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Sample records for ion coincidence eico

  1. Development of an Apparatus for High-Resolution Auger Photoelectron Coincidence Spectroscopy (APECS) and Electron Ion Coincidence (EICO) Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kakiuchi, Takuhiro; Hashimoto, Shogo; Fujita, Narihiko; Mase, Kazuhiko; Tanaka, Masatoshi; Okusawa, Makoto

    We have developed an electron electron ion coincidence (EEICO) apparatus for high-resolution Auger photoelectron coincidence spectroscopy (APECS) and electron ion coincidence (EICO) spectroscopy. It consists of a coaxially symmetric mirror electron energy analyzer (ASMA), a miniature double-pass cylindrical mirror electron energy analyzer (DP-CMA), a miniature time-of-flight ion mass spectrometer (TOF-MS), a magnetic shield, an xyz stage, a tilt-adjustment mechanism, and a conflat flange with an outer diameter of 203 mm. A sample surface was irradiated by synchrotron radiation, and emitted electrons were energy-analyzed and detected by the ASMA and the DP-CMA, while desorbed ions were mass-analyzed and detected by the TOF-MS. The performance of the new EEICO analyzer was evaluated by measuring Si 2p photoelectron spectra of clean Si(001)-2×1 and Si(111)-7×7, and by measuring Si-L23VV-Si-2p Auger photoelectron coincidence spectra (Si-L23VV-Si-2p APECS) of clean Si(001)-2×1.

  2. Secondary ion coincidence in highly charged ion based secondary ion mass spectroscopy for process characterization

    SciTech Connect

    Hamza, A.V.; Schenkel, T.; Barnes, A.V.; Schneider, D.H.

    1999-01-01

    Coincidence counting in highly charged ion based secondary ion mass spectroscopy has been applied to the characterization of selective tungsten deposition via disilane reduction of tungsten hexafluoride on a patterned SiO{sub 2}/Si wafer. The high secondary ion yield and the secondary ion emission from a small area produced by highly charged ions make the coincidence technique very powerful.

  3. Breaking through the false coincidence barrier in electron–ion coincidence experiments

    DOE PAGES

    Osborn, David L.; Hayden, Carl C.; Hemberger, Patrick; ...

    2016-10-31

    Photoelectron Photoion Coincidence (PEPICO) spectroscopy holds the promise of a universal, isomer-selective, and sensitive analytical technique for time-resolved quantitative analysis of bimolecular chemical reactions. Unfortunately, its low dynamic range of ~103 has largely precluded its use for this purpose, where a dynamic range of at least 105 is generally required. This limitation is due to the false coincidence background common to all coincidence experiments, especially at high count rates. Electron/ion pairs emanating from separate ionization events but arriving within the ion time of flight (TOF) range of interest constitute the false coincidence background. Although this background has uniform intensity atmore » every m/z value, the Poisson scatter in the false coincidence background obscures small signals. In this paper, temporal ion deflection coupled with a position-sensitive ion detector enables suppression of the false coincidence background, increasing the dynamic range in the PEPICO TOF mass spectrum by 2–3 orders of magnitude. The ions experience a time-dependent electric deflection field at a well-defined fraction of their time of flight. This deflection defines an m/z- and ionization-time dependent ion impact position for true coincidences, whereas false coincidences appear randomly outside this region and can be efficiently suppressed. When cold argon clusters are ionized, false coincidence suppression allows us to observe species up to Ar9+, whereas Ar4+ is the largest observable cluster under traditional operation. As a result, this advance provides mass-selected photoelectron spectra for fast, high sensitivity quantitative analysis of reacting systems.« less

  4. Breaking through the false coincidence barrier in electron–ion coincidence experiments

    SciTech Connect

    Osborn, David L.; Hayden, Carl C.; Hemberger, Patrick; Bodi, Andras; Voronova, Krisztina; Sztaray, Balint

    2016-10-31

    Photoelectron Photoion Coincidence (PEPICO) spectroscopy holds the promise of a universal, isomer-selective, and sensitive analytical technique for time-resolved quantitative analysis of bimolecular chemical reactions. Unfortunately, its low dynamic range of ~103 has largely precluded its use for this purpose, where a dynamic range of at least 105 is generally required. This limitation is due to the false coincidence background common to all coincidence experiments, especially at high count rates. Electron/ion pairs emanating from separate ionization events but arriving within the ion time of flight (TOF) range of interest constitute the false coincidence background. Although this background has uniform intensity at every m/z value, the Poisson scatter in the false coincidence background obscures small signals. In this paper, temporal ion deflection coupled with a position-sensitive ion detector enables suppression of the false coincidence background, increasing the dynamic range in the PEPICO TOF mass spectrum by 2–3 orders of magnitude. The ions experience a time-dependent electric deflection field at a well-defined fraction of their time of flight. This deflection defines an m/z- and ionization-time dependent ion impact position for true coincidences, whereas false coincidences appear randomly outside this region and can be efficiently suppressed. When cold argon clusters are ionized, false coincidence suppression allows us to observe species up to Ar9+, whereas Ar4+ is the largest observable cluster under traditional operation. As a result, this advance provides mass-selected photoelectron spectra for fast, high sensitivity quantitative analysis of reacting systems.

  5. Breaking through the false coincidence barrier in electron-ion coincidence experiments

    NASA Astrophysics Data System (ADS)

    Osborn, David L.; Hayden, Carl C.; Hemberger, Patrick; Bodi, Andras; Voronova, Krisztina; Sztáray, Bálint

    2016-10-01

    Photoelectron Photoion Coincidence (PEPICO) spectroscopy holds the promise of a universal, isomer-selective, and sensitive analytical technique for time-resolved quantitative analysis of bimolecular chemical reactions. Unfortunately, its low dynamic range of ˜103 has largely precluded its use for this purpose, where a dynamic range of at least 105 is generally required. This limitation is due to the false coincidence background common to all coincidence experiments, especially at high count rates. Electron/ion pairs emanating from separate ionization events but arriving within the ion time of flight (TOF) range of interest constitute the false coincidence background. Although this background has uniform intensity at every m/z value, the Poisson scatter in the false coincidence background obscures small signals. In this paper, temporal ion deflection coupled with a position-sensitive ion detector enables suppression of the false coincidence background, increasing the dynamic range in the PEPICO TOF mass spectrum by 2-3 orders of magnitude. The ions experience a time-dependent electric deflection field at a well-defined fraction of their time of flight. This deflection defines an m/z- and ionization-time dependent ion impact position for true coincidences, whereas false coincidences appear randomly outside this region and can be efficiently suppressed. When cold argon clusters are ionized, false coincidence suppression allows us to observe species up to Ar9+, whereas Ar4+ is the largest observable cluster under traditional operation. This advance provides mass-selected photoelectron spectra for fast, high sensitivity quantitative analysis of reacting systems.

  6. Coincidence studies of ion-molecule collisions

    NASA Astrophysics Data System (ADS)

    Ben-Itzhak, Itzik

    1998-05-01

    Two of the simplest collision systems one can imagine are H^+ + H(1s) and H^+ + D(1s). Electron transfer is resonant in the first and nearly resonant in the latter because of the 3.7 meV gap between the H(1s) and D(1s). Once the collision velocity becomes small enough quantum effects become more pronounced and the electron transfer rate as a function of collision energy exhibits many resonances(G. Hunter and M. Kuriyan, Proc. Roy. Soc. Lond. A 358), 321 (1977).^,(J.P. Davis and W.R. Thorson, Can. J. Phys. 56), 996 (1978).. However, most of the interesting features appear at very low energies, of a few meV, and these collision systems which are the ``theorist's dream'' become a nightmare to experimentalists. Nevertheless, we are undertaking the challenging measurement of near resonant electron transfer in the H^+ + D(1s) collision system. When a HD molecule is ionized quickly, such that the transition to the HD^+ molecular ion is vertical, about 1% of the HD^+(1sσ) is in the vibrational continuum. The transition probability falls off approximately exponentially above threshold and its width is about 200 meV. During the dissociation, the electron initially centered on the D core can make a transition to the H core when the 2pσ and 1sσ potential energy curves associated with the two dissociation limits get close to each other. It is important to note that during molecular dissociation the ``avoided crossing'' is crossed only once in contrast to twice during a full collision. Using a localized cold HD target and 3D imaging of the low energy H^+ and D^+ dissociation fragments one can experimentally determine the transition probability between these two states as a function of the dissociation energy. Clearly, a recoil energy resolution of the order of a meV is necessary, which is the primary experimental challenge.

  7. Coincidence ion imaging with a fast frame camera

    SciTech Connect

    Lee, Suk Kyoung; Cudry, Fadia; Lin, Yun Fei; Lingenfelter, Steven; Winney, Alexander H.; Fan, Lin; Li, Wen

    2014-12-15

    A new time- and position-sensitive particle detection system based on a fast frame CMOS (complementary metal-oxide semiconductors) camera is developed for coincidence ion imaging. The system is composed of four major components: a conventional microchannel plate/phosphor screen ion imager, a fast frame CMOS camera, a single anode photomultiplier tube (PMT), and a high-speed digitizer. The system collects the positional information of ions from a fast frame camera through real-time centroiding while the arrival times are obtained from the timing signal of a PMT processed by a high-speed digitizer. Multi-hit capability is achieved by correlating the intensity of ion spots on each camera frame with the peak heights on the corresponding time-of-flight spectrum of a PMT. Efficient computer algorithms are developed to process camera frames and digitizer traces in real-time at 1 kHz laser repetition rate. We demonstrate the capability of this system by detecting a momentum-matched co-fragments pair (methyl and iodine cations) produced from strong field dissociative double ionization of methyl iodide.

  8. Ion-ion coincidence imaging at high event rate using an in-vacuum pixel detector

    NASA Astrophysics Data System (ADS)

    Long, Jingming; Furch, Federico J.; Durá, Judith; Tremsin, Anton S.; Vallerga, John; Schulz, Claus Peter; Rouzée, Arnaud; Vrakking, Marc J. J.

    2017-07-01

    A new ion-ion coincidence imaging spectrometer based on a pixelated complementary metal-oxide-semiconductor detector has been developed for the investigation of molecular ionization and fragmentation processes in strong laser fields. Used as a part of a velocity map imaging spectrometer, the detection system is comprised of a set of microchannel plates and a Timepix detector. A fast time-to-digital converter (TDC) is used to enhance the ion time-of-flight resolution by correlating timestamps registered separately by the Timepix detector and the TDC. In addition, sub-pixel spatial resolution (<6 μm) is achieved by the use of a center-of-mass centroiding algorithm. This performance is achieved while retaining a high event rate (104 per s). The spectrometer was characterized and used in a proof-of-principle experiment on strong field dissociative double ionization of carbon dioxide molecules (CO2), using a 400 kHz repetition rate laser system. The experimental results demonstrate that the spectrometer can detect multiple ions in coincidence, making it a valuable tool for studying the fragmentation dynamics of molecules in strong laser fields.

  9. A tandem time–of–flight spectrometer for negative–ion/positive–ion coincidence measurements with soft x-ray excitation

    SciTech Connect

    Stråhlman, Christian Sankari, Rami; Nyholm, Ralf; Kivimäki, Antti; Richter, Robert; Coreno, Marcello

    2016-01-15

    We present a newly constructed spectrometer for negative–ion/positive–ion coincidence spectroscopy of gaseous samples. The instrument consists of two time–of–flight ion spectrometers and a magnetic momentum filter for deflection of electrons. The instrument can measure double and triple coincidences between mass–resolved negative and positive ions with high detection efficiency. First results include identification of several negative–ion/positive–ion coincidence channels following inner-shell photoexcitation of sulfur hexafluoride (SF{sub 6})

  10. A tandem time-of-flight spectrometer for negative-ion/positive-ion coincidence measurements with soft x-ray excitation

    NASA Astrophysics Data System (ADS)

    Strâhlman, Christian; Sankari, Rami; Kivimäki, Antti; Richter, Robert; Coreno, Marcello; Nyholm, Ralf

    2016-01-01

    We present a newly constructed spectrometer for negative-ion/positive-ion coincidence spectroscopy of gaseous samples. The instrument consists of two time-of-flight ion spectrometers and a magnetic momentum filter for deflection of electrons. The instrument can measure double and triple coincidences between mass-resolved negative and positive ions with high detection efficiency. First results include identification of several negative-ion/positive-ion coincidence channels following inner-shell photoexcitation of sulfur hexafluoride (SF6).

  11. Electron excited multiply charged argon ions studied by means of an energy resolved electron-ion coincidence technique

    NASA Astrophysics Data System (ADS)

    Kumar, Sunil; Prajapati, Suman; Singh, Bhupendra; Singh, Bhartendu Kumar; Shanker, Rama

    2017-03-01

    Multiply charged argon ions produced from decay of L-shell hole states by impact of a continuous beam of 3.5 keV electrons are studied for the first time using an energy resolved electron-ion coincidence technique. The TOF spectra of argon ions are measured in coincidence with 18-energy selected electrons emitted in a wide energy range (126-242 eV). The coincidence measurement between the energy selected electrons and the correlated ions specifies the individual decay channel for various multiply charged ions. New experimental data are obtained and reported on the correlation probability for production of argon ions with charge states 1+ to 4+ as a function of ejected electrons in the considered energy range. The relative correlation probability of producing different charge state ions and corresponding physical processes involved in their production are presented and discussed. It has been found that the maximum probability for production of Ar2+ ions correlated to ejected Auger electrons in the energy range of 205-209 eV is 100%. No theoretical predictions are available to compare with these results. The present study shows further that not only the auto-ionization and normal Auger transitions but also several other decay processes including Coster-Kronig transitions followed by Auger cascades with a fraction of shake process play important role in producing ions with charge states 1+ to 4+.

  12. Experimental apparatus for photon/ion coincidence measurements of dielectronic recombination

    NASA Technical Reports Server (NTRS)

    Gardner, L. D.; Kohl, J. L.; Lafyatis, G. P.; Young, A. R.; Chutjian, A.

    1986-01-01

    An inclined beams apparatus for the measurement of absolute cross sections for dielectronic recombination between free electrons and singly or multiply charged ions is described. The collision products, a photon and a lower-charge-state ion, are detected in delayed coincidence. Measurements of dielectronic recombination in C(3+) are described to illustrate the use of the apparatus and techniques. Verification of the calibrations and operation of the apparatus is demonstrated through measurements of charge transfer and electron impact excitation.

  13. A velocity map imaging spectrometer for electron?ion and ion?ion coincidence experiments with synchrotron radiation

    SciTech Connect

    Advanced Light Source; Kilcoyne, Arthur L; Rolles, D.; Pesic, Z.D.; Perri, M.; Bilodeau, R.C.; Ackerman, G.D.; Rude, B.S.; Kilcoyne, A.L.D.; Bozek, J.D.; Berrah, N.

    2007-04-27

    We have built a velocity imaging (VMI) spectrometer optimized for angle-resolved photoionization experiments with synchrotron radiation (SR) in the VUV and soft X-tay range. The spectrometer is equiped with four electrostatic lenses that focus the charged photoionization products onto a position-sensitive multi-hit delay-line anode. The use of two additional electrostatic lens elements as compared to the standard design of Eppink and Parker [T.J.B. Eppink and D.H. Parker, Rev. Sci. Instrum. 68 (1997) 3477]provides better focusing of an extended interaction region, which is crucial for most SR applications. Furthermore, the apparatus is equipped with a second micro-channel plate detector opposite to the VMI spectrometer, enabling electron-ion coincidence experiments and thereby mass-resolved ion spectroscopy independent of the time structure of the synchrotron radiation. First results for the photofragmentation of CO2 molecules are presented.

  14. Coincidence measurements between fragment ions and the number of emitted electrons in heavy ion collisions with polyatomic molecules

    NASA Astrophysics Data System (ADS)

    Murai, T.; Majima, T.; Kishimoto, T.; Tsuchida, H.; Itoh, A.

    2012-11-01

    We have studied multiple ionization and multifragmentation of a chlorofluorocarbon molecule, CH2FCF3, induced by collisions of 580-keV C+ ions. Coincidence measurements of product ions and the number of emitted electrons from CH2FCF3 were performed under charge-changing conditions of C+ → Cq+ (q = 0, 2, 3). A fully inclusive measurement regardless of outgoing projectile charge state was also performed by making coincidence with a pulsed ion beam. Mass distributions of fragment ions and number distributions of emitted electrons were both found to change greatly according to charge-changing conditions. Highly multiple ionization emitting up to about 10 electrons was observed in electron loss collisions.

  15. On the dissociation of the 2-pentanone ion studied by threshold photoelectron photoion coincidence spectroscopy

    NASA Astrophysics Data System (ADS)

    Kercher, James P.; Sztáray, Bálint; Baer, Tomas

    2006-03-01

    The photodissociation of 2-pentanone has been studied by threshold photoelectron photoion coincidence (TPEPICO) spectroscopy, in which ion time-of-flight (TOF) mass spectra are recorded as a function of the photon energy in the range of 9.6-12.2 eV. 2-Pentanone ions dissociate via four competitive channels: ethylene (C2H4) loss to produce the propen-2-ol ion, n-propyl (C3H7) loss to produce the acetyl ion, and two parallel methyl (CH3) loss channels, producing the butanoyl ion at low energies and the but-3-en-2-ol ion at higher energies. The latter dissociates further via ethylene (C2H4) loss providing a second pathway to the acetyl ion. This final dissociation channel is observed experimentally by the appearance of an asymmetric ion peak in the time-of-flight (TOF) distribution at photon energies greater than 11.5 eV. The ion TOF distributions and breakdown diagram have been modeled in terms of the statistical RRKM theory for unimolecular reactions, yielding the 0 K dissociation onsets of 10.239 +/- 0.015 eV for the butanoyl ion and 10.259 +/- 0.019 eV for the propen-2-ol (acetone enolate) ion. By relating the measured onsets with other well established heats of formation, the 298 K heat of formation of the butanoyl and propen-2-ol ions were determined to be 586.9 +/- 2.1 and 680.7 +/- 1.8 kJ/mol, respectively. The acetone enolate ion is thus 37 kJ/mol more stable than the acetone ion, a value supported by G3B3, and CBS-QB3 calculations. The but-3-en-2-ol ion was found to lose ethylene to produce the acetyl ion without an energy barrier.

  16. Scaling relationships in photoelectron-photoion coincidence studies: The aceton ion dissociation

    NASA Astrophysics Data System (ADS)

    Johnson, Kieth; Powis, I.; Danby, C. J.

    1981-12-01

    The distributions of internal energy released into translation in the fragmentation of energy-selected acetone ions (as determined by photoelectron-photoion coincidence studies) are shown to obey a scaling law, as do the calculated distributions derived from a statistical-dynamical phase space theory. A single function contains the dynamical history of the reaction system, at least at higher energies, in contrast to the predictions of the rigid rotor harmonic oscillator model. The scaling law provides an analysis of the bimodal form of the translational energy distributions which are found for the dissociation of the enol form of the acetone ion. This is shown to be consistent with the ergodic hypothesis.

  17. Electron-recoil ion and recoil ion-projectile coincidence techniques applied to obtain absolute partial collision cross sections.

    PubMed

    Wolff, W; de Souza, Ihani J; Tavares, André C; de Oliveira, G F S; Luna, H

    2012-12-01

    We present in detail an alternative experimental set-up and data analysis, based on the electron-recoil ion and recoil ion-projectile coincidence techniques, that enable the measurement of partial pure ionization and partial charge exchange cross sections for an effusive gas jet set-up, where the absolute target density and recoil ion efficiency cannot be measured directly. The method is applied to the ionization of helium atoms due to collision with partially stripped C(3 +) projectiles. In order to check the method, the results are compared to data available in the literature where the target density and recoil ion detection efficiency were measured directly. The pure ionization channel is compared to the electron capture channel.

  18. Doubly excited states of molecular nitrogen by scattered electron-ion coincidence measurements

    NASA Astrophysics Data System (ADS)

    Takahashi, Karin; Hasegawa, Toru; Sakai, Yasuhiro

    2017-03-01

    Scattered electron-ion coincidence measurements were performed on molecular nitrogen (N2) to study the relaxation dynamics of doubly excited states. Doubly excited states are typically so unstable that they result in either auto-ionization or a neutral dissociation. In auto-ionization, ionization and dissociation typically occur. Using a mixed-gas method, we determined the absolute values of the generalized oscillator strength (GOS) distributions using an incident electron energy of 200 eV and a scattering angle of 6°. The GOS distributions of N2+ and N+ were determined by combining the coincidence ion signals, which revealed some doubly excited states of N2. Since electron impact experiments can provide information on optically forbidden transitions, the contribution of optically forbidden states appears in the GOS distributions of both N2+ and N+. We observed auto-ionization and dissociative auto-ionization induced by excitation to the optically forbidden doubly excited states in the range of 30-40 eV.

  19. Doubly excited states of ammonia by scattered electron-ion coincidence measurements

    NASA Astrophysics Data System (ADS)

    Yamamoto, Karin; Sakai, Yasuhiro

    2012-03-01

    To obtain information on the optically forbidden doubly excited states of ammonia (NH3), we performed scattered electron-ion coincidence measurements. First, we observed scattered electrons using electron energy-loss spectroscopy and determined the generalized oscillator strength distribution (GOSD) under 200 eV incident electron energy at a scattering angle of 8°. Ionic GOSDs were also determined by combination with the coincidence signal, which was observed by the time-of-flight mass spectrometer at each energy-loss value, for each ion. The total and partial ionic GOSDs were compared with the experimental results of both photon and fast electron impact. Moreover, the neutral GOSD determined by subtracting the total ionic GOSD from the total was compared with previous results. In addition to the optically forbidden doubly excited states, which were identified by Kato et al (2003 J. Phys. B: At. Mol. Opt. Phys. 36 3541) and Ishikawa et al (2008 J. Phys. B: At. Mol. Opt. Phys. 41 195204), we found a new optically forbidden doubly excited state at around 35 eV.

  20. Coincidence measurements of electron capture and loss in ion-atom collisions

    SciTech Connect

    DuBois, R.D.

    1990-09-01

    Collisions between fast, fully stripped projectiles and atomic targets predominantly result in target electrons being ejected to the continuum. For fast partially stripped projectiles which bring weakly bound electrons into the collision, projectile ionization can also contribute to the observed electron spectra. At lower impact velocities, electron capture by the projectile ion becomes important and higher order processes, often referred to as transfer ionization, can be a significant source of free electrons. In recent years, coincidence techniques have been used to evaluate the relative importance of electron capture and loss in free electron production, to separate the capture and loss contributions from those resulting from target ionization alone, and to provide more detailed information about electron capture and loss mechanisms than is available from total cross section measurements. A brief survey of these experiments will be presented. 23 refs., 9 figs.

  1. Dissociation of internal energy-selected methyl bromide ion revealed from threshold photoelectron-photoion coincidence velocity imaging.

