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Sample records for incoherent scatter signal

  1. Theory of waves incoherently scattered

    NASA Technical Reports Server (NTRS)

    Bauer, P.

    1974-01-01

    Electromagnetic waves impinging upon a plasma at frequencies larger than the plasma frequency, suffer weak scattering. The scattering arises from the existence of electron density fluctuations. The received signal corresponds to a particular spatial Fourier component of the fluctuations, the wave vector of which is a function of the wavelength of the radiowave. Wavelengths short with respect to the Debye length of the medium relate to fluctuations due to non-interacting Maxwellian electrons, while larger wavelengths relate to fluctuations due to collective Coulomb interactions. In the latter case, the scattered signal exhibits a spectral distribution which is characteristic of the main properties of the electron and ion gases and, therefore, provides a powerful diagnosis of the state of the ionosphere.

  2. Requirements for Space Shuttle incoherent scatter experiments

    NASA Technical Reports Server (NTRS)

    Harker, K. J.

    1976-01-01

    The feasibility of carrying out incoherent-scatter experiments on the Space Shuttle has been analyzed. Design criteria considered were the required average transmitter power, frequency resolution, spatial resolution, and statistical accuracy. Experiments analyzed were measurement of the naturally enhanced plasma line and the ion component of the incoherent-scatter spectrum, as well as the plasma line artificially enhanced by an intense HF radiowave. The ion-component measurement does not appear feasible, while the other two appear reasonable for short ranges only.

  3. An effective method for incoherent scattering radar's detecting ability evaluation

    NASA Astrophysics Data System (ADS)

    Lu, Ziqing; Yao, Ming; Deng, Xiaohua

    2016-06-01

    Ionospheric incoherent scatter radar (ISR), which is used to detect ionospheric electrons and ions, generally, has megawatt class transmission power and hundred meter level antenna aperture. The crucial purpose of this detecting technology is to get ionospheric parameters by acquiring the autocorrelation function and power spectrum of the target ionospheric plasma echoes. Whereas the ISR's echoes are very weak because of the small radar cross section of its target, estimating detecting ability will be significantly instructive and meaningful for ISR system design. In this paper, we evaluate the detecting ability through signal-to-noise ratio (SNR). The soft-target radar equation is deduced to be applicable to ISR, through which we use data from International Reference Ionosphere model to simulate signal-to-noise ratio (SNR) of echoes, and then comparing the measured SNR from European Incoherent Scatter Scientific Association and Advanced Modular Incoherent Scatter Radar with the simulation. The simulation results show good consistency with the measured SNR. For ISR, the topic of this paper is the first comparison between the calculated SNR and radar measurements; the detecting ability can be improved through increasing SNR. The effective method for ISR's detecting ability evaluation provides basis for design of radar system.

  4. An Incoherent Scatter Radar Facility in Antarctica

    NASA Astrophysics Data System (ADS)

    Kelly, J. D.; Stromme, A.; Nicolls, M. J.; van Eyken, A. P.

    2014-12-01

    A high latitude Antarctic Incoherent Scatter Radar (ISR) facility will help to achieve the better distributed network of sophisticated observational platforms needed in order to gain transformational new knowledge of the short and long term global variability of Earth's upper atmosphere and its connection to the solar wind and space. It will facilitate moving toward a fully system level approach to upper atmosphere and space research. We have over the last few years performed a feasibility study including a site survey in McMurdo identifying a location and the needed logistics to carry this project out. This talk will provide and overview of the science rational and benefits of an Antarctic ISR facility, in addition to outline the current plans and next steps in establishing, for the first time, an Incohernet Scatter radar facility at a high southern latitude.

  5. Polyphase-coded incoherent scatter measurements at Millstone Hill

    NASA Astrophysics Data System (ADS)

    Virtanen, Ilkka I.; Lind, Frank D.; Roininen, Lassi; Erickson, Philip J.; Rideout, William C.; Orispää, Mikko; Vierinen, Juha; Lehtinen, Markku S.

    2013-09-01

    We report first results of polyphase-coded incoherent scatter measurements at Millstone Hill. To our knowledge, these are the first incoherent scatter measurements with polyphase alternating codes of Markkanen et al. (2008) and optimal quadriphase sequences of Damtie et al. (2008). The results demonstrate that an arbitrary waveform generator recently installed at the Millstone Hill incoherent scatter radar, part of the National Science Foundation Geospace Facility operated by the Massachusetts Institute of Technology Haystack Observatory, is capable of reproducing the polyphase waveforms with an accuracy sufficient for incoherent scatter measurements. Polyphase codes will allow incoherent scatter radar experiments to be better optimized, because they provide a larger variety of code and code cycle lengths than the traditional binary codes.

  6. Incoherent scatter radar observations of the ionosphere

    NASA Technical Reports Server (NTRS)

    Hagfors, Tor

    1989-01-01

    Incoherent scatter radar (ISR) has become the most powerful means of studying the ionosphere from the ground. Many of the ideas and methods underlying the troposphere and stratosphere (ST) radars have been taken over from ISR. Whereas the theory of refractive index fluctuations in the lower atmosphere, depending as it does on turbulence, is poorly understood, the theory of the refractivity fluctuations in the ionosphere, which depend on thermal fluctuations, is known in great detail. The underlying theory is one of the most successful theories in plasma physics, and allows for many detailed investigations of a number of parameters such as electron density, electron temperature, ion temperature, electron mean velocity, and ion mean velocity as well as parameters pertaining to composition, neutral density and others. Here, the author reviews the fundamental processes involved in the scattering from a plasma undergoing thermal or near thermal fluctuations in density. The fundamental scattering properties of the plasma to the physical parameters characterizing them from first principles. He does not discuss the observation process itself, as the observational principles are quite similar whether they are applied to a neutral gas or a fluctuating plasma.

  7. Concentration of hydrogen in titanium measured by neutron incoherent scattering

    SciTech Connect

    Chen-Mayer, H.H.; Mildner, D.F.R.; Lamaze, G.P.; Lindstrom, R.M.; Paul, R.L.; Kvardakov, V.V.; Richards, W.J.

    1998-12-31

    Mass fractions of hydrogen in titanium matrices have been measured using neutron incoherent scattering (NIS) and compared with results from prompt gamma activation analysis (PGAA). Qualitatively, NIS is a more efficient technique than PGAA which involves neutron absorption, and the former may be suitable for on-line analysis. However, for NIS the scattering contribution comes from both the hydrogen and the matrix, whereas prompt gamma emission has minimal matrix effect. To isolate the signal due to hydrogen scattering, a set of polypropylene films is used to simulate the increasing amount of hydrogen, and the scattered intensity is monitored. From this response, an unknown amount of the hydrogen can be deduced empirically. The authors have further attempted a first principle calculation of the intensity of the scattered signal from the experimental systems, and have obtained good agreement between calculation and the measurements. The study can be used as a reference for future applications of the scattering method to other hydrogen-in-metal systems.

  8. Diffraction pattern from thermal neutron incoherent elastic scattering and the holographic reconstruction of the coherent scattering length distribution

    SciTech Connect

    Sur, B.; Anghel, V.N.P.; Rogge, R.B.; Katsaras, J.

    2005-01-01

    The diffraction of spherical waves (S waves) interacting with a periodic scattering length distribution produces characteristic intensity patterns known as Kossel and Kikuchi lines (collectively called K lines). The K-line signal can be inverted to give the three-dimensional structure of the coherent scattering length distribution surrounding the source of S waves - a process known as 'Gabor holography' or, simply, 'holography'. This paper outlines a kinematical formulation for the diffraction pattern of monochromatic plane waves scattering from a mixed incoherent and coherent S-wave scattering length distribution. The formulation demonstrates that the diffraction pattern of plane waves incident on a sample with a uniformly random distribution of incoherent scatterers is the same as that from a sample with a single incoherent scatterer per unit cell. In practice, one can therefore reconstruct the holographic data from samples with numerous incoherent S-wave scatterers per unit cell. Thus atomic resolution thermal neutron holography is possible for materials naturally rich in incoherent thermal neutron scatterers, such as hydrogen (e.g., biological and polymeric materials). Additionally, holographic inversions from single-wavelength data have suffered from the so-called conjugate or twin-image problem. The formulation presented for holographic inversion - different from those used previously [e.g., T. Gog et al., Phys. Rev. Lett. 76, 3132 (1996)] - eliminates the twin-image problem for single-wavelength data.

  9. Processing Oscillatory Signals by Incoherent Feedforward Loops.

    PubMed

    Zhang, Carolyn; Tsoi, Ryan; Wu, Feilun; You, Lingchong

    2016-09-01

    From the timing of amoeba development to the maintenance of stem cell pluripotency, many biological signaling pathways exhibit the ability to differentiate between pulsatile and sustained signals in the regulation of downstream gene expression. While the networks underlying this signal decoding are diverse, many are built around a common motif, the incoherent feedforward loop (IFFL), where an input simultaneously activates an output and an inhibitor of the output. With appropriate parameters, this motif can exhibit temporal adaptation, where the system is desensitized to a sustained input. This property serves as the foundation for distinguishing input signals with varying temporal profiles. Here, we use quantitative modeling to examine another property of IFFLs-the ability to process oscillatory signals. Our results indicate that the system's ability to translate pulsatile dynamics is limited by two constraints. The kinetics of the IFFL components dictate the input range for which the network is able to decode pulsatile dynamics. In addition, a match between the network parameters and input signal characteristics is required for optimal "counting". We elucidate one potential mechanism by which information processing occurs in natural networks, and our work has implications in the design of synthetic gene circuits for this purpose. PMID:27623175

  10. Processing oscillatory signals by incoherent feedforward loops

    NASA Astrophysics Data System (ADS)

    Zhang, Carolyn; Wu, Feilun; Tsoi, Ryan; Shats, Igor; You, Lingchong

    From the timing of amoeba development to the maintenance of stem cell pluripotency,many biological signaling pathways exhibit the ability to differentiate between pulsatile and sustained signals in the regulation of downstream gene expression.While networks underlying this signal decoding are diverse,many are built around a common motif, the incoherent feedforward loop (IFFL),where an input simultaneously activates an output and an inhibitor of the output.With appropriate parameters,this motif can generate temporal adaptation,where the system is desensitized to a sustained input.This property serves as the foundation for distinguishing signals with varying temporal profiles.Here,we use quantitative modeling to examine another property of IFFLs,the ability to process oscillatory signals.Our results indicate that the system's ability to translate pulsatile dynamics is limited by two constraints.The kinetics of IFFL components dictate the input range for which the network can decode pulsatile dynamics.In addition,a match between the network parameters and signal characteristics is required for optimal ``counting''.We elucidate one potential mechanism by which information processing occurs in natural networks with implications in the design of synthetic gene circuits for this purpose. This work was partially supported by the National Science Foundation Graduate Research Fellowship (CZ).

  11. Innovative wavelet protocols in analyzing elastic incoherent neutron scattering.

    PubMed

    Magazù, S; Migliardo, F; Caccamo, M T

    2012-08-01

    Wavelet analysis has recently found a wide range of applications in Physics, Mathematics, and signal processing. This is mainly due to its ability to locally resolve a nonstationary signal in terms of functional forms, called mother wavelets, and to firmly locate trend anomalies in the signal. In the present paper, some examples of the application of wavelet analysis to elastic incoherent neutron scattering (EINS) data collected by the IN13 spectrometer at the Institute Laue Langevin (ILL) on water mixtures of the three homologous disaccharides, trehalose, maltose, and sucrose, and on literature data of dry and hydrated lysozyme and myoglobine as a function of temperature and of exchanged wave vector are presented. The experimental findings have been analyzed by means of a wavelet analysis that allows one to characterize the scattered elastic intensity behavior on different scales and to locate the discontinuities and the trend anomalies in the registered signal. This latter procedure is made possible thanks to the multiscale analysis, which allows, by decreasing the scale, one to localize the peculiar trend features. The entire body of the experimental findings reveals different transition temperatures for the three investigated disaccharides together with a stronger temperature dependence of the maltose/H(2)O and sucrose/H(2)O systems in comparison with the trehalose/H(2)O mixture, which signals a stronger character of this latter in comparison with the other two homologous disaccharides. These results justify the better ability of trehalose, with respect to maltose and sucrose, to encapsulate biostructures in a more rigid matrix. PMID:22793379

  12. Incoherent Scatter Radars for Global Scale Ionospheric Monitoring

    NASA Astrophysics Data System (ADS)

    Van Eyken, Anthony; Heinselman, Craig; Kelly, John; Sanchez, Ennio; Stromme, Anja

    2012-07-01

    Aeronomers have made huge strides in understanding the detailed physics and chemistry of the upper atmosphere and in designing, constructing and operating advanced facilities to monitor, measure, and in some cases, perturb that medium. However, the big picture, with its accompanying ability to predict the behavior of the geospace system both in response to natural (solar) and anthropogenic factors, remains somewhat elusive. Current incoherent scatter radars (ISRs) have the ability to operate reliably, remotely, and largely autonomously for extended periods and the procedures to build, deploy, operate, and maintain them are well developed. For the first time, it is now practical to envisage a global ISR deployment capable of providing the precision measurements required. Incoherent scatter radars have developed considerably in recent years with the deployment of multiple new systems (Poker Flat, Alaska, Resolute Bay, Canada, and in development in China, Argentina, Antarctica, Scandinavia, and elsewhere, as well as a second system at Resolute Bay) and operational changes to support continuous and remote measurements. We will discuss plans to add further observational sites, built around phased array incoherent scatter radars, to cover, for example, a complete geomagnetic meridian; plans to further integrate the routine operation of many radars around the globe; and the potential for hardware collaboration for future incoherent scatter radar systems.

  13. Theory of ghost scattering with incoherent light sources

    NASA Astrophysics Data System (ADS)

    Cheng, Jing

    2016-04-01

    Inspired by the idea of ghost imaging, we propose a ghost scattering scheme to study light scattering with incoherent light sources through the nonlocal correlation measurement of the differential scattering cross-section fluctuations in two different optical paths. We present a rigorous formal theory to describe the ghost scattering process. Also we have derived a simple and closed-form ghost scattering formula within the first-order Born approximation which is particularly suited for weak scatterers. We find that the scattering information of a test scatterer can be obtained by using only a single-pixel detector in the corresponding optical path through the nonlocal correlation measurement with the help of another reference path.

  14. Incoherent image formation in the presence of scattering eye media.

    PubMed

    Wesemann, W

    1987-08-01

    Incoherent image formation in human eyes that have scattering eye media is investigated as a function of the particle size and the optical density of the scattering medium and for test targets that differ in form and size. For single scattering by large particles (much greater than lambda), a point-spread function and the associated modulation-transfer function of the scattered light are derived from diffraction theory. It is shown that object structures with low spatial frequencies are also imaged by the scattered light. Following single scattering by small particles and/or multiple scattering, the scattered light forms an approximately uniform background. Consequently, the retinal contrast is reduced regardless of spatial frequency. The image quality is, contrary to what is found in normal image formation, extremely sensitive to the form and size of the test target. It is shown that the optimal readability of white-on-black letters is obtained at intermediate spatial frequencies. For an extended layer of arbitrary optical density and particle size, the influence of multiple scattering is approximated by using Hartel's scattering theory. It is shown that wavelength has only a small influence on retinal contrast for scattering by particles greater than lambda. PMID:3625324

  15. Incoherent neutron scattering in acetanilide and three deuterated derivatives

    NASA Astrophysics Data System (ADS)

    Barthes, Mariette; Almairac, Robert; Sauvajol, Jean-Louis; Moret, Jacques; Currat, Roland; Dianoux, José

    1991-03-01

    Incoherent-neutron-scattering measurements of the vibrational density of states of acetanilide and three deuterated derivatives are presented. These data allow one to identify an intense maximum, assigned to the N-H out-of-plane bending mode. The data display the specific behavior of the methyl torsional modes: large isotopic shift and strong low-temperature intensity; confirm our previous inelastic-neutron-scattering studies, indicating no obvious anomalies in the range of frequency of the acoustic phonons. In addition, the data show the existence of thermally activated quasielastic scattering above 100 K, assigned to the random diffusive motion of the methyl protons. These results are discussed in the light of recent theoretical models proposed to explain the anomalous optical properties of this crystal.

  16. Investigation of circumterrestrial space by means of incoherent scatter radar

    NASA Astrophysics Data System (ADS)

    Taran, V. I.; Bogovsky, V. K.; Lysenko, V. N.; Grigorenko, Ye. I.; Yemelyanov, L. Ya.

    The results of investigations of ionosphere by means of the Kharkov incoherent scatter radar are presented. The measurements realized jointly with Massachusetts Institute of Technology (Haystack Observatory) and Cornell University (Arecibo Observatory) made it possible to reveal the longitudinal and latitudinal variations of topside hydrogen ion behavior. Ionosphere observations in Kharkov during the solar eclipse on August 11, 1999 first have been carried out up to 1500-km altitude. They have shown the significant changes in state of the F region and topside ionosphere including hydrogen ion concentration, plasma fluxes, that is the evidence of significant infringement of plasma exchange processes between ionosphere and protonosphere.

  17. The Movable Antarctic Incoherent Scatter Radar (MAISR) - update and plans

    NASA Astrophysics Data System (ADS)

    van Eyken, A. P.; Kelly, J. D.; Stromme, A.; Heinselman, C. J.; Malone, M.; Maisr Proposal Team

    2010-12-01

    High latitude Antarctic Incoherent Scatter Radar will help to achieve the better distributed network of sophisticated observational platforms needed in to gain transformational new knowledge of the short and long term global variability of Earth’s upper atmosphere and its connection to the solar wind and space. It will facilitate moving toward a fully system level approach to upper atmosphere and space research. SRI has recently proposed to establish multiple space science observing facilities in the Antarctic, first at McMurdo, Antarctica, and later at an auroral or sub-auroral location. The facilities will be built around the well-proven, next-generation, Advanced Modular Incoherent Scatter Radar (AMISR) concept, and will each provide unprecedented temporal and spatial coverage of the Antarctic atmosphere. These will be the first ever ISRs in the high south, and a very important addition to the global network of observational platforms needed to address the global state and development of Earth’s upper atmosphere and its connection to interplanetary space. This poster provides an update on the progress of the project, including a construction timeline and details of how the community can become involved in the observational program. RISR-N at Resolute Bay, Canada, near the conjugate point of MAISR in Antarctica

  18. How the Saint Santin incoherent scatter system paved the way for a French involvement in EISCAT

    NASA Astrophysics Data System (ADS)

    Bauer, P.; Giraud, A.; Kofman, W.; Petit, M.; Waldteufel, P.

    2013-09-01

    This paper relates the development of a French incoherent scatter system which started its operations in 1965. This development took place several years after the initial implementation of such systems in the United States, in Peru and in the United Kingdom. The French system, owing to its bistatic configuration and the use of continuous waves, differed from the previous ones. These characteristics yielded signals of excellent spectral quality, unravelling the possibility of inferring physical parameters (Doppler shift, average ion mass) out of reach, at that time, of other systems. The possibility of making ion drift vector measurements led to extend the system into a quadristatic configuration. The multiple capabilities offered by the incoherent scatter technique, notably as concerns the thermodynamical properties of the ionosphere and of the thermosphere, led further the French community to a project of embarking an incoherent scatter radar on board a ship. Taking account of a project of a Scandinavian auroral zone radar and of the considerable interest of the study of auroral zone electrodynamics, the French community abandoned the idea of the ship and expressed an interest in joining the Scandinavian project in conjunction with Germany and the United Kingdom.

  19. Exact relativistic expressions for polarization of incoherent Thomson scattering

    NASA Astrophysics Data System (ADS)

    Mirnov, V. V.; Den Hartog, D. J.; Parke, E.

    2016-05-01

    We present a derivation of the degree of polarization for incoherent Thomson scattering (TS) using Mueller matrix formalism. An exact analytic solution is obtained for spectrum-integrated matrix elements. The solution is valid for the full range of incident polarizations, scattering angles, and electron thermal motion from non-relativistic to ultra-relativistic. It is based on a newly developed theoretical model, a finite transit time (FTT) correction to previous theoretical work on TS polarization. The Mueller matrix elements are substantially different from previous calculations without the FTT correction, even to the lowest linear order in Te/mec2≪1 . Mathematically, the derivation is a unique example of fully analytical integration of the 3D scattering operator over a relativistic Maxwellian distribution function; experimentally, the results have application to the use of the polarization properties of Thomson scattered light as a method of electron temperature measurement. The results can also be used as a reliable tool for benchmarking and verification of numerical codes for frequency resolved properties of TS polarization.

  20. Comparison of atomic oxygen measurements by incoherent scatter and satellite-borne mass spectrometer techniques

    NASA Technical Reports Server (NTRS)

    Hedin, A. E.; Alcayde, D.

    1974-01-01

    Atomic oxygen densities determined by the incoherent scatter technique are compared to densities deduced from satellite-borne mass spectrometer measurements and are found to agree within experimental error. The diurnal variations inferred from the incoherent scatter measurements do show, however, some departure from diurnal variations found by modeling the mass spectrometer results. Some implications of these departures are briefly discussed.

  1. Results of the Irkutsk Incoherent Scattering Radar for space debris studies in 2013

    NASA Astrophysics Data System (ADS)

    Lebedev, Valentin; Kushnarev, Dmitriy; Nevidimov, Nikolay

    We present result of space object (SO) registration received on the Irkutsk Incoherent Scattering Radar (IISR) in June 2013 during regular ionospheric measurement. Diagnostic the of the radar for definition of the SO characteristics: range, beam velocity, azimuth angle, elevation, and signal amplitude were improved after the carried-out technological modernization and SO we have possibility of simultaneous measurement of parameters of parameters ionosphere and SO. Now the IISR new hardware-software complex allows to operate in a mode of ionospheric measurements up to 1000 SO flights per day, and to register objects of 10 cm in size at range of 800-900 km.

  2. Incoherent signal source resolution based on coherent aperture synthesis

    NASA Astrophysics Data System (ADS)

    Zverev, V. A.

    2016-05-01

    A technique is proposed for resolving two incoherent signal sources of the same frequency and significantly different intensities with similar angular coordinates. The technique is based on aperture synthesis of a receiving array, first, by the signal of higher-power source and the estimate of its angular coordinate with subsequent subtraction of the signal spectrum from the angular spectrum of the received field. This makes it possible to achieve aperture synthesis and estimate the angle of arrival of a higher-power signal. Thus, the technique is of interest not only for synthesized apertures, but also for arrays with a filled aperture, since it eliminates the restrictions imposed by the presence of lateral lobes of the array response. Our mathematical simulation data demonstrate the efficiency of this technique in the detection and location of weak signals against the background of high-power noise sources even at their close angular positions.

  3. Incoherent Scatter Radar Long Duration Experiments at Millstone Hill

    NASA Astrophysics Data System (ADS)

    Zhang, S. R.; Holt, J. M.; Goncharenko, L. P.; Foster, J. C.; Erickson, P. J.; Lind, F. D.

    Incoherent scatter radars provide high quality physical measurements of the ionosphere which are useful for a wide variety of investigations Recently an emphasis has been placed on long duration observational runs which last on the order of one month In October 2002 EISCAT Svalbard and Millstone Hill Radars conducted first ever long duration experiments for over 30 consective days Zhang et al 2005 EISCAT Svalbard and Tromso Radars performed more long-duration runs in 2003 and 2004 In response to the demand for these long term observations the ISR community then scheduled additional month long World Day operations periods for September 2005 and March 2006 These long duration ISR experiments provides a unique opportunity to study many important ionosphere-thermosphere phenomena including the upper atmospheric climatology variability disturbances long-lasting and other types of space weather events which may not be captured by a regular run The detailed datasets cover both geomagnetically quiet and active periods under different solar activity conditions and represent one of the very finest resources for the evaluation of current and future geospace modeling efforts We present a number of examples from these datasets and describe how the user community may access them using the Madrigal database We discuss results of preliminary analyses with emphasis on the 2002 experiment in terms of the day-to-day variability and oscillations of the ionosphere during periods of quiet magnetic conditions and highlight some of the space

  4. Phase-synchronous detection of coherent and incoherent nonlinear signals

    NASA Astrophysics Data System (ADS)

    Karki, Khadga Jung; Kringle, Loni; Marcus, Andrew H.; Pullerits, Tõnu

    2016-01-01

    The nonlinear optical response of a material system contains detailed information about its electronic structure. Standard approaches to nonlinear spectroscopy often use multiple beams crossed in a sample, and detect the wave vector matched polarization in transmission. Here, we apply a phase-synchronous digital detection scheme using an excitation geometry with two phase-modulated collinear ultrafast pulses. This scheme can be used to efficiently detect nonlinear coherent signals and incoherent signals, such as higher harmonics and multiphoton fluorescence and photocurrent, from various systems including a photocell device. We present theory and experiment to demonstrate that when the phase of each laser pulse is modulated at the frequency {φ }1 and {φ }2, respectively, nonlinear signals can be isolated at the frequencies n({φ }2-{φ }1), where n=0,1,2,\\ldots . This approach holds promise for performing nonlinear spectroscopic measurements under low-signal conditions.

  5. Dynamic neutron scattering on incoherent systems using efficient resonance spin flip techniques

    SciTech Connect

    Häussler, Wolfgang; Kredler, Lukas

    2014-05-15

    We have performed numerical ray-tracing Monte-Carlo-simulations of incoherent dynamic neutron scattering experiments. We intend to optimize the efficiency of incoherent measurements depending on the fraction of neutrons scattered without and with spin flip at the sample. In addition to conventional spin echo, we have numerically and experimentally studied oscillating intensity techniques. The results point out the advantages of these different spin echo variants and are an important prerequisite for neutron resonance spin echo instruments like RESEDA (FRM II, Munich), to choose the most efficient technique depending on the scattering vector range and the properties of the sample system under study.

  6. EISCAT Incoherent Scatter Radars Probing High-Latitude Near-Earth Geospace for the EURIPOS Proposal

    NASA Astrophysics Data System (ADS)

    Turunen, E.

    2009-04-01

    EISCAT Scientific Association operates currently three incoherent scatter radars in Northern Scandinavia on behalf of its associate members in Finland, China, Germany, Japan, Norway, Sweden and United Kingdom, as well as currently supporting partners in France and Russia. The radar sites include transmitter/receiver site in Tromsø, Norway with a monostatic VHF radar and a tristatic UHF radar transmitter/receiver, UHF receiver sites in Kiruna, Sweden and Sodankylä, Finland and a 2-dish monostatic radar in Longyearbyen, Svalbard. Incoherent scatter radar method is known to be the most sophisticated radio method to remotely sense the ionosphere. The standard parameters analysed from the recorded scattered signals are the electron density, electron temperature, ion temperature, line-of-sight plasma velocity, ion-neutral collision frequency and ion mass. With more assumptions also information for example on neutral density and temperature, neutral velocity, Pedersen and Hall conductivities, electric current density and heat flux is available. Current applications of the radars include also interferometric applications for small-scale structures, mapping of meteroid orbits and monitoring space debris, as well as high-resolution mapping the radar reflectivity of the Moon surface. In addition to incoherent scatter radars, EISCAT also has a powerful HF heating facility for ionospheric modification experiments, and a dynasonde in Tromsø, as well as another dynasonde in Svalbard for routine ionospheric observations. All the current EISCAT facilities would serve the EURIPOS proposal quantifying the ionospheric variability and response to space weather events at high latitudes. Although the main ISR facilities cannot be run continuously, regular Common Programmes, measurement campaign modes - especially combined with coordinated satellite observations and specific model studies, and the continuous operation of supporting dynasondes, would greatly enhance the EURIPOS proposal

  7. Incoherent scatter from space shuttle and rocket engine plumes in the ionosphere

    NASA Astrophysics Data System (ADS)

    Bernhardt, P. A.; Huba, J. D.; Swartz, W. E.; Kelley, M. C.

    1998-02-01

    Enhanced echoes from the 430 MHz radar at Arecibo were observed during burns of the space shuttle orbital maneuver subsystem (OMS) engines near 317 km altitude. Similar radar signatures of enhanced backscatter were also obtained by the Millstone Hill radar observing the plume of a Centaur engine burning in the ionosphere. A theoretical model of incoherent scatter is presented to explain the radar backscatter observations. The theory considers molecular ion beams generated in the exhaust plume as a result of charge exchange between the ambient O+ ions and the high-speed exhaust molecules (primarily H2O). The field-aligned gyromotion of the pickup ions affects the radio wave scattering from the random thermal fluctuations of electron density. Numerical calculations are carried out for plasmas modified by the space shuttle or Centaur engines, and reasonable agreement with observations is found for the total scattered power. Incoherent backscatter spectra respond to characteristics of the exhaust plume such as vector flow velocity, temperature, and composition. The nonequilibrium velocity distributions for the ions in the pickup ion plume are similar to the distributions found in strongly convecting auroral region ionospheres. The incoherent scatter from the plume ions can be used to validate techniques used to study naturally disturbed plasmas. The predictions of our radar scatter calculations will be tested in future experiments using the space shuttle OMS engines over incoherent scatter radars located at equatorial latitudes and midlatitudes.

  8. Speed-dependent collision effects on radar back-scattering from the ionosphere. [incoherent scatter radar

    NASA Technical Reports Server (NTRS)

    Behl, Y. K.; Theimer, O. H.

    1982-01-01

    The question whether the differences between fluctuation spectra for linearly speed-dependent and speed-independent collision frequencies could account for disagreements between rocket and incoherent scatter estimate was addressed. The basic theory used for computing the fluctuation spectrum is outlined. The speed-dependence of the charge-neutral collision frequency is discussed, with special emphasis on its derivation from the mobility measurements. Various developments of the computer code used for the computation of the fluctuation spectrum are described. The range of values of input parameters typical to the collision-dominated ionosphere are briefly described. The computational results are presented, and the significance and limitation of these results and the future scope of the research are discussed.

  9. Studying the fine structure of coherent echo spectra using data from Irkutsk incoherent scatter radar

    NASA Astrophysics Data System (ADS)

    Berngardt, O. I.; Potekhin, A. P.

    2009-12-01

    Studying the processes generating different-scale inhomogeneities is one of the challenging problems of ionospheric physics. Plasma instabilities are one of the physical mechanisms by which small-scale inhomogeneities are formed. The main forms of instability in the ionospheric E-layer are two-stream and gradient-drift ones. The inhomogeneities generated by them lead to an abnormally intense radio scattering of different wavelengths (known as coherent echo (CE) or radio aurora) in the E-layer. Therefore, the method of radiowave backscattering is among the widely used methods for studying such inhomogeneities. The CE phenomenon has been investigated most intensely at high and equatorial latitudes, where the conditions for the CE origination are formed rather regularly. For the last decade, CE has also been intensely studied at midlatitudes, where it is observed less frequently and its formation conditions are less known. In 1998-2006, the purposeful studies of the midlatitude CE peculiarities were performed at the Irkutsk incoherent scatter (IS) radar, with a particular emphasis on its coherent properties. It was for the first time found out that the spectra of some data sets had a fine comb-shaped structure, which generated well-known single-humped CE spectra as a result of statistical averaging. In the scope of this study, unique coherent methods for processing individual data sets of CE signals were developed, making it possible to reveal the peculiarities of unaveraged CE-signal spectra. To describe these peculiarities, we proposed a new model of the inhomogeneity spectrum, which is the superposition of the discrete set of spatial harmonics with close wave numbers. The model was shown to adequately describe the scattered signal characteristics observed experimentally.

  10. Study of auroral dynamics with combined spacecraft and incoherent scatter radar data

    NASA Technical Reports Server (NTRS)

    Thayer, Jeffrey P.; Delabeaujardiere, Odile; Watermann, Jurgen

    1994-01-01

    The objectives of this project were to study the coupling between the ionosphere and the magnetosphere, and to understand how this coupling was affected by changes in the solar wind. The data used consisted of satellite measurements coordinated with Sondrestrom incoherent scatter radar observations. We focused our efforts on the study of temporal and spatial changes in the dayside auroral precipitation and electric field.

  11. Study of plasmasphere dynamics using incoherent scatter data from Chatanika, Alaska radar facility

    NASA Technical Reports Server (NTRS)

    Shelley, E. G.

    1975-01-01

    Results of the study of Chatanika incoherent scatter radar data and Lockheed Palo Alto Research Laboratory satellite data are reported. Specific topics covered include: determination of the effective recombination coefficient in the auroral E region; determination of the location of the auroral oval; auroral boundary characteristics; and the relationship of auroral current systems, particle precipitation, visual aurora, and radar aurora.

  12. Interference detection and correction applied to incoherent-scatter radar power spectrum measurement

    NASA Technical Reports Server (NTRS)

    Ying, W. P.; Mathews, J. D.; Rastogi, P. K.

    1986-01-01

    A median filter based interference detection and correction technique is evaluated and the method applied to the Arecibo incoherent scatter radar D-region ionospheric power spectrum is discussed. The method can be extended to other kinds of data when the statistics involved in the process are still valid.

  13. The effects of Coulomb collisions on O+, H+, and He+ plasmas for topside incoherent scatter radar applications at Jicamarca

    NASA Astrophysics Data System (ADS)

    Milla, M. A.; Kudeki, E.; Chau, J. L.

    2012-12-01

    Coulomb collision effects on incoherent scatter radar signals become important when radar beams are pointed perpendicular to the Earth's magnetic field (B). To study these effects, Milla and Kudeki [2011] developed a procedure to estimate the spectrum of plasma density fluctuations (also known as incoherent scatter spectrum) based on simulations of collisional particle trajectories in single-ion component plasmas. In these simulations, collision effects on the particle motion are modeled using the standard Fokker-Planck model of Rosenbluth et al. [1957]. We have recently generalized the procedure of Milla and Kudeki to consider the case of multiple ion components in order to study the characteristics of the incoherent scatter spectrum in O+, H+, and He+ ionospheric plasmas, which is needed for the analysis of topside perpendicular-to-B observations at the Jicamarca Radio Observatory. In this presentation, we will report on the development of this new approach and on the characteristics of the spectrum models that were developed. The simulation results show that the ion collision process can be fairly well approximated as a Gaussian motion process, a model that has been previously studied in the literature by different authors. However, in the case of electron collisions, the process is not Gaussian having a complicated dependence on plasma parameters. As it will be discussed, electron collisions have a significant impact on the shape of the incoherent scatter spectrum. The ultimate application of the models that were developed is the simultaneous estimation of plasma drifts, densities, and temperatures of the topside equatorial ionosphere in perpendicular-to-B experiments at Jicamarca. This experimental evaluation will have a broader impact since the accuracy of the Fokker-Planck collision model will be tested. References: Milla, M. A., and E. Kudeki (2011), Incoherent scatter spectral theories-Part II: Modeling the spectrum for modes propagating perpendicular to B

  14. Coherent and incoherent scattering by a plume of particles advected by turbulent velocity flow.

    PubMed

    Palmer, David R

    2009-08-01

    Studies of acoustic remote sensing of the plumes that result from the injection of particulate matter in the ocean, either naturally or by dumping or dredging activities, have assumed the scattering is incoherent. These plumes are always turbulent, however. The particle density is a passive scalar that is advected by the turbulent velocity flow. The possibility exists, therefore, that the scattered waves from a significant number of particles add coherently as a result of Bragg scattering. In this paper, we investigate this possibility. We derive an expression for the ratio of the coherent intensity to the incoherent one in terms of the turbulent spectrum and the properties of the particles that make up the plume. The sonar is modeled as a high-Q, monostatic, pulsed sonar with arbitrary pulse envelope and arbitrary, but narrow, beam pattern. We apply the formalism to acoustic remote sensing of black smoker hydrothermal plumes. We find that, at most, the coherent intensity is less than 1% of the incoherent one. The implications are that Bragg scattering does not lead to a significant coherent component and in analyses of scattering from this type of plume, one can ignore the complications of turbulence altogether. PMID:19640023

  15. Interferometric observation of Cygnus-A discrete radiosource scintillations at Irkutsk Incoherent Scatter radar

    NASA Astrophysics Data System (ADS)

    Globa, Mariya; Vasilev, Roman; Kushnaryov, Dmitriy; Medvedev, Andrey

    2016-03-01

    We propose a new method for analysis of data from Irkutsk Incoherent Scatter Radar. The method allows us to accomplish interferometric observation of discrete cosmic radio source characteristics. In this study, we analyzed ionospheric scintillations of the radio source Cygnus-A. Observations were made in 2013 during regular radar sessions within 5-15 days for different seasons, and the effective time of observation was 15-30 minutes per day. For interferometric analysis, the properties of correlation (coherence) coefficient of two independent recording channels were used. The statistical analysis of data from independent channels allows us to construct two-dimensional histograms of radio source brightness distribution with period of 18 s and to determine parameters (the maximum position and the histogram width) representing position and angular size of radio source for each histogram. It is shown that the change of statistical characteristics does not correlate with fluctuations in power (scintillations) of the signal caused by radio wave propagation through ionospheric irregularities.

  16. Comparison of F-region electron density observations by satellite radio tomography and incoherent scatter methods

    NASA Astrophysics Data System (ADS)

    Nygrén, T.; Markkanen, M.; Lehtinen, M.; Tereshchenko, E. D.; Khudukon, B. Z.; Evstafiev, O. V.; Pollari, P.

    1996-12-01

    In November 1995 a campaign of satellite radiotomography supported by the EISCAT incoherent scatter radar and several other instruments was arranged in Scandinavia. A chain of four satellite receivers extending from the north of Norway to the south of Finland was installed approximately along a geomagnetic meridian. The receivers carried out difference Doppler measurements using signals from satellites flying along the chain. The EISCAT UHF radar was simultaneously operational with its beam swinging either in geomagnetic or in geographic meridional plane. With this experimental set-up latitudinal scans of F-region electron density are obtained both from the radar observations and by tomographic inversion of the phase observations given by the difference Doppler experiment. This paper shows the first results of the campaign and compares the electron densities given by the two methods. Acknowledgements. This work has been supported by the UK Particle-Physics and Astronomy Research Council. The assistance of the director and staff of the EISCAT Scientific Association, the staff of the Norsk Polarinstitutt and the director and staff of the Swedish Institute of Space Physics is gratefully acknowledged. In addition the authors would like to thank Professor Evgeny Tereshchenko of the Polar Geophysical Institute in Mumansk, Russia and Dr Tuomo Nygrén of the University of Oulu, Finland for provision of data from EISCAT special program time during the November 1995 campaign. Topical Editor D. Alcaydé thanks E. J. Fremouw and another referee for their help in evaluating this paper.--> Correspondence to: I. K. Walker-->

  17. Incoherent scatter radar observations of irregular structure in mid-latitude sporadic E layers

    NASA Technical Reports Server (NTRS)

    Miller, K. L.; Smith, L. G.

    1978-01-01

    The basic experiments used phase-coded pulses to record electron density profiles with a resolution of 600 m in range and 300 m in horizontal extent, while scanning in azimuth. Data from incoherent scatter radar were compared with simultaneous ionosonde observations. Observations of sporadic E layers by incoherent scatter radar were discussed in terms of the effects of the neutral wind system acting on metallic ions. Several features were noted in the data, which support the wind shear mechanism of layer formation. The sporadic E layers often contained a pronounced small-scale structure, especially at times when partially transparent echoes were observed by the ionosonde. Under specific conditions, the ions in a meteor trail can be converged by a shear in the neutral wind into a relatively small irregularity at the center of a sporadic E layer.

  18. Incoherent scatter radar measurement of the average ion mass and temperature of a nighttime sporadic layer

    SciTech Connect

    Tepley, C.A.; Mathews, J.D.

    1985-04-01

    We report the results of incoherent scatter radar, total power, and ion line observations of a nighttime sporadic layer centered at 92-km altitude. The height variation of the absolute widths of the ion line yields a layer temperature of 210/sup 0/ +- 5 /sup 0/K and a mean ion mass of 50 +- 10 amu. This ion mass, when compared with average meteor composition, indicates that the layer is composed totally of metallic ions.

  19. Horizontal structure of midlatitude sporadic-E layers observed by incoherent scatter radar

    NASA Technical Reports Server (NTRS)

    Miller, K. L.; Smith, L. G.

    1975-01-01

    The investigation reported is concerned with a model considered by Whitehead (1972). The partial transparency of the sporadic-E layer observed on certain occasions is attributed to regions of high electron density embedded in the layer. Observations obtained with an incoherent scatter radar facility are presented. Taking into account all factors, it is concluded that the partial transparency of sporadic-E layers, on the occasions of these observations, are explained by the Whitehead model.

  20. Application of particle swarm optimization method to incoherent scatter radar measurement of ionosphere parameters

    NASA Astrophysics Data System (ADS)

    Wu, Li-Li; Zhou, Qihou H.; Chen, Tie-Jun; Liang, J. J.; Wu, Xin

    2015-09-01

    Simultaneous derivation of multiple ionospheric parameters from the incoherent scatter power spectra in the F1 region is difficult because the spectra have only subtle differences for different combinations of parameters. In this study, we apply a particle swarm optimizer (PSO) to incoherent scatter power spectrum fitting and compare it to the commonly used least squares fitting (LSF) technique. The PSO method is found to outperform the LSF method in practically all scenarios using simulated data. The PSO method offers the advantages of not being sensitive to initial assumptions and allowing physical constraints to be easily built into the model. When simultaneously fitting for molecular ion fraction (fm), ion temperature (Ti), and ratio of ion to electron temperature (γT), γT is largely stable. The uncertainty between fm and Ti can be described as a quadratic relationship. The significance of this result is that Ti can be retroactively corrected for data archived many years ago where the assumption of fm may not be accurate, and the original power spectra are unavailable. In our discussion, we emphasize the fitting for fm, which is a difficult parameter to obtain. PSO method is often successful in obtaining fm, whereas LSF fails. We apply both PSO and LSF to actual observations made by the Arecibo incoherent scatter radar. The results show that PSO method is a viable method to simultaneously determine ion and electron temperatures and molecular ion fraction when the last is greater than 0.3.

  1. First Detection of Meteoric Smoke using the Poker Flat Incoherent Scatter Radar (PFISR)

    NASA Astrophysics Data System (ADS)

    Hsu, V. W.; Fentzke, J. T.; Brum, C. G.; Strelnikova, I.; Nicolls, M. J.

    2011-12-01

    In this work we present the first results of meteor smoke particles (MSPs) detected in the D-region plasma above the 449 MHz Poker Flat Incoherent Scatter Radar (PFISR) in Alaska (67°N, 149°W). MSPs are believed to be the major source of condensation nuclei for the formation of ice particles, the precursor for Polar Mesospheric Clouds (PMCs) and Polar Mesospheric Summer Echoes (PMSE). In addition, they are thought to contribute to D-region chemistry by providing a surface on which heterogeneous chemistry occurs (Summers and Siskand, 1999). Our results are obtained by utilizing a similar fitting method derived for use at other High Power Large Aperture Radar (HPLA) sites that treats the measured radar signal as the sum of two Lorentzian functions [Strelnikova et al., 2007]. This method allows us to determine particle size distributions and smoke densities (when calibrated electron density data is available) in the range of approximately 70 to 90 km altitude depending on background atmospheric composition. We present results from a period of strong D-Region ionization when the detected signal-to-noise (SNR) from the D-region is strongest (12 - 19 UT). Our results provide insight into the presence and distribution of charged meteoric dust in the polar mesopause region resulting from the condensation of ablated material of meteoric origin. Furthermore, we compare our results to other HPLA radar sites at high latitude (EISCAT) as well as low latitude (Arecibo) to verify our results and investigate any latitudinal variation that may exist.

  2. Signal evaluations using singular value decomposition for Thomson scattering diagnostics.

    PubMed

    Tojo, H; Yamada, I; Yasuhara, R; Yatsuka, E; Funaba, H; Hatae, T; Hayashi, H; Itami, K

    2014-11-01

    This paper provides a novel method for evaluating signal intensities in incoherent Thomson scattering diagnostics. A double-pass Thomson scattering system, where a laser passes through the plasma twice, generates two scattering pulses from the plasma. Evaluations of the signal intensities in the spectrometer are sometimes difficult due to noise and stray light. We apply the singular value decomposition method to Thomson scattering data with strong noise components. Results show that the average accuracy of the measured electron temperature (Te) is superior to that of temperature obtained using a low-pass filter (<20 MHz) or without any filters. PMID:25430278

  3. Signal evaluations using singular value decomposition for Thomson scattering diagnostics

    SciTech Connect

    Tojo, H. Yatsuka, E.; Hatae, T.; Itami, K.; Yamada, I.; Yasuhara, R.; Funaba, H.; Hayashi, H.

    2014-11-15

    This paper provides a novel method for evaluating signal intensities in incoherent Thomson scattering diagnostics. A double-pass Thomson scattering system, where a laser passes through the plasma twice, generates two scattering pulses from the plasma. Evaluations of the signal intensities in the spectrometer are sometimes difficult due to noise and stray light. We apply the singular value decomposition method to Thomson scattering data with strong noise components. Results show that the average accuracy of the measured electron temperature (T{sub e}) is superior to that of temperature obtained using a low-pass filter (<20 MHz) or without any filters.

  4. Validation of COSMIC radio occultation electron density profiles by incoherent scatter radar data

    NASA Astrophysics Data System (ADS)

    Cherniak, Iurii; Zakharenkova, Irina

    The COSMIC/FORMOSAT-3 is a joint US/Taiwan radio occultation mission consisting of six identical micro-satellites. Each microsatellite has a GPS Occultation Experiment payload to operate the ionospheric RO measurements. FS3/COSMIC data can make a positive impact on global ionosphere study providing essential information about height electron density distribu-tion. For correct using of the RO electron density profiles for geophysical analysis, modeling and other applications it is necessary to make validation of these data with electron density distributions obtained by another measurement techniques such as proven ground based facili-ties -ionosondes and IS radars. In fact as the ionosondes provide no direct information on the profile above the maximum electron density and the topside ionosonde profile is obtained by fitting a model to the peak electron density value, the COSMIC RO measurements can make an important contribution to the investigation of the topside part of the ionosphere. IS radars provide information about the whole electron density profile, so we can estimate the agreement of topside parts between two independent measurements. To validate the reliability of COS-MIC data we have used the ionospheric electron density profiles derived from IS radar located near Kharkiv, Ukraine (geographic coordinates: 49.6N, 36.3E, geomagnetic coordinates: 45.7N, 117.8E). The Kharkiv radar is a sole incoherent scatter facility on the middle latitudes of Eu-ropean region. The radar operates with 100-m zenith parabolic antenna at 158 MHz with peak transmitted power 2.0 MW. The Kharkiv IS radar is able to determine the heights-temporal distribution of ionosphere parameters in height range of 70-1500 km. At the ionosphere in-vestigation by incoherent scatter method there are directly measured the power spectrum (or autocorrelation function) of scattered signal. With using of rather complex procedure of the received signal processing it is possible to estimate the

  5. Incoherent source angular domain imaging through complex three-dimensional scattering structures

    NASA Astrophysics Data System (ADS)

    Cheng, Rongen L. K.; Chiang, Gary; Chapman, Glenn H.

    2012-03-01

    Scattering of photons in biological imaging is a known factor of degrading image resolution and quality. Angular Domain Imaging (ADI) is a technique which utilizes the angular distribution of photons to filter out multiple-scattering photons and accept only photons with small angular deviation from their original trajectories. The advantage of ADI is that it does not require a high optical quality, coherent, or pulsed source to acquire quality image. Initial experiments with Spatialfrequency Filter (SFF) ADI on simple liquid scattering test phantom showed good results as it can image through media with scattering ratio (SR) of 106:1. Previous work with complex 3D aquatic species eliminated scattering but showed optical interference patterns from the coherent laser sources. With SFF ADI, our target is to image through a complex 3D scattering structure with multilayer of different refractive indices and scattering coefficient from an Intralipid-infused polymer/agar, and a small species called Branchiostoma lanceolatum, a lancelet that is 5-8cm long and ~5mm thick. To remove interference, several narrow wavelength-band LEDs were used as illumination sources with one peaks at 630nm and the other peaks at 415nm. The LEDs are collimated and illuminates the 3D structure/lancelet in a water-filler container while a SFF removes the scattered photons before the imager. This allows us to reduce the optical interference and to study the impact of switching from coherent laser source into an incoherent narrow wavelength-band source. Hence, it allows us to investigate the enhancement of imaging the internal structures using the incoherent narrow wavelength-band source.

  6. Comparisons of Total Electron Content with GPS and Incoherent Scatter Radar during IPY

    NASA Astrophysics Data System (ADS)

    Coster, A. J.; Zhang, S.; Rideout, W. E.

    2008-12-01

    Since the early 1990's, comparisons of the measured total electron content (TEC) have been made between GPS and incoherent scatter radar (ISR). This was first done in 1990 using data collected at the Millstone Hill ISR site in Westford, MA. The Millstone Hill ISR can measure electron density up to approximately 800 km, depending on the amount of signal integration and/or the total amount background ionization. The initial ISR and GPS TEC comparisons were somewhat surprising in that the differences between these measurements varied significantly depending on the geomagnetic conditions. Prior to a geomagnetic storm, there were indications that as much as 20 percent of the background TEC was observed to be above 800 km. Directly after the geomagnetic storm, the average difference between the ISR and GPS TEC measurements was almost zero. This has been recently explained by the IMAGE satellite observations of the plasmaspheric drainage plumes which effectively drain plasma from the plasmasphere out into space during geomagnetically active conditions. Here, we will report on comparisons of the GPS and ISR estimates of the TEC in the high latitudes from the first year of the IPY, March 1, 2007 through March 1, 2008. Our analysis will focus on data from the ISRs associated with the high latitudes: the Poker Flat radar in Alaska, the EISCAT radar in Svalbard, the Sondrestrom radar in Greenland, and the Millstone Hill radar in Massachusetts. During this time period, the Poker Flat (PFISR) and EISCAT Svalbard (ESR) radars ran continuously. The Millstone Hill and Sondrestrom ISRs ran bi-weekly throughout the year. These comparisons will utilize TEC data from the Madrigal database that was estimated from the global network of GPS receivers. In addition, TEC data collected from individual GPS receivers located near the ISRs will be examined. The GPS versus ISR TEC comparisons will be used to study the variation of the high altitude electron content as a function of latitude

  7. Mechanisms of ultrasonic modulation of multiply scattered incoherent light based on diffusion theory

    NASA Astrophysics Data System (ADS)

    Zhu, Li-Li; Li, Hui

    2015-01-01

    An analytic equation interpreting the intensity of ultrasound-modulated scattering light is derived, based on diffusion theory and previous explanations of the intensity modulation mechanism. Furthermore, an experiment of ultrasonic modulation of incoherent light in a scattering medium is developed. This analytical model agrees well with experimental results, which confirms the validity of the proposed intensity modulation mechanism. The model supplements the existing research on the ultrasonic modulation mechanism of scattering light. Project supported by the National Natural Science Foundation of China (Grant No. 61178089), the Key Program of Science and Technology of Fujian Province, China (Grant No. 2011Y0019), and the Educational Department of Fujian Province, China (Grant No. JA13074).

  8. Observations of plasma line splitting in the ionospheric incoherent scatter spectrum.

    PubMed

    Bhatt, Asti N; Nicolls, Michael J; Sulzer, Michael P; Kelley, Michael C

    2008-02-01

    Wide-bandwidth ionospheric incoherent scatter (IS) spectra obtained using the Arecibo IS radar show the occurrence of a split in the plasma line (i.e., two plasma lines) when the plasma frequency is close to the second harmonic of the electron gyrofrequency. This split is predicted in the IS theory for a magnetized plasma, but observations have never been reported. Here we present the experimental results and theoretical calculations supporting the observations. These results may assist in understanding the behavior of Langmuir waves in the magnetized plasma and are a validation of what historically was a somewhat controversial aspect of the IS theory. PMID:18352291

  9. The diurnal variation of E-F valley parameters from incoherent scatter measurements at Arecibo

    NASA Astrophysics Data System (ADS)

    Mahajan, K. K.; Sethi, N. K.; Pandey, V. K.

    1997-01-01

    The size and shape of the valley region between E and F layers is studied for nighttime conditions by using high resolution electron density profiles measured by the incoherent scatter radar at Arecibo, Puerto Rico, (18.3 degN,66.7 degW). Important valley parameters like width, depth and height of the valley minimum are derived from these measurements. By combining these nighttime results with our earlier daytime model (Mahajan, et. al, 1994), we now present a model for the full diurnal variation of the E-F valley parameters. Comparison with IRI-90 indicates significant differences between our model and the IRI valley model.

  10. Incoherent scatter radar-FAST satellite common volume observations of upflow-to-outflow conversion

    NASA Astrophysics Data System (ADS)

    Sánchez, Ennio R.; StrØmme, Anja

    2014-04-01

    Incoherent scatter radar measurements from the Sondrestrom Research Facility and the European Incoherent Scatter Svalbard radar have been combined with all-sky images, polar convection measurements, and FAST particle and field measurements to quantify the contribution of different magnetosphere-ionosphere coupling processes to the extraction efficiency of ions from the ionosphere. Upflowing ions are traced from their source vertically and horizontally to determine where and when they are likely to intersect the acceleration region observed by FAST. The duration and location of auroral emissions are used to estimate the size and duration of the acceleration region. The upflow-to-outflow efficiency is estimated for three periods of polar cap boundary intensifications and streamers during substorm recovery and steady magnetospheric convection. The extraction efficiency of conics ranges between 0.1%, for the lowest amplitude of broadband extremely low frequency waves, and 5%, for the highest-amplitude waves sampled. Simultaneous measurements of all-sky images and magnetic field-aligned radar measurements show that the most intense ion upflux occurs adjacent to the boundary of intense electron precipitation characteristic of polar cap boundary intensifications and streamers, suggesting that the most efficient acceleration mechanisms couple ionospheric heating at F region altitude with dispersive Alfvén waves that grow from horizontal gradients in electric field and conductivity.

  11. Ionosonde measurements in Bayesian statistical ionospheric tomography with incoherent scatter radar validation

    NASA Astrophysics Data System (ADS)

    Norberg, J.; Virtanen, I. I.; Roininen, L.; Vierinen, J.; Orispää, M.; Kauristie, K.; Lehtinen, M. S.

    2015-09-01

    We validate two-dimensional ionospheric tomography reconstructions against EISCAT incoherent scatter radar measurements. Our tomography method is based on Bayesian statistical inversion with prior distribution given by its mean and covariance. We employ ionosonde measurements for the choice of the prior mean and covariance parameters, and use the Gaussian Markov random fields as a sparse matrix approximation for the numerical computations. This results in a computationally efficient and statistically clear inversion algorithm for tomography. We demonstrate how this method works with simultaneous beacon satellite and ionosonde measurements obtained in northern Scandinavia. The performance is compared with results obtained with a zero mean prior and with the prior mean taken from the International Reference Ionosphere 2007 model. In validating the results, we use EISCAT UHF incoherent scatter radar measurements as the ground truth for the ionization profile shape. We find that ionosonde measurements improve the reconstruction by adding accurate information about the absolute value and the height distribution of electron density, and outperforms the alternative prior information sources. With an ionosonde at continuous disposal, the presented method enhances stand-alone near real-time ionospheric tomography for the given conditions significantly.

  12. Investigation of coherent to incoherent scattering cross section ratios of some foil metals depending on the temperature

    NASA Astrophysics Data System (ADS)

    Çatal, N.; Ertuğrul, M.; Özdemir, Y.

    2016-04-01

    In this study, it was aimed at examining the cross section ratios of coherent and incoherent scattering depending on the temperature for the elements Cd, In, Sn and Pb by 59.5 keV γ-rays from a 100 mCi 241Am radioisotope point source. The coherent and incoherent cross section of Cd, In, Sn and Pb have been measured by using a Si(Li) solid-state detector at temperature between 30-300 °C. Coherent to incoherent cross section ratios and FWHM (Full width at half maximum) of the elements have been calculated. Temperature-dependent changes of the parameters have been given in the graphical forms. Based on the results obtained, coherent to incoherent cross section ratios of the elements are dependent on the temperature. It is observed that coherent to incoherent cross section ratios of Cd, In, and Pb decrease with increasing temperature. For Sn, first of all coherent and incoherent intensity ratios decrease, then increase and decrease again respectively. To sum up, coherent to incoherent cross section ratios tend to decrease with increasing temperature.

  13. TID characterised using joint effort of incoherent scatter radar and GPS

    NASA Astrophysics Data System (ADS)

    van de Kamp, M.; Pokhotelov, D.; Kauristie, K.

    2014-12-01

    Travelling Ionospheric Disturbances (TIDs), which are caused by Atmospheric Gravity Waves (AGWs), are detected and characterised by a joint analysis of the results of two measurement techniques: incoherent scatter radar and multiple-receiver GPS measurements. Both techniques to measure TIDs are already well known, but are developed further in this study, and the strengths of the two are combined, in order to obtain semi-automatic tools for objective TID detection. The incoherent scatter radar provides a good vertical range and resolution and the GPS measurements provide a good horizontal range and resolution, while both have a good temporal resolution. Using the combination of the methods, the following parameters of the TID can be determined: the time of day when the TID occurs at one location, the period length (or frequency), the vertical phase velocity, the amplitude spectral density, the vertical wavelength, the azimuth angle of horizontal orientation, the horizontal wavelength, and the horizontal phase velocity. This technique will allow a systematic characterisation of AGW-TIDs, which can be useful, among other things, for statistical analyses. The presented technique is demonstrated on data of 20 January 2010 using data from the EISCAT incoherent scatter radar in Tromsø and from the SWEPOS GPS network in Sweden. On this day around 07:00-12:00 UT, a medium-scale TID was observed from both data sets simultaneously. The TID had a period length of around 2 h, and its wave propagated southeastward with a horizontal phase velocity of about 67 m s-1 and a wavelength of about 500 km. The TID had its maximum amplitude in Tromsø at 10:00 UT. The period length detected from the GPS results was twice the main period length detected from the radar, indicating a different harmonic of the same wave. The horizontal wavelength and phase velocity are also estimated from the radar results using Hines' theory, using the WKB approximation to account for inhomogeneity of the

  14. MIDAS-W: a workstation-based incoherent scatter radar data acquisition system

    NASA Astrophysics Data System (ADS)

    Holt, J. M.; Erickson, P. J.; Gorczyca, A. M.; Grydeland, T.

    2000-09-01

    The Millstone Hill Incoherent Scatter Data Acquisition System (MIDAS) is based on an abstract model of an incoherent scatter radar. This model is implemented in a hierarchical software system, which serves to isolate hardware and low-level software implementation details from higher levels of the system. Inherent in this is the idea that implementation details can easily be changed in response to technological advances. MIDAS is an evolutionary system, and the MIDAS hardware has, in fact, evolved while the basic software model has remained unchanged. From the earliest days of MIDAS, it was realized that some functions implemented in specialized hardware might eventually be implemented by software in a general-purpose computer. MIDAS-W is the realization of this concept. The core component of MIDAS-W is a Sun Microsystems UltraSparc 10 workstation equipped with an Ultrarad 1280 PCI bus analog to digital (A/D) converter board. In the current implementation, a 2.25 MHz intermediate frequency (IF) is bandpass sampled at 1 µs intervals and these samples are multicast over a high-speed Ethernet which serves as a raw data bus. A second workstation receives the samples, converts them to filtered, decimated, complex baseband samples and computes the lag-profile matrix of the decimated samples. Overall performance is approximately ten times better than the previous MIDAS system, which utilizes a custom digital filtering module and array processor based correlator. A major advantage of MIDAS-W is its flexibility. A portable, single-workstation data acquisition system can be implemented by moving the software receiver and correlator programs to the workstation with the A/D converter. When the data samples are multicast, additional data processing systems, for example for raw data recording, can be implemented simply by adding another workstation with suitable software to the high-speed network. Testing of new data processing software is also greatly simplified, because a

  15. Coherent and incoherent scatterings for measurement of mandibular bone density and stable iodine content of tissue

    PubMed Central

    Sharma, Amandeep; Singh, Mohinderpal; Singh, Bhajan; Sandhu, Balvir S.

    2009-01-01

    The aim of present study is to investigate the feasibility of gamma ray scattering for measurements of mandibular bone density and stable iodine content of tissue. Scattered spectra from solutions of K2HPO4 in distilled water (a phantom simulating the mandibular bone) and KI in distilled water filled in a thin plastic vial (a phantom simulating the kinetics of thyroid iodine) are recorded for 59.54 and 145 keV incident gamma rays, respectively. A high-purity germanium detector is placed at various angular positions to record the scattered spectra originating from interactions of incident gamma rays with the phantom. The measured intensity ratio of coherent to incoherent scattered gamma rays, corrected for photo-peak efficiency of HPGe detector, absorption of gamma rays in air column present between phantom and detector, and self-absorption in the phantom, is found to be increasing linearly with increase in concentration of K2HPO4 and KI in distilled water within experimental estimated error of <6%. The regression lines, obtained from experimental data for intensity ratio, provide the bone density and stable iodine contents of thyroid. The present non-destructive technique has the potential for a measure of mandibular bone density and stable iodine contents of thyroid. PMID:20098568

  16. A global thermospheric model based on mass spectrometer and incoherent scatter data MSIS. II - Composition

    NASA Technical Reports Server (NTRS)

    Hedin, A. E.; Reber, C. A.; Newton, G. P.; Spencer, N. W.; Brinton, H. C.; Mayr, H. G.; Potter, W. E.

    1977-01-01

    Measurements of O, He, and Ar from neutral gas mass spectrometers on four satellites (Ogo 6, San Marco 3, Aeros A, and AEC-C) and inferred oxygen and hydrogen densities from an ion mass spectrometer on AE-C have been combined with a neutral temperature and nitrogen density model to produce a global model of thermospheric composition in terms of inferred variations at 120 km. The data set covers the time period from mid-1969 to mid-1975. The MSIS (mass spectrometer and incoherent scatter data) model is compared with the Ogo 6 model (Hedin et al., 1974). Ar variations at 120 km tend to be in phase with temperature variations and inverse to the He, O, and H variations.

  17. Incoherent Quasielastic Neutron Scattering study of hydrogen diffusion in thorium-zirconium hydrides

    NASA Astrophysics Data System (ADS)

    Terrani, Kurt A.; Mamontov, Eugene; Balooch, Mehdi; Olander, Donald R.

    2010-06-01

    Monophase thorium-zirconium hydrides (ThZr 2H x) have been fabricated starting from a metallic alloy and the hydrogen stoichiometry determined by X-ray diffraction. Incoherent Quasielastic Neutron Scattering (IQNS) on the hydrides was conducted over the temperature range 650-750 K at the Backscattering Silicon Spectrometer (BASIS) at the Spallation Neutron Source (SNS) at ORNL. The isotropic Chudley-Elliott model was utilized to analyze the quasielastic linewidth broadening data as function of momentum transfer. The diffusion coefficient and average jump distance of hydrogen atoms in ThZr 2H 5.6 and ThZr 2H 6.2 were extracted from the measurements.

  18. Estimating the vector electric field using monostatic, multibeam incoherent scatter radar measurements

    NASA Astrophysics Data System (ADS)

    Nicolls, Michael J.; Cosgrove, Russell; Bahcivan, Hasan

    2014-11-01

    An algorithm has been developed to image the local structure in the convection electric field using multibeam incoherent scatter radar (ISR) data. The imaged region covers about 4° in magnetic latitude and 8° in magnetic longitude for the specific geometry considered (that of the Poker Flat ISR). The algorithm implements the Lagrange method of undetermined multipliers to regularize the underdetermined problem posed by the radar measurements. The error on the reconstructed image is estimated by mapping the mathematical form to a Bayesian estimate and observing that the Lagrangian method determines an effective a priori covariance matrix from a user-defined regularization metric. There exists a unique solution when the average measurement error is smaller than the average measurement amplitude. The algorithm is tested using synthetic and real data and appears surprisingly robust at estimating the divergence of the field. Future applications include imaging the current systems surrounding auroral arcs in order to distinguish physical mechanisms.

  19. Experimental and Computational Studies on Collective Hydrogen Dynamics in Ammonia Borane: Incoherent Inelastic Neutron Scattering

    SciTech Connect

    Kathmann, Shawn M.; Parvanov, Vencislav M.; Schenter, Gregory K.; Stowe, Ashley C.; Daemen, Luke L.; Hartl, Monika A.; Linehan, John C.; Hess, Nancy J.; Karkamkar, Abhijeet J.; Autrey, Thomas

    2009-02-26

    Incoherent inelastic neutron scattering can be used as a sensitive probe of the vibrational dynamics in chemical hydrogen storage materials. Thermal neutron energy loss measurements at 10K are presented and compared to the vibrational power spectrum calculated using ab initio molecular dynamics of pure and deuterated ammonia borane (NH3BH3, NH3BD3, and ND3BH3). A harmonic vibrational analysis on NH3BH3 clusters was also explored to check for consistency with experiment and the power spectrum. The measured neutron spectra and computed ab initio power spectrum compare extremely well (50 to 500 cm-1) and some assignment of modes to simple motion is possible, however, it is found that the lowest modes (below 250 cm-1) are dominated by collective motion. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for DOE.

  20. Incoherent scatter radar and in situ and chemical release measurements of

    NASA Astrophysics Data System (ADS)

    Kudeki, Erhan; Pfaff, Robert; Larsen, Miguel

    2016-07-01

    Two sounding rockets collecting DC and AC electric field and plasma density measurements were launched into the equatorial ionosphere during an active E-region sunset event being monitored by ALTAIR and IRIS (UHF and VHF) radar systems. TMA and lithium vapor releases by the rockets climbing to 180 and 330 km apogees also enabled the measurements of E- and lower F-region neutral winds during this pre-reversal enhancement period followed by spread-F activity. E-region turbulence during sunset and F-region turbulence and plasma drifts that developed subsequently were monitored by ALTAIR and IRIS (a 50 MHz two-element fixed-beam radar interferometer) systems using a combination of coherent and incoherent scatter modes. Winds, drifts, and turbulence measurements of the post sunset ionosphere conducted during this equatorial vortex experiment (EVEX) and their implications for post-sunset spread-F development will be presented and discussed.

  1. Incoherent scatter measurements of E region conductivities and currents in the auroral zone

    NASA Technical Reports Server (NTRS)

    Brekke, A.; Doupnik, J. R.; Banks, P. M.

    1974-01-01

    Data taken by incoherent scatter radar have been used to investigate ionospheric conductivities and electrical currents. During quiet days, the conductivities appear to vary in a way consistent with ionization arising from solar EUV radiation. In the evening hours, enhancements in the northward electric field are found to precede small increases in the conductivities. Strong enhancements of the Hall conductivity relative to the Pedersen conductivity occur during negative bays when the electric field is in a southwestward direction. The ionospheric currents calculated in the geomagnetic east-west direction are in good agreement with the H component measured by a nearby magnetometer; this result indicates that the current causing the ground level magnetic fluctuations is a broad horizontal sheet current. The north-south ionospheric current, however, consistently disagrees with the observed D component in a manner that cannot easily be explained unless currents parallel to the earth's magnetic field are present.

  2. Detection of artificially created negative ion clouds with incoherent scatter radar

    NASA Technical Reports Server (NTRS)

    Sultan, Peter J.; Mendillo, Michael; Oliver, William L.; Holt, John M.

