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Sample records for incoherent scatter signal

  1. The detection of the ionospheric irregularities by GNSS signal and the incoherent scatter radio measurements

    NASA Astrophysics Data System (ADS)

    Cherniak, Iurii; Shagimuratov, Irk; Krankowski, Andrzej; Sieradsky, Rafal; Zakharenkova, Irina; Rietveld, Michael; Kapcia, Jacek

    2013-04-01

    The high-latitude ionosphere has a very complicated structure and high dynamics. The ionospheric irregularities can produce scintillations of radio waves that occur predominantly in the ionosphere F-layer. The strong fluctuations can influence on the performance of the different space communication and navigation radio systems. The fluctuations of GPS/GLONASS signals are caused by the ionospheric irregularities with spatial dimensions more than 10 km. These structures can be detected by high potential incoherent scatter radars. It was proposed and carried out at the beginning of June 2012 experiment for a detailed study of the nature of the ionospheric irregularities, influencing on GPS/GLONASS signals parameters, by incoherent scatter and trans-ionospheric radio measurements simultaneously. The EISCAT facilities position provides the unique opportunity to study the ionospheric irregularities' parameters associated with TEC fluctuations and GPS/GLONASS signals scintillations. The EISCAT heating facility provides unique possibility to generate the artificial ionospheric irregularities and to estimate the impact factor of these irregularities on GPS/GLONASS signals transionospheric propagation. In order to detect the ionosphere irregularities it is used the IS radar measurements (electron density and plasma temperatures profiles) and simultaneously registered on EISCAT site amplitude and phase fluctuations in GPS/GLONASS signals by use of the Javad multi-constellation GPS/GLONASS receiver with high samples rate (100 Hz) and special scintillation GPS receiver PolaRxS PRO that dedicated to ionospheric monitoring and space weather applications and provides TEC and S4 scintillation index measurements. The low frequency fluctuations can be directly measured due to the electron density changes along the radio ray path between a GPS/GLONASS satellite and a ground-based receiver on EISCAT site. The raw data (under scintillating conditions) obtained by use of the high samples

  2. Incoherent Scatter Radar User Workshop

    NASA Astrophysics Data System (ADS)

    Richmond, A. D.

    1984-04-01

    The incoherent scatter radar technique has developed over the years into one of the most powerful tools for investigating physical processes in the upper atmosphere. The National Science Foundation (NSF) now supports a chain of four incoherent scatter facilities at Sondrestromfjord (Greenland), Millstone Hill (Massachusetts), Arecibo (Puerto Rico), and Jicamarca (PERU). Six European nations support the EISCAT facility in northern Scandinavia, and France also has a radar at St. Santin. Recently, the organizations reponsible for each of the six radars agreed to participate in a centralized data base being established at the National Center for Atmospheric Research (NCAR) to make their data more readily accessible to the scientific community at large.

  3. 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.

  4. Fiftieth Anniversary of the First Incoherent Scatter Radar Experiment

    NASA Astrophysics Data System (ADS)

    Robinson, Robert M.; van Eyken, Anthony; Farley, Donald

    2009-08-01

    In the 11 November 2008 issue of Eos (89(46), 458), Henry Rishbeth asked whether the years 2008-2010 feature any important anniversaries in solar-terrestrial physics other than those he mentioned. One such milestone is the fiftieth anniversary of the first incoherent scatter radar (ISR) experiment. At a Cornell University (Ithaca, N. Y.) departmental seminar in the spring of 1958, William Gordon showed that a powerful radar system could detect the uncorrelated and extremely weak scattered signals from individual ionospheric electrons. This process is called incoherent scatter, and studying the properties of the resulting radar echoes can reveal information about the density, temperature, and velocity of ionospheric particles. Gordon discussed this idea with Ken Bowles, a recent Ph.D. graduate of Cornell, and in a few weeks Bowles built a large but inexpensive antenna array that he connected to an existing transmitter near Havana, Ill. Using this crude radar (the data processing consisted of taking a time exposure photograph of the signal amplitude displayed on an oscilloscope), Bowles successfully measured an incoherently scattered signal on 21 October 1958. By a happy coincidence, 21 October was also the day that Gordon gave his first formal talk on the ISR concept at an International Union of Radio Science (URSI) conference at Pennsylvania State University. After calling Bowles for an update on his experiment, Gordon presented his research and added the dramatic and newsworthy note to the end of his talk on the success of the first ISR experiment!

  5. 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.

  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. Incoherent Neutron Scattering Measurements of Hydrogen-Charged Zircaloy-4

    SciTech Connect

    Garlea, Elena; Choo, Hahn; Garlea, Vasile O; Liaw, Peter K; Hubbard, Camden R

    2007-01-01

    Qualitative and quantitative phase measurements were conducted on Zircaloy-4 round bars using neutron scattering techniques. The mapping through the thickness of the specimens using neutron diffraction showed the presence of the face-centered-cubic delta zirconium hydride ({delta}-ZrH{sub 2}) phase on the surface. To determine the relative amount of hydrogen in the Zircaloy-4 samples, the increase of the incoherent scattering with the hydrogen content was calibrated using standard samples for which the hydrogen content was known.

  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. Identification of scintillation signatures on GPS signals originating from plasma structures detected with EISCAT incoherent scatter radar along the same line of sight

    NASA Astrophysics Data System (ADS)

    Forte, Biagio; Coleman, Chris; Skone, Susan; Häggström, Ingemar; Mitchell, Cathryn; Da Dalt, Federico; Panicciari, Tommaso; Kinrade, Joe; Bust, Gary

    2017-01-01

    Ionospheric scintillation originates from the scattering of electromagnetic waves through spatial gradients in the plasma density distribution, drifting across a given propagation direction. Ionospheric scintillation represents a disruptive manifestation of adverse space weather conditions through degradation of the reliability and continuity of satellite telecommunication and navigation systems and services (e.g., European Geostationary Navigation Overlay Service, EGNOS). The purpose of the experiment presented here was to determine the contribution of auroral ionization structures to GPS scintillation. European Incoherent Scatter (EISCAT) measurements were obtained along the same line of sight of a given GPS satellite observed from Tromso and followed by means of the EISCAT UHF radar to causally identify plasma structures that give rise to scintillation on the co-aligned GPS radio link. Large-scale structures associated with the poleward edge of the ionospheric trough, with auroral arcs in the nightside auroral oval and with particle precipitation at the onset of a substorm were indeed identified as responsible for enhanced phase scintillation at L band. For the first time it was observed that the observed large-scale structures did not cascade into smaller-scale structures, leading to enhanced phase scintillation without amplitude scintillation. More measurements and theory are necessary to understand the mechanism responsible for the inhibition of large-scale to small-scale energy cascade and to reproduce the observations. This aspect is fundamental to model the scattering of radio waves propagating through these ionization structures. New insights from this experiment allow a better characterization of the impact that space weather can have on satellite telecommunications and navigation services.

  12. Identification of scintillation signatures on GPS signals originating from plasma structures detected with EISCAT incoherent scatter radar along the same line of sight

    PubMed Central

    Coleman, Chris; Skone, Susan; Häggström, Ingemar; Mitchell, Cathryn; Da Dalt, Federico; Panicciari, Tommaso; Kinrade, Joe; Bust, Gary

    2017-01-01

    Abstract Ionospheric scintillation originates from the scattering of electromagnetic waves through spatial gradients in the plasma density distribution, drifting across a given propagation direction. Ionospheric scintillation represents a disruptive manifestation of adverse space weather conditions through degradation of the reliability and continuity of satellite telecommunication and navigation systems and services (e.g., European Geostationary Navigation Overlay Service, EGNOS). The purpose of the experiment presented here was to determine the contribution of auroral ionization structures to GPS scintillation. European Incoherent Scatter (EISCAT) measurements were obtained along the same line of sight of a given GPS satellite observed from Tromso and followed by means of the EISCAT UHF radar to causally identify plasma structures that give rise to scintillation on the co‐aligned GPS radio link. Large‐scale structures associated with the poleward edge of the ionospheric trough, with auroral arcs in the nightside auroral oval and with particle precipitation at the onset of a substorm were indeed identified as responsible for enhanced phase scintillation at L band. For the first time it was observed that the observed large‐scale structures did not cascade into smaller‐scale structures, leading to enhanced phase scintillation without amplitude scintillation. More measurements and theory are necessary to understand the mechanism responsible for the inhibition of large‐scale to small‐scale energy cascade and to reproduce the observations. This aspect is fundamental to model the scattering of radio waves propagating through these ionization structures. New insights from this experiment allow a better characterization of the impact that space weather can have on satellite telecommunications and navigation services. PMID:28331778

  13. Identification of scintillation signatures on GPS signals originating from plasma structures detected with EISCAT incoherent scatter radar along the same line of sight.

    PubMed

    Forte, Biagio; Coleman, Chris; Skone, Susan; Häggström, Ingemar; Mitchell, Cathryn; Da Dalt, Federico; Panicciari, Tommaso; Kinrade, Joe; Bust, Gary

    2017-01-01

    Ionospheric scintillation originates from the scattering of electromagnetic waves through spatial gradients in the plasma density distribution, drifting across a given propagation direction. Ionospheric scintillation represents a disruptive manifestation of adverse space weather conditions through degradation of the reliability and continuity of satellite telecommunication and navigation systems and services (e.g., European Geostationary Navigation Overlay Service, EGNOS). The purpose of the experiment presented here was to determine the contribution of auroral ionization structures to GPS scintillation. European Incoherent Scatter (EISCAT) measurements were obtained along the same line of sight of a given GPS satellite observed from Tromso and followed by means of the EISCAT UHF radar to causally identify plasma structures that give rise to scintillation on the co-aligned GPS radio link. Large-scale structures associated with the poleward edge of the ionospheric trough, with auroral arcs in the nightside auroral oval and with particle precipitation at the onset of a substorm were indeed identified as responsible for enhanced phase scintillation at L band. For the first time it was observed that the observed large-scale structures did not cascade into smaller-scale structures, leading to enhanced phase scintillation without amplitude scintillation. More measurements and theory are necessary to understand the mechanism responsible for the inhibition of large-scale to small-scale energy cascade and to reproduce the observations. This aspect is fundamental to model the scattering of radio waves propagating through these ionization structures. New insights from this experiment allow a better characterization of the impact that space weather can have on satellite telecommunications and navigation services.

  14. Neutron Incoherent Scattering Measurements on Hydrogen-Charged Zircaloy-4

    SciTech Connect

    Garlea, Elena; Garlea, Vasile O; Choo, Hahn; Hubbard, Camden R; Liaw, Peter K

    2006-01-01

    Neutron incoherent scattering measurements were conducted on Zircaloy-4 round bars. The specimens were charged in a tube furnace at 430 C, using a 12.5 vol. % hydrogen in an argon mixture for 30, 60, and 90 minutes at 13.8 kPa pressure. The volume-average neutron diffraction measurements showed the presence of the face-centered-cubic delta zirconium hydride ({delta}.ZrH{sub 2}) phase in the hydrogenated specimens. The assessment of the background in the diffraction profiles due to the incoherent scattering from the hydrogen atoms was carried out by performing inelastic scans around zero energy transfer and at a fixed two-theta value for which there was only flat background and no coherent scattering. To estimate the relative amount of hydrogen in the Zircaloy-4 samples, the increase in incoherent scattering intensities with hydrogen content was calibrated using samples for which the hydrogen content was known. Measurement of the background scattering from locations within the round bar was also performed to map the distribution of hydrogen content.

  15. Plasma parameter estimation from multistatic, multibeam incoherent scatter data

    NASA Astrophysics Data System (ADS)

    Virtanen, I. I.; McKay-Bukowski, D.; Vierinen, J.; Aikio, A.; Fallows, R.; Roininen, L.

    2014-12-01

    Multistatic incoherent scatter radars are superior to monostatic facilities in the sense that multistatic systems can measure plasma parameters from multiple directions in volumes limited by beam dimensions and measurement range resolution. We propose a new incoherent scatter analysis technique that uses data from all receiver beams of a multistatic, multibeam radar system and produces, in addition to the plasma parameters typically measured with monostatic radars, estimates of ion velocity vectors and ion temperature anisotropies. Because the total scattered energy collected with remote receivers of a modern multistatic, multibeam radar system may even exceed the energy collected with the core transmit-and-receive site, the remote data improve the accuracy of all plasma parameter estimates, including those that could be measured with the core site alone. We apply the new multistatic analysis method for data measured by the tristatic European Incoherent Scatter VHF radar and the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) multibeam receiver and show that a significant improvement in accuracy is obtained by adding KAIRA data in the multistatic analysis. We also demonstrate the development of a pronounced ion temperature anisotropy during high-speed ionospheric plasma flows in substorm conditions.

  16. The estimation of space debris distribution by Kharkiv incoherent scatter radar data

    NASA Astrophysics Data System (ADS)

    Cherniak, Iurii

    Currently in near space are a large number of artificial origin objects. Among them are operable spacecrafts and the so-called "space debris". The Kharkiv radar is a sole incoherent scatter instrument on the middle latitudes of European region. The radar located near Kharkiv, Ukraine (geographic coordinates: 49.6N, 36.3E, geomagnetic coordinates: 45.7N, 117.8E). This powerful radar facility operates with 100-m zenith parabolic antenna at 158 MHz with peak transmitted power 2.0 MW, and can registered scattering of electromagnetic waves from small volumes (about ten square centimeters at distance 500 km). During the ionosphere parameters measurement by incoherent scatter radar are received different radar signals, different by nature from the signal, incoherent scattered ionosphere plasma. The paper presents the results of data analysis of several measurements cycles. It was obtained the distribution characteristics of the radar reflections from objects on Earth orbit. There are two main peak reflections appearance intensity at distances 800 km and 1000 km. Two other peaks at the altitude of 600 km and 1400 km. It is from distance above 1700 km the number of reflections is insignificant. Based on the experimental data was constructed height-temporal distribution of reflection signals. The total analysis time was about 200 hours. The intensity of reflections and their peak distances not significantly changed during day. The average number of observed reflections per day was about 500.

  17. 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.

  18. The ionosphere disturbances observation on the Kharkiv incoherent scatter radar

    NASA Astrophysics Data System (ADS)

    Cherniak, Iu.; Lysenko, V.

    2009-04-01

    he ionosphere plasma characteristics are responding on variations of solar and magnetic activity. The research of an ionosphere structure and dynamics is important as for understanding physics of processes and for radiophysical problems solution. The method incoherent scatter (IS) of radio waves allows determining experimentally both regular variations of the basic parameters ionosphere, and their behavior during perturbation. The equipment and measurement technique, developed by authors, are allows obtaining certain data about behavior of an ionosphere during various origin and intensity ionosphere perturbations. The Institute of Ionsphere IS radar located near Kharkiv, Ukraine (geographic coordinates: 49.6oN, 36.3oE, geomagnetic coordinates: 45.7oN, 117.8oE) was used to observe the processes in the ionosphere. The radar is operate with 100-m zenith parabolic antenna at 158 MHz with peak transmitted power of ~2.0 MW. The double-frequency measuring channel mode with compound sounding signal was employed for experiments. That provided ~ 20-km resolution in range ~100-400 km and ~100-km in range ~200-1100 km. Over a period of series of experiment are obtained data about variations of electron density simultaneous in the heights interval 100-1000 km, including three sun eclipses, two superstrong and a few moderate magnetic storms, as well as disturbance, is caused by powerful rockets starts. During strong geomagnetic storm on November 8-12, 2004 was observed night time increasing of electronic temperature up to 3000 Љ and ions temperature up to 2000K. Usually at this time temperature of ions is equal to temperature of electrons. During negative ionosphere storm was observed decreasing of electronic density at maximum F2 layer. The height of a F2 layer maximum was increased by 150 km and 70 km at daytime. The interesting phenomenon - high-power backscatter signal coherent backscatter was observed first time during geogeomagnetic storm 29-30 may 2003. A usually

  19. First operations of the RISR-C incoherent scatter radar

    NASA Astrophysics Data System (ADS)

    Gillies, R. G.; Van Eyken, A. P.; Spanswick, E.; Nicolls, M. J.; Kelly, J. D.; Greffen, M. J.; Knudsen, D. J.; Connors, M. G.; Schutzer, M.; Valentic, T. A.; Malone, M.; St-Maurice, J. P.; Donovan, E.

    2015-12-01

    The Canadian face of the Resolute Bay Incoherent Scatter Radar (RISR-C), the newest Advanced Modular Incoherent Scatter Radar (AMISR), recently began routine operations and has been taking detailed measurements of the polar cap ionosphere. Like other AMISR radars, RISR-C has the ability to use electronic beam steering to simultaneously sample ionospheric plasma parameters in several different line-of-sight directions (over 4000 possible beam directions, of which, typically 10-50 are used in a given experiment). Electron density, electron and ion temperatures, and line-of-sight (LOS) plasma velocities are measured along these beam directions at several ranges in (typically) 1-minute intervals. Combining LOS velocity measurements from several different beam directions allows full 3-d ionospheric plasma velocities to be resolved within the field-of-view of the radar. Ionospheric measurements from the southward facing RISR-C are complemented by measurements by the co-located northward facing RISR-N radar operated by SRI International and the REGO redline optical camera operated by the University of Calgary. Initial comparisons between these instruments demonstrate that RISR-C is operating well and will provide vital new measurements of the polar cap ionosphere.

  20. Coherent Raman scattering with incoherent light for a multiply resonant mixture: Theory

    NASA Astrophysics Data System (ADS)

    Kirkwood, Jason C.; Ulness, Darin J.; Stimson, Michael J.; Albrecht, A. C.

    1998-02-01

    The theory for coherent Raman scattering (CRS) with broadband incoherent light is presented for a multiply resonant, multicomponent mixture of molecules that exhibits simultaneous multiple resonances with the frequencies of the driving fields. All possible pairwise hyperpolarizability contributions to the signal intensity are included in the theoretical treatment-(resonant-resonant, resonant-nonresonant, and nonresonant-nonresonant correlations between chromophores) and it is shown how the different types of correlations manifest themselves as differently behaved components of the signal intensity. The Raman resonances are modeled as Lorentzians in the frequency domain, as is the spectral density of the incoherent light. The analytic results for this multiply resonant mixture are presented and applied to a specific binary mixture. These analytic results will be used to recover frequencies and dephasing times in a series of experiments on multiply resonant mixtures.

  1. 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.

  2. 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.

  3. Incoherent scattering can favorably influence energy filtering in nanostructured thermoelectrics.

    PubMed

    Singha, Aniket; Muralidharan, Bhaskaran

    2017-08-11

    Investigating in detail the physics of energy filtering through a single planar energy barrier in nanostructured thermoelectric generators, we reinforce the non-trivial result that the anticipated enhancement in generated power at a given efficiency via energy filtering is a characteristic of systems dominated by incoherent scattering and is absent in ballistic devices. In such cases, assuming an energy dependent relaxation time τ(E) = kE (r) , we show that there exists a minimum value r min beyond which generation can be enhanced by embedding nanobarriers. For bulk generators with embedded nanobarriers, we delve into the details of inter sub-band scattering and show that it has finite contribution to the enhancement in generation. We subsequently discuss the realistic aspects, such as the effect of smooth transmission cut-off and show that for r > r min , the optimized energy barrier is just sufficiently wide enough to scatter off low energy electrons, a very wide barrier being detrimental to the performance. Analysis of the obtained results should provide general design guidelines for enhancement in thermoelectric generation via energy filtering. Our non-equilibrium approach is typically valid in the absence of local quasi-equilibrium and hence sets the stage for future advancements in thermoelectric device analysis, for example, Peltier cooling near a barrier interface.

  4. First observations from the RISR-C incoherent scatter radar

    NASA Astrophysics Data System (ADS)

    Gillies, R. G.; Eyken, A.; Spanswick, E.; Nicolls, M.; Kelly, J.; Greffen, M.; Knudsen, D.; Connors, M.; Schutzer, M.; Valentic, T.; Malone, M.; Buonocore, J.; St.-Maurice, J.-P.; Donovan, E.

    2016-10-01

    First-light measurements from the Canadian face of the Resolute Bay Incoherent Scatter Radar (RISR-C) were taken in August of 2015. Data were taken for roughly 25 h on both RISR-C and the North face of the Resolute Bay radar (RISR-N) in an 11-beam World Day mode. Overall, the measurements from the RISR-C radar are of high quality and consistent with results from the RISR-N radar. During the 25 h period analyzed in this study, the ionosphere responded to changes in orientation of the interplanetary magnetic field . During one particular event, a change from Bz negative to positive and By positive to negative caused the antisunward flow to stall, and a strong dawn-to-dusk flow, with decreased electron density and increased ion temperature, replaced it in the RISR-C field of view. Overall, it is clear that measurements from the RISR-C radar will complement and greatly expand the scope of ionospheric polar cap measurements.

  5. Comparison between microwave coherent and incoherent scattering models for wetland vegetation in Poyang Lake area

    NASA Astrophysics Data System (ADS)

    Xu, Tao; Liao, Jingjuan

    2014-11-01

    In order to reveal more deeply the scattering characteristics of wetland vegetation and determine the microwave scattering model suitable for the inversion of wetland vegetation parameters, the comparison and analysis between microwave coherent and incoherent scattering models for wetland vegetation in Poyang Lake area were performed in this paper. In the research, we proposed a coherent scattering model exclusive for wetland vegetation, in which, Generalized Rayleigh-Gans (GRG) approach and infinite-length dielectric cylinder were used to calculate single-scattering matrices of wetland vegetation leaves and stalks. In addition, coherent components produced from interaction among the scattering mechanisms and different scatterers were also considered and this coherent model was compared with Michigan Microwave Canopy Scattering (MIMICS) model. The measured data collected in 2011 in Poyang Lake wetland were used as the input parameters of the coherent and incoherent models. We simulated backscattering coefficients of VV, VH and HH polarization at C band and made a comparison between the simulation results and C-band data from the Radarsat-2 satellite. For both coherent and incoherent scattering model, simulation results for HH and VV polarization were better than the simulation results for HV polarization. In addition, comparisons between coherent and incoherent scattering models proved that the coherence triggered by the scattering mechanism and different scatterers can't be ignored. In the research, we analyzed differences between coherent and incoherent scattering models with change of incident angle. In most instances, the difference between coherent and incoherent scattering models is of the order of several dB.

  6. Effective subtraction technique at the Irkutsk Incoherent Scatter Radar: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Berngardt, Oleg I.; Kushnarev, Dmitrii S.

    2013-12-01

    We describe a sounding technique that allows us to improve spatial resolution at the Irkutsk Incoherent Scatter Radar (IISR) without losing spectral resolution. The technique also allows us to decrease temperature estimation errors caused by the Faraday effect. The technique is based on transmitting various duration pulses without any modulation and on subtracting correlation matrices of the received signal grouped by sounding pulse duration. We show theoretically and experimentally that the technique allows us to solve the problem of improving spatial resolution. Accumulation time for the technique is approximately four times longer than that for the alternating codes technique with the same spatial resolution. The number of lags in the correlation function with high spatial resolution does not depend on necessary spatial resolution. In the proposed technique, all the lags are obtained with the same spatial resolution and with the same signal-to-noise ratio. The technique is valid within the quasi-static ionospheric parameter approximation.

  7. 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

  8. Impact of anisotropic atomic motions in proteins on powder-averaged incoherent neutron scattering intensities

    SciTech Connect

    Kneller, Gerald R.; Chevrot, Guillaume

    2012-12-14

    This paper addresses the question to which extent anisotropic atomic motions in proteins impact angular-averaged incoherent neutron scattering intensities, which are typically recorded for powder samples. For this purpose, the relevant correlation functions are represented as multipole series in which each term corresponds to a different degree of intrinsic motional anisotropy. The approach is illustrated by a simple analytical model and by a simulation-based example for lysozyme, considering in both cases the elastic incoherent structure factor. The second example shows that the motional anisotropy of the protein atoms is considerable and contributes significantly to the scattering intensity.

  9. Impact of anisotropic atomic motions in proteins on powder-averaged incoherent neutron scattering intensities

    NASA Astrophysics Data System (ADS)

    Kneller, Gerald R.; Chevrot, Guillaume

    2012-12-01

    This paper addresses the question to which extent anisotropic atomic motions in proteins impact angular-averaged incoherent neutron scattering intensities, which are typically recorded for powder samples. For this purpose, the relevant correlation functions are represented as multipole series in which each term corresponds to a different degree of intrinsic motional anisotropy. The approach is illustrated by a simple analytical model and by a simulation-based example for lysozyme, considering in both cases the elastic incoherent structure factor. The second example shows that the motional anisotropy of the protein atoms is considerable and contributes significantly to the scattering intensity.

  10. 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.

  11. 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.

  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. 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.

  14. 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

  15. Energy resolution and dynamical heterogeneity effects on elastic incoherent neutron scattering from molecular systems.

    PubMed

    Becker, Torsten; Smith, Jeremy C

    2003-02-01

    Incoherent neutron scattering is widely used to probe picosecond-nanosecond time scale dynamics of molecular systems. In systems of spatially confined atoms the relatively high intensity of elastic incoherent neutron scattering is often used to obtain a first estimate of the dynamics present. For many complex systems, however, experimental elastic scattering is difficult to interpret unambiguously using analytical dynamical models that go beyond the determination of an average mean-square displacement. To circumvent this problem a description of the scattering is derived here that encompasses a variety of analytical models in a common framework. The framework describes the time-converged part of the dynamic structure factor [the elastic incoherent scattering function (EISF)] and lends itself to practical use by explicitly incorporating effects due to the finite energy resolution of the instrument used. The dependence of the elastic scattering on wave vector is examined, and it is shown how heterogeneity in the distribution of mean-square displacements can be related to deviations of the scattering from Gaussian behavior. In this case, a correction to fourth order in the scattering vector can be used to extract the variance of the distribution of mean-square displacements. The formalism is used in a discussion of measurements on dynamics accompanying the glass transition in molecular systems. By fitting to experimental data obtained on a protein solution the present methodology is used to show how the existence of a temperature-dependent relaxation frequency can lead to a transition in the measured mean-square displacement in the absence of an EISF change.

  16. Incoherent scattering of gamma photons for non-destructive tomographic inspection of pipeline.

    PubMed

    Sharma, Amandeep; Sandhu, B S; Singh, Bhajan

    2010-12-01

    A scanner system, operating in a non-destructive and non-invasive way, is presented for pipeline to determine its location in land soil, wall thickness, type of liquid flowing and crack/blockage position. The present experiment simulates a real case where pipe corrosion (wall thinning) under insulation can be known from the study of incoherent scattering of 662 keV gamma photons. The incoherent scattered intensity, obtained by unfolding (deconvolution) the experimental pulse-height distribution of NaI(Tl) scintillation detector with the help of inverse response matrix, provides the desired information. The method is quite sensitive for small change (approximately 1 mm) in the thickness of pipe wall, locating a defect of 1mm width under insulation and a small change (approximately 0.1 gm cm(-3)) in the density of liquid flowing through pipe. Copyright 2010 Elsevier Ltd. All rights reserved.

  17. E- and F- region incoherent scatter radar spectral measurements at mid and low-latitudes

    NASA Astrophysics Data System (ADS)

    Kudeki, Erhan; Milla, Marco

    2016-07-01

    In this talk we will contrast and compare incoherent scatter radar spectral measurements conducted using the Arecibo, ALTAIR, and Jicamarca incoherent scatter radars at ionospheric heights ranging from E-region into the topside F-region. Arecibo measurements from mid-latitudes exemplify high SNR ISR techniques utilized with large magnetic aspect angles. Low-latitude measurements at ALTAIR and Jicamarca make use of and combine large and small magnetic aspect angle techniques. Examples presented will include both natural and naturally enhanced electron and ion lines detected in the lower F region near the geomagnetic equator as well as the results of search for proton gyro-resonance peaks in the Jicamarca topside spectra.

  18. D-region incoherent scatter spectra: Discrepancies between observations and current theory

    NASA Astrophysics Data System (ADS)

    Hoppe, Ulf-Peter; Hansen, Georg; Turunen, Esa; Pollari, Paivio

    Extended D region observations were performed with the EISCAT UHF radar during the Aug. 1989 PCA (Polar Cap Absorption) event. The excellent quality of this data, together with temperature measurements by lidar about 130 km from Tromso (Norway) makes it possible to compare the observed incoherent scatter spectra with current theory. The discrepancy found, (also in data collected before the PCA event), leads to examination of other published observed D region spectral measurements. In the absence of temperature or density observations together with these earlier measurements, the new CIRA 86 model is used. The spectra of incoherent scatter from the D region are generally found to be narrower than current theory predicts, independent of radar frequency, latitude, or season. Some possible reasons for this discrepancy are discussed.

  19. 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-->

  20. Confined dynamics in poly(ethylene terephthalate): a coherent and incoherent neutron scattering study

    NASA Astrophysics Data System (ADS)

    Sanz, Alejandro; Nogales, Aurora; Puente-Orench, Inés; García-Gutiérrez, Mari-Cruz; Campo, Javier; Haussler, Wolfgang; Soccio, Michelina; Lotti, Nadia; Munari, Andrea; Ezquerra, Tiberio A.

    2014-11-01

    We show that the combination of dielectric relaxation with neutron spin echo and incoherent neutron backscattering measurements performed in deuterated and protonated poly(ethylene terephthalate) suggests that the intrinsic dynamics of semicrystalline polymers occurs in an homogeneous scenario, similar to that valid to describe the dynamics of totally amorphous polymers. The quasielastic neutron scattering data are satisfactorily described by a theoretical model that considers that the proton mobility follows a random jump-diffusion in a restricted environment.

  1. 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.

  2. Derivation of mean-square displacements for protein dynamics from elastic incoherent neutron scattering.

    PubMed

    Yi, Zheng; Miao, Yinglong; Baudry, Jerome; Jain, Nitin; Smith, Jeremy C

    2012-04-26

    The derivation of mean-square displacements from elastic incoherent neutron scattering (EINS) of proteins is examined, with the aid of experiments on camphor-bound cytochrome P450cam and complementary molecular dynamics simulations. It is shown that a q(4) correction to the elastic incoherent structure factor (where q is the scattering vector) can be simply used to reliably estimate from the experiment both the average mean-square atomic displacement, <Δr(2)> of the nonexchanged hydrogen atoms in the protein and its variance, σ(2). The molecular dynamics simulation results are in broad agreement with the experimentally derived <Δr(2)> and σ(2) derived from EINS on instruments at two different energy resolutions, corresponding to dynamics on the ∼100 ps and ∼1 ns time scales. Significant dynamical heterogeneity is found to arise from methyl-group rotations. The easy-to-apply q(4) correction extends the information extracted from elastic incoherent neutron scattering experiments and should be of wide applicability.

  3. Parallel electron streaming in the high-latitude E region and its effect on the incoherent scatter spectrum

    NASA Astrophysics Data System (ADS)

    Bahcivan, H.; Cosgrove, R. B.; Tsunoda, R. T.

    2006-07-01

    This article investigates the combined electron heating and streaming effects of low-frequency parallel electric fields on the incoherent scatter measurements of the high-latitude E region. The electric fields distort the electron distribution function, inducing changes on the amplitude and frequency of the ion-acoustic line in the measured incoherent scatter spectrum. If one assumes Maxwellian electrons, the measurements of electron and ion temperatures and electron density are subject to significant percentage errors during geomagnetically active conditions.

  4. 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.

  5. 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

  6. 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.

  7. Blue integumentary structural colours in dragonflies (Odonata) are not produced by incoherent Tyndall scattering.

    PubMed

    Prum, Richard O; Cole, Jeff A; Torres, Rodolfo H

    2004-10-01

    For nearly 80 years, the non-iridescent, blue, integumentary structural colours of dragonflies and damselflies (Odonata) have been attributed to incoherent Tyndall or Rayleigh scattering. We investigated the production of the integumentary structural colours of a damselfly--the familiar bluet, Enallagma civile (Coenagrionidae)--and a dragonfly--the common green darner, Anax junius (Aeshnidae)--using fibre optic spectrophotometry and transmission electron microscopy (TEM). The reflectance spectra of both species showed discrete reflectance peaks of approximately 30% reflectance at 475 and 460 nm, respectively. These structural colours are produced by light scattering from closely packed arrays of spheres in the endoplasmic reticulum of box-shaped epidermal pigment cells underlying the cuticle. The observed reflectance spectra do not conform to the inverse fourth power relationship predicted for Tyndall/Rayleigh scattering. Two-dimensional (2-D) Fourier analysis of the TEM images of the colour-producing arrays reveals ring-shaped distributions of Fourier power at intermediate spatial frequencies, documenting a quasiordered nanostructure. The nanostructured Fourier power spectra falsify the assumption of spatial independence of scatterers that is required for incoherent scattering. Radial averages of the Fourier power spectrum indicate that the spheres are substantially nanostructured at the appropriate spatial scale to produce visible colours by coherent scattering. However, the spatial periodicity of the arrays is apparently too large to produce the observed colour by coherent scattering. The nanospheres could have expanded substantially (approximately 50%) during preparation for TEM. Alternatively, coherent light scattering could be occurring both from the surfaces and from structures at the centre of the spheres. These arrays of colour-producing spheres within pigment cells have convergently evolved at least 11-14 times independently within the Odonata. Structural

  8. 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.

  9. Incoherent scatter radar observations during August 4-7, 1972. [of E and lower F regions

    NASA Technical Reports Server (NTRS)

    Weddle, T.; Doupnik, J. R.; Banks, P. M.; Park, R. J.; Siren, J. C.

    1977-01-01

    E- and lower F-region data obtained by the incoherent scatter radar of Chatanika, Alaska were used to analyze the height-integrated Hall and Pedersen conductivities, electric fields, ionospheric currents, electron densities, and rate of heating of the neutral atmosphere by particle precipitation and by electric current dissipation during the period of intense solar flares, August 4-7, 1972. Although the magnetosphere was unusually disturbed magnetically, the radar data were in general not particularly larger than those seen during more quiet periods. Chatanika seemed to be in the auroral oval during nearly the whole of the time period studied, implying a greatly expanded size of the oval.

  10. Space-time sampling strategies for electronically steerable incoherent scatter radar

    NASA Astrophysics Data System (ADS)

    Swoboda, John

    ncoherent scatter radar (ISR) systems allow researchers to peer into the ionosphere via remote sensing of intrinsic plasma parameters. ISR sensors have been used since the 1950s and until the past decade were mainly equipped with a single mechanically steerable antenna. As such, the ability to develop a two or three dimensional picture of the plasma parameters in the ionosphere has been constrained by the relatively slow mechanical steering of the antennas. A newer class of systems using electronically steerable array (ESA) antennas have broken the chains of this constraint, allowing researchers to create 3-D reconstructions of plasma parameters. There have been many studies associated with reconstructing 3-D fields of plasma parameters, but there has not been a systematic analysis into the sampling issues that arise. Also, there has not been a systematic study as to how to reconstruct these plasma parameters in an optimum sense as opposed to just using different forms of interpolation. The research presented here forms a framework that scientists and engineers can use to plan experiments with ESA ISR capabilities and to better analyze the resulting data. This framework attacks the problem of space-time sampling by ESA ISR systems from the point of view of signal processing, simulation and inverse theoretic image reconstruction. We first describe a physics based model of incoherent scatter from the ionospheric plasma, along with processing methods needed to create the plasma parameter measurements. Our approach leads to development of the space-time ambiguity function, forming a theoretical foundation of the forward model for ISR. This forward model is novel in that it takes into account the shape of the antenna beam and scanning method along with integration time to develop the proper statistics for a desired measurement precision. Once the forward model is developed, we present the simulation method behind the Simulator for ISR (SimISR). SimISR uses input plasma

  11. Coherent and incoherent scatter radar observations during intense mid-latitude spread F

    NASA Astrophysics Data System (ADS)

    Swartz, Wesley E.; Kelley, Michael C.; Makela, Jonathan J.; Collins, Stephen C.; Kudeki, Erhan; Franke, Steve; Urbina, Julio; Aponte, Nestor; Sulzer, Michael P.; González, Sixto A.

    2000-09-01

    An intense mid-latitude spread-F event occurred over Puerto Rico during the night of February 17, 1998. Simultaneous observations were made with the Cornell University Portable Radar Interferometer (CUPRI) located near Isabela, PR, the University of Illinois VHF radar located at Salinas, PR, GPS receivers at Isabela and St. Croix, measuring total electron content, the Arecibo incoherent scatter radar, and the Cornell All-Sky imager located at the Arecibo Observatory. This was the first time that such a broad range of complementary instrumentation captured a mid-latitude spread-F space weather event. It was the first (and still only) time that a spread-F event over the Caribbean exhibited large Doppler shifts in the VHF spectra. This event was characterized with multiple filaments that initially produced receding Doppler velocities exceeding 300 m/s as seen by CUPRI and the Illinois radar. The Arecibo incoherent scatter radar recorded line-of-sight velocities exceeding 100 m/s that moved the F-layer peak to over 400-km altitude. Airglow images of 630.0 nm emissions from F-region heights showed depleted structures oriented southeast to northwest. The large velocities observed with the radars suggest that we caught this event in a stage of explosive development. It is interesting that the first fully documented Caribbean event occurred during a magnetically active period.

  12. Validation of Special Sensor Ultraviolet Limb Imager (SSULI) Ionospheric Tomography using ALTAIR Incoherent Scatter Radar Measurements

    NASA Astrophysics Data System (ADS)

    Dymond, K.; Nicholas, A. C.; Budzien, S. A.; Stephan, A. W.; Coker, C.; Hei, M. A.; Groves, K. M.

    2015-12-01

    The Special Sensor Ultraviolet Limb Imager (SSULI) instruments are ultraviolet limb scanning sensors flying on the Defense Meteorological Satellite Program (DMSP) satellites. The SSULIs observe the 80-170 nanometer wavelength range covering emissions at 91 and 136 nm, which are produced by radiative recombination of the ionosphere. We invert these emissions tomographically using newly developed algorithms that include optical depth effects due to pure absorption and resonant scattering. We present the details of our approach including how the optimal altitude and along-track sampling were determined and the newly developed approach we are using for regularizing the SSULI tomographic inversions. Finally, we conclude with validations of the SSULI inversions against ALTAIR incoherent scatter radar measurements and demonstrate excellent agreement between the measurements.

  13. Investigations of homologous disaccharides by elastic incoherent neutron scattering and wavelet multiresolution analysis

    NASA Astrophysics Data System (ADS)

    Magazù, S.; Migliardo, F.; Vertessy, B. G.; Caccamo, M. T.

    2013-10-01

    In the present paper the results of a wavevector and thermal analysis of Elastic Incoherent Neutron Scattering (EINS) data collected on water mixtures of three homologous disaccharides through a wavelet approach are reported. The wavelet analysis allows to compare both the spatial properties of the three systems in the wavevector range of Q = 0.27 Å-1 ÷ 4.27 Å-1. It emerges that, differently from previous analyses, for trehalose the scalograms are constantly lower and sharper in respect to maltose and sucrose, giving rise to a global spectral density along the wavevector range markedly less extended. As far as the thermal analysis is concerned, the global scattered intensity profiles suggest a higher thermal restrain of trehalose in respect to the other two homologous disaccharides.

  14. 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.

  15. Modeling of Ionospheric Responses to the Solar Flux Change Based on Millstone Hill Incoherent Scatter Radar

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Holt, J. M.

    2002-12-01

    In order to develop ionospheric empirical models of electron density Ne, plasma temperatures (Te and Ti) and ion drifts based on Millstone Hill incoherent scatter radar observations, we investigate an important issue of ionospheric responses to the solar flux changes that have to be quantitatively represented. The representation is associated with selecting a mathematical function where a suitable solar flux index at a proper time ahead the observing time has to be determined. Traditionally, the solar 10.7 cm flux F107 for the previous day is applied, and a linear function is used. However, the non-linear feature of Ne responses to the solar flux was discovered previously. This paper shows the development of the non-linear feature with altitude, season and local time, and also indicates the non-linear feature for the Te and Ti responses. A mathematical function is proposed. We also discuss the use of other solar flux indices, in addition to F107.

  16. Regional and local ionospheric models based on Millstone Hill incoherent scatter radar data

    NASA Astrophysics Data System (ADS)

    Holt, John M.; Zhang, Shun-Rong; Buonsanto, Michael J.

    2002-04-01

    Local and regional statistical models to describe Millstone Hill incoherent scatter radar observations of electron density, electron temperature and ion temperature since 1976 are developed using a bin-fit technique. The local models generate ionospheric variations with local time, day number, and altitude from 150-1000 km. The prior day's F107 and the Ap index from the previous 3 hour period are keyed inputs to specify solar and geomagnetic activity. The regional models have a latitude coverage of 32-55° geodetic and an altitude coverage of 200-600 km. These climatology models are capable of reproducing primary ionospheric variation features seen in previous studies as well as several newly revealed features, such as the semiannual variation of electron density. They are accessible through the World Wide Web at the URL http://www.openmadrigal.org.

  17. Neutral atmospheric models compatible with satellite orbital decay and incoherent scatter measurements

    NASA Technical Reports Server (NTRS)

    Rohrbaugh, J. L.

    1972-01-01

    A correlation study was made of the variations of the exospheric temperature extrema with various combinations of the monthly mean and daily values of the 2800 MHz and Ca:2 solar indices. The phase and amplitude of the semi-annual component and the term dependent on Kp were found to remain almost the same for the maximum and minimum temperature. The term dependent on the 27 day component of the solar activity was found to be about four times as large for the diurnal maximum as for the minimum. Measurements at Arecibo have shown that temperature gradient changes at 125 km are consistent with the phase difference between the neutral temperature and density maxima. This is used to develop an empirical model which is compatible with both the satellite measurements and the available incoherent scatter measurements. A main feature of this model is that day length is included as a major model parameter.

  18. Morphology of the Sporadic E layers over Arecibo derived from Incoherent Scatter Radar (ISR) measurements

    NASA Astrophysics Data System (ADS)

    Franco, E.; Brum, C. G. M.; Raizada, S.

