin-echo (TR/TE in ms: 500/35, 2000/80) and opposed-phase gradient-echo (0.35 T, TR/TE in ms: 1000/30, theta = 75 degrees) magnetic resonance images. Zones with intermediate to low signal intensity on T1-weighted spin-echo and opposed-phase gradient-echo sequences representing hematopoietic marrow within high signal intensity fatty marrow were observed in 18 of the 51 patients. Five patterns of marrow signal reduction were identified; type 0: uniform high signal, i.e., no signal change; type I, focal signal loss; type II, multifocal signal loss without confluence; type III, confluent signal loss; and type IV, complete homogeneous reduction in marrow signal. Opposed-phase gradient-echo sequences demonstrated markedly greater red-yellow marrow contrast than conventional spin-echo sequences. Follow-up studies in three patients using a gradient-echo sequence with TE varying from 10 to 21 ms at 1-ms increments showed a cyclic increase and decrease in red and yellow marrow signal intensity depending on the TE. The contribution of intravoxel chemical shift effects on red-yellow marrow contrast in opposed-phase gradient-echo images was verified by almost complete cancellation of the TE-dependent marrow signal oscillation with use of a chemically selective pulse presaturating the water protons. Hematopoietic marrow in the adult distal femur in the absence of hematologic abnormalities is found primarily in women of menstruating age.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8438189

  7. Echo detection and target-ranging neurons in the auditory system of the bat Eptesicus fuscus.

    PubMed

    Feng, A S; Simmons, J A; Kick, S A

    1978-11-10

    Some of the neurons in the nucleus intercollicularis and auditory cortex of the echolocating bat Eptesicus fuscus respond selectively to sonar echoes occurring with specific echo delays or pulse-echo intervals. They do not respond for a wide range of other types of sounds or for sonar echoes at longer or shorter pulse-echo intervals; they may, therefore, be specialized for detection and ranging of sonar targets. PMID:705350

  8. Gluon density in nuclei

    SciTech Connect

    Ayala, A.L.; Ducati, M.B.G.; Levin, E.M.

    1996-10-01

    In this talk we present our detailed study (theory and numbers) on the shadowing corrections to the gluon structure functions for nuclei. Starting from rather controversial information on the nucleon structure function which is originated by the recent HERA data, we develop the Glauber approach for the gluon density in a nucleus based on Mueller formula and estimate the value of the shadowing corrections in this case. Then we calculate the first corrections to the Glauber approach and show that these corrections are big. Based on this practical observation we suggest the new evolution equation which takes into account the shadowing corrections and solve it. We hope to convince you that the new evolution equation gives a good theoretical tool to treat the shadowing corrections for the gluons density in a nucleus and, therefore, it is able to provide the theoretically reliable initial conditions for the time evolution of the nucleus-nucleus cascade. The initial conditions should be fixed both theoretically and phenomenologically before to attack such complicated problems as the mixture of hard and soft processes in nucleus-nucleus interactions at high energy or the theoretically reliable approach to hadron or/and parton cascades for high energy nucleus-nucleus interaction. 35 refs., 24 figs., 1 tab.

  9. Research on key technologies of LADAR echo signal simulator

    NASA Astrophysics Data System (ADS)

    Xu, Rui; Shi, Rui; Ye, Jiansen; Wang, Xin; Li, Zhuo

    2015-10-01

    LADAR echo signal simulator is one of the most significant components of hardware-in-the-loop (HWIL) simulation systems for LADAR, which is designed to simulate the LADAR return signal in laboratory conditions. The device can provide the laser echo signal of target and background for imaging LADAR systems to test whether it is of good performance. Some key technologies are investigated in this paper. Firstly, the 3D model of typical target is built, and transformed to the data of the target echo signal based on ranging equation and targets reflection characteristics. Then, system model and time series model of LADAR echo signal simulator are established. Some influential factors which could induce fixed delay error and random delay error on the simulated return signals are analyzed. In the simulation system, the signal propagating delay of circuits and the response time of pulsed lasers are belong to fixed delay error. The counting error of digital delay generator, the jitter of system clock and the desynchronized between trigger signal and clock signal are a part of random delay error. Furthermore, these system insertion delays are analyzed quantitatively, and the noisy data are obtained. The target echo signals are got by superimposing of the noisy data and the pure target echo signal. In order to overcome these disadvantageous factors, a method of adjusting the timing diagram of the simulation system is proposed. Finally, the simulated echo signals are processed by using a detection algorithm to complete the 3D model reconstruction of object. The simulation results reveal that the range resolution can be better than 8 cm.

  10. Stem cell mechanics: Auxetic nuclei

    NASA Astrophysics Data System (ADS)

    Wang, Ning

    2014-06-01

    The nuclei of naive mouse embryonic stem cells that are transitioning towards differentiation expand when the cells are stretched and contract when they are compressed. What drives this auxetic phenotype is, however, unclear.

  11. Alpha Condensates in Atomic Nuclei

    SciTech Connect

    Suzuki, Y.; Matsumura, H.

    2005-11-21

    Recent issues on Bose-Einstein condensation (BEC) of {alpha}-particles in nuclei are reviewed. A candidate of condensates is discussed for some states in 12C and 16O by defining the amount of {alpha} condensation.

  12. Single-shot echo-planar imaging with Nyquist ghost compensation: interleaved dual echo with acceleration (IDEA) echo-planar imaging (EPI).

    PubMed

    Poser, Benedikt A; Barth, Markus; Goa, Pål-Erik; Deng, Weiran; Stenger, V Andrew

    2013-01-01

    Echo planar imaging (EPI) is most commonly used for blood oxygen level-dependent fMRI, owing to its sensitivity and acquisition speed. A major problem with EPI is Nyquist (N/2) ghosting, most notably at high field. EPI data are acquired under an oscillating readout gradient and hence vulnerable to gradient imperfections such as eddy current delays and off-resonance effects, as these cause inconsistencies between odd and even k-space lines after time reversal. We propose a straightforward and pragmatic method herein termed "interleaved dual echo with acceleration (IDEA) EPI": two k-spaces (echoes) are acquired under the positive and negative readout lobes, respectively, by performing phase encoding blips only before alternate readout gradients. From these two k-spaces, two almost entirely ghost free images per shot can be constructed, without need for phase correction. The doubled echo train length can be compensated by parallel imaging and/or partial Fourier acquisition. The two k-spaces can either be complex averaged during reconstruction, which results in near-perfect cancellation of residual phase errors, or reconstructed into separate images. We demonstrate the efficacy of IDEA EPI and show phantom and in vivo images at both 3 T and 7 T. PMID:22411762

  13. A high success rate full-waveform lidar echo decomposition method

    NASA Astrophysics Data System (ADS)

    Xu, Lijun; Li, Duan; Li, Xiaolu

    2016-01-01

    A full-waveform Light detection and ranging (LiDAR) echo decomposition method is proposed in this paper. In this method, the peak points are used to detect the separated echo components, while the inflection points are combined with corresponding peak points to detect the overlapping echo components. The detected echo components are then sorted according to their energies in a descending order. The sorted echo components are one by one added into the decomposition model according to their orders. For each addition, the parameters of all echo components already added into the decomposition model are iteratively renewed. After renewing, the amplitudes and full width at half maximums of the echo components are compared with pre-set thresholds to determine and remove the false echo components. Both simulation and experiment were carried out to evaluate the proposed method. In simulation, 4000 full-waveform echoes with different numbers and parameters of echo components were generated and decomposed using the proposed and three other commonly used methods. Results show that the proposed method is of the highest success rate, 91.43%. In experiment, 9549 Geoscience Laser Altimeter System (GLAS) echoes for Shennongjia forest district in south China were employed as test echoes. The test echoes were first decomposed using the four methods and the decomposition results were also compared with those provided by the National Snow and Ice Data Center. Comparison results show that the determination coefficient ({{R}2} ) of the proposed method is of the largest mean, 0.6838, and the smallest standard deviation, 0.3588, and the distribution of the number of the echo components decomposed from the GLAS echoes is the most satisfied with the situation of full-waveform echoes from the forest area, implying that the superposition of the echo components decomposed from a full-waveform echo by using the proposed method can best approximate the full-waveform echo.

  14. Generalized parton distributions in nuclei

    SciTech Connect

    Vadim Guzey

    2009-12-01

    Generalized parton distributions (GPDs) of nuclei describe the distribution of quarks and gluons in nuclei probed in hard exclusive reactions, such as e.g. deeply virtual Compton scattering (DVCS). Nuclear GPDs and nuclear DVCS allow us to study new aspects of many traditional nuclear effects (nuclear shadowing, EMC effect, medium modifications of the bound nucleons) as well as to access novel nuclear effects. In my talk, I review recent theoretical progress in the area of nuclear GPDs.

  15. The nature of comet nuclei

    NASA Technical Reports Server (NTRS)

    Sykes, Mark V.; Walker, Russell G.

    1992-01-01

    The icy-conglomerate model of comet nuclei has dominated all others since its introduction. It provided a basis for understanding the non-gravitational motions of comets which had perplexed dynamicists up to that time, and provided a focus for understanding cometary composition and origin. The image of comets as dirty snowballs was quickly adopted. Comet nuclei including their trail mass loss rates and refractory to volatile mass ratios are described.

  16. X-ray shout echoing through space

    NASA Astrophysics Data System (ADS)

    2004-01-01

    a flash of X-rays hi-res Size hi-res: 3991 Kb Credits: ESA, S. Vaughan (University of Leicester) EPIC camera shows the expanding rings caused by a flash of X-rays XMM-Newton's X-ray EPIC camera shows the expanding rings caused by a flash of X-rays scattered by dust in our Galaxy. The X-rays were produced by a powerful gamma-ray burst that took place on 3 December 2003. The slowly fading afterglow of the gamma-ray burst is at the centre of the expanding rings. Other, unrelated, X-ray sources can also be seen. The time since the gamma-ray explosion is shown in each panel in hours. At their largest size, the rings would appear in the sky about five times smaller than the full moon. a flash of X-rays hi-res Size hi-res: 2153 Kb Credits: ESA, S. Vaughan (University of Leicester) EPIC camera shows the expanding rings caused by a flash of X-rays (Please choose "hi-res" version for animation) XMM-Newton's X-ray EPIC camera shows the expanding rings caused by a flash of X-rays scattered by dust in our Galaxy. The X-rays were produced by a powerful gamma-ray burst that took place on 3 December 2003. The slowly fading afterglow of the gamma-ray burst is at the centre of the expanding rings. Other, unrelated, X-ray sources can also be seen. The time since the gamma-ray explosion is shown in each panel in seconds. At their largest size, the rings would appear in the sky about five times smaller than the full moon. This echo forms when the powerful radiation of a gamma-ray burst, coming from far away, crosses a slab of dust in our Galaxy and is scattered by it, like the beam of a lighthouse in clouds. Using the expanding rings to precisely pin-point the location of this dust, astronomers can identify places where new stars and planets are likely to form. On 3 December 2003 ESA's observatory, Integral, detected a burst of gamma rays, lasting about 30 seconds, from the direction of a distant galaxy. Within minutes of the detection, thanks to a sophisticated alert network, many

  17. Spin echo versus stimulated echo diffusion tensor imaging of the in vivo human heart

    PubMed Central

    von Deuster, Constantin; Stoeck, Christian T.; Genet, Martin; Atkinson, David

    2015-01-01

    Purpose To compare signal‐to‐noise ratio (SNR) efficiency and diffusion tensor metrics of cardiac diffusion tensor mapping using acceleration‐compensated spin‐echo (SE) and stimulated echo acquisition mode (STEAM) imaging. Methods Diffusion weighted SE and STEAM sequences were implemented on a clinical 1.5 Tesla MR system. The SNR efficiency of SE and STEAM was measured (b = 50–450 s/mm2) in isotropic agar, anisotropic diffusion phantoms and the in vivo human heart. Diffusion tensor analysis was performed on mean diffusivity, fractional anisotropy, helix and transverse angles. Results In the isotropic phantom, the ratio of SNR efficiency for SE versus STEAM, SNRt(SE/STEAM), was 2.84 ± 0.08 for all tested b‐values. In the anisotropic diffusion phantom the ratio decreased from 2.75 ± 0.05 to 2.20 ± 0.13 with increasing b‐value, similar to the in vivo decrease from 2.91 ± 0.43 to 2.30 ± 0.30. Diffusion tensor analysis revealed reduced deviation of helix angles from a linear transmural model and reduced transverse angle standard deviation for SE compared with STEAM. Mean diffusivity and fractional anisotropy were measured to be statistically different (P < 0.001) between SE and STEAM. Conclusion Cardiac DTI using motion‐compensated SE yields a 2.3–2.9× increase in SNR efficiency relative to STEAM and improved accuracy of tensor metrics. The SE method hence presents an attractive alternative to STEAM based approaches. Magn Reson Med 76:862–872, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:26445426

  18. The effect of strong pitch angle scattering on the use of artificial auroral streaks for echo detection - Echo 5

    NASA Astrophysics Data System (ADS)

    Swanson, R. L.; Steffen, J. E.; Winckler, J. R.

    1986-05-01

    During the Echo 5 experiment, launched November 13, 1979 from the Poker Flat Research Range (Fairbanks, AK), a 0.75 A, 37 keV electron beam was injected both up and down the field line. The objective of the experiment was to test the use of optical and X-ray methods to detect the beam as it interacted with the atmosphere below the rocket for both the downward injections (markers) and the upward injected electrons which mirrored at the Southern Hemisphere and returned echoes. A ground-based TV system, rocket-borne photometers, and X-ray detectors viewed the interaction region. The artificial auroral streaks created by the markers were easily visible on the ground TV system but the large intensity of photons produced around the rocket masked any response to the markers by the on-board photometers and X-ray detectors. No echoes were detected with any of the detection systems although the power in some of the upward injections was 7.6 times the power in a detected downward injection, thus setting an upper limit on the loss-cone echo flux. The magnitude of the bounce averaged pitch-angle-diffusion coefficient necessary to explain the lack of observable echoes was found to be 0.0004/s. Comparison with calculations done by Lyons (1974) for the pitch angle diffusion of electrons by electrostatic waves revealed that an equatorial wave electric field of 11 mV/m would account for the lack of echoes. Such fields should cause strong pitch angle scattering of up to 10 keV natural electrons and thus be consistent with the presence of diffuse aurora on the Echo 5 trajectory. Direct measurements have also revealed such fields in equatorial regions.

  19. Faraday rotation echo spectroscopy and detection of quantum fluctuations

    PubMed Central

    Chen, Shao-Wen; Liu, Ren-Bao

    2014-01-01

    Central spin decoherence is useful for detecting many-body physics in environments and moreover, the spin echo control can remove the effects of static thermal fluctuations so that the quantum fluctuations are revealed. The central spin decoherence approach, however, is feasible only in some special configurations and often requires uniform coupling between the central spin and individual spins in the baths, which are very challenging in experiments. Here, by making analogue between central spin decoherence and depolarization of photons, we propose a scheme of Faraday rotation echo spectroscopy (FRES) for studying quantum fluctuations in interacting spin systems. The echo control of the photon polarization is realized by flipping the polarization with a birefringence crystal. The FRES, similar to spin echo in magnetic resonance spectroscopy, can suppress the effects of the static magnetic fluctuations and therefore reveal dynamical magnetic fluctuations. We apply the scheme to a rare-earth compound LiHoF4 and calculate the echo signal, which is related to the quantum fluctuations of the system. We observe enhanced signals at the phase boundary. The FRES should be useful for studying quantum fluctuations in a broad range of spin systems, including cold atoms, quantum dots, solid-state impurities, and transparent magnetic materials. PMID:24733086

  20. Light echo detection of circumstellar disks around flaring stars

    NASA Technical Reports Server (NTRS)

    Gaidos, Eric J.

    1994-01-01

    Light echoes can be used to detect and characterize disks around flaring stars. Such disks are thought to be a hallmark of planet formation but are very difficult to detect by ordinary means. Dwarf emission-line M stars experience flares with luminosities comparable to their quiescent photospheres on time scales of minutes, less than the light travel time across a disk many astronomical units in extent; they are thus ideal candidates for such a search. Bromley (1992) calculated that the detection of Jupiter-sized companions using light echoes requires photometric accuracies better than 1 part in 10(exp 6). However, a disk consisting of grains or small bodies will scatter a much larger fraction of the light than a planet of similar mass. I estimate the light echo amplitutdes from plausible geometries of circumstellar material and present simulation light curves. The light echo amplitudes are typically 1% of the flare and I conclude that such events will be detected best in cases where the flare is eclipsed by the star. An examination of the time scales associated with internal processes in a protoplanetary disks around dM stars indicates that any primordial disks may become undetectable in 10(exp 4) years and will have completely disappeared by 10(exp 8) years, the estimated age of dMe stars in the solar neighborhood. However, searches for light echoes might constrain the amount of material continuing to fall into these young stellar systems in the form of comet-like objects.

  1. Discrimination of complex synthetic echoes by an echolocating bottlenose dolphin.

    PubMed

    Helweg, David A; Moore, Patrick W; Dankiewicz, Lois A; Zafran, Justine M; Brill, Randall L

    2003-02-01

    Bottlenose dolphins (Tursiops truncatus) detect and discriminate underwater objects by interrogating the environment with their native echolocation capabilities. Study of dolphins' ability to detect complex (multihighlight) signals in noise suggest echolocation object detection using an approximate 265-micros energy integration time window sensitive to the echo region of highest energy or containing the highlight with highest energy. Backscatter from many real objects contains multiple highlights, distributed over multiple integration windows and with varying amplitude relationships. This study used synthetic echoes with complex highlight structures to test whether high-amplitude initial highlights would interfere with discrimination of low-amplitude trailing highlights. A dolphin was trained to discriminate two-highlight synthetic echoes using differences in the center frequencies of the second highlights. The energy ratio (delta dB) and the timing relationship (delta T) between the first and second highlights were manipulated. An iso-sensitivity function was derived using a factorial design testing delta dB at -10, -15, -20, and -25 dB and delta T at 10, 20, 40, and 80 micros. The results suggest that the animal processed multiple echo highlights as separable analyzable features in the discrimination task, perhaps perceived through differences in spectral rippling across the duration of the echoes. PMID:12597207

  2. Self-motion facilitates echo-acoustic orientation in humans

    PubMed Central

    Wallmeier, Ludwig; Wiegrebe, Lutz

    2014-01-01

    The ability of blind humans to navigate complex environments through echolocation has received rapidly increasing scientific interest. However, technical limitations have precluded a formal quantification of the interplay between echolocation and self-motion. Here, we use a novel virtual echo-acoustic space technique to formally quantify the influence of self-motion on echo-acoustic orientation. We show that both the vestibular and proprioceptive components of self-motion contribute significantly to successful echo-acoustic orientation in humans: specifically, our results show that vestibular input induced by whole-body self-motion resolves orientation-dependent biases in echo-acoustic cues. Fast head motions, relative to the body, provide additional proprioceptive cues which allow subjects to effectively assess echo-acoustic space referenced against the body orientation. These psychophysical findings clearly demonstrate that human echolocation is well suited to drive precise locomotor adjustments. Our data shed new light on the sensory–motor interactions, and on possible optimization strategies underlying echolocation in humans. PMID:26064556

  3. Modeling of Field-Aligned Guided Echoes in the Plasmasphere

    NASA Technical Reports Server (NTRS)

    Fung, Shing F.; Green, James L.

    2004-01-01

    The conditions under which high frequency (f>>f(sub uh)) long-range extraordinary-mode discrete field-aligned echoes observed by the Radio Plasma Imager (RPI) on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite in the plasmasphere are investigated by ray tracing modeling. Field-aligned discrete echoes are most commonly observed by RPI in the plasmasphere although they are also observed over the polar cap region. The plasmasphere field-aligned echoes appearing as multiple echo traces at different virtual ranges are attributed to signals reflected successively between conjugate hemispheres that propagate along or nearly along closed geomagnetic field lines. The ray tracing simulations show that field-aligned ducts with as little as 1% density perturbations (depletions) and less than 10 wavelengths wide can guide nearly field-aligned propagating high frequency X mode waves. Effective guidance of wave at a given frequency and wave normal angle (Psi) depends on the cross-field density scale of the duct, such that ducts with stronger density depletions need to be wider in order to maintain the same gradient of refractive index across the magnetic field. While signal guidance by field aligned density gradient without ducting is possible only over the polar region, conjugate field-aligned echoes that have traversed through the equatorial region are most likely guided by ducting.

  4. Cluster-enhanced sparse approximation of overlapping ultrasonic echoes.

    PubMed

    Mor, Etai; Aladjem, Mayer; Azoulay, Amnon

    2015-02-01

    Ultrasonic pulse-echo methods have been used extensively in non-destructive testing of layered structures. In acoustic measurements on thin layers, the resulting echoes from two successive interfaces overlap in time, making it difficult to assess the individual echo parameters. Over the last decade sparse approximation methods have been extensively used to address this issue. These methods employ a large dictionary of elementary functions (atoms) and attempt to select the smallest subset of atoms (sparsest approximation) that represent the ultrasonic signal accurately. In this paper we propose the cluster-enhanced sparse approximation (CESA) method for estimating overlapping ultrasonic echoes. CESA is specifically adapted to deal with a large number of signals acquired during an ultrasonic scan. It incorporates two principal algorithms. The first is a clustering algorithm, which divides a set of signals comprising an ultrasonic scan into groups of signals that can be approximated by the same set of atoms. The second is a two-stage iterative algorithm, which alternates between update of the atoms associated with each cluster, and re-clustering of the signals according to the updated atoms. Because CESA operates on clusters of signals, it achieves improved results in terms of approximation error and computation time compared with conventional sparse methods, which operate on each signal separately. The superior ability of CESA to approximate highly overlapping ultrasonic echoes is demonstrated through simulation and experiments on adhesively bonded structures. PMID:25643086

  5. The Light Echo around Supernova 2003gd in Messier 74

    NASA Astrophysics Data System (ADS)

    Van Dyk, Schuyler D.; Li, Weidong; Filippenko, Alexei V.

    2006-03-01

    We confirm the discovery of a light echo around the Type II-plateau supernova 2003gd in Messier 74 (NGC 628), seen in images obtained with the High Resolution Channel of the Advanced Camera for Surveys on board the Hubble Space Telescope (HST) as part of a larger Snapshot program on the late-time emission from supernovae. The analysis of the echo we present suggests that it is due to the SN light pulse scattered by a sheet of dust grains located ~113 pc in front of the SN, and that these grains are not unlike those assumed to be in the diffuse Galactic interstellar medium, both in composition and in size distribution. The echo is less consistent with scattering off carbon-rich grains, and if anything, the grains may be somewhat more silicate rich than the Galactic dust composition. The echo also appears to be more consistent with a SN distance closer to 7 Mpc than to 9 Mpc. This further supports the conclusion we reached elsewhere that the initial mass for the SN progenitor was relatively low (~8-9 Msolar). The HST should be used to continue to monitor the echo in several bands, particularly in the blue, to better constrain its origin. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555.

  6. Echo Meadows Project Winter Artificial Recharge.

    SciTech Connect

    Ziari, Fred

    2002-12-19

    This report discusses the findings of the Echo Meadows Project (BPA Project 2001-015-00). The main purpose of this project is to artificially recharge an alluvial aquifer, WITH water from Umatilla River during the winter high flow period. In turn, this recharged aquifer will discharge an increased flow of cool groundwater back to the river, thereby improving Umatilla River water quality and temperature. A considerable side benefit is that the Umatilla River should improve as a habitat for migration, spanning, and rearing of anadromous and resident fish. The scope of this project is to provide critical baseline information about the Echo Meadows and the associated reach of the Umatilla River. Key elements of information that has been gathered include: (1) Annual and seasonal groundwater levels in the aquifer with an emphasis on the irrigation season, (2) Groundwater hydraulic properties, particularly hydraulic conductivity and specific yield, and (3) Groundwater and Umatilla River water quality including temperature, nutrients and other indicator parameters. One of the major purposes of this data gathering was to develop input to a groundwater model of the area. The purpose of the model is to estimate our ability to recharge this aquifer using water that is only available outside of the irrigation season (December through the end of February) and to estimate the timing of groundwater return flow back to the river. We have found through the data collection and modeling efforts that this reach of the river had historically returned as much as 45 cubic feet per second (cfs) of water to the Umatilla River during the summer and early fall. However, this return flow was reduced to as low as 10 cfs primarily due to reduced quantities of irrigation application, gain in irrigation efficiencies and increased groundwater pumping. Our modeling indicated that it is possible to restore these critical return flows using applied water outside of the irrigation season. We further

  7. The EChO payload instrument - an overview

    NASA Astrophysics Data System (ADS)

    Eccleston, Paul; Swinyard, Bruce; Tessenyi, Marcel; Tinetti, Giovanna; Waldmann, Ingo; Ferlet, Marc; Irshad, Ranah; Lim, Tanya; Middleton, Kevin; Bradshaw, Tom; Crook, Martin; Hunt, Tom; Winter, Berend; Bryson, Ian; Bezawada, Naidu; Taylor, William; Bowles, Neil; Pascale, Enzo; Morgante, Gianluca; Pace, Emanuele; Adriani, Alberto; Reess, Jean-Michel; Ollivier, Marc; Ottensamer, Roland; Rataj, Mirek; Zapata, Gonzalo Ramos; Schrader, Jan-Rutger; Selig, Avri; Isaak, Kate; Linder, Martin; Puig, Ludovic

    2015-12-01

    The Exoplanet Characterisation Observatory (EChO) mission was one of the proposed candidates for the European Space Agency's third medium mission within the Cosmic Vision Framework. EChO was designed to observe the spectra from transiting exo-planets in the 0.55-11 micron band with a goal of covering from 0.4 to 16 micron. The mission and its associated scientific instrument has undergone a rigorous technical evaluation phase. This paper provides an overview of the payload instrument design for the mission, showing how the system acts together to fulfill the mission objectives. We report on the results of an extensive simulation of the instrument performance and show that EChO would have been photon noise dominated for targets from a faint limit similar to GJ1214 to the brightest targets similar to 55Cnc.

  8. Acoustic Echo Cancellation Using Sub-Adaptive Filter

    NASA Astrophysics Data System (ADS)

    Ohta, Satoshi; Kajikawa, Yoshinobu; Nomura, Yasuo

    In the acoustic echo canceller (AEC), the step-size parameter of the adaptive filter must be varied according to the situation if double talk occurs and/or the echo path changes. We propose an AEC that uses a sub-adaptive filter. The proposed AEC can control the step-size parameter according to the situation. Moreover, it offers superior convergence compared to the conventional AEC even when the double talk and the echo path change occur simultaneously. Simulations demonstrate that the proposed AEC can achieve higher ERLE and faster convergence than the conventional AEC. The computational complexity of the proposed AEC can be reduced by reducing the number of taps of the sub-adaptive filter.

  9. Auditory-tactile echo-reverberating stuttering speech corrector

    NASA Astrophysics Data System (ADS)

    Kuniszyk-Jozkowiak, Wieslawa; Adamczyk, Bogdan

    1997-02-01

    The work presents the construction of a device, which transforms speech sounds into acoustical and tactile signals of echo and reverberation. Research has been done on the influence of the echo and reverberation, which are transmitted as acoustic and tactile stimuli, on speech fluency. Introducing the echo or reverberation into the auditory feedback circuit results in a reduction of stuttering. A bit less, but still significant corrective effects are observed while using the tactile channel for transmitting the signals. The use of joined auditory and tactile channels increases the effects of their corrective influence on the stutterers' speech. The results of the experiment justify the use of the tactile channel in the stutterers' therapy.

  10. Echo-acoustic flow affects flight in bats.

    PubMed

    Kugler, Kathrin; Greiter, Wolfgang; Luksch, Harald; Firzlaff, Uwe; Wiegrebe, Lutz

    2016-06-15

    Flying animals need to react fast to rapid changes in their environment. Visually guided animals use optic flow, generated by their movement through structured environments. Nocturnal bats cannot make use of optic flow, but rely mostly on echolocation. Here, we show that bats exploit echo-acoustic flow to negotiate flight through narrow passages. Specifically, bats' flight between lateral structures is significantly affected by the echo-acoustic salience of those structures, independent of their physical distance. This is true even though echolocation, unlike vision, provides explicit distance cues. Moreover, the bats reduced the echolocation sound levels in stronger flow, probably to compensate for the increased summary target strength of the lateral reflectors. However, bats did not reduce flight velocity under stronger echo-acoustic flow. Our results demonstrate that sensory flow is a ubiquitous principle for flight guidance, independent of the fundamentally different peripheral representation of flow across the senses of vision and echolocation. PMID:27045094

  11. Echo-seeding options for LCLS-II

    SciTech Connect

    Xiang, D.; Stupakov, G.; /SLAC

    2010-09-14

    The success of LCLS has opened up a new era of x-ray sciences. An upgrade to LCLS is currently being planned to enhance its capabilities. In this paper we study the feasibility of using the echo-enabled harmonic generation (EEHG) technique to generate narrow bandwidth soft x-ray radiation in the proposed LCLS-II soft x-ray beam line. We focus on the conceptual design, the technical implementation and the expected performances of the echo-seeding scheme. We will also show how the echo-seeding scheme allows one to generate two color x-ray pulses with the higher energy photons leading the lower energy ones as is favored in the x-ray pump-probe experiments.

  12. Adiabatic passage in photon-echo quantum memories

    NASA Astrophysics Data System (ADS)

    Demeter, Gabor

    2013-11-01

    Photon-echo-based quantum memories use inhomogeneously broadened, optically thick ensembles of absorbers to store a weak optical signal and employ various protocols to rephase the atomic coherences for information retrieval. We study the application of two consecutive, frequency-chirped control pulses for coherence rephasing in an ensemble with a “natural” inhomogeneous broadening. Although propagation effects distort the two control pulses differently, chirped pulses that drive adiabatic passage can rephase atomic coherences in an optically thick storage medium. Combined with spatial phase-mismatching techniques to prevent primary echo emission, coherences can be rephased around the ground state to achieve secondary echo emission with close to unit efficiency. Potential advantages over similar schemes working with π pulses include greater potential signal fidelity, reduced noise due to spontaneous emission, and better capability for the storage of multiple memory channels.

  13. On the lack of southern hemisphere polar mesosphere summer echoes

    NASA Astrophysics Data System (ADS)

    Balsley, B. B.; Woodman, R. F.; Sarango, M.; RodríGuez, R.; Urbina, J.; Ragaini, E.; Carey, J.; Huaman, M.; Giraldez, A.

    1995-06-01

    We report VHF radar observations of the southern high-latitude mesopause region using wind profilers that were installed recently on King George Island, Antarctica, and Ushuaia, Argentina. Briefly, our observations, which were made during January and February 1993, show almost no evidence of so-called polar mesosphere summer echoes, or PMSE. Since these echoes are a predominant feature of the northern high-latitude mesosphere in summer, their absence in the southern hemisphere is both surprising and intriguing. In this paper we present evidence demonstrating the virtual absence of the echoes and demonstrate that our systems were capable of detecting them had they been present. We also outline some of the consequences of this intriguing result, which are supported by observed hemispheric differences in polar mesospheric clouds, mesospheric temperatures, upper atmospheric gravity wave activity, and mean circulation patterns.

  14. Polar Mesosphere Winter Echoes: Turbulence Versus Acoustic Waves

    NASA Astrophysics Data System (ADS)

    Belova, E.; Kirkwood, S.; Dalin, P. A.

    2013-12-01

    PMWE are strong echoes from 50-80 km altitudes seen by VHF radars in the equinox and winter seasons. The PMWE observational facts are controversial and the echo origin is still under debate. Two main hypotheses were proposed: one explains PMWE by scattering on turbulent structures and another one suggests these structures to be created by sound waves propagated from below. Strong PMWE are relatively rare phenomena, in most cases the radars observe them during extra ionisation in the lower ionosphere. The current solar maximum provides favourable conditions for PMWE observations and in winter 2012-2013 we collected PMWE data using a 50-MHz radar ESRAD located in the Northern Sweden. We will discuss how main characteristics of the echoes support turbulent or non-turbulent origin of PMWE.

  15. Multi-echo imaging in highly inhomogeneous magnetic fields.

    PubMed

    Casanova, F; Perlo, J; Blümich, B; Kremer, K

    2004-01-01

    A new pulsed field gradient multi-echo imaging technique to encode position in the phase of every echo generated by a CPMG sequence in the presence of a strongly inhomogeneous static magnetic field is presented. It was applied to improve the sensitivity in an imaging experiment by adding the echo train acquired during the CPMG sequence and to spatially resolve relaxation times of inhomogeneous specimens using single-sided probes. The sequence was implemented in a new bar-magnet MOUSE equipped with a gradient coil system to apply a pulsed magnetic field with a constant gradient along one spatial coordinate. An important reduction by a factor larger than two orders of magnitude in the acquisition time was obtained compared to the previously published single-point imaging technique. PMID:14675822

  16. Loschmidt echo in one-dimensional interacting Bose gases

    SciTech Connect

    Lelas, K.; Seva, T.; Buljan, H.

    2011-12-15

    We explore Loschmidt echo in two regimes of one-dimensional interacting Bose gases: the strongly interacting Tonks-Girardeau (TG) regime, and the weakly interacting mean-field regime. We find that the Loschmidt echo of a TG gas decays as a Gaussian when small (random and time independent) perturbations are added to the Hamiltonian. The exponent is proportional to the number of particles and the magnitude of a small perturbation squared. In the mean-field regime the Loschmidt echo shows richer behavior: it decays faster for larger nonlinearity, and the decay becomes more abrupt as the nonlinearity increases; it can be very sensitive to the particular realization of the noise potential, especially for relatively small nonlinearities.

  17. Properties of echo spectra observed by MST radars

    NASA Technical Reports Server (NTRS)

    Wakasugi, K.

    1983-01-01

    Turbulent scatter and Fresnel reflection are the fundamental echoing mechanisms to interpret the signals observed by Mesosphere-stratosphere-troposphere (MST) radars. Turbulent scattered echoes provide information about the turbulence structure and mean flow of the atmosphere. Observational results with VHF MST radars, however, show the importance of Fresnel reflection due to the infinite gradient of reflectivity at the edges of a scattering layer. This condition is excluded for the weak fluctuation models but it is still possible to include the observed aspect sensitivity by assuming an anisotropic structure of fluctuations. Another explanation of the aspect sensitivity observed by MST radars is advanced. Spectral estimates by the widely used periodogram were related to a four-dimensional spectrum of atmospheric fluctuations with anisotropic structure. Effects of the radar system such as antenna beam width, beam direction and Fast Fourier Transformations (FFT) data length were discussed for the anisotropic turbulent atmosphere. Echo parameters were also estimated.

  18. The EChO Visible and Near Infrared spectrometer

    NASA Astrophysics Data System (ADS)

    Adriani, A.; Bellucci, G.; Oliva, E.; Gambicorti, L.; Piccioni, G.; Pace, E.; Focardi, M.; Filacchione, G.; Pancrazzi, M.; Tozzi, A.; Del Vecchio, C.; Micela, G.

    2013-09-01

    The EChO Visible and Near Infrared (VNIR) spectrometer will able to cover the spectral range between 0.4 and 2.5 μm. It has to be designed to assure a resolving power of about 320 over whole spectral range. VNIR will be a spectrometer in a cross-dispersed configuration by using a combination of a diffraction grating and a prism to spread the light in different wavelengths and in a useful number of orders of diffraction. It will use a Mercury Cadmium Telluride detector to satisfy the requirements of low thermal noise and the EChO system to operate at the working temperature of 40-45K. The instrument will be interfaced to the telescope optics by optical fibers to assure an easier coupling and an easier colocation of the instrument inside the EChO optical bench.

  19. Light Echoes from Linear Filaments in Astronomical Settings

    NASA Astrophysics Data System (ADS)

    Zhong, Qi; Nemiroff, Robert J.

    2016-01-01

    Stellar flashes are known to create light echoes by scattering off ambient dust. Here light echoes from straight, linear, one-dimensional dust filaments are specifically considered in detail. On an infinite straight filament, a flash will necessarily create a superluminal spot pair creation event. The actual and perceived locations, speeds, and relative brightnesses of these diverging spot pairs are computed. On filaments of finite length, only one light spot will typically be seen. Geometries where this spot appears to move angularly toward the flash are shown to be possible. It is also shown that it is possible to completely orient a linear filament in three-dimensional space by recording two separated detections of the light-echo spot. Recoverable information in theory and in practice will be reviewed.

  20. Piston cylinder cell for high pressure ultrasonic pulse echo measurements

    NASA Astrophysics Data System (ADS)

    Kepa, M. W.; Ridley, C. J.; Kamenev, K. V.; Huxley, A. D.

    2016-08-01

    Ultrasonic techniques such as pulse echo, vibrating reed, or resonant ultrasound spectroscopy are powerful probes not only for studying elasticity but also for investigating electronic and magnetic properties. Here, we report on the design of a high pressure ultrasonic pulse echo apparatus, based on a piston cylinder cell, with a simplified electronic setup that operates with a single coaxial cable and requires sample lengths of mm only. The design allows simultaneous measurements of ultrasonic velocities and attenuation coefficients up to a pressure of 1.5 GPa. We illustrate the performance of the cell by probing the phase diagram of a single crystal of the ferromagnetic superconductor UGe2.

  1. Piston cylinder cell for high pressure ultrasonic pulse echo measurements.

    PubMed

    Kepa, M W; Ridley, C J; Kamenev, K V; Huxley, A D

    2016-08-01

    Ultrasonic techniques such as pulse echo, vibrating reed, or resonant ultrasound spectroscopy are powerful probes not only for studying elasticity but also for investigating electronic and magnetic properties. Here, we report on the design of a high pressure ultrasonic pulse echo apparatus, based on a piston cylinder cell, with a simplified electronic setup that operates with a single coaxial cable and requires sample lengths of mm only. The design allows simultaneous measurements of ultrasonic velocities and attenuation coefficients up to a pressure of 1.5 GPa. We illustrate the performance of the cell by probing the phase diagram of a single crystal of the ferromagnetic superconductor UGe2. PMID:27587156

  2. Study of simulating dynamic polarization laser echo signal

    NASA Astrophysics Data System (ADS)

    Yang, Di; Liu, Qing; Zhan, Yong-hong; Zeng, Chang-e.

    2014-12-01

    In the test for the laser seeker in the hardware-in-loop simulation, acquiring the effect of polarization laser echo wave to optical stress polarization of the seeker and to the polarization guidance performance was not considered. A new method to generating the dynamic polarization laser echo signal was provided based on the scene model; furthermore, the method to adding the polarization characters to the energy scene was introduced. At last, the insufficient of the method to generating and simulating the dynamic polarization signal was analyzed.

  3. Quantification of severe liver iron overload using MRI offset echoes

    PubMed Central

    Rydén, Henric

    2015-01-01

    Magnetic resonance imaging (MRI) has become the clinical standard to estimate liver iron overload. The most commonly used method is to measure the transversal relaxation time, T2*, from a multi gradient recalled echo sequence (MGRE). While this technique is reliable in low to moderate liver iron concentrations (LIC), it will be inaccurate when it is severe. We report a case with severe liver hemochromatosis and show the benefit of using an easily implemented MRI offset echo sequence to more accurately estimate LIC. After adjusting treatment, both Ferritin and LIC decreased. Using standard MGRE this reduction could not have been detected. PMID:26060576

  4. Spectrally resolved photon-echo spectroscopy of Rhodamine-6G

    PubMed Central

    Kumar, Ajitesh; Karthick, S. K.; Goswami, D.

    2013-01-01

    Wavelength dependent study of a laser dye: Rhodamine-6G (Rh6G) by using spectrally resolved photon-echo spectroscopy is presented. The coherence and population dynamics of Rh6G solution in methanol changes as the excitation wavelength is tuned near its absorption maxima of 528 nm. Specifically, the central wavelength of the femtosecond laser pulse was set to 535 nm and to 560 nm while the respective spectra of the photon-echo signals were collected. This gives information on how the ultrafast dynamics of the Rh6G molecule changes with a change in the excitation wavelength. PMID:24098869

  5. Echo-to-reverberation enhancement using a time reversal mirror

    NASA Astrophysics Data System (ADS)

    Kim, S.; Kuperman, W. A.; Hodgkiss, W. S.; Song, H. C.; Edelmann, G.; Akal, T.

    2004-04-01

    Reverberation from rough ocean boundaries often degrades the performance of active sonar systems in the ocean. The focusing capability of the time-reversal method provides a new approach to this problem. A time-reversal mirror (TRM) focuses acoustic energy on a target enhancing the target echo while shadowing the boundaries below and above the focus in a waveguide, thereby reducing reverberation. The resulting echo-to-reverberation enhancement has been demonstrated experimentally using a time-reversal mirror in the 3-4 kHz band in shallow water.