    1992-01-01

    The physical mechanisms by which negative ions change the shape of the incoherent scatter spectrum, and the way in which shape changes may be used to detect the presence of heavy positive and negative ions in an ambient ionosphere are investigated. In order to detect heavy negative ions, the temperature structure of the ionosphere is fixed to a prevent average measurement, and any changes in spectral shape during the experiment are interpreted as being caused by changes in composition, and not by changes in the temperature ratio Te/Ti. The spatial and temporal development of heavy negative ion plasma clouds created during four active chemical release experiments was observed. Concentrations of 10-40-percent SF6(-) were detected in SPINEX 1, SPINEX 2, and IMS data sets. An average uncertainty of +/-10-percent SF6(-) is present in all three experiments. Concentrations of 30-percent Br(-) were detected in the NICARE 1 release, with uncertainties of +/-4 percent.

  3. MST data exchange through the NCAR incoherent-scatter radar data base

    NASA Technical Reports Server (NTRS)

    Richmond, A. D.

    1986-01-01

    One means of making MST (mesosphere stratosphere troposphere) radar data more easily accessible for scientific research by the general scientific community is through a centralized data base. Such a data base can be designed to readily provide information on data availability and quality, and to provide copies of data from any radar in a common format to the user. The ionospheric incoherent scatter community has established a centralized data base at NCAR that may serve not only as a model for a possible MST data base, but also as a catalyst for getting an MST data base started. (Some key elements of the NCAR data base are given.) The NCAR data base can include MST data in the same framework with relatively little extra effort. They are willing to handle MST data on a limited basis in order to permit assessment of community interest and in order to provide some experience with a centralized data base for MST data.

  4. Anomalous vibrational modes in acetanilide: A F. D. S. incoherent inelastic neutron scattering study

    SciTech Connect

    Barthes, M.; Moret, J. ); Eckert, J.; Johnson, S.W.; Swanson, B.I.; Unkefer, C.J. )

    1991-01-01

    The origin of the anomalous infra-red and Raman modes in acetanilide (C{sub 6}H{sub 5}NHCOCH{sub 3}, or ACN), remains a subject of considerable controversy. One family of theoretical models involves Davydov-like solitons nonlinear vibrational coupling, or polaronic'' localized modes. An alternative interpretation of the extra-bands in terms of a Fermi resonance was proposed and recently the existence of slightly non-degenerate hydrogen atom configurations in the H-bond was suggested as an explanation for the anomalies. In this paper we report some new results on the anomalous vibrational modes in ACN that were obtained by inelastic incoherent neutron scattering (INS).

  5. Electric fields and neutral winds from monostatic incoherent scatter measurements by means of stochastic inversion

    NASA Astrophysics Data System (ADS)

    Nygrén, T.; Aikio, A. T.; Kuula, R.; Voiculescu, M.

    2011-05-01

    A new method utilizing stochastic inversion in determining the electric field and neutral wind from monostatic beam swing incoherent scatter measurements is described. The method consists of two stages. In the first stage, beam-aligned ion velocities from a chosen F region height interval and a set of subsequent beam directions are taken as measurements. The unknowns are the two electric field components and the field-aligned ion velocity profile. The solution gives the most probable values of the unknowns with error estimates. In the second stage, the measurements consist of beam-aligned ion velocities from the E region, and the electric fields given by the first inversion problem are also used as measurements. The number of applied beam directions may be greater than in the first inversion problem. This is a feasible approach since the neutral wind usually changes more slowly than the electric field. The solution of the second inversion problem gives the most probable values of the three neutral wind components. Results of the method are shown for 11 September 2005, when the European Incoherent Scatter (EISCAT) UHF radar was running in the CP2 experiment mode, which is a four-position 6 min monostatic cycle. In addition, from each beam direction a tristatic measurement at one F region range gate was made using two additional receivers. That allowed comparison between the monostatic and tristatic electric field results, which were in excellent agreement. The calculated neutral wind components were in good accordance with previous measurements during disturbed conditions from the same site.

  6. Conjugate In-situ and Incoherent Scatter Radar Observations of Radiation Belt Loss Mechanisms.

    NASA Astrophysics Data System (ADS)

    Kaeppler, S. R.; Jaynes, A. N.; Sanchez, E. R.; Nicolls, M. J.; Varney, R. H.; Marshall, R. A.

    2015-12-01

    We present results from conjugate observations between the Radiation Belt Storms Probe (RBSP) and the Poker Flat Incoherent Scatter Radar (PFISR) of energetic radiation belt precipitation. A key objective of the RBSP mission is to understand loss mechanisms of energetic particles from the radiation belt. The relative contribution from plasma waves (e.g., EMIC, hiss, chorus, and etc.) that pitch angle scatter particles into the loss cone remains an open scientific question. Rigorous experimental validation of these mechanisms is difficult to achieve because nearly simultaneous conjugate observations of in-situ pitch angle scattering and precipitation into the atmosphere are required. One ground-based signature of energetic precipitation is enhanced ionization and electron density at D-region altitudes. Incoherent scatter radar is a powerful remote sensing technique that is sensitive to electron density enhancements. By measuring the altitude profiles of ionization we infer the flux of particles precipitating into the atmosphere. PFISR observations show frequent occurrence of D-region ionization during both quiet-time and storm-time conditions. We present results from two events when the foot-points of the RBSP satellite were within 500 km of PFISR: a quiet-time event on January 13, 2015, and a storm-time event on April 16, 2015. PFISR observations of the D-region ionization signatures are presented, along with simultaneous conjugate RBSP observations of the magnetic field, electric field, and electron flux. Plasma waves are identified using the electric and magnetic field data, and evaluated as possible pitch angle scattering mechanisms. A direct comparison between the measured fluxes and loss cone fluxes predicted by theoretical wave-particle diffusion rates into the loss cone is used to test the validity of particle loss mechanisms predicted by the different theories. Preliminary results are presented of PFISR inversions of the D-region ionization to quantify the

  7. Coherent (photon) vs incoherent (current) detection of multidimensional optical signals from single molecules in open junctions

    SciTech Connect

    Agarwalla, Bijay Kumar; Hua, Weijie; Zhang, Yu; Mukamel, Shaul; Harbola, Upendra

    2015-06-07

    The nonlinear optical response of a current-carrying single molecule coupled to two metal leads and driven by a sequence of impulsive optical pulses with controllable phases and time delays is calculated. Coherent (stimulated, heterodyne) detection of photons and incoherent detection of the optically induced current are compared. Using a diagrammatic Liouville space superoperator formalism, the signals are recast in terms of molecular correlation functions which are then expanded in the many-body molecular states. Two dimensional signals in benzene-1,4-dithiol molecule show cross peaks involving charged states. The correlation between optical and charge current signal is also observed.

  8. Quasilinear theory of terahertz free-electron lasers based on Compton scattering of incoherent pump wave by intense relativistic electron beam

    NASA Astrophysics Data System (ADS)

    Ginzburg, N. S.; Kocharovskaya, E. R.

    2016-08-01

    The use of incoherent broadband pump radiation for improving the electron efficiency in the free-electron lasers (FEL) based on stimulated backscattering is considered. On the basis of a quasilinear approach, it is shown that the efficiency increases in proportion to the width of the pump spectrum. The effect is owing to a broadening of the spectrum of synchronous combination waves and realization of a mechanism of stochastic particle deceleration. The injection of a monochromatic seed signal in a single pass FEL amplifier or the implementation of a selective high-Q resonator in an FEL oscillator makes the high-frequency scattered radiation be monochromatic in spite of an incoherent pumping. In the regime of stochastic particle deceleration, the efficiency only slightly depends on the spread of the beam parameters, which is beneficial for a terahertz FEL powered by intense relativistic electron beams.

  9. Incoherent quasielastic neutron scattering study on the polymorphism of tristearin: dynamical properties of hydrocarbon chains.

    PubMed

    Takechi, Chikayo; Kawaguchi, Tatsuya; Kaneko, Fumitoshi; Yamamuro, Osamu; Akita, Hiroyuki; Ono, Machiko; Suzuki, Masao

    2007-08-23

    Dynamical properties of acyl chains in the three polymorphic phases alpha, beta', and beta of tristearin [C(3)H(5)(OCOC(17)H(35))3] have been studied by means of incoherent quasielastic neutron scattering (IQNS) using selectively deuterated samples. The mean square displacement of hydrogen atoms, , was estimated from the scattering vector Q dependence of the elastic scattering component under the harmonic approximation. It was shown that the temperature dependence of was significantly different between the three phases. There was no marked difference in between these phases up to 193 K, and the value increased linearly with temperature. Although the beta phase remained linear up to 293 K, the alpha and beta' phases started to show a nonlinear increase around 200 K, suggesting an anharmonic nature of molecular motions. The alpha phase exhibited the most conspicuous temperature dependence. These characteristics were ascribable to the difference in the lateral packing of acyl chains. Compared with the beta phase which has a tightly packed T// subcell, the beta' and alpha phases have looser O perpendicular and H subcells, respectively. The molecular motion in the alpha phase was analyzed using the model of uniaxial rotational diffusion in a onefold cosine potential. It has been clarified that the rotational fluctuation about the chain axis in the alpha phase is rather restricted compared with that in the rotator phase of n-alkanes. PMID:17661503

  10. Electroacoustical imaging technique for encoding incoherent radiance fields as Gabor elementary signals

    NASA Technical Reports Server (NTRS)

    Fales, C. L.; Huck, F. O.

    1985-01-01

    A technique is presented for directly encoding incoherent radiance fields as Gabor elementary signals. This technique uses an electro-acoustic sensor to modulate the electronic charges induced by the incident radiance field with the electric fields generated by Gaussian modulated sinusoidal acoustic waves. The resultant signal carries the amplitude and phase information required for localizing spatial frequencies of the radiance field. These localized spatial frequency representations provide a link between the either geometric or Fourier transform representations currently used in computer vision and pattern recognition.

  11. Proton vibrational dynamics in lithium imide investigated through incoherent inelastic and Compton neutron scattering.

    PubMed

    Pietropaolo, A; Colognesi, D; Catti, M; Nale, A-C; Adams, M A; Ramirez-Cuesta, A J; Mayers, J

    2012-11-28

    In the present study we report neutron spectroscopic measurements on polycrystalline lithium imide, namely, incoherent inelastic neutron scattering at 20 K, and neutron Compton scattering from 10 K up to room temperature. From the former technique the H-projected density of phonon states up to 100 meV is derived, while the latter works out the spherically averaged single-particle (i.e., H, Li, and N) momentum distributions and, from this, the mean kinetic energies. Only for H at the lowest investigated temperature, non-gaussian components of its momentum distribution are detected. However, these components do not seem directly connected to the system anharmonicity, being fully compatible with the simple N-H bond anisotropy. Neutron data are also complemented by ab initio lattice dynamics simulations, both harmonic and, at room temperature, carried out in the framework of the so-called "quantum colored noise thermostat" method. The single-particle mean kinetic energies in lithium imide as a function of temperature show a quite peculiar behavior at the moment not reproduced by ab initio lattice dynamics methods, at least as far as H and Li are concerned. As matter of fact, neither their low temperature values nor their temperature trends can be precisely explained in terms of standard phonon calculations. PMID:23206005

  12. Influence of gramicidin on the dynamics of DMPC studied by incoherent elastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Wanderlingh, U.; D'Angelo, G.; Conti Nibali, V.; Gonzalez, M.; Crupi, C.; Mondelli, C.

    2008-03-01

    By using the fixed energy window method in incoherent elastic neutron scattering, molecular motions in the 150 ps timescale in highly oriented multilayers of 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) membranes in excess of water (D2O) have been studied as a function of temperature, in the range from 27 to 325 K. The same system in partially deuterated form and with the addition of a pore-forming peptide (gramicidin) has also been investigated. By proper orientation of the membrane plane with respect to the scattering wavevector Q, information on in plane and out of plane motions of lipid membranes have been derived. Two relevant dynamical transitions were observed at T = 297 K and at T = 270 K. The former is related to the structural main transition from gel to liquid phase of the phospholipid bilayer, while the latter is related to a transition of the aqueous solvent. The inclusion of gramicidin shifts the main transition down to 294 K and the second transition up to 276 K. In both cases the observed dynamical transitions show an enhanced mobility in the direction normal to the membrane plane.

  13. EISCAT incoherent scatter radar measurements of artificial ionospheric modification at sub-ms time scales

    NASA Astrophysics Data System (ADS)

    Bahcivan, H.; Nicolls, M. J.

    2011-12-01

    Efficient generation of ELF/VLF waves through the modulation of ionospheric currents requires reliable measurements of the modulated current for different heater parameters. Incoherent scatter radar (ISR) measurements of modified plasma densities/temperatures would be ideal in quantifying the heating and cooling cycles in response to modulated heating by high-power HF waves. Considering the ms time scales of ELF/VLF generation processes, it is necessary to resolve the heating and cooling cycles at sub-ms time scales. Such measurements using ISRs have largely been avoided due to the common knowledge that the instrument requires minutes of integration. We present herein the results of an epoch averaging experiment using EISCAT that provides 0.2 ms resolution ISR power measurements as a function of phase into the HF heater ON and OFF cycle. In ELF/VLF generation, it is the electron temperature (Te) modulation that results in the modulation of electron collision frequency/mobility and therefore the electrojet modulation. Assuming a reliable electron collision frequency for transport as a function of Te, it is necessary to measure Te and electron density (Ne) simultaneously to predict the ionospheric current modulation. This is possible if (1) two incoherent scatter radars operating at sufficiently different frequencies are used and if (2) the Debye length and Bragg wavelengths are comparable. For the experiment results presented here, the ionospheric volume modified by the EISCAT heater were probed by both EISCAT UHF and VHF incoherent scatter radars operating at 0.16 m and 0.67 m Bragg wavelengths. Considering Ne=1e9 e/m3 in the D region ionosphere, for electron temperature Te=300 K, the Debye length is 0.38 m, where as for Te=1000 K the Debye length is 0.69 m; these parameters are reasonably appropriate to extract Te/Ne from simultaneous UHF/VHF data. We successfully detected ISR power modulation both in the E and F region heated ionosphere. Our findings are as

  14. Telescience capability for the Sondre Stromfjord, Greenland, incoherent-scatter radar facility

    NASA Technical Reports Server (NTRS)

    Zambre, Yadunath B.

    1993-01-01

    SRI International (SRI) operates an upper-atmospheric research facility in Sondre Stromfjord (Sondrestrom), Greenland. In the past, the facility's remote location and limited logistical support imposed constraints on the research that could be carried out at the site. Campaigns involving multiple instruments were often constrained due to limited space, and experiments requiring coordination with other geographically separated facilities, though possible, were difficult. To provide greater access to the facility, an electronic connection between Sondrestrom and the mainland U.S.A. was established, providing access to the National Science Internet. SRI developed telescience software that sends data from the incoherent scatter radar at the Sondrestrom facility to SRI's offices in Menlo Park, California. This software uses the transmission control protocol (TCP/IP) to transmit the data in near real time between the two locations and the X window system to generate displays of the data in Menlo Park. This is in contrast to using the X window system to display data remotely across a wide-area network. Using CP to transport data over the long distance network has resulted in significantly improved network throughput and latency. While currently used to transport radar data, the telescience software is designed and intended for simultaneous use with other instruments at Sondrestrom and other facilities. Work incorporating additional instruments is currently in progress.

  15. Ionospheric climatology and model from long-term databases of worldwide incoherent scatter radars

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Holt, J. M.; van Eyken, T.; McCready, M.; Amory-Mazaudier, C.; Fukao, S.; Sulzer, M.

    2005-05-01

    Long-term databases of worldwide incoherent scatter radars are utilized to study ionospheric climatology and create empirical models for electron density, ion and electron temperatures, and ion drifts. These radars, including, from magnetic north to south and east to west, EISCAT Svalbard Radar (Norway), Soundrestrom Radar (Greenland), EISCAT Tromso Radars (Norway), Millstone Hill Radar (USA), St. Santin Radar (France), Shigaraki Middle and Upper atmosphere (MU) Radar (Japan) and Arecibo Radar (Puerto Rico), are able to characterize diurnal, seasonal, and solar cycle variations of height dependent ionospheric strctures in a broad latitude and longitude area. In these huge databases, available through the MADRIGAL system (http://www.openmadrigal.org), the data cover generally 1-2 solar cycles, and for Millstone Hill and Arecibo they span nearly 3 solar cycles. Based on these data, our systematical analyses result in a comprehensive overview of various features of the ionosphere and series of web-based empirical models (http://www.haystack.mit.edu/madrigal/Models/). This presentation will review local models for each site and discuss the ionospheric climatology, with emphasis on the development of annual/semiannual electron density variations with latitudes and longitudes, and on ionospheric thermal status at midlatitudes. This presentation will also explore the long-term trend of ionospheric electron density and ion temperature variations from Millstone Hill observations.

  16. The Resolute Bay Incoherent Scatter Radar: Initial Results and Future Opportunities (Invited)

    NASA Astrophysics Data System (ADS)

    Semeter, J. L.; Dahlgren, H.; Sundberg, T.; Perry, G. W.; St-Maurice, J.; Shiokawa, K.; Hosokawa, K.; Zettergren, M. D.; Donovan, E.; Nicolls, M. J.

    2013-12-01

    The Resolute Bay Incoherent Scatter Radar (RISR) is the most recent facility developed under the NSF Advanced Modular ISR (AMISR) program, and the first ever ISR deployed to the geomagnetic polar cap region. The AMISR radars are electronically steerable, enabling the acquisition of three-dimensional, time-dependent, information over a significant regional volume. This paper provides a review of science results from the first two years of RISR operations. Of particular interest are studies that synthesize the new information about the intrinsic state variables (Ne, Te, Ti) with measurements by extant common-volume sensors (HF radar, all-sky imager, Fabry-Perot interferometer). The careful co-registration of these heterogeneous measurements is shown to provide new constraints on the nature of time-dependent solar wind-magnetosphere-ionosphere interactions in open magnetic-field regions. This capability will be further enhanced with the commissioning of the collocated Canadian facility (RISR-C) and the launch of the Enhanced Polar Outflow Probe (ePOP), both expected in 2013.

  17. Polymer Diffusion in Microgels with Upper Critical Solution Temperature as Studied by Incoherent Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Serrano Ruiz, D.; Alonso Cristobal, P.; Laurenti, M.; Rubio Retama, J.; Lopez-Cabarcos, E.

    2014-11-01

    Poly(acrylic-acrylamide) interpenetrated microgels present continuous phase transition from collapsed to swollen state around 42 °C. The upper critical solution temperature (UCST) of this polymeric system has prompted scientists to consider them candidates for its use in biological applications such as smart drug delivery devices since the swelling of the polymer matrix would permit the release of the drug previously entrapped within the microgels. In these systems the increment of the temperature can break inter-chain interactions, mainly hydrogen bonds, which reduce the elastic tension that stabilizes the microgel, favoring the polymer swelling. The microgel molecular dynamics at the UCST can be investigated using Incoherent Elastic (IENS) and Quasielastic Neutron Scattering (IQNS). From the analysis of the IQNS data we obtained that the diffusion coefficient of the polymer segments depends on the composition of the interpenetrated matrix. Thus, at room temperature, microgels with a polymer composition of 50% of each component present a diffusion coefficient 1·10-12 m2/s, while for the microgels formed by only one component the diffusion coefficient is 5.10-10 m2/s. This huge difference in the diffusion coefficient is conspicuously reduced when temperature increases, and we attribute this effect to the breaking of the inter-chain interaction. By means of FTIR-ATR analysis we have identified the groups that are involved in this phenomenon and we associate the breaking of the polyacrylic-polyacrylamide interactions with the swelling of the microgels.

  18. Study of auroral dynamics with combined spacecraft and incoherent-scatter radar data

    NASA Technical Reports Server (NTRS)

    Watermann, Juergen

    1993-01-01

    We have examined Sondrestrom incoherent-scatter radar observations of ionospheric plasma density and temperature distributions, as well as measurements of F-region ion drifts that were made during a prenoon pass by the DMSP-F7 satellite through the radar field of view. The spacecraft traversed a region of intense electron precipitation with a characteristic energy below approximately 200 eV. Particles with such low characteristic energies are believed to originate, either directly or indirectly, in the magnetosheath. The precipitation region had a width of about 2 deg invariant latitude. The corotating radar observed a patch of enhanced electron density and elevated electron temperature in the F2 region between about 10.5 and 12 magnetic local time in the same invariant latitude range where DMSP-F7 detected the soft-electron flux. The ion drift pattern, also obtained by radar, shows that it is unlikely that the plasma patch was produced by solar radiation and advected into the radar field of view. We suggest that the radar observed modifications of the ionospheric plasma distribution, which resulted from direct entry of magnetosheath electrons into the magnetosphere and down to ionospheric altitudes. Model calculations of the ionospheric response to the observed electron flux support our interpretation.

  19. Tristatic observations of meteors using the 930 MHz European Incoherent Scatter radar system

    NASA Astrophysics Data System (ADS)

    Janches, Diego; Pellinen-Wannberg, Asta; Wannberg, Gudmund; Westman, Assar; HäGgströM, Ingemar; Meisel, David D.

    2002-11-01

    We report results from the first tristatic measurements of radar meteors obtained during 17 November 1997 and 1998, using the UHF (930 MHz) European Incoherent Scatter (EISCAT) radar system. The observing technique utilized for these observations was first reported by [1998a]. This system consists of three 32-m parabolic antennae located in northern Scandinavia. Since EISCAT observes mostly meteor head echoes, a general characteristic of high-power/large-aperture radars, direct Doppler velocity (±1 km/s) determinations are possible. In addition, using the technique reported here, absolute geocentric meteor velocity and good radiant information (±5°) are deduced for those meteors that are detected simultaneously by all three receivers. An overview of the methodology and a summary of the results obtained so far are reported in this work. We compare the results obtained using this method with those reported by previous large-aperture meteor radar work at lower frequencies and find general agreement. EISCAT detects mainly sporadic particles extending the fast daily sporadic micrometeor storms first suggested by [2000b] and [2001] to submillimeter particles. To the best of our knowledge, these observations represent the first of their kind and prove EISCAT to be a crucial instrument for the study of extraterrestrial particles entering the Earth's atmosphere, in particular at very high geocentric latitudes and high geocentric speeds.

  20. Millstone Hill incoherent scatter F region observations during the disturbances of June 1991

    SciTech Connect

    Buonsanto, M.J.

    1995-04-01

    The extreme geomagnetic disturbances of early June 1991 were accompanied by dramatic effects in the Earth`s thermosphere and ionosphere which are the subject of coordinated analysis by the Coupling, Energetics, and Dynamics of Atmospheric Regions (CEDAR) Storm Study project. F region observations taken at Millstone Hill over the interval June 5-11 using a nine-position experiment allow estimation of spatial gradients in ionospheric parameters above the station. From these gradients the motion term in the F region continuity equation is obtained and combined with calculations of rates of production and loss of the major ions in a semiempirical model of the F region ionosphere above Millstone Hill. Electron densities calculated from this semiempirical model using MSIS-86 are generally much smaller than the measurements. This discrepancy could be explained by the presence of vibrationally excited N{sub 2} combined with a decrease in the atomic oxygen to molecular composition ratio of {approx}2 or more on the most disturbed days. Neutral winds calculated by using the incoherent scatter line-of-sight ion drifts show a strong equatorward surge during the day on June 5 and strong equatorward surges during all the disturbed nights. Synoptic observations taken from Millstone Hill by using elevation and azimuth scans during the nights of June 12, 13, and 14 illustrate the large-scale structure of electron density and its relation to neutral winds and electric fields observed over much of eastern North America. 58 refs., 12 figs., 1 tab.

  1. Momentum Flux Determination Using the Multi-beam Poker Flat Incoherent Scatter Radar

    NASA Technical Reports Server (NTRS)

    Nicolls, M. J.; Fritts, D. C.; Janches, Diego; Heinselman, C. J.

    2012-01-01

    In this paper, we develop an estimator for the vertical flux of horizontal momentum with arbitrary beam pointing, applicable to the case of arbitrary but fixed beam pointing with systems such as the Poker Flat Incoherent Scatter Radar (PFISR). This method uses information from all available beams to resolve the variances of the wind field in addition to the vertical flux of both meridional and zonal momentum, targeted for high-frequency wave motions. The estimator utilises the full covariance of the distributed measurements, which provides a significant reduction in errors over the direct extension of previously developed techniques and allows for the calculation of an error covariance matrix of the estimated quantities. We find that for the PFISR experiment, we can construct an unbiased and robust estimator of the momentum flux if sufficient and proper beam orientations are chosen, which can in the future be optimized for the expected frequency distribution of momentum-containing scales. However, there is a potential trade-off between biases and standard errors introduced with the new approach, which must be taken into account when assessing the momentum fluxes. We apply the estimator to PFISR measurements on 23 April 2008 and 21 December 2007, from 60-85 km altitude, and show expected results as compared to mean winds and in relation to the measured vertical velocity variances.

  2. The Science and Utility of Extended Runs and the Future Development of Incoherent Scatter Radar Observational Programs

    NASA Astrophysics Data System (ADS)

    van Eyken, T.

    2006-12-01

    Incoherent Scatter Radar (ISR) data represent the most comprehensive observations of the temporal behavior of the main parts of the ionosphere, and the associated atmosphere, available. As such, the radars are invaluable tools in characterizing the ionospheric response to energy flows in the Solar-Terrestrial system. Developments in radar operations and reliability now allow very extended data sets to be produced on a fairly routine basis and plans for the International Polar Year (IPY) include the continuous operation of at least one high latitude radar. Using data from two very different 30-day `World Day' co-ordinated observation periods in Autumn 2005 and Spring 2006, we illustrate the utility of such data sets for, inter alia, space weather observation and modeling and discuss the possible future development of such programs using the EISCAT Svalbard Radar, the soon to be completed Advanced Modular Incoherent Scatter Radar (AMISR), and the EISCAT_3D radar (currently being designed).

  3. Incoherent scattering of 137Cs gamma rays in the rare earth elements Nd, Sm, Gd, Dy, Er and Yb

    NASA Astrophysics Data System (ADS)

    Krishnaveni, S.; Gowda, Shivalinge; Yashoda, T.; Umesh, T. K.; Gowda, Ramakrishna

    2005-09-01

    The differential incoherent scattering cross sections for 661.6 keV photons have been measured with an HPGe detector in the momentum range 4⩽x⩽46 Å-1 for the rare earth elements Nd, Sm, Gd, Dy, Er and Yb. The incoherent scattering functions were evaluated from the measured cross sections and compared with the NRHF values of Hubbel et al. [1975, J. Phys. Chem. Ref. Data 4, 471], the recent DHFR values of Kahane [1998, At. Data Nucl. Data Tables 68, 323] and other measured values. The present experimental values are systematically lower than the theoretical predictions, but show a good agreement within the experimental errors except for the momentum transfers of 30.59, 34.29 and 37.72 Å -1 for Nd, 43.69 Å -1 for Gd and 22.54 and 26.66 Å -1 for Dy, which show deviations at the two sigma level.

  4. Direct comparison of elastic incoherent neutron scattering experiments with molecular dynamics simulations of DMPC phase transitions.

    PubMed

    Aoun, Bachir; Pellegrini, Eric; Trapp, Marcus; Natali, Francesca; Cantù, Laura; Brocca, Paola; Gerelli, Yuri; Demé, Bruno; Marek Koza, Michael; Johnson, Mark; Peters, Judith

    2016-04-01

    Neutron scattering techniques have been employed to investigate 1,2-dimyristoyl-sn -glycero-3-phosphocholine (DMPC) membranes in the form of multilamellar vesicles (MLVs) and deposited, stacked multilamellar-bilayers (MLBs), covering transitions from the gel to the liquid phase. Neutron diffraction was used to characterise the samples in terms of transition temperatures, whereas elastic incoherent neutron scattering (EINS) demonstrates that the dynamics on the sub-macromolecular length-scale and pico- to nano-second time-scale are correlated with the structural transitions through a discontinuity in the observed elastic intensities and the derived mean square displacements. Molecular dynamics simulations have been performed in parallel focussing on the length-, time- and temperature-scales of the neutron experiments. They correctly reproduce the structural features of the main gel-liquid phase transition. Particular emphasis is placed on the dynamical amplitudes derived from experiment and simulations. Two methods are used to analyse the experimental data and mean square displacements. They agree within a factor of 2 irrespective of the probed time-scale, i.e. the instrument utilized. Mean square displacements computed from simulations show a comparable level of agreement with the experimental values, albeit, the best match with the two methods varies for the two instruments. Consequently, experiments and simulations together give a consistent picture of the structural and dynamical aspects of the main lipid transition and provide a basis for future, theoretical modelling of dynamics and phase behaviour in membranes. The need for more detailed analytical models is pointed out by the remaining variation of the dynamical amplitudes derived in two different ways from experiments on the one hand and simulations on the other. PMID:27112937

  5. Poker Flat Incoherent Scatter Radar observations of anomalous electron heating in the E region

    NASA Astrophysics Data System (ADS)

    Makarevich, R. A.; Koustov, A. V.; Nicolls, M. J.

    2013-07-01

    A comprehensive 2-year dataset collected with the Poker Flat Incoherent Scatter Radar (PFISR) located near Fairbanks, Alaska (MLAT = 65.4° N) is employed to identify and analyse 22 events of anomalous electron heating (AEH) in the auroral E region. The overall AEH occurrence probability is conservatively estimated to be 0.3% from nearly-continuous observations of the E region by PFISR, although it increases to 0.7-0.9% in the dawn and dusk sectors where all AEH events were observed. The AEH occurrence variation with MLT is broadly consistent with those of events with high convection velocity (>1000 m s-1) or electron temperature (> 800 K), except for much smaller AEH probability and absence of AEH events near magnetic midnight. This suggests that high convection electric field by itself is necessary but not sufficient for measurable electron heating by two-stream plasma waves. The multi-point observations are utilised to investigate the fundamental dependence of the electron temperature on the convection electric field, focusing on the previously-proposed saturation effects at extreme electric fields. The AEH dataset was found to exhibit considerable scatter and, on average, similar rate of the electron temperature increase with the electric field up to 100 mV m-1 as compared with previous studies. At higher (highest) electric fields, the electron temperatures are below the linear trend on average (within uncertainty). By employing a simple fluid model of AEH, it is demonstrated that some of this deviation from the linear trend may be due to a stronger vibrational cooling at very large temperatures and electric fields.

  6. Long-range azimuthal correlations in proton–proton and proton–nucleus collisions from the incoherent scattering of partons

    SciTech Connect

    Ma, Guo -Liang; Bzdak, Adam

    2014-11-04

    In this study, we show that the incoherent elastic scattering of partons, as present in a multi-phase transport model (AMPT), with a modest parton–parton cross-section of σ = 1.5 – 3 mb, naturally explains the long-range two-particle azimuthal correlation as observed in proton–proton and proton–nucleus collisions at the Large Hadron Collider.

  7. A new High-level Gridded Madrigal Data Product for IPY Incoherent Scatter Radar Data and Model Output.

    NASA Astrophysics Data System (ADS)

    Holt, J. M.

    2008-12-01

    The World's high-latitude incoherent scatter radars are contributing to the International Polar Year (IPY) through an unprecedented set of long-duration runs. From March, 2007 through February, 2008 he EISCAT Svalbard Radar and the Poker Flat Incoherent Scatter Radar operated almost continuously and the Sondrestromfjord and Millstone Hill Radars ran on a regular biweekly schedule. These extensive data sets present a major data handling challenge as do the physics-based model runs covering this period. The radar data are all available through the distributed Madrigal Database. However, the radars employ different, sometimes complex, operating modes which can present a significant challenge to modelers and other users who are not experts in the incoherent scatter radar technique. We have addressed this problem by developing a higher level data product which casts the data from all the radars into an identical gridded form. Several modelers are also providing model output through Madrigal in the same format. For the radar data, tensor product cubic spline fits to the measured electron density, ion temperature and electron temperature are computed and output in Madrigal format at 15 minute intervals and a standard set of altitudes from 100 to 548 km. In addition, hmF2, integrated electron content and the neutral temperature are computed and included in the output Madrigal file. As an aid to studying day-to-day variability, files have been produced both for individual days of the year and monthly averages.

  8. Coherent Forward Stimulated-Brillouin Scattering of a Spatially Incoherent Laser Beam in a Plasma and Its Effect on Beam Spray

    SciTech Connect

    Grech, M.; Riazuelo, G.; Pesme, D.; Weber, S.; Tikhonchuk, V. T.

    2009-04-17

    A statistical model for forward stimulated-Brillouin scattering is developed for a spatially incoherent, monochromatic, laser beam propagating in a plasma. The threshold above which the laser beam spatial incoherence cannot prevent the coherent growth of forward stimulated-Brillouin scattering is computed. It is found to be well below the threshold for self-focusing. Three-dimensional simulations confirm its existence and reveal the onset of beam spray above it. From these results, we propose a new figure of merit for the control of propagation through a plasma of a spatially incoherent laser beam.

  9. Effect of incoherent scattering on three-terminal quantum Hall thermoelectrics

    NASA Astrophysics Data System (ADS)

    Sánchez, Rafael; Sothmann, Björn; Jordan, Andrew N.

    2016-01-01

    A three-terminal conductor presents peculiar thermoelectric and thermal properties in the quantum Hall regime: it can behave as a symmetric rectifier and as an ideal thermal diode. These properties rely on the coherent propagation along chiral edge channels. We investigate the effect of breaking the coherent propagation by the introduction of a probe terminal. It is shown that chiral effects not only survive the presence of incoherence but they can even improve the thermoelectric performance in the totally incoherent regime.

  10. Reprint of : Effect of incoherent scattering on three-terminal quantum Hall thermoelectrics

    NASA Astrophysics Data System (ADS)

    Sánchez, Rafael; Sothmann, Björn; Jordan, Andrew N.

    2016-08-01

    A three-terminal conductor presents peculiar thermoelectric and thermal properties in the quantum Hall regime: it can behave as a symmetric rectifier and as an ideal thermal diode. These properties rely on the coherent propagation along chiral edge channels. We investigate the effect of breaking the coherent propagation by the introduction of a probe terminal. It is shown that chiral effects not only survive the presence of incoherence but they can even improve the thermoelectric performance in the totally incoherent regime.

  11. Resolute Bay Incoherent Scatter Radar observations of plasma structures in the vicinity of polar holes

    NASA Astrophysics Data System (ADS)

    Makarevich, Roman A.; Lamarche, L. J.; Nicolls, M. J.

    2015-09-01

    The Resolute Bay Incoherent Scatter Radar North (RISR-N) data collected between January 2012 and June 2013 are employed to identify and analyze 14 events with significant plasma density depressions (Ne<4 × 1010 m-3) in the winter polar cap ionosphere. The RISR-N observations near a magnetic latitude (MLAT) of 85°N refer to the region poleward of the previously identified polar hole-auroral cavity region 70°-80° MLAT where extremely low densities (down to 2 × 108 m-3 near 300 km in altitude) are found at times. Multipoint observations by RISR-N are also characterized by multiple series of propagating local density enhancements (plasma structures) both well outside and in the vicinity of polar holes. A superposed epoch analysis of plasma density and convection reveals that the density depressions tend to reach their minimum near the reversal of the meridional convection component. The wavelet analysis of plasma density time series shows that the wave power is enhanced within the depressions and tends to peak near the density minimum. The plasma structures are more elongated at mesoscales (>150 km), with no apparent differences between structure shapes outside and inside low-density regions. The structure propagation velocity is perpendicular to its elongation direction and consistent with that of the large-scale plasma convection. The observations indicate that large-scale density depressions can form under a variety of convection conditions and that plasma structuring processes outside the depressions may be responsible for their partial filling.

  12. Poker Flat Incoherent Scatter Radar investigations of the nighttime E-region

    NASA Astrophysics Data System (ADS)

    Whittier, Robin L.

    Plasma within the ionosphere affects technology, such as long distance communications and satellite navigation, by scattering and altering the propagation of radio waves sent through the ionosphere. Understanding the structure and dynamics of the ionosphere that may interfere with modern technology is therefore an important aspect of Space Weather research. In this thesis, the average characteristics and dynamics of the nighttime E-region (90-150 km in altitude) are investigated during auroral disturbances and near extreme solar minimum. The near-continuous data on electron density obtained with the Poker Flat Incoherent Scatter Radar (PFISR) near Fairbanks, Alaska are utilized. A number of correlation analyses between E-region electron content and AE index are performed in order to examine the influence of geomagnetic conditions on the E-region in relation to time of the day as well as seasonal and solar cycle effects. It is shown that E-region electron content and AE index exhibit significant positive correlation, particularly near local magnetic midnight, with greater correlation generally occurring in spring and autumn. The midnight feature is interpreted as an indication that the electrojet system near midnight is mostly controlled by electric conductance. The presented statistical results on the current-conductance relationship utilizing a new dataset strengthen conclusions derived from previous studies. The extent of E-region contribution to the total electron content (TEC) is also estimated and investigated for various conditions for the first time using the full altitude profile of PFISR. The estimates ranged between 5%-60% and more active periods generally displayed a more significant contribution from the E-region to TEC. Additionally, using the AE index as an indicator of auroral disturbance onset, the evolution of auroral density enhancements is explored using the superposed epoch analysis technique. The behavior of E-region electron content, peak

  13. Vibrational dynamics in dendridic oligoarylamines by Raman spectroscopy and incoherent inelastic neutron scattering.

    PubMed

    Kulszewicz-Bajer, Irena; Louarn, Guy; Djurado, David; Skorka, Lukasz; Szymanski, Marek; Mevellec, Jean Yves; Rols, Stephane; Pron, Adam

    2014-05-15

    Vibrational dynamics in triarylamine dendrimers was studied in a complementary way by Raman and infrared (IR) spectroscopies and incoherent inelastic neutron scattering (IINS). Three molecules were investigated, namely, unsubstituted triarylamine dendrimer of the first generation and two dendrimers of the first and second generation, substituted in the crown with butyl groups. To facilitate the assignment of the observed IR and Raman modes as well as the IINS peaks, vibrational models, based on the general valence force field method (GVFF), were calculated for all three compounds studied. A perfect consistency between the calculated and experimental results was found. Moreover, an important complementarity of the vibrational spectroscopies and IINS was established for the investigated dendrimers. The IINS peaks originating mainly from the C-H motions were not restricted by particular selection rules and only dependent on the IINS cross section. To the contrary, Raman and IR bands were imposed by the selection rules and the local geometry of the dendrimers yielding mainly C-C and C-N deformation modes with those of C-H nature of much lower intensity. Raman spectroscopy was also applied to the studies of the oxidation of dendrimers to their cationic forms. A strong Raman resonance effect was observed, since the spectra of the studied compounds, registered at different levels of their oxidation, strongly depended on the position of the excitation line with respect to their electronic spectrum. In particular, the blue (458 nm) excitation line turned out to be insensitive toward the cationic forms yielding very limited spectral information. To the contrary, the use of the red (647 nm) and infrared (1064 nm) excitation lines allowed for an unambiguous monitoring of the spectral changes in dendrimers oxidized to nominally monocationic and tricationic states. The analysis of oxidation-induced spectral changes in the tricationic state indicated that the charge storage

  14. Demodulation Algorithms for the Ofdm Signals in the Time- and Frequency-Scattering Channels

    NASA Astrophysics Data System (ADS)

    Bochkov, G. N.; Gorokhov, K. V.; Kolobkov, A. V.

    2016-06-01

    We consider a method based on the generalized maximum-likelihood rule for solving the problem of reception of the signals with orthogonal frequency division multiplexing of their harmonic components (OFDM signals) in the time- and frequency-scattering channels. The coherent and incoherent demodulators effectively using the time scattering due to the fast fading of the signal are developed. Using computer simulation, we performed comparative analysis of the proposed algorithms and well-known signal-reception algorithms with equalizers. The proposed symbolby-symbol detector with decision feedback and restriction of the number of searched variants is shown to have the best bit-error-rate performance. It is shown that under conditions of the limited accuracy of estimating the communication-channel parameters, the incoherent OFDMsignal detectors with differential phase-shift keying can ensure a better bit-error-rate performance compared with the coherent OFDM-signal detectors with absolute phase-shift keying.

  15. Revolutionising incoherent scatter science with EISCAT_3D: A European three-dimensional imaging radar for atmospheric and geospace research

    NASA Astrophysics Data System (ADS)

    Turunen, Esa; McCrea, Ian; Kosch, Mike

    2010-05-01

    from the active site respectively, on baselines running East and South from the active core, is enivisaged. This provides an optimal geometry for calculation of vector velocities in the middle and upper atmosphere. The gain of the EISCAT_3D antennas and the large size of the active site arrays will deliver an enormous increase in the figure-of-merit relative to any of EISCAT's existing radars. An active site of 5,000 elements would already exceed the performance of the current EISCAT VHF system, while an active site comprising 16,000 elements, as suggested in the Design Study carried out from 2005 to 2009, will exceed the sensitivity of the present VHF radar by an order of magnitude. Each transmitter unit will have its own signal generator, allowing the generation and transmission of arbitrary waveforms, limited only by the available transmission bandwidth and spectrum allocation by the frequency management authorities. This unique innovation allows the implementation of all currently used and envisaged modulation schemes and antenna codings (such as polyphase alternating codes, array tapering, orbital angular momentum beams) and also provides the possibility to adopt any kind of future code. In addition, it will allow advanced clutter mitigation strategies such as adaptive null steering and null shaping. In this talk the upper atmosphere and geospace science case for EISCAT_3D is reviewed. Studies of the atmospheric energy budget, space plasma physics with both small-scale structures and large-scale processes, as well as geospace environment monitoring and possible service applications are reviewed, showing recent highlights from the current EISCAT incoherent scatter radars for comparison.

  16. High power incoherent beam combining of fiber lasers based on a 7 × 1 all-fiber signal combiner

    NASA Astrophysics Data System (ADS)

    Zhou, Xuanfeng; Chen, Zilun; Wang, Zefeng; Hou, Jing; Xu, Xiaojun

    2016-05-01

    We report an experiment of incoherent beam combining based on a 7×1 all-fiber signal combiner with output power up to 6.08 kW. Properties of transmission efficiency and beam quality are analyzed by beam propagation method. Based on the calculative results, a 7×1 all-fiber signal combiner is fabricated. The handle power capacity is tested with average transmission efficiency of 98.9% and beam quality of M2≈10.

  17. Disorder-induced incoherent scattering losses in photonic crystal waveguides: Bloch mode reshaping, multiple scattering, and breakdown of the Beer-Lambert law

    NASA Astrophysics Data System (ADS)

    Patterson, M.; Hughes, S.; Schulz, S.; Beggs, D. M.; White, T. P.; O'Faolain, L.; Krauss, T. F.

    2009-11-01

    Through a combined theoretical and experimental study of disorder-induced incoherent scattering losses in slow-light photonic crystal slab waveguides, we show the importance of Bloch mode reshaping and multiple scattering. We describe a convenient and fully three-dimensional theoretical treatment of disorder-induced extrinsic scattering, including the calculation of backscatter and out-of-plane losses per unit cell, and the extrapolation of the unit-cell loss to the loss for an entire disordered waveguide. The theoretical predictions, which are also compared with recent measurements on dispersion engineered silicon waveguides, demonstrate the failure of the Beer-Lambert law due to multiple scattering. We also explain why the previously assumed group velocity scalings of disorder-induced loss break down in general.

  18. The incoherent scattering of radio waves in a non-Maxwellian plasma: The effects of Coulomb collisions

    SciTech Connect

    Tereshchenko, V.D.; Tereshchanko, E.D. ); Kohl, H. )

    1991-10-01

    In this paper the formulas for the ion distribution as well as the spectrum of radio waves scattered in a magnetized plasma with a strong electric field are derived. It is shown that the presence of the electric field in the ionosphere leads to an anisotropic ion velocity distribution and, therefore, to untypical incoherent scatter spectra for the F region of the polar ionosphere which are caused by ion-neutral together with ion-ion collisions. The effect of ion-ion collisions, which has not been taken into account so far, is to reduce the anisotropy of the ion velocity distribution. Estimates of the ion-ion collision frequency derived from EISCAT measurements show that this may happen above about 300 km.

  19. Comparison of incoherent scatter radar observations of SIMPLEX electron density depletion with SAMI2 and SAMI3 model results

    NASA Astrophysics Data System (ADS)

    Bhatt, A.; Huba, J. D.; Bernhardt, P. A.; Erickson, P. J.

    2010-12-01

    The Space Shuttle's Orbital Maneuvering System (OMS) engines have been used for active ionospheric modification experiments employing ground based ionospheric radars as diagnostic tools. These experiments initiated by the Naval Research Laboratory in 1995 have been scheduled as the Shuttle Ionospheric Modification with Pulsed Localized Exhaust or SIMPLEX through the US Dept. of Defense's Space Test Program. During 2009, two SIMPLEX experiments with the shuttles STS-119 and STS-128 were viewed by the Millstone Hill 440 MHz radar in Westford, MA operated by the MIT Haystack Observatory. The objectives of these experiments were to observe local ion-acoustic turbulence and the ionospheric density irregularities created by the exhaust injection across the magnetic field that present a Bragg scattering target for the radar. The exhaust also creates a depletion in the background electron density at F-region altitudes that persists for a relatively long time and is readily detected by an incoherent scatter radar. The OMS engine burns release 10 kg/s of H2O, CO2, H2, and N2 molecules that charge exchange with ambient O+ ions at the F region heights, producing molecular ions and the electron density depletion due to the recombination with the ambient electrons. 2009 was a year of deep solar minimum that saw the background electron density values 19% lower than were expected during a solar minimum. (Emmert et al., GRL, 2010). We believe that the long recovery time from density depletion in SIMPLEX experiments of 2009 may have a root in the unique nature of the deep solar minimum. The density whole production and recovery will be modeled using NRL SAMI2 and SAMI3 model and the results will be discussed along with the observations using the incoherent scatter radar.

  20. A Study on Various Meteoroid Disintegration Mechanisms as Observed from the Resolute Bay Incoherent Scatter Radar (RISR)

    NASA Technical Reports Server (NTRS)

    Malhotra, A.; Mathews, J. D.

    2011-01-01

    There has been much interest in the meteor physics community recently regarding the form that meteoroid mass flux arrives in the upper atmosphere. Of particular interest are the relative roles of simple ablation, differential ablation, and fragmentation in the meteoroid mass flux observed by the Incoherent Scatter Radars (ISR). We present here the first-ever statistical study showing the relative contribution of the above-mentioned three mechanisms. These are also one of the first meteor results from the newly-operational Resolute Bay ISR. These initial results emphasize that meteoroid disintegration into the upper atmosphere is a complex process in which all the three above-mentioned mechanisms play an important role though fragmentation seems to be the dominant mechanism. These results prove vital in studying how meteoroid mass is deposited in the upper atmosphere which has important implications to the aeronomy of the region and will also contribute in improving current meteoroid disintegration/ablation models.

  1. Storm-induced changes of the topside ionosphere as deduced from incoherent-scatter radars. Master's thesis

    SciTech Connect

    Lunn, K.J.

    1990-01-01

    Incoherent scatter radar observations from Millstone Hill, Saint Santin, and Arecibo are used to illustrate changes of the topside ionosphere during a geomagnetic storm. These observations consist of electron density, electron and ion temperatures, and ion velocity components parallel and perpendicular to the magnetic field. These parameters can further describe changes in ion composition, electric fields, and neutral winds. Attention is given to a specific storm during the Equinox Transition Study (ETS) of September 1984. In order to isolate the storm effects in the topside ionosphere, a comparison will be made between a disturbed and quiet day. A novel result from this study is the finding of correlated oscillations between parallel and perpendicular ion velocity components which are apparently storm induced. Previously, these oscillations have been observed primarily at night, but now it's noticed that during storm conditions there are prominent oscillations during the day.

  2. The Madrigal Virtual Observatory - a Fabric for Serving Both Incoherent Scatter and MST Radar Data to the CAWSES Science Community

    NASA Astrophysics Data System (ADS)

    Holt, J. M.; Goncharenko, L. P.; Rideout, W.; Palo, S.

    2006-12-01

    Madrigal is a distributed, open source virtual observatory which has been operational for 25 years. During that time it has evolved from a simple database system for the Millstone Hill Incoherent Scatter Radar to a full-featured virtual observatory distributed among five major sites. Madrigal features interoperability with the CEDAR Database, a well-defined metadata standard, real-time capability, an interactive Web interface, provision for linking ancillary information such as html pages and figures to data, interactive plotting and a complete Web-services interface. Madrigal is the primary data repository for incoherent scatter radar data. It also contains data from a variety of other ground-based space science instruments. This paper focuses on the addition of a substantial body of meteor wind and MF radar to Madrigal in support of the CAWSES program. An initial scientific investigation using this data is now underway at MIT Haystack Observatory. Analysis of the Millstone Hill ISR (42.6 deg N, 288.5 deg E) data for the September 2005 campaign indicated that both zonal and meridional components of the neutral wind in the lower thermosphere (100-130 km) have significantly higher tidal variations than average fall equinox winds. This difference might be related to interannual variability in tidal components, the sources of which are not fully understood. Previous studies have demonstrated interannual variability in the diurnal tide in mesospheric (~80-100 km) data at low latitudes and related it to quasi-biennial oscillations. To date, there is not sufficient information about interannual variability at middle latitudes, where the diurnal tide is expected to diminish. We are using MF and meteor radar data collected during the September-October 2005 CAWSES campaign to bound the geographical and altitudinal extend of this phenomena, quantify observed variability, and assess possible mechanisms leading to the observed phenomena.

  3. A novel hybrid reconstruction algorithm for first generation incoherent scatter CT (ISCT) of large objects with potential medical imaging applications.

    PubMed

    Alpuche Aviles, Jorge E; Pistorius, Stephen; Gordon, Richard; Elbakri, Idris A

    2011-01-01

    This work presents a first generation incoherent scatter CT (ISCT) hybrid (analytic-iterative) reconstruction algorithm for accurate ρ{e}imaging of objects with clinically relevant sizes. The algorithm reconstructs quantitative images of ρ{e} within a few iterations, avoiding the challenges of optimization based reconstruction algorithms while addressing the limitations of current analytical algorithms. A 4π detector is conceptualized in order to address the issue of directional dependency and is then replaced with a ring of detectors which detect a constant fraction of the scattered photons. The ISCT algorithm corrects for the attenuation of photons using a limited number of iterations and filtered back projection (FBP) for image reconstruction. This results in a hybrid reconstruction algorithm that was tested with sinograms generated by Monte Carlo (MC) and analytical (AN) simulations. Results show that the ISCT algorithm is weakly dependent on the ρ{e} initial estimate. Simulation results show that the proposed algorithm reconstruct ρ{e} images with a mean error of -1% ± 3% for the AN model and from -6% to -8% for the MC model. Finally, the algorithm is capable of reconstructing qualitatively good images even in the presence of multiple scatter. The proposed algorithm would be suitable for in-vivo medical imaging as long as practical limitations can be addressed. PMID:21422588

  4. Fast, quantitative, and nondestructive evaluation of hydrided LWR fuel cladding by small angle incoherent neutron scattering of hydrogen

    DOE PAGESBeta

    Yan, Y.; Qian, S.; Littrell, K.; Parish, C. M.; Plummer, L. K.

    2015-02-13

    A non-destructive neutron scattering method to precisely measure the uptake of hydrogen and the distribution of hydride precipitates in light water reactor (LWR) fuel cladding was developed. Zircaloy-4 cladding used in commercial LWRs was used to produce hydrided specimens. The hydriding apparatus consists of a closed stainless steel vessel that contains Zr alloy specimens and hydrogen gas. Following hydrogen charging, the hydrogen content of the hydrided specimens was measured using the vacuum hot extraction method, by which the samples with desired hydrogen concentration were selected for the neutron study. Optical microscopy shows that our hydriding procedure results in uniform distributionmore » of circumferential hydrides across the wall. Small angle neutron incoherent scattering was performed in the High Flux Isotope Reactor at Oak Ridge National Laboratory. This study demonstrates that the hydrogen in commercial Zircaloy-4 cladding can be measured very accurately in minutes by this nondestructive method over a wide range of hydrogen concentrations from a very small amount ( 20 ppm) to over 1000 ppm. The hydrogen distribution in a tube sample was obtained by scaling the neutron scattering rate with a factor determined by a calibration process using standard, destructive direct chemical analysis methods on the specimens. This scale factor will be used in future tests with unknown hydrogen concentrations, thus providing a nondestructive method for absolute hydrogen concentration determination.« less

  5. Fast, quantitative, and nondestructive evaluation of hydrided LWR fuel cladding by small angle incoherent neutron scattering of hydrogen

    SciTech Connect

    Yan, Y.; Qian, S.; Littrell, K.; Parish, C. M.; Plummer, L. K.

    2015-02-13

    A non-destructive neutron scattering method to precisely measure the uptake of hydrogen and the distribution of hydride precipitates in light water reactor (LWR) fuel cladding was developed. Zircaloy-4 cladding used in commercial LWRs was used to produce hydrided specimens. The hydriding apparatus consists of a closed stainless steel vessel that contains Zr alloy specimens and hydrogen gas. Following hydrogen charging, the hydrogen content of the hydrided specimens was measured using the vacuum hot extraction method, by which the samples with desired hydrogen concentration were selected for the neutron study. Optical microscopy shows that our hydriding procedure results in uniform distribution of circumferential hydrides across the wall. Small angle neutron incoherent scattering was performed in the High Flux Isotope Reactor at Oak Ridge National Laboratory. This study demonstrates that the hydrogen in commercial Zircaloy-4 cladding can be measured very accurately in minutes by this nondestructive method over a wide range of hydrogen concentrations from a very small amount ( 20 ppm) to over 1000 ppm. The hydrogen distribution in a tube sample was obtained by scaling the neutron scattering rate with a factor determined by a calibration process using standard, destructive direct chemical analysis methods on the specimens. This scale factor will be used in future tests with unknown hydrogen concentrations, thus providing a nondestructive method for absolute hydrogen concentration determination.

  6. Motional heterogeneity in human acetylcholinesterase revealed by a non-Gaussian model for elastic incoherent neutron scattering

    NASA Astrophysics Data System (ADS)

    Peters, Judith; Kneller, Gerald R.

    2013-10-01

    We study the dynamical transition of human acetylcholinesterase by analyzing elastic neutron scattering data with a simulation gauged analytical model that goes beyond the standard Gaussian approximation for the elastic incoherent structure factor [G. R. Kneller and K. Hinsen, J. Chem. Phys. 131, 045104 (2009)]. The model exploits the whole available momentum transfer range in the experimental data and yields not only a neutron-weighted average of the atomic mean square position fluctuations, but also an estimation for their distribution. Applied to the neutron scattering data from human acetylcholinesterase, it reveals a strong increase of the motional heterogeneity at the two transition temperatures T = 150 K and T = 220 K, respectively, which can be located with less ambiguity than with the Gaussian model. We find that the first transition is essentially characterized by a change in the form of the elastic scattering profile and the second by a homogeneous increase of all motional amplitudes. These results are in agreement with previous combined experimental and simulation studies of protein dynamics, which attribute the first transition to an onset of methyl rotations and the second to more unspecific diffusion processes involving large amplitude motions.

  7. Coherent effects in the incoherent channel of resonant radiation scattering from excited atoms

    SciTech Connect

    Veklenko, B. A.

    2011-05-15

    Scattering of a resonance electromagnetic field from excited atoms cannot be described by the semiclassical theory of radiation operating with nonquantized electromagnetic fields. Field quantization effects are manifested in this case on the macroscopic level and lead to evolution of statistical properties of radiation in the course of scattering. It is found that a combined process coupling elastic scattering from an atom and induced emission from the same atom, which cannot be studied by the methods of the standard perturbation theory, plays a significant role in this effect. The process of combined scattering in extended media exhibits coherent properties that cannot be described by the standard refractive index.

  8. Statistical Signal Processing Methods in Scattering and Imaging

    NASA Astrophysics Data System (ADS)

    Zambrano Nunez, Maytee

    This Ph.D. dissertation project addresses two related topics in wave-based signal processing: 1) Cramer-Rao bound (CRB) analysis of scattering systems formed by pointlike scatterers in one-dimensional (1D) and three-dimensional (3D) spaces. 2) Compressive optical coherent imaging, based on the incorporation of sparsity priors in the reconstructions. The first topic addresses for wave scattering systems in 1D and 3D spaces the information content about scattering parameters, in particular, the targets' positions and strengths, and derived quantities, that is contained in scattering data corresponding to reflective, transmissive, and more general sensing modalities. This part of the dissertation derives the Cramer-Rao bound (CRB) for the estimation of parameters of scalar wave scattering systems formed by point scatterers. The results shed light on the fundamental difference between the approximate Born approximation model for weak scatterers and the more general multiple scattering model, and facilitate the identification of regions in parameter space where multiple scattering facilitates or obstructs the estimation of parameters from scattering data, as well as of sensing configurations giving maximal or minimal information about the parameters. The derived results are illustrated with numerical examples, with particular emphasis on the imaging resolution which we quantify via a relative resolution index borrowed from a previous paper. Additionally, this work investigates fundamental limits of estimation performance for the localization of the targets and the inverse scattering problem. The second topic of the effort describes a novel compressive-sensing-based technique for optical imaging with a coherent single-detector system. This hybrid opto-micro-electromechanical, coherent single-detector imaging system applies the latest developments in the nascent field of compressive sensing to the problem of computational imaging of wavefield intensity from a small number

  9. Scaling analysis of bio-molecular dynamics derived from elastic incoherent neutron scattering experiments

    SciTech Connect

    Doster, W.; Nakagawa, H.; Appavou, M. S.

    2013-07-28

    Numerous neutron scattering studies of bio-molecular dynamics employ a qualitative analysis of elastic scattering data and atomic mean square displacements. We provide a new quantitative approach showing that the intensity at zero energy exchange can be a rich source of information of bio-structural fluctuations on a pico- to nano-second time scale. Elastic intensity scans performed either as a function of the temperature (back-scattering) and/or by varying the instrumental resolution (time of flight spectroscopy) yield the activation parameters of molecular motions and the approximate structural correlation function in the time domain. The two methods are unified by a scaling function, which depends on the ratio of correlation time and instrumental resolution time. The elastic scattering concept is illustrated with a dynamic characterization of alanine-dipeptide, protein hydration water, and water-coupled protein motions of lysozyme, per-deuterated c-phycocyanin (CPC) and hydrated myoglobin. The complete elastic scattering function versus temperature, momentum exchange, and instrumental resolution is analyzed instead of focusing on a single cross-over temperature of mean square displacements at the apparent onset temperature of an-harmonic motions. Our method predicts the protein dynamical transition (PDT) at T{sub d} from the collective (α) structural relaxation rates of the solvation shell as input. By contrast, the secondary (β) relaxation enhances the amplitude of fast local motions in the vicinity of the glass temperature T{sub g}. The PDT is specified by step function in the elastic intensity leading from elastic to viscoelastic dynamic behavior at a transition temperature T{sub d}.

  10. Scaling analysis of bio-molecular dynamics derived from elastic incoherent neutron scattering experiments

    NASA Astrophysics Data System (ADS)

    Doster, W.; Nakagawa, H.; Appavou, M. S.

    2013-07-01

    Numerous neutron scattering studies of bio-molecular dynamics employ a qualitative analysis of elastic scattering data and atomic mean square displacements. We provide a new quantitative approach showing that the intensity at zero energy exchange can be a rich source of information of bio-structural fluctuations on a pico- to nano-second time scale. Elastic intensity scans performed either as a function of the temperature (back-scattering) and/or by varying the instrumental resolution (time of flight spectroscopy) yield the activation parameters of molecular motions and the approximate structural correlation function in the time domain. The two methods are unified by a scaling function, which depends on the ratio of correlation time and instrumental resolution time. The elastic scattering concept is illustrated with a dynamic characterization of alanine-dipeptide, protein hydration water, and water-coupled protein motions of lysozyme, per-deuterated c-phycocyanin (CPC) and hydrated myoglobin. The complete elastic scattering function versus temperature, momentum exchange, and instrumental resolution is analyzed instead of focusing on a single cross-over temperature of mean square displacements at the apparent onset temperature of an-harmonic motions. Our method predicts the protein dynamical transition (PDT) at Td from the collective (α) structural relaxation rates of the solvation shell as input. By contrast, the secondary (β) relaxation enhances the amplitude of fast local motions in the vicinity of the glass temperature Tg. The PDT is specified by step function in the elastic intensity leading from elastic to viscoelastic dynamic behavior at a transition temperature Td.

  11. Authentication of vegetable oils by confocal X-ray scattering analysis with coherent/incoherent scattered X-rays.

    PubMed

    Li, Fangzuo; Liu, Zhiguo; Sun, Tianxi

    2016-11-01

    This paper presents an alternative analytical method based on the Rayleigh to Compton scattering intensity ratio and effective atomic number for non-destructive identification of vegetable oils using confocal energy dispersive X-ray fluorescence and scattering spectrometry. A calibration curve for the Rayleigh to Compton scattering intensity ratio and effective atomic number was constructed on the basis of a reliable physical model for X-ray scattering. The content of light elements, which are "invisible" using X-ray fluorescence, can be calculated "by difference" from the calibration curve. In this work, we demonstrated the use of this proposed approach to identify complex organic matrices in different vegetable oils with high precision and accuracy. PMID:27211668

  12. Evidence for double incoherent Raman scattering in binary gas mixtures: SF{sub 6}-N{sub 2}

    SciTech Connect

    Verzhbitskiy, I. A.; Chrysos, M.; Rachet, F.; Kouzov, A. P.

    2010-01-15

    We report a collision-induced Raman band by room temperature gas mixtures of sulfur hexafluoride and nitrogen. The band is centered at the sum of the frequencies of the symmetric-stretching nu{sub 1} transition of SF{sub 6} and the fundamental transition of N{sub 2}, and its intensity scales as the product of the partial densities of the gases. The observed process is evidence of double incoherent Raman scattering (DRS) by SF{sub 6}-N{sub 2}, in which both molecules simultaneously undergo two Raman-allowed transitions. The band was found to be almost fully depolarized, in agreement with previous observations in other systems and with theoretical predictions. Its integrated intensity is about one-third higher than the total area predicted by the leading-order dipole-induced dipole model. This discrepancy suggests that DRS is a practical means of assessing the quality of intermolecular potential models, which, in the case of SF{sub 6}-N{sub 2}, is still believed to be not good enough. Our work is expected to open the door to a multitude of studies involving complicated processes encountered in nonpolar gases and their mixtures, which are of direct relevance to atmospheric research.

  13. Climatology of the O+ temperatures over Arecibo for the historical deep solar minimum using Incoherent Scatter Radar and airglow data.

    NASA Astrophysics Data System (ADS)

    Santos, P. T.; Brum, C. G. M.; Kerr, R.; Noto, J.

    2014-12-01

    At Arecibo Observatory (AO) a comprehensive description of the ionosphere and thermosphere environment is achieved by the synergy between the Incoherent Scatter Radar (ISR) and the optical instruments nested on site. An example of this synergy is present in his work where optical and radar techniques were reconciled in order to obtain the O+ temperature variability for 2008 and 2009. During this period, a historical deep solar minimum condition was registered with a remarkable absence of sunspots for a long period (translated into a decreasing in the EUV-UV irradiance). This particular feature implies in an important tool to investigate the variability of O+ temperature, once that any variation can be related to season (modulated by the neutral atmosphere) and/or another modulator different than solar energy input. The OII 7320 Å twilight airglow data used in this work were obtained during new moon periods using a high-spectral resolution Fabry-Perot Interferometer (FPI) with CCD array detection. The FPI was configured with 0.9 cm plate spacing, which produced a free spectral range of 0.298Å and a spectral resolution of 0.03Å, sufficient to sample line width temperatures as low as 500K. A very narrow 3Å Full Width at Half Maximum (FWHM) three-cavity interference filter was also used.

  14. Dynamic cusp at low altitudes: A case study utilizing viking, DMSP-F7, and Sondrestrom incoherent scatter radar observations

    SciTech Connect

    Watermann, J.; DeLaBeaujar, O.; Lummerzheim, D.; Woch, J.; Newell, P.T.

    1994-12-31

    Coincident multi-instrument magnetospheric and ionospheric observations have made it possible to determine the position of the ionospheric footprint of the magnetospheric cusp and to monitor its evolution over time. The data used include charged particle and magnetic field measurements from the Earth-orbiting Viking and DMSP-F7 satellites, electric field measurements from Viking, interplanetary magnetic field and plasma data from IMP-8 and Sondrestrom incoherent scatter radar observations of the ionospheric plasma density, temperature, and convection. Viking detected cusp precipitation poleward of 75.5 degrees invariant latitude. The ionospheric response to the observed electron precipitation was simulated using an auroral model. It predicts enhanced plasma density and elevated electron temperature in the upper E- and F-regions. Sondrestrom radar observations are in agreement with the predictions. The radar detected a cusp signature on each of five consecutive antenna elevation scans covering 1.2 h local time. The cusp appeared to be about 2 degrees invariant latitude wide, and its ionospheric footprint shifted equatorward by nearly 2 degrees during this time, possibly influenced by an overall decrease in the IMF B{sub Z} component The radar plasma drift data and the Viking magnetic and electric field data suggest that the cusp was associated with a continuous, rather than a patchy, merging between the IMF and the geomagnetic field.

  15. Energy dissipation drives the gradient signal amplification through an incoherent type-1 feed-forward loop

    NASA Astrophysics Data System (ADS)

    Lan, Ganhui

    2015-09-01

    We present here the analytical relation between the gain of eukaryotic gradient sensing network and the associated thermodynamic cost. By analyzing a general incoherent type-1 feed-forward loop, we derive the gain function (G ) through the reaction network and explicitly show that G depends on the nonequilibrium factor (0 ≤γ ≤1 with γ =0 and 1 representing irreversible and equilibrium reaction systems, respectively), the Michaelis constant (KM), and the turnover ratio (rcat) of the participating enzymes. We further find the maximum possible gain is intrinsically determined by KM/Gmax=(1 /KM+2 ) /4 . Our model also indicates that the dissipated energy (measured by -lnγ ), from the intracellular energy-bearing bioparticles (e.g., ATP), is used to generate a force field Fγ∝(1 -√{γ }) that reshapes and disables the effective potential around the zero gain region, which leads to the ultrasensitive response to external chemical gradients.

  16. A novel technique for studying F-region ionization patches with the Resolute Bay Incoherent Scatter Radar - North

    NASA Astrophysics Data System (ADS)

    Perry, G. W.; Hosokawa, K.; St-Maurice, J.; Shiokawa, K.