    PubMed

    Tang, Xiaofeng; Zhou, Xiaoguo; Sun, Zhongfa; Liu, Shilin; Liu, Fuyi; Sheng, Liusi; Yan, Bing

    2014-01-28

    Dissociative photoionization of methyl bromide (CH3Br) in an excitation energy range of 10.45-16.90 eV has been investigated by using threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging. The coincident time-of-flight mass spectra indicate that the ground state X(2)E of CH3Br(+) is stable, and both A(2)A1 and B(2)E ionic excited states are fully dissociative to produce the unique fragment ion of CH3 (+). From TPEPICO 3D time-sliced velocity images of CH3 (+) dissociated from specific state-selected CH3Br(+) ion, kinetic energy release distribution (KERD) and angular distribution of CH3 (+) fragment ion are directly obtained. Both spin-orbit states of Br((2)P) atom can be clearly observed in fast dissociation of CH3Br(+)(A(2)A1) ion along C-Br rupture, while a KERD of Maxwell-Boltzmann profile is obtained in dissociation of CH3Br(+)(B(2)E) ion. With the aid of the re-calculated potential energy curves of CH3Br(+) including spin-orbit coupling, dissociation mechanisms of CH3Br(+) ion in A(2)A1 and B(2)E states along C-Br rupture are revealed. For CH3Br(+)(A(2)A1) ion, the CH3 (+) + Br((2)P1/2) channel is occurred via an adiabatic dissociation by vibration, while the Br((2)P3/2) formation is through vibronic coupling to the high vibrational level of X(2)E state followed by rapid dissociation. C-Br bond breaking of CH3Br(+)(B(2)E) ion can occur via slow internal conversion to the excited vibrational level of the lower electronic states and then dissociation.

  2. Wavelength dependent photoelectron circular dichroism of limonene studied by femtosecond multiphoton laser ionization and electron-ion coincidence imaging

    NASA Astrophysics Data System (ADS)

    Rafiee Fanood, Mohammad M.; Janssen, Maurice H. M.; Powis, Ivan

    2016-09-01

    Enantiomers of the monoterpene limonene have been investigated by (2 + 1) resonance enhanced multiphoton ionization and photoelectron circular dichroism employing tuneable, circularly polarized femtosecond laser pulses. Electron imaging detection provides 3D momentum measurement while electron-ion coincidence detection can be used to mass-tag individual electrons. Additional filtering, by accepting only parent ion tagged electrons, can be then used to provide discrimination against higher energy dissociative ionization mechanisms where more than three photons are absorbed to better delineate the two photon resonant, one photon ionization pathway. The promotion of different vibrational levels and, tentatively, different electronic ion core configurations in the intermediate Rydberg states can be achieved with different laser excitation wavelengths (420 nm, 412 nm, and 392 nm), in turn producing different state distributions in the resulting cations. Strong chiral asymmetries in the lab frame photoelectron angular distributions are quantified, and a comparison made with a single photon (synchrotron radiation) measurement at an equivalent photon energy.

  3. Orientation and alignment effects in ion-induced fragmentation of water: A triple coincidence study

    SciTech Connect

    Rajput, Jyoti; Safvan, C. P.

    2014-10-28

    The technique of recoil ion momentum spectroscopy is employed to determine the complete momentum vectors for three fragment dissociation channels, [D{sub 2}O]{sup (q+2)} → (D{sup +} + D{sup +} + O{sup q+}) with q = 1, 2, or 3 formed in collisions of isolated water molecules with 450 keV Xe{sup 9+} ions. The kinetic energy released in each of these dissociation channels is measured and angular correlations between the fragment momenta are determined. From the angular correlations of the three fragment ions with the direction of the incoming beam, a strong anisotropy in the emission of recoil fragments is reported. It is inferred that the molecular plane prefers to lie orthogonal to the incoming beam direction with certain orientations being more preferred than others and a clear signature of non-coplanar dissociation is also observed.

  4. Soft-x-ray-induced ionization and fragmentation dynamics of Sc3N @C80 investigated using an ion-ion-coincidence momentum-imaging technique

    NASA Astrophysics Data System (ADS)

    Xiong, Hui; Obaid, Razib; Fang, Li; Bomme, Cédric; Kling, Nora G.; Ablikim, Utuq; Petrovic, Vladimir; Liekhus-Schmaltz, Chelsea E.; Li, Heng; Bilodeau, Rene C.; Wolf, Thomas; Osipov, Timur; Rolles, Daniel; Berrah, Nora

    2017-09-01

    The fragmentation dynamics of an endohedral fullerene, S c3N @C80 , after absorption of a soft-x-ray photon, has been studied with an ion-ion-coincidence momentum-imaging technique. Molecular inner-shell ionization at 406.5 eV, targeting the Sc (2 p ) shell of the encapsulated S c3N moiety and the C (1 s ) shell of the C80 cage, leads to the cage fragmentation through evaporation of C2, emission of small molecular carbon ions (Cn+ , n ≤24 ), and release of Sc and Sc-containing ions associated with the carbon cage opening or fragmentation. The predominant charge states of Sc and Sc-containing ionic fragments are +1 despite an effective Sc valence of 2.4, indicating that charge transfer or redistribution plays an important role in the fragmentation of the encaged S c3N . Sequential emission of two out of the three Sc atoms of the encaged moiety, via Coulomb explosion in the form of S c+ or Sc-containing ions, is significant. We also find that the resonant excitation of the Sc (2 p ) shell electrons significantly increased the yield of the parent S c3N @C80 and its fragment ions, partially attributed to the collision of the energetic Auger electrons from the Sc site with the carbon cage.

  5. Ion-coincidence momentum imaging of three-body Coulomb explosion of formaldehyde in ultrashort intense laser fields

    SciTech Connect

    Fushitani, M.; Matsuda, A.; Hishikawa, A.; Tseng, C.-M.

    2015-12-31

    Three-body Coulomb explosion of formaldehyde (H{sub 2}CO) in intense 7- and 35-fs laser fields (1.3 × 10{sup 15} W/cm{sup 2}) has been investigated by using ion-coincidence momentum imaging technique. Two types of explosion pathways from the triply charged state, H{sub 2}CO{sup 3+} → (i) H{sup +} + H{sup +} + CO{sup +} and (ii) H{sup +} + CH{sup +} + O{sup +}, have been identified. It is shown from the momentum correlation of the fragment ions of pathway (i), that the geometrical structure of the molecule is essentially frozen along the H-C-H bending coordinate for the 7-fs case. On the other hand, for a longer pulse duration (35 fs), structural deformation along the C-H stretching and H-C-H bending coordinates is identified, which is ascribed to the nuclear dynamics in the dication states populated within the laser pulse duration.

  6. A new electron-ion coincidence 3D momentum-imaging method and its application in probing strong field dynamics of 2-phenylethyl-N, N-dimethylamine.

    PubMed

    Fan, Lin; Lee, Suk Kyoung; Tu, Yi-Jung; Mignolet, Benoît; Couch, David; Dorney, Kevin; Nguyen, Quynh; Wooldridge, Laura; Murnane, Margaret; Remacle, Françoise; Bernhard Schlegel, H; Li, Wen

    2017-07-07

    We report the development of a new three-dimensional (3D) momentum-imaging setup based on conventional velocity map imaging to achieve the coincidence measurement of photoelectrons and photo-ions. This setup uses only one imaging detector (microchannel plates (MCP)/phosphor screen) but the voltages on electrodes are pulsed to push both electrons and ions toward the same detector. The ion-electron coincidence is achieved using two cameras to capture images of ions and electrons separately. The time-of-flight of ions and electrons are read out from MCP using a digitizer. We demonstrate this new system by studying the dissociative single and double ionization of PENNA (2-phenylethyl-N,N-dimethylamine). We further show that the camera-based 3D imaging system can operate at 10 kHz repetition rate.

  7. A new electron-ion coincidence 3D momentum-imaging method and its application in probing strong field dynamics of 2-phenylethyl-N, N-dimethylamine

    NASA Astrophysics Data System (ADS)

    Fan, Lin; Lee, Suk Kyoung; Tu, Yi-Jung; Mignolet, Benoît; Couch, David; Dorney, Kevin; Nguyen, Quynh; Wooldridge, Laura; Murnane, Margaret; Remacle, Françoise; Bernhard Schlegel, H.; Li, Wen

    2017-07-01

    We report the development of a new three-dimensional (3D) momentum-imaging setup based on conventional velocity map imaging to achieve the coincidence measurement of photoelectrons and photo-ions. This setup uses only one imaging detector (microchannel plates (MCP)/phosphor screen) but the voltages on electrodes are pulsed to push both electrons and ions toward the same detector. The ion-electron coincidence is achieved using two cameras to capture images of ions and electrons separately. The time-of-flight of ions and electrons are read out from MCP using a digitizer. We demonstrate this new system by studying the dissociative single and double ionization of PENNA (2-phenylethyl-N,N-dimethylamine). We further show that the camera-based 3D imaging system can operate at 10 kHz repetition rate.

  8. Multipathway dissociation dynamics of core-excited methyl chloride probed by high resolution electron spectroscopy and Auger-electron-ion coincidences.

    PubMed

    Miron, Catalin; Morin, Paul; Céolin, Denis; Journel, Loïc; Simon, Marc

    2008-04-21

    Core excitation triggers nuclear dynamics on the femtosecond time scale. A multiparametric electron/ion coincidence approach has been used to disentangle complex decay processes occurring at short (molecular) or long (atomic) time scales. Methyl chloride has been excited by scanning along the dissociative Cl2p-->sigma* resonance. The detailed chronology of the competing decay processes, leading to either the rearrangement product HCl(+), or an ultrafast dissociation leading to Cl(+), has been investigated. The observed Auger-Doppler shift has been analyzed for various orientations of the electron and fragment ion.

  9. Inner-shell multiple ionization of polyatomic molecules with an intense x-ray free-electron laser studied by coincident ion momentum imaging

    NASA Astrophysics Data System (ADS)

    Erk, B.; Rolles, D.; Foucar, L.; Rudek, B.; Epp, S. W.; Cryle, M.; Bostedt, C.; Schorb, S.; Bozek, J.; Rouzee, A.; Hundertmark, A.; Marchenko, T.; Simon, M.; Filsinger, F.; Christensen, L.; De, S.; Trippel, S.; Küpper, J.; Stapelfeldt, H.; Wada, S.; Ueda, K.; Swiggers, M.; Messerschmidt, M.; Schröter, C. D.; Moshammer, R.; Schlichting, I.; Ullrich, J.; Rudenko, A.

    2013-08-01

    The ionization and fragmentation of two selenium containing hydrocarbon molecules, methylselenol (CH3SeH) and ethylselenol (C2H5SeH), by intense (>1017 W cm-2) 5 fs x-ray pulses with photon energies of 1.7 and 2 keV has been studied by means of coincident ion momentum spectroscopy. Measuring charge states and ion kinetic energies, we find signatures of charge redistribution within the molecular environment. Furthermore, by analyzing fragment ion angular correlations, we can determine the laboratory-frame orientation of individual molecules and thus investigate the fragmentation dynamics in the molecular frame. This allows distinguishing protons originating from different molecular sites along with identifying the reaction channels that lead to their emission.

  10. An experimental setup for studying the core-excited atoms and molecules by electron impact using energy analysed electron-ion coincidence technique

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Prajapati, S.; Singh, B.; Singh, B. K.; Shanker, R.

    2017-07-01

    Operation and performance of an apparatus for studying the decay dynamics relevant to core-hole decay processes in atoms and molecules excited by energetic electrons using an energy analysed electron-ion coincidence technique are described in some detail. The setup consists of a time- and position sensitive double-field linear TOF mass spectrometer coupled with a dual MCP detector and a single-pass CMA to select the energy of detected electrons. Details of different components involved in the setup are presented and discussed. To demonstrate the performance and capability of the apparatus, we present some typical results extracted from the TOF argon ion-mass spectra observed in coincidence with 18-energy selected electrons emitted from interaction of a continuous beam of 3.5 keV electrons with a dilute gaseous target of argon atoms. Specifically, the variation of relative correlation probability for the final ion-charge states Ar1+ to Ar4+ produced in the considered collision reactions as a function of energy of emitted electrons is determined and discussed.

  11. An experimental setup for studying the core-excited atoms and molecules by electron impact using energy analysed electron-ion coincidence technique

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Prajapati, S.; Singh, B.; Singh, B. K.; Shanker, R.

    2017-02-01

    Operation and performance of an apparatus for studying the decay dynamics relevant to core-hole decay processes in atoms and molecules excited by energetic electrons using an energy analysed electron-ion coincidence technique are described in some detail. The setup consists of a time- and position sensitive double-field linear TOF mass spectrometer coupled with a dual MCP detector and a single-pass CMA to select the energy of detected electrons. Details of different components involved in the setup are presented and discussed. To demonstrate the performance and capability of the apparatus, we present some typical results extracted from the TOF argon ion-mass spectra observed in coincidence with 18-energy selected electrons emitted from interaction of a continuous beam of 3.5 keV electrons with a dilute gaseous target of argon atoms. Specifically, the variation of relative correlation probability for the final ion-charge states Ar1+ to Ar4+ produced in the considered collision reactions as a function of energy of emitted electrons is determined and discussed.

  12. Selected ion flow tube cation-molecule reaction studies and threshold photoelectron photoion coincidence spectroscopy of cyclic-C5F8.

    PubMed

    Parkes, Michael A; Ali, Sahangir; Tuckett, Richard P; Mikhailov, Victor A; Mayhew, Chris A

    2007-10-14

    The product ion branching ratios and rate coefficients have been measured using a selected ion flow tube (SIFT) at 298 K for the bimolecular reactions of cyclic-C5F8 with several atomic and molecular cations. The majority of reactions occur at the collisional rate calculated by the modified average dipole orientation theory, with the exception of H2O+ for which the reaction efficiency is only 55%. Apart from H2O+ and N+, the similarity of the product ion branching ratios determined from threshold photoelectron photoion coincidence (TPEPICO) and ion-molecule data suggests that long-range electron transfer is the dominant mechanism for reactions involving ions with recombination energies between 12 and 17 eV. For N+, the product ion branching ratios are very different to those produced by photoionisation; this result may be explained if some of the N-atom products are formed electronically excited. The onset of an ionisation signal of c-C5F8 measured by TPEPICO spectroscopy occurs at 12.25 +/- 0.05 eV. This is much higher than the value of the first adiabatic ionisation energy determined from electron ionisation (11.24 +/- 0.10 eV), He (I) photoionisation (11.30 +/- 0.05 eV), and an independent high resolution threshold photoelectron spectrum (11.237 +/- 0.002 eV). The ground electronic state of c-C5F8+ has very weak intensity under threshold electron conditions. The TPEPICO spectrum of c-C5F8 recorded from 12-23 eV shows detection of the parent ion and the daughter ions C4F6+ and C5F7+, with their appearance energies increasing in this order. Ion yield curves and branching ratios have been determined. Using Gaussian 03, the enthalpy of formation of c-C5F8 at 298 K has been determined to be -1495 kJ mol(-1).

  13. Dissociation of vibrational state-selected O2(+) Ions in the B(2)Σ(g)¯ state using threshold photoelectron-photoion coincidence velocity imaging.

    PubMed

    Tang, Xiaofeng; Zhou, Xiaoguo; Niu, Mingli; Liu, Shilin; Sheng, Liusi

    2011-06-23

    Using the recently developed threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging mass spectrometer (Tang et al. Rev. Sci. Instrum.2009, 80, 113101), dissociation of vibrational state-selected O(2)(+)(B(2)Σ(g)(¯), v(+) = 0-6) ions was investigated. Both the speed and angular distributions of the O(+) fragments dissociated from individually vibronic levels of the B(2)Σ(g)(¯) state were obtained directly from the three-dimensional time-sliced TPEPICO velocity images. Two dissociation channels, O(+)((4)S) + O((3)P) and O(+)((4)S) + O((1)D), were respectively observed, and their branching ratios were found to be heavily dependent on the vibrational states. A new intersection mechanism was suggested for the predissociation of O(2)(+)(B(2)Σ(g)(¯)) ions, especially for dissociation at the energy of the v(+) = 4 level. In addition, the anisotropic parameters for O(+) fragments from different dissociative pathways were determined to be close to zero, indicating that the v(+) = 0-6 levels of B(2)Σ(g)(¯) predissociate on a time scale that is much slower than that of molecular rotation.

  14. Vacuum upgrade and enhanced performances of the double imaging electron/ion coincidence end-station at the vacuum ultraviolet beamline DESIRS.

    PubMed

    Tang, Xiaofeng; Garcia, Gustavo A; Gil, Jean-François; Nahon, Laurent

    2015-12-01

    We report here the recent upgrade of the SAPHIRS permanent photoionization end-station at the DESIRS vacuum ultraviolet beamline of synchrotron SOLEIL, whose performances have been enhanced by installing an additional double-skimmer differential chamber. The smaller molecular beam profile obtained at the interaction region has increased the mass resolution of the double imaging photoelectron photoion coincidence (i(2)PEPICO) spectrometer, DELICIOUS III, installed in the photoionization chamber of the SAPHIRS endstation, by a factor of two, to M/ΔM ∼ 1700 (FWHM). The electron kinetic energy resolution offered by the velocity map imaging (VMI) part of the spectrometer has been improved down to 2.8% (ΔE/E) as we show on the N2 photoionization case in the double skimmer configuration. As a representative example of the overall state-of-the-art i(2)PEPICO performances, experimental results of the dissociation of state-selected O2(+)(B(2)∑(g)(-), v(+) = 0-6) molecular ions performed at the fixed photon energy of hν = 21.1 eV are presented.

  15. Vacuum upgrade and enhanced performances of the double imaging electron/ion coincidence end-station at the vacuum ultraviolet beamline DESIRS

    NASA Astrophysics Data System (ADS)

    Tang, Xiaofeng; Garcia, Gustavo A.; Gil, Jean-François; Nahon, Laurent

    2015-12-01

    We report here the recent upgrade of the SAPHIRS permanent photoionization end-station at the DESIRS vacuum ultraviolet beamline of synchrotron SOLEIL, whose performances have been enhanced by installing an additional double-skimmer differential chamber. The smaller molecular beam profile obtained at the interaction region has increased the mass resolution of the double imaging photoelectron photoion coincidence (i2PEPICO) spectrometer, DELICIOUS III, installed in the photoionization chamber of the SAPHIRS endstation, by a factor of two, to M/ΔM ˜ 1700 (FWHM). The electron kinetic energy resolution offered by the velocity map imaging (VMI) part of the spectrometer has been improved down to 2.8% (ΔE/E) as we show on the N2 photoionization case in the double skimmer configuration. As a representative example of the overall state-of-the-art i2PEPICO performances, experimental results of the dissociation of state-selected O2+ (B 2 ∑ g - , v+ = 0-6) molecular ions performed at the fixed photon energy of hν = 21.1 eV are presented.

  16. Coincidence velocity map imaging using a single detector

    NASA Astrophysics Data System (ADS)

    Zhao, Arthur; Sándor, Péter; Weinacht, Thomas

    2017-07-01

    We demonstrate a single-detector velocity map imaging setup which is capable of rapidly switching between coincidence and non-coincidence measurements. By rapidly switching the extraction voltages on the electrostatic lenses, both electrons and ions can be collected in coincidence with a single detector. Using a fast camera as the 2D detector avoids the saturation problem associated with traditional delay line detectors and allows for easy transitions between coincidence and non-coincidence data collection modes. This is a major advantage in setting up a low-cost and versatile coincidence apparatus. We present both coincidence and non-coincidence measurements of strong field atomic and molecular ionization.

  17. Coincidence Proportional Counter

    DOEpatents

    Manley, J H

    1950-11-21

    A coincidence proportional counter having a plurality of collecting electrodes so disposed as to measure the range or energy spectrum of an ionizing particle-emitting source such as an alpha source, is disclosed.

  18. Investigation of the reaction of hydroxy and carbon monoxide to form hydrogen and carbon dioxide by Photoelectron-Photofragment Coincidence spectroscopy in a cryogenic ion beam trap

    NASA Astrophysics Data System (ADS)

    Johnson, Christopher Joseph

    2011-12-01

    The HOCO radical plays a crucial role in a wide variety of chemical processes, including atmospheric CO2 regulation and combustion chemistry, as an intermediate in the elementary reaction OH + CO → H + CO2 . However, scant information exists on this species due to the difficulties in studying it. Previous photoelectron-photofragment coincidence (PPC) studies performed in this laboratory have identified key processes occurring on the HOCO potential energy surface, but are complicated by the presence of internal excitation in the precursor anions, leading to uncertainties in product energies and dynamics. To address this, a new instrument has been constructed which incorporates a cryogenically cooled linear electrostatic storage device, providing a cold source of anions for dissociative photodetachment studies by PPC spectroscopy. The enhanced resolution and well-characterized energetics provided by this instrument have allowed the fundamental energetics and processes occurring on the HOCO potential energy surface to be studied in unprecedented detail. New data shows unambiguous confirmation of the presence of tunneling in the reaction HOCO → H + CO2. Careful study of this product channel has led to the generation a model one-dimensional potential barrier describing this process directly from experimental tunneling data, and tunneling lifetimes over a range of relevant internal energies to be predicted. High resolution photodetachment experiments provide a reassignment of the electron affinities of both cis- and trans-HOCO and the determination of several normal mode frequencies not previously measured in the gas phase, each with the support of high-level ab initio quantum chemical calculations. Further details on the previously-unknown isomer well depths and the process of isomerization have been extracted using this information. Finally, nonresonant two-photon photodetachment studies of NO2 -, a species with striking electronic structure similarities to HOCO

  19. Coincident disruptive coloration

    PubMed Central

    Cuthill, Innes C.; Székely, Aron

    2008-01-01

    Even if an animal matches its surroundings perfectly in colour and texture, any mismatch between the spatial phase of its pattern and that of the background, or shadow created by its three-dimensional relief, is potentially revealing. Nevertheless, for camouflage to be fully broken, the shape must be recognizable. Disruptive coloration acts against object recognition by the use of high-contrast internal colour boundaries to break up shape and form. As well as the general outline, characteristic features such as eyes and limbs must also be concealed; this can be achieved by having the colour patterns on different, but adjacent, body parts aligned to match each other (i.e. in phase). Such ‘coincident disruptive coloration’ ensures that there is no phase disjunction where body parts meet, and causes different sections of the body to blend perceptually. We tested this theory using field experiments with predation by wild birds on artificial moth-like targets, whose wings and (edible pastry) bodies had colour patterns that were variously coincident or not. We also carried out an experiment with humans searching for analogous targets on a computer screen. Both experiments show that coincident disruptive coloration is an effective mechanism for concealing an otherwise revealing body form. PMID:18990668

  20. Triple Coincidence Radioxenon Detector

    SciTech Connect

    McIntyre, Justin I.; Aalseth, Craig E.; Bowyer, Ted W.; Hayes, James C.; Heimbigner, Tom R.; Morris, Scott J.; Reeder, Paul L.

