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Sample records for 2d-ir vibrational echo

  1. Observation of kinetic networks of hydrogen-bond exchange using 2D IR echo spectroscopy

    Kim, Yung Sam; Hochstrasser, Robin M.

    The ultrafast H-bond motion in acetonitrile/methanol and of methanol and water around a dicarbonyl (piperidone) dominates the mechanism of vibrational coherence transfer in linear and 2D IR echo spectra. Multiple state coherence transfer and energy transfer are seen at and between the two carbonyl groups of the piperidone in both water and methanol.

  2. 2D-IR spectroscopy of hydrogen-bond-mediated vibrational excitation transfer.

    Chuntonov, Lev

    2016-05-18

    Vibrational excitation transfer along the hydrogen-bond-mediated pathways in the complex of methyl acetate (MA) and 4-cyanophenol (4CP) was studied by dual-frequency femtosecond two-dimensional infrared spectroscopy. We excited the energy-donating ester carbonyl stretching vibrational mode and followed the transfer to the energy-accepting benzene ring and cyano stretching vibrations. The complexes with no, one, and two hydrogen-bonded 4CP molecules were studied. Vibrational relaxation of the carbonyl mode is more efficient in both hydrogen-bonded complexes as compared with free MA molecules. The inter-molecular transport in a hydrogen-bonded complex involving a single 4CP molecule is slower than that in a complex with two 4CP molecules. In the former, vibrational relaxation leads to local heating, as shown by the spectroscopy of the carbonyl mode, whereas the local heating is suppressed in the latter because the excitation redistribution is more efficient. At early times, the transfer to the benzene ring is governed by its direct coupling with the energy-donating carbonyl mode, whereas at later times intermediate states are involved. The transfer to a more distant site of the cyano group in 4CP involves intermediate states at all times, since no direct coupling between the energy-donating and accepting modes was observed. We anticipate that our findings will be of importance for spectroscopic studies of bio-molecular structures and dynamics, and inter- and intra-molecular signaling pathways, and for developing molecular networking applications. PMID:27145861

  3. 2D IR Spectroscopy of Histidine: Probing Side-Chain Structure and Dynamics via Backbone Amide Vibrations

    Ghosh, Ayanjeet; Tucker, Matthew J.; Gai, Feng

    2014-01-01

    It is well known that histidine is involved in many biological functions due to the structural versatility of its side chain. However, probing the conformational transitions of histidine in proteins, especially those occurring on an ultrafast time scale, is difficult. Herein we show, using a histidine dipeptide as a model, that it is possible to probe the tautomer and protonation status of a histidine residue by measuring the two-dimensional infrared (2D IR) spectrum of its amide I vibrationa...

  4. Ultrafast vibrational spectroscopy (2D-IR) of CO{sub 2} in ionic liquids: Carbon capture from carbon dioxide’s point of view

    Brinzer, Thomas; Berquist, Eric J.; Ren, Zhe; Dutta, Samrat; Johnson, Clinton A.; Krisher, Cullen S.; Lambrecht, Daniel S.; Garrett-Roe, Sean, E-mail: sgr@pitt.edu [Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260 (United States)

    2015-06-07

    The CO{sub 2}ν{sub 3} asymmetric stretching mode is established as a vibrational chromophore for ultrafast two-dimensional infrared (2D-IR) spectroscopic studies of local structure and dynamics in ionic liquids, which are of interest for carbon capture applications. CO{sub 2} is dissolved in a series of 1-butyl-3-methylimidazolium-based ionic liquids ([C{sub 4}C{sub 1}im][X], where [X]{sup −} is the anion from the series hexafluorophosphate (PF{sub 6}{sup −}), tetrafluoroborate (BF{sub 4}{sup −}), bis-(trifluoromethyl)sulfonylimide (Tf{sub 2}N{sup −}), triflate (TfO{sup −}), trifluoroacetate (TFA{sup −}), dicyanamide (DCA{sup −}), and thiocyanate (SCN{sup −})). In the ionic liquids studied, the ν{sub 3} center frequency is sensitive to the local solvation environment and reports on the timescales for local structural relaxation. Density functional theory calculations predict charge transfer from the anion to the CO{sub 2} and from CO{sub 2} to the cation. The charge transfer drives geometrical distortion of CO{sub 2}, which in turn changes the ν{sub 3} frequency. The observed structural relaxation timescales vary by up to an order of magnitude between ionic liquids. Shoulders in the 2D-IR spectra arise from anharmonic coupling of the ν{sub 2} and ν{sub 3} normal modes of CO{sub 2}. Thermal fluctuations in the ν{sub 2} population stochastically modulate the ν{sub 3} frequency and generate dynamic cross-peaks. These timescales are attributed to the breakup of ion cages that create a well-defined local environment for CO{sub 2}. The results suggest that the picosecond dynamics of CO{sub 2} are gated by local diffusion of anions and cations.

  5. Ultrafast vibrational spectroscopy (2D-IR) of CO2 in ionic liquids: Carbon capture from carbon dioxide's point of view

    Brinzer, Thomas; Berquist, Eric J.; Ren, Zhe; Dutta, Samrat; Johnson, Clinton A.; Krisher, Cullen S.; Lambrecht, Daniel S.; Garrett-Roe, Sean

    2015-06-01

    The CO2ν3 asymmetric stretching mode is established as a vibrational chromophore for ultrafast two-dimensional infrared (2D-IR) spectroscopic studies of local structure and dynamics in ionic liquids, which are of interest for carbon capture applications. CO2 is dissolved in a series of 1-butyl-3-methylimidazolium-based ionic liquids ([C4C1im][X], where [X]- is the anion from the series hexafluorophosphate (PF 6- ), tetrafluoroborate (BF 4- ), bis-(trifluoromethyl)sulfonylimide (Tf2N-), triflate (TfO-), trifluoroacetate (TFA-), dicyanamide (DCA-), and thiocyanate (SCN-)). In the ionic liquids studied, the ν3 center frequency is sensitive to the local solvation environment and reports on the timescales for local structural relaxation. Density functional theory calculations predict charge transfer from the anion to the CO2 and from CO2 to the cation. The charge transfer drives geometrical distortion of CO2, which in turn changes the ν3 frequency. The observed structural relaxation timescales vary by up to an order of magnitude between ionic liquids. Shoulders in the 2D-IR spectra arise from anharmonic coupling of the ν2 and ν3 normal modes of CO2. Thermal fluctuations in the ν2 population stochastically modulate the ν3 frequency and generate dynamic cross-peaks. These timescales are attributed to the breakup of ion cages that create a well-defined local environment for CO2. The results suggest that the picosecond dynamics of CO2 are gated by local diffusion of anions and cations.

  6. Ultrafast vibrational spectroscopy (2D-IR) of CO2 in ionic liquids: Carbon capture from carbon dioxide’s point of view

    The CO2ν3 asymmetric stretching mode is established as a vibrational chromophore for ultrafast two-dimensional infrared (2D-IR) spectroscopic studies of local structure and dynamics in ionic liquids, which are of interest for carbon capture applications. CO2 is dissolved in a series of 1-butyl-3-methylimidazolium-based ionic liquids ([C4C1im][X], where [X]− is the anion from the series hexafluorophosphate (PF6−), tetrafluoroborate (BF4−), bis-(trifluoromethyl)sulfonylimide (Tf2N−), triflate (TfO−), trifluoroacetate (TFA−), dicyanamide (DCA−), and thiocyanate (SCN−)). In the ionic liquids studied, the ν3 center frequency is sensitive to the local solvation environment and reports on the timescales for local structural relaxation. Density functional theory calculations predict charge transfer from the anion to the CO2 and from CO2 to the cation. The charge transfer drives geometrical distortion of CO2, which in turn changes the ν3 frequency. The observed structural relaxation timescales vary by up to an order of magnitude between ionic liquids. Shoulders in the 2D-IR spectra arise from anharmonic coupling of the ν2 and ν3 normal modes of CO2. Thermal fluctuations in the ν2 population stochastically modulate the ν3 frequency and generate dynamic cross-peaks. These timescales are attributed to the breakup of ion cages that create a well-defined local environment for CO2. The results suggest that the picosecond dynamics of CO2 are gated by local diffusion of anions and cations

  7. A salt-bridge structure in solution revealed by 2D-IR spectroscopy

    Huerta-Viga, Adriana; Domingos, Sérgio R.; Amirjalayer, Saeed; Woutersen, Sander

    2014-07-01

    Salt bridges are known to be important for the stability of protein conformation, but up to now it has been difficult to study their geometry in solution. Here we characterize the spatial structure of a model salt bridge between guanidinium (Gdm+) and acetate (Ac-) using two-dimensional vibrational (2D-IR) spectroscopy. We find that as a result of salt bridging the infrared response of Gdm+ and Ac- change significantly, and in the 2D-IR spectrum, salt bridging of the molecules appears as cross peaks. From the 2D-IR spectrum we determine the relative orientation of the transition-dipole moments of the vibrational modes involved in the salt bridge, as well as the coupling between them. In this manner we reconstruct the geometry of the solvated salt bridge.

  8. Structure of a model salt bridge in solution investigated with 2D-IR spectroscopy

    Huerta-Viga, Adriana; Amirjalayer, Saeed; Woutersen, Sander

    2013-01-01

    Salt bridges are known to be important for the stability of protein conformation, but up to now it has been difficult to study their geometry in solution. Here we characterize the spatial structure of a model salt bridge between guanidinium (Gdm+) and acetate (Ac-) using two-dimensional vibrational (2D-IR) spectroscopy. We find that as a result of salt bridging the infrared response of Gdm+ and Ac- change significantly, and in the 2D-IR spectrum, salt bridging of the molecules appears as cross peaks. From the 2D-IR spectrum we determine the relative orientation of the transition-dipole moments of the vibrational modes involved in the salt bridge, as well as the coupling between them. In this manner we reconstruct the geometry of the solvated salt bridge.

  9. A salt-bridge structure in solution revealed by 2D-IR spectroscopy.

    Huerta-Viga, Adriana; Domingos, Sérgio R; Amirjalayer, Saeed; Woutersen, Sander

    2014-08-14

    Salt bridges are important interactions for the stability of protein conformations, but up to now it has been difficult to determine salt-bridge geometries in solution. Here we characterize the spatial structure of a salt bridge between guanidinium (Gdm(+)) and acetate (Ac(-)) using two-dimensional vibrational (2D-IR) spectroscopy. We find that as a result of salt bridge formation there is a significant change in the infrared response of Gdm(+) and Ac(-), and cross peaks between them appear in the 2D-IR spectrum. From the 2D-IR spectrum we determine the relative orientation of the transition-dipole moments of the vibrational modes of Gdm(+) and Ac(-), as well as the coupling between them. PMID:24676430

  10. Protein Denaturation with Guanidinium: A 2D-IR Study

    Huerta-Viga, Adriana; Woutersen, Sander

    2013-01-01

    Guanidinium (Gdm+) is a widely used denaturant, but it is still largely unknown how it operates at the molecular level. In particular, the effect of guanidinium on the different types of secondary structure motifs of proteins is at present not clear. Here, we use two-dimensional infrared spectroscopy (2D-IR) to investigate changes in the secondary structure of two proteins with mainly α-helical or β-sheet content upon addition of Gdm-13C15N3·Cl. We find that upon denaturation, the β-sheet pro...

  11. Protein Denaturation with Guanidinium: A 2D-IR Study.

    Huerta-Viga, Adriana; Woutersen, Sander

    2013-10-17

    Guanidinium (Gdm(+)) is a widely used denaturant, but it is still largely unknown how it operates at the molecular level. In particular, the effect of guanidinium on the different types of secondary structure motifs of proteins is at present not clear. Here, we use two-dimensional infrared spectroscopy (2D-IR) to investigate changes in the secondary structure of two proteins with mainly α-helical or β-sheet content upon addition of Gdm-(13)C(15)N3·Cl. We find that upon denaturation, the β-sheet protein shows a complete loss of β-sheet structure, whereas the α-helical protein maintains most of its secondary structure. These results suggest that Gdm(+) disrupts β-sheets much more efficiently than α-helices, possibly because in the former, hydrophobic interactions are more important and the number of dangling hydrogen bonds is larger. PMID:24163724

  12. Determining Transition State Geometries in Liquids Using 2D-IR

    Harris, Charles; Cahoon, James F.; Sawyer, Karma R.; Schlegel, Jacob P.; Harris, Charles B.

    2007-12-11

    Many properties of chemical reactions are determined by the transition state connecting reactant and product, yet it is difficult to directly obtain any information about these short-lived structures in liquids. We show that two-dimensional infrared (2D-IR) spectroscopy can provide direct information about transition states by tracking the transformation of vibrational modes as a molecule crossed a transition state. We successfully monitored a simple chemical reaction, the fluxional rearrangement of Fe(CO)5, in which the exchange of axial and equatorial CO ligands causes an exchange of vibrational energy between the normal modes of the molecule. This energy transfer provides direct evidence regarding the time scale, transition state, and mechanism of the reaction.

  13. Probing Intermolecular Interactions in Polycyclic Aromatic Hydrocarbons with 2D IR Spectroscopy

    Krummel, Amber

    2014-03-01

    Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment and impact geochemical processes that are critical to sustainable energy resources. For example, asphaltenes exist naturally in geologic formations and their aggregates heavily impact the petroleum economy. Unfortunately, the chemical dynamics that drive asphaltene nanoaggregation processes are still poorly understood. Solvent dynamics and intermolecular interactions such as π-stacking interactions play integral roles in asphaltene nanoaggregation. Linear and nonlinear vibrational spectroscopy including two-dimensional infrared spectroscopy (2DIR), are well suited to explore these fundamental interactions. Teasing apart the vibrational characteristics in PAHs that model asphaltenic compounds represents an important step towards utilizing 2D IR spectroscopy to understand the intermolecular interactions that are prevalent in asphaltene nanoaggregation. A solar dye, N,N'-Dioctyl-3,4,9,10-perylenedicarboximide, is used in this work to model aphaltenes. Carbonyl and ring vibrations are used to probe the nanoaggregates of the model compounds. However, the characteristics of these normal modes change as a function of the size of the conjugated ring system. Thus, in order to fully understand the nature of these normal modes, we include a systematic study of a series of quinones. Our investigation employs a combination of 2DIR spectroscopy and electronic structure calculations to explore vibrational coupling in quinones and PAHs. We compare the calculated vibrational characteristics to those extracted from 2DIR spectra. ATK acknowledges the Donors of the American Chemical Society Petroleum Research Fund for support of this research.

  14. Communication: nanosecond folding dynamics of an alpha helix: time-dependent 2D-IR cross peaks observed using polarization-sensitive dispersed pump-probe spectroscopy.

    Panman, Matthijs R; van Dijk, Chris N; Meuzelaar, Heleen; Woutersen, S

    2015-01-28

    We present a simple method to measure the dynamics of cross peaks in time-resolved two-dimensional vibrational spectroscopy. By combining suitably weighted dispersed pump-probe spectra, we eliminate the diagonal contribution to the 2D-IR response, so that the dispersed pump-probe signal contains the projection of only the cross peaks onto one of the axes of the 2D-IR spectrum. We apply the method to investigate the folding dynamics of an alpha-helical peptide in a temperature-jump experiment and find characteristic folding and unfolding time constants of 260 ± 30 and 580 ± 70 ns at 298 K. PMID:25637962

  15. Communication: Nanosecond folding dynamics of an alpha helix: Time-dependent 2D-IR cross peaks observed using polarization-sensitive dispersed pump-probe spectroscopy

    Panman, Matthijs R.; van Dijk, Chris N.; Meuzelaar, Heleen; Woutersen, S.

    2015-01-01

    We present a simple method to measure the dynamics of cross peaks in time-resolved two-dimensional vibrational spectroscopy. By combining suitably weighted dispersed pump-probe spectra, we eliminate the diagonal contribution to the 2D-IR response, so that the dispersed pump-probe signal contains the projection of only the cross peaks onto one of the axes of the 2D-IR spectrum. We apply the method to investigate the folding dynamics of an alpha-helical peptide in a temperature-jump experiment and find characteristic folding and unfolding time constants of 260 ± 30 and 580 ± 70 ns at 298 K.

  16. The structure of salt bridges between Arg(+) and Glu(-) in peptides investigated with 2D-IR spectroscopy: Evidence for two distinct hydrogen-bond geometries.

    Huerta-Viga, Adriana; Amirjalayer, Saeed; Domingos, Sérgio R; Meuzelaar, Heleen; Rupenyan, Alisa; Woutersen, Sander

    2015-06-01

    Salt bridges play an important role in protein folding and in supramolecular chemistry, but they are difficult to detect and characterize in solution. Here, we investigate salt bridges between glutamate (Glu(-)) and arginine (Arg(+)) using two-dimensional infrared (2D-IR) spectroscopy. The 2D-IR spectrum of a salt-bridged dimer shows cross peaks between the vibrational modes of Glu(-) and Arg(+), which provide a sensitive structural probe of Glu(-)⋯Arg(+) salt bridges. We use this probe to investigate a β-turn locked by a salt bridge, an α-helical peptide whose structure is stabilized by salt bridges, and a coiled coil that is stabilized by intra- and intermolecular salt bridges. We detect a bidentate salt bridge in the β-turn, a monodentate one in the α-helical peptide, and both salt-bridge geometries in the coiled coil. To our knowledge, this is the first time 2D-IR has been used to probe tertiary side chain interactions in peptides, and our results show that 2D-IR spectroscopy is a powerful method for investigating salt bridges in solution. PMID:26049464

  17. The structure of salt bridges between Arg+ and Glu- in peptides investigated with 2D-IR spectroscopy: Evidence for two distinct hydrogen-bond geometries

    Huerta-Viga, Adriana; Amirjalayer, Saeed; Domingos, Sérgio R.; Meuzelaar, Heleen; Rupenyan, Alisa; Woutersen, Sander

    2015-06-01

    Salt bridges play an important role in protein folding and in supramolecular chemistry, but they are difficult to detect and characterize in solution. Here, we investigate salt bridges between glutamate (Glu-) and arginine (Arg+) using two-dimensional infrared (2D-IR) spectroscopy. The 2D-IR spectrum of a salt-bridged dimer shows cross peaks between the vibrational modes of Glu- and Arg+, which provide a sensitive structural probe of Glu-⋯Arg+ salt bridges. We use this probe to investigate a β-turn locked by a salt bridge, an α-helical peptide whose structure is stabilized by salt bridges, and a coiled coil that is stabilized by intra- and intermolecular salt bridges. We detect a bidentate salt bridge in the β-turn, a monodentate one in the α-helical peptide, and both salt-bridge geometries in the coiled coil. To our knowledge, this is the first time 2D-IR has been used to probe tertiary side chain interactions in peptides, and our results show that 2D-IR spectroscopy is a powerful method for investigating salt bridges in solution.

  18. Earle K. Plyler Prize for Molecular Spectroscopy and Dynamics Lecture: 2D IR Spectroscopy of Peptide Conformation

    Tokmakoff, Andrei

    2012-02-01

    Descriptions of protein and peptide conformation are colored by the methods we use to study them. Protein x-ray and NMR structures often lead to impressions of rigid or well-defined conformations, even though these are dynamic molecules. The conformational fluctuations and disorder of proteins and peptides is more difficult to quantify. This presentation will describe an approach toward characterizing and quantifying structural heterogeneity and disorder in peptides using 2D IR spectroscopy. Using amide I vibrational spectroscopy, isotope labeling strategies, and computational modeling based on molecular dynamics simulations and Markov state models allows us to characterize distinct peptide conformers and conformational variation. The examples illustrated include the beta-hairpin tripzip2 and elastin-like peptides.

  19. Hydrogen-bond lifetime measured by time-resolved 2D-IR spectroscopy: N-methylacetamide in methanol

    Woutersen, S.; Mu, Y.; Stock, G.; Hamm, P.

    2001-05-01

    2D vibrational spectroscopy is applied to investigate the equilibrium dynamics of hydrogen bonding of N-methylacetamide (NMA) dissolved in methanol- d4. For this particular solute-solvent system, roughly equal populations are found for two conformers of the solute-solvent complex, one of which forms a hydrogen bond from the CO group of NMA to the surrounding solvent, and one of which does not. Using time-resolved 2D-IR spectroscopy on the amide I band of NMA, the exchange between both conformers is resolved. Equilibration of each conformer is completed after 4.5 ps, while the formation and breaking of the hydrogen bond occurs on a slower, 10-15 ps time scale. This interpretation is supported by classical molecular-dynamics simulations of NMA in methanol. The calculations predict a 64% population of the hydrogen-bonded conformer and an average hydrogen-bond lifetime of ≈12 ps.

  20. Temperature-dependent vibrational dephasing: Comparison of liquid and glassy solvents using frequency-selected vibrational echoes

    Xu, Qing-Hua; Fayer, M. D.

    2002-08-01

    Frequency-selected vibrational echo experiments were used to investigate the temperature dependences of vibrational dephasing associated with the 0-1 transition of the CO stretching mode of RuTPPCOPy (TPP=5,10,15,20-tetraphenylporphyrin, Py=pyridine) in two solvents: polymethylmethacrylate (PMMA) and 2-methyltetrahydrofuran (2-MTHF). In PMMA, a glass, the echo decay is exponential at all the temperatures studied, and the dephasing rate increases linearly with increasing temperature. In 2-MTHF, there is a change in the functional form of the temperature dependence when the solvent goes through the glass transition temperature (Tg). Below Tg, the dephasing rate increases linearly with temperature, while above Tg, it rises very steeply in a nonlinear manner. In the liquid at higher temperatures, the vibrational echo decays are nonexponential. A model frequency-frequency correlation function (FFCF) is proposed in which the FFCF differs for a glass and a liquid because of the intrinsic differences in the nature of the dynamics. At least two motions, inertial and diffusive, contribute to the vibrational dephasing in the liquids. The different temperature dependences of inertial and diffusive motions are discussed. Comparison of the model calculations of the vibrational echo temperature dependence and the data show reasonable, but not quantitative agreement.

  1. Interrogating Fiber Formation Kinetics with Automated 2D-IR Spectroscopy

    Strasfeld, David B.; Ling, Yun L.; Shim, Sang-Hee; Zanni, Martin T.

    A new method for collecting 2D-IR spectra that utilizes both a pump-probe beam geometry and a mid-IR pulse shaper is used to gain a fuller understanding of fiber formation in the human islet amyloid polypeptide (hIAPP). We extract structural kinetics in order to better understand aggregation in hIAPP, the protein component of the amyloid fibers found to inhibit insulin production in type II diabetes patients.