    2013-12-01

    The northward facing Resolute Bay Incoherent Scatter Radar - North (RISR-N) and the soon to be operational southward facing RISR-Canada (RISR-C) systems are both exceptional platforms for investigating F-region ionization patches and the polar ionosphere. To advance patch research using these systems, an algorithm has been developed for detecting F-region ionization patches with the RISR-N system. The algorithm is based on the definition of a patch put forward by Crowley [1996]: a volume of F-region plasma with a density that is twice that of the background ionosphere. In this work, the algorithm is applied to the sizeable RISR-N dataset, providing valuable insight into the prevalence of patches over Resolute Bay over a time frame of several years. Additional questions concerning patches are also addressed using the algorithm, including: when compared to each other, do the occurrence rates of patches identified by the Optical Mesosphere and Thermosphere Imagers (OMTI), Polar Dual Auroral Radar Network (PolarDARN) and RISR-N instruments (whose fields-of-view overlap over Resolute Bay) agree? Namely, for every patch that is detected with RISR-N and/or PolarDARN, is there a corresponding patch seen optically? Lastly, using the algorithm, is it possible to advance our ability to distinguish patches from other coherent backscatter echoes detected by PolarDARN? Crowley, G. (1996), Critical review of ionospheric patches and blobs, in Review of Radio Science: 1993-1996, edited by W. R. Stone, pp. 619 648, Oxford Univ. Press, Oxford, U. K.

  17. A model for water motion in crystals of lysozyme based on an incoherent quasielastic neutron-scattering study.

    PubMed Central

    Bon, C; Dianoux, A J; Ferrand, M; Lehmann, M S

    2002-01-01

    This paper reports an incoherent quasielastic neutron scattering study of the single particle, diffusive motions of water molecules surrounding a globular protein, the hen egg-white lysozyme. For the first time such an analysis has been done on protein crystals. It can thus be directly related and compared with a recent structural study of the same sample. The measurement temperature ranged from 100 to 300 K, but focus was on the room temperature analysis. The very good agreement between the structural and dynamical studies suggested a model for the dynamics of water in triclinic crystals of lysozyme in the time range approximately 330 ps and at 300 K. Herein, the dynamics of all water molecules is affected by the presence of the protein, and the water molecules can be divided into two populations. The first mainly corresponds to the first hydration shell, in which water molecules reorient themselves fivefold to 10-fold slower than in bulk solvent, and diffuse by jumps from hydration site to hydration site. The long-range diffusion coefficient is five to sixfold less than for bulk solvent. The second group corresponds to water molecules further away from the surface of the protein, in a second incomplete hydration layer, confined between hydrated macromolecules. Within the time scale probed they undergo a translational diffusion with a self-diffusion coefficient reduced approximately 50-fold compared with bulk solvent. As protein crystals have a highly crowded arrangement close to the packing of macromolecules in cells, our conclusion can be discussed with respect to solvent behavior in intracellular media: as the mobility is highest next to the surface, it suggests that under some crowding conditions, a two-dimensional motion for the transport of metabolites can be dominant. PMID:12202382

  18. High-latitude E Region Ionosphere-thermosphere Coupling: A Comparative Study Using in Situ and Incoherent Scatter Radar Observations

    NASA Technical Reports Server (NTRS)

    Burchill, J. K.; Clemmons, J. H.; Knudsen, D. J.; Larsen, M.; Nicolls, M. J.; Pfaff, R. F.; Rowland, D.; Sangalli, L.

    2012-01-01

    We present in situ and ground-based measurements of the ratio k of ion cyclotronangular frequency to ion-neutral momentum transfer collision frequency to investigateionosphere-thermosphere (IT) coupling in the auroral E region. In situ observations were obtained by NASA sounding rocket 36.234, which was launched into the nightsideE region ionosphere at 1229 UT on 19 January 2007 from Poker Flat, AK. The payload carried instrumentation to determine ion drift angle and electric field vectors. Neutral winds were measured by triangulating a chemical tracer released from rocket 41.064 launched two minutes later. k is calculated from the rotation of the ion drift angle relative to the E-cross-B drift direction in a frame co-rotating with the payload. Between the altitudes of 118 km and 130 km k increases exponentially with a scale height of 9.3 +/- 0.7 km, deviating from an exponential above 130 km. k = 1 at an altitude z(sub0) of 119.9 +/- 0.5 km. The ratio was also estimated from Poker Flat Incoherent Scatter Radar (PFISR) measurements using the rotation of ion velocity with altitude. Exponential fits to the PFISR measurements made during the flight of 41.064 yield z(sub0) 115.9 +/- 1.2 km and a scale height of 9.1 +/- 1.0 km. Differences between in situ and ground-based measurements show that the E region atmospheric densities were structured vertically and/or horizontally on scales of 1 km to 10 km. There were no signs of ionospheric structure in ion density or ion temperature below scales of 1 km. The observations demonstrate the accuracy with which the in situ and PFISR data may be used as probes of IT coupling.

  19. Energy dissipation drives the gradient signal amplification through an incoherent type-1 feed-forward loop.

    PubMed

    Lan, Ganhui

    2015-09-01

    We present here the analytical relation between the gain of eukaryotic gradient sensing network and the associated thermodynamic cost. By analyzing a general incoherent type-1 feed-forward loop, we derive the gain function (G) through the reaction network and explicitly show that G depends on the nonequilibrium factor (0≤γ≤1 with γ=0 and 1 representing irreversible and equilibrium reaction systems, respectively), the Michaelis constant (K_{M}), and the turnover ratio (r_{cat}) of the participating enzymes. We further find the maximum possible gain is intrinsically determined by K_{M}/G_{max}=(1/K_{M}+2)/4. Our model also indicates that the dissipated energy (measured by -lnγ), from the intracellular energy-bearing bioparticles (e.g., ATP), is used to generate a force field F_{γ}∝(1-sqrt[γ]) that reshapes and disables the effective potential around the zero gain region, which leads to the ultrasensitive response to external chemical gradients. PMID:26465493

  20. Spatially constrained incoherent motion method improves diffusion-weighted MRI signal decay analysis in the liver and spleen

    PubMed Central

    Taimouri, Vahid; Afacan, Onur; Perez-Rossello, Jeannette M.; Callahan, Michael J.; Mulkern, Robert V.; Warfield, Simon K.; Freiman, Moti

    2015-01-01

    Purpose: To evaluate the effect of the spatially constrained incoherent motion (SCIM) method on improving the precision and robustness of fast and slow diffusion parameter estimates from diffusion-weighted MRI in liver and spleen in comparison to the independent voxel-wise intravoxel incoherent motion (IVIM) model. Methods: We collected diffusion-weighted MRI (DW-MRI) data of 29 subjects (5 healthy subjects and 24 patients with Crohn’s disease in the ileum). We evaluated parameters estimates’ robustness against different combinations of b-values (i.e., 4 b-values and 7 b-values) by comparing the variance of the estimates obtained with the SCIM and the independent voxel-wise IVIM model. We also evaluated the improvement in the precision of parameter estimates by comparing the coefficient of variation (CV) of the SCIM parameter estimates to that of the IVIM. Results: The SCIM method was more robust compared to IVIM (up to 70% in liver and spleen) for different combinations of b-values. Also, the CV values of the parameter estimations using the SCIM method were significantly lower compared to repeated acquisition and signal averaging estimated using IVIM, especially for the fast diffusion parameter in liver (CVIV IM = 46.61 ± 11.22, CVSCIM = 16.85 ± 2.160, p < 0.001) and spleen (CVIV IM = 95.15 ± 19.82, CVSCIM = 52.55 ± 1.91, p < 0.001). Conclusions: The SCIM method characterizes fast and slow diffusion more precisely compared to the independent voxel-wise IVIM model fitting in the liver and spleen. PMID:25832079

  1. Characteristics of Poker Flat Incoherent Scatter Radar (PFISR) naturally enhanced ion-acoustic lines (NEIALs) in relation to auroral forms

    NASA Astrophysics Data System (ADS)

    Michell, R. G.; Grydeland, T.; Samara, M.

    2014-10-01

    Naturally enhanced ion-acoustic lines (NEIALs) have been observed with the Poker Flat Incoherent Scatter Radar (PFISR) ever since it began operating in 2006. The nearly continuous operation of PFISR since then has led to a large number of NEIAL observations from there, where common-volume, high-resolution auroral imaging data are available. We aim to systematically distinguish the different types of auroral forms that are associated with different NEIAL features, including spectral shape and altitude extent. We believe that NEIALs occur with a continuum of morphological characteristics, although we find that most NEIALs observed with PFISR fall into two general categories. The first group occurs at fairly low altitudes - F region or below - and have power at, and spread between, the ion-acoustic peaks. The second group contains the type of NEIALs that have previously been observed with the EISCAT radars, those that extend to high altitudes (600 km or more) and often have large asymmetries in the power enhancements between the two ion-acoustic shoulders. We find that there is a correlation between the auroral structures and the type of NEIALs observed, and that the auroral structures present during NEIAL events are consistent with the likely NEIAL generation mechanisms inferred in each case. The first type of NEIAL - low altitude - is the most commonly observed with PFISR and is most often associated with active, structured auroral arcs, such as substorm growth phase, and onset arcs and are likely generated by Langmuir turbulence. The second type of NEIAL - high altitude - occurs less frequently in the PFISR radar and is associated with aurora that contains large fluxes of low-energy electrons, as can happen in poleward boundary intensifications as well as at substorm onset and is likely the result of current-driven instabilities and in some cases Langmuir turbulence as well. In addition, a preliminary auroral photometry analysis revealed that there is an

  2. Coherent to incoherent cross section ratio for 59.54 keV gamma rays at scattering angle of 110°

    SciTech Connect

    Singh, M. P.; Singh, Bhajan; Sandhu, B. S.; Sharma, Amandeep

    2015-08-28

    The coherent (Rayleigh) to incoherent (Compton) scattering cross-section ratio of elements, in the range 13 ≤ Z ≤ 82, are determined experimentally for 59.54 keV incident gamma photons. An HPGe (High purity germanium) semiconductor detector is employed, at scattering angle of 110°, to record the spectra originating from interactions of incident gamma photons with the target under investigation. The intensity ratio of Rayleigh to Compton scattered peaks observed in the recorded spectra, and corrected for photo-peak efficiency of gamma detector and absorption of photons in the target and air, along with the other required parameters provides the differential cross-section ratio. The measured values of cross-section ratio are found to agree with theoretical predictions based upon non-relativistic form factor, relativistic form factor, modified form factor and S-matrix theory.

  3. Protein Dynamics and Stability: The Distribution of Atomic Fluctuations in Thermophilic and Mesophilic Dihydrofolate Reductase Derived Using Elastic Incoherent Neutron Scattering

    SciTech Connect

    Meinhold, Lars; Clement, David; Tehei, M; Daniel, R. M.; Finney, J.L.; Smith, Jeremy C

    2008-11-01

    The temperature dependence of the dynamics of mesophilic and thermophilic dihydrofolate reductase is examined using elastic incoherent neutron scattering. It is demonstrated that the distribution of atomic displacement amplitudes can be derived from the elastic scattering data by assuming a (Weibull) functional form that resembles distributions seen in molecular dynamics simulations. The thermophilic enzyme has a significantly broader distribution than its mesophilic counterpart. Furthermore, although the rate of increase with temperature of the atomic mean-square displacements extracted from the dynamic structure factor is found to be comparable for both enzymes, the amplitudes are found to be slightly larger for the thermophilic enzyme. Therefore, these results imply that the thermophilic enzyme is the more flexible of the two.

  4. Photonic generation of bipolar direct-sequence UWB signals based on optical spectral shaping and incoherent frequency-to-time conversion

    NASA Astrophysics Data System (ADS)

    Mu, Hongqian; Wang, Muguang; Ye, Jun; Jian, Shuisheng

    2016-06-01

    A novel technology to obtain binary phase-coded ultrawideband (UWB) signals for direct-sequence spread-spectrum communication systems is investigated by using a cost-effective incoherent source. The bipolar encoding is performed based on an all-fiber spectrum shaper composed of two FBG arrays to tailor the optical spectrum, and a section of single-mode fiber to achieve incoherent frequency-to-time conversion. We demonstrate a 1.325-Gb/s UWB encoding system by the use of binary spreading codes of 4-chip length via computer simulations. The proposed bipolar UWB encoding technology can be applied to high-speed UWB-over-fiber communication systems.

  5. Mixed quantum/classical approach to OH-stretch inelastic incoherent neutron scattering spectroscopy for ambient and supercooled liquid water and ice Ih

    NASA Astrophysics Data System (ADS)

    Shi, L.; Skinner, J. L.

    2015-07-01

    OH-stretch inelastic incoherent neutron scattering (IINS) has been measured to determine the vibrational density of states (VDOS) in the OH-stretch region for liquid water, supercooled water, and ice Ih, providing complementary information to IR and Raman spectroscopies about hydrogen bonding in these phases. In this work, we extend the combined electronic-structure/molecular-dynamics (ES/MD) method, originally developed by Skinner and co-workers to simulate OH-stretch IR and Raman spectra, to the calculation of IINS spectra with small k values. The agreement between theory and experiment in the limit k → 0 is reasonable, further validating the reliability of the ES/MD method in simulating OH-stretch spectroscopy in condensed phases. The connections and differences between IINS and IR spectra are analyzed to illustrate the advantages of IINS over IR in estimating the OH-stretch VDOS.

  6. Mixed quantum/classical approach to OH-stretch inelastic incoherent neutron scattering spectroscopy for ambient and supercooled liquid water and ice Ih.

    PubMed

    Shi, L; Skinner, J L

    2015-07-01

    OH-stretch inelastic incoherent neutron scattering (IINS) has been measured to determine the vibrational density of states (VDOS) in the OH-stretch region for liquid water, supercooled water, and ice Ih, providing complementary information to IR and Raman spectroscopies about hydrogen bonding in these phases. In this work, we extend the combined electronic-structure/molecular-dynamics (ES/MD) method, originally developed by Skinner and co-workers to simulate OH-stretch IR and Raman spectra, to the calculation of IINS spectra with small k values. The agreement between theory and experiment in the limit k → 0 is reasonable, further validating the reliability of the ES/MD method in simulating OH-stretch spectroscopy in condensed phases. The connections and differences between IINS and IR spectra are analyzed to illustrate the advantages of IINS over IR in estimating the OH-stretch VDOS. PMID:26156484

  7. Mixed quantum/classical approach to OH-stretch inelastic incoherent neutron scattering spectroscopy for ambient and supercooled liquid water and ice Ih

    SciTech Connect

    Shi, L.; Skinner, J. L.

    2015-07-07

    OH-stretch inelastic incoherent neutron scattering (IINS) has been measured to determine the vibrational density of states (VDOS) in the OH-stretch region for liquid water, supercooled water, and ice Ih, providing complementary information to IR and Raman spectroscopies about hydrogen bonding in these phases. In this work, we extend the combined electronic-structure/molecular-dynamics (ES/MD) method, originally developed by Skinner and co-workers to simulate OH-stretch IR and Raman spectra, to the calculation of IINS spectra with small k values. The agreement between theory and experiment in the limit k → 0 is reasonable, further validating the reliability of the ES/MD method in simulating OH-stretch spectroscopy in condensed phases. The connections and differences between IINS and IR spectra are analyzed to illustrate the advantages of IINS over IR in estimating the OH-stretch VDOS.

  8. A New On-the-Fly Sampling Method for Incoherent Inelastic Thermal Neutron Scattering Data in MCNP6

    SciTech Connect

    Pavlou, Andrew Theodore; Brown, Forrest B.; Ji, Wei

    2014-09-02

    At thermal energies, the scattering of neutrons in a system is complicated by the comparable velocities of the neutron and target, resulting in competing upscattering and downscattering events. The neutron wavelength is also similar in size to the target's interatomic spacing making the scattering process a quantum mechanical problem. Because of the complicated nature of scattering at low energies, the thermal data files in ACE format used in continuous-energy Monte Carlo codes are quite large { on the order of megabytes for a single temperature and material. In this paper, a new storage and sampling method is introduced that is orders of magnitude less in size and is used to sample scattering parameters at any temperature on-the-fly. In addition to the reduction in storage, the need to pre-generate thermal scattering data tables at fine temperatures has been eliminated. This is advantageous for multiphysics simulations which may involve temperatures not known in advance. A new module was written for MCNP6 that bypasses the current S(α,β) table lookup in favor of the new format. The new on-the-fly sampling method was tested for graphite for two benchmark problems at ten temperatures: 1) an eigenvalue test with a fuel compact of uranium oxycarbide fuel homogenized into a graphite matrix, 2) a surface current test with a \\broomstick" problem with a monoenergetic point source. The largest eigenvalue difference was 152pcm for T= 1200K. For the temperatures and incident energies chosen for the broomstick problem, the secondary neutron spectrum showed good agreement with the traditional S(α,β) sampling method. These preliminary results show that sampling thermal scattering data on-the-fly is a viable option to eliminate both the storage burden of keeping thermal data at discrete temperatures and the need to know temperatures before simulation runtime.

  9. Modeling Incoherent Electron Cloud Effects

    SciTech Connect

    Fischer, W.; Benedetto, E.; Rumolo, G.; Schulte, D.; Tomas, R.; Zimmermann, Frank; Franchetti, G.; Ohmi, Kazuhito; Sonnad, K.G.; Vay, Jean-Luc; Pivi, M.T.F.; Raubenheimer, Tor O.; /SLAC

    2008-01-24

    Incoherent electron effects could seriously limit the beam lifetime in proton or ion storage rings, such as LHC, SPS, or RHIC, or blow up the vertical emittance of positron beams, e.g., at the B factories or in linear-collider damping rings. Different approaches to modeling these effects each have their own merits and drawbacks. We describe several simulation codes which simplify the descriptions of the beam-electron interaction and of the accelerator structure in various different ways, and present results for a toy model of the SPS. In addition, we present evidence that for positron beams the interplay of incoherent electron-cloud effects and synchrotron radiation can lead to a significant increase in vertical equilibrium emittance. The magnitude of a few incoherent e{sup +}e{sup -} scattering processes is also estimated. Options for future code development are reviewed.

  10. Modeling Incoherent Electron Cloud Effects

    SciTech Connect

    Vay, Jean-Luc; Benedetto, E.; Fischer, W.; Franchetti, G.; Ohmi, K.; Schulte, D.; Sonnad, K.; Tomas, R.; Vay, J.-L.; Zimmermann, F.; Rumolo, G.; Pivi, M.; Raubenheimer, T.

    2007-06-18

    Incoherent electron effects could seriously limit the beam lifetime in proton or ion storage rings, such as LHC, SPS, or RHIC, or blow up the vertical emittance of positron beams, e.g., at the B factories or in linear-collider damping rings. Different approaches to modeling these effects each have their own merits and drawbacks. We describe several simulation codes which simplify the descriptions of the beam-electron interaction and of the accelerator structure in various different ways, and present results for a toy model of the SPS. In addition, we present evidence that for positron beams the interplay of incoherent electron-cloud effects and synchrotron radiation can lead to a significant increase in vertical equilibrium emittance. The magnitude of a few incoherent e+e- scattering processes is also estimated. Options for future code development are reviewed.

  11. An incoherent scatter radar study of the midnight temperature maximum that occurred at Arecibo during a sudden stratospheric warming event in January 2010

    NASA Astrophysics Data System (ADS)

    Gong, Yun; Zhou, Qihou; Zhang, Shaodong; Aponte, Nestor; Sulzer, Michael

    2016-06-01

    We present an analysis of the thermospheric midnight temperature maximum, a large increment of temperature around midnight. The analysis is based on data collected from the Arecibo incoherent scatter radar during 14-21 January 2010. The experiment overlaps with a major sudden stratospheric warming (SSW) event which commenced on 18 January 2010. Throughout the observation, the ion temperature exhibited moderate increase around postmidnight during 14-17 January, while it showed more intense increment during 18-21 January. In particular, on 20 January, the amplitude of the midnight temperature maximum (MTM) is 310 K, which is seldom seen at Arecibo. During the SSW, the meridional wind reverses toward the pole just before the commencement of the MTM. Then, the poleward wind and the ion temperature maximize almost at the same time. The variation of meridional wind and the MTM are consistent with the Whole Atmosphere Model (WAM) studies, which suggested that the variation is due to effects from an upward propagating terdiurnal tide. On the nights of 18-19 January, the MTM showed clear phase variation at the heights of 265, 303, and 342 km. A strong terdiurnal tide has been observed during the SSW and it is likely generated from low atmosphere and propagating upward. Our results provide direct observational evidence that the propagating upward terdiurnal tide plays an important role in causing the MTM, which supports the WAM simulations.

  12. Comparison of IRI-2012 with JASON-1 TEC and incoherent scatter radar observations during the 2008-2009 solar minimum period

    NASA Astrophysics Data System (ADS)

    Ji, Eun-Young; Jee, Geonhwa; Lee, Changsup

    2016-08-01

    The 2008-2009 solar minimum period was unprecedentedly deep and extended. We compare the IRI-2012 with global TEC data from JASON-1 satellite and with electron density profiles observed from incoherent scatter radars (ISRs) at middle and high latitudes for this solar minimum period. Global daily mean TECs are calculated from JASON-1 TECs to compare with the corresponding IRI TECs during the 2008-2009 period. It is found that IRI underestimates the global daily mean TEC by about 20-50%. The comparison of global TEC maps further reveals that IRI overall underestimates TEC for the whole globe except for the low-latitude region around the equatorial anomaly, regardless of season. The underestimation is particularly strong in the nighttime winter hemisphere where the ionosphere seems to almost disappear in IRI. In the daytime equatorial region, however, the overestimation of IRI is mainly due to the misrepresentation of the equatorial anomaly in IRI. Further comparison with ISR electron density profiles confirms the significant underestimation of IRI at night in the winter hemisphere.

  13. Investigation of sudden electron density depletions observed in the dusk sector by the Poker Flat, Alaska incoherent scatter radar in summer

    NASA Astrophysics Data System (ADS)

    Richards, P. G.; Nicolls, M. J.; St.-Maurice, J.-P.; Goodwin, L.; Ruohoniemi, J. M.

    2014-12-01

    This paper investigates unusually deep and sudden electron density depletions (troughs) observed in the Poker Flat (Alaska) Incoherent Scatter Radar data in middle summer of 2007 and 2008. The troughs were observed in the premidnight sector during periods of weak magnetic and solar activity. The density recovered to normal levels around midnight. At the time when the electron density was undergoing its steep decrease, there was usually a surge of the order of 100 to 400 K in the ion temperature that lasted less than 1 h. The Ti surges were usually related to similar surges in the AE index, indicating that the high-latitude convection pattern was expanding and intensifying at the time of the steep electron density drop. The convection patterns from the Super Dual Auroral Radar Network also indicate that the density troughs were associated with the expansion of the convection pattern to Poker Flat. The sudden decreases in the electron density are difficult to explain in summer because the high-latitude region remains sunlit for most of the day. This paper suggests that the summer density troughs result from lower latitude plasma that had initially been corotating in darkness for several hours post sunset and brought back toward the sunlit side as the convection pattern expanded. The magnetic declination of ~22° east at 300 km at Poker Flat greatly facilitates the contrast between the plasma convecting from lower latitudes and the plasma that follows the high-latitude convection pattern.

  14. Coherent and incoherent scatter radar study of the climatology and day-to-day variability of mean F region vertical drifts and equatorial spread F

    NASA Astrophysics Data System (ADS)

    Smith, J. M.; Rodrigues, F. S.; Fejer, B. G.; Milla, M. A.

    2016-02-01

    We conducted a comprehensive analysis of the vertical drifts and equatorial spread F (ESF) measurements made by the Jicamarca incoherent scatter radar (ISR) between 1994 and 2013. The ISR measurements allowed us to construct not only updated climatological curves of quiet-time vertical plasma drifts but also time-versus-height maps of ESF occurrence over the past two solar cycles. These curves and maps allowed us to better relate the observed ESF occurrence patterns to features in the vertical drift curves than previously possible. We identified an excessively high occurrence of post-midnight F region irregularities during December solstice and low solar flux conditions. More importantly, we also found a high occurrence of ESF events during sudden stratospheric warming (SSW) events. We also proposed and evaluated metrics of evening enhancement of the vertical drifts and ESF occurrence, which allowed us to quantify the relationship between evening drifts and ESF development. Based on a day-to-day analysis of these metrics, we offer estimates of the minimum pre-reversal enhancement (PRE) peak (and mean PRE) values observed prior to ESF development for different solar flux and seasonal conditions. We also found that ESF irregularities can reach the altitudes at least as high as 800 km at the magnetic equator even during low solar flux conditions.

  15. A Local Empirical Model of the E and F Region Ionosphere Based on 30 Years of Millstone Hill Incoherent Scatter Radar Data

    NASA Astrophysics Data System (ADS)

    Holt, J. M.

    2002-12-01

    Improved specifications and predictions of the ionosphere/thermosphere system are an important objective of the National Space Weather Program. As a contribution toward meeting this objective, we are developing a series of empirical models of the average behavior and variability of key parameters which characterize the ionosphere/thermosphere system. Here we present a local model of the E and F regions above Millstone Hill (42.6 N, 288.5 W) based on Millstone Hill Incoherent Scatter Radar data from 1970 to the present. The model parameters are electron density, ion temperature, electron temperature, geomagnetic-field-aligned ion drift and electric field. Time resolution is one hour, seasonal resolution is one month, altitude coverage is 100-1000 km and altitude resolution ranges from 5 km in the lower E-region to 300 km in the upper F-region. The model includes solar flux (F10.7) and geomagnetic activity (Ap) dependencies. Software to recover model values as well as a Web interface to the model is available at http://www.openmadrigal.org.

  16. The instrumental principles of MST radars and incoherent scatter radars and the configuration of radar system hardware

    NASA Technical Reports Server (NTRS)

    Roettger, Juergen

    1989-01-01

    The principle of pulse modulation used in the case of coherent scatter radars (MST radars) is discussed. Coherent detection and the corresponding system configuration is delineated. Antenna requirements and design are outlined and the phase-coherent transmitter/receiver system is described. Transmit/receive duplexers, transmitters, receivers, and quadrature detectors are explained. The radar controller, integrator, decoder and correlator design as well as the data transfer and the control and monitoring by the host computer are delineated. Typical operation parameters of some well-known radars are summarized.

  17. Scattering of VHF and UHF radar signals from the turbulent air

    NASA Astrophysics Data System (ADS)

    Liu, C. H.; Yeh, K. C.

    1980-04-01

    In the derivation of Booker-Gordon scattering cross sections in a turbulent atmosphere, certain assumptions have been made so that the power scattered within the scattering volume will add coherently. This results in a scattered power that is proportional to the effective scattering volume. As the scattering volume increases without bound, it leads to a physically unreasonable result of infinite scattered power. The paper examines these assumptions. The scattering cross sections are studied taking into account the possible phase incoherence of the scattered fields within the scattering volume. In addition, the effect of a thin turbulent layer on the complex autocorrelation function is investigated. The turbulence is assumed to be locally frozen. Expressions for both the Doppler shift and the correlation time have been derived.

  18. Nonlinear stimulated Brillouin scattering based photonic signal processors

    SciTech Connect

    Minasian, Robert A.

    2014-10-06

    Recent new methods in photonic signal processing based on stimulated Brillouin scattering, that enable the realization of photonic mixers with high conversion efficiency, ultra-wide continuously tunable high-resolution microwave photonic filters and programmable switchable microwave photonic tunable filters, are presented. These processors provide new capabilities for the realisation of high-performance and high-resolution signal processing.

  19. Measuring predictability in ultrasonic signals: an application to scattering material characterization.

    PubMed

    Carrión, Alicia; Miralles, Ramón; Lara, Guillermo

    2014-09-01

    In this paper, we present a novel and completely different approach to the problem of scattering material characterization: measuring the degree of predictability of the time series. Measuring predictability can provide information of the signal strength of the deterministic component of the time series in relation to the whole time series acquired. This relationship can provide information about coherent reflections in material grains with respect to the rest of incoherent noises that typically appear in non-destructive testing using ultrasonics. This is a non-parametric technique commonly used in chaos theory that does not require making any kind of assumptions about attenuation profiles. In highly scattering media (low SNR), it has been shown theoretically that the degree of predictability allows material characterization. The experimental results obtained in this work with 32 cement probes of 4 different porosities demonstrate the ability of this technique to do classification. It has also been shown that, in this particular application, the measurement of predictability can be used as an indicator of the percentages of porosity of the test samples with great accuracy. PMID:24952468

  20. Digital signal processing based on inverse scattering transform.

    PubMed

    Turitsyna, Elena G; Turitsyn, Sergei K

    2013-10-15

    Through numerical modeling, we illustrate the possibility of a new approach to digital signal processing in coherent optical communications based on the application of the so-called inverse scattering transform. Considering without loss of generality a fiber link with normal dispersion and quadrature phase shift keying signal modulation, we demonstrate how an initial information pattern can be recovered (without direct backward propagation) through the calculation of nonlinear spectral data of the received optical signal. PMID:24321955

  1. Cross Comparison of Electron Density and Electron Temperature Observations from the DICE CubeSat Langmuir Probes and the Millstone Hill Incoherent Scatter Radar.

    NASA Astrophysics Data System (ADS)

    Swenson, C.; Erickson, P. J.; Crowley, G.; Pilinski, M.; Barjatya, A.; Fish, C. S.

    2014-12-01

    The Dynamic Ionosphere CubeSat Experiment (DICE) consists of two identical 1.5U CubeSats deployed simultaneously from a single P-POD (Poly Picosatellite Orbital Deployer) into the same orbit. Several observational campaigns were planned between the DICE CubeSats and the mid-latitude Millstone Hill Incoherent Scatter Radar (ISR) in order to calibrate the DICE measurements of electron density and electron temperature. In this presentation, we compare in-situ observations from the Dynamic Ionosphere CubeSat Experiment (DICE) and from the Millstone Hill ISR. Both measurements are cross-calibrated against an assimilative model of the global ionospheric electron density. The electron density and electron temperature were obtained for three Millstone Hill DICE overflights (2013-03-12, 2013-03-15, 2013-03-17). We compare the data during quiet and geomagnetically disturbed conditions and find evidence of an storm enhanced density (SED) plume in the topside ionosphere on 2013-03-17 at 19? UTC. During this disturbed interval, American longitude sector high density plasma was convected near 15 SLT towards the noontime cusp. DICE was selected for flight under the NSF "CubeSat-based Science Mission for Space Weather and Atmospheric Research" program. The DICE twin satellites were launched on a Delta II rocket on October 28, 2011. The satellites are flying in a "leader-follower" formation in an elliptical orbit which ranges from 820 to 400 km in altitude. Each satellite carries a fixed-bias DC Langmuir Probe (DCP) to measure in-situ ionospheric plasma densities and a science grade magnetometer to measure DC and AC geomagnetic fields. The purpose of these measurements was to permit accurate identification of storm-time features such as the SED bulge and plume. The mission team combines expertise from ASTRA, Utah State University/Space Dynamics Laboratory (USU/SDL), and Embry-Riddle Aeronautical University. In this paper we present a comparison of data from DICE and Millstone Hill

  2. Small angle scattering signals for (neutron) computerized tomography

    SciTech Connect

    Strobl, M.; Treimer, W.; Hilger, A.

    2004-07-19

    Small angle neutron scattering is a well-established tool for the determination of microscopic structures in various materials. With the ultrasmall angle neutron scattering technique (USANS), structures with sizes of approximately 50 nm to 50 {mu}m can be resolved by a double crystal diffractometer (DCD). USANS signals recorded with a special DCD were used for tomographic purposes investigating the macroscopic structure of a sample with a maximum resolution of 200 {mu}m. Thereby, macroscopic regions within the sample with different ultrasmall angle scattering properties, i.e., with different microscopic structures, could be imaged by the means of tomographic reconstruction from projections (on a macroscopic scale)

  3. Use of Multiband Acousto-optic Filters for Spectrally Encoded Signals Generation in Incoherent Optical Communication Systems

    NASA Astrophysics Data System (ADS)

    Byshevski-Konopko, O. A.; Proklov, V. V.; Filatov, A. L.; Lugovskoi, A. V.; Korablev, E. M.

    New acousto-optical (AO) coder of spectrally optical signals for optical code division multiple access systems (O-CDMA) was proposed and investigated. The coder was developed on a base of multi-frequency acousto-optical filter (MAOF). Control RF signals for MAOF were synthesized taking into account intermodulation distortions and interferences between different carrier frequencies incoming to MAOF. An industrial LED was used under system investigation.

  4. Brillouin amplification and processing of the Rayleigh scattered signal.

    PubMed

    Mermelstein, David; Shacham, Eliashiv; Biton, Moran; Sternklar, Shmuel

    2015-07-15

    Brillouin amplification of Rayleigh scattering is demonstrated using two different configurations. In the first technique, the Rayleigh scattering and amplification occurs simultaneously in the same fiber. In the second technique, the amplification takes place in a second fiber. The differences between the two techniques are delineated. Using the second technique, we demonstrate single-sideband off-resonant Brillouin amplification of the Rayleigh signal. This technique is shown to enhance the SNR of a signal that is due to vibration-induced strain on the fiber. PMID:26176464

  5. Persistent misconceptions about incoherence in electron microscopy.

    PubMed

    Van Dyck, D

    2011-06-01

    Incoherence in electron microscopic imaging occurs when during the observation the microscope and the object are subject to fluctuations. In order to speed up the computer simulation of the images, approximations are used that are considered as valid. In this paper we will question the validity of these approximations and show that in specific cases they can lead to erroneous results. It is shown in particular in the case of one single vibrating atom that the thermal diffuse scattering that causes the signal in HAADF STEM is not only dependent on Z but also on the mean square displacement of the atom so that it can even be large for light atoms in soft matter, provided the right HAADF aperture is used. In HREM imaging the diffuse scattering leaks out of the coherent (elastic) wave and is redistributed in the background. This might explain the mismatch in elastic contrast (Stobbs factor) especially for crystals with a thickness beyond the extinction distance, where also the HAADF signal saturates and the elastic (coherent) component vanishes. PMID:21664551

  6. Structure of hydrogenous liquids: separation of coherent and incoherent cross sections using polarised neutrons

    NASA Astrophysics Data System (ADS)

    Stunault, A.; Vial, S.; Pusztai, L.; Cuello, G. J.; Temleitner, L.

    2016-04-01

    The determination of the coherent structure factor of hydrogenous liquids is very difficult: while X-rays are barely sensitive to hydrogen, neutrons results still lack accuracy due to the contamination of the scattering intensities by a huge spin-incoherent signal from the 1H atoms. Using polarised neutrons with polarisation analysis, one can experimentally separate the coherent and incoherent contributions to the scattered intensity. We present the upgrade of the D3 polarised hot neutron diffractometer at ILL to study hydrogenated liquids. We show first data obtained from a test sample of water and detail the data reduction leading to an unprecedented accuracy in the extraction of the coherent signal, representative of the structure.

  7. Calculating incoherent diffraction MTF

    NASA Astrophysics Data System (ADS)

    Friedman, Melvin; Vizgaitis, Jay

    2008-04-01

    The incoherent diffraction MTF plays an increasingly important role in the range performance of imaging systems as the wavelength increases and the optical aperture decreases. Accordingly, all NVESD imager models have equations that describe the incoherent diffraction MTF of a circular entrance pupil. NVThermIP, a program which models thermal imager range performance, has built in equations which analytically model the incoherent diffraction MTF of a circular entrance pupil and has a capability to input a table that describes the MTF of other apertures. These can be calculated using CODE V, which can numerically calculate the incoherent diffraction MTF in the vertical or horizontal direction for an arbitrary aperture. However, we are not aware of any program that takes as input a description of the entrance pupil and analytically outputs equations that describe the incoherent diffraction MTF. This work explores the effectiveness of Mathematica to analytically and numerically calculate the incoherent diffraction MTF for an arbitrary aperture. In this work, Mathematica is used to analytically and numerically calculate the incoherent diffraction MTF for a variety of apertures and the results are compared with CODE V calculations.

  8. Cascaded-systems analyses and the detective quantum efficiency of single-Z x-ray detectors including photoelectric, coherent and incoherent interactions

    SciTech Connect

    Yun, Seungman; Tanguay, Jesse; Cunningham, Ian A.; Kim, Ho Kyung

    2013-04-15

    Purpose: Theoretical models of the detective quantum efficiency (DQE) of x-ray detectors are an important step in new detector development by providing an understanding of performance limitations and benchmarks. Previous cascaded-systems analysis (CSA) models accounted for photoelectric interactions only. This paper describes an extension of the CSA approach to incorporate coherent and incoherent interactions, important for low-Z detectors such as silicon and selenium. Methods: A parallel-cascade approach is used to describe the three types of x-ray interactions. The description of incoherent scatter required developing expressions for signal and noise transfer through an 'energy-labeled reabsorption' process where the parameters describing reabsorption are random functions of the scatter photon energy. The description of coherent scatter requires the use of scatter form factors that may not be accurate for some crystalline detector materials. The model includes the effects of scatter reabsorption and escape, charge collection, secondary quantum sinks, noise aliasing, and additive noise. Model results are validated by Monte Carlo calculations for Si and Se detectors assuming free-atom atomic form factors. Results: The new signal and noise transfer expressions were validated by showing agreement with Monte Carlo results. Coherent and incoherent scatter can degrade the DQE of Si and sometimes Se detectors depending on detector thickness and incident-photon energy. Incoherent scatter can produce a substantial low-frequency drop in the modulation transfer function and DQE. Conclusions: A generally useful CSA model of the DQE is described that is believed valid for any single-Z material up to 10 cycles/mm at both mammographic and radiographic energies within the limitations of Fourier-based linear-systems models and the use of coherent-scatter form factors. The model describes a substantial low-frequency drop in the DQE of Si systems due to incoherent scatter above 20

  9. Incoherent Light Sources

    NASA Astrophysics Data System (ADS)

    Bertram, Dietrich; Born, Matthias; Jüstel, Thomas

    Since the invention and industrialization of incandescent lamps at the end radiation of the 19th century electrical lighting has become a commodity in our daily life. Today, incoherent light sources are used for numerous application areas. Major improvements have been achieved over the past decades with respect to lamp efficiency (Fig. 10.1), lifetime and color properties.

  10. Incoherent Light Sources

    NASA Astrophysics Data System (ADS)

    Bertram, Dietrich; Born, Matthias; Jüstel, Thomas

    Since the invention and industrialization of incandescent lamps at the end of the 19th century electrical lighting has become a commodity in our daily life. Today, incoherent light sources are used for numerous application areas. Major improvements have been achieved over the past decades with respect to lamp efficiency Fig. 10.1, lifetime and color properties.

  11. Wind Speed Measurement from Bistatically Scattered GPS Signals

    NASA Technical Reports Server (NTRS)

    Garrison, James L.; Komjathy, Attila; Zavorotny, Valery U.; Katzberg, Stephen J.

    1999-01-01

    Instrumentation and retrieval algorithms are described which use the forward, or bistatically scattered range-coded signals from the Global Positioning System (GPS) radio navigation system for the measurement of sea surface roughness. This roughness is known to be related directly to the surface wind speed. Experiments were conducted from aircraft along the TOPEX ground track, and over experimental surface truth buoys. These flights used a receiver capable of recording the cross correlation power in the reflected signal. The shape of this power distribution was then compared against analytical models derived from geometric optics. Two techniques for matching these functions were studied. The first recognized the most significant information content in the reflected signal is contained in the trailing edge slope of the waveform. The second attempted to match the complete shape of the waveform by approximating it as a series expansion and obtaining the nonlinear least squares estimate. Discussion is also presented on anomalies in the receiver operation and their identification and correction.

  12. The Expected Impact of Multiple Scattering on ATLID Signals

    NASA Astrophysics Data System (ADS)

    Donovan, D. P.

    2016-06-01

    ATLID stands for "ATmospheric LIDar" and is the lidar to be flown on the Earth Clouds and Radiation Explorer (EarthCARE) platform in 2018. ATLID is a High-Spectral Resolution (HSRL) system operating at 355nm with a narrower field-of-view and lower orbit than the CALIPSO lidar. In spite of the smaller footprint multiple-scattering (MS) will have an important impact on ATLID cloud signals and, in some aspects, the accurate treatment of MS will be more important for ATLID than CALIPSO. On the other hand, the relationship between integrated backscatter and integrated MS induced depolarization in water clouds will be similar between ATLID and CALIPSO indicating that a CALIPSO-like strategy for cloud-phase identification can be successfully applied to ATLID.

  13. Discriminant Incoherent Component Analysis.

    PubMed

    Georgakis, Christos; Panagakis, Yannis; Pantic, Maja

    2016-05-01

    Face images convey rich information which can be perceived as a superposition of low-complexity components associated with attributes, such as facial identity, expressions, and activation of facial action units (AUs). For instance, low-rank components characterizing neutral facial images are associated with identity, while sparse components capturing non-rigid deformations occurring in certain face regions reveal expressions and AU activations. In this paper, the discriminant incoherent component analysis (DICA) is proposed in order to extract low-complexity components, corresponding to facial attributes, which are mutually incoherent among different classes (e.g., identity, expression, and AU activation) from training data, even in the presence of gross sparse errors. To this end, a suitable optimization problem, involving the minimization of nuclear-and l1 -norm, is solved. Having found an ensemble of class-specific incoherent components by the DICA, an unseen (test) image is expressed as a group-sparse linear combination of these components, where the non-zero coefficients reveal the class(es) of the respective facial attribute(s) that it belongs to. The performance of the DICA is experimentally assessed on both synthetic and real-world data. Emphasis is placed on face analysis tasks, namely, joint face and expression recognition, face recognition under varying percentages of training data corruption, subject-independent expression recognition, and AU detection by conducting experiments on four data sets. The proposed method outperforms all the methods that are compared with all the tasks and experimental settings. PMID:27008268

  14. Investigation on global positioning system signal scattering and propagation over the rough sea surface

    NASA Astrophysics Data System (ADS)

    Yang, Chao; Guo, Li-Xin; Wu, Zhen-Sen

    2010-05-01

    This paper is devoted to the study of polarization properties, scattering properties and propagation properties of global positioning system (GPS) scattering signal over the rough sea surface. To investigate the polarization and the scattering properties, the scattering field and the bistatic scattering coefficient of modified Kirchhoff approximation using the tapered incident wave is derived in detail. In modeling the propagation properties of the GPS scattering signal in the evaporation duct, the initial field of parabolic equation traditionally computed by the antenna pattern using fast Fourier transform (FFT) is replaced by the GPS scattering field. And the propagation properties of the GPS scattering signal in the evaporation duct with different evaporation duct heights and elevation angles of GPS are discussed by the improved discrete mixed Fourier transform taking into account the sea surface roughness.

  15. Incoherent imaging by z-contrast stem: Towards 1{angstrom} resolution

    SciTech Connect

    Pennycook, S.J.; Jesson, D.E.; McGibbon, A.J.

    1993-12-01

    By averaging phase correlations between scattered electrons a high angle detector in the scanning transmission electron microscope (STEM) can provide an incoherent, Z-contrast image at atomic resolution. Phase coherence is effectively destroyed through a combination of detector geometry (transverse incoherence) and phonon scattering (longitudinal incoherence). Besides having a higher intrinsic resolution, incoherent imaging offers the possibility of robust reconstruction to higher resolutions, provided that some lower frequency information is present in the image. this should have value for complex materials and regions of complex atomic arrangements such as grain boundaries. Direct resolution of the GaAs sublattice with a 300kV is demonstrated.

  16. Comparison between nighttime ionosonde, incoherent scatter radar, AE-E satellite, and HF Doppler observations of F region vertical electrodynamic plasma drifts in the vicinity of the magnetic equator

    NASA Astrophysics Data System (ADS)

    Oyekola, Oyedemi S.

    2006-11-01

    Nighttime F region vertical drifts were made using an ionosonde for the equatorial station Ibadan (7.4°N, 3.9°E, 6°S dip) from 1 year of data during 1957-1958 International Geophysical Year (IGY) that corresponds to a period of solar maximum for undisturbed condition. We compare the seasonal vertical drifts with measurements made by incoherent scatter radar, AE-E satellite, and HF Doppler for equatorial F region vertical drifts. We find a comparable variability pattern during periods of high F layer heights during equinox and the December solstice, and the opposite behavior occurs during June solstice. The drifts are predominantly downward between 2000 and 0500 LT intervals. Ionosonde drifts are smaller in values by either a factor of two or three than other methods, except for consistent June solstice ionosonde and satellite magnitudes. The equinoctial average prereversal enhancements measured by the four techniques are roughly comparable (about 36 m/s) and occur at the same local time (1900 LT) for all the seasons. The evening reversal times are similar, apart from June solstice that exhibits large variations. The morning reversal times are also in accord except for the equinoctial Jicamarca drift. Our observations indicate that ionosonde drifts measurements are in better agreement with vertical drifts results at other equatorial stations.

  17. System and method for linearly amplifying optical analog signals by backward Raman scattering

    DOEpatents

    Lin, Cheng-Heui

    1988-07-05

    A system for linearly amplifying an optical analog signal by backward stimulated Raman scattering comprises a laser source for generating a pump pulse; and an optic fiber having two opposed apertures, a first aperture for receiving the pump pulse and a second aperture for receiving the optical analog signal, wherein the optical analog signal is linearly amplified to an amplified optical analog signal.

  18. System and method for linearly amplifying optical analog signals by backward Raman scattering

    DOEpatents

    Lin, Cheng-Heui

    1988-01-01

    A system for linearly amplifying an optical analog signal by backward stimulated Raman scattering comprises a laser source for generating a pump pulse; and an optic fiber having two opposed apertures, a first aperture for receiving the pump pulse and a second aperture for receiving the optical analog signal, wherein the optical analog signal is linearly amplified to an amplified optical analog signal.

  19. Softness of atherogenic lipoproteins: a comparison of very low density lipoprotein (VLDL) and low density lipoprotein (LDL) using elastic incoherent neutron scattering (EINS).

    PubMed

    Mikl, Christian; Peters, Judith; Trapp, Marcus; Kornmueller, Karin; Schneider, Wolfgang J; Prassl, Ruth

    2011-08-31

    Apolipoprotein B100 (apoB100)-containing plasma lipoproteins (LDL and VLDL) supply tissues and cells with cholesterol and fat. During lipolytic conversion from VLDL to LDL the size and chemical composition of the particles change, but the apoB100 molecule remains bound to the lipids and regulates the receptor mediated uptake. The molecular physical parameters which control lipoprotein remodeling and enable particle stabilization by apoB100 are largely unknown. Here, we have compared the molecular dynamics and elasticities of VLDL and LDL derived by elastic neutron scattering temperature scans. We have determined thermal motions, dynamical transitions, and molecular fluctuations, which reflect the temperature-dependent motional coupling between lipid and protein. Our results revealed that lipoprotein particles are extremely soft and flexible. We found substantial differences in the molecular resiliences of lipoproteins, especially at higher temperatures. These discrepancies not only can be explained in terms of lipid composition and mobility but also suggest that apoB100 displays different dynamics dependent on the lipoprotein it is bound to. Hence, we suppose that the inherent conformational flexibility of apoB100 permits particle stabilization upon lipid exchange, whereas the dynamic coupling between protein and lipids might be a key determinant for lipoprotein conversion and atherogenicity. PMID:21790144

  20. A Quantitative Model of Glucose Signaling in Yeast Reveals an Incoherent Feed Forward Loop Leading to a Specific, Transient Pulse of Transcription

    NASA Astrophysics Data System (ADS)

    Kuttykrishnan, Sooraj; Sabina, Jeffrey; Langton, Laura; Johnston, Mark; Brent, Michael R.

    The ability to design and engineer organisms demands the ability to predict kinetic responses of novel regulatory networks built from well-characterized biological components. Surprisingly, few validated kinetic models of complex regulatory networks have been derived by combining models of the network components. A major bottleneck in producing such models is the difficulty of measuring in vivo rate constants for components of complex networks. We demonstrate that a simple, genetic approach to measuring rate constants in vivo produces an accurate kinetic model of the complex network that Saccharomyces cerevisiae employs to regulate the expression of genes encoding glucose transporters. The model predicts a transient pulse of transcription of HXT4 (but not HXT2 or HXT3) in response to addition of a small amount of glucose to cells, an outcome we observed experimentally. Our model also provides a mechanistic explanation for this result: HXT24 are governed by a type 2, incoherent feed forward regulatory loop involving the Rgt1 and Mig2 transcriptional repressors. The efficiency with which Rgt1 and Mig2 repress expression of each HXT gene determines which of them have a pulse of transcription in response to glucose. Finally, the model correctly predicts how lesions in the feed forward loop change the kinetics of induction of HXT4 expression.

  1. Effects Of Substrate Scattering On Bar-Code Scanning Signals

    NASA Astrophysics Data System (ADS)

    Barkan, Eric; Sklar, David

    1983-04-01

    When a beam of light strikes a piece of paper or similar substrate, a portion of its energy penetrates into the bulk and, due to multiple scattering, may re-emerge at some distance from the point of entry. We refer to this phenomenon as substrate scattering. In this paper we describe a general model for scattering substrates and, using linear systems theory, we investigate its implications for bar-code scanning. We show that the effects of substrate scattering can be represented as a modified reflectance distribution associated with the original printed reflectance pattern. This effective distribution is shown to be independent of the details of scanning system configuration. We show that under a broad range of conditions substrate scattering will decrease modulation and will cause scanners to overestimate barwidths. A specific diffusion model of the scattering process is developed, providing a family of functions which can be used in empirical studies. We conclude that the scattering distributions will not even be approximately Gaussian. Experimental results are presented which are consistent with this conclusion and inconsistent with a Gaussian model. Further experimental results are presented which show that, for typical substrates, depth of modulation may be decreased by 20 percent or more and perceived bar-width increases will be on the order of one mil.

  2. Calculates Thermal Neutron Scattering Kernel.

    Energy Science and Technology Software Center (ESTSC)

    1989-11-10

    Version 00 THRUSH computes the thermal neutron scattering kernel by the phonon expansion method for both coherent and incoherent scattering processes. The calculation of the coherent part is suitable only for calculating the scattering kernel for heavy water.

  3. Effects of multiple scattering on scintillation of transionospheric radio signals

    NASA Technical Reports Server (NTRS)

    Liu, C. H.; Yeh, K. C.; Youakim, M. Y.; Wernik, A. W.

    1974-01-01

    Recent development in the optical scintillation theory has been adapted to the ionospheric geometry in order to study the ionospheric scintillation phenomenon in the presence of multiple scattering. Under approximations well satisfied in typical ionospheres for a frequency above about 20 MHz, the first through fourth moment equations have been derived and some analytic solutions given. The fourth moment equation has also been solved numerically. The numerical results show clearly the occurrence of focusing and saturation phenomena. The new multiple-scatter effects are emphasized.

  4. Experimental Determination of Dual-Wavelength Mie Lidar Geometric form Factor Combining Side-Scatter and Back-Scatter Signals

    NASA Astrophysics Data System (ADS)

    Wang, Zhenzhu; Tao, Zongming; Liu, Dong; Xie, Chenbo; Wang, Yingjian

    2016-06-01

    In theory, lidar overlap factor can be derived from the difference between the particle backscatter coefficient retrieved from lidar elastic signal without overlap correction and the actual particle backscatter coefficient, which can be obtained by other measured techniques. The side-scatter signal using a CCD camera is testified to be a powerful tool to detect the particle backscatter coefficient in near ground layer during night time. In experiment, by combining side-scatter and backscatter signals the geometric form factor for vertically-pointing Mie lidar in 532 nm channel is determined successfully, which is corrected by an iteration algorithm combining the retrieved particle backscatter coefficient using CCD sidescatter method and Fernald method. In this study, the method will be expanded to 1064 nm channel in dual-wavelength Mie lidar during routine campaigns. The experimental results in different atmosphere conditions demonstrated that the method present in this study is available in practice.

  5. Separating Scattering from Intrinsic Attenuation

    NASA Astrophysics Data System (ADS)

    van Wijk, K.; Scales, J. A.

    2003-12-01

    The subsurface appears disordered at all length-scales. Therefore, wave propatation at seismic or ultrasonic frequencies is subject to complicated scatterings. A pulse propagating in the subsurface loses energy at each scattering off an impedance contrast, but also decreases in amplitude as the impulse interacts with fluids in the rock. We call the latter non-elastic effect "intrinsic Q", while the former is "scattering Q". It is often the fluids in the rocks that are of interest, but conventional reflection and transmission of the incident pulse only cannot deceipher the individual components of Q due to scattering and fluid movement in the pore-space. We present an approach that can unravel these two mechanisms, allowing a separate estimate of absorption. This method treats the propagation of the average intensity in the framework of radiative transfer (RT); the arrival of (what is left of) the incident pulse is modeled as the coherent energy, whereas the later arriving multiply scattered events form the incoherent intensity. The coherent pulse decays exponentially due to a combination of scattering and absorption, and so does the incoherent intensity. However, multiple scattering can re-direct energy back to the receiver, supplying a gain-term at later times that makes up the incoherent intensity. Strictly speaking, one can invert for scattering and absorption from the intensity at late times only, often modeled with the late-time equivalent of RT, diffusion. However, we will show that fitting both early- and late-time signal with RT constrains absorption and scattering constants more rigorously. These ideas are illustrated by laboratory and sonic-logging measurements.

  6. Power spectrum analysis of the x-ray scatter signal in mammography and breast tomosynthesis projections

    PubMed Central

    Sechopoulos, Ioannis; Bliznakova, Kristina; Fei, Baowei

    2013-01-01

    Purpose: To analyze the frequency domain characteristics of the signal in mammography images and breast tomosynthesis projections with patient tissue texture due to detected scattered x-rays. Methods: Acquisitions of x-ray projection images of 19 different patient breasts were simulated using previously acquired volumetric patient images. Acquisition of these images was performed with a dedicated breast CT prototype system, and the images were classified into voxels representing skin, adipose, and glandular tissue with a previously validated automated algorithm. The classified three dimensional images then underwent simulated mechanical compression representing that which is performed during acquisition of mammography and breast tomosynthesis images. The acquisition of projection images of each patient breast was simulated using Monte Carlo methods with each simulation resulting in two images: one of the primary (non-scattered) signal and one of the scatter signal. To analyze the scatter signal for both mammography and breast tomosynthesis, two projections images of each patient breast were simulated, one with the x-ray source positioned at 0° (mammography and central tomosynthesis projection) and at 30° (wide tomosynthesis projection). The noise power spectra (NPS) for both the scatter signal alone and the total signal (primary + scatter) for all images were obtained and the combined results of all patients analyzed. The total NPS was fit to the expected power-law relationship NPS(f) = k/f^β and the results were compared with those previously published on the power spectrum characteristics of mammographic texture. The scatter signal alone was analyzed qualitatively and a power-law fit was also performed. Results: The mammography and tomosynthesis projections of three patient breasts were too small to analyze, so a total of 16 patient breasts were analyzed. The values of β for the total signal of the 0° projections agreed well with previously published results

  7. TGF-β signaling deficient fibroblasts enhance Hepatocyte Growth Factor signaling in mammary carcinoma cells to promote scattering and invasion

    PubMed Central

    Cheng, Nikki; Chytil, Anna; Shyr, Yu; Joly, Alison; Moses, Harold L.

    2009-01-01

    Fibroblasts are major cellular components of the tumor microenvironment, regulating tumor cell behavior in part through secretion of extracellular matrix proteins, growth factors and angiogenic factors. In previous studies, conditional deletion of the type II TGF-β receptor in fibroblasts (Tgfbr2FspKO) was shown to promote mammary tumor metastasis in fibroblast: epithelial cell co-transplantation studies in mice, correlating with increased expression of HGF. Here, we advance our findings to show that Tgfbr2FspKO fibroblasts enhance HGF/c-Met and HGF/Ron signaling to promote scattering and invasion of mammary carcinoma cells. Blockade of c-Met and Ron by siRNA silencing and pharmacologic inhibitors significantly reduced mammary carcinoma cell scattering and invasion caused by Tgfbr2FspKO fibroblasts. Moreover, neutralizing antibodies to c-Met and Ron significantly inhibited HGF-induced cell scattering and invasion correlating with reduced Stat3 and p42/44MAPK phosphorylation. Investigation of the Stat3 and MAPK signaling pathways by pharmacologic inhibition and siRNA silencing revealed a cooperative interaction between the two pathways to regulate HGF- induced invasion, scattering and motility of mammary tumor cells. Furthermore, while c-Met was found to regulate both the Stat3 and MAPK signaling pathways, Ron was found to regulate Stat3, but not MAPK signaling in mammary carcinoma cells. These studies demonstrate a tumor suppressive role for TGF-β signaling in fibroblasts, in part by suppressing HGF signaling between mammary fibroblasts and epithelial cells. These studies characterize complex functional roles for HGF and TGF-β signaling in mediating tumor: stromal interactions during mammary tumor cell scattering and invasion, with important implications in the metastatic process. PMID:18922968

  8. Optical wavefront shaping for the enhancement of Raman signal in scattering media

    NASA Astrophysics Data System (ADS)

    Thompson, Jonathan V.; Throckmorton, Graham A.; Hokr, Brett H.; Yakovlev, Vladislav V.

    2016-03-01

    The ability to non-invasively focus light through scattering media has significant applications in many fields ranging from nanotechnology to deep tissue sensing. Until recently, the multiple light scattering events that occur in complex media such as biological tissue have inhibited the focusing ability and penetration depth of optical tools. Through the use of optical wavefront shaping, the spatial distortions due to these scattering events can be corrected, and the incident light can be focused through the scattering medium. Here, we demonstrate that wavefront shaping can be used to non-invasively enhance the Raman signal of a material through a scattering medium. Raman signal enhancement was achieved using backscattered light and a continuous sequential algorithm. Our results show the potential of wavefront shaping as an important addition to non-invasive detection techniques.

  9. Signals of strong electronic correlation in ion scattering processes

    NASA Astrophysics Data System (ADS)

    Bonetto, F.; Gonzalez, C.; Goldberg, E. C.

    2016-05-01

    Previous measurements of neutral atom fractions for S r+ scattered by gold polycrystalline surfaces show a singular dependence with the target temperature. There is still not a theoretical model that can properly describe the magnitude and the temperature dependence of the neutralization probabilities found. Here, we applied a first-principles quantum-mechanical theoretical formalism to describe the time-dependent scattering process. Three different electronic correlation approaches consistent with the system analyzed are used: (i) the spinless approach, where two charge channels are considered (S r0 and S r+ ) and the spin degeneration is neglected; (ii) the infinite-U approach, with the same charge channels (S r0 and S r+ ) but considering the spin degeneration; and (iii) the finite-U approach, where the first ionization and second ionization energy levels are considered very, but finitely, separated. Neutral fraction magnitudes and temperature dependence are better described by the finite-U approach, indicating that e -correlation plays a significant role in charge-transfer processes. However, none of them is able to explain the nonmonotonous temperature dependence experimentally obtained. Here, we suggest that small changes in the surface work function introduced by the target heating, and possibly not detected by experimental standard methods, could be responsible for that singular behavior. Additionally, we apply the same theoretical model using the infinite-U approximation for the Mg-Au system, obtaining an excellent description of the experimental neutral fractions measured.

  10. First measurement of electron temperature from signal ratios in a double-pass Thomson scattering system

    SciTech Connect

    Tojo, H.; Itami, K.; Hatae, T.; Ejiri, A.; Yamaguchi, T.; Takase, Y.; Hiratsuka, J.

    2012-02-15

    This paper presents an experimental demonstration to determine electron temperature (T{sub e}) with unknown spectral sensitivity (transmissivity) in a Thomson scattering system. In this method, a double-pass scattering configuration is used and the scattered lights from each pass (with different scattering angles) are measured separately. T{sub e} can be determined from the ratio of the signal intensities without knowing a real chromatic dependence in the sensitivity. Note that the wavelength range for each spectral channel must be known. This method was applied to the TST-2 Thomson scattering system. As a result, T{sub e} measured from the ratio (T{sub e,r}) and T{sub e} measured from a standard method (T{sub e,s}) showed a good agreement with <|T{sub e,r}-T{sub e,s}|/T{sub e,s}>= 7.3%.

  11. Enhancement of Chiroptical Signals by Circular Differential Mie Scattering of Nanoparticles.

    PubMed

    Yoo, SeokJae; Park, Q-Han

    2015-01-01

    We enhance the weak optical signals of small chiral molecules via circular differential Mie scattering (CDMS) of nanoparticles immersed in them. CDMS is the preferential Mie scattering of left- and right-handed circularly polarized light by nanoparticles whose sizes are about the same as the wavelength of light. Solving the Mie scattering theory for chiral media, we find that the CDMS signal of the particle is linearly proportional to the chirality parameter κ of the molecules. This linear amplitude enhancement by CDMS of the particle holds, even for large particles, which have a retardation effect. We also demonstrate that the CDMS of a nanoparticle is sensitive to changes of molecular concentration, and that the nanoparticle can be utilized as a chiroptical biosensor detecting the concentration of analyte. We expect that the enhancement of molecular chiroptical signals by CDMS will pave the way for novel chiroptical spectroscopy using nanostructures. PMID:26403593

  12. Heterodyne signal-to-noise ratios in acoustic mode scattering experiments

    NASA Technical Reports Server (NTRS)

    Cochran, W. R.

    1980-01-01

    The relation between the signal to noise ratio (SNR) obtained in heterodyne detection of radiation scattered from acoustic modes in crystalline solids and the scattered spectral density function is studied. It is shown that in addition to the information provided by the measured frequency shifts and line widths, measurement of the SNR provides a determination of the absolute elasto-optical (Pockel's) constants. Examples are given for cubic crystals, and acceptable SNR values are obtained for scattering from thermally excited phonons at 10.6 microns, with no external perturbation of the sample necessary. The results indicate the special advantages of the method for the study of semiconductors.

  13. Signal sources in elastic light scattering by biological cells and tissues: what can elastic light scattering spectroscopy tell us?

    NASA Astrophysics Data System (ADS)

    Xu, M.; Wu, Tao T.; Qu, Jianan Y.

    2008-02-01

    We used a unified Mie and fractal model to analyze elastic light spectroscopy of cell suspensions to obtain the size distributions of cells and nuclei, their refractive indices, and the background refractive index fluctuation inside the cell, for different types of cells, including human cervical squamous carcinoma epithelial (SiHa) cells, androgen-independent malignant rat prostate carcinoma epithelial (AT3.1) cells, non-tumorigenic fibroblast (Rat1p) cells in the plateau phase of growth, and tumorigenic fibroblast (Rat1-T1E) cells in the exponential phase of growth. Signal sources contributing to the scattering (μs) and reduced scattering (μ 's) coefficients for these cells of various types or at different growth stages are compared. It is shown that the contribution to μ s from the nucleus is much more important than that from the background refractive index fluctuation. This trend is more significant with increase of the probing wavelength. On the other hand, the background refractive index fluctuation overtakes the nucleus and may even dominate in the contribution to reduced scattering. The implications of the above findings on biomedical light scattering techniques are discussed.

  14. The upper transition height over the Kharkiv incoherent scatter radar before, during and after the extreme minimum of the solar activity: Observational results and comparison with the IRI-2012 model

    NASA Astrophysics Data System (ADS)

    Kotov, Dmytro; Truhlik, Vladimir; Richards, Philipp; Huba, Joseph; Chernogor, Leonid; Bogomaz, Oleksandr; Domnin, Igor

    2014-05-01

    Variations in the diurnal minimum of upper transition height (height at which total light ions fraction is 50%) over Kharkiv, Ukraine are considered for vernal and autumnal equinoxes from 2006 to 2010. The data were obtained using the incoherent scatter radar of the Institute of ionosphere [1]. It was found that the decrease of daily F10.7 values approximately by 22 % (from 82 for spring 2006 to 67 for autumn 2007) was accompanied by a decrease in the upper transition height approximately by 19% too (from 518 km to 436 km). The linear correlation coefficient between the upper transition height and daily F10.7 was approximately 0.81. It should be noted that according to our knowledge such low values of upper transition height is the minimum ever recorded. In 2008-2009, the upper transition height over Kharkiv was up to 40 km lower than over the equator [2] and even up to 10-15 km lower than over Arecibo [3]. A comparison of the observational results with the IRI-2012 model [4] was made. It was found that the IRI-2012 model overestimates upper transition height up to 100 km in 2006, and 2010. The model also overestimates the upper transition height up to 150 km during the extreme solar minimum (2008-2009). It is clearly seen that for solar minimum under consideration latitudinal dependence of upper transition height according to observational data have decreasing character in contrast to the model dependence. Such behavior can be called latitudinal inversion of upper transition height. Strong dependence of upper transition height on Ap index was found for the conditions under consideration. It is suggested that model values for 2006 and 2010 are overestimated due to a higher geomagnetic activity during the satellite measurements (1974) underlying the model for the low level of solar activity compared with geomagnetic conditions for 2006 and 2010. Perhaps this led to the fact that the model does not show latitudinal inversion, which occurs only at very low geomagnetic

  15. Measurements and simulation of ionospheric scattering on VHF and UHF radar signals: Channel scattering function

    NASA Astrophysics Data System (ADS)

    Rogers, Neil C.; Cannon, Paul S.; Groves, Keith M.

    2009-02-01

    The design and operation of transionospheric VHF and UHF radars requires knowledge of amplitude and phase scintillation due to ionospheric scattering. Phase coherence is of particular importance where long coherent integration periods and large bandwidths are required. A thin phase screen, parabolic equation based, Trans-Ionospheric Radio Propagation Simulator (TIRPS) is described. Modeled channel scattering functions (CSFs) are compared to experimental VHF and UHF data derived from the Advanced Research Projects Agency Long-range Tracking and Instrumentation Radar on Kwajalein Island (9.4°N, 166.8°E). TIRPS quantitatively reproduces the experimental results, including the quasi-parabolic profile observed in the measured CSFs under strong turbulence conditions. Variations in the simulated CSF with ionospheric phase screen parameters are also presented. Under conditions of high integrated strength of turbulence (CkL), a low phase spectral index (p = 1), indicating relatively dense small-scale irregularities, produces pronounced range spreading. Conversely, when the spectral index is high (p = 4), indicative of strong focusing/defocusing by large-scale irregularities, there is increased Doppler spreading and, when the outer scale of irregularities is large, a greater likelihood of asymmetry of the CSF about the zero Doppler axis.

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

    NASA Technical Reports Server (NTRS)

    Flesia, C.; Schwendimann, P.

    1992-01-01

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

  17. The effect of scattering-medium parameters on signal magnitude under acousto-optic tomography

    NASA Astrophysics Data System (ADS)

    Zyuryukina, O. V.; Volkova, E. K.; Perchenko, M. I.; Solov'ev, A. P.

    2014-04-01

    We have experimentally studied the influence of scattering anisotropy parameter g of a medium on the magnitude of signal S (visualization parameter) at an ultrasonic frequency that is registered upon acoustooptic tomography. Aqueous solutions of mixtures of cream and skimmed milk with different ratios between them were used as scattering media. The optical properties of media (absorption coefficient μa and reduced scattering coefficient μ' S ) have been measured on a spectrophotometer (Perkin-Elmer Lambda 950 UV-VIS-NIR) using the inverse adding-doubling technique. As a result of the investigation, we have found that there is a certain correlation between the value of the scattering anisotropy parameter g of aqueous solutions of investigated mixtures and the percentage of the mixture in the aqueous solution, which ensures the required small value of extinction coefficient μ of the scattering medium. An increase in signal S has been revealed with increasing anisotropy parameter g of the medium at a invariable value of extinction coefficient μ. We have concluded that, to solve an inverse problem on the acousto-optic tomography, it is necessary to take into account possible changes in the g factor in scattering media, including biological ones.