    2004-09-22

    The Automated Radioxenon Sampler/Analyzer (ARSA) built by Pacific Northwest National Laboratory (PNNL) is on e of the world’s most sensitive systems for monitoring the four radioxenon isotopes 133Xe, 133mXE, 131mXe and 135Xe. However, due to size, weight and power specifications appropriate to meet treaty-monitoring requirements; the ARSA is unsuitable for rapid deployment using modest transportation means. To transition this technology to a portable unit can be easily and rapidly deployed can be achieved by significant reductions in size, weight and power consumption if concentration were not required. As part of an exploratory effort to reduce both the size of the air sample and the gas processing requirement PNNL has developed an experimental nuclear detector to test and qualify the use of triple coincidence signatures (beta, conversion electron, x-ray) from two of the radioxenon isotopes (135Xe and 133Xe) as well as the more traditional beta-gamma coincidence signatures used by the ARSA system. The additional coincidence requirement allows for reduced passive shielding, and makes it possible for unambiguous detection of 133Xe and 153Xe in the presence of high 222Rn backgrounds. This paper will discuss the experimental setup and the results obtained for a 133Xe sample with and without 222Rn as an interference signature.

  1. Dissociative double-photoionization of butadiene in the 25-45 eV energy range using 3-D multi-coincidence ion momentum imaging spectrometry

    SciTech Connect

    Oghbaie, Shabnam; Gisselbrecht, Mathieu; Laksman, Joakim; Månsson, Erik P.; Sankari, Anna; Sorensen, Stacey L.

    2015-09-21

    Dissociative double-photoionization of butadiene in the 25-45 eV energy range has been studied with tunable synchrotron radiation using full three-dimensional ion momentum imaging. Using ab initio calculations, the electronic states of the molecular dication below 33 eV are identified. The results of the measurement and calculation show that double ionization from π orbitals selectively triggers twisting about the terminal or central C–C bonds. We show that this conformational rearrangement depends upon the dication electronic state, which effectively acts as a gateway for the dissociation reaction pathway. For photon energies above 33 eV, three-body dissociation channels where neutral H-atom evaporation precedes C–C charge-separation in the dication species appear in the correlation map. The fragment angular distributions support a model where the dication species is initially aligned with the molecular backbone parallel to the polarization vector of the light, indicating a high probability for double-ionization to the “gateway states” for molecules with this orientation.

  2. Neutral and charged photofragment coincidence imaging with soft x rays on molecular ion beams: Breakup of H3O+ at 13.5 nm

    NASA Astrophysics Data System (ADS)

    Pedersen, H. B.; Altevogt, S.; Jordon-Thaden, B.; Heber, O.; Lammich, L.; Rappaport, M. L.; Schwalm, D.; Ullrich, J.; Zajfman, D.; Treusch, R.; Guerassimova, N.; Martins, M.; Wolf, A.

    2009-07-01

    The fragmentation of the hydronium cation H3O+ after photoabsorption at 13.5 nm has been investigated with a crossed-photon-and-ion-beams experiment making pulsing and trapping techniques available for fragment momentum imaging at the intense Free-electron LASer in Hamburg. The observed photofragmentation patterns demonstrate that the photolysis of H3O+ proceeds by valence ionization into H3O2+ which subsequently fragments to mainly OH+2H+ and H2O++H+ with a branching ratio of up to 0.6:1 and with different degrees of excitation of the molecular fragment. The cross section for fragmentation into OH+2H+ is found to be (0.37±0.18)×10-18cm2 , while the total photoabsorption cross section is estimated to be greater than 0.95×10-18cm2 . The data suggest that ionization mainly occurs from the 3a1 and 1e valence orbitals and that initial ionization from 3a1 mainly leads to fragmentation into H2O+(AA21)+H+ while initial ionization from the 1e orbital predominantly populates the H2O+(BB22)+H+ and OH(XΠ2)+2H+ channels. The results are of significance for astrophysical models of gas clouds in the vicinity of hot radiating objects and for models of the chemistry of planetary and lunar ionospheres under solar irradiation.

  3. The Coincident Fission Fragment Detector (CFFD)

    NASA Astrophysics Data System (ADS)

    Wakhle, A.; Hammerton, K.; Kohley, Z.; Yurkon, J.; Stiefel, K.

    2017-08-01

    A Parallel Plate Avalanche Counter (PPAC) based fission detector system, called the Coincident Fission Fragment Detector (CFFD), has been developed for the ReA3 re-accelerator facility of the National Superconducting Cyclotron Laboratory (NSCL). Binary reaction kinematics are reconstructed based on position and time-of-flight measurements of fission fragments. Large area PPACs provide 1 ns level time resolution and mm level position resolution. The detectors allow measurements of fission product angular and mass distributions of heavy-ion induced fusion reactions. The 30 cm by 40 cm active area of each PPAC provides large solid angle coverage well suited for measurements of low intensity rare-isotope beams (RIBs).

  4. Combining attosecond XUV pulses with coincidence spectroscopy

    SciTech Connect

    Sabbar, M. Heuser, S.; Boge, R.; Lucchini, M.; Cirelli, C.; Keller, U.; Gallmann, L.

    2014-10-15

    Here we present a successful combination of an attosecond beamline with a COLTRIMS apparatus, which we refer to as AttoCOLTRIMS. The setup provides either single attosecond pulses or attosecond pulse trains for extreme ultraviolet-infrared pump-probe experiments. We achieve full attosecond stability by using an active interferometer stabilization. The capability of the setup is demonstrated by means of two measurements, which lie at the heart of the COLTRIMS detector: firstly, we resolve the rotating electric field vector of an elliptically polarized few-cycle infrared laser field by attosecond streaking exploiting the access to the 3D momentum space of the charged particles. Secondly, we show streaking measurements on different atomic species obtained simultaneously in a single measurement making use of the advantage of measuring ions and electrons in coincidence. Both of these studies demonstrate the potential of the AttoCOLTRIMS for attosecond science.

  5. Multiple channel programmable coincidence counter

    DOEpatents

    Arnone, Gaetano J.

    1990-01-01

    A programmable digital coincidence counter having multiple channels and featuring minimal dead time. Neutron detectors supply electrical pulses to a synchronizing circuit which in turn inputs derandomized pulses to an adding circuit. A random access memory circuit connected as a programmable length shift register receives and shifts the sum of the pulses, and outputs to a serializer. A counter is input by the adding circuit and downcounted by the seralizer, one pulse at a time. The decoded contents of the counter after each decrement is output to scalers.

  6. Coincidence/Multiplicity Photofission Measurements

    SciTech Connect

    J.L. Jones; M.T. Swinhoe; S.J. Tobin; W. H. Geist; D.R. Norman; R.B. Rothrock; C.R. Freeman; K. J. Haskell

    2009-09-01

    An series of experiments using the Idaho National Laboratory (INL) photonuclear inspection system and a Los Alamos National Laboratory (LANL)-supplied, list-mode data acquisition method have shown enhanced performance utilizing pulsed photofission-induced, neutron coincidence counting between pulses of an up-to-10-MeV electron accelerator for nuclear material detection and identification. The enhanced inspection methodology has applicability to homeland security, treaty-related support, and weapon dismantlement applications. For the latter, this technology can directly support of Department of Energy/NA241 programmatic mission objectives relative to future Rocky Ridge-type testing campaigns for active inspection systems.

  7. Soft coincidence in late acceleration

    SciTech Connect

    Campo, Sergio del; Herrera, Ramon; Pavon, Diego

    2005-06-15

    We study the coincidence problem of late cosmic acceleration by assuming that the present ratio between dark matter and dark energy is a slowly varying function of the scale factor. As the dark energy component we consider two different candidates, first a quintessence scalar field, and then a tachyon field. In either case analytical solutions for the scale factor, the field, and the potential are derived. Both models show a good fit to the recent magnitude-redshift supernovae data. However, the likelihood contours disfavor the tachyon field model as it seems to prefer a excessively high value for the matter component.

  8. Digital coincidence counting - initial results

    NASA Astrophysics Data System (ADS)

    Butcher, K. S. A.; Watt, G. C.; Alexiev, D.; van der Gaast, H.; Davies, J.; Mo, Li; Wyllie, H. A.; Keightley, J. D.; Smith, D.; Woods, M. J.

    2000-08-01

    Digital Coincidence Counting (DCC) is a new technique in radiation metrology, based on the older method of analogue coincidence counting. It has been developed by the Australian Nuclear Science and Technology Organisation (ANSTO), in collaboration with the National Physical Laboratory (NPL) of the United Kingdom, as a faster more reliable means of determining the activity of ionising radiation samples. The technique employs a dual channel analogue-to-digital converter acquisition system for collecting pulse information from a 4π beta detector and an NaI(Tl) gamma detector. The digitised pulse information is stored on a high-speed hard disk and timing information for both channels is also stored. The data may subsequently be recalled and analysed using software-based algorithms. In this letter we describe some recent results obtained with the new acquistion hardware being tested at ANSTO. The system is fully operational and is now in routine use. Results for 60Co and 22Na radiation activity calibrations are presented, initial results with 153Sm are also briefly mentioned.

  9. Well coincidence counting and analysis

    SciTech Connect

    Lu, Ming-Shih; Teichmann, T.; Ceo, R.N.; Collins, L.L.

    1994-03-01

    In several recent papers a physical/mathematical model was developed to describe the nuclear multiplicative processes in samples containing fissile material from a general statistical viewpoint, starting with the basic underlying physical phenomena. The results of this model agreed with the established picture used in ``standard`` HLNCC (High Level Neutron Coincidence Counter) measurements, but considerably extended them, and allowed a more detailed interpretation of the underlying physical mechanisms and of the higher moments of the neutron counts. The present paper examines some recent measurements made at Y-12 (Oak Ridge) using the AWCC, in the light of this model. The results show internal consistency under a variety of conditions, and give good agreement between experiment and theory.

  10. Concepts for Alpha Coincidence Detection

    SciTech Connect

    Warren, Glen A.; Dion, Michael P.; Miller, Brian W.; Tatishvili, Gocha

    2015-03-01

    The effectiveness of conventional measurement techniques for environmental monitoring is limited by background and other interferences. We are exploring a new measurement approach involving the detection of α particles in coincidence with conversion electrons as a means to simultaneously assay environmental samples for actinides without chemical separation. The initial target isotopes studied in this work are 238Pu, 239Pu, 240Pu and 241Am. We explore various aspects of the design, such as impact of the mounting of the source material, resolution requirements and impact of a background on isotopic uncertainties. We conclude that a dual gas proportional counter and a dual-sided, large-area silicon detector could provide similar performance for the measurement scenario examined.

  11. Coincidence laser spectroscopy: A new ultrasensitive technique for fast ionic or atomic beams

    NASA Astrophysics Data System (ADS)

    Eastham, D. A.; Walker, P. M.; Smith, J. R. H.; Griffith, J. A. R.; Evans, D. E.; Wells, S. A.; Fawcett, M. J.; Grant, I. S.

    1986-12-01

    A new technique for laser spectroscopy of fast ionic or atomic beams is described. This involves measuring coincidences between resonantly scattered photons and ions (or atoms) in the fast beam. Measurements on strontium ions have shown that Doppler-free spectroscopy is possible with fewer than 100 ions s -1.

  12. Artifacts in digital coincidence timing

    SciTech Connect

    Moses, W. W.; Peng, Q.

    2014-10-16

    Digital methods are becoming increasingly popular for measuring time differences, and are the de facto standard in PET cameras. These methods usually include a master system clock and a (digital) arrival time estimate for each detector that is obtained by comparing the detector output signal to some reference portion of this clock (such as the rising edge). Time differences between detector signals are then obtained by subtracting the digitized estimates from a detector pair. A number of different methods can be used to generate the digitized arrival time of the detector output, such as sending a discriminator output into a time to digital converter (TDC) or digitizing the waveform and applying a more sophisticated algorithm to extract a timing estimator.All measurement methods are subject to error, and one generally wants to minimize these errors and so optimize the timing resolution. A common method for optimizing timing methods is to measure the coincidence timing resolution between two timing signals whose time difference should be constant (such as detecting gammas from positron annihilation) and selecting the method that minimizes the width of the distribution (i.e. the timing resolution). Unfortunately, a common form of error (a nonlinear transfer function) leads to artifacts that artificially narrow this resolution, which can lead to erroneous selection of the 'optimal' method. In conclusion, the purpose of this note is to demonstrate the origin of this artifact and suggest that caution should be used when optimizing time digitization systems solely on timing resolution minimization.

  13. Artifacts in Digital Coincidence Timing

    PubMed Central

    Moses, W. W.; Peng, Q.

    2014-01-01

    Digital methods are becoming increasingly popular for measuring time differences, and are the de facto standard in PET cameras. These methods usually include a master system clock and a (digital) arrival time estimate for each detector that is obtained by comparing the detector output signal to some reference portion of this clock (such as the rising edge). Time differences between detector signals are then obtained by subtracting the digitized estimates from a detector pair. A number of different methods can be used to generate the digitized arrival time of the detector output, such as sending a discriminator output into a time to digital converter (TDC) or digitizing the waveform and applying a more sophisticated algorithm to extract a timing estimator. All measurement methods are subject to error, and one generally wants to minimize these errors and so optimize the timing resolution. A common method for optimizing timing methods is to measure the coincidence timing resolution between two timing signals whose time difference should be constant (such as detecting gammas from positron annihilation) and selecting the method that minimizes the width of the distribution (i.e., the timing resolution). Unfortunately, a common form of error (a nonlinear transfer function) leads to artifacts that artificially narrow this resolution, which can lead to erroneous selection of the “optimal” method. The purpose of this note is to demonstrate the origin of this artifact and suggest that caution should be used when optimizing time digitization systems solely on timing resolution minimization. PMID:25321885

  14. A portable neutron coincidence counter

    SciTech Connect

    Peurrung, A.J.; Bowyer, S.M.; Craig, R.A.; Dudder, G.B.; Knopf, M.A.; Panisko, M.E.; Reeder, P.L.; Stromswold, D.C.; Sunberg, D.S.

    1996-11-01

    Pacific Northwest National Laboratory has designed and constructed a prototype portable neutron coincidence counter intended for use in a variety of applications, such as the verification and inspection of weapons components, safety measurements for novel and challenging situations, portable portal deployment to prevent the transportation of fissile materials, uranium enrichment measurements in hard-to-reach locations, waste assays for objects that cannot be measured by existing measurement systems, and decontamination and decommissioning. The counting system weighs less than 40 kg and is composed of parts each weighing no more than 5 kg. In addition, the counter`s design is sufficiently flexible to allow rapid, reliable assembly around containers of nearly arbitrary size and shape. The counter is able to discern the presence of 1 kg of weapons-grade plutonium within an ALR-8 (30-gal drum) in roughly 100 seconds and 10 g in roughly 1000 seconds. The counter`s electronics are also designed for maximum adaptability, allowing operation under a wide variety of circumstances, including exposure to gamma-ray fields of 1 R/h. This report provides a detailed review of the design and construction process. Finally, preliminary experimental measurements that confirm the performance capabilities of this counter are discussed. 6 refs., 18 figs., 3 tabs.

  15. Multiverse understanding of cosmological coincidences

    SciTech Connect

    Bousso, Raphael; Hall, Lawrence J.; Nomura, Yasunori

    2009-09-15

    There is a deep cosmological mystery: although dependent on very different underlying physics, the time scales of structure formation, of galaxy cooling (both radiatively and against the CMB), and of vacuum domination do not differ by many orders of magnitude, but are all comparable to the present age of the universe. By scanning four landscape parameters simultaneously, we show that this quadruple coincidence is resolved. We assume only that the statistical distribution of parameter values in the multiverse grows towards certain catastrophic boundaries we identify, across which there are drastic regime changes. We find order-of-magnitude predictions for the cosmological constant, the primordial density contrast, the temperature at matter-radiation equality, the typical galaxy mass, and the age of the universe, in terms of the fine structure constant and the electron, proton and Planck masses. Our approach permits a systematic evaluation of measure proposals; with the causal patch measure, we find no runaway of the primordial density contrast and the cosmological constant to large values.

  16. Data Acquisition System for Electron Energy Loss Coincident Spectrometers

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Yu, Xiaoqi; Yang, Tao

    2005-12-01

    A Data Acquisition System (DAQ) for electron energy loss coincident spectrometers (EELCS) has been developed. The system is composed of a Multiplex Time-Digital Converter (TDC) that measures the flying time of positive and negative ions and a one-dimension position-sensitive detector that records the energy loss of scattering electrons. The experimental data are buffered in a first-in-first-out (FIFO) memory module, then transferred from the FIFO memory to PC by the USB interface. The DAQ system can record the flying time of several ions in one collision, and allows of different data collection modes. The system has been demonstrated at the Electron Energy Loss Coincident Spectrometers at the Laboratory of Atomic and Molecular Physics, USTC. A detail description of the whole system is given and experimental results shown.

  17. Line-coincidence schemes for producing laser action at soft-x-ray wavelengths

    SciTech Connect

    Chapline, G.F.

    1983-01-12

    Line-coincidence schemes for producing laser action in the wavelength regime 100-30A are reviewed. Schemes involving pumping of 2..-->..4 transitions in neon-like ions are singled out as particularly attractive.

  18. Artifacts in digital coincidence timing

    DOE PAGES

    Moses, W. W.; Peng, Q.

    2014-10-16

    Digital methods are becoming increasingly popular for measuring time differences, and are the de facto standard in PET cameras. These methods usually include a master system clock and a (digital) arrival time estimate for each detector that is obtained by comparing the detector output signal to some reference portion of this clock (such as the rising edge). Time differences between detector signals are then obtained by subtracting the digitized estimates from a detector pair. A number of different methods can be used to generate the digitized arrival time of the detector output, such as sending a discriminator output into amore » time to digital converter (TDC) or digitizing the waveform and applying a more sophisticated algorithm to extract a timing estimator.All measurement methods are subject to error, and one generally wants to minimize these errors and so optimize the timing resolution. A common method for optimizing timing methods is to measure the coincidence timing resolution between two timing signals whose time difference should be constant (such as detecting gammas from positron annihilation) and selecting the method that minimizes the width of the distribution (i.e. the timing resolution). Unfortunately, a common form of error (a nonlinear transfer function) leads to artifacts that artificially narrow this resolution, which can lead to erroneous selection of the 'optimal' method. In conclusion, the purpose of this note is to demonstrate the origin of this artifact and suggest that caution should be used when optimizing time digitization systems solely on timing resolution minimization.« less

  19. From Mere Coincidences to Meaningful Discoveries

    ERIC Educational Resources Information Center

    Griffiths, Thomas L.; Tenenbaum, Joshua B.

    2007-01-01

    People's reactions to coincidences are often cited as an illustration of the irrationality of human reasoning about chance. We argue that coincidences may be better understood in terms of rational statistical inference, based on their functional role in processes of causal discovery and theory revision. We present a formal definition of…

  20. Sensitivity to coincidences and paranormal belief.

    PubMed

    Hadlaczky, Gergö; Westerlund, Joakim

    2011-12-01

    Often it is difficult to find a natural explanation as to why a surprising coincidence occurs. In attempting to find one, people may be inclined to accept paranormal explanations. The objective of this study was to investigate whether people with a lower threshold for being surprised by coincidences have a greater propensity to become believers compared to those with a higher threshold. Participants were exposed to artificial coincidences, which were formally defined as less or more probable, and were asked to provide remarkability ratings. Paranormal belief was measured by the Australian Sheep-Goat Scale. An analysis of the remarkability ratings revealed a significant interaction effect between Sheep-Goat score and type of coincidence, suggesting that people with lower thresholds of surprise, when experiencing coincidences, harbor higher paranormal belief than those with a higher threshold. The theoretical aspects of these findings were discussed.

  1. Redesign of the GATE PET coincidence sorter

    NASA Astrophysics Data System (ADS)

    Strydhorst, Jared; Buvat, Irène

    2016-09-01

    The GATE software platform, based on the Geant4 toolkit for simulating particle interactions with matter, enables simulation of, among other medical imaging and treatment systems, positron emission tomography. However, at least one publication (Moraes et al 2015 Phys. Med. 31 43-8) has reported discrepancies between the expected results and those obtained using GATE simulations, specifically with respect to the coincidence sorter which processes single events detected by the scanner to find coincidence pairs. In particular, the current software appears to overestimate the number of ‘true’ coincidence pairs when in multi-window mode, while the delayed coincidence window, used to estimate the randoms present in the prompt coincidence window, underestimates the randoms. Both effects are particularly evident at high count rates. We have investigated this discrepancy and reproduced the reported problems. We have also rewritten the relevant portion of the GATE code to correct the issue. In this note we describe the modifications to the coincidence sorter and repeat the simulations which previously showed unexpected results. Some discrepancies remain in the estimation of the randoms with the single-window mode which are a consequence of the algorithm itself. In multi-window mode however, the simulation agrees exactly with the expected results. The modifications to the coincidence sorter code will be incorporated into the next release of GATE (> version 7.2).

  2. Velocity map photoelectron-photoion coincidence imaging on a single detector.

    PubMed

    Lehmann, C Stefan; Ram, N Bhargava; Janssen, Maurice H M

    2012-09-01

    Here we report on a new simplified setup for velocity map photoelectron-photoion coincidence imaging using only a single particle detector. We show that both photoelectrons and photoions can be extracted toward the same micro-channel-plate delay line detector by fast switching of the high voltages on the ion optics. This single detector setup retains essentially all the features of a standard two-detector coincidence imaging setup, viz., the high spatial resolution for electron and ion imaging, while only slightly decreasing the ion time-of-flight mass resolution. The new setup paves the way to a significant cost reduction in building a coincidence imaging setup for experiments aiming to obtain the complete correlated three-dimensional momentum distribution of electrons and ions.

  3. Velocity map photoelectron-photoion coincidence imaging on a single detector

    SciTech Connect

    Lehmann, C. Stefan; Ram, N. Bhargava; Janssen, Maurice H. M.

    2012-09-15

    Here we report on a new simplified setup for velocity map photoelectron-photoion coincidence imaging using only a single particle detector. We show that both photoelectrons and photoions can be extracted toward the same micro-channel-plate delay line detector by fast switching of the high voltages on the ion optics. This single detector setup retains essentially all the features of a standard two-detector coincidence imaging setup, viz., the high spatial resolution for electron and ion imaging, while only slightly decreasing the ion time-of-flight mass resolution. The new setup paves the way to a significant cost reduction in building a coincidence imaging setup for experiments aiming to obtain the complete correlated three-dimensional momentum distribution of electrons and ions.

  4. Coincidence lattices in the hyperbolic plane.

    PubMed

    Rodríguez-Andrade, M A; Aragón-González, G; Aragón, J L; Gómez-Rodríguez, A

    2011-01-01

    The problem of coincidences of lattices in the space R(p,q), with p + q = 2, is analyzed using Clifford algebra. We show that, as in R(n), any coincidence isometry can be decomposed as a product of at most two reflections by vectors of the lattice. Bases and coincidence indices are constructed explicitly for several interesting lattices. Our procedure is metric-independent and, in particular, the hyperbolic plane is obtained when p = q = 1. Additionally, we provide a proof of the Cartan-Dieudonné theorem for R(p,q), with p + q = 2, that includes an algorithm to decompose an orthogonal transformation into a product of reflections.