  2. Water of Hydration Dynamics in Minerals Gypsum and Bassanite: Ultrafast 2D IR Spectroscopy of Rocks.

    Yan, Chang; Nishida, Jun; Yuan, Rongfeng; Fayer, Michael D

    2016-08-01

    Water of hydration plays an important role in minerals, determining their crystal structures and physical properties. Here ultrafast nonlinear infrared (IR) techniques, two-dimensional infrared (2D IR) and polarization selective pump-probe (PSPP) spectroscopies, were used to measure the dynamics and disorder of water of hydration in two minerals, gypsum (CaSO4·2H2O) and bassanite (CaSO4·0.5H2O). 2D IR spectra revealed that water arrangement in freshly precipitated gypsum contained a small amount of inhomogeneity. Following annealing at 348 K, water molecules became highly ordered; the 2D IR spectrum became homogeneously broadened (motional narrowed). PSPP measurements observed only inertial orientational relaxation. In contrast, water in bassanite's tubular channels is dynamically disordered. 2D IR spectra showed a significant amount of inhomogeneous broadening caused by a range of water configurations. At 298 K, water dynamics cause spectral diffusion that sampled a portion of the inhomogeneous line width on the time scale of ∼30 ps, while the rest of inhomogeneity is static on the time scale of the measurements. At higher temperature, the dynamics become faster. Spectral diffusion accelerates, and a portion of the lower temperature spectral diffusion became motionally narrowed. At sufficiently high temperature, all of the dynamics that produced spectral diffusion at lower temperatures became motionally narrowed, and only homogeneous broadening and static inhomogeneity were observed. Water angular motions in bassanite exhibit temperature-dependent diffusive orientational relaxation in a restricted cone of angles. The experiments were made possible by eliminating the vast amount of scattered light produced by the granulated powder samples using phase cycling methods. PMID:27385320

  3. 2D IR spectra of cyanide in water investigated by molecular dynamics simulations

    Lee, Myung Won; Carr, Joshua K.; Göllner, Michael; Hamm, Peter; Meuwly, Markus

    2013-01-01

    Using classical molecular dynamics simulations, the 2D infrared (IR) spectroscopy of CN− solvated in D2O is investigated. Depending on the force field parametrizations, most of which are based on multipolar interactions for the CN− molecule, the frequency-frequency correlation function and observables computed from it differ. Most notably, models based on multipoles for CN− and TIP3P for water yield quantitatively correct results when compared with experiments. Furthermore, the recent finding that T 1 times are sensitive to the van der Waals ranges on the CN− is confirmed in the present study. For the linear IR spectrum, the best model reproduces the full widths at half maximum almost quantitatively (13.0 cm−1 vs. 14.9 cm−1) if the rotational contribution to the linewidth is included. Without the rotational contribution, the lines are too narrow by about a factor of two, which agrees with Raman and IR experiments. The computed and experimental tilt angles (or nodal slopes) α as a function of the 2D IR waiting time compare favorably with the measured ones and the frequency fluctuation correlation function is invariably found to contain three time scales: a sub-ps, 1 ps, and one on the 10-ps time scale. These time scales are discussed in terms of the structural dynamics of the surrounding solvent and it is found that the longest time scale (≈10 ps) most likely corresponds to solvent exchange between the first and second solvation shell, in agreement with interpretations from nuclear magnetic resonance measurements.

  4. Critical Slowing of Density Fluctuations Approaching the Isotropic-Nematic Transition in Liquid Crystals: 2D IR Measurements and Mode Coupling Theory.

    Sokolowsky, Kathleen P; Bailey, Heather E; Hoffman, David J; Andersen, Hans C; Fayer, Michael D

    2016-07-21

    Two-dimensional infrared (2D IR) data are presented for a vibrational probe in three nematogens: 4-cyano-4'-pentylbiphenyl, 4-cyano-4'-octylbiphenyl, and 4-(trans-4-amylcyclohexyl)-benzonitrile. The spectral diffusion time constants in all three liquids in the isotropic phase are proportional to [T*/(T - T*)](1/2), where T* is 0.5-1 K below the isotropic-nematic phase transition temperature (TNI). Rescaling to a reduced temperature shows that the decays of the frequency-frequency correlation function (FFCF) for all three nematogens fall on the same curve, suggesting a universal dynamic behavior of nematogens above TNI. Spectral diffusion is complete before significant orientational relaxation in the liquid, as measured by optically heterodyne detected-optical Kerr effect (OHD-OKE) spectroscopy, and before any significant orientational randomization of the probe measured by polarization selective IR pump-probe experiments. To interpret the OHD-OKE and FFCF data, we constructed a mode coupling theory (MCT) schematic model for the relationships among three correlation functions: ϕ1, a correlator for large wave vector density fluctuations; ϕ2, the orientational correlation function whose time derivative is the observable in the OHD-OKE experiment; and ϕ3, the FFCF for the 2D IR experiment. The equations for ϕ1 and ϕ2 match those in the previous MCT schematic model for nematogens, and ϕ3 is coupled to the first two correlators in a straightforward manner. Resulting models fit the data very well. Across liquid crystals, the temperature dependences of the coupling constants show consistent, nonmonotonic behavior. A remarkable change in coupling occurs at ∼5 K above TNI, precisely where the rate of spectral diffusion in 5CB was observed to deviate from that of a similar nonmesogenic liquid. PMID:27363680

  5. 2D IR spectroscopy at 100 kHz utilizing a Mid-IR OPCPA laser source.

    Luther, Bradley M; Tracy, Kathryn M; Gerrity, Michael; Brown, Susannah; Krummel, Amber T

    2016-02-22

    We present a 100 kHz 2D IR spectrometer. The system utilizes a ytterbium all normal dispersion fiber oscillator as a common source for the pump and seed beams of a MgO:PPLN OPCPA. The 1030 nm OPCPA pump is generated by amplification of the oscillator in cryocooled Yb:YAG amplifiers, while the 1.68 μm seed is generated in a OPO pumped by the oscillator. The OPCPA outputs are used in a ZGP DFG stage to generate 4.65 μm pulses. A mid-IR pulse shaper delivers pulse pairs to a 2D IR spectrometer allowing for data collection at 100 kHz. PMID:26907062

  6. Monitoring equilibrium reaction dynamics of a nearly barrierless molecular rotor using ultrafast vibrational echoes.

    Nilsen, Ian A; Osborne, Derek G; White, Aaron M; Anna, Jessica M; Kubarych, Kevin J

    2014-10-01

    Using rapidly acquired spectral diffusion, a recently developed variation of heterodyne detected infrared photon echo spectroscopy, we observe ∼3 ps solvent independent spectral diffusion of benzene chromium tricarbonyl (C6H6Cr(CO)3, BCT) in a series of nonpolar linear alkane solvents. The spectral dynamics is attributed to low-barrier internal torsional motion. This tripod complex has two stable minima corresponding to staggered and eclipsed conformations, which differ in energy by roughly half of kBT. The solvent independence is due to the relative size of the rotor compared with the solvent molecules, which create a solvent cage in which torsional motion occurs largely free from solvent damping. Since the one-dimensional transition state is computed to be only 0.03 kBT above the higher energy eclipsed conformation, this model system offers an unusual, nearly barrierless reaction, which nevertheless is characterized by torsional coordinate dependent vibrational frequencies. Hence, by studying the spectral diffusion of the tripod carbonyls, it is possible to gain insight into the fundamental dynamics of internal rotational motion, and we find some evidence for the importance of non-diffusive ballistic motion even in the room-temperature liquid environment. Using several different approaches to describe equilibrium kinetics, as well as the influence of reactive dynamics on spectroscopic observables, we provide evidence that the low-barrier torsional motion of BCT provides an excellent test case for detailed studies of the links between chemical exchange and linear and nonlinear vibrational spectroscopy. PMID:25296812

  7. Monitoring equilibrium reaction dynamics of a nearly barrierless molecular rotor using ultrafast vibrational echoes

    Using rapidly acquired spectral diffusion, a recently developed variation of heterodyne detected infrared photon echo spectroscopy, we observe ∼3 ps solvent independent spectral diffusion of benzene chromium tricarbonyl (C6H6Cr(CO)3, BCT) in a series of nonpolar linear alkane solvents. The spectral dynamics is attributed to low-barrier internal torsional motion. This tripod complex has two stable minima corresponding to staggered and eclipsed conformations, which differ in energy by roughly half of kBT. The solvent independence is due to the relative size of the rotor compared with the solvent molecules, which create a solvent cage in which torsional motion occurs largely free from solvent damping. Since the one-dimensional transition state is computed to be only 0.03 kBT above the higher energy eclipsed conformation, this model system offers an unusual, nearly barrierless reaction, which nevertheless is characterized by torsional coordinate dependent vibrational frequencies. Hence, by studying the spectral diffusion of the tripod carbonyls, it is possible to gain insight into the fundamental dynamics of internal rotational motion, and we find some evidence for the importance of non-diffusive ballistic motion even in the room-temperature liquid environment. Using several different approaches to describe equilibrium kinetics, as well as the influence of reactive dynamics on spectroscopic observables, we provide evidence that the low-barrier torsional motion of BCT provides an excellent test case for detailed studies of the links between chemical exchange and linear and nonlinear vibrational spectroscopy

  8. Azide-water intermolecular coupling measured by 2-color 2D IR spectroscopy

    Perakis F.

    2013-03-01

    Full Text Available We present 2-color two-dimensional infrared spectroscopy of intermolecular coupling between azide ions and their solvation shell water molecules. The cross-peak between azide asymmetric stretch vibration and the OD-stretch vibration is a result of low- probability uphill population transfer. Narrow bleach/excited state absorption peak shows selectivity to solvation shell water molecules only and the characteristics of the cross-peak suggest that the solvation shell hydrogen bond potential has similar anharmonic properties as the hydrogen bond in ice Ih. Population and depopulation of the excited state of the OD-stretch vibration happen on 150 fs and 1.7 ps timescales, respectively, with early manifesting heating effects that limit the selectivity to population times up to 1 ps.

  9. Computational Amide I 2D IR Spectroscopy as a Probe of Protein Structure and Dynamics

    Reppert, Mike; Tokmakoff, Andrei

    2016-05-01

    Two-dimensional infrared spectroscopy of amide I vibrations is increasingly being used to study the structure and dynamics of proteins and peptides. Amide I, a primarily carbonyl stretching vibration of the protein backbone, provides information on secondary structures as a result of vibrational couplings and on hydrogen-bonding contacts when isotope labeling is used to isolate specific sites. In parallel with experiments, computational models of amide I spectra that use atomistic structures from molecular dynamics simulations have evolved to calculate experimental spectra. Mixed quantum-classical models use spectroscopic maps to translate the structural information into a quantum-mechanical Hamiltonian for the spectroscopically observed vibrations. This allows one to model the spectroscopy of large proteins, disordered states, and protein conformational dynamics. With improvements in amide I models, quantitative modeling of time-dependent structural ensembles and of direct feedback between experiments and simulations is possible. We review the advances in developing these models, their theoretical basis, and current and future applications.

  10. Ultrafast slaving dynamics at the protein-water interface studied with 2D-IR spectroscopy

    Kubarych K. J.

    2013-03-01

    Full Text Available The dynamics of hen egg white lysozyme in D2O/glycerol mixtures is studied using two-dimensional infrared spectroscopy. The hydration dynamics and the protein dynamics are studied simultaneously through vibrational probes attached to the protein surface.

  11. Monitoring equilibrium reaction dynamics of a nearly barrierless molecular rotor using ultrafast vibrational echoes

    Nilsen, Ian A.; Osborne, Derek G.; White, Aaron M.; Anna, Jessica M.; Kubarych, Kevin J., E-mail: kubarych@umich.edu [Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, Michigan 48109 (United States)

    2014-10-07

    Using rapidly acquired spectral diffusion, a recently developed variation of heterodyne detected infrared photon echo spectroscopy, we observe ∼3 ps solvent independent spectral diffusion of benzene chromium tricarbonyl (C{sub 6}H{sub 6}Cr(CO){sub 3}, BCT) in a series of nonpolar linear alkane solvents. The spectral dynamics is attributed to low-barrier internal torsional motion. This tripod complex has two stable minima corresponding to staggered and eclipsed conformations, which differ in energy by roughly half of k{sub B}T. The solvent independence is due to the relative size of the rotor compared with the solvent molecules, which create a solvent cage in which torsional motion occurs largely free from solvent damping. Since the one-dimensional transition state is computed to be only 0.03 k{sub B}T above the higher energy eclipsed conformation, this model system offers an unusual, nearly barrierless reaction, which nevertheless is characterized by torsional coordinate dependent vibrational frequencies. Hence, by studying the spectral diffusion of the tripod carbonyls, it is possible to gain insight into the fundamental dynamics of internal rotational motion, and we find some evidence for the importance of non-diffusive ballistic motion even in the room-temperature liquid environment. Using several different approaches to describe equilibrium kinetics, as well as the influence of reactive dynamics on spectroscopic observables, we provide evidence that the low-barrier torsional motion of BCT provides an excellent test case for detailed studies of the links between chemical exchange and linear and nonlinear vibrational spectroscopy.

  12. Interplay of Ion-Water and Water-Water Interactions within the Hydration Shells of Nitrate and Carbonate Directly Probed with 2D IR Spectroscopy.

    Fournier, Joseph A; Carpenter, William; De Marco, Luigi; Tokmakoff, Andrei

    2016-08-01

    The long-range influence of ions in solution on the water hydrogen-bond (H-bond) network remains a topic of vigorous debate. Recent spectroscopic and theoretical studies have, for the most part, reached the consensus that weakly coordinating ions only affect water molecules in the first hydration shell. Here, we apply ultrafast broadband two-dimensional infrared (2D IR) spectroscopy to aqueous nitrate and carbonate in neat H2O to study the solvation structure and dynamics of ions on opposite ends of the Hofmeister series. By exciting both the water OH stretches and ion stretches and probing the associated cross-peaks between them, we are afforded a comprehensive view into the complex nature of ion hydration. We show in aqueous nitrate that weak ion-water H-bonding leads to water-water interactions in the ion solvation shells dominating the dynamics. In contrast, the carbonate CO stretches show significant mixing with the water OH stretches due to strong ion-water H-bonding such that the water and ion modes are intimately correlated. Further, the excitonic nature of vibrations in neat H2O, which spans multiple water molecules, is an important factor in describing ion hydration. We attribute these complex dynamics to the likely presence of intermediate-range effects influenced by waters beyond the first solvation shell. PMID:27404015

  13. Rapid discrimination of extracts of Chinese propolis and poplar buds by FT-IR and 2D IR correlation spectroscopy

    Wu, Yan-Wen; Sun, Su-Qin; Zhao, Jing; Li, Yi; Zhou, Qun

    2008-07-01

    The extract of Chinese propolis (ECP) has recently been adulterated with that of poplar buds (EPB), because most of ECP is derived from the poplar plant, and ECP and EPB have almost identical chemical compositions. It is very difficult to differentiate them by using the chromatographic methods such as high performance liquid chromatography (HPLC) and gas chromatography (GC). Therefore, how to effectively discriminate these two mixtures is a problem to be solved urgently. In this paper, a rapid method for discriminating ECP and EPB was established by the Fourier transform infrared (FT-IR) spectra combined with the two-dimensional infrared correlation (2D IR) analysis. Forty-three ECP and five EPB samples collected from different areas of China were analyzed by the FT-IR spectroscopy. All the ECP and EPB samples tested show similar IR spectral profiles. The significant differences between ECP and EPB appear in the region of 3000-2800 cm -1 of the spectra. Based on such differences, the two species were successfully classified with the soft independent modeling of class analogy (SIMCA) pattern recognition technique. Furthermore, these differences were well validated by a series of temperature-dependent dynamic FT-IR spectra and the corresponding 2D IR plots. The results indicate that the differences in these two natural products are caused by the amounts of long-chain alkyl compounds (including long-chain alkanes, long-chain alkyl esters and long chain alkyl alcohols) in them, rather than the flavonoid compounds, generally recognized as the bioactive substances of propolis. There are much more long-chain alkyl compounds in ECP than those in EPB, and the carbon atoms of the compounds in ECP remain in an order Z-shaped array, but those in EPB are disorder. It suggests that FT-IR and 2D IR spectroscopy can provide a valuable method for the rapid differentiation of similar natural products, ECP and EPB. The IR spectra could directly reflect the integrated chemical

  14. Physical understanding of an echo-Doppler test with voice-induced vibration

    Alessio D'AlessandroDipartimento di fisica & INFN Genova; Massimo Calabrese(Policlinico Pammatone - Genova); Giuseppe Minetti(Policlinico Pammatone - Genova); Franco Rosso; Alessandro Villa

    2015-01-01

    The physical understanding of a method of detecting mammalian cancer via vocalization during a normal echo-Doppler test is provided. The backscattered ultrasound frequency in the case of a vocal humming resonating in the chest wall is computed: the overall effect is that the signal/noise ratio could be easily improved at no cost. Clinical results are to appear separately elsewhere.

  15. Use Impact-Echo Method to Evaluate Bond of Reinforced Concrete Subjected to Early-Age Vibration

    Hsu, Keng-Tsang; Cheng, Chia-Chi; Lin, Yiching

    The purpose of this paper is to develop a non-destructive test method for evaluating the bond of reinforcing bars in concrete structure which was damaged by earthquake while still cast in the form. In the experimental design, the specimens containing a steel reinforcing bar with one end extruded outside were constructed. Different degrees of damage on the rebar-concrete interfaces were successfully created by the resonant vibration of exposed steel bar induced by the cyclic motion of the specimen. The local bond-loss of the steel bars was evaluated by both non-destructive impact-echo tests and the destructive pullout tests. To create different kinds of failure mode in the pullout test, some of the specimens contain stirrups surrounding reinforcing bar. Poor-bond was quantitatively evaluated before the pullout test by the amplitude of the peak corresponding to the multiple reflections from the steel bar in the normalized spectra derived from the impact-echo tests. As a result, two empirical formulas displaying the proportional relations between the percentage of loss of local bond-stress and loss of steel-amplitude for specimens failed by split failure and pull-out failure modes were established.

  16. Vibrational frequency fluctuation of ions in aqueous solutions studied by three-pulse infrared photon echo method.

    Ohta, Kaoru; Tayama, Jumpei; Saito, Shinji; Tominaga, Keisuke

    2012-11-20

    In liquid water, hydrogen bonds form three-dimensional network structures, which have been modeled in various molecular dynamics simulations. Locally, the hydrogen bonds continuously form and break, and the network structure continuously fluctuates. In aqueous solutions, the water molecules perturb the solute molecules, resulting in fluctuations of the electronic and vibrational states. These thermal fluctuations are fundamental to understanding the activation processes in chemical reactions and the function of biopolymers. In this Account, we review studies of the vibrational frequency fluctuations of solute molecules in aqueous solutions using three-pulse infrared photon echo experiments. For comparison, we also briefly describe dynamic fluorescence Stokes shift experiments for investigating solvation dynamics in water. The Stokes shift technique gives a response function, which describes the energy relaxation in the nonequilibrium state and corresponds to the transition energy fluctuation of the electronic state at thermal equilibrium in linear response theorem. The dielectric response of water in the megahertz to terahertz frequency region is a key physical quantity for understanding both of these frequency fluctuations because of the influence of electrostatic interactions between the solute and solvent. We focus on the temperature dependence of the three experiments to discuss the molecular mechanisms of both the frequency fluctuations in aqueous solutions. We used a biexponential function with sub-picosecond and picosecond time constants to characterize the time-correlation functions of both the vibrational and electronic frequency fluctuations. We focus on the slower component, with time constants of 1-2 ps for both the frequency fluctuations at room temperature. However, the temperature dependence and isotope effect for the time constants differ for these two types of fluctuations. The dielectric interactions generally describe the solvation dynamics of

  17. Volatility-dependent 2D IR correlation analysis of traditional Chinese medicine ‘Red Flower Oil’ preparation from different manufacturers

    Wu, Yan-Wen; Sun, Su-Qin; Zhou, Qun; Tao, Jia-Xun; Noda, Isao

    2008-06-01

    As a traditional Chinese medicine (TCM), 'Red Flower Oil' preparation is widely used as a household remedy in China and Southeast Asia. Usually, the preparation is a mixture of several plant essential oils with different volatile features, such as wintergreen oil, turpentine oil and clove oil. The proportions of these plant essential oils in 'Red Flower Oil' vary from different manufacturers. Thus, it is important to develop a simple and rapid evaluation method for quality assurance of the preparations. Fourier transform infrared (FT-IR) was applied and two-dimensional correlation infrared spectroscopy (2D IR) based on the volatile characteristic of samples was used to enhance the resolution of FT-IR spectra. 2D IR technique could, not only easily provide the composition and their volatile sequences in 'Red flower Oil' preparations, but also rapidly discriminate the subtle differences in products from different manufacturers. Therefore, FT-IR combined with volatility-dependent 2D IR correlation analysis provides a very fast and effective method for the quality control of essential oil mixtures in TCM.

  18. Bimodal dynamics of mechanically constrained hydrogen bonds revealed by vibrational photon echoes.

    Bodis, Pavol; Yeremenko, Sergiy; Berná, José; Buma, Wybren J; Leigh, David A; Woutersen, Sander

    2011-04-01

    We have investigated the dynamics of the hydrogen bonds that connect the components of a [2]rotaxane in solution. In this rotaxane, the amide groups in the benzylic-amide macrocycle and the succinamide thread are connected by four equivalent N-H⋅⋅⋅O=C hydrogen bonds. The fluctuations of these hydrogen bonds are mirrored by the frequency fluctuations of the NH-stretch modes, which are probed by means of three-pulse photon-echo peak shift spectroscopy. The hydrogen-bond fluctuations occur on three different time scales, with time constants of 0.1, 0.6, and ≥200 ps. Comparing these three time scales to the ones found in liquid formamide, which contains the same hydrogen-bonded amide motif but without mechanical constraints, we find that the faster two components, which are associated with small-amplitude fluctuations in the strength of the N-H⋅⋅⋅O=C hydrogen bonds, are very similar in the liquid and the rotaxane. However, the third component, which is associated with the breaking and subsequent reformation of hydrogen bonds, is found to be much slower in the rotaxane than in the liquid. It can be concluded that the mechanical bonding in a rotaxane does not influence the amplitude and time scale of the small-amplitude fluctuations of the hydrogen bonds, but strongly slows down the complete dissociation of these hydrogen bonds. This is probably because in a rotaxane breaking of the macrocycle-axle contacts is severely hindered by the mechanical constraints. The hydrogen-bond dynamics in rotaxane-based molecular machines can therefore be regarded as liquidlike on a time scale 1 ps and less, but structurally frozen on longer (up to at least 200 ps) time scales. PMID:21476761

  19. Bimodal dynamics of mechanically constrained hydrogen bonds revealed by vibrational photon echoes

    Bodis, Pavol; Yeremenko, Sergiy; Berná, José; Buma, Wybren J.; Leigh, David A.; Woutersen, Sander

    2011-04-01

    We have investigated the dynamics of the hydrogen bonds that connect the components of a [2]rotaxane in solution. In this rotaxane, the amide groups in the benzylic-amide macrocycle and the succinamide thread are connected by four equivalent N-HṡṡṡO=C hydrogen bonds. The fluctuations of these hydrogen bonds are mirrored by the frequency fluctuations of the NH-stretch modes, which are probed by means of three-pulse photon-echo peak shift spectroscopy. The hydrogen-bond fluctuations occur on three different time scales, with time constants of 0.1, 0.6, and ⩾200 ps. Comparing these three time scales to the ones found in liquid formamide, which contains the same hydrogen-bonded amide motif but without mechanical constraints, we find that the faster two components, which are associated with small-amplitude fluctuations in the strength of the N-HṡṡṡO=C hydrogen bonds, are very similar in the liquid and the rotaxane. However, the third component, which is associated with the breaking and subsequent reformation of hydrogen bonds, is found to be much slower in the rotaxane than in the liquid. It can be concluded that the mechanical bonding in a rotaxane does not influence the amplitude and time scale of the small-amplitude fluctuations of the hydrogen bonds, but strongly slows down the complete dissociation of these hydrogen bonds. This is probably because in a rotaxane breaking of the macrocycle-axle contacts is severely hindered by the mechanical constraints. The hydrogen-bond dynamics in rotaxane-based molecular machines can therefore be regarded as liquidlike on a time scale 1 ps and less, but structurally frozen on longer (up to at least 200 ps) time scales.