  18. Correlation between light scattering signal and tissue reversibility in rat brain exposed to hypoxia

    NASA Astrophysics Data System (ADS)

    Kawauchi, Satoko; Sato, Shunichi; Uozumi, Yoichi; Nawashiro, Hiroshi; Ishihara, Miya; Kikuchi, Makoto

    2010-02-01

    Light scattering signal is a potential indicator of tissue viability in brain because cellular and subcellular structural integrity should be associated with cell viability in brain tissue. We previously performed multiwavelength diffuse reflectance measurement for a rat global ischemic brain model and observed a unique triphasic change in light scattering at a certain time after oxygen and glucose deprivation. This triphasic scattering change (TSC) was shown to precede cerebral ATP exhaustion, suggesting that loss of brain tissue viability can be predicted by detecting scattering signal. In the present study, we examined correlation between light scattering signal and tissue reversibility in rat brain in vivo. We performed transcranial diffuse reflectance measurement for rat brain; under spontaneous respiration, hypoxia was induced for the rat by nitrogen gas inhalation and reoxygenation was started at various time points. We observed a TSC, which started at 140 +/- 15 s after starting nitrogen gas inhalation (mean +/- SD, n=8). When reoxygenation was started before the TSC, all rats survived (n=7), while no rats survived when reoxygenation was started after the TSC (n=8). When reoxygenation was started during the TSC, rats survived probabilistically (n=31). Disability of motor function was not observed for the survived rats. These results indicate that TSC can be used as an indicator of loss of tissue reversibility in brains, providing useful information on the critical time zone for treatment to rescue the brain.

  19. An experimental study of the temporal statistics of radio signals scattered by rain

    NASA Technical Reports Server (NTRS)

    Hubbard, R. W.; Hull, J. A.; Rice, P. L.; Wells, P. I.

    1973-01-01

    A fixed-beam bistatic CW experiment designed to measure the temporal statistics of the volume reflectivity produced by hydrometeors at several selected altitudes, scattering angles, and at two frequencies (3.6 and 7.8 GHz) is described. Surface rain gauge data, local meteorological data, surveillance S-band radar, and great-circle path propagation measurements were also made to describe the general weather and propagation conditions and to distinguish precipitation scatter signals from those caused by ducting and other nonhydrometeor scatter mechanisms. The data analysis procedures were designed to provide an assessment of a one-year sample of data with a time resolution of one minute. The cumulative distributions of the bistatic signals for all of the rainy minutes during this period are presented for the several path geometries.

  20. The experimental study on Doppler echo signals with different scattering surfaces for velocity measurement

    NASA Astrophysics Data System (ADS)

    Wang, Leng-ping; Feng, Di; Ou, Pan; Yang, De-zhao

    2011-06-01

    Laser Doppler velocimetry has the ability to measure speed and surface vibrations non-intrusively with high precision. In this study the Doppler spectrum shift and spectrum broadening of echo signals by moving targets are investigated. The interaction between moving object and the laser beam of laser Doppler velocimetry have been described by varying rotating velocity, the angular velocity, distance and incident facula. By using different scattering surfaces, such as Polytetrafluoroethylene (PTFE) and sandpaper with different grain sizes, the characteristics of echo signals' Doppler spectra have been studied experimentally in detail. The results show that Doppler spectrum distribution is changed with different scattering surfaces. Meanwhile, in order to get a high measuring accuracy, the moving object's scattering characteristics must be considered carefully.

  1. Equations for Estimating the Strength of TV Signals Scattered by Wind Turbines

    NASA Technical Reports Server (NTRS)

    Spera, David A.; Sengupta, Dipak L.

    1994-01-01

    purposes of consistency. Next, the concept of a signal scatter ratio is introduced, which defines the fraction of the signal impinging on a wind turbine that is scattered by its blades onto a nearby receiver. Equations from references are modified for the calculation of experimental scatter ratios (from measured signals containing interference) and idealized scatter ratios (from rotor characteristics and relative locations of the transmitter, the turbine, and the receiver). Experimental and idealized scatter ratios are then calculated and compared for 75 cases from the literature, in which TVI measurements were made around a variety of wind turbines. An empirical equation is then defined for estimating the probability that an actual scatter ratio will differ from an idealized ratio by a given amount. Finally a sample calculation of the size of a potential TV interference zone around a hypothetical wind power station is presented.

  2. Equations for estimating the strength of TV signals scattered by wind turbines

    NASA Astrophysics Data System (ADS)

    Spera, David A.; Sengupta, Dipak L.

    1994-05-01

    purposes of consistency. Next, the concept of a signal scatter ratio is introduced, which defines the fraction of the signal impinging on a wind turbine that is scattered by its blades onto a nearby receiver. Equations from references are modified for the calculation of experimental scatter ratios (from measured signals containing interference) and idealized scatter ratios (from rotor characteristics and relative locations of the transmitter, the turbine, and the receiver). Experimental and idealized scatter ratios are then calculated and compared for 75 cases from the literature, in which TVI measurements were made around a variety of wind turbines. An empirical equation is then defined for estimating the probability that an actual scatter ratio will differ from an idealized ratio by a given amount. Finally a sample calculation of the size of a potential TV interference zone around a hypothetical wind power station is presented.

  3. Improved Reconstruction of Radio Holographic Signal for Forward Scatter Radar Imaging.

    PubMed

    Hu, Cheng; Liu, Changjiang; Wang, Rui; Zeng, Tao

    2016-01-01

    Forward scatter radar (FSR), as a specially configured bistatic radar, is provided with the capabilities of target recognition and classification by the Shadow Inverse Synthetic Aperture Radar (SISAR) imaging technology. This paper mainly discusses the reconstruction of radio holographic signal (RHS), which is an important procedure in the signal processing of FSR SISAR imaging. Based on the analysis of signal characteristics, the method for RHS reconstruction is improved in two parts: the segmental Hilbert transformation and the reconstruction of mainlobe RHS. In addition, a quantitative analysis of the method's applicability is presented by distinguishing between the near field and far field in forward scattering. Simulation results validated the method's advantages in improving the accuracy of RHS reconstruction and imaging. PMID:27164114

  4. Improved Reconstruction of Radio Holographic Signal for Forward Scatter Radar Imaging

    PubMed Central

    Hu, Cheng; Liu, Changjiang; Wang, Rui; Zeng, Tao

    2016-01-01

    Forward scatter radar (FSR), as a specially configured bistatic radar, is provided with the capabilities of target recognition and classification by the Shadow Inverse Synthetic Aperture Radar (SISAR) imaging technology. This paper mainly discusses the reconstruction of radio holographic signal (RHS), which is an important procedure in the signal processing of FSR SISAR imaging. Based on the analysis of signal characteristics, the method for RHS reconstruction is improved in two parts: the segmental Hilbert transformation and the reconstruction of mainlobe RHS. In addition, a quantitative analysis of the method’s applicability is presented by distinguishing between the near field and far field in forward scattering. Simulation results validated the method’s advantages in improving the accuracy of RHS reconstruction and imaging. PMID:27164114

  5. Development of a Technique for Separating Raman Scattering Signals from Background Emission with Single-Shot Measurement Potential

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Dobson, Chris; Eskridge, Richard; Wehrmeyer, Joseph A.

    1997-01-01

    A novel technique for extracting Q-branch Raman signals scattered by a diatomic species from the emission spectrum resulting from the irradiation of combustion products using a broadband excimer laser has been developed. This technique is based on the polarization characteristics of vibrational Raman scattering and can be used for both single-shot Raman extraction and time-averaged data collection. The Q-branch Raman signal has a unique set of polarization characteristics which depend on the direction of the scattering while fluorescence signals are unpolarized. For the present work, a calcite crystal is used to separate the horizonal component of a collected signal from the vertical component. The two components are then sent through a UV spectrometer and imaged onto an intensified CCD camera separately. The vertical component contains both the Raman signal and the interfering fluorescence signal. The horizontal component contains the fluorescence signal and a very weak component of the Raman signal; hence, the Raman scatter can be extracted by taking the difference between the two signals. The separation of the Raman scatter from interfering fluorescence signals is critically important to the interpretation of the Raman for cases in which a broadband ultraviolet (UV) laser is used as an excitation source in a hydrogen-oxygen flame and in all hydrocarbon flames. The present work provides a demonstration of the separation of the Raman scatter from the fluorescence background in real time.

  6. The No-Higgs Signal: Strong WW Scattering at the LHC

    SciTech Connect

    Michael S. Chanowitz

    2004-12-07

    Strong WW scattering at the LHC is discussed as a manifestation of electroweak symmetry breaking in the absence of a light Higgs bosom. The general framework of the Higgs mechanism--with or without a Higgs boson--is reviewed, and unitarity is shown to fix the scale of strong WW scattering. Strong WW scattering is also shown to be a possible outcome of five-dimensional models, which do not employ the usual Higgs mechanism at the TeV scale. Precision electroweak constraints are briefly discussed. Illustrative LHC signals are reviewed for models with QCD-like dynamics, stressing the complementarity of the W{sup {+-}}Z and like-charge W{sup +}W{sup +} + W{sup -}W{sup -} channels.

  7. DOA estimation for local scattered CDMA signals by particle swarm optimization.

    PubMed

    Chang, Jhih-Chung

    2012-01-01

    This paper deals with the direction-of-arrival (DOA) estimation of local scattered code-division multiple access (CDMA) signals based on a particle swarm optimization (PSO) search. For conventional spectral searching estimators with local scattering, the searching complexity and estimating accuracy strictly depend on the number of search grids used during the search. In order to obtain high-resolution and accurate DOA estimation, a smaller grid size is needed. This is time consuming and it is unclear how to determine the required number of search grids. In this paper, a modified PSO is presented to reduce the required search grids for the conventional spectral searching estimator with the effects of local scattering. Finally, several computer simulations are provided for illustration and comparison. PMID:22737004

  8. Quasi-periodic variations in the Doppler shift of HF signals scattered by artificial ionospheric turbulence

    SciTech Connect

    Belenov, A.F.; Ponomarenko, P.V.; Sinitsyn, V.G.; Yampol`skii, Yu.M.

    1994-06-01

    The results of an experimental study of quasi-periodic variations of the Doppler shift (DS) of decimeter-wave signals scattered by artificial ionospheric turbulence are presented. It is suggested that ionospheric MHD waves of natural origin are a possible cause of such variations. The amplitude of the magnetic component of such waves that leads to observable values of DS variations is estimated to be 1{gamma}.

  9. Quasi-periodic variations in the Doppler shift of HF signals scattered by artificial ionospheric turbulence

    NASA Astrophysics Data System (ADS)

    Belenov, A. F.; Ponomarenko, P. V.; Sinitsyn, V. G.; Yampol'Skii, Yu. M.

    1993-12-01

    The results of an experimental study of quasi-periodic variations of the Doppler shift (DS) of decimeter-wave signals scattered by artificial ionospheric turbulence are presented. It is suggested that ionospheric MHD waves of natural origin are a possible cause of such variations. The amplitude of the magnetic component of such waves that leads to observable values of DS variations is estimated to be 1γ.

  10. Digital spatially incoherent Fresnel holography

    NASA Astrophysics Data System (ADS)

    Rosen, Joseph; Brooker, Gary

    2007-04-01

    We present a new method for recording digital holograms under incoherent illumination. Light is reflected from a 3D object, propagates through a diffractive optical element (DOE), and is recorded by a digital camera. Three holograms are recorded sequentially, each for a different phase factor of the DOE. The three holograms are superposed in the computer, such that the result is a complex-valued Fresnel hologram. When this hologram is reconstructed in the computer, the 3D properties of the object are revealed.

  11. Two-component dual-scatter laser Doppler velocimeter with frequency burst signal readout.

    PubMed

    Brayton, D B; Kalb, H T; Crosswy, F L

    1973-06-01

    A dual-scatter laser Doppler velocimeter (LDV) system designed for measuring wind tunnel flow velocity is described. The system simultaneously measures two orthogonal velocity components of a flowing fluid at a common point in the flow. Essential single-velocity component dual-scatter concepts are presented to simplify the description of the more sophisticated two-component system. To implement the two-component system three laser beams with a 0 degrees , 45 degrees , and 90 degrees polarization plane relationship are focused to a common point in the flow by the system-transmitting optics. The beams interfere to form two perpendicular sets of interference fringe planes that are orthogonally polarized. The system-receiving optics collect and separate the orthogonally polarized components of laser radiation scattered from micron-size particles moving with the flowing fluid through the ringes. The system requires no artificial seeding, since intrinsic test section aerosols are utilized for radiation scattering. The passage of each scatter particle through the interference fringes simultaneously produces two frequency-burst-type photodetected signals, the frequencies of which are directly proportional to two perpendicular components of particle velocity. The system photodetection, signal-conditioning, and data acquisition instrumentation is specifically designed to process the frequency burst information in the time domain as opposed to spectrum analysis or frequency domain processing. The system was initially evaluated in an AEDC wind tunnel operating over a Mach number range from 0.6 to 1.5. The LDV and calculated wind tunnel mean velocity data agreed to within 1.25%; flow direction deviations of a few milliradians were resolved. PMID:20125494

  12. Applying an optical space-time coding method to enhance light scattering signals in microfluidic devices.

    PubMed

    Mei, Zhe; Wu, Tsung-Feng; Pion-Tonachini, Luca; Qiao, Wen; Zhao, Chao; Liu, Zhiwen; Lo, Yu-Hwa

    2011-09-01

    An "optical space-time coding method" was applied to microfluidic devices to detect the forward and large angle light scattering signals for unlabelled bead and cell detection. Because of the enhanced sensitivity by this method, silicon pin photoreceivers can be used to detect both forward scattering (FS) and large angle (45-60°) scattering (LAS) signals, the latter of which has been traditionally detected by a photomultiplier tube. This method yields significant improvements in coefficients of variation (CV), producing CVs of 3.95% to 10.05% for FS and 7.97% to 26.12% for LAS with 15 μm, 10 μm, and 5 μm beads. These are among the best values ever demonstrated with microfluidic devices. The optical space-time coding method also enables us to measure the speed and position of each particle, producing valuable information for the design and assessment of microfluidic lab-on-a-chip devices such as flow cytometers and complete blood count devices. PMID:21915241

  13. Shuttle Imaging Radar - Physical controls on signal penetration and subsurface scattering in the Eastern Sahara

    NASA Technical Reports Server (NTRS)

    Schaber, G. G.; Mccauley, J. F.; Breed, C. S.; Olhoeft, G. R.

    1986-01-01

    Interpretation of Shuttle Imaging Radar-A (SIR-A) images by McCauley et al. (1982) dramatically changed previous concepts of the role that fluvial processes have played over the past 10,000 to 30 million years in shaping this now extremely flat, featureless, and hyperarid landscape. In the present paper, the near-surface stratigraphy, the electrical properties of materials, and the types of radar interfaces found to be responsible for different classes of SIR-A tonal response are summarized. The dominant factors related to efficient microwave signal penetration into the sediment blanket include (1) favorable distribution of particle sizes, (2) extremely low moisture content and (3) reduced geometric scattering at the SIR-A frequency (1.3 GHz). The depth of signal penetration that results in a recorded backscatter, here called 'radar imaging depth', was documented in the field to be a maximum of 1.5 m, or 0.25 of the calculated 'skin depth', for the sediment blanket. Radar imaging depth is estimated to be between 2 and 3 m for active sand dune materials. Diverse permittivity interfaces and volume scatterers within the shallow subsurface are responsible for most of the observed backscatter not directly attributable to grazing outcrops. Calcium carbonate nodules and rhizoliths concentrated in sandy alluvium of Pleistocene age south of Safsaf oasis in south Egypt provide effective contrast in premittivity and thus act as volume scatterers that enhance SIR-A portrayal of younger inset stream channels.

  14. Nonlinear dispersion-based incoherent photonic processing for microwave pulse generation with full reconfigurability.

    PubMed

    Bolea, Mario; Mora, José; Ortega, Beatriz; Capmany, José

    2012-03-12

    A novel all-optical technique based on the incoherent processing of optical signals using high-order dispersive elements is analyzed for microwave arbitrary pulse generation. We show an approach which allows a full reconfigurability of a pulse in terms of chirp, envelope and central frequency by the proper control of the second-order dispersion and the incoherent optical source power distribution, achieving large values of time-bandwidth product. PMID:22418557

  15. Design and development of detector signal conditioning electronics for SST-1 Thomson scattering system

    SciTech Connect

    Thakar, Aruna; Kumar, Ajai; Thomas, Jinto; Chavda, Chhaya

    2008-09-15

    An IR enhanced thermoelectrically cooled Si-avalanche photodiode (Si-APD) module is used for detection of scattered photons from plasma electrons. Present design of signal conditioning electronics for the APD has fast (50 MHz) and slow (500 kHz) channels to measure scattered and plasma background light, respectively. We report design analysis for different stages and their performance. The performance of fast channel is analyzed for two different group delays, speed, linearity, and its cross-talk with slow channel. Temperature dependence of APD's responsivity is studied in the wavelength range of 900-1060 nm. A minimum detection of {approx}25 photoelectrons (with S/N=1) in the range of 5 to 25 deg. C is achieved at an APD gain of 75 in the present design.

  16. Design and development of detector signal conditioning electronics for SST-1 Thomson scattering system.

    PubMed

    Thakar, Aruna; Kumar, Ajai; Thomas, Jinto; Chavda, Chhaya

    2008-09-01

    An IR enhanced thermoelectrically cooled Si-avalanche photodiode (Si-APD) module is used for detection of scattered photons from plasma electrons. Present design of signal conditioning electronics for the APD has fast (50 MHz) and slow (500 kHz) channels to measure scattered and plasma background light, respectively. We report design analysis for different stages and their performance. The performance of fast channel is analyzed for two different group delays, speed, linearity, and its cross-talk with slow channel. Temperature dependence of APD's responsivity is studied in the wavelength range of 900-1060 nm. A minimum detection of approximately 25 photoelectrons (with SN=1) in the range of 5 to 25 degrees C is achieved at an APD gain of 75 in the present design. PMID:19044411

  17. The Detection of Protein via ZnO Resonant Raman Scattering Signal

    NASA Astrophysics Data System (ADS)

    Shan, Guiye; Yang, Guoliang; Wang, Shuang; Liu, Yichun

    2008-03-01

    Detecting protein with high sensitivity and specificity is essential for disease diagnostics, drug screening and other application. Semiconductor nanoparticles show better properties than organic dye molecules when used as markers for optical measurements. We used ZnO nanoparticles as markers for detecting protein in resonant Raman scattering measurements. The highly sensitive detection of proteins was achieved by an antibody-based sandwich assay. A probe for the target protein was constructed by binding the ZnO/Au nanoparticles to a primary antibody by eletrostatic interaction between Au and the antibody. A secondary antibody, which could be specifically recognized by target protein, was attached to a solid surface. The ZnO/Au-antibody probe could specifically recognize and bind to the complex of the target protein and secondary antibody. Our measurements using the resonant Raman scattering signal of ZnO nanoparticles showed good selectivity and sensitivity for the target protein.

  18. Doppler shift simulation of scattered HF signals during the Tromsø HF pumping experiment on 16 February 1996

    NASA Astrophysics Data System (ADS)

    Borisova, T. D.; Blagoveshchenskaya, N. F.; Moskvin, I. V.; Rietveld, M. T.; Kosch, M. J.; Thidé, B.

    2002-09-01

    Comparisons between bistatic scatter measurements and simulation results during the Tromsø HF pumping experiment on 16 February 1996 are made. Doppler measurements of an HF diagnostic signal scattered from the field-aligned irregularities (FAIs) in the auroral E-region were carried out on the London Tromsø St. Petersburg path at 9410 kHz from 21:00 to 22:00 UT. The scattered signals were observed both from natural and artificial ionospheric irregularities located in the vicinity of Tromsø. To simulate the Doppler frequency shifts, fd , of scattered signals, a radio channel model, named CONE, was developed. The model allows for ray tracing, group and phase paths, and Doppler frequency shift calculations. The calculated Doppler shifts were analyzed for dependence on the magnitude and direction of plasma velocities in the scattering volume. It was found that the velocity components in the north-south direction are crucial for explaining the Doppler frequency shifts of the scattered diagnostic signals. To simulate fd , real velocities obtained from the EISCAT UHF radar at an altitude of 278 km and from the digital all-sky imager during the experiment were employed. The simulation results of Doppler frequency shift variations with time are in reasonable agreement with the experimental Doppler shifts of scattered signals on the London Tromsø St. Petersburg path.

  19. Signal, noise, and resolution in correlated fluctuations from snapshot small-angle x-ray scattering

    SciTech Connect

    Kirian, Richard A.; Schmidt, Kevin E.; Wang Xiaoyu; Doak, R. Bruce; Spence, John C. H.

    2011-07-15

    It has been suggested that the three-dimensional structure of one particle may be reconstructed using the scattering from many identical, randomly oriented copies ab initio, without modeling or a priori information. This may be possible if these particles are frozen in either space or time, so that the conventional two-dimensional small-angle x-ray scattering (SAXS) distribution contains fluctuations and is no longer isotropic. We consider the magnitude of the correlated fluctuation SAXS (CFSAXS) signal for typical x-ray free-electron laser (XFEL) beam conditions and compare this against the errors derived with the inclusion of Poisson photon counting statistics. The resulting signal-to-noise ratio (SNR) is found to rapidly approach a limit independent of the number of particles contributing to each diffraction pattern, so that the addition of more particles to a ''single-particle-per-shot'' experiment may be of little value, apart from reducing solvent background. When the scattering power is significantly less than one photon per particle per Shannon pixel, the SNR grows in proportion to incident flux. We provide simulations for protein molecules in support of these analytical results, and discuss the effects of solvent background scatter. We consider the SNR dependence on resolution and particle size, and discuss the application of the method to glasses and liquids, and the implications of more powerful XFELs, smaller focused beams, and higher pulse repetition rates for this approach. We find that an accurate CFSAXS measurement may be acquired to subnanometer resolution for protein molecules if a 9-keV beam containing 10{sup 13} photons is focused to a {approx}100-nm spot diameter, provided that the effects of solvent background can be reduced sufficiently.

  20. Abl Kinases Regulate HGF/Met Signaling Required for Epithelial Cell Scattering, Tubulogenesis and Motility

    PubMed Central

    Li, Ran; Knight, Jennifer F.; Park, Morag; Pendergast, Ann Marie

    2015-01-01

    Tight regulation of receptor tyrosine kinases (RTKs) is crucial for normal development and homeostasis. Dysregulation of RTKs signaling is associated with diverse pathological conditions including cancer. The Met RTK is the receptor for hepatocyte growth factor (HGF) and is dysregulated in numerous human tumors. Here we show that Abl family of non-receptor tyrosine kinases, comprised of Abl (ABL1) and Arg (ABL2), are activated downstream of the Met receptor, and that inhibition of Abl kinases dramatically suppresses HGF-induced cell scattering and tubulogenesis. We uncover a critical role for Abl kinases in the regulation of HGF/Met-dependent RhoA activation and RhoA-mediated actomyosin contractility and actin cytoskeleton remodeling in epithelial cells. Moreover, treatment of breast cancer cells with Abl inhibitors markedly decreases Met-driven cell migration and invasion. Notably, expression of a transforming mutant of the Met receptor in the mouse mammary epithelium results in hyper-activation of both Abl and Arg kinases. Together these data demonstrate that Abl kinases link Met activation to Rho signaling and Abl kinases are required for Met-dependent cell scattering, tubulogenesis, migration, and invasion. Thus, inhibition of Abl kinases might be exploited for the treatment of cancers driven by hyperactivation of HGF/Met signaling. PMID:25946048

  1. Optimum Physics-Based Signal Processing in a Random Wave Scattering Environment

    NASA Astrophysics Data System (ADS)

    Premus, Vincent E.

    A physics-based approach to the design of optimum signal processing algorithms for ocean acoustic remote sensing is presented. The approach merges physical and statistical modeling of acoustic scattering from a randomly rough ocean bottom with the principles of Bayesian inference and parameter estimation theory. The work seeks to exploit the synergistic relationship between accurate physical modeling of the propagation/scattering medium and optimum detection/estimation theory. Within this framework, the problems of acoustic seafloor characterization and robust target detection in the presence of environmental uncertainty are addressed. Accurate modeling of the wave scattering physics, based on the 3-dimensional Helmholtz-Kirchhoff theory and a geologically motivated parametrization of seafloor morphology, is of central importance to this work. In the seafloor characterization problem, the approach attempts to connect the correlation statistics of the scattered acoustic field with the seafloor microroughness wavenumber spectrum by constructing the a posteriori probability density function of the spectrum parameters. Maximum a posteriori probability estimates of the surface model parameters are obtained from two forms of acoustic data, backscattering strength angular dependence and backscatter spatial coherence. In the detection problem, a general theoretical framework for deriving the optimum detector in the case of uncertain reverberation spatial coherence is first presented in which the exact analytical form of the scattered field pdf is presumed to be arbitrary or unknown. A specialization to the case of Gaussian reverberation is then made. Simulation results, presented in terms of receiver operation characteristic (ROC) curves, illustrate the robust performance realizable by the optimum detection algorithm that properly accounts for environmental uncertainty within a Bayesian framework.

  2. Forward scattering of a pulsed continuous wave signal through laminar and turbulent thermal plumes

    NASA Astrophysics Data System (ADS)

    Bowen, Stephen G.

    1993-09-01

    The results of an experiment examining the forward propagation of an acoustic signal through a buoyant plume are discussed. Two distinct testing sights were used. One made use of a small fresh water tank in NUWC to provide a controlled plume. The other used a larger salt water tank at Woods Hole Oceanographic Institute (WHOI) to create a more realistic oceanic model. Using the Born and Rytov approximations, an estimation of the effects of the laminar plume on the propagated signal are shown. As the plume moves from laminar to turbulent, the scintillation index and the Fourier transform of the magnitude square response provide insight into the nature of the transition. Finally, from the turbulent response a model for the scattering function is developed.

  3. Stimulated Brillouin scattering gain bandwidth reduction and applications in microwave photonics and optical signal processing

    NASA Astrophysics Data System (ADS)

    Preussler, Stefan; Schneider, Thomas

    2016-03-01

    Stimulated Brillouin scattering (SBS) is one of the most dominant nonlinear effects in standard single-mode fibers and its unique spectral characteristics, especially the narrow bandwidth, enable many different applications. Most of the applications would benefit from a narrower bandwidth. Different methods for the bandwidth reduction of SBS in optical fibers are presented and discussed. A bandwidth reduction down to 17% of the natural gain can be achieved by the superposition of the gain with two losses or the utilization of a multistage system. Furthermore, applications in the field of microwave photonics and optical signal processing like high-resolution spectroscopy of communication signals, the storage of optical data packets as well as the processing of frequency combs including generation of millimeter waves and ideal sinc-shaped Nyquist pulses are presented.

  4. Quantitative phase imaging through scattering media

    NASA Astrophysics Data System (ADS)

    Kollárová, Vera; Colláková, Jana; Dostál, Zbynek; Slabý, Tomas; Veselý, Pavel; Chmelík, Radim

    2015-03-01

    Coherence-controlled holographic microscope (CCHM) is an off-axis holographic system. It enables observation of a sample and its quantitative phase imaging with coherent as well as with incoherent illumination. The spatial and temporal coherence can be modified and thus also the quality and type of the image information. The coherent illumination provides numerical refocusing in wide depth range similarly to a classic coherent-light digital holographic microscopy (HM). Incoherent-light HM is characterized by a high quality, coherence-noise-free imaging with up to twice higher resolution compared to coherent illumination. Owing to an independent, free of sample reference arm of the CCHM the low spatial light coherence induces coherence-gating effect. This makes possible to observe specimen also through scattering media. We have described theoretically and simulated numerically imaging of a two dimensional object through a scattering layer by CCHM using the linear systems theory. We have investigated both strongly and weakly scattering media characterized by different amount of ballistic and diffuse light. The influence of a scattering layer on the quality of a phase signal is discussed for both types of the scattering media. A strong dependence of the imaging process on the light coherence is demonstrated. The theoretical calculations and numerical simulations are supported by experimental data gained with model samples, as well as real biologic objects particularly then by time-lapse observations of live cells reactions to substances producing optically turbid emulsion.

  5. Applying new data-entropy and data-scatter methods for optical digital signal analysis

    NASA Astrophysics Data System (ADS)

    McMillan, N. D.; Egan, J.; Denieffe, D.; Riedel, S.; Tiernan, K.; McGowan, G.; Farrell, G.

    2005-06-01

    This paper introduces for the first time a numerical example of the data-entropy 'quality-budget' method. The paper builds on an earlier theoretical investigation into the application of this information theory approach for opto-electronic system engineering. Currently the most widely used way of analysing such a system is with the power budget. This established method cannot however integrate noise of different generic types. The traditional power budget approach is not capable of allowing analysis of a system with different noise types and specifically providing a measure of signal quality. The data-entropy budget first introduced by McMillan and Reidel on the other hand is able to handle diverse forms of noise. This is achieved by applying the dimensionless 'bit measure' in a quality-budget to integrate the analysis of all types of losses. This new approach therefore facilitates the assessment of both signal quality and power issues in a unified way. The software implementation of data-entropy has been utilised for testing on a fiber optic network. The results of various new quantitative data-entropy measures on the digital system are given and their utility discussed. A new data mining technique known as data-scatter also introduced by McMillan and Reidel provides a useful visualisation of the relationships between data sets and is discussed. The paper ends by giving some perspective on future work in which the data-entropy technique, providing the objective difference measure on the signals, and data-scatter technique, providing qualitative information on the signals, are integrated together for optical communication applications.

  6. Dark matter scattering on electrons: Accurate calculations of atomic excitations and implications for the DAMA signal

    NASA Astrophysics Data System (ADS)

    Roberts, B. M.; Dzuba, V. A.; Flambaum, V. V.; Pospelov, M.; Stadnik, Y. V.

    2016-06-01

    We revisit the WIMP-type dark matter scattering on electrons that results in atomic ionization and can manifest itself in a variety of existing direct-detection experiments. Unlike the WIMP-nucleon scattering, where current experiments probe typical interaction strengths much smaller than the Fermi constant, the scattering on electrons requires a much stronger interaction to be detectable, which in turn requires new light force carriers. We account for such new forces explicitly, by introducing a mediator particle with scalar or vector couplings to dark matter and to electrons. We then perform state-of-the-art numerical calculations of atomic ionization relevant to the existing experiments. Our goals are to consistently take into account the atomic physics aspect of the problem (e.g., the relativistic effects, which can be quite significant) and to scan the parameter space—the dark matter mass, the mediator mass, and the effective coupling strength—to see if there is any part of the parameter space that could potentially explain the DAMA modulation signal. While we find that the modulation fraction of all events with energy deposition above 2 keV in NaI can be quite significant, reaching ˜50 %, the relevant parts of the parameter space are excluded by the XENON10 and XENON100 experiments.

  7. Enhancement of Raman scattering signal of a few molecules using photonic nanojet mediated SERS technique

    NASA Astrophysics Data System (ADS)

    Das, G. M.; Parit, M. K.; Laha, R.; Dantham, V. R.

    2016-05-01

    Now a days, single molecule surface enhanced Raman spectroscopy (SMSERS) has become a fascinating tool for studying the structural properties, static and dynamic events of single molecules (instead of ensemble average), with the help of efficient plasmonic nanostructures. This is extremely useful in the field of proteomics because the structural properties of protein molecules are heterogeneous. Even though, SMSERS provides wealthy information about single molecules, it demands high quality surface enhanced Raman scattering (SERS) substrates. So far, a very few researchers succeeded in demonstrating the single molecule Raman scattering using conventional SERS technique. However, the experimental S/N of the Raman signal has been found to be very poor. Recently, with the help of photonic nanojet of an optical microsphere, we were able to enhance the SERS signal of a few molecules adsorbed on the SERS substrates (gold symmetric and asymmetric nanodimers and trimers dispersed on a glass slide). Herein, we report a few details about photonic nanojet mediated SERS technique, a few experimental results and a detailed theoretical study on symmetric and asymmetric nanosphere dimers to understand the dependence of localised surface plasmon resonance (LSPR) wavelength of a nanodimer on the nanogap size and polarization of the excitation light.

  8. Optimal coherent control of coherent anti-Stokes Raman scattering: Signal enhancement and background elimination

    NASA Astrophysics Data System (ADS)

    Gao, Fang; Shuang, Feng; Shi, Junhui; Rabitz, Herschel; Wang, Haifeng; Cheng, Ji-Xin

    2012-04-01

    The ability to enhance resonant signals and eliminate the non-resonant background is analyzed for coherent anti-Stokes Raman scattering (CARS). The analysis is done at a specific frequency as well as for broadband excitation using femtosecond pulse-shaping techniques. An appropriate objective functional is employed to balance resonant signal enhancement against non-resonant background suppression. Optimal enhancement of the signal and minimization of the background can be achieved by shaping the probe pulse alone while keeping the pump and Stokes pulses unshaped. In some cases analytical forms for the probe pulse can be found, and numerical simulations are carried out for other circumstances. It is found that a good approximate optimal solution for resonant signal enhancement in two-pulse CARS is a superposition of linear and arctangent-type phases for the pump. The well-known probe delay method is shown to be a quasi-optimal scheme for broadband background suppression. The results should provide a basis to improve the performance of CARS spectroscopy and microscopy.

  9. Identification of complex scattered signals with a fast real-time hybrid electro-optical correlator

    NASA Astrophysics Data System (ADS)

    Majumdar, Arun K.; Sandomirsky, Sergey

    1997-10-01

    The goal of this work was to develop a fast optical correlator for automatic real-time target recognition. The tremendous importance of optical correlators for military and civilian applications was recognized recently and approved by a US conference committee of senators nd representatives. This publication presents the experimental results of detecting and identifying complex scattered signals by using an innovative, hybrid electro-optical correlator. Our technique is based on achieving optical correlation by utilizing state-of-the-art devices: time delay integration, charge coupled devices, liquid crystal displays, and electronically controllable light sources. Results of the experiment with our optical correlator, performed with simulated sonar signals with a center frequency of 100 kHz and duration of 8 to 512 pulses, show the possibility of recognizing a Doppler shift of 20 Hz. This Doppler shift corresponds to a target velocity of 20.7 m/sec. Simulation results indicate that we can achieve significant correlation for a noisy signal by using appropriate signal length. Our experiments demonstrate that we can perform approximately 1010 multiply accumulate operations per second with the high parallel optical corrector, compared to approximately 106 multiply accumulate operations per second using a Pentium 133 MHz personal computer. This new optical correlation scheme can provide solutions for overcoming the inherent shortcomings attributable to the low dynamic range of CCD, and the problem of compatibility caused by different pixel patterns between LCD and CCD by making use of high-quality optics and modern means of achieving uniform illumination.

  10. Optical telecommunications system and signal analysis using data-entropy and multiple-centroid data-scatter

    NASA Astrophysics Data System (ADS)

    Egan, J.; McMillan, N. D.; Denieffe, D.; Riedel, S.; Doyle, G.; Farrell, G.

    2005-09-01

    The data-entropy quality-budget developed by the authors is used as an alternative to the conventional power budget. The traditional power budget approach is not capable of providing a full analysis of a system with different noise types and specifically providing a measure of signal quality. The quality-budget addressed this issue by applying its dimensionless 'bit measure' to integrate the analysis of all types of losses. A data-entropy visualisation is produced for each set of points in a reference and test signal. This data-entropy signal is a measure of signal disorder and reflects the power loss and types of signal degradation experienced by the test signal. To analyse the differences between two signals an algorithm known as phase-coherent data-scatter (PCDS) is used to assess levels of attenuation, dispersion, jitter, etc. Practical analysis of telecommunications signals using the new multiple-centroid (MC) PCDS is presented here for the first time. MC-PCDS is then used to analyse differences between sets of data-entropy signals and digital signals. The theory behind MC data-scatter is discussed and its advantages for the quantification of signal degradations are assessed. Finally, a brief consideration is given to the use of pattern recognition algorithms to measure optical signal degrading factors.

  11. SHUTTLE IMAGING RADAR: PHYSICAL CONTROLS ON SIGNAL PENETRATION AND SUBSURFACE SCATTERING IN THE EASTERN SAHARA.

    USGS Publications Warehouse

    Schaber, Gerald G.; McCauley, John F.; Breed, Carol S.; Olhoeft, Gary R.

    1986-01-01

    It is found that the Shuttle Imaging Radar A (SIR-A) signal penetration and subsurface backscatter within the upper meter or so of the sediment blanket in the Eastern Sahara of southern Egypt and northern Sudan are enhanced both by radar sensor parameters and by the physical and chemical characteristics of eolian and alluvial materials. The near-surface stratigraphy, the electrical properties of materials, and the types of radar interfaces found to be responsible for different classes of SIR-A tonal response are summarized. The dominant factors related to efficient microwave signal penetration into the sediment blanket include 1) favorable distribution of particle sizes, 2) extremely low moisture content and 3) reduced geometric scattering at the SIR-A frequency (1. 3 GHz). The depth of signal penetration that results in a recorded backscatter, called radar imaging depth, was documented in the field to be a maximum of 1. 5 m, or 0. 25 times the calculated skin depth, for the sediment blanket. The radar imaging depth is estimated to be between 2 and 3 m for active sand dune materials.

  12. A scattering analysis of echoes due to biosonar signals emitted by foraging beaked whales

    NASA Astrophysics Data System (ADS)

    Jones, Benjamin A.; Stanton, Timothy K.; Lavery, Andone C.; Johnson, Mark P.; Madsen, Peter T.; Tyack, Peter L.

    2005-09-01

    Blainville's beaked whales (Mesoplodon densirostris) hunt their prey by echolocation at depths of more than 500 meters. These whales use a FM upswept, ultrasonic click, of greater than an octave bandwidth to search for, localize, and close on individual prey which generally consist of mesopelagic fishes and squid. It is well known that acoustic scattering from organisms of varying morphology (e.g., swimbladder-bearing or fluidlike) is strongly frequency dependent. However, it is unknown if the broadband nature of the whales' outgoing signal, and the frequency dependence of the echoes, is a key component in the classification and selection of their prey. Non-invasive, acoustic ``Dtags,'' which sample stereo acoustic data at a rate which satisfies the high-frequency Nyquist criterion for the animal's transmit signal, were affixed to beaked whales. The Dtags successfully recorded transmitted signals and associated echoes. Structure was observed in the frequency content of echoes from isolated targets in the water column which may be used for classification by the whales. An analysis of the echoes identified as possibly due to prey has demonstrated that multiple classes of frequency responses are present. These results will be compared with the frequency responses of possible prey types.

  13. Signal intensity transfer function determination on thermal systems with stray light or scattering present

    NASA Astrophysics Data System (ADS)

    Burks, Stephen D.; Haefner, David P.; Burks, Thomas J.

    2015-05-01

    Accurate Signal Intensity Transfer Functions (SITF) measurements are necessary to determine the calibration factor in the 3D noise calculation of an electro-optical imaging system. The typical means for measuring a sensor's SITF is to place the sensor in a flooded field environment at a distance that is relatively close to the aperture of the emitter. Unfortunately, this arrangement has the potential to allow for additional contributions to the SITF in the form of scattering or stray light if the optics are not designed properly in the system under test. Engineers at the US Army Night Vision and Electronic Sensors Directorate are working to determine a means of evaluating the contribution due to scatting or stray light.

  14. Simulating x-ray Thomson scattering signals from high-density, millimetre-scale plasmas at the National Ignition Facility

    SciTech Connect

    Chapman, D. A.; Kraus, D.; Falcone, R. W.; Kritcher, A. L.; Bachmann, B.; Collins, G. W.; Gaffney, J. A.; Hawreliak, J. A.; Landen, O. L.; Le Pape, S.; Ma, T.; Nilsen, J.; Pak, A.; Swift, D. C.; Döppner, T.; Gericke, D. O.; Glenzer, S. H.; Guymer, T. M.; Neumayer, P.; Redmer, R.; and others

    2014-08-15

    We have developed a model for analysing x-ray Thomson scattering data from high-density, millimetre-scale inhomogeneous plasmas created during ultra-high pressure implosions at the National Ignition Facility in a spherically convergent geometry. The density weighting of the scattered signal and attenuation of the incident and scattered x-rays throughout the target are included using radial profiles of the density, opacity, ionization state, and temperature provided by radiation-hydrodynamics simulations. These simulations show that the scattered signal is strongly weighted toward the bulk of the shocked plasma and the Fermi degenerate material near the ablation front. We show that the scattered signal provides a good representation of the temperature of this highly nonuniform bulk plasma and can be determined to an accuracy of ca. 15% using typical data analysis techniques with simple 0D calculations. On the other hand, the mean ionization of the carbon in the bulk is underestimated. We suggest that this discrepancy is due to the convolution of scattering profiles from different regions of the target. Subsequently, we discuss modifications to the current platform to minimise the impact of inhomogeneities, as well as opacity, and also to enable probing of conditions more strongly weighted toward the compressed core.

  15. Measurement of the sound velocity in fluids using the echo signals from scattering particles.

    PubMed

    Lenz, Michael; Bock, Martin; Kühnicke, Elfgard; Pal, Josef; Cramer, Andreas

    2012-01-01

    With conventional methods the sound velocity c in fluids can be determined using the back wall echo. This paper proposes a novel technique, in which the signals reflected by scattering particles suspended in a fluid are analysed instead. The basic idea is that the particles generate the strongest echo signal when being located in the sound field maximum. Therefore the position of the echo signal maximum is a measure for the propagation time to the sound field maximum. Provided that calibration data or sound field simulations for the ultrasonic transducer are available, this propagation time suffices to determine both sound velocity and the location of the sound field maximum. The feasibility of the new approach is demonstrated by different kinds of experiments: (i) Measurements of the sound velocity c in four fluids covering the wide range between 1116 and 2740m/s. The results show good agreement with values published elsewhere. (ii) Using the dependence of the sound velocity on temperature, it is possible to vary c over the comparatively small range between 1431 and 1555m/s with increments of less than 10m/s. The measured statistical variation of 1.4m/s corresponds to a relative uncertainty not worse than 0.1%. (iii) The focus position, i.e. the distance of the maximum of the sound field from the transducer, was varied by time-shifted superposition of the receive signals belonging to the different elements of an annular array. The results indicate that the novel method is even capable of measuring profiles of the sound velocity along the ultrasonic beam non-invasively. PMID:21824636

  16. Thomson Scattering on the HBT-EP Tokamak

    NASA Astrophysics Data System (ADS)

    Levesque, J. P.; Litzner, K. D.; Hanson, J. M.; James, R.; Maurer, D. A.; Mauel, M. E.; Navratil, G. A.; Pedersen, T. S.

    2007-11-01

    Thomson scattering can be used as a non-invasive method for measuring local electron density and temperature in plasmas. We describe the HBT-EP Thomson Scattering diagnostic, which is based on a design in use at DIII-D [1]. A five-channel interference filter polychrometer measures incoherent scattered light from an 8ns, 800mJ, 1064nm Nd:YAG laser pulse. A set of pre-amplification circuits designed by Princeton Scientific Instruments [2] has recently been installed for signal detection using avalanche photodiodes. System layout, alignment, and straylight level reduction techniques will be outlined. Rayleigh and Raman scattering calibration procedures have been used to absolutely calibrate the collection optics and detection system. Recent progress on diagnosing different HBT-EP plasmas using the Thomson scattering diagnostic will be presented. [1] T. N. Carlstrom, et al, Rev. Sci. Instr. 61, 2858, 1990. [2] D. Johnson, et al, Rev. Sci. Instr. 72, 1, 1129, 2001.

  17. Optimized Signal-To Ratio with Shot Noise Limited Detection in Stimulated Raman Scattering Microscopy

    NASA Astrophysics Data System (ADS)

    Moester, M. J. B.; Ariese, F.; de Boer, J. F.

    2015-04-01

    We describe our set-up for Stimulated Raman Scattering (SRS) microscopy with shot noise limited detection for a broad window of biologically relevant laser powers. This set-up is used to demonstrate that the highest signal-to-noise ratio (SNR) in SRS with shot noise limited detection is achieved with a time-averaged laser power ratio of 1:2 of the unmodulated and modulated beam. In SRS, two different coloured laser beams are incident on a sample. If the energy difference between them matches a molecular vibration of a molecule, energy can be transferred from one beam to the other. By applying amplitude modulation to one of the beams, the modulation transfer to the other beam can be measured. The efficiency of this process is a direct measure for the number of molecules of interest in the focal volume. Combined with laser scanning microscopy, this technique allows for fast and sensitive imaging with sub-micrometre resolution. Recent technological advances have resulted in an improvement of the sensitivity of SRS applications, but few show shot noise limited detection. The dominant noise source in this SRS microscope is the shot noise of the unmodulated, detected beam. Under the assumption that photodamage is linear with the total laser power, the optimal SNR shifts away from equal beam powers, where the most signal is generated, to a 1:2 power ratio. Under these conditions the SNR is maximized and the total laser power that could induce photodamage is minimized. Compared to using a 1:1 laser power ratio, we show improved image quality and a signal-to-noise ratio improvement of 8 % in polystyrene beads and C. Elegans worms. Including a non-linear damage mechanism in the analysis, we find that the optimal power ratio converges to a 1:1 ratio with increasing order of the non-linear damage mechanism.

  18. Decoupled polarization dynamics of incoherent waves and bimodal spectral incoherent solitons.

    PubMed

    Fusaro, A; Garnier, J; Michel, C; Xu, G; Fatome, J; Wright, L G; Wise, F W; Picozzi, A

    2016-09-01

    We consider the propagation of strongly incoherent waves in optical fibers in the framework of the vector nonlinear Schrödinger equation (VNLSE) accounting for the Raman effect. On the basis of the wave turbulence theory, we derive a kinetic equation that greatly simplifies the VNLSE and provides deep physical insight into incoherent wave dynamics. When applied to the study of polarization effects, the theory unexpectedly reveals that the linear polarization components of the incoherent wave evolve independently from each other, even in the presence of weak fiber birefringence. When applied to light propagation in bimodal fibers, the theory reveals that the incoherent modal components can be strongly coupled. After a complex transient, the modal components self-organize into a vector spectral incoherent soliton: The two solitons self-trap and propagate with a common velocity in frequency space. PMID:27607955

  19. Incoherent radar measurements from the D-Region: What can we learn from the spectral shape?

    NASA Astrophysics Data System (ADS)

    Strelnikova, Irina

    Radar backscatter is a widely used powerful tool for studying the mesosphere. Coherent radar systems are especially useful for studying such phenomena as PMSE and PMWE. They are capable of measuring power, wind velocity, and spectral width during the time and in the height range of the PMSE/PMWE events. The Incoherent Scatter Radars (ISR) are additionally capable of measuring collision frequencies, temperatures, electron density, and many other derived parameters in the altitude range from 70 to 90 km regardless of the special events but when the background ionization is sufficiently high. In the tropo - and mesosphere, the Doppler spectra from coherent scatter have a well-known Gaussian form. The shape of the Doppler spectra of the ISR can be different depending on the physical process producing the radar echo. Therefore, the shape of the spectra or the Autocorrelation function (ACF) can be used to derive some characteristics of the scattering media. ISR Doppler spectra have a Gaussian shape when the correlation length of the plasma motion is much larger than the observed fluctuation wavelength. When the correlation length of the plasma motion is much shorter than the observed fluctuation wavelength, the Doppler spectrum exhibits the Lorentzian shape. This means, that Lorentzian type Doppler spectra are usually prevalent in mesospheric measurements. As an example, the main effect of charged dust on the radar Doppler spectrum is a very narrow Lorentzian line superimposed on the well-known background spectrum. From the characteristics of this additional Lorentzian line, we are able to obtain altitude profiles of the smoke particle number density and the mean particle radius. We present some results of the dust particle properties derived from Arecibo ISR measurements (18 ° N, 66 ° E, 430 MHz). We also show a comparison of spectra measured by the EISCAT VHF (224 MHz) and UHF (929 MHz) radars at Tromsø (69 ° N, 19 ° E). During strong PMSE events, i.e., when

  20. Compton Scattering from Bulk and Surface of Water

    NASA Astrophysics Data System (ADS)

    Wang, Wenjie; Kuzmenko, Ivan; Vaknin, David

    2014-03-01

    Elastic and Compton scattering at grazing angle X-ray incidence from water show distinct behaviors below and above the critical angle for total reflections suggesting surface restructuring of the water surface. Using X-ray synchrotron radiation in reflectivity mode, we collect the Thomson and Compton scattering signals with energy dispersive detector at various angles near the normal to surface as a function of the angle of incidence. Analysis of the ratio between the Thomson and Compton intensity above the critical angle (which mainly probes bulk water) is a constant as expected from incoherent scattering from single water molecule, whereas the signal from the surface shows strong angular dependence on the incident angle. Although we do not fully understand the phenomena, we attribute the observation to more organized water at the interface. Ames Laboratory, DOE under contract No. DE-AC02-07CH11358 and Advanced Photon Source, DOE under contract No. DE-AC02-06CH11357.

  1. Full-field spatially incoherent illumination interferometry: a spatial resolution almost insensitive to aberrations

    NASA Astrophysics Data System (ADS)

    Xiao, Peng; Fink, Mathias; Boccara, A. Claude

    2016-09-01

    We show that with spatially incoherent illumination, the point spread function width of an imaging interferometer like that used in full-field optical coherence tomography (FFOCT) is almost insensitive to aberrations that mostly induce a reduction of the signal level without broadening. This is demonstrated by comparison with traditional scanning OCT and wide-field OCT with spatially coherent illuminations. Theoretical analysis, numerical calculation as well as experimental results are provided to show this specific merit of incoherent illumination in full-field OCT. To the best of our knowledge, this is the first time that such result has been demonstrated.

  2. Rapidly pulsed, high intensity, incoherent light source

    NASA Technical Reports Server (NTRS)

    Evans, J. C., Jr.; Brandhorst, H. W., Jr. (Inventor)

    1974-01-01

    A rapid pulsing, high intensity, incoherent light is produced by selectively energizing a plurality of discharge lamps with a triggering circuit. Each lamp is connected to a capacitor, and a power supply is electrically connected to all but one of the capacitors. This last named capacitor is electrically connected to a discharge lamp which is connected to the triggering circuit.

  3. Coherent versus incoherent sequential quantum measurements

    SciTech Connect

    Filip, Radim

    2011-03-15

    We compare a trade-off between knowledge and decoherence for the incoherent and coherent partial sequential compatible measurements on single-qubit systems. The individual partial measurement nondestructively monitors basis states of the system by single-qubit meter. For the same decoherence caused by this unbiased measurement, the individual coherent measurement gives more knowledge than the incoherent one. For identical sequential coherent measurements, knowledge accumulated not additively increases more slowly than for the incoherent measurements. The overall knowledge can be accumulated using an adaptive measurement strategy on the meters if the single-qubit coherence of meters is kept. On the other hand, preservation of the mutual qubit coherence between the meters necessary for the collective measurement strategy is not required. A loss of single-qubit coherence degrades the coherent measurements back to the incoherent ones. Since the decoherence caused by the measurement process is a quadratic function of knowledge extracted by the individual measurement, Zeno-like behavior can be observed for repetitive weak compatible measurements. This unconditional universal effect does not depend on any dynamics of the qubit and it is a direct consequence of optimally controlled sequential evolution of quantum information.

  4. Incoherently coupled dark-bright photorefractive solitons

    NASA Astrophysics Data System (ADS)

    Chen, Zhigang; Segev, Mordechai; Coskun, Tamer H.; Christodoulides, Demetrios N.; Kivshar, Yuri S.; Afanasjev, Vsevolod V.

    1996-11-01

    We report the observation of incoherently coupled dark-bright spatial soliton pairs in a biased bulk photorefractive crystal. When such a pair is decoupled, the dark component evolves into a triplet structure, whereas the bright one decays into a self-defocusing beam.

  5. Signal degradation by multiple scattering in optical coherence tomography of dense tissue: a Monte Carlo study towards optical clearing of biotissues

    NASA Astrophysics Data System (ADS)

    Wang, Ruikang K.

    2002-07-01

    Multiple scattering is a major source that limits light penetration into biotissues, thereby preventing visualization of the deep microstructures for high-resolution optical imaging techniques. The optical clearing approach is a new adventure in biomedical optics for manipulating the optical properties of tissue; for example, the scattering coefficient and the degree of forward scattering of photons, by the use of the chemical administration method in order to improve the optical imaging depth, particularly for the recently developed optical coherence tomography (OCT). This paper investigates systematically how the multiple scattering affects signal attenuation and localization in general, and how the alterations of optical properties of tissue enhance the optical imaging depth and signal localization in particular, by the use of Monte Carlo simulations through the separate considerations of the least scattered photons (LSP) and multiple scattered photons (MSP). The LSP are those photons that contribute to the precise OCT signal, i.e. localization, and the MSP are those that degrade the OCT signal. It is shown that with either the reduction of the scattering coefficient or the increase of the degree of forward scattering, signal localization and imaging depth for OCT is enhanced. Whilst the increase of the anisotropic factor of the medium is more efficient in improving signal localization, it introduces more scattering events for the photons travelling within the tissue for both the LSP and MSP. It is also found that the OCT imaging resolution is almost reduced exponentially with the increase of the probing depth as opposed to the claimed system resolution. We demonstrate that optical clearing could be a useful tool to improve the imaging resolution when the light progressively penetrates the high scattering medium. Experimental results are also presented to show intuitively how multiple scattering affects OCT signal profiles by the use of intralipid solution and

  6. An analytic formula for the relativistic incoherent Thomson backscattering spectrum for a drifting bi-Maxwellian plasma

    SciTech Connect

    Naito, O.

    2015-08-15

    An analytic formula has been derived for the relativistic incoherent Thomson backscattering spectrum for a drifting anisotropic plasma when the scattering vector is parallel to the drifting direction. The shape of the scattering spectrum is insensitive to the electron temperature perpendicular to the scattering vector, but its amplitude may be modulated. As a result, while the measured temperature correctly represents the electron distribution parallel to the scattering vector, the electron density may be underestimated when the perpendicular temperature is higher than the parallel temperature. Since the scattering spectrum in shorter wavelengths is greatly enhanced by the existence of drift, the diagnostics might be used to measure local electron current density in fusion plasmas.

  7. Image contrast of diffraction-limited telescopes for circular incoherent sources of uniform radiance

    NASA Technical Reports Server (NTRS)

    Shackleford, W. L.

    1980-01-01

    A simple approximate formula is derived for the background intensity beyond the edge of the image of uniform incoherent circular light source relative to the irradiance near the center of the image. The analysis applies to diffraction-limited telescopes with or without central beam obscuration due to a secondary mirror. Scattering off optical surfaces is neglected. The analysis is expected to be most applicable to spaceborne IR telescopes, for which diffraction can be the major source of off-axis response.

  8. Synchronized operation by field programmable gate array based signal controller for the Thomson scattering diagnostic system in KSTAR

    SciTech Connect

    Lee, W. R.; Park, M. K.; Lee, J. H.; Kim, H. S.; Kim, K. H.

    2012-09-15

    The Thomson scattering diagnostic system is successfully installed in the Korea Superconducting Tokamak Advanced Research (KSTAR) facility. We got the electron temperature and electron density data for the first time in 2011, 4th campaign using a field programmable gate array (FPGA) based signal control board. It operates as a signal generator, a detector, a controller, and a time measuring device. This board produces two configurable trigger pulses to operate Nd:YAG laser system and receives a laser beam detection signal from a photodiode detector. It allows a trigger pulse to be delivered to a time delay module to make a scattered signal measurement, measuring an asynchronous time value between the KSTAR timing board and the laser system injection signal. All functions are controlled by the embedded processor running on operating system within a single FPGA. It provides Ethernet communication interface and is configured with standard middleware to integrate with KSTAR. This controller has operated for two experimental campaigns including commissioning and performed the reconfiguration of logic designs to accommodate varying experimental situation without hardware rebuilding.

  9. Ballistic protons in incoherent exclusive vector meson production as a measure of rare parton fluctuations at an electron-ion collider

    DOE PAGESBeta

    Lappi, T.; Venugopalan, R.; Mantysaari, H.

    2015-02-25

    We argue that the proton multiplicities measured in Roman pot detectors at an electron ion collider can be used to determine centrality classes in incoherent diffractive scattering. Incoherent diffraction probes the fluctuations in the interaction strengths of multi-parton Fock states in the nuclear wavefunctions. In particular, the saturation scale that characterizes this multi-parton dynamics is significantly larger in central events relative to minimum bias events. As an application, we examine the centrality dependence of incoherent diffractive vector meson production. We identify an observable which is simultaneously very sensitive to centrality triggered parton fluctuations and insensitive to details of the model.

  10. Ballistic protons in incoherent exclusive vector meson production as a measure of rare parton fluctuations at an electron-ion collider.

    PubMed

    Lappi, T; Mäntysaari, H; Venugopalan, R

    2015-02-27

    We argue that the proton multiplicities measured in Roman pot detectors at an electron ion collider can be used to determine centrality classes in incoherent diffractive scattering. Incoherent diffraction probes the fluctuations in the interaction strengths of multiparton Fock states in the nuclear wave functions. In particular, the saturation scale that characterizes this multiparton dynamics is significantly larger in central events relative to minimum bias events. As an application, we study the centrality dependence of incoherent diffractive vector meson production. We identify an observable which is simultaneously very sensitive to centrality triggered parton fluctuations and insensitive to details of the model. PMID:25768758

  11. Report on coordinated satellite and incoherent scatter observations

    NASA Technical Reports Server (NTRS)

    Calderon, C. H. J.

    1975-01-01

    Measurements taken at the Jicamarca Radar Observatory at Lima, Peru during the cooperative sounding rocket program are reported. The following types of data were acquired: (1) electron density and temperature; (2) vertical plasma drift, (3) electrojet relative echo power density; (4) electrojet doppler shift and condition; and (5) 150 km echoing region.

  12. Coordinated satellite and incoherent scatter observations. [of the ionosphere

    NASA Technical Reports Server (NTRS)

    Calderon, C. H. J.

    1975-01-01

    Measurements taken at the Jicamarca Radar Observatory at Lima, Peru during the Cooperative Sounding Rocket Program are reported. The following types of data were acquired: (1) electron density and temperature, (2) vertical plasma drift, (3) electrojet relative echo power density, (4) electrojet Doppler shift and condition, and (5) 150 km echoing region.

  13. Vertical spatial coherence model for a transient signal forward-scattered from the sea surface

    USGS Publications Warehouse

    Yoerger, E.J.; McDaniel, S.T.

    1996-01-01

    The treatment of acoustic energy forward scattered from the sea surface, which is modeled as a random communications scatter channel, is the basis for developing an expression for the time-dependent coherence function across a vertical receiving array. The derivation of this model uses linear filter theory applied to the Fresnel-corrected Kirchhoff approximation in obtaining an equation for the covariance function for the forward-scattered problem. The resulting formulation is used to study the dependence of the covariance on experimental and environmental factors. The modeled coherence functions are then formed for various geometrical and environmental parameters and compared to experimental data.

  14. Pulsed-incoherent-light-injected Fabry-Perot laser diode for WDM passive optical networks.

    PubMed

    Kim, Hoon

    2010-01-18

    We propose and demonstrate a pulsed-incoherent-light-injected Fabry-Perot laser diode (FP-LD) which generates incoherent return-to-zero (RZ) signals for wavelength-division-multiplexing passive optical networks. For the generation of the RZ signals, we first convert the continuous-wave (CW) amplified spontaneous emission (ASE) into an ASE pulse train with a pulse carver, spectrum-slice it into multiple channels with a waveguide grating router, and then inject them into FP-LDs for data modulation. Thanks to a wide slicing bandwidth of the injected incoherent light, the spectral linewidth of the generated RZ signals is determined by the slicing bandwidth, without being affected by the use of the RZ format. Thus, compared to incoherent non-return-to-zero (NRZ) signals generated with CW-ASE-injected FP-LDs, the RZ signals have a similar spectral linewidth but a wide timing margin between adjacent bits. Thus, the proposed transmitter can offer better dispersion tolerance than the NRZ signals. For example, our experimental demonstration performed at 1.25 Gb/s shows approximately 50% higher dispersion tolerance than the NRZ signals generated with CW ASE-injected FP-LDs. Despite the large slicing bandwidth of 0.67 nm for the injected ASE, we were able to transmit 1.25-Gb/s signals over 45-km standard single-mode fiber without dispersion compensation. The receiver sensitivity is also improved by 1.5 dB by using the RZ format. PMID:20173999

  15. Incoherent neutral pion photoproduction on 12C.

    PubMed

    Tarbert, C M; Watts, D P; Aguar, P; Ahrens, J; Annand, J R M; Arends, H J; Beck, R; Bekrenev, V; Boillat, B; Braghieri, A; Branford, D; Briscoe, W J; Brudvik, J; Cherepnya, S; Codling, R; Downie, E J; Föhl, K; Glazier, D I; Grabmayr, P; Gregor, R; Heid, E; Hornidge, D; Jahn, O; Kashevarov, V L; Knezevic, A; Kondratiev, R; Korolija, M; Kotulla, M; Krambrich, D; Krusche, B; Lang, M; Lisin, V; Livingston, K; Lugert, S; Macgregor, I J D; Manley, D M; Martinez, M; McGeorge, J C; Mekterovic, D; Metag, V; Nefkens, B M K; Nikolaev, A; Novotny, R; Owens, R O; Pedroni, P; Polonski, A; Prakhov, S N; Price, J W; Rosner, G; Rost, M; Rostomyan, T; Schadmand, S; Schumann, S; Sober, D; Starostin, A; Supek, I; Thomas, A; Unverzagt, M; Walcher, Th; Zehr, F

    2008-04-01

    We present the first detailed measurement of incoherent photoproduction of neutral pions to a discrete state of a residual nucleus. The 12C(gamma,pi(0))(12)C*(4.4 MeV) reaction has been studied with the Glasgow photon tagger at MAMI employing a new technique which uses the large solid angle Crystal Ball detector both as a pi(0) spectrometer and to detect decay photons from the excited residual nucleus. The technique has potential applications to a broad range of future nuclear measurements with the Crystal Ball and similar detector systems elsewhere. Such data are sensitive to the propagation of the Delta in the nuclear medium and will give the first information on matter transition form factors from measurements with an electromagnetic probe. The incoherent cross sections are compared to two theoretical predictions including a Delta-hole model. PMID:18517938

  16. Ultrasonic Thermometry Inside Tissues Based on High-resolution Detection of Spectral Shifts in Overtones of Scattering Signals

    NASA Astrophysics Data System (ADS)

    Bazán, I.; Ramos, A.; Ramírez, A.; Leija, L.

    Some research results of cooperation works in biomedical engineering, established among current national projects of Mexico and Spain, are resumed. They are related to coordinated activities of three R & D groups, with the aim to achieve high-resolution ultrasonic thermometry into tissue phantoms with internal reflectors of a non-invasive way. Advanced spectral techniques are being used to extract thermal information in echo-signals acquired from biological phantoms with internal structures having a quasi-regular scattering distribution as, for instance, it happens in the liver tissues where a rather regular separation between scatterers has been reported. These techniques can indicate pathologies related to thermal increases due to the presence of disease. Small changes with temperature can be detected in the location of overtones of the fundamental resonance related to the separation of internal reflectors. But, this requires discarding the influence of the echoes noise on the thermal estimation results. A first evaluation of these spectral analysis techniques is performed, using echo-signals acquired from a phantom in the temperature range with medical interest, where the noise influence is shown for different levels of SNR in the echoes, using signals derived of a mathematical model for hepatic tissue echoes, where the average power, signal to noise ratio and inter-arrival time standard deviation, were taken into account. It seems that our high-resolution spectral option could be applied to detect some pathologies in tissues having regular scattering, but new advances must be performed with real tissues, in order to confirm the potential resolution of this approach.

  17. A setup for simultaneous measurement of infrared spectra and light scattering signals: Watching amyloid fibrils grow from intact proteins

    SciTech Connect

    Li, Yang; Maurer, Jürgen; Roth, Andreas; Vogel, Vitali; Winter, Ernst; Mäntele, Werner

    2014-08-15

    A setup for the simultaneous measurement of mid-infrared spectra and static light scattering is described that can be used for the analysis of the formation of nanoscale and microscopic aggregates from smaller molecules to biopolymers. It can be easily integrated into sample chambers of infrared spectrometers or combined with laser beams from tunable infrared lasers. Here, its use for the analysis of the formation of amyloid fibrils from intact proteins is demonstrated. The formation of amyloid fibrils or plaques from proteins is a widespread and pathogenetic relevant process, and a number of diseases are caused and correlated with the deposition of amyloid fibrils in cells and tissues. The molecular mechanisms of these transformations, however, are still unclear. We report here the simultaneous measurement of infrared spectra and static light scattering for the analysis of fibril formation from egg-white lysozyme. The transformation of the native form into non-native forms rich in β-sheet structure is measured by analysis of the amide I spectral region in the infrared spectra, which is sensitive for local structures. At the same time, light scattering signals at forward direction as well as the forward/backward ratio, which are sensitive for the number of scattering centers and their approximate sizes, respectively, are collected for the analysis of fibril growth. Thermodynamic and kinetic parameters as well as mechanistic information are deduced from the combination of the two complementary techniques.

  18. Spectrometer-free vibrational imaging by retrieving stimulated Raman signal from highly scattered photons

    PubMed Central

    Liao, Chien-Sheng; Wang, Pu; Wang, Ping; Li, Junjie; Lee, Hyeon Jeong; Eakins, Gregory; Cheng, Ji-Xin

    2015-01-01

    In vivo vibrational spectroscopic imaging is inhibited by relatively slow spectral acquisition on the second scale and low photon collection efficiency for a highly scattering system. Recently developed multiplex coherent anti-Stokes Raman scattering and stimulated Raman scattering techniques have improved the spectral acquisition time down to microsecond scale. These methods using a spectrometer setting are not suitable for turbid systems in which nearly all photons are scattered. We demonstrate vibrational imaging by spatial frequency multiplexing of incident photons and single photodiode detection of a stimulated Raman spectrum within 60 μs. Compared to the spectrometer setting, our method improved the photon collection efficiency by two orders of magnitude for highly scattering specimens. We demonstrated in vivo imaging of vitamin E distribution on mouse skin and in situ imaging of human breast cancerous tissues. The reported work opens new opportunities for spectroscopic imaging in a surgical room and for development of deep-tissue Raman spectroscopy toward molecular level diagnosis. PMID:26601311

  19. Color transparency in incoherent electroproduction of {rho} mesons off nuclei

    SciTech Connect

    Nemchik, J.; Kopeliovich, B. Z.; Potashnikova, I. K.

    2013-04-15

    Color transparency (CT) phenomena in elastic electroproduction of vector mesons off nuclei are usually infected by the onset of coherence length (CL) effects. However, at low energies corresponding to the CLAS experiment at Jefferson Lab (JLab), one can study practically the net CT effects, since CL is much shorter than the nuclear radius. We investigate various manifestations of CT effects using rigorous quantum mechanical approach based on the path integral technique. We include also the effects of {rho} meson decay inside the nucleus leading to a rise of the nuclear suppression towards small values of Q{sup 2}. Motivated by the last CLAS data we predict the A, Q{sup 2} and l{sub c} dependence of nuclear transparency for {rho}{sup 0} mesons produced incoherently off nuclei. We also perform predictions for expected signal of CT corresponding to the planned JLab upgrade to 12 GeV electron beam.