  5. Coincident indices of exons and introns.

    PubMed

    Xu, J; Chen, R; Ling, L; Shen, R; Sun, J

    1993-07-01

    In this paper, the coincident index, proposed by W. F. Friedman in cryptology, is made use of in DNA sequence analysis and exon prediction. The coincident index of exons exceeds that of introns by many times, and is mainly affected by window length, which is correlated negatively with the coincident index. An optimal exon prediction scheme was obtained by experimental analysis with an orthogonal table. Besides exons, many other special sites such as tandem repeats can be identified by using the coincident index approach. The application of this approach to the ARV-2 (AIDS associated retrovirus 2) genome found three new possible coding regions and some unusual base composition regions which are probably related to definite biological functions.

  6. Highly charged ion secondary ion mass spectroscopy

    DOEpatents

    Hamza, Alex V.; Schenkel, Thomas; Barnes, Alan V.; Schneider, Dieter H.

    2001-01-01

    A secondary ion mass spectrometer using slow, highly charged ions produced in an electron beam ion trap permits ultra-sensitive surface analysis and high spatial resolution simultaneously. The spectrometer comprises an ion source producing a primary ion beam of highly charged ions that are directed at a target surface, a mass analyzer, and a microchannel plate detector of secondary ions that are sputtered from the target surface after interaction with the primary beam. The unusually high secondary ion yield permits the use of coincidence counting, in which the secondary ion stops are detected in coincidence with a particular secondary ion. The association of specific molecular species can be correlated. The unique multiple secondary nature of the highly charged ion interaction enables this new analytical technique.

  7. Determining activities of radionuclides from coincidence signatures

    NASA Astrophysics Data System (ADS)

    Warren, Glen A.; Smith, L. Eric; Aalseth, Craig E.; Ellis, Edward; Hossbach, Todd W.; Valsan, Andrei B.

    2006-05-01

    The spectral analysis of simultaneously observed photons in separate detectors may provide an invaluable tool for radioisotope identification applications. A general recursive method to determine the activity of an isotope from the observed coincidence signature rate is discussed. The method coherently accounts for effects of true coincidence summing within a single detector and detection efficiencies. A verification of the approach with computer simulations is also discussed.

  8. Simulation of triple coincidences in PET.

    PubMed

    Cal-González, J; Lage, E; Herranz, E; Vicente, E; Udias, J M; Moore, S C; Park, M-A; Dave, S R; Parot, V; Herraiz, J L

    2015-01-07

    Although current PET scanners are designed and optimized to detect double coincidence events, there is a significant amount of triple coincidences in any PET acquisition. Triple coincidences may arise from causes such as: inter-detector scatter (IDS), random triple interactions (RT), or the detection of prompt gamma rays in coincidence with annihilation photons when non-pure positron-emitting radionuclides are used (β(+)γ events). Depending on the data acquisition settings of the PET scanner, these triple events are discarded or processed as a set of double coincidences if the energy of the three detected events is within the scanner's energy window. This latter option introduces noise in the data, as at most, only one of the possible lines-of-response defined by triple interactions corresponds to the line along which the decay occurred. Several novel works have pointed out the possibility of using triple events to increase the sensitivity of PET scanners or to expand PET imaging capabilities by allowing differentiation between radiotracers labeled with non-pure and pure positron-emitting radionuclides. In this work, we extended the Monte Carlo simulator PeneloPET to assess the proportion of triple coincidences in PET acquisitions and to evaluate their possible applications. We validated the results of the simulator against experimental data acquired with a modified version of a commercial preclinical PET/CT scanner, which was enabled to acquire and process triple-coincidence events. We used as figures of merit the energy spectra for double and triple coincidences and the triples-to-doubles ratio for different energy windows and radionuclides. After validation, the simulator was used to predict the relative quantity of triple-coincidence events in two clinical scanners assuming different acquisition settings. Good agreement between simulations and preclinical experiments was found, with differences below 10% for most of the observables considered. For clinical

  9. Continuum studies in Gd nuclei by particle- γ coincidences

    NASA Astrophysics Data System (ADS)

    Ross, T. J.; Hughes, R. O.; Beausang, C. W.; Allmond, J. M.; Burke, J. T.; Phair, L. W.; Scielzo, N.; Angell, C. T.; Basunia, M. S.; Bleuel, D. L.; Casperson, R. J.; Fallon, P.; Hatarik, R.; Munson, J.; Paschalis, S.; Petri, M.; Ressler, J. J.

    2011-04-01

    An experiment was carried out at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory to study Gd isotopes in the vicinity of the N=90 transitional region. A 25 MeV proton beam was incident on 158 / 155 / 154Gd targets and used to populate states in 152-158Gd by (p,p'), (p,d) and (p,t) reactions. The exit channel is selected by gating on charged particles using the STARS Si-Telescope array, which also gives the excitation energy of the residual nucleus. Coincident γ information is obtained using the LIBERACE Clover array. Particle- γ coincidences provide a powerful tool for probing the residual nucleus [1]. For example, particles in coincidence with a specific γ ray produce a spectrum representing all levels populated in the nucleus that subsequently decay into the state from which the γ ray originates. Results will be presented that give an insight into the population distribution of the high level density region above the pair gap in the even-even Gd nuclei via light ion reactions.

  10. Coincidence imaging system with electron optics

    NASA Astrophysics Data System (ADS)

    Kroupa, Martin; Jakubek, Jan; Krejci, Frantisek; Zemlicka, J.; Horacek, M.; Radlicka, T.; Vlcek, I.

    2011-05-01

    As a part of multiple-detector system for coincidence instrumental neutron activation analysis (CINAA) a new method which includes a devoted electron optic unit has been built. In order to achieve higher sensitivity, enhanced contrast and higher spatial resolution the new coincidence imaging arrangement newly incorporates to electron optic unit, source, the gamma detector and the Timepix electron detector. The electron optic unit can be configured for different electron energies. The description of the assembled apparatus, calibration and performance for different electron energies are presented.

  11. On Points of Coincidence of Two Mappings

    NASA Astrophysics Data System (ADS)

    Davidjan, V. R.

    1981-02-01

    This paper is devoted to the coincidence theory of two continuous mappings.A definition is given, in cohomological terms, of the coincidence index I_{f, g} of two continuous mappings f, g \\colon M \\to N, where M and N are connected (not necessarily compact), orientable, n-dimensional topological manifolds without boundary, f is a compact mapping and g is a proper mapping.Invariance of the index I_{f, g} under compact homotopies of f and proper homotopies of g is proved. It is shown that I_{f, g} \

  12. A generalized model for coincidence counting

    SciTech Connect

    Lu, Ming-Shih; Teichmann, T.

    1993-12-31

    A generalized model for coincidence counting has been developed based on the dual probability generating function introduced. The model accounts explicitly and simultaneously the effects of multiplication, absorption by poison and instrument detection and is applicable for a wide class of NDA including Pu in waste.

  13. Using Compton scattering for random coincidence rejection

    NASA Astrophysics Data System (ADS)

    Kolstein, M.; Chmeissani, M.

    2016-12-01

    The Voxel Imaging PET (VIP) project presents a new approach for the design of nuclear medicine imaging devices by using highly segmented pixel CdTe sensors. CdTe detectors can achieve an energy resolution of ≈ 1% FWHM at 511 keV and can be easily segmented into submillimeter sized voxels for optimal spatial resolution. These features help in rejecting a large part of the scattered events from the PET coincidence sample in order to obtain high quality images. Another contribution to the background are random events, i.e., hits caused by two independent gammas without a common origin. Given that 60% of 511 keV photons undergo Compton scattering in CdTe (i.e. 84% of all coincidence events have at least one Compton scattering gamma), we present a simulation study on the possibility to use the Compton scattering information of at least one of the coincident gammas within the detector to reject random coincidences. The idea uses the fact that if a gamma undergoes Compton scattering in the detector, it will cause two hits in the pixel detectors. The first hit corresponds to the Compton scattering process. The second hit shall correspond to the photoelectric absorption of the remaining energy of the gamma. With the energy deposition of the first hit, one can calculate the Compton scattering angle. By measuring the hit location of the coincident gamma, we can construct the geometric angle, under the assumption that both gammas come from the same origin. Using the difference between the Compton scattering angle and the geometric angle, random events can be rejected.

  14. Toward a solution of the coincidence problem

    SciTech Connect

    Campo, Sergio del; Herrera, Ramon; Pavon, Diego

    2008-07-15

    The coincidence problem of late cosmic acceleration constitutes a serious riddle with regard to our understanding of the evolution of the Universe. Here we argue that this problem may someday be solved - or better understood - by expressing the Hubble expansion rate as a function of the ratio of densities (dark matter/dark energy) and observationally determining the said rate in terms of the redshift.

  15. Fast coincidence counting with active inspection systems

    NASA Astrophysics Data System (ADS)

    Mullens, J. A.; Neal, J. S.; Hausladen, P. A.; Pozzi, S. A.; Mihalczo, J. T.

    2005-12-01

    This paper describes 2nd and 3rd order time coincidence distributions measurements with a GHz processor that synchronously samples 5 or 10 channels of data from radiation detectors near fissile material. On-line, time coincidence distributions are measured between detectors or between detectors and an external stimulating source. Detector-to-detector correlations are useful for passive measurements also. The processor also measures the number of times n pulses occur in a selectable time window and compares this multiplet distribution to a Poisson distribution as a method of determining the occurrence of fission. The detectors respond to radiation emitted in the fission process induced internally by inherent sources or by external sources such as LINACS, DT generators either pulsed or steady state with alpha detectors, etc. Data can be acquired from prompt emission during the source pulse, prompt emissions immediately after the source pulse, or delayed emissions between source pulses. These types of time coincidence measurements (occurring on the time scale of the fission chain multiplication processes for nuclear weapons grade U and Pu) are useful for determining the presence of these fissile materials and quantifying the amount, and are useful for counter terrorism and nuclear material control and accountability. This paper presents the results for a variety of measurements.

  16. Cosmic Coincidences: Investigations for Neutron Background Suppression

    PubMed Central

    Heimbach, Craig R.

    2007-01-01

    Two experimental investigations were made in order to reduce background counts in neutron detectors. Each investigation relied upon the fact that neutron background is largely due to cosmic ray interactions with the air and ground. The first attempt was to look at neutron arrival times. Neutron events close in time were taken to have been of a common origin due to cosmic rays. The second investigation was similar, but based on coincident neutron/muon events. The investigations showed only a small effect, not practical for the suppression of neutron background. PMID:27110457

  17. Cosmic Coincidences: Investigations for Neutron Background Suppression.

    PubMed

    Heimbach, Craig R

    2007-01-01

    Two experimental investigations were made in order to reduce background counts in neutron detectors. Each investigation relied upon the fact that neutron background is largely due to cosmic ray interactions with the air and ground. The first attempt was to look at neutron arrival times. Neutron events close in time were taken to have been of a common origin due to cosmic rays. The second investigation was similar, but based on coincident neutron/muon events. The investigations showed only a small effect, not practical for the suppression of neutron background.

  18. A method for coincidence timing resolution enhancement

    SciTech Connect

    Ermis, E. E. Celiktas, C.; Pilicer, E.

    2016-05-15

    A method including the coincidence time resolution improvement for a TOF/positron emission tomography system was suggested. The spectrometer for this aim was composed of two NaI(Tl) and two plastic scintillation detectors. Experimental results were supported by FLUKA Monte Carlo simulation program by constructing the detector setup in software medium. Present experimental results verified our previous results and conclusions obtained from the suggested method. It was concluded that better resolutions would help the improvement not only on the TOF gain but also on the spatial resolution, leading to better images and helping the Physician in his/her diagnosis and treatment.

  19. A coincidence detection system based on real-time software

    NASA Astrophysics Data System (ADS)

    Ayuso, Sindulfo; José Blanco, Juan; Medina, José; Gómez-Herrero, Raúl; García-Población, Oscar; García Tejedor, Ignacio

    2016-09-01

    Conventional real-time coincidence systems use electronic circuitry to detect coincident pulses (hardware coincidence). In this work, a new concept of coincidence system based on real-time software (software coincidence) is presented. This system is based on the recurrent supervision of the analogue-to-digital converters status, which is described in detail. A prototype has been designed and built using a low-cost development platform. It has been applied to two different experimental sets for cosmic ray muon detection. Experimental muon measurements recorded simultaneously using conventional hardware coincidence and our software coincidence system have been compared, yielding identical results. These measurements have also been validated using simultaneous neutron monitor observations. This new software coincidence system provides remarkable advantages such as higher simplicity of interconnection and adjusting. Thus, our system replaces, at least, three Nuclear Instrument Modules (NIMs) required by conventional coincidence systems, reducing its cost by a factor of 40 and eliminating pulse delay adjustments.

  20. Estimates and Recommendations for Coincidence Geometry

    SciTech Connect

    Younes, W.; Ressler, J. J.

    2013-05-23

    When two truly coincident gamma-rays deposit their energy within the same detector, a composite pulse which is indistinguishable from one due to a single event may be recorded by that detector. This summing e effct is known to become more important as the distance from source to detector is decreased [1]. In this short report, we give a rough estimate for the size of this e ect as a function of source-to-detector distance. The formalism used in this report is taken mainly from [2], and similar results can also be found, e.g., in [1, 3, 4]. In general, the size of the e ect will depend on the exact level scheme of the nucleus studied, but for the sake of extracting numerical values, we will assume a particular level scheme in this report.

  1. Alpha Coincidence Spectroscopy studied with GEANT4

    SciTech Connect

    Dion, Michael P.; Miller, Brian W.; Tatishvili, Gocha; Warren, Glen A.

    2013-11-02

    Abstract The high-energy side of peaks in alpha spectra, e.g. 241Am, as measured with a silicon detector has structure caused mainly by alpha-conversion electron and to some extent alphagamma coincidences. We compare GEANT4 simulation results to 241Am alpha spectroscopy measurements with a passivated implanted planar silicon detector. A large discrepancy between the measurements and simulations suggest that the GEANT4 photon evaporation database for 237Np (daughter of 241Am decay) does not accurately describe the conversion electron spectrum and therefore was found to have large discrepancies with experimental measurements. We describe how to improve the agreement between GEANT4 and alpha spectroscopy for actinides of interest by including experimental measurements of conversion electron spectroscopy into the photon evaporation database.

  2. Response attenuation during coincident afferent excitatory inputs.

    PubMed

    Kogo, N; Ariel, M

    1999-06-01

    The linearity of the synaptic summation of two unitary excitatory synaptic events was investigated during whole cell recordings from retinal target neurons in an eye-attached isolated brain stem preparation. Pairs of unitary excitatory postsynaptic potentials (EPSPs) were evoked by bipolar stimulation electrodes that were directed to two distinct foci on the retinal surface based on the visual receptive field boundaries. The interval between stimulation of each retinal site was incremented by 0.5-1 ms to quantify the time course of nonlinear summation using an exponential fit. Response facilitation was never observed; however, the coincident arrival of synaptic inputs caused a response attenuation in 26 of the 37 pairs studied. Twelve of the 26 pairs had time constants of their attenuation that were similar to the time constants of the decaying phases of the first EPSPs of each pair. This suggests that the attenuation of these 12 pairs may be entirely due to voltage-dependent mechanisms, such as a reduction in driving force or a change of the activity of voltage-sensitive channels. On the other hand, the 14 other pairs had their time constant of attenuation shorter than the time constants of the decaying phase of the first EPSP. In fact, the attenuation time constants were often closer to the time constants of the decaying phases of the first excitatory postsynaptic currents of each pair. This finding suggests that the attenuation of these 14 pairs involve a shunting mechanism due to the opening of synaptic channels. The presence of this conductance-dependent mechanism is supported by the finding of asymmetric effects on the time course of attenuation when the stimulation sequence was reversed. These results are discussed in terms of the processing by neurons of coincident excitatory inputs onto spatially distinct points of their dendritic trees.

  3. On coincident loop transient electromagnetic induction logging

    DOE PAGES

    Swidinsky, Andrei; Weiss, Chester J.

    2017-05-31

    Coincident loop transient induction wireline logging is examined as the borehole analog of the well-known land and airborne time-domain electromagnetic (EM) method. The concept of whole-space late-time apparent resistivity is modified from the half-space version commonly used in land and airborne geophysics and applied to the coincident loop voltages produced from various formation, borehole, and invasion models. Given typical tool diameters, off-time measurements with such an instrument must be made on the order of nanoseconds to microseconds — much more rapidly than for surface methods. Departure curves of the apparent resistivity for thin beds, calculated using an algorithm developed tomore » model the transient response of a loop in a multilayered earth, indicate that the depth of investigation scales with the bed thickness. Modeled resistivity logs are comparable in accuracy and resolution with standard frequency-domain focused induction logs. However, if measurement times are longer than a few microseconds, the thicknesses of conductors can be overestimated, whereas resistors are underestimated. Thin-bed resolution characteristics are explained by visualizing snapshots of the EM fields in the formation, where a conductor traps the electric field while two current maxima are produced in the shoulder beds surrounding a resistor. Radial profiling is studied using a concentric cylinder earth model. Results found that true formation resistivity can be determined in the presence of either oil- or water-based mud, although in the latter case, measurements must be taken several orders of magnitude later in time. Lastly, the ability to determine true formation resistivity is governed by the degree that the EM field heals after being distorted by borehole fluid and invasion, a process visualized and particularly evident in the case of conductive water-based mud.« less

  4. Direct-Reaction Studies by Particle-Gamma Coincidence Spectroscopy Using HPGe-CsI and HPGe-Si Arrays

    SciTech Connect

    Allmond, James M

    2013-01-01

    Particle- and particle- - coincidence spectroscopy has several advantages in the study of direct reactions(particularly in inverse kinematics) since it can generally allow determination of: decay paths; high-precision level energies; multipolarities of transitions; and cross sections. Techniques for studying direct reactions by particle- coincidence spectroscopy are presented for two cases: (1) heavy-ion reactions with HPGe-CsI, and (2) light-ion reactions with HPGe-Si. Future direct-reaction studies with radioactive ion beams (RIBs) will mostly involve low beam intensities and inverse kinematics (i.e., Abeam>Atarget), which eliminates the traditional use of magnetic spectrometers. Particle- coincidence spectroscopy currently provides the most viable method to study direct reactions with nuclei of any level density. In the present study, the capabilities and limitations of the technique are explored.

  5. Direct-reaction studies by particle-{gamma} coincidence spectroscopy using Csi-Hpge and Si-Hpge arrays

    SciTech Connect

    Allmond, J. M.

    2013-04-19

    Particle-{gamma} and particle-{gamma}-{gamma} coincidence spectroscopy has several advantages in the study of direct reactions (particularly in inverse kinematics) since it can generally allow determination of: decay paths; high-precision level energies; multipolarities of transitions; and cross sections. Techniques for studying direct reactions by particle-{gamma} coincidence spectroscopy are presented for two cases: (1) heavy-ion reactions with CsI-HPGe, and (2) light-ion reactions with Si-HPGe. Future direct-reaction studies with radioactive ion beams (RIBs) will mostly involve low beam intensities and inverse kinematics (i.e., A{sub beam}>A{sub target}), which eliminates the traditional use of magnetic spectrometers. Particle-{gamma} coincidence spectroscopy currently provides the most viable method to study direct reactions with nuclei of any level density. In the present study, the capabilities and limitations of the technique are explored.

  6. K-chameleon and the coincidence problem

    SciTech Connect

    Wei Hao; Cai Ronggen

    2005-02-15

    In this paper we present a hybrid model of k-essence and chameleon, named as k-chameleon. In this model, due to the chameleon mechanism, the directly strong coupling between the k-chameleon field and matters (cold dark matters and baryons) is allowed. In the radiation-dominated epoch, the interaction between the k-chameleon field and background matters can be neglected; the behavior of the k-chameleon therefore is the same as that of the ordinary k-essence. After the onset of matter domination, the strong coupling between the k-chameleon and matters dramatically changes the result of the ordinary k-essence. We find that during the matter-dominated epoch, only two kinds of attractors may exist: one is the familiar K attractor and the other is a completely new, dubbed C attractor. Once the Universe is attracted into the C attractor, the fraction energy densities of the k-chameleon {omega}{sub {phi}} and dust matter {omega}{sub m} are fixed and comparable, and the Universe will undergo a power-law accelerated expansion. One can adjust the model so that the K attractor does not appear. Thus, the k-chameleon model provides a natural solution to the cosmological coincidence problem.

  7. Coincidence avoidance principle in surface haptic interpretation

    PubMed Central

    Manuel, Steven G.; Klatzky, Roberta L.; Peshkin, Michael A.; Colgate, James Edward

    2015-01-01

    When multiple fingertips experience force sensations, how does the brain interpret the combined sensation? In particular, under what conditions are the sensations perceived as separate or, alternatively, as an integrated whole? In this work, we used a custom force-feedback device to display force signals to two fingertips (index finger and thumb) as they traveled along collinear paths. Each finger experienced a pattern of forces that, taken individually, produced illusory virtual bumps, and subjects reported whether they felt zero, one, or two bumps. We varied the spatial separation between these bump-like force-feedback regions, from being much greater than the finger span to nearly exactly the finger span. When the bump spacing was the same as the finger span, subjects tended to report only one bump. We found that the results are consistent with a quantitative model of perception in which the brain selects a structural interpretation of force signals that relies on minimizing coincidence stemming from accidental alignments between fingertips and inferred surface structures. PMID:25675477

  8. Coincidence avoidance principle in surface haptic interpretation.

    PubMed

    Manuel, Steven G; Klatzky, Roberta L; Peshkin, Michael A; Colgate, James Edward

    2015-02-24

    When multiple fingertips experience force sensations, how does the brain interpret the combined sensation? In particular, under what conditions are the sensations perceived as separate or, alternatively, as an integrated whole? In this work, we used a custom force-feedback device to display force signals to two fingertips (index finger and thumb) as they traveled along collinear paths. Each finger experienced a pattern of forces that, taken individually, produced illusory virtual bumps, and subjects reported whether they felt zero, one, or two bumps. We varied the spatial separation between these bump-like force-feedback regions, from being much greater than the finger span to nearly exactly the finger span. When the bump spacing was the same as the finger span, subjects tended to report only one bump. We found that the results are consistent with a quantitative model of perception in which the brain selects a structural interpretation of force signals that relies on minimizing coincidence stemming from accidental alignments between fingertips and inferred surface structures.

  9. Broadband Electromagnetic Pulses Coinciding with Sprite Luminosity

    NASA Astrophysics Data System (ADS)

    Fullekrug, M.; Roussel-Dupre, R. A.; Symbalisty, E.; Chanrion, O.; van der Velde, O. A.; Odzimek, A.; Whitley, T.; Neubert, T.