  20. 2D IR spectroscopy reveals the role of water in the binding of channel-blocking drugs to the influenza M2 channel

    Ghosh, Ayanjeet, E-mail: ayanjeet@sas.upenn.edu, E-mail: gai@sas.upenn.edu; Gai, Feng, E-mail: ayanjeet@sas.upenn.edu, E-mail: gai@sas.upenn.edu; Hochstrasser, Robin M. [Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Wang, Jun; DeGrado, William F. [Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94143 (United States); Moroz, Yurii S.; Korendovych, Ivan V. [Department of Chemistry, Syracuse University, Syracuse, New York 13244 (United States); Zanni, Martin [Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706 (United States)

    2014-06-21

    Water is an integral part of the homotetrameric M2 proton channel of the influenza A virus, which not only assists proton conduction but could also play an important role in stabilizing channel-blocking drugs. Herein, we employ two dimensional infrared (2D IR) spectroscopy and site-specific IR probes, i.e., the amide I bands arising from isotopically labeled Ala30 and Gly34 residues, to probe how binding of either rimantadine or 7,7-spiran amine affects the water dynamics inside the M2 channel. Our results show, at neutral pH where the channel is non-conducting, that drug binding leads to a significant increase in the mobility of the channel water. A similar trend is also observed at pH 5.0 although the difference becomes smaller. Taken together, these results indicate that the channel water facilitates drug binding by increasing its entropy. Furthermore, the 2D IR spectral signatures obtained for both probes under different conditions collectively support a binding mechanism whereby amantadine-like drugs dock in the channel with their ammonium moiety pointing toward the histidine residues and interacting with a nearby water cluster, as predicted by molecular dynamics simulations. We believe these findings have important implications for designing new anti-influenza drugs.

  1. Characterization by Fourier transform infrared spectroscopy (FT-IR) and 2D IR correlation spectroscopy of a carbosilane dendrimer with peripheral ammonium groups

    Popescu, Maria-Cristina, E-mail: cpopescu@icmpp.ro [' Petru Poni' Institute of Macromolecular Chemistry (Romania); Gomez, Rafael; Mata, Fco Javier de la; Rasines, Beatriz [Universidad de Alcala, Departamento de Quimica Inorganica (Spain); Simionescu, Bogdan C. [' Petru Poni' Institute of Macromolecular Chemistry (Romania)

    2013-06-15

    Fourier transform infrared spectroscopy and 2D correlation spectroscopy were used to study the microstructural changes occurring on heating of a new carbosilane dendrimer with peripheral ammonium groups. Temperature-dependent spectral variations in the 3,010-2,710, 1,530-1,170, and 1,170-625 cm{sup -1} regions were monitored during the heating process. The dependence, on temperature, of integral absorptions and position of spectral bands was established and the spectral modifications associated with molecular conformation rearrangements, allowing molecular shape changes, were found. Before 180 Degree-Sign C, the studied carbosilane dendrimer proved to be stable, while at higher temperatures it oxidizes and Si-O groups appear. 2D IR correlation spectroscopy gives new information about the effect of temperature on the structure and dynamics of the system. Synchronous and asynchronous spectra indicate that, at low temperature, conformational changes of CH{sub 3} and CH{sub 3}-N{sup +} groups take place first. With increasing temperature, the intensity variation of the CH{sub 2}, C-N, Si-C and C-C groups from the dendritic core is faster than that of the terminal units. This indicates that, with increasing temperature, the segments of the dendritic core obtain enough energy to change their conformation more easily as compared to the terminal units, due to their internal flexibility.

  2. Two Keggin-type heteropolytungstates with transition metal as a central atom: Crystal structure and magnetic study with 2D-IR correlation spectroscopy

    Two Keggin-type heteropolytungstates, [Co(phen)3]3[CoW12O40]·9H2O 1 (phen=1,10-phenanthroline) and [Fe(phen)3]2[FeW12O40]·H3O·H2O 2, have been synthesized via the hydrothermal technique and characterized by single crystal X-ray diffraction analyses, IR, XPS, TG analysis, UV–DRS, XRD, thermal-dependent and magnetic-dependent 2D-COS IR (two-dimensional infrared correlation spectroscopy). Crystal structure analysis reveals that the polyanions in compound 1 are linked into 3D supramolecule through hydrogen bonding interactions between lattice water molecules and terminal oxygen atoms of polyanion units, and [Co(phen)3]2+ cations distributed in the polyanion framework with many hydrogen bonding interactions. The XPS spectra indicate that all the Co atoms in 1 are +2 oxidation state, the Fe atoms in 2 existing with +2 and +3 mixed oxidation states. - Graphical abstract: The magnetic-dependent synchronous 2D correlation IR spectra of 1 (a), 2 (b) over 0–50 mT in the range of 600–1000 cm−1, the obvious response indicate two Keggin polyanions skeleton susceptible to applied magnetic field. - Highlights: • Two Keggin-type heteropolytungstates with transition metal as a central atom has been obtained. • Compound 1 forms into 3D supramolecular architecture through hydrogen bonding between water molecules and polyanions. • Magnetic-dependent 2D-IR correlation spectroscopy was introduced to discuss the magnetism of polyoxometalate

  3. ECHO virus

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

  4. Fractional Echoes

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

    2016-01-01

    We report the observation of fractional echoes in a double-pulse excited nonlinear system. Unlike standard echoes which appear periodically at delays which are integer multiple of the delay between the two exciting pulses, the fractional echoes appear at rational fractions of this delay. We discuss the mechanism leading to this phenomenon, and provide the first experimental demonstration of fractional echoes by measuring third harmonic generation in a thermal gas of CO2 molecules excited by a pair of femtosecond laser pulses.

  5. Study on the Processing of Leech by FTIR and 2D-IR Correlation Spectroscopy%应用红外光谱技术研究中药水蛭的炮制过程

    李冰宁; 武彦文; 欧阳杰; 孙素琴; 陈舜琮

    2011-01-01

    考察水蚝炮制前后化学成分产生的变化,文章采用红外光谱(FTlR)二维相关红外谱图(2D-IR)对中药水蛭鲜品和制品进行了研究.结果表明:水蛭具有明显的酰胺Ⅰ和Ⅱ带蛋白质特征峰,其中鲜品的酰胺Ⅱ带吸收峰在1543 cm-1,而生品和炮制品的向低频位移至1 535cm-1;采用热微扰模拟水蛭炮制过程并分析水蛭的2D-IR,结果显示水蛭鲜品中的酰胺Ⅰ带与酰胺Ⅱ带的自动峰的强度比炮制品的更为显著.说明水蛭在炮制过程中蛋白质的空间构象破损、氢键断裂,导致变性失活,部分脂肪酸和甾醇类组分在炮制中发生氧化分解.%The chemical differences of traditional Chinese medicine leech before and after processing were analyzed by FTIR and two-dimensional correlation infrared (2D-IR) spectroscopy. The result showed that the leech was high in protein, with characteristic peaks of amide Ⅰ, Ⅱ bands. Comparing the IR spectra of samples, the primary difference was that the characteristic peak of fresh leech was at 1 543 cm-1, while that of crude and processed leech was at 1 535 cm-1. A 2D-IR spectrum with heating perturbation was used to track the processing dynamics of leech. In the 2D-IR correlation spectra, fresh leech exhibited stronger automatic peaks of the amide Ⅰ and Ⅱ hands than that of processed leech, which indicates that the protein components of the fresh leech were more sensitive to heat perturhation than the processed one. Moreover, the result of FTIR and 2D-IR correlation spectra validated that the 3-dimensional structure of protein was damaged and hydrogen bonds were broken after processing, which resulted in the inactivation of protein. The fatty acids and cholesterol components of leech were also oxidized in this process.

  6. ECHO virus

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

  7. Echoes of the supernova

    Malin, D.; Allen, D. (Anglo-Australian Observatory, Epping (Australia))

    1990-01-01

    The light echoes of SN 1987A are studied using photographs of the Tarantula nebula, including Sanduleak -69 deg 202, taken from 1984 to 1988. The formation of light echoes, and the process of extracting echo images for photographs are examined. The technique of photographic subtraction is described. Consideration is given to the formation of well-defined rings by light echoes. The possibility of using the photographs of SN 1987A light echoes in the construction of a three-dimensional model of the dust sheet in the LMC is noted.

  8. Structural Dynamics of Rotaxanes Studied by Infrared Photon Echo Spectroscopy

    Yeremenko, Sergey; Larsen, Olaf F. A.; Bodis, Pavol; Buma, Wybren Jan; Hannam, Jeffrey S.; Leigh, David A.; Woutersen, Sander

    The structural dynamics of a rotaxane is investigated using infrared photon echo peak shift spectroscopy on the N-H stretch vibrational mode. The results demonstrate non-Markovian character of the dynamics of this vibrational mode and an oscillatory component related to the presence of low-frequency modes that are anharmonically coupled to the N-H stretch mode.

  9. Moessbauer gamma echo

    By applying stepwise phase modulation of recoilless gamma radiation in a coincidence experiment, constructive interference is produced in transmission geometry between the source and the absorber fields. The resulting regenerated decay signal is called a gamma echo. Here it is demonstrated that during the decay of the 14.4 keV state of 57Fe multiple echo signals can be generated. (orig.)

  10. Photon Echoes Made Simple

    BEACH, R; Brody, B.; Hartmann, S. R.

    1983-01-01

    Photon Echoes in gases are analyzed via the Billiard Ball Echo Model both in the short and long pulse limit where the “atoms” are represented as spherical and elliptical billiard balls, respectively. Recent experiments demonstrating the elliptical billiard ball shape are presented using intensity data which ranges over close to eleven orders of magnitude.

  11. Happy birthday Echo!

    Staff Association

    2010-01-01

    You are reading the number hundred and one (no. 101) edition of our bulletin Echo. Just over four years ago, on 27th March 2006, the first untitled edition was published (Fig. 1 on the left). The title Echo appeared on the second edition on 10th April 2006 (Fig. 1 in the centre). Today (see Fig. 1 on the right), the layout is slightly different, but the structure of each edition has remained more or less the same: an editorial informing you of the important issues, followed by articles on club life, cultural activities (exhibitions and conferences), information from GAC-EPA, and special offers for our members.     Fig. 1 : Nos. 1, 2 and 100 of our twice-monthly publication Echo Echo was created in March 2006 when, much to our regret, CERN official communication and that of your representatives were separated. November 2009 saw a return to normal practice, and since then the CERN st...

  12. Supernovae light echoes

    The sudden brilliance of a supernova (SN) eruption will be reflected on surrounding dust grains to create a phantom nebula. If the SN is far away, the phantom nebula will be unresolved from the SN itself, and will appear as light added to the light curve and spectrum. For nearby SN like SN 1987A, the echo can be resolved as being separate from the SN itself. The dust responsible for the echo can be either in the interstellar medium (ISM) up to many parsecs away from the explosion or it can be in a circumstellar shell previously ejected by the progenitor star. The effects from echoes will be significant only if the optical depth of the dust is significant. SN 1987A, type Ia SN, and some type II SN do not have thick circumstellar shells, and hence can show echo effects only from reflections off the intervening ISM. The author reports on Monte Carlo calculations for echoes from circumstellar shells. The author has found that echo effects will often dominate the light curve and spectrum of SN at late times

  13. Generation of incoherent mid-infrared photon echoes with parametrically downconverted light

    Woutersen, Sander; Bonn, Mischa; Brugmans, Marco J. P.; Emmerichs, Uli; Bakker, Huib J.

    1996-10-01

    We present a demonstration of mid-infrared photon echoes generated with parametrically downconverted incoherent light. The photon echoes generated in this way enable one to study the dynamics of vibrations in the 1.5-4.0- mu m wavelength region with subpicosecond time resolution.

  14. Network of echoes

    The decision making model (DMM) previously developed [3,35] has been shown to generate phase transitions, to be topologically complex as manifest by inverse power-law (IPL) degree distributions, and to produce temporal complexity through IPL distributions in the switching times between the two critical states of consensus. These properties are entailed by the fundamental assumption that the network elements in the DMM imperfectly imitate one another, which is postulated herein as the echo response hypothesis; an echo being an imperfect copy of an original signal. Some implications of this hypothesis for the human sciences are explored

  15. Robust Echo Control Using a Simple Echo Path Model

    Faller, Christof; Tournery, Christophe

    2006-01-01

    In handsfree tele or video conferencing acoustic echoes arise due to the coupling between the loudspeaker and microphone. Usually an acoustic echo canceler (AEC) is used for eliminating the undesired echoes. The weaknesses of AEC are that it is relatively complex and that it is not robust against non-linearities occurring when using low-end components such as small loudspeakers. We are describing an algorithm which models the acoustic echo path by means of an overall delay and a coloration ef...

  16. Improved Echo cancellation in VOIP

    Patrashiya Magdolina Halder

    2011-11-01

    Full Text Available VoIP (voice over internet protocol is very popular communication technology of this century and has played tremendous role in communication system. It is preferred by all because it deploys many benefits it uses Internet protocol (IP networks to deliver multimedia information such as speech over a data network. VoIP system can be configured in these connection modes respectively; PC to PC, Telephony to Telephony and PC to Telephony. Echo is very annoying problem which occurs in VoIP and echo reduces the voice quality of VoIP. It is not possible to remove echo 100% from echoed signal because if echo is tried to be eliminated completely then the attempt may distort the main signal. That is why echo cannot be eliminated echo perfectly but the echo to a tolerable range. Clipping is not a good solution to suppress echo because part of speech may erroneously removed. Besides an NLP does not respond rapidly enough and also confuses the fading of the voice level at the end of a sentence with a residual echo. This paper has proposed echo cancellation in VoIP that has been tested and verified by MATLAB. The goal was to suppress echo without clipping and distorting the main signal. By the help of MATLAB program the echo is minimized to enduring level so that the received signal seems echo free. The percentage of suppressing echo varies with the amplitude of the main signal. With regarding the amplitude variation in received (echo free signal the proposed method performs better in finding the echo free signal than the other conventional system.

  17. Echo Boom Impact

    Dordai, Phillipe; Rizzo, Joseph

    2006-01-01

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

  18. Long-Range Vibrational Dynamics Are Directed by Watson-Crick Base Pairing in Duplex DNA.

    Hithell, Gordon; Shaw, Daniel J; Donaldson, Paul M; Greetham, Gregory M; Towrie, Michael; Burley, Glenn A; Parker, Anthony W; Hunt, Neil T

    2016-05-01

    Ultrafast two-dimensional infrared (2D-IR) spectroscopy of a 15-mer A-T DNA duplex in solution has revealed structure-dependent vibrational coupling and energy transfer processes linking bases with the sugar-phosphate backbone. Duplex melting induces significant changes in the positions of off-diagonal peaks linking carbonyl and ring-stretching vibrational modes of the adenine and thymine bases with vibrations of the phosphate group and phosphodiester linkage. These indicate that Watson-Crick hydrogen bonding and helix formation lead to a unique vibrational coupling arrangement of base vibrational modes with those of the phosphate unit. On the basis of observations from time-resolved 2D-IR data, we conclude that rapid energy transfer processes occur between base and backbone, mediated by additional modes located on the deoxyribose moiety within the same nucleotide. These relaxation dynamics are insensitive to duplex melting, showing that efficient intramolecular energy relaxation to the solvent via the phosphate groups is the key to excess energy dissipation in both single- and double-stranded DNA. PMID:27079484

  19. Hydrophobic Solvation : A 2D IR Spectroscopic Inquest

    Bakulin, Artem A.; Liang, Chungwen; Jansen, Thomas La Cour; Wiersma, Douwe A.; Bakker, Huib J.; Pshenichnikov, Maxim S.

    2009-01-01

    For decades, the enigma of the hydrophobic force has captured the imagination of scientists. in particular, Frank and Evans' idea that the hydrophobic effect was mainly due to some kind of "iceberg" formation around a hydrophobic solute stimulated many experiments and molecular dynamics simulation s

  20. Echoes from the Moon

    Girlanda, Luca

    2009-01-01

    We report on a determination of the Earth-Moon distance performed by students of an Italian high school, based on measurements of the time delay of the "echo" in the radio communications between Nasa mission control in Houston and the Apollo astronauts on the lunar surface. By using an open-source audio-editing software, the distance can be determined with three digits accuracy, allowing to detect the effect due to the eccentricity of the orbit of the Moon.

  1. Spin Echo in Synchrotrons

    Chao, Alexander W.; /SLAC; Courant, Ernest D.; /Brookhaven

    2006-12-01

    As a polarized beam is accelerated through a depolarization resonance, its polarization is reduced by a well-defined calculable reduction factor. When the beam subsequently crosses a second resonance, the final beam polarization is considered to be reduced by the product of the two reduction factors corresponding to the two crossings, each calculated independently of the other. This is a good approximation when the spread of spin precession frequency {Delta}{nu}{sub spin} of the beam (particularly due to its energy spread) is sufficiently large that the spin precession phases of individual particles smear out completely during the time {tau} between the two crossings. This approximate picture, however, ignores two spin dynamics effects: an interference effect and a spin echo effect. This paper is to address these two effects. The interference effect occurs when {Delta}{nu}{sub spin} is too small, or when {tau} is too short, to complete the smearing process. In this case, the two resonance crossings interfere with each other, and the final polarization exhibits constructive or destructive patterns depending on the exact value of {tau}. Typically, the beam's energy spread is large and this interference effect does not occur. To study this effect, therefore, it is necessary to reduce the beam energy spread and to consider two resonance crossings very close to each other. The other mechanism, also due to the interplay between two resonance crossings, is spin echo. It turns out that even when the precession phases appear to be completely smeared between the two crossings, there will still be a sudden and short-lived echo signal of beam polarization at a time {tau} after the second crossing; the magnitude of which can be as large as 57%. This echo signal exists even when the beam has a sizable energy spread and when {tau} is very large, and could be a sensitive (albeit challenging) way to experimentally test the intricate spin dynamics in a synchrotron. After giving

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

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

    2016-08-01

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

  3. Echo Cancellation I: Algorithms Simulation

    P. Sovka

    2000-04-01

    Full Text Available Echo cancellation system used in mobile communications is analyzed.Convergence behavior and misadjustment of several LMS algorithms arecompared. The misadjustment means errors in filter weight estimation.The resulting echo suppression for discussed algorithms with simulatedas well as rela speech signals is evaluated. The optional echocancellation configuration is suggested.

  4. Echo-planar imaging

    This paper demonstrates state-of-the-art echo-planar imaging (EPI) and its potential as a diagnostic modality. EPI provides 128 x 128- and 256 x 128-pixel MR images in 64 or 128 msec. The module structure of EPI, with separate spin-parameter encoding and image acquisition, allows flexible pulse sequence tailoring and interactive scanning with real-time feedback. We report the experience we have gained in over 200 EPI studies of head and body in adult and pediatric patients as well as fetuses in utero. EPI provides resolution in the millimeter range, T1 and T2 contrast, and dynamic morphologic as well as functional information. Parameters, including flow, perfusion, and relaxation, can be quantified in seconds. EPI can provide functional and morphologic information in a single examination, which is particularly useful in studies of cardiac dynamics, blood and cerebrospinal fluid flow, brain perfusion, and the GI tract

  5. The ECHo experiment

    The determination of the absolute scale of the neutrino masses is one of the most challenging questions in particle physics. Different approaches are followed to achieve a sensitivity on neutrino masses in the sub-eV range. Among them, experiments exploring the beta decay and electron capture processes of suitable nuclides can provide necessary information on the electron neutrino mass value. In this talk we present the Electron Capture 163Ho experiment ECHo, which aims to investigate the electron neutrino mass in the sub-eV range by means of the analysis of the calorimetrically measured energy spectrum following the electron capture process of 163Ho. A high precision and high statistics spectrum is measured by means of low temperature magnetic calorimeter arrays. We present preliminary results obtained with a first prototype of single channel detectors as well as the participating groups and their on-going developments.