    2014-12-01

    One of the interesting phenomena of the ionosphere is the occurrence of Sporadic E layers (Es), which is characterized by strong electron concentrations, and is related to the vertical tidal wind shear in the lower thermosphere. We will use the incoherent Scatter Radar (ISR) data from Arecibo to investigate the characteristics of the Es below 110km during nighttime. The goal of this project is to study the variability of the nighttime ionization using electron density profiles obtained at the Arecibo Observatory. We will focus on determining the strength of Es, their peak altitude and other parameters between the 90 - 110 km altitude ranges. Previous work has showed that the descending layers are dominated by the tidal influence that displays seasonal variability. To understand the reasons of this variability, we will fit Gaussian profiles to electron density concentrations to extract the layer parameters. Such analysis will allow us to study the role of solar activity, and geomagnetic indices on the layer distributions.

  19. 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).

  20. Experimental Demonstration of Incoherent and Coherent Relativistic Thomson Scattering in Plasmas

    NASA Astrophysics Data System (ADS)

    Umstadter, Donald; Chen, Szu-Yuan; Maksimchuk, Anatoly

    2000-04-01

    Short-wavelength ultrashort-duration laser-produced light sources enable a marriage between observations on the ultra-fast with those on the ultra-small scales, giving scientists novel and exciting research capabilities. We discuss recent experimental results on relativistic Thomson scattering from free electrons in plasmas, which may lead to such a source. In this case, electrons radiate harmonics due to their highly nonlinear relativistic motion in the focus of an intense laser field (10^18 W/cm^2 for 1-μm light). Results on both incoherent and phase-matched harmonic generation by this novel mechanism are described. In the latter case, we report the observation of a five-degree cone of third-harmonic emission in the forward direction.

  1. 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.

  2. Thermospheric Gravity Wave Characteristics Obtained Using the Poker Flat Incoherent Scatter Radar

    NASA Astrophysics Data System (ADS)

    Negale, M.; Nielsen, K.; Taylor, M. J.; Nicolls, M. J.

    2014-12-01

    Atmospheric gravity waves are known to play an important role in atmospheric circulation through momentum deposition in the mesosphere and lower thermosphere (MLT) region (~80 - 110 km). Over the past decade, modeling and observational studies have shown that these waves can penetrate to high altitudes and play similar roles in the thermospheric region (~110 - 400 km). Several case studies have revealed their presence in the thermosphere, but the distributions and variability of thermospheric gravity wave parameters are currently unknown. Using methods developed by Nicolls and Heinselman (2007), we present new high-latitude thermospheric wave characteristic distributions obtained using the Poker Flat Incoherent Scatter Radar (PFISR) during a one year period from August 2010 - July 2011. Their winter season distributions (January 2010 - April 2011) are compared to recent results obtained using a co-located all sky airglow imager measuring the MLT gravity wave field.

  3. Feasibility of an Incoherent-scatter Radar Aboard the Space Shuttle

    NASA Technical Reports Server (NTRS)

    Baron, M. J.; Tsunoda, R. T.; Petriceks, J.; Kunnes, H.

    1976-01-01

    The results of a preliminary study to investigate the feasibility of conducting an incoherent scatter radar experiment on board the space shuttle are presented. The results indicate that such an experiment is technically feasible. The more difficult questions to answer are whether the system can be made flexible enough to justify the problems and costs involved. The design parameters and the tradeoffs that are available in the consideration of these questions are evaluated. Some of the more serious limitations pertain to: (1) the presence of ground clutter and F region auroral clutter; (2) available average power; (3) weight and volume associated with required antenna size, transmitter, and energy storage devices; and (4) antenna breakdown associated with high power transmitter problems.

  4. Observability of NEIALs with the Sondrestrom and Poker Flat incoherent scatter radars

    NASA Astrophysics Data System (ADS)

    Michell, R. G.; Samara, M.

    2013-12-01

    We present coordinated optical and radar observations using the Poker Flat Incoherent Scatter Radar (PFISR) in Alaska and the Sondrestrom radar in Greenland. Several cases were examined where intense, similar-looking dynamic auroral structures were observed in the magnetic zenith. The presence or absence of Naturally Enhanced Ion Acoustic Lines (NEIALs) was investigated in both sets of radar data. In all cases, the aurora exhibited small-scale (∼0.1-1 km), dynamic features that were observed with both all-sky and narrow-field of view (19°) imagers. In all of the cases examined, the PFISR radar observed NEIALs while the Sondrestrom radar did not, despite similar auroral morphology. The main difference between the radars, namely the probing wave number, provides strong evidence for a limiting spatial scale of between 10 and 15 cm for the enhanced wave activity responsible for NEIALs. This has implications for constraining the models of NEIAL generation mechanisms.

  5. Analysis of incoherent scatter during ionospheric heating near the fifth electron gyrofrequency

    NASA Astrophysics Data System (ADS)

    Jun, WU; Jian, WU; Haisheng, ZHAO; Zhengwen, XU

    2017-04-01

    The observation of ultra-high frequency radar during an ionospheric heating experiment carried out at Tromsø site of European Incoherent Scatter Scientific Association, Norway, is analyzed. When pump is operating slightly above the fifth electron gyrofrequency, some strong enhancements in radar echo and electron density occur in a wide altitude range and are in sync with the shifting and spread of plasma line around the reflection altitude, which may be due to the focusing or collimating of radar wave by irregularities. While some strong enhancements in electron density and radar echo around the reflection altitude do not correspond to the true increase in electron density, but due to the enhanced ion acoustic wave by parametric decay instability and oscillation two stream instability. In addition, the different heating rates and cooling rates at the pump frequencies below, around and above fifth gyrofrequency respectively result in the dependence of the enhancements in electron temperature on the pump frequency.

  6. Measurement uncertainty analysis in incoherent Doppler lidars by a new scattering approach.

    PubMed

    Belmonte, Aniceto; Lázaro, Antonio

    2006-08-21

    We need to examine the uncertainty added to the Doppler measurement process of atmospheric wind speeds of a practical incoherent detection lidar. For this application, the multibeam Fizeau wedge has the advantage over the Fabry-Perot interferometer of defining linear fringe patterns. Unfortunately, the convenience of using the transfer function for angular spectrum transmission has not been available because the nonparallel mirror geometry of Fizeau wedges. In this paper, we extent the spatial-frequency arguments used in Fabry-Perot etalons to the Fizeau geometry by using a generalized scattering matrix method based on the propagation of optical vortices. Our technique opens the door to consider complex, realistic configurations for any Fizeau-based instrument.

  7. Elastic incoherent neutron scattering from homologous disaccharides/H2O mixtures

    NASA Astrophysics Data System (ADS)

    Magazú, S.; Migliardo, F.; Mondelli, C.

    2003-12-01

    An analysis in terms of elastic scans of the neutron intensity of homologous disaccharide (trehalose, maltose, sucrose)/H2O mixtures as a function of temperature and exchanged wave vector has been carried out. The experimental findings, showing a crossover in molecular fluctuations between harmonic and anharmonic dynamical regimes, allow us to characterize the system "flexibility." A new operative definition for the "fragility" degree, by using elastic incoherent neutron scattering, is furnished. In this frame the lower flexibility and fragility character of trehalose/H2O mixture with respect to maltose and sucrose/H2O mixtures indicate a better attitude to encapsulate biostructures in more rigid and temperature insensitive structures in approaching the glass transition.

  8. 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.

  9. 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

  10. Imaging of Vector Electric Fields Surrounding Auroral Arcs from Multibeam Incoherent Scatter Radar Measurements.

    NASA Astrophysics Data System (ADS)

    Maksimova, N.; Varney, R. H.; Cosgrove, R. B.; Kaeppler, S. R.; Nicolls, M. J.

    2015-12-01

    Evaluating the ionospheric electric fields and current systems surrounding auroral arcs aids in distinguishing physical mechanisms that drive arc generation and current closure. Auroral forms involve spatial scales that are small in comparison with the magnetosphere-ionosphere-thermosphere (MIT) system, and yet these forms are thought to be closely tied to the overall system response. Spatially resolved measurements of the horizontal ionospheric current can, in principle, be used to determine the field-aligned currents (FAC) that are responsible for energy transfer between the magnetosphere and the ionosphere/thermosphere, leading to heating and upwelling of the neutral gas and acceleration of ion upflows and outflows. Furthermore, the closure of FACs in the ionosphere regulates modes of magnetospheric convection and substorms. An algorithm has been developed to image the local structure in the convection electric field using multibeam incoherent scatter radar (ISR) measurements. Given the inherent difficulty of reconstructing vector quantities from line of sight (LOS) velocity measurements, the algorithm's aim is to select from the solution space for the possible field configurations a unique solution for the electric field distribution by constraining the reconstructed electric field to reproduce the LOS measurements within measurement errors while simultaneously minimizing a measure of the field's curvature and absolute gradient. Using the method of Lagrange multipliers, the algorithm regularizes the underdetermined problem defined by the LOS radar velocity measurements and guarantees a unique solution when the average measurement error is smaller than the average measurement amplitude. The algorithm is tested on a variety of simulated fields in a sensitivity study to determine the extent to which the solution depends on the a priori assumptions and the observation geometry. In addition, a case study of a quiescent auroral arc observed by the Poker Flat

  11. Ionospheric footprint of magnetosheathlike particle precipitation observed by an incoherent scatter radar

    NASA Technical Reports Server (NTRS)

    Watermann, Jurgen; Lummerzheim, Dirk; De La Beaujardiere, Odile; Newell, Patrick T.; Rich, Frederic J.

    1994-01-01

    We have examined Sondrestrom incoherent scatter radar observations of ionospheric plasma density and temperature distributions and measurements of F region ion drifts that were made during a prenoon pass of the Defense Meteorological Satellite Program (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 be directly or indirectly of magnetosheath origin. The precipitation region had a width about 2 deg invariant latitude and covered the low-latitude boundary layer (LLBL), the cusp, and the equatorward section of the plasma mantle (PM). 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 precipitation support our interpretation. The spectral characteristics of the electron flux in the LLBL, cusp, and equatorward section of the PM were in this case too similar to allow to distinguish between them by using incoherent scatter radar measurements only.

  12. EISCAT 3D - The Next Generation European Incoherent Scatter Radar System

    NASA Astrophysics Data System (ADS)

    Turunen, E.

    2009-04-01

    A major new research European infrastructure will be constructed in Northern Scandinavia, combining several very large phased-array transmitters/receivers with multiple receiver arrays. The new EISCAT 3D radar system has a design goal of ten times higher temporal and spatial resolution than the present radars, a volumetric radar imaging capability in an extended spatial area with simultaneous full-vector drift velocities, avoiding spatial and temporal ambiguities, having continuous operation modes, short baseline interferometry capability for imaging sub-beamwidth scales, real-time data access for applications and extensive data archiving facilities. Some arrays are very large, in the scale of 30 000 individual antenna elements. The receiver arrays will be located at 50-150 km distance from the illuminators, so that the total system will comprise in the order of 100 000 elements. These extremely large scale atmospheric and space environment radar arrays open up unprecedented science and technology application opportunities, well beyond the traditional ground-based ionospheric remote sensing role of the old incoherent scatter radars. EISCAT 3D was accepted on the European Roadmap for Research Infrastructures by the European Strategy Forum on Research Infrastructures in December 2008. The facility will be constructed as a modular concept by year 2015. The current status of the project is approaching the end of the first 4 MEUR design study, conducted during 2005-2009 by EISCAT Scientific Association, University of Tromsø, Luleå University of Technology, Swedish Institute of Space Physics, Rutherford Appleton Laboratory, and supported by EU FP6 funding. 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.

  13. 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.

  14. Dynamics of water studied by coherent and incoherent inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Bellissent-Funel, M.-C.; Teixeira, J.

    1991-11-01

    This paper reviews the more recent results obtained on the dynamics of water by neutron scattering and shows that some information can be obtained by this technique at the microscopic level of the hydrogen bond. It also accounts for some very recent results obtained with the hydrated protein C-phycocyanin. Incoherent quasi-elastic and inelastic neutron scattering by water has been performed in a temperature range extending to the supercooled state. The analysis of the quasi-elastic spectrum separates two main components and gives two characteristic times, one of them being related to the hydrogen-bond lifetime. The inelastic spectra extend until 600 meV, i.e. covering the intramolecular vibration region, showing for the first time the stretching band. Collective excitations propagating at 3310 m s -1 have been observed by coherent inelastic neutron scattering. This result was predicted by previous computer molecular dynamics simulations of water. The data are interpreted as a manifestation of short wavelength collective modes propagating within patches of highly bonded water molecules, and distinct from the ordinary sound wave.

  15. The role of momentum transfer during incoherent neutron scattering is explained by the energy landscape model

    PubMed Central

    Frauenfelder, Hans; Young, Robert D.; Fenimore, Paul W.

    2017-01-01

    We recently introduced a model of incoherent quasielastic neutron scattering (QENS) that treats the neutrons as wave packets of finite length and the protein as a random walker in the free energy landscape. We call the model ELM for “energy landscape model.” In ELM, the interaction of the wave packet with a proton in a protein provides the dynamic information. During the scattering event, the momentum Q(t) is transferred by the wave packet to the struck proton and its moiety, exerting the force F(t)=dQ(t)/dt. The resultant energy E⋆ is stored elastically and returned to the neutron as it exits. The energy is given by E⋆=kB(T0+χQ), where T0 is the ambient temperature and χ (≈ 91 K Å) is a new elastobaric coefficient. Experiments yield the scattering intensity (dynamic structure factor) S(Q;T) as a function of Q and T. To test our model, we use published data on proteins where only thermal vibrations are active. ELM competes with the currently accepted theory, here called the spatial motion model (SMM), which explains S(Q,T) by motions in real space. ELM is superior to SMM: It can explain the experimental angular and temperature dependence, whereas SMM cannot do so. PMID:28461503

  16. 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.

  17. Separation of Coherent and Incoherent Scattering Components from Delay/Doppler Altimeter Waveforms over Sea-Ice

    NASA Astrophysics Data System (ADS)

    Egido, A.; Smith, W. H. F.

    2015-12-01

    One of the main benefits of the delay-Doppler altimeter (DDA) is the improved resolution of the system along the satellite track. By means of an unfocussed Synthetic Aperture Radar (SAR) processing technique, the altimeter footprint along the flight direction can be reduced by an order of magnitude with respect to conventional altimeters. However, with the delay-Doppler processing the resolution improvement occurs only on the along-track direction, while the across-track direction remains pulse-limited. The result is an elongated footprint perpendicular to the satellite flight path. The combination of the effects of several scatterers within the footprint can lead to random variations of the DDA waveforms, preventing conventional retracking techniques from retrieving geophysical parameters from altimeter data. This is particularly significant in the case of sea ice, where the coherent response from leads can completely exceed the response from the actual ice surface. We have developed a processing technique that allows the separation of the coherent and incoherent scattering components from SAR altimetry waveforms. The technique is similar to the one used in imaging SAR systems, and is based in the exploitation of the phase history of coherent targets during their illumination period with the antenna beam. For the development of the technique we have used the CryoSat-2 SAR Mode data. The starting point of our processing is the full bit rate (FBR) I/Q complex echo samples. By accounting for the phase evolution of the static targets in the scene, it is possible to correct the phase of the FBR complex echoes along the aperture, which allows to perform an inter-burst coherent averaging, potentially, as long as the target illumination time. This reduces the incoherent components of the radar signal, which results in a radar waveform that contains only the coherent scattering component. The coherent component can later be removed from the original delay-Doppler waveform

  18. Neutral Winds through the Mesosphere and Thermosphere derived from Incoherent Scatter Radar: Variability and Climatology

    NASA Astrophysics Data System (ADS)

    Nicolls, M. J.

    2014-12-01

    Incoherent Scatter Radar (ISR) measurements of ion drifts in the ionosphere are sensitive to neutral motions through ion-neutral collisions. At D-region / mesospheric altitudes, the plasma is collisional on scales of the radar wavelength and thus ion drifts can be used as a direct proxy for neutral motions. At E-region / lower-thermospheric altitudes, the ions undergo a transition whereby the mean free path approaches the scale of the Bragg-scattering wavelength. In the F-region / upper thermosphere, the ions are collisionless and drift at the ExB velocity. The sensing of ion motions is thus extremely useful for the assessment of ionospheric electrodynamics. We utilize case studies from the Poker Flat and Arecibo ISRs to illustrate the utility of this feature of ion motions by showing (a) examples of neutral wind measurements from the mesosphere through the thermosphere, (b) the impact of derived neutral winds on the interpretation of gravity wave dissipation and forcing, and (c) climatological variations of the lower thermospheric winds and the response of the high-latitude lower thermospheric winds to forcing.

  19. Ultrasonic imaging of highly scattering media from local measurements of the diffusion constant: Separation of coherent and incoherent intensities

    NASA Astrophysics Data System (ADS)

    Aubry, Alexandre; Derode, Arnaud

    2007-02-01

    As classical imaging fails with diffusive media, one way to image a multiple-scattering medium is to achieve local measurements of the dynamic transport properties of a wave undergoing diffusion. This paper presents a method to obtain local measurements of the diffusion constant D in a multiple-scattering medium. The experimental setup consists in an array of programmable transducers placed in front of the multiple-scattering medium to be imaged. By achieving Gaussian beamforming both at emission and reception, an array of virtual sources and receivers located in the near field is constructed. The time evolution of the incoherent component of the intensity backscattered on this virtual array is shown to represent directly the growth of the diffusive halo as Dt . A matrix treatment is proposed to separate the incoherent intensity from the coherent backscattering peak. Once the incoherent contribution is isolated, a local measurement of the diffusion constant is possible. The technique is applied to image the long-scale variations of D in a random-scattering sample made of two parts with a different concentration of cylindrical scatterers. This experimental result is obtained with ultrasonic waves around 3MHz . It illustrates the possibility of imaging diffusive media from local measurements of the diffusion constant, based on coherent Gaussian beamforming and a matrix “antisymmetrization,” which creates a virtual antireciprocity.

  20. Fiber-Optic Delay Line Signal Processing: Coherent and Incoherent Systems.

    NASA Astrophysics Data System (ADS)

    Jackson, Kenneth Paul

    Single-mode optical fiber is an attractive delay line medium due to its extremely low-loss (fractional dB/km) and large modulation bandwidth ((GREATERTHEQ)100 GHz(.)km). By connecting lengths of single-mode fiber in prescribed ways, two basic delay line devices can be constructed: the tapped delay line and the recirculating delay line.These two devices form the basis of fiber-optic delay line signal processing in which a variety of operations can be performed. The operations include coded sequence generation, convolution, correlation, matrix-vector multiplication, frequency filtering and many other operations based on delay line concepts. Because of the unique characteristics of single-mode fiber (low -loss and large modulation bandwidth), these operations can be performed at speeds far higher than those that are possible with more conventional signal processing techniques such as surface acoustic wave or charge-coupled devices. Fiber delay line devices can be operated either coherently or incoherently. If incoherent, the device discards optical phase whereas if coherent, the device retains phase. Coherent and incoherent fiber delay line processors each have advantages depending on the application. The goal of this work has been to demonstrate the feasibility of single-mode fibers for delay line signal processing. This goal was achieved through the development of several delay line devices capable of providing elementary processing functions. The work described here develops and analyzes the basic concepts of fiber-optic delay line signal processing with both coherent and incoherent systems. Prototype devices are presented that demonstrate simple processing capabilities. Presently, the processing speed of these fiber -optic devices is limited by the electro-optic interfaces (i.e. sources, modulators and detectors). However, with recent developments in high-speed sources, modulators and detectors, the possibility of performing real time signal processing operations

  1. 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.

  2. Seasonal variations of lower thermospheric winds from the Millstone Hill incoherent scatter radar

    NASA Astrophysics Data System (ADS)

    Wand, R. H.

    1983-11-01

    Steerable (L band) and fixed (UHF) radars were used in making regular incoherent scatter observations of E and F region ion drifts between July 1976 and November 1977. The semidiurnal winds typically grew in amplitude, reaching a maximum in the vicinity of 125 km and having larger values at the equinoxes than the solstices. The wind field at 105 km exhibited a significant polarization, with southward and wind amplitudes larger than eastward amplitudes. It is noted that the seasonal variations in tidal phase were generally less than one hour. For the in situ tidal component, the amplitude and phase of the measured diurnal wind were in reasonable agreement with theoretical expectations, and there was no indication of the presence of an upward propagating diurnal component. However, the measured semidiurnal winds were consistent with being the result of the upward propagation of tidal energy from below 100 km rather than in situ tidal excitation. No definite mode identification is obtained from attempts to match the measured vertical wind structure with that expected for the different semidiurnal Hough mode extensions in the lower thermosphere.

  3. 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.

  4. 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.

  5. 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.

  6. Comparison of the UAF Ionosphere Model with Incoherent-Scatter Radar Data

    NASA Astrophysics Data System (ADS)

    McAllister, J.; Maurits, S.; Kulchitsky, A.; Watkins, B.

    2004-12-01

    The UAF Eulerian Parallel Polar Ionosphere Model (UAF EPPIM) is a first-principles three-dimensional time-dependent representation of the northern polar ionosphere (>50 degrees north latitude). The model routinely generates short-term (~2 hours) ionospheric forecasts in real-time. It may also be run in post-processing/batch mode for specific time periods, including long-term (multi-year) simulations. The model code has been extensively validated (~100k comparisons/model year) against ionosonde foF2 data during quiet and moderate solar activity in 2002-2004 with reasonable fidelity (typical relative RMS 10-20% for summer daytime, 30-50% winter nighttime). However, ionosonde data is frequently not available during geomagnetic disturbances. The objective of the work reported here is to compare model outputs with available incoherent-scatter radar data during the storm period of October-November 2003. Model accuracy is examined for this period and compared to model performance during geomagnetically quiet and moderate circumstances. Possible improvements are suggested which are likely to boost model fidelity during storm conditions.

  7. A statistical study of meteoroid fragmentation and differential ablation using the Resolute Bay Incoherent Scatter Radar

    NASA Astrophysics Data System (ADS)

    Malhotra, Akshay; Mathews, John D.

    2011-04-01

    There has been much interest in the meteor physics community recently regarding the detailed processes by which the meteoroid mass flux arrives in the upper atmosphere. Of particular interest are the relative roles of simple ablation, differential ablation, and fragmentation in interpretation of the meteor events observed by the high-power large-aperture (HPLA) radars. An understanding of the relative roles of these mechanisms is necessary to determine whether the considerable meteor mass flux arriving in the upper atmosphere arrives mostly in nanometer dust/smoke (via fragmentation) or atomic form (via ablation), which in turn has important consequences in understanding not only the aeronomy of the region but also the formation and evolution of various upper atmospheric phenomenon such as Polar Mesospheric Summer Echoes. Using meteor observations from the newly operational Resolute Bay Incoherent Scatter Radar (RISR), we present the first statistical study showing the relative contribution of these mechanisms. We find that RISR head echoes exhibited ˜48% fragmentation, ˜32% simple ablation, and ˜20% differential ablation. We also report existence of compound meteor events exhibiting signatures of more than one mass loss mechanism. These results emphasize that the processes by which the meteoroid mass is deposited into the upper atmosphere are complex and involve all three mechanisms described here. This conclusion is unlike the previously reported results that stress the importance of one or the other of these mechanisms. These results will also contribute in improving current meteoroid disintegration/ablation models.

  8. Low-density lipoproteins investigated under high hydrostatic pressure by elastic incoherent neutron scattering.

    PubMed

    Peters, J; Martinez, N; Lehofer, B; Prassl, R

    2017-07-01

    Human low-density lipoprotein (LDL) is a highly complex nano-particle built up of various lipid classes and a single large protein moiety (apoB-100) owning essential physiological functions in the human body. Besides its vital role as a supplier of cholesterol and fat for peripheral tissues and cells, it is also a known key player in the formation of atherosclerosis. Due to these important roles in physiology and pathology the elucidation of structural and dynamical details is of great interest. In the current study we drew a broader picture of LDL dynamics using elastic incoherent neutron scattering (EINS) as a function of specified temperature and pressure points. We not only investigated a normolipidemic LDL sample, but also a triglyceride-rich and an oxidized one to mimic pathologic conditions as found under hyperlipidemic conditions or in atherosclerotic plaques, respectively. We could show that pressure has a significant effect on atomic motions in modified forms of LDL, whereas the normolipidemic sample seems to cope much better with high-pressure conditions irrespective of temperature. These findings might be explained by the altered lipid composition, which is either caused through elevated triglyceride content or modifications through lipid peroxidation.

  9. 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.

  10. Theoretical and experimental study of gravity waves in the ionosphere observed with incoherent scatter radar

    SciTech Connect

    Sheen, D.R.

    1987-01-01

    In the Worldwide Atmospheric Gravity Wave Study (WAGS) campaign, the source-response relationship between the auroral activities and the gravity waves observed in the ionosphere was studied. Ionospheric parameters observed with the incoherent scatter radars at Sondrestrom and Millstone Hill were compared with predicted results based on gravity-wave theory. In the observed data, usually two types of disturbances can be identified. One is the distinct, semiperiodic traveling ionospheric disturbance. The other is the ever-present, semirandom perturbations. The first type is classified as the special event, and one which was observed on October 18, 1985 during a moderately magnetic-active period is analyzed. The second type is classified as the background wave spectra, and these spectra under various levels of magnetic activity are analyzed. The observed parameters used in this study are the ionization density and the line-of-sight ion velocity. This provides more information than in most of the previous investigations of traveling ionospheric disturbances, in which only electron-density perturbations were used.

  11. Comparison of DMSP SSIES Density and Temperature Measurements With Ground-Based Incoherent Scatter Radar Data

    NASA Astrophysics Data System (ADS)

    Keyser, H. L.; Green, B. S.; della-Rose, D. J.; Sojka, J. J.; Erickson, P. J.; Hairston, M. R.; Rich, F. J.

    2003-12-01

    We have compared electron density and temperature data, measured aboard the Defense Meteorological Satellite Program (DMSP) spacecraft, against POLITE campaign data collected by the Millstone Hill incoherent scatter radar. The POLITE data span the period between February 1996 (near solar minimum) and July 2000 (near solar maximum). Following the work of Sultan and Rich [2000], we averaged the DMSP data within a five-degree circle of Millstone Hill, and averaged the corresponding radar data within +/-30 minutes of the satellite overflight time. Our study revealed that the average electron density difference between DMSP and Millstone data exceeds 20 percent, which is statistically significant compared to the published DMSP topside ionospheric plasma monitor (SSIES) instrument accuracy. Further, DMSP density values are typically lower than the corresponding radar measurements; this negative bias is largest near solar minimum. Conversely, DMSP electron temperature values are an average 23 percent higher than the radar-derived temperature. This difference is statistically significant compared to both the DMSP and radar errors. As with the electron density, the bias lessens toward solar maximum. This temperature bias appears to decrease as the DMSP zenith angle increases, and this suggests the possibility of increased photoelectron contamination of the Langmuir probe for smaller zenith angles. Apart from this, however, the root cause(s) for these density and temperature differences remain under study.

  12. A global thermospheric model based on mass spectrometer and incoherent scatter data MSIS. I - N2 density and temperature

    NASA Technical Reports Server (NTRS)

    Hedin, A. E.; Reber, C. A.; Newton, G. P.; Spencer, N. W.; Salah, J. E.; Evans, J. V.; Kayser, D. C.; Alcayde, D.; Bauer, P.; Cogger, L.

    1977-01-01

    Measurements of neutral nitrogen density from mass spectrometers on five satellites (AE-B, Ogo 6, San Marco 3, Aeros A, and AE-C) and neutral temperatures inferred from incoherent scatter measurements at four ground stations are combined to produce a model of thermospheric neutral temperatures and nitrogen densities similar to the Ogo 6 empirical model (Hedin et al., 1974). This global model is designated MSIS (mass spectrometer and incoherent scatter). The global average temperature, the annual temperature variation, lower bound density, and lower bound temperature are discussed. The data set covers the time period from the end of 1965 to mid-1975 and also a wide range of solar activities. Diurnal and semidiurnal variations in lower bound density and temperature are considered, as is magnetic activity.

  13. 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).

  14. A global thermospheric model based on mass spectrometer and incoherent scatter data MSIS. I - N2 density and temperature

    NASA Technical Reports Server (NTRS)

    Hedin, A. E.; Reber, C. A.; Newton, G. P.; Spencer, N. W.; Salah, J. E.; Evans, J. V.; Kayser, D. C.; Alcayde, D.; Bauer, P.; Cogger, L.

    1977-01-01

    Measurements of neutral nitrogen density from mass spectrometers on five satellites (AE-B, Ogo 6, San Marco 3, Aeros A, and AE-C) and neutral temperatures inferred from incoherent scatter measurements at four ground stations are combined to produce a model of thermospheric neutral temperatures and nitrogen densities similar to the Ogo 6 empirical model (Hedin et al., 1974). This global model is designated MSIS (mass spectrometer and incoherent scatter). The global average temperature, the annual temperature variation, lower bound density, and lower bound temperature are discussed. The data set covers the time period from the end of 1965 to mid-1975 and also a wide range of solar activities. Diurnal and semidiurnal variations in lower bound density and temperature are considered, as is magnetic activity.

  15. 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.

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

    SciTech Connect

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

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

    DOE PAGES

    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.

  18. 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.

  19. 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.

  20. 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.

  1. Nonlinear Interaction of Langmuir and Whistler Waves Observed with Incoherent Scatter Radar

    NASA Astrophysics Data System (ADS)

    Akbari, H.; Semeter, J. L.

    2016-12-01

    High-latitude ionosphere is characterized by particle precipitations of different origins. Among these are electron precipitation caused by quasi-static parallel electric fields and Alfven wave-particle interactions. In-situ measurements of fields and particles have commonly detected various plasma modes, such as Langmuir and whistler, enhanced by these precipitating electrons. The waves have been shown to undergo various nonlinear wave-wave and wave-particle interaction including parametric type instabilities. Detecting such processes with in-situ instruments however is not always straightforward and certain processes may remain undetected. We present new incoherent scatter radar data from the auroral F-region where strong echoes simultaneously appear in the ion- and both up- and down-shifted plasma lines channels. While aspects of these observations have been previously discussed in detail in terms of electron beam-generated Langmuir turbulence, some new aspects, namely the presence of two peaks separated by 300 kHz in both the up- and down-shifted plasma line channels are discussed in this paper. The unique and asymmetric displacement of the peaks with respect to the radar transmitting frequency suggests that the anomalous spectra are produced as a result of the existence of non-resonant waves generated by nonlinear beating between intense Langmuir and whistler modes. The results suggest that such nonlinear interactions contribute to the appearance of wave activities close to the plasma frequency as observed by in-situ electric field spectral measurements and that not all these wave activities are directly generated by the initial electron beam. The anomalous plasma lines spectra are often observed just above the altitude where Langmuir turbulence is observed. This altitudinal morphology and its implications are also discussed is this paper.

  2. 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

  3. Ionospheric variability from an incoherent scatter radar long-duration experiment at Millstone Hill

    NASA Astrophysics Data System (ADS)

    Zhang, Shun-Rong; Holt, John M.

    2008-03-01

    An incoherent scatter radar experiment at Millstone Hill covering 30 consecutive days in September 2005 has enabled this study of day-to-day ionospheric variability. This was a period of low solar activity with few magnetically disturbed periods. Our discussion focuses on ionospheric variability during quiet magnetic activity in the 100-500 km height range, with emphasis on its height variation at noon. (1) Very large midday variability is present for the ion temperature Ti near 120 km, which is verified by two other 30-d experiments at Millstone Hill. This is not apparently associated with solar flux and magnetic activity. The percentage variability in the midday electron density Ne changes with height, being smaller between 150 and 250 km and larger in the topside. (2) With increasing solar flux, Ne decreases between 170 km and the F2 peak and increases elsewhere, being essentially unchanged near the F2 peak. With increasing magnetic activity, Ne decreases between 160 and 325 km. Ti increases with solar flux and magnetic activity, in particular in the F2 region. (3) There is a time lag of ionospheric responses, varying with height, to changes in solar-geophysical conditions: In the E region, the lag is almost zero; above the F2 peak, both Ne and Ti respond to F10.7 with a 2-3-d delay. The delay in response to 3-hourly ap index changes for Ne above the F2 peak can be 9-12 h and between 160 km and the F2 peak can be 0-3 h. The time delay for Ti is 6-9 h. (4) We estimate that the majority of the topside variability in Ti and Ne can be explained in terms of solar flux F107 and magnetic activity ap effects. Near the F2 peak, Ne variability seems to be complicated, and nearly one half (10%) of it cannot be ascribed directly to F10.7 and ap effects.

  4. 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

  5. Detection of F-region electron density irregularities using incoherent-scatter radar

    NASA Astrophysics Data System (ADS)

    Gudivada, Krishna Prasad

    Incoherent-scatter radar data from Poker Flat, Alaska has been used to determine size distributions of electron density structures in the evening time sector of the auroral zone. At high latitudes ionospheric plasma typically moves east-west with speeds of several hundred meters per second. Density irregularities that rapidly move through the radar beam are therefore observed as time-varying power fluctuations. The new phased array radar used for this study has been operated with several antenna directions with successive pulses transmitted in each direction. It is therefore possible to observe plasma Doppler velocities in multiple directions and determine the vector direction of the plasma motion. This near-simultaneous observation of the plasma velocity in conjunction with the electron density height profile data enable a new technique to determine the scale sizes of electron density fluctuations that move horizontally through the radar beam. The study focuses on the collision-less F-region ionosphere where the plasma drift is approximately constant with altitude. The experimental technique limits the range of scale sizes that may be studied to relatively large-scale sizes (i.e. greater than few tens of km). Results show that during magnetically disturbed conditions (Kp ≥ 4) when westward plasma velocities are relatively high (500-1000 m/s) the scale sizes of irregularities (often called plasma blobs) are in the range of 100-300 km and predominantly originate from the polar cap and are transported over long distances (˜1000 km) due to the long chemical recombination times (30-90 minutes). Some irregularities are caused by local auroral particle precipitation and have been identified with associated electron temperature enhancements. For cases of low magnetic activity (Kp ≤ 1), when the radar is located in a region of low plasma velocities (100-500 m/s) well south of the auroral oval (essentially a mid-latitude type ionosphere), the density distribution is

  6. Determination of hydrogen in niobium by cold neutron prompt gamma ray activation analysis and neutron incoherent scattering

    SciTech Connect

    R.L. Paul; H.H. Cheu-Maya; G.R. Myneni

    2002-11-01

    The presence of trace amounts of hydrogen in niobium is believed to have a detrimental effect on the mechanical and superconducting properties. Unfortunately, few techniques are capable of measuring hydrogen at these levels. We have developed two techniques for measuring hydrogen in materials. Cold neutron prompt gamma-ray activation analysis (PGAA) has proven useful for the determination of hydrogen and other elements in a wide variety of materials. Neutron incoherent scattering (NIS), a complementary tool to PGAA, has been used to measure trace hydrogen in titanium. Both techniques were used to study the effects of vacuum heating and chemical polishing on the hydrogen content of superconducting niobium.

  7. 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.

  8. 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.

  9. 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.

  10. Validation of GRACE electron densities by incoherent scatter radar data and estimation of plasma scale height in the topside ionosphere

    NASA Astrophysics Data System (ADS)

    Xiong, Chao; Lühr, Hermann; Ma, ShuYing; Schlegel, Kristian

    2015-04-01

    This paper presents an effort of using incoherent scatter radar data for validating electron density (Ne) measurements performed by the GRACE satellites from year 2002 to 2012. For adjusting the bias of GRACE Ne data, the observations at high latitudes from EISCAT at Tromsø and Svalbard, as well as two incoherent scatter radars (ISR) at mid- and low latitudes, Millstone Hill and Arecibo, are used. The adjusted GRACE Ne data are further compared with the observations from the four ISRs. For EISCAT observations at Tromsø and Svalbard the comparison results are quite consistent, yielding correlation coefficients as high as 0.92, and an average bias value of about 3 · 1010 m-3 is obtained. For the radars at Millstone Hill and Arecibo the results show excellent agreement, yielding correlation coefficients as high as 0.97 and an average bias of 1 · 1010 m-3. The scale factor of adjusted GRACE Ne data is lower by 1% and 5% compared to Millstone Hill and Arecibo readings, respectively. We consider these differences as within the uncertainty of radar measurements. Using the adjusted GRACE Ne as well as CHAMP observations during four periods of coplanar orbits between 2003 and 2008, the plasma scale heights of the topside ionosphere are determined and further compared with IRI model predictions. We find significantly larger scale heights in particular at middle and high latitudes than expected from IRI. Outstanding are the regions of the mid-latitude electron density trough.

  11. Internal Molecular Motions of Bacteriorhodopsin: Hydration-Induced Flexibility Studied by Quasielastic Incoherent Neutron Scattering Using Oriented Purple Membranes

    NASA Astrophysics Data System (ADS)

    Fitter, J.; Lechner, R. E.; Buldt, G.; Dencher, N. A.

    1996-07-01

    Quasielastic incoherent neutron scattering from hydrogen atoms, which are distributed nearly homogeneously in biological molecules, allows the investigation of diffusive motions occurring on the pico- to nanosecond time scale. A quasielastic incoherent neutron scattering study was performed on the integral membrane protein bacteriorhodopsin (BR), which is a light-driven proton pump in Halobacterium salinarium. BR is embedded in lipids, forming patches in the cell membrane of the organism, which are the so called purple membranes (PMs). Measurements were carried out at room temperature on oriented PM-stacks hydrated at two different levels (low hydration, h = 0.03 g of D2O per g of PM; high hydration, h = 0.28 g of D2O per g of PM) using time-of-flight spectrometers. From the measured spectra, different diffusive components were identified and analyzed with respect to the influence of hydration. This study supports the idea that a decrease in hydration results in an appreciable decrease in internal molecular flexibility of the protein structure. Because it is known from studies on the function of BR that the pump activity is reduced if the hydration level of the protein is insufficient, we conclude that the observed diffusive motions are essential for the function of this protein. A detailed analysis and classification of the different kinds of diffusive motions, predominantly occurring in PMs under physiological conditions, is presented.

  12. 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.

  13. Influence of incoherent scattering on stochastic deflection of high-energy negative particle beams in bent crystals

    NASA Astrophysics Data System (ADS)

    Kirillin, I. V.; Shul'ga, N. F.; Bandiera, L.; Guidi, V.; Mazzolari, A.

    2017-02-01

    An investigation on stochastic deflection of high-energy negatively charged particles in a bent crystal was carried out. On the basis of analytical calculation and numerical simulation it was shown that there is a maximum angle at which most of the beam is deflected. The existence of a maximum, which is taken in the correspondence of the optimal radius of curvature, is a novelty with respect to the case of positively charged particles, for which the deflection angle can be freely increased by increasing the crystal length. This difference has to be ascribed to the stronger contribution of incoherent scattering affecting the dynamics of negative particles that move closer to atomic nuclei and electrons. We therefore identified the ideal parameters for the exploitation of axial confinement for negatively charged particle beam manipulation in future high-energy accelerators, e.g., ILC or muon colliders.

  14. 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.

  15. 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.

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

    DOE PAGES

    Yan, Y.; Qian, S.; Littrell, 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

  17. 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.

  18. Non-Gaussian behavior of elastic incoherent neutron scattering profiles of proteins studied by molecular dynamics simulation

    SciTech Connect

    Tokuhisa, Atsushi; Joti, Yasumasa; Kitao, Akio; Nakagawa, Hiroshi; Kataoka, Mikio

    2007-04-15

    Elastic incoherent neutron scattering (EINS) data can be approximated with a Gaussian function of q in a low q region. However, in a higher q region the deviation from a Gaussian function becomes non-negligible. Protein dynamic properties can be derived from the analyses of the non-Gaussian behavior, which has been experimentally investigated. To evaluate the origins of the non-Gaussian behavior of protein dynamics, we conducted a molecular dynamics (MD) simulation of staphylococcal nuclease. Instead of the ordinary cumulant expansion, we decomposed the non-Gaussian terms into three components: (i) the component originating from the heterogeneity of the mean-square fluctuation (ii) that from the anisotropy, and (iii) that from higher-order terms such as anharmonicity. The MD simulation revealed various dynamics for each atom. The atomic motions are classified into three types: (i) 'harmonic', (ii) 'anisotropic', and (iii) 'anharmonic'. However, each atom has a different degree of anisotropy. The contribution of the anisotropy to the total scattering function averages out due to these differences. Anharmonic motion is described as the jump among multiple minima. The jump distance and the probability of the residence at one site vary from atom to atom. Each anharmonic component oscillates between positive and negative values. Thus, the contribution of the anharmonicity to the total scattering is canceled due to the variations in the anharmonicity. Consequently, the non-Gaussian behavior of the total EINS from a protein can be analyzed by the dynamical heterogeneity.

  19. Incoherent scatter measurements of ring-ion beam distributions produced by space shuttle exhaust injections into the ionosphere

    NASA Astrophysics Data System (ADS)

    Bernhardt, P. A.; Sulzer, M. P.

    2004-02-01

    When the space shuttle Orbiting Maneuver Subsystem (OMS) engines burn in the ionosphere, two types of effects are produced. First, charge exchange between the exhaust molecules and the ambient O+-ions yields beams of high-speed molecular ions that can excite plasma turbulence. Second, the molecular ions eventually recombine with electrons to yield a plasma hole. The ion-beam interactions and the formation of artificial plasma holes in the ionosphere have been studied with ground-based, incoherent-scatter radars (ISRs) during the Shuttle Ionospheric Modification with Pulsed Localized Exhaust (SIMPLEX) series of experiments. The SIMPLEX II experiment took place in late July 1999 during the STS-93 flight of the Space Shuttle Columbia. The Orbital Maneuver Subsystem (OMS) engines provided controlled ion injections over the incoherent scatter radar (ISR) facilities located at Arecibo, Puerto Rico to excite unusual radar signatures. After charge exchange between the exhaust and the ambient plasma, pickup ions were produced with velocities near 10 km/s using a ram-burn orientation of the OMS engines relative to the vehicle orbit vector. During the SIMPLEX II experiment, the ISR spectra of the exhaust-modified plasma were obtained for the first time. The formation of ring-ion beam distributions was determined from curve fitting to the radar spectra. These spectra show the presence of the nonthermal ion distributions and enhanced scatter from electrons for thermal ion distributions with elevated ion temperatures. Analysis of the ion distributions in the modified ionosphere indicates that they were unstable and may have quickly generated plasma waves that along with ion-neutral collisions changed the ion-velocity distributions. The observations show that the perpendicular ion speed was rapidly reduced from 10 km/s to about 1 km/s. These observations open up the possibility of conducting a new series of experiments studying ring-ion beam instabilities that occur naturally in

  20. Ciphertext-only attack on optical cryptosystem with spatially incoherent illumination: from the view of imaging through scattering medium.