  6. Fish target strength estimation using multiple echo statistics

    NASA Astrophysics Data System (ADS)

    Moszynski, M.

    2002-03-01

    When fish strength is estimated indirectly from the sounder echo amplitudes, the inverse techniques of solving the so-called “single-beam integral equation” are quite satisfactorily used. This approach needs prior knowledge of the beam pattern PDF, as it represents the kernel of the integral equation to be solved and is usually calculated under the assumption of a uniform spatial distribution of fish. However, it may be shown that in some cases this assumption is not necessarily justified. For instance, when the density of fish increases, one receives multiple echoes from the same single fish in successive transmissions, which results in observing so-called fish echo traces. Typically used fish counting methods are either simple direct echo counting statistics or fish traces statistics [1]. Increased fish concentration is not only the reason of multiple echo formation resulting in the fish traces in consecutive pings. As it is easily seen from the geometry of the phenomenon, even a relatively low-density fish aggregation forms multiple echoes and, hence, fish traces if the vessel (or fish) relative speed is low enough and the beam pattern angular width (sampling volume) is large enough. In some situations, the uniform assumption works properly only for the cases of large numbers of samples. Taking into account this phenomenon, the accuracy of the solution can be improved by including the fish traces counting statistics in calculating the beam pattern PDF. In this paper, two different models of fish traces statistics are investigated: one assuming the vessel movement with stationary fish and the other with a stationary vessel and moving fish. Both approaches are modeled numerically and verified experimentally using the data obtained from a dual-beam system. The comparison of both approaches, i.e., for single echo traces and multiple echoes, is carried out using Windowed Singular Value Decomposition (WSVD) and Expectation Maximization and Smoothing (EMS) inverse

  7. Quantification of severe liver iron overload using MRI offset echoes.

    PubMed

    Rydén, Henric; Skorpil, Mikael

    2015-05-01

    Magnetic resonance imaging (MRI) has become the clinical standard to estimate liver iron overload. The most commonly used method is to measure the transversal relaxation time, T2*, from a multi gradient recalled echo sequence (MGRE). While this technique is reliable in low to moderate liver iron concentrations (LIC), it will be inaccurate when it is severe. We report a case with severe liver hemochromatosis and show the benefit of using an easily implemented MRI offset echo sequence to more accurately estimate LIC. After adjusting treatment, both Ferritin and LIC decreased. Using standard MGRE this reduction could not have been detected. PMID:26060576

  8. Spearhead echo and downburst in the crash of an airliner

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.; Byers, H. R.

    1977-01-01

    Meteorological conditions leading to the crash of an airliner short of the runway of a New York airport were studied. Thunderstorm downdrafts much stronger than those measured on the 1946-47 Thunderstorm Project were found. These exceptional downdrafts have been designated as 'downbursts'. The violent cloud systems that produce downburst cells can be identified in the form of forward extensions of radar echoes designed as 'spearhead echoes' which move with unusual speed. The development of downburst cells appears to be tied in with overshooting tops of clouds at the anvil level.

  9. Code division in optical memory devices based on photon echo

    NASA Astrophysics Data System (ADS)

    Kalachev, Alexey A.; Vlasova, Daria D.

    2006-03-01

    The theory of multi-channel optical memory based on photon echo is developed. It is shown that under long-lived photon echo regime the writing and reading of information with code division is possible using phase modulation of reference and reading pulses. A simple method for construction of a system of noise-like signals, which is based on the segmentation of Frank sequence is proposed. It is shown that in comparison to the system of random biphase signals this system leads to the efficient decreasing of mutual influence of channels and increasing of random/noise ratio under reading of information.

  10. Cavitation inception from bubble nuclei.

    PubMed

    Mørch, K A

    2015-10-01

    The tensile strength of ordinary water such as tap water or seawater is typically well below 1 bar. It is governed by cavitation nuclei in the water, not by the tensile strength of the water itself, which is extremely high. Different models of the nuclei have been suggested over the years, and experimental investigations of bubbles and cavitation inception have been presented. These results suggest that cavitation nuclei in equilibrium are gaseous voids in the water, stabilized by a skin which allows diffusion balance between gas inside the void and gas in solution in the surrounding liquid. The cavitation nuclei may be free gas bubbles in the bulk of water, or interfacial gaseous voids located on the surface of particles in the water, or on bounding walls. The tensile strength of these nuclei depends not only on the water quality but also on the pressure-time history of the water. A recent model and associated experiments throw new light on the effects of transient pressures on the tensile strength of water, which may be notably reduced or increased by such pressure changes. PMID:26442138

  11. Quadrupolar transients, cosine correlation functions, and two-dimensional exchange spectra of non-selectively excited spin-3/2 nuclei: A 7Li NMR study of the superionic conductor lithium indium phosphate

    NASA Astrophysics Data System (ADS)

    Storek, M.; Böhmer, R.

    2015-11-01

    Cos-cos stimulated echoes of non-selectively excited spin-3/2 nuclei were not exploited in studies of slow motional processes in solids and solid-like samples, so far. Based on a theoretical analysis of the quadrupolar transients which hitherto obviously precluded the application of such echoes, their utility is demonstrated for the example of 7Li NMR on the polycrystalline fast ion conductor lithium indium phosphate. Quadrupolar transients can adversely affect the shape of two- and three-pulse echo spectra and strategies are successfully tested that mitigate their impact. Furthermore, by means of suitably adapted cos-cos echo sequences an effective suppression of central-line contributions to the NMR spectra is achieved. By combining cos-cos and sin-sin datasets static two-dimensional exchange spectra were recorded that display quadrupolarly modulated off-diagonal intensity indicative of ionic motion.

  12. Photodissociation of neutron deficient nuclei

    NASA Astrophysics Data System (ADS)

    Sonnabend, K.; Babilon, M.; Hasper, J.; Müller, S.; Zarza, M.; Zilges, A.

    2006-03-01

    The knowledge of the cross sections for photodissociation reactions like e.g. (γ, n) of neutron deficient nuclei is of crucial interest for network calculations predicting the abundances of the so-called p nuclei. However, only single cross sections have been measured up to now, i.e., one has to rely nearly fully on theoretical predictions. While the cross sections of stable isotopes are accessible by experiments using real photons, the bulk of the involved reactions starts from unstable nuclei. Coulomb dissociation (CD) experiments in inverse kinematics might be a key to expand the experimental database for p-process network calculations. The approach to test the accuracy of the CD method is explained.

  13. Polarized EMC Effect in Nuclei

    SciTech Connect

    Ian Cloet; A. W. Thomas; W. Bentz

    2006-06-05

    The discovery of the EMC effect and the proton spin crisis by the European Muon Collaboration are two of the standout experiments of the last 25 years. It is therefore surprising that there has been no experimental and little theoretical investigation of the spin structure functions of atomic nuclei. To address this we present results for the spin-dependent structure functions of nuclei. The quark degrees of freedom in nuclei are accessed via the convolution formalism. Where the nucleon bound state is obtained by solving the relativistic Faddeev equation, and a relativistic shell model is used to model the atomic nucleus. We find the important result that the medium modifications to the polarized structure functions are about twice that of the unpolarized case.

  14. Level densities of heaviest nuclei

    NASA Astrophysics Data System (ADS)

    Bezbakh, A. N.; Shneidman, T. M.; Adamian, G. G.; Antonenko, N. V.

    2014-06-01

    The intrinsic level densities of superheavy nuclei in the α-decay chains of 296,298,300120 are calculated using the single-particle spectra obtained with the modified two-center shell model. The role of the shell and pairing effects on the level density as well as their quenching with excitation energy are studied. The extracted level density parameter is expressed as a function of mass number, ground-state shell correction, and excitation energy. The results are compared with the phenomenological values of level density parameters used to calculate the survival of excited heavy nuclei.

  15. Colored models for anomalous nuclei

    SciTech Connect

    Watson, P.J.S.; Saly, R.; Romo, W.J.; Sundaresan, M.K.; Campbell, B.; Elias, V.

    1983-04-01

    There seems to be good experimental evidence that anomalous nuclei are produced in heavy-ion collisions; they are anomalous in that they have an abnormally short mean free path, for example, in nuclear emulsions. Here we consider the possibility that anomalous nuclei are combinations of a colored anomalous particle fragment (based on theories with spontaneous breakdown of color symmetry) with ordinary nucleons. Phenomenological implications of various possible models in which the anomalous particle fragment is considered to be a colored particle with the color symmetry SU(3)/sub c/ explicitly broken are given.

  16. Neutron scattering on deformed nuclei

    NASA Astrophysics Data System (ADS)

    Hansen, L. F.; Haight, R. C.; Pohl, B. A.; Wong, C.; Lagrange, Ch.

    1985-01-01

    Measurements of neutron elastic and inelastic differential cross sections around 14 MeV for 9Be, C, 181Ta, 232Th, 238U, and 239Pu have been analyzed using a coupled channel (CC) formalism for deformed nuclei and phenomenological global optical model potentials (OMP). For the actinide targets these results are compared with the predictions of a semi-microscopic calculation using Jeukenne, Lejeune, and Mahaux (JLM) microscopic OMP and a deformed ground state nuclear density. The overall agreement between calculations and the measurements is reasonably good even for the very light nuclei, where the quality of the fits is better than those obtained with spherical OMP.

  17. Octupole shapes in heavy nuclei

    SciTech Connect

    Ahmad, I.

    1994-08-01

    Theoretical calculations and measurements show the presence of strong octupole correlations in thecyround states and low-lying states of odd-mass and odd-odd nuclei in the RaPa region. Evidence for octupole correlations is provided by the observation of parity doublets and reductions in M1 matrix elements, decoupling parameters, and Coriolis matrix elements Involving high-j states. Enhancement of E1 transition rates has also been observed for some of the octupole deformed nuclei. The most convincing argument for octupole deformation is provided by the similarities of the reduced alpha decay rates to the two members of parity doublets.

  18. Harmonic Components Based Post-Filter Design for Residual Echo Suppression

    NASA Astrophysics Data System (ADS)

    Lee, Minwoo; Lee, Yoonjae; Kim, Kihyeon; Ko, Hanseok

    In this Letter, a residual acoustic echo suppression method is proposed to enhance the speech quality of hands-free communication in an automobile environment. The echo signal is normally a human voice with harmonic characteristics in a hands-free communication environment. The proposed algorithm estimates the residual echo signal by emphasizing its harmonic components. The estimated residual echo is used to obtain the signal-to-interference ratio (SIR) information at the acoustic echo canceller output. Then, the SIR based Wiener post-filter is constructed to reduce both the residual echo and noise. The experimental results confirm that the proposed algorithm is superior to the conventional residual echo suppression algorithm in terms of the echo return loss enhancement (ERLE) and the segmental signal-to-noise ratio (SEGSNR).

  19. Spin-echo sup 1 H NMR studies of differential mobility in gizzard myosin and its subfragments

    SciTech Connect

    Sommervile, L.E. ); Henry, G.D.; Sykes, B.D. ); Harshorne, D.J. )

    1990-12-01

    The unexpectedly narrow resonances in the {sup 1}H NMR spectra of gizzard myosin, heavy meromyosin, and subfragment 1 were examined by spin-echo NMR spectroscopy. These resonances originated predominantly in the myosin heads, or subfragment 1 units. Smooth muscle myosin undergoes a dramatic change in hydrodynamic properties and can exist either as a folded (10S) or as an extended (6S) species. Factors that influence this transition, namely, ionic strength and phosphorylation (or thiophosphorylation), were varied in the NMR experiments. T{sub 2} relaxation experiments on dephosphorylated myosin indicated several components of different relaxation times that were not influenced by changes in ionic strength. The experiments focused on the components with longer relaxation times, i.e., corresponding to nuclei with more mobility, and these were observed selectively in a spin-echo experiment. With dephosphorylated myosin and HMM, increases in ionic strength caused an increased intensity in several of the narrower resonances. The ionic strength dependence of these changes paralleled that for the 10S and 6S transition. With thiophosphorylated myosin and HMM, changes in ionic strength also influenced the intensities of the narrower resonances, and in addition changes in the {sup 1}H NMR spectrum due to thiophosphorylation were observed. These results suggest that a fraction of the {sup 1}H resonances in smooth muscle myosin and its fragments originates from both aliphatic and aromatic residues of increased mobility compared to the mobility expected from hydrodynamic properties of these proteins.

  20. Echoed time series predictions, neural networks and genetic algorithms

    NASA Astrophysics Data System (ADS)

    Conway, A.

    This work aims to illustrate a potentially serious and previously unrecognised problem in using Neural Networks (NNs), and possibly other techniques, to predict Time Series (TS). It also demonstrates how a new training scheme using a genetic algorithm can alleviate this problem. Although it is already established that NNs can predict TS such as Sunspot Number (SSN) with reasonable success, the accuracy of these predictions is often judged solely by an RMS or related error. The use of this type of error overlooks the presence of what we have termed echoing, where the NN outputs its most recent input as its prediction. Therefore, a method of detecting echoed predictions is introduced, called time-shifting. Reasons for the presence of echo are discussed and then related to the choice of TS sampling. Finally, a new specially designed training scheme is described, which is a hybrid of a genetic algorithm search and back propagation. With this method we have successfully trained NNs to predict without any echo.

  1. The first satellite laser echoes recorded on the streak camera

    NASA Technical Reports Server (NTRS)

    Hamal, Karel; Prochazka, Ivan; Kirchner, Georg; Koidl, F.

    1993-01-01

    The application of the streak camera with the circular sweep for the satellite laser ranging is described. The Modular Streak Camera system employing the circular sweep option was integrated into the conventional Satellite Laser System. The experimental satellite tracking and ranging has been performed. The first satellite laser echo streak camera records are presented.

  2. A Windowing Frequency Domain Adaptive Filter for Acoustic Echo Cancellation

    NASA Astrophysics Data System (ADS)

    Wu, Sheng; Qiu, Xiaojun

    This letter proposes a windowing frequency domain adaptive algorithm, which reuses the filtering error to apply window function in the filter updating symmetrically. By using a proper window function to reduce the negative influence of the spectral leakage, the proposed algorithm can significantly improve the performance of the acoustic echo cancellation for speech signals.

  3. Participatory Culture at the Echo Park Film Center

    ERIC Educational Resources Information Center

    Rosales, Jennifer Ann

    2013-01-01

    The Echo Park Film Center, a Los Angeles nonprofit media education organization, teaches underprivileged youth how to comprehend and make media in order to empower them to speak and be heard. Due to the organization's nonmainstream media courses and its connection to its community, the Center is able to create a participatory and socially…

  4. Scheduling the EChO survey with known exoplanets

    NASA Astrophysics Data System (ADS)

    Morales, J. C.; Beaulieu, J.-P.; Coudé du Foresto, V.; Ollivier, M.; Castello, I. Ortega; Clédassou, R.; Jaubert, J.; Van-Troostenberghe, P.; Varley, R.; Waldmann, I. P.; Pascale, E.; Tessenyi, M.

    2015-12-01

    The Exoplanet Characterization Observatory ( EChO) is a concept of a dedicated space telescope optimized for low-resolution transit and occultation spectroscopy to study the exoplanet diversity through the composition of their atmospheres. The scope of this paper is to answer the following question: Can we schedule a nominal EChO mission, with targets known today (in mid 2013), given the science requirements, realistic performances and operational constraints? We examine this issue from the point of view of duration of the mission and the scheduling restrictions with a sample of exoplanet systems known nowadays. We choose different scheduling algorithms taking into account the science and operational constraints and we verified that it is fairly straightforward to schedule a mission scenario over the lifetime of EChO compliant with the science requirements. We identified agility as a critical constraint that reduces significantly the efficiency of the survey. We conclude that even with known targets today the EChO science objectives can be reached in the 4.5 years duration of the mission. We also show that it is possible to use gaps between exoplanet observations, to fit the required calibration observations, data downlinks and station keeping operations or even to observe more exoplanet targets to be discovered in the coming years.

  5. Echo thresholds for reflections from acoustically diffusive architectural surfaces.

    PubMed

    Robinson, Philip W; Walther, Andreas; Faller, Christof; Braasch, Jonas

    2013-10-01

    When sound reflects from an irregular architectural surface, it spreads spatially and temporally. Extensive research has been devoted to prediction and measurement of diffusion, but less has focused on its perceptual effects. This paper examines the effect of temporal diffusion on echo threshold. There are several notable differences between the waveform of a reflection identical to the direct sound and one from an architectural surface. The onset and offset are damped and the energy is spread in time; hence, the reflection response has a lower peak amplitude, and is decorrelated from the direct sound. The perceptual consequences of these differences are previously undocumented. Echo threshold tests are conducted with speech and music signals, using direct sound and a simulated reflection that is either identical to the direct sound or has various degrees of diffusion. Results indicate that for a speech signal, diffuse reflections are less easily detectable as a separate auditory event than specular reflections of the same total energy. For a music signal, no differences are observed between the echo thresholds for reflections with and without temporal diffusion. Additionally, echo thresholds are found to be shorter for speech than for music, and shorter for spatialized than for diotic presentation of signals. PMID:24116414

  6. The Baby Boom Echo: Implications for School Enrollments and Programs.

    ERIC Educational Resources Information Center

    ERS Spectrum, 1996

    1996-01-01

    Based on NCES statistics, the school-age population (the baby boom echo) will pose major challenges for education. Between 1996 and 2006, total public and private school enrollment will rise from a record 51.7 million to 54.6 million. The nation will need 190,000 additional teachers, 6,000 more schools, and $15 billion in additional annual…

  7. 21 CFR 892.1560 - Ultrasonic pulsed echo imaging system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ultrasonic pulsed echo imaging system. 892.1560 Section 892.1560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... pulsed sound beam into body tissue to determine the depth or location of the tissue interfaces and...

  8. 21 CFR 892.1560 - Ultrasonic pulsed echo imaging system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ultrasonic pulsed echo imaging system. 892.1560 Section 892.1560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... pulsed sound beam into body tissue to determine the depth or location of the tissue interfaces and...

  9. 21 CFR 892.1560 - Ultrasonic pulsed echo imaging system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ultrasonic pulsed echo imaging system. 892.1560 Section 892.1560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... pulsed sound beam into body tissue to determine the depth or location of the tissue interfaces and...

  10. 21 CFR 892.1560 - Ultrasonic pulsed echo imaging system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ultrasonic pulsed echo imaging system. 892.1560 Section 892.1560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... pulsed sound beam into body tissue to determine the depth or location of the tissue interfaces and...

  11. Spectrally resolved femtosecond photon echo spectroscopy of astaxanthin

    NASA Astrophysics Data System (ADS)

    Kumar, Ajitesh; Karthick Kumar, S. K.; Gupta, Aditya; Goswami, Debabrata

    2010-12-01

    We have studied the coherence and population dynamics of Astaxanthin solution in methanol and acetonitrile by spectrally resolving their photon echo signals. Our experiments indicate that methanol has a much stronger interaction with the ultrafast dynamics of Astaxanthin in comparison to that of acetonitrile.

  12. Spectrally resolved femtosecond photon echo spectroscopy of astaxanthin

    NASA Astrophysics Data System (ADS)

    Kumar, Ajitesh; Karthick Kumar, S. K.; Gupta, Aditya; Goswami, Debabrata

    2011-08-01

    We have studied the coherence and population dynamics of Astaxanthin solution in methanol and acetonitrile by spectrally resolving their photon echo signals. Our experiments indicate that methanol has a much stronger interaction with the ultrafast dynamics of Astaxanthin in comparison to that of acetonitrile.

  13. Pulse-echo probe of rock permeability near oil wells

    NASA Technical Reports Server (NTRS)

    Narasimhan, K. Y.; Parthasarathy, S. P.

    1978-01-01

    Processing method involves sequential insonifications of borehole wall at number of different frequencies. Return signals are normalized in amplitude, and root-mean-square (rms) value of each signal is determined. Values can be processed to yield information on size and number density of microfractures at various depths in rock matrix by using averaging methods developed for pulse-echo technique.

  14. Larry Echo Hawk: A Rising Star from Idaho.

    ERIC Educational Resources Information Center

    Wisecarver, Charmaine

    1993-01-01

    Larry Echo Hawk, Idaho attorney general and former state legislator, discusses success factors in college and law school; early experiences as an Indian lawyer; first election campaign; and his views on tribal sovereignty, state-tribal relationship, gambling, and his dual responsibility to the general public and Native American issues. (SV)

  15. Exotic nuclei and nuclear forces

    NASA Astrophysics Data System (ADS)

    Otsuka, Takaharu

    2013-01-01

    I overview new aspects of the structure of exotic nuclei as compared to stable nuclei, focusing on several characteristic effects of nuclear forces. The shell structure of nuclei has been proposed by Mayer and Jensen, and has been considered to be kept valid basically for all nuclei, with well-known magic numbers, 2, 8, 20, 28, 50, …. Nuclear forces were shown, very recently, to change this paradigm. It will be presented that the evolution of shell structure occurs in various ways as more neutrons and/or protons are added, and I will present basic points of this shell evolution in terms of the monopole interaction of nuclear forces. I will discuss three types of nuclear forces. The first one is the tensor force. The tensor force is one of the most fundamental nuclear forces, but its first-order effect on the shell structure has been clarified only recently in studies on exotic nuclei. The tensor force can change the spin-orbit splitting depending on the occupation of specific orbits. This results in changes of the shell structure in many nuclei, and consequently some of Mayer-Jensen's magic numbers are lost and new ones emerge, in certain nuclei. This mechanism can be understood in an intuitive way, meaning that the effect is general and robust. The second type of nuclear forces is central force. I will show a general but unknown property of the central force in the shell-model Hamiltonian that can describe nuclear properties in a good agreement with experiment. I will then demonstrate how it can be incorporated into a simple model of the central force, and will discuss how this force works in the shell evolution. Actually, by combining this central force with the tensor force, one can understand and foresee how the same proton-neutron interaction drives the shell evolution, for examples such as Sn/Sb isotopes, N = 20 nuclei and Ni/Cu isotopes. The distribution of single-particle strength is discussed also in comparison to (e,e‧p) experiment on 48Ca. The shell

  16. Bright Lower Echo in Radargram of South Polar Layered Deposits

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Annotated Version

    The upper image is a radargram from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), showing data from the subsurface of Mars in the ice-rich layered deposits that surround the south pole. The lower image shows the position of the ground track (white line) on a topographic map of the area based on Mars Orbiter Laser Altimeter data. The images are 1,250 kilometers (775 miles) wide.

    The MARSIS echo trace splits into two traces on the left side of the image, at the point where the ground track crosses from the surrounding plains onto the elevated layered deposits. The upper trace is the echo from the surface of the deposits, while the lower trace is interpreted to be the boundary between the lower surface of the deposits and the underlying material. The strength of the lower echo suggests that the intervening material is nearly pure water ice. Near the image center, the bright lower echo abruptly disappears for unknown reasons. The time delay between the two echoes reaches a maximum of 42 microseconds left of center, corresponding to a thickness of 3.5 kilometers (2.2 miles) of ice. The total elevation difference shown in the topographic map is about 4 kilometers (2.5 miles) between the lowest surface (purple) and the highest (red).

    MARSIS is an instrument on the European Space Agency's Mars Express orbiter. NASA and the Italian Space Agency jointly funded the instrument. The Mars Orbiter Laser Altimeter flew on NASA's Mars Global Surveyor orbiter.

  17. A Year in the Life of an Infrared Echo

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure 1: Supernova Remnant Cassiopeia A One Year Apart

    These Spitzer Space Telescope images, taken one year apart, show the supernova remnant Cassiopeia A (yellow ball) and surrounding clouds of dust (reddish orange). The pictures illustrate that a blast of light from Cassiopeia A is waltzing outward through the dusty skies. This dance, called an 'infrared echo,' began when the remnant erupted about 50 years ago.

    Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion 325 years ago. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died. This remnant is located 10,000 light-years away in the northern constellation Cassiopeia.

    Infrared echoes are created when a star explodes or erupts, flashing light into surrounding clumps of dust. As the light zips through the dust clumps, it heats them up, causing them to glow successively in infrared, like a chain of Christmas bulbs lighting up one by one. The result is an optical illusion, in which the dust appears to be flying outward at the speed of light. Echoes are distinct from supernova shockwaves, which are made up material that is swept up and hurled outward by exploding stars.

    This infrared echo is the largest ever seen, stretching more than 50 light-years away from Cassiopeia A. If viewed from Earth, the entire movie frame would take up the same amount of space as two full moons.

    Hints of an older infrared echo from Cassiopeia A's supernova explosion hundreds of years ago can also be seen.

    The top Spitzer image was taken on November 30, 2003, and the bottom, on December 2, 2004.

  18. Use of earth field spin echo NMR to search for liquid minerals

    DOEpatents

    Stoeffl, Wolfgang

    2001-01-01

    An instrument for measuring the spatial, qualitative and quantitative parameters of an underground nuclear magnetic resonance (NMR) active liquid mineral deposit, including oil and water. A phased array of excitation and receiver antennas on the surface and/or in a borehole excites the NMR active nuclei in the deposit, and using known techniques from magnetic resonance imaging (MRI), the spatial and quantitative distribution of the deposit can be measured. A surface array may utilize, for example, four large (50-500 diameter) diameter wire loops laid on the ground surface, and a weak (1.5-2.5 kHz) alternating current (AC) field applied, matching the NMR frequency of hydrogen in the rather flat and uniform earth magnetic field. For a short duration (a few seconds) an additional gradient field can be generated, superimposed to the earth field, by applying direct current (DC) to the grid (wire loops), enhancing the position sensitivity of the spin-echo and also suppressing large surface water signals by shifting them to a different frequency. The surface coil excitation can be combined with downhole receivers, which are much more radio-quiet compared to surface receivers, and this combination also enhances the position resolution of the MRI significantly. A downhole receiver module, for example, may have a 5.5 inch diameter and fit in a standard six inch borehole having a one-quarter inch thick stainless steel casing. The receiver module may include more than one receiver units for improved penetration and better position resolution.

  19. Electromagnetic structure of light nuclei

    DOE PAGESBeta

    Pastore, Saori

    2016-03-25

    Here, the present understanding of nuclear electromagnetic properties including electromagnetic moments, form factors and transitions in nuclei with A ≤ 10 is reviewed. Emphasis is on calculations based on nuclear Hamiltonians that include two- and three-nucleon realistic potentials, along with one- and two-body electromagnetic currents derived from a chiral effective field theory with pions and nucleons.

  20. Proton Distribution in Heavy Nuclei

    DOE R&D Accomplishments Database

    Johnson, M. H; Teller, E.

    1953-11-13

    It is reasoned that, from considerations connected with beta-decay stability and Coulomb repulsion forces, a neutron excess is developed on the surface of heavy nuclei. Several consequences of this qualitative analysis in nucleon interactions are briefly noted. (K.S.)

  1. Octupole correlation effects in nuclei

    SciTech Connect

    Chasman, R.R.

    1992-08-01

    Octupole correlation effects in nuclei are discussed from the point of view of many-body wavefunctions as well as mean-field methods. The light actinides, where octupole effects are largest, are considered in detail. Comparisons of theory and experiment are made for energy splittings of parity doublets; E1 transition matrix elements and one-nucleon transfer reactions.

  2. Octupole correlation effects in nuclei

    SciTech Connect

    Chasman, R.R.

    1992-01-01

    Octupole correlation effects in nuclei are discussed from the point of view of many-body wavefunctions as well as mean-field methods. The light actinides, where octupole effects are largest, are considered in detail. Comparisons of theory and experiment are made for energy splittings of parity doublets; E1 transition matrix elements and one-nucleon transfer reactions.

  3. Transitional nuclei near shell closures

    SciTech Connect

    Mukherjee, G.

    2014-08-14

    High spin states in Bismuth and Thallium nuclei near the Z = 82 shell closure and Cesium nuclei near the N = 82 shell closure in A = 190 and A = 130 regions, respectively, have been experimentally investigated using heavy-ion fusion evaporation reaction and by detecting the gamma rays using the Indian National Gamma Array (INGA). Interesting shape properties in these transitional nuclei have been observed. The results were compared with the neighboring nuclei in these two regions. The total Routhian surface (TRS) calculations have been performed for a better understanding of the observed properties. In mass region A = 190, a change in shape from spherical to deformed has been observd around neutron number N = 112 for the Bi (Z = 83) isotopes with proton number above the magic gap Z = 82, whereas, the shape of Tl (Z = 81) isotopes with proton number below the magic gap Z = 82 remains stable as a function of neutron number. An important transition from aplanar to planar configuration of angular momentum vectors leading to the occurance of nuclar chirality and magnetic rotation, respectively, has been proposed for the unique parity πh{sub 11/2}⊗νh{sub 11/2} configuration in Cs isotopes in the mass region A ∼ 130 around neutron number N = 79. These results are in commensurate with the TRS calculations.

  4. International Symposium on Exotic Nuclei

    NASA Astrophysics Data System (ADS)

    Penionzhkevich, Yu. E.; Cherepanov, E. A.

    Methods of production of light exotic nuclei and study of their ptoperties -- Superheavy elements. Syhnthesis and properties -- Nuclear fission -- Nuclear reactions -- rare processes, decay and nuclear structure -- Experimental set-ups and future projects -- Radioactive beams. Production and research programmes -- Public relations.

  5. Clutter interference and the integration time of echoes in the echolocating bat, Eptesicus fuscus.

    PubMed

    Simmons, J A; Freedman, E G; Stevenson, S B; Chen, L; Wohlgenant, T J

    1989-10-01

    The ability of the echolocating bat, Eptesicus fuscus, to detect a sonar target is affected by the presence of other targets along the same axis at slightly different ranges. If echoes from one target arrive at about the same delay as echoes from another target, clutter interference occurs and one set of echoes masks the other. Although the bat's sonar emissions and the echoes themselves are 2 to 5 ms long, echoes (of approximately equal sensation levels--around 15 dB SL) only interfere with each other if they arrive within 200 to 400 microseconds of the same arrival time. This figure is an estimate of the integration time of the bat's sonar receiver for echoes. The fine structure of the clutter-interference data reflects the reinforcement and cancellation of echoes according to their time separation. When clutter interference first occurs, the waveforms of test and cluttering echoes already overlap for much of their duration. The masking effect underlying clutter interference appears specifically due to overlap, not between raw echo waveforms, but between the patterns of mechanical excitation created when echoes pass through bandpass filters equivalent to auditory-nerve tuning curves. While the time scale of clutter interference is substantially shorter than the duration of echo waveforms, it still is much longer than the eventual width of a target's range-axis image expressed in terms of echo delay. PMID:2808907

  6. Detection of a Light Echo from the Otherwise Normal SN 2007af

    NASA Astrophysics Data System (ADS)

    Drozdov, D.; Leising, M. D.; Milne, P. A.; Pearcy, J.; Riess, A. G.; Macri, L. M.; Bryngelson, G. L.; Garnavich, P. M.

    2015-05-01

    We present the discovery of a light echo from SN 2007af, a normal Type Ia supernova (SN Ia) in NGC 5584. Hubble Space Telescope images taken three years post explosion reveal two separate echoes: an outer echo and an extended central region, which we propose to be an inner echo for which details are unresolved. Multiple images were obtained in the F160W, F350LP, F555W, and F814W using the Wide Field Camera 3. If the outer echo is produced by an interstellar dust sheet perpendicular to the line of sight, it is located ∼800 pc in front of the SN. The dust for the inner echo is 0.45 pc \\lt d\\lt 90 pc away from the SN. The inner echo color is consistent with typical interstellar dust wavelength-dependent scattering cross-sections, while the outer echo is redder than predicted. Both dust sheets, if in the foreground, are optically thin for scattering, and the outer echo sheet thickness is consistent with the inferred extinction from peak brightness. Whether the inner echo is from interstellar or circumstellar dust is ambiguous. Overall, the echo characteristics are quite similar to previously observed SN Ia echoes.

  7. CLOUD CONDENSATION NUCLEI MEASUREMENTS WITHIN CLOUDS

    EPA Science Inventory

    Measurements of the spectra of cloud condensation nuclei (CCN) within and near the boundaries of clouds are presented. Some of the in-cloud measurements excluded the nuclei within cloud droplets (interstitial CCN) while others included all nuclei inside the cloud (total CCN). The...

  8. From crystalline to glassy gallium fluoride materials: an NMR study of 69Ga and 71Ga quadrupolar nuclei.

    PubMed

    Bureau, B; Silly, G; Buzaré, J Y; Legein, C; Massiot, D

    1999-11-01

    Owing to the implementation of acquisition techniques specific for nuclei with very large quadrupolar interaction (full shifted echo and variable offset cumulative spectra (VOCS)), NMR spectra of 69Ga and 71Ga are obtained in crystallised (PbGaF5, Pb3Ga2F12, Pb9Ga2F24 and CsZnGaF6) and glassy (PbF2-ZnF2-GaF3) gallium fluorides. Simulations of both static (full echo or VOCS) and 15 kHz MAS spectra allow to obtain consistent determinations of isotropic chemical shifts and very large quadrupolar parameters (nuQ up to 14 MHz). In the crystalline compounds whose structures are unknown, the number and the local symmetry of the different gallium sites are tentatively worked out. For the glassy systems, a continuous Czjzek's distribution of the NMR quadrupolar parameters accounts for the particular shape of the NMR spectrum. PMID:10670905

  9. From crystalline to glassy gallium fluoride materials: an NMR study of 69Ga and 71Ga quadrupolar nuclei.

    PubMed

    Bureau, B; Silly, G; Buzaré, J Y; Legein, C; Massiot, D

    1999-09-01

    Owing to the implementation of acquisition techniques specific for nuclei with very large quadrupolar interaction (full shifted echo and variable offset cumulative spectra (VOCS)), NMR spectra of 69Ga and 71Ga are obtained in crystallised (PbGaF5, Pb3Ga2F12, Pb9Ga2F24 and CsZnGaF6) and glassy (PbF2-ZnF2-GaF3) gallium fluorides. Simulations of both static (full echo or VOCS) and 15 kHz MAS spectra allow to obtain consistent determinations of isotropic chemical shifts and very large quadrupolar parameters (nu(Q) up to 14 MHz). In the crystalline compounds whose structures are unknown, the number and the local symmetry of the different gallium sites are tentatively worked out. For the glassy systems, a continuous Czjzek's distribution of the NMR quadrupolar parameters accounts for the particular shape of the NMR spectrum. PMID:10499664

  10. Echo movement and evolution from real-time processing.

    NASA Technical Reports Server (NTRS)

    Schaffner, M. R.

    1972-01-01

    Preliminary experimental data on the effectiveness of conventional radars in measuring the movement and evolution of meteorological echoes when the radar is connected to a programmable real-time processor are examined. In the processor programming is accomplished by conceiving abstract machines which constitute the actual programs used in the methods employed. An analysis of these methods, such as the center of gravity method, the contour-displacement method, the method of slope, the cross-section method, the contour crosscorrelation method, the method of echo evolution at each point, and three-dimensional measurements, shows that the motions deduced from them may differ notably (since each method determines different quantities) but the plurality of measurement may give additional information on the characteristics of the precipitation.

  11. Birefringent neutron prisms for spin echo scattering angle measurement

    NASA Astrophysics Data System (ADS)

    Pynn, Roger; Fitzsimmons, M. R.; Lee, W. T.; Stonaha, P.; Shah, V. R.; Washington, A. L.; Kirby, B. J.; Majkrzak, C. F.; Maranville, B. B.

    2009-09-01

    In the first decade of the 19th century, an English chemist, William Wollaston, invented an arrangement of birefringent prisms that splits a beam of light into two spatially separated beams with orthogonal polarizations. We have constructed similar devices for neutrons using triangular cross-section solenoids and employed them for Spin Echo Scattering Angle Measurement (SESAME). A key difference between birefringent neutron prisms and their optical analogues is that it is hard to embed the former in a medium which has absolutely no birefringence because this implies the removal of all magnetic fields. We have overcome this problem by using the symmetry properties of the Wollaston neutron prisms and of the overall spin echo arrangement. These symmetries cause a cancellation of Larmor phase aberrations and provide robust coding of neutron scattering angles with simple equipment.

  12. Spin-echo entanglement protection from random telegraph noise

    NASA Astrophysics Data System (ADS)

    Lo Franco, R.; D'Arrigo, A.; Falci, G.; Compagno, G.; Paladino, E.

    2013-03-01

    We analyze local spin-echo procedures for protecting entanglement between two non-interacting qubits, each subject to pure-dephasing random telegraph noise. For superconducting qubits, this simple model captures the characteristic features of the effect of bistable impurities coupled to the device. An analytic expression for the entanglement dynamics is reported. Peculiar features related to the non-Gaussian nature of the noise already observed in the single-qubit dynamics also occur in the entanglement dynamics for proper values of the ratio g = v/γ, between the qubit-impurity coupling strength and the switching rate of the random telegraph process, and of the separation between the pulses Δt. We found that the echo procedure may delay the disappearance of entanglement, cancel the dynamical structure of entanglement revivals and dark periods and induce peculiar plateau-like behaviors of the concurrence.

  13. Echo-enabled x-ray vortex generation.

    PubMed

    Hemsing, E; Marinelli, A

    2012-11-30

    A technique to generate high-brightness electromagnetic vortices with tunable topological charge at extreme ultraviolet and x-ray wavelengths is described. Based on a modified version of echo-enabled harmonic generation for free-electron lasers, the technique uses two lasers and two chicanes to produce high-harmonic microbunching of a relativistic electron beam with a corkscrew distribution that matches the instantaneous helical phase structure of the x-ray vortex. The strongly correlated electron distribution emerges from an efficient three-dimensional recoherence effect in the echo-enabled harmonic generation transport line and can emit fully coherent vortices in a downstream radiator for access to new research in x-ray science. PMID:23368128

  14. Mean-field theory of echo state networks

    NASA Astrophysics Data System (ADS)

    Massar, Marc; Massar, Serge

    2013-04-01

    Dynamical systems driven by strong external signals are ubiquitous in nature and engineering. Here we study “echo state networks,” networks of a large number of randomly connected nodes, which represent a simple model of a neural network, and have important applications in machine learning. We develop a mean-field theory of echo state networks. The dynamics of the network is captured by the evolution law, similar to a logistic map, for a single collective variable. When the network is driven by many independent external signals, this collective variable reaches a steady state. But when the network is driven by a single external signal, the collective variable is non stationary but can be characterized by its time averaged distribution. The predictions of the mean-field theory, including the value of the largest Lyapunov exponent, are compared with the numerical integration of the equations of motion.

  15. Mean-field theory of echo state networks.

    PubMed

    Massar, Marc; Massar, Serge

    2013-04-01

    Dynamical systems driven by strong external signals are ubiquitous in nature and engineering. Here we study "echo state networks," networks of a large number of randomly connected nodes, which represent a simple model of a neural network, and have important applications in machine learning. We develop a mean-field theory of echo state networks. The dynamics of the network is captured by the evolution law, similar to a logistic map, for a single collective variable. When the network is driven by many independent external signals, this collective variable reaches a steady state. But when the network is driven by a single external signal, the collective variable is non stationary but can be characterized by its time averaged distribution. The predictions of the mean-field theory, including the value of the largest Lyapunov exponent, are compared with the numerical integration of the equations of motion. PMID:23679475

  16. Benefits of the Multiple Echo Technique for Ultrasonic Thickness Testing

    SciTech Connect

    Elder, J.; Vandekamp, R.

    2011-02-10

    Much effort has been put into determining methods to make accurate thickness measurements, especially at elevated temperatures. An accuracy of +/- 0.001 inches is typically noted for commercial ultrasonic thickness gauges and ultrasonic thickness techniques. Codes and standards put limitations on many inspection factors including equipment, calibration tolerance and temperature variations. These factors are important and should be controlled, but unfortunately do not guarantee accurate and repeatable measurements in the field. Most technicians long for a single technique that is best for every situation, unfortunately, there are no 'silver bullets' when it comes to nondestructive testing. This paper will describe and discuss some of the major contributors to measurement error as well as some advantages and limitations of multiple echo techniques and why multiple echo techniques should be more widely utilized for ultrasonic thickness measurements.