  6. Neutron phase spin echo

    Piegsa, Florian M; Schanzer, Christian

    2016-01-01

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

  7. Neutron phase spin echo

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

    2016-04-01

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

  8. High-spatial-resolution isotropic three-dimensional fast-recovery fast spin-echo magnetic resonance dacryocystography combined with topical administration of sterile saline solution

    Objective: This study aims to investigate the clinical performance of three-dimensional (3D) fast-recovery fast spin-echo (FRFSE) magnetic resonance dacryocystography (MRD) with topical administration of sterile saline solution for the assessment of the lacrimal drainage system (LDS). Methods: A total of 13 healthy volunteers underwent both 3D-FRFSE MRD and two-dimensional (2D)-impulse recovery (IR)-single-shot fast spin-echo (SSFSE) MRD after topical administration of sterile saline solution, and 31 patients affected by primary LDS outflow impairment or postsurgical recurrent epiphora underwent 3D-FRFSE MRD and conventional T1- and T2-weighted sequences. All patients underwent lacrimal endoscopy or surgery, which served as a standard of reference for confirming the MRD findings. Results: 3D-FRFSE MRD detected more visualized superior and inferior canaliculi and nasolacrimal duct than 2D-IR-SSFSE MRD. Compared with 2D-IR-SSFSE MRD, 3D-FRFSE MRD showed more visualized segments per LDS, although the difference was not statistically significant. Significant improvements in the inferior canaliculus and nasolacrimal duct visibility grades were achieved using 3D-FRFSE MRD. 3D-FRFSE MRD had 100% sensitivity and 63.6% specificity for detecting LDS obstruction. In 51 out of the 62 LDSs that were assessed, a 90% agreement was noted between the findings of 3D-FRFSE MRD and lacrimal endoscopy in detecting the obstruction level. Conclusion: 3D-FRFSE MRD combined with topical administration of sterile saline solution is a simple and noninvasive method of obtaining detailed morphological and functional information on the LDS. Overall, 3D-FRFSE MRD could be used as a reliable diagnostic method in many patients with epiphora prior to surgery

  9. High-spatial-resolution isotropic three-dimensional fast-recovery fast spin-echo magnetic resonance dacryocystography combined with topical administration of sterile saline solution

    Jing, Zhang, E-mail: hbtjzj@yahoo.com.cn [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Lang, Chen, E-mail: langc731@yahoo.com.cn [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Qiu-Xia, Wang, E-mail: guaiqiuqiu1981@163.com [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Rong, Liu, E-mail: rongr007@yahoo.com.cn [Department of Ophthalmology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Xin, Luo, E-mail: hoyoho2000@sina.com [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Wen-Zhen, Zhu, E-mail: zhuwenzhen@hotmail.com [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Li-Ming, Xia, E-mail: limingxia@tjh.tjmu.edu.cn [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Jian-Pin, Qi, E-mail: qijp2k01@yahoo.com [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); He, Wang, E-mail: he.wang@ge.com [GE Healthcare, 1 Build, 2F C109, 1 Hua TuoRoad, Zhang Jiang Hi-Tech Park, Shanghai 201203 (China)

    2013-09-15

    Objective: This study aims to investigate the clinical performance of three-dimensional (3D) fast-recovery fast spin-echo (FRFSE) magnetic resonance dacryocystography (MRD) with topical administration of sterile saline solution for the assessment of the lacrimal drainage system (LDS). Methods: A total of 13 healthy volunteers underwent both 3D-FRFSE MRD and two-dimensional (2D)-impulse recovery (IR)-single-shot fast spin-echo (SSFSE) MRD after topical administration of sterile saline solution, and 31 patients affected by primary LDS outflow impairment or postsurgical recurrent epiphora underwent 3D-FRFSE MRD and conventional T1- and T2-weighted sequences. All patients underwent lacrimal endoscopy or surgery, which served as a standard of reference for confirming the MRD findings. Results: 3D-FRFSE MRD detected more visualized superior and inferior canaliculi and nasolacrimal duct than 2D-IR-SSFSE MRD. Compared with 2D-IR-SSFSE MRD, 3D-FRFSE MRD showed more visualized segments per LDS, although the difference was not statistically significant. Significant improvements in the inferior canaliculus and nasolacrimal duct visibility grades were achieved using 3D-FRFSE MRD. 3D-FRFSE MRD had 100% sensitivity and 63.6% specificity for detecting LDS obstruction. In 51 out of the 62 LDSs that were assessed, a 90% agreement was noted between the findings of 3D-FRFSE MRD and lacrimal endoscopy in detecting the obstruction level. Conclusion: 3D-FRFSE MRD combined with topical administration of sterile saline solution is a simple and noninvasive method of obtaining detailed morphological and functional information on the LDS. Overall, 3D-FRFSE MRD could be used as a reliable diagnostic method in many patients with epiphora prior to surgery.

  10. Balanced echo state networks.

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

    2012-12-01

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

  11. Simple echoes and subtle reverberations

    Keeports, David

    2010-03-01

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

  12. X-ray Echo Spectroscopy

    Shvyd'ko, Yuri

    2016-02-01

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

  13. X-ray echo spectroscopy

    Shvyd'ko, Yuri

    2015-01-01

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

  14. Investigation of organometallic reaction mechanisms with one and two dimensional vibrational spectroscopy

    Cahoon, James Francis

    2008-12-16

    One and two dimensional time-resolved vibrational spectroscopy has been used to investigate the elementary reactions of several prototypical organometallic complexes in room temperature solution. The electron transfer and ligand substitution reactions of photogenerated 17-electron organometallic radicals CpW(CO){sub 3} and CpFe(CO){sub 2} have been examined with one dimensional spectroscopy on the picosecond through microsecond time-scales, revealing the importance of caging effects and odd-electron intermediates in these reactions. Similarly, an investigation of the photophysics of the simple Fischer carbene complex Cr(CO){sub 5}[CMe(OMe)] showed that this class of molecule undergoes an unusual molecular rearrangement on the picosecond time-scale, briefly forming a metal-ketene complex. Although time-resolved spectroscopy has long been used for these types of photoinitiated reactions, the advent of two dimensional vibrational spectroscopy (2D-IR) opens the possibility to examine the ultrafast dynamics of molecules under thermal equilibrium conditions. Using this method, the picosecond fluxional rearrangements of the model metal carbonyl Fe(CO){sub 5} have been examined, revealing the mechanism, time-scale, and transition state of the fluxional reaction. The success of this experiment demonstrates that 2D-IR is a powerful technique to examine the thermally-driven, ultrafast rearrangements of organometallic molecules in solution.

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

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

    2011-06-02

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

  16. Entanglement Echoes in Quantum Computation

    Rossini, Davide; Benenti, Giuliano; Casati, Giulio

    2003-01-01

    We study the stability of entanglement in a quantum computer implementing an efficient quantum algorithm, which simulates a quantum chaotic dynamics. For this purpose, we perform a forward-backward evolution of an initial state in which two qubits are in a maximally entangled Bell state. If the dynamics is reversed after an evolution time $t_r$, there is an echo of the entanglement between these two qubits at time $t_e=2t_r$. Perturbations attenuate the pairwise entanglement echo and generate...

  17. Multifractal Modelling of Aircraft Echoes from Low-resolution Radars Based on Structural Functions

    Qiu Sheng Li

    2013-09-01

    Full Text Available As a kind of complex targets, the nonrigid vibration and attitude change of an aircraft as well as the rotation of its rotating parts will induce complex nonlinear modulation on its echo from low-resolution radars. If one performs the multifractal analysis of measures on an aircraft echo, it may offer a fine description of the dynamic characteristics which induce the echo structure. On basis of introducing multifractal theory based on structural functions, the paper models real recorded aircraft echo data from a low-resolution radar by using the random walk process and the incremental process respectively, and investigates the application of echo multifractal characteristics in aircraft target classification with low-resolution radars. The analysis shows that aircraft echoes from low-resolution radars have clear multifractal characteristics, and one should take an aircraft echo series as a random walk process to perform the multifractal analysis. The experimental results validate the classification method based on multifractal signatures.Defence Science Journal, 2013, 63(5, pp.515-520, DOI:http://dx.doi.org/10.14429/dsj.63.3773

  18. Phenomenological theory of echo poles

    In scattering theory the effect associated with the downward crossing of the phase-shift δℓ(k) (ℓ being the orbital angular momentum and k the momentum) through δℓ=π/2 (mod π) is called echo. In the standard nuclear theory (Breit–Wigner theory) the echo is described and evaluated in terms of scattering by an impenetrable sphere. However, this model holds only at sufficiently high energy, while it is inadequate at low energy. In this paper we show that the echo effect can be associated with two different regimes acting at low and high energy, respectively. At high energy the hard-sphere scattering model seems to describe appropriately the phenomenon. At low energy we propose a mechanism due to the exchange forces induced by the Pauli exclusion principle in the fermionic interaction, which leads to nonlocal potentials. These potentials admit for the scattering amplitude pole singularities in the fourth quadrant of the complex angular momentum plane. This paper analyzes the role played by this class of poles in the description of the low energy regime of echoes. A specific phenomenological analysis is performed, taking as typical example the α–α elastic scattering

  19. Acoustic echoes reveal room shape.

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

    2013-07-23

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

  20. Dance of the Light Echoes

    2008-01-01

    [figure removed for brevity, see original site] Click on image for larger poster version This composite image from NASA's Spitzer Space Telescope shows the remnant of a star that exploded, called Cassiopeia A (center) and its surrounding 'light echoes' -- dances of light through dusty clouds, created when stars blast apart. The light echoes are colored and the surrounding clouds of dust are gray. In figure 1, dramatic changes are highlighted in phenomena referred to as light echoes (colored areas) around the Cassiopeia A supernova remnant (center). Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died. A light echo occurs when a star explodes, acting like a cosmic flashbulb. The light from this explosion zips through nearby dust clumps, illuminating and heating them up slightly. This brief period of warming causes them to glow in infrared, like a chain of Christmas bulbs lighting up one by one. The result is an optical illusion, in which the dust appears to be flying outward at the speed of light. In figure 1, this apparent motion can be seen here by the shift in colored dust clumps Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died. This remnant is located 11,000 light-years away in the northern constellation Cassiopeia. This composite consists of six processed images taken over a time span of three years. Dust features that have not changed over time appear gray, while those that have changed are colored blue or orange. Bluer colors represent an earlier time and redder ones, a later time. The progression of the light echo through the dust can be seen here by the shift in colored dust clumps. This light echo is the largest ever seen

  1. PHONON ECHOES IN BULK AND POWDERED MATERIALS

    Kajimura, K.

    1981-01-01

    Experimental and theoretical studies of phonon echoes in bulk and powdered materials are reviewed. Phonon echoes have been observed in many materials such as bulk piezoelectric crystals, paramagnets, glasses, doped semiconductors, and piezoelectric, magnetic, and metallic powders, etc. The echoes arise from a time reversal of the phase, like spin echoes, of a primary pulsed acoustic excitation due to a second acoustic or rf pulse. The phase reversal occurs through the nonlinear interactions o...

  2. Comparison of third-order plasma wave echoes with ballistic second-order plasma wave echoes

    The apparent dispersion of third-order plasma wave echoes observed in a high frequency plasma is compared with that of simultaneously observed ballistic second-order echoes. Amplitude and wavelength of third-order echoes are found to be always smaller than those of second-order echoes, however, the dispersion curves of both types of echoes are very similar. These observations are in qualitative agreement with calculations of special ballistic third-order echoes. The ballistic nature of the observed third-order echoes may, therefore, be concluded from these measurements. (author)

  3. Distinguishing gramicidin D conformers through two-dimensional infrared spectroscopy of vibrational excitons

    Stevenson, Paul; Tokmakoff, Andrei

    2015-06-01

    Gramicidin D is a short peptide which dimerizes to form helical pores, adopting one of two conformations in the process. These conformations differ primarily in number of residues per turn and the hydrogen-bond registry between rungs of the helix. Using amide I 2D infrared (IR) and FTIR, we have demonstrated that it is possible to distinguish between the different conformers of gramicidin D in solution. We show that the spectra observed for this helical peptide bear no resemblance to the spectra of α- or 310-helices and that while the FTIR spectra appear similar to spectra of β-sheets, 2D IR reveals that the observed resonances arise from vibrational modes unlike those observed in β-sheets. We also present an idealized model which reproduces the experimental data with high fidelity. This model is able to explain the polarization-dependence of the experimental 2D IR data. Using this model, we show the coupling between the rungs of the helix dominates the spectra, and as a consequence of this, the number of residues per turn can greatly influence the amide I spectra of gramicidin D.

  4. Harmonic Motion Detection in a Vibrating Scattering Medium

    Urban, Matthew W.; Chen, Shigao; Greenleaf, James F.

    2008-01-01

    Elasticity imaging is an emerging medical imaging modality that seeks to map the spatial distribution of tissue stiffness. Ultrasound radiation force excitation and motion tracking using pulse-echo ultrasound have been used in numerous methods. Dynamic radiation force is used in vibrometry to cause an object or tissue to vibrate, and the vibration amplitude and phase can be measured with exceptional accuracy. This paper presents a model that simulates harmonic motion detection in a vibrating ...

  5. Molecular echoes in space and time

    Lin, Kang; Ma, Junyang; Gong, Xiaochun; Song, Qiying; Ji, Qinying; Zhang, Wenbin; Zeng, Heping; Wu, Jian; Karras, Gabriel; Siour, Guillaume; Hartmann, Jean-Michel; Faucher, Olivier; Gershnabel, Erez; Prior, Yehiam; Averbukh, Ilya Sh

    2016-01-01

    Mountain echoes are a well-known phenomenon, where an impulse excitation is mirrored by the rocks to generate a replica of the original stimulus, often with reverberating recurrences. For spin echoes in magnetic resonance and photon echoes in atomic and molecular systems the role of the mirror is played by a second, time delayed pulse which is able to reverse the ow of time and recreate the original event. Recently, laser-induced rotational alignment and orientation echoes were introduced for molecular gases, and discussed in terms of rotational-phase-space filamentation. Here we present, for the first time, a direct spatiotemporal analysis of various molecular alignment echoes by means of coincidence Coulomb explosion imaging. We observe hitherto unreported spatially rotated echoes, that depend on the polarization direction of the pump pulses, and find surprising imaginary echoes at negative times.

  6. Independence of echo-threshold and echo-delay in the barn owl.

    Brian S Nelson

    Full Text Available Despite their prevalence in nature, echoes are not perceived as events separate from the sounds arriving directly from an active source, until the echo's delay is long. We measured the head-saccades of barn owls and the responses of neurons in their auditory space-maps while presenting a long duration noise-burst and a simulated echo. Under this paradigm, there were two possible stimulus segments that could potentially signal the location of the echo. One was at the onset of the echo; the other, after the offset of the direct (leading sound, when only the echo was present. By lengthening the echo's duration, independently of its delay, spikes and saccades were evoked by the source of the echo even at delays that normally evoked saccades to only the direct source. An echo's location thus appears to be signaled by the neural response evoked after the offset of the direct sound.

  7. Principles of angular echo-spectroscopy

    Khasanov, O.K. [Joint Institute of Solid State and Semiconductor Physics, NAS Belarus, 17 P. Brovki Str., Minsk 220072 (Belarus)]. E-mail: khasanov@ifttp.bas-net.by; Fedotova, O.M. [Joint Institute of Solid State and Semiconductor Physics, NAS Belarus, 17 P. Brovki Str., Minsk 220072 (Belarus); Samartsev, V.V. [Zavoisky Physical-Technical Institute KSC RAS, Sibirskii Trakt Str., 10/7, Kazan' 420029, Tatarstan (Russian Federation)

    2007-11-15

    We study the two-pulse photon echo generation process in thin polymer films doped with organic dye, when the angle between wave vectors of the excitation pulses is varied. The temporal structure as well as the spectral features of the echo-response are analyzed. The evolution from the gradual blue shift of the echo-signal frequency to the red switch of it is predicted.

  8. Optical echo in photonic crystals

    Antipov, A E

    2006-01-01

    The dynamics of photonic wavepacket in the effective oscillator potential is studied. The oscillator potential is constructed on a base of one dimensional photonic crystal with a period of unit cell adiabatically varied in space. The structure has a locally equidistant discrete spectrum. This leads to an echo effect, i.e. the periodical reconstruction of the packet shape. The effect can be observed in a nonlinear response of the system. Numerical estimations for porous-silicon based structures are presented for femtosecond Ti:Sapphire laser pump.

  9. Acoustic Echoes Reveal Room Shape

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

    2013-01-01

    Imagine that you are blindfolded inside an unknown room. You snap your fingers and listen to the room’s response. Can you hear the shape of the room? Some people can do it naturally, but can we design computer algorithms that hear rooms? We show how to compute the shape of a convex polyhedral room from its response to a known sound, recorded by a few microphones. Geometric relationships between the arrival times of echoes enable us to “blindfoldedly” estimate the room geometry. This is achiev...

  10. Collision induced photon echo in ytterbium vapour

    Rubtsova, N. N.; Khvorostov, E. B.; Kochubei, S. A.; Ishchenko, V. N.; Yevseyev, I. V.

    2006-01-01

    Collision induced photon echo observed in ytterbium vapour at the inter-combination transition (6s6p) P-8(1) (6s(2)) S-1(0) in the presence of Kr gas as buffer. Collision echo is generated by two unidirectional resonant dye laser pulses of linear mutually orthogonal polarizations. There is practical

  11. Ultrafast dynamics in iron tetracarbonyl olefin complexes investigated with two-dimensional vibrational spectroscopy.

    Panman, Matthijs R; Newton, Arthur C; Vos, Jannie; van den Bosch, Bart; Bocokić, Vladica; Reek, Joost N H; Woutersen, Sander

    2013-01-28

    The dynamics of iron tetracarbonyl olefin complexes has been investigated using two-dimensional infrared (2D-IR) spectroscopy. Cross peaks between all CO-stretching bands show that the CO-stretch modes are coupled, and from the cross-peak anisotropies we can confirm previous assignments of the absorption bands. From the pump-probe delay dependence of the diagonal peaks in the 2D-IR spectrum we obtain a correlation time of ∼3 ps for the spectral fluctuations of the CO-stretch modes. We observe a multi-exponential pump-probe delay dependence of the cross-peak intensities, with rate constants ranging from 0.1 ps(-1) to 0.6 ps(-1). To determine whether this delay dependence originates from fluxionality of the complex or from intramolecular vibrational relaxation (IVR), we modulate the free-energy barrier of fluxional rearrangement by varying the pi-backbonding capacities of the olefin ligand in two iron tetracarbonyl olefin complexes: Fe(CO)(4)(cinnamic acid) and Fe(CO)(4)(dimethyl fumarate). Since the pi-backbonding strongly influences the rate of fluxionality, comparing the dynamics in the two complexes allows us to determine to what extent the observed dynamics is caused by fluxionality. We conclude that on the time scale of our experiments (up to 100 ps) the cross-peak dynamics in the iron complexes is determined by intramolecular vibrational energy relaxation. Hence, in contrast to previously investigated irontricarbonyl and ironpentacarbonyl complexes, iron tetracarbonyl olefin complexes exhibit no fluxionality on the picosecond time scale. PMID:23223560

  12. Nonlinear Echoes from Encapsulated Antibubbles

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

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

  13. Two-dimensional vibrational spectroscopy of rotaxane-based molecular machines.

    Bodis, Pavol; Panman, Matthijs R; Bakker, Bert H; Mateo-Alonso, Aurelio; Prato, Maurizio; Buma, Wybren Jan; Brouwer, Albert M; Kay, Euan R; Leigh, David A; Woutersen, Sander

    2009-09-15

    model rotaxane and a rotaxane-based molecular shuttle. Our results demonstrate the feasibility of using time-resolved 2D-IR experiments to measure externally triggered structural changes of molecular devices with subpicosecond time resolution. We can observe each of the elementary events that underlie the mechanical motion separately. With this ability to investigate the nature of the mechanical motions at the molecular level and with unprecedented time resolution, we expect that 2D-IR spectroscopy on molecular machines will lead to new insights into their function. PMID:19650645

  14. Ship Vibrations

    Sørensen, Herman

    1997-01-01

    Methods for calculating natural frequencies for ship hulls and for plates and panels.Evaluation of the risk for inconvenient vibrations on board......Methods for calculating natural frequencies for ship hulls and for plates and panels.Evaluation of the risk for inconvenient vibrations on board...

  15. Sparse adaptive filters for echo cancellation

    Paleologu, Constantin

    2011-01-01

    Adaptive filters with a large number of coefficients are usually involved in both network and acoustic echo cancellation. Consequently, it is important to improve the convergence rate and tracking of the conventional algorithms used for these applications. This can be achieved by exploiting the sparseness character of the echo paths. Identification of sparse impulse responses was addressed mainly in the last decade with the development of the so-called ``proportionate''-type algorithms. The goal of this book is to present the most important sparse adaptive filters developed for echo cancellati

  16. Echoes in correlated neural systems

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

    2013-02-01

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

  17. MEASUREMENT OF TRANSVERSE ECHOES IN RHIC.

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

    2005-05-16

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

  18. Enforcement and Compliance History Online (ECHO) Facilities

    U.S. Environmental Protection Agency — ECHO provides integrated compliance and enforcement information for about 800,000 regulated facilities nationwide. Its features range from simple to advanced,...

  19. Time Delay Estimation Algoritms for Echo Cancellation

    Boris Simak

    2011-01-01

    Full Text Available The following case study describes how to eliminate echo in a VoIP network using delay estimation algorithms. It is known that echo with long transmission delays becomes more noticeable to users. Thus, time delay estimation, as a part of echo cancellation, is an important topic during transmission of voice signals over packetswitching telecommunication systems. An echo delay problem associated with IP-based transport networks is discussed in the following text. The paper introduces the comparative study of time delay estimation algorithm, used for estimation of the true time delay between two speech signals. Experimental results of MATLab simulations that describe the performance of several methods based on cross-correlation, normalized crosscorrelation and generalized cross-correlation are also presented in the paper.

  20. EChO - Exoplanet Characterisation Observatory

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

    2011-01-01

    A dedicated mission to investigate exoplanetary atmospheres represents a major milestone in our quest to understand our place in the universe by placing our Solar System in context and by addressing the suitability of planets for the presence of life. EChO -the Exoplanet Characterisation Observatory- is a mission concept specifically geared for this purpose. EChO will provide simultaneous, multi-wavelength spectroscopic observations on a stable platform that will allow very long exposures. EChO will build on observations by Hubble, Spitzer and groundbased telescopes, which discovered the first molecules and atoms in exoplanetary atmospheres. EChO will simultaneously observe a broad enough spectral region -from the visible to the mid-IR- to constrain from one single spectrum the temperature structure of the atmosphere and the abundances of the major molecular species. The spectral range and resolution are tailored to separate bands belonging to up to 30 molecules to retrieve the composition and temperature str...

  1. Enforcement and Compliance History Online (ECHO) Widget

    U.S. Environmental Protection Agency — The Enforcement and Compliance History Online (ECHO) widget displays the compliance records of larger facilities within a user-specified area of interest as...

  2. Geometric spin echo under zero field.

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

    2016-01-01

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

  3. Echo Theatre: From Experience to Performance

    Ulvund, Marit

    2013-01-01

    This research project investigates the characteristics of Echo Theatre, its potential to foster performative and narrative competencies in students, and the role of the teacher in this performative and educational practice. Echo Theatre is a method devised during my storytelling practice and this research confirms that there is no identical research or teaching practice which involves students staging personal narratives in the classroom in this way.The study has been informed by cross discip...