    PubMed

    Liao, Meihua; He, Wenqi; Lu, Dajiang; Peng, Xiang

    2017-01-31

    Security analysis is important and necessary for a new cryptosystem. In this paper, we evaluate the security risk of the optical cryptosystem with spatially incoherent illumination from the view of imaging through scattering medium and then demonstrate that it is vulnerable to ciphertext-only attack. The proposed ciphertext-only attack method relies on the optical memory effect for speckle correlations, which reveals a fact that the ciphertext's autocorrelation is essentially identical to the plaintext's own autocorrelation. Furthermore, by employing of an improved dynamic hybrid input-output phase-retrieval algorithm, we show that a plaintext image can be directly reconstructed from the autocorrelation of its corresponding ciphertext without any prior knowledge about the plaintext or the phase keys. Meanwhile, the theory analysis and experiment results will also be provided to verify the validity and feasibility of our proposed ciphertext-only attack method. To the best of our knowledge, this is the first time to report optical cryptanalysis from the point of view of imaging through scattering medium and we believe this contribution will open up an avenue to deepen the investigation of optical cryptosystems.

  1. Ciphertext-only attack on optical cryptosystem with spatially incoherent illumination: from the view of imaging through scattering medium

    PubMed Central

    Liao, Meihua; He, Wenqi; Lu, Dajiang; Peng, Xiang

    2017-01-01

    Security analysis is important and necessary for a new cryptosystem. In this paper, we evaluate the security risk of the optical cryptosystem with spatially incoherent illumination from the view of imaging through scattering medium and then demonstrate that it is vulnerable to ciphertext-only attack. The proposed ciphertext-only attack method relies on the optical memory effect for speckle correlations, which reveals a fact that the ciphertext’s autocorrelation is essentially identical to the plaintext’s own autocorrelation. Furthermore, by employing of an improved dynamic hybrid input-output phase-retrieval algorithm, we show that a plaintext image can be directly reconstructed from the autocorrelation of its corresponding ciphertext without any prior knowledge about the plaintext or the phase keys. Meanwhile, the theory analysis and experiment results will also be provided to verify the validity and feasibility of our proposed ciphertext-only attack method. To the best of our knowledge, this is the first time to report optical cryptanalysis from the point of view of imaging through scattering medium and we believe this contribution will open up an avenue to deepen the investigation of optical cryptosystems. PMID:28139729

  2. Ciphertext-only attack on optical cryptosystem with spatially incoherent illumination: from the view of imaging through scattering medium

    NASA Astrophysics Data System (ADS)

    Liao, Meihua; He, Wenqi; Lu, Dajiang; Peng, Xiang

    2017-01-01

    Security analysis is important and necessary for a new cryptosystem. In this paper, we evaluate the security risk of the optical cryptosystem with spatially incoherent illumination from the view of imaging through scattering medium and then demonstrate that it is vulnerable to ciphertext-only attack. The proposed ciphertext-only attack method relies on the optical memory effect for speckle correlations, which reveals a fact that the ciphertext’s autocorrelation is essentially identical to the plaintext’s own autocorrelation. Furthermore, by employing of an improved dynamic hybrid input-output phase-retrieval algorithm, we show that a plaintext image can be directly reconstructed from the autocorrelation of its corresponding ciphertext without any prior knowledge about the plaintext or the phase keys. Meanwhile, the theory analysis and experiment results will also be provided to verify the validity and feasibility of our proposed ciphertext-only attack method. To the best of our knowledge, this is the first time to report optical cryptanalysis from the point of view of imaging through scattering medium and we believe this contribution will open up an avenue to deepen the investigation of optical cryptosystems.

  3. Imaging of Polar Mesosphere Summer Echoes with the 450 MHz Poker Flat Advanced Modular Incoherent Scatter Radar

    NASA Astrophysics Data System (ADS)

    Nicolls, M. J.; Heinselman, C. J.; Hope, E. A.; Ranjan, S.; Kelley, M. C.; Kelly, J. D.

    2007-10-01

    Polar Mesosphere Summer Echoes (PMSE) occur near the mesopause during the polar summer months. PMSE are primarily studied at VHF, however there have been some detections at higher frequencies. Here, we report on some of the first detections of PMSE with the 450 MHz (67 cm) Poker Flat Advanced Modular Incoherent Scatter Radar (PFISR). Echoes were observed with volume reflectivities (radar scattering cross section per unit volume) near 2-3 × 10-17 m-1. On 11 June 2007, PFISR was operating in a 26-beam position mode, with look directions spread over an approximately 80 by 80 km2 region at 85 km altitude with elevation angles as low as ~50°. The measurements showed patchy (tens of kilometer) irregularity regions drifting in from the north, in addition to smaller, more localized structures. There was no evidence for strong aspect sensitivity of these UHF echoes, as PMSE was observed in all look directions with relatively uniform intensity. The observations indicate the presence of fossilized irregularities drifting with the background wind field as well as areas of developing irregularities possibly associated with the presence of active neutral air turbulence.

  4. Coherent and incoherent Thomson scattering on an argon/hydrogen microwave plasma torch with transient behaviour

    NASA Astrophysics Data System (ADS)

    Obrusník, A.; Synek, P.; Hübner, S.; van der Mullen, J. J. A. M.; Zajíčková, L.; Nijdam, S.

    2016-10-01

    A new method of processing time-integrated coherent Thomson scattering spectra is presented, which provides not only the electron density and temperature but also information about the transient behaviour of the plasma. Therefore, it is an alternative to single-shot Thomson scattering measurements as long as the scattering is coherent. The method is applied to a microwave plasma torch operating in argon or a mixture of argon with hydrogen at atmospheric pressure. Electron densities up to 8\\cdot {{10}21} m-3 (ionization degree above 10-3) were observed, which is more than two times higher than presented in earlier works on comparable discharges. Additionally, a parametric study with respect to the argon/hydrogen ratio and the input power was carried out and the results are discussed together with earlier Stark broadening measurements on the same plasma.

  5. 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.

  6. 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}.

  7. 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.

  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. Changes in dynamics of α-chymotrypsin due to covalent inhibitors investigated by elastic incoherent neutron scattering.

    PubMed

    Andersson, C D; Martinez, N; Zeller, D; Rondahl, S H; Koza, M M; Frick, B; Ekström, F; Peters, J; Linusson, A

    2017-09-12

    An essential role of enzymes is to catalyze various chemical reactions in the human body and inhibition of the enzymatic activity by small molecules is the mechanism of action of many drugs or tool compounds used to study biological processes. Here, we investigate the effect on the dynamics of the serine protease α-chymotrypsin when in complex with two different covalently bound inhibitors using elastic incoherent neutron scattering. The results show that the inhibited enzyme displays enhanced dynamics compared to the free form. The difference was prominent at higher temperatures (240-310 K) and the type of motions that differ include both small amplitude motions, such as hydrogen atom rotations around a methyl group, and large amplitude motions, such as amino acid side chain movements. The measurements were analyzed with multivariate methods in addition to the standard univariate methods, allowing for a more in-depth analysis of the types of motions that differ between the two forms. The binding strength of an inhibitor is linked to the changes in dynamics occurring during the inhibitor-enzyme binding event and thus these results may aid in the deconvolution of this fundamental event and in the design of new inhibitors.

  10. Crossover from Collective to Incoherent Spin Excitations in Superconducting Cuprates Probed by Detuned Resonant Inelastic X-Ray Scattering

    NASA Astrophysics Data System (ADS)

    Minola, M.; Lu, Y.; Peng, Y. Y.; Dellea, G.; Gretarsson, H.; Haverkort, M. W.; Ding, Y.; Sun, X.; Zhou, X. J.; Peets, D. C.; Chauviere, L.; Dosanjh, P.; Bonn, D. A.; Liang, R.; Damascelli, A.; Dantz, M.; Lu, X.; Schmitt, T.; Braicovich, L.; Ghiringhelli, G.; Keimer, B.; Le Tacon, M.

    2017-09-01

    Spin excitations in the overdoped high temperature superconductors Tl2 Ba2 CuO6 +δ and (Bi ,Pb )2(Sr ,La )2CuO6 +δ were investigated by resonant inelastic x-ray scattering (RIXS) as functions of doping and detuning of the incoming photon energy above the Cu -L3 absorption peak. The RIXS spectra at optimal doping are dominated by a paramagnon feature with peak energy independent of photon energy, similar to prior results on underdoped cuprates. Beyond optimal doping, the RIXS data indicate a sharp crossover to a regime with a strong contribution from incoherent particle-hole excitations whose maximum shows a fluorescencelike shift upon detuning. The spectra of both compound families are closely similar, and their salient features are reproduced by exact-diagonalization calculations of the single-band Hubbard model on a finite cluster. The results are discussed in the light of recent transport experiments indicating a quantum phase transition near optimal doping.

  11. Variations of Substorm Electric-field Components Measured with the Poker-Flat Incoherent-Scatter Radar

    NASA Astrophysics Data System (ADS)

    Gudivada, K.; Watkins, B.

    2011-12-01

    North-South and East-West components of the auroral-zone electric field have been measured with the incoherent-scatter radar at Poker-Flat, Alaska. The phased-array technology incorporated with the radar system provides a new method to determine electric fields as a function of latitude with minimal spatial and temporal ambiguity. Successive radar pulses are transmitted in thirteen antenna directions. Doppler data are combined and integrated to determine electric field values from 66 to 68 degrees latitude in 0.25 degree steps. Data periods have been selected when substorm currents, as detected from the Alaskan magnetometer chain, are within range of the radar. Specific events near the onset of magnetic substorms have been examined to determine average variations of the electric field with respect to substorm onset time. The northward component of the field is typically about 20-30mV/m in the evening and transitions to values near zero about one hour before substorm onset (we identify this period as the substorm growth phase) and then adopts southward values about 20-30mV/m at the time of substorm onset. The east-west component values of the electric field are near zero in the evening, and then go to about 10mV/m directed westward during the growth phase and after substorm onset.

  12. 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.

  13. Accuracy of IRI profiles of ionospheric density and temperatures derived from comparisons to Kharkov incoherent scatter radar measurements

    NASA Astrophysics Data System (ADS)

    Cherniak, Iu. V.; Zakharenkova, I. E.; Dzyubanov, D. A.

    2013-02-01

    The incoherent scatter radar (ISR) facility in Kharkov, Ukraine (49.6°N, 36.3°E) measures vertical profiles of electron density, electron and ion temperature, and ion composition of the ionospheric plasma up to 1100 km altitude. Acquired measurements constitute an accurate ionospheric reference dataset for validation of the variety of models and alternative measurement techniques. We describe preliminary results of comparing the Kharkov ISR profiles to the international reference ionosphere (IRI), an empirical model recognized for its reliable representation of the monthly-median climatology of the density and temperature profiles during quiet-time conditions, with certain extensions to the storm times. We limited our comparison to only quiet geomagnetic conditions during the autumnal equinoxes of 2007 and 2008. Overall, we observe good qualitative agreement between model and data both in time and with altitude. Magnitude-wise, the measured and modeled electron density and plasma temperatures profiles appear different. We discovered that representation accuracy improves significantly when IRI is driven by observed-averaged values of the solar activity index rather than their predictions. This result motivated us to study IRI performance throughout protracted solar minimum of the 24th cycle. The paper summarizes our observations and recommendations for optimal use of the IRI.

  14. Dielectric Susceptibility of Liquid Water: Microscopic Insights from Coherent and Incoherent Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Arbe, A.; Malo de Molina, P.; Alvarez, F.; Frick, B.; Colmenero, J.

    2016-10-01

    The analysis of neutron scattering results on H dynamics (H2O ) and the dynamic structure factor (D2O ) around the intermolecular peak and at intermediate length scales in terms of the susceptibilities reveals three processes (diffusive, local relaxational and vibrational) at frequencies below 3 THz, to which the contributions commonly invoked in dielectric studies can be directly mapped. We achieve a unified description of the results from both techniques, clarifying the nature of the molecular motions involved in the dielectric spectra and their impact on the structural relaxation.

  15. Accuracy of Sea Surface Topography with GPS Scattered Signals

    NASA Astrophysics Data System (ADS)

    Zuffada, C.; Zavorotny, V. U.; Lowe, S.

    2001-12-01

    The concept of using GPS reflected signals for ocean and land remote sensing is based on the use of one airborne (or space-based) GPS receiver working simultaneously with a constellation of several signal-transmitting GPS satellites. This would offer an advantage in terms of spatial coverage compared to a conventional monostatic radar system and possibly allow new scientific applications to be pursued. However, the limited power of GPS transmitters and a relatively low surface cross section would require either large receiving antennas or longer integration times to optimize the signal-to-noise ratio. Analogously to the case of a conventional radar altimeter, the reflected GPS signal acquired by the receiver is the average power versus time (a range measurement) and generally represents the contributions from surfaces which scatter incoherently. This waveform is derived as a function of viewing geometry, system parameters, surface roughness and dielectric properties of underlying covers. This work investigates the spatial-temporal coherence properties and statistics of the measured reflected GPS signal that describes variability from one sample to another. This information is needed to choose an optimal strategy for a successful signal processing. We examine the above-mentioned properties of the modeled received power as a function of surface state and scattering geometry. Its impact on the accuracy of sea surface topography, both from airborne and orbital platforms is addressed. A characterization of error and expected spatial resolution in relation to existing instruments is discussed. Furthermore, in examining the coherence time, we analyze the spectral behavior of the reflected signal versus sea state parameters, such as wind vector. In addition, we compare the predictions with data available from recent airplane measurements taken in the Pacific Ocean off the coast of Southern California obtaining preliminary validations of our models.

  16. Crossover from incoherent to coherent phonon scattering in epitaxial oxide superlattices.

    PubMed

    Ravichandran, Jayakanth; Yadav, Ajay K; Cheaito, Ramez; Rossen, Pim B; Soukiassian, Arsen; Suresha, S J; Duda, John C; Foley, Brian M; Lee, Che-Hui; Zhu, Ye; Lichtenberger, Arthur W; Moore, Joel E; Muller, David A; Schlom, Darrell G; Hopkins, Patrick E; Majumdar, Arun; Ramesh, Ramamoorthy; Zurbuchen, Mark A

    2014-02-01

    Elementary particles such as electrons or photons are frequent subjects of wave-nature-driven investigations, unlike collective excitations such as phonons. The demonstration of wave-particle crossover, in terms of macroscopic properties, is crucial to the understanding and application of the wave behaviour of matter. We present an unambiguous demonstration of the theoretically predicted crossover from diffuse (particle-like) to specular (wave-like) phonon scattering in epitaxial oxide superlattices, manifested by a minimum in lattice thermal conductivity as a function of interface density. We do so by synthesizing superlattices of electrically insulating perovskite oxides and systematically varying the interface density, with unit-cell precision, using two different epitaxial-growth techniques. These observations open up opportunities for studies on the wave nature of phonons, particularly phonon interference effects, using oxide superlattices as model systems, with extensive applications in thermoelectrics and thermal management.

  17. Crossover from incoherent to coherent phonon scattering in epitaxial oxide superlattices

    NASA Astrophysics Data System (ADS)

    Ravichandran, Jayakanth; Yadav, Ajay K.; Cheaito, Ramez; Rossen, Pim B.; Soukiassian, Arsen; Suresha, S. J.; Duda, John C.; Foley, Brian M.; Lee, Che-Hui; Zhu, Ye; Lichtenberger, Arthur W.; Moore, Joel E.; Muller, David A.; Schlom, Darrell G.; Hopkins, Patrick E.; Majumdar, Arun; Ramesh, Ramamoorthy; Zurbuchen, Mark A.

    2014-02-01

    Elementary particles such as electrons or photons are frequent subjects of wave-nature-driven investigations, unlike collective excitations such as phonons. The demonstration of wave-particle crossover, in terms of macroscopic properties, is crucial to the understanding and application of the wave behaviour of matter. We present an unambiguous demonstration of the theoretically predicted crossover from diffuse (particle-like) to specular (wave-like) phonon scattering in epitaxial oxide superlattices, manifested by a minimum in lattice thermal conductivity as a function of interface density. We do so by synthesizing superlattices of electrically insulating perovskite oxides and systematically varying the interface density, with unit-cell precision, using two different epitaxial-growth techniques. These observations open up opportunities for studies on the wave nature of phonons, particularly phonon interference effects, using oxide superlattices as model systems, with extensive applications in thermoelectrics and thermal management.

  18. 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.

  19. 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.

  20. Ion layers, tides, gravity waves, and electric fields in the upper atmosphere, inferred from Arecibo incoherent scatter radar measurements

    SciTech Connect

    Morton, Y.T.

    1991-01-01

    This thesis uses data accumulated during 1980-1989 by the Arecibo incoherent scatter radar to study the behavior and physics of ionization irregularities. Low latitude ionization irregularities, known as sporadic-E and intermediate layers, undergo a regular daily descent, convergence, and dumping of ion layers controlled by the neutral tidal wind. A useful way of studying ion layers and their motion is by ion layer trajectory maps which consist of points representing the altitude and time of ionization layers. Two types of maps were used which assigned either a uniform layer intensity or a gray level/pseudo-color to indicate different layer intensities. Important aspects of layer formation are revealed by map analysis. During January, intermediate layers consistently appeared four times per day instead of the normal twice per day pattern. Simulation of ion trajectories based on the ion momentum equation, which includes both Lorentzian and collisional forces, shows that a combination of diurnal, semidiurnal, and six-hour tides is necessary for such a feature to exist, whereas only diurnal and semidiurnal tides are needed to create the normal pattern. The six-hour period tide has not been previously reported. Extra or irregular layers appear frequently in layer trajectory maps, which can be simulated by the addition of gravity waves to the regular tidal wind system. Electric field effects are normally not a factor in low latitude ion layer formation because they are relatively weak and not commonly observed. Layer configurations during a geomagnetic storm, however, indicate that the electric field played an important role in controlling ion motion.

  1. Determination of auroral heat fluxes and thermal ion outflows using a numerical ionospheric model and incoherent-scatter radar data

    SciTech Connect

    Min, Q.L.; Watkins, B.J.

    1995-01-01

    A comprehensive one-dimensional model of the polar ionosphere has been used in conjunction with incoherent-scatter radar data from Sondrestrom, Greenland, to determine downward heat fluxes and thermal ion outflows at very high latitudes. For periods of very quiet geomagnetic activity the model closely simulates the observed time-dependent behavior of the electron density, ion and electron temperatures. To obtain this similarity between model and data, the upper boundary conditions of the model, namely downward heat flux, and magnetic field-aligned ion flows, are continually adjusted with time to provide a best fit with data. The heat fluxes and ion flows are determined indirectly from this fitting procedure. The technique has been applied to a 10-hour daytime data set for February 12, 1990, to search for enhanced downward heat fluxes and outward thermal ion fluxes associated with dayside auroral oval. Variations of heat flux ranged from about 2 x 10{sup 9} to 2 x 10{sup 10} eVcm{sup {minus}2}s{sup {minus}1}, and vertical outward fluxes of ionization ranged from about zero to 8 x 10{sup 8} cm{sup {minus}2}s{sup {minus}1}. For both quantities the peak values occurred when the radar site was located under the dayside auroral oval. It is suggested that these marked upward thermal ion flows in the dayside auroral ionosphere may be associated with energetic O{sup +} ion outflows that have been observed at high altitudes with spacecraft. 12 refs., 6 figs.

  2. C-Phycocyanin Hydration Water Dynamics in the Presence of Trehalose: An Incoherent Elastic Neutron Scattering Study at Different Energy Resolutions

    PubMed Central

    Gabel, Frank; Bellissent-Funel, Marie-Claire

    2007-01-01

    We present a study of C-phycocyanin hydration water dynamics in the presence of trehalose by incoherent elastic neutron scattering. By combining data from two backscattering spectrometers with a 10-fold difference in energy resolution we extract a scattering law S(Q,ω) from the Q-dependence of the elastic intensities without sampling the quasielastic range. The hydration water is described by two dynamically different populations—one diffusing inside a sphere and the other diffusing quasifreely—with a population ratio that depends on temperature. The scattering law derived describes the experimental data from both instruments excellently over a large temperature range (235–320 K). The effective diffusion coefficient extracted is reduced by a factor of 10–15 with respect to bulk water at corresponding temperatures. Our approach demonstrates the benefits and the efficiency of using different energy resolutions in incoherent elastic neutron scattering over a large angular range for the study of biological macromolecules and hydration water. PMID:17350998

  3. C-phycocyanin hydration water dynamics in the presence of trehalose: an incoherent elastic neutron scattering study at different energy resolutions.

    PubMed

    Gabel, Frank; Bellissent-Funel, Marie-Claire

    2007-06-01

    We present a study of C-phycocyanin hydration water dynamics in the presence of trehalose by incoherent elastic neutron scattering. By combining data from two backscattering spectrometers with a 10-fold difference in energy resolution we extract a scattering law S(Q,omega) from the Q-dependence of the elastic intensities without sampling the quasielastic range. The hydration water is described by two dynamically different populations--one diffusing inside a sphere and the other diffusing quasifreely--with a population ratio that depends on temperature. The scattering law derived describes the experimental data from both instruments excellently over a large temperature range (235-320 K). The effective diffusion coefficient extracted is reduced by a factor of 10-15 with respect to bulk water at corresponding temperatures. Our approach demonstrates the benefits and the efficiency of using different energy resolutions in incoherent elastic neutron scattering over a large angular range for the study of biological macromolecules and hydration water.

  4. 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

  5. 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.

  6. 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.

  7. Characterizing near-surface firn using the scattered signal component of the glacier surface return from airborne radio-echo sounding

    NASA Astrophysics Data System (ADS)

    Rutishauser, Anja; Grima, Cyril; Sharp, Martin; Blankenship, Donald D.; Young, Duncan A.; Cawkwell, Fiona; Dowdeswell, Julian A.

    2016-12-01

    We derive the scattered component (hereafter referred to as the incoherent component) of glacier surface echoes from airborne radio-echo sounding measurements over Devon Ice Cap, Arctic Canada, and compare the scattering distribution to firn stratigraphy observations from ground-based radar data. Low scattering correlates to laterally homogeneous firn above 1800 m elevation containing thin, flat, and continuous ice layers and below 1200 m elevation where firn predominantly consists of ice. Increased scattering between elevations of 1200-1800 m corresponds to firn with inhomogeneous, undulating ice layers. No correlation was found to surface roughness and its theoretical incoherent backscattering values. This indicates that the scattering component is mainly influenced by the near-surface firn stratigraphy, whereas surface roughness effects are minor. Our results suggest that analyzing the scattered signal component of glacier surface echoes is a promising approach to characterize the spatial heterogeneity of firn that is affected by melting and refreezing processes.

  8. Investigating the ionosphere response to exhaust products of ``Progress'' cargo spacecraft engines on the basis of Irkutsk Incoherent Scatter Radar data

    NASA Astrophysics Data System (ADS)

    Shpynev, Boris; Alsatkin, Sergei; Khakhinov, Vitaliy; Lebedev, Valentin

    2017-04-01

    The FSUE Central Research Institute of Machine Building (TsNIIMash), Rocket and Space Corporation "Energia", and Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of Sciences (ISTP SB RAS) jointly conducted the active space experiment "Radar-Progress" in 2007-2015. During this experiment, we used the Irkutsk Incoherent Scatter Ra-dar to study space-time characteristics of ionospheric disturbances generated by exhaust products of "Progress" cargo spacecraft engines. As the basic effect during exhaust product injection we consider the formation of new centers for recombination of ambient ionospheric ions O+ on molecules of water and carbon dioxide. This produces an ionization "hole" in the region of injection. In nighttime conditions when the majority of experiments were performed, this hole was filled by hydrogen ions from the plasmasphere, thus the ion composition in the vicinity of the hole and incoherent scatter spectra were changed. For successful obser-vation of the ionization hole dynamics, the critical fac-tors are the degree of radar antenna diagram filling by exhaust products and the velocity of the thermospheric neutral wind, which makes exhaust gases move from the antenna diagram. These two factors lead to poor repeatability of successful experiments. Successful experiments recorded a decrease in electron density up to 35 % in the hole that existed for 30 min. The lifetime of the region with high concentration of H+ ions can be as long as one hour.

  9. 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

  10. High resolution general purpose D-layer experiment for EISCAT incoherent scatter radars using selected set of random codes

    NASA Astrophysics Data System (ADS)

    Turunen, T.; Westman, A.; Häggström, I.; Wannberg, G.

    2002-09-01

    The ionospheric D-layer is a narrow bandwidth radar target often with a very small scattering cross section. The target autocorrelation function can be obtained by transmitting a series of relatively short coded pulses and computing the correlation between data obtained from different pulses. The spatial resolution should be as high as possible and the spatial side lobes of the codes used should be as small as possible. However, due to the short pulse repetition period (in the order of milliseconds) at any instant, the radar receives detectable scattered signals not only from the pulse illuminating the D-region but also from 3 5 ambiguous-range pulses, which makes it difficult to produce a reliable estimate near zero lag of the autocorrelation function. A new experimental solution to this measurement problem, using a selected set of 40-bit random codes with 4 µs elements giving 600 m spatial resolution is presented. The zero lag is approximated by dividing the pulse into two 20-bit codes and computing the correlation between those two pulses. The lowest altitudes of the E-layer are measured by dividing the pulse into 5 pieces of 8 bits, which allows for computation of 4 lags. In addition, coherent integration of data from four pulses is used for obtaining separately the autocorrelation function estimate for the lowest altitudes and in cases when the target contains structures with a long coherence time. Design details and responses of the experiment are given, and analysed test data are shown.

  11. Derivation of realistic surface and particulate scatter transfer functions and their application to incoherent imaging of high-contrast fine-detail scenes

    NASA Astrophysics Data System (ADS)

    Greynolds, Alan W.

    2016-09-01

    Previous research on optical surface scatter either assumed for the ACV (Auto-Covariance function) a simple analytical but unrealistic Gaussian form or depended on intensive numerical integrations. Measurements of polished optical surfaces indicate they accurately follow a simple inverse power law for the BSDF (Bi-directional Scatter Distribution Function) and the related PSD (Power Spectral Density) of their random height variations, i.e. they are fractal-like. By applying the appropriate limits to the scale-invariant (no intrinsic correlation length) PSD, a general analytic form for the corresponding ACV and STF (Surface or Scatter Transfer Function) can be derived. Combined with other Fourier-Bessel transform pairs, it's possible to accurately simulate the effect of not only diffraction and aberrations such as defocus (via the system OTF or Optical Transfer Function) but also surface and particulate scatter on the incoherent imaging of highcontrast fine-detail scenes. Simple examples of Gaussian and point objects are first presented followed by application to digital cameras that require integrating the aerial image over each pixel's active area. The needed subsampling for a camera with over ten million pixels (each only few microns in size) requires two-dimensional FFTs (Fast Fourier Transforms) of many gigabytes to accurately perform the detailed imaging calculations.

  12. 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

    2015-07-07

    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.

  13. 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.

  14. Combined incoherent scatter radar and Fabry-Perot interferometer measurements of frictional heating effects over Millstone Hill during March 7-10, 1989

    SciTech Connect

    Hagan, M.E.; Sipler, D.P. )

    1991-01-01

    The authors introduce a methodology to calculate the effects of frictional heating associated with geomagnetic activity using simultaneous incoherent scatter radar and Fabry-Perot interferometer measurements. Vector measurements of ion drift from radar backscatter and neutral wind from optical shifts in the atomic oxygen red line over Millstone Hill, Massachusetts (43{degree}N) for the nights of March 7-10, 1989 are presented and are characterized by the magnetic storm activity which prevailed. They combine these measurements to calculate differences in the ion and neutral velocity fields which approach 350 m/s during the most geomagnetically active period that they monitored near 01 UT on March 9. This velocity difference results in a 110{degree}K heating of the ion gas at that time.

  15. 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.

  16. Dynamic properties of photosystem II membranes at physiological temperatures characterized by elastic incoherent neutron scattering. Increased flexibility associated with the inactivation of the oxygen evolving complex.

    PubMed

    Nagy, Gergely; Pieper, Jörg; Krumova, Sashka B; Kovács, László; Trapp, Marcus; Garab, Győző; Peters, Judith

    2012-03-01

    Elastic incoherent neutron scattering (EINS), a non-invasive technique which is capable of measuring the mean square displacement of atoms in the sample, has been widely used in biology for exploring the dynamics of proteins and lipid membranes but studies on photosynthetic systems are scarce. In this study we investigated the dynamic characteristics of Photosystem II (PSII) membrane fragments between 280 and 340 K, i.e., in the physiological temperature range and in the range of thermal denaturation of some of the protein complexes. The mean square displacement values revealed the presence of a hydration-sensitive transition in the sample between 310 and 320 K, suggesting that the oxygen evolving complex (OEC) plays an important role in the transition. Indeed, in samples in which the OEC had been removed by TRIS- or heat-treatments (323 and 333 K) no such transition was found. Further support on the main role of OEC in these reorganizations is provided by data obtained from differential scanning calorimetry experiments, showing marked differences between the untreated and TRIS-treated samples. In contrast, circular dichroism spectra exhibited only minor changes in the excitonic interactions below 323 K, showing that the molecular organization of the pigment-protein complexes remains essentially unaffected. Our data, along with earlier incoherent neutron scattering data on PSII membranes at cryogenic temperatures (Pieper et al., Biochemistry 46:11398-11409, 2007), demonstrate that this technique can be applied to characterize the dynamic features of PSII membranes, and can be used to investigate photosynthetic membranes under physiologically relevant experimental conditions.

  17. 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.

  18. The dynamic cusp at low altitudes: A case study utilizing Viking, DMSP-F7 and Sondrestrom incoherent scatter radar observations

    NASA Technical Reports Server (NTRS)

    Watermann, J.; De La Beaujardiere, O.; Lummerzheim, D.; Woch, J.; Newell, P. T.; Potemra, T. A.; Rich, F. J.; Shapshak, M.

    1994-01-01

    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 deg 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 1.2h local time. The cusp appeared to be about 2 deg invariant latitude wide, and its ionospheric footprint shifted equatorward by nearly 2 deg during this time, possibly influenced by an overall decrease in the interplanetary magnetic field (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.

  19. 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.

  20. Diurnal variations of the ionospheric electron density height profiles over Irkutsk: Comparison of the incoherent scatter radar measurements, GSM TIP simulations and IRI predictions

    NASA Astrophysics Data System (ADS)

    Zherebtsov, G. A.; Ratovsky, K. G.; Klimenko, M. V.; Klimenko, V. V.; Medvedev, A. V.; Alsatkin, S. S.; Oinats, A. V.; Lukianova, R. Yu.

    2017-07-01

    The long-duration continuous Irkutsk incoherent scatter radar (ISR) measurements allowed us to obtain the monthly averaged height-diurnal variations of the electron density in the 180-600 km altitudinal range for 4 four seasons (winter, spring, summer, autumn) and for two solar activity levels (low and moderate). Considering these electron density variations as ;quiet ionosphere patterns; we compared them with the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) simulations and the International Reference Ionosphere (IRI) predictions. It was found that some observational features revealed from the ISR measurements are reproduced nicely by both the theoretical and empirical models, and some features agree better with the GSM TIP than with IRI. None of the models is able to reproduce a detailed multi-peak behavior of the electron density observed by ISR at ∼300 km and above for the spring and autumn under low solar activity, while for the spring the GSM TIP tends to reproduce the morning and daytime peaks at the same local times as they are seen from the ISR observations.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Power coupling characteristics between FBG and back-scattering signals

    NASA Astrophysics Data System (ADS)

    Li, Jianzhi; Zhao, Desheng; Hou, Yuemin; Sun, Baochen

    2017-03-01

    The property and compatibility between fiber Bragg grating (FBG) and back-scattering signals are investigated by employing optical time domain reflectometry. We compare the power spectrums of spontaneous Brillouin scattering (SpBS), simultaneous Brillouin scattering (SBS) and Rayleigh scattering (RS), and coupling mechanism between FBG and back-scattering signal is explored. Experimental results show that the region of FBG contributes to the backscatter power and causes the desired reflection, and the power peak of FBG in SBS power spectrum is the sharpest among back-scattering light power spectrums and broadens with the decrease of spatial resolution. Moreover, the FBG-based method is used to find the location of temperature or stain event for scatter-based distributed sensors.

  8. An inelastic incoherent neutron scattering study of water in small-pored zeolites and other water-bearing minerals

    NASA Astrophysics Data System (ADS)

    Line, Christina M. B.; Kearley, G. J.

    2000-05-01

    Inelastic neutron scattering spectra of the zeolites natrolite Na2Al2Si3O10 2H2O, wairakite CaAl2Si4O12 2H2O, scolecite CaAl2Si3O10 3H2O, and bikitaite Li2Al2Si4O12. 2H2O, together with the sheet silicate apophyllite KCa4Si8O20(F, OH) 8H2O, are shown here. We show clear trends across these minerals, illustrating the relative influence of hydrogen bonding and cation bonding. For some of these spectra, the bands are clearly separated, permitting a discussion of their assignments. In particular, we can identify librational bands (L) or librational edge (LE) and translational (cation-water stretch) bands (C), and by elimination can tentatively assign bands as hydrogen-bond stretch bands (H), as follows (frequencies given in meV): Natrolite: 13,18 (C) 26 (H), 64,68,87 (L); Apophyllite 17,26 (C), 35 (H) 64,79,98 (L); Scolecite 10 (C), 22,29,36,41 (H), 46 (LE); Wairakite 12 (C), 30 (LE); Bikitaite 13 (C), 22 (H), 34 (LE), 70(L). The results are compared with those for ice and are explained in terms of the nearest-neighbor environment of the water molecule.

  9. Mid-latitude ionospheric plasma temperature climatology and model based on Saint Santin incoherent scatter radar data from 1966-1987

    NASA Astrophysics Data System (ADS)

    Zhang, S. R.; Holt, J. M.; Zalucha, A. M.; Amory-Mazaudier, C.

    Zhang and Holt (2003, Ionospheric plasma temperatures during 1976-2001 over Millstone Hill, Adv. Space Res.) have reported the ionospheric plasma temperature variation based on incoherent scatter radar (ISR) observations between 1976 and 2001 at Millstone Hill, a typical sub-auroral mid-latitude site in North America. The French Saint Santin ISR, with a geographic latitude slightly higher but an apex latitude 7 degress lower than Millstone, collected bistatic and quadristatic measurements for 2 solar cycles beginning in September 1965.A database of these data from 1966 and 1987 has been used in this study in order to establish the mid-latitude ionospheric climatology, in particular that of the upper atmosphere thermal status, as well as empirical models for space weather applications. This paper presents, in comparison with the Millstone results, the variation of ion and electron temperature (Ti and Te) with solar activity, season, time of the day, and altitude. It is found that the F2 region Te at St Santin is not as high as in Millstone between May and September, when electron density (Ne) is relatively higher. The midday Te increases below 300 km with F107, as at Millstone Hill. However, above 300 km it tends to decrease with F107 at St Santin and increases between May and September at Millstone Hill. Ti between 250-350 km peaks not in summer but around May. Based on this database, Saint Saintin ionospheric models for Ne, Te, and Ti have also been created using a bin-fit technique similar to that used for the Millstone Hill models. Comparisions with corresponding IRI predications indicate good agreement in Ti at high solar activity, and IRI tends to give Te above the F2 peak higher than both the Saint Santin and Millstone Hill models.

  10. Ionospheric incoherent scatter measurements with the middle and upper atmosphere radar: Observations during the large magnetic storm of February 6--8, 1986

    SciTech Connect

    Oliver, W.L.; Fukao, S.; Sato, T.; Tsuda, T.; Kato, S.; Kimura, I.; Ito, A.; Saryou, T.; Araki, T.

    1988-12-01

    The middle and upper atmosphere (MU) radar of Japan is a 46.5-MHz, pulse-modulated, monostatic, Doppler radar with an active phased-array antenna which consists of 475 crossed yagis. This system has been used primarily, since its initial observations with a partial system in 1983, to observe the coherent backscatter from irregularities in the troposphere, stratosphere, and mesosphere (MST radar). However, this system was also designed to be able to observe the weak incoherent scatter (IS) from the free electrons of the ionosphere. We report here the MU radar IS observations made during the strong geomagnetic storm of 6--8, February 1986. During this period the MU radar observed the echo power (an approximate measure of electron density) simultaneously in four antenna beam positions. Coincident with the rise in the K/sub p/ index from 3+ to 6- near 1800 LT (0900 UT) on February 7, the MU radar detected the beginning of several hours of wave activity having a period of 100 min. By correlating the density observations in the different beams and at different altitudes, we were able to compute the phase speed (410 m/s), direction of travel (9/sup 0/ west of south), and horizontal (2500 km) and vertical 290--490 km) wavelengths of the wave. The F layer peak density and height oscillated during this nighttime period, and we consider several mechanisms that might cause these effects. We find that the density oscillation was too large to be caused solely by wave dynamics. We suggest that an influx of ionization from the plasmasphere, and a wave-induced modulation of the assimilation of this plasma flux into the ambient density, may have been the cause of the observed density increases.

  11. Storm/Quiet Ratio Comparisons Between TIMED/SABER NO (sup +)(v) Volume Emission Rates and Incoherent Scatter Radar Electron Densities at E-Region Altitudes

    NASA Technical Reports Server (NTRS)

    Fernandez, J. R.; Mertens, C. J.; Bilitza, D.; Xu, X.; Russell, J. M., III; Mlynczak, M. G.

    2009-01-01

    Broadband infrared limb emission at 4.3 microns is measured by the TIMED/SABER instrument. At night, these emission observations at E-region altitudes are used to derive the so called NO+(v) Volume Emission Rate (VER). NO+(v) VER can be derived by removing the background CO2(v3) 4.3 microns radiance contribution using SABER-based non-LTE radiation transfer models, and by performing a standard Abel inversion on the residual radiance. SABER observations show that NO+(v) VER is significantly enhanced during magnetic storms in accordance with increased ionization of the neutral atmosphere by auroral electron precipitation, followed by vibrational excitation of NO+ (i.e., NO+(v)) from fast exothermic ion-neutral reactions, and prompt infrared emission at 4.3 m. Due to charge neutrality, the NO+(v) VER enhancements are highly correlated with electron density enhancements, as observed for example by Incoherent Scatter Radar (ISR). In order to characterize the response of the storm-time E-region from both SABER and ISR measurements, a Storm/Quiet ratio (SQR) quantity is defined as a function of altitude. For SABER, the SQR is the ratio of the storm-to-quiet NO+(v) VER. SQR is the storm-to-quiet ratio of electron densities for ISR. In this work, we compare SABER and ISR SQR values between 100 to 120 km. Results indicate good agreement between these measurements. SQR values are intended to be used as a correction factor to be included in an empirical storm-time correction to the International Reference Ionosphere model at E-region altitudes.

  12. Radar Array Signal Processing in the Presence of Scattering Effects

    DTIC Science & Technology

    2008-01-15

    for detecting/ tracking targets in clutter; microstrip antennas design with suppressed radiation in horizontal directions and reduced coupling, and 6D...e.g., brain) signals. 15. SUBJECT TERMS Radar, target detection, tracking , performance analysis, electromagnetic modeling, scattering phenomena...challenging and common problems in detecting and estimating a target with radar systems is the presence of scatterers in the environment. The echoes

  13. Rigid and elastic acoustic scattering signal separation for underwater target.

    PubMed

    Jia, Hongjian; Li, Xiukun; Meng, Xiangxia

    2017-08-01

    Underwater target elastic acoustic scattering and other acoustic scattering components are aliasing together in the time and frequency domains, and the existing signal processing methods cannot recognize the elastic scattering features under the aliasing condition because of the resolution limitation. To address this problem, this study, which is based on the target echo highlight model, analyzes the characteristics of target acoustic scattering components when the transmitted signal is a linear frequency modulation pulse. The target acoustic scattering structure in the fractional Fourier transform (FRFT) domain is deduced theoretically. Then, filtering is used in the FRFT domain to separate the target elastic acoustic scattering components. In addition, noise suppression performance and filter resolution are discussed. The target rigid and elastic acoustic scattering components are separated. Experimental results show that filtering in the FRFT domain can separate the elastic scattering components from the target echoes. Moreover, separated elastic acoustic scattering components have consistent theoretical features, which lay the foundation for studying the elastic scattering characteristics further.

  14. Effect of scattering on coherent anti-Stokes Raman scattering (CARS) signals

    NASA Astrophysics Data System (ADS)

    Ranasinghesagara, Janaka C.; De Vito, Giuseppe; Piazza, Vincenzo; Potma, Eric O.; Venugopalan, Vasan

    2017-04-01

    We develop a computational framework to examine the factors responsible for scattering-induced distortions of coherent anti-Stokes Raman scattering (CARS) signals in turbid samples. We apply the Huygens-Fresnel Wave-based Electric Field Superposition (HF-WEFS) method combined with the radiating dipole approximation to compute the effects of scattering-induced distortions of focal excitation fields on the far-field CARS signal. We analyze the effect of spherical scatterers, placed in the vicinity of the focal volume, on the CARS signal emitted by different objects (2{\\mu}m diameter solid sphere, 2{\\mu}m diameter myelin cylinder and 2{\\mu}m diameter myelin tube). We find that distortions in the CARS signals arise not only from attenuation of the focal field but also from scattering-induced changes in the spatial phase that modifies the angular distribution of the CARS emission. Our simulations further show that CARS signal attenuation can be minimized by using a high numerical aperture condenser. Moreover, unlike the CARS intensity image, CARS images formed by taking the ratio of CARS signals obtained using x- and y-polarized input fields is relatively insensitive to the effects of spherical scatterers. Our computational framework provide a mechanistic approach to characterizing scattering-induced distortions in coherent imaging of turbid media and may inspire bottom-up approaches for adaptive optical methods for image correction.