  17. Demonstration of photon-echo rephasing of spontaneous emission.

    PubMed

    Beavan, Sarah E; Hedges, Morgan P; Sellars, Matthew J

    2012-08-31

    In this paper we report the first demonstration of "rephased amplified spontaneous emission" (RASE) with photon-counting detection. This protocol provides an all-in-one photon-pair source and quantum-memory that has applications as a quantum repeater node. The RASE protocol is temporally multimode, and in this demonstration the photon echo was generated in a way that is spatially multimode and includes intermediate storage between two potentially long-lived spin states. A correlation between spontaneous emission and its photon echo was observed, using an ensemble of Pr(3+) ions doped into a Y2SiO5 crystal. Alterations that would allow for the measurement of nonclassical correlations are identified. These should generally apply for future experiments in rare-earth ion crystals, which are promising systems for implementing highly-multiplexed quantum repeater operations. PMID:23002833

  18. Elasticity reconstructive imaging by means of stimulated echo MRI.

    PubMed

    Chenevert, T L; Skovoroda, A R; O'Donnell, M; Emelianov, S Y

    1998-03-01

    A method is introduced to measure internal mechanical displacement and strain by means of MRI. Such measurements are needed to reconstruct an image of the elastic Young's modulus. A stimulated echo acquisition sequence with additional gradient pulses encodes internal displacements in response to an externally applied differential deformation. The sequence provides an accurate measure of static displacement by limiting the mechanical transitions to the mixing period of the simulated echo. Elasticity reconstruction involves definition of a region of interest having uniform Young's modulus along its boundary and subsequent solution of the discretized elasticity equilibrium equations. Data acquisition and reconstruction were performed on a urethane rubber phantom of known elastic properties and an ex vivo canine kidney phantom using <2% differential deformation. Regional elastic properties are well represented on Young's modulus images. The long-term objective of this work is to provide a means for remote palpation and elasticity quantitation in deep tissues otherwise inaccessible to manual palpation. PMID:9498605

  19. Physiological noise compensation in gradient-echo myelin water imaging.

    PubMed

    Nam, Yoonho; Kim, Dong-Hyun; Lee, Jongho

    2015-10-15

    In MRI, physiological noise which originates from cardiac and respiratory functions can induce substantial errors in detecting small signals in the brain. In this work, we explored the effects of the physiological noise and their compensation methods in gradient-echo myelin water imaging (GRE-MWI). To reduce the cardiac function induced inflow noise, flow saturation RF pulses were applied to the inferior portion of the head, saturating inflow blood signals. For the respiratory function induced B0 fluctuation compensation, a navigator echo was acquired, and respiration induced phase errors were corrected during reconstruction. After the compensations, the resulting myelin water images show substantially improved image quality and reproducibility. These improvements confirm the importance and usefulness of the physiological noise compensations in GRE-MWI. PMID:26172308

  20. Stochastic Maximum Likelihood (SML) parametric estimation of overlapped Doppler echoes

    NASA Astrophysics Data System (ADS)

    Boyer, E.; Petitdidier, M.; Larzabal, P.

    2004-11-01

    This paper investigates the area of overlapped echo data processing. In such cases, classical methods, such as Fourier-like techniques or pulse pair methods, fail to estimate the first three spectral moments of the echoes because of their lack of resolution. A promising method, based on a modelization of the covariance matrix of the time series and on a Stochastic Maximum Likelihood (SML) estimation of the parameters of interest, has been recently introduced in literature. This method has been tested on simulations and on few spectra from actual data but no exhaustive investigation of the SML algorithm has been conducted on actual data: this paper fills this gap. The radar data came from the thunderstorm campaign that took place at the National Astronomy and Ionospheric Center (NAIC) in Arecibo, Puerto Rico, in 1998.

  1. Spin-Echo Modulation Experiments with Soft Gaussian Pulses

    NASA Astrophysics Data System (ADS)

    Miao, Xijia; Freeman, Ray

    An analysis is presented for a homonuclear spin-echo experiment in which refocusing and spin inversion are implemented by simultaneous soft 180° pulses applied to two weakly coupled spins. It is shown that for this experiment, simple pulses of short duration (for example, Gaussian pulses) are preferable to more complex shapes such as BURP pulses or Gaussian cascades, since this limits the generation of undesirable multiple-quantum coherence. An expression is derived for the optimum delay between excitation and detection for the generation of anti-phase magnetization at the two sites. The theoretical results are in good agreement with experiment. The doubly selective spin-echo technique is shown to be useful for the determination of small unresolved spin-spin splittings, and this is illustrated with results from the 400 MHz proton spectrum of strychnine.

  2. Neutron nano-spin-echo spectrometer based on magnetic nanostructures

    NASA Astrophysics Data System (ADS)

    Aksenov, V. L.; Nikitenko, Yu. V.; Osipov, A. A.

    2007-09-01

    A neutron spin-echo spectrometer based on spin precessors in the form of magnetic layered nanostructures is described. A model of a spin-echo spectrometer is developed on beam no. 9 in the IBR-2 reactor. In this model, spin precession occurs during motion of neutrons in a magnetic field and their double reflection from Al(30 nm)/Fe(15 nm)/Al(120 nm)/Cu(150 nm) magnetic layered structures. The obtained spectrometer parameters make it possible to investigate excitations in films with a wave vector oriented along the neutron beam direction in the range from 10-3 to 10-1 Å-1 and perpendicularly to the beam in the range from 10-4 to 10-5 Å-1.

  3. Infrared Echoes and the Structure of the ISM

    NASA Astrophysics Data System (ADS)

    Rieke, George; Kim, Yeunjin; Krause, Oliver

    2007-05-01

    We propose to continue a program to map the interstellar medium in three dimensions. Our technique uses infrared echoes from the supernova Cas A, which we discovered during In-Orbit Checkout. We have observed the echoes every six months since, observing the changes in the patterns of heated dust as the light pulse from the supernova propagates through the surrounding ISM. We have developed methods to invert this series of snapshots of planes in the ISM into three dimensional images. By the end of the Spitzer mission, our 3D images will have a depth of 1.5pc at a resolution of about 0.1 pc. This detailed information about the structure of the ISM will have important applications in understanding extinction in dense regions, the radiative transfer and heating of such regions, and in how the ISM fragments, for example to form stars.

  4. Pairing in hot rotating nuclei

    SciTech Connect

    Hung, N. Quang; Dang, N. Dinh

    2008-12-15

    Nuclear pairing properties are studied within an approach that includes the quasiparticle-number fluctuation (QNF) and coupling to the quasiparticle-pair vibrations at finite temperature and angular momentum. The formalism is developed to describe noncollective rotations about the symmetry axis. The numerical calculations are performed within a doubly folded equidistant multilevel model as well as several realistic nuclei. The results obtained for the pairing gap, total energy, and heat capacity show that the QNF smoothes out the sharp SN phase transition and leads to the appearance of a thermally assisted pairing gap in rotating nuclei at finite temperature. The corrections due to the dynamic coupling to SCQRPA vibrations and particle-number projection are analyzed. The effect of backbending of the momentum of inertia as a function of squared angular velocity is also discussed.

  5. Superheavy nuclei and fission barriers

    NASA Astrophysics Data System (ADS)

    Lu, Bing-Nan; Zhao, Jie; Zhao, En-Guang; Zhou, Shan-Gui

    In this chapter, we will present relativistic mean field (RMF) description of heavy and superheavy nuclei (SHN). We will discuss the shell structure and magic numbers in the mass region of SHN, binding energies and α decay Q values, shapes of ground states and potential energy surfaces and fission barriers. We particularly focus on the multidimensionally-constrained covariant density functional theories (CDFT) and the applications of CDFT to the study of exotic nuclear shapes and fission barriers.

  6. Direct Reactions with Exotic Nuclei

    SciTech Connect

    Baur, G.; Typel, S.

    2005-10-14

    We discuss recent work on Coulomb dissociation and an effective-range theory of low-lying electromagnetic strength of halo nuclei. We propose to study Coulomb dissociation of a halo nucleus bound by a zero-range potential as a homework problem. We study the transition from stripping to bound and unbound states and point out in this context that the Trojan-Horse method is a suitable tool to investigate subthreshold resonances.

  7. High Efficiency Gradient Echo Memory with 3-Level Atoms

    NASA Astrophysics Data System (ADS)

    Buchler, B. C.; Hosseini, M.; Hétet, G.; Sparkes, B. M.; Longdell, J. J.; Sellars, M. J.; Lam, P. K.

    2011-10-01

    We present experimental results demonstrating 87% efficiency for single pulse recall, and storage of up to 20 pulses using a three level gradient echo memory with hot rubidium vapour as the storage medium. We also present results showing pulse resequencing, as well as pulse splitting and spectral manipulation. The decoherence mechanisms affecting the system, in particular scattering due to the control field and how it can be minimised by turning the control field off during storage, are also discussed.

  8. MISTY ECHO proof test of the GRMPY system

    SciTech Connect

    Deupree, R.G.; Flicker, S.L.; Turner, W.J.; Watson, C.A. ); Khalsa, N.; Macy, D. )

    1990-01-01

    The GRMPY system that was fielded on the MISTY ECHO event demonstrated that a small cadre of people could perform all fielding tasks. This report describes each task in detail and outlines the components of the GRMPY system. Suggestions are made for system improvement. The data are presented that were obtained on eight of the nine GRMPY stations fielded. 2 refs., 22 figs., 3 tabs.

  9. The visible and near infrared module of EChO

    NASA Astrophysics Data System (ADS)

    Adriani, A.; Bellucci, G.; Gambicorti, L.; Focardi, M.; Oliva, E.; Farina, M.; Di Giorgio, A. M.; Santoli, F.; Pace, E.; Piccioni, G.; Filacchione, G.; Pancrazzi, M.; Tozzi, A.; Micela, G.

    2015-12-01

    The Visible and Near Infrared (VNIR) is one of the modules of EChO, the Exoplanets Characterization Observatory proposed to ESA for an M-class mission. EChO is aimed to observe planets while transiting by their suns. Then the instrument had to be designed to assure a high efficiency over the whole spectral range. In fact, it has to be able to observe stars with an apparent magnitude Mv = 9-12 and to see contrasts of the order of 10-4-10-5 necessary to reveal the characteristics of the atmospheres of the exoplanets under investigation. VNIR is a spectrometer in a cross-dispersed configuration, covering the 0.4-2.5 μm spectral range with a resolving power of about 330 and a field of view of 2 arcsec. It is functionally split into two channels respectively working in the 0.4-1.0 μm and 1.0-2.5 μm spectral ranges. Such a solution is imposed by the fact the light at short wavelengths has to be shared with the EChO Fine Guiding System (FGS) devoted to the pointing of the stars under observation. The spectrometer makes use of a HgCdTe detector of 512 by 512 pixels, 18 μm pitch and working at a temperature of 45 K as the entire VNIR optical bench. The instrument has been interfaced to the telescope optics by two optical fibers, one per channel, to assure an easier coupling and an easier colocation of the instrument inside the EChO optical bench.

  10. Loschmidt Echo in a System of Interacting Electrons

    SciTech Connect

    Manfredi, G.; Hervieux, P.-A.

    2006-11-10

    We study the Loschmidt echo for a system of electrons interacting through mean-field Coulomb forces. The electron gas is modeled by a self-consistent set of hydrodynamic equations. It is observed that the quantum fidelity drops abruptly after a time that is proportional to the logarithm of the perturbation amplitude. The fidelity drop is related to the breakdown of the symmetry properties of the wave function.

  11. PREFACE: Correlation Dynamics in Nuclei

    NASA Astrophysics Data System (ADS)

    Suzuki, Toshio; Otsuka, Takaharu; Ichimura, Munetake

    2005-01-01

    The International Symposium on `Correlation Dynamics in Nuclei' was held at the Sanjo Kaikan, the University of Tokyo, from the 31 January to 4 February 2005. This symposium was organized on the occasion of the 50th anniversary of the Configuration Mixing theory of Arima and Horie. The symposium was hosted by the University of Tokyo, and supported by the Inoue Foundation for Science, the Japan Atomic Energy Research Institute and the Ministry of Education, Culture, Sports, Science and Technology. The purpose of the symposium was to discuss theoretical and experimental developments and future prospects in physics of correlation dynamics in nuclei, including topics such as effective interactions, shell model studies of configuration mixing and spin-isospin modes in nuclei. It was shown in many ways and angles that the Arima-Horie theory has been a starting point of a variety of developments of the studies in these fields over many decades. The developments have been enhanced by the expansion of computational capabilities and the progress in accelerators, detectors and radioactive beam facilities. We enjoyed 28 excellent and lively invited talks and 30 oral presentations in the symposium with about 90 participants. A special session was dedicated to celebrate the 80th birthday of Professor Igal Talmi, who made invaluable and pioneering works in the shell model theory. Finally, we would like to thank all the speakers and the participants as well as the other organizers for their contributions which made the symposium very successful.

  12. NUCLEI AT HIGH ANGULAR MOMENTUM

    SciTech Connect

    Diamond, R.M.; Stephens, F.S.

    1980-06-01

    It appears that most nuclei show a compromise between purely collective and purely non-collective behavior at very high spins.non~collective behavior in nuclei has been seen only as high as 36 or 37{bar h}, at which point a more collective structure seems to develop. The concepts underlying the study of high angular momentum states are discussed. The factors that limit angular momentum in nuclei are considered. The currently emerging state of physics of very high spin states is reviewed. The detailed calculations currently made for high spin states are described, focusing not on the calculations themselves, but on the physical input to them and results that come out. Production of high-spin states using heavy-ion reactions is reviewed. Studies of {gamma}-rays de-exciting the evaporation residues from heavy-ion reactions are covered. Two types of {gamma} rays occur: those that cool the nucleus to or toward the yrast line, called "statistical," and those that are more or less parallel to the yrast line and remove the angular momentum, called "yrast~like." Collective rotation, in simplest form the motion of a deformed nucleus around an axis perpendicular to its symmetry axis, is also covered.

  13. Structure functions for light nuclei

    SciTech Connect

    S.A. Kulagin, R. Petti

    2010-11-01

    We discuss the nuclear EMC effect with particular emphasis on recent data for light nuclei including 2H, 3He, 4He, 9Be, 12C and 14N. In order to verify the consistency of available data, we calculate the \\chi^2 deviation between different data sets. We find a good agreement between the results from the NMC, SLAC E139, and HERMES experiments. However, our analysis indicates an overall normalization offset of about 2% in the data from the recent JLab E03-103 experiment with respect to previous data for nuclei heavier than 3He. We also discuss the extraction of the neutron/proton structure function ratio F2n/F2p from the nuclear ratios 3He/2H and 2H/1H. Our analysis shows that the E03-103 data on 3He/2H require a renormalization of about 3% in order to be consistent with the F2n/F2p ratio obtained from the NMC experiment. After such a renormalization, the 3He data from the E03-103 data and HERMES experiments are in a good agreement. Finally, we present a detailed comparison between data and model calculations, which include a description of the nuclear binding, Fermi motion and off-shell corrections to the structure functions of bound proton and neutron, as well as the nuclear pion and shadowing corrections. Overall, a good agreement with the available data for all nuclei is obtained.

  14. Improved spin-echo-edited NMR diffusion measurements.

    PubMed

    Otto, W H; Larive, C K

    2001-12-01

    The need for simple and robust schemes for the analysis of ligand-protein binding has resulted in the development of diffusion-based NMR techniques that can be used to assay binding in protein solutions containing a mixture of several ligands. As a means of gaining spectral selectivity in NMR diffusion measurements, a simple experiment, the gradient modified spin-echo (GOSE), has been developed to reject the resonances of coupled spins and detect only the singlets in the (1)H NMR spectrum. This is accomplished by first using a spin echo to null the resonances of the coupled spins. Following the spin echo, the singlet magnetization is flipped out of the transverse plane and a dephasing gradient is applied to reduce the spectral artifacts resulting from incomplete cancellation of the J-coupled resonances. The resulting modular sequence is combined here with the BPPSTE pulse sequence; however, it could be easily incorporated into any pulse sequence where additional spectral selectivity is desired. Results obtained with the GOSE-BPPSTE pulse sequence are compared with those obtained with the BPPSTE and CPMG-BPPSTE experiments for a mixture containing the ligands resorcinol and tryptophan in a solution of human serum albumin. PMID:11740906

  15. Optimized 3D Ultrashort Echo Time Pulmonary MRI

    PubMed Central

    Johnson, Kevin M.; Fain, Sean B.; Schiebler, Mark L.; Nagle, Scott

    2012-01-01

    Purpose To optimize 3D radial ultrashort echo time MRI for high resolution whole-lung imaging. Methods 3D radial ultrashort echo time was implemented on a 3T scanner to investigate the effects of: (1) limited field-of-view excitation, (2) variable density readouts, and (3) radial oversampling. Improvements in noise performance and spatial resolution were assessed through simulation and phantom studies. Their effects on lung and airway visualization in five healthy male human subjects (mean age 32 years) were compared qualitatively through blinded ordinal scoring by two cardiothoracic radiologists using a nonparametric Friedman test (P < 0.05). Relative signal difference between endobronchial air and adjacent lung tissue, normalized to nearby vessel, was used as a surrogate for lung tissue signal. Quantitative measures were compared using the paired Student's t-test (P < 0.05). Finally, clinical feasibility was investigated in a patient with interstitial fibrosis. Results Simulation and phantom studies showed up to 67% improvement in SNR and reduced blurring for short T2* species using all three optimizations. In vivo images showed decreased artifacts and improved lung tissue and airway visualization both qualitatively and quantitatively. Conclusion The use of limited field-of-view excitation, variable readout gradients, and radial oversampling significantly improve the technical quality of 3D radial ultrashort echo time lung images. PMID:23213020

  16. Counting spins with a new spin echo double resonance

    PubMed

    Cull; Joers; Gullion; Norberg; Conradi

    1998-08-01

    In traditional spin echo double resonance (SEDOR), the echo amplitude M is decreased when the observed spins S are flipped by pi together with the pi refocusing pulse on the observed spins I; the dependence on tau is then determined. In the new version of SEDOR, the echo amplitude is measured as a function of the S spin flip angle theta at a constant pulse spacing tau. The analysis is simple and powerful for long tau, where the strong collision limit applies. There, the variation of M with theta can be fit, yielding the number n of spins S to which each spin I is coupled. Data from amorphous silicon with 1H and 2D show the described effect. A MAS version of the new method is used on multiply labeled alanine and urea, with results in good agreement with the predictions for n = 2, as expected. By Fourier transforming M with respect to the flip angle theta, a stick spectrum results; the largest numbered non-vanishing stick yields the number n of spins S coupled to each spin I. Simulations are presented for an n = 2 system. The present technique is compared to the multiple-quantum spin-counting method. Copyright 1998 Academic Press. PMID:9716478

  17. Evaluation of Gravity Wave Effects on Bow Echo Development

    NASA Astrophysics Data System (ADS)

    Adams-Selin, R.; Johnson, R. H.

    2012-12-01

    A numerical simulation of the 13 March 2003 bow echo over Oklahoma is used to evaluate bow echo development and its relationship with gravity wave generation. The research is also directed at an explanation of recent observations of surface pressure surges ahead of convective lines prior to the bowing process. Multiple fast-moving n = 1 gravity waves are generated in association with fluctuations in the first vertical mode of heating in the convective line, and each wave modifies the pre-system environment. The surface impacts of four such waves are observed in Oklahoma Mesonet data during this case. A slower gravity wave is also produced in the simulation, which is responsible for the pre-bowing pressure surge in the model. This gravity wave is generated by an increase in low-level microphysical cooling associated with strengthened rear-to-front flow and low-level downdrafts shortly before bowing. The low-level upward vertical motion associated with this wave, in conjunction with higher-frequency gravity waves generated by the multicellularity of the convective line, increases the immediate pre-system CAPE by approximately 250 J kg-1. Statistical methods are used to evaluate the significance of each vertical mode within the microphysical heating profile at the time of the pressure surge. The contribution of each microphysical process to the overall profile, particularly that of cooling by melting and evaporation, is also examined in an attempt to connect the processes generating the slower gravity wave with those producing bow echo development.

  18. Background analysis and reduction for the ECHo experiment

    NASA Astrophysics Data System (ADS)

    Scholl, Stephan

    2016-05-01

    ECHo-lk is a new experiment which is designed to investigate the electron neutrino mass from the calorimetric measurement of the electron capture spectrum of 163Ho. In this presentation, we give an overview of our recent activities in the background analysis and reduction. Low background measurements of the radiopurity of the implanted Holmium in the ECHo detectors have been used to constrain the maximum activity of 166mHo in the sample to be less than ~ 0.4 mBq. On top of this, the background spectrum introduced by coimplanted 166Ho in the absorber of the ECHo detectors has been obtained with a GEANT4 simulation showing that if the projected reduction of coimplanted 166mHo to 163Ho of 10-10 can be achieved, the background contribution of 166mHo is negligible. Additional GEANT4 based Monte-Carlo simulations of test contaminations have been conducted. Simulations have been completed for internal 210Pb contamination in the absorber and 55Fe contaminations on the surface of the absorber.

  19. Shift-driven modulations of spin-echo signals

    PubMed Central

    Smith, Pieter E. S.; Bensky, Guy; Álvarez, Gonzalo A.; Kurizki, Gershon; Frydman, Lucio

    2012-01-01

    Since the pioneering works of Carr-Purcell and Meiboom-Gill [Carr HY, Purcell EM (1954) Phys Rev 94:630; Meiboom S, Gill D (1985) Rev Sci Instrum 29:688], trains of π-pulses have featured amongst the main tools of quantum control. Echo trains find widespread use in nuclear magnetic resonance spectroscopy (NMR) and imaging (MRI), thanks to their ability to free the evolution of a spin-1/2 from several sources of decoherence. Spin echoes have also been researched in dynamic decoupling scenarios, for prolonging the lifetimes of quantum states or coherences. Inspired by this search we introduce a family of spin-echo sequences, which can still detect site-specific interactions like the chemical shift. This is achieved thanks to the presence of weak environmental fluctuations of common occurrence in high-field NMR—such as homonuclear spin-spin couplings or chemical/biochemical exchanges. Both intuitive and rigorous derivations of the resulting “selective dynamical recoupling” sequences are provided. Applications of these novel experiments are given for a variety of NMR scenarios including determinations of shift effects under inhomogeneities overwhelming individual chemical identities, and model-free characterizations of chemically exchanging partners. PMID:22474339

  20. 15 K pulse tube design for ECHO mission

    NASA Astrophysics Data System (ADS)

    Duval, J. M.; Charles, I.; Chassaing, C.; Butterworth, J.; Aigouy, G.; Mullié, J.

    2014-01-01

    The Exoplanet Characterisation Observatory (EChO) is a proposed space telescope designed to characterize the atmospheres of nearby transiting exoplanets. Its detectors will operate in the 0.4 to 11 micromillimeter range. Two kinds of detectors are currently able to provide the desired sensitivity in this range. Depending on the technology used, cooling to either 6 K or about 30 K will be required. For the former solution, a JT cooler coupled to a pulse tube cooler could be used whereas for the latter, a pulse tube cooler would provide the cooling power. Pulse tube coolers are particularly well adapted for the cryogenics for such mission because of the low level of vibration required and of the temperature range. We developed multistage pulse tube coolers able to cool down to temperature as low as 6 K, with efficient operation from 10 K to 40 K. A design based on our tested prototypes is proposed to fulfill the need for the ECHO missions. This paper describes the experimental results measured with demonstrator models. In particular measured performances of efficient cooling power at 10 K are presented. Several possible configurations for the ECHO cooler will be discussed as well.

  1. A general Kirchhoff approximation for echo simulation in ultrasonic NDT

    NASA Astrophysics Data System (ADS)

    Dorval, V.; Chatillon, S.; Lu, B.; Darmon, M.; Mahaut, S.

    2012-05-01

    The Kirchhoff approximation is commonly used for the modeling of echoes in ultrasonic NDE. It consists in locally approximating the illuminated surface by an infinite plane to compute elastic fields. A model based on this approximation is used in the CIVA software, developed at CEA LIST, to compute echoes from cracks and backwalls. In its current version, it is limited to stress-free surfaces. A new model using a more general formalism has been developed. It is based on reciprocity principles and is valid for any host and flaw materials (liquids, isotropic and anisotropic solids). Experimental validations confirm that this new model can be used for a wider range of applications than the previous one. A second part of this communication deals with the improvement of the Kirchhoff approximation in the aim of predicting diffraction echoes. It is based on an approach called refined Kirchhoff, which combines the Kirchhoff and Geometrical Theory of Diffraction (GTD) models. An illustration of this method for the case of a rigid obstacle in a fluid is given.

  2. A pilot validation of multi-echo based echo-planar correlated spectroscopic imaging in human calf muscles.

    PubMed

    Furuyama, Jon K; Nagarajan, Rajakumar; Roberts, Christian K; Lee, Cathy C; Hahn, Theodore J; Thomas, M Albert

    2014-10-01

    A current limitation of MR spectroscopic imaging of multiple skeletal muscles is prolonged scan duration. A significant reduction in the total scan duration using the echo-planar correlated spectroscopic imaging (EP-COSI) sequence was accomplished using two bipolar readout trains with different phase-encoded echoes for one of two spatial dimensions within a single repetition time (TR). The second bipolar readout was used for spatially encoding the outer k-space, whereas the first readout was used for the central k-space only. The performance of this novel sequence, called multi-echo based echo-planar correlated spectroscopic imaging (ME-EPCOSI), was demonstrated by localizing specific key features in calf muscles and bone marrow of 11 healthy volunteers and five subjects with type 2 diabetes (T2D). A 3 T MRI-MRS scanner equipped with a transmit-receive extremity coil was used. Localization of the ME-EPCOSI sequence was in good agreement with the earlier single-readout based EP-COSI sequence and the required scan time was reduced by a factor of two. In agreement with an earlier report using single-voxel based 2D MRS, significantly increased unsaturated pools of intramyocellular lipid (IMCL) and extramyocellular lipid (EMCL) and decreased IMCL and EMCL unsaturation indices (UIs) were observed in the soleus and tibialis anterior muscle regions of subjects with T2D compared with healthy controls. In addition, significantly decreased choline content was observed in the soleus of T2D subjects compared with healthy controls. Multi-voxel characterization of IMCL and EMCL ratios and UI in the calf muscle may be useful for the non-invasive assessment of altered lipid metabolism in the pathophysiology of T2D. PMID:25132520

  3. A new technique for MR elastography of the supraspinatus muscle: A gradient-echo type multi-echo sequence.

    PubMed

    Ito, Daiki; Numano, Tomokazu; Mizuhara, Kazuyuki; Takamoto, Koichi; Onishi, Takaaki; Nishijo, Hisao

    2016-10-01

    Magnetic resonance elastography (MRE) can measure tissue stiffness quantitatively and noninvasively. Supraspinatus muscle injury is a significant problem among throwing athletes. The purpose of this study was to develop an MRE technique for application to the supraspinatus muscle by using a conventional magnetic resonance imaging (MRI). MRE acquisitions were performed with a gradient-echo type multi-echo MR sequence at 100Hz pneumatic vibration. A custom-designed vibration pad was used as a pneumatic transducer in order to adapt to individual shoulder shapes. In a gradient-echo type multi-echo MR sequence, without motion encoding gradient (MEG) that synchronizes with vibrations, bipolar readout gradient lobes achieved a similar function to MEG (MEG-like effect). In other words, a dedicated MRE sequence (built-in MEG) is not always necessary for MRE. In this study, 7 healthy volunteers underwent MRE. We investigated the effects of direction of the MEG-like effect and selected imaging planes on the patterns of wave propagation (wave image). The results indicated that wave images showed clear wave propagation on a condition that the direction of the MEG-like effect was nearly perpendicular to the long axis of the supraspinatus muscle, and that the imaging plane was superior to the proximal supraspinatus muscle. This limited condition might be ascribed to specific features of fibers in the supraspinatus muscle and wave reflection from the boundaries of the supraspinous fossa. The mean stiffness of the supraspinatus muscle was 10.6±3.17kPa. Our results demonstrated that using MRE, our method can be applied to the supraspinatus muscle by using conventional MRI. PMID:27374984

  4. Physical characteristics of mouse sperm nuclei.

    PubMed Central

    Wyrobek, A J; Meistrich, M L; Furrer, R; Bruce, W R

    1976-01-01

    The nuclei of epididymal sperm, isolated from C57BL/6J and CBA/J inbred mice by their resistance to trypsin digestion, retain the shape differences of the intact sperm head. Various physical characteristics of these nuclei were measured and compared. The measurement of the projected dimensions of nuclei showed that the CBA nuclei are 13.5% longer than C57BL/6 nuclei (8.64 +/- 0.02 mum compared with 7.61 +/- 0.02 mum), 0.8% narrower (3.51 +/- 0.01 vs. 3.54 +/-0.01 mum) with 6.8% more area (22.34 +/- 0.10 vs. 20.91 +/- 0.09 mum2). However, the volumes of the nuclei as based on reconstructing calibrated electronmicrographs of serial sections of the nuclei indicated that CBA are about 7% smaller than C57BL/6 nuclei (3.72 +/- 0.08 vs. 4.01 +/- 0.03 mum3). The buoyant density of the CBA nuclei is 1.435 +/- 0.002 g/cm3 compared with 1.433 +/- 0.002 g/cm3 for the C57BL/6 nuclei as determined on linear CsCl and Renografin-76 density gradients and confirmed by a technique utilizing physiological tonicities. Therefore, the average mass of the CBA nuclei is less than that of the C57BL/6 nuclei (5.34 +/- 0.12 vs. 5.75 +/- 0.05 pg). The sedimentation velocities at unit gravity of nuclei from 11 inbred strains differ over a range of more than 6% with CBA nuclei sedimenting about 2.0% more slowly than C57BL/6 nuclei. We show that for these nuclei the sedimentation velocity can be related to their buoyant density, volume and a sedimentation shape factor. Within the errors of our measurements of these various characteristics, it was found that C57BL/6 and CBA nuclei have similar sedimentation shape factors. Therefore, the difference in sedimentation velocity between these nuclei appears to be primarily a result of differences in volume. The possible applications of these techniques to the physical separation of sperm are evaluated in the discussion. Images FIGURE 1 PMID:938720

  5. Apparatus and method for measuring relative phase of signals in a multiple-echo system

    NASA Technical Reports Server (NTRS)

    Froggatt, Mark E. (Inventor)

    1998-01-01

    An apparatus and method for measuring the relative phase of echo signals in a multiple-echo system. A signal generator generates an exciting tone burst and subsequent tone bursts delayed in phase from the exciting tone burst. The exciting tone burst is gated into a transducer coupled to the multiple-echo system. Each subsequent tone burst is converted into a series of pulses. Each pulse triggers a sample/hold circuit to sample each echo signal. The samples of the echo signal are averaged and then compared to a reference value. The signal generator is controlled to vary the subsequent tone burst phase delay to determine for each echo signal a subsequent tone burst phase delay that causes the average of the samples of the echo signal to be substantially equal to the reference value wherein the determined subsequent tone burst phase delay is the phase delay of the echo signal with respect to the exciting tone burst. The control circuit then determines the difference in phase delay between echo signals to determine the relative phase delay of the echo signals.

  6. Electrically and optically detected spin echo of hopping carriers in organic semiconductors

    NASA Astrophysics Data System (ADS)

    Mkhitaryan, Vagharsh; Dobrovitski, Viatcheslav

    We develop a theory for electrically and optically detected primary (2-pulse) and stimulated (3-pulse) spin echo produced by the polaron pairs coupled to the nuclear spins in organic semiconductors. The theory employs fully quantum description of the nuclear and polaron spins, and explains how the structure of the echo signal (electron spin echo envelope modulation, ESEEM) depends on the statistics and rate of the polaron hopping. For the primary spin echo the envelope modulation is strong for slow hopping; both modulation amplitude and dephasing time T2 decrease with increasing hopping rate. As the hopping rate increases further, T2 starts to increase again due to motional narrowing, while the primary echo signal becomes exponential without modulation. The stimulated spin echo signal also shows strong envelope modulation for slow polaron hopping. For faster hopping the stimulated echo (unlike the primary echo) shows a modulation which does not disappear for fast hopping, and has the frequency of the nuclear Larmor precession. Besides describing the recent spin echo measurements in π-conjugated polymers, our work provides a way to directly determine the polaron hopping dynamics from the spin echo experiments. This work was supported by the Department of Energy-Basic Energy Sciences under Contract No. DE-AC02-07CH11358.

  7. Variabilities of low latitude mesospheric and E region echoes: linked to common sources?

    NASA Astrophysics Data System (ADS)

    Dharmalingam, Selvaraj; Patra, Amit; Sathishkumar, Sundararaman; Narayana Rao, D.

    2016-07-01

    Variability in dynamics of the mesospheric and E region echoes have been studied in isolation. Both echoing phenomena are directly or indirectly coupled with each other through neutral dynamics. This is especially so for the low-latitudes outside the equatorial electrojet belt, where E region plasma irregularities causing radar echoes are governed by neutral dynamics, such as tides and gravity waves. Although these regions are close to each other, no effort has been made yet to understand the dynamical coupling processes manifesting the observed variabilities in the two echoing phenomena. To investigate linkage between the two phenomena, if any, we conducted systematic observations of low latitude mesospheric and E region echoes during 2011-2012 using the Gadanki MST radar and used these in conjunction with SABER temperature, MF radar wind, and sporadic E observations. Both echoes are found to occur in the height regions where temperature observations show negative gradients. Mesospheric echoes are collocated with temperature gradient associated with mesospheric temperature inversion while the E region echoes are collocated with negative temperature gradient close to the mesopause. Observations have revealed a common signature of semi-annual variations in the occurrence of both mesospheric and ionospheric E-region - occurrences peak in the equinoxes. The E region echoes have an additional peak occurring in the summer and this occurrence is well correlated with the enhancement in the diurnal tidal amplitude. We surmise that the enhancement in the diurnal tidal amplitude is linked with non-migrating tide of tropospheric weather phenomena in summer. Intriguingly, mesospheric echoing layers display descending pattern quite similar to the E region echoes and sporadic E layer, which have been used to invoke tidal dynamics in manifesting similar morphology in both mesospheric and E region echoes. These results will be presented and the role of tidal dynamics on the

  8. Light Echoes and Late-Time Emissions of Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Drozdov, Dina

    2016-05-01

    Type Ia supernovae have many applications in astronomy, yet with fundamental properties still not fully understood, new methods for investigating the environment of a supernova need to be developed. A light echo is produced from the scattering of light from a bright source and can be used to analyze the dust in the vicinity of the supernova and learn invaluable information about the source. These techniques can put constraints on explosion and progenitor models. Although light echo detections from Type Ia supernovae are rare, with only seven total extragalactic detections, this could be due to the lack of thorough late-epoch monitoring. Since key information is determined from even a single light echo detection, light echo searches should be undertaken in the future to supplement our understanding of supernovae. As part of our collaborative campaign for studying the emission of supernovae at late epochs, we have added two light echoes to a small sample size of Type Ia supernova light echo detections: SN 2009ig in NGC 1015 and a dual echo from SN 2007af in NGC 5584. Both echoes were observed with the Hubble Space Telescope and allow for the most detailed images of Type Ia supernova light echoes to date. Three filters (F555W, F814W, and F350LP) captured the echoes obtained with the Wide Field Camera 3, and since both host galaxies were imaged as part of the same observing program, these cases will be the best comparable light echo pairs. We also further investigate the light echoes from SN 2006X in NGC 4321 and SN 1998bu in NGC 3368 from Hubble Space Telescope archival images. Analyses performed on the images gives crucial insight into the dusty environment of the host galaxy and the surroundings of the supernova. The outer echo from SN 2007af was created from an interstellar dust sheet located ~800 pc in front of the supernova, while the inner echo could be from interstellar or circumstellar origin. A circumstellar light echo could imply a single degenerate

  9. Structure functions for light nuclei

    SciTech Connect

    Kulagin, S. A.; Petti, R.

    2010-11-15

    We discuss the nuclear EMC effect with particular emphasis on recent data for light nuclei including {sup 2}H, {sup 3}He, {sup 4}He, {sup 9}Be, {sup 12}C, and {sup 14}N. In order to verify the consistency of available data, we calculate the {chi}{sup 2} deviation between different data sets. We find a good agreement between the results from the NMC, SLAC E139, and HERMES experiments. However, our analysis indicates an overall normalization offset of about 2% in the data from the recent JLab E03-103 experiment with respect to previous data for nuclei heavier than {sup 3}He. We also discuss the extraction of the neutron/proton structure function ratio F{sub 2}{sup n}/F{sub 2}{sup p} from the nuclear ratios {sup 3}He/{sup 2}H and {sup 2}H/{sup 1}H. Our analysis shows that the E03-103 data on {sup 3}He/{sup 2}H require a renormalization of about 3% in order to be consistent with the F{sub 2}{sup n}/F{sub 2}{sup p} ratio obtained from the NMC experiment. After such a renormalization, the {sup 3}He data from the E03-103 and HERMES experiments are in a good agreement. Finally, we present a detailed comparison between data and model calculations, which include a description of the nuclear binding, Fermi motion, and off-shell corrections to the structure functions of bound proton and neutron, as well as the nuclear pion and shadowing corrections. Overall, a good agreement with the available data for all nuclei is obtained.

  10. The rotation of comet nuclei

    NASA Technical Reports Server (NTRS)

    Whipple, F. L.

    1982-01-01

    Spin-vector research on cometary nuclei is reviewed with emphasis on the actual determination of rotation period and spin-axis orientation. The rotation periods of 47 comets are compared with those of 41 asteroids with diameters of not more than 40 km. It is shown that the median periods for the comets is 15.0 hr as compared with 6.8 hr for the asteroids and that the preliminary distribution curve for the logarithms of the comet periods is not Gaussian and is flatter than the corresponding curve for the asteroids. Slow accumulation at low relative velocities is suggested as the cause of the longer comet rotation periods.

  11. Short Range Correlations in Nuclei

    SciTech Connect

    L. B. Weinstein

    2006-11-01

    Short range correlations (SRC) are an extremely important part of nuclear structure. They are responsible for the high momentum part of the nuclear wavefunction. Instantaneous densities can significantly exceed the average neutron star density. Recent (e,e[prime]) measurements at Jefferson Lab have shown that SRC are universal in nuclei from deuterium to gold, that the probability of two-nucleon SRC is 5-25%, and that the probability of three-nucleon SRC is less than 1%. Recent (e,e[prime]pn) measurements have measured the SRC probabilities as a function of proton momentum and have measured the joint NN momentum distributions.

  12. Superdeformation in the mercury nuclei

    SciTech Connect

    Janssens, R.V.F.; Carpenter, M.P.; Fernandez, P.B.; Moore, E.F.; Ahmad, I.; Khoo, T.L.; Wolfs, F.L.H. ); Drigert, M.W. ); Ye, D.; Beard, K.B.; Garg, U.; Reviol, W. ); Bearden, I.G.; Benet, P.; Daly, P.J.; Grabowski, Z.W. )

    1990-01-01

    We shall first summarize the present experimental situation concerning {sup 192}Hg, the nucleus regarded as the analog of {sup 152}Dy for this superdeformation (SD) region in that gaps are calculated to occur at large deformation for Z = 80 and N = 112. Proton and neutron excitations out of the {sup 192}Hg core will then be reviewed with particular emphasis on {sup 191}Hg and {sup 193}Tl. The presentation will conclude with a brief discussion on limits of the SD region for neutron deficient Hg nuclei. 26 refs., 10 figs.

  13. Dependence of ultrasound echo decorrelation on local tissue temperature during ex vivo radiofrequency ablation

    NASA Astrophysics Data System (ADS)

    Subramanian, Swetha; Schmidt, Daniel T.; Rao, Marepalli B.; Mast, T. Douglas

    2016-03-01

    This study investigates echo decorrelation imaging, an ultrasound method for thermal ablation monitoring. The effect of tissue temperature on the mapped echo decorrelation parameter was assessed in radiofrequency ablation experiments performed on ex vivo bovine liver tissue. Echo decorrelation maps were compared with corresponding tissue temperatures simulated using the finite element method. For both echo decorrelation imaging and integrated backscatter imaging, the mapped tissue parameters correlated significantly but weakly with local tissue temperature. Receiver operating characteristic (ROC) curves were used to assess the ability of echo decorrelation and integrated backscatter to predict tissue temperature greater than 40, 60, and 80 °C. Significantly higher area under the ROC curve (AUROC) values were obtained for prediction of tissue temperatures greater than 40, 60, and 80 ° C using echo decorrelation imaging (AUROC =0.871,~0.948 and 0.966) compared to integrated backscatter imaging (AUROC =0.865,~0.877 and 0.832).