  4. Vibration sensor

    This invention relates to a sensor for detecting the vibrations of a liquid, specifically designed for detecting low frequency vibrations transmitted by a high temperature liquid, particularly the liquid metal coolant of a fast reactor. It comprises a piezoelectric transducer inside a cavity closed by a membrane in contact with the liquid and in which a vacuum is made. The membrane is connected to one of the sides of the transducer, called the first side, through a mechanical vibration transmitting part made of a thermal insulation material. The other side of the transducer, termed second side, is blocked and the cavity has at least one leak-tight passage for an electric conductor

  5. Echo cancellation techniques for ADSL transceivers

    Multicarrier transmission methods have long known to optimize the performance of data transceivers on bandlimited communication channels. One form of multicarrier transmission, known as discrete multitone modulation (DMT), is particularly attractive for its ability to be implemented using efficient digital signal processing techniques. The ANSI Tl committee has standardized discrete multitone modulation (DMT) as the line code to be used in the ADSL transmission system, due to its unique ability to overcome the severe distortion of the copper line at this frequency band. Given a basic DMT system, it is possible to increase the aggregate data rate with full duplex transmission using echo cancellation. This paper presents high speed echo cancellation techniques for full duplex data transmission using G. Lite ADSL standards. Time domain echo cancellation and mixed time and frequency domain echo cancellation techniques have been implemented for G. Lite ADSL applications. It has been observed that Time and frequency domain echo canceller (TAFDEC) achieve lower complexity for G. Lite ADSL systems that required by time domain echo canceller (TDEC) using traditional single carrier technique, such as least mean square (LMS) Hi algorithm. (author)

  6. On the Search for Quasar Light Echoes

    Visbal, Eli

    2007-01-01

    The UV radiation from a quasar leaves a characteristic pattern in the distribution of ionized hydrogen throughout the surrounding space. This pattern or light echo propagates through the intergalactic medium at the speed of light, and can be observed by its imprint on the Ly-alpha forest spectra of background sources. As the echo persists after the quasar has switched off, it offers the possibility of searching for dead quasars, and constraining their luminosities and lifetimes. We outline a technique to search for and characterize these light echoes. To test the method, we create artificial Ly-alpha forest spectra from cosmological simulations at z=3, apply light echoes and search for them. We show how the simulations can also be used to quantify the significance level of any detection. We find that light echoes from the brightest quasars could be found in observational data. With absorption line spectra of 100 redshift z~3-3.5 quasars or galaxies in a 1 square degree area, we expect that ~10 echoes from qua...

  7. Probing intermolecular couplings in liquid water with two-dimensional infrared photon echo spectroscopy

    Paarmann, A.; Hayashi, T.; Mukamel, S.; Miller, R. J. D.

    2008-05-01

    Two-dimensional infrared photon echo and pump probe studies of the OH stretch vibration provide a sensitive probe of the correlations and couplings in the hydrogen bond network of liquid water. The nonlinear response is simulated using numerical integration of the Schrödinger equation with a Hamiltonian constructed to explicitly treat intermolecular coupling and nonadiabatic effects in the highly disordered singly and doubly excited vibrational exciton manifolds. The simulated two-dimensional spectra are in close agreement with our recent experimental results. The high sensitivity of the OH stretch vibration to the bath dynamics is found to arise from intramolecular mixing between states in the two-dimensional anharmonic OH stretch potential. Surprisingly small intermolecular couplings reproduce the experimentally observed intermolecular energy transfer times.

  8. Random Vibrations

    Messaro. Semma; Harrison, Phillip

    2010-01-01

    Ares I Zonal Random vibration environments due to acoustic impingement and combustion processes are develop for liftoff, ascent and reentry. Random Vibration test criteria for Ares I Upper Stage pyrotechnic components are developed by enveloping the applicable zonal environments where each component is located. Random vibration tests will be conducted to assure that these components will survive and function appropriately after exposure to the expected vibration environments. Methodology: Random Vibration test criteria for Ares I Upper Stage pyrotechnic components were desired that would envelope all the applicable environments where each component was located. Applicable Ares I Vehicle drawings and design information needed to be assessed to determine the location(s) for each component on the Ares I Upper Stage. Design and test criteria needed to be developed by plotting and enveloping the applicable environments using Microsoft Excel Spreadsheet Software and documenting them in a report Using Microsoft Word Processing Software. Conclusion: Random vibration liftoff, ascent, and green run design & test criteria for the Upper Stage Pyrotechnic Components were developed by using Microsoft Excel to envelope zonal environments applicable to each component. Results were transferred from Excel into a report using Microsoft Word. After the report is reviewed and edited by my mentor it will be submitted for publication as an attachment to a memorandum. Pyrotechnic component designers will extract criteria from my report for incorporation into the design and test specifications for components. Eventually the hardware will be tested to the environments I developed to assure that the components will survive and function appropriately after exposure to the expected vibration environments.

  9. Re-visiting the echo state property.

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

    2012-11-01

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

  10. Modelling of Oscillations in Two-Dimensional Echo-Spectra of the Fenna-Matthews-Olson Complex

    Hein, Birgit; Kramer, Tobias; Rodríguez, Mirta

    2011-01-01

    Recent experimental observations of time-dependent beatings in the two-dimensional echo-spectra of light-harvesting complexes at ambient temperatures have opened up the question whether coherence and wave-like behaviour plays a significant role in photosynthesis. We perform a numerical study of the absorption and echo-spectra of the Fenna-Matthews-Olson (FMO) complex in chlorobium tepidum and analyse the requirements in the theoretical model needed to reproduce beatings in the calculated spectra. The energy transfer in the FMO pigment-protein complex is theoretically described by an exciton Hamiltonian coupled to a phonon bath which account for the pigments electronic and vibrational excitations respectively. We use the hierarchical equations of motions method to treat the strong couplings in a non-perturbative way. We show that the oscillations in the two-dimensional echo-spectra persist in the presence of thermal noise and static disorder.

  11. Urban vibrations

    Morrison, Ann; Knudsen, L.; Andersen, Hans Jørgen

    2012-01-01

    In   this   paper   we   describe   a   field   study   conducted   with   a   wearable   vibration   belt   where   we   test   to   determine   the   vibration   intensity   sensitivity   ranges   on   a   large   diverse   group   of   participants   with   evenly   distributed  ages  and......   lab   studies   in   that   we   found   a   decreased   detection   rate   in   busy   environments.   Here   we   test   with   a   much   larger   sample   and   age   range,   and   contribute   with   the   first   vibration  sensitivity  testing  outside  the  lab  in  an  urban   public...

  12. Meteor head echoes - observations and models

    A. Pellinen-Wannberg

    2005-01-01

    Full Text Available Meteor head echoes - instantaneous echoes moving with the velocities of the meteors - have been recorded since 1947. Despite many attempts, this phenomenon did not receive a comprehensive theory for over 4 decades. The High Power and Large Aperture (HPLA features, combined with present signal processing and data storage capabilities of incoherent scatter radars, may give an explanation for the old riddle. The meteoroid passage through the radar beam can be followed with simultaneous spatial-time resolution of about 100m-ms class. The current views of the meteor head echo process will be presented and discussed. These will be related to various EISCAT observations, such as dual-frequency target sizes, altitude distributions and vector velocities.

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

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

    2011-06-01

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

  14. Multi-Echo-Based Echo-Planar Spectroscopic Imaging Using a 3T MRI Scanner

    Jon K. Furuyama

    2011-10-01

    Full Text Available The use of spin-echoes has been employed in an Echo-Planar Spectroscopic Imaging (EPSI sequence to collect multiple phase encoded lines within a single TR in a Multi-Echo-based Echo-Planar Spectroscopic Imaging technique (MEEPSI. Despite the T2 dependence on the amplitude of the spin-echoes, the Full Width at Half Maximum (FWHM of the derived multi-echo Point Spread Function (PSF is shown to decrease, indicating an improved overall spatial resolution without requiring any additional scan time. The improved spatial resolution is demonstrated in the one-dimensional (1D spatial profiles of the N-Acetyl Aspartate (NAA singlet along the phase encode dimension in a gray matter phantom. Although the improved spatial resolution comes at the expense of spectral resolution, it is shown in vivo that peak broadening due to T2* decay is more significant than the loss of resolution from using spin-echoes and therefore does not affect the ability to quantify metabolites using the LCModel fitting algorithm.

  15. How can dolphins recognize fish according to their echoes? A statistical analysis of fish echoes.

    Yossi Yovel

    Full Text Available Echo-based object classification is a fundamental task of animals that use a biosonar system. Dolphins and porpoises should be able to rely on echoes to discriminate a predator from a prey or to select a desired prey from an undesired object. Many studies have shown that dolphins and porpoises can discriminate between objects according to their echoes. All of these studies however, used unnatural objects that can be easily characterized in human terminologies (e.g., metallic spheres, disks, cylinders. In this work, we collected real fish echoes from many angles of acquisition using a sonar system that mimics the emission properties of dolphins and porpoises. We then tested two alternative statistical approaches in classifying these echoes. Our results suggest that fish species can be classified according to echoes returning from porpoise- and dolphin-like signals. These results suggest how dolphins and porpoises can classify fish based on their echoes and provide some insight as to which features might enable the classification.

  16. Nanosecond image processing using stimulated photon echoes.

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

    1990-05-15

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

  17. Nanosecond image processing using stimulated photon echoes

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

    1990-01-01

    Processing of two-dimensional images on a nanosecond time scale is demonstrated using the stimulated photon echoes in a rare-earth-doped crystal (0.1 at. \\% Pr3$+$:LaF3). Two spatially encoded laser pulses (pictures) resonant with the 3P0-3H4 transition of Pr3$+$ were stored by focusing the image pulses sequentially into the Pr3$+$:LaF3 crystal. The stored information is retrieved and processed by a third read pulse, generating the echo that is the spatial convolution or correlation of the in...

  18. Research of laser echo signal simulator

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

    2015-11-01

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

  19. GESTATIONAL ECHO BIOMETRY IN BRACHYCEPHALIC PREGNANT BITCHES

    Marcus Antônio Rossi Feliciano; Giovanna Serpa Maciel; Leandro Nassar Coutinho; Vívian Tavares Almeida; Ricardo Ramirez Uscategui; Wilter Ricardo Russiano Vicente

    2015-01-01

    Ultrasonography is an accurate pregnancy diagnostic method, besides being completely innocuous for female and fetuses evaluation. The objective of this paper was to determine the reference values for gestational echo biometry of different breeds of bitches. A total of 25 multiparous females were included in the experiment, five English Bulldog bitches, five Pugs and 15 Shih Tzu, weighing 4-25 kg and aged 4-6 years. The echo biometric assessments were performed during the 2nd, 5th, 6th, 7th an...

  20. TOPICAL REVIEW: Nonlinear two-dimensional vibrational spectroscopy of peptides

    Woutersen, Sander; Hamm, Peter

    2002-10-01

    In this overview, we discuss theoretical and experimental aspects of nonlinear two-dimensional infrared (2D-IR) spectroscopy. With this technique both peptide conformation and conformational flexibility can be probed. The quantitative relation between the experimental 2D-IR spectrum and the peptide conformation is discussed, and examples of how the conformation of a peptide and the timescale of its fluctuations are derived from its (time-resolved) 2D spectrum are presented.

  1. Vibration sensor

    Matěj, J.

    2015-01-01

    This paper lays out a design of a system for reading the radar antenna gearbox vibrations. Firstly it names different types of sensors and defines their suitability for this usage. It describes their important electric and frequency properties. Secondly it shows a design of the data transmission system from the transducer to a computer and describes measured data changes according to the gearbox faults.

  2. Vibrating minds

    2009-01-01

    Ed Witten is one of the leading scientists in the field of string theory, the theory that describes elementary particles as vibrating strings. This week he leaves CERN after having spent a few months here on sabbatical. His wish is that the LHC will unveil supersymmetry.

  3. Vibrating Manipulation

    SHEN Guo-quan; CUI Yi-jun

    2003-01-01

    @@ As a manipulation with unique therapeutic effect in TCM Tuina manipulations, Vibrating manipulation has significantly stronger effection on viscera, blood vessel, smooth muscle and gland secretion than other Tuina manipulations and it is mainly used in internal medicine, gynecology and miscellaneous diseases.

  4. Location Detection and Tracking of Moving Targets by a 2D IR-UWB Radar System

    Van-Han Nguyen

    2015-03-01

    Full Text Available In indoor environments, the Global Positioning System (GPS and long-range tracking radar systems are not optimal, because of signal propagation limitations in the indoor environment. In recent years, the use of ultra-wide band (UWB technology has become a possible solution for object detection, localization and tracking in indoor environments, because of its high range resolution, compact size and low cost. This paper presents improved target detection and tracking techniques for moving objects with impulse-radio UWB (IR-UWB radar in a short-range indoor area. This is achieved through signal-processing steps, such as clutter reduction, target detection, target localization and tracking. In this paper, we introduce a new combination consisting of our proposed signal-processing procedures. In the clutter-reduction step, a filtering method that uses a Kalman filter (KF is proposed. Then, in the target detection step, a modification of the conventional CLEAN algorithm which is used to estimate the impulse response from observation region is applied for the advanced elimination of false alarms. Then, the output is fed into the target localization and tracking step, in which the target location and trajectory are determined and tracked by using unscented KF in two-dimensional coordinates. In each step, the proposed methods are compared to conventional methods to demonstrate the differences in performance. The experiments are carried out using actual IR-UWB radar under different scenarios. The results verify that the proposed methods can improve the probability and efficiency of target detection and tracking.

  5. Location Detection and Tracking of Moving Targets by a 2D IR-UWB Radar System

    Van-Han Nguyen; Jae-Young Pyun

    2015-01-01

    In indoor environments, the Global Positioning System (GPS) and long-range tracking radar systems are not optimal, because of signal propagation limitations in the indoor environment. In recent years, the use of ultra-wide band (UWB) technology has become a possible solution for object detection, localization and tracking in indoor environments, because of its high range resolution, compact size and low cost. This paper presents improved target detection and tracking techniques for moving obj...

  6. Location detection and tracking of moving targets by a 2D IR-UWB radar system.

    Nguyen, Van-Han; Pyun, Jae-Young

    2015-01-01

    In indoor environments, the Global Positioning System (GPS) and long-range tracking radar systems are not optimal, because of signal propagation limitations in the indoor environment. In recent years, the use of ultra-wide band (UWB) technology has become a possible solution for object detection, localization and tracking in indoor environments, because of its high range resolution, compact size and low cost. This paper presents improved target detection and tracking techniques for moving objects with impulse-radio UWB (IR-UWB) radar in a short-range indoor area. This is achieved through signal-processing steps, such as clutter reduction, target detection, target localization and tracking. In this paper, we introduce a new combination consisting of our proposed signal-processing procedures. In the clutter-reduction step, a filtering method that uses a Kalman filter (KF) is proposed. Then, in the target detection step, a modification of the conventional CLEAN algorithm which is used to estimate the impulse response from observation region is applied for the advanced elimination of false alarms. Then, the output is fed into the target localization and tracking step, in which the target location and trajectory are determined and tracked by using unscented KF in two-dimensional coordinates. In each step, the proposed methods are compared to conventional methods to demonstrate the differences in performance. The experiments are carried out using actual IR-UWB radar under different scenarios. The results verify that the proposed methods can improve the probability and efficiency of target detection and tracking. PMID:25808773

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

    Forbes, G. S.

    1975-01-01

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

  8. Acoustic Echo Cancellation: Dual Architecture Implementation

    B. Stark

    2010-01-01

    Full Text Available Problem statement: With the rise in mobile communication, it is becoming more frequent to use a communication device in an enclosed noisy environment, such as a subway or in a lobby. In this setting however, the received microphone is severely degraded by the echo from the speaker and background noise. The audio processing necessary to clarify the desired speech can be broken down into two parts, removal of the acoustic echo and removal of the background noise. Approach: This study proposed an ‘external-switched’ algorithm of a dual architecture implementation for acoustic echo cancellation. Using the orthogonality property of adaptive algorithms to detect convergence, two complete adaptive filters can be run in parallel to take advantage of each filter’s particular configuration. By configuring one filter for fast adaptation and the second for minimizing the steady state error, a system can be designed with the advantages of both without suffering from increased computational cost. Results: A slight performance improvement can be demonstrated with this system; however the greatest advantage is in the reduced filter size and calculation cost. Conclusion: This parallel approach is suitable for systems in which a single approach to acoustic echo cancellation is insufficient. Disadvantages of one algorithm can be mitigated by being able to switch to a more effective algorithm seamlessly.

  9. An Echo of Supernova 2008bk

    Van Dyk, Schuyler D

    2013-01-01

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

  10. Implementation Issues for acoustic echo cancellers

    Berkeman, Anders; Öwall, Viktor; Torkelson, Mats

    1999-01-01

    The high computational complexity of acoustic echo cancellation algorithms requires application specific implementations to sustain real time signal processing with affordable power consumption. This is especially true for systems where a delayless approach is considered important, e.g. wireless communication systems. The proposed paper presents architectural considerations to reach a feasible hardware solution.

  11. Echo voltage reflected by turtle on various angles

    Sunardi Sunardi; Anton Yudhana; Azrul Mahfurdz; Sharipah Salwa Mohamed

    2015-01-01

    This research proposes the acoustic measurement by using echo sounder for green turtle detection of 1 year, 12 and 18 years. Various positions or angles of turtles are head, tail, shell, lung, left and right side. MATLAB software and echo sounder are used to analyse the frequency and the response of the turtle as echo voltage and target strength parameter. Based on the experiment and analysis have been conducted, the bigger size of the turtle, the higher echo voltage and target strength. The ...

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

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

    2010-06-15

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

  13. Echo Cancellation II: Double Talk Detection and Environmental Noise Influence

    P. Sovka

    2000-04-01

    Full Text Available Two problems arising in the real-life application of echo cancellationsystems are analysed.The first, simultaneous activity of both telephoneusers (double talk deteriorates the echo suppression. The second,environmental noise is the crucial point in echo cancellation systemapplications. Experimental evaluation of the influence of bothphenomena is given together with possible solution.

  14. Vibration sensors

    These sensors, which aim is the surveillance of the fast breeder reactor internal structure, were designed considering the following requirements: - long term utilization under low frequencies conditions (1 to 50 Hz) and detection of accelerations lower than 0,01 g, - operation with a temperature up to 6000C and receiving important neutron and gamma flux. Monoaxial sensors with a liquid vibrating mass (sodium) were thus developed, based on the electromagnetic flow meter principles (Faraday effect)

  15. Microscopic imaging of slow flow and diffusion: a pulsed field gradient stimulated echo sequence combined with turbo spin echo imaging

    Scheenen, T.W.J.; Vergeldt, F.J.; Windt, C.W.; Jager, de P.A.; As, van H.

    2001-01-01

    In this paper we present a pulse sequence that combines a displacement-encoded stimulated echo with rapid sampling of k-space by means of turbo spin echo imaging. The stimulated echo enables the use of long observation times between the two pulsed field gradients that sample q-space completely. Prop

  16. Anharmonicities and coherent vibrational dynamics of phosphate ions in bulk H2O.

    Costard, Rene; Tyborski, Tobias; Fingerhut, Benjamin P

    2015-11-28

    Phosphates feature prominently in the energetics of metabolism and are important solvation sites of DNA and phospholipids. Here we investigate the ion H2PO4(-) in aqueous solution combining 2D IR spectroscopy of phosphate stretching vibrations in the range from 900-1300 cm(-1) with ab initio calculations and hybrid quantum-classical molecular dynamics based simulations of the non-linear signal. While the line shapes of diagonal peaks reveal ultrafast frequency fluctuations on a sub-100 fs timescale caused by the fluctuating hydration shell, an analysis of the diagonal and cross-peak frequency positions allows for extracting inter-mode couplings and anharmonicities of 5-10 cm(-1). The excitation with spectrally broad pulses generates a coherent superposition of symmetric and asymmetric PO2(-) stretching modes resulting in the observation of a quantum beat in aqueous solution. We follow its time evolution through the time-dependent amplitude and the shape of the cross peaks. The results provide a complete characterization of the H2PO4(-) vibrational Hamiltonian including fluctuations induced by the native water environment. PMID:26488541

  17. Features of underwater echo extraction based on signal sparse decomposition

    YANG Bo; BU Yinyong; ZHAO Haiming

    2012-01-01

    In order to better realize sound echo recognition of underwater materials with heavily uneven surface, a features abstraction method based on the theory of signal sparse decomposition has been proposed. Instead of the common time frequency dictionary, sets of training echo samples are used directly as dictionary to realize echo sparse decomposition under L1 optimization and abstract a kind of energy features of the echo. Experiments on three kinds of bottom materials including the Cobalt Crust show that the Fisher distribution with this method is superior to that of edge features and of Singular Value Decomposition (SVD) features in wavelet domain. It means no doubt that much better classification result of underwater bottom materials can be obtained with the proposed energy features than the other two. It is concluded that echo samples used as a dictionary is feasible and the class information of echo introduced by this dictionary can help to obtain better echo features.

  18. Workshop on neutron spin-echo

    Aynajian, P.; Habicht, K.; Keller, Th.; Keimer, B.; Mezei, F.; Monkenbusch, M.; Allgaier, J.; Richter, D.; Fetters, L.J.; Muller, K.; Kreiling, S.; Dehnicke, K.; Greiner, A.; Ehlers, G.; Arbe, A.; Colmenero, J.; Richter, D.; Farago, B.; Monkenbusch, M.; Ohl, M.; Butzek, M.; Kozielewski, T.; Monkenbusch, M.; Richter, D.; Pappas, C.; Hillier, A.; Manuel, P.; Cywinski, R.; Bentley, P.; Alba, M.; Mezei, F.; Campbell, I.A.; Zimmermann, U.; Ellis, J.; Jobic, H.; Pickup, R.M.; Pappas, C.; Farago, B.; Cywinski, R.; Haussler, W.; Holderer, O.; Frielinghaus, H.; Byelov, D.; Monkenbusch, M.; Allgaier, J.; Richter, D.; Egger, H.; Hellweg, Th.; Malikova, N.; Cadene, A.; Marry, V.; Dubois, E.; Turq, P.; Gardner, J.S.; Ehlers, G.; Bramwell, St.S.; Grigoriev, S.; Kraan, W.; Rekveldt, T.; Bouwman, W.; Van Dijk, N.; Falus, P.; Vorobiev, A.; Major, J.; Felcher, G.P.; Te-velthuis, S.; Dosch, H.; Vorobiev, A.; Dridi, M.H.; Major, J.; Dosch, H.; Falus, P.; Felcher, G.P.; Te Velthuis, S.G.E.; Bleuel, M.; Broell, M.; Lang, E.; Littrell, K.; Gahler, R.; Lal, J.; Lauter, H.; Toperverg, B.; Lauter, V.; Jernenkov, M.; Stueber, S.; Enderle, M.; Janoschek, M.; Keller, Th.; Klimko, S.; Boeni, P.; Nagao, M.; Yamada, N.; Kawabata, Y.; Seto, H.; Takeda, T.; Yoshizawa, H.; Yoshida, K.; Yamaguchi, T.; Bellissent-Funel, M.C.; Longeville, St

    2005-07-01

    This document gathers the abstracts of most papers presented at the workshop. Neutron spin-echo (NSE) spectroscopy is a well established technique with a growing expert user community, the aim of the meeting was to discuss the latest achievements in neutron spin-echo science and instrumentation. One of the applications presented is the investigation on the microscopic scale of the dynamics of water in montmorillonite clays with Na{sup +} and Cs{sup +} ions in monolayer and bilayer states. The NSE technique has been used in the normal and resonance modes. NSE results show consistently slower dynamics (higher relaxation times) than both time-of-flight technique (TOF) and classical molecular dynamics simulations (MD). In the present TOF and NSE experiments, anisotropy of the water motion in the interlayer is almost impossible to detect, due to the use of powder samples and insufficient resolution. (A.C.)