  15. Effect of scattering on coherent anti-Stokes Raman scattering (CARS) signals.

    PubMed

    Ranasinghesagara, Janaka C; De Vito, Giuseppe; Piazza, Vincenzo; Potma, Eric O; Venugopalan, Vasan

    2017-04-17

    We develop a computational framework to examine the factors responsible for scattering-induced distortions of coherent anti-Stokes Raman scattering (CARS) signals in turbid samples. We apply the Huygens-Fresnel wave-based electric field superposition (HF-WEFS) method combined with the radiating dipole approximation to compute the effects of scattering-induced distortions of focal excitation fields on the far-field CARS signal. We analyze the effect of spherical scatterers, placed in the vicinity of the focal volume, on the CARS signal emitted by different objects (2μm diameter solid sphere, 2μm diameter myelin cylinder and 2μm diameter myelin tube). We find that distortions in the CARS signals arise not only from attenuation of the focal field but also from scattering-induced changes in the spatial phase that modifies the angular distribution of the CARS emission. Our simulations further show that CARS signal attenuation can be minimized by using a high numerical aperture condenser. Moreover, unlike the CARS intensity image, CARS images formed by taking the ratio of CARS signals obtained using x- and y-polarized input fields is relatively insensitive to the effects of spherical scatterers. Our computational framework provide a mechanistic approach to characterizing scattering-induced distortions in coherent imaging of turbid media and may inspire bottom-up approaches for adaptive optical methods for image correction.

  16. Vibrations and reorientations of H2O molecules in [Sr(H2O)6]Cl2 studied by Raman light scattering, incoherent inelastic neutron scattering and proton magnetic resonance.

    PubMed

    Hetmańczyk, Joanna; Hetmańczyk, Lukasz; Migdał-Mikuli, Anna; Mikuli, Edward; Florek-Wojciechowska, Małgorzata; Harańczyk, Hubert

    2014-04-24

    Vibrational-reorientational dynamics of H2O ligands in the high- and low-temperature phases of [Sr(H2O)6]Cl2 was investigated by Raman Spectroscopy (RS), proton magnetic resonance ((1)H NMR), quasielastic and inelastic incoherent Neutron Scattering (QENS and IINS) methods. Neutron powder diffraction (NPD) measurements, performed simultaneously with QENS, did not indicated a change of the crystal structure at the phase transition (detected earlier by differential scanning calorimetry (DSC) at TC(h)=252.9 K (on heating) and at TC(c)=226.5K (on cooling)). Temperature dependence of the full-width at half-maximum (FWHM) of νs(OH) band at ca. 3248 cm(-1) in the RS spectra indicated small discontinuity in the vicinity of phase transition temperature, what suggests that the observed phase transition may be associated with a change of the H2O reorientational dynamics. However, an activation energy value (Ea) for the reorientational motions of H2O ligands in both phases is nearly the same and equals to ca. 8 kJ mol(-1). The QENS peaks, registered for low temperature phase do not show any broadening. However, in the high temperature phase a small QENS broadening is clearly visible, what implies that the reorientational dynamics of H2O ligands undergoes a change at the phase transition. (1)H NMR line is a superposition of two powder Pake doublets, differentiated by a dipolar broadening, suggesting that there are two types of the water molecules in the crystal lattice of [Sr(H2O)6]Cl2 which are structurally not equivalent average distances between the interacting protons are: 1.39 and 1.18 Å. However, their reorientational dynamics is very similar (τc=3.3⋅10(-10) s). Activation energies for the reorientational motion of these both kinds of H2O ligands have nearly the same values in an experimental error limit: and equal to ca. 40 kJ mole(-1). The phase transition is not seen in the (1)H NMR spectra temperature dependencies. Infrared (IR), Raman (RS) and inelastic

  17. Effect of scattering anisotropy on acoustooptic tomography signal

    NASA Astrophysics Data System (ADS)

    Soloviev, A. P.; Perchenko, M. I.; Zyuryukina, O. V.

    2013-02-01

    Investigation of a dependence of a registered signal on an extinction parameter μ of a scattering media (the water solution of milk, thickness L) at an acoustooptic tomography showed the signal values could be essentially differed at the same μL in various charges of milk. It was essentially noticeable at the medium parameter μL <18. In the present work the influence of medium scattering anisotropy parameter g on the registered signal value S was experimentally studied. As the scattering media the water solutions of the mixtures of a skimmed milk and cream in some proportions were used. The result of the study is the necessity to take into consideration the possible g-factor change in the scattering media including biological ones at a decision of the acoustooptic tomography inverse problem.

  18. 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

  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. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. 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.

  1. 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.

  2. 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. Copyright © 2011 Elsevier B.V. All rights reserved.

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

    PubMed

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

    2013-04-01

    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. 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. 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. 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 20-40 keV.

  4. 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

  5. Frequency-resolved nonlinear interferometry with incoherent light and applications to coherent Raman spectroscopies

    NASA Astrophysics Data System (ADS)

    Stimson, Michael Jay

    1997-12-01

    Demonstrations of several frequency resolved incoherent field non-linear interferometric spectroscopies are presented with emphasis on applications to coherent Raman scattering (two incoherent field actions- I(2)CRS). The properties of the incoherent (noisy) laser sources used for time resolution of ultrafast dynamics are explored in detail theoretically and experimentally. A new technique for the measurement of noisy light correlation functions (I(2)FROG-two incoherent field actions in frequency resolved optical gating) is developed theoretically and used for experimental explorations of the nature of noisy optical fields and their relation to coherent short pulsed optical fields. I(2)FROG and I(2)CRS signals are frequency dispersed and multichannel detected, which when combined with interferometric time resolution allows the creation of two-dimensional representations of these signals (spectrally resolved interferograms, or spectrograms). Spectrograms offer a large redundancy in the sampling of signals, thus allowing great precision in the measurement of observable parameters. In I(2)FROG, the observable parameters characterize the noisy light in the form of the intensity and phase of cross correlation functions between beams of broadband light. In I(2)CRS, the observable parameters quantify material properties such as lineshape parameters, transition frequencies and ratios of resonant to non-resonant contributions to molecular hyperpolarizability tensor elements. Algorithms for the recovery of the observable parameters are developed and applied to the spectrograms derived from many condensed phase materials. Systems explored via spectrogram representation include pure substances and non-reactive mixtures. A novel modification of the original I(2)CRS experiment is presented in which spectrally tailored fields are used to control the properties of the I(2)CRS signals. Newly predicted fifth order signals (I(3)FOOCRS-three incoherent field actions in fifth order

  6. On the optimum polarizations of incoherently reflected waves

    NASA Technical Reports Server (NTRS)

    Van Zyl, Jakob J.; Elachi, Charles; Papas, Charles H.

    1987-01-01

    The Stokes scattering operator is noted to be the most useful characterization of incoherent scattering in radar imaging; the polarization that would yield an optimum amount of power received from the scatterer is obtained by assuming a knowledge of the Stokes scattering operator instead of the 2x2 scattering matrix with complex elements. It is thereby possible to find the optimum polarizations for the case in which the scatterers can only be fully characterized by their Stokes scattering operator, and the case in which the scatterer can be fully characterized by the complex 2x2 scattering matrix. It is shown that the optimum polarizations reported in the literature form the solution for a subset of a more general class of problems, so that six optimum polarizations can exist for incoherent scattering.

  7. Spatially incoherent Fourier digital holography

    NASA Astrophysics Data System (ADS)

    Nomura, Takanori; Watanabe, Kaho

    2017-05-01

    The possibility of incoherent digital holography has been widely studied because it is free from coherent light sources. Here spatially incoherent Fourier digital holography is described. The incoherent hologram is obtained by a rotational shearing interferometer. The hologram obtained by the interferometer is a cosine transform of a spatially incoherent object. After describing the principle of a rotational shearing interferometer, methods to obtain Fourier transform of an object presented.

  8. 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.

  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 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 Diffractive Imaging via Intensity Correlations of Hard X Rays

    NASA Astrophysics Data System (ADS)

    Classen, Anton; Ayyer, Kartik; Chapman, Henry N.; Röhlsberger, Ralf; von Zanthier, Joachim

    2017-08-01

    Established x-ray diffraction methods allow for high-resolution structure determination of crystals, crystallized protein structures, or even single molecules. While these techniques rely on coherent scattering, incoherent processes like fluorescence emission—often the predominant scattering mechanism—are generally considered detrimental for imaging applications. Here, we show that intensity correlations of incoherently scattered x-ray radiation can be used to image the full 3D arrangement of the scattering atoms with significantly higher resolution compared to conventional coherent diffraction imaging and crystallography, including additional three-dimensional information in Fourier space for a single sample orientation. We present a number of properties of incoherent diffractive imaging that are conceptually superior to those of coherent methods.

  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. Incoherent population mixing contributions to phase-modulation two-dimensional coherent excitation spectra.

    PubMed

    Grégoire, Pascal; Srimath Kandada, Ajay Ram; Vella, Eleonora; Tao, Chen; Leonelli, Richard; Silva, Carlos

    2017-09-21

    We present theoretical and experimental results showing the effects of incoherent population mixing on two-dimensional (2D) coherent excitation spectra that are measured via a time-integrated population and phase-sensitive detection. The technique uses four collinear ultrashort pulses and phase modulation to acquire two-dimensional spectra by isolating specific nonlinear contributions to the photoluminescence or photocurrent excitation signal. We demonstrate that an incoherent contribution to the measured line shape, arising from nonlinear population dynamics over the entire photoexcitation lifetime, generates a similar line shape to the expected 2D coherent spectra in condensed-phase systems. In those systems, photoexcitations are mobile such that inter-particle interactions are important on any time scale, including those long compared with the 2D coherent experiment. Measurements on a semicrystalline polymeric semiconductor film at low temperatures show that, in some conditions in which multi-exciton interactions are suppressed, the technique predominantly detects coherent signals and can be used, in our example, to extract homogeneous line widths. The same method used on a lead-halide perovskite photovoltaic cell shows that incoherent population mixing of mobile photocarriers can dominate the measured signal since carrier-carrier bimolecular scattering is active even at low excitation densities, which hides the coherent contribution to the spectral line shape. In this example, the intensity dependence of the signal matches the theoretical predictions over more than two orders of magnitude, confirming the incoherent nature of the signal. While these effects are typically not significant in dilute solution environments, we demonstrate the necessity to characterize, in condensed-phase materials systems, the extent of nonlinear population dynamics of photoexcitations (excitons, charge carriers, etc.) in the execution of this powerful population-detected coherent

  14. Incoherent population mixing contributions to phase-modulation two-dimensional coherent excitation spectra

    NASA Astrophysics Data System (ADS)

    Grégoire, Pascal; Srimath Kandada, Ajay Ram; Vella, Eleonora; Tao, Chen; Leonelli, Richard; Silva, Carlos

    2017-09-01

    We present theoretical and experimental results showing the effects of incoherent population mixing on two-dimensional (2D) coherent excitation spectra that are measured via a time-integrated population and phase-sensitive detection. The technique uses four collinear ultrashort pulses and phase modulation to acquire two-dimensional spectra by isolating specific nonlinear contributions to the photoluminescence or photocurrent excitation signal. We demonstrate that an incoherent contribution to the measured line shape, arising from nonlinear population dynamics over the entire photoexcitation lifetime, generates a similar line shape to the expected 2D coherent spectra in condensed-phase systems. In those systems, photoexcitations are mobile such that inter-particle interactions are important on any time scale, including those long compared with the 2D coherent experiment. Measurements on a semicrystalline polymeric semiconductor film at low temperatures show that, in some conditions in which multi-exciton interactions are suppressed, the technique predominantly detects coherent signals and can be used, in our example, to extract homogeneous line widths. The same method used on a lead-halide perovskite photovoltaic cell shows that incoherent population mixing of mobile photocarriers can dominate the measured signal since carrier-carrier bimolecular scattering is active even at low excitation densities, which hides the coherent contribution to the spectral line shape. In this example, the intensity dependence of the signal matches the theoretical predictions over more than two orders of magnitude, confirming the incoherent nature of the signal. While these effects are typically not significant in dilute solution environments, we demonstrate the necessity to characterize, in condensed-phase materials systems, the extent of nonlinear population dynamics of photoexcitations (excitons, charge carriers, etc.) in the execution of this powerful population-detected coherent

  15. Ultraviolet-excimer laser-based incoherent Doppler lidar system

    NASA Technical Reports Server (NTRS)

    Mcdermid, I. Stuart; Laudenslager, James B.; Rees, David

    1985-01-01

    The topics covered include the following: principles of Doppler measurements, laser backscatter, eye safety, demonstration concepts, the wavelength-meter, the interferometer detector, return signal model, and comparison of incoherent and coherent lidars.

  16. Volume cross section of auroral radar backscatter and RMS plasma fluctuations inferred from coherent and incoherent scatter data: a response on backscatter volume parameters

    NASA Astrophysics Data System (ADS)

    Uspensky, M. V.; Janhunen, P.; Koustov, A. V.; Kauristie, K.

    2011-06-01

    Norway and Finland STARE radar measurements in the eastward auroral electrojet are combined with EISCAT CP-1 measurements of the electron density and electric field vector in the common scattering volume to investigate the variation of the auroral radar volume cross section (VCS) with the flow angle of observations (radar look direction with respect to the E×B electron drift). The data set available consists of ~6000 points for flow angles of 40-85° and electron drifts between 500 and 2000 m s-1. The EISCAT electron density N(h)-profile data are used to estimate the effective electron density, aspect angle and thickness of the backscattering layer. It is shown that the flow angle variation of the VCS is rather weak, only ~5 dB within the range of the considered flow angles. The VCS values themselves respond almost linearly to the square of both the electron drift velocity magnitude and the effective electron density. By adopting the inferred shape of the VCS variation with the flow angle and the VCS dependence upon wavelength, the relative amplitude of electrostatic electron density fluctuations over all scales is estimated. Inferred values of 2-4 percent react nearly linearly to the electron drift velocity in the range of 500-1000 m s-1 but the rate of increase slows down at electron drifts >1000 m s-1 and density fluctuations of ~5.5 percent due to, perhaps, progressively growing nonlinear wave losses.

  17. 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.

  18. Doppler Optical Coherence Tomography Signals: Analysis in Low and High Scattering Media

    NASA Astrophysics Data System (ADS)

    Bykov, Alexander V.; Kalkman, Jeroen

    In this chapter, Doppler OCT signals (OCT magnitude and flow velocity profile) for low and high scattering media are analyzed. For low scattering media, we demonstrate the use of the single scattering model to determine the optical properties of the sample. For high scattering media, the effects of multiple scattering are stronger and the single scattering description breaks down. An alternative approach, based on Monte Carlo simulations, is proposed as it gives a more appropriate description of the Doppler OCT signal by taking into account multiple scattering effects. Using Monte Carlo simulations, we analyze the deviation of the OCT slope from the value predicted by the single scattering model and analyze the distortions in the measured Doppler OCT flow profile. Monte Carlo simulations are compared to Doppler OCT measurements for Intralipid and blood.

  19. Coherent and incoherent ultrasound backscatter from cell aggregates.

    PubMed

    de Monchy, Romain; Destrempes, François; Saha, Ratan K; Cloutier, Guy; Franceschini, Emilie

    2016-09-01

    The effective medium theory (EMT) was recently developed to model the ultrasound backscatter from aggregating red blood cells [Franceschini, Metzger, and Cloutier, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 58, 2668-2679 (2011)]. The EMT assumes that aggregates can be treated as homogeneous effective scatterers, which have effective properties determined by the aggregate compactness and the acoustical characteristics of the cells and the surrounding medium. In this study, the EMT is further developed to decompose the differential backscattering cross section of a single cell aggregate into coherent and incoherent components. The coherent component corresponds to the squared norm of the average scattering amplitude from the effective scatterer, and the incoherent component considers the variance of the scattering amplitude (i.e., the mean squared norm of the fluctuation of the scattering amplitude around its mean) within the effective scatterer. A theoretical expression for the incoherent component based on the structure factor is proposed and compared with another formulation based on the Gaussian direct correlation function. This theoretical improvement is assessed using computer simulations of ultrasound backscatter from aggregating cells. The consideration of the incoherent component based on the structure factor allows us to approximate the simulations satisfactorily for a product of the wavenumber times the aggregate radius krag around 2.

  20. 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.

  1. 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.

  2. Quantum-electrodynamical parametric instability in the incoherent photon gas.

    PubMed

    Wang, Yunliang; Shukla, P K; Eliasson, B

    2013-02-01

    We present a theory for the quantum-electrodynamical (QED) parametric scattering instability of an intense photon pulse in an incoherent radiation background. The pump electromagnetic (EM) wave can decay into a scattered daughter EM wave and an acousticlike wave due to the QED vacuum polarization nonlinearity. By a linear instability analysis we obtain a nonlinear dispersion relation for the growth rate of the scattering instability. The nonlinear QED scattering instability can give rise to the exchange of orbital angular momentum between intense Laguerre-Gaussian mode photon pulses and the two daughter waves, which may be a useful method to detect the highly energetic photon gases existing in the vicinity of rotating dense bodies in the Universe, such as pulsars and magnetars. The observation of the scattered waves may reveal information about the twisted acoustic waves in the incoherent photon gas.

  3. Correlation-based virtual source imaging in strongly scattering random media

    NASA Astrophysics Data System (ADS)

    Garnier, Josselin; Papanicolaou, George

    2012-07-01

    Array imaging in a strongly scattering medium is limited because coherent signals recorded at the array and coming from a reflector to be imaged are weak and dominated by incoherent signals coming from multiple scattering by the medium. If, however, an auxiliary passive array can be placed between the reflector to be imaged and the scattering medium then the cross correlations of the incoherent signals on this array can also be used to image the reflector. In this paper, we show both in the weakly scattering paraxial regime and in strongly scattering layered media that this cross-correlation approach produces images as if the medium between the sources and the passive array was homogeneous and the auxiliary passive array was an active one made up of both sources and receivers.

  4. 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.

  5. Frequency domain and full waveform time domain inversion of ground based magnetometer, electrometer and incoherent scattering radar arrays to image strongly heterogenous 3-D Earth structure, ionospheric structure, and to predict the intensity of GICs in the power grid

    NASA Astrophysics Data System (ADS)

    Schultz, A.; Imamura, N.; Bonner, L. R., IV; Cosgrove, R. B.

    2016-12-01

    Ground-based magnetometer and electrometer arrays provide the means to probe the structure of the Earth's interior, the interactions of space weather with the ionosphere, and to anticipate the intensity of geomagnetically induced currents (GICs) in power grids. We present a local-to-continental scale view of a heterogeneous 3-D crust and mantle as determined from magnetotelluric (MT) observations across arrays of ground-based electric and magnetic field sensors. MT impedance tensors describe the relationship between electric and magnetic fields at a given site, thus implicitly they contain all known information on the 3-D electrical resistivity structure beneath and surrounding that site. By using multivariate transfer functions to project real-time magnetic observatory network data to areas surrounding electric power grids, and by projecting those magnetic fields through MT impedance tensors, the projected magnetic field can be transformed into predictions of electric fields along the path of the transmission lines, an essential element of predicting the intensity of GICs in the grid. Finally, we explore GICs, i.e. Earth-ionosphere coupling directly in the time-domain. We consider the fully coupled EM system, where we allow for a non-stationary ionospheric source field of arbitrary complexity above a 3-D Earth. We solve the simultaneous inverse problem for 3-D Earth conductivity and source field structure directly in the time domain. In the present work, we apply this method to magnetotelluric data obtained from a synchronously operating array of 25 MT stations that collected continuous MT waveform data in the interior of Alaska during the autumn and winter of 2015 under the footprint of the Poker Flat (Alaska) Incoherent Scattering Radar (PFISR). PFISR data yield functionals of the ionospheric electric field and ionospheric conductivity that constrain the MT source field. We show that in this region conventional robust MT processing methods struggle to produce

  6. Detecting Forward-Scattered Radio Signals from Atmospheric Meteors Using Low-Cost Software Defined Radio

    ERIC Educational Resources Information Center

    Snjegota, Ana; Rattenbury, Nicholas James

    2017-01-01

    The forward scattering of radio signals from atmospheric meteors is a known technique used to detect meteor trails. This article outlines the project that used the forward-scattering technique to observe the 2015 August, September, and October meteor showers, as well as sporadic meteors, in the Southern Hemisphere. This project can easily be…

  7. Adaptive phase matching probe-injection technique for enhancement of Brillouin scattering signal

    NASA Astrophysics Data System (ADS)

    Li, Hongwei; Shi, Guangyao; Lv, Yuelan; Zhang, Hongying; Gao, Wei

    2017-08-01

    We report on a simple and efficient method for enhancing Brillouin scattering signal, i.e., adaptive phase matching (APM) probe-injection technique. In this technique, a low-polarization broad-spectrum probe wave is injected opposite to the pump, which can enhance any stokes signal in its APM range instantly by selective stimulated Brillouin amplification. With advantages of simple scheme, real-time multi-signal enhancement and sweep-free measurement, this technique has a great potential for improving the signal-to-noise ratio of Brillouin gain spectrum in the Brillouin scattering application systems.

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

    PubMed

    Sechopoulos, Ioannis; Bliznakova, Kristina; Fei, Baowei

    2013-10-01

    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. 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. 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. As expected, the scatter

  9. Accelerating incoherent dedispersion

    NASA Astrophysics Data System (ADS)

    Barsdell, B. R.; Bailes, M.; Barnes, D. G.; Fluke, C. J.

    2012-05-01

    Incoherent dedispersion is a computationally intensive problem that appears frequently in pulsar and transient astronomy. For current and future transient pipelines, dedispersion can dominate the total execution time, meaning its computational speed acts as a constraint on the quality and quantity of science results. It is thus critical that the algorithm be able to take advantage of trends in commodity computing hardware. With this goal in mind, we present an analysis of the 'direct', 'tree' and 'sub-band' dedispersion algorithms with respect to their potential for efficient execution on modern graphics processing units (GPUs). We find all three to be excellent candidates, and proceed to describe implementations in C for CUDA using insight gained from the analysis. Using recent CPU and GPU hardware, the transition to the GPU provides a speed-up of nine times for the direct algorithm when compared to an optimized quad-core CPU code. For realistic recent survey parameters, these speeds are high enough that further optimization is unnecessary to achieve real-time processing. Where further speed-ups are desirable, we find that the tree and sub-band algorithms are able to provide three to seven times better performance at the cost of certain smearing, memory consumption and development time trade-offs. We finish with a discussion of the implications of these results for future transient surveys. Our GPU dedispersion code is publicly available as a C library at .

  10. Time-reversal imaging with multiple signal classification considering multiple scattering between the targets

    NASA Astrophysics Data System (ADS)

    Gruber, Fred K.; Marengo, Edwin A.; Devaney, Anthony J.

    2004-06-01

    The time-reversal imaging with multiple signal classification method for the location of point targets developed within the framework of the Born approximation in Lehman and Devaney [``Transmission mode time-reversal super-resolution imaging,'' J. Acoust. Soc. Am. 113, 2742-2753 (2003)] is generalized to incorporate multiple scattering between the targets. It is shown how the same method can be used in the location of point targets even if there is multiple scattering between them. On the other hand, both the conventional images and the calculated values of the target scattering amplitudes are scattering model-dependent.

  11. Interstellar scattering effects on the detection of narrow-band signals

    SciTech Connect

    Cordes, J.M.; Lazio, T.J. )

    1991-07-01

    The detection and decoding of narrow-band radio signals are investigated after propagation through the turbulent, ionized interstellar medium. For most lines of sight through the Galaxy, spectral broadening due to scattering below about 0.1 Hz at 1 GHz occurs. Spectral broadening is therefore unimportant for the detection of hypothesized signals from extraterrestrial intelligence. Intensity scintillations, however, are of considerable importance. They both help and hinder detection: signals too weak to be detected without the scattering medium may be modulated above the detection threshold while, conversely, signals above threshold can be modulated below. In strong scattering (distances above about 100 pc at 1 GHz), multiple observations of a given target comprise a strategy that is superior to single observations even when the total time per target is held fixed. Decoding information carrying signals may encounter difficulties due to intensity scintillations. 49 refs.

  12. Photoacoustic signal formation in absorbing and scattering liquids

    NASA Astrophysics Data System (ADS)

    Nissilae, Seppo M.; Ahola, Onni; Kopola, Harri K.; Myllylae, Risto A.; Tenhunen, Jussi; Zhao, Zuomin

    1998-01-01

    The so-called photoacoustic technique combines optical properties, such as absorption and scattering, with acoustic properties, such as sound velocity and absorption, to monitor and measure the physical properties of materials. This paper comprises a theoretical study on the properties of acoustic pulses and a discussion on earlier theories presented in literature. It also describes and analyzes the results of simulation tests based on the Monte-Carlo method, undertaken to examine the effects that absorption and scattering co-efficients of two-layer media have on the shape of the acoustic transmitter. Finally, the theoretical results are corroborated with measurements using a CO2 laser and a two-wavelength diode laser PA system, developed during the study.

  13. Photoacoustic signal formation in absorbing and scattering liquids

    NASA Astrophysics Data System (ADS)

    Nissila, Seppo M.; Ahola, Onni; Kopola, Harri K.; Myllyla, Risto A.; Tenhunen, Jussi; Zhao, Zuomin

    1997-12-01

    The so-called photoacoustic technique combines optical properties, such as absorption and scattering, with acoustic properties, such as sound velocity and absorption, to monitor and measure the physical properties of materials. This paper comprises a theoretical study on the properties of acoustic pulses and a discussion on earlier theories presented in literature. It also describes and analyzes the results of simulation tests based on the Monte-Carlo method, undertaken to examine the effects that absorption and scattering co-efficients of two-layer media have on the shape of the acoustic transmitter. Finally, the theoretical results are corroborated with measurements using a CO2 laser and a two-wavelength diode laser PA system, developed during the study.

  14. Enhancement of the Raman scattering signal due to a nanolens effect.

    PubMed

    Desmedt, A; Talaga, D; Bruneel, J L

    2007-06-01

    The Raman scattering signal of a substrate is investigated using a polystyrene nanolens of a few hundred nanometers inserted within the light path of a confocal microspectrometer. As observed in solid immersion microscopy, the nanolens is at the origin of the improvement of the spatial resolution. Furthermore, enhancement of the Raman scattering signal of the substrate is observed when measuring through the polystyrene bead. The enhancement factors have been measured for silicon, highly ordered pyrolytic graphite, and gallium arsenide substrates. This setup provides a new way of enhancing the Raman signal by means of a nanolens.

  15. Relationship between scattered power and correlation time in VHF radar signals

    NASA Technical Reports Server (NTRS)

    Royrvik, O.

    1985-01-01

    Equations describing the wave number spectra of wind shear-generated turbulent velocities and refractive index irregularities are discussed, and relations between radar echo power and signal correlation time are derived. If the radar backscatter wavelength is within the inertial subrange of the spectrum, a positive correlation between the scattered power and the signal correlation time is expected. For radar Bragg wavelengths within the dissipative subrange of turbulence, the correlation between scattered power and signal correlation time will be negative as usually expected in turbulence.

  16. Effects of Interior Velocity Models and Scattering Structure on the Coda Decay Properties of Seismic Signals

    NASA Astrophysics Data System (ADS)

    Blanchette-guertin, J.; Johnson, C. L.; Lawrence, J. F.

    2013-12-01

    We investigate the effects of scattering on the coda rise and decay times of synthetic seismic signals using an adapted version of the seismic phonon method. We examine the amplitudes and dependence on epicentral distance of decay times for a range of interior models with 1D velocity structure as well as intrinsic attenuation that can be specified as a function of depth and frequency. Scattering is 3D, assuming longitudinal symmetry, and occurs globally within layer(s) of prescribed thickness. Scatterers within the layer(s) have random orientations, defined length-scales distributions (distance between scatterers), and random velocity and density perturbations within a prescribed range. We demonstrate that variations in the signal's coda decay attributes can be analyzed to assess the first-order structural properties of highly scattering bodies such as Earth's moon. The variation of decay time with epicentral distance is most affected by the event source depth (surface impact vs. deep event), the frequency content, the background velocity model and intrinsic attenuation. On the other hand, the magnitude of the decay times is controlled by the size-frequency distribution of scatterers, the thickness and location of the scattering layer(s) and the presence of a low velocity layer. We use this new understanding of the effects of interior scattering structure on coda decay times to examine suites of lunar interior models that produce rise and decay characteristics similar to those observed in the Apollo Passive Seismic Experiment data.

  17. 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.

  18. 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

  19. 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.

  20. Detecting Forward-Scattered Radio Signals from Atmospheric Meteors Using Low-Cost Software Defined Radio

    NASA Astrophysics Data System (ADS)

    Snjegota, Ana; Rattenbury, Nicholas James

    2017-02-01

    The forward scattering of radio signals from atmospheric meteors is a known technique used to detect meteor trails. This article outlines the project that used the forward-scattering technique to observe the 2015 August, September, and October meteor showers, as well as sporadic meteors, in the Southern Hemisphere. This project can easily be replicated in any part of the world and is a suitable, low-cost project designed for students who are interested in astronomy.

  1. The Interaction of Intense Incoherent Light and Matter

    NASA Astrophysics Data System (ADS)

    van Wagenen, Lindsey Gay

    One of the long standing difficulties in working with intense incoherent light has been the lack of a theory for predicting and explaining experimental results. This thesis investigates the diagrammatic theory of Freidberg and Hartmann which provides a solution to this problem. Photon echo experiments are performed with intense incoherent light in atomic sodium vapor, the dependence of the resulting echo signal on the intensity of the constituent pulses is studied and experimental results are then compared with theoretical predictions. When the finite lifetimes of the sodium sample are included in the calculations, experimental results show good qualitative agreement with the theoretical predictions for the two and three-pulse echo.

  2. 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.

  3. Spotlight-mode incoherently synthetic aperture imaging ladar: fundamentals

    NASA Astrophysics Data System (ADS)

    Liu, Liren

    2010-08-01

    In this paper, a concept of spotlight-mode incoherently-synthetic aperture imaging ladar (SAIL) is proposed on the basis of computer tomography (CT). This incoherent SAIL has three operations of conventional, inverse and CT spotlight-modes with two sensing techniques of range and Doppler resolutions, and supplies a variety of dimensional transformations for 2-D range- and Doppler-resolved imaging of 2-D objects and for 3-D range-resolved imaging or in the depth compressed 2-D range- and Doppler-resolved imaging of 3-D objects. Due to the simplification in both the construction and the algorithm the difficulties in the signal collection and data processing are importantly relaxed. The incoherent SAIL provides a great potential for applications in the extensive fields. The paper gives the detailed analysis.

  4. 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.

  5. 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.

  6. Virtual experiments: Combining realistic neutron scattering instrument and sample simulations

    NASA Astrophysics Data System (ADS)

    Farhi, E.; Hugouvieux, V.; Johnson, M. R.; Kob, W.

    2009-08-01

    A new sample component is presented for the Monte Carlo, ray-tracing program, McStas, which is widely used to simulate neutron scattering instruments. The new component allows the sample to be described by its material dynamic structure factor, which is separated into coherent and incoherent contributions. The effects of absorption and multiple scattering are treated and results from simulations and previous experiments are compared. The sample component can also be used to treat any scattering material which may be close to the sample and therefore contaminates the total, measured signal.

  7. 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.

  8. 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.

  9. Direction Finding of HF Signals Scattered by Ionospheric Irregularities Using Small Size Antenna

    NASA Astrophysics Data System (ADS)

    Galushko, V. G.; Zalizovski, A. V.; Kascheev, S. B.; Pikulik, I. I.; Charkina, O. V.

    2016-09-01

    Purpose: A modification of the Doppler Interferometry Technique is suggested to enable estimating angles of arrival of comparatively broadband HF signals scattered by random irregularities of the ionospheric plasma with the use of small-size near-omnidirectional antennas. Desing/methodology/approach: The technique is based on the measurements of cross-spectra phases of the probe radiation recorded at least in three spaced points. Findings: The developed algorithm has been used to investigate the angular and time-and-frequency characteristics of HF signals propagating at frequencies above the maximum usable one for the direct radio path Moscow–Kharkiv. The received signal spectra show presence of three families of spatial components attributed, respectively, to scattering by plasma irregularities near the middle point of the radio path, ground backscatter signals and scattering of the sounding signals by the intense plasma turbulence associated with auroral activations. It has been shown that the regions responsible for the formation of the third family components are located on the equatorial slope of the maximum of the precipitating particle energy. The drift velocity and direction of the polar ionosphere plasma has been determined. Conclusions: The obtained estimates are consistent with the classical conception on the magnetospheric convection and plasma convection in the polar regions and do not contradict to the results of investigations of the auroral ionosphere dynamics using the SuperDARN network.

  10. 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

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

    PubMed

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

    2016-05-07

    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.

  12. Incoherence-Mediated Remote Synchronization

    NASA Astrophysics Data System (ADS)

    Zhang, Liyue; Motter, Adilson E.; Nishikawa, Takashi

    2017-04-01

    In previously identified forms of remote synchronization between two nodes, the intermediate portion of the network connecting the two nodes is not synchronized with them but generally exhibits some coherent dynamics. Here we report on a network phenomenon we call incoherence-mediated remote synchronization (IMRS), in which two noncontiguous parts of the network are identically synchronized while the dynamics of the intermediate part is statistically and information-theoretically incoherent. We identify mirror symmetry in the network structure as a mechanism allowing for such behavior, and show that IMRS is robust against dynamical noise as well as against parameter changes. IMRS may underlie neuronal information processing and potentially lead to network solutions for encryption key distribution and secure communication.

  13. Incoherent blocker soliton interactions in Kerr waveguide arrays.

    PubMed

    Meier, J; Stegeman, G I; Christodoulides, D N; Morandotti, R; Salamo, G; Yang, H; Sorel, M; Silberberg, Y; Aitchison, J S

    2005-12-01

    We have observed the incoherent interaction between a highly confined (blocker) soliton and wide, moving signal beams of a different wavelength in a one-dimensional discrete Kerr medium. Digital switching of the blocker solitons to successive adjacent channels was measured with increasing signal power via both one and two cascaded interactions in an AlGaAs waveguide array, operations equivalent to a reconfigurable three-output router.

  14. Strong correlations between incoherent vortices.

    PubMed

    Jesus-Silva, A J; Hickmann, J M; Fonseca, E J S

    2012-08-27

    We establish a correlation rule of which the value of the topological charge obtained in intensity correlation between two coherence vortices is such that this value is bounded by the topological charge of each coherence vortex. The original phase information is scrambled in each speckle pattern and unveiled using numerical intensity correlation. According to this rule, it is also possible to obtain a coherence vortex stable, an integer vortex, even when each incoherent vortex beam is instable, non-integer vortex.

  15. Experimental photonic generation of chirped pulses using nonlinear dispersion-based incoherent processing.

    PubMed

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

    2015-05-18

    We experimentally demonstrate, for the first time, a chirped microwave pulses generator based on the processing of an incoherent optical signal by means of a nonlinear dispersive element. Different capabilities have been demonstrated such as the control of the time-bandwidth product and the frequency tuning increasing the flexibility of the generated waveform compared to coherent techniques. Moreover, the use of differential detection improves considerably the limitation over the signal-to-noise ratio related to incoherent processing.

  16. 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.

  17. 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.

  18. Light-scattering signal may indicate critical time zone to rescue brain tissue after hypoxia

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

    A light-scattering signal, which is sensitive to cellular/subcellular structural integrity, is a potential indicator of brain tissue viability because metabolic energy is used in part to maintain the structure of cells. We previously observed a unique triphasic scattering change (TSC) at a certain time after oxygen/glucose deprivation for blood-free rat brains; TSC almost coincided with the cerebral adenosine triphosphate (ATP) depletion. We examine whether such TSC can be observed in the presence of blood in vivo, for which transcranial diffuse reflectance measurement is performed for rat brains during hypoxia induced by nitrogen gas inhalation. At a certain time after hypoxia, diffuse reflectance intensity in the near-infrared region changes in three phases, which is shown by spectroscopic analysis to be due to scattering change in the tissue. During hypoxia, rats are reoxygenated at various time points. When the oxygen supply is started before TSC, all rats survive, whereas no rats survive when the oxygen supply is started after TSC. Survival is probabilistic when the oxygen supply is started during TSC, indicating that the period of TSC can be regarded as a critical time zone for rescuing the brain. The results demonstrate that light scattering signal can be an indicator of brain tissue reversibility.

  19. Light-scattering signal may indicate critical time zone to rescue brain tissue after hypoxia.

    PubMed

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

    2011-02-01

    A light-scattering signal, which is sensitive to cellular/subcellular structural integrity, is a potential indicator of brain tissue viability because metabolic energy is used in part to maintain the structure of cells. We previously observed a unique triphasic scattering change (TSC) at a certain time after oxygen/glucose deprivation for blood-free rat brains; TSC almost coincided with the cerebral adenosine triphosphate (ATP) depletion. We examine whether such TSC can be observed in the presence of blood in vivo, for which transcranial diffuse reflectance measurement is performed for rat brains during hypoxia induced by nitrogen gas inhalation. At a certain time after hypoxia, diffuse reflectance intensity in the near-infrared region changes in three phases, which is shown by spectroscopic analysis to be due to scattering change in the tissue. During hypoxia, rats are reoxygenated at various time points. When the oxygen supply is started before TSC, all rats survive, whereas no rats survive when the oxygen supply is started after TSC. Survival is probabilistic when the oxygen supply is started during TSC, indicating that the period of TSC can be regarded as a critical time zone for rescuing the brain. The results demonstrate that light scattering signal can be an indicator of brain tissue reversibility.

  20. Amplification of femtosecond signals by stimulated Raman scattering in hydrogen gas

    NASA Astrophysics Data System (ADS)

    Rebane, Aleksander; Krylov, Vitaly N.; Erni, Daniel; Ollikainen, Olavi; Wild, Urs P.; Bespalov, Victor G.; Staselko, Dmitry I.

    1996-05-01

    We report efficient amplification of weak femtosecond signals by a stimulated Raman scattering process on vibrational and rotational components of pressurized H2 gas excited with 200-fs-duration frequency-doubled pulses from a regenerative-amplified Ti:sapphire laser. The amplification factor of 108 is obtained at the wavelength of 465 nm for weak seed pulses produced by white light continuum generation in glass.

  1. Coherent and incoherent structural dynamics in laser-excited antimony

    NASA Astrophysics Data System (ADS)

    Waldecker, Lutz; Vasileiadis, Thomas; Bertoni, Roman; Ernstorfer, Ralph; Zier, Tobias; Valencia, Felipe H.; Garcia, Martin E.; Zijlstra, Eeuwe S.

    2017-02-01

    We investigate the excitation of phonons in photoexcited antimony and demonstrate that the entire electron-lattice interactions, in particular coherent and incoherent electron-phonon coupling, can be probed simultaneously. Using femtosecond electron diffraction (FED) with high temporal resolution, we observe the coherent excitation of the fully symmetric A1 g optical phonon mode via the shift of the minimum of the atomic potential energy surface. Ab initio molecular dynamics simulations on laser excited potential energy surfaces are performed to quantify the change in lattice potential and the associated real-space amplitude of the coherent atomic oscillations. Good agreement is obtained between the parameter-free calculations and the experiment. In addition, our experimental configuration allows observing the energy transfer from electrons to phonons via incoherent electron-lattice scattering events. The electron-phonon coupling is determined as a function of electronic temperature from our DFT calculations and the data by applying different models for the energy transfer.

  2. Measurements of incoherent light and background structure at exo-Earth detection levels in the High Contrast Imaging Testbed

    NASA Astrophysics Data System (ADS)

    Cady, Eric; Shaklan, Stuart

    2014-08-01

    A major component of the estimation and correction of starlight at very high contrasts is the creation of a dark hole: a region in the vicinity of the core of the stellar point spread function (PSF) where speckles in the PSF wings have been greatly attenuated, up to a factor of 1010 for the imaging of terrestrial exoplanets. At these very high contrasts, removing these speckles requires distinguishing between light from the stellar PSF scattered by instrument imperfections, which may be partially corrected across a broad band using deformable mirrors in the system, from light from other sources which generally may not. These other sources may be external or internal to the instrument (e.g. planets, exozodiacal light), but in either case, their distinguishing characteristic is their inability to interfere coherently with the PSF. In the following we discuss the estimation, structure, and expected origin of this incoherent" signal, primarily in the context of a series of experiments made with a linear band-limited mask in Jan-Mar 2013. We find that the incoherent" signal at moderate contrasts is largely estimation error of the coherent signal, while at very high contrasts it represents a true floor which is stable over week-timescales.

  3. Analysis of coherent and diffuse scattering using a reference phantom

    PubMed Central

    Rosado-Mendez, Ivan M.; Drehfal, Lindsey C.; Zagzebski, James A.; Hall, Timothy J.