    2009-12-01

    This study reports novel optical sprite observations in southern France during the summer months 2009 and the associated electromagnetic radiation emitted in the frequency range >50 kHz. About 10% of the observed sprites are associated with consecutive pulses of >50 kHz electromagnetic radiation. Some of these broadband pulses occur simultaneously with the sprite luminosity. In particular, the electromagnetic radiation of the sprite itself can coincide with a broadband pulse. This behaviour is predicted by the relativistic runaway breakdown theory, in which the lightning electromagnetic field accelerates free electrons to form a narrow particle beam shooting upward into near-Earth space. This vertical relativistic runaway breakdown describes a novel physical process within the Earth's atmosphere, even though it may occur only on extremely rare occasions, i.e., ~100 upward particle beams per day around the globe. The wealth of currently planned future space missions in this research area will greatly enhance the detection likelihood of the predicted particle beams.

  10. Incoherent coincidence imaging of space objects

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  11. The Higgs and top mass coincidence problem

    NASA Astrophysics Data System (ADS)

    Torrente-Lujan, E.

    2015-05-01

    On the light of the recent LHC boson discovery, we present a phenomenological evaluation of the ratio ρt = mZmt/m2H, from the LHC combined mH value, we get ((1σ)) {ρ _t}(exp) = 0.9956 ± 0.0081. This value is close to one with a precision of the order ˜ 1%. Similarly we evaluate the ratio ρWt = (mW + mt)/(2mH). From the up-to-date mass values we get ρ(exp)wt = 1.0066 ± 0.0035 (1σ). The Higgs mass is numerically close (at the 1% level) to the mH ˜ (mW + mt)/2. From these relations we can write any two mass ratios as a function of, exclusively, the Weinberg angle (with a precision of the order of 1% or better): {{{m_i}} over {{m_j}}} ≃ {fij}({θ _W}), i, j = W,Z, H, t. For example: mH/mZ ≃ 1 + √2s2θW/2, mH/mtcθW ≃ 1 - √2s2θW/2. In the limit cos θW → 1 all the masses would become equal mZ = mW = mt = mH. It is tempting to think that such a value, it is not a mere coincidence but, on naturalness grounds, a signal of some more deeper symmetry. In a model independent way, ρt can be viewed as the ratio of the highest massive representatives of the spin (0, 1/2, 1) SM and, to a very good precision the LHC evidence tell us that ms=1ms=1/2/m2s=0 ≃ 1. Somehow the "lowest" scalar particle mass is the geometric mean of the highest spin 1, 1/2 masses. We review the theoretical situation of this ratio in the SM and beyond. In the SM these relations are rather stable under RGE pointing out to some underlying UV symmetry. In the SM such a ratio hints for a non-casual relation of the type λ ≃ κ(g2 + g'2) with κ ≃ 1 + o(g/gt). Moreover the existence of relations mi/mj ≃ fij(θW) could be interpreted as a hint for a role of the SU(2)c custodial symmetry, together with other unknown mechanism. Without a symmetry at hand to explain then in the SM, it arises a Higgs mass coincidence problem, why the ratios ρt, ρWt are so close to one, can we find a mechanism that naturally

  12. Advances in coincidence time resolution for PET.

    PubMed

    Cates, Joshua W; Levin, Craig S

    2016-03-21

    Coincidence time resolution (CTR), an important parameter for time-of-flight (TOF) PET performance, is determined mainly by properties of the scintillation crystal and photodetector used. Stable production techniques for LGSO:Ce (Lu1.8Gd0.2SiO5:Ce) with decay times varying from ∼ 30-40 ns have been established over the past decade, and the decay time can be accurately controlled with varying cerium concentration (0.025-0.075 mol%). This material is promising for TOF-PET, as it has similar light output and equivalent stopping power for 511 keV annihilation photons compared to industry standard LSO:Ce and LYSO:Ce, and the decay time is improved by more than 30% with proper Ce concentration. This work investigates the achievable CTR with LGSO:Ce (0.025 mol%) when coupled to new silicon photomultipliers. Crystal element dimension is another important parameter for achieving fast timing. 20 mm length crystal elements achieve higher 511 keV photon detection efficiency, but also introduce higher scintillation photon transit time variance. 3 mm length crystals are not practical for PET, but have reduced scintillation transit time spread. The CTR between pairs of 2.9 × 2.9 × 3 mm(3) and 2.9 × 2.9 × 20 mm(3) LGSO:Ce crystals was measured to be 80 ± 4 and 122 ± 4 ps FWHM, respectively. Measurements of light yield and intrinsic decay time are also presented for a thorough investigation into the timing performance with LGSO:Ce (0.025 mol%).

  13. Imaging photoelectron circular dichroism of chiral molecules by femtosecond multiphoton coincidence detection.

    PubMed

    Lehmann, C Stefan; Ram, N Bhargava; Powis, Ivan; Janssen, Maurice H M

    2013-12-21

    Here, we provide a detailed account of novel experiments employing electron-ion coincidence imaging to discriminate chiral molecules. The full three-dimensional angular scattering distribution of electrons is measured after photoexcitation with either left or right circular polarized light. The experiment is performed using a simplified photoelectron-photoion coincidence imaging setup employing only a single particle imaging detector. Results are reported applying this technique to enantiomers of the chiral molecule camphor after three-photon ionization by circularly polarized femtosecond laser pulses at 400 nm and 380 nm. The electron-ion coincidence imaging provides the photoelectron spectrum of mass-selected ions that are observed in the time-of-flight mass spectra. The coincident photoelectron spectra of the parent camphor ion and the various fragment ions are the same, so it can be concluded that fragmentation of camphor happens after ionization. We discuss the forward-backward asymmetry in the photoelectron angular distribution which is expressed in Legendre polynomials with moments up to order six. Furthermore, we present a method, similar to one-photon electron circular dichroism, to quantify the strength of the chiral electron asymmetry in a single parameter. The circular dichroism in the photoelectron angular distribution of camphor is measured to be 8% at 400 nm. The electron circular dichroism using femtosecond multiphoton excitation is of opposite sign and about 60% larger than the electron dichroism observed before in near-threshold one-photon ionization with synchrotron excitation. We interpret our multiphoton ionization as being resonant at the two-photon level with the 3s and 3p Rydberg states of camphor. Theoretical calculations are presented that model the photoelectron angular distribution from a prealigned camphor molecule using density functional theory and continuum multiple scattering X alpha photoelectron scattering calculations

  14. An imaging photoelectron-photoion coincidence investigation of homochiral 2R,3R-butanediol clusters

    NASA Astrophysics Data System (ADS)

    Daly, Steven; Powis, Ivan; Garcia, Gustavo A.; Tia, Maurice; Nahon, Laurent

    2017-07-01

    We report an experimental investigation of homochiral cluster formation in seeded molecular beam expansions of (2R,3R)-butanediol. Synchrotron radiation vacuum ultraviolet photoionization measurements have been performed using a double imaging electron-ion spectrometer in various configurations and modes of operation. These include measurements of the cluster ion mass spectra, wavelength scanned ion yields, and threshold electron spectra. Protonated cluster ions ranging up to n = 7 have been observed and size-selected photoelectron spectra and photoelectron circular dichroism (PECD) have been recorded by velocity map imaging, recorded in coincidence with ions, at a number of fixed photon energies. Translation temperatures of the cluster ions have been further examined by ion imaging measurements. As well as the sequence of protonated clusters with integral numbers of butanediol monomer units, a second series with half-integral monomer masses is observed and deduced to result from a facile cleavage of a butanediol monomer moiety within the nascent cluster. This second sequence of half-integral masses displays quite distinct behaviours. PECD measurements are used to show that the half-integral mass cluster ions do not share a common parentage with whole integer masses. Using an analogy developed with simple theoretical calculations of butanediol dimer structures, it is inferred that the dissociative branching into integral and half-integral ion mass sequences is controlled by the presence of different butanediol monomer conformations within the hydrogen bonded clusters.

  15. Neutron coincidence counting with digital signal processing

    NASA Astrophysics Data System (ADS)

    Bagi, Janos; Dechamp, Luc; Dransart, Pascal; Dzbikowicz, Zdzislaw; Dufour, Jean-Luc; Holzleitner, Ludwig; Huszti, Joseph; Looman, Marc; Marin Ferrer, Montserrat; Lambert, Thierry; Peerani, Paolo; Rackham, Jamie; Swinhoe, Martyn; Tobin, Steve; Weber, Anne-Laure; Wilson, Mark

    2009-09-01

    Neutron coincidence counting is a widely adopted nondestructive assay (NDA) technique used in nuclear safeguards to measure the mass of nuclear material in samples. Nowadays, most neutron-counting systems are based on the original-shift-register technology, like the (ordinary or multiplicity) Shift-Register Analyser. The analogue signal from the He-3 tubes is processed by an amplifier/single channel analyser (SCA) producing a train of TTL pulses that are fed into an electronic unit that performs the time- correlation analysis. Following the suggestion of the main inspection authorities (IAEA, Euratom and the French Ministry of Industry), several research laboratories have started to study and develop prototypes of neutron-counting systems with PC-based processing. Collaboration in this field among JRC, IRSN and LANL has been established within the framework of the ESARDA-NDA working group. Joint testing campaigns have been performed in the JRC PERLA laboratory, using different equipment provided by the three partners. One area of development is the use of high-speed PCs and pulse acquisition electronics that provide a time stamp (LIST-Mode Acquisition) for every digital pulse. The time stamp data can be processed directly during acquisition or saved on a hard disk. The latter method has the advantage that measurement data can be analysed with different values for parameters like predelay and gate width, without repeating the acquisition. Other useful diagnostic information, such as die-away time and dead time, can also be extracted from this stored data. A second area is the development of "virtual instruments." These devices, in which the pulse-processing system can be embedded in the neutron counter itself and sends counting data to a PC, can give increased data-acquisition speeds. Either or both of these developments could give rise to the next generation of instrumentation for improved practical neutron-correlation measurements. The paper will describe the

  16. Is the ``IR Coincidence'' Just That?

    NASA Astrophysics Data System (ADS)

    Nowak, Michael A.; Wilms, Jörn; Heinz, Sebastian; Pooley, Guy; Pottschmidt, Katja; Corbel, Stephane

    2005-06-01

    Previous work by Motch et al. suggested that in the low/hard state of GX 339-4 the soft X-ray power law extrapolated backward in energy agrees with the IR flux level. Corbel & Fender later showed that the typical hard-state radio power law extrapolated forward in energy meets the backward-extrapolated X-ray power law at an IR spectral break, which was explicitly observed twice in GX 339-4. This IR coincidence has been cited as further evidence that synchrotron radiation from a jet might make a significant contribution to the observed X-rays in hard-state black hole systems. We quantitatively explore this hypothesis with a series of simultaneous radio/X-ray observations of GX 339-4, taken during its 1997, 1999, and 2002 hard states. We fit these spectra, in detector space, with a simple, but remarkably successful, doubly broken power-law model that indeed requires an IR spectral break. For these observations, the break position and the integrated radio/IR flux have stronger dependences upon the X-ray flux than the simplest jet model predictions. If one allows for a softening of the X-ray power law with increasing flux, then the jet model can agree with the observed correlation. We also find evidence that the radio flux-X-ray flux correlation previously observed in the 1997 and 1999 GX 339-4 hard states shows a parallel track for the 2002 hard state. The slope of the 2002 correlation is consistent with observations taken in prior hard states; however, the radio amplitude is reduced. We then examine the radio flux-X-ray flux correlation in Cyg X-1 through the use of 15 GHz radio data obtained with the Ryle radio telescope and Rossi X-Ray Timing Explorer data from the All-Sky Monitor and pointed observations. We again find evidence of parallel tracks, and here they are associated with ``failed transitions,'' or the beginning of a transition, to the soft state. We also find that for Cyg X-1 the radio flux is more fundamentally correlated with the hard, rather than the

  17. Is the `IR Coincidence' Just That?

    NASA Astrophysics Data System (ADS)

    Nowak, M.

    2005-09-01

    Previous work by Motch (1985) suggested that in the low/hard state of GX 339-4 the soft X-ray power-law extrapolated backward in energy agrees with the IR flux level. Corbel & Fender (2002) later showed that the typical hard state radio power-law extrapolated forward in energy meets the backward extrapolated X-ray power-law at an IR spectral break, which was explicitly observed twice in GX 339-4. This `IR coincidence' has been cited as further evidence that synchrotron radiation from a jet might make a significant contribution to the observed X-rays in hard state black hole systems. We quantitatively explore this hypothesis with a series of simultaneous radio/X-ray observations of GX 339-4, taken during its 1997, 1999, and 2002 hard states. We fit these spectra, in detector space, with a simple, but remarkably successful, doubly broken power-law model that indeed requires an IR spectral break. For these observations, the break position and the integrated radio/IR flux have stronger dependences upon the X-ray flux than the simplest jet model predictions. If one allows for a softening of the X-ray power law with increasing flux, then the jet model can agree with the observed correlation. We also find evidence that the radio flux/X-ray flux correlation previously observed in the 1997 and 1999 GX 339-4 hard states shows a `parallel track' for the 2002 hard state. The slope of the 2002 correlation is consistent with observations taken in prior hard states; however, the radio amplitude is reduced. We then examine the radio flux/X-ray flux correlation in Cyg X-1 through the use of 15 GHz radio data, obtained with the Ryle radio telescope, and Rossi X-ray Timing Explorer data, from the All Sky Monitor and pointed observations. We again find evidence of `parallel tracks', and here they are associated with `failed transitions' to, or the beginning of a transition to, the soft state. We also find that for Cyg X-1 the radio flux is more fundamentally correlated with the hard

  18. Direct decomposition of the experimental γ-γ coincidence matrix

    NASA Astrophysics Data System (ADS)

    Emelianov, B. A.; Kabina, L. P.; Kondurov, I. A.; Loginov, Yu. E.; Sushkov, P. A.

    1980-12-01

    Development here is the direct method of decomposition of the experimental matrix of γ-γ coincidences. Intensities of coincidences are calculated by an approximation of the total coincidence matrix within the framework of the chosen model of the coincidence spectra with the instrumental parameters and the a priori data on the scheme of the excited states of the nucleus under study. A two-dimensional Gaussian is used to describe an elementary coincidence peak. The volume value of the Gaussian is a measure of the γ-γ coincidence intensity in the given cascade. The method described was used for processing the experimental data in 104Rh, 108Ag, 122,124Sb and 134Cs studies via the (n, γ) reaction. The method is also valid in the analysis of any of two-parameter distributions which correspond to correlated events and which can be presented as two-dimensional matrices.

  19. Calculations of coincident ionization plus excitation

    SciTech Connect

    Becker, R.L.

    1986-01-01

    For Li- and Be-like ions, K x-ray yields, together with detection that the ionic charge has increased, give the cross section for ionization plus excitation (IE), a process which can exhibit electron-electron correlations. Measurements of IE for /sub 14/Si/sup 11 +/ + He stimulated our coupled-channels calculations in the independent-Fermi-particle model (IFPM), which includes Pauli correlations. We discuss how the IFPM expressions, generalized here to include an open shell, differ from those for distinguishable electrons. The sensitivity of sigma/sub IE/ to correlations is shown. Recent additional measurements and future ones giving excitation functions for resolved configurations and complementary Auger data will provide even more sensitive tests of collisional correlation theory. 15 refs., 3 figs., 1 tab.

  20. Introduction to Neutron Coincidence Counter Design Based on Boron-10

    SciTech Connect

    Kouzes, Richard T.; Ely, James H.; Lintereur, Azaree T.; Siciliano, Edward R.

    2012-01-22

    The Department of Energy Office of Nonproliferation Policy (NA-241) is supporting the project 'Coincidence Counting With Boron-Based Alternative Neutron Detection Technology' at Pacific Northwest National Laboratory (PNNL) for development of an alternative neutron coincidence counter. The goal of this project is ultimately to design, build and demonstrate a boron-lined proportional tube based alternative system in the configuration of a coincidence counter. This report, providing background information for this project, is the deliverable under Task 1 of the project.

  1. Clifford algebra approach to the coincidence problem for planar lattices.

    PubMed

    Rodríguez, M A; Aragón, J L; Verde-Star, L

    2005-03-01

    The problem of coincidences of planar lattices is analyzed using Clifford algebra. It is shown that an arbitrary coincidence isometry can be decomposed as a product of coincidence reflections and this allows planar coincidence lattices to be characterized algebraically. The cases of square, rectangular and rhombic lattices are worked out in detail. One of the aims of this work is to show the potential usefulness of Clifford algebra in crystallography. The power of Clifford algebra for expressing geometric ideas is exploited here and the procedure presented can be generalized to higher dimensions.

  2. Uranium Neutron Coincidence Collar Model Utilizing Boron-10 Lined Tubes

    SciTech Connect

    Rogers, Jeremy L.; Ely, James H.; Kouzes, Richard T.; Lintereur, Azaree T.; Siciliano, Edward R.

    2012-09-18

    The Department of Energy Office of Nuclear Safeguards and Security (NA-241) is supporting the project Coincidence Counting With Boron-Based Alternative Neutron Detection Technology at Pacific Northwest National Laboratory (PNNL) for the development of a 3He proportional counter alternative neutron coincidence counter. The goal of this project is to design, build and demonstrate a system based upon 10B-lined proportional tubes in a configuration typical for 3He-based coincidence counter applications. This report, providing results for model development of Alternative Boron-Based Uranium Neutron Coincidence Collar (ABUNCL) designs, is a deliverable under Task 2 of the project.

  3. Coincidence technique to reduce geometry and matrix effects in assay

    SciTech Connect

    Zucker, M.S.; Gozani, T.; Bernatowicz, H.

    1983-01-01

    Algebraic combinations of coincidence multiplicities can be formed which are relatively independent of detection efficiency, yet proportional to the amount of nuclear material being assayed. Considering these combinations, rather than the coincidence alone as signatures, has the demonstrable advantage that the assay results are comparatively independent of sample geometry or even matrix.

  4. A recent coincidence experiment of gravitational waves with long baseline

    NASA Astrophysics Data System (ADS)

    Hu, Enke; Guan, Tongren; Yu, Bo; Tang, Mengxi; Chen, Shusen; Zheng, Qingzhang; P, F. Michelson; B, E. Moskowitz; M, S. McAshan; W, M. Fairbank; M, Bassan

    1986-12-01

    The results of coincidence experiment which was carried out in the whole month of April, 1985 by two gravitational wave detectors in stanford and in Guangzhou are presented. It is found that up to sensitivity of h cong 10-16 the number of coincident events did not excess the number expected statistically.

  5. Novel Beta-Gamma Coincidence Measurements Using Phoswich Detectors

    SciTech Connect

    Ely, James H.; Aalseth, Craig E.; Hayes, James C.; Heimbigner, Tom R.; McIntyre, Justin I.; Miley, Harry S.; Panisko, Mark E.; Ripplinger, Mike D.

    2003-09-30

    The PNNL has developed an Automated Radio-xenon Sampler/Analyzer (ARSA) for the CTBT to measure four radio-xenon isotopes using a beta-gamma coincidence counting detector. A novel method to measure beta-gamma coincidences using a phoswich detector with state-of-the-art pulse shape discrimination techniqueses has been investigated.

  6. Coincidence Prompt Gamma-Ray Neutron Activation Analysis

    SciTech Connect

    R.P. gandner; C.W. Mayo; W.A. Metwally; W. Zhang; W. Guo; A. Shehata

    2002-11-10

    The normal prompt gamma-ray neutron activation analysis for either bulk or small beam samples inherently has a small signal-to-noise (S/N) ratio due primarily to the neutron source being present while the sample signal is being obtained. Coincidence counting offers the possibility of greatly reducing or eliminating the noise generated by the neutron source. The present report presents our results to date on implementing the coincidence counting PGNAA approach. We conclude that coincidence PGNAA yields: (1) a larger signal-to-noise (S/N) ratio, (2) more information (and therefore better accuracy) from essentially the same experiment when sophisticated coincidence electronics are used that can yield singles and coincidences simultaneously, and (3) a reduced (one or two orders of magnitude) signal from essentially the same experiment. In future work we will concentrate on: (1) modifying the existing CEARPGS Monte Carlo code to incorporate coincidence counting, (2) obtaining coincidence schemes for 18 or 20 of the common elements in coal and cement, and (3) optimizing the design of a PGNAA coincidence system for the bulk analysis of coal.

  7. Shift-register coincidence electronics system for thermal neutron counters

    SciTech Connect

    Swansen, J.E.; Collinsworth, P.R.; Krick, M.S.

    1980-04-01

    An improved shift-register, coincidence-counting logic circuit, developed for use with thermal neutron well counters, is described in detail. A distinguishing feature of the circuit is its ability to operate usefully at neutron counting rates of several hundred kHz. A portable electronics package incorporating the new coincidence logic and support circuits is also described.

  8. Recovery and normalization of triple coincidences in PET

    SciTech Connect

    Lage, Eduardo Parot, Vicente; Dave, Shivang R.; Herraiz, Joaquin L.; Moore, Stephen C.; Sitek, Arkadiusz; Park, Mi-Ae; Udías, Jose M.; Vaquero, Juan J.

    2015-03-15

    Purpose: Triple coincidences in positron emission tomography (PET) are events in which three γ-rays are detected simultaneously. These events, though potentially useful for enhancing the sensitivity of PET scanners, are discarded or processed without special consideration in current systems, because there is not a clear criterion for assigning them to a unique line-of-response (LOR). Methods proposed for recovering such events usually rely on the use of highly specialized detection systems, hampering general adoption, and/or are based on Compton-scatter kinematics and, consequently, are limited in accuracy by the energy resolution of standard PET detectors. In this work, the authors propose a simple and general solution for recovering triple coincidences, which does not require specialized detectors or additional energy resolution requirements. Methods: To recover triple coincidences, the authors’ method distributes such events among their possible LORs using the relative proportions of double coincidences in these LORs. The authors show analytically that this assignment scheme represents the maximum-likelihood solution for the triple-coincidence distribution problem. The PET component of a preclinical PET/CT scanner was adapted to enable the acquisition and processing of triple coincidences. Since the efficiencies for detecting double and triple events were found to be different throughout the scanner field-of-view, a normalization procedure specific for triple coincidences was also developed. The effect of including triple coincidences using their method was compared against the cases of equally weighting the triples among their possible LORs and discarding all the triple events. The authors used as figures of merit for this comparison sensitivity, noise-equivalent count (NEC) rates and image quality calculated as described in the NEMA NU-4 protocol for the assessment of preclinical PET scanners. Results: The addition of triple-coincidence events with the

  9. A precise calculation of delayed coincidence selection efficiency and accidental coincidence rate

    NASA Astrophysics Data System (ADS)

    Yu, Jing-Yi; Wang, Zhe; Chen, Shao-Min

    2015-05-01

    A precise background evaluation model is proposed to address the complex data structure of the delayed coincidence method, which is widely used in reactor electron-antineutrino oscillation experiments. In this model, effects from the muon veto, uncorrelated random background, and background are all studied analytically, simplifying the estimation of the systematic uncertainties of signal efficiency and accidental background rate. The results of the calculations are validated numerically with a number of simulation studies and also applied and validated in the recent Daya Bay hydrogen-capture based oscillation measurement. Supported by Ministry of Science and Technology of China (2013CB834302), National Natural Science Foundation of China (11235006, 11475093), Tsinghua University Initiative Scientific Research Program (2012Z02161), and Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education.