  19. Wind Shear Target Echo Modeling and Simulation

    Xiaoyang Liu

    2015-01-01

    Full Text Available Wind shear is a dangerous atmospheric phenomenon in aviation. Wind shear is defined as a sudden change of speed or direction of the wind. In order to analyze the influence of wind shear on the efficiency of the airplane, this paper proposes a mathematical model of point target rain echo and weather target signal echo based on Doppler effect. The wind field model is developed in this paper, and the antenna model is also studied by using Bessel function. The spectrum distribution of symmetric and asymmetric wind fields is researched by using the mathematical model proposed in this paper. The simulation results are in accordance with radial velocity component, and the simulation results also confirm the correctness of the established model of antenna.

  20. Workshop on neutron spin-echo

    This document gathers the abstracts of most papers presented at the workshop. Neutron spin-echo (NSE) spectroscopy is a well established technique with a growing expert user community, the aim of the meeting was to discuss the latest achievements in neutron spin-echo science and instrumentation. One of the applications presented is the investigation on the microscopic scale of the dynamics of water in montmorillonite clays with Na+ and Cs+ ions in monolayer and bilayer states. The NSE technique has been used in the normal and resonance modes. NSE results show consistently slower dynamics (higher relaxation times) than both time-of-flight technique (TOF) and classical molecular dynamics simulations (MD). In the present TOF and NSE experiments, anisotropy of the water motion in the interlayer is almost impossible to detect, due to the use of powder samples and insufficient resolution. (A.C.)

  1. The EChO science case

    Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul;

    2015-01-01

    as possible, to probe the thermal structure of the planetary atmospheres and to correct for the contaminating effects of the stellar photosphere. This requires wavelength coverage of at least 0.55 to 11 μm with a goal of covering from 0.4 to 16 μm. Only modest spectral resolving power is needed, with...... systems work and what causes the exceptional diversity observed as compared to the Solar System? The EChO (Exoplanet Characterisation Observatory) space mission was conceived to take up the challenge to explain this diversity in terms of formation, evolution, internal structure and planet and atmospheric...... composition. This requires in-depth spectroscopic knowledge of the atmospheres of a large and well-defined planet sample for which precise physical, chemical and dynamical information can be obtained. In order to fulfil this ambitious scientific program, EChO was designed as a dedicated survey mission for...

  2. The EChO science case

    Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul; Hartogh, Paul; Isaak, Kate; Linder, Martin; Lovis, Christophe; Micela, Giusi; Ollivier, Marc; Puig, Ludovic; Ribas, Ignasi; Gear, W.; Gesa, L; Giani, E.; Gianotti, F

    2015-01-01

    The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? What causes the exceptional diversity observed as compared to the Solar System? EChO (Exoplanet Characterisation Observatory) has b...

  3. Echoes of Sophocles's Antigone in Auster's Invisible

    Waller, Kathleen

    2011-01-01

    In her article "Echoes of Sophocles's Antigone in Auster's Invisible" Kathleen Waller discusses Paul Auster's Invisible, a novel that explores Deleuze's and Guattari's ontological idea of becoming in a virtual world versus merely living in the actual, physical world. Sexual and immortal desires in the protagonist's virtual world show a near achieved nothingness, or "a space which is unlimited" and filled with the being's energy, and a being who is becoming, a "univocal being" as a "free spiri...

  4. GESTATIONAL ECHO BIOMETRY IN BRACHYCEPHALIC PREGNANT BITCHES

    Marcus Antônio Rossi Feliciano

    2015-07-01

    Full Text Available Ultrasonography is an accurate pregnancy diagnostic method, besides being completely innocuous for female and fetuses evaluation. The objective of this paper was to determine the reference values for gestational echo biometry of different breeds of bitches. A total of 25 multiparous females were included in the experiment, five English Bulldog bitches, five Pugs and 15 Shih Tzu, weighing 4-25 kg and aged 4-6 years. The echo biometric assessments were performed during the 2nd, 5th, 6th, 7th and 8th weeks of pregnancy, including gestational vesicle diameter, femur length, placenta thickness, parietal diameter, liver, heart and abdominal diameter and area. Early echo biometric study started at the second week of gestation. Measurements like fetal heart and liver diameter and area are still poorly studied, but can provide useful information for early detection of congenital anomalies that may reduce the viability of pregnancy. The significant results (P < 0.001 obtained for biometrics (P < 0.001 of the parietal (r2 = 81% and abdominal diameter (r2 = 86%, abdominal area (r2 = 80%, femur length (r2 = 84%, cardiac length (r2 = 79%, width (r2 = 79%, area (r2 = 82% and volume (r2 = 72% and liver area (r2 = 71% in brachycephalic conceptus may help to assess the development of fetuses, complementing the conventional gestational ultrasound of bitches and become a model for the study in other breeds of dogs and alternative animal species.

  5. Single-shot echo-planar imaging of multiple sclerosis: effects of varying echo time

    Our aim was to determine the relative merits of short and long echo times (TE) with single-shot echo-planar imaging for imaging cerebral lesions such as multiple sclerosis. We examined seven patients with clinically definite multiple sclerosis were imaged at 1.5 T. Patients were scanned with spin-echo, single-shot echo-planar imaging, using TEs of 45, 75, 105, and 135 ms. Region of interest (ROI) measurements were performed on 36 lesions at or above the level of the corona radiata. The mean image contrast (IC) was highest (231.1) for a TE of 45 ms, followed by 75 ms (218.9), 105 ms (217.9), and 135 ms (191.6). When mean contrast-to-noise ratios (C/N) were compared, the value was again highest (29.7) for TE 45 ms, followed by 75 ms (28.9), 105 ms (28.5), and 135 ms (26.3). In a lesion-by-lesion comparison, TE 45 ms had the highest IC and C/N in the largest number of cases (50 % and 47.2 %, respectively). IC and C/N for TE 45 ms were superior to those of 75 ms in 64 % and 58 %, respectively. These results support the use of relatively short TEs for single-shot echo-planar imaging in the setting of cerebral lesions such as multiple sclerosis. (orig.) (orig.)

  6. Temperature sheets and aspect sensitive radar echoes

    H. Luce

    Full Text Available here have been years of discussion and controversy about the existence of very thin and stable temperature sheets and their relationship to the VHF radar aspect sensitivity. It is only recently that very high-resolution in situ temperature observations have brought credence to the reality and ubiquity of these structures in the free atmosphere and to their contribution to radar echo enhancements along the vertical. Indeed, measurements with very high-resolution sensors are still extremely rare and rather difficult to obtain outside of the planetary boundary layer. They have only been carried out up to the lower stratosphere by Service d’A´ eronomie (CNRS, France for about 10 years. The controversy also persisted due to the volume resolution of the (Mesosphere-Stratosphere-Troposphere VHF radars which is coarse with respect to sheet thickness, although widely sufficient for meteorological or mesoscale investigations. The contribution within the range gate of many of these structures, which are advected by the wind, and decay and grow at different instants and could be distorted either by internal gravity waves or turbulence fields, could lead to radar echoes with statistical properties similar to those produced by anisotropic turbulence. Some questions thus remain regarding the manner in which temperature sheets contribute to VHF radar echoes. In particular, the zenithal and azimuthal angular dependence of the echo power may not only be produced by diffuse reflection on stable distorted or corrugated sheets, but also by extra contributions from anisotropic turbulence occurring in the stratified atmosphere. Thus, for several years, efforts have been put forth to improve the radar height resolution in order to better describe thin structures. Frequency interferometric techniques are widely used and have been recently further developed with the implementation of high-resolution data processings. We begin by reviewing briefly some characteristics

  7. The EChO science case

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

    2015-12-01

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

  8. EChO. Exoplanet characterisation observatory

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

    2012-10-01

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

  9. Vibration syndrome and vibration in pedestal grinding.

    Starck, J; Färkkilä, M; Aatola, S; Pyykkö, I; Korhonen, O.

    1983-01-01

    At one Finnish foundry all the workers had typical symptoms of vibration induced white finger (VWF) after they began using a new type of pedestal grinding machine. The objectives of this study were to establish the severity of the symptoms and the difference in vibration exposure between the new and the old machines. Vibration detection thresholds and grip forces were measured, as well as the vibration in the casting and in the wrist simultaneously. The mean latency for VWF among the grinders...

  10. Theory of vibration protection

    Karnovsky, Igor A

    2016-01-01

    This text is an advancement of the theory of vibration protection of mechanical systems with lumped and distributed parameters. The book offers various concepts and methods of solving vibration protection problems, discusses the advantages and disadvantages of different methods, and the fields of their effective applications. Fundamental approaches of vibration protection, which are considered in this book, are the passive, parametric and optimal active vibration protection. The passive vibration protection is based on vibration isolation, vibration damping and dynamic absorbers. Parametric vibration protection theory is based on the Shchipanov-Luzin invariance principle. Optimal active vibration protection theory is based on the Pontryagin principle and the Krein moment method. The book also contains special topics such as suppression of vibrations at the source of their occurrence and the harmful influence of vibrations on humans. Numerous examples, which illustrate the theoretical ideas of each chapter, ar...

  11. Echo Cancellation Research of Channel Estimation based on PN Sequence

    Yongqin Zhou

    2010-11-01

    Full Text Available For the problem of estimation sequence effect on channel estimation accuracy and echo cancellation effect, this paper, based on the basic principle of echo cancellation, analyses the effect of PN sequence mechanism and the correlation on the channel estimation parameters. Comparing with using the input signal itself as the estimation sequence. With the input signal OFDM, the results of simulation and actual operation show that the method can increase both the accuracy of channel estimation and echo cancellation effect effectively.

  12. Preprocessing of ionospheric echo Doppler spectra

    FANG Liang; ZHAO Zhengyu; WANG Feng; SU Fanfan

    2007-01-01

    The real-time information of the distant ionosphere can be acquired by using the Wuhan ionospheric oblique backscattering sounding system(WIOBSS),which adopts a discontinuous wave mechanism.After the characteristics of the ionospheric echo Doppler spectra were analyzed,the signal preprocessing was developed in this paper,which aimed at improving the Doppler spectra.The results indicate that the preprocessing not only makes the system acquire a higher ability of target detection but also suppresses the radio frequency interference by 6-7 dB.

  13. Decoherence and Spin Echo in Biological Systems

    Nesterov, Alexander I

    2015-01-01

    The spin echo approach is extended to include bio-complexes for which the interaction with dynamical noise is strong. Significant restoration of the free induction decay signal due to homogeneous (decoherence) and inhomogeneous (dephasing) broadening is demonstrated analytically and numerically, for both an individual dimer of interacting chlorophylls and for an ensemble of dimers. This approach is based on an exact and closed system of ordinary differential equations that can be easily solved for a wide range of parameters that are relevant for bio-applications.

  14. Nuclear spin echo model based on Floquet-Lyapunov theory

    The method of nuclear spin-echo amplitude calculation based on the density matrix technique is improved. The Floquet-Lyapunov theorem for a system of the ordinary differential equations with coefficients periodically dependent on time is used to find the solution of the Schroedinger equation for the time-evolution operator which describes behavior of a nuclear spin in the presence of a radiofrequency pulsed magnetic field. NQR spin echo for the case of nuclear spin I = 1 and NMR spin echo for I = 1/2 are considered as the simplest illustrations of the approach. The appearance of multiple spin echoes is predicted in the case of strong radiofrequency field.

  15. Performance Analysis of Acoustic Echo Cancellation Techniques

    Rajeshwar Dass

    2014-07-01

    Full Text Available Mainly, the adaptive filters are implemented in time domain which works efficiently in most of the applications. But in many applications the impulse response becomes too large, which increases the complexity of the adaptive filter beyond a level where it can no longer be implemented efficiently in time domain. An example of where this can happen would be acoustic echo cancellation (AEC applications. So, there exists an alternative solution i.e. to implement the filters in frequency domain. AEC has so many applications in wide variety of problems in industrial operations, manufacturing and consumer products. Here in this paper, a comparative analysis of different acoustic echo cancellation techniques i.e. Frequency domain adaptive filter (FDAF, Least mean square (LMS, Normalized least mean square (NLMS &Sign error (SE is presented. The results are compared with different values of step sizes and the performance of these techniques is measured in terms of Error rate loss enhancement (ERLE, Mean square error (MSE& Peak signal to noise ratio (PSNR.

  16. The EChO science case

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

    2015-01-01

    The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? What causes the exceptional diversity observed as compared to the Solar System? EChO (Exoplanet Characterisation Observatory) has been designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large and diverse planet sample within its four-year mission lifetime. EChO can target the atmospheres of super-Earths, Neptune-like, and Jupiter-like planets, in the very hot to temperate zones (planet temperatures of 300K-3000K) of F to M-type host stars. Over the next ten years, several new ground- and space-based transit surveys will come on-line (e.g. NGTS, CHEOPS, TESS, PLATO), which will specifically focus on find...

  17. Vibration of machine

    This book deals with vibration of machine which gives descriptions of free vibration using SDOF system, forced vibration using SDOF system, vibration of multi-degree of freedom system like introduction and normal form, distribution system such as introduction, free vibration of bar and practice problem, approximate solution like lumped approximations and Raleigh's quotient, engineering by intuition and experience, real problem and experimental method such as technology of signal, fourier transform analysis, frequency analysis and sensor and actuator.

  18. The EChO science case

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

    2015-12-01

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

  19. Echo Shaping Using Sums of Damped Complex Sinusoids

    Putnam, Lance Jonathan

    2015-01-01

    Feedback delay lines are the basis of myriad audio effects and reverberation schemes. The feedback delay line, by itself, is limited to producing an infinite sequence of exponentially decaying echoes. We introduce a new type of linear time-invariant echo effect whose impulse response is a...

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

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

    2013-01-01

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

  1. Coherent Optical Information Processing Using a Stimulated Echo Hologram

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

    2016-01-01

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

  2. Long-lasting inverted photon echo and optical memory

    Akhmediev, N.N.; Borisov, B.S.; Zuikov, V.A.; Samartsev, V.V.; Stel' makh, M.F.

    1988-06-01

    Experimental results are presented on the formation of the long-lasting inverted stimulated photon echo in the LaF3:Pr(3+) crystal. The physics of this phenomenon is explained on the basis of a three-level model. The feasibility of using this echo effect in the development of optical-memory systems is considered. 18 references.

  3. Myocardial contractility in the stress echo lab: from pathophysiological toy to clinical tool.

    Bombardini, Tonino; Zoppè, Monica; Ciampi, Quirino; Cortigiani, Lauro; Agricola, Eustachio; Salvadori, Stefano; Loni, Tiziana; Pratali, Lorenza; Picano, Eugenio

    2013-01-01

    vibration amplitude. We demonstrated that the sensor-derived force changes at increasing heart rates are highly related with both max dP/dt in animal models, and with the stress echo FFR in 220 humans, opening a new window for pervasive cardiac heart failure monitoring in telemedicine systems. PMID:24246005

  4. Revival of Silenced Echo and Quantum Memory for Light

    Damon, V; Louchet-Chauvet, A; Chanelière, T; Gouët, J -L Le

    2011-01-01

    We propose an original quantum memory protocol. It belongs to the class of rephasing processes and is closely related to two-pulse photon echo. It is known that the strong population inversion produced by the rephasing pulse prevents the plain two-pulse photon echo from serving as a quantum memory scheme. Indeed gain and spontaneous emission generate prohibitive noise. A second $\\pi$-pulse can be used to simultaneously reverse the atomic phase and bring the atoms back into the ground state. Then a secondary echo is radiated from a non-inverted medium, avoiding contamination by gain and spontaneous emission noise. However, one must kill the primary echo, in order to preserve all the information for the secondary signal. In the present work, spatial phase mismatching is used to silence the standard two-pulse echo. An experimental demonstration is presented.

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

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

    2005-12-22

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

  6. Echo chambers in the age of misinformation

    Del Vicario, Michela; Zollo, Fabiana; Petroni, Fabio; Scala, Antonio; Caldarelli, Guido; Stanley, H Eugene; Quattrociocchi, Walter

    2015-01-01

    The wide availability of user-provided content in online social media facilitates the aggregation of people around common interests, worldviews, and narratives. Despite the enthusiastic rhetoric on the part of some that this process generates "collective intelligence", the WWW also allows the rapid dissemination of unsubstantiated conspiracy theories that often elicite rapid, large, but naive social responses such as the recent case of Jade Helm 15 -- where a simple military exercise turned out to be perceived as the beginning of the civil war in the US. We study how Facebook users consume information related to two different kinds of narrative: scientific and conspiracy news. We find that although consumers of scientific and conspiracy stories present similar consumption patterns with respect to content, the sizes of the spreading cascades differ. Homogeneity appears to be the primary driver for the diffusion of contents, but each echo chamber has its own cascade dynamics. To mimic these dynamics, we introdu...

  7. The Electron Capture $^{163}$Ho Experiment ECHo

    Blaum, K; Duellmann, C E; Eberhardt, K; Eliseev, S; Enss, C; Faessler, A; Fleischmann, A; Gastaldo, L; Kempf, S; Krivoruchenko, M; Lahiri, S; Maiti, M; Novikov, Yu N; Ranitzsch, P C -O; Simkovic, F; Szusc, Z; Wegner, M

    2013-01-01

    The determination of the absolute scale of the neutrino masses is one of the most challenging questions in particle physics. Different approaches are followed to achieve a sensitivity on neutrino masses in the sub-eV range. Among them, experiments exploring the beta decay and electron capture processes of suitable nuclides can provide necessary information on the electron neutrino mass value. In this talk we present the Electron Capture 163-Ho experiment ECHo, which aims to investigate the electron neutrino mass in the sub-eV range by means of the analysis of the calorimetrically measured energy spectrum following the electron capture process of 163-Ho. A high precision and high statistics spectrum will be measured by means of low temperature magnetic calorimeter arrays. We present preliminary results obtained with a first prototype of single channel detectors as well as the participating groups and their on-going developments.

  8. Spin Echo Studies on Cellular Water

    Chang, D C; Nichols, B L; Rorschach, H E

    2014-01-01

    Previous studies indicated that the physical state of cellular water could be significantly different from pure liquid water. To experimentally investigate this possibility, we conducted a series of spin-echo NMR measurements on water protons in rat skeletal muscle. Our result indicated that the spin-lattice relaxation time and the spin-spin relaxation time of cellular water protons are both significantly shorter than that of pure water (by 4.3-fold and 34-fold, respectively). Furthermore, the spin diffusion coefficient of water proton is almost 1/2 of that of pure water. These data suggest that cellular water is in a more ordered state in comparison to pure water.

  9. Dual-rail optical gradient echo memory

    Higginbottom, Daniel B; Campbell, Geoff T; Hosseini, Mahdi; Cao, Ming Tao; Sparkes, Ben M; Bernu, Julian; Robins, Nick P; Lam, Ping Koy; Buchler, Ben C

    2016-01-01

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

  10. MR cisternography using 'long echo train length fast spin echo sequence' for demonstrating the inner ear

    Excellent quality of MR cisternography was acquired using 'long echo train length fast spin echo sequence' (TR/TE=2666/200, ETL=24.6 or 8 NEX, 3 mm thickness, 0 mm interslice gap, 19 cm FOV, 512*384, 2 DFT method). The inner ear anatomy such as canaliculus cochleae or lamina spiralis ossea were well visualized. The VII, VIIIth nerve bundles within the internal auditory canal were detectable as 1 to 4 bundles. The vessels in the cerebello-pontine angle or the internal auditory canal were also demarcated from the VII, VIIIth nerve bundles because of their flow void. Signal to noise ratio seemed to be better than 3 DFT method; however, limited spatial resolution in the cranio-caudal direction might require additional sagittal or coronal scan. (author)

  11. Recent Results for the ECHo Experiment

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

    2016-08-01

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

  12. Recent Results for the ECHo Experiment

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

    2016-02-01

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

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

    Piero Chiacchiaretta

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

  14. Do triatomic molecules echo atomic periodicity?

    Hefferlin, R., E-mail: hefferln@southern.edu; Barrow, J. [Southern Adventist University, PO Box 370, Collegedale, Tennessee 37315 (United States)

    2015-03-30

    Demonstrations of periodicity among triatomic-molecular spectroscopic constants underscore the role of the periodic law as a foundation of chemistry. The objective of this work is to prepare for another test using vibration frequencies ν{sub 1} of free, ground-state, main-group triatomic molecules. Using data from four data bases and from computation, we have collected ν{sub 1} data for molecules formed from second period atoms.

  15. Prognostic for hydraulic pump based upon DCT-composite spectrum and the modified echo state network.

    Sun, Jian; Li, Hongru; Xu, Baohua

    2016-01-01

    Prognostic is a key step of the condition-based maintenance (CBM). In order to improve the predicting performance, a novel method for prognostic for the hydraulic pump is proposed in this paper. Based on the improvement of the traditional composite spectrum, the DCT-composite spectrum (DCS) fusion algorithm is initially presented to make fusion of multi-channel vibration signals. The DCS composite spectrum entropy is extracted as the feature. Furthermore, the modified echo state networks (ESN) model is established for prognostic using the extracted feature. The reservoir is updated and the elements of the neighboring matrix are redefined for improving predicting accuracy. Analysis of the application in the hydraulic pump degradation experiment demonstrates that the proposed algorithm is feasible and is meaningful for CBM. PMID:27547667

  16. Nonlinear two-dimensional terahertz photon echo and rotational spectroscopy in the gas phase

    Lu, Jian; Hwang, Harold Y; Ofori-Okai, Benjamin K; Fleischer, Sharly; Nelson, Keith A

    2016-01-01

    Ultrafast two-dimensional spectroscopy utilizes correlated multiple light-matter interactions for retrieving dynamic features that may otherwise be hidden under the linear spectrum. Its extension to the terahertz regime of the electromagnetic spectrum, where a rich variety of material degrees of freedom reside, remains an experimental challenge. Here we report ultrafast two-dimensional terahertz spectroscopy of gas-phase molecular rotors at room temperature. Using time-delayed terahertz pulse pairs, we observe photon echoes and other nonlinear signals resulting from molecular dipole orientation induced by three terahertz field-dipole interactions. The nonlinear time-domain orientation signals are mapped into the frequency domain in two-dimensional rotational spectra which reveal J-state-resolved nonlinear rotational dynamics. The approach enables direct observation of correlated rotational transitions and may reveal rotational coupling and relaxation pathways in the ground electronic and vibrational state.

  17. Vibrations and Stability

    Thomsen, Jon Juel

    About this textbook An ideal text for students that ties together classical and modern topics of advanced vibration analysis in an interesting and lucid manner. It provides students with a background in elementary vibrations with the tools necessary for understanding and analyzing more complex...... dynamical phenomena that can be encountered in engineering and scientific practice. It progresses steadily from linear vibration theory over various levels of nonlinearity to bifurcation analysis, global dynamics and chaotic vibrations. It trains the student to analyze simple models, recognize nonlinear...... and physics. This edition includes a new chapter on the useful effects of fast vibrations and many new exercise problems. Written for: Students in mechanical or structural engineering. Keywords: Nonlinear Vibrations, Bifurcations, Chaotic Vibrations, Vibrations and Stability....