    2016-01-01

    The estimation of many spectral-based, Quantitative Ultrasound parameters assumes that backscattered echo signals are from a stationary, incoherent scattering process. The accuracy of these assumptions in real tissue can limit the diagnostic value of these parameters and the physical insight about tissue microstructure they can convey. This work presents an empirical decision test to determine the presence of significant coherent contributions to echo signals and whether they are caused by low scatterer number densities or the presence of specular reflectors or scatterers with periodic spacing. This is achieved by computing parameters from echo signals that quantify stationary or non-stationary features related to coherent scattering, and then comparing their values to thresholds determined from a reference material providing diffuse scattering. The paper first presents a number of parameters with demonstrated sensitivity to coherent scattering and describes criteria to select those with highest sensitivity using simulated and phantom-based echo data. Results showed that the echo amplitude signal-to-noise ratio and the multitaper generalized spectrum were the parameters with highest sensitivity to coherent scattering with stationary and non-stationary features, respectively. These parameters were incorporated into the reference-based decision test, which successfully identified regions in simulated and tissue-mimicking phantoms with different incoherent and coherent scattering conditions. When scatterers with periodic organization were detected, the combination of stationary and non-stationary analysis permitted the estimation of the mean spacing below and above the resolution limit imposed by the pulse size. Preliminary applications of this algorithm to human cervical tissue ex vivo showed correspondence between regions of B-mode images showing bright reflectors, tissue interfaces, and hypoechoic regions with regions classified as specular reflectors and low

  4. The scatter factor signaling pathways as therapeutic associated target in cancer treatment.

    PubMed

    Accornero, P; Pavone, L M; Baratta, M

    2010-01-01

    Receptor tyrosine kinases (RTKs) are key regulators of critical cellular processes such as proliferation, differentiation, neo-vascularization, and tissue repair. In addition to their importance in the regulation of normal physiology, aberrant expression of certain RTKs has also been associated to the development and progression of many types of cancer. c-Met and RON are two RTKs with closely related sequences, structural homology, and similar functional properties. Both these receptors, once activated by their respective ligands, the Hepatocyte Growth Factor/Scatter Factor (HGF/SF1) and the Macrophage Stimulating Protein/Scatter Factor 2 (MSP/SF2), can induce cell migration, invasion and proliferation. Soon after its discovery in the mid-1980s, c-Met attracted a great interest because of its role in modulating cell motility. Moreover, the causal role for c-Met activating mutations in human cancer propelled an intensive drug discovery effort throughout academic institutions and pharmaceutical companies. While c-Met is now a well-accepted target for anticancer drug design, less is known about the role of RON in cancer and less has been done to target this receptor. In this review we will discuss the biological relevance of c-Met and RON, their deregulation in human cancers and the progress, so far, in identifying c-Met and RON signaling inhibitors. Finally, we will focus on the development of therapeutic strategies and drug efficacy studies based on interfering the scatter factor signaling pathways.

  5. 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.

  6. Can dark matter-electron scattering explain the DAMA annual modulation signal?

    NASA Astrophysics Data System (ADS)

    Foot, R.

    2014-12-01

    The annually modulating ˜keV scintillations observed in the DAMA/NaI and DAMA/Libra experiments might be due to dark matter-electron scattering. Such an explanation is now favored given the stringent constraints on nuclear recoil rates obtained by LUX, SuperCDMS, and other experiments. We suggest that multicomponent dark matter models featuring light dark matter particles of mass ˜MeV can potentially explain the data. A specific example, kinetically mixed mirror dark matter, is shown to have the right broad properties to consistently explain the experiments via dark matter-electron scattering. If this is the explanation of the annual modulation signal found in the DAMA experiments then a sidereal diurnal modulation signal is also anticipated. We point out that the data from the DAMA experiments show a diurnal variation at around 2.3 σ C.L. with phase consistent with that expected. This electron scattering interpretation of the DAMA experiments can potentially be probed in large xenon experiments (LUX, XENON1T,…), as well as in low threshold experiments (CoGeNT, CDEX, C4,…) by searching for annually and diurnally modulated electron recoils.

  7. Two-photon fluorescence microscopy signal formation in highly scattering media: theoretical and numerical simulation

    SciTech Connect

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

    2011-01-24

    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. (application of lasers and laser-optical methods in life sciences)

  8. Phase modulation signals optimization automatically for suppression of stimulated Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Jiang, Min; Ran, Yang; Su, Rongtao; Zhou, Pu

    2016-11-01

    Phase modulation of the signal laser into multiple laser-lines is one of the common methods to suppress the stimulated Brillouin scattering (SBS) effect in high power narrow linewidth fiber amplifiers. In order to achieve optimal effect, the multiple laser-lines should have equal amplitudes. In this paper, the phase modulation signal we employed is the sum of a finite number of sinusoidal signals with different initial phases and different weights. The stochastic parallel gradient descent (SPGD) algorithm is used to search for the optimal initial phases and weights. Through numerical simulation, we obtain homogeneous symmetrical spectra with 11, 19 and 29 lines whose mean square errors of power density are less than 3%.

  9. 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.

  10. Incoherent method for rotation-invariant recognition.

    PubMed

    Arsenault, H H; Hsu, Y N; Yang, Y

    1982-02-15

    An optodigital hybrid system using an incoherent circular correlator that has features suitable for space and industrial applications is introduced. The incoherent circular correlator uses a fiber-optics sampler and carries out the correlations in white light. The trade offs involved for efficient detection of objects are discussed. The system has been built, and experimental results on a real air photograph are presented.

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

    PubMed

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

    2011-07-01

    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(13) photons is focused to a ~100-nm spot diameter, provided that the effects of solvent background can be reduced sufficiently.

  12. Coherent imaging with incoherent light in digital holographic microscopy

    NASA Astrophysics Data System (ADS)

    Chmelik, Radim

    2012-01-01

    Digital holographic microscope (DHM) allows for imaging with a quantitative phase contrast. In this way it becomes an important instrument, a completely non-invasive tool for a contrast intravital observation of living cells and a cell drymass density distribution measurement. A serious drawback of current DHMs is highly coherent illumination which makes the lateral resolution worse and impairs the image quality by a coherence noise and a parasitic interference. An uncompromising solution to this problem can be found in the Leith concept of incoherent holography. An off-axis hologram can be formed with arbitrary degree of light coherence in systems equipped with an achromatic interferometer and thus the resolution and the image quality typical for an incoherent-light wide-field microscopy can be achieved. In addition, advanced imaging modes based on limited coherence can be utilized. The typical example is a coherence-gating effect which provides a finite axial resolution and makes DHM image similar to that of a confocal microscope. These possibilities were described theoretically using the formalism of three-dimensional coherent transfer functions and proved experimentally by the coherence-controlled holographic microscope which is DHM based on the Leith achromatic interferometer. Quantitative-phase-contrast imaging is demonstrated with incoherent light by the living cancer cells observation and their motility evaluation. The coherence-gating effect was proved by imaging of model samples through a scattering layer and living cells inside an opalescent medium.

  13. Experimental evidence for importance of Hund's exchange interaction for incoherence of charge carriers in iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Fink, J.; Rienks, E. D. L.; Thirupathaiah, S.; Nayak, J.; van Roekeghem, A.; Biermann, S.; Wolf, T.; Adelmann, P.; Jeevan, H. S.; Gegenwart, P.; Wurmehl, S.; Felser, C.; Büchner, B.

    2017-04-01

    Angle-resolved photoemission spectroscopy is used to study the scattering rates of charge carriers from the hole pockets near Γ in the iron-based high-Tc hole-doped superconductors KxBa1 -xFe2As2 , x =0.4 , and KxEu1 -xFe2As2 , x =0.55 , and the electron-doped compound Ba (Fe1-xCox) 2As2 , x =0.075 . The scattering rate for any given band is found to depend linearly on the energy, indicating a non-Fermi-liquid regime. The scattering rates in the hole-doped compound are considerably higher than those in the electron-doped compounds. In the hole-doped systems the scattering rate of the charge carriers of the inner hole pocket is about three times higher than the binding energy, indicating that the spectral weight is heavily incoherent. The strength of the scattering rates and the difference between electron- and hole-doped compounds signals the importance of Hund's exchange coupling for correlation effects in these iron-based high-Tc superconductors. The experimental results are in qualitative agreement with theoretical calculations in the framework of combined density functional dynamical mean-field theory.

  14. Relationship between the Amplitude and Phase of a Signal Scattered by a Point-Like Acoustic Inhomogeneity

    NASA Astrophysics Data System (ADS)

    Burov, V. A.; Morozov, S. A.

    2001-11-01

    Wave scattering by a point-like inhomogeneity, i.e., a strong inhomogeneity with infinitesimal dimensions, is described. This type of inhomogeneity model is used in investigating the point-spread functions of different algorithms and systems. Two approaches are used to derive the rigorous relationship between the amplitude and phase of a signal scattered by a point-like acoustic inhomogeneity. The first approach is based on a Marchenko-type equation. The second approach uses the scattering by a scatterer whose size decreases simultaneously with an increase in its contrast. It is shown that the retarded and advanced waves are scattered differently despite the relationship between the phases of the corresponding scattered waves.

  15. Estimating the image spectrum signal-to-noise ratio for imaging through scattering media

    NASA Astrophysics Data System (ADS)

    Hanafy, Mohamed E.; Roggemann, Michael C.; Guney, Durdu O.

    2015-01-01

    The image spectrum signal-to-noise ratio (SNR) provides a means of estimating the noise effective spatial resolution of an imaging system and a means of estimating the highest spatial frequency which can be reconstructed with a postdetection image reconstruction algorithm. Previous work has addressed the effects of aerosol scattering on the overall point spread function (PSF). Here, we seek to extend these results to also account for the effects of measurement noise and to then estimate the noise effective resolution of the system, which accounts for scattering effects on the PSF and measurement noise in the detector. We use a previously published approach to estimating the effective PSF and radiometric calculations to estimate the mean numbers of direct and scattered photons detected by an imaging system due to reflected radiation in the visible and near-infrared, and emitted radiation in mid-infrared (MIR) band, for a horizontal near-ground imaging scenario. The analysis of the image spectrum SNR presented here shows a reduction in the value of noise effective cutoff spatial frequency for images taken through fog aerosol media, and hence emphasizes the degrading effect of fog aerosol models on the spatial resolution of imaging systems.

  16. Single-shot incoherent digital holography using a dual-focusing lens with diffraction gratings.

    PubMed

    Quan, Xiangyu; Matoba, Osamu; Awatsuji, Yasuhiro

    2017-02-01

    A new optical configuration of incoherent digital holography is presented to improve the quality of reconstructed images when the random polarization state of incoherent light is used. The proposed system improves the signal-to-noise ratio of the holograms by suppressing the unmodulated terms of a spatial light modulator. To generate the self-interference of a quasi-incoherent point-like source, we use a dual-focusing lens with diffraction gratings. The preliminary experimental results confirm the validity of the proposed method by reconstructing two point-like sources generated by a LED light source. When the pixel pitch of the phase-mode SLM is small enough, the off-axis hologram can be generated. The single-shot recording of the incoherent digital holography is expected.

  17. 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.

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

    SciTech Connect

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

    2016-05-06

    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.

  19. An Investigation of the Relationship between Emission and Scattering Signals in SSM/I Data.

    NASA Astrophysics Data System (ADS)

    Liu, Guosheng; Curry, Judith A.

    1998-05-01

    To provide guidance for the development of satellite microwave rainfall-retrieval algorithms, the basic relationships between emission and scattering signals in natural clouds must be understood. In this study, the relationship between two parameters observed from microwave satellite data-the polarization difference at 19 GHz D and the polarization-corrected temperature PCT-is investigated over the global ocean on a monthly and 5° (lat) × 5° (long) mean basis. Using data from January and July 1993, the occurrence frequencies and latitudinal variation and horizontal distribution of the D-PCT relationships are investigated. The D-PCT slope is studied by dividing the entire weather range into three regimes: nonprecipitation, light precipitation, and heavy precipitation. The analysis shows that small variation of PCT in the nonprecipitation regime could be achieved by employing a variable coefficient in the PCT definition equation. The slopes in the light precipitation regime are latitude dependent. Although the interpretation is inconclusive, it is felt that the differences in the fractional coverage and the rain layer depth in different latitudes is responsible for the latitudinal dependence. No clear latitudinal dependence of slopes in the heavy precipitation regime is found.The connection of the D-PCT relationship to the performances of an emission-based and a scattering-based rainfall algorithm are investigated using the Second WetNet Precipitation Intercomparison Project rainfall cases. The results of this study emphasize the necessity of incorporating the scattering signal in rainfall rate retrieval algorithms. Additionally, the D-PCT slope information can be used to help categorize precipitation types, which may be useful in determining the specific algorithm best used for a certain precipitation type and/or regime.

  20. Synthetic aperture imaging of objects embedded within scattering media (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Kang, Pilsung; Choi, Wonshik

    2016-03-01

    Optical imaging of objects embedded within scattering media such as biological tissues suffers from the strong background noise due to multiple light scattering. The signal strength from the target objects decays exponentially at the length scale of the scattering mean free path, which is typically on the order of 100 micron for biological tissues. As a consequence, targets located at a depth of just a few scattering mean free paths lose their fine details. In this work, we performed synthetic aperture imaging of targets embedded within a scattering medium and demonstrated that the aperture synthesis process can suppress multiple scattering background better than conventional incoherent imaging. In the reflection geometry, we sent planar waves of various incidence angles and recorded the phase and amplitude maps of the reflected waves using off-axis digital holographic microscopy. A He-Ne laser was used as a light source and target objects were sandwiched between scattering layers made of PDMS mixed with polystyrene beads. We converted each reflected images taken at specific incidence angles into the maps of in-plane momentum difference between reflected and incidence waves. We then synthesized the maps in such a way that the scattered waves with the same momentum differences were added together. In this way, single-scattered waves from the targets were added coherently, which made them outgrow the incoherently added multiple-scattered waves. We achieved 1 micron lateral resolution for a target located deeper than four times the scattering mean free path in which conventional incoherent imaging fails to work.

  1. Research on Doppler frequency in incoherent FM/CW laser detection

    NASA Astrophysics Data System (ADS)

    Liu, Kai; Cui, Zhanzhong

    2010-10-01

    The principle of transmitted and received laser in incoherent FM/CW laser detection is different from the one in coherent FM/CW laser detection. The methods for distance solution in both detections are similar. Incoherent FM/CW laser detection uses subcarrier to modulate the intensity of laser, and the photodetector detects the intensity of received signal. The amplified photocurrent is mixed with local oscillator signal, and the intermediate frequency (IF) signal contains the information of distance from sensor to target. The Doppler frequency for this detection is related with the relative radial velocity between sensor and target. The optical frequency is directly modulated with electro-optic device in coherent FM/CW laser detection and the received laser signal is photomixed with transmitted laser signal. The Doppler frequency in the detection relates to the optical frequency. In distance-measuring lidar, the Doppler frequency affects the solution. The Doppler frequency in incoherent FM/CW laser detection is unrelated with optical frequency, and it is much less than the one in coherent FM/CW laser detection, correspondingly. The error in incoherent FM/CW laser detection is smaller. As a result, the incoherent FM/CW laser detection is more suitable for the use of distance-measuring lidar.

  2. Scattering height estimation using scintillating Wide Area Augmentation System/Satellite Based Augmentation System and GPS satellite signals

    NASA Astrophysics Data System (ADS)

    Cerruti, A. P.; Ledvina, B. M.; Kintner, P. M.

    2006-12-01

    An experiment to measure equatorial amplitude scintillations on the geostationary Wide Area Augmentation System (WAAS) Satellite Based Augmentation System (SBAS) signal was conducted in Cachoeira Paulista (22.70°S, 45.01°W geographic coordinates; -17.74°N, 21.74°E geomagnetic coordinates), Brazil from December 2003 through February 2004. The purpose of this paper is to estimate the scattering height of the irregularities using the WAAS signal scintillations as compared to nearby Global Positioning System (GPS) signal scintillations. Estimating the scattering height is important because the calculated zonal drift velocity of the irregularities using the measured scintillation pattern velocity on the ground is height dependent. Accurate height estimation is also required if one wishes to develop phase screen scintillation models. The difference in the pattern velocities is due to the different signal puncture point velocities with respect to the ionospheric drift. Two east-west receivers are used to measure the scintillation pattern drift velocity and to compare the results of the geostationary WAAS satellite signal to that of a GPS satellite signal, which has a nonzero ionospheric signal puncture point velocity. By varying the assumed scattering height for the measurements from the nearby GPS signal, the zonal velocity measurements from the GPS scintillations can be matched to those of the WAAS scintillations, and a scattering height estimate can be made. When the puncture points have minimal separation, the inferred ionospheric irregularity zonal velocities should be equal. On the two nights for which data are available, scattering height estimates of 669 ± 209 km for the first night and 388 ± 139 km for the second night were obtained. On the second night, the reported mean hmF2 as calculated using a collocated Digisonde was 385 ± 17 km over the same period as the GPS/WAAS scattering height estimate. The geometry of this experiment was not optimal, but

  3. A resolution insensitive to geometrical aberrations by using incoherent illumination and interference imaging

    NASA Astrophysics Data System (ADS)

    Xiao, Peng; Fink, Mathias; Gandjbakhche, Amir H.; Claude Boccara, A.

    2017-05-01

    This contribution is another opportunity to acknowledge the influence of Roger Maynard on our research work when he pushed one of us (ACB) to explore the field of waves propagating in complex media rather than limiting ourselves to the wavelength scale of thermal waves or near field phenomena. Optical tomography is used for imaging in-depth scattering media such as biological tissues. Optical coherence tomography (OCT) plays an important role in imaging biological samples. Coupling OCT with adaptive optics (AO) in order to correct eye aberrations has led to cellular imaging of the retina. By using our approach called Full-Field OCT (FFOCT) we show that, with spatially incoherent illumination, the width of the point-spread function (PSF) that governs the resolution is not affected by aberrations that induce only a reduction of the signal level. We will describe our approach by starting with the PSF experimental data followed by a simple theoretical analysis, and numerical calculations. Finally full images obtained through or inside scattering and aberrating media will be shown.

  4. An Improved InSAR Image Co-Registration Method for Pairs with Relatively Big Distortions or Large Incoherent Areas

    PubMed Central

    Chen, Zhenwei; Zhang, Lei; Zhang, Guo

    2016-01-01

    Co-registration is one of the most important steps in interferometric synthetic aperture radar (InSAR) data processing. The standard offset-measurement method based on cross-correlating uniformly distributed patches takes no account of specific geometric transformation between images or characteristics of ground scatterers. Hence, it is inefficient and difficult to obtain satisfying co-registration results for image pairs with relatively big distortion or large incoherent areas. Given this, an improved co-registration strategy is proposed in this paper which takes both the geometric features and image content into consideration. Firstly, some geometric transformations including scale, flip, rotation, and shear between images were eliminated based on the geometrical information, and the initial co-registration polynomial was obtained. Then the registration points were automatically detected by integrating the signal-to-clutter-ratio (SCR) thresholds and the amplitude information, and a further co-registration process was performed to refine the polynomial. Several comparison experiments were carried out using 2 TerraSAR-X data from the Hong Kong airport and 21 PALSAR data from the Donghai Bridge. Experiment results demonstrate that the proposed method brings accuracy and efficiency improvements for co-registration and processing abilities in the cases of big distortion between images or large incoherent areas in the images. For most co-registrations, the proposed method can enhance the reliability and applicability of co-registration and thus promote the automation to a higher level. PMID:27649207

  5. An Improved InSAR Image Co-Registration Method for Pairs with Relatively Big Distortions or Large Incoherent Areas.

    PubMed

    Chen, Zhenwei; Zhang, Lei; Zhang, Guo

    2016-09-17

    Co-registration is one of the most important steps in interferometric synthetic aperture radar (InSAR) data processing. The standard offset-measurement method based on cross-correlating uniformly distributed patches takes no account of specific geometric transformation between images or characteristics of ground scatterers. Hence, it is inefficient and difficult to obtain satisfying co-registration results for image pairs with relatively big distortion or large incoherent areas. Given this, an improved co-registration strategy is proposed in this paper which takes both the geometric features and image content into consideration. Firstly, some geometric transformations including scale, flip, rotation, and shear between images were eliminated based on the geometrical information, and the initial co-registration polynomial was obtained. Then the registration points were automatically detected by integrating the signal-to-clutter-ratio (SCR) thresholds and the amplitude information, and a further co-registration process was performed to refine the polynomial. Several comparison experiments were carried out using 2 TerraSAR-X data from the Hong Kong airport and 21 PALSAR data from the Donghai Bridge. Experiment results demonstrate that the proposed method brings accuracy and efficiency improvements for co-registration and processing abilities in the cases of big distortion between images or large incoherent areas in the images. For most co-registrations, the proposed method can enhance the reliability and applicability of co-registration and thus promote the automation to a higher level.

  6. Theoretical and experimental study of EKB radar ground-scatter signals at nearby frequencies

    NASA Astrophysics Data System (ADS)

    Kutelev, Konstantin; Berngardt, Oleg; Grkovich, Konstantin; Mikhailov, Nikita

    SuperDARN radars have wide possibilities for diagnostics of different motions in the ionosphere. The radars allow studying small-, medium- and large-scale irregularities. The radars have good time resolution (about 1 minute for full scan) and wide territory coverage (azimuthal coverage - 50 degrees, maximal range — 3000 km). EKB radar is the first russian radar of SuperDARN kind, installed by ISTP SB RAS near Ekaterinburg. The radar started its operation in December 2012. Mostly SuperDARN radars are used to investigate irregular structure of the ionosphere. In the work we present original approach that allows diagnose regular ionosphere. The approach is based on sounding at three close frequencies and on analysis of ground-scattered signal properties. As theoretical analysis shows the use of three-frequency sounding technique allows one to estimate following characteristics of the model quasiparabolic F-layer in a middle point of path: its critical frequency, the height of its maximum and layer thickness. For this purpose we use known dependence of a minimal group path of signal on radar frequency. The key problem for the described technique is optimizing the frequency step between sounding signals. From the one side, the frequency step should be large enough. This is necessary for the difference in group delays be larger than radar range resolution (15-60km). From the other side, significant variation of frequency leads to a significant movement of path midpoint. This leads to signifficant errors in estimating ionospheric paramters due to theirs horizontal gradients. To solve this problem we perform a simulation of ground-scattered signal at EKB radar in different geophysical conditions. We use IRI-2007 as a model of the ionosphere. We simulate experiment at different levels of solar activity, in different seasons and daytime. By using geometrooptical ray tracing method we calculate a signal minimal group paths for a set of frequencies. According to these data

  7. 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.

  8. 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.

  9. Impact of signal scattering and parametric uncertainties on receiver operating characteristics

    NASA Astrophysics Data System (ADS)

    Wilson, D. Keith; Breton, Daniel J.; Hart, Carl R.; Pettit, Chris L.

    2017-05-01

    The receiver operating characteristic (ROC curve), which is a plot of the probability of detection as a function of the probability of false alarm, plays a key role in the classical analysis of detector performance. However, meaningful characterization of the ROC curve is challenging when practically important complications such as variations in source emissions, environmental impacts on the signal propagation, uncertainties in the sensor response, and multiple sources of interference are considered. In this paper, a relatively simple but realistic model for scattered signals is employed to explore how parametric uncertainties impact the ROC curve. In particular, we show that parametric uncertainties in the mean signal and noise power substantially raise the tails of the distributions; since receiver operation with a very low probability of false alarm and a high probability of detection is normally desired, these tails lead to severely degraded performance. Because full a priori knowledge of such parametric uncertainties is rarely available in practice, analyses must typically be based on a finite sample of environmental states, which only partially characterize the range of parameter variations. We show how this effect can lead to misleading assessments of system performance. For the cases considered, approximately 64 or more statistically independent samples of the uncertain parameters are needed to accurately predict the probabilities of detection and false alarm. A connection is also described between selection of suitable distributions for the uncertain parameters, and Bayesian adaptive methods for inferring the parameters.

  10. 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.

  11. Note: automatic laser-to-optical-fiber coupling system based on monitoring of Raman scattering signal.

    PubMed

    Park, Kyoung-Duck; Kim, Yong Hwan; Park, Jin-Ho; Yim, Sang-Youp; Jeong, Mun Seok

    2012-09-01

    We developed an automatic laser-to-optical-fiber coupling (ALOC) system that is based on the difference in the Raman scattering signals of the core and cladding of the optical fiber. This system can be easily applied to all fields of fiber optics since it can perform automatic optical coupling within a few seconds regardless of the core size or the condition of the output end of the optical fiber. The coupling time for a commercial single-mode fiber for a wavelength of 632.8 nm (core diameter: 9 μm, cladding diameter: 125 μm) is ~1.5 s. The ALOC system was successfully applied to single-mode-fiber Raman endoscopy for the measurement of the Raman spectrum of carbon nanotubes.

  12. Radar Information from the Partial Derivatives of the Echo Signal Phase from a Point Scatterer

    DTIC Science & Technology

    1988-02-17

    with the target information from a point scatterer as obtained form the partial derivatives of the echo-signal phase r, a function of freq -xency...report, but not in as direct a manner as that of Lees. I. 1. "A Generalized Theory of Radar Observations," by R. J. Lees, AVIONICS RESEARCH: SATELLITES ...j27r(x/x)u jw(-d+D)u/X -jn(d+D)u/x ! j2wu j2w u ! - -(d+D)/2 -,Jw(d/X)u( jf(Dlx)u -j=(rD/X u) j2w u -jwr(d/x)u = . sin[ir(D/x)u] iTU 37 2d integral

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

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy

    1996-01-01

    Raman scattering is a powerful technique for quantitatively probing high temperature and high speed flows. However, this technique has typically been limited to clean hydrogen flames because of the broadband fluorescence interference which occurs in hydrocarbon flames. Fluorescence can also interfere with the Raman signal in clean hydrogen flames when broadband UV lasers are used as the scattering source. A solution to this problem has been demonstrated. The solution to the fluorescence interference lies in the fact that the vibrational Q-branch Raman signal is highly polarized for 90 deg. signal collection and the fluorescence background is essentially unpolarized. Two basic schemes are available for separating the Raman from the background. One scheme involves using a polarized laser and collecting a signal with both horizontal and vertical laser polarizations separately. The signal with the vertical polarization will contain both the Raman and the fluorescence while the signal with the horizontal polarization will contain only the fluorescence. The second scheme involves polarization discrimination on the collection side of the optical setup. For vertical laser polarization, the scattered Q-branch Raman signal will be vertically polarized; hence the two polarizations can be collected separately and the difference between the two is the Raman signal. This approach has been used for the work found herein and has the advantage of allowing the data to be collected from the same laser shot(s). This makes it possible to collect quantitative Raman data with single shot resolution in conditions where interference cannot otherwise be eliminated.

  14. 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.

  15. A design of DDS single-frequency signal generator based on phrase jitter technology to reduce scattering noise

    NASA Astrophysics Data System (ADS)

    Liu, Zhihui; Fan, Muwen; Zhou, Luchun

    2015-10-01

    In order to test the working status of adaptive optics systems, it is necessary to design a disturbance signal module. Disturbance signal module based on DDS (Direct Digital frequency Synthesis) is used to generate single-frequency disturbance signal to test the working conditions of deformable mirror and adaptive optics systems. But DDS is a periodic sampling sequence and will inevitably lead to the introduction of periodic noise which makes the disturbance signal scattering. This paper uses two methods to reduce the scattering of the single-frequency signal generated by DDS technology. The first method is the compression ROM table. In the case of the same ROM capacity, it is equivalent to extend the compressed ROM table with 256 points to ROM table with 1024 points. In this process, Oversampling is introduced to improve spectral purity to reduce the scattering of the single-frequency signal. The second method is the random phase jitter technology. It introduces m sequence as DDS sampling output random phase jitter unit. The purpose is to generate some random number added at the end of the phase accumulator. As a result, the output does not always push back than ideal, but randomly in advance, thus breaking its periodicity. This method changes the original uniform look-up sampling into a random non-uniform look-up sampling, making DDS output spectrum white. It can also improve spectral purity of the DDS output, thereby reducing the scatting of the single-frequency signal generated by DDS technology.

  16. Simple model to simulate OCT-depth signal in weakly and strongly scattering homogeneous media

    NASA Astrophysics Data System (ADS)

    Varkentin, Arthur; Otte, Maya; Meinhardt-Wollweber, Merve; Rahlves, Maik; Mazurenka, Mikhail; Morgner, Uwe; Roth, Bernhard

    2016-12-01

    We present a simple and efficient Monte Carlo model to predict the scattering coefficients and the influence of multiple photon scattering with increasing concentration of scattering centers from optical coherence tomography (OCT) data. While the model reliably estimates optical sample parameters for a broad range of concentrations, it does not require inclusion of more complex phenomena such as dependent scattering. Instead, it relies on a particular weighting function which is introduced to describe various orders of multiple scattering events. In weakly scattering homogeneous media the measured scattering coefficient {μ }s depends linearly on the concentration of scattering centers. In the case of strong scattering, the dependence becomes nonlinear. Our model is able to accurately predict this nonlinearity and can be applied to extend the OCT studies of biological tissue towards determination of optical properties in the future.

  17. Self-trapping of incoherent light beams

    NASA Astrophysics Data System (ADS)

    Mitchell, Matthew L.

    1998-09-01

    This thesis presents an experimental and theoretical study of self-trapping beams of light from incoherent sources such as light emitting diodes and sunlight. The self-trapping of an optical beam occurs when a beam of light induces a change in the index of refraction through a nonlinear interaction. This induced index change can then fully compensate for diffraction of the optical beam in both transverse directions. When this process occurs, the trapped light is called a soliton. Until 1996, all experimental and theoretical studies of optical spatial solitons in nature employed a coherent beam, either in space, time, or both. In 1996 I demonstrated for the first time that self-trapping of beams upon which the phase varied randomly in time/space across any plane was possible. The optical beams were self-trapped by making use of the photorefractive nonlinearity. The self-trapping of these incoherent light sources has opened up a new subfield in the study of optical spatial solitons. Experimental and theoretical results of self-trapping both bright and dark incoherent solitons will be presented. In the first experiment, a quasi-monochromatic partially spatially-incoherent light beam was self-trapped, while the second experiment shows the self-trapping of an incoherent white light beam originating from an incandescent light bulb. In this second experiment, the self-trapped beam contained wavelengths between 380 and 720 nm. Theoretical work has shown that these incoherent light sources create effective multi-mode solitons. Existence conditions and the resulting coherence properties of such self-trapped beams have been examined. The theoretical methods used in describing these effects are general and can be extended for use with any form of nonlinearity. Experimental and theoretical results of creating dark incoherent solitons shows the possibility of self- trapping a dark notch sitting upon an incoherent background beam. Theoretical work shows that such dark incoherent

  18. Visual sandwich immunoassay system on the basis of plasmon resonance scattering signals of silver nanoparticles.

    PubMed

    Ling, Jian; Li, Yuan Fang; Huang, Cheng Zhi

    2009-02-15

    In this contribution, we established a sandwich immunoassay system with a common spectrofluorometer to collect the plasmon resonance scattering (PRS) signals from silver nanoparticles (AgNPs) immunotargeted on glass slides. By taking the immunoreactions of goat antihuman IgG (Fc fragment specific) antibody (GAH-IgG), human immunoglobulin (H-IgG), and rabbit antihuman IgG (Fab fragment specific) antibody (RAH-IgG) as an example, we found that if a primary antibody (GAH-IgG) was first immobilized on the surface of glass slides and applied to capture target antigen (H-IgG), AgNPs-labeled secondary antibody (RAH-IgG) could be employed to detect the target antigen (H-IgG) by forming a sandwich immune complex on the surface of the glass slide. It was found that the PRS signals resulting from the AgNPs immunotargeted on the glass slides could be applied to the quantitative detection of H-IgG target antigen in the range of 10-1000 ng/mL with the limit of determination of 1.46 ng/mL (3sigma) under optimal conditions, which is sensitive and comparable with reported chemiluminescence immunoassays. With a dark-field microscope coupled with a spectral system, we measured the PRS features of single AgNPs immunotargeted on the glass slides, showing that the PRS of single nanoparticles might have potential applications in analytical chemistry. Further findings showed that the strong PRS signals from the AgNPs immunotargeted on the glass slides can be clearly seen and distinguished by naked eyes under the excitation of a common white light-emitting diode (LED) torch. Therefore, a visual PRS immunoassay system can be established easily with common glass slides and an LED torch.

  19. Thomson scattering on non-equilibrium low density plasmas: principles, practice and challenges

    NASA Astrophysics Data System (ADS)

    Carbone, Emile; Nijdam, Sander

    2015-01-01

    In this paper, we review the main challenges related to laser Thomson scattering on low temperature plasmas. The main features of the triple grating spectrometer used to discriminate Thomson and Raman scattering signals from Rayleigh scattering and stray light are presented. The main parameters influencing the detection limit of Thomson scattering are reviewed. Laser stray light and plasma emission are two limiting factors, but Raman scattering from molecules inside the plasma will further decrease it. In the case of non-thermal plasmas at high pressure, Thomson scattering is the only technique which allows us to obtain the electron density without any prior knowledge of the plasma properties. Moreover, very high 3D spatial and temporal resolutions can easily be achieved. However, special care still needs to be taken to verify that Thomson scattering is non intrusive. The mechanisms that will lead to possible measurement errors are discussed. The wavelength-resolved scattering signal also allows us to get direct information about the electron energy distribution function in the case of incoherent light scattering. Finally, we discuss some recent applications of Thomson scattering on atmospheric pressure plasma jets, but also in the field of electron collision kinetics. Thomson scattering can be applied on atomic but also molecular plasmas. In the latter case, one needs to take into account the possible contribution of rotational Raman scattering.

  20. Incoherent {pi}{sup 0} photoproduction from complex nuclei

    SciTech Connect

    Rodrigues, T.E.; Mesa, J.; Garcia, C.; Arruda-Neto, J.D.T.; Dale, D.; Nakagawa, I.

    2005-05-01

    Incoherent {pi}{sup 0} photoproduction from nuclei is evaluated via a multicollisional intranuclear cascade framework. In-medium modifications are taken into account, including a realistic dynamical treatment of multiple {pi}N and {delta}N scattering processes throughout the cascade. This time-dependent analysis yields structures in the {sup 12}C {pi}{sup 0} differential cross section both in the {delta} region and in the photon energy range from 5 to 6 GeV, with the former in very nice agreement with recent results from Mainz Microton. For heavy nuclei, however, such structures disappear because of a more effective Fermi motion and a relatively higher final state interaction of the produced pions as they exit the nucleus. The calculation of the incoherent part of the total {pi}{sup 0} photoproduction propitiates a clean and powerful kinematical separation from competitive (electromagnetic/nuclear) production processes, which currently is a theoretical challenge for the PrimEx experiment at the Jefferson Lab.

  1. Signal enhancement of surface enhanced Raman scattering and surface enhanced resonance Raman scattering using in situ colloidal synthesis in microfluidics.

    PubMed

    Wilson, Rab; Bowden, Stephen A; Parnell, John; Cooper, Jonathan M

    2010-03-01

    We demonstrate the enhanced analytical sensitivity of both surface enhanced Raman scattering (SERS) and surface enhanced resonance Raman scattering (SERRS) responses, resulting from the in situ synthesis of silver colloid in a microfluidic flow structure, where both mixing and optical interrogation were integrated on-chip. The chip-based sensor was characterized with a model Raman active label, rhodamine-6G (R6G), and had a limit of detection (LOD) of ca. 50 fM (equivalent to single molecule detection). The device was also used for the determination of the natural pigment, scytonemin, from cyanobacteria (as an analogue for extraterrestrial life existing in extreme environments). The observed LOD of approximately 10 pM (ca. <400 molecules) demonstrated the analytical advantages of working with freshly synthesized colloid in such a flow system. In both cases, sensitivities were between 1 and 2 orders of magnitude greater in the microfluidic system than those measured using the same experimental parameters, with colloid synthesized off-chip, under quiescent conditions.

  2. 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.

  3. 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.

  4. Incoherent Multifocus Hololens Design and Fabrication

    NASA Astrophysics Data System (ADS)

    Rallison, Richard D.

    1990-04-01

    Several 5 x 5 multifocus Hololenses have been produced with diffraction efficiencies between 20% and 75%. Low intermodulation noise was achieved by going off axis 16 degrees and using SHG and DCG materials to record the master and copies respectively. Astigmatism and Bragg tilt errors were minimized but images showed more coma than prior art. Both coherent and incoherent copies were made, the oherent copies were always low in efficiency because of very high intermodulation noise or because beam ratios were made high to avoid intermodulation noise. Incoherent copies proved to be only a little more difficult to fabricate and the master copy process in an index matching fluid proved to be more versatile as well as optically cleaner. Problems with uniformity from exposure to exposure were found and cured or probable causes were found. A limit to uniformity probably exists that relates to random coherent phasing of overlapping Bragg structures added to very small thermal and mechanical instabilities during exposure. All copies are made in a contact copy jig with each exposure running about 2 seconds. The process for obtaining an unaberrated master at 633 nm while making copies at 488 nm is described for both the coherent and incoherent methods. Test results for an incoherent 5x5 array working at 633 nm are given including an intensity profile of a spot, power distribution and output with crosstalk. Suggestions for further improvements are given.

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

    PubMed

    Wang, Ruikang K

    2002-07-07

    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. Image encryption under spatially incoherent illumination

    NASA Astrophysics Data System (ADS)

    Xie, Zhenwei; Zang, Jinliang; Zhang, Yan

    2013-06-01

    A novel method for image encryption under spatially incoherent illumination is proposed. The LED array is used as the spatially incoherent source. Both the encryption process and decryption process are numerically simulated. Experiments are carried out to demonstrate the basic ideal of the proposed method. The incoherent light is modulated by the spatial light modulator on the input plane as the input image to be encrypted. Then a random phase only mask is used as the key to encode the image, finally a Fourier lens is adopted to image the encrypted image on the output plane. The encrypted intensity distribution is recorded by a CCD. In the numerical simulations, the random phase only mask is generated by a rand function. The incoherent image is composed of many source points, and any two points of these sources are spatially incoherent, but each point is self-spatially coherent. Under this property, the point spread function for the encryption system can be considered as the interference of two beams, one is the spherical beam and the other is the random phase beam. Once the point spread function is given, the system's optical transfer function can be calculated easily. Then the encryption system can be considered as a decryption system, and the output image is the same as the original image. The encrypted image can be calculated with the system's optical transfer function and the output image. The random phase mask, the distance between the random phase mask and the SLM, and the wavelength of the laser can be seen as the keys of the encryption systems. Only when all these parameters are correct, can one get the right decrypted image. The factors which could affect the practical experiment, such as quantization noise and displacement tolerances are also investigated. Compared with the conventional coherent encryption system, the incoherent encryption system proposed in this paper is free of the flaws of the optical elements, the dust particles on the elements, and

  7. 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.

  8. 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.

  9. EISCAT (European Incoherent Scatter Radar) Electron Density Studies.

    DTIC Science & Technology

    1987-09-08

    lists the corresponding measurements of electron content made by HILAT and calculated from SPI03 measurements for each of the 7 coincident runs. The...TEC measured by HILAT and TEC calculated from EISCAT measurements, the HILAT values being always larger than those from EISCAT. The measurements...HILAT results could be due to several factors. The EISCAT value was calculated by integrating electron density over the range gates 184 km to 746.5

  10. High-altitude incoherent-scatter measurements at Jicamarca

    NASA Astrophysics Data System (ADS)

    Hysell, D. L.; Milla, M. A.; Woodman, R. F.

    2017-02-01

    In an attempt to reproduce experimental results obtained in the early days of operations, electron density profiles have been measured at the Jicamarca Radio Observatory at altitudes reaching L=2. The methodology involves using a combination of pulses, including pulses as long as 4 ms, and processing the data with matched filtering. The modern experiments are complicated by systemic, time-dependent bias in the noise estimators as well as by clutter from satellites and space debris, including a geosynchronous satellite. Ultimately, experiment performance comparable to what was achieved in the original experiments could be achieved and should be surpassed in future experiments when all four of the Jicamarca transmitters will be utilized.

  11. Expressive Incoherence and Alexithymia in Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Costa, Andreia P.; Steffgen, Georges; Samson, Andrea C.

    2017-01-01

    Expressive incoherence can be implicated in socio-emotional communicative problems in autism spectrum disorder (ASD). The present study examined expressive incoherence in 37 children with ASD and 41 typically developing (TD) children aged 3-13 years old during a frustration task. The role of alexithymia in expressive incoherence was also assessed.…

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

    DOE PAGES

    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.

  13. 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.

  14. 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.

  15. 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.

  16. Enhancement of Raman scattering signals from gaseous medium near the surface of a holographic aluminum diffraction grating

    NASA Astrophysics Data System (ADS)

    Petrov, D. V.; Sedinkin, D. O.; Zaripov, A. R.

    2016-11-01

    The possibility of applying surface-enhanced Raman scattering (RS) for amplification of RS intensity in gaseous media is investigated. A more than sixfold enhancement of the RS signal is detected experimentally from the main atmospheric air components during interaction of continuous-wave laser radiation with a holographic aluminum diffraction grating. The averaged value of the RS signals' amplification factor in the near-surface 30-nm-thick layer at the boundary between the diffraction grating and gaseous medium amounted to 3 × 103.

  17. QR code optical encryption using spatially incoherent illumination

    NASA Astrophysics Data System (ADS)

    Cheremkhin, P. A.; Krasnov, V. V.; Rodin, V. G.; Starikov, R. S.

    2017-02-01

    Optical encryption is an actively developing field of science. The majority of encryption techniques use coherent illumination and suffer from speckle noise, which severely limits their applicability. The spatially incoherent encryption technique does not have this drawback, but its effectiveness is dependent on the Fourier spectrum properties of the image to be encrypted. The application of a quick response (QR) code in the capacity of a data container solves this problem, and the embedded error correction code also enables errorless decryption. The optical encryption of digital information in the form of QR codes using spatially incoherent illumination was implemented experimentally. The encryption is based on the optical convolution of the image to be encrypted with the kinoform point spread function, which serves as an encryption key. Two liquid crystal spatial light modulators were used in the experimental setup for the QR code and the kinoform imaging, respectively. The quality of the encryption and decryption was analyzed in relation to the QR code size. Decryption was conducted digitally. The successful decryption of encrypted QR codes of up to 129  ×  129 pixels was demonstrated. A comparison with the coherent QR code encryption technique showed that the proposed technique has a signal-to-noise ratio that is at least two times higher.

  18. Limits of applicability of the concept of scattering amplitude in small-angle scattering problems

    NASA Astrophysics Data System (ADS)

    Dzheparov, F. S.; Lvov, D. V.