  14. Pattern recognition for rapid T2 mapping with Stimulate Echo Compensation

    PubMed Central

    Huang, Chuan; Altbach, Maria I; Fakhri, Georges El

    2014-01-01

    Indirect echoes (such as stimulated echoes) are a source of signal contamination in a multi-echo spin-echo T2 quantification, and can lead to T2 overestimation if a conventional exponential T2 decay model is assumed. Recently, nonlinear least square fitting of a slice-resolve extended phase graph (SEPG) signal model has been shown to provide accurate T2 estimates with indirect echo compensation. However, the iterative nonlinear least square fitting is computationally expensive and the T2 map generation time is long. In this work, we present a pattern recognition T2 mapping technique based on the SEPG model that can be performed with a single pre-computed dictionary for any arbitrary echo spacing. Almost identical T2 and B1 maps were obtained from in vivo data using the proposed technique compared to conventional iterative nonlinear least square fitting, while the computation time was reduced by more than 14 fold. PMID:24853466

  15. Pattern recognition for rapid T2 mapping with stimulated echo compensation.

    PubMed

    Huang, Chuan; Altbach, Maria I; El Fakhri, Georges

    2014-09-01

    Indirect echoes (such as stimulated echoes) are a source of signal contamination in multi-echo spin-echo T2 quantification and can lead to T2 overestimation if a conventional exponential T2 decay model is assumed. Recently, nonlinear least square fitting of a slice-resolved extended phase graph (SEPG) signal model has been shown to provide accurate T2 estimates with indirect echo compensation. However, the iterative nonlinear least square fitting is computationally expensive and the T2 map generation time is long. In this work, we present a pattern recognition T2 mapping technique based on the SEPG model that can be performed with a single pre-computed dictionary for any arbitrary echo spacing. Almost identical T2 and B1 maps were obtained from in vivo data using the proposed technique compared to conventional iterative nonlinear least square fitting, while the computation time was reduced by more than 14-fold. PMID:24853466

  16. Photon echo transients from an inhomogeneous ensemble of semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Poltavtsev, S. V.; Salewski, M.; Kapitonov, Yu. V.; Yugova, I. A.; Akimov, I. A.; Schneider, C.; Kamp, M.; Höfling, S.; Yakovlev, D. R.; Kavokin, A. V.; Bayer, M.

    2016-03-01

    An ensemble of quantum dot excitons may be used for coherent information manipulation. Due to the ensemble inhomogeneity any optical information retrieval occurs in the form of a photon echo. We show that the inhomogeneity can lead to a significant deviation from the conventional echo timing sequence. Variation of the area of the initial rotation pulse, which generates excitons in a dot subensemble only, reveals this complex picture of photon echo formation. We observe a retarded echo for π /2 pulses, while for 3 π /2 the echo is advanced in time as evidenced through monitoring the Rabi oscillations in the time-resolved photon echo amplitude from (In,Ga)As/GaAs self-assembled quantum dot structures and confirmed by detailed calculations.

  17. Dependence of ultrasound echo decorrelation on local tissue temperature during ex vivo radiofrequency ablation.

    PubMed

    Subramanian, Swetha; Schmidt, Daniel T; Rao, Marepalli B; Mast, T Douglas

    2016-03-21

    This study investigates echo decorrelation imaging, an ultrasound method for thermal ablation monitoring. The effect of tissue temperature on the mapped echo decorrelation parameter was assessed in radiofrequency ablation experiments performed on ex vivo bovine liver tissue. Echo decorrelation maps were compared with corresponding tissue temperatures simulated using the finite element method. For both echo decorrelation imaging and integrated backscatter imaging, the mapped tissue parameters correlated significantly but weakly with local tissue temperature. Receiver operating characteristic (ROC) curves were used to assess the ability of echo decorrelation and integrated backscatter to predict tissue temperature greater than 40, 60, and 80 °C. Significantly higher area under the ROC curve (AUROC) values were obtained for prediction of tissue temperatures greater than 40, 60, and 80 ° C using echo decorrelation imaging (AUROC [Formula: see text] and 0.966) compared to integrated backscatter imaging (AUROC [Formula: see text] and 0.832). PMID:26943026

  18. NovoPen Echo(®) insulin delivery device.

    PubMed

    Hyllested-Winge, Jacob; Sparre, Thomas; Pedersen, Line Kynemund

    2016-01-01

    The introduction of insulin pen devices has provided easier, well-tolerated, and more convenient treatment regimens for patients with diabetes mellitus. When compared with vial and syringe regimens, insulin pens offer a greater clinical efficacy, improved quality of life, and increased dosing accuracy, particularly at low doses. The portable and discreet nature of pen devices reduces the burden on the patient, facilitates adherence, and subsequently contributes to the improvement in glycemic control. NovoPen Echo(®) is one of the latest members of the NovoPen(®) family that has been specifically designed for the pediatric population and is the first to combine half-unit increment (=0.5 U of insulin) dosing with a simple memory function. The half-unit increment dosing amendments and accurate injection of 0.5 U of insulin are particularly beneficial for children (and insulin-sensitive adults/elders), who often require small insulin doses. The memory function can be used to record the time and amount of the last dose, reducing the fear of double dosing or missing a dose. The memory function also provides parents with extra confidence and security that their child is taking insulin at the correct doses and times. NovoPen Echo is a lightweight, durable insulin delivery pen; it is available in two different colors, which may help to distinguish between different types of insulin, providing more confidence for both users and caregivers. Studies have demonstrated a high level of patient satisfaction, with 80% of users preferring NovoPen Echo to other pediatric insulin pens. PMID:26793007

  19. NovoPen Echo® insulin delivery device

    PubMed Central

    Hyllested-Winge, Jacob; Sparre, Thomas; Pedersen, Line Kynemund

    2016-01-01

    The introduction of insulin pen devices has provided easier, well-tolerated, and more convenient treatment regimens for patients with diabetes mellitus. When compared with vial and syringe regimens, insulin pens offer a greater clinical efficacy, improved quality of life, and increased dosing accuracy, particularly at low doses. The portable and discreet nature of pen devices reduces the burden on the patient, facilitates adherence, and subsequently contributes to the improvement in glycemic control. NovoPen Echo® is one of the latest members of the NovoPen® family that has been specifically designed for the pediatric population and is the first to combine half-unit increment (=0.5 U of insulin) dosing with a simple memory function. The half-unit increment dosing amendments and accurate injection of 0.5 U of insulin are particularly beneficial for children (and insulin-sensitive adults/elders), who often require small insulin doses. The memory function can be used to record the time and amount of the last dose, reducing the fear of double dosing or missing a dose. The memory function also provides parents with extra confidence and security that their child is taking insulin at the correct doses and times. NovoPen Echo is a lightweight, durable insulin delivery pen; it is available in two different colors, which may help to distinguish between different types of insulin, providing more confidence for both users and caregivers. Studies have demonstrated a high level of patient satisfaction, with 80% of users preferring NovoPen Echo to other pediatric insulin pens. PMID:26793007

  20. Review of metastable states in heavy nuclei.

    PubMed

    Dracoulis, G D; Walker, P M; Kondev, F G

    2016-07-01

    The structure of nuclear isomeric states is reviewed in the context of their role in contemporary nuclear physics research. Emphasis is given to high-spin isomers in heavy nuclei, with [Formula: see text]. The possibility to exploit isomers to study some of the most exotic nuclei is a recurring theme. In spherical nuclei, the role of octupole collectivity is discussed in detail, while in deformed nuclei the limitations of the K quantum number are addressed. Isomer targets and isomer beams are considered, along with applications related to energy storage, astrophysics, medicine, and experimental advances. PMID:27243336

  1. Mirror nuclei constraint in nuclear mass formula

    SciTech Connect

    Wang Ning; Liang Zuoying; Liu Min; Wu, Xizhen

    2010-10-15

    The macroscopic-microscopic mass formula is further improved by considering mirror nuclei constraint. The rms deviation with respect to 2149 measured nuclear masses is reduced to 0.441 MeV. The shell corrections, the deformations of nuclei, the neutron and proton drip lines, and the shell gaps are also investigated to test the model. The rms deviation of {alpha}-decay energies of 46 superheavy nuclei is reduced to 0.263 MeV. The predicted central position of the superheavy island could lie around N=176{approx}178 and Z=116{approx}120 according to the shell corrections of nuclei.

  2. Review of metastable states in heavy nuclei

    NASA Astrophysics Data System (ADS)

    Dracoulis, G. D.; Walker, P. M.; Kondev, F. G.

    2016-07-01

    The structure of nuclear isomeric states is reviewed in the context of their role in contemporary nuclear physics research. Emphasis is given to high-spin isomers in heavy nuclei, with A≳ 150 . The possibility to exploit isomers to study some of the most exotic nuclei is a recurring theme. In spherical nuclei, the role of octupole collectivity is discussed in detail, while in deformed nuclei the limitations of the K quantum number are addressed. Isomer targets and isomer beams are considered, along with applications related to energy storage, astrophysics, medicine, and experimental advances.

  3. Physical Processing of Cometary Nuclei

    NASA Technical Reports Server (NTRS)

    Weissman, Paul R.; Stern, S. Alan

    1997-01-01

    Cometary nuclei preserve a cosmo-chemical record of conditions and processes in the primordial solar nebula, and possibly even the interstellar medium. However, that record is not perfectly preserved over the age of the solar system due to a variety of physical processes which act to modify cometary surfaces and interiors. Possible structural and/or internal processes include: collisional accretion, disruption, and reassembly during formation; internal heating by long and short-lived radionuclides; amorphous to crystalline phase transitions, and thermal stresses. Identified surface modification processes include: irradiation by galactic cosmic rays, solar protons, UV photons, and the Sun's T Tauri stage mass outflow; heating by passing stars and nearby supernovae; gardening by debris impacts; the accretion of interstellar dust and gas and accompanying erosion by hypervelocity dust impacts and sputtering; and solar heating with accompanying crust formation. These modification processes must be taken into account in both the planning and the interpretation of the results of a Comet Nucleus Sample Return Mission. Sampling of nuclei should be done at as great a depth below the surface crust as technically feasible, and at vents or fissures leading to exposed volatiles at depth. Samples of the expected cometary crust and near-surface layers also need to be returned for analysis to achieve a better understanding of the effects of these physical processes. We stress that comets are still likely less modified dm any other solar system bodies, but the degree of modification can vary greatly from one comet to the next.

  4. Mass-23 nuclei in astrophysics

    NASA Astrophysics Data System (ADS)

    Fraser, P. R.; Amos, K.; Canton, L.; Karataglidis, S.; Svenne, J. P.; van der Kniff, D.

    2015-09-01

    The formation of mass-23 nuclei by radiative capture is of great interest in astrophysics. A topical problem associated with these isobars is the so-called 22Na puzzle of ONe white dwarf novae, where the abundance of 22Na observed is not as is predicted by current stellar models, indicating there is more to learn about how the distribution of elements in the universe occurred. Another concerns unexplained variations in elements abundance on the surface of aging red giant stars. One method for theoretically studying nuclear scattering is the Multi-Channel Algebraic Scattering (MCAS) formalism. Studies to date have used a simple collective-rotor prescription to model the target states which couple to projectile nucleons. While, in general, the target states considered all belong to the ground state rotor band, for some systems it is necessary to include coupling to states outside of this band. Herein we discuss an extension of MCAS to allow coupling of different strengths between such states and the ground state band. This consideration is essential when studying the scattering of neutrons from 22Ne, a necessary step in studying the mass-23 nuclei mentioned above.

  5. The structure of light nuclei

    NASA Astrophysics Data System (ADS)

    Gao, H.

    2002-04-01

    In the last several years, tremendous advances both in experiment and theory have been made in understanding the structure of light nuclei. The experimental advances have benefited greatly from the new, high intensity CW machine (CEBAF) at Jefferson Lab and new experimental techniques utilizing polarization degrees of freedom at various laboratories. Tremendous progress has also been made in nuclear few-body theory, from a successful standard model of nuclear physics based on modern two-nucleon potentials as well as modern three-nucleon forces to the exact three-body calculation extended into the continuum by solving the corresponding Faddeev equations. In this talk, I will review recent experimental progress in understanding the structure of light nuclei focusing on the results of deuteron elastic form factors, deuteron tensor polarization, deuteron photodisintegration, and that of the 3He magnetic form factor. I will also highlight some recent results on the experimental search for the three-nucleon force, the short-range nucleon-nucleon correlation, and the nucleon structure study using a polarized 3He target as an effective neutron target. To summarize, I will provide some future outlook on this subject in the light of the upcoming BLAST program at the MIT-Bates Laboratory and the possible future 12 GeV upgrade at the Jefferson Lab.

  6. Selfconsistent calculations for hyperdeformed nuclei

    SciTech Connect

    Molique, H.; Dobaczewski, J.; Dudek, J.; Luo, W.D.

    1996-12-31

    Properties of the hyperdeformed nuclei in the A {approximately} 170 mass range are re-examined using the self-consistent Hartree-Fock method with the SOP parametrization. A comparison with the previous predictions that were based on a non-selfconsistent approach is made. The existence of the {open_quotes}hyper-deformed shell closures{close_quotes} at the proton and neutron numbers Z=70 and N=100 and their very weak dependence on the rotational frequency is suggested; the corresponding single-particle energy gaps are predicted to play a role similar to that of the Z=66 and N=86 gaps in the super-deformed nuclei of the A {approximately} 150 mass range. Selfconsistent calculations suggest also that the A {approximately} 170 hyperdeformed structures have neglegible mass asymmetry in their shapes. Very importantly for the experimental studies, both the fission barriers and the {open_quotes}inner{close_quotes} barriers (that separate the hyperdeformed structures from those with smaller deformations) are predicted to be relatively high, up to the factor of {approximately}2 higher than the corresponding ones in the {sup 152}Dy superdeformed nucleus used as a reference.

  7. Contrast variation in spin-echo small angle neutron scattering

    SciTech Connect

    Chen, Wei-Ren; Herwig, Kenneth W; Li, Xin; Liu, Emily; Liu, Yun; Pynn, Roger; Robertson, J. L.; Shew, Chwen-Yang; Smith, Gregory Scott; Wu, Bin

    2012-01-01

    The principle of using contrast variation spin-echo small angle neutron scattering (SESANS) technique for colloidal structural investigation is discussed. Based on the calculations of several model systems, we find that the contrast variation SESANS technique is not sensitive in detecting the structural characteristics of colloidal suspensions consisting of particles with uniform scattering length density profiles. However, its capability of resolving the structural heterogeneity, at both intra- and inter-colloidal length scales, is clearly demonstrated. The prospect of using this new technique to investigate the structural information that is difficult to be probed by other ways is also explored.

  8. Chandra Discovers Light Echo from the Milky Way's Black Hole

    NASA Astrophysics Data System (ADS)

    2007-01-01

    Like cold case investigators, astronomers have used NASA's Chandra X-ray Observatory to uncover evidence of a powerful outburst from the giant black hole at the Milky Way's center. A light echo was produced when X-ray light generated by gas falling into the Milky Way's supermassive black hole, known as Sagittarius A* (pronounced "A-star"), was reflected off gas clouds near the black hole. While the primary X-rays from the outburst would have reached Earth about 50 years ago, the reflected X-rays took a longer path and arrived in time to be recorded by Chandra. Variability in Chandra Images of Light Echo Variability in Chandra Images of Light Echo "This dramatic event happened before we had satellites in space that could detect it," said Michael Muno of the California Institute of Technology in Pasadena. "So, it's remarkable that we can use Chandra to dig into the past and see this monster black hole's capacity for destruction." Previously, scientists have used Chandra to directly detect smaller and more recent outbursts from the black hole. This latest outburst revealed by the X-ray echo was about 1,000 times brighter and lasted well over 1,000 times longer than any of the recent outbursts observed by Chandra. Theory predicts that an outburst from Sagittarius A* would cause X-ray emission from the clouds to vary in both intensity and shape. Muno and his team found these changes for the first time, thus ruling out other interpretations. The latest results corroborate other independent, but indirect, evidence for light echoes generated by the black hole in the more distant past. Illustrations of Light Echo Illustrations of Light Echo Scientists have long known that Sagittarius A*, with a mass of about 3 million suns, lurked at the center for Milky Way. However, the black hole is incredibly faint at all wavelengths, especially in X-rays. "This faintness implies that stars and gas rarely get close enough to the black hole to be in any danger," said co-author Frederick

  9. Results of forward-scatter radio echo observations in 2000

    NASA Astrophysics Data System (ADS)

    Ueda, Masayoshi; Maegawa, Kimio

    2001-11-01

    We had been performing a forward scatter radio observation of meteor since 1996. The transmitting station was at Fukui (Japan), and the frequency is 53.750 MHz and the power is 50W. The receiving station is Osaka (Japan) and base line has 160 km distance and NE-SW direction. 504,588 meteor echoes have been observed from January to December 2000. Total of radio observation was 8,238 hours. We made the activities of these showers (June), δ Aquarids (July), Perseids (August), Leonids (November), Geminids (December) and Ursids (December). Moreover, we reported the daily variation of mean meteor rates and the annual variation of mean meteor rates.

  10. Efficient Fast Stereo Acoustic Echo Cancellation Based on Pairwise Optimal Weight Realization Technique

    NASA Astrophysics Data System (ADS)

    Yukawa, Masahiro; Murakoshi, Noriaki; Yamada, Isao

    2006-12-01

    In stereophonic acoustic echo cancellation (SAEC) problem, fast and accurate tracking of echo path is strongly required for stable echo cancellation. In this paper, we propose a class of efficient fast SAEC schemes with linear computational complexity (with respect to filter length). The proposed schemes are based on pairwise optimal weight realization (POWER) technique, thus realizing a "best" strategy (in the sense of pairwise and worst-case optimization) to use multiple-state information obtained by preprocessing. Numerical examples demonstrate that the proposed schemes significantly improve the convergence behavior compared with conventional methods in terms of system mismatch as well as echo return loss enhancement (ERLE).

  11. Echo scintillation Index affected by cat-eye target's caliber with Cassegrain lens

    NASA Astrophysics Data System (ADS)

    Shan, Cong-miao; Sun, Hua-yan; Zhao, Yan-zhong; Zheng, Yong-hui

    2015-10-01

    The optical aperture of cat-eye target has the aperture averaging effect to the active detecting laser of active laser detection system, which can be used to identify optical targets. The echo scintillation characteristics of the transmission-type lens target have been studied in previous work. Discussing the differences of the echo scintillation characteristics between the transmission-type lens target and Cassegrain lens target can be helpful to targets classified. In this paper, the echo scintillation characteristics of Cat-eye target's caliber with Cassegrain lens has been discussed . By using the flashing theory of spherical wave in the weak atmospheric turbulence, the annular aperture filter function and the Kolmogorov power spectrum, the analytic expression of the scintillation index of the cat-eye target echo of the horizontal path two-way transmission was given when the light is normal incidence. Then the impact of turbulence inner and outer scale to the echo scintillation index and the analytic expression of the echo scintillation index at the receiving aperture were presented using the modified Hill spectrum and the modified Von Karman spectrum. Echo scintillation index shows the tendency of decreasing with the target aperture increases and different ratios of the inner and outer aperture diameter show the different echo scintillation index curves. This conclusion has a certain significance for target recognition in the active laser detection system that can largely determine the target type by largely determining the scope of the cat-eye target which depending on echo scintillation index.

  12. Streamlining Metadata Ingest and Discovery Using ECHO's REST-based API

    NASA Astrophysics Data System (ADS)

    Ericson, R.; Baynes, K.; Pilone, D.

    2012-12-01

    Enabling user access to Earth science data is a primary goal of NASA's Earth Observing System Data and Information Systems (EOSDIS) programs. NASA's Earth Observing System ClearingHOuse (ECHO) acts as the core metadata repository for EOSDIS's data centers, providing a centralized mechanism for metadata and data discovery and retrieval. ECHO has recently made strides to restructure its API; allowing data partners to streamline and synchronize their metadata ingest using RESTful web services. ECHO's legacy ingest process involves data uploads via FTP with asynchronous result reporting. Data centers provide single xml files or compressed data (zip) files that are unpacked, indexed and stored in ECHO data tables for future search and retrieval. Any problems related to metadata validation and ingest are reported after batch processing of discrete jobs have been completed. With ECHO's new REST-based web services, data providers will receive immediate feedback about the status of their ingested data and can ensure that their data exports are successful as soon as the data is posted to our repository. This presentation will introduce ECHO's potential new and existing data partners to the process of implementing data ingest via its RESTful web services API, providing real-world examples of end-to-end metadata management. Examples of ECHO's support of multi-format metadata ingest using both ECHO10 and ISO 19115 metadata formats will be showcased. This presentation will also pay special attention to tuning a provider's metadata, making it more easily searched and accessed via ECHO's various interfaces.

  13. Volumetric Echocardiographic Particle Image Velocimetry (V-Echo-PIV)

    NASA Astrophysics Data System (ADS)

    Falahatpisheh, Ahmad; Kheradvar, Arash

    2015-11-01

    Measurement of 3D flow field inside the cardiac chambers has proven to be a challenging task. Current laser-based 3D PIV methods estimate the third component of the velocity rather than directly measuring it and also cannot be used to image the opaque heart chambers. Modern echocardiography systems are equipped with 3D probes that enable imaging the entire 3D opaque field. However, this feature has not yet been employed for 3D vector characterization of blood flow. For the first time, we introduce a method that generates velocity vector field in 4D based on volumetric echocardiographic images. By assuming the conservation of brightness in 3D, blood speckles are tracked. A hierarchical 3D PIV method is used to account for large particle displacement. The discretized brightness transport equation is solved in a least square sense in interrogation windows of size 163 voxels. We successfully validate the method in analytical and experimental cases. Volumetric echo data of a left ventricle is then processed in the systolic phase. The expected velocity fields were successfully predicted by V-Echo-PIV. In this work, we showed a method to image blood flow in 3D based on volumetric images of human heart using no contrast agent.

  14. [Minimally invasive hemodynamic monitoring with esophageal echoDoppler].

    PubMed

    Monge, M I; Estella, A; Díaz, J C; Gil, A

    2008-01-01

    Hemodynamic monitoring is a key element in the care of the critical patients, providing an unquestionable aid in the attendance to diagnosis and the choice of the adequate treatment. Minimally invasive devices have been emerging over the past few years as an effective alternative to classic monitoring tools. The esophageal echoDoppler is among these. It makes it possible to obtain continuous and minimally invasive monitoring of the cardiac output in addition to other useful parameters by measuring the blood flow rate and the diameter of the thoracic descending aorta, which provides a sufficiently extensive view of the hemodynamic state of the patient and facilitates early detection of the changes produced by a sudden clinical derangement. Although several studies have demonstrated the usefulness of the esophageal Doppler in the surgical scene, there is scarce and dispersed evidence in the literature on its benefits in critical patients. Nevertheless, its advantages make it an attractive element to take into account within the diagnostic arsenal in the intensive care. The purpose of the following article is to describe how it works, its degree of validation with other monitoring methods and the role of esophageal echoDoppler as a minimally invasive monitoring tool for measuring cardiac output in the daily clinical practice, contributing with our own experience in the critical patient. PMID:18221711

  15. The science of EChO - Exoplanet Characterisation Obseravtory

    NASA Astrophysics Data System (ADS)

    Tinetti, G.; Drossart, P.; Hartogh, P.; Isaak, K.; Linder, M.; Lovis, C.; Micela, G.; Puig, L.; Ollivier, M.; Ribas, I.; Snellen, I.; Swinyard, B.

    2013-09-01

    It is now accepted that exoplanets are ubiquitous in our Galaxy. The planetary parameters mass, radius and temperature alone do not explain the diversity revealed by current observations. The chemical composition of these planets is needed to trace back their formation history and evolution, as was the case for the Solar System. Pioneering results were obtained through transit spectroscopy with Hubble, Spitzer and groundbased facilities, enabling the detection of a few, most abundant ionic, atomic and molecular species and to constrain the planet's thermal structure. With the arrival of EChO in the coming decade, planetary science will expand beyond the narrow boundaries of our Solar System to encompass our whole Galaxy. EChO will address the following fundamental questions: - Why are exoplanets as they are? - What are the causes for the observed diversity? - Can their formation history be traced back from their current composition and evolution? Spectroscopic observations from the visible to Mid-IR of a large, select sample of exoplanets, will allow us to use the chemical composition as a powerful diagnostic of the history, formation mechanisms and evolution of gaseous and rocky exoplanets. Our strategy is to balance statistical information, obtainable through a chemical survey of a large and diverse sample of objects - as it is traditionally done for stars - with deep, repeated observations of a more restricted, select sample of planets - a strategy that will enable the kind of science that was accomplished for Solar System planets.

  16. ESA M3 mission candidate EChO

    NASA Astrophysics Data System (ADS)

    Puig, L.; Isaak, K. G.; Escudero, I.; Martin, D.; Crouzet, P.-E.; Rando, N.

    2011-09-01

    The Exoplanet Characterisation Observatory (EChO) is a medium class mission candidate within the science program Cosmic Vision 2015-2025 of the European Space Agency. It was selected in February 2011 as one of 4 M3 mission candidates to enter an assessment phase. The assessment activities start with the definition of science and mission requirements as well as of a preliminary model payload, followed by an internal Concurrent Design Facility (CDF) study. Parallel industrial studies will follow in 2012, after which the 4 missions will be reviewed to identify candidates entering definition phase studies in 2013. EChO aims at characterising the atmosphere of known transiting exoplanets, potentially from giant Hot Jupiters down to Super-Earths orbiting in the habitable zone of M-dwarf stars. It will use a 1 m class telescope, feeding a spectrometer covering the wave lengths from 0.4 to 11 microns with a potential extension to 16 microns. While spatial differentiation of the exoplanet and its host star is not necessary, spectral differentiation will be achieved by making differential measurements of in- and out- of transit frames to cancel the star signal. This paper describes critical requirements, and gives an overview of the model payload design. It also reports on the results of the CDF.

  17. Modeling of cortical signals using echo state networks

    NASA Astrophysics Data System (ADS)

    Zhou, Hanying; Wang, Yongji; Huang, Jiangshuai

    2009-10-01

    Diverse modeling frameworks have been utilized with the ultimate goal of translating brain cortical signals into prediction of visible behavior. The inputs to these models are usually multidimensional neural recordings collected from relevant regions of a monkey's brain while the outputs are the associated behavior which is typically the 2-D or 3-D hand position of a primate. Here our task is to set up a proper model in order to figure out the move trajectories by input the neural signals which are simultaneously collected in the experiment. In this paper, we propose to use Echo State Networks (ESN) to map the neural firing activities into hand positions. ESN is a newly developed recurrent neural network(RNN) model. Besides its dynamic property and short term memory just as other recurrent neural networks have, it has a special echo state property which endows it with the ability to model nonlinear dynamic systems powerfully. What distinguished it from transitional recurrent neural networks most significantly is its special learning method. In this paper we train this net with a refined version of its typical training method and get a better model.

  18. Echo-Enabled Harmonic Generation for Seeded FELs

    SciTech Connect

    Stupakov, G.; /SLAC

    2011-05-19

    In the x-ray wavelengths, the two leading FEL concepts are the self-amplified spontaneous emission (SASE) configuration and the high-gain harmonic generation (HGHG) scheme. While the radiation from a SASE FEL is coherent transversely, it typically has rather limited temporal coherence. Alternatively, the HGHG scheme allows generation of fully coherent radiation by up-converting the frequency of a high-power seed laser. However, due to the relatively low up-frequency conversion efficiency, multiple stages of HGHG FEL are needed in order to generate x-rays from a UV laser. The up-frequency conversion efficiency can be greatly improved with the recently proposed echo-enabled harmonic generation (EEHG) technique. In this work we will present the concept of EEHG, and address some practically important issues that affect the performance of the seeding. We show how the EEHG can be incorporated in the FEL scheme and what is the expected performance of the EEHG seeded FEL. We will then briefly describe the first proof-of-principle EEHG experiment carried out at the Next Linear Collider Test Accelerator (NLCTA) at SLAC. We will also discuss latest advances in the echo-scheme approach, and refer to subsequent modifications of the original concept.

  19. Photon echo spectroscopy reveals structure-dynamics relationships in carotenoids

    NASA Astrophysics Data System (ADS)

    Christensson, N.; Polivka, T.; Yartsev, A.; Pullerits, T.

    2009-06-01

    Based on simultaneous analysis of the frequency-resolved transient grating, peak shift, and echo width signals, we present a model for the third-order optical response of carotenoids including population dynamics and system-bath interactions. Our frequency-resolved photon echo experiments show that the model needs to incorporate the excited-state absorption from both the S2 and the S1 states. We apply our model to analyze the experimental results on astaxanthin and lycopene, aiming to elucidate the relation between structure and system-bath interactions. Our analysis allows us to relate structural motifs to changes in the energy-gap correlation functions. We find that the terminal rings of astaxanthin lead to increased coupling between slow molecular motions and the electronic transition. We also find evidence for stronger coupling to higher frequency overdamped modes in astaxanthin, pointing to the importance of the functional groups in providing coupling to fluctuations influencing the dynamics in the passage through the conical intersection governing the S2-S1 relaxation.

  20. Photon Echo Studies of MEH-PPV with Broken Conjugation

    NASA Astrophysics Data System (ADS)

    Dykstra, Tieneke E.; Yang, Xiujuan; Scholes, Gregory D.

    2004-03-01

    Conjugated polymers are of great interest due to applications in opto-electronic and photonic devices. The degree of conjugation along the polymer backbone plays an important role in the photophysics of these systems. We report three pulse photon echo (3PE) studies on poly[2-methoxy, <5-(2'-ethyl-hexoxy)-1,4-phenylene vinylene] (MEH-PPV) polymers with varying degrees of breaks in conjugation introduced by intentional chemical defects. We report three pulse photon echo peak shift (3PEPS) and 2D-3PE measurements in each of the -k1+k2+k3, k1-k2+k3, and k1+k2-k3 phase-matching directions. Each of these phase-matching directions can provide different information about the dephasing processes. The experimental data are interpreted using a model that incorporates both the coupling of torsional motions to electronic transitions and the conformational disorder introduced by the presence of isomers and the distribution of conjugation lengths.

  1. Plasma Density and Radio Echoes in the Magnetosphere

    NASA Technical Reports Server (NTRS)

    Calvert, W.

    1995-01-01

    This project provided a opportunity to study a variety of interesting topics related to radio sounding in the magnetosphere. The results of this study are reported in two papers which have been submitted for publication in the Journal of Geophysical Research and Radio Science, and various aspects of this study were also reported at meetings of the American Geophysical Union (AGU) at Baltimore, Maryland and the International Scientific Radio Union (URSI) at Boulder, Colorado. The major results of this study were also summarized during a one-day symposium on this topic sponsored by Marshall Space Flight Center in December 1994. The purpose of the study was to examine the density structure of the plasmasphere and determine the relevant mechanisms for producing radio echoes which can be detected by a radio sounder in the magnetosphere. Under this study we have examined density irregularities, biteouts, and outliers of the plasmasphere, studied focusing, specular reflection, ducting, and scattering by the density structures expected to occur in the magnetosphere, and predicted the echoes which can be detected by a magnetospheric radio sounder.

  2. Echo Park controversy and the American conservation movement

    SciTech Connect

    Harvey, M.W.T.

    1986-01-01

    During the twentieth century, a few conservation battles have pitted in as classic a fashion the foes of preservation and development as that waged during the 1950s over Dinosaur National Monument. The issue was whether to build the proposed Echo Park Dam within Dinosaur National Monument. The Monument spans the Utah-Colorado border, and comprises the confluence of the Green and Yampa Rivers. Echo Park, a lovely, peaceful meadow flanked by massive sandstone walls at the rivers' confluence, became the storm-center of controversy when the Bureau of Reclamation made plans to dam the Green River just two miles to the south. The dam would have flooded a hundred miles of this canyon country, and the proposal startled the nation's major conservation organizations and occupied their attention for several years. Their effort to prevent the dam ultimately succeeded, and their story is critical in tracing the roots of contemporary conservation. In the end, pressure from conservation groups helped to delete the dam from the legislation, and Dinosaur's river canyons were preserved.

  3. Probing lung microstructure with hyperpolarized 3He gradient echo MRI.

    PubMed

    Sukstanskii, Alexander L; Quirk, James D; Yablonskiy, Dmitriy A

    2014-12-01

    In this paper we demonstrate that gradient echo MRI with hyperpolarized (3)He gas can be used for simultaneously extracting in vivo information about lung ventilation properties, alveolar geometrical parameters, and blood vessel network structure. This new approach is based on multi-gradient-echo experimental measurements of hyperpolarized (3)He gas MRI signal from human lungs and a proposed theoretical model of this signal. Based on computer simulations of (3)He atoms diffusing in the acinar airway tree in the presence of an inhomogeneous magnetic field induced by the susceptibility differences between lung tissue (alveolar septa, blood vessels) and lung airspaces, we derive analytical expressions relating the time-dependent MR signal to the geometrical parameters of acinar airways and the blood vessel network. Data obtained on eight healthy volunteers are in good agreement with literature values. This information is complementary to the information obtained by means of the in vivo lung morphometry technique with hyperpolarized 3He diffusion MRI previously developed by our group, and opens new opportunities to study lung microstructure in health and disease. PMID:24920182

  4. Quantum and classical correlations in electron-nuclear spin echo

    SciTech Connect

    Zobov, V. E.

    2014-11-15

    The quantum properties of dynamic correlations in a system of an electron spin surrounded by nuclear spins under the conditions of free induction decay and electron spin echo have been studied. Analytical results for the time evolution of mutual information, classical part of correlations, and quantum part characterized by quantum discord have been obtained within the central-spin model in the high-temperature approximation. The same formulas describe discord in both free induction decay and spin echo although the time and magnetic field dependences are different because of difference in the parameters entering into the formulas. Changes in discord in the presence of the nuclear polarization β{sub I} in addition to the electron polarization β{sub S} have been calculated. It has been shown that the method of reduction of the density matrix to a two-spin electron-nuclear system provides a qualitatively correct description of pair correlations playing the main role at β{sub S} ≈ β{sub I} and small times. At large times, such correlations decay and multispin correlations ensuring nonzero mutual information and zero quantum discord become dominant.

  5. Intramembrane Polarity by Electron Spin Echo Spectroscopy of Labeled Lipids

    PubMed Central

    Bartucci, Rosa; Guzzi, Rita; Marsh, Derek; Sportelli, Luigi

    2003-01-01

    The association of water (D2O) with phospholipid membranes was studied by using pulsed-electron spin resonance techniques. We measured the deuterium electron spin echo modulation of spin-labeled phospholipids by D2O in membranes of dipalmitoyl phosphatidylcholine with and without 50 mol% of cholesterol. The Fourier transform of the relaxation-corrected two-pulse echo decay curve reveals peaks, at one and two times the deuterium NMR frequency, that arise from the dipolar hyperfine interaction of the deuterium nucleus with the unpaired electron spin of the nitroxide-labeled lipid. For phosphatidylcholine spin-labeled at different positions down the sn-2 chain, the amplitude of the deuterium signal decreases toward the center of the membrane, and is reduced to zero from the C-12 atom position onward. At chain positions C-5 and C-7 closer to the phospholipid headgroups, the amplitude of the deuterium signal is greater in the presence of cholesterol than in its absence. These results are in good agreement with more indirect measurements of the transmembrane polarity profile that are based on the 14N-hyperfine splittings in the conventional continuous-wave electron spin resonance spectrum. PMID:12547783

  6. Meteoroid mass determination using head echoes detected at multiple frequencies

    NASA Astrophysics Data System (ADS)

    Close, Sigrid; Oppenheim, Meers; Hunt, Stephen; McKeen, Fred; Coster, Anthea

    2002-11-01

    Meteor data collected at the Kwajalein Missile Range (KMR) during the peak of the 1998 Leonid storm comprise the only simultaneous data collection of meteor head echoes and trails using seven frequencies (VHF, UHF, L-, S-, C-, Ka- and W-band). The primary sensor was the ALTAIR radar operating at 160 MHz with 30-m range resolution and 422 MHz with 7.5-m range resolution, which has both interferometric and polarization capabilities. This paper presents an alaysis of these high-resolution data in support of the following ideas: First, head echo scattering appears to arise from an ionized region with a density sufficiently high that its plasma frequency exceeds the radar frequency (overdense reflection). Second, the Radar-cross-section (RCS) values, which decrease with decreasing wavelength, peak near 105 km altitude at the point where the meteoroid gives up the most kinetic energy during its descent. Third, these RCS measurements were used to compute electron line densities, which provide estimates of a meteoroid's mass. By combining these data and simple ablation models, we can constrain meteoroid mass as it loses material during its passage through the atmosphere.

  7. Echoes of Historical Supernovae in the Milky Way Galaxy

    NASA Astrophysics Data System (ADS)

    Rest, Armin; Badenes, Carles; Blondin, Stephane; Challis, Peter; Clocchiatti, Alejandro; Filippenko, Alex; Foley, Ryan; Huber, Mark E.; Matheson, Thomas; Mazzali, Paolo; Olsen, Knut; Sauer, Daniel; Sinnott, Brendan; Smith, R. Chris; Suntzeff, Nicholas; Welch, Doug; Bergmann, Marcel

    2010-08-01

    We propose to discover the first light echoes (LEs) associated with the historical Galactic supernovae SN 1181 (3C 58) and SN 1054 (Crab), and to locate additional LE complexes from SN 1680 (Cas A) and SN 1572 (Tycho). Using other facilities, we will obtain spectra of the LEs to determine the nature and properties of these important events. This is a continuation of a previously approved NOAO program to obtain images of regions of significant dust concentration near these Galactic supernova remnants. With data from previous semesters, we found LEs from the Cas A and Tycho supernovae teRest08b. We then used the rich set of LEs from Cas A to examine the Cas A SN from different viewing angles teRest10_casaspec, Rest10_leprofile, finding that in one direction the He I (lambda) 5876 and H(alpha) features are blue-shifted by an additional about 4000 km/s relative to the other directions teRest10_casaspec, which is direct evidence that the SN was asymmetric. The study of scattered-light echoes from Galactic supernovae provides a host of newly-recognized observational benefits which have only just begun to be exploited including (1) a direct comparison of a supernova and its remnant, (2) a three-dimensional view of a supernova, and (3) a Galactic network of absolute distance differences.