  10. Roles for Coincidence Detection in Coding Amplitude-Modulated Sounds.

    PubMed

    Ashida, Go; Kretzberg, Jutta; Tollin, Daniel J

    2016-06-01

    Many sensory neurons encode temporal information by detecting coincident arrivals of synaptic inputs. In the mammalian auditory brainstem, binaural neurons of the medial superior olive (MSO) are known to act as coincidence detectors, whereas in the lateral superior olive (LSO) roles of coincidence detection have remained unclear. LSO neurons receive excitatory and inhibitory inputs driven by ipsilateral and contralateral acoustic stimuli, respectively, and vary their output spike rates according to interaural level differences. In addition, LSO neurons are also sensitive to binaural phase differences of low-frequency tones and envelopes of amplitude-modulated (AM) sounds. Previous physiological recordings in vivo found considerable variations in monaural AM-tuning across neurons. To investigate the underlying mechanisms of the observed temporal tuning properties of LSO and their sources of variability, we used a simple coincidence counting model and examined how specific parameters of coincidence detection affect monaural and binaural AM coding. Spike rates and phase-locking of evoked excitatory and spontaneous inhibitory inputs had only minor effects on LSO output to monaural AM inputs. In contrast, the coincidence threshold of the model neuron affected both the overall spike rates and the half-peak positions of the AM-tuning curve, whereas the width of the coincidence window merely influenced the output spike rates. The duration of the refractory period affected only the low-frequency portion of the monaural AM-tuning curve. Unlike monaural AM coding, temporal factors, such as the coincidence window and the effective duration of inhibition, played a major role in determining the trough positions of simulated binaural phase-response curves. In addition, empirically-observed level-dependence of binaural phase-coding was reproduced in the framework of our minimalistic coincidence counting model. These modeling results suggest that coincidence detection of excitatory

  11. Roles for Coincidence Detection in Coding Amplitude-Modulated Sounds

    PubMed Central

    Ashida, Go; Kretzberg, Jutta; Tollin, Daniel J.

    2016-01-01

    Many sensory neurons encode temporal information by detecting coincident arrivals of synaptic inputs. In the mammalian auditory brainstem, binaural neurons of the medial superior olive (MSO) are known to act as coincidence detectors, whereas in the lateral superior olive (LSO) roles of coincidence detection have remained unclear. LSO neurons receive excitatory and inhibitory inputs driven by ipsilateral and contralateral acoustic stimuli, respectively, and vary their output spike rates according to interaural level differences. In addition, LSO neurons are also sensitive to binaural phase differences of low-frequency tones and envelopes of amplitude-modulated (AM) sounds. Previous physiological recordings in vivo found considerable variations in monaural AM-tuning across neurons. To investigate the underlying mechanisms of the observed temporal tuning properties of LSO and their sources of variability, we used a simple coincidence counting model and examined how specific parameters of coincidence detection affect monaural and binaural AM coding. Spike rates and phase-locking of evoked excitatory and spontaneous inhibitory inputs had only minor effects on LSO output to monaural AM inputs. In contrast, the coincidence threshold of the model neuron affected both the overall spike rates and the half-peak positions of the AM-tuning curve, whereas the width of the coincidence window merely influenced the output spike rates. The duration of the refractory period affected only the low-frequency portion of the monaural AM-tuning curve. Unlike monaural AM coding, temporal factors, such as the coincidence window and the effective duration of inhibition, played a major role in determining the trough positions of simulated binaural phase-response curves. In addition, empirically-observed level-dependence of binaural phase-coding was reproduced in the framework of our minimalistic coincidence counting model. These modeling results suggest that coincidence detection of excitatory

  12. Active dendrites mediate stratified gamma-range coincidence detection in hippocampal model neurons

    PubMed Central

    Das, Anindita; Narayanan, Rishikesh

    2015-01-01

    Hippocampal pyramidal neurons exhibit gamma-phase preference in their spikes, selectively route inputs through gamma frequency multiplexing and are considered part of gamma-bound cell assemblies. How do these neurons exhibit gamma-frequency coincidence detection capabilities, a feature that is essential for the expression of these physiological observations, despite their slow membrane time constant? In this conductance-based modelling study, we developed quantitative metrics for the temporal window of integration/coincidence detection based on the spike-triggered average (STA) of the neuronal compartment. We employed these metrics in conjunction with quantitative measures for spike initiation dynamics to assess the emergence and dependence of coincidence detection and STA spectral selectivity on various ion channel combinations. We found that the presence of resonating conductances (hyperpolarization-activated cyclic nucleotide-gated or T-type calcium), either independently or synergistically when expressed together, led to the emergence of spectral selectivity in the spike initiation dynamics and a significant reduction in the coincidence detection window (CDW). The presence of A-type potassium channels, along with resonating conductances, reduced the STA characteristic frequency and broadened the CDW, but persistent sodium channels sharpened the CDW by strengthening the spectral selectivity in the STA. Finally, in a morphologically precise model endowed with experimentally constrained channel gradients, we found that somatodendritic compartments expressed functional maps of strong theta-frequency selectivity in spike initiation dynamics and gamma-range CDW. Our results reveal the heavy expression of resonating and spike-generating conductances as the mechanism underlying the robust emergence of stratified gamma-range coincidence detection in the dendrites of hippocampal and cortical pyramidal neurons. PMID:26018187

  13. 48-channel coincidence counting system for multiphoton experiment

    NASA Astrophysics Data System (ADS)

    Zhang, Chen; Li, Wei; Hu, Yi; Yang, Tao; Jin, Ge; Jiang, Xiao

    2016-11-01

    In this paper, we demonstrate a coincidence counting system with 48 input channels which is aimed to count all coincidence events, up to 531 441 kinds, in a multiphoton experiment. Using the dynamic delay adjusting inside the Field Programmable Gate Array, the alignment of photon signals of 48 channels is achieved. After the alignment, clock phase shifting is used to sample signal pulses. Logic constraints are used to stabilize the pulse width. The coincidence counting data stored in a 1G bit external random access memory will be sent to the computer to analyze the amount of 2-, 3-, 4-, 5-, and 6-fold coincidence events. This system is designed for multiphoton entanglement experiments with multiple degrees of freedom of photons.

  14. Computed neutron coincidence counting applied to passive waste assay

    SciTech Connect

    Bruggeman, M.; Baeten, P.; De Boeck, W.; Carchon, R.

    1997-11-01

    Neutron coincidence counting applied for the passive assay of fissile material is generally realised with dedicated electronic circuits. This paper presents a software based neutron coincidence counting method with data acquisition via a commercial PC-based Time Interval Analyser (TIA). The TIA is used to measure and record all time intervals between successive pulses in the pulse train up to count-rates of 2 Mpulses/s. Software modules are then used to compute the coincidence count-rates and multiplicity related data. This computed neutron coincidence counting (CNCC) offers full access to all the time information contained in the pulse train. This paper will mainly concentrate on the application and advantages of CNCC for the non-destructive assay of waste. An advanced multiplicity selective Rossi-alpha method is presented and its implementation via CNCC demonstrated. 13 refs., 4 figs., 2 tabs.

  15. Glycinergic inhibition tunes coincidence detection in the auditory brainstem.

    PubMed

    Myoga, Michael H; Lehnert, Simon; Leibold, Christian; Felmy, Felix; Grothe, Benedikt

    2014-05-07

    Neurons in the medial superior olive (MSO) detect microsecond differences in the arrival time of sounds between the ears (interaural time differences or ITDs), a crucial binaural cue for sound localization. Synaptic inhibition has been implicated in tuning ITD sensitivity, but the cellular mechanisms underlying its influence on coincidence detection are debated. Here we determine the impact of inhibition on coincidence detection in adult Mongolian gerbil MSO brain slices by testing precise temporal integration of measured synaptic responses using conductance-clamp. We find that inhibition dynamically shifts the peak timing of excitation, depending on its relative arrival time, which in turn modulates the timing of best coincidence detection. Inhibitory control of coincidence detection timing is consistent with the diversity of ITD functions observed in vivo and is robust under physiologically relevant conditions. Our results provide strong evidence that temporal interactions between excitation and inhibition on microsecond timescales are critical for binaural processing.

  16. Glycinergic inhibition tunes coincidence detection in the auditory brainstem

    PubMed Central

    Myoga, Michael H.; Lehnert, Simon; Leibold, Christian; Felmy, Felix; Grothe, Benedikt

    2014-01-01

    Neurons in the medial superior olive (MSO) detect microsecond differences in the arrival time of sounds between the ears (interaural time differences or ITDs), a crucial binaural cue for sound localization. Synaptic inhibition has been implicated in tuning ITD sensitivity, but the cellular mechanisms underlying its influence on coincidence detection are debated. Here we determine the impact of inhibition on coincidence detection in adult Mongolian gerbil MSO brain slices by testing precise temporal integration of measured synaptic responses using conductance-clamp. We find that inhibition dynamically shifts the peak timing of excitation, depending on its relative arrival time, which in turn modulates the timing of best coincidence detection. Inhibitory control of coincidence detection timing is consistent with the diversity of ITD functions observed in vivo and is robust under physiologically relevant conditions. Our results provide strong evidence that temporal interactions between excitation and inhibition on microsecond timescales are critical for binaural processing. PMID:24804642

  17. On the structure of the set of coincidence points

    NASA Astrophysics Data System (ADS)

    Arutyunov, A. V.; Gel'man, B. D.

    2015-03-01

    We consider the set of coincidence points for two maps between metric spaces. Cardinality, metric and topological properties of the coincidence set are studied. We obtain conditions which guarantee that this set (a) consists of at least two points; (b) consists of at least n points; (c) contains a countable subset; (d) is uncountable. The results are applied to study the structure of the double point set and the fixed point set for multivalued contractions. Bibliography: 12 titles.

  18. Neutron coincidence imaging for active and passive neutron assays

    SciTech Connect

    Estep, R. J.; Brunson, G. S.; Melton, S. G.

    2001-01-01

    Neutron multiplicity assay algorithms for {sup 240}Pu assume a point source of fission neutrons that are detected in a single detector channel. The {sup 240}Pu in real waste, however, is more likely to be distributed throughout the container in some random way. For different reasons, this leads to significant errors when using either multiplicity or simpler coincidence analyses. Reduction of these errors can be achieved using tomographic imaging. In this talk we report on our results from using neutron singles and coincidence data between tagged detector pairs to provide enhanced tomographic imaging capabilities to a crate nondestructive assay system. Only simulated passive coincidence data is examined here, although the higher signal rates from active coincidence counting hold more promise for waste management. The active coincidence approach has significantly better sensitivity than the passive and is not significantly perturbed by (alpha,n) contributions. Our study was based primarily on simulated neutron pulse trains derived from the Los Alamos SIM3D software, which were subjected to analysis using the Los Alamos CTEN-FIT and TGS-FIT software. We found significantly improved imaging capability using the coincidence and singles rate data than could be obtained using the singles rate alone.

  19. Note: An improved 3D imaging system for electron-electron coincidence measurements

    SciTech Connect

    Lin, Yun Fei; Lee, Suk Kyoung; Adhikari, Pradip; Herath, Thushani; Lingenfelter, Steven; Winney, Alexander H.; Li, Wen

    2015-09-15

    We demonstrate an improved imaging system that can achieve highly efficient 3D detection of two electrons in coincidence. The imaging system is based on a fast frame complementary metal-oxide semiconductor camera and a high-speed waveform digitizer. We have shown previously that this detection system is capable of 3D detection of ions and electrons with good temporal and spatial resolution. Here, we show that with a new timing analysis algorithm, this system can achieve an unprecedented dead-time (<0.7 ns) and dead-space (<1 mm) when detecting two electrons. A true zero dead-time detection is also demonstrated.

  20. Triple ionization spectra by coincidence measurements of double Auger decay: The case of OCS.

    PubMed

    Eland, J H D; Hochlaf, M; Linusson, P; Andersson, E; Hedin, L; Feifel, R

    2010-01-07

    By combining multiple electron coincidence detection with ionization by synchrotron radiation, we have obtained resolved spectra of the OCS(3+) ion created through the double Auger effect. The form of the spectra depends critically on the identity of the atom bearing the initial hole. High and intermediate level electron structure calculations lead to an assignment of the resolved spectrum from ionization via the S 2p hole. From the analysis it appears that the double Auger effect from closed shell molecules favors formation of doublet states over quartet states. Molecular field effects in the double Auger effect are similar to those in the single Auger effect in linear molecules.

  1. a Reflection (electron, 2ELECTRON) Coincidence Experiment for Solid Surfaces.

    NASA Astrophysics Data System (ADS)

    Zhu, Hong

    A state-of-the-art reflection (e,2e) coincidence experiment for solid surfaces has been designed, constructed, and implemented. Single crystal silicon reconstructed surfaces were studied to establish the feasibility of applying the coincidence spectroscopy technique to solid surfaces. The ultra high vacuum system necessary for clean surface studies has achieved a base pressure of 3 times 10^{-11} Torr. A narrow angle electron gun with a LaB_6 offset-cathode was designed to meet the specifications of the experiment. In order to improve the time resolution of the apparatus, so as to enhance the true-to-accidental coincidence ratio, a compensation method utilizing lens -coupled spectrometers was developed for the electron energy analyzers used in the experiment. The components of the apparatus were characterized, and the surface conditions of the sample were monitored by the spectrometer systems used in the (e,2e) experiment: energy loss spectra, silicon Auger peaks, and a limited angular range of the electron diffraction pattern from silicon have been measured. Computer control of voltage supplies to the gun and the spectrometer systems, and automatic data acquisition have been achieved for total automation of the experiment. For the first time true coincidences have been searched for on solid surfaces, using the configuration for the determination of electron momentum distributions. In the experiment, surface contamination has been found and verified. Although the observation of true coincidences was hindered due to the contamination, the accidental coincidence count rates were measured. This measurement has led to an estimate of the lower limit of the triple differential cross section for the (e,2e) reaction, which is needed to observe true coincidences. The result suggests that the experiment is feasible only if the contamination problem is overcome.

  2. A new double imaging velocity focusing coincidence experiment: i{sup 2}PEPICO

    SciTech Connect

    Bodi, Andras; Hemberger, Patrick; Gerber, Thomas; Sztaray, Balint

    2012-08-15

    The vacuum ultraviolet (VUV) beamline of the Swiss Light Source has been upgraded after two years of operation. A new, turntable-type monochromator was constructed at the Paul Scherrer Institut, which allows for fast yaw-alignment as well as quick grating change and exchange. In addition to the original imaging photoelectron photoion coincidence endstation (iPEPICO), a second, complementary double imaging setup (i{sup 2}PEPICO) has been built. Volatile samples can be introduced at room temperature or in a molecular beam, a pyrolysis source allows for radical production, and non-volatile solids can be evaporated in a heated cell. Monochromatic VUV radiation ionizes the sample and both photoelectrons and photoions are velocity map imaged onto two fast position sensitive detectors and detected in delayed coincidence. High intensity synchrotron radiation leads to ionization rates above 10{sup 5} s{sup -1}. New data acquisition and processing approaches are discussed for recording coincidence processes at high rates. The setup is capable of resolving pulsed molecular beam profiles and the synchrotron time structure temporally. The latter is shown by photoelectron autocorrelation, which displays both the 1.04 MHz ring clock frequency as well as resolving the micro-pulses with a separation of 2 ns. Kinetic energy release analysis on the dissociative photoionization of CF{sub 4} indicates a dissociation mechanism change in the Franck-Condon allowed energy range of the first ion state.

  3. Study of a coincident observation between the ROCSAT-1 density irregularity and Ascension Island scintillation

    NASA Astrophysics Data System (ADS)

    Liu, Y. H.; Chao, C. K.; Su, S.-Y.; Liu, C. H.

    2012-10-01

    A coincident observation that occurred on 24 March 2000 between the irregularity structure measured by ROCSAT-1 and the scintillation experiment at the Ascension Island has been studied. The study of scintillation statistics is carried out first, and the results show that the Nakagami distribution can portray the normalized intensity of the L-band scintillation at various S4 values, up to S4 equal to 1.4. Moreover, the departure of frequency dependence on S4 predicted by the weak scintillation is noticed due to multiple forward scattering effects. The coincident feature between the characteristics of irregularity structure and the scintillation variation are then studied. The causal relationship between the fluctuation of ion density and the scintillation variation is obtained. A numerical simulation using the parabolic wave equation has been carried out with the ROCSAT-1 data in space to compare with the ground scintillation observation. The results show the reasonable scintillation level at the coincident time to indicate a direct relationship between the irregularity structure and the scintillation in both temporal and amplitudinal variations. Finally, some assumptions and limitations of the simulation model are discussed.

  4. Multiple-Coincidence Active Neutron Interrogation of Fissionable Materials

    SciTech Connect

    Tinsley, J.R., Hurley, J.P., Trainham, R., Keegan, R.P.

    2008-11-14

    In an extension of the Associated Particle Imaging technique that is used for the detection and imaging of hidden explosives, the present measurements use a beam of tagged 14.1 MeV neutrons in coincidence with two or more gammas to probe for the presence of fissionable materials. We have measured neutron-gamma-gamma coincidences with targets of depleted uranium, tungsten, lead, iron, and carbon and will present results that show the multiple-coincidence counting rate for the depleted uranium is substantially higher than any of the non-fissionable materials. In addition, the presence of coincidences involving delayed particle spectra provides a signature for fissionable materials that is distinct from that for non-fissionable ones. Information from the tagged neutron involved in the coincidence event is used to compute the position of the fissionable material in all three dimensions. The result is an imaging probe for fissionable materials that is compact and portable, and produces relatively low levels of background radiation. Simultaneous measurements on packages of interest for both explosives and fissionable materials are now feasible.

  5. Development of coincidence-anticipation timing in a catching task.

    PubMed

    Kim, Robyn; Nauhaus, Genevieve; Glazek, Kuba; Young, Douglas; Lin, Sherry

    2013-08-01

    This study examined the effects of age, target location, and stimulus speed on coincidence-anticipation timing in a catching task. Males aged 11 to 18 years made simulated catching movements toward a light stimulus that rapidly approached the head or chest at various speeds. Coincidence-anticipation timing accuracy, movement onset times, and movement times did not differ by age. However, 17- to 18-year-olds exhibited significantly faster movement speeds than 14- to 16-year-olds. Target location (head or chest) did not affect coincidence-anticipation timing accuracy or movement speed. However, movements toward the head were initiated earlier and took longer than movements to the chest. Finally, stimulus speed had statistically significant effects on all measures: faster stimuli were associated with longer delays in coincidence-anticipation timing responses, earlier movement onset times, shorter movement times, and faster movement speeds. These results underscore the adaptability of coincidence-anticipation timing abilities for responding to stimuli under varying temporal and spatial constraints.

  6. Implications on the cosmic coincidence by a dynamical extrinsic curvature

    NASA Astrophysics Data System (ADS)

    Capistrano, Abraão J. S.; Cabral, Luis A.

    2016-12-01

    In this work, we apply the smooth deformation concept in order to obtain a modification of Friedmann’s equations. It is shown that the cosmic coincidence can be at least alleviated using the dynamical properties of the extrinsic curvature. We investigate the transition from nucleosynthesis to the coincidence era obtaining a very small variation of the ratio r=\\tfrac{{ρ }{{m}}}{{ρ }{{ext}}} that compares the matter energy density to extrinsic energy density, compatible with the known behavior of the deceleration parameter. We also show that the calculated ‘equivalence’ redshift matches the transition redshift from a deceleration to accelerated phase and the coincidence ceases to be. The dynamics on r is also studied based on Hubble parameter observations as the latest Baryons Acoustic Oscillations/Cosmic Microwave Background Radiation (BAO/CMBR) + SNIa.

  7. Instrument for determining coincidence and elapse time between independent sources of random sequential events

    NASA Technical Reports Server (NTRS)

    Clemmons, J. I., Jr. (Inventor)

    1983-01-01

    An instrument that receives pulses from a primary external source and one or more secondary external sources and determines when there is coincidence between the primary and one of the secondary sources is described. The instrument generates a finite time window (coincidence aperture) during which coincidence is defined to have occurred. The time intervals between coincidence apertures in which coincidences occur are measured.

  8. On the structure of the set of coincidence points

    SciTech Connect

    Arutyunov, A V; Gel'man, B D

    2015-03-31

    We consider the set of coincidence points for two maps between metric spaces. Cardinality, metric and topological properties of the coincidence set are studied. We obtain conditions which guarantee that this set (a) consists of at least two points; (b) consists of at least n points; (c) contains a countable subset; (d) is uncountable. The results are applied to study the structure of the double point set and the fixed point set for multivalued contractions. Bibliography: 12 titles.

  9. Non-coincident multi-wavelength emission absorption spectroscopy

    SciTech Connect

    Baumann, L.E.

    1995-02-01

    An analysis is presented of the effect of noncoincident sampling on the measurement of atomic number density and temperature by multiwavelength emission absorption. The assumption is made that the two signals, emission and transmitted lamp, are time resolved but not coincident. The analysis demonstrates the validity of averages of such measurements despite fluctuations in temperature and optical depth. At potassium-seeded MHD conditions, the fluctuations introduce additional uncertainty into measurements of potassium atom number density and temperature but do not significantly bias the average results. Experimental measurements in the CFFF aerodynamic duct with coincident and noncoincident sampling support the analysis.

  10. Detection of helium in irradiated Fe9Cr alloys by coincidence Doppler broadening of slow positron annihilation

    NASA Astrophysics Data System (ADS)

    Cao, Xingzhong; Zhu, Te; Jin, Shuoxue; Kuang, Peng; Zhang, Peng; Lu, Eryang; Gong, Yihao; Guo, Liping; Wang, Baoyi

    2017-03-01

    An element analysis method, coincidence Doppler broadening spectroscopy of slow positron annihilation, was employed to detect helium in ion-irradiated Fe9Cr alloys. Spectra with higher peak to background ratio were recorded using a two-HPGe detector coincidence measuring system. It means that information in the high-momentum area of the spectra can be used to identify helium in metals. This identification is not entirely dependent on the helium concentration in the specimens, but is related to the structure and microscopic arrangement of atoms surrounding the positron annihilation site. The results of Doppler broadening spectroscopy and transmission electron microscopy show that vacancies and dislocations were formed in ion-irradiated specimens. Thermal helium desorption spectrometry was performed to obtain the types of He traps.

  11. Coincidence studies of capture and ionization in highly charged Iq+-He and Uq+-He collisions at medium velocities

    NASA Astrophysics Data System (ADS)

    Datz, S.; Hippler, R.; Andersen, L. H.; Dittner, P. F.; Knudsen, H.; Krause, H. F.; Miller, P. D.; Pepmiller, P. L.; Rosseel, T.; Schuch, R.; Stolterfoht, N.; Yamazaki, Y.; Vane, C. R.