    2014-01-01

    The applicability of the concept of scattering amplitude to the description of small-angle scattering experiments has been considered. An expression has been obtained for a scattered radiation flux on a detector under much milder conditions than the condition of Fraunhofer diffraction. The influence of incoherence of the source on the results has been evaluated.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    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.

  20. 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.

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

    PubMed

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

    2012-09-01

    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.

  2. 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.

  3. Selective Two-Photon-Absorption-Induced Reactions of Anthracene-2-Carboxylic Acid on Tunable Plasmonic Substrate with Incoherent Light Source.

    PubMed

    Pincella, Francesca; Isozaki, Katsuhiro; Taguchi, Tomoya; Song, Yeji; Miki, Kazushi

    2015-02-01

    In this research, we report the development, characterization and application of various plasmonic substrates (with localized surface plasmon resonance wavelength tunable by gold nanoparticle size) for two-photon absorption (TPA)-induced photodimerization of an anthracene derivative, anthracene carboxylic acid, in both surface and solution phase under incoherent visible light irradiation. Despite the efficient photoreaction property of anthracene derivatives and the huge number of publications about them, there has never been a report of a multiphoton photoreaction involving an anthracene derivative with the exception of a reverse photoconversion of anthracene photodimer to monomer with three-photon absorption. We examined the progress of the TPA-induced photoreaction by means of surface-enhanced Raman scattering, taking advantage of the ability of our plasmonic substrate to enhance and localize both incident light for photoreaction and Raman scattering signal for analysis of photoreaction products. The TPA-induced photoreaction in the case of anthracene carboxylic acid coated 2D array of gold nanoparticles gave different results according to the properties of the plasmonic substrate, such as the size of the gold nanoparticle and also its resultant optical properties. In particular, a stringent requirement to achieve TPA-induced photodimerization was found to be the matching between irradiation wavelength, localized surface plasmon resonance of the 2D array, and twice the wavelength of the molecular excitation of the target material (in this case, anthracene carboxylic acid). These results will be useful for the future development of efficient plasmonic substrates for TPA-induced photoreactions with various materials.

  4. 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

    2008-04-04

    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.

  5. Incoherently pumped continuous wave dye laser

    NASA Astrophysics Data System (ADS)

    Thiel, E.; Zander, C.; Drexhage, K. H.

    1987-05-01

    Continuous wave operation of a dye laser, pumped by an incoherent light source, is reported. A jet of a water-based solution of Rhodamine 6G is used as the laser medium in a spherical cavity with high reflectivity mirrors. Two high pressure arcs generated by electrical discharge between tungsten electrodes serve as pump source. They produce a power density of 0.5-10 kW/cm 2 in the jet causing the dye to lase at 615 nm.

  6. A PSF width independent of aberrations in spatially incoherent interferometry (Conference Presentation)

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

    Optical imaging usually suffers from aberrations that are induced by various structures when imaging biological samples. Usually aberrations degrade the imaging system performances by broadening the point spread function (PSF). Unexpectedly we show that in spatially incoherent interferometry like full-filed optical coherence tomography (FFOCT), the system PSF width is almost insensitive to aberrations. Instead of considering the PSF of a classical imaging system such as a microscope, we specifically pay attention to the system PSF of interferometric imaging systems for which an undistorted wavefront from a reference beam interferes with the distorted wavefront of the object beam. By comparing the cases of scanning OCT with spatially coherent illumination, wide-field OCT with spatially coherent illumination and FFOCT with spatially incoherent illumination, we found that in FFOCT with spatially incoherent illumination the system PSF width is almost independent of the aberrations and only its amplitude varies. This is demonstrated by theoretical analysis as well as numerical calculations for different aberrations, and confirmed by experiments with a FFOCT system. It is the first time to the best of our knowledge that such specific merit of incoherent illumination in FFOCT has been demonstrated. Based on this, the signal level is used as metric in our adaptive optics FFOCT system for retinal imaging. Only the main aberrations (defocus and astigmatism) that are dominating in eye are corrected to improve the signal to noise ratio and the high order aberrations are skipped. This would increase the correction speed thus reducing the imaging time.

  7. Impact of Rayleigh backscattering on Stimulated Brillouin Scattering threshold evaluation for 10 Gb/s NRZ-OOK signals.

    PubMed

    Ferrario, M; Marazzi, Lucia; Boffi, Pierpaolo; Righetti, Aldo; Martinelli, Mario

    2009-09-28

    At bit rates comparable with the Brillouin shift, i.e. higher than 10 Gbit/s, the signal and the Brillouin backscattered spectra partially overlap. This implies an interaction between different scattering phenomena occurring through out the optical fiber. In particular we believe that an evaluation of how Rayleigh backscattered components of the modulated signal are subjected to Stokes gain is required. This interaction may lead to an increased backscattered power, which in turn will affect Brillouin threshold estimation. We experimentally verified a decrease of Stimulated Brillouin Scattering (SBS) threshold for 10 Gb/s NRZ-OOK signals with respect to theoretical predictions. Simulations carried out with a numerical model of SBS, accounting for Rayleigh contributions, well predict measured backscattered power levels. On the other hand we also experimentally verified that this SBS threshold decrease does not degrade transmission system performance. Indeed, measured BER curves put into evidence a penalty reduction for signal powers just before the saturation regime, which should be usefully taken into consideration in optical systems power budget planning.

  8. 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.

  9. Scattered radiation in flat-detector based cone-beam CT: propagation of signal, contrast, and noise into reconstructed volumes

    NASA Astrophysics Data System (ADS)

    Wiegert, Jens; Hohmann, Steffen; Bertram, Matthias

    2007-03-01

    This paper presents a novel framework for the systematic assessment of the impact of scattered radiation in .at-detector based cone-beam CT. While it is well known that scattered radiation causes three di.erent types of artifacts in reconstructed images (inhomogeneity artifacts such as cupping and streaks, degradation of contrast, and enhancement of noise), investigations in the literature quantify the impact of scatter mostly only in terms of inhomogeneity artifacts, giving little insight, e.g., into the visibility of low contrast lesions. Therefore, for this study a novel framework has been developed that in addition to normal reconstruction of the CT (HU) number allows for reconstruction of voxelized expectation values of three additional important characteristics of image quality: signal degradation, contrast reduction, and noise variances. The new framework has been applied to projection data obtained with voxelized Monte-Carlo simulations of clinical CT data sets of high spatial resolution. Using these data, the impact of scattered radiation was thoroughly studied for realistic and clinically relevant patient geometries of the head, thorax, and pelvis region. By means of spatially resolved reconstructions of contrast and noise propagation, the image quality of a scenario with using standard antiscatter grids could be evaluated with great detail. Results show the spatially resolved contrast degradation and the spatially resolved expected standard deviation of the noise at any position in the reconstructed object. The new framework represents a general tool for analyzing image quality in reconstructed images.

  10. Photic modulation of a highly sensitive, near-infrared light-scattering signal recorded from intact retinal photoreceptors.

    PubMed Central

    Pepperberg, D R; Kahlert, M; Krause, A; Hofmann, K P

    1988-01-01

    On stimulation by green flashes, the isolated, aspartate-treated bovine retina exhibits transient changes in the scattering of near-infrared (880 nm) light. A single component, termed the "ATR" (a flash-induced scattering signal, where ATR designates amplified transient-retina), dominates the amplitude and rising-phase kinetics of the initial peak of the light-scattering response. Superfusion with physiological solution containing low Na+ concentration reversibly abolishes the photoreceptor electroretinographic response but preserves the ATR signal, indicating a receptoral origin for the ATR. The increase of ATR amplitude (A/Amax) with flash intensity (R*/R, where R indicates rhodopsin) is described by A/Amax = (1- e-kR*/R), with R*/R = k-1 occurring on generation of approximately two photoactivated rhodopsins (R*s) per disc surface in the rod outer segment. Weak background light and bright flashes reversibly depress the ATR. Kinetic and sensitivity data suggest a basis of the ATR in stochastic, unit activation events, each initiated by a single R*. They further suggest an essential invariance of the unit event under differing conditions of illumination. A delay, apparently governed by the lifetime of a light-activated substance regulating ATR generation, precedes ATR recovery after a bright flash. The flash dependence of the delay period indicates an upper limit of 3 s for the lifetime of R* in the ATR-generating process. The unit event appears to be an R*-catalyzed and disc-localized reaction of phototransduction. PMID:3399504

  11. 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

  12. 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.

  13. Broadband true time delay for microwave signal processing, using slow light based on stimulated Brillouin scattering in optical fibers.

    PubMed

    Chin, Sanghoon; Thévenaz, Luc; Sancho, Juan; Sales, Salvador; Capmany, José; Berger, Perrine; Bourderionnet, Jérôme; Dolfi, Daniel

    2010-10-11

    We experimentally demonstrate a novel technique to process broadband microwave signals, using all-optically tunable true time delay in optical fibers. The configuration to achieve true time delay basically consists of two main stages: photonic RF phase shifter and slow light, based on stimulated Brillouin scattering in fibers. Dispersion properties of fibers are controlled, separately at optical carrier frequency and in the vicinity of microwave signal bandwidth. This way time delay induced within the signal bandwidth can be manipulated to correctly act as true time delay with a proper phase compensation introduced to the optical carrier. We completely analyzed the generated true time delay as a promising solution to feed phased array antenna for radar systems and to develop dynamically reconfigurable microwave photonic filters.

  14. On the coherence/incoherence of electron transport in semiconductor heterostructure optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Harrison, P.; Indjin, D.; Savić, I.; Ikonić, Z.; Evans, C. A.; Vukmirović, N.; Kelsall, R. W.; McTavish, J.; Jovanović, V. D.; Milanović, V.

    2008-02-01

    This paper compares and contrasts different theoretical approaches based on incoherent electron scattering transport with experimental measurements of optoelectronic devices formed from semiconductor heterostructures. The Monte Carlo method which makes no a priori assumptions about the carrier distribution in momentum or phase space is compared with less computationally demanding energy-balance rate equation models which assume thermalised carrier distributions. It is shown that the two approaches produce qualitatively similar results for hole transport in p-type Si 1-xGe x/Si superlattices designed for terahertz emission. The good agreement of the predictions of rate equation calculations with experimental measurements of mid- and far-infrared quantum cascade lasers, quantum well infrared photodetectors and quantum dot infrared photodetectors substantiate the assumption of incoherent scattering dominating the transport in these quantum well based devices. However, the paper goes on to consider the possibility of coherent transport through the density matrix method and suggests an experiment that could allow coherent and incoherent transport to be distinguished from each other.

  15. Signal processing based method for modeling and solving inverse scattering problems

    NASA Astrophysics Data System (ADS)

    Ritter, Richard Shane

    A mature and difficult problem, still preoccupying many research communities in different application areas, is the recovery of a quantitative image of some unknown penetrable strongly scattering object. In most fields, such as ground penetrating radar, seismic and medical applications, the problem is compounded by the availability of only limited angle and noisy data. One of the more common approximate solution methods is based on diffraction tomography that relies on the first Born approximation method, which limits applications to weakly scattering situations. More sophisticated methods are typically iterative in nature, computationally intense and may not converge. We have studied an alternative nonlinear filtering approach and developed a new way to implement it, as well as evaluating different filter functions to find an optimal form. We have applied this approach to a number of classes of objects and developed a user-friendly scattered field simulator as a resource for this and related inverse scattering problems. We also re-investigated the widely accepted limitations of the first Born approximation and found that when close to a scattering resonance, the first Born approximation can yield a good estimate of the object's scattering cross section. Tied to all of these imaging applications is the issue of limited data: how many sources and how many receivers are required for a given quality and reliability of the resulting image. We took a fundamental look at this issue in terms of the number of degrees of freedom of the entire source-measurement domain and deduced clear guidelines on the minimum data sets necessary that should be measured, in order to expect a reasonable image.

  16. Coherent-incoherent random lasing based on nano-rubbing induced cavities

    NASA Astrophysics Data System (ADS)

    Sznitko, Lech; Cyprych, Konrad; Szukalski, Adam; Miniewicz, Andrzej; Mysliwiec, Jaroslaw

    2014-02-01

    In this letter we present the results of studies carried out on poly(n-vinylcarbazole) doped with the well-known DCM laser dye. We show that the simple incorporation of highly luminescent dye into a polymeric matrix can form an efficient solid state laser material. Naturally occurring inhomogeneities of a polymeric layer prepared by a drop casting process can scatter out light emitted in the process of photoluminescence in such a way that feedback is introduced to the system and coherent and incoherent random lasing can be observed. Moreover we show that after a nano-scale rubbing process the random lasing phenomenon occurs for a lower energy density of pumping light as compared to the virgin sample, and changes the light amplification nature from incoherent to coherent.

  17. Coherent imaging of a pure phase object with classical incoherent light

    SciTech Connect

    Bache, M.; Magatti, D.; Ferri, F.; Gatti, A.; Brambilla, E.; Lugiato, L. A.

    2006-05-15

    By using the ghost imaging technique, we experimentally demonstrate the reconstruction of the diffraction pattern of a pure phase object by using the classical correlation of incoherent thermal light split on a beam splitter. The results once again underline that entanglement is not a necessary feature of ghost imaging. The light we use is spatially highly incoherent with respect to the object ({approx_equal}2 {mu}m speckle size) and is produced by a pseudo-thermal source relying on the principle of near-field scattering. We show that in these conditions no information on the phase object can be retrieved by only measuring the light that passed through it, neither in a direct measurement nor in a Hanbury Brown-Twiss (HBT) scheme. In general, we show a remarkable complementarity between ghost imaging and the HBT scheme when dealing with a phase object.

  18. Incoherent and Laser Photodeposition on Thin Films.

    DTIC Science & Technology

    1980-09-01

    wavelength, an incoherent Oriel Mercury arc lamp (model HR-l) with a 1000 watt u-v out- a put centered at 2537A was used. This source emitted o down...Royal Society of London Series A, 156: 108-129 (1936). 18. Gutowsky, H.S.. "The Infra-Red and Raman Spectra of Dimethyl Mercury and Dimethyl Zinc," The...II), - Cadmium (II) and - Mercury (II)," Spectrochimica Acta, 33A: 669-680 (1977). 20. Bakke, A.M.W.. "A Molecular Structure Study of Dimethylmercury

  19. Spontaneous Pattern Formation with Incoherent White Light

    NASA Astrophysics Data System (ADS)

    Schwartz, Tal; Carmon, Tal; Buljan, Hrvoje; Segev, Mordechai

    2004-11-01

    We present the first experimental observation of modulation instability and spontaneous pattern formation with incoherent white light emitted from an incandescent light bulb. We show experimentally that modulation instability of white light propagating in a noninstantaneous self-focusing medium is a collective effect, where the entire temporal spectrum of the light beam becomes unstable at the same threshold value and collectively forms a pattern with a single periodicity. We experimentally demonstrate that the temporal spectrum of the evolving perturbation self-adjusts to match the collective pattern formation phenomenon.

  20. Universal diffusion in incoherent black holes

    NASA Astrophysics Data System (ADS)

    Blake, Mike

    2016-10-01

    We study charge and energy diffusion in simple holographic theories with broken translational symmetry. We find that when the effects of momentum relaxation are very strong the diffusion constants take universal values Dc˜De˜ℏvB2/(kBT ) . Here vB is the velocity of the butterfly effect and the coefficients of proportionality depend only on the scaling exponents of the infra-red fixed point. Our results suggest that diffusion in these incoherent black holes is controlled by τ ˜ℏ/(kBT ) independently of the mechanism of momentum relaxation.

  1. 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.

  2. 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

  3. Is the Precautionary Principle Really Incoherent?

    PubMed

    Boyer-Kassem, Thomas

    2017-02-28

    The Precautionary Principle has been an increasingly important principle in international treaties since the 1980s. Through varying formulations, it states that when an activity can lead to a catastrophe for human health or the environment, measures should be taken to prevent it even if the cause-and-effect relationship is not fully established scientifically. The Precautionary Principle has been critically discussed from many sides. This article concentrates on a theoretical argument by Peterson (2006) according to which the Precautionary Principle is incoherent with other desiderata of rational decision making, and thus cannot be used as a decision rule that selects an action among several ones. I claim here that Peterson's argument fails to establish the incoherence of the Precautionary Principle, by attacking three of its premises. I argue (i) that Peterson's treatment of uncertainties lacks generality, (ii) that his Archimedian condition is problematic for incommensurability reasons, and (iii) that his explication of the Precautionary Principle is not adequate. This leads me to conjecture that the Precautionary Principle can be envisaged as a coherent decision rule, again.

  4. Incoherent single pion electroproduction on the deuteron with polarization effects

    NASA Astrophysics Data System (ADS)

    Tammam, M.; Fix, A.; Arenhövel, H.

    2006-10-01

    Incoherent pion electroproduction on the deuteron is studied from threshold up to the second resonance region with special emphasis on the influence of the final-state interaction, in particular on polarization observables. The elementary γN→πN amplitude is taken from the MAID-2003 model. The final-state interaction is included by considering complete rescattering in the final NN and πN subsystems. Investigated in detail is their influence on the structure functions governing the semi-exclusive differential cross section, where besides the scattered electron only the produced pion is detected. For charged pion-production the effect of NN rescattering is moderate whereas πN rescattering is almost negligible, except very close to threshold. NN rescattering appears much stronger in neutral pion production for which the primary mechanism is the elimination of a significant spurious coherent contribution in the impulse approximation. Sizeable effects are also found in some of the polarization structure functions for beam and/or target polarizations.

  5. 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.

  6. 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.

  7. 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

    2016-08-07

    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.

  8. 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

  9. 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.

  10. 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.

  11. Hyper-Rayleigh light scattering from an aqueous suspension of purple membrane.

    PubMed

    Schmidt, P K; Rayfield, G W

    1994-07-01

    Here we report the first observation of hyper-Rayleigh light scattering from bacteriorhodopsin in the form of an aqueous suspension of unoriented purple membranes. A typical purple membrane suspension used in our experiments contains approximately 10(8) randomly oriented purple membranes. Each purple membrane contains approximately 10(5) bacteriorhodopsin molecules in a two-dimensional crystallinearray. Hyper-Rayleigh light scattering is observed when the purple membrane suspension is illuminated with light that has a wavelength of 1064 nm. We propose that the 532-nm scattered light from each of the bacteriorhodopsin molecules in a single purple membrane is coherent, and that the scattered light from different purple membranes is incoherent. This proposal is supported by the following experimental observations: (a) the 532-nm light intensity is proportional to the square of the incident power, (b) the intensity of the 532-nm signal is linearly proportional to the concentration of purple membrane in solution, (c) the scattered 532-nm light is incoherent, (d) the scattered 532-nm light intensity decreases if the size of the purple membranes is reduced while the bacteriorhodopsin concentration is kept constant, and (e) the 532-nm light is due to the retinal chromophore of the bacteriorhodopsin molecule. The ratio of horizontal polarized hyper-Rayleigh scattered light to vertically polarized hyper-Rayleigh scattered light gives the angle (23 ± 4°) of the retinal axis with respect to the plane of the purple membrane. The hyperpolarizability of the bacteriorhodopsin molecule is found to be 5 ± 0.4 × 10(-27) esu.

  12. A quantitative method for determination of Co(II) based on the inner filter effect of reagents on the Raman scattering signals of water.

    PubMed

    Wang, Hui Ying; Huang, Cheng Zhi

    2007-03-21

    It is known that Raman scattering signals are one of main interference sources leading up to determination errors in spectrofluorometry, and thus the signals can be easily detected with a common spectrofluorometer. In this contribution, we propose a quantitative method based on the inner filter effect (IFE) of reagents on the Raman scattering signals of solvent by taking the complexation of divalent cobalt ion with 4-[(5-chloro-2-pyridyl)azo]-1,3-diaminobenzene (5-Cl-PADAB) as a model system. By adjusting the excitation wavelength of the spectrofluorometer, we could easily detect the Raman scattering signals of water at 424 nm where the maximum absorption of 5-Cl-PADAB reagent is located. In a solution of 5-Cl-PADAB, the Raman scattering signals of water are decreased owing to the IFE of 5-Cl-PADAB. If Co(II), which could form the binary complex of Co(II)/5-Cl-PADAB and consumes the 5-Cl-PADAB reagent, is present in such a case for a given amount of 5-Cl-PADAB solution, recovered Raman scattering signals could be observed and measured with a spectrofluorometer. It was found that the intensity of the enhanced Raman scattering signals is proportional to the Co(II) concentration over the range from 2.0 x 10(-7) mol L(-1) to 1.0 x 10(-5) mol L(-1), and the detection limit could reach 1.2 x 10(-7) mol L(-1). With that, Co(II) in samples could be detected with R.S.D. values lower than 2.6% and recoveries over the range of 97.2-104.7%.

  13. Characterizing near-surface firn from the scattered signal component of glacier surface reflections detected in airborne radio-echo sounding measurements

    NASA Astrophysics Data System (ADS)

    Rutishauser, A.; Grima, C.; Sharp, M. J.; Blankenship, D. D.; Young, D. A.; Cawkwell, F.; Dowdeswell, J. A.

    2016-12-01

    With recent summer warming, surface melt on Canadian Arctic ice caps has intensified and extended to higher elevations in ice cap accumulation areas. Consequently, more meltwater percolates into the near-surface firn, and refreezes as ice layers where firn temperatures are below freezing. This process can increase firn densification rates, causing a lowering of the glacier surface height even in the absence of mass changes. Thus, knowledge of spatio-temporal variations in the near-surface firn stratigraphy is important for interpreting altimetrically-derived estimates of ice cap mass balance. We investigate the use of the scattering signal component of glacier surface reflections in airborne radio-echo sounding (RES) measurements to characterize the near-surface firn stratigraphy. The scattering signal distribution over Devon Ice Cap is compared to firn stratigraphy derived from ground-based radar data. We identify three distinct firn facies zones at different elevation ranges. The scattered signal component changes significantly between the different firn facies zones: low scattering correlates to laterally homogeneous firn containing thin, flat and continuous ice layers at elevations above 1800 m and below 1200 m, where firn consists mainly of ice. Higher scattering values are found from 1200-1800 m where the firn contains discrete, undulating ice layers. No correlation was found between the scattering component and surface roughness. Modelled scattering values for the measured roughness were significantly less than the observed values, and did not reproduce their observed spatial distribution. This indicates that the scattering component is determined mainly by the structure of near-surface firn. Our results suggest that the scattering component of surface reflections from airborne RES measurements has potential for characterizing heterogeneity in the spatial structure of firn that is affected by melting and refreezing processes.

  14. The effect of induced spatial incoherence on the absolute Raman instability

    NASA Astrophysics Data System (ADS)

    Guzdar, P. N.; Tan, W.; Lee, Y. C.; Liu, C. S.; Lehmberg, R. H.

    1991-03-01

    A numerical and analytical study of the Raman instability in a homogeneous plasma is presented in which the pump has been modeled to include the effects of broad bandwidth and the induced spatial incoherence (ISI) method of beam smoothing. For a time-averaged homogeneous growth rate γ¯0 and a bandwidth σ, there is a significant reduction in Raman backscattering when σ≳2γ0, for γ¯20 near threshold intensity. However, for γ¯20 very large compared to the threshold, neither ISI nor bandwidth affects Raman scattering.

  15. Incoherent η-electroproduction off the deuteron

    NASA Astrophysics Data System (ADS)

    Tammam, Mahmoud

    2009-10-01

    Incoherent eta meson electroproduction off the deuteron is studied in the impulse approximation (IA) or spectator model in which the eta production takes place on a single nucleon inside the deuteron while the other nucleon acts as a spectator only, i.e., neglecting eta rescattering on the spectator nucleon and nucleon two-body effects. The elementary operator for eta electroproduction off a nucleon is taken from the MAID analysis. The semi-exclusive structure functions, determining the differential cross section of the outgoing eta meson without detection of the final nucleons, are calculated and their dependence on the squared four momentum transfer K and the lab energy transfer k0lab are studied.

  16. 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.

  17. 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.

  18. 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.

  19. Incoherent correlator system for satellite orientation control

    NASA Astrophysics Data System (ADS)

    Kouris, Aristodemos; Young, Rupert C. D.; Chatwin, Christopher R.; Birch, Philip M.

    2002-03-01

    An incoherent correlator configuration is proposed and experimentally demonstrated that is capable of recognizing star patterns. The device may thus be employed for the orientation and navigation of a satellite or spacecraft. The correlator employs starlight directly and requires no laser or input spatial light modulator for operation. The filter is constructed form an array of mirrors that may be individually appropriately tilted so as recognize a particular star arrangement. The only other components of the system are a converging lens and CCD array detector. The device is capable of determining the pointing direction and rotation of a satellite or space vehicle. Experimental results employing the mirror array device illuminated with a point source early to simulate starlight are presented.

  20. Dephasing-assisted selective incoherent quantum transport.

    PubMed

    Behzadi, Naghi; Ahansaz, Bahram; Kasani, Hadi

    2015-10-01

    Selective energy transport throughout a quantum network connected to more than one reaction center can play an important role in many natural and technological considerations in photosystems. In this work, we propose a method in which an excitation can be transported from the original site of the network to one of the reaction centers arbitrarily using independent sources of dephasing noises. We demonstrate that in the absence of dephasing noises, the coherent evolution of the system does not have any role in energy transport in the network. Therefore, incoherent evolution via application of dephasing noises throughout a selected path of the network leads to complete transferring of the excitation to a desired reaction center.

  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. 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.

  3. Electromagnetic scattering from turbulent plasmas

    SciTech Connect

    Resendes, D.G. Instituto Superior Tecnico, Rua Rovisco Pais, Lisboa )

    1992-11-15

    A self-consistent multiple-scattering theory of vector electromagnetic waves scattered from a turbulent plasma is presented. This approach provides a general and systematic treatment to all orders in turbulence of the scattering of electromagnetic waves in terms of the properties of the turbulent structure of the scattering system and is applicable in the full regime from underdense to overdense plasmas. To illustrate the theory, a plasma consisting of a finite number density of discrete scatterers with a simple geometry and statistical properties is chosen. In this approach the exact solution for a single scatterer is obtained first. From it the configuration-dependent solution for {ital N} scatterers is constructed. Rather than solving explicitly for this solution and then averaging, the averaging operation will be taken first in order to find an approximate equation obeyed by the mean or coherent field. The coherent and incoherent scattering are then determined in terms of the coherent field and the backscatter is evaluated. The coherent and incoherent scattering, our principal results, are expressed in a plane-wave basis in a form suitable for numerical computation. A number of interesting phenomena which may readily be incorporated into the theory are indicated.

  4. 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.

  5. Bulk metallic glass-like scattering signal in small metallic nanoparticles.

    PubMed

    Doan-Nguyen, Vicky V T; Kimber, Simon A J; Pontoni, Diego; Reifsnyder Hickey, Danielle; Diroll, Benjamin T; Yang, Xiaohao; Miglierini, Marcel; Murray, Christopher B; Billinge, Simon J L

    2014-06-24

    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.

  6. 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.

  7. Retrieving the Ultrasmall-Angle X-Ray Scattering Signal with Polychromatic Radiation in Speckle-Tracking and Beam-Tracking Phase-Contrast Imaging

    NASA Astrophysics Data System (ADS)

    Vittoria, Fabio A.; Endrizzi, Marco; Olivo, Alessandro

    2017-03-01

    We present an experimental comparison between two x-ray phase-contrast imaging techniques currently under development, speckle tracking and beam tracking. The comparison is centered on the absorption and ultrasmall-angle scattering signals retrieved with polychromatic radiation from homogeneous and inhomogeneous samples of different thicknesses. Our analysis shows that the ultrasmall-angle scattering signal retrieved with speckle tracking does not increase linearly with the thickness for the inhomogeneous sample, and is different from zero for the homogeneous sample. The results obtained from beam tracking, instead, are in good agreement with the expectation.

  8. Atmospheric anisotropy and its effect on the delay power spectra of tropospheric scatter radio signals

    NASA Astrophysics Data System (ADS)

    Ibrahim, H. M.

    The atmospheric anisotropy and its effect on the delay power spectra of signals received on troposcatter radio links were studied. A simplified model for determining an anisotropy coefficient is suggested. Theoretical and measured anisotropy profiles are utilized in the calculations of the delay power spectra of tropospheric links. The impact of the anisotropy on the troposcatter channel as a communication link is studied. Bello's model for the troposcatter channel is modified to include the effect of the anisotropy on the delay power spectra. Several theoretical anisotropy profiles based on the experimental observations and the corresponding spectra are evaluated. It was found that the anisotropy results in increased multipath spread and mean delay parameters. This has a direct effect on the irreducible bit error rate (BER) due to intermodulation distortion. Calculations indicate that an order of magnitude increase in the BER due to the atmospheric anisotropy could result.

  9. Optical Asymmetry and Nonlinear Light Scattering from Colloidal Gold Nanorods

    DOE PAGES

    Lien, Miao-Bin; Kim, Ji-Young; Han, Myung-Geun; ...

    2017-05-16

    A systematic study is presented of the intensity-dependent nonlinear light scattering spectra of gold nanorods under resonant excitation of the longitudinal surface plasmon resonance (SPR). The spectra exhibit features due to coherent second and third harmonic generation as well as a broadband feature that has been previously attributed to multiphoton photoluminescence arising primarily from interband optical transitions in the gold. A detailed study of the spectral dependence of the scaling of the scattered light with excitation intensity shows unexpected scaling behavior of the coherent signals, which is quantitatively accounted for by optically induced damping of the SPR mode through amore » Fermi liquid model of the electronic scattering. The broadband feature is shown to arise not from luminescence, but from scattering of the secondorder longitudinal SPR mode with the electron gas, where efficient excitation of the 2nd order mode arises from an optical asymmetry of the nanorod. The electronic-temperature-dependent plasmon damping and the Fermi-Dirac distribution together determine the intensity dependence of the broadband emission, and the structure-dependent absorption spectrum determines the spectral shape through the fluctuation-dissipation theorem. Hence a complete self-consistent picture of both coherent and incoherent light scattering is obtained with a single set of physical parameters.« less

  10. Optical Asymmetry and Nonlinear Light Scattering from Colloidal Gold Nanorods.

    PubMed

    Lien, Miao-Bin; Kim, Ji-Young; Han, Myung-Geun; Chang, You-Chia; Chang, Yu-Chung; Ferguson, Heather J; Zhu, Yimei; Herzing, Andrew A; Schotland, John C; Kotov, Nicholas A; Norris, Theodore B

    2017-06-27

    A systematic study is presented of the intensity-dependent nonlinear light scattering spectra of gold nanorods under resonant excitation of the longitudinal surface plasmon resonance (SPR). The spectra exhibit features due to coherent second and third harmonic generation as well as a broadband feature that has been previously attributed to multiphoton photoluminescence arising primarily from interband optical transitions in the gold. A detailed study of the spectral dependence of the scaling of the scattered light with excitation intensity shows unexpected scaling behavior of the coherent signals, which is quantitatively accounted for by optically induced damping of the SPR mode through a Fermi liquid model of the electronic scattering. The broadband feature is shown to arise not from luminescence, but from scattering of the second-order longitudinal SPR mode with the electron gas, where efficient excitation of the second order mode arises from an optical asymmetry of the nanorod. The electronic-temperature-dependent plasmon damping and the Fermi-Dirac distribution together determine the intensity dependence of the broadband emission, and the structure-dependent absorption spectrum determines the spectral shape through the fluctuation-dissipation theorem. Hence a complete self-consistent picture of both coherent and incoherent light scattering is obtained with a single set of physical parameters.

  11. Introduction to Wave Turbulence Formalisms for Incoherent Optical Waves

    NASA Astrophysics Data System (ADS)

    Picozzi, Antonio; Garnier, Josselin; Xu, Gang; Rica, Sergio

    We provide an introduction to different wave turbulence formalisms describing the propagation of partially incoherent optical waves in nonlinear media. We consider the nonlinear Schrödinger equation as a representative model accounting for a nonlocal or a noninstantaneous nonlinearity, as well as higher-order dispersion effects. We discuss the wave turbulence kinetic equation describing, e.g., wave condensation or wave thermalization through supercontinuum generation; the Vlasov formalism describing incoherent modulational instabilities and the formation of large scale incoherent localized structures in analogy with long-range gravitational systems; and the weak Langmuir turbulence formalism describing spectral incoherent solitons, as well as spectral shock or collapse singularities. Finally, recent developments and some open questions are discussed, in particular in relation with a wave turbulence formulation of laser systems and different mechanisms of breakdown of thermalization.

  12. Incidental experiences of affective coherence and incoherence influence persuasion.

    PubMed

    Huntsinger, Jeffrey R

    2013-06-01

    When affective experiences are inconsistent with activated evaluative concepts, people experience what is called affective incoherence; when affective experiences are consistent with activated evaluative concepts, people experience affective coherence. The present research asked whether incidental feelings of affective coherence and incoherence would regulate persuasion. Experiences of affective coherence and incoherence were predicted and found to influence the processing of persuasive messages when evoked prior to receipt of such messages (Experiments 1 and 3), and to influence the confidence with which thoughts generated by persuasive messages were held when evoked after presentation of such messages (Experiments 2 and 3). These results extend research on affective coherence and incoherence by showing that they exert a broader impact on cognitive activity than originally assumed.

  13. Incoherent coincidence imaging of space objects

    NASA Astrophysics Data System (ADS)

    Mao, Tianyi; Chen, Qian; He, Weiji; Gu, Guohua

    2016-10-01

    Incoherent Coincidence Imaging (ICI), which is based on the second or higher order correlation of fluctuating light field, has provided great potentialities with respect to standard conventional imaging. However, the deployment of reference arm limits its practical applications in the detection of space objects. In this article, an optical aperture synthesis with electronically connected single-pixel photo-detectors was proposed to remove the reference arm. The correlation in our proposed method is the second order correlation between the intensity fluctuations observed by any two detectors. With appropriate locations of single-pixel detectors, this second order correlation is simplified to absolute-square Fourier transform of source and the unknown object. We demonstrate the image recovery with the Gerchberg-Saxton-like algorithms and investigate the reconstruction quality of our approach. Numerical experiments has been made to show that both binary and gray-scale objects can be recovered. This proposed method provides an effective approach to promote detection of space objects and perhaps even the exo-planets.

  14. Incoherent digital holography with phase-only spatial light modulators

    NASA Astrophysics Data System (ADS)

    Rosen, Joseph; Kelner, Roy; Kashter, Yuval

    2015-10-01

    Today, spatial light modulators (SLMs) offer the world of digital holography a robust technology that can be incorporated into hologram recorders. This review surveys recent developments related to the role of SLMs in a family of incoherent digital hologram recorders termed Fresnel incoherent correlation holography (FINCH). Two systems branching out from FINCH, and discussed herein, are a confocal version of FINCH and a synthetic aperture FINCH-based system.

  15. Coherent and incoherent beam combination using thick holographic substrates

    NASA Astrophysics Data System (ADS)

    Shahriar, M. S.; Riccobono, J.; Kleinschmit, M.; Shen, J. T.

    2003-05-01

    We present a mathematical model of coherent and incoherent beam combination in a thick hologram. We also derive the formulae relating the read and write angles to the read and write wavelengths for the combiner. Furthermore, we present a new technique for determining the M#, and establish that the M# required for a coherent combiner is substantially less than that needed for an incoherent one.

  16. Time-frequency signal processing techniques for radar remote sensing

    NASA Astrophysics Data System (ADS)

    Wen, Chun-Hsien

    The Arecibo 430 MHz Incoherent Scatter Radar (ISR) has been used to observe the vertical ionospheric electron concentration profiles for many years. Earlier studies are dated back to 1970s. The meteor observations grew from the ISR observations of the ionosphere in the last 10 years. The techniques for meteor observation have evolved significantly since then. It has become a regular observation at Arecibo Observatory (AO). In this work we introduce signal processing techniques to detect meteor events and determine their parameters for the meteor observation data. We also propose techniques to separate the meteor and the incoherent scatter signals for the ISR observation data. The large aperture AO radar is susceptible to the interference from other communication systems because of its sensitivity. The interference contaminates the radar data and sometimes seriously degrades the performance of the meteor detection. We introduce signal processing techniques to remove the interference for both the meteor and the ISR observation data in this work. Other applications for proposed techniques are introduced in this work too.

  17. Propagation behavior of incoherent beams in one-dimensional photonic crystals.

    PubMed

    Ding, Fei-Na; Chen, Yuan-Yuan; Shi, Jie-Long

    2010-03-01

    The propagation properties of Gaussian Schell-model spatially incoherent beams through a one-dimensional photonic crystal (1DPC) are investigated. The dynamical evolution of incoherent beams in 1DPC and the Goos-Hänchen lateral shift of the transmitted beams are obtained. The mutual effects of coherence and bandgap of the PC on the evolution of incoherent beams are analyzed. The incidence angle of the incoherent beam also has an influence on the incoherent electric field and the lateral shift.

  18. 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.

  19. First Structural Glimpse of CCN3 and CCN5 Multifunctional Signaling Regulators Elucidated by Small Angle X-ray Scattering*

    PubMed Central

    Holbourn, Kenneth P.; Malfois, Marc; Acharya, K. Ravi

    2011-01-01

    The CCN (cyr61, ctgf, nov) proteins (CCN1–6) are an important family of matricellular regulatory factors involved in internal and external cell signaling. They are central to essential biological processes such as adhesion, proliferation, angiogenesis, tumorigenesis, wound healing, and modulation of the extracellular matrix. They possess a highly conserved modular structure with four distinct modules that interact with a wide range of regulatory proteins and ligands. However, at the structural level, little is known although their biological function(s) seems to require cooperation between individual modules. Here we present for the first time structural determinants of two of the CCN family members, CCN3 and CCN5 (expressed in Escherichia coli), using small angle x-ray scattering. The results provide a description of the overall molecular shape and possible general three-dimensional modular arrangement for CCN proteins. These data unequivocally provide insight of the nature of CCN protein(s) in solution and thus important insight into their structure-function relationships. PMID:21543320

  20. Incoherent shock waves in long-range optical turbulence

    NASA Astrophysics Data System (ADS)

    Xu, G.; Garnier, J.; Faccio, D.; Trillo, S.; Picozzi, A.

    2016-10-01

    Considering the nonlinear Schrödinger (NLS) equation as a representative model, we report a unified presentation of different forms of incoherent shock waves that emerge in the long-range interaction regime of a turbulent optical wave system. These incoherent singularities can develop either in the temporal domain through a highly noninstantaneous nonlinear response, or in the spatial domain through a highly nonlocal nonlinearity. In the temporal domain, genuine dispersive shock waves (DSW) develop in the spectral dynamics of the random waves, despite the fact that the causality condition inherent to the response function breaks the Hamiltonian structure of the NLS equation. Such spectral incoherent DSWs are described in detail by a family of singular integro-differential kinetic equations, e.g. Benjamin-Ono equation, which are derived from a nonequilibrium kinetic formulation based on the weak Langmuir turbulence equation. In the spatial domain, the system is shown to exhibit a large scale global collective behavior, so that it is the fluctuating field as a whole that develops a singularity, which is inherently an incoherent object made of random waves. Despite the Hamiltonian structure of the NLS equation, the regularization of such a collective incoherent shock does not require the formation of a DSW - the regularization is shown to occur by means of a different process of coherence degradation at the shock point. We show that the collective incoherent shock is responsible for an original mechanism of spontaneous nucleation of a phase-space hole in the spectrogram dynamics. The robustness of such a phase-space hole is interpreted in the light of incoherent dark soliton states, whose different exact solutions are derived in the framework of the long-range Vlasov formalism.

  1. Three-Dimensional Imaging by Self-Reference Single-Channel Digital Incoherent Holography

    PubMed Central

    Rosen, Joseph; Kelner, Roy

    2016-01-01

    Digital holography offers a reliable and fast method to image a three-dimensional scene from a single perspective. This article reviews recent developments of self-reference single-channel incoherent hologram recorders. Hologram recorders in which both interfering beams, commonly referred to as the signal and the reference beams, originate from the same observed objects are considered as self-reference systems. Moreover, the hologram recorders reviewed herein are configured in a setup of a single channel interferometer. This unique configuration is achieved through the use of one or more spatial light modulators. PMID:28757811

  2. Three-Dimensional Imaging by Self-Reference Single-Channel Digital Incoherent Holography.

    PubMed

    Rosen, Joseph; Kelner, Roy

    2016-08-01

    Digital holography offers a reliable and fast method to image a three-dimensional scene from a single perspective. This article reviews recent developments of self-reference single-channel incoherent hologram recorders. Hologram recorders in which both interfering beams, commonly referred to as the signal and the reference beams, originate from the same observed objects are considered as self-reference systems. Moreover, the hologram recorders reviewed herein are configured in a setup of a single channel interferometer. This unique configuration is achieved through the use of one or more spatial light modulators.

  3. 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.

  4. 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)

  5. Wavelength conversion of incoherent light by sum-frequency generation.

    PubMed

    Arahira, Shin; Murai, Hitoshi

    2014-06-02

    In this paper, we reveal that some kinds of optical nonlinearities are further enhanced when incoherent light, instead of a laser, is used as a pump light. This idea was confirmed both theoretically and experimentally in the case of sum-frequency generation (SFG) using the optical second nonlinearity. The conversion efficiency of the SFG with incoherent light pumping increased as the bandwidth of the incoherent pump light decreased, finally reaching twice the conversion efficiency of conventional second harmonic generation (SHG) by laser pumping. This method dramatically relaxes the severe requirements of phase matching in the nonlinear optical process. The conversion efficiency became less sensitive to misalignment of the wavelength of pump light and also of device operation temperature when the bandwidth of the incoherent pump light was sufficiently broad, although the improvement of the conversion efficiency had an inverse relationship with the insensitivity to the phase-matching condition. The temperature tuning range was enhanced by more than two orders of magnitude in comparison with the conventional SHG method. As an example of a promising application of this new idea, we performed the generation of quantum entangled photon-pairs using cascaded optical nonlinearities (SFG and the subsequent spontaneous parametric down conversion) in a single periodically poled LiNbO3 waveguide device, in which the incoherent light was used as the pump source for both the parametric processes. We have achieved high fidelity exceeding 99% in quantum-state tomography experiments.