  8. An energetic stellar outburst accompanied by circumstellar light echoes.

    PubMed

    Bond, Howard E; Henden, Arne; Levay, Zoltan G; Panagia, Nino; Sparks, William B; Starrfield, Sumner; Wagner, R Mark; Corradi, R L M; Munari, U

    2003-03-27

    Some classes of stars, including novae and supernovae, undergo explosive outbursts that eject stellar material into space. In 2002, the previously unknown variable star V838 Monocerotis brightened suddenly by a factor of approximately 10(4). Unlike a supernova or nova, it did not explosively eject its outer layers; rather, it simply expanded to become a cool supergiant with a moderate-velocity stellar wind. Superluminal light echoes were discovered as light from the outburst propagated into the surrounding, pre-existing circumstellar dust. Here we report high-resolution imaging and polarimetry of those light echoes, which allow us to set direct geometric distance limits to the object. At a distance of >6 kpc, V838 Mon at its maximum brightness was temporarily the brightest star in the Milky Way. The presence of the circumstellar dust implies that previous eruptions have occurred, and spectra show it to be a binary system. When combined with the high luminosity and unusual outburst behaviour, these characteristics indicate that V838 Mon represents a hitherto unknown type of stellar outburst, for which we have no completely satisfactory physical explanation. PMID:12660776

  9. Emergence of metapopulations and echo chambers in mobile agents.

    PubMed

    Starnini, Michele; Frasca, Mattia; Baronchelli, Andrea

    2016-01-01

    Multi-agent models often describe populations segregated either in the physical space, i.e. subdivided in metapopulations, or in the ecology of opinions, i.e. partitioned in echo chambers. Here we show how both kinds of segregation can emerge from the interplay between homophily and social influence in a simple model of mobile agents endowed with a continuous opinion variable. In the model, physical proximity determines a progressive convergence of opinions but differing opinions result in agents moving away from each others. This feedback between mobility and social dynamics determines the onset of a stable dynamical metapopulation scenario where physically separated groups of like-minded individuals interact with each other through the exchange of agents. The further introduction of confirmation bias in social interactions, defined as the tendency of an individual to favor opinions that match his own, leads to the emergence of echo chambers where different opinions coexist also within the same group. We believe that the model may be of interest to researchers investigating the origin of segregation in the offline and online world. PMID:27572928

  10. Spectral correlation in ultrasonic pulse echo signal processing.

    PubMed

    Donohue, K D; Bressler, J M; Varghese, T; Bilgutay, N M

    1993-01-01

    The effects of using spectral correlation in a maximum-likelihood estimator (MLE) for backscattered energy corresponding to coherent reflectors embedded in media of microstructure scatterers is considered. The spectral autocorrelation (SAC) function is analyzed for various scatterer configurations based on the regularity of the interspacing distance between scatterers. It is shown that increased regularity gives rise to significant spectral correlation, whereas uniform distribution of scatters throughout a resolution cell results in no significant correlation between spectral components. This implies that when a true uniform distribution for the effective scatterers exists, the power spectral density (PSD) is sufficient to characterize their echoes. However, as the microstructure scatterer distribution becomes more regular, SAC terms become more significant. MLE results for 15 A-scans from stainless steel specimens with three different grain sizes indicate an average 6-dB signal-to-noise ratio (SNR) improvement in the coherent scatterer (flat-bottom hole) echo intensities for estimators using the SAC characterization as opposed to the PSD characterization. PMID:18263188

  11. Emergence of metapopulations and echo chambers in mobile agents

    PubMed Central

    Starnini, Michele; Frasca, Mattia; Baronchelli, Andrea

    2016-01-01

    Multi-agent models often describe populations segregated either in the physical space, i.e. subdivided in metapopulations, or in the ecology of opinions, i.e. partitioned in echo chambers. Here we show how both kinds of segregation can emerge from the interplay between homophily and social influence in a simple model of mobile agents endowed with a continuous opinion variable. In the model, physical proximity determines a progressive convergence of opinions but differing opinions result in agents moving away from each others. This feedback between mobility and social dynamics determines the onset of a stable dynamical metapopulation scenario where physically separated groups of like-minded individuals interact with each other through the exchange of agents. The further introduction of confirmation bias in social interactions, defined as the tendency of an individual to favor opinions that match his own, leads to the emergence of echo chambers where different opinions coexist also within the same group. We believe that the model may be of interest to researchers investigating the origin of segregation in the offline and online world. PMID:27572928

  12. Motion and distortion correction of skeletal muscle echo planar images.

    PubMed

    Davis, Andrew D; Noseworthy, Michael D

    2016-07-01

    This paper examines two artifacts facing researchers who use gradient echo (GRE) echo planar imaging (EPI) for time series studies of skeletal muscles in limbs. The first is through-plane blood flow during the acquisition, causing a vessel motion artifact that inhibits proper motion correction of the data. The second is distortion of EPI images caused by B0 field inhomogeneities. Though software tools are available for correcting these artifacts in brain EPI images, the tools do not perform well on muscle images. The severity of the two artifacts was described using image similarity measures, and the data was processed with both a conventional motion correction program and custom written tools. The conventional program did not perform well on the limb images, in fact significantly degrading image quality in some trials. Data is presented which proves that arterial pulsatile signal caused the impairment in motion correction. The new tools were shown to perform much better, achieving substantial motion correction and distortion correction of the muscle EPI images. PMID:26972774

  13. EChO fine guidance sensor design and architecture

    NASA Astrophysics Data System (ADS)

    Ottensamer, Roland; Rataj, Miroslaw; Schrader, Jan-Rutger; Ferstl, Roman; Güdel, Manuel; Kerschbaum, Franz; Luntzer, Armin

    2014-08-01

    EChO, the Exoplanet Characterization Observatory, is an M-class candidate in the ESA Comic Vision programme. It will provide high resolution, multi-wavelength spectroscopic observations of exoplanets, measure their atmospheric composition, temperature and albedo. The scientific payload is a spectrometer covering the 0.4-11 micron waveband. High photometric stability over a time scale of about 10 hours is one of the most stringent requirements of the EChO mission. As a result, fine pointing stability relative to the host star is mandatory. This will be achieved through a Fine Guidance Sensor (FGS), a separate photometric channel that uses a fraction of the target star signal from the optical channel. The main task of the FGS is to ensure the centering, focusing and guiding of the satellite, but it will also provide supplemental high-precision astrometry and photometry of the target to ground for de-trending the spectra and complementary science. In this paper we give an overview of the current architectural design of the FGS subsystem and discuss related requirements as well as the expected performance.

  14. Gravity wave and microphysical effects on bow echo development

    NASA Astrophysics Data System (ADS)

    Selin, Rebecca Denise Adams

    Numerical simulations of the 13 March 2003 bow echo over Oklahoma are used to evaluate bow echo development and its relationship with gravity wave generation and microphysical heating profile variations. The first part of the research is directed at an explanation of recent observations of surface pressure surges ahead of convective lines prior to the bowing process. Multiple fast-moving n = 1 gravity waves are generated in association with fluctuations in the first vertical mode of heating in the convective line. The surface impacts of four such waves are observed in Oklahoma mesonet data during this case. A slower gravity wave is also produced in the simulation, which is responsible for the pre-bowing pressure surge in the model. This gravity wave is generated by an increase in low-level microphysical cooling associated with an increase in rear-to-front flow and low-level downdrafts shortly before bowing. The wave moves ahead of the convective line and is manifested at the surface by a positive pressure surge ahead of the convective line. The low-level upward vertical motion associated with this wave, in conjunction with higher-frequency gravity waves generated by the multicellularity of the convective line, increases the immediate pre-system CAPE by approximately 250 J/kg-1. Two-dimensional heating profiles from this idealized, full-physics bow echo simulation are placed as a constant heat source in another simulation without moisture, to evaluate what type of gravity waves are produced by a heating profile from a given instance in time. A one-dimensional vertical mean heating profile is calculated from each two-dimensional profile, and a statistical method is used to evaluate the significance of each vertical mode. A number of gravity waves are produced in the dry simulation despite their vertical mode lacking statistical significance in the one-dimensional profile, suggesting that horizontal variations in the heating profile are important to consider

  15. Structure of A=6 Nuclei:

    NASA Astrophysics Data System (ADS)

    Abbas, Afsar

    It is commonly believed that (α-d) and 3He-3H) represent equivalent states of 6Li. It is shown here that this is not correct. These two are actually orthogonal to each other. It is shown here that these two with very different shapes and forms actually co-exist for the ground state of 6Li. This shape co-existence is the same as similar phenomenon in heavy nuclei. The puzzling anomaly of extremely small branching ratio for beta delayed deuteron emission in 6He is explained here. In addition the anomalously large branching ratio for beta delayed triton emission in 8He is explained. The cluster structure of the ground state and of the low-lying states of 6He, 6Li and 6Be is clarified.

  16. Single Pion production from Nuclei

    SciTech Connect

    Singh, S. K.; Athar, M. Sajjad; Ahmed, S.

    2007-12-21

    We have studied charged current one pion production induced by {nu}{sub {mu}}({nu}-bar{sub {mu}}) from some nuclei. The calculations have been done for the incoherent pion production processes from these nuclear targets in the {delta} dominance model and take into account the effect of Pauli blocking, Fermi motion and renormalization of {delta} properties in the nuclear medium. The effect of final state interactions of pions has also been taken into account. The numerical results have been compared with the recent results from the MiniBooNE experiment for the charged current 1{pi} production, and also with some of the older experiments in Freon and Freon-Propane from CERN.

  17. The Physics of Cometary Nuclei

    NASA Technical Reports Server (NTRS)

    Whipple, Fred L.

    1997-01-01

    The recent developments in cometary studies suggest rather low mean densities and weak structures for the nuclei. They appear to be accumulations of fairly discrete units loosely bound together, as deduced from the observations of Comet Shoemaker-Levy 9 during its encounter with Jupiter. The compressive strengths deduced from comet splitting by Opik and Sekanina are extremely low. These values are confirmed by theory developed here. assuming that Comet P/Holmes had a companion that collided with it in 1892. There follows a short discussion that suggests that the mean densities of comets should increase with comet dimensions. The place of origin of short-period comets may relate to these properties.

  18. Chemical composition of cometary nuclei

    NASA Technical Reports Server (NTRS)

    Delsemme, A. H.

    1982-01-01

    Observational evidence pertaining to the origin and composition of cometary material is reviewed. Arguments favoring the undifferentiated character of the icy conglomerate are summarized. Theoretical descriptions of the sublimation of a cometary nucleus and the velocity field of the expanding gas are presented and compared with observations. The nature of cometary dust and the atomic abundances of H, C, N, O, and S in the volatile fraction are examined, and data on the dust and volatile fractions are combined to derive elemental abundances. It is shown that O, N, and S in cometary nuclei appear to have essentially cosmic abundances but that both H and C are drastically depleted with respect to the cosmic abundances. The apparent depletion of C by a factor of more than three is discussed. It is suggested that the missing carbon might be hidden in the dust fraction in the form of heavy organic molecules or might have remained in either the primeval solar nebula or interstellar space.

  19. Radiative muon capture in nuclei

    SciTech Connect

    Doebeli, M.; Doser, M.; van Elmbt, L.; Schaad, M.W.; Truoel, P.; Bay, A.; Perroud, J.P.; Imazato, J.; Ishikawa, T.

    1988-04-01

    The energy spectra of photons following negative muon absorption in /sup 12/C, /sup 16/O, /sup 27/Al, /sup 40/Ca, /sup nat/Fe, /sup 165/Ho, and /sup 209/Bi have been measured with two NaI spectrometers. The branching ratios for the emission of high energy photons give information on the induced pseudoscalar coupling constant g/sub P/ in nuclear matter. The data for light nuclei are in agreement with the theoretical calculations using the nucleonic value of g/sub P/approx. =7g/sub A/ predicted by the partially conserved axial vector current hypothesis, while significantly lower values of g/sub P/ are required to fit the data of the heavier elements with presently existing theoretical predictions. Disregarding the remaining theoretical uncertainties, these results can be interpreted as a further indication of the renormalization of the nucleonic form factors inside the nucleus.

  20. Theory of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Shields, G. A.

    1986-01-01

    The involvement of accretion disks around supermassive black holes in the theory of active galactic nuclei (AGN) is discussed. The physics of thin and thick accretion disks is discussed and the partition between thermal and nonthermal energy production in supermassive disks is seen as uncertain. The thermal limit cycle may operate in supermassive disks (Shields, 1985), with accumulation of gas in the disk for periods of 10 to the 4th to 10 to the 7th years, punctuated by briefer outbursts during which the mass is rapidly transferred to smaller radii. An extended X-ray source in AGN is consistent with observations (Tennant and Mushotsky, 1983), and a large wind mass loss rate exceeding the central accretion rate means that only a fraction of the mass entering the disk will reach the central object; the rest being lost to the wind. Controversy in the relationship between the broad lines and the disk is also discussed.

  1. Clusterization and Deformation in Heavy Nuclei

    SciTech Connect

    Algora, A.; Cseh, J.; Darai, J.; Hess, P.O.; Antonenko, N.V.; Jolos, R.V.; Scheid, W.

    2005-11-21

    The deformation-dependence of clusterization in heavy nuclei is investigated. In particular, allowed and forbidden cluster-configurations are determined for the ground, superdeformed, and hyperdeformed states of some nuclei, based on a microscopic (effective SU(3)) selection rule. The stability of the different cluster configurations from the viewpoint of the binding energy and the dinuclear system model (DNS) is also investigated.

  2. Study of Nuclear Moments on Exotic Nuclei

    SciTech Connect

    Ishihara, Masayasu

    2010-04-30

    Nuclear moments have been measured for a few tens of light unstable nuclei located very far from the line of stability using beta-NMR methods and spin-polarized RI beams. The obtained values of those moments provided indispensable information to reveal/disentangle unique properties of exotic nuclei.

  3. Thalamic nuclei after human blunt head injury.

    PubMed

    Maxwell, William L; MacKinnon, Mary Anne; Smith, Douglas H; McIntosh, Tracy K; Graham, David I

    2006-05-01

    Paraffin-embedded blocks from the thalamus of 9 control patients, 9 moderately disabled, 12 severely disabled, and 10 vegetative head-injured patients assessed using the Glasgow Outcome Scale and identified from the Department of Neuropathology archive. Neurons, astrocytes, macrophages, and activated microglia were differentiated by Luxol fast blue/cresyl violet, GFAP, CD68, and CR3/43 staining and stereological techniques used to estimate cell number in a 28-microm-thick coronal section. Counts were made in subnuclei of the mediodorsal, lateral posterior, and ventral posterior nuclei, the intralaminar nuclei, and the related internal lamina. Neuronal loss occurred from mediodorsal parvocellularis, rostral center medial, central lateral and paracentral nuclei in moderately disabled patients; and from mediodorsal magnocellularis, caudal center medial, rhomboid, and parafascicular nuclei in severely disabled patients; and all of the above and the centre median nucleus in vegetative patients. Neuronal loss occurred primarily from cognitive and executive function nuclei, a lesser loss from somatosensory nuclei and the least loss from limbic motor nuclei. There was an increase in the number of reactive astrocytes, activated microglia, and macrophages with increasing severity of injury. The study provides novel quantitative evidence for differential neuronal loss, with survival after human head injury, from thalamic nuclei associated with different aspects of cortical activation. PMID:16772871

  4. Proton-Rich Nuclei in Nuclear Astrophysics

    SciTech Connect

    Rehm, K. E.

    2007-11-30

    The stable isotopes which we observe on Earth are to a large extent, produced in nature via a 'detour' through unstable nuclei. The reaction path leading through proton-rich nuclei is the so-called rapid proton capture process, where, starting from carbon, nitrogen and oxygen through successive capture or protons and alphas, followed by beta decays, nuclei up to the mass 100 region can be produced. In order to understand the reaction paths and the conditions at various astrophysical sites (e.g. Novae and X-ray bursts) cross sections, masses and half-lives of unstable nuclei have to be measured. In this contribution recent results involving proton-rich nuclei are discussed.

  5. Proton-rich nuclei in nuclear astrophysics.

    SciTech Connect

    Rehm, K. E.; Physics

    2007-01-01

    The stable isotopes which we observe on Earth are to a large extent, produced in nature via a 'detour' through unstable nuclei. The reaction path leading through proton-rich nuclei is the so-called rapid proton capture process, where, starting from carbon, nitrogen and oxygen through successive capture or protons and alphas, followed by beta decays, nuclei up to the mass 100 region can be produced. In order to understand the reaction paths and the conditions at various astrophysical sites (e.g. Novae and X-ray bursts) cross sections, masses and half-lives of unstable nuclei have to be measured. In this contribution recent results involving proton-rich nuclei are discussed.

  6. Nuclei embedded in an electron gas

    SciTech Connect

    Buervenich, Thomas J.; Mishustin, Igor N.; Greiner, Walter

    2007-09-15

    The properties of nuclei embedded in an electron gas are studied within the relativistic mean-field approach. These studies are relevant for nuclear properties in astrophysical environments such as neutron-star crusts and supernova explosions. The electron gas is treated as a constant background in the Wigner-Seitz cell approximation. We investigate the stability of nuclei with respect to {alpha} and {beta} decay. Furthermore, the influence of the electronic background on spontaneous fission of heavy and superheavy nuclei is analyzed. We find that the presence of the electrons leads to stabilizing effects for both {alpha} decay and spontaneous fission at high electron densities. Furthermore, the screening effect shifts the proton dripline to more proton-rich nuclei, and the stability line with respect to {beta}-decay is shifted to more neutron-rich nuclei. Implications for the creation and survival of very heavy nuclear systems are discussed.

  7. Spectroscopy of Neutron-rich Pu Nuclei

    SciTech Connect

    Chowdhury, P.; Hota, S.; Lakshmi, S.; Tandel, S. K.; Harrington, T.; Jackson, E.; Moran, K.; Shirwadkar, U.; Ahmad, I.; Carpenter, M. P.; Greene, J.; Hoffman, C. R.; Janssens, R. V. F.; Khoo, T. L.; Kondev, F. G.; Lauritsen, T.; Lister, C. J.; McCutchan, E. A.; Seweryniak, D.; Stefanescu, I.

    2011-10-28

    Spectroscopic studies of nuclei in the A{approx}250, Z{approx}100 region provide critical input to theoretical models that attempt to describe the structure and stability of the heaviest elements. We report here on new spectroscopic studies in the N = 150,151 nuclei {sup 244,245}Pu. (Z = 94). Excitations in these nuclei on the neutron-rich side of the valley of stability, accessed via inelastic and transfer reactions, complement fusion-evaporation studies of Z{>=}100 nuclei. States in {sup 244,245}Pu were populated using {sup 47}Ti and {sup 208}Pb beams incident on a {sup 244}Pu target, with delayed and prompt gamma rays detected by the Gammasphere array. The new results are discussed in the context of emerging systematics of one- and two-quasiparticle excitations in N{>=}150 nuclei.

  8. A Comparison Study of Single-Echo Susceptibility Weighted Imaging and Combined Multi-Echo Susceptibility Weighted Imaging in Visualizing Asymmetric Medullary Veins in Stroke Patients

    PubMed Central

    Wang, Chao; Qiu, Tiantian; Song, Ruirui; Jiaerken, Yerfan; Yang, Linglin; Wang, Shaoze

    2016-01-01

    Background Asymmetric medullary veins (AMV) are frequently observed in stroke patients and single-echo susceptibility weighted imaging (SWIs) is the main technique in detecting AMV. Our study aimed to investigate which echo time (TE) on single-echo susceptibility is the optimal echo for visualizing AMV and to compare the ability in detecting AMV in stroke patients between SWIs and multi-echo susceptibility weighted imaging (SWIc). Materials and Methods Twenty patients with middle cerebral artery stroke were included. SWI was acquired by using a multi-echo gradient-echo sequence with six echoes ranging from 5 ms to 35.240 ms. Three different echoes of SWIs including SWIs1 (TE = 23.144 ms), SWIs2 (TE = 29.192 ms) and SWIs3 (TE = 35.240 ms) were reconstructed. SWIc was averaged using the three echoes of SWIs. Image quality and venous contrast of medullary veins were compared between SWIs and SWIc using peak signal-to-noise ratio (PSNR), mean opinion score (MOS), contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR). The presence of AMV was evaluated in each SWIs (1–3) and SWIc. Results SWIs2 had the highest PSNR, MOS and CNR and SWIs1 had the highest SNR among three different echoes of SWIs. No significant difference was found in SNR between SWIs1 and SWIs2. PSNR, MOS and CNR in SWIc were significantly increased by 27.9%, 28.2% and 17.2% compared with SWIs2 and SNR in SWIc was significantly increased by 32.4% compared with SWIs1. 55% of patients with AMV were detected in SWIs2, SWIs3 and SWIc, while 50% AMV were found in SWIs1. Conclusions SWIs using TE around 29ms was optimal in visualizing AMV. SWIc could improve image quality and venous contrast, but was equal to SWIs using a relative long TE in evaluating AMV. These results provide the technique basis for further research of AMV in stroke. PMID:27494171

  9. Comparison of Multi-Echo Dixon Methods with Volume Interpolated Breath-Hold Gradient Echo Magnetic Resonance Imaging in Fat-Signal Fraction Quantification of Paravertebral Muscle

    PubMed Central

    Yoo, Yeon Hwa; Kim, Hak-Sun; Lee, Young Han; Yoon, Choon-Sik; Paek, Mun Young; Yoo, Hanna; Kannengiesser, Stephan; Chung, Tae-Sub; Song, Ho-Taek; Suh, Jin-Suck

    2015-01-01

    Objective To assess whether multi-echo Dixon magnetic resonance (MR) imaging with simultaneous T2* estimation and correction yields more accurate fat-signal fraction (FF) measurement of the lumbar paravertebral muscles, in comparison with non-T2*-corrected two-echo Dixon or T2*-corrected three-echo Dixon, using the FF measurements from single-voxel MR spectroscopy as the reference standard. Materials and Methods Sixty patients with low back pain underwent MR imaging with a 1.5T scanner. FF mapping images automatically obtained using T2*-corrected Dixon technique with two (non-T2*-corrected), three, and six echoes, were compared with images from single-voxel MR spectroscopy at the paravertebral muscles on levels L4 through L5. FFs were measured directly by two radiologists, who independently drew the region of interest on the mapping images from the three sequences. Results A total of 117 spectroscopic measurements were performed either bilaterally (57 of 60 subjects) or unilaterally (3 of 60 subjects). The mean spectroscopic FF was 14.3 ± 11.7% (range, 1.9-63.7%). Interobserver agreement was excellent between the two radiologists. Lin's concordance correlation between the spectroscopic findings and all the imaging-based FFs were statistically significant (p < 0.001). FFs obtained from the T2*-corrected six-echo Dixon sequences showed a significantly better concordance with the spectroscopic data, with its concordance correlation coefficient being 0.99 and 0.98 (p < 0.001), as compared with two- or three-echo methods. Conclusion T2*-corrected six-echo Dixon sequence would be a better option than two- or three-echo methods for noninvasive quantification of lumbar muscle fat quantification. PMID:26357503

  10. The Echo Approach in Developing Items for Student Evaluation of Teaching Performance

    ERIC Educational Resources Information Center

    Cunningham, J. Barton; MacGregor, James N.

    2006-01-01

    This article illustrates the application of the Echo approach, originally designed to identify values of different cultures and subcultures, to the generation of questionnaire items for students to evaluate faculty teaching performance. Students preferred items generated using the Echo method over faculty-designed items and items developed by…

  11. Variations in the occurrence of SuperDARN F region echoes

    NASA Astrophysics Data System (ADS)

    Ghezelbash, M.; Fiori, R. A. D.; Koustov, A. V.

    2014-02-01

    The occurrence of F region ionospheric echoes observed by a number of SuperDARN HF radars is analyzed statistically in order to infer solar cycle, seasonal, and diurnal trends. The major focus is on Saskatoon radar data for 1994-2012. The distribution of the echo occurrence rate is presented in terms of month of observation and magnetic local time. Clear repetitive patterns are identified during periods of solar maximum and solar minimum. For years near solar maximum, echoes are most frequent near midnight during winter. For years near solar minimum, echoes occur more frequently near noon during winter, near dusk and dawn during equinoxes and near midnight during summer. Similar features are identified for the Hankasalmi and Prince George radars in the northern hemisphere and the Bruny Island TIGER radar in the southern hemisphere. Echo occurrence for the entire SuperDARN network demonstrates patterns similar to patterns in the echo occurrence for the Saskatoon radar and for other radars considered individually. In terms of the solar cycle, the occurrence rate of nightside echoes is shown to increase by a factor of at least 3 toward solar maximum while occurrence of the near-noon echoes does not significantly change with the exception of a clear depression during the declining phase of the solar cycle.

  12. Echo-level compensation and delay tuning in the auditory cortex of the mustached bat.

    PubMed

    Macías, Silvio; Mora, Emanuel C; Hechavarría, Julio C; Kössl, Manfred

    2016-06-01

    During echolocation, bats continuously perform audio-motor adjustments to optimize detection efficiency. It has been demonstrated that bats adjust the amplitude of their biosonar vocalizations (known as 'pulses') to stabilize the amplitude of the returning echo. Here, we investigated this echo-level compensation behaviour by swinging mustached bats on a pendulum towards a reflective surface. In such a situation, the bats lower the amplitude of their emitted pulses to maintain the amplitude of incoming echoes at a constant level as they approach a target. We report that cortical auditory neurons that encode target distance have receptive fields that are optimized for dealing with echo-level compensation. In most cortical delay-tuned neurons, the echo amplitude eliciting the maximum response matches the echo amplitudes measured from the bats' biosonar vocalizations while they are swung in a pendulum. In addition, neurons tuned to short target distances are maximally responsive to low pulse amplitudes while neurons tuned to long target distances respond maximally to high pulse amplitudes. Our results suggest that bats dynamically adjust biosonar pulse amplitude to match the encoding of target range and to keep the amplitude of the returning echo within the bounds of the cortical map of echo delays. PMID:27037932

  13. Spin Dynamics Simulations of Multiple Echo Spacing Pulse Sequences in Grossly Inhomogeneous Fields

    SciTech Connect

    Heidler, R.; Bachman, H. N.; Johansen, Y.

    2008-12-05

    Pulse sequences with multiple lengths of echo spacings are used in oilfield NMR logging for diffusion-based NMR applications such as rock and fluid characterization. One specific implementation is the so-called diffusion editing sequence comprising two long echo spacings followed by a standard CPMG at a shorter echo spacing. The echoes in the CPMG portion contain signal from both the direct and stimulated echoes.Modern oilfield NMR logging tools are designed for continuous depth logging of earth formations by projecting both the static (B{sub 0}) and dynamic (B{sub 1}) fields into the formation. Both B{sub 0} and B{sub 1} profiles are grossly inhomogeneous which results in non-steady-state behavior in the early echoes. The spin dynamics effects present a challenge for processing the echo amplitudes to measure porosity (amplitude extrapolated to zero time) and attenuations for fluid or pore size characterization.In this work we describe a calculation of the spin dynamics of the diffusion editing sequence with two long echo spacings. The calculation takes into account full B{sub 1} and B{sub 0} field maps, and comparisons will be made for sensors and parameters typical of oilfield logging tools and environments.

  14. Strong correlation between quasiperiodic echoes and plasma drift in the E region

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Jin, Han; Huang, Xueqin; Zhong, Dingkun; Yan, Chunxiao; Yang, Guotao

    2015-10-01

    Simultaneous observations of quasiperiodic (QP) echoes and plasma drift in the ionospheric E region were conducted in Fuke (19.5°N, 109.1°E), Hainan province, China, to investigate the QP striation tilts under varying plasma drift conditions. The E region field-aligned irregularities (FAIs), observed using the Hainan VHF radar, and the drift velocities of the plasma blobs in the Es layer, recorded by the Hainan Digisonde operating in drift mode, are reported. The QP echoes and drift data recorded during the entire year of 2013 were analyzed and compared. A surprising consistency between the striation tilt of the QP echoes and the drift direction of the plasma blobs was discovered. A negative echo striation of the QP FAIs was recorded when the measured drift direction of the plasma blobs was southward, whereas a positive echo striation was observed during the northward drift. Furthermore, the echo trace was continuous, whereas the QP striation changed from negative to positive, and vice versa. Thus, it can be concluded that the morphology of the QP echoes may be controlled by the background wind fields in the E region. The northward/southward-drifting striated FAIs in the observation region of a coherent scatter radar might induce the positive/negative QP echo striation in the range-time-intensity plots.

  15. Analysis of tissue changes, measurement system effects, and motion artifacts in echo decorrelation imaging

    PubMed Central

    Hooi, Fong Ming; Nagle, Anna; Subramanian, Swetha; Douglas Mast, T.

    2015-01-01

    Echo decorrelation imaging, a method for mapping ablation-induced ultrasound echo changes, is analyzed. Local echo decorrelation is shown to approximate the decoherence spectrum of tissue reflectivity. Effects of the ultrasound measurement system, echo signal windowing, electronic noise, and tissue motion on echo decorrelation images are determined theoretically, leading to a method for reduction of motion and noise artifacts. Theoretical analysis is validated by simulations and experiments. Simulated decoherence of the scattering medium was recovered with root-mean-square error less than 10% with accuracy dependent on the correlation window size. Motion-induced decorrelation measured in an ex vivo pubovisceral muscle model showed similar trends to theoretical motion-induced decorrelation for a 2.1 MHz curvilinear array with decorrelation approaching unity for 3–4 mm elevational displacement or 1–1.6 mm range displacement. For in vivo imaging of porcine liver by a 7 MHz linear array, theoretical decorrelation computed using image-based motion estimates correlated significantly with measured decorrelation (r = 0.931, N = 10). Echo decorrelation artifacts incurred during in vivo radiofrequency ablation in the same porcine liver were effectively compensated based on the theoretical echo decorrelation model and measured pre-treatment decorrelation. These results demonstrate the potential of echo decorrelation imaging for quantification of heat-induced changes to the scattering tissue medium during thermal ablation. PMID:25697993

  16. Sonar gain control and echo detection thresholds in the echolocating bat, Eptesicus fuscus.

    PubMed

    Simmons, J A; Moffat, A J; Masters, W M

    1992-02-01

    The echolocating bat, Eptesicus fuscus, detects sonar echoes with a sensitivity that changes according to the time elapsed between broadcasting of each sonar signal and reception of echoes. When tested in an electronic target simulator on a two-choice echo-detection task, the bat's threshold improved by 11.5 dB as echo delay changed from 2.3 to 4.6 ms (target ranges of 40 and 80 cm). Earlier experiments measured the change in detection threshold for delays from 1 to 6.4 ms (target ranges from about 17 to 110 cm) and obtained about 11 dB of improvement per doubling of delay. The new experiments used electronic delay lines to simulate echo delay, thus avoiding movement of loudspeakers to different distances and the possible creation of delay-dependent backward masking between stimulus echoes and cluttering echoes from the loudspeaker surfaces. The slope of the threshold shift defines an echo gain control that keeps echoes from point targets at a fixed sensation level--reducing sensitivity by 11 to 12 dB as echo amplitude increases by 12 dB per halving of range during the bat's approach to the target. A recent experiment using loudness discrimination of echoes at 70 to 80 dB SPL (roughly 50 dB above threshold) found a slope of about 6 dB per halving of range, so the gain-control effect may be level dependent. The observed effect is operationally equivalent to forward masking of echoes by the transmission, but any events correlated with vocalization which impair hearing sensitivity for a short interval following transmissions could cause a decline in sensitivity to echoes. Contractions of the bat's middle-ear muscles synchronized to transmissions may account for the observed threshold shift, at least for a span of echo delays associated with the most critical portion of the approach stage of pursuit. Forward masking by the sonar transmissions may contribute to the threshold shift, too, but middle-ear muscle contractions do occur and must be a significant part of the

  17. High-Frequency/High-field electron spin echo envelope modulation study of nitrogen hyperfine and quadrupole interactions on a disordered powder sample

    PubMed

    Bloess; Mobius; Prisner

    1998-09-01

    High-frequency/high-field (95 GHz/3.4 T) electron spin echo envelope modulation (ESEEM) experiments on single crystals and disordered samples of dianisyl-nitroxide (DANO) radicals are reported. At these high microwave frequencies (W-band), the anisotropic g-matrix of the nitroxide radical is resolved in the EPR spectrum. Additionally ESEEM modulations from other than nitrogen nuclei, such as protons, are highly suppressed at these frequencies, because they are too far from the cancellation condition for effective mixing of the nuclear spin functions. Therefore the nitrogen (14N) hyperfine and quadrupole coupling tensors could be determined without ambiguity from powder measurements. The results obtained were checked by ESEEM measurements on single crystals. Advantages and disadvantages of high-field ESEEM on nitrogen couplings are briefly discussed and compared with electron nuclear double resonance (ENDOR) and X-band ESEEM. Copyright 1998 Academic Press. PMID:9740727

  18. Echo-acoustic flow dynamically modifies the cortical map of target range in bats.

    PubMed

    Bartenstein, Sophia K; Gerstenberg, Nadine; Vanderelst, Dieter; Peremans, Herbert; Firzlaff, Uwe

    2014-01-01

    Echolocating bats use the delay between their sonar emissions and the reflected echoes to measure target range, a crucial parameter for avoiding collisions or capturing prey. In many bat species, target range is represented as an orderly organized map of echo delay in the auditory cortex. Here we show that the map of target range in bats is dynamically modified by the continuously changing flow of acoustic information perceived during flight ('echo-acoustic flow'). Combining dynamic acoustic stimulation in virtual space with extracellular recordings, we found that neurons in the auditory cortex of the bat Phyllostomus discolor encode echo-acoustic flow information on the geometric relation between targets and the bat's flight trajectory, rather than echo delay per se. Specifically, the cortical representation of close-range targets is enlarged when the lateral passing distance of the target decreases. This flow-dependent enlargement of target representation may trigger adaptive behaviours such as vocal control or flight manoeuvres. PMID:25131175

  19. The Search for Light Echoes of Historic SNe in the Southern Hemisphere with DECam

    NASA Astrophysics Data System (ADS)

    Rest, Armin; Bianco, Federica; Chornock, Ryan; Clocchiatti, Alejandro; Foley, Ryan J.; James, David; Matheson, Thomas; Narayan, Gautham; Olsen, Knut A.; Points, Sean; Prieto, Jose Luis; Smith, R. Chris; Smith, Nathan; Suntzeff, Nicholas B.; Welch, Douglas L.; Zenteno, Alfredo

    2015-01-01

    In recent years, light echoes of ancient SNe have been discovered with the Mosaic II cameras at the CTIO Blanco and KPNO Mayall telescopes. We have found light echoes in the LMC (Rest et al. 2005, 2008a) and near the historical Galactic events Cas A, Tycho, and Eta Car (Rest et al. 2008b, 2011a, 2012). However, searches for light echoes near the Kepler SN and SN 1006 have not yet been successful. We have started a search for light echoes in the southern hemisphere using DECam at the CTIO Blanco telescope. DECam is an excellent light echo detection system with its larger field of view and much faster read time compared to Mosaic II. This increases the efficiency of the search by more than a factor of 10, allowing us to cover significantly larger areas of the sky. We report on strategy, progress, current coverage, and first results of our project.

  20. Echo-acoustic flow dynamically modifies the cortical map of target range in bats

    NASA Astrophysics Data System (ADS)

    Bartenstein, Sophia K.; Gerstenberg, Nadine; Vanderelst, Dieter; Peremans, Herbert; Firzlaff, Uwe

    2014-08-01

    Echolocating bats use the delay between their sonar emissions and the reflected echoes to measure target range, a crucial parameter for avoiding collisions or capturing prey. In many bat species, target range is represented as an orderly organized map of echo delay in the auditory cortex. Here we show that the map of target range in bats is dynamically modified by the continuously changing flow of acoustic information perceived during flight (‘echo-acoustic flow’). Combining dynamic acoustic stimulation in virtual space with extracellular recordings, we found that neurons in the auditory cortex of the bat Phyllostomus discolor encode echo-acoustic flow information on the geometric relation between targets and the bat’s flight trajectory, rather than echo delay per se. Specifically, the cortical representation of close-range targets is enlarged when the lateral passing distance of the target decreases. This flow-dependent enlargement of target representation may trigger adaptive behaviours such as vocal control or flight manoeuvres.

  1. Transcranial magnetic stimulation-induced 'visual echoes' are generated in early visual cortex.

    PubMed

    Jolij, Jacob; Lamme, Victor A F

    2010-11-01

    Transcranial magnetic stimulation (TMS) of the early visual areas can trigger perception of a flash of light, a so-called phosphene. Here we show that a very brief presentation of a stimulus can modulate features of a subsequent TMS-induced phosphene, to a level that participants mistake phosphenes for real stimuli, inducing 'visual echoes' of a previously seen stimulus. These 'echoes' are modulated by visual context at the moment of magnetic stimulation, showing that they are generated in early visual areas, and that the brain processes these 'echoes' as if they are factually presented stimuli. This shows that TMS can re-activate weak visual representations in early visual areas. Based on the pattern of contextual modulation of visual echoes, we theorize that perception of these echoes is not a passive reactivation of residual activity in early visual cortex, but an active interpretation of the combined activity of TMS-induced neural noise and cortical state. PMID:20732388

  2. Surveying for Historical Supernovae Light Echoes in the Milky Way Field

    NASA Astrophysics Data System (ADS)

    Welch, D. L.

    2014-05-01

    Very luminous, transient events can produce detectable "light echoes" - light scattered by interstellar dust which can arrive much later than the direct light from an outburst. In the last 1000 years, there have been half a dozen supernovae in the Milky Way which are capable of producing detectable light echoes. Light echo systems have already been found for Tycho (SN 1572) and Cas A. The three-dimensional distribution of light echoes provides one of the few means for an astronomical source to be inspected from more than one viewpoint. Indications of the degree of asymmetry of supernovae are extremely valuable for understanding the details of the event itself. Amateurs are well-equipped to find the brighter light echoes and in this work I will provide practical guidance on how such surveys may be accomplished and the various science opportunities they provide.

  3. RADIO VARIABILITY IN SEYFERT NUCLEI

    SciTech Connect

    Mundell, C. G.; Ferruit, P.; Nagar, N.; Wilson, A. S.

    2009-09-20

    Comparison of 8.4 GHz radio images of a sample of eleven, early-type Seyfert galaxies with previous observations reveals possible variation in the nuclear radio flux density in five of them over a seven year period. Four Seyferts (NGC 2110, NGC 3081, MCG -6-30-15, and NGC 5273) show a decline in their 8.4 GHz nuclear flux density between 1992 and 1999, while one (NGC 4117) shows an increase; the flux densities of the remaining six Seyferts (Mrk 607, NGC 1386, Mrk 620, NGC 3516, NGC 4968, and NGC 7465) have remained constant over this period. New images of MCG -5-23-16 are also presented. We find no correlation between radio variability and nuclear radio luminosity or Seyfert nuclear type, although the sample is small and dominated by type 2 Seyferts. Instead, a possible correlation between the presence of nuclear radio variability and the absence of hundred parsec-scale radio emission is seen, with four out of five marginally resolved or unresolved nuclei showing a change in nuclear flux density, while five out of six extended sources show no nuclear variability despite having unresolved nuclear sources. NGC 2110 is the only source in our sample with significant extended radio structure and strong nuclear variability ({approx}38% decline in nuclear flux density over seven years). The observed nuclear flux variability indicates significant changes are likely to have occurred in the structure of the nucleus on scales smaller than the VLA beam size (i.e., within the central {approx}0.''1 (15 pc)), between the two epochs, possibly due to the appearance and fading of new components or shocks in the jet, consistent with previous detection of subparsec-scale nuclear structure in this Seyfert. Our results suggest that all Seyferts may exhibit variation in their nuclear radio flux density at 8.4 GHz, but that variability is more easily recognized in compact sources in which emission from the variable nucleus is not diluted by unresolved, constant flux density radio jet

  4. Star formation around active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Keel, William C.

    1987-01-01

    Active galactic nuclei (Seyfert nuclei and their relatives) and intense star formation can both deliver substantial amounts of energy to the vicinity of a galactic nucleus. Many luminous nuclei have energetics dominated by one of these mechanisms, but detailed observations show that some have a mixture. Seeing both phenomena at once raises several interesting questions: (1) Is this a general property of some kinds of nuclei? How many AGNs have surround starbursts, and vice versa? (2) As in 1, how many undiscovered AGNs or starbursts are hidden by a more luminous instance of the other? (3) Does one cause the other, and by what means, or do both reflect common influences such as potential well shape or level of gas flow? (4) Can surrounding star formation tell us anything about the central active nuclei, such as lifetimes, kinetic energy output, or mechanical disturbance of the ISM? These are important points in the understanding of activity and star formation in galactic nuclei. Unfortunately, the observational ways of addressing them are as yet not well formulated. Some preliminary studies are reported, aimed at clarifying the issues involved in study of the relationships between stellar and nonstellar excitement in galactic nuclei.

  5. Test plan for the forest-echo experiment

    SciTech Connect

    Jelinek, D.A.

    1984-07-01

    In this report, we describe a test plan to determine the characteristics of the average radar echo from a number of forested terrains. The data required to do this will be obtained by using a very narrow pulse-width (20 ns) radar and associated hardware on board a helicopter. Data will be taken as the helicopter makes straight and level passes over each terrain at a number of altitudes. Both deciduous and conifer forests will be overflown at different times of the year to determine the effect of seasonal changes. The report describes the hardware that will be used and the procedure that will be followed to gather the data. It also gives the theoretical statistical characteristics of the radar's video output and the amount of intrapulse and interpulse correlation expected.

  6. Heavy ion collision evolution modeling with ECHO-QGP

    NASA Astrophysics Data System (ADS)

    Rolando, V.; Inghirami, G.; Beraudo, A.; Del Zanna, L.; Becattini, F.; Chandra, V.; De Pace, A.; Nardi, M.

    2014-11-01

    We present a numerical code modeling the evolution of the medium formed in relativistic heavy ion collisions, ECHO-QGP. The code solves relativistic hydrodynamics in (3 + 1)D, with dissipative terms included within the framework of Israel-Stewart theory; it can work both in Minkowskian and in Bjorken coordinates. Initial conditions are provided through an implementation of the Glauber model (both Optical and Monte Carlo), while freezeout and particle generation are based on the Cooper-Frye prescription. The code is validated against several test problems and shows remarkable stability and accuracy with the combination of a conservative (shock-capturing) approach and the high-order methods employed. In particular it beautifully agrees with the semi-analytic solution known as Gubser flow, both in the ideal and in the viscous Israel-Stewart case, up to very large times and without any ad hoc tuning of the algorithm.

  7. An overview on optimized NLMS algorithms for acoustic echo cancellation

    NASA Astrophysics Data System (ADS)

    Paleologu, Constantin; Ciochină, Silviu; Benesty, Jacob; Grant, Steven L.

    2015-12-01

    Acoustic echo cancellation represents one of the most challenging system identification problems. The most used adaptive filter in this application is the popular normalized least mean square (NLMS) algorithm, which has to address the classical compromise between fast convergence/tracking and low misadjustment. In order to meet these conflicting requirements, the step-size of this algorithm needs to be controlled. Inspired by the pioneering work of Prof. E. Hänsler and his collaborators on this fundamental topic, we present in this paper several solutions to control the adaptation of the NLMS adaptive filter. The developed algorithms are "non-parametric" in nature, i.e., they do not require any additional features to control their behavior. Simulation results indicate the good performance of the proposed solutions and support the practical applicability of these algorithms.