  20. A high temperature high pressure cell for quasielastic neutron scattering

    SciTech Connect

    Yang, F.; Meyer, A.; Kaplonski, J.; Unruh, T.; Mamontov, E.

    2011-08-15

    We present our recent development of a high temperature high pressure cell for neutron scattering. Combining a water cooled Nb1Zr pressure cell body with an internal heating furnace, the sample environment can reach temperatures of up to 1500 K at a pressure of up to 200 MPa at the sample position, with an available sample volume of about 700 mm{sup 3}. The cell material Nb1Zr is specifically chosen due to its reasonable mechanical strength at elevated temperatures and fairly small neutron absorption and incoherent scattering cross sections. With this design, an acceptable signal-to-noise ratio of about 10:1 can be achieved. This opens new possibilities for quasielastic neutron scattering studies on different types of neutron spectrometers under high temperature high pressure conditions, which is particularly interesting for geological research on, e.g., water dynamics in silicate melts.

  1. A high temperature high pressure cell for quasielastic neutron scattering.

    PubMed

    Yang, F; Kaplonski, J; Unruh, T; Mamontov, E; Meyer, A

    2011-08-01

    We present our recent development of a high temperature high pressure cell for neutron scattering. Combining a water cooled Nb1Zr pressure cell body with an internal heating furnace, the sample environment can reach temperatures of up to 1500 K at a pressure of up to 200 MPa at the sample position, with an available sample volume of about 700 mm(3). The cell material Nb1Zr is specifically chosen due to its reasonable mechanical strength at elevated temperatures and fairly small neutron absorption and incoherent scattering cross sections. With this design, an acceptable signal-to-noise ratio of about 10:1 can be achieved. This opens new possibilities for quasielastic neutron scattering studies on different types of neutron spectrometers under high temperature high pressure conditions, which is particularly interesting for geological research on, e.g., water dynamics in silicate melts. PMID:21895254

  2. Nonlinear light scattering in molecules triggered by an impulsive X-ray Raman process

    PubMed Central

    Dorfman, Konstantin E.; Bennett, Kochise; Zhang, Yu; Mukamel, Shaul

    2013-01-01

    The time-and-frequency resolved nonlinear light scattering (NLS) signals from a time evolving charge distribution of valence electrons prepared by impulsive X-ray pulses are calculated using a superoperator Green's function formalism. The signal consists of a coherent ~ N2-scaling difference frequency generation and an incoherent fluorescence ~ N-scaling component where N is the number of active molecules. The former is given by the classical Larmor formula based on the time-dependent charge density. The latter requires additional information about the electronic structure and may be recast in terms of transition amplitudes representing quantum matter pathways. PMID:24465122

  3. Experimental confirmation of neoclassical Compton scattering theory

    SciTech Connect

    Aristov, V. V.; Yakunin, S. N.; Despotuli, A. A.

    2013-12-15

    Incoherent X-ray scattering spectra of diamond and silicon crystals recorded on the BESSY-2 electron storage ring have been analyzed. All spectral features are described well in terms of the neoclassical scattering theory without consideration for the hypotheses accepted in quantum electrodynamics. It is noted that the accepted tabular data on the intensity ratio between the Compton and Rayleigh spectral components may significantly differ from the experimental values. It is concluded that the development of the general theory (considering coherent scattering, incoherent scattering, and Bragg diffraction) must be continued.

  4. Neutron diffraction of hydrogenous materials: Measuring incoherent and coherent intensities separately

    NASA Astrophysics Data System (ADS)

    Temleitner, László; Stunault, Anne; Cuello, Gabriel J.; Pusztai, László

    2015-07-01

    Accurate determination of the coherent static structure factor of any disordered material containing substantial amounts of proton nuclei has proven to be rather problematic by neutron diffraction, due to the large incoherent cross section of 1H. This problem has continued to set severe obstacles to the reliable determination of liquid structures of hydrogenous materials up to this day, by introducing large uncertainties whenever a sample with a 1H content larger than about 20% had to be investigated by neutron diffraction. Huge theoretical efforts over the past 40 years which were aimed at estimating the incoherent background of such data did not result in any practical solution to the problem. Here, we present data for the coherent and incoherent contributions to the total static structure of mixtures of light and heavy water. The measurements were done using the polarized neutron diffraction technique, which uniquely allows determination of the two contributions separately. The data covers a wide range of momentum transfer (0.8-21 Å-1) and the entire composition range, i.e., light water contents between 0 and 100% at five different values. We show that the measured incoherent scattering can be approximated by a Gaussian function. The separately measured coherent intensities exhibit signs of small inelastic contributions. Out of several possible approaches, we have chosen to subtract a cubic background using the reverse Monte Carlo algorithm. This algorithm has the advantage of requiring an actual physical model with thousands of realistic water molecules at the correct density describing the corrected data. Finally, coherent static structure factors for five different compositions of liquid H2O and D2O mixtures are presented for which the huge incoherent background could actually be measured and separated, instead of being approximated as it has been done so far. These experimental results provide a strong hope that determining the structure of hydrogenous

  5. [The Mie scattering lidar return signal denoising research based on EMD-DISPO].

    PubMed

    Zhang, Yi-Kun; Ma, Xiao-Chang; Hua, Deng-Xin; Chen, Hao; Liu, Cai-Xuan

    2011-11-01

    Lidar echo signal is a typical non-steady-state, non-stationary signal, and difficult to be dealt with by the traditional filtering methods. As a new signal processing theory proposed in recent years, empirical mode decomposition method can adaptively divide the lidar echo signal into different intrinsic mode function (IMF) components according to different time scale, and noise mainly concentrates in the high-frequency component. However, when filtered with simply removing high frequency component, the useful signal will be possibly reduced. In the present paper, a new method which combines empirical mode decomposition (EMD) with Savitzky-Golay filter is proposed. With experiments, it is indicated that our approach not only removes the noise component effectively but also maintains the useful signal, then will improve the accuracy in the next phase of data processing. PMID:22242503

  6. GNSS Ocean Reflected Signals

    NASA Astrophysics Data System (ADS)

    Hoeg, P.

    2012-12-01

    Ocean reflected signals from the GNSS satellites (received at low-Earth orbiting satellites, airplanes and fixed mountain locations) describe the ocean surface mean height, waves, roughness, spectral reflectivity and emissivity. The estimated accuracy of the average surface height is of the order of 10 cm for smooth conditions. Thus global observations could be an important new contribution to long-term variations of the ocean mean height as well as the monitoring of ocean mesoscale eddies, which result in sea-height changes much larger than the accuracy of the GNSS technique for reflected signals. The ocean reflected signals can be divided into two set of measurements, 1) high elevation measurements (equal to low incidence angles) and 2) low elevation grazing angle measurements. For the first type the ocean reflection cross-section has a limited extent. The reflected signal is coherent with smaller errors due to ocean waves, sampling rate and the internal processing method of the receiver. For low elevations, the signal reveals the incoherent scatter process at the reflection zone. To quantify the potential of the GNSS signals for determining spectral reflectivity at low elevations, we present ocean reflection GPS measurements from the Haleakala Summit on Maui, Hawaii, revealing the spectral characteristics of both the direct satellite signal and the ocean reflected signal for low elevation angles. The characteristics of the reflected signal depend on the scattering properties of the sea surface and the footprint of the reflection zone. While the footprint size and shape in turn depends on the signal incidence angle, the ocean mean tilt, and the relative velocities of transmitter and receiver to the reflection point. Thus the scattering properties of the sea surface are related to the sea surface roughness. We present the spectral properties of the signals as received by a high precision GPS instrument, simultaneously in both phase-locked mode and open-loop raw

  7. Enhancing signal detection and completely eliminating scattering using quasi-phase-cycling in 2D IR experiments.

    PubMed

    Bloem, Robbert; Garrett-Roe, Sean; Strzalka, Halina; Hamm, Peter; Donaldson, Paul

    2010-12-20

    We demonstrate how quasi-phase-cycling achieved by sub-cycle delay modulation can be used to replace optical chopping in a box-CARS 2D IR experiment in order to enhance the signal size, and, at the same time, completely eliminate any scattering contamination. Two optical devices are described that can be used for this purpose, a wobbling Brewster window and a photoelastic modulator. They are simple to construct, easy to incorporate into any existing 2D IR setup, and have attractive features such as a high optical throughput and a fast modulation frequency needed to phase cycle on a shot-to-shot basis. PMID:21196983

  8. Quantum Radiation Reaction: From Interference to Incoherence

    NASA Astrophysics Data System (ADS)

    Dinu, Victor; Harvey, Chris; Ilderton, Anton; Marklund, Mattias; Torgrimsson, Greger

    2016-01-01

    We investigate quantum radiation reaction in laser-electron interactions across different energy and intensity regimes. Using a fully quantum approach which also accounts exactly for the effect of the strong laser pulse on the electron motion, we identify in particular a regime in which radiation reaction is dominated by quantum interference. We find signatures of quantum radiation reaction in the electron spectra which have no classical analogue and which cannot be captured by the incoherent approximations typically used in the high-intensity regime. These signatures are measurable with presently available laser and accelerator technology.

  9. Incoherent beam shaping with freeform mirror

    NASA Astrophysics Data System (ADS)

    Michaelis, Dirk; Kudaev, Sergey; Steinkopf, Ralf; Gebhardt, Andreas; Schreiber, Peter; Bräuer, Andreas

    2008-08-01

    Beam shaping of incoherent light sources (LEDs, halogen lamps) for arbitrary target light distribution is obtained by a single free-shape mirror. Special design algorithm ensures continuous profile without abrupt changes and shadowing regions. The mirror is manufactured by single point diamond turning combined with Fast-Tool-Servo (FTS) for simultaneous figuring of base surface and fine structure (for redistributing the light energy). Lateral and axial resolution of the fine structure is determined by FTS and considered during the design and data transfer. Directly turned surfaces can be used as replication tools for polymer or glass moulding and embossing.

  10. Nonlinear optical interference of two successive coherent anti-Stokes Raman scattering signals for biological imaging applications.

    PubMed

    Lee, Eun Seong; Lee, Jae Yong; Yoo, Yong Shim

    2007-01-01

    The nonlinear optical interference of two successively generated coherent anti-Stokes Raman scattering (CARS) signals from two different samples placed in series is demonstrated for the imaging performance, in which a collinear phase matching geometry is used. The relative phase of two CARS signals is controlled by a phase-shifting unit made of dispersive glass materials of which the thickness can be precisely varied. The clear interference fringes are observed as the thickness of the phase-shifting unit changes. The interference effect is then utilized to achieve a better quality CARS image of a biological tissue taken from a mouse skin. Placing the tissue in the second sample position and performing raster scans of the laser beams on it, we can acquire a CARS image of higher contrast compared to the normal image obtained without interferometric implementation. PMID:17477725

  11. Full-field spatially incoherent illumination interferometry: a spatial resolution almost insensitive to aberrations.

    PubMed

    Xiao, Peng; Fink, Mathias; Boccara, A Claude

    2016-09-01

    We show that with spatially incoherent illumination, the point spread function (PSF) width/spatial resolution of an imaging interferometer like that used in full-field optical coherence tomography (OCT) is almost insensitive to aberrations. In these systems, aberrations mostly induce a reduction of the signal level that leads to a loss of the signal-to-noise ratio without broadening the system PSF. This is demonstrated by comparison with traditional scanning OCT and wide-field OCT with spatially coherent illuminations. Theoretical analysis and numerical calculation as well as experimental results are provided to show this specific merit of incoherent illumination in full-field OCT. To the best of our knowledge, this is the first time that such a result has been demonstrated. PMID:27607937

  12. Development of Multi-Field of view-Multiple-Scattering-Polarization Lidar : analysis of angular resolved backscattered signals

    NASA Astrophysics Data System (ADS)

    Makino, T.; Okamoto, H.; Sato, K.; Tanaka, K.; Nishizawa, T.; Sugimoto, N.; Matsui, I.; Jin, Y.; Uchiyama, A.; Kudo, R.

    2014-12-01

    We have developed a new type of ground-based lidar, Multi-Field of view-Multiple-Scattering-Polarization Lidar (MFMSPL), to analyze multiple scattering contribution due to low-level clouds. One issue of the ground based lidar is the limitation of optical thickness of about 3 due to the strong attenuation in the lidar signals so that only the cloud bottom part can be observed. In order to overcome the problem, we have proposed the MFMSPL that has been designed to observe similar degree of multiple scattering contribution expected from space-borne lidar CALIOP on CALIPSO satellite. The system consists of eight detectors; four telescopes for parallel channels and four for perpendicular channels. The four pairs of telescope have been mounted with four different off-beam angles, ranging from -5 to 35mrad, where the angle is defined as the one between the direction of laser beam and the direction of telescope. Consequently, similar large foot print (100m) as CALIOP can be achieved in the MFMSPL observations when the altitude of clouds is located at about 1km. The use of multi-field of views enables to measure depolarization ratio from optically thick clouds. The outer receivers attached with larger angles generally detect backscattered signals from clouds located at upper altitudes due to the enhanced multiple scattering compared with the inner receiver that detects signals only from cloud bottom portions. Therefore the information of cloud microphysics from optically thicker regions is expected by the MFMSPL observations compared with the conventional lidar with small FOV. The MFMSPL have been continuously operated in Tsukuba, Japan since June 2014.Initial analyses have indicated expected performances from the theoretical estimation by backward Monte-Carlo simulations. The depolarization ratio from deeper part of the clouds detected by the receiver with large off-beam angle showed much larger values than those from the one with small angle. The calibration procedures

  13. Incoherent control of locally controllable quantum systems

    SciTech Connect

    Dong Daoyi; Zhang Chenbin; Rabitz, Herschel; Pechen, Alexander; Tarn, T.-J.

    2008-10-21

    An incoherent control scheme for state control of locally controllable quantum systems is proposed. This scheme includes three steps: (1) amplitude amplification of the initial state by a suitable unitary transformation, (2) projective measurement of the amplified state, and (3) final optimization by a unitary controlled transformation. The first step increases the amplitudes of some desired eigenstates and the corresponding probability of observing these eigenstates, the second step projects, with high probability, the amplified state into a desired eigenstate, and the last step steers this eigenstate into the target state. Within this scheme, two control algorithms are presented for two classes of quantum systems. As an example, the incoherent control scheme is applied to the control of a hydrogen atom by an external field. The results support the suggestion that projective measurements can serve as an effective control and local controllability information can be used to design control laws for quantum systems. Thus, this scheme establishes a subtle connection between control design and controllability analysis of quantum systems and provides an effective engineering approach in controlling quantum systems with partial controllability information.

  14. Sparsely corrupted stimulated scattering signals recovery by iterative reweighted continuous basis pursuit.

    PubMed

    Wang, Kunpeng; Chai, Yi; Su, Chunxiao

    2013-08-01

    In this paper, we consider the problem of extracting the desired signals from noisy measurements. This is a classical problem of signal recovery which is of paramount importance in inertial confinement fusion. To accomplish this task, we develop a tractable algorithm based on continuous basis pursuit and reweighted [script-l]1-minimization. By modeling the observed signals as superposition of scale time-shifted copies of theoretical waveform, structured noise, and unstructured noise on a finite time interval, a sparse optimization problem is obtained. We propose to solve this problem through an iterative procedure that alternates between convex optimization to estimate the amplitude, and local optimization to estimate the dictionary. The performance of the method was evaluated both numerically and experimentally. Numerically, we recovered theoretical signals embedded in increasing amounts of unstructured noise and compared the results with those obtained through popular denoising methods. We also applied the proposed method to a set of actual experimental data acquired from the Shenguang-II laser whose energy was below the detector noise-equivalent energy. Both simulation and experiments show that the proposed method improves the signal recovery performance and extends the dynamic detection range of detectors. PMID:24007049

  15. Sparsely corrupted stimulated scattering signals recovery by iterative reweighted continuous basis pursuit

    NASA Astrophysics Data System (ADS)

    Wang, Kunpeng; Chai, Yi; Su, Chunxiao

    2013-08-01

    In this paper, we consider the problem of extracting the desired signals from noisy measurements. This is a classical problem of signal recovery which is of paramount importance in inertial confinement fusion. To accomplish this task, we develop a tractable algorithm based on continuous basis pursuit and reweighted ℓ1-minimization. By modeling the observed signals as superposition of scale time-shifted copies of theoretical waveform, structured noise, and unstructured noise on a finite time interval, a sparse optimization problem is obtained. We propose to solve this problem through an iterative procedure that alternates between convex optimization to estimate the amplitude, and local optimization to estimate the dictionary. The performance of the method was evaluated both numerically and experimentally. Numerically, we recovered theoretical signals embedded in increasing amounts of unstructured noise and compared the results with those obtained through popular denoising methods. We also applied the proposed method to a set of actual experimental data acquired from the Shenguang-II laser whose energy was below the detector noise-equivalent energy. Both simulation and experiments show that the proposed method improves the signal recovery performance and extends the dynamic detection range of detectors.

  16. GPS Signal Scattering from Sea Surface: Wind Speed Retrieval Using Experimental Data and Theoretical Model

    NASA Technical Reports Server (NTRS)

    Komjathy, Attila; Zavorotny, Valery U.; Axelrad, Penina; Born, George H.; Garrison, James L.

    2000-01-01

    Global Positioning System (GPS) signals reflected from the ocean surface have potential use for various remote sensing purposes. Some possibilities arc measurements of surface roughness characteristics from which ware height, wind speed, and direction could be determined. For this paper, GPS-reflected signal measurements collected at aircraft altitudes of 2 km to 5 km with a delay-Doppler mapping GPS receiver arc used to explore the possibility of determining wind speed. To interpret the GPS data, a theoretical model has been developed that describes the power of the reflected GPS signals for different time delays and Doppler frequencies as a function of geometrical and environmental parameters. The results indicate a good agreement between the measured and the modeled normalized signal power waveforms during changing surface wind conditions. The estimated wind speed using surface- reflected GPS data, obtained by comparing actual and modeled waveforms, shows good agreement (within 2 m/s) with data obtained from a nearby buoy and independent wind speed measurements derived from the TOPEX/Poseidon altimetric satellite.

  17. Emergence of extreme events in fiber-based parametric processes driven by a partially incoherent pump wave.

    PubMed

    Hammani, Kamal; Finot, Christophe; Millot, Guy

    2009-04-15

    We present experimental and theoretical results showing efficient emergence of rogue wavelike extreme intensity spikes during the fiber-based induced-modulational instability process driven by a partially incoherent pump. In particular, we show that the rogue event probability can be easily controlled by adjusting the pump-signal detuning. PMID:19370096

  18. Highly sensitive detection of melamine based on gemini surfactant using enhanced resonance Rayleigh scattering signals

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Dong, Jiang Xue; Li, Nian Bing; Luo, Hong Qun

    2013-02-01

    We present here a resonance Rayleigh scattering (RRS) spectrum method for the determination of melamine at the nanogram level using a gemini surfactant (disodium 4-dodecyl-2,4'-oxydibenzenesulfonate, DDOF). It was found that DDOF could react with cationic melamine to form an ion-association complex, which induced the enhancement of RRS intensity and the appearance of a new RRS spectrum in acetate buffer (pH 3.6). The RRS spectral characteristics of the melamine-DDOF system, the optimum conditions of the reaction, and the influencing factors have been investigated. Under optimum conditions, the enhanced RRS intensity was proportional to the concentration of melamine in the range of 0.38-6.30 μg/mL. The method has high sensitivity, and the detection limit for melamine is 8.48 ng/mL. Furthermore, the reaction mechanism and the reasons of RRS enhancement were evaluated.

  19. 1 Tbit/inch2 Recording in Angular-Multiplexing Holographic Memory with Constant Signal-to-Scatter Ratio Schedule

    NASA Astrophysics Data System (ADS)

    Hosaka, Makoto; Ishii, Toshiki; Tanaka, Asato; Koga, Shogo; Hoshizawa, Taku

    2013-09-01

    We developed an iterative method for optimizing the exposure schedule to obtain a constant signal-to-scatter ratio (SSR) to accommodate various recording conditions and achieve high-density recording. 192 binary images were recorded in the same location of a medium in approximately 300×300 µm2 using an experimental system embedded with a blue laser diode with a 405 nm wavelength and an objective lens with a 0.85 numerical aperture. The recording density of this multiplexing corresponds to 1 Tbit/in.2. The recording exposure time was optimized through the iteration of a three-step sequence consisting of total reproduced intensity measurement, target signal calculation, and recording energy density calculation. The SSR of pages recorded with this method was almost constant throughout the entire range of the reference beam angle. The signal-to-noise ratio of the sampled pages was over 2.9 dB, which is higher than the reproducible limit of 1.5 dB in our experimental system.

  20. Electromagnetically induced absorption via incoherent collisions

    SciTech Connect

    Yang Xihua; Sheng Jiteng; Xiao Min

    2011-10-15

    We conduct theoretical studies on electromagnetically induced absorption via incoherent collisions in an inhomogeneously broadened ladder-type three-level system with the density-matrix approach. The effects of the collision-induced coherence decay rates as well as the probe laser field intensity on the probe field absorption are examined. It is shown that with the increase of the collisional decay rates in a moderate range, a narrow dip due to electromagnetically induced transparency superimposed on the Doppler-broadened absorption background can be turned into a narrow peak under the conditions that the probe field intensity is not very weak as compared to the pump field, which results from the enhancement of constructive interference and suppression of destructive interference between one-photon and multiphoton transition pathways. The physical origin of the collision-assisted electromagnetically induced absorption is analyzed with a power-series solution of the density-matrix equations.

  1. Long working distance incoherent interference microscope

    DOEpatents

    Sinclair, Michael B.; De Boer, Maarten P.

    2006-04-25

    A full-field imaging, long working distance, incoherent interference microscope suitable for three-dimensional imaging and metrology of MEMS devices and test structures on a standard microelectronics probe station. A long working distance greater than 10 mm allows standard probes or probe cards to be used. This enables nanometer-scale 3-dimensional height profiles of MEMS test structures to be acquired across an entire wafer while being actively probed, and, optionally, through a transparent window. An optically identical pair of sample and reference arm objectives is not required, which reduces the overall system cost, and also the cost and time required to change sample magnifications. Using a LED source, high magnification (e.g., 50.times.) can be obtained having excellent image quality, straight fringes, and high fringe contrast.

  2. Robust incoherent fiber optic bundle decoder

    NASA Technical Reports Server (NTRS)

    Roberts, Hilary E. (Inventor); DePlachett, Charles P. (Inventor); Deason, Brent E. (Inventor); Pilgrim, Robert A. (Inventor); Sanford, Harold S. (Inventor)

    2003-01-01

    Apparatus and method for calibrating an incoherent fiber optic bundle for use in transmitting visual or infrared coherent images. The apparatus includes a computer, a computer video monitor, an objective lens adjacent to the input end of the bundle, a second lens adjacent the output end of the bundle, and a CCD camera. The camera transmits video data to the monitor to produce an illuminated fiber optic image. The coordinates for the center of each fiber is found through an imaging process and the output fibers coordinates are related to the input fiber coordinates and processed in the computer to produce a mapping lookup-table (LUT) unique to the specific fiber bundle. Remapping of the LUT due to changes in the lens focus, CCD camera, or the addition of an infrared filter is accomplished by a software utility in the computer.

  3. Coherent and incoherent processes in resonant photoemission

    SciTech Connect

    Magnuson, M.; Karis, O.; Weinelt, M.

    1997-04-01

    In this contribution the authors present the distinction between coherent and incoherent processes in resonant photoemission. As a first step they determine whether an autoionization process is photoemission-like or Auger-like. The discussion is based on measurements for a weakly bonded adsorption system, Ar/Pt(111). This type of system is well adapted to investigate these effects since it yields distinctly shifted spectral features depending on the nature of the process. After this, the question of resonance photoemission in metallic systems is addressed. This is done in connection with measurements at the 2p edges for Ni metal. Ni has been one of the prototype systems for resonant photoemission. The resonances have been discussed in connection with the strong correlation and d-band localization effects in this system. Based on the results some general comments about the appearance of resonant effects in metallic systems are made.

  4. Large capacity spatially multiplexed optical memories for incoherent correlator application

    NASA Astrophysics Data System (ADS)

    Yu, Francis T.

    1987-05-01

    We have, in this research program, completed various significant aspects on the study of a Large Capacity Spatially Multiplexed Optical Correlator. They are summarized in the following paragraphs: We have quantitatively analyzed the noise performance of an incoherent optical signal processor. The effects due to temporal coherence and due to spatial coherence were studied. In this period, we have also completed research on a real-time large-capacity rapid-scanning optical correlator utilizing a rotating grating concept. We have shown that the proposed optical scanning correlator is capable of processing large-capacity optical memories with rapid spectrum scanning. With the implementation of a closed-circuit TV system the OSC system can be applied in real-world situations. A study of polychromatic correlation by spectral-spatial matched filtering has been conducted. Application of this technique to large capability spatially multiplexing matched filter synthesis is discussed. This technique offers true color signal detection, which is suitable for color image recognition and identification. We have also developed a joint transform correlation concept. This technique utilizes a magneto-optic device with a liquid crystal light valve.

  5. Evaluation of light scattering properties and chromophore concentrations in skin tissue based on diffuse reflectance signals at isosbestic wavelengths of hemoglobin

    NASA Astrophysics Data System (ADS)

    Yokokawa, Takumi; Nishidate, Izumi

    2016-04-01

    We investigate a method to evaluate light-scattering properties and chromophore concentrations in human skin tissue through diffuse reflectance spectroscopy using the reflectance signals acquired at isosbestic wavelengths of hemoglobin (420, 450, 500, and 585 nm). In the proposed method, Monte Carlo simulation-based empirical formulas are used to specify the scattering parameters of skin tissue, such as the scattering amplitude a and the scattering power b, as well as the concentration of melanin C m and the total blood concentration C tb. The use of isosbestic wavelengths of hemoglobin enables the values of C m, C tb, a, and b to be estimated independently of the oxygenation of hemoglobin. The spectrum of the reduced scattering coefficient is reconstructed from the scattering parameters. Experiments using in vivo human skin tissues were performed to confirm the feasibility of the proposed method for evaluating the changes in scattering properties and chromophore concentrations in skin tissue. The experimental results revealed that light scattering is significantly reduced by the application of a glycerol solution, which indicates an optical clearing effect due to osmotic dehydration and the matching of the refractive indices of scatterers in the epidermis.

  6. Observations of aspect sensitive RF-enhanced incoherent backscatter in the polar cap ionosphere

    NASA Astrophysics Data System (ADS)

    Dhillon, Ranvir; Robinson, T. R.; Yeoman, Timothy K.

    RF-induced plasma instabilities give rise to characteristic spectral enhancements in incoherent scatter spectra. The aspect sensitivity of these enhancements provides valuable information regarding the physical processes that occur within the RF-affected ionospheric patch. These direction-dependent signatures exhibit significant variability and help shed light on possible coupling between artificial field-aligned irregularities generated at the upper-hybrid height and RF-induced instabilities excited near the reflection height for O-mode-polarized radio waves. This directional dependence of RF-enhanced incoherent radar backscatter has been shown using data from the high-latitude ionosphere, and the significant features included consistent field-aligned signatures that may be related to the presence of artificial field-aligned irregularities. These earlier high-latitude results provided motivation for repeating the investigation in the different geophysical conditions that obtain in the polar cap ionosphere. The Space Plasma Exploration by Active Radar (SPEAR) facility is located within the polar cap and has provided observations of RF-enhanced ion and plasma line spectra recorded by the EISCAT Svalbard UHF incoherent scatter radar system (ESR), which is collocated with SPEAR. We present observations of aspect sensitive E-and F-region SPEAR-induced ion and plasma line enhance-ments from several directions in the magnetic meridian plane, centred on field-aligned. These enhancements indicate excitation of both the purely growing mode and the parametric decay instability, together with sporadic E-layer results that may indicate the presence of cavitons. We note consistent enhancements from field-aligned, vertical and also from 5 degrees south of field-aligned. We attribute the prevalence of vertical scatter to the importance of the Spitze region, and of that from field-aligned to possible wave/irregularity coupling.

  7. Multibeam Approach to Pulse Scattering from Discrete Random Media.

    NASA Astrophysics Data System (ADS)

    Kilic, Ozlem

    The problem of a pulsed aperture illuminating a two dimensional layer of discrete random medium over a flat, homogenous background is considered. The layer consists of sparsely distributed dielectric scatterers that are randomly oriented in space. The behavior of the backscattered signal from the medium is examined in the time domain for the case of a short pulse incidence. The excitation of the antenna is assumed to be arbitrary, and is represented as a discrete sum of shifted and tilted Gaussian beams by using Gabor expansion. The expansion is exact, and with the appropriate choice of beam parameters, the radiation pattern can be matched by considering only a few beams. The beams in the expansion represent the main and side lobes of the antenna, making it possible to examine the individual effects of each lobe on the backscattered signature. The received power at the antenna is composed of a coherent and an incoherent part associated respectively with the mean and the fluctuating parts of the scattered fields from the medium. The coherent term is observed as a sharp peak, while the incoherent term builds up and decays more slowly. The incoherent response is dominated by three terms: direct, direct reflected and reflected. The direct term is associated with the volume scattering and arrives first at the antenna. The second term observed at the antenna is the direct reflected component, which results from a single interaction between the scatterer and the ground. Depending on the attenuation inside the medium, this term can be the strongest return at the antenna. The reflected term which involves a double bounce from the ground arrives last due to the relatively longer path it travels. Using the multibeam representation, it is possible to examine individual returns from the side and main lobes of the antenna radiation pattern. The interference of the antenna lobes with each other can also be formulated via the multibeam representation. Strong responses from the

  8. Depth-resolved incoherent and coherent wide-field high-content imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    So, Peter T.

    2016-03-01

    Recent advances in depth-resolved wide-field imaging technique has enabled many high throughput applications in biology and medicine. Depth resolved imaging of incoherent signals can be readily accomplished with structured light illumination or nonlinear temporal focusing. The integration of these high throughput systems with novel spectroscopic resolving elements further enable high-content information extraction. We will introduce a novel near common-path interferometer and demonstrate its uses in toxicology and cancer biology applications. The extension of incoherent depth-resolved wide-field imaging to coherent modality is non-trivial. Here, we will cover recent advances in wide-field 3D resolved mapping of refractive index, absorbance, and vibronic components in biological specimens.

  9. Use of fluorescence signals generated by elastic scattering under monochromatic incident light for determining the scattering efficiencies of various plasmonic nanoparticles.

    PubMed

    Song, Ji Eun; Park, Ji Hoon; La, Ju A; Park, Seyeon; Jeong, Min Kuk; Cho, Eun Chul

    2016-08-01

    We present a route that estimates the scattering/absorption characteristics of plasmonic nanoparticles by using fluorescence and UV-visible spectroscopy. Because elastic scattering of nanoparticles caused by a monochromatic incident light is reflected in fluorescence emission spectra when recording at the excitation wavelength, the scattering intensities at the excitation wavelength during fluorescence emission scans are used to compare the scattering characteristics of various plasmonic nanoparticles under conditions where the extinction values of all of the nanoparticles are kept constant at this wavelength. For the two excitation wavelengths (519 and 560 nm) we investigated, the scattering intensities of spherical gold nanoparticles increase with increasing size (15, 33, 51, 73, and 103 nm in diameter). These results are correlated with the nanoparticles' scattering efficiencies (the ratios of scattering to the extinction cross-sections), which are theoretically calculated in the literature using Mie theory. Then, linear calibration equations at each wavelength are derived to estimate the scattering efficiencies of two Au nanorods, Au nanocages, and spherical Ag nanoparticles (15, 25, 37, and 62 nm). The values are very comparable with literature values. For various purposes such as biomedicine and optoelectronics, the present method could be beneficial to those who wish to easily compare and determine the scattering characteristics of various plasmonic nanoparticles at a certain wavelength by using commercially-available spectroscopic techniques. PMID:27215291

  10. Long-Lived Raman Resonance Amid Incoherence Above T_c

    NASA Astrophysics Data System (ADS)

    Klein, Miles V.

    1998-03-01

    Electronic Raman scattering from high and low energy excitations was studied as a function of temperature, hole doping, and energy of the incident photons in Bi_2Sr_2CaCu_2O8 ± δ superconductors. Short range antiferromagnetic correlations were found to persist when holes were doped into the insulating state, and excitations of the holes were found to be incoherent. Above the superconducting transition temperature Tc the system exhibits a sharp Raman resonance of B_1g symmetry and 75 meV energy with a pseudogap (PG) for electron-hole excitations below 75 meV.(G. Blumberg et al.), Science 278, 1427 (1997);

  11. Scattering of Radar Waves on Areosols in Plasmas

    NASA Astrophysics Data System (ADS)

    Bergstrom, R.; Crimella, M.; Ivchenko, N.; Karlsson, A.; Lindberg, H.; Persson, L.; Schlatter, N.; Tibert, G.; Westerlund, S.

    2015-09-01

    To study the physical mechanisms of phenomena such as polar mesospheric summer echoes, the SCRAP (Scattering of Radar waves on Aerosols in Plasmas) experiment aimed to validate theories on density fluctuations in dusty plasmas. The SCRAP team developed two identical free falling units (FFUs) designed to create a cloud of copper particles once they eject from the REXUS 17 sounding rocket 124 seconds after launch. By using the EISCAT incoherent scatter radar system to observe the cloud, the SCRAP experiment proposed to relate theoretical predictions to a controlled object. The SCRAP experiment was launched from ESRANGE on March the 17th 2015. The FFUs GPS signal was lost during launch and the units were therefore not found. Moreover, no backscattering from the copper cloud was observed by the radar.

  12. Bulk Metallic Glass-like Scattering Signal in Small Metallic Nanoparticles

    SciTech Connect

    Doan-Nguyen, VVT; Kimber, SAJ; Pontoni, D; Hickey, DR; Diroll, BT; Yang, XH; Miglierini, M; Murray, CB; Billinge, SJL

    2014-06-01

    The atomic structure of Ni-Pd nanoparticles has been studied using atomic pair distribution function (PDF) analysis of X-ray total scattering data and with transmission electron microscopy (TEM). Larger nanoparticles have PDFs corresponding to the bulk face-centered cubic packing. However, the smallest nanoparticles have PDFs that strongly resemble those obtained from bulk metallic glasses (BMGs). In fact, by simply scaling the distance axis by the mean metallic radius, the curves may be collapsed onto each other and onto the PDF from a metallic glass sample. In common with a wide range of BMG materials, the intermediate range order may be fit with a damped single-frequency sine wave. When viewed in high-resolution TEM, these nanoparticles exhibit atomic fringes typical of those seen in small metallic clusters with icosahedral or decahedral order. These two seemingly contradictory results are reconciled by calculating the PDFs of models of icosahedra that would be consistent with the fringes seen in TEM. These model PDFs resemble the measured ones when significant atom-position disorder is introduced, drawing together the two diverse fields of metallic nanoparticles and BMGs and supporting the view that BMGs may contain significant icosahedral or decahedral order.

  13. Discrete spectral incoherent solitons in nonlinear media with noninstantaneous response

    SciTech Connect

    Michel, Claire; Kibler, Bertrand; Picozzi, Antonio

    2011-02-15

    We show theoretically that nonlinear optical media characterized by a finite response time may support the existence of discrete spectral incoherent solitons. The structure of the soliton consists of three incoherent spectral bands that propagate in frequency space toward the low-frequency components in a discrete fashion and with a constant velocity. Discrete spectral incoherent solitons do not exhibit a confinement in the space-time domain, but exclusively in the frequency domain. The kinetic theory describes in detail all the essential properties of discrete spectral incoherent solitons: A quantitative agreement has been obtained between simulations of the kinetic equation and the nonlinear Schroedinger equation. Discrete spectral incoherent solitons may be supported in both the normal dispersion regime or the anomalous dispersion regime. These incoherent structures find their origin in the causality condition inherent to the nonlinear response function of the material. Considering the concrete example of the Raman effect, we show that discrete incoherent solitons may be spontaneously generated through the process of supercontinuum generation in photonic crystal fibers.

  14. Statistical theory for incoherent light propagation in nonlinear media.

    PubMed

    Hall, B; Lisak, M; Anderson, D; Fedele, R; Semenov, V E

    2002-03-01

    A statistical approach based on the Wigner transform is proposed for the description of partially incoherent optical wave dynamics in nonlinear media. An evolution equation for the Wigner transform is derived from a nonlinear Schrödinger equation with arbitrary nonlinearity. It is shown that random phase fluctuations of an incoherent plane wave lead to a Landau-like damping effect, which can stabilize the modulational instability. In the limit of the geometrical optics approximation, incoherent, localized, and stationary wave fields are shown to exist for a wide class of nonlinear media. PMID:11909156

  15. The measurement of self-diffusion coefficients in liquid metals with quasielastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Meyer, Andreas

    2015-01-01

    Quasielastic incoherent neutron scattering (QENS) has proven to be a versatile tool to study self diffusion of atoms in liquid metals. Here it is shown, that coherent contributions to the signal in the small q limit appear as a flat and energy independent constant to the QENS signal in single-component liquid metals even for systems with a small incoherent scattering cross section, like aluminum. Container-less processing via electromagnetic or electrostatic levitation devices, especially designed for QENS, enables the in-situ measurement on liquid metallic droplets of sizes between 5 mm to 10 mm in diameter. This gives access to the study of chemically reactive, refractory metallic melts and extends the accessible temperature range to undercoolings of several hundred Kelvin below the respective melting point. Compared to experiments using a thin-walled crucible giving hollow-cylindrical sample geometry it is shown that multiple scattering on levitated droplets is negligible for the analysis of the self-diffusion coefficient. QENS results of liquid germanium and 73germanium isotope mixtures, titanium, nickel, copper and aluminum are reviewed. The self-diffusion coefficients of these systems are best described by an Arrhenius-type temperature dependence around their respective melting points.

  16. Aspect sensitive E- and F-region SPEAR-enhanced incoherent backscatter observed by the EISCAT Svalbard radar

    NASA Astrophysics Data System (ADS)

    Dhillon, R. S.; Robinson, T. R.; Yeoman, T. K.

    2009-01-01

    Previous studies of the aspect sensitivity of heater-enhanced incoherent radar backscatter in the high-latitude ionosphere have demonstrated the directional dependence of incoherent scatter signatures corresponding to artificially excited electrostatic waves, together with consistent field-aligned signatures that may be related to the presence of artificial field-aligned irregularities. These earlier high-latitude results have provided motivation for repeating the investigation in the different geophysical conditions that obtain in the polar cap ionosphere. The Space Plasma Exploration by Active Radar (SPEAR) facility is located within the polar cap and has provided observations of RF-enhanced ion and plasma line spectra recorded by the EISCAT Svalbard UHF incoherent scatter radar system (ESR), which is collocated with SPEAR. In this paper, we present observations of aspect sensitive E- and F-region SPEAR-induced ion and plasma line enhancements that indicate excitation of both the purely growing mode and the parametric decay instability, together with sporadic E-layer results that may indicate the presence of cavitons. We note consistent enhancements from field-aligned, vertical and also from 5° south of field-aligned. We attribute the prevalence of vertical scatter to the importance of the Spitze region, and of that from field-aligned to possible wave/irregularity coupling.

  17. Magnetic-bead-based sub-femtomolar immunoassay using resonant Raman scattering signals of ZnS nanoparticles.

    PubMed

    Ding, Yadan; Cong, Tie; Chu, Xueying; Jia, Yan; Hong, Xia; Liu, Yichun

    2016-07-01

    Highly sensitive, specific, and selective immunoassays are of great significance for not only clinical diagnostics but also food safety, environmental monitoring, and so on. Enzyme-linked immunosorbent assays and fluorescence-based and electrochemical immunoassays are important intensively investigated immunoassay techniques. However, they might suffer from low sensitivity or false-positive results. In this work, a simple, reliable, and ultrasensitive magnetic-bead-based immunoassay was performed using biofunctionalized ZnS semiconductor nanocrystals as resonant Raman probes. The resonant Raman scattering of ZnS nanocrystals displays evenly spaced multi-phonon resonant Raman lines with narrow bandwidths and has strong resistance to environmental variation due to the nature of the electron-phonon interaction, thus rendering reliable signal readout in the immunoassays. The superparamagnetic Fe3O4 nanoparticles facilitated greatly the separation, purification, and concentration processes. It is beneficial for both reducing the labor intensity and amplifying the detection signals. The immobilization of antibodies on the surface of magnetic beads, the preparation of resonant Raman probes, and the immunological recognition between the antibody and analyte all occurred in the liquid phase, which minimized the diffusion barriers and boundary layer constraints. All these factors contributed to the ultralow detection limit of human IgG, which was determined to be about 0.5 fM (∼0.08 pg/ml). It is nearly the highest sensitivity obtained for IgG detection. This work shall facilitate the design of nanoplatforms for ultrasensitive detections of proteins, DNAs, bacteria, explosives, and so on. Graphical abstract An ultrasensitive magnetic-bead-based immunoassay was performed using multi-phonon resonant Raman lines of ZnS nanoparticles as detection signals. PMID:27173389

  18. From incoherence to synchronicity in the network Kuramoto model

    NASA Astrophysics Data System (ADS)

    Kalloniatis, Alexander C.

    2010-12-01

    We study the synchronization properties of the Kuramoto model of coupled phase oscillators on a general network. Here we distinguish the ability of such a system to self-synchronize from the stability of this behavior. While self-synchronization is a consequence of genuine nonperturbative dynamics, the stability in dynamical systems is usually accessible by fluctuations about a fixed point, here taken to be the phase synchronized solution. We examine this problem in terms of modes of the graph Laplacian, by which the absolute Lyapunov stability of the phase synchronized fixed point is readily demonstrated. Departures from stability are seen to arise at the next order in fluctuations where, depending on a truncation in the number of time-dependent Laplacian modes, the dynamical equations can be reduced to forms resembling those for species population models, the logistic and the Lotka-Volterra equations. Methods from these systems are exploited to analytically derive new critical couplings signaling deviation from classical stability. We thereby analytically explain the existence of an intermediate regime of behavior between incoherence and synchronization, where system wide periodic behaviors are exhibited and stable, unstable, and hyperbolic fixed points can be identified. We discuss these results in light of numerical solutions of the equations of motion for various networks.

  19. Incoherent interlayer conduction in twisted bilayer graphene

    NASA Astrophysics Data System (ADS)

    Kim, Youngwook; Nam, S.-G.; Lee, H.-J.; Kim, Jun Sung; Yun, H.; Lee, S. W.; Son, M.; Choi, H. C.; Lee, D. S.; Kim, D. C.; Seo, S.

    2014-03-01

    Coherent motion of the electrons in the Bloch states often breaks down for the interlayer conduction in layered materials where the interlayer coupling is significantly reduced by e.g. large interlayer separation. Here, we report complete suppression of coherent conduction in twisted bilayer graphene even with an atomic length scale of layer separation. The interlayer conduction were investigated using a cross junction of monolayer graphene layers. The interlayer resistivity is much higher than the c-axis resistivity of Bernal-stacked graphite and exhibits strong dependence on temperature as well as on external electric fields. These results suggest that the graphene layers are significantly decoupled by rotation, and the incoherent electron tunneling is the main interlayer conduction channel. In this regime, the interlayer conduction is determined by the overlap of the Dirac Fermi surfaces (FS) from each layer. The angle dependence of the interlayer resistivity is found to be relatively strong at low temperatures, while it becomes moderate and monotonous at high temperatures. This demonstrates the importance of phonon-mediated conduction at high temperatures, which enhances the overlap between the momentum-mismatched FS's in twisted bilayer graphene.

  20. Optimal wavefront estimation of incoherent sources

    NASA Astrophysics Data System (ADS)

    Riggs, A. J. Eldorado; Kasdin, N. Jeremy; Groff, Tyler

    2014-08-01

    Direct imaging is in general necessary to characterize exoplanets and disks. A coronagraph is an instrument used to create a dim (high-contrast) region in a star's PSF where faint companions can be detected. All coronagraphic high-contrast imaging systems use one or more deformable mirrors (DMs) to correct quasi-static aberrations and recover contrast in the focal plane. Simulations show that existing wavefront control algorithms can correct for diffracted starlight in just a few iterations, but in practice tens or hundreds of control iterations are needed to achieve high contrast. The discrepancy largely arises from the fact that simulations have perfect knowledge of the wavefront and DM actuation. Thus, wavefront correction algorithms are currently limited by the quality and speed of wavefront estimates. Exposures in space will take orders of magnitude more time than any calculations, so a nonlinear estimation method that needs fewer images but more computational time would be advantageous. In addition, current wavefront correction routines seek only to reduce diffracted starlight. Here we present nonlinear estimation algorithms that include optimal estimation of sources incoherent with a star such as exoplanets and debris disks.

  1. Holography of incoherently illuminated 3D scenes

    NASA Astrophysics Data System (ADS)

    Shaked, Natan T.; Rosen, Joseph

    2008-04-01

    We review several methods of generating holograms of 3D realistic objects illuminated by incoherent white light. Using these methods, it is possible to obtain holograms with a simple digital camera, operating in regular light conditions. Thus, most disadvantages characterizing conventional holography, namely the need for a powerful, highly coherent laser and meticulous stability of the optical system are avoided. These holograms can be reconstructed optically by illuminating them with a coherent plane wave, or alternatively by using a digital reconstruction technique. In order to generate the proposed hologram, the 3D scene is captured from multiple points of view by a simple digital camera. Then, the acquired projections are digitally processed to yield the final hologram of the 3D scene. Based on this principle, we can generate Fourier, Fresnel, image or other types of holograms. To obtain certain advantages over the regular holograms, we also propose new digital holograms, such as modified Fresnel holograms and protected correlation holograms. Instead of shifting the camera mechanically to acquire a different projection of the 3D scene each time, it is possible to use a microlens array for acquiring the entire projections in a single camera shot. Alternatively, only the extreme projections can be acquired experimentally, while the middle projections are predicted digitally by using the view synthesis algorithm. The prospective goal of these methods is to facilitate the design of a simple, portable digital holographic camera which can be useful for a variety of practical applications.

  2. Robust and Adaptive MicroRNA-Mediated Incoherent Feedforward Motifs

    NASA Astrophysics Data System (ADS)

    Xu, Feng-Dan; Liu, Zeng-Rong; Zhang, Zhi-Yong; Shen, Jian-Wei

    2009-02-01

    We integrate transcriptional and post-transcriptional regulation into microRNA-mediated incoherent feedforward motifs and analyse their dynamical behaviour and functions. The analysis show that the behaviour of the system is almost uninfluenced by the varying input in certain ranges and by introducing of delay and noise. The results indicate that microRNA-mediated incoherent feedforward motifs greatly enhance the robustness of gene regulation.

  3. Demonstration of improvement in the signal-to-noise ratio of Thomson scattering signal obtained by using a multi-pass optical cavity on the Tokyo Spherical Tokamak-2.

    PubMed

    Togashi, H; Ejiri, A; Hiratsuka, J; Nakamura, K; Takase, Y; Yamaguchi, T; Furui, H; Imamura, K; Inada, T; Kakuda, H; Nakanishi, A; Oosako, T; Shinya, T; Sonehara, M; Tsuda, S; Tsujii, N; Wakatsuki, T; Hasegawa, M; Nagashima, Y; Narihara, K; Yamada, I; Tojo, H

    2014-11-01

    The multi-pass Thomson scattering (TS) scheme enables obtaining many photons by accumulating multiple TS signals. The signal-to-noise ratio (SNR) depends on the accumulation number. In this study, we performed multi-pass TS measurements for ohmically heated plasmas, and the relationship between SNR and the accumulation number was investigated. As a result, improvement of SNR in this experiment indicated similar tendency to that calculated for the background noise dominant situation. PMID:25430259

  4. Demonstration of improvement in the signal-to-noise ratio of Thomson scattering signal obtained by using a multi-pass optical cavity on the Tokyo Spherical Tokamak-2

    SciTech Connect

    Togashi, H. Ejiri, A.; Nakamura, K.; Takase, Y.; Yamaguchi, T.; Furui, H.; Imamura, K.; Inada, T.; Nakanishi, A.; Oosako, T.; Shinya, T.; Tsuda, S.; Tsujii, N.; Hiratsuka, J.; Kakuda, H.; Sonehara, M.; Wakatsuki, T.; Hasegawa, M.; Nagashima, Y.; Narihara, K.; and others

    2014-11-15

    The multi-pass Thomson scattering (TS) scheme enables obtaining many photons by accumulating multiple TS signals. The signal-to-noise ratio (SNR) depends on the accumulation number. In this study, we performed multi-pass TS measurements for ohmically heated plasmas, and the relationship between SNR and the accumulation number was investigated. As a result, improvement of SNR in this experiment indicated similar tendency to that calculated for the background noise dominant situation.

  5. A probabilistic theory of electromagnetic wave scattering from a slightly random surface 2. Vertical polarization

    NASA Astrophysics Data System (ADS)

    Nakayama, J.; Sakata, M.; Ogura, H.

    1981-09-01

    The scattering of an electromagnetic wave from an infinite random surface is studied by the probabilistic method developed in a previous paper. For a vertical polarized plane wave incident on a slightly random and perfectly conductive surface a new stochastic wave solution involving multiple scattering is obtained. The stochastic solution is free from the divergence difficulty as in the small perturbation method but gives an anomaly such that for a grazing angle of incidence the coherent scattering almost disappears and instead the incoherent scattering becomes dominant. In terms of the stochastic solution, a number of statistical properties of the scattering are calculated concretely for a perfectly conductive surface, such as the complex amplitude of the coherent scattering, the variance of the electric field, the optical theorem describing the power relation between the coherent and the incoherent scattering, the angular distribution of the incoherent scattering, the scattering cross section per unit area, and the surface wave flow, which are all illustrated in the figures.

  6. Quantitative nanoimmunosensor based on dark-field illumination with enhanced sensitivity and on-off switching using scattering signals.

    PubMed

    Lee, Seungah; Nan, He; Yu, Hyunung; Kang, Seong Ho

    2016-05-15

    A nanoimmunosensor based on wavelength-dependent dark-field illumination with enhanced sensitivity was used to detect a disease-related protein molecule at zeptomolar (zM) concentrations. The assay platform of 100-nm gold nanospots could be selectively acquired using the wavelength-dependence of enhanced scattering signals from antibody-conjugated plasmonic silver nanoparticles (NPs) with on-off switching using optical filters. Detection of human thyroid-stimulating hormone (hTSH) at a sensitivity of 100 zM, which corresponds to 1-2 molecules per gold spot, was possible within a linear range of 100 zM-100 fM (R=0.9968). A significantly enhanced sensitivity (~4-fold) was achieved with enhanced dark-field illumination compared to using a total internal reflection fluorescence immunosensor. Immunoreactions were confirmed via optical axial-slicing based on the spectral characteristics of two plasmonic NPs. This method of using wavelength-dependent dark-field illumination had an enhanced sensitivity and a wide, linear dynamic range of 100 zM-100 fM, and was an effective tool for quantitatively detecting a single molecule on a nanobiochip for molecular diagnostics. PMID:26774086

  7. Elimination of light scatter interference in dual-laser flow cytometry by synchronous detection of emitted fluorescence: theory and demonstration using simulated signals

    NASA Astrophysics Data System (ADS)

    Steinkamp, John A.; Keij, Jan F.

    1999-06-01

    Light scatter is often a source of interference in dual-laser excitation experiments by flow cytometry. If the two laser beams are not adequately separated or optical masking is not used, and if gated sequential fluorescence signal detection is not employed, light scatter from particles/cells as they pass across one beam can interfere in the fluorescence measurement channel of the other laser excitation beam. In this study we discuss the problem and present the theory for improving fluorescence measurements in dual-laser flow cytometry by use of modulated laser excitation and synchronous (phase- sensitive) detection of the resulting fluorescence emission to eliminate light scatter interference from particles/cells. Fluorescence emission from particles/cells generated by the first laser beam (unmodulated cw) is measured using conventional means (detection channel no. 1). Light scatter interference from particles/cells as they pass across the first laser excitation beam, whose wavelength lies in the fluorescence measurement region of detection channel no. 2, is rejected by the synchronously tuned phase-sensitive channel no. 2 detector, whereas the fluorescence emission corresponding to laser no. 2 excitation is detected and measured. The efficacy of the technology in relation to analytical cytology measurements is demonstrated using simulated fluorescence and light scatter signals.

  8. Spatially-constrained probability distribution model of incoherent motion (SPIM) for abdominal diffusion-weighted MRI.

    PubMed

    Kurugol, Sila; Freiman, Moti; Afacan, Onur; Perez-Rossello, Jeannette M; Callahan, Michael J; Warfield, Simon K

    2016-08-01

    Quantitative diffusion-weighted MR imaging (DW-MRI) of the body enables characterization of the tissue microenvironment by measuring variations in the mobility of water molecules. The diffusion signal decay model parameters are increasingly used to evaluate various diseases of abdominal organs such as the liver and spleen. However, previous signal decay models (i.e., mono-exponential, bi-exponential intra-voxel incoherent motion (IVIM) and stretched exponential models) only provide insight into the average of the distribution of the signal decay rather than explicitly describe the entire range of diffusion scales. In this work, we propose a probability distribution model of incoherent motion that uses a mixture of Gamma distributions to fully characterize the multi-scale nature of diffusion within a voxel. Further, we improve the robustness of the distribution parameter estimates by integrating spatial homogeneity prior into the probability distribution model of incoherent motion (SPIM) and by using the fusion bootstrap solver (FBM) to estimate the model parameters. We evaluated the improvement in quantitative DW-MRI analysis achieved with the SPIM model in terms of accuracy, precision and reproducibility of parameter estimation in both simulated data and in 68 abdominal in-vivo DW-MRIs. Our results show that the SPIM model not only substantially reduced parameter estimation errors by up to 26%; it also significantly improved the robustness of the parameter estimates (paired Student's t-test, p < 0.0001) by reducing the coefficient of variation (CV) of estimated parameters compared to those produced by previous models. In addition, the SPIM model improves the parameter estimates reproducibility for both intra- (up to 47%) and inter-session (up to 30%) estimates compared to those generated by previous models. Thus, the SPIM model has the potential to improve accuracy, precision and robustness of quantitative abdominal DW-MRI analysis for clinical applications. PMID

  9. Rough-surface effects on incoherent scattering from random volumetric scatterers: Approximate analytic series solution

    SciTech Connect

    Bilgen, M.; Rose, J.H. )

    1994-11-01

    An approximate analytic series solution is obtained for the effects of randomly rough surfaces on the time-dependent ultrasonic backscatter that are due to beam-microstructure interactions. The transmission of sound through the rough surface is modeled by scalar waves by use of the phase-screen and Fresnel approximations, whereas the transducer is assumed to produce a focused normally oriented Gaussian beam. The beam-microstructure interaction is described by a simple, generic model that attributes backscattering to inhomogeneities in the elastic constants of the sample; density variations are ignored. Key predictions of the approximate series solution are that (a) acoustic backscatter is relatively insensitive to surface roughness for unfocused probes, (b) roughness can dramatically reduce the backscatter noise seen by focused probes, (c) backscatter is increased at early times because of weak localization, and (d) backscatter is reduced at late times because of increased diffraction. The predictions of the series solution are briefly compared with available experiment. 32 refs., 10 figs.

  10. Modeling of digital information optical encryption system with spatially incoherent illumination

    NASA Astrophysics Data System (ADS)

    Bondareva, Alyona P.; Cheremkhin, Pavel A.; Krasnov, Vitaly V.; Rodin, Vladislav G.; Starikov, Rostislav S.; Starikov, Sergey N.

    2015-10-01

    State of the art micromirror DMD spatial light modulators (SLM) offer unprecedented framerate up to 30000 frames per second. This, in conjunction with high speed digital camera, should allow to build high speed optical encryption system. Results of modeling of digital information optical encryption system with spatially incoherent illumination are presented. Input information is displayed with first SLM, encryption element - with second SLM. Factors taken into account are: resolution of SLMs and camera, holograms reconstruction noise, camera noise and signal sampling. Results of numerical simulation demonstrate high speed (several gigabytes per second), low bit error rate and high crypto-strength.

  11. Simulations of a spatially resolved reflectometry signal from a highly scattering three-layer medium applied to the problem of glucose sensing in human skin

    SciTech Connect

    Bykov, A V; Kirillin, M Yu; Priezzhev, A V; Myllylae, Risto

    2006-12-31

    The possibility of using spatially resolved reflectometry (SRR) at a wavelength of 820 nm to detect changes in the optical properties of a highly scattering layered random medium simulating a biological tissue caused by changes in the glucose level is analysed. Model signals from a three-layer biological tissue phantom consisting of two skin layers and a blood layer located between them are obtained by the Monte-Carlo method. It was assumed that variations in the glucose level induce variations in the optical parameters of the blood layer and the bottom skin layer. To analyse the trajectories of photons forming the SRR signal, their scattering maps are obtained. The ratio of the photon path in layers sensitive to the glucose level to the total path in the medium was used as a parameter characterising these trajectories. The relative change in the reflected signal caused by a change in the glucose concentration is analysed depending on the distance between a probe radiation source and a detector. It is shown that the maximum relative change in the signal (about 7%) takes place for the source - detector separation in the range from 0.3 to 0.5 mm depending on the model parameters. (special issue devoted to multiple radiation scattering in random media)

  12. CINCH (confocal incoherent correlation holography) super resolution fluorescence microscopy based upon FINCH (Fresnel incoherent correlation holography)

    PubMed Central

    Siegel, Nisan; Storrie, Brian; Bruce, Marc

    2016-01-01

    FINCH holographic fluorescence microscopy creates high resolution super-resolved images with enhanced depth of focus. The simple addition of a real-time Nipkow disk confocal image scanner in a conjugate plane of this incoherent holographic system is shown to reduce the depth of focus, and the combination of both techniques provides a simple way to enhance the axial resolution of FINCH in a combined method called “CINCH”. An important feature of the combined system allows for the simultaneous real-time image capture of widefield and holographic images or confocal and confocal holographic images for ready comparison of each method on the exact same field of view. Additional GPU based complex deconvolution processing of the images further enhances resolution. PMID:26839443

  13. Incoherent synchrotron emission of laser-driven plasma edge

    SciTech Connect

    Serebryakov, D. A. Nerush, E. N.; Kostyukov, I. Yu.

    2015-12-15

    When a relativistically intense linearly polarized laser pulse is incident on an overdense plasma, a dense electron layer is formed on the plasma edge which relativistic motion results in high harmonic generation, ion acceleration, and incoherent synchrotron emission of gamma-photons. Here we present a self-consistent analytical model that describes the edge motion and apply it to the problem of incoherent synchrotron emission by ultrarelativistic plasma electrons. The model takes into account both coherent radiation reaction from high harmonics and incoherent radiation reaction in the Landau–Lifshitz form. The analytical results are in agreement with 3D particle-in-cell simulations in a certain parameter region that corresponds to the relativistic electronic spring interaction regime.

  14. Quantifying coherent and incoherent cathodoluminescence in semiconductors and metals

    SciTech Connect

    Brenny, B. J. M.; Coenen, T.; Polman, A.

    2014-06-28

    We present a method to separate coherent and incoherent contributions to cathodoluminescence from bulk materials by using angle-resolved cathodoluminescence spectroscopy. Using 5 and 30 keV electrons, we measure the cathodoluminescence spectra for Si, GaAs, Al, Ag, Au, and Cu and determine the angular emission distributions for Al, GaAs, and Si. Aluminium shows a clear dipolar radiation profile due to coherent transition radiation, while GaAs shows incoherent luminescence characterized by a Lambertian angular distribution. Silicon shows both transition radiation and incoherent radiation. From the angular data, we determine the ratio between the two processes and decompose their spectra. This method provides a powerful way to separate different radiative cathodoluminescence processes, which is useful for material characterization and in studies of electron- and light-matter interaction in metals and semiconductors.

  15. Affective Incoherence: When Affective Concepts and Embodied Reactions Clash

    PubMed Central

    Centerbar, David B.; Clore, Gerald L.; Schnall, Simone; Garvin, Erika

    2008-01-01

    In five studies, we examined the effects on cognitive performance of coherence and incoherence between conceptual and experiential sources of affective information. The studies crossed the priming of happy and sad concepts with affective experiences. In different experiments, these included: approach or avoidance actions, happy or sad feelings, and happy or sad expressive behaviors. In all studies, coherence between affective concepts and affective experiences led to better recall of a story than affective incoherence. We suggested that the experience of such experiential affective cues serves as evidence of the appropriateness of affective concepts that come to mind. The results suggest that affective coherence has epistemic benefits, and that incoherence is costly, for cognitive performance. PMID:18361672

  16. Tunable, anomalous Mie scattering using spatial coherence.

    PubMed

    Wang, Yangyundou; Schouten, Hugo F; Visser, Taco D

    2015-10-15

    We demonstrate that a J0-Bessel-correlated beam that is incident on a homogeneous sphere produces a highly unusual distribution of the scattered field, with the maximum no longer occurring in the forward direction. Such a beam can be easily generated using a spatially incoherent, annular source. Moreover, the direction of maximal scattering can be shifted by changing the spatial coherence length. In this process, the total power that is scattered remains constant. This new tool to control scattering directionality may be used to steer the scattered field away from the forward direction and selectively address detectors situated at different angles. PMID:26469618

  17. Understanding and eliminating artifact signals from diffusely scattered pump beam in measurements of rough samples by time-domain thermoreflectance (TDTR).

    PubMed

    Sun, Bo; Koh, Yee Kan

    2016-06-01

    Time-domain thermoreflectance (TDTR) is a pump-probe technique frequently applied to measure the thermal transport properties of bulk materials, nanostructures, and interfaces. One of the limitations of TDTR is that it can only be employed to samples with a fairly smooth surface. For rough samples, artifact signals are collected when the pump beam in TDTR measurements is diffusely scattered by the rough surface into the photodetector, rendering the TDTR measurements invalid. In this paper, we systemically studied the factors affecting the artifact signals due to the pump beam leaked into the photodetector and thus established the origin of the artifact signals. We find that signals from the leaked pump beam are modulated by the probe beam due to the phase rotation induced in the photodetector by the illumination of the probe beam. As a result of the modulation, artifact signals due to the leaked pump beam are registered in TDTR measurements as the out-of-phase signals. We then developed a simple approach to eliminate the artifact signals due to the leaked pump beam. We verify our leak-pump correction approach by measuring the thermal conductivity of a rough InN sample, when the signals from the leaked pump beam are significant. We also discuss the advantages of our new method over the two-tint approach and its limitations. Our new approach enables measurements of the thermal conductivity of rough samples using TDTR. PMID:27370481

  18. Incoherent averaging of phase singularities in speckle-shearing interferometry.

    PubMed

    Mantel, Klaus; Nercissian, Vanusch; Lindlein, Norbert

    2014-08-01

    Interferometric speckle techniques are plagued by the omnipresence of phase singularities, impairing the phase unwrapping process. To reduce the number of phase singularities by physical means, an incoherent averaging of multiple speckle fields may be applied. It turns out, however, that the results may strongly deviate from the expected √N behavior. Using speckle-shearing interferometry as an example, we investigate the mechanism behind the reduction of phase singularities, both by calculations and by computer simulations. Key to an understanding of the reduction mechanism during incoherent averaging is the representation of the physical averaging process in terms of certain vector fields associated with each speckle field. PMID:25078215

  19. Short-time-interaction quantum measurement through an incoherent mediator

    SciTech Connect

    Casanova, J.; Romero, G.; Lizuain, I.; Muga, J. G.; Retamal, J. C.; Roos, C. F.; Solano, E.

    2010-06-15

    We propose a method of indirect measurements where a probe is able to read, in short interaction times, the quantum state of a remote system through an incoherent third party, hereafter called a mediator. The probe and system can interact briefly with the mediator in an incoherent state but not directly among themselves and, nevertheless, the transfer of quantum information can be achieved with robustness. We exemplify our measurement scheme with a paradigmatic example of this tripartite problem--a qubit-oscillator-qubit setup--and discuss different physical scenarios, pointing out the associated advantages and limitations.

  20. Incoherent control of topological charges in nonequilibrium polariton condensates

    NASA Astrophysics Data System (ADS)

    Ma, Xuekai; Peschel, Ulf; Egorov, Oleg A.

    2016-01-01

    We study stability and switching dynamics of topological dislocations forming in a nonequilibrium polariton condensate sustained by an incoherent ring-shaped optical pump. In particular, we report on an elegant method for creation of vortices with predefined angular momenta by means of a purely incoherent (off-resonant) elliptically-shaped control beam. The control beam breaks the radiale symmetry of the system and induces chirality required for a topological charge transfer with a predefined sign. Numerical analysis encloses the optimal parameters for an effective switching between states with opposite orbital angular momenta.

  1. Incoherent neutrinoproduction of photons and pions in a chiral effective field theory for nuclei

    NASA Astrophysics Data System (ADS)

    Zhang, Xilin; Serot, Brian D.

    2012-09-01

    We study the incoherent neutrinoproduction of photons and pions with neutrino energy Eν⩽0.5GeV. These processes are relevant to the background analysis in neutrino-oscillation experiments [for example, MiniBooNE; A. A. Aquilar-Arevalo (MiniBooNE Collaboration), Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.100.032301 100, 032301 (2008)]. The calculations are carried out using a Lorentz-covariant effective field theory (EFT), which contains nucleons, pions, the Delta (1232) (Δ), isoscalar scalar (σ) and vector (ω) fields, and isovector vector (ρ) fields, and has SU(2)L⊗SU(2)R chiral symmetry realized nonlinearly. The contributions of one-body currents are studied in the local Fermi gas approximation. The current form factors are generated by meson dominance in the EFT Lagrangian. The conservation of the vector current and the partial conservation of the axial current are satisfied automatically, which is crucial for photon production. The Δ dynamics in nuclei, as a key component in the study, is explored. Introduced Δ-meson couplings explain the Δ spin-orbit coupling in nuclei, and this leads to interesting constraints on the theory. Meanwhile, a phenomenological approach is applied to parametrize the Δ width. To benchmark our approximations, we calculate the differential cross sections for quasielastic scattering and incoherent electroproduction of pions without a final-state interaction (FSI). The FSI can be ignored for photon production.

  2. A phenomenological description of an incoherent Fermi liquid near optimal doping in high Tc cuprates.

    PubMed

    Kim, Ki-Seok; Kim, Hyun-Chul

    2011-12-14

    Marginal Fermi-liquid physics near optimal doping in high T(c) cuprates has been explained within two competing scenarios such as the spin-fluctuation theory based on an itinerant picture and the slave-particle approach based on a localized picture. In this study we propose an alternative scenario for the anomalous transport within the context of the slave-particle approach. Although the marginal Fermi-liquid phenomenology was interpreted previously within deconfinement of the compact gauge theory, referred to as the strange metal phase, we start from confinement, introducing the Polyakov loop parameter into an SU(2) gauge theory formulation of the t-J model. The Polyakov loop parameter gives rise to incoherent electrons through the confinement of spinons and holons, which result from huge imaginary parts of self-energy corrections for spinons and holons. This confinement scenario serves a novel mechanism for the marginal Fermi-liquid transport in the respect that the scattering source has nothing to do with symmetry breaking. Furthermore, the incoherent Fermi-liquid state evolves into the Fermi-liquid phase through crossover instead of an artificial second-order transition as temperature is lowered, where the crossover phenomenon does not result from the Anderson-Higgs mechanism but originates from an energy scale in the holon sector. We fit experimental data for the electrical resistivity around the optimal doping and find a reasonable match between our theory and the experiment. PMID:22101360

  3. Ghost imaging of phase objects with classical incoherent light

    SciTech Connect

    Shirai, Tomohiro; Setaelae, Tero; Friberg, Ari T.