  6. 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

  7. SPECIAL ISSUE DEVOTED TO MULTIPLE RADIATION SCATTERING IN RANDOM MEDIA: Simulations of a spatially resolved reflectometry signal from a highly scattering three-layer medium applied to the problem of glucose sensing in human skin

    NASA Astrophysics Data System (ADS)

    Bykov, A. V.; Kirillin, M. Yu; Priezzhev, A. V.; Myllylä, Risto

    2006-12-01

    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.

  8. Beam cleaning of an incoherent laser via plasma Raman amplification

    DOE PAGES

    Edwards, Matthew R.; Qu, Kenan; Mikhailova, Julia M.; ...

    2017-09-25

    We show that backward Raman amplification in plasma can efficiently compress a temporally incoherent pump laser into an intense coherent amplified seed pulse, provided that the correlation time of the pump is longer than the inverse plasma frequency. One analytical theory for Raman amplification using pump beams with different correlation functions is developed and compared to numerical calculations and particle-in-cell simulations. Since incoherence on scales shorter than the instability growth time suppresses spontaneous noise amplification, we point out a broad regime where quasi-coherent sources may be used as efficient low-noise Raman amplification pumps. As the amplified seed is coherent, Ramanmore » amplification provides an additional a beam-cleaning mechanism for removing incoherence. At near-infrared wavelengths, finite coherence times as short as 50 fs allow amplification with only minor losses in efficiency.« less

  9. Beam cleaning of an incoherent laser via plasma Raman amplification

    NASA Astrophysics Data System (ADS)

    Edwards, Matthew R.; Qu, Kenan; Mikhailova, Julia M.; Fisch, Nathaniel J.

    2017-10-01

    We show that backward Raman amplification in plasma can efficiently compress a temporally incoherent pump laser into an intense coherent amplified seed pulse, provided that the correlation time of the pump is longer than the inverse plasma frequency. An analytical theory for Raman amplification using pump beams with different correlation functions is developed and compared to numerical calculations and particle-in-cell simulations. Since incoherence on scales shorter than the instability growth time suppresses spontaneous noise amplification, we point out a broad regime where quasi-coherent sources may be used as efficient low-noise Raman amplification pumps. As the amplified seed is coherent, Raman amplification additionally provides a beam-cleaning mechanism for removing incoherence. At near-infrared wavelengths, finite coherence times as short as 50 fs allow amplification with only minor losses in efficiency.

  10. Electromagnetically Induced Grating Without Absorption Using Incoherent Pump

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Yuan; Liu, Zhuan-Zhuan; Wan, Ren-Gang

    2017-10-01

    We propose a scheme for creating electromagnetically induced grating in a four-level double- Λ atomic system driven by a coupling field and an incoherent pump field. Owing to the incoherent pumping process, large refractivity accompanied with vanishing absorption or even gain across the probe field can be built up in the atoms, thus phase grating or gain-phase grating, which diffracts a probe light into different directions, can be formed with the help of a standing-wave coupling field. The diffraction efficiency of the gratings can be tuned by the coupling field intensity and the incoherent pump rate, hence the proposed gratings should be suitable for beam splitter and optical switching in optical communication and networking.

  11. 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

  12. Affective incoherence: when affective concepts and embodied reactions clash.

    PubMed

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

    2008-04-01

    In five studies, the authors 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 did affective incoherence. The authors suggest 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 in terms of cognitive performance. (c) 2008 APA, all rights reserved.

  13. Electromagnetically Induced Grating Without Absorption Using Incoherent Pump

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Yuan; Liu, Zhuan-Zhuan; Wan, Ren-Gang

    2017-07-01

    We propose a scheme for creating electromagnetically induced grating in a four-level double- Λ atomic system driven by a coupling field and an incoherent pump field. Owing to the incoherent pumping process, large refractivity accompanied with vanishing absorption or even gain across the probe field can be built up in the atoms, thus phase grating or gain-phase grating, which diffracts a probe light into different directions, can be formed with the help of a standing-wave coupling field. The diffraction efficiency of the gratings can be tuned by the coupling field intensity and the incoherent pump rate, hence the proposed gratings should be suitable for beam splitter and optical switching in optical communication and networking.

  14. 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.

  15. Circuit theory of multiple Andreev reflections in diffusive SNS junctions: The incoherent case

    NASA Astrophysics Data System (ADS)

    Bezuglyi, E. V.; Bratus', E. N.; Shumeiko, V. S.; Wendin, G.; Takayanagi, H.

    2000-12-01

    The incoherent regime of multiple Andreev reflections (MAR) is studied in long diffusive SNS junctions at applied voltages larger than the Thouless energy. Incoherent MAR are treated as a transport problem in energy space by means of a circuit theory for an equivalent electrical network. The current through NS interfaces is explained in terms of diffusion flows of electrons and holes through ``tunnel'' and ``Andreev'' resistors. These resistors in diffusive junctions play roles analogous to the normal and Andreev reflection coefficients in Octavio-Tinkham-Blonder-Klapwijk theory for ballistic junctions. The theory is applied to the subharmonic gap structure (SGS); simple analytical results are obtained for the distribution function and current spectral density for the limiting cases of resistive and transparent NS interfaces. In the general case, the exact solution is found in terms of chain fractions, and the current is calculated numerically. SGS shows qualitatively different behavior for even and odd subharmonic numbers n=2Δ/eV, and the maximum slopes of the differential resistance correspond to the gap subharmonics, eV=2Δ/n. The influence of inelastic scattering on the subgap anomalies of the differential resistance is analyzed.

  16. 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.

  17. Single-shot phase-shifting incoherent digital holography

    NASA Astrophysics Data System (ADS)

    Tahara, Tatsuki; Kanno, Takeya; Arai, Yasuhiko; Ozawa, Takeaki

    2017-06-01

    We propose single-shot incoherent digital holography in which a single-path in-line configuration and phase-shifting interferometry are adopted. Space-division multiplexing and polarization states of the waves are utilized to implement parallel phase-shifting holography. A single-path setup in parallel phase-shifting is constructed to capture an incoherent hologram easily with a compact system. An instantaneous and three-dimensional (3D) object image is obtained without undesired diffraction waves using parallel phase-shifting. The validity of the proposed technique is experimentally demonstrated for both transparent and reflective objects.

  18. Analysis of off-axis incoherent digital holographic microscopy

    NASA Astrophysics Data System (ADS)

    Quan, Xiangyu; Matoba, Osamu; Awatsuji, Yasuhiro

    2017-05-01

    Off-axis incoherent digital holography that enables single-shot three-dimensional (3D) distribution is introduced in the paper. Conventional fluorescence microscopy images 3D fields by sectioning, this prevents instant imaging of fast reactions of living cells. In order to realize digital holography from incoherent light, we adapted common path configuration to achieve the best temporal coherence. And by introducing gratings, we shifted the direction of each light to achieve off-axis interference. Simulations and preliminary experiments using LED light have confirmed the results. We expect to use this method to realize 3D phase imaging and fluorescent imaging at the same time from the same biological sample.

  19. 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

  20. 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.

  1. 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.

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

    SciTech Connect

    Sun, Bo; Koh, Yee Kan

    2016-06-15

    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.

  3. Influence of Spectral Transfer Processes in Compressible Low Frequency Plasma Turbulence on Scattering and Refraction of Electromagnetic Signals

    DTIC Science & Technology

    2015-01-01

    nonlinear interaction [2]. Scattering can also take place due to the interaction of HF waves with electrostatic solitons [3] or from charged dust ...Scattering can also take place due to the interaction of HF waves with electrostatic solitons or from charged dust particles. In this project, we seek...1995. [2] W. E. Amatucci, D. N. Walker, G. Ganguli, J. A. Antoniades, D. Duncan, J. H. Bowles , V. Gavirshchaka and M. E. Koepke, "Plasma response

  4. Depth enhancement of 3D microscopic living-cell image using incoherent fluorescent digital holography.

    PubMed

    Bang, L T; Wu, H Y; Zhao, Y; Kim, E G; Kim, N

    2017-03-01

    Multilayer images of living cells are typically obtained using confocal or multiphoton microscopy. However, limitations on the distance between consecutive scan layers hinder high-resolution three-dimensional reconstruction, and scattering strongly degrades images of living cell components. Consequently, when overlapping information from different layers is focused on a specific point in the camera, this causes uncertainty in the depiction of the cell components. We propose a method that combines the Fresnel incoherent correlation holography and a depth-of-focus reduction algorithm to enhance the depth information of three-dimensional cell images. The proposed method eliminates overlap between light elements in the different layers inside living cells and limitations on the interlayer distance, and also enhances the contrast of the reconstructed holograms of living cells. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

  5. 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.

  6. Detection of a Novel Mechanism of Acousto-Optic Modulation of Incoherent Light

    PubMed Central

    Jarrett, Christopher W.; Caskey, Charles F.; Gore, John C.

    2014-01-01

    A novel form of acoustic modulation of light from an incoherent source has been detected in water as well as in turbid media. We demonstrate that patterns of modulated light intensity appear to propagate as the optical shadow of the density variations caused by ultrasound within an illuminated ultrasonic focal zone. This pattern differs from previous reports of acousto-optical interactions that produce diffraction effects that rely on phase shifts and changes in light directions caused by the acoustic modulation. Moreover, previous studies of acousto-optic interactions have mainly reported the effects of sound on coherent light sources via photon tagging, and/or the production of diffraction phenomena from phase effects that give rise to discrete sidebands. We aimed to assess whether the effects of ultrasound modulation of the intensity of light from an incoherent light source could be detected directly, and how the acoustically modulated (AOM) light signal depended on experimental parameters. Our observations suggest that ultrasound at moderate intensities can induce sufficiently large density variations within a uniform medium to cause measurable modulation of the intensity of an incoherent light source by absorption. Light passing through a region of high intensity ultrasound then produces a pattern that is the projection of the density variations within the region of their interaction. The patterns exhibit distinct maxima and minima that are observed at locations much different from those predicted by Raman-Nath, Bragg, or other diffraction theory. The observed patterns scaled appropriately with the geometrical magnification and sound wavelength. We conclude that these observed patterns are simple projections of the ultrasound induced density changes which cause spatial and temporal variations of the optical absorption within the illuminated sound field. These effects potentially provide a novel method for visualizing sound fields and may assist the

  7. Incoherent vector vortex-mode solitons in self-focusing nonlinear media.

    PubMed

    Motzek, Kristian; Kaiser, Friedemann; Salgueiro, José R; Kivshar, Yuri; Denz, Cornelia

    2004-10-01

    We suggest a novel type of composite spatial optical soliton created by a coherent vortex beam guiding a partially incoherent light beam in a self-focusing nonlinear medium. We show that the incoherence of the guided mode may enhance, rather than suppress, the vortex azimuthal instability, and we also demonstrate strong destabilization of dipole-mode solitons by partially incoherent light.

  8. 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.

  9. Coherent and incoherent inference in phylogeography and human evolution.

    PubMed

    Templeton, Alan R

    2010-04-06

    A hypothesis is nested within a more general hypothesis when it is a special case of the more general hypothesis. Composite hypotheses consist of more than one component, and in many cases different composite hypotheses can share some but not all of these components and hence are overlapping. In statistics, coherent measures of fit of nested and overlapping composite hypotheses are technically those measures that are consistent with the constraints of formal logic. For example, the probability of the nested special case must be less than or equal to the probability of the general model within which the special case is nested. Any statistic that assigns greater probability to the special case is said to be incoherent. An example of incoherence is shown in human evolution, for which the approximate Bayesian computation (ABC) method assigned a probability to a model of human evolution that was a thousand-fold larger than a more general model within which the first model was fully nested. Possible causes of this incoherence are identified, and corrections and restrictions are suggested to make ABC and similar methods coherent. Another coalescent-based method, nested clade phylogeographic analysis, is coherent and also allows the testing of individual components of composite hypotheses, another attribute lacking in ABC and other coalescent-simulation approaches. Incoherence is a highly undesirable property because it means that the inference is mathematically incorrect and formally illogical, and the published incoherent inferences on human evolution that favor the out-of-Africa replacement hypothesis have no statistical or logical validity.

  10. In-plane vibration characterization of microelectromechanical systems using acousto-optic modulated partially incoherent stroboscopic imaging

    NASA Astrophysics Data System (ADS)

    Wang, Dung-An; Sheu, Fang-Wen; Chiu, Yen-Sih

    2011-07-01

    A technique using acousto-optic modulated partially incoherent stroboscopic imaging for measurement of in-plane motion of microelectromechanical systems (MEMS) is presented. Vibration measurement is allowed by using flashes of the partially incoherent light source to freeze the positions of the microstructure at 12 equally spaced phases of the vibration period. The first-order diffracted beam taken out by an acousto-optic modulator (AOM) from the light beam of a laser is made partially incoherent by a rotating diffuser and then serves as the stroboscopic light source. Both the MEMS excitation signal and the flash control signal are provided by a dual-channel function generator. The main advantage of this measurement method is the absence of a stroboscopic generator and a high speed digital camera. Microscale prototypes are fabricated and tested. Quantitative estimates of the harmonic responses of the prototypes are obtained from the recorded images. The results agree with those obtained with a commercial MEMS motion analyzer TM with relative errors less than 2%.

  11. Influence of the cavity parameters on the output intensity in incoherent broadband cavity-enhanced absorption spectroscopy.

    PubMed

    Fiedler, Sven E; Hese, Achim; Heitmann, Uwe

    2007-07-01

    The incoherent broadband cavity-enhanced absorption spectroscopy is a technique in measuring small absorptions over a broad wavelength range. The setup consists of a conventional absorption spectrometer using an incoherent lamp and a charge coupled device detector, as well as a linear optical cavity placed around the absorbing sample, which enhances the effective path length through the sample. In this work the consequences of cavity length, mirror curvature, reflectivity, different light injection geometries, and spot size of the light source on the output intensity are studied and the implications to the signal-to-noise ratio of the absorption measurement are discussed. The symmetric confocal resonator configuration is identified as a special case with optimum imaging characteristics but with higher requirements for mechanical stability. Larger spot sizes of the light source were found to be favorable in order to reduce the negative effects of aberrations on the intensity.

  12. Sparsity and incoherence in compressive sampling

    NASA Astrophysics Data System (ADS)

    Candès, Emmanuel; Romberg, Justin

    2007-06-01

    We consider the problem of reconstructing a sparse signal x^0\\in{\\bb R}^n from a limited number of linear measurements. Given m randomly selected samples of Ux0, where U is an orthonormal matrix, we show that ell1 minimization recovers x0 exactly when the number of measurements exceeds m\\geq \\mathrm{const}^{\\vphantom{\\frac12}}_{\\vphantom{\\frac12}} \\cdot\\mu^2(U)\\cdot S\\cdot\\log n, where S is the number of nonzero components in x0 and μ is the largest entry in U properly normalized: \\mu(U) = \\sqrt{n} \\cdot \\max_{k,j} |U_{k,j}| . The smaller μ is, the fewer samples needed. The result holds for 'most' sparse signals x0 supported on a fixed (but arbitrary) set T. Given T, if the sign of x0 for each nonzero entry on T and the observed values of Ux0 are drawn at random, the signal is recovered with overwhelming probability. Moreover, there is a sense in which this is nearly optimal since any method succeeding with the same probability would require just about as many samples.

  13. 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.

  14. X-ray scatter tomography using coded apertures

    NASA Astrophysics Data System (ADS)

    MacCabe, Kenneth P.

    This work proposes and studies a new field of x-ray tomography which combines the principles of scatter imaging and coded apertures, termed "coded aperture x-ray scatter imaging" (CAXSI). Conventional x-ray tomography reconstructs an object's electron density distribution by measuring a set of line integrals known as the x-ray transform, based physically on the attenuation of incident rays. More recently, scatter imaging has emerged as an alternative to attenuation imaging by measuring radiation from coherent and incoherent scattering. The information-rich scatter signal may be used to infer density as well as molecular structure throughout a volume. Some scatter modalities use collimators at the source and detector, resulting in long scan times due to the low efficiency of scattering mechanisms combined with a high degree of spatial filtering. CAXSI comes to the rescue by employing coded apertures. Coded apertures transmit a larger fraction of the scattered rays than collimators while also imposing structure to the scatter signal. In a coded aperture system each detector is sensitive to multiple ray paths, producing multiplexed measurements. The coding problem is then to design an aperture which enables de-multiplexing to reconstruct the desired physical properties and spatial distribution of the target. In this work, a number of CAXSI systems are proposed, analyzed, and demonstrated. One-dimensional "pencil" beams, two-dimensional "fan" beams, and three-dimensional "cone" beams are considered for the illumination. Pencil beam and fan beam CAXSI systems are demonstrated experimentally. The utility of energy-integrating (scintillation) detectors and energy-sensitive (photon counting) detectors are evaluated theoretically, and new coded aperture designs are presented for each beam geometry. Physical models are developed for each coded aperture system, from which resolution metrics are derived. Systems employing different combinations of beam geometry, coded

  15. Incoherent holography to obtain depth information by a rotational shearing interferometer

    NASA Astrophysics Data System (ADS)

    Watanabe, Kaho; Nomura, Takanori

    2015-09-01

    The system to record incoherent holograms using a rotational shearing interferometer is proposed. It enables us to record a hologram without coherent illumination such as a laser. The systems can record an incoherent hologram by self-interference. A rotational shearing interferometer to record incoherent cosine hologram is described. Furthermore, a rotational shearing interferometer with lenses to record incoherent hologram is described. It has the advantage of obtaining depth information by the reconstruction owing to lenses for the shear which is parallel to the optical axis. The preliminary experiments were performed. An LED and a liquid crystal display with an LED backlight were used as incoherent objects. The incoherent holograms were recorded. The object images were reconstructed numerically. The experimental results confirm the proposed incoherent holography using a rotational shearing interferometer.

  16. Differential two-signal picosecond-pulse coherent anti-Stokes Raman scattering imaging microscopy by using a dual-mode optical parametric oscillator.

    PubMed

    Yoo, Yong Shim; Lee, Dong-Hoon; Cho, Hyuck

    2007-11-15

    We propose and demonstrate a novel differential two-signal technique of coherent anti-Stokes Raman scattering (CARS) imaging microscopy using a picosecond (ps) optical parametric oscillator (OPO). By adjusting a Lyot filter inside the cavity, we operated the OPO oscillating in two stable modes separated by a few nanometers. The CARS images generated by the two modes are separated by a spectrograph behind the microscope setup, and their differential image is directly obtained by balanced lock-in detection. The feasibility of the technique is experimentally verified by imaging micrometer-sized polystyrene beads immersed in water.

  17. 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.

  18. Incoherent pair generation in a beam-beam interaction simulation

    NASA Astrophysics Data System (ADS)

    Rimbault, C.; Bambade, P.; Mönig, K.; Schulte, D.

    2006-03-01

    This paper deals with two topics: the generation of incoherent pairs in two beam-beam simulation programs, GUINEA-PIG and CAIN, and the influence of the International Linear Collider (ILC) beam parameter choices on the background in the micro vertex detector (VD) induced by direct hits. One of the processes involved in incoherent pair creation (IPC) is equivalent to a four fermions interaction and its cross section can be calculated exactly with a dedicated generator, BDK. A comparison of GUINEA-PIG and CAIN results with BDK allows to identify and quantify the uncertainties on IPC background predictions and to benchmark the GUINEA-PIG calculation. Based on this simulation and different VD designs, the five currently suggested ILC beam parameter sets have been compared regarding IPC background induced in the VD by direct IPC hits. We emphasize that the high luminosity set, as it is currently defined, would constrain both the choices of magnetic field and VD inner layer radius.

  19. Electromagnetically induced two-dimensional grating assisted by incoherent pump

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Yuan; Liu, Zhuan-Zhuan; Wan, Ren-Gang

    2017-04-01

    We propose a scheme for realizing electromagnetically induced two-dimensional grating in a double-Λ system driven simultaneously by a coherent field and an incoherent pump field. In such an atomic configuration, the absorption is suppressed owing to the incoherent pumping process and the probe can be even amplified, while the refractivity is mainly attributed to the dynamically induced coherence. With the help of a standing-wave pattern coherent field, we obtain periodically modulated refractive index without or with gain, and therefore phase grating or gain-phase grating which diffracts a probe light into high-order direction efficiently can be formed in the medium via appropriate manipulation of the system parameters. The diffraction efficiency attainable by the present gratings can be controlled by tuning the coherent field intensity or the interaction length. Hence, the two-dimensional grating can be utilized as all-optical splitter or router in optical networking and communication.

  20. Revealing proton shape fluctuations with incoherent diffraction at high energy

    SciTech Connect

    Mantysaari, H.; Schenke, B.

    2016-08-30

    The di erential cross section of exclusive di ractive vector meson production in electron proton collisions carries important information on the geometric structure of the proton. More speci cally, the coherent cross section as a function of the transferred transverse momentum is sensitive to the size of the proton, while the incoherent, or proton dissociative cross section is sensitive to uctuations of the gluon distribution in coordinate space. We show that at high energies the experimentally measured coherent and incoherent cross sections for the production of J= mesons are very well reproduced within the color glass condensate framework when strong geometric uctuations of the gluon distribution in the proton are included. For meson production we also nd reasonable agreement. We study in detail the dependence of our results on various model parameters, including the average proton shape, analyze the e ect of saturation scale and color charge uctuations and constrain the degree of geometric uctuations.

  1. Revealing proton shape fluctuations with incoherent diffraction at high energy

    SciTech Connect

    Mantysaari, H.; Schenke, B.

    2016-08-30

    The di erential cross section of exclusive di ractive vector meson production in electron proton collisions carries important information on the geometric structure of the proton. More speci cally, the coherent cross section as a function of the transferred transverse momentum is sensitive to the size of the proton, while the incoherent, or proton dissociative cross section is sensitive to uctuations of the gluon distribution in coordinate space. We show that at high energies the experimentally measured coherent and incoherent cross sections for the production of J= mesons are very well reproduced within the color glass condensate framework when strong geometric uctuations of the gluon distribution in the proton are included. For meson production we also nd reasonable agreement. We study in detail the dependence of our results on various model parameters, including the average proton shape, analyze the e ect of saturation scale and color charge uctuations and constrain the degree of geometric uctuations.

  2. 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.

  3. Phase diagram of incoherently driven strongly correlated photonic lattices

    NASA Astrophysics Data System (ADS)

    Biella, Alberto; Storme, Florent; Lebreuilly, José; Rossini, Davide; Fazio, Rosario; Carusotto, Iacopo; Ciuti, Cristiano

    2017-08-01

    We explore theoretically the nonequilibrium photonic phases of an array of coupled cavities in presence of incoherent driving and dissipation. In particular, we consider a Hubbard model system where each site is a Kerr nonlinear resonator coupled to a two-level emitter, which is pumped incoherently. Within a Gutzwiller mean-field approach, we determine the steady-state phase diagram of such a system. We find that, at a critical value of the intercavity photon hopping rate, a second-order nonequilibrium phase transition associated with the spontaneous breaking of the U(1 ) symmetry occurs. The transition from an incompressible Mott-like photon fluid to a coherent delocalized phase is driven by commensurability effects and not by the competition between photon hopping and optical nonlinearity. The essence of the mean-field predictions is corroborated by finite-size simulations obtained with matrix product operators and corner-space renormalization methods.

  4. Incoherent magnetization reversal in 30-nm Ni particles

    NASA Astrophysics Data System (ADS)

    Ross, C. A.; Chantrell, R.; Hwang, M.; Farhoud, M.; Savas, T. A.; Hao, Y.; Smith, Henry I.; Ross, F. M.; Redjdal, M.; Humphrey, F. B.

    2000-12-01

    The magnetic properties of a 100-nm-period large-area array of regular, 30-nm polycrystalline nickel particles have been studied. The particles are found to reverse incoherently, and their hysteresis behavior has been compared with a computational model over a range of temperatures. Excellent agreement with the model is obtained, indicating that switching of the particles is dominated by the reversal of approximately 10-nm-diameter volumes within each particle. These switching volumes are identified with the columnar grains in the polycrystalline nickel, showing that the microstructure determines the magnetic behavior of the particles. This explains the anisotropy distribution and the onset of superparamagnetism in the sample. Incoherent reversal occurs even though the particles are only 1.5 times the exchange length in nickel, a size at which nearly uniform rotation is expected to occur if the particles were homogeneous.

  5. Axial asymmetry in holographic and incoherent correlation imaging

    NASA Astrophysics Data System (ADS)

    Běhal, Jaromír.; Bouchal, Petr; Schovánek, Petr; Fordey, Tomáš; Bouchal, Zdeněk

    2016-12-01

    In optical lens imaging, the main attention has traditionally been paid to the lateral resolution roughly estimated by a two-dimensional point spread function (PSF) describing sharp image of a point object. In three-dimensional (3D) imaging and methods based on depth information, an axial profile of the PSF becomes of particular importance. In studies on the 3D PSF, the axial image asymmetry and shift of the intensity maximum out of the focal plane were revealed for optical systems characterized by low Fresnel numbers. In this paper, the 3D PSF is examined in terms of digital imaging, where a point object is recorded optically and its image reconstructed numerically. The analysis includes methods of digital holography, in which the axial image asymmetry is examined in relation to different geometries of coherent recording waves. Attention is also devoted to the Fresnel incoherent correlation imaging that enables recording of 3D objects in spatially incoherent light.

  6. Revealing proton shape fluctuations with incoherent diffraction at high energy

    DOE PAGES

    Mantysaari, H.; Schenke, B.

    2016-08-30

    The di erential cross section of exclusive di ractive vector meson production in electron proton collisions carries important information on the geometric structure of the proton. More speci cally, the coherent cross section as a function of the transferred transverse momentum is sensitive to the size of the proton, while the incoherent, or proton dissociative cross section is sensitive to uctuations of the gluon distribution in coordinate space. We show that at high energies the experimentally measured coherent and incoherent cross sections for the production of J= mesons are very well reproduced within the color glass condensate framework when strongmore » geometric uctuations of the gluon distribution in the proton are included. For meson production we also nd reasonable agreement. We study in detail the dependence of our results on various model parameters, including the average proton shape, analyze the e ect of saturation scale and color charge uctuations and constrain the degree of geometric uctuations.« less

  7. Preliminary results toward injection locking of an incoherent laser array

    NASA Technical Reports Server (NTRS)

    Daher, J.

    1986-01-01

    The preliminary results of phase locking an incoherent laser array to a master source in an attempt to achieve coherent operation are presented. The techniques necessary to demonstrate phase locking are described along with some topics for future consideration. As expected, the results obtained suggest that injection locking of an array, where the spacing between adjacent longitudinal modes of its elements is significantly larger than the locking bandwidth, may not be feasible.

  8. 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.

  9. Evidence of strong proton shape fluctuations from incoherent diffraction

    SciTech Connect

    Mantysaari, H.; Schenke, B.

    2016-07-25

    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.

  10. Evidence of strong proton shape fluctuations from incoherent diffraction

    DOE PAGES

    Mantysaari, H.; Schenke, B.

    2016-07-25

    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.

  11. 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.

  12. Absolute Bunch Length Measurements by Incoherent Radiation Fluctuation Analysis

    SciTech Connect

    Sannibale, F.; Stupakov, G.V.; Zolotorev, M.S.; Filippetto, D.; Jagerhofer, L.; /Vienna, Tech. U.

    2009-12-09

    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 successfully tested a simple scheme based on this principle that allows for the absolute measurement of the rms bunch length. A description of the method and the experimental results are presented.

  13. Absolute bunch length measurements by incoherent radiation fluctuation analysis

    SciTech Connect

    Sannibale, Fernando; Stupakov, Gennady; Zolotorev, Max; Filippetto, Daniele; Jagerhofer, Lukas

    2008-09-29

    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 successfully tested a simple scheme based on this principle that allows for the absolute measurement of the rms bunch length. A description of the method and the experimental results are presented.

  14. Investigation of optimum anti-scatter grid selection for digital radiography: physical imaging properties and detectability of low-contrast signals.

    PubMed

    Tanaka, Nobukazu; Naka, Kentaro; Saito, Aya; Morishita, Junji; Toyofuku, Fukai; Ohki, Masafumi; Higashida, Yoshiharu

    2013-01-01

    Our aim in this study was to evaluate the effect of the grid variations on the imaging performance for a computed radiographic system under identical exposure condition. Digital radiographies using a 20-cm Lucite phantom were performed without grid and with grid ratios of 5:1, 8:1, 10:1, 12:1, and 14:1. The scatter fraction, the incident dose to the image receptor, the Wiener spectrum (WS), and the noise-equivalent quanta (NEQ) were measured. Visibility of low-contrast signals was evaluated using a contrast-detail phantom. The scatter fractions decreased considerably with an increase in the grid ratio. On the other hand, the WSs were increased (the noise property deteriorated) as the grid ratio increased due to a decreased incident dose to the image receptor under the identical exposure condition. The NEQs were improved as the grid ratio increased. The high grid ratios provided higher low-contrast detectability compared to the low grid ratios. Our results indicated that the removal of scattered radiation was very effective in improvement of the NEQ in the digital system under the identical exposure condition.

  15. A coupled reagent of o-phthalaldehyde and sulfanilic acid for protein detection based on the measurements of light scattering signals with a common spectrofluorometer.

    PubMed

    Li, Yuan Fang; Shen, Xiao Wei; Huang, Cheng Zhi

    2008-05-30

    A rapid and sensitive method for the determination of proteins is proposed with a coupled reagent of o-phthalaldehyde and sulfanilic acid by measuring the light scattering (LS) signals with a common spectrofluorometer. Mechanism investigations showed that o-phthalaldehyde couples at first with sulfanilic acid with fast speed and forms a new synthesized Schiff base dye, which then interacts with protein rapidly on acidic condition, resulting in greatly enhanced LS signals with the maximum peak located at 344 nm. Based on the linear relationship between enhanced LS intensities and concentrations of proteins, a novel assay of HSA and BSA is established in the linear range of 0.1-25.0 microg ml(-1) with the limits of detection (3sigma) being 13 ng ml(-1) depending on the concentration of the reagent. Results for sample detections of our method were consistent with the documented spectrophotometric method with CBB G250 assay.

  16. 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.

  17. Fresnel incoherent correlation holography and its imaging properties

    NASA Astrophysics Data System (ADS)

    Wang, Zhipeng; Ma, Haotong; Ren, Ge; Xie, Zongliang; Yu, Huan

    2016-09-01

    The incoherent digital holography makes it possible to record holograms under incoherent illumination, which lowers requirement for the coherence of light sources and results in expanding its application to white-light and fluorescence illuminating circumstances. The Fresnel Incoherent Correlation Holography (FINCH) technology achieves diverging the incident beam and shifting phase by mounting phase masks on the phase modulator. Then it obtains holograms with phase difference and reconstructs the image. In this paper, we explain the principles of the FINCH technology, and introduce the n-step phase-shifting method which is utilized to eliminate the twin image and bias term in holograms. During the research, we studied what impact the term n may have on imaging performance, compared imaging performances when different phase masks are mounted on SLM, and established simulation system on imaging with which imaging performances are deeply inspected. At last, it is shown in the research that the FINCH technology could record holograms of objects, from which clear images could be reconstructed digitally.

  18. Incoherent acousto-optic image correlator with the kinoform

    NASA Astrophysics Data System (ADS)

    Starikov, Sergey N.; Rodin, Vladislav G.; Solyakin, Ivan V.; Shapkarina, Ekaterina A.; Chervonkin, Alexander P.

    2004-04-01

    Fourier holograms are commonly used for reference images storing in diffraction correlators with spatially coherent or spatially incoherent illumination. Kinoforms can be a real alternative to Fourier holograms in the correlators. The kinoform represents a computer-synthesized optical element which performs only a phase modulation of a light wave. The kinoform restores true intensity of the recorded image and random distribution of phase. Therefore, it can be utilized for storing reference images, first of all, in correlators with spatially incoherent illumination. The absence of carrier frequency reduces demanded number of pixels of the spatial light modulator being used. Since the kinoform provides reconstruction of reference image in zero diffraction order, requirement on monochromaticity of illumination are decreased as well. The diffraction correlator with the kinoform used as spatial frequency filter is considered. The 2-D acoustooptic deflector was employed to form input images in real time by monochromatic spatially incoherent light. The reference images were recorded on the commercially available kinoforms. The input and reference images were of 256×256 pixels and 200×200 pixels respectively. Since input images were consisted of approximately 400 pixels with non-zero brightness, the image update frequency was gained at 200 Hz. The experimental setup and experimental results on images recognition are presented.

  19. 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.

  20. Optimal resolution in Fresnel incoherent correlation holographic fluorescence microscopy

    PubMed Central

    Brooker, Gary; Siegel, Nisan; Wang, Victor; Rosen, Joseph

    2011-01-01

    Fresnel Incoherent Correlation Holography (FINCH) enables holograms and 3D images to be created from incoherent light with just a camera and spatial light modulator (SLM). We previously described its application to microscopic incoherent fluorescence wherein one complex hologram contains all the 3D information in the microscope field, obviating the need for scanning or serial sectioning. We now report experiments which have led to the optimal optical, electro-optic, and computational conditions necessary to produce holograms which yield high quality 3D images from fluorescent microscopic specimens. An important improvement from our previous FINCH configurations capitalizes on the polarization sensitivity of the SLM so that the same SLM pixels which create the spherical wave simulating the microscope tube lens, also pass the plane waves from the infinity corrected microscope objective, so that interference between the two wave types at the camera creates a hologram. This advance dramatically improves the resolution of the FINCH system. Results from imaging a fluorescent USAF pattern and a pollen grain slide reveal resolution which approaches the Rayleigh limit by this simple method for 3D fluorescent microscopic imaging. PMID:21445140

  1. Blind separation of incoherent and spatially disjoint sound sources

    NASA Astrophysics Data System (ADS)

    Dong, Bin; Antoni, Jérôme; Pereira, Antonio; Kellermann, Walter

    2016-11-01

    Blind separation of sound sources aims at reconstructing the individual sources which contribute to the overall radiation of an acoustical field. The challenge is to reach this goal using distant measurements when all sources are operating concurrently. The working assumption is usually that the sources of interest are incoherent - i.e. statistically orthogonal - so that their separation can be approached by decorrelating a set of simultaneous measurements, which amounts to diagonalizing the cross-spectral matrix. Principal Component Analysis (PCA) is traditionally used to this end. This paper reports two new findings in this context. First, a sufficient condition is established under which "virtual" sources returned by PCA coincide with true sources; it stipulates that the sources of interest should be not only incoherent but also spatially orthogonal. A particular case of this instance is met by spatially disjoint sources - i.e. with non-overlapping support sets. Second, based on this finding, a criterion that enforces both statistical and spatial orthogonality is proposed to blindly separate incoherent sound sources which radiate from disjoint domains. This criterion can be easily incorporated into acoustic imaging algorithms such as beamforming or acoustical holography to identify sound sources of different origins. The proposed methodology is validated on laboratory experiments. In particular, the separation of aeroacoustic sources is demonstrated in a wind tunnel.

  2. 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.

  3. Influence of soot aggregate size and internal multiple scattering on LII signal and the absorption function variation with wavelength determined by the TEW-LII method

    NASA Astrophysics Data System (ADS)

    Yon, J.; Therssen, E.; Liu, F.; Bejaoui, S.; Hebert, D.

    2015-05-01

    Laser-induced incandescence (LII) is a powerful and robust optical method for in situ determination of soot volume fraction and/or soot absorption/emission properties in flames and engine exhaust. The laser-induced signal is interpreted as thermal emission based on the Planck law. Up to now, the evaluation and interpretation of LII signal have been largely based on contributions from isolated primary particles that are assumed much smaller than wavelengths. In the present paper, the morphology, wavelength, and aggregate size-dependent effects of multiple scattering within fractal soot aggregates on their absorption and emission cross sections are taken into account in the evaluation of LII signal by proposing correction terms to the traditional model. The impact of accounting for the correction to soot aggregate emission due to multiple scattering on LII signal and on the two excitation wavelength-induced incandescence method for inferring the soot absorption function, E(m), is discussed. For wavelengths shorter than 532 nm, E(m, λ)/E(m, 1064 nm) increases more significantly with decreasing wavelength. For wavelengths longer than 532 nm, the wavelength dependence of E(m, λ)/E(m, 1064 nm) becomes very small and can be neglected. The proposed corrections, along with the soot morphology, are applied to re-analyze the experimental data of Bejaoui et al. (Appl Phys B Lasers Opt, 116:313, 2014) for deriving the relative soot absorption function variation with wavelength at different locations in a rich premixed methane flat flame at atmospheric pressure. The present analysis showed that the soot absorption function varies with the height above the burner exit and can be correlated with the degree of soot maturation.

  4. Neutron Scattering Structure and Dynamics in Hydrazine

    NASA Astrophysics Data System (ADS)

    Acatrinei, Alice; Hartl, Monika; Daemen, Luke; Forster, Diana; Kickbusch, Rainer; Luger, Peter; Lentz, Dieter

    2007-10-01

    The Lewis Acid Base theory is a fundamental concept in chemistry. One way of describing a chemical bond is to look at the charge distribution within a molecule. By studying the charge densities in electron-deficient compounds such as hydrazine borane, a more detailed view of the bonding situations is achieved. Our interest in hydrazine borane comes from many reasons. First of all it allows examining the experimental charge density of a so called donor acceptor bond on one of the simplest molecules. N2H4BH3 is a potential hydrogen storage material which has not been studied in detail so far. Finally, it contains N-N bonds that are of interest due to their torsional vibrations. We performed neutron powder diffraction on the powder diffractometer NPDF at 15K and 95K and determined the hydrogen positions in N2H4BH3. We synthesized the completely labelled compound N2D4(11BD3)2. We investigated the hydrogen bonding and the N-N torsional dynamics by using incoherent inelastic neutron scattering on the Filter Difference Spectrometer FDS. While IR and RAMAN spectroscopy only show weak signal for torsional and librational modes, these modes are quite strong in neutron vibrational spectroscopy. We present neutron diffraction data and vibrational spectra and their interpretation using molecular modelling calculations.

  5. Thermal neutron scattering data for 7LiF and BeF2

    NASA Astrophysics Data System (ADS)

    Wang, Jia; Song, Hongzhou; Hu, Zehua; Ye, Tao; Sun, Weili

    2017-09-01

    Based on the coherent elastic, incoherent elastic, coherent inelastic and incoherent inelastic scattering processes, a code named SIRIUS is developed to produce thermal neutron scattering data for crystals in ENDF-6 format. The phonon band structures and projected phonon densities of states of 7LiF and BeF2 crystals were calculated by Hellman-Feynman Theorem combined with a lattice dynamics direct method. Finally the thermal neutron scattering data for 7LiF and BeF2 crystals are given.

  6. Selective microvascular muscle perfusion imaging in the shoulder with intravoxel incoherent motion (IVIM).

    PubMed

    Nguyen, Audrey; Ledoux, Jean-Baptiste; Omoumi, Patrick; Becce, Fabio; Forget, Joachim; Federau, Christian

    2017-01-01

    The evaluation of local muscle recruitment during a specific movement can be done indirectly by measuring changes in local blood flow. Intravoxel incoherent motion perfusion imaging exploits some properties of the magnetic resonance to measure locally microvascular perfusion, and seems ideally suited for this task. We studied the selectivity of the increase in intravoxel incoherent motion blood flow related parameter fD* in the muscles of 24 shoulders after two physical exam maneuvers, Jobe and Lift-off test (test order reversed in half of the volunteers) each held 2min against resistance. After a lift-off, IVIM blood flow-related fD* was increased in the subscapularis (in 10(-3)mm(2)s(-1), 3.24±0.86 vs. rest 1.37±0.58, p<0.001) and the posterior bundle of deltoid (2.62±1.34 vs. rest 0.77±0.32, p<0.001). Those increases were selective when compared with other rotator cuff muscles and deltoid bundles respectively. After a Jobe test, increase in fD* was scattered within the rotator cuff muscles, but was selective for the lateral deltoid compared to the other deltoid bundles (anterior, p<0.001; posterior, p<0.05). Those results were similar when the testing order was reversed. In conclusion, this study demonstrated a selective increase in local microvascular perfusion after specific muscle testing of the shoulder muscles with IVIM. This technique has the potential to non-invasively characterize perfusion-related musculoskeletal physiological as well as pathological processes. Copyright © 2016 Elsevier Inc. All rights reserved.

  7. Diffuse inelastic scattering of atoms from surfaces

    SciTech Connect

    Manson, J.R.; Celli, V.

    1989-02-15

    We consider the large-angle diffuse scattering of thermal-energy atoms by defects or adsorbates on a surface. We obtain the Debye-Waller factor for the thermal attenuation of the incoherent elastic peak. When the Debye exponent is small, the diffuse inelastic contribution is dominated by the single-phonon exchange, and is proportional to the frequency distribution function of the defect or adsorbate. We discuss its magnitude compared to the multiphonon background.

  8. Deeply virtual Compton scattering off nuclei

    SciTech Connect

    Voutier, Eric

    2009-01-01

    Deeply virtual Compton scattering (DVCS) is the golden exclusive channel for the study of the partonic structure of hadrons, within the universal framework of generalized parton distributions (GPDs). This paper presents the aim and general ideas of the DVCS experimental program off nuclei at the Jefferson Laboratory. The benefits of the study of the coherent and incoherent channels to the understanding of the EMC (European Muon Collaboration) effect are discussed, along with the case of nuclear targets to access neutron GPDs.

  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. 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.