    1990-04-01

    Electron capture and ionization processes were investigated for Iq+-He and Uq+-He collisions at incident energies 0.1-1.0 MeV/nucleon and for incident charge states q=5-44. Cross sections for single-electron capture, transfer ionization, single ionization, and double ionization were obtained using a projectile-ion recoil-ion coincidence technique. A pronounced interplay among the different electronic processes was observed. Cross sections for single ionization show a rather weak charge-state dependence, in disagreement with recent calculations of McKenzie and Olson [Phys. Rev. A 35, 2863 (1987)]. In a second experiment, photon recoil-ion coincidences were measured to obtain partial cross sections for capture into certain projectile n states. These measurements provide strong evidence that transfer ionization populates lower projectile n states than does single-electron capture. Zero-degree electron spectroscopy, coincident with charge capture for 0.5 MeV/nucleon U30+ projectiles revealed that the free electron in transfer ionization is released from the projectile to its continuum and from high-lying Rydberg states of the projectile.

  12. Ultrasonic nondestructive testing of composite materials using disturbed coincidence conditions

    NASA Astrophysics Data System (ADS)

    Bause, F.; Olfert, S.; Schröder, A.; Rautenberg, J.; Henning, B.; Moritzer, E.

    2012-05-01

    In this contribution we present a new method detecting changes in the composite material's acoustic behavior by analyzing disturbed coincidence conditions on plate-like test samples. The coincidence condition for an undamaged GFRP test sample has been experimentally identified using Schlieren measurements. Disturbances of this condition follow from a disturbed acoustic behavior of the test sample which is an indicator for local damages in the region inspected. An experimental probe has been realized consisting of two piezoceramic elements adhered to the nonparallel sides of an isosceles trapezoidal body made of silicone. The base angles of the trapezoidal body have been chosen such that the incident wave meets pre-measured condition of coincidence. The receiving element receives the geometric reflection of the acoustic wave scattered at the test sample's surface which corresponds to the non-coupled part of the incident wave as send by the sending element. Analyzing the transfer function or impulse response of the electro-acoustic system (transmitter, scattering at test sample, receiver), it is possible to detect local disturbances with respect to Cramer's coincidence rule. Thus, it is possible to realize a very simple probe for local ultrasonic nondestructive testing of composite materials (as well as non-composite material) which can be integrated in a small practical device and is good for small size inspection areas.

  13. Study of inner-shell vacancy cascades by coincidence techniques

    SciTech Connect

    LeBrun, T.; Arp, U.; MacDonald, M.; Southworth, S.H.

    1995-08-01

    An inner-shell vacancy in an atom decays by an intricate combination of Auger and fluorescence processes. The interrelation between these processes is not well understood because traditional studies of core-excited atoms focus on only one of the many particles that participate in the relaxation - largely ignoring the other components and the correlations between them. To understand these correlations we developed a coincidence technique that uses coincident detection of X-rays and electrons to select decay pathways that involve emission of both an X-ray photon and electrons. In the first application of this technique, the Ar 1s photoelectron spectrum was recorded selectively in coincidence with X-ray fluorescence to eliminate the asymmetric broadening and shifting of the energy distribution which results due to post-collision interaction with K-Auger electrons. This allowed the direct observation of the interaction between the photoelectron and the decay of core holes created after the initial photoionization event. We have also applied this technique to the much more complex problem of understanding Auger-electron spectra produced by vacancy cascades following inner-shell excitation. For example, we previously recorded non-coincident electron spectra of L{sub 2,3}MM Auger transitions following K-shell excitation of argon. Interpretation of these spectra is difficult because they are complicated and consist of many overlapping or unresolved Auger transitions between different ionic states.

  14. Multiple channel coincidence detector and controller for microseismic data analysis

    DOEpatents

    Fasching, George E.

    1976-11-16

    A multiple channel coincidence detector circuit is provided for analyzing data either in real time or recorded data on a magnetic tape during an experiment for determining location and progression of fractures in an oil field or the like while water is being injected at high pressure in wells located in the field. The circuit is based upon the utilization of a set of parity generator trees combined with monostable multivibrators to detect the occurrence of two events at any pair of channel input terminals that are within a preselected time frame and have an amplitude above a preselected magnitude. The parity generators perform an exclusive OR function in a timing circuit composed of monostable multivibrators that serve to yield an output when two events are present in the preselected time frame. Any coincidences falling outside this time frame are considered either noise or not otherwise useful in the analysis of the recorded data. Input pulses of absolute magnitude below the low-level threshold setting of a bipolar low-level threshold detector are unwanted and therefore rejected. A control output is provided for a utilization device from a coincidence hold circuit that may be used to halt a tape search unit at the time of coincidence or perform other useful control functions.

  15. Fission measurements with PPAC detectors using a coincidence technique

    SciTech Connect

    Paradela, C.; Duran, I.; Tarrio, D.; Audouin, L.; Tassan-Got, L.; Stephan, C.

    2011-07-01

    A fission detection setup based on Parallel Plate Avalanche Counters (PPAC) has been constructed and used at the CERN n-TOF facility. The setup takes advantage of the coincidence detection of both fission fragments to discriminate the background reactions produced by high energy neutrons and it allows obtaining neutron-induced fission cross section up to 1 GeV. (authors)

  16. The Galileo/Mars Observer/Ulysses Coincidence Experiment

    NASA Technical Reports Server (NTRS)

    Armstrong, J. W.

    1997-01-01

    From March 21 to April 11, 1993 the Galileo, Mars Observer and Ulysses spacecraft were tracked in a coincidence experiment, searching for low-frequency (millihertz) gravitational radiation. In the spacecraft Doppler technique, the earth and a distant spacecraft act as separated test masses.

  17. Coincidence doppler broadening study in electron-irradiated polyurethane

    NASA Astrophysics Data System (ADS)

    Yang, D. J.; Zhang, J. D.; Leung, J. K. C.; Beling, C. D.; Liu, L. B.

    2007-06-01

    Coincidence doppler broadening measurements on electron-irradiated polyurethanes were performed in the presence of air. It is shown that, after a certain electron irradiation, the momentum density distributions of annihilation electrons have obvious changes for the high crosslinking polyurethane, but no significant changes have been observed for the low crosslinking polyurethane. The results were performed to analyse by irradiation crosslinking and degradation principles.

  18. Uranium Neutron Coincidence Collar Model Utilizing 3He

    SciTech Connect

    Siciliano, Edward R.; Rogers, Jeremy L.; Schweppe, John E.; Lintereur, Azaree T.; Kouzes, Richard T.

    2012-07-30

    The Department of Energy Office of Nuclear Safeguards (NA-241) is supporting the project 'Coincidence Counting With Boron-Based Alternative Neutron Detection Technology' at Pacific Northwest National Laboratory (PNNL) for development of an alternative neutron coincidence counter. The goal of this project is to design, build and demonstrate a boron-lined proportional tube based alternative system in a configuration typically used for 3He-based coincidence counter applications. The specific application selected for boron-lined tube replacement in this project was one of the Uranium Neutron Coincidence Collar (UNCL) designs. This report, providing results for model development of a UNCL, is a deliverable under Task 2 of the project. The current UNCL instruments utilize 3He tubes. As the first step in developing and optimizing a boron-lined proportional counter based version of the UNCL, models of eight different 3He-based UNCL detectors currently in use were developed and evaluated. A comparison was made between the simulated results and measured efficiencies for those systems with values reported in the literature. The reported experimental measurements for efficiencies and die-away times agree to within 10%.

  19. Threshold Photoelectron Photoion Coincidence (TPEPICO) Studies. The Road to ± 0.1 kJ/mol Thermochemistry

    SciTech Connect

    Baer, Tomas

    2013-10-14

    The threshold photoelectron photoion coincidence (TPEPICO) technique is utilized to investigate the dissociation dynamics and thermochemistry of energy selected medium to large organic molecular ions. The reactions include parallel and consecutive steps that are modeled with the statistical theory in order to extract dissociation onsets for multiple dissociation paths. These studies are carried out with the aid of molecular orbital calculations of both ions and the transition states connecting the ion structure to their products. The results of these investigations yield accurate heats of formation of ions, free radicals, and stable molecules. In addition, they provide information about the potential energy surface that governs the dissociation process. Isomerization reactions prior to dissociation are readily inferred from the TPEPICO data.

  20. Ion-Ion Neutralization.

    DTIC Science & Technology

    1982-05-31

    Accession No. 3. Recipient’s Catalog Number FGL -TR-82 -0202 b- /- 4. Title (and Subtitle) 5. Type of Report & Period Covered ION-ION NEUTRALIZATION Final...few years under the terms of the grant has been the detailed study of binary ion-ion neutralization reactions involving ions of atmospheric...2TT, England. 1. INTRODUCTION Binary positive-ion negative-ion mutual neutralization viz: A+ + B->C + D (1) can be an important loss process for

  1. Search for gamma ray bursts with coincident balloon flights

    NASA Technical Reports Server (NTRS)

    Cline, T. L.; Desai, U. D.; Schmidt, W. K. H.; Teegarden, B. J.

    1976-01-01

    A search was conducted for cosmic gamma ray bursts of small size and of sufficient frequency of occurrence to be detected during a one day observation program. Two similar detectors, successfully balloon-borne from launch sites in South Dakota and Texas, achieved about 20 hours of simultaneous operation at several millibars atmospheric depth, with continuous separation of over 1,500 km. Fluctuations of the counting rates of less than 150 keV photons with temporal structures from microseconds to several minutes were compared in order to detect coincident or associated responses from the two instruments. No coincident gamma-ray burst events were detected. The resulting integral size spectrum of small bursts, from this and from all other searches, remains a spectrum of upper limits, consistent with an extrapolation of the size spectrum of the largest known bursts, fitting a power low of index -1.5.

  2. Using CHIMERA detector at LNS for gamma-particle coincidences

    NASA Astrophysics Data System (ADS)

    Cardella, G.; Acosta, L.; Auditore, L.; Chatterjiee, M. B.; Castoldi, A.; De Filippo, E.; Dell'Aquila, D.; De Luca, S.; Gnoffo, B.; Guazzoni, C.; Francalanza, L.; Lanzalone, G.; Lombardo, I.; Martorana, N.; Norella, S.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Quattrocchi, L.; Rizzo, F.; Russotto, P.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

    2016-05-01

    We have recently evaluated the quality of γ-ray angular distributions that can be extracted in particle-gamma coincidence measurements using the CHIMERA detector at LNS. γ-rays have been detected using the CsI(Tl) detectors of the spherical part of the CHIMERA array. Very clean γ-rays angular distributions were extracted in reactions induced by different stable beams impinging on 12C thin targets. The results evidenced an effect of projectile spin flip on the γ-rays angular distributions. γ-particle coincidence measurements were also performed in reactions induced by neutron rich exotic beams produced through in-flight fragmentation at LNS. In recent experiments also the Farcos array was used to improve energy and angular resolution measurements of the detected charged particles. Results obtained with both stable and radioactive beams are reported.

  3. A new opportunity: coincident spectroscopy in neutron-deficient actinides

    NASA Astrophysics Data System (ADS)

    Gothe, Oliver; Gates, J. M.; Gregorich, K. E.; Baartman, B.; Fallon, P.; Esker, N. E.; Kwarsick, J.; Machiavelli, A. O.; Mudder, P. R.; Olive, D. T.; Pang, G.; Rissanen, J.; Nitsche, H.

    2014-09-01

    Due to high γ-ray background rates heavy element production facilities are usually not sensitive to the electron capture decay of neutron deficient actinides. We have developed new capabilities at the Berkeley Gas Filled Separator (BGS) that allow us to study these isotopes. The highly selective and efficient separation of compound nucleus evaporation residue products using the BGS couple with a rapid delivery to a low-background detector facility, opens up many new possibilities for nuclear decay and structure studies in the neutron deficient actinides. The decay of these actinides produces vacancies in the K-shell resulting in x-rays uniquely identifying the Z of the decay products. We present the first results of this new methodology in studying the nuclear structure of fermium-254 by observing the gamma rays in coincidence with fermium x-rays. Coincident gamma-decay spectroscopy gives us a new tool to study the nuclear structure of previously inaccessible systems.

  4. System for monitoring non-coincident, nonstationary process signals

    DOEpatents

    Gross, Kenneth C.; Wegerich, Stephan W.

    2005-01-04

    An improved system for monitoring non-coincident, non-stationary, process signals. The mean, variance, and length of a reference signal is defined by an automated system, followed by the identification of the leading and falling edges of a monitored signal and the length of the monitored signal. The monitored signal is compared to the reference signal, and the monitored signal is resampled in accordance with the reference signal. The reference signal is then correlated with the resampled monitored signal such that the reference signal and the resampled monitored signal are coincident in time with each other. The resampled monitored signal is then compared to the reference signal to determine whether the resampled monitored signal is within a set of predesignated operating conditions.

  5. Spatial coincidence modulates interaction between visual and somatosensory evoked potentials.

    PubMed

    Schürmann, Martin; Kolev, Vasil; Menzel, Kristina; Yordanova, Juliana

    2002-05-07

    The time course of interaction between concurrently applied visual and somatosensory stimulation with respect to evoked potentials (EPs) was studied. Visual stimuli, either in the left or right hemifield, and electric stimuli to the left wrist were delivered either alone or simultaneously. Visual and somatosensory EPs were summed and compared to bimodal EPs (BiEP, response to actual combination of both modalities). Temporal coincidence of stimuli lead to sub-additive or over-additive amplitudes in BiEPs in several time windows between 75 and 275 ms. Additional effects of spatial coincidence (left wrist with left hemifield) were found between 75 and 300 ms and beyond 450 ms. These interaction effects hint at a temporo-spatial pattern of multiple brain areas participating in the process of multimodal integration.

  6. Momentum spectrometer for electron-electron coincidence studies on superconductors

    SciTech Connect

    Wallauer, Robert; Voss, Stefan; Bauer, Tobias; Schneider, Deborah; Titze, Jasmin; Ulrich, Birte; Kreidi, Katharina; Neumann, Nadine; Havermeier, Tilo; Schoeffler, Markus; Jahnke, Till; Czasch, Achim; Schmidt, Lothar; Schmidt-Boecking, Horst; Doerner, Reinhard; Kanigel, Amit; Campuzano, Juan Carlos; Jeschke, Harald; Valenti, Roser [Institut fuer Theoretische Physik, Universitaet Frankfurt, Max-von-Laue-Str. 1, 60438 Frankfurt and others

    2012-10-15

    We present a new experimental setup to study electron-electron coincidences from superconducting surfaces. In our approach, electrons emitted from a surface are projected onto a time- and position-sensitive microchannel plate detector with delayline position readout. Electrons that are emitted within 2 {pi} solid angle with respect to the surface are detected in coincidence. The detector used is a hexagonal delayline detector with enhanced multiple hit capabilities. It is read out with a Flash analog-to-digital converter. The three-dimensional momentum vector is obtained for each electron. The intrinsic dead time of the detector has been greatly reduced by implementing a new algorithm for pulse analysis. The sample holder has been matched to fit the spectrometer while being capable of cooling down the sample to 4.5 K during the measurement and heating it up to 420 K for the cleaning procedure.

  7. Momentum spectrometer for electron-electron coincidence studies on superconductors

    NASA Astrophysics Data System (ADS)

    Wallauer, Robert; Voss, Stefan; Foucar, Lutz; Bauer, Tobias; Schneider, Deborah; Titze, Jasmin; Ulrich, Birte; Kreidi, Katharina; Neumann, Nadine; Havermeier, Tilo; Schöffler, Markus; Jahnke, Till; Czasch, Achim; Schmidt, Lothar; Kanigel, Amit; Campuzano, Juan Carlos; Jeschke, Harald; Valenti, Roser; Müller, Andreas; Berner, Götz; Sing, Michael; Claessen, Ralph; Schmidt-Böcking, Horst; Dörner, Reinhard

    2012-10-01

    We present a new experimental setup to study electron-electron coincidences from superconducting surfaces. In our approach, electrons emitted from a surface are projected onto a time- and position-sensitive microchannel plate detector with delayline position readout. Electrons that are emitted within 2 π solid angle with respect to the surface are detected in coincidence. The detector used is a hexagonal delayline detector with enhanced multiple hit capabilities. It is read out with a Flash analog-to-digital converter. The three-dimensional momentum vector is obtained for each electron. The intrinsic dead time of the detector has been greatly reduced by implementing a new algorithm for pulse analysis. The sample holder has been matched to fit the spectrometer while being capable of cooling down the sample to 4.5 K during the measurement and heating it up to 420 K for the cleaning procedure.

  8. Momentum spectrometer for electron-electron coincidence studies on superconductors.

    PubMed

    Wallauer, Robert; Voss, Stefan; Foucar, Lutz; Bauer, Tobias; Schneider, Deborah; Titze, Jasmin; Ulrich, Birte; Kreidi, Katharina; Neumann, Nadine; Havermeier, Tilo; Schöffler, Markus; Jahnke, Till; Czasch, Achim; Schmidt, Lothar; Kanigel, Amit; Campuzano, Juan Carlos; Jeschke, Harald; Valenti, Roser; Müller, Andreas; Berner, Götz; Sing, Michael; Claessen, Ralph; Schmidt-Böcking, Horst; Dörner, Reinhard

    2012-10-01

    We present a new experimental setup to study electron-electron coincidences from superconducting surfaces. In our approach, electrons emitted from a surface are projected onto a time- and position-sensitive microchannel plate detector with delayline position readout. Electrons that are emitted within 2 π solid angle with respect to the surface are detected in coincidence. The detector used is a hexagonal delayline detector with enhanced multiple hit capabilities. It is read out with a Flash analog-to-digital converter. The three-dimensional momentum vector is obtained for each electron. The intrinsic dead time of the detector has been greatly reduced by implementing a new algorithm for pulse analysis. The sample holder has been matched to fit the spectrometer while being capable of cooling down the sample to 4.5 K during the measurement and heating it up to 420 K for the cleaning procedure.

  9. Characteristic evaluation of a Lithium-6 loaded neutron coincidence spectrometer.

    PubMed

    Hayashi, M; Kaku, D; Watanabe, Y; Sagara, K

    2007-01-01

    Characteristics of a (6)Li-loaded neutron coincidence spectrometer were investigated from both measurements and Monte Carlo simulations. The spectrometer consists of three (6)Li-glass scintillators embedded in a liquid organic scintillator BC-501A, which can detect selectively neutrons that deposit the total energy in the BC-501A using a coincidence signal generated from the capture event of thermalised neutrons in the (6)Li-glass scintillators. The relative efficiency and the energy response were measured using 4.7, 7.2 and 9.0 MeV monoenergetic neutrons. The measured ones were compared with the Monte Carlo calculations performed by combining the neutron transport code PHITS and the scintillator response calculation code SCINFUL. The experimental light output spectra were in good agreement with the calculated ones in shape. The energy dependence of the detection efficiency was reproduced by the calculation. The response matrices for 1-10 MeV neutrons were finally obtained.

  10. Quality of Coincidence Detection and Itd Tuning: a Theoretical Framework

    NASA Astrophysics Data System (ADS)

    Kempter, Richard; Gerstner, Wulfram; Wagner, Hermann; van Hemmed, J. Leo

    Coincidence detector neurons increase their firing rate significantly if the input changes from random to coherent. Similarly, neurons in the avian nucleus laminaris vary their firing rate as a function of the interaural time difference (ITD). In both cases, neurons transform temporally coded input into a rate-coded output. To characterize the quality of this transformation we define a new measure, which explicitly takes noisy spike output of neurons into account. As an application, we investigate the coincidence detection properties of an integrate-and-fire (I&F) neuron in dependence on internal parameters and input statistics. We show that there is an optimal threshold and, furthermore, that there is a broad range of near-optimal threshold values. The theoretical results are applied to ITD-tuning of neurons in the laminar nucleus of the barn owl.

  11. Coincidence probabilities for spacecraft gravitational wave experiments - Massive coalescing binaries

    NASA Technical Reports Server (NTRS)

    Tinto, Massimo; Armstrong, J. W.

    1991-01-01

    Massive coalescing binary systems are candidate sources of gravitational radiation in the millihertz frequency band accessible to spacecraft Doppler tracking experiments. This paper discusses signal processing and detection probability for waves from coalescing binaries in the regime where the signal frequency increases linearly with time, i.e., 'chirp' signals. Using known noise statistics, thresholds with given false alarm probabilities are established for one- and two-spacecraft experiments. Given the threshold, the detection probability is calculated as a function of gravitational wave amplitude for both one- and two-spacecraft experiments, assuming random polarization states and under various assumptions about wave directions. This allows quantitative statements about the detection efficiency of these experiments and the utility of coincidence experiments. In particular, coincidence probabilities for two-spacecraft experiments are insensitive to the angle between the directions to the two spacecraft, indicating that near-optical experiments can be done without constraints on spacecraft trajectories.

  12. Anti-anthropic solutions to the cosmic coincidence problem

    SciTech Connect

    Fedrow, Joseph M.; Griest, Kim E-mail: kgriest@ucsd.edu

    2014-01-01

    A cosmological constant fits all current dark energy data, but requires two extreme fine tunings, both of which are currently explained by anthropic arguments. Here we discuss anti-anthropic solutions to one of these problems: the cosmic coincidence problem- that today the dark energy density is nearly equal to the matter density. We replace the ensemble of Universes used in the anthropic solution with an ensemble of tracking scalar fields that do not require fine-tuning. This not only does away with the coincidence problem, but also allows for a Universe that has a very different future than the one currently predicted by a cosmological constant. These models also allow for transient periods of significant scalar field energy (SSFE) over the history of the Universe that can give very different observational signatures as compared with a cosmological constant, and so can be confirmed or disproved in current and upcoming experiments.

  13. Dead time correction in coincidence counting of photon pairs

    NASA Astrophysics Data System (ADS)

    Kang, M. S.; Lee, D.-H.; Lee, J.; Lee, J. Y.; Choi, S.-K.; Park, H. S.

    2008-08-01

    We describe two methods for evaluating the dead time of a time-to-amplitude converter (TAC). The dead time is obtained by measuring either the corresponding time interval in an oscilloscope trace or the relation between the single count rate and the coincidence count rate. Values for the TAC dead time are obtained in the range from 3.4 µs to 14.3 µs for the two methods with respective standard uncertainties of 2.9 × 10-8 s and 3.3 × 10-9 s. The TAC dead time is applied to the calibration of coincidence-counting measurements of optical transmission and photon-heralding efficiency.

  14. Neutron depth profiling by large angle coincidence spectroscopy

    SciTech Connect

    Vacik, J.; Cervena, J.; Hnatowicz, V.; Havranek, V.; Fink, D.

    1995-12-31

    Extremely low concentrations of several technologically important elements (mainly lithium and boron) have been studied by a modified neutron depth profiling technique. Large angle coincidence spectroscopy using neutrons to probe solids with a thickness not exceeding several micrometers has proved to be a powerful analytical method with an excellent detection sensitivity. Depth profiles in the ppb atomic range are accessible for any solid material. A depth resolution of about 20 nanometers can be achieved.