    2011-10-15

    We describe an optical setup for performing spatial Fourier filtering in ghost imaging with classical incoherent light. This is achieved by a modification of the conventional geometry for lensless ghost imaging. It is shown on the basis of classical coherence theory that with this technique one can realize what we call phase-contrast ghost imaging to visualize pure phase objects.

  4. Thermalization and condensation in an incoherently pumped passive optical cavity

    NASA Astrophysics Data System (ADS)

    Michel, C.; Haelterman, M.; Suret, P.; Randoux, S.; Kaiser, R.; Picozzi, A.

    2011-09-01

    We study theoretically and numerically the condensation and the thermalization of classical optical waves in an incoherently pumped passive Kerr cavity. We show that the dynamics of the cavity exhibits a turbulent behavior that can be described by the wave turbulence theory. A mean-field kinetic equation is derived, which reveals that, in its high finesse regime, the cavity behaves essentially as a conservative Hamiltonian system. In particular, the intracavity turbulent field is shown to relax adiabatically toward a thermodynamic equilibrium state of energy equipartition. As a consequence of this effect of wave thermalization, the incoherent optical field undergoes a process of condensation, characterized by the spontaneous emergence of a plane wave from the incoherently pumped cavity. The condensation process is an equilibrium phase transition that occurs below a critical value of the (kinetic) energy of the incoherent pump. In spite of the dissipative nature of the cavity dynamics, the condensate fraction of the high-finesse cavity field is found in quantitative agreement with the theory inherited from the purely conservative (Hamiltonian) nonlinear Schrödinger equation.

  5. Coherent and incoherent tunneling in asymmetric double-well potentials

    SciTech Connect

    Ranfagni, A.; Cacciari, I.; Vitali, M. A.; Viliani, G.; Moretti, P.; Ruggeri, R.

    2006-07-15

    The determination of the time scale for coherent and incoherent tunneling in asymmetric double-well potentials is reconsidered according to the instanton-bounce method. In particular, by making use of Feynman's transition elements, a different, relatively simpler approach to this problem, with respect to conventional quantum-mechanical treatments, is obtained.

  6. Requirements for space shuttle scatter radar experiments

    NASA Technical Reports Server (NTRS)

    Harker, K. J.

    1975-01-01

    The feasibility of carrying out scatter radar experiments on the space shuttle was analyzed. Design criteria considered were the required average transmitter power, frequency resolution, spatial resolution, and statistical accuracy. Experiments analyzed were measurement of the naturally enhanced plasma line and the ion component of the incoherent scatter spectrum, and the plasma line artificially enhanced by an intense HF radio wave. The ion component measurement does not appear feasible, while the other two appear reasonable for short ranges only.

  7. APPLICATION OF LASERS AND LASER-OPTICAL METHODS IN LIFE SCIENCES Two-photon fluorescence microscopy signal formation in highly scattering media: theoretical and numerical simulation

    NASA Astrophysics Data System (ADS)

    Sergeeva, Ekaterina A.; Katichev, A. R.; Kirillin, M. Yu

    2011-01-01

    Using the radiative transfer theory and Monte Carlo simulations, we analyse the effect of scattering in a medium and of the size of the detector pinhole on the formation of the fluorescent signal in standard two-photon fluorescence microscopy (TPFM) systems. The theoretical analysis is based on a small-angle diffusion approximation of the radiative transfer equation, adapted to calculate the propagation of focused infrared radiation in media similar to the biological tissues in their optical properties. The accuracy of the model is evaluated by comparing the calculated excitation intensity in a highly scattering medium with the results of Monte Carlo simulations. To simulate a tightly focused Gaussian beam by the Monte Carlo method, the so called 'ray-optics' approach that correctly takes into account the finite size and shape of the beam waist is applied. It is shown that in the combined confocal and two-photon scanning microscopy systems not equipped with an external 'nondescanned' detector, the scattering significantly affects both the nonlinear excitation efficiency in the medium and the fluorescence collection efficiency of the system. In such systems, the rate of the useful TPFM signal in-depth decay is 1.5 — 2 times higher than in systems equipped with a 'nondescanned' detector.

  8. Advanced Spectral Analysis Methods for Quantification of Coherent Ultrasound Scattering: Applications in the Breast

    NASA Astrophysics Data System (ADS)

    Rosado-Mendez, Ivan M.

    The goal of this dissertation was to improve the diagnostic value of parametric images generated from Quantitative Ultrasound (QUS) methods based on the power spectral density (PSD) of radiofrequency echo signals. This was achieved by testing for local adherence to conventional QUS assumptions that echo signals originate from incoherent scattering, and that signals are stationary over PSD estimation windows. For this purpose, we designed a novel algorithm that empirically evaluates the statistical significance of coherent-scattering signatures in the echo signals. Signatures are quantified through a set of optimized metrics describing the stationary or non-stationary features of the echo signals. We compared Nakagami-model based metrics and model-free metrics of the statistics of the echo signal amplitude for analyzing stationary features. For non-stationary features, we advanced the use of the echo-signal generalized spectrum by comparing single- and multi-taper estimators of this spectrum to the time-domain singular spectrum analysis method. Tests of statistical significance were done through empirical comparisons with values of the same metrics estimated from a uniform reference material exhibiting incoherent scattering. The metrics that quantify these features were selected after simulation- and phantom-based optimizations centered on the task of creating parametric images, where tradeoffs must be made between spatial resolution and detection performance. The connection of the analyses of the stationary and the non-stationary features provided a way to estimate descriptors of the tissue organization scales below and above the resolution limit imposed by the size of the acoustic pulse. A preliminary application of the developed algorithm was done on echo data from human breast lesions scanned in vivo. Results supported the idea of a more homogeneously random distribution of subresolution scatterers within invasive ductal carcinomas than within fibroadenomas

  9. Maximum-likelihood and other processors for incoherent and coherent matched-field localization.

    PubMed

    Dosso, Stan E; Wilmut, Michael J

    2012-10-01

    This paper develops a series of maximum-likelihood processors for matched-field source localization given various states of information regarding the frequency and time variation of source amplitude and phase, and compares these with existing approaches to coherent processing with incomplete source knowledge. The comparison involves elucidating each processor's approach to source spectral information within a unifying formulation, which provides a conceptual framework for classifying and comparing processors and explaining their relative performance, as quantified in a numerical study. The maximum-likelihood processors represent optimal estimators given the assumption of Gaussian noise, and are based on analytically maximizing the corresponding likelihood function over explicit unknown source spectral parameters. Cases considered include knowledge of the relative variation in source amplitude over time and/or frequency (e.g., a flat spectrum), and tracking the relative phase variation over time, as well as incoherent and coherent processing. Other approaches considered include the conventional (Bartlett) processor, cross-frequency incoherent processor, pair-wise processor, and coherent normalized processor. Processor performance is quantified as the probability of correct localization from Monte Carlo appraisal over a large number of random realizations of noise, source location, and environmental parameters. Processors are compared as a function of signal-to-noise ratio, number of frequencies, and number of sensors. PMID:23039424

  10. A proposal for the holographic correction of incoherent aberrations by tilted reference waves.

    PubMed

    Röder, Falk; Lubk, Axel

    2015-05-01

    The recently derived general transfer theory for off-axis electron holography provides a new approach for reconstructing the electron wave beyond the conventional sideband information limit. Limited ensemble coherence of the electron beam between object and reference area leads to an attenuation of spatial frequencies of the object exit wave in the presence of aberrations of the objective lens. Concerted tilts of the reference wave under the condition of an invariant object exit wave are proposed to diminish the aberration impact on spatial frequencies even beyond the sideband information limit allowing its transfer with maximum possible contrast. In addition to the theoretical considerations outlined in detail, an experimental proof-of-principle is presented. A fully controlled tilt of the reference wave, however, remains as a promising task for the future. The use of a hologram series with varying reference wave tilt is considered for linearly synthesizing an effective aperture for the transfer into the sideband with broader bandwidth compared to conventional off-axis electron holography allowing us to correct the incoherent aberrations in transmission electron microscopy. Furthermore, tilting a reference wave with respect to a plane wave is expected to be an alternative way for measuring the coherent and incoherent aberrations of a transmission electron microscope. The capability of tilting the reference wave is expected to be beneficial for improving the signal-to-noise ratio in dark-field off-axis electron holography as well. PMID:25680104

  11. Wide-Field Common-Path Incoherent Correlation Microscopy with a Perfect Overlapping of Interfering Beams

    NASA Astrophysics Data System (ADS)

    Bouchal, P.; Bouchal, Z.

    2013-01-01

    Incoherent correlation microscopy is recently discovered technique for digital imaging of three-dimensional objects in a quasimonochromatic spatially incoherent light. Its operation is based on wavefront division carried out by a spatial light modulator and capturing correlation recordings of the observed scene. To achieve image reconstruction, at least a partial overlapping of the signal and reference waves created by the spatial light modulator is necessary. In the known experimental configurations, the overlapping of interfering beams is strongly reduced in off-axis areas of the object and the image can be reconstructed only in a very small portion of the field of view provided by the used microscope objective lens. Here, we propose and successfully demonstrate modified experimental system working with two-component relay optics inserted between the microscope objective and the spatial light modulator and providing full overlapping of correlated beams in all areas of the field of view of the objective lens. The benefits and applicability of the proposed system design are clearly demonstrated on the imaging of the USAF resolution targets.

  12. Electron density of Rhizophora spp. wood using Compton scattering technique at 15.77, 17.48 and 22.16 keV XRF energies

    NASA Astrophysics Data System (ADS)

    Shakhreet, B. Z.; Bauk, S.; Shukri, A.

    2015-02-01

    Compton (incoherently) scattered photons which are directly proportional to the electron density of the scatterer, have been employed in characterizing Rhizophora spp. as breast tissue equivalent. X-ray fluorescent scattered incoherently from Rhizophora spp. sample was measured using Si-PIN detector and three XRF energy values 15.77, 17.48 and 22.16 keV. This study is aimed at providing electron density information in support of the introduction of new tissue substitute materials for mammography phantoms.

  13. Incoherent Neutral Pion Photoproduction on {sup 12}C

    SciTech Connect

    Tarbert, C. M.; Watts, D. P.; Branford, D.; Foehl, K.; Glazier, D. I.; Aguar, P.; Ahrens, J.; Arends, H. J.; Heid, E.; Jahn, O.; Krambrich, D.; Martinez, M.; Rost, M.; Thomas, A.; Walcher, Th.; Annand, J. R. M.; Codling, R.; Downie, E. J.; Livingston, K.; MacGregor, I. J. D.

    2008-04-04

    We present the first detailed measurement of incoherent photoproduction of neutral pions to a discrete state of a residual nucleus. The {sup 12}C({gamma},{pi}{sup 0}){sup 12}C{sub 4.4} {sub MeV}* reaction has been studied with the Glasgow photon tagger at MAMI employing a new technique which uses the large solid angle Crystal Ball detector both as a {pi}{sup 0} spectrometer and to detect decay photons from the excited residual nucleus. The technique has potential applications to a broad range of future nuclear measurements with the Crystal Ball and similar detector systems elsewhere. Such data are sensitive to the propagation of the {delta} in the nuclear medium and will give the first information on matter transition form factors from measurements with an electromagnetic probe. The incoherent cross sections are compared to two theoretical predictions including a {delta}-hole model.

  14. Scintillation characterization for multiple incoherent uplink Gaussian beams

    NASA Astrophysics Data System (ADS)

    Wu, Wu-Ming; Ning, Yu; Ma, Yan-Xing; Xi, Fen-Jie; Xu, Xiao-Jun

    2014-09-01

    By means of numerical simulations, we analyze the scintillation characterization for multiple incoherent uplink Gaussian beams under weak fluctuations cases. Because truly independent beams are difficult to create, we present a more general but approximate model for the multiple of beams traveling through partially correlated paths. This model compares with wave-optics simulations and highlights the reduced correlation coefficient as the beam separation is increased. The scintillation index of three and six incoherent uplink Gaussian beams is also induced. The result shows that the scintillation index decreases with the increase of beams amount and beam separation. When the beams amount and strength of atmospheric turbulence are fixed, the reduction of scintillation index is affected by the ratio of beams separation and the Fried length. The corresponding physical mechanisms for the results are discussed.

  15. Spectrum of second-harmonic radiation generated from incoherent light

    SciTech Connect

    Stabinis, A.; Pyragaite, V.; Tamosauskas, G.; Piskarskas, A.

    2011-10-15

    We report on the development of the theory of second-harmonic generation by an incoherent pump with broad angular and frequency spectra. We show that spatial as well as temporal walk-off effects in a nonlinear crystal result in angular dispersion of the second-harmonic radiation. We demonstrate that the acceptance angle in second-harmonic generation by incoherent light is caused by the width of the pump angular spectrum and the resulting angular dispersion of second-harmonic radiation but does not depend on crystal length. In this case the frequency spectrum of second-harmonic radiation is determined by its angular dispersion and the pump angular spectrum. The theory is supported by an experiment in which a LiIO{sub 3} crystal was pumped by a tungsten halogen lamp.

  16. Radiative cooling of bulk silicon by incoherent light pump

    SciTech Connect

    Malyutenko, V. K. Bogatyrenko, V. V.; Malyutenko, O. Yu.

    2013-12-23

    In contrast to radiative cooling by light up conversion caused exclusively by a low-entropy laser pump and employing thermally assisted fluorescence/luminescence as a power out, we demonstrate light down conversion cooling by incoherent pumps, 0.47–0.94 μm light emitting diodes, and employing thermal emission (TE) as a power out. We demonstrate ≤3.5 K bulk cooling of Si at 450 K because overall energy of multiple below bandgap TE photons exceeds the energy of a single above bandgap pump photon. We show that using large entropy TE as power out helps avoid careful tuning of an incoherent pump wavelength and cool indirect-bandgap semiconductors.

  17. Analysis of distortions in the velocity profiles of suspension flows inside a light-scattering medium upon their reconstruction from the optical coherence Doppler tomograph signal

    SciTech Connect

    Bykov, A V; Kirillin, M Yu; Priezzhev, A V

    2005-11-30

    Model signals from one and two plane flows of a particle suspension are obtained for an optical coherence Doppler tomograph (OCDT) by the Monte-Carlo method. The optical properties of particles mimic the properties of non-aggregating erythrocytes. The flows are considered in a stationary scattering medium with optical properties close to those of the skin. It is shown that, as the flow position depth increases, the flow velocity determined from the OCDT signal becomes smaller than the specified velocity and the reconstructed profile extends in the direction of the distant boundary, which is accompanied by the shift of its maximum. In the case of two flows, an increase in the velocity of the near-surface flow leads to the overestimated values of velocity of the reconstructed profile of the second flow. Numerical simulations were performed by using a multiprocessor parallel-architecture computer. (laser applications in medicine)

  18. Incoherent Control of the Retinal Isomerization in Rhodopsin

    NASA Astrophysics Data System (ADS)

    Lucas, Felix; Hornberger, Klaus

    2014-08-01

    We propose to control the retinal photoisomerization yield through the backaction dynamics imparted by a nonselective optical measurement of the molecular electronic state. This incoherent effect is easier to implement than comparable coherent pulse shaping techniques, and is also robust to environmental noise. A numerical simulation of the quantum dynamics shows that the isomerization yield of this important biomolecule can be substantially increased above the natural limit.

  19. Evidence of Strong Proton Shape Fluctuations from Incoherent Diffraction

    NASA Astrophysics Data System (ADS)

    Mäntysaari, Heikki; Schenke, Björn

    2016-07-01

    We show within the saturation framework that measurements of exclusive vector meson production at high energy provide evidence for strong geometric fluctuations of the proton. In comparison, the effect of saturation scale and color charge fluctuations is weak. This knowledge will allow detailed future measurements of the incoherent cross section to tightly constrain the fluctuating geometry of the proton as a function of the parton momentum fraction x .

  20. Evidence of Strong Proton Shape Fluctuations from Incoherent Diffraction.

    PubMed

    Mäntysaari, Heikki; Schenke, Björn

    2016-07-29

    We show within the saturation framework that measurements of exclusive vector meson production at high energy provide evidence for strong geometric fluctuations of the proton. In comparison, the effect of saturation scale and color charge fluctuations is weak. This knowledge will allow detailed future measurements of the incoherent cross section to tightly constrain the fluctuating geometry of the proton as a function of the parton momentum fraction x. PMID:27517767

  1. Incoherent GaAlAs/GaAs semiconductor laser arrays

    NASA Technical Reports Server (NTRS)

    Hwang, C. J.; Chen, J. S.; Fu, R. J.; Wu, D. H.; Wang, C. S.

    1988-01-01

    The fabrication of an incoherent laser array is reported. The main features of the arrays are low threshold index-guided laser elements, single-lobe far-field pattern, low astigmatism, low current operation, dense packing, and total electrical and optical isolation. With further development, this device should have applications in multihead optical-disk reading and writing, multifiber optical communications, and line-of-sight communications.

  2. Holographic fluorescence microscopy with incoherent digital holographic adaptive optics.

    PubMed

    Jang, Changwon; Kim, Jonghyun; Clark, David C; Lee, Seungjae; Lee, Byoungho; Kim, Myung K

    2015-01-01

    Introduction of adaptive optics technology into astronomy and ophthalmology has made great contributions in these fields, allowing one to recover images blurred by atmospheric turbulence or aberrations of the eye. Similar adaptive optics improvement in microscopic imaging is also of interest to researchers using various techniques. Current technology of adaptive optics typically contains three key elements: a wavefront sensor, wavefront corrector, and controller. These hardware elements tend to be bulky, expensive, and limited in resolution, involving, for example, lenslet arrays for sensing or multiactuator deformable mirrors for correcting. We have previously introduced an alternate approach based on unique capabilities of digital holography, namely direct access to the phase profile of an optical field and the ability to numerically manipulate the phase profile. We have also demonstrated that direct access and compensation of the phase profile are possible not only with conventional coherent digital holography, but also with a new type of digital holography using incoherent light: selfinterference incoherent digital holography (SIDH). The SIDH generates a complex—i.e., amplitude plus phase—hologram from one or several interferograms acquired with incoherent light, such as LEDs, lamps, sunlight, or fluorescence. The complex point spread function can be measured using guide star illumination and it allows deterministic deconvolution of the full-field image. We present experimental demonstration of aberration compensation in holographic fluorescence microscopy using SIDH. Adaptive optics by SIDH provides new tools for improved cellular fluorescence microscopy through intact tissue layers or other types of aberrant media. PMID:26146767

  3. Holographic fluorescence microscopy with incoherent digital holographic adaptive optics

    NASA Astrophysics Data System (ADS)

    Jang, Changwon; Kim, Jonghyun; Clark, David C.; Lee, Seungjae; Lee, Byoungho; Kim, Myung K.

    2015-11-01

    Introduction of adaptive optics technology into astronomy and ophthalmology has made great contributions in these fields, allowing one to recover images blurred by atmospheric turbulence or aberrations of the eye. Similar adaptive optics improvement in microscopic imaging is also of interest to researchers using various techniques. Current technology of adaptive optics typically contains three key elements: a wavefront sensor, wavefront corrector, and controller. These hardware elements tend to be bulky, expensive, and limited in resolution, involving, for example, lenslet arrays for sensing or multiactuator deformable mirrors for correcting. We have previously introduced an alternate approach based on unique capabilities of digital holography, namely direct access to the phase profile of an optical field and the ability to numerically manipulate the phase profile. We have also demonstrated that direct access and compensation of the phase profile are possible not only with conventional coherent digital holography, but also with a new type of digital holography using incoherent light: self­interference incoherent digital holography (SIDH). The SIDH generates a complex-i.e., amplitude plus phase-hologram from one or several interferograms acquired with incoherent light, such as LEDs, lamps, sunlight, or fluorescence. The complex point spread function can be measured using guide star illumination and it allows deterministic deconvolution of the full-field image. We present experimental demonstration of aberration compensation in holographic fluorescence microscopy using SIDH. Adaptive optics by SIDH provides new tools for improved cellular fluorescence microscopy through intact tissue layers or other types of aberrant media.

  4. Robust Mapping of Incoherent Fiber-Optic Bundles

    NASA Technical Reports Server (NTRS)

    Roberts, Harry E.; Deason, Brent E.; DePlachett, Charles P.; Pilgrim, Robert A.; Sanford, Harold S.

    2007-01-01

    A method and apparatus for mapping between the positions of fibers at opposite ends of incoherent fiber-optic bundles have been invented to enable the use of such bundles to transmit images in visible or infrared light. The method is robust in the sense that it provides useful mapping even for a bundle that contains thousands of narrow, irregularly packed fibers, some of which may be defective. In a coherent fiber-optic bundle, the input and output ends of each fiber lie at identical positions in the input and output planes; therefore, the bundle can be used to transmit images without further modification. Unfortunately, the fabrication of coherent fiber-optic bundles is too labor-intensive and expensive for many applications. An incoherent fiber-optic bundle can be fabricated more easily and at lower cost, but it produces a scrambled image because the position of the end of each fiber in the input plane is generally different from the end of the same fiber in the output plane. However, the image transmitted by an incoherent fiber-optic bundle can be unscrambled (or, from a different perspective, decoded) by digital processing of the output image if the mapping between the input and output fiber-end positions is known. Thus, the present invention enables the use of relatively inexpensive fiber-optic bundles to transmit images.

  5. Effect of reflected and refracted signals on coherent underwater acoustic communication: results from the Kauai experiment (KauaiEx 2003).

    PubMed

    Rouseff, Daniel; Badiey, Mohsen; Song, Aijun

    2009-11-01

    The performance of a communications equalizer is quantified in terms of the number of acoustic paths that are treated as usable signal. The analysis uses acoustical and oceanographic data collected off the Hawaiian Island of Kauai. Communication signals were measured on an eight-element vertical array at two different ranges, 1 and 2 km, and processed using an equalizer based on passive time-reversal signal processing. By estimating the Rayleigh parameter, it is shown that all paths reflected by the sea surface at both ranges undergo incoherent scattering. It is demonstrated that some of these incoherently scattered paths are still useful for coherent communications. At range of 1 km, optimal communications performance is achieved when six acoustic paths are retained and all paths with more than one reflection off the sea surface are rejected. Consistent with a model that ignores loss from near-surface bubbles, the performance improves by approximately 1.8 dB when increasing the number of retained paths from four to six. The four-path results though are more stable and require less frequent channel estimation. At range of 2 km, ray refraction is observed and communications performance is optimal when some paths with two sea-surface reflections are retained. PMID:19894819

  6. Coherent and incoherent internal tides in the southern South China Sea

    NASA Astrophysics Data System (ADS)

    Liu, Qian; Xie, Xiaohui; Shang, Xiaodong; Chen, Guiying

    2016-03-01

    Coherent and incoherent internal tides (CITs and ICITs) in the southern South China Sea were investigated from two sets of 18-month mooring current records. The CITs were mainly composed of diurnal Q 1, O 1, P 1 and K 1 and semidiurnal M 2. The observed diurnal internal tides (ITs) were more coherent than the semidiurnal constituents. Coherent diurnal variance accounted for approximately 58% of the diurnal motion, whereas semidiurnal tides contained a much smaller fraction (35%) of coherent motion. The ICITs mainly consisted of motion at non-tidal harmonic frequencies around the tidal frequency, and showed clear intermittency. The modal decomposition of CITs and ICITs showed that CITs were dominated by mode- 1, whereas mode-1 and higher modes in ICITs signals showed comparable amplitudes. CITs and ICITs accounted for approximately 64% and 36% of the total kinetic energy of internal tides, respectively.

  7. All-incoherent wavelength conversion in highly nonlinear fiber using four-wave mixing

    NASA Astrophysics Data System (ADS)

    Kharraz, Osayd M.; Ahmad, Harith; Forsyth, David I.; Dernaika, Mohamad; Zulkifli, Mohd Zamani B.; Ismail, Mohd Faizal B.; Mohammad, Abu Bakar B.

    2014-09-01

    This work describes efficient and polarization insensitive, all-incoherent four-wave mixing wavelength conversion achieved within a short length of highly nonlinear fiber medium, created by using both spectrally sliced pump and probe channels from a single-amplified spontaneous emission source coupled to two narrowband Fiber Bragg grating (FBG) filters. This simple and cost-effective scheme is capable of generating a down-converted probe channel across a 17.2-nm wavelength span, while still maintaining a high conversion efficiency of around -22 dB and an optical-signal-to-noise ratio of ˜21 dB. The effects of pump power, FBG detuning, and polarization are also reported.

  8. Acoustic Phase Measurements from Volume Scatter in the Ocean.

    NASA Astrophysics Data System (ADS)

    Huston, Robert Delmar

    A primary goal of this thesis has been to demonstrate that stable, useful measurements of the orientation of the acoustic signal vector as a function of range and time can be obtained from ocean backscatter, and that this orientation, or acoustic phase, can be related to the local sound speed distribution. Consistent and useful measurement of absolute phase depends upon the positions of individual scatterers, which are normally random and sparse relative to the acoustic wavelength. This difficulty has been overcome by coherent super-position of echoes from successive transmissions, such that the effective density of acoustic targets progressively increases as the summation proceeds. The theoretical basis of this type of coherent processing has been developed and examined in the limiting case, in which it approximates a scatterer continuum for which an analytic expression has been found. The theory provides fundamental insights to the behaviour of both the amplitude and phase of volume scatter. As the ratio of coherent to incoherent signal increases with successive superposition of the echoes (coherent processing), the phase statistics evolve from a uniform to a nearly Gaussian distribution. Once the phase signal is bounded to within +/-45 ^circ, the basic requirement for a coherent 'volume mirror' has been met and reliable interferometric estimates are possible. The experimental work used a bistatic configuration with a multi-beam projector and narrow beam hydrophone operating at 215 kHz. The results confirm the theoretical concepts and demonstrate that within the quite limited range of environmental conditions that were studied, the coherently processed acoustic signals are consistent with independent measurements of the evolving sound speed profile. The main contribution of this thesis has been to lay a firm theoretical and experimental foundation for the use of volume backscatter in acoustic interferometer devices. Based on these results, the potential for new

  9. Evidence for a dibaryon signal in the measurement of elastic. pi. /sup +/-d/sub pol/ scattering

    SciTech Connect

    Bolger, J.; Boschitz, E.; Proebstle, G.; Smith, G.R.; Mango, S.; Vogler, F.; Johnson, R.R.; Arvieux, J.

    1981-01-19

    The vector analyzing power (iT/sub 11/) in elastic ..pi..-d/sub pol/ scattering has been measured for several angles at T/sub ..pi../=142 and 256 MeV. The results are compared with calculations reported in the literature. At the lower energies, Faddeev calculations agree fairly well with the data. At the higher energies, the experimental results differ markedly from any conventional calculation, but agree surprisingly well with predictions in which effects of dibaryon resonances are explicitly included.

  10. Picosecond Photobiology: Watching a Signaling Protein Function in Real Time via Time-Resolved Small- and Wide-Angle X-ray Scattering.

    PubMed

    Cho, Hyun Sun; Schotte, Friedrich; Dashdorj, Naranbaatar; Kyndt, John; Henning, Robert; Anfinrud, Philip A

    2016-07-20

    The capacity to respond to environmental changes is crucial to an organism's survival. Halorhodospira halophila is a photosynthetic bacterium that swims away from blue light, presumably in an effort to evade photons energetic enough to be genetically harmful. The protein responsible for this response is believed to be photoactive yellow protein (PYP), whose chromophore photoisomerizes from trans to cis in the presence of blue light. We investigated the complete PYP photocycle by acquiring time-resolved small and wide-angle X-ray scattering patterns (SAXS/WAXS) over 10 decades of time spanning from 100 ps to 1 s. Using a sequential model, global analysis of the time-dependent scattering differences recovered four intermediates (pR0/pR1, pR2, pB0, pB1), the first three of which can be assigned to prior time-resolved crystal structures. The 1.8 ms pB0 to pB1 transition produces the PYP signaling state, whose radius of gyration (Rg = 16.6 Å) is significantly larger than that for the ground state (Rg = 14.7 Å) and is therefore inaccessible to time-resolved protein crystallography. The shape of the signaling state, reconstructed using GASBOR, is highly anisotropic and entails significant elongation of the long axis of the protein. This structural change is consistent with unfolding of the 25 residue N-terminal domain, which exposes the β-scaffold of this sensory protein to a potential binding partner. This mechanistically detailed description of the complete PYP photocycle, made possible by time-resolved crystal and solution studies, provides a framework for understanding signal transduction in proteins and for assessing and validating theoretical/computational approaches in protein biophysics. PMID:27305463

  11. Physical mechanisms associated with long-range propagation of the signals from ionospheric heating experiments

    NASA Astrophysics Data System (ADS)

    Zabotin, Nikolay A.; Zavorotny, Valery U.; Rietveld, Michael T.

    2014-10-01

    Long-range propagation of heater-produced signals has been studied in experiments with the European Incoherent Scatter Scientific Association ionospheric heating facility and with several globally distributed receiving sites by Zalizovski et al. [2009]. Two distinctive components were present in the signals' spectra, and these can be attributed to two modes of propagation of the signals. One of the components is narrowband and stable; it obviously can be associated with the multihop ionospheric propagation of HF waves radiated by the side lobes of the heater's antenna array. Prominent features of the second component are its wider spectral band (up to few tens of hertz) and strong variations in the average Doppler frequency shift and in the power, which in many cases were synchronous at the different receiving sites. These effects are most likely produced by the ionospheric scattering and dynamics within the heater's main beam. The tricky part is to explain how a portion of the HF energy contained in the relatively narrow main beam of the heater is redirected toward the remote receiving locations. We suggest a robust mechanism explaining the long-range propagation of the wideband component of the heater-generated signal based on the theory of scattering from rough surfaces. This mechanism preserves all the observed properties of the remote signals. We show that mountain relief in the vicinity of the heater plays the role of the rough surface causing almost isotropic scattering of the heater's main beam after it is reflected by the ionosphere. Multiple scattering by natural and artificial field-aligned irregularities in the ionospheric layer may be related to the ground-scattered remote signals through its role in spatial redistribution of the heater's radiation.

  12. Dense Matter Characterization by X-ray Thomson Scattering

    SciTech Connect

    Landen, O L; Glenzer, S H; Edwards, M J; Lee, R W; Collins, G W; Cauble, R C; Hsing, W W; Hammel, B A

    2000-12-29

    We discuss the extension of the powerful technique of Thomson scattering to the x-ray regime for providing an independent measure of plasma parameters for dense plasmas. By spectrally-resolving the scattering, the coherent (Rayleigh) unshifted scattering component can be separated from the incoherent Thomson component, which is both Compton and Doppler shifted. The free electron density and temperature can then be inferred from the spectral shape of the high frequency Thomson scattering component. In addition, as the plasma temperature is decreased, the electron velocity distribution as measured by incoherent Thomson scattering will make a transition from the traditional Gaussian Boltzmann distribution to a density-dependent parabolic Fermi distribution to. We also present a discussion for a proof-of-principle experiment appropriate for a high energy laser facility.

  13. Fast and Broadband Signal Integrity Analysis of Multiple Vias in Heterogeneous 3D IC and Die-Level Packaging by Using Generalized Foldy-Lax Scattering Method

    NASA Astrophysics Data System (ADS)

    Chang, Xin

    This dissertation proposal is concerned with the use of fast and broadband full-wave electromagnetic methods for modeling high speed interconnects (e.g, vertical vias and horizontal traces) and passive components (e.g, decoupling capacitors) for structures of PCB and packages, in 3D IC, Die-level packaging and SIW based devices, to effectively modeling the designs signal integrity (SI) and power integrity (PI) aspects. The main contributions finished in this thesis is to create a novel methodology, which hybridizes the Foldy-Lax multiple scattering equations based fast full wave method, method of moment (MoM) based 1D technology, modes decoupling based geometry decomposition and cavity modes expansions, to model and simulate the electromagnetic scattering effects for the irregular power/ground planes, multiple vias and traces, for fast and accurate analysis of link level simulation on multilayer electronic structures. For the modeling details, the interior massively-coupled multiple vias problem is modeled most-analytically by using the Foldy-Lax multiple scattering equations. The dyadic Green's functions of the magnetic field are expressed in terms of waveguide modes in the vertical direction and vector cylindrical wave expansions or cavity modes expansions in the horizontal direction, combined with 2D MoM realized by 1D technology. For the incident field of the case of vias in the arbitrarily shaped antipad in finite large cavity/waveguide, the exciting and scattering field coefficients are calculated based on the transformation which converts surface integration of magnetic surface currents in antipad into 1D line integration of surface charges on the vias and on the ground plane. Geometry decomposition method is applied to model and integrate both the vertical and horizontal interconnects/traces in arbitrarily shaped power/ground planes. Moreover, a new form of multiple scattering equations is derived for solving coupling effects among mixed metallic

  14. Holographic fluorescence microscopy with incoherent digital holographic adaptive optics

    NASA Astrophysics Data System (ADS)

    Jang, Changwon; Kim, Jonghyun; Clark, David C.; Lee, Byoungho; Kim, Myung K.

    2015-03-01

    Introduction of adaptive optics technology into astronomy and ophthalmology has made great contributions in these fields, allowing one to recover images blurred by atmospheric turbulence or aberrations of the eye. Similar adaptive optics improvement in microscopic imaging is also of interest to researchers using various techniques. Current technology of adaptive optics typically contains three key elements: wavefront sensor, wavefront corrector and controller. These hardware elements tend to be bulky, expensive, and limited in resolution, involving, e.g., lenslet arrays for sensing or multi-acuator deformable mirrors for correcting. We have previously introduced an alternate approach to adaptive optics based on unique capabilities of digital holography, namely direct access to the phase profile of an optical field and the ability to numerically manipulate the phase profile. We have also demonstrated that direct access and compensation of the phase profile is possible not only with the conventional coherent type of digital holography, but also with a new type of digital holography using incoherent light: self-interference incoherent digital holography (SIDH). The SIDH generates complex - i.e. amplitude plus phase - hologram from one or several interferograms acquired with incoherent light, such as LEDs, lamps, sunlight, or fluorescence. The complex point spread function can be measured using a guide star illumination and it allows deterministic deconvolution of the full-field image. We present experimental demonstration of aberration compensation in holographic fluorescence microscopy using SIDH. The adaptive optics by SIDH provides new tools for improved cellular fluorescence microscopy through intact tissue layers or other types of aberrant media.

  15. Linear light-scattering of gold nanostars for versatile biosensing of nucleic acids and proteins using exonuclease III as biocatalyst to signal amplification.

    PubMed

    Bi, Sai; Jia, Xiaoqiang; Ye, Jiayan; Dong, Ying

    2015-09-15

    Gold nanomaterials promise a wide range of potential applications in chemical and biological sensing, imaging, and catalysis. In this paper, we demonstrate a facile method for room-temperature synthesis of gold nanostars (AuNSs) with a size of ~50 nm via seeded growth. Significantly, the AuNSs are found to have high light-scattering properties, which are successfully used as labels for sensitive and selective detection of nucleic acids and proteins by using exonuclease III (Exo III) as a biocatalyst. For DNA detection, the binding of targets to the functionalized AuNS probes leads to the Exo III-stimulated cascade recycling amplification. As a result, a large amount of AuNSs are released from magnetic nanoparticles (MNPs) into solution, providing a greatly enhanced light-scattering signal for amplified sensing process. Moreover, a binding-induced DNA three-way junction (DNA TWJ) is introduced to thrombin detection, in which the binding of two aptamers to thrombin triggers assembly of the DNA motifs and initiates the subsequent DNA strand displacement reaction (SDR) and Exo III-assisted cascade recycling amplification. The detection limits of 89 fM and 5.6 pM are achieved for DNA and thrombin, respectively, which are comparable to or even exceed that of the reported isothermal amplification methods. It is noteworthy that based on the DNA TWJ strategy the sequences are independent on target proteins. Additionally, the employment of MNPs in the assays can not only simplify the operations but also improve the detection sensitivity. Therefore, the proposed amplified light-scattering assay with high sensitivity and selectivity, acceptable accuracy, and satisfactory versatility of analytes provides various applications in bioanalysis. PMID:25950939

  16. Normal state incoherent pseudogap in FeSe superconductor

    NASA Astrophysics Data System (ADS)

    Craco, Luis; Laad, Mukul S.

    2016-05-01

    The normal state of Iron chalcogenide superconductors show a range of unconventional features. Bad-metallic resistivity and proximity to insulating state manifest themselves in spectral and transport responses. In particular, obervation of low-energy pseudogap feature in the normal state raises the issue of the nature of processes underpinning its emergence as well as its relation to unconventional superconductivity. Here, using the LDA+DMFT method, we show how correlation-induced orbital-selective pseudogap-like physics underpin these incoherent features in stoichimetric and electron-doped FeSe superconductor. We discuss the pseudogap regime microscopically, along with implications for the superconductive instability.

  17. Real-time incoherent-to-coherent optical converter

    NASA Technical Reports Server (NTRS)

    Vohl, P.; Nisenson, P.; Oliver, D. S.

    1973-01-01

    Description of a real-time incoherent-to-coherent optical converter designed for application in image processing systems. The converter utilizes the photoconductivity effect of the compound Bi(12)SiO(20) for spatial modulation of electrical polarization in the compound. An optically absorbed write-in image is stored as an image polarization pattern in the device. Readout is effectuated electrooptically by using phase retardation in a polarized coherent light beam during the passage through the crystal. The operating mode required for achieving continuous image conversion with a high-speed recyclability is discussed. The performance characteristics of the converter are given and the fabrication technology is described.

  18. Two-step phase-shifting fluorescence incoherent holographic microscopy

    PubMed Central

    Qin, Wan; Yang, Xiaoqi; Li, Yingying; Peng, Xiang; Yao, Hai; Qu, Xinghua; Gao, Bruce Z.

    2014-01-01

    Abstract. Fluorescence holographic microscope (FINCHSCOPE) is a motionless fluorescence holographic imaging technique based on Fresnel incoherent correlation holography (FINCH) that shows promise in reconstructing three-dimensional fluorescence images of biological specimens with three holograms. We report a developing two-step phase-shifting method that reduces the required number of holograms from three to two. Using this method, we resolved microscopic fluorescent beads that were three-dimensionally distributed at different depths with two interferograms captured by a CCD camera. The method enables the FINCHSCOPE to work in conjunction with the frame-straddling technique and significantly enhance imaging speed. PMID:24972355

  19. Scattering Models and Basic Experiments in the Microwave Regime

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  20. The Applicability of Incoherent Array Processing to IMS Seismic Array Stations

    NASA Astrophysics Data System (ADS)

    Gibbons, S. J.

    2012-04-01

    The seismic arrays of the International Monitoring System for the CTBT differ greatly in size and geometry, with apertures ranging from below 1 km to over 60 km. Large and medium aperture arrays with large inter-site spacings complicate the detection and estimation of high frequency phases since signals are often incoherent between sensors. Many such phases, typically from events at regional distances, remain undetected since pipeline algorithms often consider only frequencies low enough to allow coherent array processing. High frequency phases that are detected are frequently attributed qualitatively incorrect backazimuth and slowness estimates and are consequently not associated with the correct event hypotheses. This can lead to missed events both due to a lack of contributing phase detections and by corruption of event hypotheses by spurious detections. Continuous spectral estimation can be used for phase detection and parameter estimation on the largest aperture arrays, with phase arrivals identified as local maxima on beams of transformed spectrograms. The estimation procedure in effect measures group velocity rather than phase velocity and the ability to estimate backazimuth and slowness requires that the spatial extent of the array is large enough to resolve time-delays between envelopes with a period of approximately 4 or 5 seconds. The NOA, AKASG, YKA, WRA, and KURK arrays have apertures in excess of 20 km and spectrogram beamforming on these stations provides high quality slowness estimates for regional phases without additional post-processing. Seven arrays with aperture between 10 and 20 km (MJAR, ESDC, ILAR, KSRS, CMAR, ASAR, and EKA) can provide robust parameter estimates subject to a smoothing of the resulting slowness grids, most effectively achieved by convolving the measured slowness grids with the array response function for a 4 or 5 second period signal. The MJAR array in Japan recorded high SNR Pn signals for both the 2006 and 2009 North Korea

  1. Large reverse saturable absorption under weak continuous incoherent light

    NASA Astrophysics Data System (ADS)

    Hirata, Shuzo; Totani, Kenro; Yamashita, Takashi; Adachi, Chihaya; Vacha, Martin

    2014-10-01

    In materials showing reverse saturable absorption (RSA), the optical absorbance increases as the power of the light incident on them increases. To date, RSA has only been observed when very intense light sources, such as short-pulse lasers, are used. Here, we show that hydroxyl steroidal matrices embedding properly designed aromatic molecules as acceptors and transition-metal complexes as donors exhibit high RSA on exposure to weak incoherent light at room temperature and in air. Accumulation by photosensitization of long-lived room-temperature triplet excitons in acceptors with a large triplet-triplet absorption coefficient allows a nonlinear increase in absorbance also under low-power irradiation conditions. As a consequence, continuous exposure to weak light significantly decreases the transmittance of thin films fabricated with these compounds. These optical limiting properties may be used to protect eyes and light sensors from exposure to intense radiation generated by incoherent sources and for other light-absorption applications that have not been realized with conventional RSA materials.

  2. Visual resolution in incoherent and coherent light: preliminary investigation

    NASA Astrophysics Data System (ADS)

    Sarnowska-Habrat, Katarzyna; Dubik, Boguslawa; Zajac, Marek

    2001-05-01

    In ophthalmology and optometry a number of measures are used for describing quality of human vision such as resolution, visual acuity, contrast sensitivity function, etc. In this paper we will concentrate on the vision quality understood as a resolution of periodic object being a set of equidistant parallel lines of given spacing and direction. The measurement procedure is based on presenting the test to the investigated person and determining the highest spatial frequency he/she can still resolve. In this paper we describe a number of experiments in which we use test tables illuminated with light both coherent and incoherent of different spectral characteristics. Our experiments suggest that while considering incoherent polychromatic illumination the resolution in blue light is substantially worse than in white light. In coherent illumination speckling effect causes worsening of resolution. While using laser light it is easy to generate a sinusoidal interference pattern which can serve as test object. In the paper we compare the results of resolution measurements with test tables and interference fringes.

  3. Coherence and incoherence collective behavior in financial market

    NASA Astrophysics Data System (ADS)

    Zhao, Shangmei; Xie, Qiuchao; Lu, Qing; Jiang, Xin; Chen, Wei

    2015-10-01

    Financial markets have been extensively studied as highly complex evolving systems. In this paper, we quantify financial price fluctuations through a coupled dynamical system composed of phase oscillators. We find that a Financial Coherence and Incoherence (FCI) coexistence collective behavior emerges as the system evolves into the stable state, in which the stocks split into two groups: one is represented by coherent, phase-locked oscillators, the other is composed of incoherent, drifting oscillators. It is demonstrated that the size of the coherent stock groups fluctuates during the economic periods according to real-world financial instabilities or shocks. Further, we introduce the coherent characteristic matrix to characterize the involvement dynamics of stocks in the coherent groups. Clustering results on the matrix provides a novel manifestation of the correlations among stocks in the economic periods. Our analysis for components of the groups is consistent with the Global Industry Classification Standard (GICS) classification and can also figure out features for newly developed industries. These results can provide potentially implications on characterizing the inner dynamical structure of financial markets and making optimal investment into tragedies.

  4. On the inversion of the scattering polarization and the Hanle effect signals in the hydrogen Lyα line

    SciTech Connect

    Ishikawa, R.; Asensio Ramos, A.; Manso Sainz, R.; Trujillo Bueno, J.; Belluzzi, L.; Štěpán, J.; Goto, M.; Tsuneta, S.

    2014-06-01

    Magnetic field measurements in the upper chromosphere and above, where the gas-to-magnetic pressure ratio β is lower than unity, are essential for understanding the thermal structure and dynamical activity of the solar atmosphere. Recent developments in the theory and numerical modeling of polarization in spectral lines have suggested that information on the magnetic field of the chromosphere-corona transition region could be obtained by measuring the linear polarization of the solar disk radiation at the core of the hydrogen Lyα line at 121.6 nm, which is produced by scattering processes and the Hanle effect. The Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) sounding rocket experiment aims to measure the intensity (Stokes I) and the linear polarization profiles (Q/I and U/I) of the hydrogen Lyα line. In this paper, we clarify the information that the Hanle effect can provide by applying a Stokes inversion technique based on a database search. The database contains all theoretical Q/I and U/I profiles calculated in a one-dimensional semi-empirical model of the solar atmosphere for all possible values of the strength, inclination, and azimuth of the magnetic field vector, though this atmospheric region is highly inhomogeneous and dynamic. We focus on understanding the sensitivity of the inversion results to the noise and spectral resolution of the synthetic observations as well as the ambiguities and limitation inherent to the Hanle effect when only the hydrogen Lyα is used. We conclude that spectropolarimetric observations with CLASP can indeed be a suitable diagnostic tool for probing the magnetism of the transition region, especially when complemented with information on the magnetic field azimuth that can be obtained from other instruments.

  5. Relating surface-enhanced Raman scattering signals of cells to gold nanoparticle aggregation as determined by LA-ICP-MS micromapping.

    PubMed

    Büchner, Tina; Drescher, Daniela; Traub, Heike; Schrade, Petra; Bachmann, Sebastian; Jakubowski, Norbert; Kneipp, Janina

    2014-11-01

    The cellular response to nanoparticle exposure is essential in various contexts, especially in nanotoxicity and nanomedicine. Here, 14-nm gold nanoparticles in 3T3 fibroblast cells are investigated in a series of pulse-chase experiments with a 30-min incubation pulse and chase times ranging from 15 min to 48 h. The gold nanoparticles and their aggregates are quantified inside the cellular ultrastructure by laser ablation inductively coupled plasma mass spectrometry micromapping and evaluated regarding the surface-enhanced Raman scattering (SERS) signals. In this way, both information about their localization at the micrometre scale and their molecular nanoenvironment, respectively, is obtained and can be related. Thus, the nanoparticle pathway from endocytotic uptake, intracellular processing, to cell division can be followed. It is shown that the ability of the intracellular nanoparticles and their accumulations and aggregates to support high SERS signals is neither directly related to nanoparticle amount nor to high local nanoparticle densities. The SERS data indicate that aggregate geometry and interparticle distances in the cell must change in the course of endosomal maturation and play a critical role for a specific gold nanoparticle type in order to act as efficient SERS nanoprobe. This finding is supported by TEM images, showing only a minor portion of aggregates that present small interparticle spacing. The SERS spectra obtained after different chase times show a changing composition and/or structure of the biomolecule corona of the gold nanoparticles as a consequence of endosomal processing. PMID:25120183

  6. Incoherent Bi off-centering in Bi₂Ti₂O₆O' and Bi₂Ru₂O₆O': Insulator versus metal

    DOE PAGESBeta

    Shoemaker, Daniel P.; Seshadri, Ram; Tachibana, Makoto; Hector, Andrew L.

    2011-08-24

    In the cubic, stoichiometric oxide compounds Bi₂Ti₂O₆O' (also written as Bi₂Ti₂O₇) and Bi₂Ru₂O₆O' (also written as Bi₂Ru₂O₇) Bi³⁺ ions on the pyrochlore A site display a propensity to off-center. Unlike Bi₂Ti₂O₆O', Bi₂Ru₂O₆O' is a metal, so it is of interest to ask whether conduction electrons and/or involvement of Bi 6s states at the Fermi energy influence Bi³⁺ displacements. The Bi³⁺ off-centering in Bi₂Ti₂O₆O' has previously been revealed to be incoherent from detailed reverse Monte Carlo analysis of total neutron scattering. Similar analysis of Bi₂Ru₂O₆O' reveals incoherent off-centering as well, but of smaller magnitude and with distinctly different orientational preference. Analysismore » of the distributions of metal to oxygen distances presented suggests that Bi in both compounds is entirely Bi³⁺. Disorder in Bi₂Ti₂O₆O' has the effect of stabilizing valence while simultaneously satisfying the steric constraint imposed by the presence of the lone pair of electrons. In Bi₂Ru₂O₆O', off-centering is not required to satisfy valence and seems to be driven by the lone pair. Decreased volume of the lone pair may be a result of partial screening by conduction electrons.« less

  7. Incoherent Bi off-centering in Bi₂Ti₂O₆O' and Bi₂Ru₂O₆O': Insulator versus metal

    SciTech Connect

    Shoemaker, Daniel P.; Seshadri, Ram; Tachibana, Makoto; Hector, Andrew L.

    2011-08-24

    In the cubic, stoichiometric oxide compounds Bi₂Ti₂O₆O' (also written as Bi₂Ti₂O₇) and Bi₂Ru₂O₆O' (also written as Bi₂Ru₂O₇) Bi³⁺ ions on the pyrochlore A site display a propensity to off-center. Unlike Bi₂Ti₂O₆O', Bi₂Ru₂O₆O' is a metal, so it is of interest to ask whether conduction electrons and/or involvement of Bi 6s states at the Fermi energy influence Bi³⁺ displacements. The Bi³⁺ off-centering in Bi₂Ti₂O₆O' has previously been revealed to be incoherent from detailed reverse Monte Carlo analysis of total neutron scattering. Similar analysis of Bi₂Ru₂O₆O' reveals incoherent off-centering as well, but of smaller magnitude and with distinctly different orientational preference. Analysis of the distributions of metal to oxygen distances presented suggests that Bi in both compounds is entirely Bi³⁺. Disorder in Bi₂Ti₂O₆O' has the effect of stabilizing valence while simultaneously satisfying the steric constraint imposed by the presence of the lone pair of electrons. In Bi₂Ru₂O₆O', off-centering is not required to satisfy valence and seems to be driven by the lone pair. Decreased volume of the lone pair may be a result of partial screening by conduction electrons.

  8. Remote sensing of the magnetospheric plasma by means of whistler mode signals

    SciTech Connect

    Carpenter, D.L.

    1988-08-01

    The type of data obtained by the whistler mode probing of the magnetosphere are discussed together with various whistler probing methods and the uses of whistler data. Consideration is given to the intercomparison of whistler results with data from satellites and incoherent scatter radar; the role of whistlers in various magnetosphere/ionosphere probing experiments; the results of whistler studies of geomagnetic-field-aligned propagation 'ducts' and their excitation by ground sources; the direction finding using a tracking receiver/direction finder; the use of whistlers to measure hot plasma effects; and the phase measurements of whistler mode signals, with special consideration given to the application of a new phase measurement method to Siple signals. 76 references.

  9. A high-power incoherent light source for ultra-precise optical trapping

    NASA Astrophysics Data System (ADS)

    Schittko, Robert; Mazurenko, Anton; Greiner, Markus

    2016-05-01

    The ability to engineer arbitrary optical potentials using spatial light modulation has opened up exciting possibilities in ultracold quantum gas experiments. Yet, despite the high trap quality currently achievable, interference-induced distortions caused by scattering along the optical path continue to impede more sensitive measurements. We present a design of a high-power, spatially and temporally incoherent light source that dramatically reduces the impact of such distortions. The device is based on an array of non-lasing semiconductor emitters mounted on a single chip, whose optical output is coupled into a multi-mode fiber. The fiber is used to populate a large number of transverse modes, each of which experiences a different optical path length. This effect, combined with the small coherence length of the light, dramatically reduces the spatial coherence of the output. In addition to theoretical calculations showcasing the feasibility of this approach, we present various experimental measurements verifying the low degree of spatial coherence exhibited by the source, including a detailed analysis of the speckle contrast at the fiber end.

  10. Cross-Beam Energy Transfer Driven by Incoherent Laser Beams with Colors

    NASA Astrophysics Data System (ADS)

    Maximov, A. V.; Myatt, J. F.; Short, R. W.; Igumenshchev, I. V.; Seka, W.

    2014-10-01

    Recently, the effect of cross-beam energy transfer (CBET) has become one of the most important challenges for the effective coupling of laser energy to the target in inertial confinement fusion (ICF) (see, e.g., Ref. 1). CBET is based on the process of stimulated Brillouin scattering (SBS) driven by multiple crossing laser beams in the regime of moderate SBS amplification gains, and is consequently sensitive to the frequency characteristics of the laser beams driving the ICF targets: smoothing by spectral dispersion or frequency shifts between the beams (colors). Different from reduced ray-type models used in large-scale hydrodynamic simulations with CBET, we have developed a laser-plasma interaction (LPI)-type model of CBET that is capable of capturing the effects of laser speckles and the non-paraxial propagation of multiple laser beams. The LPI-type CBET model has been applied to the interaction between incoherent laser beams with different colors and the differences from the ray-type CBET model have been shown. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  11. Ultrafast coherent lattice and incoherent carrier dynamics in bismuth: time-domain results

    NASA Astrophysics Data System (ADS)

    Chekalin, S. V.; Melnikov, A. A.; Misochko, O. V.

    2014-09-01

    The investigations of transient electronic processes and their influence on coherent lattice dynamics in Bi by different femtosecond spectroscopy methods are reviewed. The results of broadband optical, x-ray, and ultrashort electron beam probes in the study of coherent phonons and incoherent carrier dynamics are compared. Some coherent phonon peculiarities arising at high excitation are described. The difference between phonons of different symmetries and various generation mechanisms are discussed, highlighting their assignment to the decay of particular excited electronic states of bismuth. Data analysis revealed significant wavevector dependence of electron-hole and electron-phonon coupling strength along the Г-T direction of the Brillouin zone. Comparison of the coherent amplitude as a function of the pump photon wavelength from 400 to 2500 nm for two different in symmetry Eg and A1g phonon modes with respective spontaneous resonance Raman profiles revealed that their generation mechanisms are quite distinct. Displacive excitation, which is the main mechanism for the generation of coherent A1g phonons, cannot be reduced to the Raman scattering responsible for the generation of lower symmetry coherent lattice modes.

  12. Two-dimensional electronic spectroscopy using incoherent light: theoretical analysis.

    PubMed

    Turner, Daniel B; Howey, Dylan J; Sutor, Erika J; Hendrickson, Rebecca A; Gealy, M W; Ulness, Darin J

    2013-07-25

    Electronic energy transfer in photosynthesis occurs over a range of time scales and under a variety of intermolecular coupling conditions. Recent work has shown that electronic coupling between chromophores can lead to coherent oscillations in two-dimensional electronic spectroscopy measurements of pigment-protein complexes measured with femtosecond laser pulses. A persistent issue in the field is to reconcile the results of measurements performed using femtosecond laser pulses with physiological illumination conditions. Noisy-light spectroscopy can begin to address this question. In this work we present the theoretical analysis of incoherent two-dimensional electronic spectroscopy, I((4)) 2D ES. Simulations reveal diagonal peaks, cross peaks, and coherent oscillations similar to those observed in femtosecond two-dimensional electronic spectroscopy experiments. The results also expose fundamental differences between the femtosecond-pulse and noisy-light techniques; the differences lead to new challenges and new opportunities. PMID:23176195

  13. Regimes of strong light-matter coupling under incoherent excitation

    SciTech Connect

    Valle, E. del; Laussy, F. P.

    2011-10-15

    We study a two-level system (atom, superconducting qubit, or quantum dot) strongly coupled to a single photonic mode of a cavity, in the presence of incoherent pumping and including detuning and dephasing. This system displays a striking quantum-to-classical transition. On the grounds of several approximations that reproduce to various degrees exact results obtained numerically, we separate five regimes of operations, that we term ''linear,''''quantum,''''lasing,''''quenching,'' and ''thermal.'' In the fully quantized picture, the lasing regime arises as a condensation of dressed states and manifests itself as a Mollow triplet structure in the direct emitter photoluminescence spectrum, which embeds fundamental features of the full-field quantization description of light-matter interaction.

  14. Fast full resolution saliency detection based on incoherent imaging system

    NASA Astrophysics Data System (ADS)

    Lin, Guang; Zhao, Jufeng; Feng, Huajun; Xu, Zhihai; Li, Qi; Chen, Yueting

    2016-05-01

    Image saliency detection is widely applied in many tasks in the field of the computer vision. In this paper, we combine the saliency detection with the Fourier optics to achieve acceleration of saliency detection algorithm. An actual optical saliency detection system is constructed within the framework of incoherent imaging system. Additionally, the application of our system to implement the bottom-up rapid pre-saliency process of primate visual saliency is discussed with dual-resolution camera. A set of experiments over our system are conducted and discussed. We also demonstrate the comparisons between our method and pure computer methods. The results show our system can produce full resolution saliency maps faster and more effective.

  15. Lineshape analysis of coherent multidimensional optical spectroscopy using incoherent light

    SciTech Connect

    Ulness, Darin J.; Turner, Daniel B.

    2015-06-07

    Coherent two-dimensional electronic spectroscopy using incoherent (noisy) light, I{sup (4)} 2D ES, holds intriguing challenges and opportunities. One challenge is to determine how I{sup (4)} 2D ES compares to femtosecond 2D ES. Here, we merge the sophisticated energy-gap Hamiltonian formalism that is often used to model femtosecond 2D ES with the factorized time-correlation formalism that is needed to describe I{sup (4)} 2D ES. The analysis reveals that in certain cases the energy-gap Hamiltonian is insufficient to model the spectroscopic technique correctly. The results using a modified energy-gap Hamiltonian show that I{sup (4)} 2D ES can reveal detailed lineshape information, but, contrary to prior reports, does not reveal dynamics during the waiting time.

  16. Fast full resolution saliency detection based on incoherent imaging system

    NASA Astrophysics Data System (ADS)

    Lin, Guang; Zhao, Jufeng; Feng, Huajun; Xu, Zhihai; Li, Qi; Chen, Yueting

    2016-08-01

    Image saliency detection is widely applied in many tasks in the field of the computer vision. In this paper, we combine the saliency detection with the Fourier optics to achieve acceleration of saliency detection algorithm. An actual optical saliency detection system is constructed within the framework of incoherent imaging system. Additionally, the application of our system to implement the bottom-up rapid pre-saliency process of primate visual saliency is discussed with dual-resolution camera. A set of experiments over our system are conducted and discussed. We also demonstrate the comparisons between our method and pure computer methods. The results show our system can produce full resolution saliency maps faster and more effective.

  17. Incoherent systems and coverings in finite dimensional Banach spaces

    SciTech Connect

    Temlyakov, V N

    2014-05-31

    We discuss the construction of coverings of the unit ball of a finite dimensional Banach space. There is a well-known technique based on comparing volumes which gives upper and lower bounds on covering numbers. However, this technique does not provide a method for constructing good coverings. Here we study incoherent systems and apply them to construct good coverings. We use the following strategy. First, we build a good covering using balls with a radius close to one. Second, we iterate this construction to obtain a good covering for any radius. We shall concentrate mainly on the first step of this strategy. Bibliography: 14 titles.

  18. Anti-Stokes Fluorescent Probe with Incoherent Excitation

    PubMed Central

    Li, Yang; Zhou, Shifeng; Dong, Guoping; Peng, Mingying; Wondraczek, Lothar; Qiu, Jianrong

    2014-01-01

    Although inorganic anti-Stokes fluorescent probes have long been developed, the operational mode of today's most advanced examples still involves the harsh requirement of coherent laser excitation, which often yields unexpected light disturbance or even photon-induced deterioration during optical imaging. Here, we demonstrate an efficient anti-Stokes fluorescent probe with incoherent excitation. We show that the probe can be operated under light-emitting diode excitation and provides tunable anti-Stokes energy shift and decay kinetics, which allow for rapid and deep tissue imaging over a very large area with negligible photodestruction. Charging of the probe can be achieved by either X-rays or ultraviolet-visible light irradiation, which enables multiplexed detection and function integration with standard X-ray medical imaging devices. PMID:24518662

  19. An efficient central DOA tracking algorithm for multiple incoherently distributed sources

    NASA Astrophysics Data System (ADS)

    Hassen, Sonia Ben; Samet, Abdelaziz

    2015-12-01

    In this paper, we develop a new tracking method for the direction of arrival (DOA) parameters assuming multiple incoherently distributed (ID) sources. The new approach is based on a simple covariance fitting optimization technique exploiting the central and noncentral moments of the source angular power densities to estimate the central DOAs. The current estimates are treated as measurements provided to the Kalman filter that model the dynamic property of directional changes for the moving sources. Then, the covariance-fitting-based algorithm and the Kalman filtering theory are combined to formulate an adaptive tracking algorithm. Our algorithm is compared to the fast approximated power iteration-total least square-estimation of signal parameters via rotational invariance technique (FAPI-TLS-ESPRIT) algorithm using the TLS-ESPRIT method and the subspace updating via FAPI-algorithm. It will be shown that the proposed algorithm offers an excellent DOA tracking performance and outperforms the FAPI-TLS-ESPRIT method especially at low signal-to-noise ratio (SNR) values. Moreover, the performances of the two methods increase as the SNR values increase. This increase is more prominent with the FAPI-TLS-ESPRIT method. However, their performances degrade when the number of sources increases. It will be also proved that our method depends on the form of the angular distribution function when tracking the central DOAs. Finally, it will be shown that the more the sources are spaced, the more the proposed method can exactly track the DOAs.

  20. Anomalous vibrational modes in acetanilide: a F.D.S. incoherent inelastic neutron scattering study

    NASA Astrophysics Data System (ADS)

    Barthes, Mariette; Eckert, Juergen; Johnson, Susanna W.; Moret, Jacques; Swanson, Basil I.; Unkefer, Clifford J.

    The origin of the anomalous infra-red and Raman modes in acetanilide (C6H5NHCOCH3, or ACN)(1) , remains a subject of considerable controversy. One family of theoretical models involves Davydov-like solitons (2) nonlinear vibrational coupling (3), or "polaronic" localized modes (4)(5). An alternative interpretation of the extra-bands in terms of a Fermi resonance was proposed (6) and recently the existence of slightly non-degenerate hydrogen atom configurations (7) in the H-bond was suggested as an explanation for the anomalies.

  1. High-Latitude Incoherent-Scatter Radar Measurements for the ISTP Program

    NASA Technical Reports Server (NTRS)

    Kelly, John D.

    1999-01-01

    Over the course of this contract, the ISTP mission became a reality and proved to be one of NASA's success stories. SRI and the NSF-sponsored Sondrestrom radar contributed significantly to the success. We provided dedicated radar experiment time with operation modes specifically designed to complement the ISTP spacecraft. Data collected during coronal mass ejection events indicated that at times significant energy is fed from the ionosphere to the magnetosphere. A model of global conductance is emerging from combined POLAR and Sondrestrom data sets. We initiated a study to investigate the behavior of the global energy budget during the evolution of magnetospheric storms and substorms using a number of ground-based and satellite data sets.

  2. Dynamic processes in the ionosphere during magnetic storms from the Kharkov incoherent scatter radar observations

    NASA Astrophysics Data System (ADS)

    Chernogor, L. F.; Grigorenko, Ye. I.; Lysenko, V. N.; Taran, V. I.

    2007-10-01

    [1] Results of studying the ionosphere behavior during several magnetic storms of various intensities are presented. The features of pronounced negative ionospheric disturbances accompanying the severe magnetic storms on 25 September 1998 and 29-30 May 2003 (Kp ≍ 8) are considered. Among them there are a decrease in the electron density by a factor of 3-4, uplifting of the ionospheric F2 layer by 100-160 km, increase in the temperature of the charged and neutral atmospheric components, and infringement of plasma transfer processes and thermal balance in the ionosphere-plasmasphere system. In the morning of 25 September 1998, an unusual increase in the upward plasma drift velocity was registered. On 29-30 May 2003 during the storm main phase, a depletion of the relative density of hydrogen ions by more than an order of magnitude was observed that could manifest an emptying of the magnetic flux tube over Kharkov. These effects are explained in terms of thermospheric disturbances, Joule heating, particle precipitation, penetration of magnetospheric electric fields to midlatitudes, the shift of the main ionospheric trough and related structures toward the radar latitude, etc. The ionospheric storm on 20-21 March 2003 had two phases. Its strong negative phase proceeded against a background of a minor geomagnetic disturbance (Kp ≍ 5). The destabilizing impact of the electric field pulse and traveling atmospheric disturbance generated by magnetospheric substorms could be the cause of the change in the storm phase that occurred in the sunset period.

  3. D region meteoric smoke and neutral temperature retrieval using the poker flat incoherent scatter radar

    NASA Astrophysics Data System (ADS)

    Fentzke, J. T.; Hsu, V.; Brum, C. G. M.; Strelnikova, I.; Rapp, M.; Nicolls, M.

    2012-11-01

    This brief note describes the first measurement of the microphysical properties and variability of meteoric smoke particles (MSPs) at high latitude using the Poker Flat ISR (65.1°N, 147.5°W). We present a novel technique for determining height resolved daytime D region neutral temperatures, which takes into account the presence of charged dust. We discuss the temporal/spatial variability and the relation to meteoric input observed and MSP microphysical properties in the polar mesopause region. The derived nanometer sized MSPs are consistent with size profiles derived previously using radar/rocket techniques and we note that our results imply a lack of heavy cluster ions below 85 km during the observing period. This provides a template for potential use at many other radar sites for the determination of microphysical properties of MSPs and day-time neutral temperature in the D region that show good general agreement with model and satellite temperature data during the observing period.

  4. Coherent anti-Stokes Raman scattering microscope with a high-signal-to-noise ratio, high stability, and high-speed imaging for live cell observation

    NASA Astrophysics Data System (ADS)

    Hayashi, Shinichi; Takimoto, Shinichi; Hashimoto, Takeshi

    2007-02-01

    Coherent anti-Stokes Raman scattering (CARS) microscopy, which can produce images of specific molecules without staining, has attracted the attention of researchers, as it matches the need for molecular imaging and pathway analysis of live cells. In particular, there have been an increasing number of CARS experimental results regarding lipids in live cells, which cannot be fluorescently tagged while keeping the cells alive. One of the important applications of lipid research is for the metabolic syndrome. Since the metabolic syndrome is said to be related to the lipids in lipocytes, blood, arterial vessels, and so on, the CARS technique is expected to find application in this field. However, CARS microscopy requires a pair of picosecond laser pulses, which overlap both temporally and spatially. This makes the optical adjustments of a CARS microscope challenging. The authors developed a CARS unit that includes optics for easy and stable adjustment of the overlap of these laser pulses. Adding the CARS unit to a laser scanning microscope provides CARS images of a high signal-to-noise ratio, with an acquisition rate as high as 2 microseconds per pixel. Thus, images of fast-moving lipid droplets in Hela cells were obtained.