  18. A comparison of multi-echo spin-echo and triple-echo steady-state T2 mapping for in vivo evaluation of articular cartilage

    Juras, Vladimir; Szomolanyi, Pavol [Medical University of Vienna, High Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Vienna (Austria); Institute of Measurement Science, Department of Imaging Methods, Bratislava (Slovakia); Bohndorf, Klaus; Kronnerwetter, Claudia; Hager, Benedikt; Zbyn, Stefan [Medical University of Vienna, High Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Vienna (Austria); Heule, Rahel; Bieri, Oliver [University of Basel Hospital, Division of Radiological Physics, Department of Radiology, Basel (Switzerland); Trattnig, Siegfried [Medical University of Vienna, High Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Vienna (Austria); Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna (Austria); Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Austrian Cluster for Tissue Regeneration, Vienna (Austria)

    2016-06-15

    To assess the clinical relevance of T{sub 2} relaxation times, measured by 3D triple-echo steady-state (3D-TESS), in knee articular cartilage compared to conventional multi-echo spin-echo T{sub 2}-mapping. Thirteen volunteers and ten patients with focal cartilage lesions were included in this prospective study. All subjects underwent 3-Tesla MRI consisting of a multi-echo multi-slice spin-echo sequence (CPMG) as a reference method for T{sub 2} mapping, and 3D TESS with the same geometry settings, but variable acquisition times: standard (TESSs 4:35min) and quick (TESSq 2:05min). T{sub 2} values were compared in six different regions in the femoral and tibial cartilage using a Wilcoxon signed ranks test and the Pearson correlation coefficient (r). The local ethics committee approved this study, and all participants gave written informed consent. The mean quantitative T{sub 2} values measured by CPMG (mean: 46±9ms) in volunteers were significantly higher compared to those measured with TESS (mean: 31±5ms) in all regions. Both methods performed similarly in patients, but CPMG provided a slightly higher difference between lesions and native cartilage (CPMG: 90ms→61ms [31%],p=0.0125;TESS 32ms→24ms [24%],p=0.0839). 3D-TESS provides results similar to those of a conventional multi-echo spin-echo sequence with many benefits, such as shortening of total acquisition time and insensitivity to B{sub 1} and B{sub 0} changes. (orig.)

  19. Vibrational Spectroscopy and Dynamics of Water.

    Perakis, Fivos; Marco, Luigi De; Shalit, Andrey; Tang, Fujie; Kann, Zachary R; Kühne, Thomas D; Torre, Renato; Bonn, Mischa; Nagata, Yuki

    2016-07-13

    We present an overview of recent static and time-resolved vibrational spectroscopic studies of liquid water from ambient conditions to the supercooled state, as well as of crystalline and amorphous ice forms. The structure and dynamics of the complex hydrogen-bond network formed by water molecules in the bulk and interphases are discussed, as well as the dissipation mechanism of vibrational energy throughout this network. A broad range of water investigations are addressed, from conventional infrared and Raman spectroscopy to femtosecond pump-probe, photon-echo, optical Kerr effect, sum-frequency generation, and two-dimensional infrared spectroscopic studies. Additionally, we discuss novel approaches, such as two-dimensional sum-frequency generation, three-dimensional infrared, and two-dimensional Raman terahertz spectroscopy. By comparison of the complementary aspects probed by various linear and nonlinear spectroscopic techniques, a coherent picture of water dynamics and energetics emerges. Furthermore, we outline future perspectives of vibrational spectroscopy for water researches. PMID:27096701

  20. Survey of Sparse Adaptive Filters for Acoustic Echo Cancellation

    Krishna Samalla

    2013-01-01

    Full Text Available This paper reviews the existing developments of adaptive methods of sparse adaptive filters for the identification of sparse impulse response in both network and acoustic echo cancellation from the last decade. A variety of different architectures and novel training algorithms have been proposed in literature. At present most of the work in echo cancellation on using more than one method. Sparse adaptive filters take the advantage of each method and showing good improvement in the sparseness measure performance. This survey gives an overview of existing sparse adaptive filters mechanisms and discusses their advantages over the traditional adaptive filters developed for echo cancellation.

  1. First HF radar measurements of summer mesopause echoes at SURA

    A. N. Karashtin

    Full Text Available HF sounding of the mesosphere was first carried out at SURA in summer 1994 at frequencies in the range 8–9 MHz using one of the sub-arrays of the SURA heating facility. The observations had a range resolution of 3 km. Almost all measurements indicated the presence of strong radar returns from altitudes between 83 and 90 km with features very similar to VHF measurements of mesopause summer echoes at mid-latitudes and polar mesopause summer echoes. In contrast to VHF observations, HF mesopause echoes are almost always present.

  2. Vibration of plates

    Chakraverty, Snehashish

    2008-01-01

    Plates are integral parts of most engineering structures and their vibration analysis is required for safe design. This work provides a comprehensive introduction to vibration theory and analysis of two-dimensional plates. It offers information on vibration problems along with a discussion of various plate geometries and boundary conditions.

  3. Quaternion-valued echo state networks.

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

    2015-04-01

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

  4. Measuring Light Echos in NGC 4051

    Turner, Tracey Jane; Reeves, James N; Braito, Valentina

    2016-01-01

    We have analyzed five archived X-ray observations of NGC~4051 taken using the NuSTAR observatory. The data show lags between flux variations in bands of different X-ray photon energy. In all pairs of bands compared, the harder band consistently lags the softer band by at least 1000s, at temporal frequencies ~5 x 10^-5 Hz. In addition, soft-band lags up to 400s are measured at temporal frequencies ~2 x 10^-4 Hz. Light echos from the inner accretion disk cannot explain the lags in these data, as a sharp soft-band lag is seen in cross-correlations where the softer band is expected to have no contribution from reflection. We find a simple top hat model to be consistent with the response function producing the reprocessed signal. The scattered fraction of X-rays is high, indicating the reprocessor to have a global covering fraction ~50% around the continuum source. The scattered fraction increases with increasing photon energy, while the maximum time delay decreases. Such a scenario may be explained by a higher fr...

  5. Loschmidt echo and time reversal in complex systems.

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

    2016-06-13

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

  6. Classification of Underwater Target Echoes Based on Auditory Perception Characteristics

    Xiukun Li; Xiangxia Meng; Hang Liu; Mingye Liu

    2014-01-01

    In underwater target detection, the bottom reverberation has some of the same properties as the target echo, which has a great impact on the performance. It is essential to study the difference between target echo and reverberation. In this paper, based on the unique advantage of human listening ability on objects distinction, the Gammatone filter is taken as the auditory model. In addition, time-frequency perception features and auditory spectral features are extracted for active sonar target echo and bottom reverberation separation. The features of the experimental data have good concentration characteristics in the same class and have a large amount of differences between different classes, which shows that this method can effectively distinguish between the target echo and reverberation.

  7. Rotary echos for the preservation of quantum memories

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

    2011-05-01

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

  8. Loschmidt echo and time reversal in complex systems

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

    2016-01-01

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

  9. Vibration of hydraulic machinery

    Wu, Yulin; Liu, Shuhong; Dou, Hua-Shu; Qian, Zhongdong

    2013-01-01

    Vibration of Hydraulic Machinery deals with the vibration problem which has significant influence on the safety and reliable operation of hydraulic machinery. It provides new achievements and the latest developments in these areas, even in the basic areas of this subject. The present book covers the fundamentals of mechanical vibration and rotordynamics as well as their main numerical models and analysis methods for the vibration prediction. The mechanical and hydraulic excitations to the vibration are analyzed, and the pressure fluctuations induced by the unsteady turbulent flow is predicted in order to obtain the unsteady loads. This book also discusses the loads, constraint conditions and the elastic and damping characters of the mechanical system, the structure dynamic analysis, the rotor dynamic analysis and the system instability of hydraulic machines, including the illustration of monitoring system for the instability and the vibration in hydraulic units. All the problems are necessary for vibration pr...

  10. Performance Evaluation of Adaptive Filters Structures for Acoustic Echo Cancellation

    Sanjeev Dhull

    2011-05-01

    Full Text Available We have designed and simulated an acoustic echo cancellation system for conferencing. This system is based upon a least-mean-square (LMS adaptive algorithm and uses multi filter technique. A comparative study of both structure has been carried out and it is found that this new multi-filter converge faster than similar single long adaptive filter. Index Terms: LMS,Multiple sub filter ,Echo cancellation

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

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

    2010-05-23

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

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

    Cui, Hongyan; Liu, Xiang; Li, Lixiang

    2012-09-01

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

  13. Multiple photon-echo rephasing of coherent matter waves

    Pan, Ruizhi; Yue, Xuguang; Xu, Xia; Lu, Haichang; Zhou, Xiaoji, E-mail: xjzhou@pku.edu.cn

    2015-03-20

    We investigate the multiple photon echo processes in a Bose–Einstein condensate (BEC) with inhomogeneous momentum broadening. By applying Bragg pulses with adjusted frequency mismatch to induce multiple rephasing, the BEC satisfies the coherence condition for successive superradiance. The atomic system can be efficiently transferred to a high momentum state step by step and emits multiple photon echo signals. These echo signals as a sequence show increasing widths and descending peaks, reflecting a residual dephasing effect due to kinetic-energy phase discrepancy during the population inversions. Our work may contribute to the coherence maintenance for ultracold atomic gas in the quantum information area and the high-precision measurement of atomic momentum width. - Highlights: • A multipulse protocol to induce multiple photon echo rephasing of a BEC is proposed. • Our method is a new and efficient way to transfer the BEC to high momentum modes. • Our method can extend a BEC's coherence time. • The echo sequence is analyzed to study the residual dephasing effect. • The echo decaying is useful in high-precision measurement of BEC's momentum width.

  14. Wavelets for ultrasonic echo identification in aircraft fuel tanks

    Sadok, Mokhtar

    2002-03-01

    Recently, Goodrich Corp.- Fuels and Utility systems Division, has launched a research effort to investigate various sensing and computing techniques to gauge fuel in commercial and military aircrafts. Ultrasonics are among other techniques that were tested for such purpose. Generally, in ultrasonic fuel measurement systems, a transducer is excited to create sonic bursts into fuel and measure reflected echo off the fuel surface. A fixed target or pin is usually disposed at a fixed and predetermined distance from the ultrasonic transducer within the tank so as to compute the speed of sound through across fuel in the tank. Knowing the speed of sound in fuel and being able to measure the round trip time from when an ultrasonic burst is generated until its reflected off the fuel surface, the fuel height may be calculated. With a priori knowledge of the tank geometry, the fuel quantity can be estimated. This measurement process seems straightforward. A problem however is being able to discriminate between echoes reflected off various objects within the tank. In particular, it is crucial to discriminate among echoes reflected off various objects within the tank. In particular, it is crucial to discriminate among echoes reflected off the fuel surface and echoes reflected off other object withhin the tank, like the fixed target or tank sides. This paper presents a discrimination method based on wavelets to assign various ultrasonic echoes to their appropriate reflective surfaces.

  15. Velocities of auroral coherent echoes at 12 and 144 MHz

    A. V. Koustov

    Full Text Available Two Doppler coherent radar systems are currently working at Hankasalmi, Finland, the STARE and CUTLASS radars operating at ~144 MHz and ~12 MHz, respectively. The STARE beam 3 is nearly co-located with the CUTLASS beam 5, providing an opportunity for echo velocity comparison along the same direction but at significantly different radar frequencies. In this study we consider an event when STARE radar echoes are detected at the same ranges as CUT-LASS radar echoes. The observations are complemented by EISCAT measurements of the ionospheric electric field and electron density behaviour at one range of 900 km. Two separate situations are studied; for the first one, CUTLASS observed F-region echoes (including the range of the EIS-CAT measurements, while for the second one CUTLASS observed E-region echoes. In both cases STARE E-region measurements were available. We show that F-region CUT-LASS velocities agree well with the convection component along the CUTLASS radar beam, while STARE velocities are typically smaller by a factor of 2–3. For the second case, STARE velocities are found to be either smaller or larger than CUTLASS velocities, depending on the range. Plasma physics of E-and F-region irregularities is discussed in attempt to explain the inferred relationship between various velocities. Special attention is paid to ionospheric refraction that is important for the detection of 12-MHz echoes.

    Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; auroral ionosphere

  16. Multiple photon-echo rephasing of coherent matter waves

    We investigate the multiple photon echo processes in a Bose–Einstein condensate (BEC) with inhomogeneous momentum broadening. By applying Bragg pulses with adjusted frequency mismatch to induce multiple rephasing, the BEC satisfies the coherence condition for successive superradiance. The atomic system can be efficiently transferred to a high momentum state step by step and emits multiple photon echo signals. These echo signals as a sequence show increasing widths and descending peaks, reflecting a residual dephasing effect due to kinetic-energy phase discrepancy during the population inversions. Our work may contribute to the coherence maintenance for ultracold atomic gas in the quantum information area and the high-precision measurement of atomic momentum width. - Highlights: • A multipulse protocol to induce multiple photon echo rephasing of a BEC is proposed. • Our method is a new and efficient way to transfer the BEC to high momentum modes. • Our method can extend a BEC's coherence time. • The echo sequence is analyzed to study the residual dephasing effect. • The echo decaying is useful in high-precision measurement of BEC's momentum width

  17. Evaluation of spatial resolution on fast spin-echo images. Effect of echo train length and interecho spacing

    Fast spin echo (FSE) imaging technique has been indispensable in clinical MRI. This technique reduces acquisition time compared with conventional spin echo sequences. However, this technique introduces new factors, such as echo train length (ETL) and interecho spacing and is susceptible to a new set of artifacts, such as image blurring secondary to nonuniform sampling of K-space. Therefore, the effects of spatial resolution of FSE images on echo train length and interecho spacing were measured using the final MTF. FSE images of the chart phantom with some ETLs and bandwidth were exposed on laser films and measured by micro-densitometer in the phase-encoding direction. Using the final MTF method, the FSE images were evaluated for spatial resolution. Increasing ETL reduced spatial resolution on FSE images. The proton-density-weighted images were more conspicuous. Decreasing the bandwidth reduced spatial resolution on FSE images because of increasing interecho spacing. (author)

  18. LRS data processing methods for detection of lunar subsurface echoes

    Oshigami, Shoko; Mochizuki, Kengo; Watanabe, Shiho; Watanabe, Toshiki; Yamaguchi, Yasushi; Yamaji, Atsushi; Ono, Takayuki; Kumamoto, Atsushi; Nakagawa, Hiromu; Kobayashi, Takao; Kasahara, Yoshiya

    Lunar Radar Sounder (LRS) is an instrument for one of fifteen science missions of SE- LENE (KAGUYA). LRS is a ground-penetrating FM-CW radar system of HF-band. LRS detects echoes reflected from subsurface discontinuities where dielectric constants of the rocks change. The range resolution of LRS is 75 m in free space, whereas the sampling interval in the flight direction is about 75 m when the spacecraft altitude is 100 km. The primary objective of LRS is to investigate lunar subsurface structures. We plan to perform global soundings by LRS to contribute to studying the evolution of the Moon. In this presentation, we introduce the techniques to process LRS data to produce data products and to detect subsurface echoes. We have two standard data products of LRS under consideration. The time series data of ‘A-scope' which is a plot of signal power spectrum as a function of range derived from of the waveform data are called ‘B-scan'. Because LRS instruments change timing of data recording (measurement delay time) according to the predicted distance between KAGUYA spacecraft and lunar surface, observation range with respect to the spacecraft varies from pulse to pulse. In addition, flight altitude of KAGUYA changes in the range of several tens of kilometers. Therefore a trace of surface nadir echoes in unprocessed B-scan images does not correspond to actual lunar topography. We corrected variations of the measurement delay time and flight altitude of KAGUYA to produce a B-scan data product with the original spatial resolution (BScan high) and a reduced spatial resolution product (BScan low) both in the PDS format. The echo signals in A-scope data might be classified in the following categories; (1) a surface nadir echo, (2) surface off-nadir backscattering echoes, and (3) subsurface echoes. The most intense signal usually comes from the nadir point, when KAGUYA is flying over a level surface. The A-scope data also include various noises resulted from, for example

  19. Fast spin echo vs conventional spin echo in cervical spine imaging

    The major attraction of fast-spin-echo (FSE) imaging is reduced acquisition time; however, careful review of the literature reveals many weaknesses: phase-encoded blurring, truncation artefact, bright fat signal, reduced magnetic susceptibility and increased motion artefact. Our aim was a prospective, blinded comparison of FSE and conventional spin echo (CSE) in the cervical spine. Both sequences were performed in 43 patients (19 males and 24 females; mean age 45 years, range 15-66 years). Twenty-eight patients were studied at 1.5 T and 15 at 0.5 T. Typical sequence parameters were: at 1.5 T, TR/TE 2000/90 CSE and 3000/120 FSE, and at 0.5 T, 2200/80 CSE and 2800/120 FSE. Time saved on the FSE was used to increase the matrix and the number of acquisitions. Two neuroradiologists evaluated the images for pathology, artefacts, disc signal intensity, thecal sac compression and image quality. Ten patients had cord lesions; 2 (20%) were missed on CSE. In 4 of 10 patients with moderate/severe thecal sac compression, the degree of stenosis was apparently exaggerated on CSE. The mean degree of confidence for the CSE sequences was 1.8 and for the FSE 1.1, where 1 is optimal. For cervical spine imaging, FSE should be preferred to CSE. (orig.). With 3 figs

  20. About AGN ionization echoes, thermal echoes, and ionization deficits in low redshift Lyman-alpha blobs

    Schirmer, Mischa; Levenson, Nancy A; Fu, Hai; Davies, Rebecca L; Keel, William C; Torrey, Paul; Bennert, Vardha N; Pancoast, Anna; Turner, James E H

    2016-01-01

    We report the discovery of 14 Lyman-alpha blobs (LABs) at z~0.3, existing at least 4-7 billion years later in the Universe than all other LABs known. Their optical diameters are 20-70 kpc, and GALEX data imply Ly-alpha luminosities of (0.4-6.3)x10^43 erg/s. Contrary to high-z LABs, they live in low-density areas. They are ionized by AGN, suggesting that cold accretion streams as a power source must deplete between z=2 and z=0.3. We also show that transient AGN naturally explain the ionization deficits observed in many LABs: Their Ly-alpha and X-ray fluxes decorrelate below 10^6 years because of the delayed escape of resonantly scattering Ly-alpha photons. High Ly-alpha luminosities do not require currently powerful AGN, independent of obscuration. Chandra X-ray data reveal intrinsically weak AGN, confirming the luminous optical nebulae as impressive ionization echoes. For the first time, we also report mid-infrared thermal echoes from the dusty tori. We conclude that the AGN have faded by 3-4 orders of magnit...

  1. A Pilot Validation of Multi-Echo Based Echo-Planar Correlated Spectroscopic Imaging in Human Calf Muscles

    Furuyama, JK; R. Nagarajan; Roberts, CK; Lee, CC; Hahn, TJ; Thomas, MA

    2014-01-01

    A current limitation of MR spectroscopic imaging of multiple skeletal muscles is prolonged scan duration. A significant reduction in the total scan duration using the echo-planar correlated spectroscopic imaging (EP-COSI) sequence was accomplished using two bipolar readout trains with different phase-encoded echoes for one of two spatial dimensions within a single repetition time (TR). The second bipolar readout was used for spatially encoding the outer k-space, whereas the first readout was ...

  2. Landau damping and the echo effect in a confined Bose-Einstein condensate

    Kuklov, A. B.

    1998-01-01

    Low energy collective mode of a confined Bose-Einstein condensate should demonstrate the echo effect in the regime of Landau damping. This echo is a signature of reversible nature of Landau damping. General expression for the echo profile is derived in the limit of small amplitudes of the external pulses. Several universal features of the echo are found. The existence of echo in other cases of reversible damping -- Fano effect and Caldeira-Leggett model -- is emphasized. It is suggested to te...

  3. Coherent radar imaging of mesosphere summer echoes: Influence of radar beam pattern and tilted structures on atmospheric echo center

    Chen, Jenn-Shyong; Hoffmann, Peter; Zecha, Marius; Hsieh, Cheng-Hsiung

    2008-02-01

    Multiple echo centers of a mesosphere-summer-echo layer (MSE) observed by the six-receiver OSWIN VHF radar (54.1°N, 11.8°E) were examined with the coherent radar imaging (CRI) technique. The data were collected by different observational modes: vertical and oblique radar beams with the receiving configurations of 3 × 2, 6 × 1 (meridional alignment) and 1 × 6 (zonal alignment) antenna groups. The unique receiving configurations of meridional and zonal aligned antenna groups reveal that the echo centers clustered in three distinct groups above the range height of ˜86 km. The central group of echo centers was around the direction of radar beam; however, the off-zenith angles of the two side groups, ranging between several and 20 degrees, increased with ascendant range height. Two potential causes of the echoes in the two side groups were examined on the basis of simulation calculation, namely, tilted structures in the layer and additionally, the influence of radar beam pattern. It is indicated that some echoes, originating from the lower part (˜86 km) at larger off-zenith angles. The tilted structures, which are considered to be related to wave activities, can also produce the features similar to the observations. This is demonstrated by simulation calculation with wavy reflecting layers, in which the waves are supposed to modulate the multiple reflecting layers, with increasing amplitudes, tilted shapes, asynchronous phases, and horizontal travel.

  4. Research on key technologies of LADAR echo signal simulator

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

    2015-10-01

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

  5. Bandshapes in vibrational spectroscopy

    A detailed account is given of the development of modern bandshape theories since 1965. An investigation into the relative contributions of statistical irreversible relaxation processes is described, for a series of molecules in which gradually the length of one molecular axis is increased. An investigation into the theoretical and experimental investigation of the broadening brought about by the effect of fluctuating intermolecular potentials on the vibrational frequency is also described. The effect of an intermolecular perturbative potential on anharmonic and Morse oscillators is discussed and the results are presented of a computation on the broadening of the vibrational band of some diatomic molecules in a rigid lattice type solvent. The broadening of the OH-stretching vibration in a number of aliphatic alcohols, the vibrational bandshapes of the acetylenic C-H stretching vibration and of the symmetric methyl stretching vibration are investigated. (Auth./ C.F.)

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

    Xu, Lijun; Li, Duan; Li, Xiaolu

    2016-01-01

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

  7. Vibrational properties of uracil

    WANG Zhiping; ZHANG Fengshou; ZENG Xianghua; ZHOU Hongyu; GU Bin; CHENG Wei

    2006-01-01

    A semiempirical molecular dynamics model is developed to study the vibrational frequencies of uracil at very low kinetic temperature by using the Fourier transform of velocity autocorrelation function of trajectories of molecular dynamics simulations. The finite difference harmonic method is used to assign the vibrational frequency of each mode. The calculated frequencies are found to be in good agreement with experimental measurements. Moreover, we make up for the lost vibrational modes in experiments self-consistently. A total of 30 vibrational modes and their corresponding frequencies are reported.