  11. Scatter factor/hepatocyte growth factor and its receptor, the c-met tyrosine kinase, can mediate a signal exchange between mesenchyme and epithelia during mouse development

    PubMed Central

    1993-01-01

    Scatter factor/hepatocyte growth factor (SF/HGF) has potent motogenic, mitogenic, and morphogenetic activities on epithelial cells in vitro. The cell surface receptor for this factor was recently identified: it is the product of the c-met protooncogene, a receptor-type tyrosine kinase. We report here the novel and distinct expression patterns of SF/HGF and its receptor during mouse development, which was determined by a combination of in situ hybridization and RNase protection experiments. Predominantly, we detect transcripts of c-met in epithelial cells of various developing organs, whereas the ligand is expressed in distinct mesenchymal cells in close vicinity. In addition, transient SF/HGF and c-met expression is found at certain sites of muscle formation; transient expression of the c-met gene is also detected in developing motoneurons. SF/HGF and the c-met receptor might thus play multiple developmental roles, most notably, mediate a signal given by mesenchyme and received by epithelial. Mesenchymal signals are known to govern differentiation and morphogenesis of many epithelia, but the molecular nature of the signals has remained poorly understood. Therefore, the known biological activities of SF/HGF in vitro and the embryonal expression pattern reported here indicate that this mesenchymal factor can transmit morphogenetic signals in epithelial development and suggest a molecular mechanism for mesenchymal epithelial interactions. PMID:8408200

  12. Source self-mixing in the detection of extended incoherent sources. [in optical heterodyne radiometry

    NASA Technical Reports Server (NTRS)

    Cohen, S. C.

    1975-01-01

    We consider the self-beating of incoherent light from an extended source at a wideband photomixer. The intermediate frequency mean squared current is found to be proportional to the product of the direct detected source power and the power within the IF bandpass about the optical frequency and within the heterodyne field of view. Thus the ratio of the heterodyne signal to self-beating power is proportional to the ratio of local oscillator power to direct detected power. This ratio is usually large for systems employing efficient local oscillators that generate shot-noise-limited operation. In less efficient systems, such as those employing tunable diode lasers, the effects of self-mixing may be significant.

  13. Coherent and incoherent seeding of dissipative modulation instability in a nonlinear fiber ring cavity.

    PubMed

    Bendahmane, A; Fatome, J; Finot, C; Millot, G; Kibler, B

    2017-01-15

    We investigate the coherent or incoherent seeding of dissipative modulation instability (MI) in a nonlinear fiber ring cavity. By varying wavelength and degree of coherence of the seed signal across the MI gain band, we observe a strong sensitivity of the resulting MI sidebands in terms of bandwidth and amplification. Both spectral and temporal characterizations are performed to reveal intensity coherence properties (over a single round-trip) of the generated temporal patterns. Experimental observations are well confirmed by numerical simulations. Our results provide new insights into the control of dissipative MI through a specific seeding in optical resonators with a moderate free-spectral range. In particular, a large tunability of the subsequent Kerr comb spacing is achieved by means of the early transient stage of seeded MI growth.

  14. Coherent and incoherent internal tides in the southern South China Sea

    NASA Astrophysics Data System (ADS)

    Liu, Qian; Xie, Xiaohui; Shang, Xiaodong; Chen, Guiying

    2016-11-01

    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.

  15. Measurement of low energy ionization signals from Compton scattering in a charge-coupled device dark matter detector

    NASA Astrophysics Data System (ADS)

    Ramanathan, K.; Kavner, A.; Chavarria, A. E.; Privitera, P.; Amidei, D.; Chou, T.-L.; Matalon, A.; Thomas, R.; Estrada, J.; Tiffenberg, J.; Molina, J.

    2017-08-01

    An important source of background in direct searches for low-mass dark matter particles are the energy deposits by small-angle scattering of environmental γ rays. We report detailed measurements of low-energy spectra from Compton scattering of γ rays in the bulk silicon of a charge-coupled device (CCD). Electron recoils produced by γ rays from 57Co and 241Am radioactive sources are measured between 60 eV and 4 keV. The observed spectra agree qualitatively with theoretical predictions, and characteristic spectral features associated with the atomic structure of the silicon target are accurately measured for the first time. A theoretically motivated parametrization of the data that describes the Compton spectrum at low energies for any incident γ -ray flux is derived. The result is directly applicable to background estimations for low-mass dark matter direct-detection experiments based on silicon detectors, in particular for the DAMIC experiment down to its current energy threshold.

  16. 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

  17. Performance Comparison between Stereausis and Incoherent Wideband Music for Localization of Ground Vehicles

    DTIC Science & Technology

    1999-09-01

    PERFORMANCE COMPARISON BETWEEN STEREAUSIS AND INCOHERENT WIDEBAND MUSIC FOR LOCALIZATION OF GROUND VEHICLES September 1999 Tien Pham U.S. Army...present experimental results comparing the incoherent wideband MUSIC (IWM) algorithm developed by the Army Research Laboratory (ARL)1, 2 and the...Type N/A Dates Covered (from... to) ("DD MON YYYY") Title and Subtitle Performance Comparison Between Stereausis and Incoherent Wideband Music for

  18. An incoherent feed-forward loop mediates robustness and tunability in a plant immune network.

    PubMed

    Mine, Akira; Nobori, Tatsuya; Salazar-Rondon, Maria C; Winkelmüller, Thomas M; Anver, Shajahan; Becker, Dieter; Tsuda, Kenichi

    2017-03-01

    Immune signaling networks must be tunable to alleviate fitness costs associated with immunity and, at the same time, robust against pathogen interferences. How these properties mechanistically emerge in plant immune signaling networks is poorly understood. Here, we discovered a molecular mechanism by which the model plant species Arabidopsis thaliana achieves robust and tunable immunity triggered by the microbe-associated molecular pattern, flg22. Salicylic acid (SA) is a major plant immune signal molecule. Another signal molecule jasmonate (JA) induced expression of a gene essential for SA accumulation, EDS5 Paradoxically, JA inhibited expression of PAD4, a positive regulator of EDS5 expression. This incoherent type-4 feed-forward loop (I4-FFL) enabled JA to mitigate SA accumulation in the intact network but to support it under perturbation of PAD4, thereby minimizing the negative impact of SA on fitness as well as conferring robust SA-mediated immunity. We also present evidence for evolutionary conservation of these gene regulations in the family Brassicaceae Our results highlight an I4-FFL that simultaneously provides the immune network with robustness and tunability in A. thaliana and possibly in its relatives. © 2017 The Authors.

  19. 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.

  20. 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

  1. Characterization of a space orbited incoherent fiber optic bundle

    NASA Technical Reports Server (NTRS)

    Dewalt, Stephen A.; Taylor, Edward W.

    1993-01-01

    The results of a study performed to determine the effects of adverse space environments on a bundle of over 1800 optical fibers orbited for 69 months are reported. Experimental results are presented on an incoherent fiber optic bundle oriented in low Earth orbit aboard the Long Duration Exposure Facility (LDEF) satellite as part of the Space Environment Effects Experiment (M0006). Measurements were performed to determine if space induced radiation effects changed the fiber bundle characteristics. Data demonstrating the success of light transmitting fibers to withstand the adverse space environment are presented.

  2. Two-step phase-shifting fluorescence incoherent holographic microscopy.

    PubMed

    Qin, Wan; Yang, Xiaoqi; Li, Yingying; Peng, Xiang; Yao, Hai; Qu, Xinghua; Gao, Bruce Z

    2014-06-01

    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.

  3. Speed and efficiency limits of multilevel incoherent heat engines

    NASA Astrophysics Data System (ADS)

    Mukherjee, V.; Niedenzu, W.; Kofman, A. G.; Kurizki, G.

    2016-12-01

    We present a comprehensive theory of heat engines (HE) based on a quantum-mechanical "working fluid" (WF) with periodically modulated energy levels. The theory is valid for any periodicity of driving Hamiltonians that commute with themselves at all times and do not induce coherence in the WF. Continuous and stroke cycles arise in opposite limits of this theory, which encompasses hitherto unfamiliar cycle forms, dubbed here hybrid cycles. The theory allows us to discover the speed, power, and efficiency limits attainable by incoherently operating multilevel HE depending on the cycle form and the dynamical regimes.

  4. Coherent and incoherent features, seasonal behaviors and spatial variations of internal tides in the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Cao, Anzhou; Guo, Zheng; Lv, Xianqing; Song, Jinbao; Zhang, Jicai

    2017-08-01

    Based on observations of the currents at six moorings from March 2010 to April 2011, the coherent and incoherent features, seasonal behaviors and spatial variations of internal tides (ITs) in the northern South China Sea (SCS) are investigated. Measurements of the currents indicate that both diurnal and semidiurnal ITs contain stronger coherent signals than incoherent ones at all moorings. In the measuring range, coherent internal tidal current variances explain 70% of the semidiurnal motion at most moorings. However, the proportion of coherent signals in the diurnal motion shows a non-monotonically decreasing trend with the westward propagation of diurnal ITs. Coherent signals of diurnal and semidiurnal ITs exhibit different seasonal variability at the six moorings: Diurnal ITs are stronger in winter (December to February) and summer (June to August) than in spring (March to May) and autumn (September to November), whereas stronger semidiurnal ITs always appear in spring and autumn. Combining these results with the temporal variation of barotropic tidal currents at the Luzon Strait (LS), it can be concluded that the seasonal variability of ITs at the six moorings are determined by the barotropic tides at the LS. In addition, this study shows that there are asymmetric features of ITs to the east and west of the LS.

  5. 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

  6. A large Raman scattering cross-section molecular embedded SERS aptasensor for ultrasensitive Aflatoxin B1 detection using CS-Fe3O4 for signal enrichment.

    PubMed

    Chen, Quansheng; Yang, Mingxiu; Yang, Xiaojing; Li, Huanhuan; Guo, Zhiming; Rahma, M H

    2018-01-15

    With growing concern on oil safety problems, developing a simple and sensitive method to detect Aflatoxin B1 (AFB1), a common mycotoxin in peanut oil, is very necessary. In this study, Surface-enhanced Raman Scattering (SERS) aptasensor was developed for ultrasensitive AFB1 detection using the amino-terminal AFB1 aptamer (NH2-DNA1); and thiol-terminal AFB1 complementary aptamer (SH-DNA2) conjugated magnetic-beads (CS-Fe3O4) as enrichment nanoprobe and AuNR@DNTB@Ag nanorods (ADANRs) as reporter nanoprobe respectively. 5,5'-Dithiobis(2-nitrobenzoicacid) (DNTB) with large Raman scattering cross-section and no fluorescence interference was embedded in Au and Ag core/shell nanorods as Raman reporter molecules. CS-Fe3O4 possessed excellent biocompatibility and superparamagnetism for rapid signal enrichment. Therefore, NH2-DNA1-CS-Fe3O4 and SH-DNA2-ADANRs were fabricated via the hybrid reaction between aptamers and complementary aptamers. When there is AFB1, AFB1 would competitively combine with the NH2-DNA1-CS-Fe3O4 inducing the dissociation of SH-DNA2-ADANRs from CS-Fe3O4 and further decreasing the SERS signal. Based on this developed SERS aptasensor, a low limit of 0.0036ng/mL and an effective linear detection range from 0.01 to 100ng/mL with the correlation coefficient up to 0.986 for AFB1 detection were obtained. Moreover, the specificity of this SERS aptasensor was demonstrated by detecting other two mycotoxins and its accuracy for AFB1 detection in real peanut oil was further confirmed by standard addition recovery test. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Redox cycling effect on the surface-enhanced Raman scattering signal of crystal violet molecules at nanostructured interdigitated array electrodes.

    PubMed

    Islam, Md Monirul; Ueno, Kosei; Misawa, Hiroaki

    2010-01-01

    Nanostructured interdigitated array (IDA) electrodes with different inter-electrode spacing were demonstrated to improve the detection sensitivity of short-lived electroactive species and to follow interfacial dynamics by their surface-enhanced Raman scattering (SERS) functionality. Nanostructured IDA electrodes fabricated using electron beam lithography were used for an electrochemical SERS study of irreversible electroactive species, crystal violet (CV), in an aqueous KCl solution in single and generation-collection (GC) mode experiments. The GC mode enabled us to amplify the SERS intensity. An inter-electrode spacing dependent study found the maximum number of redox cycling, collection efficiency and amplification of the SERS intensity. Its SERS function disclosed the potential-dependent dynamics of CV molecules at the electrode surface, which was not observed in the redox current. Miniaturized nanostructured IDA electrodes are of great importance for developing lab on chip devices, and are useful for analyzing dynamical features within small space/volume domains, which require small amounts and/or concentration of analytes.

  8. 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

  9. Off-axis self-interference incoherent digital holographic microscopy

    NASA Astrophysics Data System (ADS)

    Jeon, Philjun; Lee, Heejung; So, Byunghwy; Hwang, Wonsang; Bae, Yoonsung; Kim, Dugyoung

    2017-03-01

    3D imaging is demanding technology required in fluorescence microscopy. Even though holography is a powerful technique, it could not be used easily in fluorescence microscopy because of low coherence of fluorescence light. Lately, several incoherent holographic methods such as scanning holography, Fresnel in coherent correlation holography (FINCH), and self-interference incoherent digital holography (SIDH) have been proposed. However, these methods have many problems to be overcome for practical applications. For example, DC term removal, twin image ambiguity, and phase unwrapping problems need to be resolved. Off-axis holography is a straightforward solution which can solve most of these problems. We built an off-axis SIDH system for fluorescence imaging, and investigated various conditions and requirements for practical holographic fluorescence microscopy. Our system is based on a modified Michelson interferometer with a flat mirror at one arm and a curved mirror at the other arm of the interferometer. We made a phantom 3D fluorescence object made of 2 single-mode fibers coupled to a single red LED source to mimic 2 fluorescence point sources distributed by a few tens of micrometers apart. A cooled EM-CCD was used to take holograms of these fiber ends which emit only around 180 nW power.

  10. 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.

  11. Large reverse saturable absorption under weak continuous incoherent light.

    PubMed

    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.

  12. 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.

  13. Incoherent Bi off-centering in Bi₂Ti₂O₆O' and Bi₂Ru₂O₆O': Insulator versus metal

    DOE PAGES

    Shoemaker, Daniel P.; Seshadri, Ram; Tachibana, Makoto; ...

    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

  14. 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.

  15. Near-field-far-field transition of a finite line source using incoherent light: A student laboratory experiment

    NASA Astrophysics Data System (ADS)

    Yan, Xincheng; Yu, Yixin; Shen, Louis; Wanser, Keith H.

    1995-01-01

    A simple experiment employing low cost apparatus is presented which demonstrates the falloff of intensity with distance and the transition from the near field to the far field of a line source filament incandescent light bulb. A derivation of the Poynting vector as a function of the distance away from the filament is presented which shows an exact correspondence to the derivation for the electric field from a finite line charge source in electrostatics. The experimental data of power vs distance from the filament show an inverse first power of the distance falloff in the near field, with a smooth transition to an inverse square law behavior in the far field, in good agreement with the theoretical expression when corrections for the measured angular response of the detector are included. The experiment provides an illustration of the inverse square law falloff of intensity at large distances from the source, experience with simple concepts and techniques of optical radiometry and incoherent light sources, and the analogy between incoherent light sources and electrostatics in an undergraduate laboratory. An additional short experiment provides an illustration of electrical-to-optical power conversion efficiency and temperature dependent resistance associated with electron-phonon scattering in metals. A derivation of isotropic, unpolarized elementary radiators from anisotropic dipole radiation is presented in the Appendix.

  16. 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.

  17. On the Inversion of the Scattering Polarization and the Hanle Effect Signals in the Hydrogen Lyα Line

    NASA Astrophysics Data System (ADS)

    Ishikawa, R.; Asensio Ramos, A.; Belluzzi, L.; Manso Sainz, R.; Štěpán, J.; Trujillo Bueno, 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.

  18. Incoherent pion photoproduction on the deuteron in the first resonance region

    NASA Astrophysics Data System (ADS)

    Levchuk, M. I.; Loginov, A. Yu.; Sidorov, A. A.; Stibunov, V. N.; Schumacher, M.

    2006-07-01

    Incoherent pion photoproduction on the deuteron is studied in the first resonance region. The unpolarized cross section, the beam asymmetry, and the vector and tensor target asymmetries are calculated in the framework of a diagrammatic approach. Pole diagrams and one-loop diagrams with NN scattering in the final state are taken into account. An elementary operator for pion photoproduction on the nucleon is taken in various on-shell forms and calculated using the SAID and MAID multipole analyses. Model dependence of the obtained results is discussed in some detail. A comparison with predictions of other works is given. Although a reasonable description of many available experimental data on the unpolarized total and differential cross sections and photon asymmetry has been achieved, in some cases a significant disagreement between the theory and experiment has been found. Invoking known information on the reactions γd→π0d and γd→np we predict the total photoabsorption cross section for deuterium. We find that our values strongly overestimate experimental data in the vicinity of the Δ peak.

  19. Reflective Metasurfaces for Incoherent Light To Bring Computer Graphics Tricks to Optical Systems.

    PubMed

    Minovich, Alexander E; Peter, Manuel; Bleckmann, Felix; Becker, Manuel; Linden, Stefan; Zayats, Anatoly V

    2017-07-12

    The normal mapping technique is widely used in computer graphics to visualize three-dimensional (3D) objects displayed on a flat screen. Taking advantage of optical properties of metasurfaces, which provide a highly efficient approach for manipulation of incident light wavefront, we have designed a metasurface to implement diffuse reflection and used the concept of normal mapping to control its scattering properties. As a proof of principle, we have fabricated and characterized a flat diffuse metasurface imitating lighting and shading effects of a 3D cube. The 3D image is displayed directly on the illuminated metasurface and it is brighter than a standard white paper by up to 2.4 times. The designed structure performs equally well under coherent and incoherent illumination. The normal mapping approach based on metasurfaces can complement traditional optical engineering methods of surface profiling and gradient refractive index engineering in the design of 3D security features, high-performance planar optical diffusers, novel optical elements, and displays.

  20. 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.

  1. Real-time ultrawide-band group delay profile monitoring through low-noise incoherent temporal interferometry.

    PubMed

    Park, Yongwoo; Malacarne, Antonio; Azaña, José

    2011-02-28

    A simple, highly accurate measurement technique for real-time monitoring of the group delay (GD) profiles of photonic dispersive devices over ultra-broad spectral bandwidths (e.g. an entire communication wavelength band) is demonstrated. The technique is based on time-domain self-interference of an incoherent light pulse after linear propagation through the device under test, providing a measurement wavelength range as wide as the source spectral bandwidth. Significant enhancement in the signal-to-noise ratio of the self-interference signal has been observed by use of a relatively low-noise incoherent light source as compared with the theoretical estimate for a white-noise light source. This fact combined with the use of balanced photo-detection has allowed us to significantly reduce the number of profiles that need to be averaged to reach a targeted GD measurement accuracy, thus achieving reconstruction of the device GD profile in real time. We report highly-accurate monitoring of (i) the group-delay ripple (GDR) profile of a 10-m long chirped fiber Bragg grating over the full C band (~42 nm), and (ii) the group velocity dispersion (GVD) and dispersion slope (DS) profiles of a ~2-km long dispersion compensating fiber module over an ~72-nm wavelength range, both captured at a 15 frames/s video rate update, with demonstrated standard deviations in the captured GD profiles as low as ~1.6 ps.

  2. Bidirectional reflectance distribution function of Spectralon white reflectance standard illuminated by incoherent unpolarized and plane-polarized light.

    PubMed

    Bhandari, Anak; Hamre, Børge; Frette, Øvynd; Zhao, Lu; Stamnes, Jakob J; Kildemo, Morten

    2011-06-01

    A Lambert surface would appear equally bright from all observation directions regardless of the illumination direction. However, the reflection from a randomly scattering object generally has directional variation, which can be described in terms of the bidirectional reflectance distribution function (BRDF). We measured the BRDF of a Spectralon white reflectance standard for incoherent illumination at 405 and 680 nm with unpolarized and plane-polarized light from different directions of incidence. Our measurements show deviations of the BRDF for the Spectralon white reflectance standard from that of a Lambertian reflector that depend both on the angle of incidence and the polarization states of the incident light and detected light. The non-Lambertian reflection characteristics were found to increase more toward the direction of specular reflection as the angle of incidence gets larger.

  3. Recent Incoherent Scatter Radar Results with Artificial Ionospheric Heating at EISCAT

    NASA Astrophysics Data System (ADS)

    Rietveld, Michael

    2010-05-01

    During the last few years the solar minimum has made many HF heater-induced phenomena difficult to excite, particularly those where the heater frequency needs to be near or below the O-mode penetration frequency. This condition is even more difficult to meet at night. Consequently the types of experiments performed have been more mesospheric or D region heating experiments, more daytime F region experiments and X-mode heating of the F region. Experiments where electron temperature modulation of the D region affects mesospheric dust charging and thereby the backscatter cross-section of irregularities in the neutral gas, have been particularly fruitful in unraveling the physical processes involved. Four radars covering HF (8 MHz) to UHF (933 MHz) have been used to measure the effects at the various scales. X-mode transmission has also produced, at times, surprisingly strong heating in the F region. This allows us to extend some experiments to lower density conditions, as well as giving us more input to models of the ionospheric energy balance. Some highlights from these and other experiments will be shown.

  4. Crossover from Incoherent to Coherent Phonon Scattering in Epitaxial Oxide Superlattices

    DTIC Science & Technology

    2013-12-08

    nature. Such phenomena are the consequence of the quantum -mechanical nature of particles such as electrons, photons and phonons. Despite widespread and...largely monochromatic optical and acoustic phonons using laser pump–probe techniques5 and superconducting tunnel junctions6, or, alternatively, the...structurally compatible perovskites with different acoustic impedance mismatches, tunable through chemical substitutions, makes perovskites an

  5. 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.

  6. Storm Induced Changes of the Topside Ionosphere as Deduced from Incoherent Scatter Radars

    DTIC Science & Technology

    1990-01-01

    11484 Sep 18 05 16 to 1q84 Sep1, 9 05.16 UT Millstone Hill Ion teOMPO’dture (Til (K 2 4 6 8 10 12 14 16 18 20 22 24 LT 600 550 (b) j 500 450 350 b B 10 2...l 350 320 L/ 2 4 6 8 10 12 Id 16. )s 20 22 24 -1 1q84 Oct 17 00 08 o 19)84 Oct 18 00 08 UT Arecibo 22 24 2 4 6 8 0 12 14 16 8 20L 600 I (b) 450 400Y...22 24 UT 19B4 Sep iq 00.08 to 1q84 Sop 20 eZ.OB UT Arecibo Ion, tomp.o-atw-. IT1 K 1 22 24 2 4 6 8 10 12 14 16 18 20 LT 550 500J.50 (b) 45 400 350

  7. Optical aurora and its relationship to measurements from satellites, VHF radar and incoherent scatter radars

    NASA Technical Reports Server (NTRS)

    Romick, G. J.

    1974-01-01

    Examples are given of coordinated programs in Alaska which involve satellites, radars, ground optical instrumentation, and other types of observing satellites for the study of atmospheric and magnetospheric geophysics. Programs include coincidence data acquisition, scheduled data acquisition, and planned experiments. The use of optical triangulation techniques to determine the position of the aurora in order to place the other measurements in the perspective of the overall auroral morphology is detailed.

  8. 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.

  9. The solar flare of 18 August 1979: Incoherent scatter radar data and photochemical model comparisons

    SciTech Connect

    Zinn, J.; Sutherland, C.D.; Fenimore, E.E.; Ganguly, S.

    1988-04-01

    Measurements of electron density at seven D-region altidues were made with the Arecibo radar during a Class-X solar flare on 18 August 1979. Measurements of solar x-ray fluxes during the same period were available from the GOES-2 satellite (0.5 to 4 /angstrom/ and 1 to 8 /angstrom/) and from ISEE-3 (in four bands between 26 and 400 keV). From the x-ray flux data we computed ionization rates in the D-region and the associated chemical changes, using a coupled atmospheric chemistry and diffusion model (with 836 chemical reactions and 19 vertical levels). The computed electron densities matched the data fairly well after we had adjusted the rate coefficients of two reactions. We discuss the hierarchies among the many flare-induced chemical reactions in two altitude ranges within the D-region and the effects of adjusting several other rate coefficients. 51 refs., 6 figs., 3 tabs.

  10. A revised thermospheric model based on mass spectrometer and incoherent scatter data - MSIS-83

    NASA Technical Reports Server (NTRS)

    Hedin, A. E.

    1983-01-01

    It is noted that the model presented here extends the previous description of neutral parameters to the base of the thermosphere in a continuous manner while maintaining the basic structure of the MSIS model at higher altitudes. As the altitude decreases, the composition approaches lower atmosphere values, whereas yearly, and to a lesser extent daily, variations in temperature and density are in reasonable agreement with earlier results for the lower thermosphere. An alternate description is given of magnetic storm variations on the basis of the three hour ap indices and an 8- to 10-hour exponential decay in thermospheric density and temperature response after a heating event. Additional coefficients are included for the time independent and magnetic activity terms, among them a longitudinally dependent seasonal magnetic activity effect. The description of molecular oxygen derives from mass spectrometer and EUV absorption measurements rather than ion chemistry.

  11. Brillouin scattering signal in polymer optical fiber enhanced by exploiting pulsed pump with multimode-fiber-assisted coupling technique.

    PubMed

    Mizuno, Yosuke; Hayashi, Neisei; Nakamura, Kentaro

    2013-05-01

    A cost-effective technique for coupling a polymer optical fiber (POF) with 50 μm core diameter to a silica single-mode fiber (SMF) with 8 μm core diameter is proposed, which can, by exploiting a multimode fiber with 50 μm core diameter, avoid the damage or burning at the butt-coupled POF/SMF interface. Using this coupling technique, we also show that the Brillouin signal in a POF can be enhanced by combined use of pulsed pump and an erbium-doped fiber amplifier. When the pulsed pump with average optical power of 18 dBm (63 mW), duty ratio of 15%, and pulse period of 2 μs is launched into a 200 m-long POF, 4 dB enhancement of the Stokes power is obtained compared to that with 18 dBm continuous wave pump. The relatively small enhancement is probably caused by the high Brillouin threshold of POFs. The Stokes power dependence on duty ratio is nonmonotonic, which might originate from a longer phonon lifetime in POFs than that in silica SMFs.

  12. 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)

  13. 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)

  14. Excess noise in Lidar Thomson scattering methods

    NASA Astrophysics Data System (ADS)

    Smith, R. J.; Drake, L. A. P.; Lestz, J. B.

    2012-02-01

    Fundamental detection limits for the Lidar Thomson scattering technique and in particular pulsed polarimetry are presented for the first time for the long wavelength limit of incoherent Thomson scattering. Pulsed polarimetry generalizes Lidar Thomson scattering to include local magnetic field sensing. The implication for these techniques is explored for two experimental regimes where shot limited detection no longer applies: tokamaks of ITER size and cm-size wire Z pinch plasmas of High Energy Density (HED) science. The utility and importance of developing Lidar Thomson scattering at longer wavelengths for the magnetic fusion program is illustrated by a study of sightline (local) polarimetry measurements on a 15MA ITER scenario. Polarimetric measurements in the far infrared regime are shown to reach sensitivities that are instructive and useful but with a complex behaviour that make spatially resolved measurements all but mandatory.

  15. Measurements and simulation of ionospheric scattering on VHF and UHF radar signals: Coherence times, coherence bandwidths, and S4

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

    Irregularities in the electron density of the ionosphere cause phase and amplitude scintillation on transionospheric VHF and UHF radar signals, particularly at lower radio frequencies. The design of radar and other transionospheric systems requires good estimates of the coherence bandwidth (CB) and coherence time (CT) imposed by a turbulent ionosphere. CB and CT measurements of the equatorial ionosphere, made using the Advanced Research Project Agency Long-range Tracking and Identification Radar 158 MHz and 422 MHz phase coherent radar located on Kwajalein (9.4°N, 167.5°E), are presented as a function of the two-way S4 scintillation index at 422 MHz The log linear regression equations are CT = 1.46 exp(-1.40 S4) s at 158 MHz and CT = 2.31 exp(-1.10 S4) s at 422 MHz. CT also varies by a factor of 2-3 depending on the effective scan velocity through the ionosphere, veff. The CT and CB, as a function of S4, have been compared to those from the Trans-Ionospheric Radio Propagation Simulator, a phase screen model. A close agreement is achieved using appropriate values of veff and midrange values of phase spectral index and outer scale. Validation of CB is, however, limited by insufficient radar chirp bandwidth. Formulating the model in terms of the two-way S4 index (an easily measurable parameter) rather than more fundamental phase screen parameters (which are difficult to obtain), improves its utility for the systems engineer. The frequency dependencies (spectral indices) of S4 and of CT are also presented to allow interpolation and some extrapolation of these results to other frequencies.

  16. Incoherent dynamics in the toric code subject to disorder

    NASA Astrophysics Data System (ADS)

    Röthlisberger, Beat; Wootton, James R.; Heath, Robert M.; Pachos, Jiannis K.; Loss, Daniel

    2012-02-01

    We numerically study the effects of two forms of quenched disorder on the anyons of the toric code. First, a class of codes based on random lattices of stabilizer operators is presented and shown to be superior to the standard square-lattice toric code for certain forms of biased noise. It is further argued that these codes are close to optimal, in that they tightly reach the upper bound of error thresholds beyond which no correctable Calderbank-Shore-Steane codes can exist. Additionally, we study the classical motion of anyons in toric codes with randomly distributed on-site potentials. In the presence of repulsive long-range interaction between the anyons, a surprising increase in the lifetime of encoded states with disorder strength is reported and explained by an entirely incoherent mechanism. Finally, the coherent transport of the anyons in the presence of both forms of disorder is investigated and a significant suppression of the anyon motion is found.

  17. 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.

  18. 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.

  19. 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

  20. Fault Tolerant Algorithm for Structured Illumination Microscopy with Incoherent Light

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Heidingsfelder, Philipp; Gao, Jun; Yu, Liandong; Ott, Peter

    2015-04-01

    In this contribution we present a new algorithm for structured illumination microscopy with incoherent light. Existing algorithms for determining the contrast values of the focal depth response require a high accurate phase shift of the fringe pattern illumination. The presented algorithm, which is robust against inaccurate phase shift of the fringe pattern, reduces significantly the requirements for the phase shift and consequently the costs of the microscope. The new algorithm was tested by a preliminary experiment, whereby the grating was shifted by an elastic guided micro-motion mechanism employing a low-cost stepper motor replacing the conventional expensive piezo drive. The determined focal depth response is very smooth and corresponds very well to the theoretical focal depth response.

  1. Weak value measurement with an incoherent measuring device

    NASA Astrophysics Data System (ADS)

    Cho, Young-Wook; Lim, Hyang-Tag; Ra, Young-Sik; Kim, Yoon-Ho

    2010-02-01

    In the Aharonov-Albert-Vaidman (AAV) weak measurement, it is assumed that the measuring device or the pointer is in a quantum mechanical pure state. In reality, however, it is often not the case. In this paper, we generalize the AAV weak measurement scheme to include more generalized situations in which the measuring device is in a mixed state. We also report an optical implementation of the weak value measurement in which the incoherent pointer is realized with the pseudo-thermal light. The theoretical and experimental results show that the measuring device under the influence of partial decoherence could still be used for amplified detection of minute physical changes and is applicable for implementing the weak value measurement for massive particles.

  2. Incoherent twin boundary migration induced by ion irradiation in Cu

    NASA Astrophysics Data System (ADS)

    Li, N.; Wang, J.; Wang, Y. Q.; Serruys, Y.; Nastasi, M.; Misra, A.

    2013-01-01

    Grain boundaries can act as sinks for radiation-induced point defects. The sink capability is dependent on the atomic structures and varies with the type of point defects. Using high-resolution transmission electron microscopy, we observed that Σ3{112} incoherent twin boundary (ITB) in Cu films migrates under Cu3+ ion irradiation. Using atomistic modeling, we found that Σ3{112} ITB has the preferred sites for adsorbing interstitials and the preferential diffusion channels along the Shockley partial dislocations. Coupling with the high mobility of grain boundary Shockley dislocations within Σ3{112} ITB, we infer that Σ3{112} ITB migrates through the collective glide of grain boundary Shockley dislocations, driven by a concurrent reduction in the density of radiation-induced defects, which is demonstrated by the distribution of nearby radiation-induced defects.

  3. Delineating incoherent non-Markovian dynamics using quantum coherence

    SciTech Connect

    Chanda, Titas Bhattacharya, Samyadeb

    2016-03-15

    We introduce a method of characterization of non-Markovianity using coherence of a system interacting with the environment. We show that under the allowed incoherent operations, monotonicity of a valid coherence measure is affected due to non-Markovian features of the system–environment evolution. We also define a measure to quantify non-Markovianity of the underlying dynamics based on the non-monotonic behavior of the coherence measure. We investigate our proposed non-Markovianity marker in the behavior of dephasing and dissipative dynamics for one and two qubit cases. We also show that our proposed measure captures the back-flow of information from the environment to the system and compatible with well known distinguishability criteria of non-Markovianity.

  4. 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.

  5. 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.

  6. 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.

  7. Generation and detection of incoherent phonons in picosecond ultrasonics.

    PubMed

    Perrin, B; Péronne, E; Belliard, L

    2006-12-22

    In picosecond ultrasonics experiments the absorption of a femtosecond laser pulse in a thin metallic transducer is used to generate very short acoustic pulses. These pulses are made of coherent longitudinal waves with a frequency spectrum that can reach 100-200 GHz. The laser pulse absorption gives rise to a heating of the film of a few Kelvin within a typical time of 1 ps. Later on, the heat goes in the substrate through an interface thermal resistance and is diffused by thermal conduction. At very low temperature and in pure crystals the thermal phonons emitted by the heated metallic film can propagate ballistically over large distances and produce a so-called heat pulse. We report on the experimental evidence of the coexistence of the coherent acoustic pulse and the incoherent heat pulse generated and detected by laser ultrasonics.

  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. Interference by rain scatter

    NASA Technical Reports Server (NTRS)

    Crane, Robert K.

    1988-01-01

    The data from Japan and the U.S. (the Virginia Precipitation Scatter Experiment) show excellent agreement between the two-component rain scatter model predictions and bistatic scatter measurements. In employing the model, all the scattering geometries should be classified as backscattering as defined by Crane (1974). The forward scatter model should only be used for great circle paths with both antennas pointed at the horizon and at each other in a typical troposcatter communication system geometry. The forward scatter model can also be used for main-lobe, side-lobe coupling when one antenna is pointed toward the other along the great circle path. The forward scatter observations made over the Prospect Hill - Mt Tug path show that the two-component model is incomplete. Much stronger signals were observed at Ku-band than expected based on simultaneous C-band measurements. The discrepancies may be due to: (1) scattering by ice/snow at height (posssible in April) at the 1 km height of the scattering volume), (2) the coherent effects of turbulent fluctuations in the hydrometeor number densities and (3) errors in the modeling of the statistical relationship between attenuation along the path and scattering in the common volume.

  10. Interference by rain scatter

    NASA Astrophysics Data System (ADS)

    Crane, Robert K.

    1988-08-01

    The data from Japan and the U.S. (the Virginia Precipitation Scatter Experiment) show excellent agreement between the two-component rain scatter model predictions and bistatic scatter measurements. In employing the model, all the scattering geometries should be classified as backscattering as defined by Crane (1974). The forward scatter model should only be used for great circle paths with both antennas pointed at the horizon and at each other in a typical troposcatter communication system geometry. The forward scatter model can also be used for main-lobe, side-lobe coupling when one antenna is pointed toward the other along the great circle path. The forward scatter observations made over the Prospect Hill - Mt Tug path show that the two-component model is incomplete. Much stronger signals were observed at Ku-band than expected based on simultaneous C-band measurements. The discrepancies may be due to: (1) scattering by ice/snow at height (posssible in April) at the 1 km height of the scattering volume), (2) the coherent effects of turbulent fluctuations in the hydrometeor number densities and (3) errors in the modeling of the statistical relationship between attenuation along the path and scattering in the common volume.

  11. Thermal transport in phononic crystals and the observation of coherent phonon scattering at room temperature.

    PubMed

    Alaie, Seyedhamidreza; Goettler, Drew F; Su, Mehmet; Leseman, Zayd C; Reinke, Charles M; El-Kady, Ihab

    2015-06-24

    Large reductions in the thermal conductivity of thin silicon membranes have been demonstrated in various porous structures. However, the role of coherent boundary scattering in such structures has become a matter of some debate. Here we report on the first experimental observation of coherent phonon boundary scattering at room temperature in 2D phononic crystals formed by the introduction of air holes in a silicon matrix with minimum feature sizes >100 nm. To delaminate incoherent from coherent boundary scattering, phononic crystals with a fixed minimum feature size, differing only in unit cell geometry, were fabricated. A suspended island technique was used to measure the thermal conductivity. We introduce a hybrid thermal conductivity model that accounts for partially coherent and partially incoherent phonon boundary scattering. We observe excellent agreement between this model and experimental data, and the results suggest that significant room temperature coherent phonon boundary scattering occurs.

  12. Coherent effects upon the scattering of fast electrons by clusters

    SciTech Connect

    Zon, B. A.

    2016-02-15

    The ratio of the cross section for inelastic scattering to the total cross section for scattering of a fast electron by a cluster, depending on the number of atoms in the cluster, is shown to be not a monotonic function. This nonmonotonicity is not related to the well-known nonmonotonic dependences determined, for example, by the magic numbers in the shell model of clusters but is of purely quantum origin: the coherence of elastic electron scattering and the incoherence of inelastic one by a multipartice target.

  13. 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.

  14. 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.

  15. A new way to detect the interaction of DNA and anticancer drugs based on the decreased resonance light scattering signal and its potential application.

    PubMed

    Chen, Zhanguang; Song, Tianhe; Peng, Yurui; Chen, Xi; Chen, Junhui; Zhang, Guomin; Qian, Sihua

    2011-10-07

    A novel assay has been developed to detect the interaction of DNA and anticancer drugs based on the decreased resonance light scattering (RLS) technique. The proposed method can be used to study those drugs which do not produce a RLS-signal after binding to DNA. RLS was used to monitor the interaction of five anticancer drugs with DNA. The reaction between anticancer drugs and DNA took place in BR buffer solution. From the RLS assay, the sequence of five anticancer drugs activities was as follows: CTX < MTX < Pt < MMC < 5-Fu. Mammary cancer cell DNA (mcDNA) was involved to validate the RLS assay. The results showed that the sensitivities of the five anticancer drugs targeting both mcDNA and ctDNA increased in the same order. However the sensitivity of each drug to mcDNA was higher than that to ctDNA It is a significant innovation of the RLS method to detect the interaction of DNA and anticancer drugs and to obtain drug sensitivity, which provides new strategies to screen DNA targeted anticancer drugs.

  16. Phase-coherence classification: A new wavelet-based method to separate local field potentials into local (in)coherent and volume-conducted components.

    PubMed

    von Papen, M; Dafsari, H; Florin, E; Gerick, F; Timmermann, L; Saur, J

    2017-11-01

    Local field potentials (LFP) reflect the integrated electrophysiological activity of large neuron populations and may thus reflect the dynamics of spatially and functionally different networks. We introduce the wavelet-based phase-coherence classification (PCC), which separates LFP into volume-conducted, local incoherent and local coherent components. It allows to compute power spectral densities for each component associated with local or remote electrophysiological activity. We use synthetic time series to estimate optimal parameters for the application to LFP from within the subthalamic nucleus of eight Parkinson patients. With PCC we identify multiple local tremor clusters and quantify the relative power of local and volume-conducted components. We analyze the electrophysiological response to an apomorphine injection during rest and hold. Here we show medication-induced significant decrease of incoherent activity in the low beta band and increase of coherent activity in the high beta band. On medication significant movement-induced changes occur in the high beta band of the local coherent signal. It increases during isometric hold tasks and decreases during phasic wrist movement. The power spectra of local PCC components is compared to bipolar recordings. In contrast to bipolar recordings PCC can distinguish local incoherent and coherent signals. We further compare our results with classification based on the imaginary part of coherency and the weighted phase lag index. The low and high beta band are more susceptible to medication- and movement-related changes reflected by incoherent and local coherent activity, respectively. PCC components may thus reflect functionally different networks. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Transform-limited-pulse representation of excitation with natural incoherent light

    SciTech Connect

    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.

  18. Single-shot self-interference incoherent digital holography using off-axis configuration.

    PubMed

    Hong, Jisoo; Kim, Myung K

    2013-12-01

    We propose a single-shot incoherent holographic imaging technique that adopts self-interference incoherent digital holography (SIDH) with slight tilt of the plane mirror in the optical configuration. The limited temporal coherence length of the illumination leads the guide-star hologram of the proposed system to have a Gaussian envelope of elliptical ring shape. The observation shows that the reconstruction by cross correlation with the guide-star hologram achieves better quality than the usual propagation methods. Experimentally, we verify that the hologram and 3D reconstruction can be implemented incoherently with the proposed single-shot off-axis SIDH.

  19. Incoherent vector mesons production in PbPb ultraperipheral collisions at the LHC

    NASA Astrophysics Data System (ADS)

    Xie, Ya-Ping; Chen, Xurong

    2017-03-01

    The incoherent rapidity distributions of vector mesons are computed in dipole model in PbPb ultraperipheral collisions at the CERN Large Hadron Collider (LHC). The IIM model fitted from newer data is employed in the dipole amplitude. The Boosted Gaussian and Gaus-LC wave functions for vector mesons are implemented in the calculations as well. Predictions for the J / ψ, ψ (2 s), ρ and ϕ incoherent rapidity distributions are evaluated and compared with experimental data and other theoretical predictions in this paper. We obtain closer predictions of the incoherent rapidity distributions for J / ψ than previous calculations in the IIM model.

  20. Generation of coherent waves by frequency up-conversion and down-conversion of incoherent light

    SciTech Connect

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

    2010-11-15

    It is revealed that the generation of a coherent wave by frequency conversion of incoherent waves is a characteristic feature of three-wave interaction in a nonlinear medium when angular dispersion of input waves is properly chosen. In this case the combining action of the pairs of spectral components of incoherent waves may result in the cumulative driving of a single plane monochromatic wave in up-conversion and down-conversion processes. As a fundamental result we point out an enhancement of the spectral radiance of the generated wave in comparison with incoherent waves.