  5. Evidence of Spin Resonance Signal in Oxygen Free Superconducting CaFe0.88Co0.12AsF: An Inelastic Neutron Scattering Study

    NASA Astrophysics Data System (ADS)

    Price, Stephen; Su, Yixi; Xiao, Yinguo; Adroja, Devashibhai T.; Guidi, Tatiana; Mittal, Ranjan; Nandi, Shibabrata; Matsuishi, Satoru; Hosono, Hideo; Brückel, Thomas

    2013-10-01

    The spin excitation spectrum of optimally doped superconducting CaFe0.88Co0.12AsF (Tc˜ 22 K) was studied by means of time-of-flight (ToF) inelastic neutron scattering experiments on a powder sample for temperatures above and below Tc and energies up to 15 meV. In the superconducting state, the spin resonance signal is observed as an enhancement of spectral weight of particle hole excitations of approximately 1.5 times relative to normal state excitations. The resonance energy ER˜ 7 meV scales to Tc via 3.7 kBTc which is in reasonable agreement to the scaling relation reported for other Fe-based compositions. For energies below 5 meV the spectrum of spin flip particle hole excitations in the superconducting state exhibits a strong reduction in spectral weight, indicating the opening of the spin gap. Nonetheless, a complete suppression of magnetic response cannot be observed. In contrast, the normal state spin excitations are not gapped and strongly two dimensional spin fluctuations persist up to temperatures at least as high as 150 K.

  6. Small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Cousin, Fabrice

    2015-10-01

    Small Angle Neutron Scattering (SANS) is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ˜ 1 nm up to ˜ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ˜ 1 cm3. This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area…) through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer), form factor analysis (I(q→0), Guinier regime, intermediate regime, Porod regime, polydisperse system), structure factor analysis (2nd Virial coefficient, integral equations, characterization of aggregates), and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast). It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of spectrometer

  7. Measurement of the Mutual Coherence Function of an Incoherent Infrared Field with a Gold Nano-wire Dipole Antenna Array

    NASA Astrophysics Data System (ADS)

    Middlebrook, Christopher; Roggemann, Michael; Boreman, Glenn; Subotic, Nikola; Cooper, Kyle; Buller, William; Yang, Weidong; Alda, Javier

    2008-02-01

    The first direct measurement of the mutual coherence function of a spatially incoherent infrared beam was performed at 10.6 μm using a pair of infrared dipole nano-wire antennas that were connected to a common bolometer in the center of the pair by short lengths of coplanar strip transmission line. A spatially incoherent source was constructed by dithering a BaF2 diffuser near the focus of a CO2 laser beam. The distance from the diffuser to the nano-wire antenna pair was held constant while the distance from the focus of the laser beam to the diffuser was varied to control the effective diameter of the source. The measured bolometer signal was proportional to the magnitude of the mutual coherence function at the plane of the antennas. The experimental results were found to match the predicted performance closely. If this technology can be extended to large arrays, a form of synthetic aperture optical imaging based on the Van Cittert-Zernike theorem is possible, similar to that performed at microwave frequencies now by astronomers. This has the potential to greatly increase the angular resolution attainable with optical instruments.

  8. Temporal dynamics of incoherent waves in noninstantaneous response nonlinear Kerr media.

    PubMed

    Kibler, B; Michel, C; Garnier, J; Picozzi, A

    2012-07-01

    We consider the temporal evolution of an incoherent optical wave that propagates in a noninstantaneous response nonlinear medium, such as single mode optical fibers. In contrast with the expected Raman-like spectral redshift due to a delayed nonlinear response, we show that a highly noninstantaneous response leads to a genuine modulational instability of the incoherent optical wave. We derive a Vlasov-like kinetic equation that provides a detailed description of this process of incoherent modulational instability in the temporal domain. PMID:22743425

  9. Enhanced super resolution using Fresnel incoherent correlation holography with structured illumination.

    PubMed

    Kashter, Yuval; Vijayakumar, A; Miyamoto, Yoko; Rosen, Joseph

    2016-04-01

    The structured illumination (SI) technique has already been well established as a resolution enhancer in many studies and well demonstrated in many optical imaging systems during the past decade. The ability to use the SI in incoherent imaging systems was also introduced, especially in fluorescence microscopy. In this Letter, we propose and demonstrate a new approach to combine the SI technique with the recently innovated motionless incoherent holographic system, called Fresnel incoherent correlation holography (FINCH), in order to enhance the resolution beyond the limits achieved in regular imaging with SI. The results obtained by use of SI-FINCH were compared against regular imaging, regular FINCH and SI-imaging. PMID:27192286

  10. Transform-limited-pulse representation of excitation with natural incoherent light.

    PubMed

    Chenu, Aurélia; Brumer, Paul

    2016-01-28

    The excitation of molecular systems by natural incoherent light relevant, for example, to photosynthetic light-harvesting is examined. We show that the result of linear excitation with natural incoherent light can be obtained using incident light described in terms of transform limited pulses, as opposed to conventional classical representations with explicit random character. The derived expressions allow for computations to be done directly for any thermal light spectrum using a simple wave function formalism and provide a route to the experimental determination of natural incoherent excitation using pulsed laser techniques. Pulses associated with solar and cosmic microwave background radiation are provided as examples. PMID:26827198

  11. Transform-limited-pulse representation of excitation with natural incoherent light

    NASA Astrophysics Data System (ADS)

    Chenu, Aurélia; Brumer, Paul

    2016-01-01

    The excitation of molecular systems by natural incoherent light relevant, for example, to photosynthetic light-harvesting is examined. We show that the result of linear excitation with natural incoherent light can be obtained using incident light described in terms of transform limited pulses, as opposed to conventional classical representations with explicit random character. The derived expressions allow for computations to be done directly for any thermal light spectrum using a simple wave function formalism and provide a route to the experimental determination of natural incoherent excitation using pulsed laser techniques. Pulses associated with solar and cosmic microwave background radiation are provided as examples.

  12. Advances in white-light optical signal processing

    NASA Technical Reports Server (NTRS)

    Yu, F. T. S.

    1984-01-01

    A technique that permits signal processing operations which can be carried out by white light source is described. The method performs signal processing that obeys the concept of coherent light rather than incoherent optics. Since the white light source contains all the color wavelengths of the visible light, the technique is very suitable for color signal processing.

  13. Long working-distance, incoherent light interference microscope

    SciTech Connect

    Sinclair, Michael B.; de Boer, Maarten Pieter; Corwin, Alex David

    2005-06-01

    We describe the design and operation of a long-working-distance, incoherent light interference microscope that has been developed to address the growing demand for new microsystem characterization tools. The design of the new microscope is similar to that of a Linnik interference microscope and thus preserves the full working distance of the long-working-distance objectives utilized. However, in contrast to a traditional Linnik microscope, the new microscope does not rely on the use of matched objectives in the sample and the reference arms of the interferometer. An adjustable optical configuration has been devised that allows the total optical path length, wavefront curvature, and dispersion of the reference arm to be matched to the sample arm of the interferometer. The reference arm configuration can be adjusted to provide matching for 5x, 10x, and 20x long-working-distance objectives in the sample arm. In addition to retaining the full working distance of the sample arm objectives, the new design allows interference images to be acquired in situations in which intervening windows are necessary, such as occur with packaged microsystems, microfluidic devices, and cryogenic, vacuum, or environmental chamber studies of microsystem performance. The interference microscope is compatible with phase-shifting interferometry, vertical scanning interferometry, and stroboscopic measurement of dynamic processes.

  14. Probe and object function reconstruction in incoherent stem imaging

    SciTech Connect

    Nellist, P.D.; Pennycook, S.J.

    1996-09-01

    Using the phase-object approximation it is shown how an annular dark- field (ADF) detector in a scanning transmission electron microscope (STEM) leads to an image which can be described by an incoherent model. The point spread function is found to be simply the illuminating probe intensity. An important consequence of this is that there is no phase problem in the imaging process, which allows various image processing methods to be applied directly to the image intensity data. Using an image of a GaAs<110>, the probe intensity profile is reconstructed, confirming the existence of a 1.3 {Angstrom} probe in a 300kV STEM. It is shown that simply deconvolving this reconstructed probe from the image data does not improve its interpretability because the dominant effects of the imaging process arise simply from the restricted resolution of the microscope. However, use of the reconstructed probe in a maximum entropy reconstruction is demonstrated, which allows information beyond the resolution limit to be restored and does allow improved image interpretation.

  15. Strategical incoherence regulates cooperation in social dilemmas on multiplex networks

    NASA Astrophysics Data System (ADS)

    Matamalas, Joan T.; Poncela-Casasnovas, Julia; Gómez, Sergio; Arenas, Alex

    2015-04-01

    Cooperation is a very common, yet not fully-understood phenomenon in natural and human systems. The introduction of a network within the population is known to affect the outcome of cooperative dynamics, allowing for the survival of cooperation in adverse scenarios. Recently, the introduction of multiplex networks has yet again modified the expectations for the outcome of the Prisoner's Dilemma game, compared to the monoplex case. However, much remains unstudied regarding other social dilemmas on multiplex, as well as the unexplored microscopic underpinnings of it. In this paper, we systematically study the evolution of cooperation in all four games in the T - S plane on multiplex. More importantly, we find some remarkable and previously unknown features in the microscopic organization of the strategies, that are responsible for the important differences between cooperative dynamics in monoplex and multiplex. Specifically, we find that in the stationary state, there are individuals that play the same strategy in all layers (coherent), and others that don't (incoherent). This second group of players is responsible for the surprising fact of a non full-cooperation in the Harmony Game on multiplex, never observed before, as well as a higher-than-expected cooperation rates in some regions of the other three social dilemmas.

  16. Long-working-distance incoherent-light interference microscope

    NASA Astrophysics Data System (ADS)

    Sinclair, Michael B.; de Boer, Maarten P.; Corwin, Alex D.

    2005-12-01

    We describe the design and operation of a long-working-distance, incoherent light interference microscope that has been developed to address the growing demand for new microsystem characterization tools. The design of the new microscope is similar to that of a Linnik interference microscope and thus preserves the full working distance of the long-working-distance objectives utilized. However, in contrast to a traditional Linnik microscope, the new microscope does not rely on the use of matched objectives in the sample and the reference arms of the interferometer. An adjustable optical configuration has been devised that allows the total optical path length, wavefront curvature, and dispersion of the reference arm to be matched to the sample arm of the interferometer. The reference arm configuration can be adjusted to provide matching for 5×, 10×, and 20× long-working-distance objectives in the sample arm. In addition to retaining the full working distance of the sample arm objectives, the new design allows interference images to be acquired in situations in which intervening windows are necessary, such as occur with packaged microsystems, microfluidic devices, and cryogenic, vacuum, or environmental chamber studies of microsystem performance. The interference microscope is compatible with phase-shifting interferometry, vertical scanning interferometry, and stroboscopic measurement of dynamic processes.

  17. Mobile incoherent Doppler lidar using fiber-based lidar receivers

    NASA Astrophysics Data System (ADS)

    Hu, Dongdong; Sun, Dongsong; Shu, Zhifeng; Shangguan, Mingjia; Gao, Yuanyuan; Dou, Xiankang

    2014-09-01

    A mobile incoherent Doppler lidar was developed at the University of Science and Technology of China. The lidar consists of three subsystems. All subsystems are designed based on the well-proven double-edge technique, operate at 354.7 nm, and use Fabry-Perot etalons as frequency discriminators. The whole system is designed for wind measurement from 15- to 60-km height. In order to make the lidar receiver more compact and stable and to reduce interference between optical paths inside the receiver box, fiber splitters are introduced into the lidar receivers as a substitute for normally used discrete components. According to the stability of the splitter, the wind error dominated by the splitting ratio would be <0.49 m/s. To reduce luminance heterogeneity's influence on the splitter performance, an integrating sphere is used in the system. Multiple measurements of transmission curves have a maximum mean squared error of 9.674E-5. A typical result of wind profile is also given to help demonstrate the reliability of the lidar and the fiber-based receiver.

  18. Kondo hole route to incoherence in the periodic Anderson model

    NASA Astrophysics Data System (ADS)

    Kumar, Pramod; Vidhyadhiraja, N. S.

    2013-03-01

    The interplay of disorder and interactions in strongly correlated electronic systems is a subject of perennial interest. In this work, we have investigated the effect of Kondo-hole type disorder on the dynamics and transport properties of heavy fermion systems. We employ the periodic Anderson model within the framework of coherent potential approximation and dynamical mean field theory. The crossover from lattice coherent behaviour to an incoherent single-impurity behaviour is reflected in all aspects: a highly frequency (ω)-dependent hybridization becomes almost flat, the coherence peak in resistivity (per impurity) gives way to a Hammann form that saturates at low temperature (T); the Drude peak and the mid-infrared peak in the optical conductivity vanish almost completely. The zero temperature resistivity can be captured in a closed form expression, and we show how the Nordheim's rule gets strongly modified in these systems. The thermopower exhibits a characteristic peak, which changes sign with increasing disorder, and its location is shown to correspond to the low energy scale of the system (ωL). In fact, the thermopower appears to be much more sensitive to disorder variations than the resistivity. A comparison to experiments yields quantitative agreement. JNCASR and CSIR

  19. Incoherent imaging with the soft X-ray microscope

    PubMed

    Burge; Yuan; Morrison; Charalambous; Browne; An

    2000-05-01

    The imaging characteristics for X-ray wavelengths in the "water window" under incoherent imaging conditions (large detector aperture) are examined for the King's College London scanning transmission X-ray microscope with zone-plate objective installed at the Daresbury (UK) synchrotron. The principal consideration was to express image theory, incorporating wave aberrations and apodised zone plates, and to apply the theory to experimental data. Comparisons are made, showing reasonable agreement, for a range of defocus values and two wavelengths. Due to problems in fabrication it was necessary to determine the effective, or operational, zone-plate parameters (radius of outermost active zone rN, width of outermost active zone drN); this was accomplished by through-focus series. Calculated point spread functions were used to deblurr images, in through-focus series of two-dimensional scanned X-ray images of specimen holes and test grating patterns. Significant contrast enhancement is achieved after deconvolution with a best point-to-point resolution of about 35 nm. PMID:10805394

  20. Depth classification based solely on incoherent sonar information

    NASA Astrophysics Data System (ADS)

    Miklovic, Donald W.

    2005-09-01

    Most work on sonar contact depth estimation has been based on deterministic, coherent propagation modeling of the sound channel, e.g., matched-field processing. This has met with limited success due to the inability to precisely predict the sound-pressure field in realistic scenarios. This paper addresses the problem of using probabilistic, incoherent information from the sonar itself for depth classification with active sonar, without having to depend on precise and accurate propagation models and ancillary environmental measurements. In particular, the problem of deciding whether or not a given contact is on the bottom based solely on the sonar data is looked at, i.e., without resorting to the use of any additional environmental measurements or predictive models. To do this, the in situ local bottom reverberation is used to calibrate the channel. Probability theory is explored to provide a theoretical basis for the development of a single-hypothesis decision metric to best exploit this information. The methods are tested on a combination of broadband sonar data and detailed ocean simulations. The particular metric proposed for this problem seems to be important for achieving good performance, and may be of some interest in its own right for other types of single-hypothesis decision problems.

  1. In situ nanoindentation study on plasticity and work hardening in aluminium with incoherent twin boundaries

    NASA Astrophysics Data System (ADS)

    Bufford, D.; Liu, Y.; Wang, J.; Wang, H.; Zhang, X.

    2014-09-01

    Nanotwinned metals have been the focus of intense research recently, as twin boundaries may greatly enhance mechanical strength, while maintaining good ductility, electrical conductivity and thermal stability. Most prior studies have focused on low stacking-fault energy nanotwinned metals with coherent twin boundaries. In contrast, the plasticity of twinned high stacking-fault energy metals, such as aluminium with incoherent twin boundaries, has not been investigated. Here we report high work hardening capacity and plasticity in highly twinned aluminium containing abundant Σ3{112} incoherent twin boundaries based on in situ nanoindentation studies in a transmission electron microscope and corresponding molecular dynamics simulations. The simulations also reveal drastic differences in deformation mechanisms between nanotwinned copper and twinned aluminium ascribed to stacking-fault energy controlled dislocation-incoherent twin boundary interactions. This study provides new insight into incoherent twin boundary-dominated plasticity in high stacking-fault energy twinned metals.

  2. Incoherent holography by a Michelson type interferometer with a lens for a radial shear

    NASA Astrophysics Data System (ADS)

    Watanabe, Kaho; Nomura, Takanori

    2016-06-01

    The modified Michelson type interferometer with lenses for a radial shear to record incoherent holograms is proposed. It enables us to record a hologram by self-interference without coherent illumination such as a laser. The interferometer has two wave plates which can realize phase-shifting incoherent holography. The feature can avoid a very large bias term and the twin image, which are the inherent problem of incoherent holography by self-interference. The advantages of the proposed method using lenses and wave plates are easy adjustment of the zone plate and simplification of the optical system. A preliminary experiment using an LED as an incoherent object was performed to confirm the four step phase-shifting by wave plates.

  3. Nonlinearity compensation and complex-to-phase conversion of complex incoherent digital holograms for optical reconstruction.

    PubMed

    Liu, Jung-Ping; Wang, Sheng-Yen; Tsang, P W M; Poon, Ting-Chung

    2016-06-27

    Incoherent digital holography (IDH) can be realized by optical scanning holography or self-interference incoherent holography. Although IDH can exhibit high quality reconstruction due to its inherently speckle-free property, direct display of an incoherent hologram is a challenge because of its amplitude nonlinearity and the demand of complex modulation. In this paper we propose to compensate the amplitude nonlinearity at the object plane, and use bidirectional error-diffusion method to convert the complex-type incoherent Fresnel hologram to a phase-only Fresnel hologram for display. A spatial light modulator is used to reconstruct the phase-only hologram optically to demonstrate the validity of our proposed method. PMID:27410610

  4. Unified kinetic formulation of incoherent waves propagating in nonlinear media with noninstantaneous response

    SciTech Connect

    Garnier, Josselin; Picozzi, Antonio

    2010-03-15

    This article presents a unified kinetic formulation of partially coherent nonlinear optical waves propagating in a noninstantaneous response Kerr medium. We derive a kinetic equation that combines the weak Langmuir turbulence kinetic equation and a Vlasov-like equation within a general framework: It describes the evolution of the spectrum of a random field that exhibits a quasistationary statistics in the presence of a noninstantaneous nonlinear response. The kinetic equation sheds new light on the dynamics of partially coherent nonlinear waves and allows for a qualitative interpretation of the interplay between the noninstantaneous nonlinearity and the nonstationary statistics of the incoherent field. It is shown that the incoherent modulational instability of a random nonlinear wave can be suppressed by the noninstantaneous nonlinear response. Moreover, incoherent modulational instability can prevent the generation of spectral incoherent solitons.

  5. Coherent Random Fiber Laser Based on Nanoparticles Scattering in the Extremely Weakly Scattering Regime

    NASA Astrophysics Data System (ADS)

    Hu, Zhijia; Zhang, Qun; Miao, Bo; Fu, Qiang; Zou, Gang; Chen, Yang; Luo, Yi; Zhang, Douguo; Wang, Pei; Ming, Hai; Zhang, Qijin

    2012-12-01

    We demonstrate the realization of a coherent random fiber laser (RFL) in the extremely weakly scattering regime, which contains a dispersive solution of polyhedral oligomeric silsesquioxanes nanoparticles (NPs) and laser dye pyrromethene 597 in carbon disulfide that was injected into a hollow optical fiber. Multiple scattering of polyhedral oligomeric silsesquioxanes NPs greatly enhanced by the waveguide confinement effect was experimentally verified to account for coherent lasing observed in our RFL system. This Letter extends the NPs-based RFLs from the incoherent regime to the coherent regime.

  6. A new SERS: scattering enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Bixler, Joel N.; Yakovlev, Vladislav V.

    2014-03-01

    Raman spectroscopy is a powerful technique that can be used to obtain detailed chemical information about a system without the need for chemical markers. It has been widely used for a variety of applications such as cancer diagnosis and material characterization. However, Raman scattering is a highly inefficient process, where only one in 1011 scattered photons carry the needed information. Several methods have been developed to enhance this inherently weak effect, including surface enhanced Raman scattering and coherent anti-Stokes Raman scattering. These techniques suffer from drawbacks limiting their commercial use, such as the need for spatial localization of target molecules to a `hot spot', or the need for complex laser systems. Here, we present a simple instrument to enhance spontaneous Raman scattering using elastic light scattering. Elastic scattering is used to substantially increase the interaction volume. Provided that the scattering medium exhibits very low absorption in the spectral range of interest, a large enhancement factor can be attained in a simple and inexpensive setting. In our experiments, we demonstrate an enhancement of 107 in Raman signal intensity. The proposed novel device is equally applicable for analyzing solids, liquids, and gases.

  7. Quantifying incoherence in speech: An automated methodology and novel application to schizophrenia

    PubMed Central

    Elvevåg, Brita; Foltz, Peter W.; Weinberger, Daniel R.; Goldberg, Terry E.

    2007-01-01

    Incoherent discourse, with a disjointed flow of ideas, is a cardinal symptom in several psychiatric and neurological conditions. However, measuring incoherence has often been complex and subjective. We sought to validate an objective, intrinsically reliable, computational approach to quantifying speech incoherence. Patients with schizophrenia and healthy control volunteers were administered a variety of language tasks. The speech generated was transcribed and the coherence computed using Latent Semantic Analysis (LSA). The discourse was also analyzed with a standard clinical measure of thought disorder. In word association and generation tasks LSA derived coherence scores were sensitive to differences between patients and controls, and correlated with clinical measures of thought disorder. In speech samples LSA could be used to localize where in sentence production incoherence occurs, predict levels of incoherence as well as whether discourse “belonged” to a patient or control. In conclusion, LSA can be used to assay disordered language production so as to both complement human clinical ratings as well as experimentally parse this incoherence in a theory-driven manner. PMID:17433866

  8. Near-threshold incoherent ϕ photoproduction on the deuteron: Searching for traces of a resonance

    NASA Astrophysics Data System (ADS)

    Kiswandhi, Alvin; Yang, Shin Nan; Dong, Yu Bing

    2016-07-01

    We study the near-threshold incoherent ϕ photoproduction on the deuteron based on a model of γ N →ϕ N , consisting of Pomeron, (π ,η ) exchanges, and a JP=3 /2- resonance, which describes the low-energy γ p →ϕ p LEPS data well, including the peak in the forward differential cross section. The calculation is done up to double rescatterings, with the spin dependence of the elementary γ N →ϕ N amplitude retained throughout the calculation. The Fermi motion and final-state interactions (FSIs) are all properly treated as prescribed by realistic nucleon-nucleon interaction. The couplings of the resonance to γ n and ϕ n channels are estimated with the help of a constituent quark model. The main features of the LEPS and CLAS data are described reasonably well except for some quantitative discrepancies at very low energies and low-momentum-transfer regions. It is found that contributions of Fermi motion, p n FSI, and resonance are all indispensable in bridging the differences between the single-scattering results and the data. The off-shell rescattering is found to be important because it cancels out a large portion of the on-shell contribution. The discrepancies at low-momentum-transfer regions might be related to the binning size of the data. No peak is found to be associated with the weak resonance because it gets smeared out by the Fermi motion and FSI with the deuterium target. The problem at very-low-energy regions hints at the possible contributions from other mechanisms and should be investigated in depth with the use of recent high-statistics γ p →ϕ p data from CLAS.

  9. An optical tomography PSF almost insensitive to aberrations: the benefit of a spatial incoherent illumination (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Xiao, Peng; Fink, Mathias; Boccara, A. Claude

    2016-03-01

    An aberrated imaging system PSF is broadened; this broadening is responsible of the blurring of the images. A lot of effort has been carried out to correct the effects of aberrations on OCT images for eye examination or biological samples. We have worked on quantifying the effect of geometrical aberrations on Full-Field OCT images and found that there is mostly no loss of resolution but a decrease of the signal level. This is obviously why we use these signals as metric to correct the wavefront distortion. Moreover we found that this absence of blurring, which is due to the fact that we record the dot product of a diffraction limited reference signal and the distorted sample signal, is specific to the use of an incoherent illumination and did not show up with OCT approaches that use spatially coherent sources. More precisely the loss in signal is roughly proportional to the square root of the Strehl ratio: for example, a Strehl ratio of 1/9, which is considered to give a low quality image, would only be 1/3 in Full-Field OCT while keeping the sharpness of the image. Using both an USAF resolution target and a transmissive SLM we have demonstrated this unique feature of sharpness conservation. It was also confirmed by using biological samples. We think that we can thus restrict the aberration corrections in eye examination to the main aberrations (e.g. focus and astigmatism) that will increase the speed of the correction.

  10. Characteristic length scale of the magnon accumulation in Fe3O4/Pt bilayer structures by incoherent thermal excitation

    NASA Astrophysics Data System (ADS)

    Anadón, A.; Ramos, R.; Lucas, I.; Algarabel, P. A.; Morellón, L.; Ibarra, M. R.; Aguirre, M. H.

    2016-07-01

    The dependence of Spin Seebeck effect (SSE) with the thickness of the magnetic materials is studied by means of incoherent thermal excitation. The SSE voltage signal in Fe3O4/Pt bilayer structure increases with the magnetic material thickness up to 100 nm, approximately, showing signs of saturation for larger thickness. This dependence is well described in terms of a spin current pumped in the platinum film by the magnon accumulation in the magnetic material. The spin current is generated by a gradient of temperature in the system and detected by the Pt top contact by means of inverse spin Hall effect. Calculations in the frame of the linear response theory adjust with a high degree of accuracy the experimental data, giving a thermal length scale of the magnon accumulation (Λ) of 17 ± 3 nm at 300 K and Λ = 40 ± 10 nm at 70 K.

  11. Rayleigh Scattering.

    ERIC Educational Resources Information Center

    Young, Andrew T.

    1982-01-01

    The correct usage of such terminology as "Rayleigh scattering,""Rayleigh lines,""Raman lines," and "Tyndall scattering" is resolved during an historical excursion through the physics of light-scattering by gas molecules. (Author/JN)

  12. Signal enhanced holographic fluorescence microscopy with guide-star reconstruction

    PubMed Central

    Jang, Changwon; Clark, David C.; Kim, Jonghyun; Lee, Byoungho; Kim, Myung K.

    2016-01-01

    We propose a signal enhanced guide-star reconstruction method for holographic fluorescence microscopy. In the late 00’s, incoherent digital holography started to be vigorously studied by several groups to overcome the limitations of conventional digital holography. The basic concept of incoherent digital holography is to acquire the complex hologram from incoherent light by utilizing temporal coherency of a spatially incoherent light source. The advent of incoherent digital holography opened new possibility of holographic fluorescence microscopy (HFM), which was difficult to achieve with conventional digital holography. However there has been an important issue of low and noisy signal in HFM which slows down the system speed and degrades the imaging quality. When guide-star reconstruction is adopted, the image reconstruction gives an improved result compared to the conventional propagation reconstruction method. The guide-star reconstruction method gives higher imaging signal-to-noise ratio since the acquired complex point spread function provides optimal system-adaptive information and can restore the signal buried in the noise more efficiently. We present theoretical explanation and simulation as well as experimental results. PMID:27446653

  13. Signal enhanced holographic fluorescence microscopy with guide-star reconstruction.

    PubMed

    Jang, Changwon; Clark, David C; Kim, Jonghyun; Lee, Byoungho; Kim, Myung K

    2016-04-01

    We propose a signal enhanced guide-star reconstruction method for holographic fluorescence microscopy. In the late 00's, incoherent digital holography started to be vigorously studied by several groups to overcome the limitations of conventional digital holography. The basic concept of incoherent digital holography is to acquire the complex hologram from incoherent light by utilizing temporal coherency of a spatially incoherent light source. The advent of incoherent digital holography opened new possibility of holographic fluorescence microscopy (HFM), which was difficult to achieve with conventional digital holography. However there has been an important issue of low and noisy signal in HFM which slows down the system speed and degrades the imaging quality. When guide-star reconstruction is adopted, the image reconstruction gives an improved result compared to the conventional propagation reconstruction method. The guide-star reconstruction method gives higher imaging signal-to-noise ratio since the acquired complex point spread function provides optimal system-adaptive information and can restore the signal buried in the noise more efficiently. We present theoretical explanation and simulation as well as experimental results. PMID:27446653

  14. Intravoxel Incoherent Motion MR Imaging for Staging of Hepatic Fibrosis

    PubMed Central

    Zhang, Bin; Liang, Long; Dong, Yuhao; Lian, Zhouyang; Chen, Wenbo; Liang, Changhong; Zhang, Shuixing

    2016-01-01

    Objectives To determine the potential of intravoxel incoherent motion (IVIM) MR imaging for staging of hepatic fibrosis (HF). Methods We searched PubMed and EMBASE from their inception to 31 July 2015 to select studies reporting IVIM MR imaging and HF staging. We defined F1-2 as non-advanced HF, F3-4 as advanced HF, F0 as normal liver, F1 as very early HF, and F2-4 as significant HF. Then we compared stage F0 with F1, F0-1 with F2-3, and F1-2 with F3-4 using IVIM-derived parameters (pseudo-diffusion coefficient D*, perfusion fraction f, and pure molecular diffusion parameter D). The effect estimate was expressed as a pooled weighted mean difference (WMD) with 95% confidence interval (CI), using the fixed-effects model. Results Overall, we included six papers (406 patients) in this study. Significant differences in D* were observed between F0 and F1, F0-1 and F2-3, and F1-2 and F3-4 (WMD 2.46, 95% CI 0.83–4.09, P = 0.006; WMD 13.10, 95% CI 9.53–16.67, P < 0.001; WMD 14.34, 95% CI 10.26–18.42, P < 0.001, respectively). Significant differences in f were also found between F0 and F1, F0-1 and F2-3, and F1-2 and F3-4 (WMD 1.62, 95% CI 0.06–3.18, P = 0.027; WMD 5.63, 95% CI 2.74–8.52, P < 0.001; WMD 3.30, 95% CI 2.10–4.50, P < 0.001, respectively). However, D showed no differences between F0 and F1, F0-1 and F2-3, and F1-2 and F3-4 (WMD 0.05, 95% CI -0.01─0.11, P = 0.105; WMD 0.04, 95% CI -0.01─0.10, P = 0.230; WMD 0.02, 95% CI -0.02─0.06, P = 0.378, respectively). Conclusions IVIM MR imaging provides an effective method of staging HF and can distinguish early HF from normal liver, significant HF from normal liver or very early HF, and advanced HF from non-advanced HF. PMID:26820668

  15. Neutron Scattering and Dielectric Study on the Structural and Dynamical Peculiar Properties of Poly(vinyl chloride)

    SciTech Connect

    Arbe, A.; Farago, B.; Frick, B.

    2004-04-30

    In this work we have studied the anomalous dynamical behavior of poly(vinyl chloride) (PVC) searching its origin in the dynamical heterogeneities arising from the structural peculiarities of this polymer. For this purpose we have combined dielectric spectroscopy, coherent and incoherent neutron scattering for the dynamics investigation, and SANS for resolving the heterogeneous structure of PVC. The SANS experiments indicate the existence of structural modulations that persist in the temperature range T < 430 K. We show that a distribution of glass transition temperatures due to these density modulations causes the broadening of the response from the structural relaxation and the anomalous momentum transfer dependence of the incoherent scattering function.

  16. A-dependence of the Beam-Spin Azimuthal Asymmetry in Deeply Virtual Compton Scattering

    SciTech Connect

    Guler, Hayg

    2007-06-13

    The nuclear-mass dependence of the beam-spin asymmetry (BSA) in deeply virtual Compton scattering has been measured at HERMES. The BSA ratios of Nuclei to Hydrogen or Deuterium BSAs have been extracted in coherent and incoherent-enriched kinematic regions separately.

  17. Thermal neutron scattering in graphite

    NASA Astrophysics Data System (ADS)

    Al-Qasir, Iyad Ibrahim

    below the Bragg cutoff (˜1.8 meV). Consequently, this motivated the examination of the principal assumption in thermal scattering cross section calculations for graphite, i.e., the incoherent approximation. For a strongly coherent scatterer like graphite, the coherent one-phonon scattering law and corresponding cross section were calculated exactly and without approximations. The required input to perform such calculation, e.g., the dispersion relations and polarization vectors were taken from the results of the graphite lattice dynamics calculations mentioned above. As a result, significant improvements were achieved especially in the scattering law characteristic behavior at small momentum and energy transfers, and excellent agreement was found between the calculated inelastic scattering cross sections and the experimental data of pyrolytic graphite. Furthermore, a consistent approach for defining the parabolic region in the phonon frequency distribution of graphite for use in calculations using the incoherent approximation was developed. This approach is based on the graphite mean square displacement and the agreement of the one-phonon cross sections as generated using both the incoherent approximation and the self part of the coherent one-phonon cross section. In this case, the parabolic energy cutoff was found to be 5.60 meV (equivalent to 65 K). Finally, the effect of temperature (anharmonicity) on the phonon frequency distribution was addressed and investigated by estimating the effects of energy shift and broadening of the distribution as a function of temperature. It was found that in graphite at low energies an energy shift is expected towards higher values. This is due to negative Gruniesen parameters. The phonon frequency distribution was broadened using a Lorentzian distribution, where the broadening effect has linear temperature dependence at high temperatures. Therefore, the broadening and shift operations are two competing processes at low energies

  18. From coherent to incoherent mismatched interfaces: A generalized continuum formulation of surface stresses

    NASA Astrophysics Data System (ADS)

    Dingreville, Rémi; Hallil, Abdelmalek; Berbenni, Stéphane

    2014-12-01

    The equilibrium of coherent and incoherent mismatched interfaces is reformulated in the context of continuum mechanics based on the Gibbs dividing surface concept. Two surface stresses are introduced: a coherent surface stress and an incoherent surface stress, as well as a transverse excess strain. The coherent surface stress and the transverse excess strain represent the thermodynamic driving forces of stretching the interface while the incoherent surface stress represents the driving force of stretching one crystal while holding the other fixed and thereby altering the structure of the interface. These three quantities fully characterize the elastic behavior of coherent and incoherent interfaces as a function of the in-plane strain, the transverse stress and the mismatch strain. The isotropic case is developed in detail and particular attention is paid to the case of interfacial thermo-elasticity. This exercise provides an insight on the physical significance of the interfacial elastic constants introduced in the formulation and illustrates the obvious coupling between the interface structure and its associated thermodynamics quantities. Finally, an example based on atomistic simulations of Cu/Cu2O interfaces is given to demonstrate the relevance of the generalized interfacial formulation and to emphasize the dependence of the interfacial thermodynamic quantities on the incoherency strain with an actual material system.

  19. Partial secular Bloch-Redfield master equation for incoherent excitation of multilevel quantum systems

    SciTech Connect

    Tscherbul, Timur V. Brumer, Paul

    2015-03-14

    We present an efficient theoretical method for calculating the time evolution of the density matrix of a multilevel quantum system weakly interacting with incoherent light. The method combines the Bloch-Redfield theory with a partial secular approximation for one-photon coherences, resulting in a master equation that explicitly exposes the reliance on transition rates and the angles between transition dipole moments in the energy basis. The partial secular Bloch-Redfield master equation allows an unambiguous distinction between the regimes of quantum coherent vs. incoherent energy transfer under incoherent light illumination. The fully incoherent regime is characterized by orthogonal transition dipole moments in the energy basis, leading to a dynamical evolution governed by a coherence-free Pauli-type master equation. The coherent regime requires non-orthogonal transition dipole moments in the energy basis and leads to the generation of noise-induced quantum coherences and population-to-coherence couplings. As a first application, we consider the dynamics of excited state coherences arising under incoherent light excitation from a single ground state and observe population-to-coherence transfer and the formation of non-equilibrium quasisteady states in the regime of small excited state splitting. Analytical expressions derived earlier for the V-type system [T. V. Tscherbul and P. Brumer, Phys. Rev. Lett. 113, 113601 (2014)] are found to provide a nearly quantitative description of multilevel excited-state populations and coherences in both the small- and large-molecule limits.

  20. From coherent to incoherent mismatched interfaces. A generalized continuum formulation of surface stresses

    SciTech Connect

    Dingreville, Rémi; Hallil, Abdelmalek; Berbenni, Stéphane

    2014-08-19

    The equilibrium of coherent and incoherent mismatched interfaces is reformulated in the context of continuum mechanics based on the Gibbs dividing surface concept. Two surface stresses are introduced: a coherent surface stress and an incoherent surface stress, as well as a transverse excess strain. Additionally, the coherent surface stress and the transverse excess strain represent the thermodynamic driving forces of stretching the interface while the incoherent surface stress represents the driving force of stretching one crystal while holding the other fixed and thereby altering the structure of the interface. These three quantities fully characterize the elastic behavior of coherent and incoherent interfaces as a function of the in-plane strain, the transverse stress and the mismatch strain. The isotropic case is developed in detail and particular attention is paid to the case of interfacial thermo-elasticity. This exercise provides an insight on the physical significance of the interfacial elastic constants introduced in the formulation and illustrates the obvious coupling between the interface structure and its associated thermodynamics quantities. Finally, an example based on atomistic simulations of Cu/Cu2O interfaces is given to demonstrate the relevance of the generalized interfacial formulation and to emphasize the dependence of the interfacial thermodynamic quantities on the incoherency strain with an actual material system.

  1. From coherent to incoherent mismatched interfaces. A generalized continuum formulation of surface stresses

    DOE PAGESBeta

    Dingreville, Rémi; Hallil, Abdelmalek; Berbenni, Stéphane

    2014-08-19

    The equilibrium of coherent and incoherent mismatched interfaces is reformulated in the context of continuum mechanics based on the Gibbs dividing surface concept. Two surface stresses are introduced: a coherent surface stress and an incoherent surface stress, as well as a transverse excess strain. Additionally, the coherent surface stress and the transverse excess strain represent the thermodynamic driving forces of stretching the interface while the incoherent surface stress represents the driving force of stretching one crystal while holding the other fixed and thereby altering the structure of the interface. These three quantities fully characterize the elastic behavior of coherent andmore » incoherent interfaces as a function of the in-plane strain, the transverse stress and the mismatch strain. The isotropic case is developed in detail and particular attention is paid to the case of interfacial thermo-elasticity. This exercise provides an insight on the physical significance of the interfacial elastic constants introduced in the formulation and illustrates the obvious coupling between the interface structure and its associated thermodynamics quantities. Finally, an example based on atomistic simulations of Cu/Cu2O interfaces is given to demonstrate the relevance of the generalized interfacial formulation and to emphasize the dependence of the interfacial thermodynamic quantities on the incoherency strain with an actual material system.« less

  2. Partial secular Bloch-Redfield master equation for incoherent excitation of multilevel quantum systems.

    PubMed

    Tscherbul, Timur V; Brumer, Paul

    2015-03-14

    We present an efficient theoretical method for calculating the time evolution of the density matrix of a multilevel quantum system weakly interacting with incoherent light. The method combines the Bloch-Redfield theory with a partial secular approximation for one-photon coherences, resulting in a master equation that explicitly exposes the reliance on transition rates and the angles between transition dipole moments in the energy basis. The partial secular Bloch-Redfield master equation allows an unambiguous distinction between the regimes of quantum coherent vs. incoherent energy transfer under incoherent light illumination. The fully incoherent regime is characterized by orthogonal transition dipole moments in the energy basis, leading to a dynamical evolution governed by a coherence-free Pauli-type master equation. The coherent regime requires non-orthogonal transition dipole moments in the energy basis and leads to the generation of noise-induced quantum coherences and population-to-coherence couplings. As a first application, we consider the dynamics of excited state coherences arising under incoherent light excitation from a single ground state and observe population-to-coherence transfer and the formation of non-equilibrium quasisteady states in the regime of small excited state splitting. Analytical expressions derived earlier for the V-type system [T. V. Tscherbul and P. Brumer, Phys. Rev. Lett. 113, 113601 (2014)] are found to provide a nearly quantitative description of multilevel excited-state populations and coherences in both the small- and large-molecule limits. PMID:25770526

  3. Partial secular Bloch-Redfield master equation for incoherent excitation of multilevel quantum systems

    NASA Astrophysics Data System (ADS)

    Tscherbul, Timur V.; Brumer, Paul

    2015-03-01

    We present an efficient theoretical method for calculating the time evolution of the density matrix of a multilevel quantum system weakly interacting with incoherent light. The method combines the Bloch-Redfield theory with a partial secular approximation for one-photon coherences, resulting in a master equation that explicitly exposes the reliance on transition rates and the angles between transition dipole moments in the energy basis. The partial secular Bloch-Redfield master equation allows an unambiguous distinction between the regimes of quantum coherent vs. incoherent energy transfer under incoherent light illumination. The fully incoherent regime is characterized by orthogonal transition dipole moments in the energy basis, leading to a dynamical evolution governed by a coherence-free Pauli-type master equation. The coherent regime requires non-orthogonal transition dipole moments in the energy basis and leads to the generation of noise-induced quantum coherences and population-to-coherence couplings. As a first application, we consider the dynamics of excited state coherences arising under incoherent light excitation from a single ground state and observe population-to-coherence transfer and the formation of non-equilibrium quasisteady states in the regime of small excited state splitting. Analytical expressions derived earlier for the V-type system [T. V. Tscherbul and P. Brumer, Phys. Rev. Lett. 113, 113601 (2014)] are found to provide a nearly quantitative description of multilevel excited-state populations and coherences in both the small- and large-molecule limits.

  4. Compressive imaging in scattering media.

    PubMed

    Durán, V; Soldevila, F; Irles, E; Clemente, P; Tajahuerce, E; Andrés, P; Lancis, J

    2015-06-01

    One challenge that has long held the attention of scientists is that of clearly seeing objects hidden by turbid media, as smoke, fog or biological tissue, which has major implications in fields such as remote sensing or early diagnosis of diseases. Here, we combine structured incoherent illumination and bucket detection for imaging an absorbing object completely embedded in a scattering medium. A sequence of low-intensity microstructured light patterns is launched onto the object, whose image is accurately reconstructed through the light fluctuations measured by a single-pixel detector. Our technique is noninvasive, does not require coherent sources, raster scanning nor time-gated detection and benefits from the compressive sensing strategy. As a proof of concept, we experimentally retrieve the image of a transilluminated target both sandwiched between two holographic diffusers and embedded in a 6mm-thick sample of chicken breast. PMID:26072804

  5. Four-dimensional tracking of spatially incoherent illuminated samples using self-interference digital holography

    NASA Astrophysics Data System (ADS)

    Man, Tianlong; Wan, Yuhong; Wu, Fan; Wang, Dayong

    2015-11-01

    We present a new method for the four-dimensional tracking of a spatially incoherent illuminated object. Self-interference digital holography is utilized for recording the hologram of the spatially incoherent illuminated object. Three-dimensional spatial coordinates encoded in the hologram are extracted by holographic reconstruction procedure and tracking algorithms, while the time information is reserved by the single-shot configuration. Applications of the holographic tracking methods are expanded to the incoherent imaging areas. Speckles and potential damage to the samples of the coherent illuminated tracking methods are overcome. Results on the quantitative tracking of three-dimensional spatial position over time are reported. In practical, living zebra fish larva is used to demonstrate one of the applications of the method.

  6. Measurement and analysis of the impact of transverse incoherent wakefields in a light source storage ring

    NASA Astrophysics Data System (ADS)

    Brunelle, P.; Nagaoka, R.; Sreedharan, R.

    2016-04-01

    The influence of incoherent wakefields arising from a high current beam circulating in a ring composed of many flat chambers on the beam is analyzed numerically and experimentally for the SOLEIL storage ring. Three distinct ranges of the excited field are studied: the long multiturn regime in multibunch fillings, the medium regime involving neighboring bunches, and the short intrabunch regime. Two theoretical models, which both take into account the field diffusion across chamber walls of finite thickness, are employed to compare the measurement with theoretical expectations. Specific experimental methods, based respectively upon orbit analysis, bunch-by-bunch transverse feedback and a single particle betatron resonance, are introduced to measure the incoherent focusing effect in the three regimes. It is found that the excited incoherent fields can be large enough to affect the ring performance. The non-negligible contribution of nonevaporable getter coating is shown to improve the agreement between measurements and calculations.

  7. Diffusive to quasi-ballistic random laser: incoherent and coherent models

    NASA Astrophysics Data System (ADS)

    Guerin, W.; Chong, Y. D.; Baudouin, Q.; Liertzer, M.; Rotter, S.; Kaiser, R.

    2016-09-01

    We study the crossover between the diffusive and quasi-ballistic regimes of random lasers. In particular, we compare incoherent models based on the diffusion equation and the radiative transfer equation (RTE), which neglect all wave effects, with a coherent wave model for the random laser threshold. We show that both the incoherent and the coherent models predict qualitatively similar thresholds, with a smooth transition from a diffuse to a quasi-ballistic regime. The shape of the intensity distribution in the sample as predicted by the RTE model at threshold is also in good agreement with the coherent model. The approximate incoherent models thus provide useful analytical predictions for the threshold of random lasers as well as the shape of the random laser modes at threshold.

  8. Feasibility of Coherent and Incoherent Backscatter Experiments from the AMPS Laboratory. Technical Section

    NASA Technical Reports Server (NTRS)

    Mozer, F. S.

    1976-01-01

    A computer program simulated the spectrum which resulted when a radar signal was transmitted into the ionosphere for a finite time and received for an equal finite interval. The spectrum derived from this signal is statistical in nature because the signal is scattered from the ionosphere, which is statistical in nature. Many estimates of any property of the ionosphere can be made. Their average value will approach the average property of the ionosphere which is being measured. Due to the statistical nature of the spectrum itself, the estimators will vary about this average. The square root of the variance about this average is called the standard deviation, an estimate of the error which exists in any particular radar measurement. In order to determine the feasibility of the space shuttle radar, the magnitude of these errors for measurements of physical interest must be understood.

  9. Fast Imaging with Inelastically Scattered Electrons by Off-Axis Chromatic Confocal Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Zheng, Changlin; Zhu, Ye; Lazar, Sorin; Etheridge, Joanne

    2014-04-01

    We introduce off-axis chromatic scanning confocal electron microscopy, a technique for fast mapping of inelastically scattered electrons in a scanning transmission electron microscope without a spectrometer. The off-axis confocal mode enables the inelastically scattered electrons to be chromatically dispersed both parallel and perpendicular to the optic axis. This enables electrons with different energy losses to be separated and detected in the image plane, enabling efficient energy filtering in a confocal mode with an integrating detector. We describe the experimental configuration and demonstrate the method with nanoscale core-loss chemical mapping of silver (M4,5) in an aluminium-silver alloy and atomic scale imaging of the low intensity core-loss La (M4,5@840 eV) signal in LaB6. Scan rates up to 2 orders of magnitude faster than conventional methods were used, enabling a corresponding reduction in radiation dose and increase in the field of view. If coupled with the enhanced depth and lateral resolution of the incoherent confocal configuration, this offers an approach for nanoscale three-dimensional chemical mapping.

  10. Incoherent sub-terahertz radiation source with a photomixer array for active imaging in smoky environments

    NASA Astrophysics Data System (ADS)

    Shimizu, Naofumi; Matsuyama, Ken; Uchida, Hidetake

    2015-03-01

    We propose a sub-terahertz (THz) illuminator suitable for use with a THz camera when exploring objects within and behind smoke at the scene of a fire. The illuminator contains a photomixer array and each photomixer generates incoherent sub-THz waves from a single-mode laser light and optical noise using photomixing. The incoherency of the generated sub-THz waves enables us to raise their intensity by increasing the number of photomixers in operation, which makes it possible to realize very bright sub-THz illumination. Consequently, objects being under searched for within or behind smoke can be clearly illuminated using the illuminator and visualized by the THz camera even though they are surrounded by thick and/or high-temperature smoke. To verify our concept, we conducted active imaging with coherent and incoherent sub-THz radiation from a photomixer array utilizing reflection geometry. Although the contrast of the image was improved by increasing number of photomixers in operation on the imaging with coherent radiation, the shape of the target was degraded by the interference pattern of the illuminated sub-THz waves. The contrast of the image when using incoherent radiation was improved without obscuring the shape of the target by increasing the number of photomixers. We also confirmed that there was good visibility for active imaging using incoherent sub-THz illumination even though thick smoke was presented. These results indicate that the use of incoherent sub-THz waves and an array of photomixers should enable a sub-THz illuminator with a high level of brightness to be used for active imaging

  11. Self-generated loss of coherency in Brillouin scattering and reduction of reflectivity

    SciTech Connect

    Casanova, M.; Laval, G.; Pellat, R.; Pesme, D.

    1985-05-20

    Low reflectivity of stimulated Brillouin scattering is shown to result from wave-interaction incoherency caused by the ion sound-wave nonlinearity. The Brillouin reflectivity is numerically found to display a chaotic time evolution at laser fluxes below those at which ion sound-wave harmonic generation takes place. At these fluxes, the scattered light exhibits a spiky frequency spectrum. Scaling laws for the reflectivity are given.

  12. Investigation on the synchronized characteristics of the incoherent optical feedback chaotic system

    NASA Astrophysics Data System (ADS)

    Xu, Li; Wu, Zhengmao; Li, Linfu; Fan, Li; Fan, Yan; Xia, Guangqiong

    2007-11-01

    Based on the theoretical model of the synchronization system with incoherent optical feedback, the influence of the internal parameter mismatch on the synchronized characteristics of the chaotic system has been investigated. The result shows that the chaotic system with incoherent optical feedback can be realized more easily than the complete synchronized system, and has higher security than injection locking synchronization system. Using encoding of chaos shift keying, the message can be hidden efficiently during the transmission in the system and decoded easily in receiver.

  13. From incoherent to coherent x-rays with ICS sources

    NASA Astrophysics Data System (ADS)

    Nanni, Emilio A.; Graves, William S.; Moncton, David E.

    2015-08-01

    We present the design and performance parameters for a compact x-ray light source (CXLS), which is presently under construction, based on inverse Compton scattering (ICS) of a high brightness electron bunch on a picosecond laser pulse. The flux and brilliance of this source are orders of magnitude beyond existing laboratory scale sources. The accelerator operates at a repetition rate of 1 kHz with 100 bunches of 100 pC charge, each separated by 5 ns, in each shot. The entire CXLS is a few meters in length and produces hard x-rays tunable over a wide range of photon energies. The scattering laser is a Yb:YAG solid-state amplifier producing 100 mJ pulses at 1030 nm. The laser pulse is frequency-doubled and coupled into a ringdown cavity to match the linac pulse structure. At a photon energy of 12.4 keV, the predicted x-ray flux is 5×1011 photons/second in a 5% bandwidth and the brilliance is 2×1012 photons/(secmm2mrad20.1%) with a RMS pulse length of 490 fs. Novel concepts for improving the performance of the CXLS with the generation of relativistic electron beams having current modulation at nanometer scale and below are also discussed. This tunable longitudinal modulation enables the production of coherent hard x-rays with ICS.

  14. Alpha particle collective Thomson scattering in TFTR

    SciTech Connect

    Machuzak, J.S.; Woskov, P.P.; Rhee, D.Y.; Gilmore, J.; Bretz, N.L.; Park, H.K.; Aamodt, R.E.; Cheung, P.Y.; Russell, D.A.; Bindslev, H.

    1993-11-01

    A collective Thomson scattering diagnostic is being implemented on TFTR to measure alpha particle, energetic and thermal ion densities and velocity distributions. A 60 GHz, 0.1-1 kW gyrotron will be used as the transmitter source, and the scattering geometry will be perpendicular to the magnetic field in the extraordinary mode polarization. An enhanced scattered signal is anticipated from fluctuations in the lower hybrid frequency range with this scattering geometry. Millimeter wave collective Thomson scattering diagnostics have the advantage of larger scattering angles to decrease the amount of stray light, and long, high power, modulated pulses to obtain improved signal to noise through synchronous detection techniques.

  15. LASER APPLICATIONS IN MEDICINE: Analysis of distortions in the velocity profiles of suspension flows inside a light-scattering medium upon their reconstruction from the optical coherence Doppler tomograph signal

    NASA Astrophysics Data System (ADS)

    Bykov, A. V.; Kirillin, M. Yu; Priezzhev, A. V.

    2005-11-01

    Model signals from one and two plane flows of a particle suspension are obtained for an optical coherence Doppler tomograph (OCDT) by the Monte-Carlo method. The optical properties of particles mimic the properties of non-aggregating erythrocytes. The flows are considered in a stationary scattering medium with optical properties close to those of the skin. It is shown that, as the flow position depth increases, the flow velocity determined from the OCDT signal becomes smaller than the specified velocity and the reconstructed profile extends in the direction of the distant boundary, which is accompanied by the shift of its maximum. In the case of two flows, an increase in the velocity of the near-surface flow leads to the overestimated values of velocity of the reconstructed profile of the second flow. Numerical simulations were performed by using a multiprocessor parallel-architecture computer.

  16. Detection of Heater Generated Super Small Scale Striations Using GPS Signal Diagnostics

    NASA Astrophysics Data System (ADS)

    Najmi, A. C.; Milikh, G. M.; Chiang, K.; Psiaki, M.; Secan, J. A.; Bernhardt, P. A.; Briczinski, S. J.; Siefring, C. L.; Papadopoulos, K.

    2013-12-01

    Recent theoretical models predict that super small striations (SSS) of the electron density, on the order of ten centimeters, can be excited by HF waves with frequency close to multiples of the electron gyro frequency [Gurevich et al., 2006]. The first experimental verification of SSS was made at HAARP [Milikh et al., 2008]. We present results of HAARP experiments that include simultaneous observations of GPS carrier phase and SEE observations of ionospheric turbulence. These observations show that SSS excited by HF frequencies near the fourth harmonic of the gyro frequency scatter GPS signals, and in three out of six experiments indicate the presence of strong turbulence, similar to that observed in descending artificial ionized layer experiments [Pedersen et al., 2010]. This turbulence is capable of generating suprathermal electrons, and in one of the experiments, the presence of fast electrons was confirmed by the HAARP incoherent scattering radar. Estimates on the SSS shows that they correspond to 3-10% electron density depletions. Such irregularities affect UHF signals including GPS, and thus can be important in applications. Gurevich, A.V. and K.P. Zybin (2006), Phys. Lett. A, 358, 159. Milikh, G., et al. (2008), Geophys. Res. Let., 35, L22102, doi:10.1029/2008GL035527. Pedersen, T. et al. (2010), Geophys. Res. Let., 37, L02106, doi:10.1029/2009GL041895.

  17. Fluorescence and Light Scattering

    ERIC Educational Resources Information Center

    Clarke, Ronald J.; Oprysa, Anna

    2004-01-01

    The aim of the mentioned experiment is to aid students in developing tactics for distinguishing between signals originating from fluorescence and light scattering. Also, the experiment provides students with a deeper understanding of the physicochemical bases of each phenomenon and shows that the techniques are actually related.

  18. Conceptual Incoherence as a Result of the Use of Multiple Historical Models in School Textbooks

    ERIC Educational Resources Information Center

    Gericke, Niklas M.; Hagberg, Mariana

    2010-01-01

    This paper explores the occurrence of conceptual incoherence in upper secondary school textbooks resulting from the use of multiple historical models. Swedish biology and chemistry textbooks, as well as a selection of books from English speaking countries, were examined. The purpose of the study was to identify which models are used to represent…

  19. Optical sectioning using a digital Fresnel incoherent-holography-based confocal imaging system

    PubMed Central

    Kelner, Roy; Katz, Barak; Rosen, Joseph

    2015-01-01

    We propose a new type of confocal microscope using Fresnel incoherent correlation holography (FINCH). Presented here is a confocal configuration of FINCH using a phase pinhole and point illumination that is able to suppress out-of-focus information from the recorded hologram and hence combine the super-resolution capabilities of FINCH with the sectioning capabilities of confocal microscopy. PMID:26413560

  20. Quantitative evaluation of spatial phase light modulator characteristics in Fresnel incoherent correlation holography

    NASA Astrophysics Data System (ADS)

    Man, Tianlong; Wan, Yuhong; Chen, Hao; Jiang, Zhuqing; Wang, Dayong

    2012-11-01

    Fresnel incoherent correlation holography (FINCH) is one of the methods for recording holograms of 3D samples under incoherent illumination. The FINCH combines the theory of spatial self-coherence and the in-line phase-shift technology together to form a complex hologram. A spatial phase light modulator (SPLM) plays important roles as the dynamic diffraction optical element (DOE) and phase shifter. When the incoherent light generated from each object point of the 3D samples incidents to a SPLM, it can be split into two spatial self-coherent beams with different curvatures. The hologram caused by these two beams can then be captured by an image detector. Three holograms with different phase shift are recorded sequentially for eliminating the zero-order and twin image, and then a complex valued hologram is obtained by superposing the three holograms. In this paper, the modulation characteristics of SPLM and phase shift error in FINCH are investigated. Based on digital holography, phase modulation characteristics of SPLM are measured under coherent and narrow-bandwidth incoherent illumination respectively. Phase shift error due to quasi monochromatic light illumination is then analyzed in FINCH. The effect of phase shift error on the quality of reconstructed image is also investigated. It is demonstrated the FINCH setup has a smaller phase shift error by experiment.

  1. Time-stretch microscopy based on time-wavelength sequence reconstruction from wideband incoherent source

    SciTech Connect

    Zhang, Chi Xu, Yiqing; Wei, Xiaoming; Tsia, Kevin K.; Wong, Kenneth K. Y.

    2014-07-28

    Time-stretch microscopy has emerged as an ultrafast optical imaging concept offering the unprecedented combination of the imaging speed and sensitivity. However, dedicated wideband and coherence optical pulse source with high shot-to-shot stability has been mandated for time-wavelength mapping—the enabling process for ultrahigh speed wavelength-encoded image retrieval. From the practical point of view, exploiting methods to relax the stringent requirements (e.g., temporal stability and coherence) for the source of time-stretch microscopy is thus of great value. In this paper, we demonstrated time-stretch microscopy by reconstructing the time-wavelength mapping sequence from a wideband incoherent source. Utilizing the time-lens focusing mechanism mediated by a narrow-band pulse source, this approach allows generation of a wideband incoherent source, with the spectral efficiency enhanced by a factor of 18. As a proof-of-principle demonstration, time-stretch imaging with the scan rate as high as MHz and diffraction-limited resolution is achieved based on the wideband incoherent source. We note that the concept of time-wavelength sequence reconstruction from wideband incoherent source can also be generalized to any high-speed optical real-time measurements, where wavelength is acted as the information carrier.

  2. Field-aligned electric currents and their measurement by the incoherent backscatter technique

    NASA Technical Reports Server (NTRS)

    Bauer, P.; Cole, K. D.; Lejeume, G.

    1975-01-01

    Field aligned electric currents flow in the magnetosphere in many situations of fundamental geophysical interest. It is shown here that the incoherent backscatter technique can be used to measure these currents when the plasma line can be observed. The technique provides a ground based means of measuring these currents which complements the rocket and satellite ones.

  3. Lasing without inversion and enhancement of the index of refraction via interference of incoherent pump processes

    NASA Astrophysics Data System (ADS)

    Fleischhauer, M.; Keitel, C. H.; Scully, M. O.; Su, C.

    1992-01-01

    For the Λ quantum beat laser we investigate the generation of coherence between the two lower levels via incoherent pumping of these two levels to a fourth auxiliary level. It will be shown that this way of establishing coherence also leads to lasing without inversion and to an enhancement of the index of refraction at a point of vanishing absorption.

  4. The Wigner–Yanase information can increase under phase sensitive incoherent operations

    SciTech Connect

    Du, Shuanping Bai, Zhaofang

    2015-08-15

    We found that the Wigner-Yanase skew information, which has been recently proposed as a measure of coherence in Girolami (2014), can increase under a class of operations which may be interpreted as incoherent following the framework of Baumgratz et al., while being phase sensitive.

  5. A decision directed detector for the phase incoherent Gaussian channel

    NASA Technical Reports Server (NTRS)

    Kazakos, D.

    1975-01-01

    A vector digital signalling scheme is proposed for simultaneous adaptive data transmission and phase estimation. The use of maximum likelihood estimation methods predicts a better performance than the phase-locked loop. The phase estimate is shown to converge to the true value, so that the adaptive nature of the detector effectively achieves phase acquisition and improvement in performance. No separate synchronization interval is required and phase fluctuations can be tracked simultaneously with the transmission of information.

  6. Measurement of spin coherence using Raman scattering

    NASA Astrophysics Data System (ADS)

    Sun, Z.; Delteil, A.; Faelt, S.; Imamoǧlu, A.

    2016-06-01

    Ramsey interferometry provides a natural way to determine the coherence time of most qubit systems. Recent experiments on quantum dots, however, demonstrated that dynamical nuclear spin polarization can strongly influence the measurement process, making it difficult to extract the T2* coherence time using standard optical Ramsey pulses. Here, we demonstrate an alternative method for spin coherence measurement that is based on first-order coherence of photons generated in spin-flip Raman scattering. We show that if a quantum emitter is driven by a weak monochromatic laser, Raman coherence is determined exclusively by spin coherence, allowing for a direct determination of spin T2* time. When combined with coherence measurements on Rayleigh scattered photons, our technique enables us to identify coherent and incoherent contributions to resonance fluorescence, and to minimize the latter. We verify the validity of our technique by comparing our results to those determined from Ramsey interferometry for electron and heavy-hole spins.

  7. The Applicability of Incoherent Array Processing to IMS Seismic Arrays

    NASA Astrophysics Data System (ADS)

    Gibbons, Steven J.

    2014-03-01

    The seismic arrays of the International Monitoring System (IMS) for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) are highly diverse in size and configuration, with apertures ranging from under 1 km to over 60 km. Large and medium aperture arrays with large inter-site spacings complicate the detection and estimation of high-frequency phases lacking coherence between sensors. Pipeline detection algorithms often miss such phases, since they only consider frequencies low enough to allow coherent array processing, and phases that are detected are often attributed qualitatively incorrect backazimuth and slowness estimates. This can result in missed events, due to either a lack of contributing phases or by corruption of event hypotheses by spurious detections. It has been demonstrated previously that continuous spectral estimation can both detect and estimate phases on the largest aperture arrays, with arrivals identified as local maxima on beams of transformed spectrograms. The estimation procedure in effect measures group velocity rather than phase velocity, as is the case for classical f-k analysis, and the ability to estimate slowness vectors requires sufficiently large inter-sensor distances to resolve time-delays between pulses with a period of the order 4-5 s. Spectrogram beampacking works well on five IMS arrays with apertures over 20 km (NOA, AKASG, YKA, WRA, and KURK) without additional post-processing. Seven arrays with 10-20 km aperture (MJAR, ESDC, ILAR, KSRS, CMAR, ASAR, and EKA) can provide robust parameter estimates subject to a smoothing of the resulting slowness grids, most effectively achieved by convolving the measured slowness grids with the array response function for a 4 or 5 s period signal. Even for medium aperture arrays which can provide high-quality coherent slowness estimates, a complementary spectrogram beampacking procedure could act as a quality control by providing non-aliased estimates when the coherent slowness grids display

  8. Signal Subspace Processing Of Experimental Radio Data

    NASA Astrophysics Data System (ADS)

    Martin, Gordon E.

    1988-02-01

    The research related to this paper was concerned with the application of EigenVector EigenValue ( EVEV ) signal processing techniques to experimental data. The signal subspace methods of Schmidt (called MUSIC), Johnson, and Pisarenko were considered and compared with results of conventional beamformers. Almost all oral and written papers regarding these EVEV processors involve theoretical studies, possibly using simulated data and incoherent noise, but not experimental data. Contrary to that trend, we have reported behavior of EVEV processors using experimental data in this and other papers. The data used here are predominantly due to an HF radio experiment, but the distribution of eigenvalues is also reported for acoustic data. The paper emphasizes two general subtopics of signal subspace processing. First, the eigenvalues of sampled covariance matrices are examined and related to those of incoherent noise. These results include actual data, all of which we found were not Gaussian incoherent noise. A new test related to the ratio of eigenvalues is developed. The MDL and AIC criteria give misleading results with actual noise. Second, directional responses of EVEV and conventional processors are compared using HF radio data that has high signal-to-noise ratio in the non-Gaussian noise. MUSIC is found to have very favorable directional characteristics.

  9. Device convolution effects on the collective scattering signal of the E Multiplication-Sign B mode from Hall thruster experiments: 2D dispersion relation

    SciTech Connect

    Cavalier, J.; Lemoine, N.; Bonhomme, G.; Tsikata, S.; Honore, C.; Gresillon, D.

    2012-08-15

    The effect of the collective light scattering diagnostic transfer function is considered in the context of the dispersion relation of the unstable E Multiplication-Sign B mode previously reported. This transfer function is found to have a contribution to the measured frequencies and mode amplitudes which is more or less significant depending on the measurement wavenumbers and angles. After deconvolution, the experimental data are found to be possibly compatible with the idea that the mode frequency in the jet frame (after subtraction of the Doppler effect due to the plasma motion along the thruster axis) is independent of the orientation of the wave vector in the plane orthogonal to the local magnetic field.

  10. Scattering measurements on natural and model trees

    NASA Technical Reports Server (NTRS)

    Rogers, James C.; Lee, Sung M.

    1990-01-01

    The acoustical back scattering from a simple scale model of a tree has been experimentally measured. The model consisted of a trunk and six limbs, each with 4 branches; no foliage or twigs were included. The data from the anechoic chamber measurements were then mathematically combined to construct the effective back scattering from groups of trees. Also, initial measurements have been conducted out-of-doors on a single tree in an open field in order to characterize its acoustic scattering as a function of azimuth angle. These measurements were performed in the spring, prior to leaf development. The data support a statistical model of forest scattering; the scattered signal spectrum is highly irregular but with a remarkable general resemblance to the incident signal spectrum. Also, the scattered signal's spectra showed little dependence upon scattering angle.

  11. Atomic beam scattering from single crystal surfaces

    NASA Astrophysics Data System (ADS)

    Frankl, Daniel R.

    Application of atom-scattering to a variety of surface problems is expanding rapidly, owing in large part to the extreme surface- sensitivity of this probe. Helium is particularly useful because of its low mass and chemical inertness. Beams with velocity spreads of less than one percent and wavelength of the order of one Angstrom can be formed by nozzle expansion. The scattered flux from a clean, well-ordered crystal surface contains elastic and inelastic, coherent and incoherent, components. The coherent elastic component (i.e., the specular and diffracted beams) contains information about the crystallographic structure of the outer- most atomic layer of the crystal and about the interaction potential between the crystal and the scattered particle. The latter manifests itself in the form of resonances between the incoming free-particle state, and the two-dimensional Bloch states bound in the potential well at the surface. Elastic scattering theory has reached the point where the resonance signatures in the various diffracted beams can be predicted accurately. Crystallographic information resides in the diffracted beam intensities. Theoretical interpretation is less well advanced, though some progress has been made with “hard-wall” models. Experimental studies of reconstructed surfaces and chemisorbed overlayers appear very promising. In inelastic scattering, energy resolution has been achieved by both time-of-flight and diffraction methods. High-resolution studies on alkali halide surfaces have led to experimental determination of Rayleighwave dispersion relations over the full Brillouin zone. Preliminary results have also been obtained on some metals.