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

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

    1986-05-01

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

  9. E-region echo characteristics governed by auroral arc electrodynamics

    S. E. Milan

    Full Text Available Observations of a pair of auroral arc features by two imagers, one ground- and one space-based, allows the associated field-aligned current (FAC and electric field structure to be inferred. Simultaneous observations of HF radar echoes provide an insight into the irregularity-generating mechanisms. This is especially interesting for the E-region echoes observed, which form the focus of our analysis, and from which several conclusions can be drawn, summarized as follows. Latitudinal variations in echo characteristics are governed by the FAC and electric field background. Particularly sharp boundaries are found at the edges of auroral arcs. Within regions of auroral luminosity, echoes have Doppler shifts below the ion-acoustic speed and are proportional to the electric field, suggesting scatter from gradient drift waves. Regions of downward FAC are associated with mixed high and low Doppler shift echoes. The high Doppler shift component is greatly in excess of the ion-acoustic speed, but seems to be commensurate with the driving electric field. The low Doppler shift component appears to be much depressed below expectations.

    Key words. Ionosphere (ionospheric irregularities; electric fields and currents

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

    Mor, Etai; Aladjem, Mayer; Azoulay, Amnon

    2015-02-01

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

  11. Mechanical vibration and shock analysis, sinusoidal vibration

    Lalanne, Christian

    2014-01-01

    Everything engineers need to know about mechanical vibration and shock...in one authoritative reference work! This fully updated and revised 3rd edition addresses the entire field of mechanical vibration and shock as one of the most important types of load and stress applied to structures, machines and components in the real world. Examples include everything from the regular and predictable loads applied to turbines, motors or helicopters by the spinning of their constituent parts to the ability of buildings to withstand damage from wind loads or explosions, and the need for cars to m

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

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

    1995-06-01

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

  13. On the theory of proton solid echo in polymer melts

    Fatkullin, N; Mattea, C; Stapf, S

    2015-01-01

    Based on a modified Anderson-Weiss approximation (N. Fatkullin, A. Gubaidullin, C. Mattea, S.Stapf, J. Chem. Phys. 137 (2012), 224907) an improved theory of proton spin solid echo in polymer melts is formulated, taking into account contribution from intermolecular magnetic dipole-dipole interactions. The solid echo build-up function defined by the relation , where , and are the respective signals arising from ( ),( ) and ( ) spin echo experiments, where is an operator rotating the spin system on the angle relatively axis , is investigated. It is shown that the intermolecular part of this function at short times , where is a characteristic time for flip-flop transitions between proton spins, contains information about the relative mean squared displacements of polymer segments at different macromolecules, opening up a new opportunity for obtaining information about polymer dynamics in the millisecond regime.

  14. Spin echo diffraction in disordered media with single length scales

    The spin echo diffraction observed in a pulsed field gradient NMR experiment is studied by simulation in computer generated two-dimensional disordered porous media characterized by a single length scale such as their mean pore diameter. In the propagator formulation of the pulsed field gradient experiments carried out in fluids confined inside porous media one expects to see a diffraction pattern characterizing the above length scale. We have explored the possibility of using this echo diffraction technique as a practical noninvasive tool to extract information about the pore geometries. It turns out that even for a disordered medium, the echo-diffraction pattern picks up the dominant length scale. copyright 1997 The American Physical Society

  15. Field integral correction in neutron resonance spin echo

    Neutron resonance spin echo (NRSE) as a variant of neutron spin echo (NSE) has the advantage that it needs only relatively small magnetic coils. Field inhomogeneities are therefore less important than in NSE. We have built a new type of NRSE spectrometer that overcomes the main limitation of NRSE towards high-energy resolution. Our setup profits from a new longitudinal NRSE field geometry which allows to use Fresnel coils correcting for the beam divergence effect, while former NRSE setups with transversal static magnetic fields could not use Fresnel coils. We demonstrate the function of the longitudinal resonance flip coils, and show first results of spin echo test measurements performed by means of the new setup

  16. Properties of echo spectra observed by MST radars

    Wakasugi, K.

    1983-01-01

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

  17. Picking up good vibrations

    Eijk, A.

    2010-01-01

    The methods that need to be employed to develop the better vibration guidelines to assess the integrity of a reciprocating compressor system are discussed. An R&D project of the European Forum of Reciprocating Compressors (EFRC) has been initiated to develop guidelines for vibrations in reciprocatin

  18. Vibration Theory, Vol. 3

    Nielsen, Søren R. K.

    The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 4th edition of this textbook on linear stochastic vibration...

  19. Vibration Theory, Vol. 3

    Nielsen, Søren R. K.

    The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 2nd edition of this textbook on linear stochastic vibration...

  20. Hydroelastic Vibrations of Ships

    Jensen, Jørgen Juncher; Folsø, Rasmus

    2002-01-01

    A formula for the necessary hull girder bending stiffness required to avoid serious springing vibrations is derived. The expression takes into account the zero crossing period of the waves, the ship speed and main dimensions. For whipping vibrations the probability of exceedance for the combined...

  1. Model Indepedent Vibration Control

    Yuan, Jing

    2010-01-01

    A NMIFC system is proposed for broadband vibration control. It has two important features. Feature F1 is that the NMIFC is stable without introducing any invasive effects, such as probing signals or controller perturbations, into the vibration system; feature F2 is

  2. Design And Simulation Of An Acoustic Echo Cancellation System For Hand-Free Telecommunication

    Ein Gyin Pwint

    2015-06-01

    Full Text Available Abstract Acoustic echo cancellation is a common occurrence in todays telecommunication systems. The signal interference caused by acoustic echo is distracting to users and causes a reduction in the quality of the communication. This paper is implementing the overall system of acoustic echo cancellation system using LMS and NLMS algorithms for adaptive filter normalized cross correlation NCC algorithm double talk detector. The result of echo return loss enhancement ERLE and mean squared error MSE which show that how much the amount of echo signal cancelled and the amount of residual error signal for cancelling acoustic echo cancellation on a PC with the help of the MATLAB software.

  3. Handbook Of Noise And Vibration

    This book is about noise and vibration. The first chapter has explanations of noise such as basic of sound, influence of noise, assessment of noise, measurement of prevention of noise and technology, case of noise measurement and soundproof. The second chapter describes vibration with outline, theory of vibration, interpretation of vibration, measurement for reduction of vibration, case of design of protection against vibration. It deals with related regulation and method of measurement.

  4. Vibration Testing for Small Satellites

    Wilson, Delbert

    1989-01-01

    Most people involved in the design and construction of small satellites are unfamiliar with vibration testing. Yet most satellites undergo vibration testing to qualify them for flight. Some familiarity with the basic aspects of vibration testing is needed to insure that a vibration test on a satellite is valid. This paper sets forth the basic equipment, practices and concepts of vibration testing. It provides guidelines for specifying a vibration test, designing fixtures, attaching instrument...

  5. Vibration control in accelerators

    Montag, C.

    2011-01-01

    In the vast majority of accelerator applications, ground vibration amplitudes are well below tolerable magnet jitter amplitudes. In these cases, it is necessary and sufficient to design a rigid magnet support structure that does not amplify ground vibration. Since accelerator beam lines are typically installed at an elevation of 1-2m above ground level, special care has to be taken in order to avoid designing a support structure that acts like an inverted pendulum with a low resonance frequency, resulting in untolerable lateral vibration amplitudes of the accelerator components when excited by either ambient ground motion or vibration sources within the accelerator itself, such as cooling water pumps or helium flow in superconducting magnets. In cases where ground motion amplitudes already exceed the required jiter tolerances, for instance in future linear colliders, passive vibration damping or active stabilization may be considered.

  6. Review on vibration transducers

    The vibrational behavior of a rotating machine at a certain rotational speed is carried out by a suitable non-contact transducer placed in precise selected position relative to the rotating machine. For the proper application of vibration measuring devices to the vibration parameters, these devices are classified with respect to the citation frequency and machine frequency. Sensors and transducers are categorized according to their applications. One variable can be converted into other by using electrical integrating or differentiating circuit. The differentiation accentuates the high frequency end of the spectrum while integration reduces the high frequency components. This paper presents different types of transducers, which can be used for vibration analysis purposes in rotating machinery. Factually sensors play an important role in the measurement of vibrations. Their characteristics are discussed and the sensitivity of mounting, installation and working principle is presented. The transduction mechanism has been discussed in a straightforward manner and comparison between different sensors and transduction is presented here. (author)

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

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

  8. Causality and Intervention in the Spin-Echo Experiments

    Fernanda Samaniego Bañuelos

    2013-09-01

    Full Text Available In the so-called “Spin-Echo Experiments” the behaviour of a spin’s system seems to violate the second law of thermodynamics. For this reason the “Spin-Echo Experiments” are considered of particular interest for the Foundations of Physics. Interventionists have provided a classical explanation (Blatt, 1959; Ridderbos & Redhead, 1998 and a quantum-based explanation (Hemmo & Shenker, 2005 of these experiments. Here both interventionist explanations are assessed by means of the Manipulability Theory of Causal Explanation (Woodward, 2003. It is argued that interventionism would gain explanatory depth by providing functional relations and predicting relaxation times.

  9. Evaluation of combination echo sequence in knee joint MRI

    Combination echo sequence (CE) can obtain the T2-weighted SE images and gradient echo sequence (GRE) images at the same time. The CE technique was performed in 42 cases with knee joint disease and its usefulness was examined. The knee joint consists of complex elements, therefore, all sequences of T1-weighted, T2-weighted and GRE are necessary in order to clearly visualize. Thus, The CE technique, which yields the T2-weighted and GRE images is useful for routine examination of knee joint. (author)

  10. Echoes of Hylas and the Poetics of Allusion in Propertius

    Mariapia Pietropaolo

    2012-12-01

    Full Text Available For Propertius the myth of Hylas exemplifies a poetics of selective appropriation and transformation by means of echoes and allusions. He brings it into his poetry as an exemplum, both erotic and metapoetic, and offers evidence that his penchant for echoes and allusions is essentially the result of a Hylan poetics of elegy. By using the echoic mode of composition inherent in the myth of Hylas, Propertius illustrates the principle that elegiac poetry is grounded in a complex dialogue of intertextual and intratextual allusion and citations.

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

    Kalachev, Alexey A.; Vlasova, Daria D.

    2006-03-01

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

  12. Electrorheological vibration system

    Korobko, Evguenia V.; Shulman, Zinovy P.; Korobko, Yulia O.

    2001-07-01

    The present paper is devoted to de3velopment and testing of an active vibration system. The system is intended for providing efficient motion of a piston in a hydraulic channel for creation of shocks and periodic vibrations in a low frequency range by means of the ER-valves based on an electrosensitive working me dium, i.e. electrorheological fluids. The latter manifests the electrorheological (ER) effect, i.e. a reversible change in the rheological characteristics of weak-conducting disperse compositions in the presence of constant and alternating electric fields. As a result of the experimental study of the dependence of viscoelastic properties of the ER-fluid on the magnitude and type of an electric field, the optimum dimensions of the vibrator and the its valves characteristics of the optimal electrical signal are determined. For control of an ER- vibrator having several valves we have designed a special type of a high-voltage two-channel impulse generator. Experiments were conducted at the frequencies ranged from 1- 10 Hz. It has been shown, that a peak force made 70% of the static force exercised by the vibrator rod. A phase shift between the input voltage and the load acceleration was less than 45 degree(s)C which allowed servocontrol and use of the vibrator for attendant operations. It was noted that a response of the vibrator to a stepwise signal has a delay only of several milliseconds.

  13. Seafloor characterisation using echo peak amplitudes of multibeam hydrosweep system - A preliminary study at Arabian Sea

    Chakraborty, B.; Sudhakar, T.

    In this paper an interface to acquire 59-beams echo peak amplitudes of the Hydrosweep Multibeam system is established. The echo peak amplitude values collected at varying seabed provinces of Arabian sea are presented. The study reveals...

  14. Coherent vibrational dynamics

    Lanzani, Guglielmo; De Silvestri, Sandro

    2007-01-01

    Vibrational spectroscopy is a powerful investigation tool for a wide class of materials covering diverse areas in physics, chemistry and biology. The continuous development in the laser field regarding ultrashort pulse generation has led to the possibility of producing light pulses that can follow vibrational motion coupled to the electronic transitions in molecules and solids in real time. Aimed at researchers and graduate students using vibrational spectroscopy, this book provides both introductory chapters as well as more advanced contents reporting on recent progress. It also provides a good starting point for scientists seeking a sound introduction to ultrafast optics and spectroscopic techniques.

  15. Vibrational optical activity

    Recent vibrational activity (VOA) research is discussed. The vibrational circular dichroism (VCD) experiments were carried out with a Fourier transform infrared spectrometer. One of the major anticipations from VOA spectroscopy is to be able to derive new pathways for determining the molecular structure. Shown is Fourier transform infrared absorption and VCD spectra of lyxopyranose in pyradine-d5 solvent. Raman optical activity measurements are discussed, and depolarized Raman and Raman optical activity spectra for (+)-alpha-pinene are presented. It was concluded that at present Raman optical activity can be measured in the entire vibrational spectral region, where as VCD has not been measured below 600 cm-1

  16. Edward Albee’s The Zoo Story: Echo/es of Contemporary Subversive Culture

    Naqibun Nabi

    2016-02-01

    Full Text Available The post-world war II American social and cultural setting was ambiguously featured with enforced conformity in the name of prosperity and Americanization of the nation. Despite of this fact, American writers, especially, dramatists conveyed their message against this fixation through variety and intellectuality. Edward Albee’s The Zoo Story is one of those literary assets which dedicatedly cut through the illusions of contemporary American social and cultural ethos. Here, his characters are seen struggling constantly with their insecurities and existential angst in the society. He presents America, the so-called ‘Land of Free and Home of Braves’ (note 1, in such a portrayal that unveils the traps of cages and confinement underneath. The target of this paper is to trace Edward Albee’s heightened awareness about the post-war American socio-cultural reality evident in The Zoo Story. It also looks for the voice in which the text echoes out the anti-communist, materialistic, gender-coded boundaries, coupled with paradoxical media representations, religious bordering and how Albee challenges these issues with an anti-establishment tone.Keywords: subversive culture, anti-communism, media, religion and homosexuality

  17. Performance Evaluation of Adaptive Filters Structures for Acoustic Echo Cancellation

    Sanjeev Dhull

    2011-05-01

    Full Text Available We have designed and simulated an acoustic echo cancellation system for conferencing. Thissystem is based upon a least-mean-square (LMS adaptive algorithm and uses multi filtertechnique. A comparative study of both structure has been carried out and it is found that thisnew multi-filter converge faster than similar single long adaptive filter.

  18. Control of spatial correlations between Rydberg excitations using rotary echo

    Thaicharoen, N; Raithel, G

    2016-01-01

    We manipulate correlations between Rydberg excitations in cold atom samples using a rotary-echo technique. The correlations are due to interactions between the Rydberg atoms. In the rotary-echo excitation sequence, the phase of the excitation pulse is flipped at a selected time during the pulse. We measure the resultant change in the spatial pair correlation function of the excitations via direct position-sensitive atom imaging. For zero detuning of the lasers from the interaction-free Rydberg-excitation resonance, the pair-correlation value at the most likely nearest-neighbor Rydberg-atom distance is substantially enhanced when the phase is flipped at the middle of the excitation pulse. In this case, the rotary echo eliminates most uncorrelated (un-paired) atoms, leaving an abundance of correlated atom pairs at the end of the sequence. In off-resonant cases, a complementary behavior is observed. We further characterize the effect of the rotary-echo excitation sequence on the excitation-number statistics of t...

  19. Characterization of trehalose aqueous solutions by neutron spin echo

    Branca, C; Magazù, S; Maisano, G; Mangione, A; Pappas, C; Triolo, A

    2002-01-01

    The present work reports neutron spin-echo (NSE) results on aqueous mixtures of trehalose, a naturally occurring disaccharide of glucose, which shows an extraordinary bioprotective effectiveness against dehydration and freezing. The aim of the work is to furnish new results on the dynamics of the trehalose/water system on the nano- and picosecond scales. (orig.)

  20. Infrasound - the cause of strong Polar Mesosphere Winter Echoes?

    S. Kirkwood

    2006-03-01

    Full Text Available The ESRAD 52-MHz and the EISCAT 224-MHz radars in northern Scandinavia observed thin layers of strongly enhanced radar echoes from the mesosphere (Polar Mesosphere Winter Echoes - PMWE during a solar proton event in November 2004. Using the interferometric capabilities of ESRAD it was found that the scatterers responsible for PMWE show very high horizontal travel speeds, up to 500 ms-1 or more, and high aspect sensitivity, with echo arrival angles spread over as little as 0.3°. ESRAD also detected, on some occasions, discrete scattering regions moving across the field of view with periodicities of a few seconds. The very narrow, vertically directed beam of the more powerful EISCAT radar allowed measurements of the spectral widths of the radar echoes both inside the PMWE and from the background plasma above and below the PMWE. Spectral widths inside the PMWE were found to be indistinguishable from those from the background plasma. We propose that scatter from highly-damped ion-acoustic waves generated by partial reflection of infrasonic waves provides a reasonable explanation of the characteristics of the very strong PMWE reported here.

  1. Analysis of multibeam-hydrosweep echo peaks for seabed characterisation

    Chakraborty, B.; Schenke, H.W.; Kodagali, V.N.; Hagen, R.

    , in general, Gaussian in nature except in the case of the Kainan Maru seamount summit (area D). The outer beams of the Enderby abyssal plain (area C) echo-peak PDF statistics reveal the highest possible large-scale feature dominance. Interestingly, Extremal...

  2. System for measuring magnetic fields using spin echo

    Description of an on-line system for magnetic field measurements on the storage rings using spin echo method is presented. In the system described the magnetic field measurement is performed in the following way. In a specimen with the required atoms (e.g. protons or lithium nuclei) spin echo is induced by effect of a pair of pulses. A NMR frequency echo-signal received from the transducer is transferred to a lower intermediate frequency where it is transformed into a digital form using analog-to-digital converter and then spectral analysis using Fourier fast transformation method is performed. Echo-signal frequency and magnetic induction values, corresponding to it are determined according to the spectrum calculated and to a certain heterodyne frequency. The system allows one to measure fields within 0.05-1 T range using two proton detectors (with 2.1-42 MHz frequency range). Relative measurement error does not exceed 3x10-6. The detecor tubes are 5 mm in diameter with 10 mm winding length and are encased into a copper shield

  3. LEGUS Discovery of a Light Echo Around Supernova 2012aw

    Van Dyk, Schuyler D; Anderson, Jay; Andrews, Jennifer E; Calzetti, Daniela; Bright, Stacey N; Ubeda, Leonardo; Smith, Linda J; Sabbi, Elena; Grebel, Eva K; Herrero, Artemio; de Mink, Selma E

    2015-01-01

    We have discovered a luminous light echo around the normal Type II-Plateau Supernova (SN) 2012aw in Messier 95 (M95; NGC 3351), detected in images obtained approximately two years after explosion with the Wide Field Channel 3 on-board the Hubble Space Telescope (HST) by the Legacy ExtraGalactic Ultraviolet Survey (LEGUS). The multi-band observations span from the near-ultraviolet through the optical (F275W, F336W, F438W, F555W, and F814W). The apparent brightness of the echo at the time was ~21--22 mag in all of these bands. The echo appears circular, although less obviously as a ring, with an inhomogeneous surface brightness, in particular, a prominent enhanced brightness to the southeast. The SN itself was still detectable, particularly in the redder bands. We are able to model the light echo as the time-integrated SN light scattered off of diffuse interstellar dust in the SN environment. We have assumed that this dust is analogous to that in the Milky Way with R_V=3.1. The SN light curves that we consider ...

  4. Echo voltage reflected by turtle on various angles

    Sunardi Sunardi

    2015-03-01

    Full Text Available This research proposes the acoustic measurement by using echo sounder for green turtle detection of 1 year, 12 and 18 years. Various positions or angles of turtles are head, tail, shell, lung, left and right side. MATLAB software and echo sounder are used to analyse the frequency and the response of the turtle as echo voltage and target strength parameter. Based on the experiment and analysis have been conducted, the bigger size of the turtle, the higher echo voltage and target strength. The target strength of turtle for lung and shell for all ages are -26.52 dB and –26.17 dB respectively. The target strength of turtles in this research is different with target strength of fish in our previous research. Therefore, for future research, the repellant system based on differences of target strength the turtle and fish for avoided the turtle trapping in the net can be implemented to protect the population of turtle from extinction

  5. Spectrally resolved femtosecond photon echo spectroscopy of astaxanthin

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

    2011-08-01

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

  6. Spectrally Resolved Femtosecond Photon Echo Spectroscopy of Astaxanthin

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

    2011-01-01

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

  7. Echo width of foam supports used in scattering measurements

    Appel-Hansen, Jørgen; Solodukhov, V. V.

    1979-01-01

    Theoretically and experimentally determined echo widths of dielectric cylinders having circular, triangular, and quadratic cross sections have been compared. The cylinders were made of foam material having a relative dielectric constant of about 1.035. The purpose of the investigation was to find a...

  8. Echo phenomenon associated with lower-hybrid-wave launching

    Lower hybrid waves at two different frequencies f1 and f2 are launched simultaneously from two localized antennas, and a third wave is observed to arise near the plasma edge at the frequency f = f2 - f1. This phenomenon can be explained by an echo effect near the plasma surface

  9. Echo phenomenon associated with lower-hybrid wave launching

    Lower-hybrid waves at two different frequencies f1 and f2 are launched simultaneously from two localized antennas, and a third wave is observed to arise near the plasma edge at the frequency f = f2-f1. This phenomenon can be explained by an echo effect near the plasma surface

  10. Subband Affine Projection Algorithm for Acoustic Echo Cancellation System

    Choi Hun

    2007-01-01

    Full Text Available We present a new subband affine projection (SAP algorithm for the adaptive acoustic echo cancellation with long echo path delay. Generally, the acoustic echo canceller suffers from the long echo path and large computational complexity. To solve this problem, the proposed algorithm combines merits of the affine projection (AP algorithm and the subband filtering. Convergence speed of the proposed algorithm is improved by the signal-decorrelating property of the orthogonal subband filtering and the weight updating with the prewhitened input signal of the AP algorithm. Moreover, in the proposed algorithms, as applying the polyphase decomposition, the noble identity, and the critical decimation to subband the adaptive filter, the sufficiently decomposed SAP updates the weights of adaptive subfilters without a matrix inversion. Therefore, computational complexity of the proposed method is considerably reduced. In the SAP, the derived weight updating formula for the subband adaptive filter has a simple form as ever compared with the normalized least-mean-square (NLMS algorithm. The efficiency of the proposed algorithm for the colored signal and speech signal was evaluated experimentally.