  8. Spatial-mode storage in a gradient-echo memory

    NASA Astrophysics Data System (ADS)

    Higginbottom, D. B.; Sparkes, B. M.; Rancic, M.; Pinel, O.; Hosseini, M.; Lam, P. K.; Buchler, B. C.

    2012-08-01

    Three-level atomic gradient echo memory (Λ-GEM) is a proposed candidate for efficient quantum storage and for linear optical quantum computation with time-bin multiplexing [Hosseini , Nature (London)NATUAS0028-083610.1038/nature08325 461, 241 (2009)]. In this paper we investigate the spatial multimode properties of a Λ-GEM system. Using a high-speed triggered CCD, we demonstrate the storage of complex spatial modes and images. We also present an in-principle demonstration of spatial multiplexing by showing selective recall of spatial elements of a stored spin wave. Using our measurements, we consider the effect of diffusion within the atomic vapor and investigate its role in spatial decoherence. Our measurements allow us to quantify the spatial distortion due to both diffusion and inhomogeneous control field scattering and compare these to theoretical models.

  9. Recurrent kernel machines: computing with infinite echo state networks.

    PubMed

    Hermans, Michiel; Schrauwen, Benjamin

    2012-01-01

    Echo state networks (ESNs) are large, random recurrent neural networks with a single trained linear readout layer. Despite the untrained nature of the recurrent weights, they are capable of performing universal computations on temporal input data, which makes them interesting for both theoretical research and practical applications. The key to their success lies in the fact that the network computes a broad set of nonlinear, spatiotemporal mappings of the input data, on which linear regression or classification can easily be performed. One could consider the reservoir as a spatiotemporal kernel, in which the mapping to a high-dimensional space is computed explicitly. In this letter, we build on this idea and extend the concept of ESNs to infinite-sized recurrent neural networks, which can be considered recursive kernels that subsequently can be used to create recursive support vector machines. We present the theoretical framework, provide several practical examples of recursive kernels, and apply them to typical temporal tasks. PMID:21851278

  10. Acoustic Echo-Sounding Experiments in an Urban Environment

    NASA Technical Reports Server (NTRS)

    Damkevala, R. J.

    1971-01-01

    A 1320 Hz tuned source was mounted on a 4 ft diameter parabolic reflector, with the same driver working as the receiving transducer. This highly directional system is able to detect the small amount of energy backscattered from a vertically directed pulse of sound by inhomogeneities in the density structure of the atmosphere even in the presence of city noises which include rapid-transit and express-way traffic sounds. Results showing thermal plumes and the formation and breakup of radiation inversions are presented. A network of such echo-sounding stations in and around a city could be used to give early warning of atmospheric conditions which might lead to a pollution incident.

  11. REDOR with a relative full-echo reference

    NASA Astrophysics Data System (ADS)

    Mehta, Anil K.; Cegelski, Lynette; O'Connor, Robert D.; Schaefer, Jacob

    2003-07-01

    REDOR and REDOR-like 13C{ 19F} and 2H{ 19F} NMR experiments have been performed on lyophilized whole cells of Staphylococcus aureus. The bacteria were grown to maturity on media containing L-[ 13C3]alanine or L-[methyl- d3]alanine, and then complexed with the 4-fluorobiphenyl derivative of chloroeremomycin, an analogue of the widely used antibiotic, vancomycin. The position of the 19F of the drug bound in the bacterial cell wall was determined relative to L-alanine 13C and 2H labels in the peptidoglycan peptide stem that was closest to the fluorinated biphenyl moiety of the drug. These determinations were made by dipolar recoupling methods that do not require an absolute measurement of the REDOR full echo (the signal observed without rotor-synchronized dephasing pulses) of the labels in the peptide stem.

  12. Non-Fourier encoding with multiple spin echoes.

    PubMed

    Panych, L P; Mulkern, R V; Saiviroonporn, P; Zientara, G P; Jolesz, F A

    1997-12-01

    The advantages and limitations of multiple spin-echo sequences for non-Fourier encoding are investigated. Complications caused by improper encoding of alternate magnetization pathways due to imperfect refocusing pulses are analyzed. It is shown that mirror image ghosts result if the encoding RF pulse matrix is real-valued. These ghosts can be avoided as long as the rows of the RF pulse matrix are conjugate symmetric, which implies that spatial profiles are real valued. Non-Fourier encoding using bases derived from wavelet, Hadamard, and other real-valued orthogonal functions does not result in a mirror ghost artifact. A RARE sequence for non-Fourier encoding has been implemented on a clinical imaging system and successfully applied for brain imaging. PMID:9402198

  13. Echo Tomography of Reprocessing Sites in X-Ray Binaries

    NASA Technical Reports Server (NTRS)

    Patterson, Joseph; Haswell, Carole

    1998-01-01

    We discovered correlated rapid variability between the optical/UV and X-ray emission for the first time in a soft X-ray transient, GRO J1655-40. Hubble Space Telescope light curves show features similar to those seen by the Rossi X-ray Timing Explorer, but with a mean delay of up to 10 - 20 s. We interpret the correlation as the result of reprocessing of X-rays into optical and UV emission, with a delay owing to finite light travel time; this assumption enables us to perform echo mapping of the system. The time-delay distribution has a mean of 14.6 +/-1.4 s and a dispersion of 10.5+/-1.9 s at binary phase 0.4. This establishes that the reprocessing region is the accretion disk around the compact star, rather than the mass-donating secondary. These results have been published.

  14. Loschmidt echoes in two-body random matrix ensembles

    NASA Astrophysics Data System (ADS)

    Pižorn, Iztok; Prosen, Tomaž; Seligman, Thomas H.

    2007-07-01

    Fidelity decay is studied for quantum many-body systems with a dominant independent particle Hamiltonian resulting, e.g., from a mean field theory with a weak two-body interaction. The diagonal terms of the interaction are included in the unperturbed Hamiltonian, while the off-diagonal terms constitute the perturbation that distorts the echo. We give the linear response solution for this problem in a random matrix framework. While the ensemble average shows no surprising behavior, we find that the typical ensemble member as represented by the median displays a very slow fidelity decay known as “freeze.” Numerical calculations confirm this result and show that the ground state even on average displays the freeze. This may contribute to explanation of the “unreasonable” success of mean field theories.

  15. Electron spin echo modulation study of AOT reverse micelles

    SciTech Connect

    Baglioni, P. ); Nakamura, Hiroshi ); Kevan, L. )

    1991-05-02

    Electron spin echo deuterium modulation studies have been carried out for x-doxylstearic acid spin probes in frozen reversed micellar solutions of sodium bis(2-ethyl-1-hexyl) sulfosuccinate (AOT)/isooctane as a function of the water pool size with deuterium located in the isooctane or in the water. The results determine the probe location and conformation in the reverse micelle and the amount of water and isooctane penetration into the AOT interface. Modulation effects due to the interaction of the unpaired electron with deuterated isooctane or deuterated water show that the probes are in an extended conformation and are located at the interface of the reverse micelle. The results obtained are in good agreement with the current view of the structure of AOT reversed micelles in liquids and demonstrate at a molecular level that the micellar structure is retained upon fast freezing.

  16. Thermal evolution of cometary nuclei

    NASA Astrophysics Data System (ADS)

    Prialnik, D.

    2014-07-01

    Thermal modeling of comet nuclei and similar objects involves the solution of conservation equations for energy and masses of the various components over time. For simplicity, the body is generally, but not necessarily, assumed to be of spherical shape. The processes included in such calculations are heat transfer, gas flow, dust drag, phase transitions, internal heating by various sources, internal structure alterations, surface sublimation. Physical properties --- such as the thermal conductivity, permeability, material strength, and porous structure --- are assumed, based on the best available estimates from laboratory experiments and space-mission results. Calculations employ various numerical procedures and require significant computational power, data analysis, and often sophisticated methods of graphical presentation. They start with a body of given size, mass, and composition, as well as a given orbit. The results yield properties and activity patterns that can be confronted with observations. Initial parameters may be adjusted until agreement is achieved. A glimpse into the internal structure of the object, which is inaccessible to direct observation, is thus obtained. The last decade, since the extensive overview of the subject was published (Modeling the structure and activity of comet nuclei, Prialnik, D.; Benkhoff, J.; Podolak, M., in Comets II, M. C. Festou, H. U. Keller, and H. A. Weaver, eds., University of Arizona Press, Tucson, p.359-387), thermal modeling has significantly advanced. This was prompted both by new properties and phenomena gleaned from observations, one example being main-belt comets, and the continual increase in computational power and performance. Progress was made on two fronts. On the computational side, multi-dimensional models have been developed, adaptive-grid and moving-boundaries techniques have been adopted, and long-term evolutionary calculations have become possible, even spanning the lifetime of the Solar System. On

  17. Fusion probability in heavy nuclei

    NASA Astrophysics Data System (ADS)

    Banerjee, Tathagata; Nath, S.; Pal, Santanu

    2015-03-01

    Background: Fusion between two massive nuclei is a very complex process and is characterized by three stages: (a) capture inside the potential barrier, (b) formation of an equilibrated compound nucleus (CN), and (c) statistical decay of the CN leading to a cold evaporation residue (ER) or fission. The second stage is the least understood of the three and is the most crucial in predicting yield of superheavy elements (SHE) formed in complete fusion reactions. Purpose: A systematic study of average fusion probability, , is undertaken to obtain a better understanding of its dependence on various reaction parameters. The study may also help to clearly demarcate onset of non-CN fission (NCNF), which causes fusion probability, PCN, to deviate from unity. Method: ER excitation functions for 52 reactions leading to CN in the mass region 170-220, which are available in the literature, have been compared with statistical model (SM) calculations. Capture cross sections have been obtained from a coupled-channels code. In the SM, shell corrections in both the level density and the fission barrier have been included. for these reactions has been extracted by comparing experimental and theoretical ER excitation functions in the energy range ˜5 %-35% above the potential barrier, where known effects of nuclear structure are insignificant. Results: has been shown to vary with entrance channel mass asymmetry, η (or charge product, ZpZt ), as well as with fissility of the CN, χCN. No parameter has been found to be adequate as a single scaling variable to determine . Approximate boundaries have been obtained from where starts deviating from unity. Conclusions: This study quite clearly reveals the limits of applicability of the SM in interpreting experimental observables from fusion reactions involving two massive nuclei. Deviation of from unity marks the beginning of the domain of dynamical models of fusion. Availability of precise ER cross

  18. Trawling bats exploit an echo-acoustic ground effect

    PubMed Central

    Zsebok, Sandor; Kroll, Ferdinand; Heinrich, Melina; Genzel, Daria; Siemers, Björn M.; Wiegrebe, Lutz

    2013-01-01

    A water surface acts not only as an optic mirror but also as an acoustic mirror. Echolocation calls emitted by bats at low heights above water are reflected away from the bat, and hence the background clutter is reduced. Moreover, targets on the surface create an enhanced echo. Here, we formally quantified the effect of the surface and target height on both target detection and -discrimination in a combined laboratory and field approach with Myotis daubentonii. In a two-alternative, forced-choice paradigm, the bats had to detect a mealworm and discriminate it from an inedible dummy (20 mm PVC disc). Psychophysical performance was measured as a function of height above either smooth surfaces (water or PVC) or above a clutter surface (artificial grass). At low heights above the clutter surface (10, 20, or 35 cm), the bats' detection performance was worse than above a smooth surface. At a height of 50 cm, the surface structure had no influence on target detection. Above the clutter surface, also target discrimination was significantly impaired with decreasing target height. A detailed analysis of the bats' echolocation calls during target approach shows that above the clutter surface, the bats produce calls with significantly higher peak frequency. Flight-path reconstruction revealed that the bats attacked an target from below over water but from above over a clutter surface. These results are consistent with the hypothesis that trawling bats exploit an echo-acoustic ground effect, in terms of a spatio-temporal integration of direct reflections with indirect reflections from the water surface, to optimize prey detection and -discrimination not only for prey on the water but also for some range above. PMID:23576990

  19. Polar mesosphere winter echoes and ionospheric heating experiments

    NASA Astrophysics Data System (ADS)

    Belova, Evgenia

    Polar Mesosphere Winter Echoes (PMWE) are strong radar backscatters from altitudes between 50 and 80 km observed by VHF radars in the polar latitudes during winter time. They are seen when there is extra D-region ionization due to e.g. energetic solar protons or magnetospheric electron precipitation. Last 5 years there were many studies related to the properties, conditions and generation mechanism of PMWE, however for their complete and clear understanding more work is definitely needed. On the other hand, with studying PMWE we have possibility to learn about properties of their background, i.e. the polar winter mesosphere, the region, which is very difficult for diagnostics. Havnes (2004) proposed a new experimental method for probing ionospheric plasma during P(olar) M(esosphere) S(ummer) E(choes), called the PMSE overshoot effect. It is based on artificial heating of electrons in the PMSE region by HF radiowave with a special modulation pattern. It was shown to be capable of estimation of properties of background dusty plasma, electron temperature enhancement, and even of detection of the electron byte-outs. The method applied for PMSE conditions confirmed a presence of charged particles of a few tens nm size in the summer polar mesosphere. Recently this method was applied for winter conditions in the polar mesosphere where such particles composed of water ice are not expected because of higher temperatures. However, a weak overshoot effect was detected, and it was speculated to be indication of a presence of very small dust particles, likely meteoric smoke particles. We present the results of the experiment on January 16, 2008 where strong PMWE were detected with the European incoherent scatter (EISCAT) VHF radar (224 MHz) located near Tromso, Norway and the Heating facility was used for the PMWE overshoot modulation.

  20. The Exoplanet Characterisation Observatory (EChO) payload electronics

    NASA Astrophysics Data System (ADS)

    Focardi, M.; Pancrazzi, M.; Di Giorgio, A. M.; Pezzuto, S.; Micela, G.; Pace, E.

    2012-09-01

    The EChO Payload is an integrated spectrometer designed to cover the 0.55-16 μm (11 to 16 μm as a goal) wavelength band, subdivided into 5 channels from visible to thermal IR with a common set of optics spectrally dividing the field of view by means of dichroics and a unique electronics interface to the spacecraft, the Data Control Unit (DCU). DCU is mainly a digital unit with processing capabilities based on a rad-hard space qualified processor running the main Application SW (the scientific SW) and some programmable logics. DCU will host the detector’s warm front-end electronics (FEEs) and its main tasks are to implement the payload instruments commanding, the science and housekeeping (HK) data acquisition, conversion and packetisation, the onboard spectra pre-processing, and, finally, to provide finely regulated voltage levels to FEEs. Detector’s proximity cold electronics send analog data and HKs to DCU for digital conversion by sharing a redundant ADC aboard DCU. Analog HKs are previously multiplexed, elaborated and converted to digital format before sending them to the satellite platform, via the SpaceWire (SpW) links. DCU controls the FEEs syncronization (interpreting and routing sync signals and time stamps sent by OBC by means of SpW Time Codes) and runs the main logics to perform all the required tasks and memory management. The EChO DCU electronics basically focuses on the data and command flows, the clock/synchronization and power distribution network and on an overall architecture for a trade-off solution removing or reducing any electronics single-point failure.

  1. Artificial intelligence for the EChO mission planning tool

    NASA Astrophysics Data System (ADS)

    Garcia-Piquer, Alvaro; Ribas, Ignasi; Colomé, Josep

    2015-12-01

    The Exoplanet Characterisation Observatory (EChO) has as its main goal the measurement of atmospheres of transiting planets. This requires the observation of two types of events: primary and secondary eclipses. In order to yield measurements of sufficient Signal-to-Noise Ratio to fulfil the mission objectives, the events of each exoplanet have to be observed several times. In addition, several criteria have to be considered to carry out each observation, such as the exoplanet visibility, its event duration, and no overlapping with other tasks. It is expected that a suitable mission plan increases the efficiency of telescope operation, which will represent an important benefit in terms of scientific return and operational costs. Nevertheless, to obtain a long term mission plan becomes unaffordable for human planners due to the complexity of computing the huge number of possible combinations for finding an optimum solution. In this contribution we present a long term mission planning tool based on Genetic Algorithms, which are focused on solving optimization problems such as the planning of several tasks. Specifically, the proposed tool finds a solution that highly optimizes the defined objectives, which are based on the maximization of the time spent on scientific observations and the scientific return (e.g., the coverage of the mission survey). The results obtained on the large experimental set up support that the proposed scheduler technology is robust and can function in a variety of scenarios, offering a competitive performance which does not depend on the collection of exoplanets to be observed. Specifically, the results show that, with the proposed tool, EChO uses 94% of the available time of the mission, so the amount of downtime is small, and it completes 98% of the targets.

  2. Coupled-cluster computations of atomic nuclei.

    PubMed

    Hagen, G; Papenbrock, T; Hjorth-Jensen, M; Dean, D J

    2014-09-01

    In the past decade, coupled-cluster theory has seen a renaissance in nuclear physics, with computations of neutron-rich and medium-mass nuclei. The method is efficient for nuclei with product-state references, and it describes many aspects of weakly bound and unbound nuclei. This report reviews the technical and conceptual developments of this method in nuclear physics, and the results of coupled-cluster calculations for nucleonic matter, and for exotic isotopes of helium, oxygen, calcium, and some of their neighbors. PMID:25222372

  3. Critical Symmetry and Supersymmetry in Nuclei

    SciTech Connect

    Iachello, Francesco

    2006-04-26

    The role of dynamic symmetries and supersymmetries in nuclei is reviewed. The concept of critical symmetry, appropriate to describe bosonic systems (even-even nuclei) at the critical point of a phase transition, is introduced, and the symmetry, E(5), at the critical point of spherical to {gamma}-unstable shape phase transition, is discussed. The recently introduced concept of critical supersymmetry, appropriate to describe mixed systems of bosons and fermions (odd-even nuclei) at the critical point of a phase transition is presented. The case of a j=3/2 particle at the critical point of spherical to {gamma}-unstable transition, called E(5/4), is discussed.

  4. Separating Cloud Forming Nuclei from Interstitial Aerosol

    SciTech Connect

    Kulkarni, Gourihar R.

    2012-09-12

    It has become important to characterize the physicochemical properties of aerosol that have initiated the warm and ice clouds. The data is urgently needed to better represent the aerosol-cloud interaction mechanisms in the climate models. The laboratory and in-situ techniques to separate precisely the aerosol particles that act as cloud condensation nuclei (CCN) and ice nuclei (IN), termed as cloud nuclei (CN) henceforth, have become imperative in studying aerosol effects on clouds and the environment. This review summarizes these techniques, design considerations, associated artifacts and challenges, and briefly discusses the need for improved designs to expand the CN measurement database.

  5. Spearhead echo and downburst near the approach end of a John F. Kennedy Airport runway, New York City

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.

    1976-01-01

    Radar echoes of a storm at John F. Kennedy International Airport are examined. Results regarding the phenomena presented suggest the existence of downburst cells. These cells are characterized by spearhead echoes. About 2% of the echoes in the New York area were spearhead echoes. The detection and identification of downburst cells, their potential hazard to approaching and landing aircraft, and communication of this information to the pilots of those aircraft are discussed.

  6. Molecular outflows in starburst nuclei

    NASA Astrophysics Data System (ADS)

    Roy, Arpita; Nath, Biman B.; Sharma, Prateek; Shchekinov, Yuri

    2016-08-01

    Recent observations have detected molecular outflows in a few nearby starburst nuclei. We discuss the physical processes at work in such an environment in order to outline a scenario that can explain the observed parameters of the phenomenon, such as the molecular mass, speed and size of the outflows. We show that outflows triggered by OB associations, with NOB ≥ 105 (corresponding to a star formation rate (SFR)≥1 M⊙ yr-1 in the nuclear region), in a stratified disk with mid-plane density n0 ˜ 200-1000 cm-3 and scale height z0 ≥ 200(n0/102 cm-3)-3/5 pc, can form molecules in a cool dense and expanding shell. The associated molecular mass is ≥107 M⊙ at a distance of a few hundred pc, with a speed of several tens of km s-1. We show that a SFR surface density of 10 ≤ ΣSFR ≤ 50 M⊙ yr-1 kpc-2 favours the production of molecular outflows, consistent with observed values.

  7. Neurotransmitters of the suprachiasmatic nuclei

    PubMed Central

    Reghunandanan, Vallath; Reghunandanan, Rajalaxmy

    2006-01-01

    There has been extensive research in the recent past looking into the molecular basis and mechanisms of the biological clock, situated in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus. Neurotransmitters are a very important component of SCN function. Thorough knowledge of neurotransmitters is not only essential for the understanding of the clock but also for the successful manipulation of the clock with experimental chemicals and therapeutical drugs. This article reviews the current knowledge about neurotransmitters in the SCN, including neurotransmitters that have been identified only recently. An attempt was made to describe the neurotransmitters and hormonal/diffusible signals of the SCN efference, which are necessary for the master clock to exert its overt function. The expression of robust circadian rhythms depends on the integrity of the biological clock and on the integration of thousands of individual cellular clocks found in the clock. Neurotransmitters are required at all levels, at the input, in the clock itself, and in its efferent output for the normal function of the clock. The relationship between neurotransmitter function and gene expression is also discussed because clock gene transcription forms the molecular basis of the clock and its working. PMID:16480518

  8. Chemical complexity in galactic nuclei

    NASA Astrophysics Data System (ADS)

    Martin-Pintado, Jesus

    2007-12-01

    In recent years our knowledge of the chemical complexity in the nuclei of galaxies has dramatically changed. Recent observations of the nucleus of the Milky Way, of the starburst galaxy NGC253 and of the ultraluminous infrared galaxy (ULIRG) Arp220 have shown large abundance of complex organic molecules believed to be formed on grains. The Galactic center appears to be the largest repository of complex organic molecule like aldehydes and alcohols in the galaxy. We also measure large abundance of methanol in starburst galaxies and in ULIRGs suggesting that complex organic molecules are also efficiently produced in the central region of galaxies with strong star formation activity. From the systematic observational studies of molecular abundance in regions dominated by different heating processes like shocks, UV radiation, X-rays and cosmic rays in the center of the Milky Way, we are opening the possibility of using chemistry as a diagnostic tool to study the highly obscured regions of galactic centers. The templates found in the nucleus of the Milky Way will be used to establish the main mechanisms driving the heating and the chemistry of the molecular clouds in galaxies with different type of activity. The role of grain chemistry in the chemical complexity observed in the center of galaxies will be also briefly discussed.

  9. Hunting η-bound nuclei

    NASA Astrophysics Data System (ADS)

    Machner, H.

    2010-09-01

    The η meson can be bound to atomic nuclei. Experimental search is discussed in the form of final state interaction for the reactions dp → 3Heη and dd → 4Heη. For the latter case tensor polarized deuterons were used in order to extract the s-wave strength. For both reactions complex scattering lengths are deduced: a3Heη = [± (10.7 ± 0.8+0.1-0.5) + i. (1.5 ± 2.6 +1.0-0.9)] fm and a4Heη = [±(3.1 ±0.5) + i. (0 ±0.5)] fm. In a two-nucleon transfer reaction under quasi-free conditions, p27 Al → 3HeX, was investigated. The system X can be the bound 25Mgotimesη at rest. When a possible decay of an intermediate N* (1535) is required, a highly significant bump shows up in the missing mass spectrum. The data give for a bound state a binding energy of 13.3 ±1.6 MeV and a width of σ = 4.4±1.3 MeV.

  10. Unbound Resonances in Light Nuclei

    NASA Astrophysics Data System (ADS)

    Havens, Elizabeth; Finck, Joseph; Gueye, Paul; Thoennessen, Michael; MoNA Collaboration

    2014-09-01

    Currently there has been no comprehensive study undertaken to compile experimental results from neutron unbound spectroscopy using invariant mass measurements, gamma resolutions, and half-lives. At Central Michigan University, Hampton University, and the NSCL, a project was initiated to catalog all unbound resonances in light nuclei (Z = 1-12). Unbound resonances were characterized by having a confirmed neutron decay branch and/or an energy level greater than the neutron binding energy listed for that isotope according to either the National Nuclear Data Center's Evaluated Nuclear Structure Files or Experimental Unevaluated Nuclear Data List and the referred journals therein. Unbound resonances will be presented for twelve elements: H, He, Li, Be, B, C, N, O, Fl, Ne, Na, and Mg. The isotopes in which unbound resonances occur will be identified, along with unbound energy levels for these isotopes. If known, each unbound resonance's gamma resolution, half-life, method of production and journal reference were also determined and a selection of these will be presented.

  11. The morphology of cometary nuclei

    NASA Astrophysics Data System (ADS)

    Keller, H. U.; Jorda, L.

    comets display residual activity or clouds of dust grains around their nuclei. Taking the residual signal into account (mostly using simple models for the brightness distribution) the size estimates of the nuclei could be improved. The (nuclear) magnitude of a comet depends on the product of its albedo and cross-section. Only in a few cases could the albedo and size of a cometary nucleus be separated by additional observation of its thermal emission at infrared wavelengths. By comparison with outer Solar System asteroids Cruikshank et al. (1985) derived a surprisingly low albedo of about 0.04. A value in clear contradiction to the perception of an icy surface but fully confirmed by the first resolved images of a cometary nucleus during the flybys of the Vega and Giotto spacecraft of comet Halley (Sagdeev et al. 1986, Keller et al. 1986). The improvements of radar techniques led to the detection of reflected signals and finally to the derivation of nuclear dimensions and rotation rates. The observations, however, are also model dependent (rotation and size are similarly interwoven as are albedo and size) and sensitive to large dust grains in the vicinity of a nucleus. As an example, Kamoun et al. (1982) determined the radius of comet Encke to 1.5 (2.3, 1.0) km using the spin axis determination of Whipple and Sekanina (1979). The superb spatial resolution of the Hubble Space Telescope (HST) is not quite sufficient to resolve a cometary nucleus. The intensity distribution of the inner coma, however, can be observed and extrapolated toward the nucleus based on models of the dust distribution. If this contribution is subtracted from the central brightness the signal of the nucleus can be derived and hence its product of albedo times cross-section (Lamy and Toth 1995, Rembor 1998, Keller and Rembor 1998; Section 4.3). It has become clear that cometary nuclei are dark, small, often irregular bodies with dimensions ranging from about a kilometre (comet Wirtanen, the target of

  12. Multifrequency electron spin-echo envelope modulation studies of nitrogen ligation to the manganese cluster of photosystem II.

    PubMed

    Yeagle, Gregory J; Gilchrist, M Lane; Walker, Lee M; Debus, Richard J; Britt, R David

    2008-03-27

    The CalEPR Center at UC-Davis (http://brittepr.ucdavis.edu) is equipped with five research grade electron paramagnetic resonance (EPR) instruments operating at various excitation frequencies between 8 and 130GHz. Of particular note for this RSC meeting are two pulsed EPR spectrometers working at the intermediate microwave frequencies of 31 and 35GHz. Previous lower frequency electron spin-echo envelope modulation (ESEEM) studies indicated that histidine nitrogen is electronically coupled to the Mn cluster in the S2 state of photosystem II (PSII). However, the amplitude and resolution of the spectra were relatively poor at these low frequencies, precluding any in-depth analysis of the electronic structure properties of this closely associated nitrogen nucleus. With the intermediate frequency instruments, we are much closer to the 'exact cancellation' limit, which optimizes ESEEM spectra for hyperfine-coupled nuclei such as 14N and 15N. Herein, we report the results from ESEEM studies of both 14N- and 15N-labelled PSII at these two frequencies. Spectral simulations were constrained by both isotope datasets at both frequencies, with a focus on high-resolution spectral examination of the histidine ligation to the Mn cluster in the S2 state. PMID:17954435

  13. Clusterization and quadrupole deformation in nuclei

    SciTech Connect

    Cseh, J.; Algora, A.; Antonenko, N. V.; Jolos, R. V.; Scheid, W.; Darai, J.; Hess, P. O.

    2006-04-26

    We study the interrelation of the clusterization and quadrupole deformation of atomic nuclei, by applying cluster models. Both the energetic stability and the exclusion principle is investigated. Special attention is paid to the relative orientations of deformed clusters.

  14. From Nucleons To Nuclei To Fusion Reactions

    SciTech Connect

    Quaglioni, S; Navratil, P; Roth, R; Horiuchi, W

    2012-02-15

    Nuclei are prototypes of many-body open quantum systems. Complex aggregates of protons and neutrons that interact through forces arising from quantum chromo-dynamics, nuclei exhibit both bound and unbound states, which can be strongly coupled. In this respect, one of the major challenges for computational nuclear physics, is to provide a unified description of structural and reaction properties of nuclei that is based on the fundamental underlying physics: the constituent nucleons and the realistic interactions among them. This requires a combination of innovative theoretical approaches and high-performance computing. In this contribution, we present one of such promising techniques, the ab initio no-core shell model/resonating-group method, and discuss applications to light nuclei scattering and fusion reactions that power stars and Earth-base fusion facilities.

  15. Few-Body Universality in Halo Nuclei

    NASA Astrophysics Data System (ADS)

    Hammer, H.-W.

    2016-03-01

    Few-body systems with resonant S-wave interactions show universal properties which are independent of the interaction at short distances. These properties include a geometric spectrum of three- and higher-body bound states and universal correlations between few-body observables. They can be observed on a wide range of scales from hadrons and nuclei to ultracold atoms. In this contribution, we focus on few-body universality in halo nuclei which can be considered as effective few-body systems consisting of halo nucleons and a core. This concept provides a unifying framework for halo nuclei with calculable corrections. Recent progress in this field with an emphasis on the possibility of finding Efimov states in halo nuclei is discussed.

  16. Infrared Observations of Cometary Dust and Nuclei

    NASA Technical Reports Server (NTRS)

    Lisse, Carey

    2004-01-01

    This bibliography lists citations for publications published under the grant. Subjects of the publications include cometary dust, instellar and interplanetary dust, comet nuclei and comae, Comet Hale-Bopp, infrared observations of comets, mass loss, and comet break-up.

  17. Very elongated nuclei near A = 194

    SciTech Connect

    Becker, J.A.; Henry, E.A.; Yates, S.W.; Wang, T.F.; Kuhnert, A. ); Brinkman, M.J.; Cizewski, J.A. ); Deleplanque, M.A.; Diamond, R.M.; Stephens, F.S.; Azaiez, F.; Korten, W.; Draper, J.E. )

    1990-10-01

    A {gamma}-ray cascade in {sup 191}Hg of 12 members with average energy spacing 37 keV and Q{sub t} {equals} 18(3)eb was reported by Moore, and coworkers in 1989. This was the first report of very elongated nuclei (superdeformation) in this mass region. Since then, some 25 {gamma}-ray cascades have been observed in 11 (slightly neutron deficient) Hg, Pb and Tl nuclei. The bands have similar dynamic moments-of-inertia. Some nuclei exhibit multiple bands, and the backbending phenomena has been observed. Level spins can be obtained from comparison of transition energies to rotational model formulas. Selected bands (in different nuclei) have equal transition energies (within 0.1%). Alignment in integer multiples of {h bar} has been observed. Properties of these bands will be described. 27 refs., 3 figs.

  18. Superheavy Nuclei - Clusters of Matter and Antimatter

    SciTech Connect

    Greiner, Walter; Buervenich, Thomas J.

    2005-03-31

    The extension of the periodic system into various new areas is investigated. Experiments for the synthesis of superheavy elements and the predictions of magic numbers with modern meson field theories are reviewed. Different channels of nuclear decay are discussed including cluster radioactivity, cold fission and cold multifragmentation Furthermore, we present the vacuum for the e+-e- field of QED and show how it is modified for baryons in nuclear environment. Then we discuss the possibility of producing new types of nuclear systems by implanting an antibaryon into ordinary nuclei. The structure of nuclei containing one antiproton or antilambda is investigated within the framework of a relativistic mean-field model. Self-consistent calculations predict very enhanced binding and considerable compression in such systems as compared with normal nuclei. We present arguments that the life time of such nuclei with respect to the antibaryon annihilation might be long enough for their observation. A perspective for future research is given.

  19. True ternary fission of superheavy nuclei

    SciTech Connect

    Zagrebaev, V. I.; Karpov, A. V.; Greiner, Walter

    2010-04-15

    True ternary fission with formation of a heavy third fragment is quite possible for superheavy nuclei because of the strong shell effects leading to a three-body clusterization with the two doubly magic tinlike cores. The simplest way to discover this phenomenon in the decay of excited superheavy nuclei is a detection of two tinlike clusters with appropriate kinematics in low-energy collisions of medium-mass nuclei with actinide targets. The three-body quasi-fission process could be even more pronounced for giant nuclear systems formed in collisions of heavy actinide nuclei. In this case a three-body clusterization might be proved experimentally by the detection of two coincident leadlike fragments in low-energy U + U collisions.

  20. The Heavy Nuclei Explorer (HNX) Mission

    NASA Technical Reports Server (NTRS)

    Binns, W. R.

    2001-01-01

    The Heavy Nuclei eXplorer (HNX) mission was recently selected by NASA for a Small Explorer (SMEX) Mission Concept Study to begin in 2001. The primary scientific objectives of HNX are to measure the age of the galactic cosmic rays (GCR) since nucleosynthesis, determine the injection mechanism for the GCR accelerator (Volatility or FIP), and study the mix of nucleosynthetic processes that contribute to the source of GCRs. The experimental goal of HNX is to measure the elemental abundances of all individual stable nuclei from neon through the actinides and possibly beyond. HNX is composed of two instruments: ECCO, which measures elemental abundances of nuclei with Z(sup 3)72, and ENTICE, which measures elemental abundances of nuclei with 10(f)Z(f)82. We will discuss the mission and the science that can be addressed by HNX.

  1. Perspectives of production of superheavy nuclei

    NASA Astrophysics Data System (ADS)

    Adamian, G. G.; Antonenko, N. V.; Bezbakh, A. N.; Sargsyan, V. V.; Scheid, W.

    2016-07-01

    Possible ways of production of superheavies are discussed. Impact of nuclear structure on the production of superheavy nuclei in complete fusion reactions is discussed. The proton shell closure at Z = 120 is discussed.

  2. Where Should the Nuclei Be Located?

    ERIC Educational Resources Information Center

    Ying Liu; Yue Liu; Drew, Michael G. B.

    2005-01-01

    The approach of determining the nature of the electron wave function via orbital representations qualitatively and via numerical calculations quantitatively is demonstrated. The angular part of the wave function provides suitable representation of the positions of the nuclei.

  3. Understanding nuclei in the upper sd - shell

    SciTech Connect

    Sarkar, M. Saha; Bisoi, Abhijit; Ray, Sudatta; Kshetri, Ritesh; Sarkar, S.

    2014-08-14

    Nuclei in the upper-sd shell usually exhibit characteristics of spherical single particle excitations. In the recent years, employment of sophisticated techniques of gamma spectroscopy has led to observation of high spin states of several nuclei near A ≃ 40. In a few of them multiparticle, multihole rotational states coexist with states of single particle nature. We have studied a few nuclei in this mass region experimentally, using various campaigns of the Indian National Gamma Array setup. We have compared and combined our empirical observations with the large-scale shell model results to interpret the structure of these nuclei. Indication of population of states of large deformation has been found in our data. This gives us an opportunity to investigate the interplay of single particle and collective degrees of freedom in this mass region.

  4. Organization of projections from the raphe nuclei to the vestibular nuclei in rats

    NASA Technical Reports Server (NTRS)

    Halberstadt, A. L.; Balaban, C. D.

    2003-01-01

    Previous anatomic and electrophysiological evidence suggests that serotonin modulates processing in the vestibular nuclei. This study examined the organization of projections from serotonergic raphe nuclei to the vestibular nuclei in rats. The distribution of serotonergic axons in the vestibular nuclei was visualized immunohistochemically in rat brain slices using antisera directed against the serotonin transporter. The density of serotonin transporter-immunopositive fibers is greatest in the superior vestibular nucleus and the medial vestibular nucleus, especially along the border of the fourth ventricle; it declines in more lateral and caudal regions of the vestibular nuclear complex. After unilateral iontophoretic injections of Fluoro-Gold into the vestibular nuclei, retrogradely labeled neurons were found in the dorsal raphe nucleus (including the dorsomedial, ventromedial and lateral subdivisions) and nucleus raphe obscurus, and to a minor extent in nucleus raphe pallidus and nucleus raphe magnus. The combination of retrograde tracing with serotonin immunohistofluorescence in additional experiments revealed that the vestibular nuclei receive both serotonergic and non-serotonergic projections from raphe nuclei. Tracer injections in densely innervated regions (especially the medial and superior vestibular nuclei) were associated with the largest numbers of Fluoro-Gold-labeled cells. Differences were observed in the termination patterns of projections from the individual raphe nuclei. Thus, the dorsal raphe nucleus sends projections that terminate predominantly in the rostral and medial aspects of the vestibular nuclear complex, while nucleus raphe obscurus projects relatively uniformly throughout the vestibular nuclei. Based on the topographical organization of raphe input to the vestibular nuclei, it appears that dense projections from raphe nuclei are colocalized with terminal fields of flocculo-nodular lobe and uvula Purkinje cells. It is hypothesized that

  5. Cosmic Ray Nuclei (CRN) detector investigation

    NASA Technical Reports Server (NTRS)

    Meyer, Peter; Muller, Dietrich; Lheureux, Jacques; Swordy, Simon

    1991-01-01

    The Cosmic Ray Nuclei (CRN) detector was designed to measure elemental composition and energy spectra of cosmic radiation nuclei ranging from lithium to iron. CRN was flown as part of Spacelab 2 in 1985, and consisted of three basic components: a gas Cerenkov counter, a transition radiation detector, and plastic scintillators. The results of the experiment indicate that the relative abundance of elements in this range, traveling at near relativistic velocities, is similar to those reported at lower energy.

  6. Synthesis of superheavy nuclei: Obstacles and opportunities

    NASA Astrophysics Data System (ADS)

    Zagrebaev, V. I.; Karpov, A. V.; Greiner, Walter

    2015-01-01

    There are only 3 methods for the production of heavy and superheavy (SH) nuclei, namely, fusion reactions, a sequence of neutron capture and beta(-) decay and multinucleon transfer reactions. Low values of the fusion cross sections and very short half-lives of nuclei with Z<120 put obstacles in synthesis of new elements. At the same time, an important area of SH isotopes located between those produced in the cold and hot fusion reactions remains unstudied yet. This gap could be filled in fusion reactions of 48Ca with available lighter isotopes of Pu, Am, and Cm. New neutron-enriched isotopes of SH elements may be produced with the use of a 48Ca beam if a 250Cm target would be prepared. In this case we get a real chance to reach the island of stability owing to a possible beta(+) decay of 291114 and 287112 nuclei formed in this reaction with a cross section of about 0.8 pb. A macroscopic amount of the long-living SH nuclei located at the island of stability may be produced by using the pulsed nuclear reactors of the next generation only if the neutron fluence per pulse will be increased by about three orders of magnitude. Multinucleon transfer processes look quite promising for the production and study of neutron-rich heavy nuclei located in upper part of the nuclear map not reachable by other reaction mechanisms. Reactions with actinide beams and targets are of special interest for synthesis of new neutron-enriched transfermium nuclei and not-yet-known nuclei with closed neutron shell N=126 having the largest impact on the astrophysical r-process. The estimated cross sections for the production of these nuclei allows one to plan such experiments at currently available accelerators.

  7. Reaction cross sections of unstable nuclei

    SciTech Connect

    Ozawa, Akira

    2006-11-02

    Experimental studies on reaction cross sections are reviewed. The recent developments of radioactive nuclear beams have enabled us to measure reaction cross-sections for unstable nuclei. Using Glauber-model analysis, effective nuclear matter density distributions of unstable nuclei can be studied. Recent measurements in RIBLL at IMP and RIPS at RIKEN are introduced. The effective matter density distributions for 14-18C are also mentioned.

  8. A Sample of Seyfert-2 Galaxies with Ultraluminous Galaxy-wide Narrow-line Regions: Quasar Light Echoes?

    NASA Astrophysics Data System (ADS)

    Schirmer, M.; Diaz, R.; Holhjem, K.; Levenson, N. A.; Winge, C.