  12. Investigating the existence of coherent phonon scattering in silicon using phononic crystals

    NASA Astrophysics Data System (ADS)

    Goettler, Drew

    In silicon the majority of heat energy is transported by phonons, which are discrete lattice vibrations. Phonon scattering due to the presence of voids in silicon can further alter the material's thermal conductivity. There is a question about the possibility of some of this scattering being coherent rather than purely incoherent. Coherent phonon scattering is defined as constructive interference of phonons scattered from the inclusions in the phononic crystal. The intent of this work is to investigate the existence of coherent scattering in Si via phononic crystals. A phononic crystal is a periodic array of inclusions inside a host material. The inclusions could be a second material or a void. In this work five different supercell phononic crystals comprised of holes in silicon will be used to investigate the existence of coherent phonon scattering. Each of the supercells had nearly identical critical lengths in order to keep the amount of incoherent scattering equal among all of the PnCs. Porosity differences among the supercells were also minimized. All of the PnCs were fabricated with a focused ion beam (FIB). During fabrication a protective layer of Ti was used to protect the Si from unintentional Ga doping from the FIB. The Ti layer also helped generate voids with more vertical sidewalls. A set of experiments was performed to measure the thermal conductivity of each PnC. Thermal conductivity measurements were carried out on a silicon nitride suspended island platform with platinum resistance temperature detectors and coated with aluminum nitride. A silicon slab was concurrently measured with each PnC, and relative thermal conductivity values were determined. The addition of the PnC decreased Si's thermal conductivity to less than 22% of its original value. An analysis of the results shows there is a reduction in thermal conductivity beyond the effects of porosity and incoherent scattering. This enhanced reduction in thermal conductivity is due to coherent

  13. From coherent shocklets to giant collective incoherent shock waves in nonlocal turbulent flows

    NASA Astrophysics Data System (ADS)

    Xu, G.; Vocke, D.; Faccio, D.; Garnier, J.; Roger, T.; Trillo, S.; Picozzi, A.

    2015-09-01

    Understanding turbulent flows arising from random dispersive waves that interact strongly through nonlinearities is a challenging issue in physics. Here we report the observation of a characteristic transition: strengthening the nonlocal character of the nonlinear response drives the system from a fully turbulent regime, featuring a sea of coherent small-scale dispersive shock waves (shocklets) towards the unexpected emergence of a giant collective incoherent shock wave. The front of such global incoherent shock carries most of the stochastic fluctuations and is responsible for a peculiar folding of the local spectrum. Nonlinear optics experiments performed in a solution of graphene nano-flakes clearly highlight this remarkable transition. Our observations shed new light on the role of long-range interactions in strongly nonlinear wave systems operating far from thermodynamic equilibrium, which reveals analogies with, for example, gravitational systems, and establishes a new scenario that can be common to many turbulent flows in photonic quantum fluids, hydrodynamics and Bose-Einstein condensates.

  14. Coherent and Incoherent Coupling Dynamics between Neutral and Charged Excitons in Monolayer MoSe2.

    PubMed

    Hao, Kai; Xu, Lixiang; Nagler, Philipp; Singh, Akshay; Tran, Kha; Dass, Chandriker Kavir; Schüller, Christian; Korn, Tobias; Li, Xiaoqin; Moody, Galan

    2016-08-10

    The optical properties of semiconducting transition metal dichalcogenides are dominated by both neutral excitons (electron-hole pairs) and charged excitons (trions) that are stable even at room temperature. While trions directly influence charge transport properties in optoelectronic devices, excitons may be relevant through exciton-trion coupling and conversion phenomena. In this work, we reveal the coherent and incoherent nature of exciton-trion coupling and the relevant time scales in monolayer MoSe2 using optical two-dimensional coherent spectroscopy. Coherent interaction between excitons and trions is definitively identified as quantum beating of cross peaks in the spectra that persists for a few hundred femtoseconds. For longer times up to 10 ps, surprisingly, the relative intensity of the cross peaks increases, which is attributed to incoherent energy transfer likely due to phonon-assisted up-conversion and down-conversion processes that are efficient even at cryogenic temperature. PMID:27428509

  15. Critical Examination of Incoherent Operations and a Physically Consistent Resource Theory of Quantum Coherence.

    PubMed

    Chitambar, Eric; Gour, Gilad

    2016-07-15

    Considerable work has recently been directed toward developing resource theories of quantum coherence. In this Letter, we establish a criterion of physical consistency for any resource theory. This criterion requires that all free operations in a given resource theory be implementable by a unitary evolution and projective measurement that are both free operations in an extended resource theory. We show that all currently proposed basis-dependent theories of coherence fail to satisfy this criterion. We further characterize the physically consistent resource theory of coherence and find its operational power to be quite limited. After relaxing the condition of physical consistency, we introduce the class of dephasing-covariant incoherent operations as a natural generalization of the physically consistent operations. Necessary and sufficient conditions are derived for the convertibility of qubit states using dephasing-covariant operations, and we show that these conditions also hold for other well-known classes of incoherent operations. PMID:27472102

  16. Simulation of the Recharging Method of Implantable Biosensors Based on a Wearable Incoherent Light Source

    PubMed Central

    Song, Yong; Hao, Qun; Kong, Xianyue; Hu, Lanxin; Cao, Jie; Gao, Tianxin

    2014-01-01

    Recharging implantable electronics from the outside of the human body is very important for applications such as implantable biosensors and other implantable electronics. In this paper, a recharging method for implantable biosensors based on a wearable incoherent light source has been proposed and simulated. Firstly, we develop a model of the incoherent light source and a multi-layer model of skin tissue. Secondly, the recharging processes of the proposed method have been simulated and tested experimentally, whereby some important conclusions have been reached. Our results indicate that the proposed method will offer a convenient, safe and low-cost recharging method for implantable biosensors, which should promote the application of implantable electronics. PMID:25372616

  17. Critical Examination of Incoherent Operations and a Physically Consistent Resource Theory of Quantum Coherence

    NASA Astrophysics Data System (ADS)

    Chitambar, Eric; Gour, Gilad

    2016-07-01

    Considerable work has recently been directed toward developing resource theories of quantum coherence. In this Letter, we establish a criterion of physical consistency for any resource theory. This criterion requires that all free operations in a given resource theory be implementable by a unitary evolution and projective measurement that are both free operations in an extended resource theory. We show that all currently proposed basis-dependent theories of coherence fail to satisfy this criterion. We further characterize the physically consistent resource theory of coherence and find its operational power to be quite limited. After relaxing the condition of physical consistency, we introduce the class of dephasing-covariant incoherent operations as a natural generalization of the physically consistent operations. Necessary and sufficient conditions are derived for the convertibility of qubit states using dephasing-covariant operations, and we show that these conditions also hold for other well-known classes of incoherent operations.

  18. Propagation characteristics of Bessel beams generated by continuous, incoherent light sources.

    PubMed

    Altıngöz, Ceren; Yalızay, Berna; Akturk, Selcuk

    2015-08-01

    We investigate the propagation behavior of Bessel beams generated by incoherent, continuous light sources. We perform experiments with narrowband and broadband light emitting diodes, and, for comparison, with a laser diode. We observe that the formation of Bessel beams is affected minimally by temporal coherence, while spatial coherence determines the longitudinal evolution of the beam profile. With spatially incoherent beams, the fringe contrast is comparable to the coherent case at the beginning of the Bessel zone, while it completely fades away by propagation, turning into a cylindrical light pipe. Our results show that beam shaping methods can be extended to cases of limited spatial coherence, paving the way for potential new uses and applications of such sources. PMID:26367302

  19. Coherent and Incoherent Coupling Dynamics between Neutral and Charged Excitons in Monolayer MoSe2

    NASA Astrophysics Data System (ADS)

    Hao, Kai; Xu, Lixiang; Nagler, Philipp; Singh, Akshay; Tran, Kha; Dass, Chandriker Kavir; Schüller, Christian; Korn, Tobias; Li, Xiaoqin; Moody, Galan

    2016-08-01

    The optical properties of semiconducting transition metal dichalcogenides are dominated by both neutral excitons (electron-hole pairs) and charged excitons (trions) that are stable even at room temperature. While trions directly influence charge transport properties in optoelectronic devices, excitons may be relevant through exciton-trion coupling and conversion phenomena. In this work, we reveal the coherent and incoherent nature of exciton-trion coupling and the relevant timescales in monolayer MoSe2 using optical two-dimensional coherent spectroscopy. Coherent interaction between excitons and trions is definitively identified as quantum beating of cross-coupling peaks that persists for a few hundred femtoseconds. For longer times up to 10 ps, surprisingly, the relative intensity of the cross-coupling peaks increases, which is attributed to incoherent energy transfer likely due to phonon-assisted up-conversion and down-conversion processes that are efficient even at cryogenic temperature.

  20. Compressive sensing sectional imaging for single-shot in-line self-interference incoherent holography

    NASA Astrophysics Data System (ADS)

    Weng, Jiawen; Clark, David C.; Kim, Myung K.

    2016-05-01

    A numerical reconstruction method based on compressive sensing (CS) for self-interference incoherent digital holography (SIDH) is proposed to achieve sectional imaging by single-shot in-line self-interference incoherent hologram. The sensing operator is built up based on the physical mechanism of SIDH according to CS theory, and a recovery algorithm is employed for image restoration. Numerical simulation and experimental studies employing LEDs as discrete point-sources and resolution targets as extended sources are performed to demonstrate the feasibility and validity of the method. The intensity distribution and the axial resolution along the propagation direction of SIDH by angular spectrum method (ASM) and by CS are discussed. The analysis result shows that compared to ASM the reconstruction by CS can improve the axial resolution of SIDH, and achieve sectional imaging. The proposed method may be useful to 3D analysis of dynamic systems.

  1. Coded aperture correlation holography-a new type of incoherent digital holograms.

    PubMed

    Vijayakumar, A; Kashter, Yuval; Kelner, Roy; Rosen, Joseph

    2016-05-30

    We propose and demonstrate a new concept of incoherent digital holography termed coded aperture correlation holography (COACH). In COACH, the hologram of an object is formed by the interference of light diffracted from the object, with light diffracted from the same object, but that passes through a coded phase mask (CPM). Another hologram is recorded for a point object, under identical conditions and with the same CPM. This hologram is called the point spread function (PSF) hologram. The reconstructed image is obtained by correlating the object hologram with the PSF hologram. The image reconstruction of multiplane object using COACH was compared with that of other equivalent imaging systems, and has been found to possess a higher axial resolution compared to Fresnel incoherent correlation holography. PMID:27410157

  2. Incoherent and coherent eavesdropping in the six-state protocol of quantum cryptography

    NASA Astrophysics Data System (ADS)

    Bechmann-Pasquinucci, H.; Gisin, N.

    1999-06-01

    All incoherent as well as 2- and 3-qubit coherent eavesdropping strategies on the six-state protocol of quantum cryptography are classified. For a disturbance of 1/6, the optimal incoherent eavesdropping strategy reduces to the universal quantum cloning machine. Coherent eavesdropping cannot increase Eve's Shannon information, neither on the entire string of bits, nor on the set of bits received undisturbed by Bob. However, coherent eavesdropping can increase as well Eve's Renyi information as her probability of guessing correctly all bits. The case that Eve delays the measurement of her probe until after the public discussion on error correction and privacy amplification is also considered. It is argued that by doing so, Eve gains only negligibly small additional information.

  3. Quasi-Linear Evolution of the Modulational Instability in the Presence of Partial Incoherence

    NASA Astrophysics Data System (ADS)

    Lisak, M.; Anderson, D.; Helczynski-Wolf, L.; Berczynski, P.; Fedele, R.; Semenov, V.

    2004-01-01

    A basic system of model equations describing the quasi-linear development of the modulational instability in the presence of partial incoherence is derived. This system can be interpreted as balance equations for the number of quasi-particles in the Wigner spectrum where the basic processes which are active are emission and absorption of quasi-particles by quasi-particles with different wave vectors.

  4. Proposed ground-based incoherent Doppler lidar with iodine filter discriminator for atmospheric wind profiling

    SciTech Connect

    Liu, Z.S.; Chen, W.B.; Hair, J.W.; She, C.Y.

    1996-12-31

    A new incoherent lidar for measuring atmospheric wind using iodine molecular filter is proposed. A unique feature of the proposed lidar lies in its capability for simultaneous measurement of aerosol mixing ratio, with which the radial wind can be determined uniquely from lidar return. A preliminary laboratory experiment using a dye laser at 589 nm and a rotating wheel has been performed demonstrating the feasibility of the proposed wind measurement.

  5. Nematic liquid crystals: a suitable medium for self-confinement of coherent and incoherent light.

    PubMed

    Peccianti, Marco; Assanto, Gaetano

    2002-03-01

    Nematic liquid crystals exhibit a saturable, non-instantaneous nonlinear response through light-induced reorientation. In such a material, we demonstrate that (2+1)-dimensional spatial solitary waves can be generated at milliwatt power levels not only with a coherent optical beam, but also with incoherent excitations. Self-trapping also allows the efficient guidance of a weak co-polarized probe. PMID:11909157

  6. Observation of incoherent relaxation by tunneling in a macroscopic two-state system

    SciTech Connect

    Han, S.; Lapointe, J.; Lukens, J.E. )

    1991-02-11

    The dynamics of a dissipative, quantized macroscopic two-state system have been experimentally investigated through the measurement of tunneling transitions between the adjacent, equal-energy fluxoid states of a superconducting loop containing Josephson junctions. The tunneling rate {Gamma} has been observed to approach zero as a power law in the temperature, giving a damping parameter {alpha}=1.44, in the incoherent relaxation regime. The predicted exponential dependence of {Gamma} on barrier height has been quantitatively confirmed.

  7. Optical Encryption of Arrays of Binary Digits in Spatially Incoherent Light

    NASA Astrophysics Data System (ADS)

    Krasnov, V. V.; Starikov, S. N.; Starikov, R. S.; Cheremkhin, P. A.

    2016-02-01

    Optical encryption of arrays of binary digits in spatially incoherent light is experimentally implemented. Successful optical encryption and numerical decryption of images of binary arrays using a developed setup is demonstrated. Faultless decryption of arrays with normalized average energies (NAEs) up to 0.3 inclusive has been implemented. It is demonstrated that a decrease in the NAE of arrays to be encrypted leads to a decrease in the encryption error rate.

  8. Incoherent collisions between two-dimensional bright steady-state photorefractive spatial screening solitons

    NASA Astrophysics Data System (ADS)

    Shih, Ming-Feng; Segev, Mordechai

    1996-10-01

    We report the observation of incoherent collisions between two-dimensional bright photorefractive screening solitons. The solitons remain intact and do not exchange energy whenever the collision angle exceeds the critical angle for guidance in the waveguide that each soliton induces, which is, in turn, fully controlled by the soliton parameters. When the collision angle is much smaller than the critical angle the solitons fuse to form a single beam.

  9. Absolute Bunch Length Measurements at the ALS by Incoherent Synchrotron Radiation Fluctuation Analysis

    SciTech Connect

    Filippetto, D.; Sannibale, F.; Zolotorev, Max Samuil; Stupakov, G.V.; /SLAC

    2008-01-24

    By analyzing the pulse to pulse intensity fluctuations of the radiation emitted by a charge particle in the incoherent part of the spectrum, it is possible to extract information about the spatial distribution of the beam. At the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory, we have developed and tested a simple scheme based on this principle that allows for the absolute measurement of the bunch length. A description of the method and the experimental results are presented.

  10. Scattering of radio frequency waves by density fluctuations

    NASA Astrophysics Data System (ADS)

    Ram, A. K.; Hizanidis, K.; Ioannidis, Z.; Tigelis, I.

    2015-11-01

    The scattering of radio frequency waves by density fluctuations in magnetized fusion plasmas is studied theoretically and computationally. For coherent fluctuations, such as filaments in the edge region, we use a full-wave model for which the theory is similar to that for Mie scattering of electromagnetic waves by dielectric objects. The filaments are considered to be cylindrical with their axes aligned along the magnetic field. The results from the theoretical model are compared with numerical simulations using COMSOL. The simulations are extended to plasma conditions that are beyond the scope of the theoretical model, e.g., multiple filaments and filaments with density gradients. For incoherent planar fluctuations, which can be either in the core of the plasma or in the edge region, our theory is based on the Kirchhoff approach in tandem with Huygen's principle. The coherent and incoherent fluctuations scatter the incident plane wave, as well as couple some of the power to different plasma waves. The scattered spectrum is affected by the size of the fluctuations, the frequency, and the direction of propagation of the incident wave.

  11. Transfer-matrix Formalism for the Calculation of Optical Response in Multilayer Systems: from Coherent to Incoherent Interference

    SciTech Connect

    Troparevski, Claudia; Sabau, Adrian S; Lupini, Andrew R; Zhang, Zhenyu

    2010-01-01

    We present a novel way to account for partially coherent and incoherent interference phenomena in optical multilayer systems via the transfer-matrix method. The transfer matrix method is employed in its usual way via Fresnel coefficients in a 2x2 matrix configuration. The novel feature is that there is no need to use modified Fresnel coefficients or the square of their amplitudes to work in the incoherent limit. The transition from coherent, to partially coherent, to incoherent interference is achieved by introducing a random phase of increasing intensity in the propagating media. This random phase can simulate the effect of defects or impurities in the media. This method provides a general way of dealing with optical multilayer systems, in which coherent and incoherent interference are treated on equal footing.

  12. Nature of quantum states created by one photon absorption: pulsed coherent vs pulsed incoherent light.

    PubMed

    Han, Alex C; Shapiro, Moshe; Brumer, Paul

    2013-08-29

    We analyze electronically excited nuclear wave functions and their coherence when subjecting a molecule to the action of natural, pulsed incoherent solar-like light and to that of ultrashort coherent light assumed to have the same center frequencies and spectral bandwidths. Specifically, we compute the spatiotemporal dependence of the excited wave packets and their electronic coherence for these two types of light sources, on different electronic potential energy surfaces. The resultant excited state wave functions are shown to be dramatically different, reflecting the light source from which they originated. In addition, electronic coherence is found to decay significantly faster for incoherent light than for coherent ultrafast excitation, for both continuum and bound wave packets. These results confirm that the dynamics observed from ultrashort coherent excitation does not reflect what happens in processes induced by solar-like radiation, and conclusions drawn from one do not, in general, apply to the other. These results provide further support to the view that the dynamics observed in studies using ultrashort coherent pulses can be significantly different than those that would result from excitation with natural incoherent light. PMID:23879891

  13. Overview of Techniques Applicable to Self-Interference Incoherent Digital Holography

    NASA Astrophysics Data System (ADS)

    Hong, J.; Kim, M. K.

    2013-12-01

    Self-interference incoherent digital holography (SIDH) retrieves the complex hologram from the object illuminated by the incoherent light. Supported by the adaptive optic feature, SIDH is readily applicable to the ocular imaging to investigate the human retinal cells. Considering the practical issues, issues related to resolution, phase-shifting, and contrast should be addressed to implement the viable SIDH system which is capable of recording the holographic information of human retinal cells under the incoherent illumination. Super resolution image reconstruction technique can be directly applied to SIDH to enhance the resolution of the system without any change of configuration. We present the improved way to incorporate the phase-shifting itself into the lateral shift required by the super resolution technique. To deal with the phase-shifting issue, we present an arbitrary phase shift retrieval algorithm which can reduce the number of phase-shift and accept the blind phase-shift. The single-shot imaging is also possible by adopting the off-axis configuration of SIDH. We will provide the detailed procedures to retrieve the complex hologram using the proposed arbitrary phase shifting algorithm and the off-axis configuration.

  14. A comparison between using incoherent or coherent sources to align and test an adaptive optical telescope

    NASA Technical Reports Server (NTRS)

    Anderson, Richard

    1994-01-01

    The concept in the initial alignment of the segmented mirror adaptive optics telescope called the phased array mirror extendable large aperture telescope (Pamela) is to produce an optical transfer function (OTF) which closely approximates the diffraction limited value which would correspond to a system pupil function that is unity over the aperture and zero outside. There are differences in the theory of intensity measurements between coherent and incoherent radiation. As a result, some of the classical quantities which describe the performance of an optical system for incoherent radiation can not be defined for a coherent field. The most important quantity describing the quality of an optical system is the OTF and for a coherent source the OTF is not defined. Instead a coherent transfer function (CTF) is defined. The main conclusion of the paper is that an incoherent collimated source and not a collimated laser source is preferred to calibrate the Hartmann wavefront sensor (WFS) of an aligned adaptive optical system. A distant laser source can be used with minimum problems to correct the system for atmospheric turbulence. The collimation of the HeNe laser alignment source can be improved by using a very small pin hole in the spatial filter so only the central portion of the beam is transmitted and the beam from the filter is nearly constant in amplitude. The size of this pin hole will be limited by the sensitivity of the lateral effect diode (LEDD) elements.

  15. Pseudo-random Center Placement O-space Imaging for Improved Incoherence Compressed Sensing Parallel MRI

    PubMed Central

    Tam, Leo K.; Galiana, Gigi; Stockmann, Jason P.; Tagare, Hemant; Peters, Dana C.; Constable, R. Todd

    2014-01-01

    Purpose Nonlinear spatial encoding magnetic (SEM) field strategies such as O-space imaging have previously reported dispersed artifacts during accelerated scans. Compressed sensing (CS) has shown a sparsity-promoting convex program allows image reconstruction from a reduced data set when using the appropriate sampling. The development of a pseudo-random center placement (CP) O-space CS approach optimizes incoherence through SEM field modulation to reconstruct an image with reduced error. Theory and Methods The incoherence parameter determines the sparsity levels for which CS is valid and the related transform point spread function measures the maximum interference for a single point. The O-space acquisition is optimized for CS by perturbing the Z2 strength within 30% of the nominal value and demonstrated on a human 3T scanner. Results Pseudo-random CP O-space imaging is shown to improve incoherence between the sensing and sparse domains. Images indicate pseudo-random CP O-space has reduced mean squared error compared with a typical linear SEM field acquisition method. Conclusion Pseudo-random CP O-space imaging, with a nonlinear SEM field designed for CS, is shown to reduce mean squared error of images at high acceleration over linear encoding methods for a 2D slice when using an eight channel circumferential receiver array for parallel imaging. PMID:25042143

  16. Characteristics of ultraviolet scattering and turbulent channels.

    PubMed

    Wang, Peng; Xu, Zhengyuan

    2013-08-01

    The nonline of sight (NLOS) ultraviolet (UV) scattering communication channel and atmospheric optical turbulent channel have been extensively but independently studied in the rich literature. However, the new characteristics of NLOS UV scattering and turbulent channels have not been comprehensively investigated. We propose a configurable framework, unifying the traditional line of sight turbulence theory and the Monte Carlo simulation framework for random scattering of photons. Results show that the scattering link geometry can significantly alter the received signal distribution. Irradiance fluctuations at the receiver may become much weaker due to the smoothing effect of impinging photons from different scattering paths, even though each scattering path undergoes strong turbulence. PMID:23903138

  17. Scattering of electromagnetic waves from a half space of densely distributed dielectric scatterers

    NASA Technical Reports Server (NTRS)

    Tsang, L.; Kong, J. A.

    1983-01-01

    The scattering of a plane wave obliquely incident on a half space of densely distributed spherical dielectric scatterers is studied. The quasi-crystalline approximation is applied to truncate the hierarchy of multiple scattering equations, and the Percus-Yevick and the Verlet-Weis results are used to represent the pair distribution function. The coherent reflected wave is studied with these approximations. The incoherent scattered wave is calculated with the distorted Born approximation. In the low-frequency limit, closed-form expressions are obtained for the effective propagation constants, the coherent reflected wave, and the bistatic scattering coeficients. Results at higher frequencies are calculated numerically. The advantage of the present approach is that, in the low-frequency limit, it reproduces the effects of specular reflection, Fresnel reflection coefficient, Brewster angle, and Clausius-Mosotti relation. In addition to the classical results, the bistatic scattering coefficients are also calculated. The theory is also applied to match backscattering data from dry snow at microwave frequencies.

  18. The theory and measurement of noncoherent microwave scattering parameters. [for remote sensing of scenes via radar scatterometry

    NASA Technical Reports Server (NTRS)

    Claassen, J. P.; Fung, A. K.

    1977-01-01

    The radar equation for incoherent scenes is derived and scattering coefficients are introduced in a systematic way to account for the complete interaction between the incident wave and the random scene. Intensity (power) and correlation techniques similar to that for coherent targets are proposed to measure all the scattering parameters. The sensitivity of the intensity technique to various practical realizations of the antenna polarization requirements is evaluated by means of computer simulated measurements, conducted with a scattering characteristic similar to that of the sea. It was shown that for scenes satisfying reciprocity one must admit three new cross-correlation scattering coefficients in addition to the commonly measured autocorrelation coefficients.

  19. Spectrum bandwidth narrowing of Thomson scattering X-rays with energy chirped electron beams from laser wakefield acceleration

    SciTech Connect

    Xu, Tong; Chen, Min Li, Fei-Yu; Yu, Lu-Le; Sheng, Zheng-Ming; SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG ; Zhang, Jie; Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190

    2014-01-06

    We study incoherent Thomson scattering between an ultrashort laser pulse and an electron beam accelerated from a laser wakefield. The energy chirp effects of the accelerated electron beam on the final radiation spectrum bandwidth are investigated. It is found that the scattered X-ray radiation has the minimum spectrum width and highest intensity as electrons are accelerated up to around the dephasing point. Furthermore, it is proposed that the electron acceleration process inside the wakefield can be studied by use of 90° Thomson scattering. The dephasing position and beam energy chirp can be deduced from the intensity and bandwidth of the scattered radiation.

  20. Optimal Prediction by Cellular Signaling Networks

    NASA Astrophysics Data System (ADS)

    Becker, Nils B.; Mugler, Andrew; ten Wolde, Pieter Rein

    2015-12-01

    Living cells can enhance their fitness by anticipating environmental change. We study how accurately linear signaling networks in cells can predict future signals. We find that maximal predictive power results from a combination of input-noise suppression, linear extrapolation, and selective readout of correlated past signal values. Single-layer networks generate exponential response kernels, which suffice to predict Markovian signals optimally. Multilayer networks allow oscillatory kernels that can optimally predict non-Markovian signals. At low noise, these kernels exploit the signal derivative for extrapolation, while at high noise, they capitalize on signal values in the past that are strongly correlated with the future signal. We show how the common motifs of negative feedback and incoherent feed-forward can implement these optimal response functions. Simulations reveal that E. coli can reliably predict concentration changes for chemotaxis, and that the integration time of its response kernel arises from a trade-off between rapid response and noise suppression.

  1. Laser light scattering review

    NASA Technical Reports Server (NTRS)

    Schaetzel, Klaus

    1989-01-01

    Since the development of laser light sources and fast digital electronics for signal processing, the classical discipline of light scattering on liquid systems experienced a strong revival plus an enormous expansion, mainly due to new dynamic light scattering techniques. While a large number of liquid systems can be investigated, ranging from pure liquids to multicomponent microemulsions, this review is largely restricted to applications on Brownian particles, typically in the submicron range. Static light scattering, the careful recording of the angular dependence of scattered light, is a valuable tool for the analysis of particle size and shape, or of their spatial ordering due to mutual interactions. Dynamic techniques, most notably photon correlation spectroscopy, give direct access to particle motion. This may be Brownian motion, which allows the determination of particle size, or some collective motion, e.g., electrophoresis, which yields particle mobility data. Suitable optical systems as well as the necessary data processing schemes are presented in some detail. Special attention is devoted to topics of current interest, like correlation over very large lag time ranges or multiple scattering.

  2. Laser light scattering review

    NASA Astrophysics Data System (ADS)

    Schaetzel, Klaus

    1989-08-01

    Since the development of laser light sources and fast digital electronics for signal processing, the classical discipline of light scattering on liquid systems experienced a strong revival plus an enormous expansion, mainly due to new dynamic light scattering techniques. While a large number of liquid systems can be investigated, ranging from pure liquids to multicomponent microemulsions, this review is largely restricted to applications on Brownian particles, typically in the submicron range. Static light scattering, the careful recording of the angular dependence of scattered light, is a valuable tool for the analysis of particle size and shape, or of their spatial ordering due to mutual interactions. Dynamic techniques, most notably photon correlation spectroscopy, give direct access to particle motion. This may be Brownian motion, which allows the determination of particle size, or some collective motion, e.g., electrophoresis, which yields particle mobility data. Suitable optical systems as well as the necessary data processing schemes are presented in some detail. Special attention is devoted to topics of current interest, like correlation over very large lag time ranges or multiple scattering.

  3. Scattering of teleseismic waves in the lower crust Observations in the Massif Central, France

    NASA Astrophysics Data System (ADS)

    Ritter, Joachim R. R.; Martin Mai, P.; Stoll, Gerald; Fuchs, Karl

    1997-02-01

    High-frequency coda signals consistently recorded by a temporary seismic network of 29 short-period stations during a 6-month survey in the French Massif Central are concordant with independent evidence for a heterogeneous lower crust obtained from wide-angle and near-vertical reflection experiments in the same region. The teleseismic recordings of 22 events have been analysed in record sections rather than as single station seismograms. Following the low-frequency (LF; 0.5-1.5 Hz) first P-arrival a high-frequency (HF) coda (2-4 Hz dominant frequency) extends over several seconds duration. The HF signals become clearly visible after bandpass filtering, but can also be identified in the original seismograms. In event sections the HF coda forms a consistent pattern of reverberations which is characterized by the following properties: (1) the duration is typically longer on the radial (4-15 s) than on the vertical (3-11 s) component; (2) the beginning of the HF coda, referred to the picked LF first P-arrivals varies between 0-2.5 s, with a dominance around 1.5-2 s; (3) the amplitude of the HF coda is about 3%-10% of the primary LF P-phase amplitude; (4) the signals are incoherent between neighbouring stations and over the network; (5) the HF coda arrives dominantly around the plane of incidence of the teleseismic wave in the first 2 s to maximum 4 s; afterwards a widening of the particle motion to an elliptical shape is observed, indicating arrivals off the sagittal plane. The data parameters (1) to (5) point to the conclusion that the HF signals are generated by a scattering process. Wide-angle and CDP-reflection experiments in the same region measured a similar reverberating coda pattern and located the origin also in the lower crust. These observations and the data parameters of the HF coda suggest that the HF teleseismic waves are scattered at heterogeneities in the lower crust in the Massif Central. In this contribution we mainly concentrate on the presentation

  4. Hydration-dependent internal dynamics of reverse micelles: A quasielastic neutron scattering study

    NASA Astrophysics Data System (ADS)

    Freda, Mariangela; Onori, Giuseppe; Paciaroni, Alessandro; Santucci, Aldo

    2003-08-01

    We studied the overall atomic mobility of sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles in deuterated cyclohexane (C6D12) as a function of the molar ratio W=[D2O]/[AOT] with an incoherent quasielastic neutron scattering experiment at high energy resolution. For the almost anhydrous sample, the quasielastic broadening can be entirely attributed to the reverse micelle global motion, by considering explicitly both the rotational and the translational terms. As W increases above a threshold value W˜1 a wide quasielastic signal appears, which has been interpreted as the onset of a hydration-dependent intrinsic micelle dynamics. Such a contribution, which involves the AOT monomer hydrogen atoms, has a characteristic time of 0.2 ns. This result has been compared with previous dielectric measurements, which detected a relaxation process of the AOT fully hydrated head groups with the same characteristic time. The internal macromolecule mobility evaluated as a function of W numerically correlates with that of the mobile head groups, calculated by dielectric measurements. These findings suggest that both the hydrophobic and hydrophilic moieties dynamics is activated by the progressive hydration of the reverse micelle.

  5. Inelastic incoherent neutron scattering study of the molecular properties of pure hydrogen peroxide and its water mixtures of different concentration

    SciTech Connect

    Albers, Peter W.; Glenneberg, Jürgen; Refson, Keith; Parker, Stewart F.

    2014-04-28

    We have investigated the spectra of shock-frozen H{sub 2}O{sub 2}–H{sub 2}O mixtures across the full composition range 99.1%–0.0% H{sub 2}O{sub 2}. In contrast to literature reports, we find that intermediate compositions (30%–70% H{sub 2}O{sub 2}) freeze to a solid solution rather than phase separating, which only occurs on annealing to just below the melting point. We have fully characterised the dihydrate H{sub 2}O{sub 2}·2H{sub 2}O (48.6% H{sub 2}O{sub 2}) for the first time and shown that its spectrum can account for the features previously observed on the surface of a Au/TiO{sub 2} catalyst.

  6. Sensitivity Analysis of Meteor Smoke Size and Derived Daytime Temperature Structure derived from the Poker Flat Incoherent Scatter Radar (PFISR)

    NASA Astrophysics Data System (ADS)

    Abe, G.; Fentzke, J.; Hsu, V. W.; Brum, C. G.

    2012-12-01

    This work describes the microphysical properties and variability of meteoric smoke particles (MSPs) at high latitude using the Poker Flat ISR (65.1N, 147.5W). In addition, we present a novel technique for determining height resolved daytime D region neutral temperatures, which takes into account the presence of charged dust. We discuss the temporal/spatial variability and the relation to meteoric input observed and MSP microphysical properties in the polar mesopause region. The derived nanometer sized MSPs are consistent with size profiles derived previously using radar/rocket techniques and we note that our results imply a lack of heavy cluster ions below 85 km during the observing period. We examine the sensitivity of the derived sizes and temperatures to background atmospheric models and compare the results with available data sets. We find that he sizes in the range of approximately 0.5 to 1.5nm are in good general agreement with previous radar/rocket studies, but that the variability both temporally and with altitude are greater than at lower latitudes. The observed neutral temperatures are in the nominal range of 130 - 160 K between 70-90 km with several instances of larger departures up to 200 K indicating that wave activity may be present. This work provides a template for potential use at many other radar sites for the determination of microphysical properties of MSPs and day-time neutral temperature in the D region that show good general agreement with NRL-MSISE-00 temperatures during the observing period.

  7. The dynamic cusp at low altitudes: A case study combining Viking, DMSP, and Sondrestrom incoherent scatter radar observations

    SciTech Connect

    Watermann, J.; Delabeaujardiere, O.; Lummerzheim, D.; Woch, J.; Newell, P.T.; Potemra, T.A.; Rich, F.J.; Shapshak, M.

    1992-01-01

    A case study involving data from three satellites and a ground-based radar are presented. Focus is on a detailed discussion of observations of the dynamic cusp made on 24 Sep. 1986 in the dayside high-latitude ionosphere and interior magnetosphere. The relevant data from space-borne and ground-based sensors is presented. They include in-situ particle and field measurements from the DMSP-F7 and Viking spacecraft and Sondrestrom radar observations of the ionosphere. These data are augmented by observations of the IMF and the solar wind plasma. The observations are compared with predictions about the ionospheric response to the observed particle precipitation, obtained from an auroral model. It is shown that observations and model calculations fit well and provide a picture of the ionospheric footprint of the cusp in an invariant latitude versus local time frame. The combination of Viking, Sondrestrom radar, and IMP-8 data suggests that an ionospheric signature of the dynamic cusp was observed. Its spatial variation over time which appeared closely related to the southward component of the IMF was monitored.

  8. Inelastic incoherent neutron scattering study of the molecular properties of pure hydrogen peroxide and its water mixtures of different concentration.

    PubMed

    Albers, Peter W; Glenneberg, Jürgen; Refson, Keith; Parker, Stewart F

    2014-04-28

    We have investigated the spectra of shock-frozen H2O2-H2O mixtures across the full composition range 99.1%-0.0% H2O2. In contrast to literature reports, we find that intermediate compositions (30%-70% H2O2) freeze to a solid solution rather than phase separating, which only occurs on annealing to just below the melting point. We have fully characterised the dihydrate H2O2·2H2O (48.6% H2O2) for the first time and shown that its spectrum can account for the features previously observed on the surface of a Au/TiO2 catalyst. PMID:24784284

  9. Coherent scattering of electromagnetic waves by self-organized dust structures: Degree of coherence

    SciTech Connect

    Tsytovich, Vadim; Gusein-zade, Namik; Ignatov, Alexander

    2015-02-15

    It is demonstrated explicitly that the scattering of electromagnetic waves by dust structures can be strongly enhanced as compared to incoherent scattering by random electrons. If the size of the dust structure is much less than the wavelength of the incident radiation, the scattering is coherent. In this case, the scattering is proportional to the square of the total number of electrons in the structure. In the opposite limit, the scattering is incoherent being proportional to the total number of electrons in the structure. The factor describing the degree of coherency is calculated numerically for several models of self-organized structures. It is demonstrated in general way that for sudden heating of electrons, the factor of coherency in scattering by structures can decrease by several orders of magnitude with subsequent increase after the heating is switched off. In laboratory dusty plasmas, the coherent scattering is proposed for diagnostics of universal structuring instability and as a probe for determining the properties typical for self-organized nature of structures that are observed in recent experiments.

  10. Coherent scattering of electromagnetic waves by self-organized dust structures: Degree of coherence

    NASA Astrophysics Data System (ADS)

    Tsytovich, Vadim; Gusein-zade, Namik; Ignatov, Alexander

    2015-02-01

    It is demonstrated explicitly that the scattering of electromagnetic waves by dust structures can be strongly enhanced as compared to incoherent scattering by random electrons. If the size of the dust structure is much less than the wavelength of the incident radiation, the scattering is coherent. In this case, the scattering is proportional to the square of the total number of electrons in the structure. In the opposite limit, the scattering is incoherent being proportional to the total number of electrons in the structure. The factor describing the degree of coherency is calculated numerically for several models of self-organized structures. It is demonstrated in general way that for sudden heating of electrons, the factor of coherency in scattering by structures can decrease by several orders of magnitude with subsequent increase after the heating is switched off. In laboratory dusty plasmas, the coherent scattering is proposed for diagnostics of universal structuring instability and as a probe for determining the properties typical for self-organized nature of structures that are observed in recent experiments.

  11. Scattering of electromagnetic waves from a randomly perturbed quasiperiodic surface

    NASA Technical Reports Server (NTRS)

    Shin, R. T.; Kong, J. A.

    1984-01-01

    Electromagnetic-wave scattering by a quasi-periodic surface with random perturbations (as in the remote sensing of plowed fields) is investigated analytically, applying the Kirchhoff approximation and modeling the plowed fields by means of Gaussian random variation, sinusoidal variation, and Gaussian random variation about the spatial frequency. Coherent and incoherent bistatic scattering coefficients are derived in closed form by evaluating the physical-optics integral and shown to be proportional, in the geometric-optics limit, to the occurrence probability of slopes which reflect the incident wave specularly in the direction of the scattered wave. Backscattering cross sections are plotted as functions of incidence angle for a number of cases, demonstrating the strong effect of row direction.

  12. Anomalous vibrational modes in acetanilide as studied by inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Barthes, Mariette; Eckert, Juegen; Johnson, Susanna W.; Moret, Jacques; Swanson, Basil I.; Unkefer, Clifford J.

    1992-10-01

    A study of the anomalous modes in acetanilide and five deuterated derivatives by incoherent inelastic neutron scattering is reported. These data show that the dynamics of the amide and methyl groups influence each other. In addition, the anomalous temperature behaviour of the NH out-of-plane bending mode is confirmed. These observations suggest that the self-trapping mechanism in ACN may be more complex than hitherto assumed.

  13. A large area Thomson-scattering stellar X-ray polarimeter.

    NASA Technical Reports Server (NTRS)

    Novick, R.; Wolff, R. S.

    1971-01-01

    An instrument for measuring the polarization of stellar X-ray emission has been designed, constructed, and tested. The polarization dependence of incoherent Thomson scattering in lithium metal is utilized. Means for suppression of cosmic ray background effects have been provided. The apparatus has been flown in rockets to obtain data in the polarization of X-ray sources in Sco X-1 and Tau X-1.

  14. Scattering intensities for a white beam (120 kV) presenting a semi-empirical model to preview scattered beams

    NASA Astrophysics Data System (ADS)

    Gonçalves, O. D.; Boldt, S.; Kasch, K. U.

    2016-09-01

    This work aims at measuring the scattering cross sections for white beams and the verification of a semi-empirical model predicting scattered energy spectra of an X-ray beam produced by an industrial X-ray tube (Pantack Sievert, 120 kV, tungsten target) incident on a water sample. Both, theoretical and semi-empirical results presented are based on the form factor approach with results well corresponding to performed measurements. The elastic (Rayleigh) scattering cross sections are based on Thomson scattering with a form factor correction as published by Morin (1982). The inelastic (Compton) contribution is based on the Klein Nishina equation (Klein and Nishina, 1929) multiplied by the incoherent scattering factors calculated by Hubbel et al. (1975). Two major results are presented: first, the experimental integrated in energy cross sections corresponds with theoretical cross sections obtained at the mean energy of the measured scattered spectra at a given angle. Secondly, the measured scattered spectra at a given angle correspond to those obtained utilizing the semi-empirical model as proposed here. A good correspondence of experimental results and model predictions can be shown. The latter, therefore, proves to be a useful method to calculate the scattering contributions in a number of applications as for example cone beam tomography.

  15. Quantum Radiation Reaction Effects in Multiphoton Compton Scattering

    SciTech Connect

    Di Piazza, A.; Hatsagortsyan, K. Z.; Keitel, C. H.

    2010-11-26

    Radiation reaction effects in the interaction of an electron and a strong laser field are investigated in the realm of quantum electrodynamics. We identify the quantum radiation reaction with the multiple photon recoils experienced by the laser-driven electron due to consecutive incoherent photon emissions. After determining a quantum radiation dominated regime, we demonstrate how in this regime quantum signatures of the radiation reaction strongly affect multiphoton Compton scattering spectra and that they could be measurable in principle with presently available laser technology.

  16. Parametric instabilities of parallel propagating incoherent Alfven waves in a finite ion beta plasma

    SciTech Connect

    Nariyuki, Y.; Hada, T.; Tsubouchi, K.

    2007-12-15

    Large amplitude, low-frequency Alfven waves constitute one of the most essential elements of magnetohydrodynamic (MHD) turbulence in the fast solar wind. Due to small collisionless dissipation rates, the waves can propagate long distances and efficiently convey such macroscopic quantities as momentum, energy, and helicity. Since loading of such quantities is completed when the waves damp away, it is important to examine how the waves can dissipate in the solar wind. Among various possible dissipation processes of the Alfven waves, parametric instabilities have been believed to be important. In this paper, we numerically discuss the parametric instabilities of coherent/incoherent Alfven waves in a finite ion beta plasma using a one-dimensional hybrid (superparticle ions plus an electron massless fluid) simulation, in order to explain local production of sunward propagating Alfven waves, as suggested by Helios/Ulysses observation results. Parameter studies clarify the dependence of parametric instabilities of coherent/incoherent Alfven waves on the ion and electron beta ratio. Parametric instabilities of coherent Alfven waves in a finite ion beta plasma are vastly different from those in the cold ions (i.e., MHD and/or Hall-MHD systems), even if the collisionless damping of the Alfven waves are neglected. Further, ''nonlinearly driven'' modulational instability is important for the dissipation of incoherent Alfven waves in a finite ion beta plasma regardless of their polarization, since the ion kinetic effects let both the right-hand and left-hand polarized waves become unstable to the modulational instability. The present results suggest that, although the antisunward propagating dispersive Alfven waves are efficiently dissipated through the parametric instabilities in a finite ion beta plasma, these instabilities hardly produce the sunward propagating waves.

  17. Coherent-Incoherent Transition of ɛ-Carbide in Steels Found with Mechanical Spectroscopy

    NASA Astrophysics Data System (ADS)

    Shimotomai, Michio

    2016-03-01

    Although a coherent-incoherent transition in the ɛ-carbide precipitated in steels is supposedly linked to hardening and microstructural changes, the existence of this transition has not yet been confirmed. In this paper, we investigate this subject using mechanical spectroscopy. By measuring mechanical loss spectra below room temperature of quench-aged Fe-C alloys, mild steel, and pearlitic steel, we reveal a new broad peak (NBP). This peak is related to thermal activation, and its line shape obeys the equation of the Debye peak with a distribution in relaxation time. The Arrhenius plot yielded a large activation energy and gigantic pre-exponential factor. Its intensity grew by aging at temperatures where precipitation of ɛ-carbide has been reported. However, it starts to decay at duration far too early for ɛ-carbide to transform to cementite. For isothermal aging at 393 K (120 °C), the intensity sharply decreased at durations over 3 hours. This decay was accompanied by appearance of another similar peak (NBP'), which had a peak frequency two orders higher than that of NBP. These peaks had comparable intensity. We attribute NBP and NBP' to coherent and incoherent ɛ-carbides, respectively. We produced a model that attributes the relaxation peaks to reorientations of extra carbon pairs in the ɛ-carbide. The extraordinary values of the Arrhenius parameters may be interpreted by using this model. Based on these results, we assert that mechanical spectroscopy can detect the coherent-incoherent transition in carbon steels. This method will be powerful in studying problems related to the coherency in carbon steels.

  18. Incoherent holography

    NASA Astrophysics Data System (ADS)

    Abramson, Nils H.

    2000-10-01

    Dennis Gabor invented in-line holography in 1947, but at that time the coherent light from a laser did not yet exist and therefore the holograms he produced were of very low quality. When the laser was born in 1960 beautiful 3-D off- center holograms were for the first time produced by Emmett Leith and Juris Upatnieks. However, already as early as 1934 the inventor and artist Hans Weil patented a method to produce simple pictures that appeared floating in space, by scratching a transparent or metallic surface in certain directions. In 1995 William J. Beaty published a method for Hand-Drawn Holograms. Then it became possible for any artist to draw his own 3-D pictures of simple objects and using his ingenious techniques these hand drawn images will mimic many of the qualities of ordinary holograms.

  19. Sensing atmospheric reactive species using light emitting diode by incoherent broadband cavity enhanced absorption spectroscopy.

    PubMed

    Yi, Hongming; Wu, Tao; Wang, Guishi; Zhao, Weixiong; Fertein, Eric; Coeur, Cécile; Gao, Xiaoming; Zhang, Weijun; Chen, Weidong

    2016-05-16

    We overview our recent progress in the developments and applications of light emitting diode-based incoherent broadband cavity enhanced absorption spectroscopy (LED-IBBCEAS) techniques for real-time optical sensing chemically reactive atmospheric species (HONO, NO3, NO2) in intensive campaigns and in atmospheric simulation chamber. New application of optical monitoring of NO3 concentration-time profile for study of the NO3-initiated oxidation process of isoprene in a smog chamber is reported. PMID:27409951

  20. Optical implementation of the generalized Hough transform with totally incoherent light.

    PubMed

    Fernández, Ariel; Alonso, Julia R; Ayubi, Gastón A; Osorio, Matías; Ferrari, José A

    2015-08-15

    The generalized Hough transform is a well-established technique for detecting complex shapes in images containing noisy or missing data. We present an efficient optical implementation of this transform using an electrical lens with variable focal length and a rotating pupil mask matching the pattern to be found. The proposed setup works under fully (i.e., both spatially and temporally) incoherent illumination and can handle orientation changes or scale variations in the pattern. Validation experiments showing its real-time application are presented. PMID:26274689

  1. Coexistence of synchrony and incoherence in oscillatory media under nonlinear global coupling

    NASA Astrophysics Data System (ADS)

    Schmidt, Lennart; Schönleber, Konrad; Krischer, Katharina; García-Morales, Vladimir

    2014-03-01

    We report a novel mechanism for the formation of chimera states, a peculiar spatiotemporal pattern with coexisting synchronized and incoherent domains found in ensembles of identical oscillators. Considering Stuart-Landau oscillators, we demonstrate that a nonlinear global coupling can induce this symmetry breaking. We find chimera states also in a spatially extended system, a modified complex Ginzburg-Landau equation. This theoretical prediction is validated with an oscillatory electrochemical system, the electro-oxidation of silicon, where the spontaneous formation of chimeras is observed without any external feedback control.

  2. Conditional cooling limit for a quantum channel going through an incoherent environment

    PubMed Central

    Straka, Ivo; Miková, Martina; Mičuda, Michal; Dušek, Miloslav; Ježek, Miroslav; Filip, Radim

    2015-01-01

    We propose and experimentally verify a cooling limit for a quantum channel going through an incoherent environment. The environment consists of a large number of independent non-interacting and non-interfering elementary quantum systems – qubits. The qubits travelling through the channel can only be randomly replaced by environmental qubits. We investigate a conditional cooling limit that exploits an additional probing output. The limit specifies when the single-qubit channel is quantum, i.e. it preserves entanglement. It is a fundamental condition for entanglement-based quantum technology. PMID:26568362

  3. Coexistence of synchrony and incoherence in oscillatory media under nonlinear global coupling

    SciTech Connect

    Schmidt, Lennart; García-Morales, Vladimir; Schönleber, Konrad; Krischer, Katharina

    2014-03-15

    We report a novel mechanism for the formation of chimera states, a peculiar spatiotemporal pattern with coexisting synchronized and incoherent domains found in ensembles of identical oscillators. Considering Stuart-Landau oscillators, we demonstrate that a nonlinear global coupling can induce this symmetry breaking. We find chimera states also in a spatially extended system, a modified complex Ginzburg-Landau equation. This theoretical prediction is validated with an oscillatory electrochemical system, the electro-oxidation of silicon, where the spontaneous formation of chimeras is observed without any external feedback control.

  4. Quantum dynamics of incoherently driven V-type systems: Analytic solutions beyond the secular approximation.

    PubMed

    Dodin, Amro; Tscherbul, Timur V; Brumer, Paul

    2016-06-28

    Closed-form analytic solutions to non-secular Bloch-Redfield master equations for quantum dynamics of a V-type system driven by weak coupling to a thermal bath, relevant to light harvesting processes, are obtained and discussed. We focus on noise-induced Fano coherences among the excited states induced by incoherent driving of the V-system initially in the ground state. For suddenly turned-on incoherent driving, the time evolution of the coherences is determined by the damping parameter ζ=12(γ1+γ2)/Δp, where γi are the radiative decay rates of the excited levels i = 1, 2, and Δp=Δ(2)+(1-p(2))γ1γ2 depends on the excited-state level splitting Δ > 0 and the angle between the transition dipole moments in the energy basis. The coherences oscillate as a function of time in the underdamped limit (ζ ≫ 1), approach a long-lived quasi-steady state in the overdamped limit (ζ ≪ 1), and display an intermediate behavior at critical damping (ζ = 1). The sudden incoherent turn-on is shown to generate a mixture of excited eigenstates |e1〉 and |e2〉 and their in-phase coherent superposition |ϕ+〉=1r1+r2(r1|e1〉+r2|e2〉), which is remarkably long-lived in the overdamped limit (where r1 and r2 are the incoherent pumping rates). Formation of this coherent superposition enhances the decay rate from the excited states to the ground state. In the strongly asymmetric V-system where the coupling strengths between the ground state and the excited states differ significantly, additional asymptotic quasistationary coherences are identified, which arise due to slow equilibration of one of the excited states. Finally, we demonstrate that noise-induced Fano coherences are maximized with respect to populations when r1 = r2 and the transition dipole moments are fully aligned. PMID:27369498

  5. Quantum dynamics of incoherently driven V-type systems: Analytic solutions beyond the secular approximation

    NASA Astrophysics Data System (ADS)

    Dodin, Amro; Tscherbul, Timur V.; Brumer, Paul

    2016-06-01

    Closed-form analytic solutions to non-secular Bloch-Redfield master equations for quantum dynamics of a V-type system driven by weak coupling to a thermal bath, relevant to light harvesting processes, are obtained and discussed. We focus on noise-induced Fano coherences among the excited states induced by incoherent driving of the V-system initially in the ground state. For suddenly turned-on incoherent driving, the time evolution of the coherences is determined by the damping parameter ζ = /1 2 ( γ 1 + γ 2) / Δ p , where γi are the radiative decay rates of the excited levels i = 1, 2, and Δ p = √{ Δ 2 + ( 1 - p 2) γ 1 γ 2 } depends on the excited-state level splitting Δ > 0 and the angle between the transition dipole moments in the energy basis. The coherences oscillate as a function of time in the underdamped limit (ζ ≫ 1), approach a long-lived quasi-steady state in the overdamped limit (ζ ≪ 1), and display an intermediate behavior at critical damping (ζ = 1). The sudden incoherent turn-on is shown to generate a mixture of excited eigenstates |e1> and |e2> and their in-phase coherent superposition | ϕ + > = /1 √{ r 1 + r 2 } ( √{ r 1 } | e 1 > + √{ r 2 } | e 2 >) , which is remarkably long-lived in the overdamped limit (where r1 and r2 are the incoherent pumping rates). Formation of this coherent superposition enhances the decay rate from the excited states to the ground state. In the strongly asymmetric V-system where the coupling strengths between the ground state and the excited states differ significantly, additional asymptotic quasistationary coherences are identified, which arise due to slow equilibration of one of the excited states. Finally, we demonstrate that noise-induced Fano coherences are maximized with respect to populations when r1 = r2 and the transition dipole moments are fully aligned.

  6. Coherent and incoherent terahertz beams measured from a terahertz photoconductive antenna

    SciTech Connect

    Ho Wu, Dong; Graber, Benjamin; Kim, Christopher; Qadri, S. B.; Garzarella, Anthony

    2014-02-03

    We have systematically measured and analyzed the terahertz beams of a photoconductive antenna fabricated on a GaAs substrate. Our data indicate that the antenna produces both coherent and incoherent terahertz beams. The former is produced largely by the plasmon, and the latter is believed to be due to the black body radiation resulting from the thermal excitations and Joule heating by both the femto-second laser and the bias voltage, applied across the electrodes of the antenna. The terahertz-beam property is greatly affected by the operating condition of the photoconductive antenna.

  7. Transition from the incoherent to the coherent regime for propagative-wave based thermal radiation

    NASA Astrophysics Data System (ADS)

    Tsurimaki, Y.; Chapuis, P.-O.; Okajima, J.; Komiya, A.; Maruyama, S.; Vaillon, R.

    2016-01-01

    The transition from the incoherent to the coherent regime for thermal radiation between bodies trough a transparent medium is discussed. The canonical case of two parallel semi-infinite planar media is used as a basis to provide an insight into the physics and quantities ruling the distance at which coherent effects have an impact on the propagative component of the net heat flux exchanged. A practical criterion is proposed to define the distance below which radiation intensity framework should not be used, but instead fluctuational electrodynamics.

  8. Photon trajectories in incoherent atomic radiation trapping as Lévy flights.

    PubMed

    Pereira, Eduardo; Martinho, José M G; Berberan-Santos, Mário N

    2004-09-17

    Photon trajectories in incoherent radiation trapping for Doppler, Lorentz, and Voigt line shapes under complete frequency redistribution are shown to be Lévy flights. The jump length (r) distributions display characteristic long tails. For the Lorentz line shape, the asymptotic form is a strict power law r(-3/2), while for Doppler the asymptotic is r(-2)(ln(r)(-1/2). For the Voigt profile, the asymptotic form always has a Lorentz character, but the trajectory is a self-affine fractal with two characteristic Hausdorff scaling exponents. PMID:15447233

  9. Using an incoherent target return to adaptively focus through atmospheric turbulence.

    PubMed

    Nelson, W; Palastro, J P; Wu, C; Davis, C C

    2016-03-15

    A laser beam propagating to a remote target through atmospheric turbulence acquires intensity fluctuations. If the target is cooperative and provides a coherent return beam, the phase measured near the beam transmitter and adaptive optics, in principle, can correct these fluctuations. Generally, however, the target is uncooperative. In this case, we show that an incoherent return from the target can be used instead. Using the principle of reciprocity, we derive a novel relation between the field at the target and the returned field at a detector. We simulate an adaptive optics system that utilizes this relation to focus a beam through atmospheric turbulence onto a rough surface. PMID:26977694

  10. Coulomb blockade and incoherent tunneling of Cooper pairs in ultrasmall junctions affected by strong quantum fluctuations

    NASA Astrophysics Data System (ADS)

    Kuzmin, L. S.; Nazarov, Yu. V.; Haviland, D. B.; Delsing, P.; Claeson, T.

    1991-08-01

    We have fabricated and investigated submicron-size (0.01 and 0.04 μm2) Pb-alloy single Josephson junctions attached to high-resistance thin-film NiCr or Cr leads which provide the necessary conditions for a strong charging effect. When the Josephson coupling energy is less than the charging energy, we find a novel shape of the current-voltage curves, with a Coulomb gap at small voltages, and a current peak at larger voltages. A theory based on the concept of incoherent Cooper-pair tunneling has explained the data well.

  11. On the character of the coherent and incoherent excitations of electron-doped SrTiO3

    NASA Astrophysics Data System (ADS)

    Ishida, Yukiaki; Eguchi, Ritsuko; Matsunami, Masaharu; Horiba, Koji; Taguchi, Munetaka; Chainani, Ashishi; Senba, Yasunori; Ohashi, Haruhiko; Ohta, Hiromichi; Shin, Shik

    2007-03-01

    Lightly-electron-doped SrTiO3 shows little sign of electron correlation effects in the transport and thermodynamic properties, but photoemission spectra show not only coherent excitations from the Fermi level but also broad incoherent excitations positioned ˜1.5 eV below the Fermi level [1]. We have investigated the near-EF electronic structures of Nb-doped SrTiO3 thin film [2] by performing resonant photoemission at the Ti 2p and O 1s absorption edges. Both the coherent and incoherent excitations showed giant resonances at the Ti 2p edge, while at the O 1s edge, resonance occurred mainly in the incoherent excitations. This indicates that the coherent excitations have mainly Ti 3d character, while the incoherent excitations have mixed character of Ti 3d and O 2p states. We attribute the incoherent and coherent excitations to locally and non-locally screened final states, respectively, similar to that argued in Ca1-xSrxVO3 [3]. [1] A. Fujimori et al., Phys. Rev. B 46, 9841 (1992). [2] S. Ohta, H. Ohta et al., Appl. Phys. Lett. 87, 092108 (2006). [3] R.J.O. Mossanek, M. Abbate, and A. Fujimori, cond-mat/0606253.

  12. Scattering of radiation in collisionless dusty plasmas

    SciTech Connect

    Tolias, P.; Ratynskaia, S.

    2013-04-15

    Scattering of electromagnetic waves in collisionless dusty plasmas is studied in the framework of a multi-component kinetic model. The investigation focuses on the spectral distribution of the scattered radiation. Pronounced dust signatures are identified in the coherent spectrum due to scattering from the shielding cloud around the dust grains, dust acoustic waves, and dust-ion acoustic waves. The magnitude and shape of the scattered signal near these spectral regions are determined with the aid of analytical expressions and its dependence on the dust parameters is investigated. The use of radiation scattering as a potential diagnostic tool for dust detection is discussed.

  13. Change Detection Based on Persistent Scatterer Interferometry - a New Method of Monitoring Building Changes

    NASA Astrophysics Data System (ADS)

    Yang, C. H.; Kenduiywo, B. K.; Soergel, U.

    2016-06-01

    Persistent Scatterer Interferometry (PSI) is a technique to detect a network of extracted persistent scatterer (PS) points which feature temporal phase stability and strong radar signal throughout time-series of SAR images. The small surface deformations on such PS points are estimated. PSI particularly works well in monitoring human settlements because regular substructures of man-made objects give rise to large number of PS points. If such structures and/or substructures substantially alter or even vanish due to big change like construction, their PS points are discarded without additional explorations during standard PSI procedure. Such rejected points are called big change (BC) points. On the other hand, incoherent change detection (ICD) relies on local comparison of multi-temporal images (e.g. image difference, image ratio) to highlight scene modifications of larger size rather than detail level. However, image noise inevitably degrades ICD accuracy. We propose a change detection approach based on PSI to synergize benefits of PSI and ICD. PS points are extracted by PSI procedure. A local change index is introduced to quantify probability of a big change for each point. We propose an automatic thresholding method adopting change index to extract BC points along with a clue of the period they emerge. In the end, PS ad BC points are integrated into a change detection image. Our method is tested at a site located around north of Berlin main station where steady, demolished, and erected building substructures are successfully detected. The results are consistent with ground truth derived from time-series of aerial images provided by Google Earth. In addition, we apply our technique for traffic infrastructure, business district, and sports playground monitoring.

  14. Modern Techniques for Inelastic Thermal Neutron Scattering Analysis

    NASA Astrophysics Data System (ADS)

    Hawari, A. I.

    2014-04-01

    A predictive approach based on ab initio quantum mechanics and/or classical molecular dynamics simulations has been formulated to calculate the scattering law, S(κ⇀,ω), and the thermal neutron scattering cross sections of materials. In principle, these atomistic methods make it possible to generate the inelastic thermal neutron scattering cross sections of any material and to accurately reflect the physical conditions of the medium (i.e, temperature, pressure, etc.). In addition, the generated cross sections are free from assumptions such as the incoherent approximation of scattering theory and, in the case of solids, crystalline perfection. As a result, new and improved thermal neutron scattering data libraries have been generated for a variety of materials. Among these are materials used for reactor moderators and reflectors such as reactor-grade graphite and beryllium (including the coherent inelastic scattering component), silicon carbide, cold neutron media such as solid methane, and neutron beam filters such as sapphire and bismuth. Consequently, it is anticipated that the above approach will play a major role in providing the nuclear science and engineering community with its needs of thermal neutron scattering data especially when considering new materials where experimental information may be scarce or nonexistent.

  15. Coherent Scatter Imaging Measurements

    NASA Astrophysics Data System (ADS)

    Ur Rehman, Mahboob

    In conventional radiography, anatomical information of the patients can be obtained, distinguishing different tissue types, e.g. bone and soft tissue. However, it is difficult to obtain appreciable contrast between two different types of soft tissues. Instead, coherent x-ray scattering can be utilized to obtain images which can differentiate between normal and cancerous cells of breast. An x-ray system using a conventional source and simple slot apertures was tested. Materials with scatter signatures that mimic breast cancer were buried in layers of fat of increasing thickness and imaged. The result showed that the contrast and signal to noise ratio (SNR) remained high even with added fat layers and short scan times.

  16. Seamount acoustic scattering

    NASA Astrophysics Data System (ADS)

    Boehlert, George W.

    The cover of the March 1 issue of Eos showed a time series of acoustic scattering above Southeast Hancock Seamount (29°48‧N, 178°05‧E) on July 17-18, 1984. In a comment on that cover Martin Hovland (Eos, August 2, p. 760) argued that gas or “other far reaching causes” may be involved in the observed acoustic signals. He favors a hypothesis that acoustic scattering observed above a seeping pockmark in the North Sea is a combination of bubbles, stable microbubbles, and pelagic organisms and infers that this may be a more general phenomenon and indeed plays a role in the attraction of organisms to seamounts

  17. From coherent shocklets to giant collective incoherent shock waves in nonlocal turbulent flows

    PubMed Central

    Xu, G.; Vocke, D.; Faccio, D.; Garnier, J.; Roger, T.; Trillo, S.; Picozzi, A.

    2015-01-01

    Understanding turbulent flows arising from random dispersive waves that interact strongly through nonlinearities is a challenging issue in physics. Here we report the observation of a characteristic transition: strengthening the nonlocal character of the nonlinear response drives the system from a fully turbulent regime, featuring a sea of coherent small-scale dispersive shock waves (shocklets) towards the unexpected emergence of a giant collective incoherent shock wave. The front of such global incoherent shock carries most of the stochastic fluctuations and is responsible for a peculiar folding of the local spectrum. Nonlinear optics experiments performed in a solution of graphene nano-flakes clearly highlight this remarkable transition. Our observations shed new light on the role of long-range interactions in strongly nonlinear wave systems operating far from thermodynamic equilibrium, which reveals analogies with, for example, gravitational systems, and establishes a new scenario that can be common to many turbulent flows in photonic quantum fluids, hydrodynamics and Bose–Einstein condensates. PMID:26348292

  18. From coherent shocklets to giant collective incoherent shock waves in nonlocal turbulent flows.

    PubMed

    Xu, G; Vocke, D; Faccio, D; Garnier, J; Roger, T; Trillo, S; Picozzi, A

    2015-01-01

    Understanding turbulent flows arising from random dispersive waves that interact strongly through nonlinearities is a challenging issue in physics. Here we report the observation of a characteristic transition: strengthening the nonlocal character of the nonlinear response drives the system from a fully turbulent regime, featuring a sea of coherent small-scale dispersive shock waves (shocklets) towards the unexpected emergence of a giant collective incoherent shock wave. The front of such global incoherent shock carries most of the stochastic fluctuations and is responsible for a peculiar folding of the local spectrum. Nonlinear optics experiments performed in a solution of graphene nano-flakes clearly highlight this remarkable transition. Our observations shed new light on the role of long-range interactions in strongly nonlinear wave systems operating far from thermodynamic equilibrium, which reveals analogies with, for example, gravitational systems, and establishes a new scenario that can be common to many turbulent flows in photonic quantum fluids, hydrodynamics and Bose-Einstein condensates. PMID:26348292

  19. Artificial Incoherent Speckles Enable Precision Astrometry and Photometry in High-contrast Imaging

    NASA Astrophysics Data System (ADS)

    Jovanovic, N.; Guyon, O.; Martinache, F.; Pathak, P.; Hagelberg, J.; Kudo, T.

    2015-11-01

    State-of-the-art coronagraphs employed on extreme adaptive optics enabled instruments are constantly improving the contrast detection limit for companions at ever-closer separations from the host star. In order to constrain their properties and, ultimately, compositions, it is important to precisely determine orbital parameters and contrasts with respect to the stars they orbit. This can be difficult in the post-coronagraphic image plane, as by definition the central star has been occulted by the coronagraph. We demonstrate the flexibility of utilizing the deformable mirror in the adaptive optics system of the Subaru Coronagraphic Extreme Adaptive Optics system to generate a field of speckles for the purposes of calibration. Speckles can be placed up to 22.5 λ/D from the star, with any position angle, brightness, and abundance required. Most importantly, we show that a fast modulation of the added speckle phase, between 0 and π, during a long science integration renders these speckles effectively incoherent with the underlying halo. We quantitatively show for the first time that this incoherence, in turn, increases the robustness and stability of the adaptive speckles, which will improve the precision of astrometric and photometric calibration procedures. This technique will be valuable for high-contrast imaging observations with imagers and integral field spectrographs alike.

  20. Comparison of coherent and incoherent laser beam combination for tactical engagements

    NASA Astrophysics Data System (ADS)

    Van Zandt, Noah R.; Cusumano, Salvatore J.; Bartell, Richard J.; Basu, Santasri; McCrae, Jack E.; Fiorino, Steven T.

    2012-10-01

    The performance of a multibeam laser system is evaluated for coherent and incoherent beam combination under tactical scenarios. For direct comparison, identical aperture geometries are used for both, coherent or incoherent, combination methods. The analysis assumes a multilaser source coupled with a conventional 0.32 m diameter, on-axis, beam director. Parametric analysis includes variations over residual errors, beam quality, atmospheric effects, and scenario geometry. Analytical solutions from previous results are used to evaluate performance for the vacuum case, providing an upper bound on performance and a backdrop for organizing the multitude of effects as they are analyzed. Wave optics simulations are used for total system performance. Each laser in the array has a wavelength of 1.07 μm, 10 kW (25 kW) output power, and Gaussian exitance profile. Both tracking and full-aperture adaptive optics are modeled. Three tactical engagement geometries, air to surface, surface to air, and surface to surface, are evaluated for slant ranges from 2.5 to 10 km. Two near-median atmospheric profiles were selected based upon worldwide climatological data. The performance metric used is beam propagation efficiency for circular target diameters of 5 and 10 cm.