    2013-01-01

    We report the discovery of Seyfert-2 galaxies in SDSS-DR8 with galaxy-wide, ultraluminous narrow-line regions (NLRs) at redshifts z = 0.2-0.6. With a space density of 4.4 Gpc-3 at z ~ 0.3, these "green beans" (GBs) are amongst the rarest objects in the universe. We are witnessing an exceptional and/or short-lived phenomenon in the life cycle of active galactic nuclei (AGNs). The main focus of this paper is on a detailed analysis of the GB prototype galaxy J2240-0927 (z = 0.326). Its NLR extends over 26 × 44 kpc and is surrounded by an extended NLR. With a total [O III] λ5008 luminosity of (5.7 ± 0.9) × 1043 erg s-1, this is one of the most luminous NLRs known around any type-2 galaxy. Using VLT/XSHOOTER, we show that the NLR is powered by an AGN, and we derive resolved extinction, density, and ionization maps. Gas kinematics is disturbed on a global scale, and high-velocity outflows are absent or faint. This NLR is unlike any other NLR or extended emission line region known. Spectroscopy with Gemini/GMOS reveals extended, high-luminosity [O III] emission also in other GBs. WISE 24 μm luminosities are 5-50 times lower than predicted by the [O III] fluxes, suggesting that the NLRs reflect earlier, very active quasar states that have strongly subsided in less than a galaxy's light-crossing time. These light echoes, or ionization echoes, are about 100 times more luminous than any other such echo known to date. X-ray data are needed for photoionization modeling and to verify the light echoes. Based on observations made with ESO Telescopes at the La Silla and Paranal Observatories, Chile. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. Based on observations

  9. Time-dependent ultrasound echo changes occur in tendon during viscoelastic testing.

    PubMed

    Duenwald-Kuehl, Sarah; Kobayashi, Hirohito; Lakes, Roderic; Vanderby, Ray

    2012-11-01

    The viscoelastic behavior of tendons has been extensively studied in vitro. A noninvasive method by which to acquire mechanical data would be highly beneficial, as it could lead to the collection of viscoelastic data in vivo. Our lab has previously presented acoustoelasticity as an alternative ultrasound-based method of measuring tendon stress and strain by reporting a relationship between ultrasonic echo intensity (B mode ultrasound image brightness) and mechanical behavior of tendon under pseudoelastic in vitro conditions [Duenwald, S., Kobayashi, H., Frisch, K., Lakes, R., and Vanderby Jr, R., 2011, "Ultrasound Echo is Related to Stress and Strain in Tendon," J. Biomech., 44(3), pp. 424-429]. Viscoelastic properties of the tendons were not examined in that study, so the presence of time-dependent echo intensity changes has not been verified. In this study, porcine flexor tendons were subjected to relaxation and cyclic testing while ultrasonic echo response was recorded. We report that time- and strain history-dependent mechanical properties during viscoelastic testing are manifested in ultrasonic echo intensity changes. We also report that the patterns of the echo intensity changes do not directly mimic the patterns of viscoelastic load changes, but the intensity changed in a repeatable (and therefore predictable) fashion. Although mechanisms need further elucidation, viscoelastic behavior can be anticipated from echo intensity changes. This phenomenon could potentially lead to a more extensive characterization of in vivo tissue behavior. PMID:23387788

  10. Phase-corrected Bipolar Gradients in Multiecho Gradient-echo Sequences for Quantitative Susceptibility Mapping

    PubMed Central

    Li, Jianqi; Chang, Shixin; Liu, Tian; Jiang, Hongwei; Dong, Fang; Pei, Mengchao; Wang, Qianfeng; Wang, Yi

    2016-01-01

    Object The large echo spacing of unipolar readout gradients in current multiecho gradient-echo sequences for mapping fields in quantitative susceptibility mapping (QSM) can be reduced using bipolar readout gradients to improve acquisition efficiency. Materials and Methods Phase discrepancies between odd and even echoes in the bipolar readout gradients caused by non-ideal gradient behaviors were measured, modeled as polynomials in space and corrected for accordingly in field mapping. The bipolar approach for multiecho gradient-echo field mapping was compared with the unipolar approach for QSM. Results The odd-even-echo phase discrepancies were approximately constant along the phase encoding direction and linear along the readout and slice-selection directions. A simple linear phase correction in all three spatial directions was shown to enable accurate QSM in the human brain using a bipolar multiecho GRE sequence. Bipolar multiecho acquisition provides QSM in good quantitative agreement with unipolar acquisition while also reducing noise. Conclusion With a linear phase correction between odd-even echoes, bipolar readout gradients can be used in multiecho gradient-echo sequences for QSM. PMID:25408108

  11. Light Echoes from Luminous Transients - Status of the Field and Future Prospects

    NASA Astrophysics Data System (ADS)

    Welch, Douglas L.; Rest, Armin

    2014-06-01

    Scattered-light echoes from luminous transients (supernovae, luminous blue variables/supernova impostors) are unique in their ability to preserve an observable record of the state of a transient in outburst for centuries. Unlike conventional (i.e. intentional) time-series records, the presence of interstellar dust on the light echo ellipsoid from a given outburst allows photometric and spectroscopic study at any epoch where the scattered-light signal reaches a useful signal-to-noise threshold. Additionally, dust located at different positions on an outburst's light-echo ellipsoid will preserve a record of the hemispheric emission of light from the outburst as seen from each dust location, allowing the degree of asymmetry of an outburst to be studied.A more recent application of scattered-light echoes employs the fact that multiple outbursts of high-amplitude, unstable, luminous variables each produce their own light-echo ellipsoids and dust located on such ellipsoids provides an opportunity for multiple outbursts to be studied at the same (modern) epoch.This talk will provide a brief summary of the evolution of light echoes from use as a tool to map out the interstellar medium around luminous events to their richer and more recent use of investigating the outbursts themselves. Important findings from observations of scattered-light echoes regarding SN1987A, Cas A, and eta Car will be highlighted and near-term prospects for new work and new observational opportunities will be presented.

  12. Strong Correlation between Quasi-periodic Echoes and Plasma Drift in E-region

    NASA Astrophysics Data System (ADS)

    Jin, H.; Chen, G.

    2015-12-01

    It is for the first time that the simultaneous observations of the quasi-periodic (QP) echoes and the plasma drift in the ionospheric E-region. This experiment was carried out in Fuke (19.5ºN, 109.1ºE), Hainan province, China. The Hainan VHF radar was used to observe the E-region field-aligned irregularities (FAIs) and the Hainan Digisonde was operated in the drift mode to record the drift velocities of the plasma blobs in the Es-layer. The QP echoes and the drift data of the whole year of 2013 were analyzed and compared. A surprising consistency between the striation tilt of the QP echoes and the drift direction of the plasma blobs was discovered. When the measured drift direction of the plasma blobs was southward, the negative echo striation of the QP FAIs was recorded, and vice versa. Furthermore, the phase of the echo trace was continuous, while the QP striation changed from negative to positive, or in contrary. Thus, a conclusion can be reached that the morphology of the QP echoes may be controlled by the background wind fields in the E-region. The northward/ southward drifting striated FAIs in the observing region of a coherent scatter radar possibly induce the positive/ negative QP echo striation in the range-time-intensity plots.

  13. 3D hyperpolarized He-3 MRI of ventilation using a multi-echo projection acquisition

    PubMed Central

    Holmes, James H.; O’Halloran, Rafael L.; Brodsky, Ethan K.; Jung, Youngkyoo; Block, Walter F.; Fain, Sean B.

    2010-01-01

    A method is presented for high resolution 3D imaging of the whole lung using inhaled hyperpolarized (HP) He-3 MR with multiple half-echo radial trajectories that can accelerate imaging through undersampling. A multiple half-echo radial trajectory can be used to reduce the level of artifact for undersampled 3D projection reconstruction (PR) imaging by increasing the amount of data acquired per unit time for HP He-3 lung imaging. The point spread functions (PSFs) for breath-held He-3 MRI using multiple half-echo trajectories were evaluated using simulations to predict the effects of T2* and gas diffusion on image quality. Results from PSF simulations were consistent with imaging results in volunteer studies showing improved image quality with increasing number of echoes using up to 8 half-echoes. The 8 half-echo acquisition is shown to accommodate lost breath-holds as short as 6 s using a retrospective reconstruction at reduced resolution as well as to allow reduced breath-hold time compared to an equivalent Cartesian trajectory. Furthermore, preliminary results from a 3D dynamic inhalation-exhalation maneuver are demonstrated using the 8 half-echo trajectory. Results demonstrate the first high resolution 3D PR imaging of ventilation and respiratory dynamics in humans using HP He-3 MR. PMID:18429034

  14. Reaction theories for exotic nuclei

    SciTech Connect

    Bonaccorso, Angela

    2012-11-20

    This contribution discusses two important dynamical effects in the scattering of exotic beams. The first part deals proton breakup. The Coulomb interactions between the core and the target and the proton and the target are treated to all orders, including also the full multipole expansion of the Coulomb potential. The dynamics of proton Coulomb breakup is compared to that of an equivalent neutron of larger binding energy in order to elucidate the differences with the well understood neutron breakup mechanism. With respect to nuclear breakup it is found that a proton behaves exactly as a neutron of larger binding energy. The extra 'effective energy' is due to the combined core-target Coulomb barrier. In Coulomb breakup we distinguish the effect of the core-target Coulomb potential (called recoil effect), with respect to which the proton behaves again as a more bound neutron, from the direct proton-target Coulomb potential. The latter gives cross sections about an order of magnitude larger than the recoil term. The two effects give rise to complicated interferences in the parallel momentum distributions. They are instead easily separable in the proton angular distributions which are therefore suggested as a very useful observable for future experimental studies. The second part has to do with the dynamics of one-neutron and one-proton removal from unstable nuclei with large asymmetry {Delta}S S{sub n}-S{sub p} in the separation energies and incident energies below 80 MeV/nucleon. Strong non-sudden effects are observed in the case of deeply-bound-nucleon removal. The corresponding parallel momentum distributions exhibit an abrupt cutoff at high momentum that corresponds to an energy threshold occurring when the incident energy per particle is of comparable magnitude as the nucleon separation energy.

  15. Properties of the hypothetical spherical superheavy nuclei

    SciTech Connect

    Smolanczuk, R. |

    1997-08-01

    Theoretical results on the ground-state properties of the hypothetical spherical superheavy atomic nuclei are presented and discussed. Even-even isotopes of elements Z=104{minus}120 are considered. Certain conclusions are also drawn for odd-A and odd-odd superheavy nuclei. Results obtained earlier for even-even deformed superheavy nuclei with Z=104{minus}114 are given for completeness. Equilibrium deformation, nuclear mass, {alpha}-decay energy, {alpha}-decay half-life, dynamical fission barrier, as well as spontaneous-fission half-life are considered. {beta}-stability of superheavy nuclei is also discussed. The calculations are based on the macroscopic-microscopic model. A multidimensional deformation space describing axially symmetric nuclear shapes is used in the analysis of masses and decay properties of superheavy nuclei. We determined the boundaries of the region of superheavy nuclei which are expected to live long enough to be detected after the synthesis in a present-day experimental setup. {copyright} {ital 1997} {ital The American Physical Society}

  16. Major new sources of biological ice nuclei

    NASA Astrophysics Data System (ADS)

    Moffett, B. F.; Hill, T.; Henderson-Begg, S. K.

    2009-12-01

    Almost all research on biological ice nucleation has focussed on a limited number of bacteria. Here we characterise several major new sources of biogenic ice nuclei. These include mosses, hornworts, liverworts and cyanobacteria. Ice nucleation in the eukaryotic bryophytes appears to be ubiquitous. The temperature at which these organisms nucleate is that at which the difference in vapour pressure over ice and water is at or close to its maximum. At these temperatures (-8 to -18 degrees C) ice will grow at the expense of supercooled water. These organisms are dependent for their water on occult precipitation - fog, dew and cloudwater which by its nature is not collected in conventional rain gauges. Therefore we suggest that these organism produce ice nuclei as a water harvesting mechanism. Since the same mechanism would also drive the Bergeron-Findeisen process, and as moss is known to become airborne, these nuclei may have a role in the initiation of precipitation. The properties of these ice nuclei are very different from the well characterised bacterial nuclei. We will also present DNA sequence data showing that, although related, the proteins responsible are only very distantly related to the classical bacterial ice nuclei.

  17. Echo SPL influences the ranging performance of the big brown bat, Eptesicus fuscus.

    PubMed

    Denzinger, A; Schnitzler, H U

    1994-11-01

    Four bats of the species Eptesicus fuscus were trained in a two-alternative forced-choice procedure to discriminate between two phantom targets that differed in range. The rewarded stimulus was located at a distance of 52.7 cm, while the other unrewarded stimulus was further away. Only one target was presented at a time. In the first experiment we measured the range discrimination performance at an echo SPL of -28 dB relative to the bat's sonar transmission. A 75% correct performance level was arbitrarily defined as threshold and was obtained at a delay difference of 80 microseconds, corresponding to a range difference of 13.8 mm. In the second experiment the delay difference was fixed at 150 microseconds and the echo SPL varied between -8 and -48 dB relative to sonar emissions. The performance of the bats depended on the relative echo SPL. AT -28 dB the bats showed the best performance. It deteriorated at an increase of the relative echo SPL to -18 dB and -8 dB. The performance also deteriorated when the relative echo SPL was reduced to -38 dB and -48 dB. Only at low relative echo SPLs did the bats partially compensate for the reduction in echo SPL and increased the SPL of their emitted signals by a few dB. Our results support the hypothesis that neurons exhibiting paradoxical latency shift may be involved in encoding target range. This hypothesis predicts a decrease in performance at high echo SPLs as we found it in our experiments. The observed reduction in performance at very low echo SPLs may be due to a decrease in S/N ratio. PMID:7965921

  18. General analysis of (14)N (I = 1) electron spin echo envelope modulation.

    PubMed

    Lee, H I; Doan, P E; Hoffman, B M

    1999-09-01

    The analysis methods described to date for (14)N electron spin echo envelope modulation (ESEEM) mostly deal with isotropic g- and (14)N hyperfine coupling tensors. However, many cases of rhombic tensors are encountered. In the present report we present general equations for analyzing orientation-selective ESEEM and illustrate their use. (i) We present general equations for the nuclear interactions in an electron spin system where the EPR signal arises from an isolated Kramers doublet, then give the nuclear (electron-nuclear double resonance) frequencies for I = 1 associated with such a system. (ii) These are incorporated into equations for single-crystal ESEEM amplitudes, which in turn are incorporated into general equations for the orientation-selective ESEEM that arises when the EPR envelope of a frozen-solution (powder) sample is determined by g anisotropy. (iii) This development is first used in the simplest limit of an isotropic g-tensor and leads to a more general picture of the response of the I = 1 modulation amplitude to variations in the nuclear hyperfine and quadrupole coupling constants, relative to the nuclear Zeeman interaction, than had been presented previously. We find that strong modulation occurs not only in the well-known regime where the "exact/near cancellation" condition (A/2 approximately nu(N)) is satisfied, but also when the nuclear hyperfine interaction is much larger than the nuclear Zeeman interaction (A/nu(N) > 3) with A/K = 4 approximately 5. (iv) We then describe the orientation-selective (14)N ESEEM frequency-domain patterns (g vs frequency) in the presence of anisotropic (rhombic) hyperfine and electron Zeeman interactions for both coaxial and noncoaxial cases. We derive analytical solutions when the g-, hyperfine, and nuclear quadrupole tensors are coaxial. (v) The method is applied to the ESEEM of the nitrogenase MoFe protein (Av1) to determine the full hyperfine and nuclear quadrupole tensors of (14)N nuclei interacting with the

  19. W-Disjoint Orthogonality Based Residual Acoustic Echo Cancellation for Hands-Free Communication

    NASA Astrophysics Data System (ADS)

    Lee, Yoonjae; Kim, Kihyeon; Yoon, Jongsung; Ko, Hanseok

    A simple and novel residual acoustic echo cancellation method that employs binary masking is proposed to enhance the speech quality of hands-free communication in an automobile environment. In general, the W-disjoint orthogonality assumption is used for blind source separation using multi-microphones. However, in this Letter, it is utilized to mask the residual echo component in the time-frequency domain using a single microphone. The experimental results confirm the effectiveness of the proposed method in terms of the echo return loss enhancement and speech enhancement.

  20. Masking Property Based Residual Acoustic Echo Cancellation for Hands-Free Communication in Automobile Environment

    NASA Astrophysics Data System (ADS)

    Lee, Yoonjae; Jeong, Seokyeong; Ko, Hanseok

    A residual acoustic echo cancellation method that employs the masking property is proposed to enhance the speech quality of hands-free communication devices in an automobile environment. The conventional masking property is employed for speech enhancement using the masking threshold of the desired clean speech signal. In this Letter, either the near-end speech or residual noise is selected as the desired signal according to the double-talk detector. Then, the residual echo signal is masked by the desired signal (masker). Experiments confirm the effectiveness of the proposed method by deriving the echo return loss enhancement and by examining speech waveforms and spectrograms.

  1. Examination of the Spatial Correlation of Statistics Information in the Ultrasonic Echo from Diseased Liver

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Tadashi; Hachiya, Hiroyuki; Kamiyama, Naohisa; Moriyasu, Fuminori

    2002-05-01

    To realize a quantitative diagnosis of liver cirrhosis, we have been analyzing the characteristics of echo amplitude in B-mode images. Realizing the distinction between liver diseases such as liver cirrhosis and chronic hepatitis is required in the field of medical ultrasonics. In this study, we examine the spatial correlation, with the coefficient of correlation between the frames and the amplitude characteristics of each frame, using the volumetric data of RF echo signals from normal and diseased liver. It is found that there is a relationship between the tissue structure of liver and the spatial correlation of echo information.

  2. Middle ear muscle contractions and their relation to pulse and echo evoked potentials in the bat

    NASA Technical Reports Server (NTRS)

    Henson, O. W., Jr.; Henson, M. M.

    1972-01-01

    An analysis is made of pulse and echo orientation cries of the Mustache Bat. That bat's cries are characterized by a long, 60 to 30 msec, pure tone component and brief beginning and terminal FM sweeps. In addition to obvious echo overlap and middle ear muscle contractions, the following are examined: (1) characteristics of pulse- and echo-evoked potential under various conditions, (2) evidence of changes in hearing sensitivity during and after pulse emission, and (3) the role of the middle ear muscles in bringing about these changes.

  3. Precision spectral manipulation of optical pulses using a coherent photon echo memory.

    PubMed

    Buchler, B C; Hosseini, M; Hétet, G; Sparkes, B M; Lam, P K

    2010-04-01

    Photon echo schemes are excellent candidates for high efficiency coherent optical memory. They are capable of high-bandwidth multipulse storage, pulse resequencing and have been shown theoretically to be compatible with quantum information applications. One particular photon echo scheme is the gradient echo memory (GEM). In this system, an atomic frequency gradient is induced in the direction of light propagation leading to a Fourier decomposition of the optical spectrum along the length of the storage medium. This Fourier encoding allows precision spectral manipulation of the stored light. In this Letter, we show frequency shifting, spectral compression, spectral splitting, and fine dispersion control of optical pulses using GEM. PMID:20364227

  4. Trial of Human Bone Cross-Sectional Imaging In vivo, Using Ultrasonic Echo Waves

    NASA Astrophysics Data System (ADS)

    Mano, Isao; Horii, Kaoru; Matsukawa, Mami; Otani, Takahiko

    2013-07-01

    We have tried in vivo imaging of the distal forearm bone using ultrasonic echo waves. The obtained ultrasonic echo images were compared with X-ray computed tomography (CT) images. In the case of vertical incidence of an ultrasonic wave to the cortical bone surface, not only the outer and inner boundaries of the near side of the cortical bone but also the inner and outer boundaries of the far side of the cortical bone were identified. The thicknesses of the cortical bone and cancellous bone calculated using the echo waves approximately agreed with those determined from X-ray CT images.

  5. Estimating evaporation duct heights from radar sea echo

    NASA Astrophysics Data System (ADS)

    Rogers, L. Ted; Hattan, Claude P.; Stapleton, Janet K.

    2000-07-01

    The evaporation duct is a downward refracting layer that results from the rapid decrease in humidity with respect to altitude occurring in the atmospheric surface layer above bodies of water. The evaporation duct affects radar detection ranges at frequencies of approximately 1 GHz and above. Models based on Monin-Obukhov similarity theory are usually used to calculate evaporation duct refractivity profiles from bulk measurements of air temperature, humidity, wind speed, and the sea surface temperature. Modeling results by Pappert et al. [1992] indicated that the falloff of radar sea echo as a function of range was an increasing function of the evaporation duct height. On the basis of those results, the authors proposed inferring the evaporation duct height by a slope fit to modeled clutter power, a nonlinear least squares inversion procedure. Data for testing the inversion procedure were obtained using the S band Space Range Radar at Wallops Island, Virginia. Evaporation duct heights were inferred from the radar data on the basis of the assumption of a range-independent evaporation duct height and sea clutter radar cross section (σ°). Validation data consist of buoy and boat in situ bulk measurements. The result of comparing the radar-inferred evaporation duct heights and those calculated from bulk measurements indicates that the radar-inferred duct heights are strongly correlated with those from the in situ measurements, but there is some uncertainty as to whether they are biased or unbiased. That uncertainty arises from the assumed dependence of σ° on the grazing angle ψ. That dependence is currently a matter of debate in the open literature, with the lower and upper ends of modeling results being σ° ∝ ψ0; and σ° ∝ ψ4, respectively. We show results for both dependencies and note that the σ° ∝ ψ0; provides the best agreement with our measurements. It should be noted that inferring the evaporation duct height from radar sea echo is a problem

  6. 76 FR 63702 - In the Matter of the Designation of Conspiracy of Fire Nuclei, aka Conspiracy of the Nuclei of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-13

    ... Matter of the Designation of Conspiracy of Fire Nuclei, aka Conspiracy of the Nuclei of Fire, aka Conspiracy of Cells of Fire, aka Synomosia of Pyrinon Tis Fotias, aka Thessaloniki-Athens Fire Nuclei... January 23, 2003, I hereby determine that the organization known as Conspiracy of Fire Nuclei, also...

  7. Correction of Excitation Profile in Zero Echo Time (ZTE) Imaging Using Quadratic Phase-Modulated RF Pulse Excitation and Iterative Reconstruction

    PubMed Central

    Li, Cheng; Magland, Jeremy F.; Seifert, Alan C.

    2014-01-01

    Zero-echo Time (ZTE) imaging is a promising technique for magnetic resonance imaging (MRI) of short-T2 tissue nuclei in tissues. A problem inherent to the method currently hindering its translation to the clinic is the presence of a spatial encoding gradient during excitation, which causes the hard pulse to become spatially selective, resulting in blurring and shadow artifacts in the image. While shortening radiofrequency (RF) pulse duration alleviates this problem the resulting elevated RF peak power and specific absorption rate (SAR) in practice impede such a solution. In this work, an approach is described to correct the artifacts by applying quadratic phase-modulated RF excitation and iteratively solving an inverse problem formulated from the signal model of ZTE imaging. A simple pulse sequence is also developed to measure the excitation profile of the RF pulse. Results from simulations, phantom and in vivo studies, demonstrate the effectiveness of the method in correcting image artifacts caused by inhomogeneous excitation. The proposed method may contribute toward establishing ZTE MRI as a routine 3D pulse sequence for imaging protons and other nuclei with quasi solid-state behavior on clinical scanners. PMID:24710164

  8. Fast-recovery fast spin-echo T2-weighted MR imaging: a free-breathing alternative to fast spin-echo in the pediatric abdomen.

    PubMed

    Huang, I-Hua; Emery, Kathleen H; Laor, Tal; Valentine, Mona; Tiefermann, Jan

    2008-06-01

    In the mid 1990s, the fast spin-echo (FSE) and turbo spin-echo (TSE) T2-weighted (T2-W) sequences became available and are now widely accepted alternatives to conventional spin-echo sequences since they result in reduced acquisition times while maintaining tissue contrast. Since that time, there has been continued development of new sequences to further decrease acquisition times, minimize artifacts, and preserve lesion detection. The purpose of this pictorial essay is to qualitatively illustrate the newly available fast recovery (FR) FSE T2-W MR images of the abdomen compared with the images acquired using the routine FSE T2-W sequence in non-breath-hold studies in children. PMID:18345537

  9. Echo-sounding method aids earthquake hazard studies

    USGS Publications Warehouse

    U.S. Geological Survey

    1995-01-01

    Dramatic examples of catastrophic damage from an earthquake occurred in 1989, when the M 7.1 Lorna Prieta rocked the San Francisco Bay area, and in 1994, when the M 6.6 Northridge earthquake jolted southern California. The surprising amount and distribution of damage to private property and infrastructure emphasizes the importance of seismic-hazard research in urbanized areas, where the potential for damage and loss of life is greatest. During April 1995, a group of scientists from the U.S. Geological Survey and the University of Tennessee, using an echo-sounding method described below, is collecting data in San Antonio Park, California, to examine the Monte Vista fault which runs through this park. The Monte Vista fault in this vicinity shows evidence of movement within the last 10,000 years or so. The data will give them a "picture" of the subsurface rock deformation near this fault. The data will also be used to help locate a trench that will be dug across the fault by scientists from William Lettis & Associates.

  10. Unusual radar echoes from the Greenland ice sheet

    NASA Technical Reports Server (NTRS)

    Rignot, E. J.; Vanzyl, J. J.; Ostro, S. J.; Jezek, K. C.

    1993-01-01

    In June 1991, the NASA/Jet Propulsion Laboratory airborne synthetic-aperture radar (AIRSAR) instrument collected the first calibrated data set of multifrequency, polarimetric, radar observations of the Greenland ice sheet. At the time of the AIRSAR overflight, ground teams recorded the snow and firn (old snow) stratigraphy, grain size, density, and temperature at ice camps in three of the four snow zones identified by glaciologists to characterize four different degrees of summer melting of the Greenland ice sheet. The four snow zones are: (1) the dry-snow zone, at high elevation, where melting rarely occurs; (2) the percolation zone, where summer melting generates water that percolates down through the cold, porous, dry snow and then refreezes in place to form massive layers and pipes of solid ice; (3) the soaked-snow zone where melting saturates the snow with liquid water and forms standing lakes; and (4) the ablation zone, at the lowest elevations, where melting is vigorous enough to remove the seasonal snow cover and ablate the glacier ice. There is interest in mapping the spatial extent and temporal variability of these different snow zones repeatedly by using remote sensing techniques. The objectives of the 1991 experiment were to study changes in radar scattering properties across the different melting zones of the Greenland ice sheet, and relate the radar properties of the ice sheet to the snow and firn physical properties via relevant scattering mechanisms. Here, we present an analysis of the unusual radar echoes measured from the percolation zone.

  11. Return Echoes from Medium-Large Footprint Laser Altimeters

    NASA Technical Reports Server (NTRS)

    Blair, J. Bryan; Hofton, Michelle A.; Rabine, David L.

    1999-01-01

    For just over 10 years, NASA Goddard Space Flight Center has been at the forefront of developing return echo laser altimeters and analysis techniques for a variety of both space and airborne applications. In 1991, the Laser Remote Sensing Branch began investigating the use of medium-large diameter footprint return waveforms for measuring vegetation height and structure and sub-canopy topography. Over the last 8 years, using a variety of profiling and scanning laser altimeters (i.e. ATLAS, SLICER, SLA, and LVIS), we have collected return waveforms over a variety of terrestrial surface types. We describe the effects of instrument characteristics and within-footprint surface structure on the shape of the return waveform and suggest several techniques for extracting this information. Specifically for vegetation returns, we describe the effects of canopy parameters such as architecture and closure on the shape of the return waveform. Density profiles, statistics, and examples from a variety of vegetation types will be presented, as well as comparisons with small-footprint laser altimeter data.

  12. Pulse-Echo Technique for Angular Dependent Magnetoacoustic Studies

    NASA Astrophysics Data System (ADS)

    Suslov, A.; Svitelskiy, O.; Palm, E.; Murphy, T.; Shulyatev, D.

    2006-09-01

    The pulse-echo ultrasonic technique is the only method to investigate the tensor of the so-called area coefficient, which describes the strain influence on the Fermi surface of a material. This technique has been used to study the layered superconductor Sr2RuO4 at temperatures down to 45 mK and in fields of up to 33 T. We scanned the orientation of the field in the bc-plane of the crystal and performed field and temperature sweeps at specific angles selected with a precision of about 1 degree. The wave vector of studied c11 mode coincided with the axis of rotation and was always perpendicular to the field direction. The observed quantum oscillations were the strongest at small angles between the field and the c direction of the crystal. The three frequencies of the quantum oscillations Fα = 3.02 kTesla, Fβ = 12.74 kTesla and Fγ = 18.44 kTesla as well as two values of the effective masses mα = 3.2mc and mβ = 5.5me associated with the α, β, and γ sheets of the Fermi surface measured at zero angle, are in good agreement with the known values. As expected for the cylindrical Fermi surfaces, the frequencies followed a 1/cosθ law. These results demonstrate that the technique has good performance.

  13. Searching for Cosmic Ray Radar Echos In TARA Data

    NASA Astrophysics Data System (ADS)

    Myers, Isaac

    2013-04-01

    The TARA (Telescope Array Radar) cosmic ray detector has been in operation for about a year and half. This bi-static CW radar detector was designed with the goal of detecting cosmic rays in coincidence with Telescope Array (TA). For the majority of its operation it has been in the TARA1.5 phase in which a 1.5 kW transmitter broadcasts from a single Yagi antenna across the TA surface detector array to our receiver station 50 km away. Our initial DAQ system has obtained millions of triggers utilizing a USRP2 PC controlled radio. During recent months, we have commissioned a 250 MHz sample rate detector with an intelligent self-triggering algorithm that can detect radar echo chirp signals below the noise. I will describe the stages of analysis used for comparing TARA radar triggers with TA data and present a synopsis of the analysis of the USRP2 data and preliminary results from the more advanced DAQ system.

  14. [Echo-color-Doppler in male pelvic congestion syndrome].

    PubMed

    Sarteschi, Lelio Mario; Simi, Stefano; Turchi, Paolo; DeMaria, Maurizio; Morelli, Girolamo

    2002-12-01

    The pelvic congestion syndrome has been widely studied in the female sex, while there are not many publications on the male equivalent. Prostatitis represent the most frequent affections of the genito-urinary male tract that require the urologic consult, but in the majority of the cases the etiology of such affections remains unknown. Some forms of microscopic hematuria or macroscopic hematuria are also cryptogenetic. Varicocelectomy is widely given in the infertile patients, but not always the intervention achieves a recovery of the semen quality. In this work we revisit the anatomy of the pelvic male venous drain and we depict its objective findings with the echo-color-Doppler sonography (ECD). The purpose of the study is to encourage a polycentric uro-andrologic search on large numbers, with the goal of resolve if the ECD pictures of congestion pelvic syndrome could have relation with some "prostatitis syndromes", with some cryptogenetic hematuria and/or with the prognosis of the infertile patients undergone to varicocelectomy. PMID:12508723

  15. Learning to decode human emotions with Echo State Networks.

    PubMed

    Bozhkov, Lachezar; Koprinkova-Hristova, Petia; Georgieva, Petia

    2016-06-01

    The aim of this paper is to identify the common neural signatures based on which the positive and negative valence of human emotions across multiple subjects can be reliably discriminated. The brain activity is observed via Event Related Potentials (ERPs). ERPs are transient components in the Electroencephalography (EEG) generated in response to a stimulus. ERPs were collected while subjects were viewing images with positive or negative emotional content. Building inter-subject discrimination models is a challenging problem due to the high ERPs variability between individuals. We propose to solve this problem with the aid of the Echo State Networks (ESN) as a general framework for extracting the most relevant discriminative features between multiple subjects. The original feature vector is mapped into the reservoir feature space defined by the number of the reservoir equilibrium states. The dominant features are extracted iteratively from low dimensional combinations of reservoir states. The relevance of the new feature space was validated by experiments with standard supervised and unsupervised machine learning techniques. From one side this proof of concept application enhances the usability context of the reservoir computing for high dimensional static data representations by low-dimensional feature transformation as functions of the reservoir states. From other side, the proposed solution for emotion valence detection across subjects is suitable for brain studies as a complement to statistical methods. This problem is important because such decision making systems constitute "virtual sensors" of hidden emotional states, which are useful in psychology science research and clinical applications. PMID:26422421

  16. Observational Definition of Future AGN Echo-Mapping Experiments

    NASA Technical Reports Server (NTRS)

    Collier, Stefan; Peterson, Bradley M.; Horne, Keith

    2001-01-01

    We describe numerical simulations we have begun in order to determine the observational requirements for future echo-apping experiments. We focus on two particular problems: (1) determination of the structure and kinematics of the broad-line region through emission- line reverberation mapping, and (2) detection of interband continuum lags that may be used as a probe of the continuum source, presumably a temperature-stratified accretion disk. Our preliminary results suggest the broad-line region can be reverberation-mapped to good precision with spectra of signal-to-noise ratio per pixel S/N approx. = 30, time resolution (Delta)t approx. = 0.1 day, and duration of about 60 days (which is a factor of three larger than the longest time scale in the input models); data that meet these requirements do not yet exist. We also find that interband continuum lags of approx. greater than 0.5 days can be detected at approx. greater than 95% confidence with at least daily observations for about 6 weeks, or rather more easily and definitively with shorter programs undertaken with satellite-based observatories. The results of these simulations show that significant steps forward in multiwavelength monitoring will almost certainly require dedicated facilities.

  17. A consistent tissue attenuation coefficient estimator using bubble harmonic echoes.

    PubMed

    Tsao, Sheng-Kai; Tsao, Jenho

    2010-12-01

    The ultrasonic property of soft tissue can be quantified by its attenuation coefficient α. Traditionally the backscattering signal of tissue is used to estimate α. To improve precision, a large number of spatially independent samples of tissue echoes are required for averaging. In this paper, we propose a new estimation method, which makes use of microbubbles to provide temporally independent samples for averaging. It is easier for temporal sampling to maintain ergodicity and provide a large number of independent samples for statistical averaging. A stochastic model for the harmonic signals of an ideal bubble attenuated by tissue is derived based on Kuc's and Miller's works. An estimator of α is then presented. This estimator is consistent and could be biased because of the unknown squarelaw relation between the second and fundamental harmonics for non-ideal bubble oscillation. In experimental works, we design a simplified phantom for demonstrating the performance of the proposed estimator. It is shown that both first and second harmonics can estimate α consistently. However, the interference of the tissue backscattering signal may cause additional estimation error using the first harmonic. PMID:21156361

  18. Architectural and Markovian factors of echo state networks.

    PubMed

    Gallicchio, Claudio; Micheli, Alessio

    2011-06-01

    Echo State Networks (ESNs) constitute an emerging approach for efficiently modeling Recurrent Neural Networks (RNNs). In this paper we investigate some of the main aspects that can be accounted for the success and limitations of this class of models. In particular, we propose complementary classes of factors related to contractivity and architecture of reservoirs and we study their relative relevance. First, we show the existence of a class of tasks for which ESN performance is independent of the architectural design. The effect of the Markovian factor, characterizing a significant class within these cases, is shown by introducing instances of easy/hard tasks for ESNs featured by contractivity of reservoir dynamics. In the complementary cases, for which architectural design is effective, we investigate and decompose the aspects of network design that allow a larger reservoir to progressively improve the predictive performance. In particular, we introduce four key architectural factors: input variability, multiple time-scales dynamics, non-linear interactions among units and regression in an augmented feature space. To investigate the quantitative effects of the different architectural factors within this class of tasks successfully approached by ESNs, variants of the basic ESN model are proposed and tested on instances of datasets of different nature and difficulty. Experimental evidences confirm the role of the Markovian factor and show that all the identified key architectural factors have a major role in determining ESN performances. PMID:21376531

  19. Gradient Echo Quantum Memory in Warm Atomic Vapor

    PubMed Central

    Pinel, Olivier; Hosseini, Mahdi; Sparkes, Ben M.; Everett, Jesse L.; Higginbottom, Daniel; Campbell, Geoff T.; Lam, Ping Koy; Buchler, Ben C.

    2013-01-01

    Gradient echo memory (GEM) is a protocol for storing optical quantum states of light in atomic ensembles. The primary motivation for such a technology is that quantum key distribution (QKD), which uses Heisenberg uncertainty to guarantee security of cryptographic keys, is limited in transmission distance. The development of a quantum repeater is a possible path to extend QKD range, but a repeater will need a quantum memory. In our experiments we use a gas of rubidium 87 vapor that is contained in a warm gas cell. This makes the scheme particularly simple. It is also a highly versatile scheme that enables in-memory refinement of the stored state, such as frequency shifting and bandwidth manipulation. The basis of the GEM protocol is to absorb the light into an ensemble of atoms that has been prepared in a magnetic field gradient. The reversal of this gradient leads to rephasing of the atomic polarization and thus recall of the stored optical state. We will outline how we prepare the atoms and this gradient and also describe some of the pitfalls that need to be avoided, in particular four-wave mixing, which can give rise to optical gain. PMID:24300586

  20. Noise pair velocity and range echo location system

    SciTech Connect

    Erskine, David J.

    1999-01-01

    An echo-location method for microwaves, sound and light capable of using incoherent and arbitrary waveforms of wide bandwidth to measure velocity and range (and target size) simultaneously to high resolution. Two interferometers having very long and nearly equal delays are used in series with the target interposed. The delays can be longer than the target range of interest. The first interferometer imprints a partial coherence on an initially incoherent source which allows autocorrelation to be performed on the reflected signal to determine velocity. A coherent cross-correlation subsequent to the second interferometer with the source determines a velocity discriminated range. Dithering the second interferometer identifies portions of the cross-correlation belonging to a target apart from clutter moving at a different velocity. The velocity discrimination is insensitive to all slowly varying distortions in the signal path. Speckle in the image of target and antenna lobing due to parasitic reflections is minimal for an incoherent source. An arbitrary source which varies its spectrum dramatically and randomly from pulse to pulse creates a radar elusive to jamming. Monochromatic sources which jigger in frequency from pulse to pulse or combinations of monochromatic sources can simulate some benefits of incoherent broadband sources. Clutter which has a symmetrical velocity spectrum will self-cancel for short wavelengths, such as the apparent motion of ground surrounding target from a sidelooking airborne antenna.

  1. Noise pair velocity and range echo location system

    DOEpatents

    Erskine, D.J.

    1999-02-16

    An echo-location method for microwaves, sound and light capable of using incoherent and arbitrary waveforms of wide bandwidth to measure velocity and range (and target size) simultaneously to high resolution is disclosed. Two interferometers having very long and nearly equal delays are used in series with the target interposed. The delays can be longer than the target range of interest. The first interferometer imprints a partial coherence on an initially incoherent source which allows autocorrelation to be performed on the reflected signal to determine velocity. A coherent cross-correlation subsequent to the second interferometer with the source determines a velocity discriminated range. Dithering the second interferometer identifies portions of the cross-correlation belonging to a target apart from clutter moving at a different velocity. The velocity discrimination is insensitive to all slowly varying distortions in the signal path. Speckle in the image of target and antenna lobing due to parasitic reflections is minimal for an incoherent source. An arbitrary source which varies its spectrum dramatically and randomly from pulse to pulse creates a radar elusive to jamming. Monochromatic sources which jigger in frequency from pulse to pulse or combinations of monochromatic sources can simulate some benefits of incoherent broadband sources. Clutter which has a symmetrical velocity spectrum will self-cancel for short wavelengths, such as the apparent motion of ground surrounding target from a sidelooking airborne antenna. 46 figs.

  2. 8Be and 9B nuclei in dissociation of relativistic 10B and 11C nuclei

    NASA Astrophysics Data System (ADS)

    Artemenkov, D. A.; Bradnova, V.; Firu, E.; Kornegrutsa, N. K.; Haiduc, M.; Mamatkulov, K. Z.; Kattabekov, R. R.; Neagu, A.; Rukoyatkin, P. A.; Rusakova, V. V.; Stanoeva, R.; Zaitsev, A. A.; Zarubin, P. I.; Zarubina, I. G.

    2016-02-01

    Progress in the study of nuclear clustering in the relativistic 10B and 11C nuclei dissociation in nuclear track emulsion is presented. The contribution of the unbound 8Be and 9B nuclei to their structure is determined on the basis of measurements of the emission angles of relativistic He and H fragments.

  3. 8Be and 9B nuclei in dissociation of relativistic 10C and 11C nuclei

    NASA Astrophysics Data System (ADS)

    Artemenkov, D. A.; Bradnova, V.; Firu, E.; Kornegrutsa, N. K.; Haiduc, M.; Mamatkulov, K. Z.; Kattabekov, R. R.; Neagu, A.; Rukoyatkin, P. A.; Rusakova, V. V.; Stanoeva, R.; Zaitsev, A. A.; Zarubin, P. I.; Zarubina, I. G.

    2016-05-01

    Progress in the study of nuclear clustering in the relativistic 10C and 11C nuclei dissociation in nuclear track emulsion is presented. The contribution of the unbound 8Be and 9B nuclei to their structure is determined on the basis of measurements of the emission angles of relativistic He and H fragments.

  4. Transition (LINER/HII) nuclei as evolved Composite (Seyfert 2/Starburst) nuclei

    NASA Astrophysics Data System (ADS)

    Storchi-Bergmann, Thaisa; Brandt, C. H.; Cid Fernandes, R.; Schmitt, H. R.; González Delgado, R.

    2004-11-01

    We compare the circumnuclear stellar population and environmental properies of Seyfert and Composite (Seyfert + Starburst) nuclei with those of LINERs and LINER/HII transition galaxies (TOs), and discuss evidence for evolution from Seyfert/Composite to LINER/TO nuclei.

  5. Rapid decrease of radar cross section of meteor head echo observed by the MU radar

    NASA Astrophysics Data System (ADS)

    Nakamura, T.; Nishio, M.; Sato, T.; Tsutsumi, S.; Tsuda, T.; Fushimi, K.

    The meteor head echo observation using the MU (Middle and Upper atmosphere) radar (46.5M Hz, 1MW), Shigaraki, Japan, was carried out simultaneously with a high sensitive ICCD (Image-intensified CCD) camera observation in November 2001. The time records were synchronized using GPS satellite signals, in order to compare instantaneous radar and optical meteor magnitudes. 26 faint meteors were successfully observed simultaneously by both equipments. Detailed comparison of the time variation of radar echo intensity and absolute optical magnitude showed that the radar scattering cross section is likely to decrease rapidly by 5 - 20 dB without no corresponding magnitude variation in the optical data. From a simple modeling, we concluded that such decrease of RCS (radar cross section ) is probably due to the transition from overdense head echo to underd ense head echo.

  6. Impossibility of faithfully storing single photons with the three-pulse photon echo

    SciTech Connect

    Sangouard, Nicolas; Minar, Jiri; Afzelius, Mikael; Gisin, Nicolas; Riedmatten, Hugues de; Simon, Christoph; Tittel, Wolfgang; Chaneliere, Thierry; Le Goueet, Jean-Louis

    2010-06-15

    The three-pulse photon echo is a well-known technique to store intense light pulses in an inhomogeneously broadened atomic ensemble. This protocol is attractive because it is relatively simple and it is well suited for the storage of multiple temporal modes. Furthermore, it offers very long storage times, greater than the phase relaxation time. Here, we consider the three-pulse photon echo in both two- and three-level systems as a potential technique for the storage of light at the single-photon level. By explicit calculations, we show that the ratio between the echo signal corresponding to a single-photon input and the noise is smaller than one. This severely limits the achievable fidelity of the quantum state storage, making the three-pulse photon echo unsuitable for single-photon quantum memory.

  7. Ultrasonic echo waveshape features extraction based on QPSO-matching pursuit for online wear debris discrimination

    NASA Astrophysics Data System (ADS)

    Xu, Chao; Zhang, Peilin; Wang, Huaiguang; Li, Yining; Lv, Chun

    2015-08-01

    The ultrasonic echoes reflected from debris in lubricant contain a lot of useful information, which can represent the size, material and geometric characteristics of the debris. Our preliminary simulation investigations and physical model analysis results show that the waveshape features are feasible and essential to discriminate debris in lubricant. An accurate waveshape features extraction method of debris echoes is presented based on the matching pursuit (MP). The dictionary of Gabor functions, which is suitable for ultrasonic signal processing, is adopted for MP. To seek faster and more accurate calculation of MP, quantum-behaved particle swarm optimization (QPSO) is introduced to optimize the MP algorithm. The simulation and experimental results reveal that the proposed method can effectively extract the waveshape features of debris echoes and air bubble echoes. Utilizing the extracted waveshape features, the debris with different shapes and air bubble can be distinguished.

  8. Detection and quantification of recent myocardial infarction: diagnostic value of multiecho multislice spin echo imaging.

    PubMed

    Kastler, B; Germain, P; Roul, G; Constantinesco, A; Dietemmen, J L; Sacrez, A; Wackenheim, A

    1991-01-01

    Thirty-four patients with documented transmural MI were studied with gated three echo, multislice MR imaging. In 12 patients MRI MI size was compared with CK release measurement, Tl-201 SPECT defect, and with Tc-99m LVEF. Infarct was visualised in 29/34 patients on 3rd echo images (18/34 on 2nd and 6/34 on 1st echo images). Mean MR infarct size (planimetered from 3rd echo images): 33.1 +/- 9% overestimated the SPECT defect (mean value of 23.8 +/- 15%). However, the overall correlation between MRI and Tl-201 sizing was significant: r = 0.82; p less than 0.001; SEE = 5.5%. The correlation with LVEF also appeared significant: r = -0.61; p less than 0.038. PMID:2059944

  9. Signal processing for the detection of multiple imperfection echoes drowned in the structural noise.

    PubMed

    Drai, R; Benammar, A; Benchaala, A

    2004-04-01

    In this work, we propose to develop algorithms based on the split spectrum processing method associated with the multi-steps method based on "Group delay moving entropy" (GDME) allowing detecting and locating multiple imperfection echoes drowned in the structural noise of materials. In fact, GDME is based on the fact that defect echoes have a constant group delay while the noise has a random group delay. The investigation is performed with 4 known defect echoes with different characteristics (position, center frequency and bandwidth). The defect echo frequency is varied around the frequency of the input signal in order to evaluate, by signal to noise ratio calculation, the robustness of the detection method. The grain noise signal is generated first, by a simple clutter model which consider the noise, in the time domain, as the superimposed of signal coming from backscaterers in the medium and second, experimentally by a material with coarse grains. PMID:15047392

  10. Multi-Scale Structure of Solar Wind Transients Coincident with Electron Drift-Echoes

    NASA Astrophysics Data System (ADS)

    Mulligan, T. L.; O'Brien, T. P., III; Claudepierre, S. G.; Roeder, J. L.; Green, J. C.; Fennell, J. F.

    2014-12-01

    It is well known that impulsive substorm dipolarizations on the night side produce dispersionless injections of keV particles, for which multiple drift echoes can be observed. The impact these injections have on radiation belt particles is less well understood. We present a preliminary investigation into the types of solar wind transients (i.e. coronal mass ejections (CMEs), co-rotational and/or stream interaction regions (CIRs and/or SIRs), high-speed streams (HSS), interplanetary shock events, etc.) that correlate with observations of electron drift echoes during the Van Allen Probes mission. We use data from ACE and Wind during the current solar cycle (24) to establish criteria for determining critical regions and sub-structures within these transients that correlate with observed drift echoes. This initial study is part of a more comprehensive characterization of the multi-scale structure of solar wind drivers coincident with drift echoes through different phases of the solar cycle.

  11. Conditions for Using Stimulated Photon Echo to Record and Reproduce Information in Three-Level Systems

    NASA Astrophysics Data System (ADS)

    Nefediev, L. A.; Nizamova, E. I.

    2016-01-01

    The conditions for observing photon echo signals in crystals with excitation and detection in different resonant transitions with a single common energy level are studied. Uncorrelated inhomogeneous broadening in different resonance transitions is shown to influence the formation of stimulated photon echo in three-level systems. Lowering the sample temperature makes it possible to increase the relaxation time, which is used in experiments for observing photon echo. Uncorrelated inhomogeneous broadening in different resonance transitions is temperature independent and affects the intensity of the response at low temperatures, as well. Observation of stimulated photon echo in solid three-level samples requires a correct choice of the time interval between the first and second exciting pulses, but is not related to the magnitude of the irreversible transverse relaxation of the system.

  12. Surveying for Historical Supernovae Light Echoes in the Milky Way Field (Abstract)

    NASA Astrophysics Data System (ADS)

    Welch, D. L.

    2014-12-01

    (Abstract only) Very luminous, transient events can produce detectable “light echoes”—light scattered by interstellar dust which can arrive much later than the direct light from an outburst. In the last 1,000 years, there have been half a dozen supernovae in the Milky Way which are capable of producing detectable light echoes. Light echo systems have already been found for Tycho (SN 1572) and Cas A. The three-dimensional distribution of light echoes provides one of the few menas for an astronomical source to be inspected from more than one viewpoint. Indications of the degree of asymmetry of supernovae are extremely valuable for understanding the details of the event itself. Amateurs are well-equipped to find the brighter light echoes and in this work I will provide practical guidance on how such surveys may be accomplished and the various science opportunities they provide.

  13. Compact Nuclei in Galaxies at Moderate Redshift

    NASA Astrophysics Data System (ADS)

    Sarajedini, Vicki Lynn

    The purpose of this study is to understand the space density and properties of active galaxies to z ≃ 0.8. We have investigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as Active Galactic Nuclei (AGN) or starbursts. Candidates are selected by fitting imaged galaxies with multi-component models using maximum likelihood estimate techniques to determine the best model fit. We select those galaxies requiring an unresolved, point source component in the galaxy nucleus, in addition to a disk and/or bulge component, to adequately model the galaxy light. We have searched 70 WFPC2 images primarily from the Medium Deep Survey for galaxies containing compact nuclei. In our survey of 1033 galaxies, the fraction containing an unresolved nuclear component ≥3% of the total galaxy light is 16±3% corrected for incompleteness and 9±1% for nuclei ≥5% of the galaxy light. Most of the nuclei are ~<20% of the total galaxy light. The majority of the host galaxies are spirals with little or no bulge component. The V-I colors of the nuclei are compared with synthetic colors for Seyferts and starburst nuclei to help differentiate between AGNs and starbursts in our sample. Spectroscopic redshifts have been obtained for 35 of our AGN/starburst candidates and photometric redshifts are estimated to an accuracy of σz≃0.1 for the remaining sample. We present the upper limit luminosity function (LF) for low-luminosity AGN (LLAGN) in two redshift bins to z = 0.8. We detect mild number density evolution of the form φ∝ (1+z)1.9 for nuclei at -18 ~

  14. Stability and production of superheavy nuclei

    SciTech Connect

    Moeller, P. |; Nix, J.R.

    1997-12-31

    Beyond uranium heavy elements rapidly become increasingly unstable with respect to spontaneous fission as the proton number Z increases, because of the disruptive effect of the long-range Coulomb force. However, in the region just beyond Z = 100 magic proton and neutron numbers and the associated shell structure enhances nuclear stability sufficient to allow observation of additional nuclei. Some thirty years ago it was speculated that an island of spherical, relatively stable superheavy nuclei would exist near the next doubly magic proton-neutron combination beyond {sup 208}Pb, that is, at proton number Z = 114 and neutron number N = 184. Theory and experiment now show that there also exists a rock of stability in the vicinity of Z = 110 and N = 162 between the actinide region, which previously was the end of the peninsula of known elements, and the predicted island of spherical superheavy nuclei slightly southwest of the magic numbers Z = 114 and N = 184. The authors review here the stability properties of the heavy region of nuclei. Just as the decay properties of nuclei in the heavy region depend strongly on shell structure, this structure also dramatically affects the fusion entrance channel. The six most recently discovered new elements were all formed in cold-fusion reactions. They discuss here the effect of the doubly magic structure of the target in cold-fusion reactions on the fusion barrier and on dissipation.

  15. IN VITRO AND PRELIMINARY IN VIVO VALIDATION OF ECHO PARTICLE IMAGE VELOCIMETRY IN CAROTID VASCULAR IMAGING

    PubMed Central

    Zhang, Fuxing; Lanning, Craig; Mazzaro, Luciano; Barker, Alex J.; Gates, Philip; Strain, W. David; Fulford, Jonathan; Gosling, Oliver E.; Shore, Angela C.; Bellenger, Nick G.; Rech, Bryan; Chen, Jiusheng; Chen, James; Shandas, Robin

    2012-01-01

    Non-invasive, easy-to-use and accurate measurements of wall shear stress (WSS) in human blood vessels have always been challenging in clinical applications. Echo particle image velocimetry (Echo PIV) has shown promise for clinical measurements of local hemodynamics and wall shear rate. So far, however, the method has only been validated under simple flow conditions. In this study, we validated Echo PIV under in-vitro and in-vivo conditions. For in-vitro validation, we used an anatomically-correct, compliant carotid bifurcation flow phantom with pulsatile flow conditions, using optical particle image velocimetry (optical PIV) as the reference standard. For in-vivo validation, we compared Echo PIV-derived two dimensional velocity fields obtained at the carotid bifurcation in 5 normal subjects against phase-contrast MRI-derived velocity measurements obtained at the same locations. For both studies, time-dependent, two-dimensional two-component velocity vectors, peak/centerline velocity, flow rate and wall shear rate (WSR) waveforms at the common carotid artery (CCA), carotid bifurcation and distal internal carotid artery (ICA) were examined. Linear regression, correlation analysis and Bland-Altman analysis were used to quantify the agreement of different waveforms measured by the two techniques. In-vitro results showed that Echo PIV produced good images of time-dependent velocity vector maps over the cardiac cycle with excellent temporal (up to 0.7 msec) and spatial (~0.5 mm) resolutions and quality, on par with optical PIV results. Further, good agreement was found between Echo PIV and optical PIV results for velocity and WSR measurements. In-vivo results also showed good agreement between Echo PIV velocities and PC-MRI velocities. We conclude that Echo PIV provides accurate velocity vector and WSR measurements in the carotid bifurcation and has significant potential as a clinical tool for cardiovascular hemodynamics evaluation. PMID:21316562

  16. Generation of an optimal target list for the exoplanet characterisation observatory (EChO)

    NASA Astrophysics Data System (ADS)

    Varley, R.; Waldmann, I.; Pascale, E.; Tessenyi, M.; Hollis, M.; Morales, J. C.; Tinetti, G.; Swinyard, B.; Deroo, P.; Ollivier, M.; Micela, G.

    2015-12-01

    The Exoplanet Characterisation Observatory (EChO) has been studied as a space mission concept by the European Space Agency in the context of the M3 selection process. Through direct measurement of the atmospheric chemical composition of hundreds of exoplanets, EChO would address fundamental questions such as: What are exoplanets made of? How do planets form and evolve? What is the origin of exoplanet diversity? More specifically, EChO is a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large, diverse and well-defined planetary sample within its four to six year mission lifetime. In this paper we use the end-to-end instrument simulator EChOSim to model the currently discovered targets, to gauge which targets are observable and assess the EChO performances obtainable for each observing tier and time. We show that EChO would be capable of observing over 170 relativity diverse planets if it were launched today, and the wealth of optimal targets for EChO expected to be discovered in the next 10 years by space and ground-based facilities is simply overwhelming. In addition, we build on previous molecular detectability studies to show what molecules and abundances will be detectable by EChO for a selection of real targets with various molecular compositions and abundances. EChO's unique contribution to exoplanetary science will be in identifying the main constituents of hundreds of exoplanets in various mass/temperature regimes, meaning that we will be looking no longer at individual cases but at populations. Such a universal view is critical if we truly want to understand the processes of planet formation and evolution in various environments. In this paper we present a selection of key results. The full results are available in Online Resource 1.

  17. On the origin of 150-km echoes: Recent observational results and current understanding

    NASA Astrophysics Data System (ADS)

    Patra, Amit

    2012-07-01

    Discovered nearly 45 years ago, the so-called 150-km echoing phenomenon continues to be a puzzle. These are the coherent radar echoes coming from the height region of 140-180 km during daytime and are of special interest to the ionospheric scientists since they are very useful means for estimating the daytime electric fields, a crucial parameter for studying daytime electrodynamics and plasma physics, and can be observed by radar with moderate sensitivity. Although the 150-km echoes are being regularly used for studying low latitude electrodynamics, it is a bit awkward using them in the scientific work without knowing their origin. This paper is meant to present and discuss new results obtained from Gadanki (13.5o N, 79.2o E, mag. lat. 6.5o N), India to elucidate the underlying physical processes, not considered before. Two new findings, one obtained during the passage of a solar eclipse and another linked with the intermediate layer type descending properties of 150-km echoes, clearly indicate the role of electron density gradient in generating the irregularities responsible for the 150-km radar echoes, not envisioned before. Given the fact that Gadanki is located at magnetically low latitude, it is proposed that the descending echoing layers are produced by interchange instability on the gradient of daytime descending ion layer formed by meridional wind shear associated with tidal/gravity waves quite similar to that observed during nighttime. Comparative anatomy of daytime 150-km echoes and nighttime intermediate layer echoes will also be presented and discussed in an effort to have a deeper understanding on the underlying instability processes.

  18. Mars radar mapping: Strong depolarized echoes from the Elysium/Amazonis outflow channel complex

    NASA Technical Reports Server (NTRS)

    Harmon, J. K.; Sulzer, M. P.; Perillat, P.

    1991-01-01

    A new technique was used to make radar maps of Mars with the Arecibo radiotelescope. The observations were made during the 1990 opposition (close approach) of Mars. Among the most interesting of the preliminary results is the discovery of strong depolarized echoes from the enormous Elysium/Amazonis outflow channel complex. These strong echoes may represent rough-surface scattering off the youngest lava flows on Mars.

  19. Mono-Exponential Fitting in T2-Relaxometry: Relevance of Offset and First Echo

    PubMed Central

    Milford, David; Rosbach, Nicolas; Bendszus, Martin; Heiland, Sabine

    2015-01-01

    Introduction T2 relaxometry has become an important tool in quantitative MRI. Little focus has been put on the effect of the refocusing flip angle upon the offset parameter, which was introduced to account for a signal floor due to noise or to long T2 components. The aim of this study was to show that B1 imperfections contribute significantly to the offset. We further introduce a simple method to reduce the systematic error in T2 by discarding the first echo and using the offset fitting approach. Materials and Methods Signal curves of T2 relaxometry were simulated based on extended phase graph theory and evaluated for 4 different methods (inclusion and exclusion of the first echo, while fitting with and without the offset). We further performed T2 relaxometry in a phantom at 9.4T magnetic resonance imaging scanner and used the same methods for post-processing as in the extended phase graph simulated data. Single spin echo sequences were used to determine the correct T2 time. Results The simulation data showed that the systematic error in T2 and the offset depends on the refocusing pulse, the echo spacing and the echo train length. The systematic error could be reduced by discarding the first echo. Further reduction of the systematic T2 error was reached by using the offset as fitting parameter. The phantom experiments confirmed these findings. Conclusion The fitted offset parameter in T2 relaxometry is influenced by imperfect refocusing pulses. Using the offset as a fitting parameter and discarding the first echo is a fast and easy method to minimize the error in T2, particularly for low to intermediate echo train length. PMID:26678918

  20. Low-altitude quasi-periodic echoes studied using a large database of Gadanki radar observations

    NASA Astrophysics Data System (ADS)

    Venkateswara Rao, N.; Patra, A. K.; Rao, S. V. B.

    2009-01-01

    In this paper we present studies on low-altitude quasiperiodic (LQP) echoes based on a large database of Gadanki radar observations. LQP echoes have been observed 33% of the time during daytime and 39% during nighttime. Their occurrence is found to be maximum in the summer (daytime, 58% nighttime, 57%), followed by the September equinox (daytime, 32% nighttime, 48%), the March equinox (daytime, 26% nighttime, 36%), and minimum in the winter (daytime, 25% nighttime, 26%). Height-time occurrence of LQP echoes shows two local time maxima: one in the morning (0700-1100 LT) and another in the evening (1900-0000 LT). The most significant results not reported earlier are the large occurrence rate of LQP echoes and the height-time occurrence maps showing a descending pattern with close resemblance to tidal wind behavior. The Doppler velocities are upward-northward (downward-southward) for positive- (negative-) sloped LQP echoes. Also, we find the Doppler spread as high as 200 m s-1 at times underlining the presence of strong plasma turbulence in the collision-dominated lower E region. These results are discussed in the light of the current understanding of the LQP echoes.

  1. Increasing sensitivity of pulse EPR experiments using echo train detection schemes

    NASA Astrophysics Data System (ADS)

    Mentink-Vigier, F.; Collauto, A.; Feintuch, A.; Kaminker, I.; Tarle, V.; Goldfarb, D.

    2013-11-01

    Modern pulse EPR experiments are routinely used to study the structural features of paramagnetic centers. They are usually performed at low temperatures, where relaxation times are long and polarization is high, to achieve a sufficient Signal/Noise Ratio (SNR). However, when working with samples whose amount and/or concentration are limited, sensitivity becomes an issue and therefore measurements may require a significant accumulation time, up to 12 h or more. As the detection scheme of practically all pulse EPR sequences is based on the integration of a spin echo - either primary, stimulated or refocused - a considerable increase in SNR can be obtained by replacing the single echo detection scheme by a train of echoes. All these echoes, generated by Carr-Purcell type sequences, are integrated and summed together to improve the SNR. This scheme is commonly used in NMR and here we demonstrate its applicability to a number of frequently used pulse EPR experiments: Echo-Detected EPR, Davies and Mims ENDOR (Electron-Nuclear Double Resonance), DEER (Electron-Electron Double Resonance|) and EDNMR (Electron-Electron Double Resonance (ELDOR)-Detected NMR), which were combined with a Carr-Purcell-Meiboom-Gill (CPMG) type detection scheme at W-band. By collecting the transient signal and integrating a number of refocused echoes, this detection scheme yielded a 1.6-5 folds SNR improvement, depending on the paramagnetic center and the pulse sequence applied. This improvement is achieved while keeping the experimental time constant and it does not introduce signal distortion.

  2. An efficient 2D-WTMM and PNN approach to remove spurious radar echoes

    NASA Astrophysics Data System (ADS)

    Khider, Mohamed; Haddad, Boualem

    2013-03-01

    The proposed method aims to reduce the spurious echoes in weather radar images collected at Melbourne radar site, using parameters from 2D-WTMM method based on the continuous wavelet transform, and including the PNN probabilistic neural network for the classification of pixels into two types of echoes : precipitation or parasite. Indeed, we propose the introduction of parameters related to wavelet transform skeletons, these parameters are proportional to the image texture roughness, anisotropy and the distance of separation between non-zero radar echoes cells and give good separation between rain and non-rain echoes. Radar image is first segmented with Voronoi's cells according to the spatial distribution of Holder exponents. By comparing with a direct method of classification which takes into account only one parameter at a time by using a threshold, it was found that the combination of these three parameters with PNN approach improves the final results in terms of preserving precipitation echoes and elimination of weather radar clutter. Initial results show approximately the removal of 98% of clutter and preservation of 97% of precipitation echoes.

  3. Performance Analysis for Acoustic Echo Cancellation Systems based on Variable Step Size NLMS algorithms

    NASA Astrophysics Data System (ADS)

    Hegde, Rajeshwari; Balachandra, K.; Rao, Madhusudhan

    2011-12-01

    Acoustic echo cancellation is an essential signal enhancement tool in hands-free communication. Loudspeaker signals are picked up by a microphone and are fed back to the correspondent, resulting in an undesired echo. Nowadays, adaptive filtering techniques are typically employed to suppress this echo. In acoustic applications long filters need to be adapted for sufficient echo suppression. Classical adaptation schemes such as LMS are quite expensive for accurate echo path modeling in highly reverberating environments. In order to cope with dynamic signals, step-size μ is often normalized by taking it inversely proportional to the energy of x. This normalized version of LMS (NLMS) is typically used in practice. This paper discusses various variable step-size NLMS based algorithms which can be implemented in acoustic echo cancelling applications. The performance of these algorithms in terms of ERLE and NSEC curves are obtained and comparison between them is done. Also a simple and novel Double-Talk Detection scheme is proposed in this paper.

  4. Software Applications to Access Earth Science Data: Building an ECHO Client

    NASA Astrophysics Data System (ADS)

    Cohen, A.; Cechini, M.; Pilone, D.

    2010-12-01

    Historically, developing an ECHO (NASA’s Earth Observing System (EOS) ClearingHOuse) client required interaction with its SOAP API. SOAP, as a framework for web service communication has numerous advantages for Enterprise applications and Java/C# type programming languages. However, as interest has grown for quick development cycles and more intriguing “mashups,” ECHO has seen the SOAP API lose its appeal. In order to address these changing needs, ECHO has introduced two new interfaces facilitating simple access to its metadata holdings. The first interface is built upon the OpenSearch format and ESIP Federated Search framework. The second interface is built upon the Representational State Transfer (REST) architecture. Using the REST and OpenSearch APIs to access ECHO makes development with modern languages much more feasible and simpler. Client developers can leverage the simple interaction with ECHO to focus more of their time on the advanced functionality they are presenting to users. To demonstrate the simplicity of developing with the REST API, participants will be led through a hands-on experience where they will develop an ECHO client that performs the following actions: + Login + Provider discovery + Provider based dataset discovery + Dataset, Temporal, and Spatial constraint based Granule discovery + Online Data Access

  5. Electron ECHO 6: a study by particle detectors of electrons artificially injected into the magnetosphere

    SciTech Connect

    Malcolm, P.R.

    1986-01-01

    The ECHO-6 sounding rocket was launched from the Poke Flat Research Range, Alaska on 30 March 1983. A Terrier-Black Brant launch vehicle carried the payload on a northward trajectory over an auroral arc and to an apogee of 216 kilometers. The primary objective of the ECHO-6 experiment was to evaluate electric fields, magnetic fields, and plasma processes in the distant magnetosphere by injecting electron beams in the ionosphere and observing conjugate echoes. The experiment succeeded in injection 10-36 keV beams during the existence of a moderate growth-phase aurora, an easterly electrojet system, and a pre-midnight inflation condition of the magnetosphere. The ECHO-6 payload system consisted of an accelerator MAIN payload, a free-flying Plasma Diagnostics Package (PDP), and four rocket-propelled Throw Away Detectors (TADs). The PDP was ejected from the MAIN payload to analyze electric fields, plasma particles, energetic electrons, and photometric effects produced by beam injections. The TADs were ejected from the MAIN payload in a pattern to detect echoes in the conjugate echo region south of the beam-emitting MAIN payload. The TADs reached distances exceeding 3 kilometers from the MAIN payload and made measurements of the ambient electrons by means of solid-state detectors and electrostatic analyzers.

  6. On the detectability of infrared echo arcs around supernova 1987A

    NASA Technical Reports Server (NTRS)

    Felten, James E.; Dwek, Eli

    1989-01-01

    The ring-like interstellar visual echoes of radii 33 and 54 arcsec detected around SN 1987A should coincide with infrared echoes (thermal reradiation) from dust at T approximately equal to 15 to 30 K. Whether these infrared echoes are detectable at present is considered. They will be brightest at approximately 100 microns, the range of the Texas infrared photometer. Detectability depends on the ratio zeta congruent to tan(sub a)/tan(sub s)P(theta), where tan(sub a) and tan(sub s) are the visual absorption and scattering optical thicknesses of the echo layer, and P is the phase function function for small-angle scattering (theta approximately equal to 2 to 4 degrees). Zeta approximately greater than 1 is needed for a detectable signal (approximately 0.3 Jy), but zeta cannot be much less than 1; otherwise the visual echoes could not be as bright as they are. Typical dust mixtures of Mathis-Rumpl-Nordsieck type have zeta much less than 1. Zeta remains small even if a population of very small grains with power-law index as steep as approximately 5.5 is added. A population with even more small grains and/or fewer large grains could have a zeta similar to 1 and be detectable at present, but this seems unlikely. The echoes will move, but should remain accessible for many years and should be detected eventually.

  7. Bottlenose dolphin (Tursiops truncatus) detection of simulated echoes from normal and time-reversed clicks.

    PubMed

    Finneran, James J; Wu, Teri; Borror, Nancy; Tormey, Megan; Brewer, Arial; Black, Amy; Bakhtiari, Kimberly

    2013-12-01

    In matched filter processing, a stored template of the emitted sonar pulse is compared to echoes to locate individual replicas of the emitted pulse embedded in the echo stream. A number of experiments with bats have suggested that bats utilize matched filter processing for target ranging, but not for target detection. For dolphins, the few available data suggest that dolphins do not utilize matched filter processing. In this study, the effect of time-reversing a dolphin's emitted click was investigated. If the dolphin relied upon matched filter processing, time-reversal of the click would be expected to reduce the correlation between the (unaltered) click and the echoes and therefore lower detection performance. Two bottlenose dolphins were trained to perform a phantom echo detection task. On a small percentage of trials ("probe trials"), a dolphin's emitted click was time-reversed before interacting with the phantom echo system. Data from the normal and time-reversed trials were then analyzed and compared. There were no significant differences in detection performance or click emissions between the normal and time-reversed conditions for either subject, suggesting that the dolphins did not utilize matched filter processing for this echo detection task. PMID:25669264

  8. Expanding Health Care Access Through Education: Dissemination and Implementation of the ECHO Model.

    PubMed

    Katzman, Joanna G; Galloway, Kevin; Olivas, Cynthia; McCoy-Stafford, Kimberly; Duhigg, Daniel; Comerci, George; Kalishman, Summers; Buckenmaier, Chester C; McGhee, Laura; Joltes, Kristin; Bradford, Andrea; Shelley, Brian; Hernandez, Jessica; Arora, Sanjeev

    2016-03-01

    Project ECHO (Extension for Community Healthcare Outcomes) is an evidence-based model that provides high-quality medical education for common and complex diseases through telementoring and comanagement of patients with primary care clinicians. In a one to many knowledge network, the ECHO model helps to bridge the gap between primary care clinicians and specialists by enhancing the knowledge, skills, confidence, and practice of primary care clinicians in their local communities. As a result, patients in rural and urban underserved areas are able to receive best practice care without long waits or having to travel long distances. The ECHO model has been replicated in 43 university hubs in the United States and five other countries. A new replication tool was developed by the Project ECHO Pain team and U.S. Army Medical Command to ensure a high-fidelity replication of the model. The adoption of the tool led to successful replication of ECHO in the Army Pain initiative. This replication tool has the potential to improve the fidelity of ECHO replication efforts around the world. PMID:26926747

  9. High altitude E region echoes observed with the MAARSY VHF radar

    NASA Astrophysics Data System (ADS)

    Chau, J. L.; Renkwitz, T.; Stober, G.; Latteck, R.; Schult, C.; Sommer, S.

    2013-12-01

    We present the observations of unique high altitude E region echoes with the VHF MAARSY located at Andøya, Norway. Previously using a smaller radar system (ALWIN), weak E region echoes occurring between 93 and 114 km and mainly during the local summer have been reported by Rapp et al, [2011]. Such echoes lasted for few minutes and its occurrence was explained in terms of partial reflection in association with sporadic E layers. The new echoes we report here occur in altitudes as high as 130-140 km, last between hundreds of milliseconds to few seconds, and expand from few hundred meters to few kilometers. These new observations have been made possible due to: (a) the higher radar sensitivity (~13 dB), and (b) the possibility of recording raw data voltages with a larger sampling window. Preliminary results indicate that the echoes present a wide variety of spectral signatures (narrow and wide), are highly localized, and occur all year long. We will discuss the occurrence of these echoes in terms of partial reflection, turbulence, and enhanced incoherent scattering.

  10. The Detection of a Light Echo from Type Ia SN 2007af in NGC 5584

    NASA Astrophysics Data System (ADS)

    Drozdov, Dina; Leising, M. D.; Milne, P.; Riess, A. G.

    2013-06-01

    We report the discovery of a light echo (LE) at t ~1000 days past maximum from the normal Type Ia supernova (SNe Ia) SN 2007af in the spiral galaxy NGC 5584. The presence of a LE is supported by photometric data and analysis of the images acquired during the Cepheid campaign using the Hubble Space Telescope (HST) Wide Field Camera 3 (Riess et al. 2011). The F350 and F555 images show a distinct ring-like structure with an additional central source. The images, taken months apart, show an evolution of the ring structure, which is consistent with a growing light echo in time. We find an angular radius of the outer echo to be ~0.29'' - 0.36''. Using the Cepheid distance to NGC 5584 of 24 Mpc, we find the dust illuminated by the light echo to be at a distance ~800 pc from the supernova. This rare discovery adds to the select few light echoes found in Type Ia SNe: SN 1572, SN 1991T, SN 1995E, SN 1998bu, and SN 2006X. Light echoes are powerful tools that probe the environment around supernovae, determine dust properties and characteristics, and could provide constraints on the progenitors, which are not fully understood for SN Ia.

  11. Shape-based nuclei area of digitized pap smear images

    NASA Astrophysics Data System (ADS)

    Muhimmah, Izzati; Kurniawan, Rahadian

    2012-04-01

    Nuclei of the epithelial of Pap smear cells are important risk indicator of cervical cancers. Pathologist uses the changing of the area of the nuclei to determine whether cells are normal or abnormal. It means that having correct measurement of the area of nuclei is important on the pap smears assessment. Our paper present a novel approach to analyze the shape of nuclei in pap smear images and measuring the area of nuclei. We conducted a study to measure the area of nuclei automatically by calculating the number of pixels contained in each of the segmented nuclei. For comparison, we performed measurements of nuclei area using the ellipse area approximation. The result of the t-test confirmed that there were similarity between elliptical area approximation and automatic segmented nuclei-area at 0.5% level of significance.

  12. Quantum Monte Carlo calculations of light nuclei.

    SciTech Connect

    Pieper, S. C.; Physics

    2008-01-01

    Variational Monte Carlo and Green's function Monte Carlo are powerful tools for cal- culations of properties of light nuclei using realistic two-nucleon (NN) and three-nucleon (NNN) potentials. Recently the GFMC method has been extended to multiple states with the same quantum numbers. The combination of the Argonne v18 two-nucleon and Illinois-2 three-nucleon potentials gives a good prediction of many energies of nuclei up to 12 C. A number of other recent results are presented: comparison of binding energies with those obtained by the no-core shell model; the incompatibility of modern nuclear Hamiltonians with a bound tetra-neutron; difficulties in computing RMS radii of very weakly bound nuclei, such as 6He; center-of-mass effects on spectroscopic factors; and the possible use of an artificial external well in calculations of neutron-rich isotopes.

  13. Quantum Monte Carlo calculations of light nuclei

    SciTech Connect

    Pieper, S.C.

    1998-12-01

    Quantum Monte Carlo calculations using realistic two- and three-nucleon interactions are presented for nuclei with up to eight nucleons. We have computed the ground and a few excited states of all such nuclei with Greens function Monte Carlo (GFMC) and all of the experimentally known excited states using variational Monte Carlo (VMC). The GFMC calculations show that for a given Hamiltonian, the VMC calculations of excitation spectra are reliable, but the VMC ground-state energies are significantly above the exact values. We find that the Hamiltonian we are using (which was developed based on {sup 3}H,{sup 4}He, and nuclear matter calculations) underpredicts the binding energy of p-shell nuclei. However our results for excitation spectra are very good and one can see both shell-model and collective spectra resulting from fundamental many-nucleon calculations. Possible improvements in the three-nucleon potential are also be discussed. {copyright} {ital 1998 American Institute of Physics.}

  14. Quantum Monte Carlo calculations of light nuclei

    SciTech Connect

    Pieper, Steven C.

    1998-12-21

    Quantum Monte Carlo calculations using realistic two- and three-nucleon interactions are presented for nuclei with up to eight nucleons. We have computed the ground and a few excited states of all such nuclei with Greens function Monte Carlo (GFMC) and all of the experimentally known excited states using variational Monte Carlo (VMC). The GFMC calculations show that for a given Hamiltonian, the VMC calculations of excitation spectra are reliable, but the VMC ground-state energies are significantly above the exact values. We find that the Hamiltonian we are using (which was developed based on {sup 3}H,{sup 4}He, and nuclear matter calculations) underpredicts the binding energy of p-shell nuclei. However our results for excitation spectra are very good and one can see both shell-model and collective spectra resulting from fundamental many-nucleon calculations. Possible improvements in the three-nucleon potential are also be discussed.

  15. Quantum Monte Carlo calculations of light nuclei.

    SciTech Connect

    Pieper, S. C.

    1998-08-25

    Quantum Monte Carlo calculations using realistic two- and three-nucleon interactions are presented for nuclei with up to eight nucleons. We have computed the ground and a few excited states of all such nuclei with Greens function Monte Carlo (GFMC) and all of the experimentally known excited states using variational Monte Carlo (VMC). The GFMC calculations show that for a given Hamiltonian, the VMC calculations of excitation spectra are reliable, but the VMC ground-state energies are significantly above the exact values. We find that the Hamiltonian we are using (which was developed based on {sup 3}H, {sup 4}He, and nuclear matter calculations) underpredicts the binding energy of p-shell nuclei. However our results for excitation spectra are very good and one can see both shell-model and collective spectra resulting from fundamental many-nucleon calculations. Possible improvements in the three-nucleon potential are also be discussed.

  16. The scattering of fast nucleons from nuclei

    SciTech Connect

    Kerman, A. K.; McManus, H.; Thaler, R. M.

    2000-04-10

    The formal theory of the scattering of high-energy nucleons by nuclei is developed in terms of the nucleon nucleon scattering amplitude. The most important approximations necessary to make numerical calculation feasible are then examined. The optical model potential is derived on this basis and compared with the optical model parameters found from experiment. The elastic scattering and polarization of nucleons from light nuclei is predicted and compared with experiment. The effect of nuclear correlations is discussed. The polarization of inelastically scattered nucleons is discussed and predictions compared with experiments. To within the validity of the approximations the experimental data on the scattering of nucleons from nuclei at energies above {approx}100 Mev appears to be consistent with the theory. (c) 2000 Academic Press, Inc.

  17. Pair correlations in neutron-rich nuclei

    SciTech Connect

    Esbensen, H.

    1995-08-01

    We started a program to study the ground-state properties of heavy, neutron-rich nuclei using the Hartree-Fock-Bogolyubov (HFB) approximation. This appears at present to be the most realistic approach for heavy nuclei that contain many loosely bound valence neutrons. The two-neutron density obtained in this approach can be decomposed into two components, one associated with the mean field and one associated with the pairing field. The latter has a structure that is quite similar to the pair-density obtained by diagonalizing the Hamiltonian for a two-neutron halo, which was studied earlier. This allows comparison of the HFB solutions against numerically exact solutions for two-neutron halos. This work is in progress. We intend to apply the HFB method to predict the ground-state properties of heavier, more neutron-rich nuclei that may be produced at future radioactive beam facilities.

  18. Fission barriers of compound superheavy nuclei.

    PubMed

    Pei, J C; Nazarewicz, W; Sheikh, J A; Kerman, A K

    2009-05-15

    The dependence of fission barriers on the excitation energy of the compound nucleus impacts the survival probability of superheavy nuclei synthesized in heavy-ion fusion reactions. In this work, we investigate the isentropic fission barriers by means of the self-consistent nuclear density functional theory. The relationship between isothermal and isentropic descriptions is demonstrated. Calculations have been carried out for 264Fm, 272Ds, ;{278}112, ;{292}114, and ;{312}124. For nuclei around ;{278}112 produced in "cold-fusion" reactions, we predict a more rapid decrease of fission barriers with excitation energy as compared to the nuclei around ;{292}114 synthesized in "hot-fusion" experiments. This is explained in terms of the difference between the ground-state and saddle-point temperatures. The effect of the particle gas is found to be negligible in the range of temperatures studied. PMID:19518948

  19. Structure and spectroscopy of transcurium nuclei.

    SciTech Connect

    Ahmad, I.

    2001-11-09

    The stability of the superheavy elements depends on the shell corrections which are governed by the single-particle spectra. Ideally one would like to experimentally determine the single-particle levels in the superheavy nuclei but the production of only a few atoms of these nuclides precludes such measurements. One therefore has to identify single-particle levels in the heaviest nuclei which are available in at least nanoCurie amounts. They have studied the structure of such heavy nuclei in the Z=98 region and identified many single-particle states. In particular, they have studied the structure of {sup 251}Cf and {sup 249}Bk by measuring the radiations emitted in the {alpha} decay of {sup 255}Fm and {sup 253}Es. These single-particle spectra can be used to test theoretical models for superheavy elements.

  20. Alpha-cluster model of atomic nuclei

    NASA Astrophysics Data System (ADS)

    Sosin, Zbigniew; Błocki, Jan; Kallunkathariyil, Jinesh; Łukasik, Jerzy; Pawłowski, Piotr

    2016-05-01

    The description of a nuclear system in its ground state and at low excitations based on the equation of state (EoS) around normal density is presented. In the expansion of the EoS around the saturation point, additional spin polarization terms are taken into account. These terms, together with the standard symmetry term, are responsible for the appearance of the α-like clusters in the ground-state configurations of the N = Z even-even nuclei. At the nuclear surface these clusters can be identified as alpha particles. A correction for the surface effects is introduced for atomic nuclei. Taking into account an additional interaction between clusters the binding energies and sizes of the considered nuclei are very accurately described. The limits of the EoS parameters are established from the properties of the α, 3He and t particles.