  15. Beta-gated gamma coincidence counting with a phoswich detector

    SciTech Connect

    Kaye, J.H.; Warner, R.A.

    1981-01-01

    A special type of phoswich detector system has been evaluated for measurement of radionuclides which decay with emission of time coincident beta and gamma radiation. Background reductions of more than two orders of magnitude have been obtained for the energy region from 500 to 950 keV. Both NE 102 plastic scintillators and anthracene were evaluated. Advantages and disadvantages of the method are discussed.

  16. Coincidence of cerebrovascular accident and silent myocardial infarction.

    PubMed

    Badui, E; Estañol, B; Garcia-Rubi, D

    1982-11-01

    Although it is well known that a myocardial and a cerebral infarction may be coincident, the nature of this association is not clear. The problem is further complicated because the myocardial infarction may be silent. This is a report of 3 patients with cerebral infarct in whom a silent recent myocardial infarction was found. All patients with cerebrovascular disease should be screened for a possible myocardial lesion.

  17. Glyphosate applications on arable fields considerably coincide with migrating amphibians.

    PubMed

    Berger, Gert; Graef, Frieder; Pfeffer, Holger

    2013-01-01

    Glyphosate usage is increasing worldwide and the application schemes of this herbicide are currently changing. Amphibians migrating through arable fields may be harmed by Glyphosate applied to field crops. We investigated the population-based temporal coincidence of four amphibian species with Glyphosate from 2006 to 2008. Depending on a) age- and species-specific main migration periods, b) crop species, c) Glyphosate application mode for crops, and d) the presumed DT50 value (12 days or 47 days) of Glyphosate, we calculated up to 100% coincidence with Glyphosate. The amphibians regularly co-occur with pre-sowing/pre-emerging Glyphosate applications to maize in spring and with stubble management prior to crop sowing in late summer and autumn. Siccation treatment in summer coincides only with early pond-leaving juveniles. We suggest in-depth investigations of both acute and long-term effects of Glyphosate applications on amphibian populations not only focussed on exposure during aquatic periods but also terrestrial life stages.

  18. Volcanism, impact and mass extinctions: incredible or credible coincidences?

    NASA Astrophysics Data System (ADS)

    White, Rosalind V.; Saunders, Andrew D.

    2005-02-01

    Massive continental volcanism and/or bolide impacts are considered by many authors to have caused three major mass extinction events during the last 300 million years: the end-Permian, end-Cretaceous and end-Triassic extinctions. However, re-evaluation of the frequency of bolide impacts and plume-related flood basalt provinces indicates that both types of event occur much more frequently than mass extinctions, and so, in isolation, may not be responsible for the largest extinctions. Furthermore, the kill mechanisms associated with either flood basalts or impacts do not appear to be sufficiently powerful to cause worldwide collapse of ecosystems leading to the largest mass extinctions. Contemporaneous flood basalts and bolide impact may be prerequisites for the largest mass extinctions. We present a statistical analysis of the probability of coincidence between volcanism and impact, and show that three random coincidences of these events in the last 300 m.y. are likely. No causal relationship between impact and volcanism is necessary. The lesser mass extinctions, on the other hand, may not require juxtaposition of two such catastrophic events; such coincidences occurring on more than three occasions during the last 300 m.y. become increasingly unlikely.

  19. Particle-Gamma Coincidence Studies of Uranium Nuclei

    NASA Astrophysics Data System (ADS)

    Hughes, R. O.; Ross, T. J.; Beausang, C. W.; Burke, J. T.; Scielzo, N. D.; Basunia, M. S.; Campbell, C. M.; Casperson, R. J.; Crawford, H. L.; Munson, J.; Phair, L.; Ressler, J. J.; Stars-Liberace Collaboration

    2011-10-01

    The STARS/LIBERACE array at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory is proving to be an extremely versatile device for probing nuclear structure via (charged) particle- γ coincidence spectroscopy. The technique enables the properties of low- and medium-spin states up to and beyond the neutron separation energy to be probed and give rare insights into the high-level density nuclear continuum well above the pair gap. Recently, 234U, 235U, 236U and 237U were studied via (p,d) and (p,t) reactions on 236U and 238U targets. The exit channel and excitation energy of the residual nucleus are selected by measuring the outgoing charged particle using the STARS silicon telescope array, while coincident gamma rays are detected with the LIBERACE clover array. The subsequent particle spectra show the ensemble of states that were directly populated by the reaction while γ-ray coincidences reveal the decay path from a given level. Results from our recent experiment will be presented. This work was supported by DoE Grant Numbers: DE-FG52-06 NA26206 and DE-FG02-05 ER41379.

  20. Dissociation limit and dissociation dynamic of CF4(+): application of threshold photoelectron-photoion coincidence velocity imaging.

    PubMed

    Tang, Xiaofeng; Zhou, Xiaoguo; Wu, Manman; Gao, Zhi; Liu, Shilin; Liu, Fuyi; Shan, Xiaobin; Sheng, Liusi

    2013-03-07

    Dissociation of internal energy selected CF4(+) ions in an excitation energy range of 15.40-19.60 eV has been investigated using threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging. Only CF3(+) fragment ions are observed in coincident mass spectra, indicating all the X(2)T1, A(2)T2, and B(2)E ionic states of CF4(+) are fully dissociative. Both kinetic energy released distribution (KERD) and angular distribution in dissociation of CF4(+) ions have been derived from three-dimensional TPEPICO time-sliced images. A parallel distribution of CF3(+) fragments along the polarization vector of photon is observed for dissociation of CF4(+) ions in all the low-lying electronic states. With the aid of F-loss potential energy curves, dissociation mechanisms of CF4(+) ions in these electronic states have been proposed. CF4(+) ions in both X(2)T1 and A(2)T2 states directly dissociate to CF3(+) and F fragments along the repulsive C-F coordinate, while a two-step dissociation mechanism is suggested for B(2)E state: CF4(+)(B(2)E) ion first converts to the lower A(2)T2 state via internal conversion, then dissociates to CF3(+) and F fragments along the steep A(2)T2 potential energy surface. In addition, an adiabatic appearance potential of AP0(CF3(+)∕CF4) has also been established to be 14.71 ± 0.02 eV, which is very consistent with the recent calculated values.

  1. High spatial resolution two-dimensional position sensitive detector for the performance of coincidence experiments

    SciTech Connect

    Ceolin, D.; Chaplier, G.; Lemonnier, M.; Garcia, G.A.; Miron, C.; Nahon, L.; Simon, M.; Leclercq, N.; Morin, P.

    2005-04-01

    A position sensitive detector (PSD) adapted to the technical and mechanical specifications of our angle and energy resolved electron-ion(s) coincidence experiments is described in this article. The device, whose principle is very similar to the one detailed by J. H. D. Eland [Meas. Sci. Technol. 5, 1501 (1994)], is composed by a set of microchannel plates and a delay line anode. The originality comes from the addition in front of the encoding surface of a ceramic disk covered by a resistive surface. The capacitive coupling between the anode and the resistive plane has the double advantage of eliminating the spatial modulations due to the lattice of the anode and also of sensitizing a greater number of electrodes, increasing thus considerably the accuracy of the position measurements. The tests carried out with a time to digital conversion module of 250 ps resolution showed that a spatial resolution better than 50 {mu}m and a dead time of 160 ns can be achieved. Typical images obtained with the help of the EPICEA and DELICIOUS coincidence setups are also shown.

  2. Uncovering Highly-Excited State Mixing in Acetone Using Ultrafast VUV Pulses and Coincidence Imaging Techniques

    DOE PAGES

    Couch, David E.; Kapteyn, Henry C.; Murnane, Margaret M.; ...

    2017-03-17

    Here, understanding the ultrafast dynamics of highly-excited electronic states of small molecules is critical for a better understanding of atmospheric and astrophysical processes, as well as for designing coherent control strategies for manipulating chemical dynamics. In highly excited states, nonadiabatic coupling, electron-electron interactions, and the high density of states govern dynamics. However, these states are computationally and experimentally challenging to access. Fortunately, new sources of ultrafast vacuum ultraviolet pulses, in combination with electron-ion coincidence spectroscopies, provide new tools to unravel the complex electronic landscape. Here we report time-resolved photoelectron-photoion coincidence experiments using 8 eV pump photons to study the highlymore » excited states of acetone. We uncover for the first time direct evidence that the resulting excited state consists of a mixture of both ny → 3p and π → π* character, which decays with a time constant of 330 fs. In the future, this approach can inform models of VUV photochemistry and aid in designing coherent control strategies for manipulating chemical reactions.« less

  3. Coincident site lattice bi-crystals growth-Impurity segregation towards grain boundaries

    NASA Astrophysics Data System (ADS)

    Autruffe, Antoine; Vines, Lasse; Arnberg, Lars; Di Sabatino, Marisa

    2015-04-01

    Bi-crystal silicon ingots with coincident site lattice (CSL) grain boundaries (GB), namely Σ3, Σ9, Σ27a, have been grown in a small scale Bridgman type furnace at 3 μm/s. Melts have been intentionally polluted with 25 ppma of copper and indium. Segregation of these impurities towards the central grain boundaries has been assessed by secondary ion mass spectrometry (SIMS). Influence of topological imperfections and grain boundary nature has been investigated. While copper segregation towards Σ3 GB has not been detected, copper has been found to diffuse towards Σ9 and Σ27a GB, especially at steps and GB junctions. Indium segregation has not been detected at any GB. This indicates that slow-diffusing element segregation towards GB depends on the boundary nature, and/or the grains orientation.

  4. Stormtime Subauroral Density Troughs: Ion-Molecule Kinetics Effects

    DTIC Science & Technology

    2007-11-02

    trap to measure the total ion density (ni); and (4) a coincided with an increase in the energy and intensity of spherical Langmuir probe to measure...Experiments Figure 3. Rate coefficients for the reaction (RI). Circles in a high-temperature flowing afterglow device (HTFA) and squares show the HTFA and...poleward part coincided with strong wave structures, energetic (ring current) ion precipitations, and enhanced vertical ion flows . One or several narrow

  5. The ZEPLIN-III anti-coincidence veto detector

    NASA Astrophysics Data System (ADS)

    Akimov, D. Yu.; Araújo, H. M.; Barnes, E. J.; Belov, V. A.; Burenkov, A. A.; Chepel, V.; Currie, A.; Edwards, B.; Francis, V.; Ghag, C.; Hollingsworth, A.; Horn, M.; Kalmus, G. E.; Kobyakin, A. S.; Kovalenko, A. G.; Lebedenko, V. N.; Lindote, A.; Lopes, M. I.; Lüscher, R.; Lyons, K.; Majewski, P.; Murphy, A. St. J.; Neves, F.; Paling, S. M.; Pinto da Cunha, J.; Preece, R.; Quenby, J. J.; Reichhart, L.; Scovell, P. R.; Solovov, V. N.; Smith, N. J. T.; Smith, P. F.; Stekhanov, V. N.; Sumner, T. J.; Taylor, R.; Thorne, C.; Walker, R. J.

    2010-10-01

    The design, optimisation and construction of an anti-coincidence veto detector to complement the ZEPLIN-III direct dark matter search instrument is described. One tonne of plastic scintillator is arranged into 52 bars individually read out by photomultipliers and coupled to a gadolinium-loaded passive polypropylene shield. Particular attention has been paid to radiological content. The overall aim has been to achieve a veto detector of low threshold and high efficiency without the creation of additional background in ZEPLIN-III, all at a reasonable cost. Extensive experimental measurements of the components have been made, including radioactivity levels and performance characteristics. These have been used to inform a complete end-to-end Monte Carlo simulation that has then been used to calculate the expected performance of the new instrument, both operating alone and as an anti-coincidence detector for ZEPLIN-III. The veto device will be capable of rejecting over 65% of coincident nuclear recoil events from neutron background in the energy range of interest in ZEPLIN-III. This will reduce the background in ZEPLIN-III from ≃0.4 to ≃0.14 events per year in the WIMP acceptance region, a significant factor in the event of a non-zero observation. Furthermore, in addition to providing valuable diagnostic capabilities, the veto is capable of tagging over 15% for γ-ray rejection, all whilst contributing no significant additional background. In conjunction with the replacement of the internal ZEPLIN-III photomultiplier array, the new veto is expected to improve significantly the sensitivity of the ZEPLIN-III instrument to dark matter, allowing spin-independent WIMP-nucleon cross sections below 10 -8 pb to be probed.

  6. Synchrotron-based double imaging photoelectron/photoion coincidence spectroscopy of radicals produced in a flow tube: OH and OD

    DOE PAGES

    Garcia, Gustavo A.; Tang, Xiaofeng; Gil, Jean -Francois; ...

    2015-04-23

    In this study, we present a microwave discharge flow tube coupled with a double imaging electron/ion coincidence device and vacuum ultraviolet (VUV) synchrotron radiation. The system has been applied to the study of the photoelectron spectroscopy of the well-known radicals OH and OD. The coincidence imaging scheme provides a high selectivity and yields the spectra of the pure radicals, removing the ever-present contributions from excess reactants, background, or secondary products, and therefore obviating the need for a prior knowledge of all possible byproducts. The photoelectron spectra encompassing the X3Σ– ground state of the OH+ and OD+ cations have been extractedmore » and the vibrational constants compared satisfactorily to existing literature values. Future advantages of this approach include measurement of high resolution VUV spectroscopy of radicals, their absolute photoionization cross section, and species/isomer identification in chemical reactions as a function of time.« less

  7. Synchrotron-based double imaging photoelectron/photoion coincidence spectroscopy of radicals produced in a flow tube: OH and OD

    SciTech Connect

    Garcia, Gustavo A.; Tang, Xiaofeng; Gil, Jean -Francois; Nahon, Laurent; Ward, Michael; Batut, Sebastien; Fittschen, Christa; Taatjes, Craig A.; Osborn, David L.; Loison, Jean -Christophe

    2015-04-23

    In this study, we present a microwave discharge flow tube coupled with a double imaging electron/ion coincidence device and vacuum ultraviolet (VUV) synchrotron radiation. The system has been applied to the study of the photoelectron spectroscopy of the well-known radicals OH and OD. The coincidence imaging scheme provides a high selectivity and yields the spectra of the pure radicals, removing the ever-present contributions from excess reactants, background, or secondary products, and therefore obviating the need for a prior knowledge of all possible byproducts. The photoelectron spectra encompassing the X3Σ ground state of the OH+ and OD+ cations have been extracted and the vibrational constants compared satisfactorily to existing literature values. Future advantages of this approach include measurement of high resolution VUV spectroscopy of radicals, their absolute photoionization cross section, and species/isomer identification in chemical reactions as a function of time.

  8. Synchrotron-based double imaging photoelectron/photoion coincidence spectroscopy of radicals produced in a flow tube: OH and OD

    SciTech Connect

    Garcia, Gustavo A.; Tang, Xiaofeng; Gil, Jean-François; Nahon, Laurent; Ward, Michael; Batut, Sebastien; Fittschen, Christa; Taatjes, Craig A.; Osborn, David L.; Loison, Jean-Christophe

    2015-04-28

    We present a microwave discharge flow tube coupled with a double imaging electron/ion coincidence device and vacuum ultraviolet (VUV) synchrotron radiation. The system has been applied to the study of the photoelectron spectroscopy of the well-known radicals OH and OD. The coincidence imaging scheme provides a high selectivity and yields the spectra of the pure radicals, removing the ever-present contributions from excess reactants, background, or secondary products, and therefore obviating the need for a prior knowledge of all possible byproducts. The photoelectron spectra encompassing the X{sup 3}Σ{sup −} ground state of the OH{sup +} and OD{sup +} cations have been extracted and the vibrational constants compared satisfactorily to existing literature values. Future advantages of this approach include measurement of high resolution VUV spectroscopy of radicals, their absolute photoionization cross section, and species/isomer identification in chemical reactions as a function of time.

  9. Alpha and conversion electron spectroscopy of 238,239Pu and 241Am and alpha-conversion electron coincidence measurements

    SciTech Connect

    Dion, Michael P.; Miller, Brian W.; Warren, Glen A.

    2016-09-01

    A technique to determine the isotopics of a mixed actinide sample has been proposed by measuring the coincidence of the alpha particle during radioactive decay with the conversion electron (or Auger) emitted during the relaxation of the daughter isotope. This presents a unique signature to allow the deconvolution of isotopes that possess overlapping alpha particle energy. The work presented here are results of conversion electron spectroscopy of 241Am, 238Pu and 239Pu using a dual-stage peltier-cooled 25 mm2 silicon drift detector. A passivated ion implanted planar silicon detector provided measurements of alpha spectroscopy. The conversion electron spectra were evaluated from 20–55 keV based on fits to the dominant conversion electron emissions, which allowed the relative conversion electron emission intensities to be determined. These measurements provide crucial singles spectral information to aid in the coincident measurement approach.

  10. Data acquisition and analysis software for gamma coincidence spectrometry

    PubMed Central

    Shetty, Martin; Şahin, Dağıstan

    2016-01-01

    Coincidence counting in neutron activation analysis has well-known advantages, most importantly improvement of detection limits. One obstacle to the wider use of this technique is the complexity of the data acquisition and reduction systems that it requires. The usual approaches to multi-detector data acquisition incur significant dead-time, involve redundant work in repeatedly developing limited tools and risk potential errors in low-level code. The paper describes progress made in developing a software framework to address these shortcomings. PMID:27325905

  11. Enhanced Photofission-based, Coincidence/Multiplicity Inspection Measurements

    SciTech Connect

    J.L. Jones; D.R. Norman; K.J. Haskell; M.T. Swinhoe; S.J. Tobin; W.H. Geist; R.B. Rothrock; C.R. Freeman

    2010-07-01

    An enhanced active interrogation system has been developed that integrates a transportable Idaho National Laboratory (INL) photonuclear inspection system, using a pulsed bremsstrahlung source and a reconfigurable neutron detection system, with a Los Alamos National Laboratory (LANL) list-mode data acquisition system. A series of active interrogation experiments have shown enhanced nuclear material detection and identification utilizing pulsed photofission-induced, neutron coincidence/multiplicity counting between pulses of an up-to-10-MeV electron accelerator. This paper describes the integrated inspection system and presents some key shielded and unshielded nuclear material inspection results. The enhanced inspection methodology has applicability to homeland security and possible nuclear weapon dismantlement treaties.

  12. Coincidence corrected efficiency calibration of Compton-suppressed HPGe detectors

    SciTech Connect

    Aucott, Timothy; Brand, Alexander; DiPrete, David

    2015-04-20

    The authors present a reliable method to calibrate the full-energy efficiency and the coincidence correction factors using a commonly-available mixed source gamma standard. This is accomplished by measuring the peak areas from both summing and non-summing decay schemes and simultaneously fitting both the full-energy efficiency, as well as the total efficiency, as functions of energy. By using known decay schemes, these functions can then be used to provide correction factors for other nuclides not included in the calibration standard.

  13. High-level neutron coincidence counter maintenance manual

    SciTech Connect

    Swansen, J.; Collinsworth, P.

    1983-05-01

    High-level neutron coincidence counter operational (field) calibration and usage is well known. This manual makes explicit basic (shop) check-out, calibration, and testing of new units and is a guide for repair of failed in-service units. Operational criteria for the major electronic functions are detailed, as are adjustments and calibration procedures, and recurrent mechanical/electromechanical problems are addressed. Some system tests are included for quality assurance. Data on nonstandard large-scale integrated (circuit) components and a schematic set are also included.

  14. Coincident systemic lupus erythematosus and psoriasis vulgaris: a case report.

    PubMed

    Wang, Y; Da, G; Yu, Y; Han, J; Li, H

    2015-12-01

    Psoriasis vulgaris is an autoimmune chronic inflammatory skin disease, but its association with other typical autoimmune disease such as systemic lupus erythematosus has only occasionally been reported. We presented a 25-year-old female who developed systemic lupus erythematosus associated with psoriasis vulgaris. Her conditions were in good control after she got administration of prednisolone (5 mg/day) and Tripterygium Wilfordii Hook (20 mg/day). It is necessary to integrate past history and physical examination to diagnose coincident SLE and psoriasis, and combined treatment with prednisolone and Tripterygium Wilfordii Hook proves effective.

  15. Coincidence problem in YM field dark energy model

    NASA Astrophysics Data System (ADS)

    Zhao, Wen; Zhang, Yang

    2006-09-01

    The coincidence problem is studied in the effective Yang Mills condensate dark energy model. As the effective YM Lagrangian is completely determined by quantum field theory, there is no adjustable parameter in this model except the energy scale, and the cosmic evolution only depends on the initial conditions. For generic initial conditions with the YM condensate subdominant to the radiation and matter, the model always has a tracking solution, the Universe transits from matter-dominated into the dark energy dominated stage only recently z˜0.3, and evolve to the present state with Ω˜0.73 and Ω˜0.27.

  16. Correlated multiphoton holes: absence of multiphoton coincidence events.

    PubMed

    Afek, I; Ambar, O; Silberberg, Y

    2010-08-27

    We generate bipartite states of light which exhibit an absence of multiphoton coincidence events between two modes amid a constant background flux. These "correlated photon holes" are produced by mixing a coherent state and relatively weak spontaneous parametric down-conversion by using a balanced beam splitter. Correlated holes with arbitrarily high photon numbers may be obtained by adjusting the relative phase and amplitude of the inputs. We measure states of up to five photons and verify their nonclassicality. The scheme provides a route for observation of high-photon-number nonclassical correlations without requiring intense quantum resources.

  17. Enhanced PET resolution by combining pinhole collimation and coincidence detection

    NASA Astrophysics Data System (ADS)

    DiFilippo, Frank P.

    2015-10-01

    Spatial resolution of clinical PET scanners is limited by detector design and photon non-colinearity. Although dedicated small animal PET scanners using specialized high-resolution detectors have been developed, enhancing the spatial resolution of clinical PET scanners is of interest as a more available alternative. Multi-pinhole 511 keV SPECT is capable of high spatial resolution but requires heavily shielded collimators to avoid significant background counts. A practical approach with clinical PET detectors is to combine multi-pinhole collimation with coincidence detection. In this new hybrid modality, there are three locations associated with each event, namely those of the two detected photons and the pinhole aperture. These three locations over-determine the line of response and provide redundant information that is superior to coincidence detection or pinhole collimation alone. Multi-pinhole collimation provides high resolution and avoids non-colinearity error but is subject to collimator penetration and artifacts from overlapping projections. However the coincidence information, though at lower resolution, is valuable for determining whether the photon passed near a pinhole within the cone acceptance angle and for identifying through which pinhole the photon passed. This information allows most photons penetrating through the collimator to be rejected and avoids overlapping projections. With much improved event rejection, a collimator with minimal shielding may be used, and a lightweight add-on collimator for high resolution imaging is feasible for use with a clinical PET scanner. Monte Carlo simulations were performed of a 18F hot rods phantom and a 54-pinhole unfocused whole-body mouse collimator with a clinical PET scanner. Based on coincidence information and pinhole geometry, events were accepted or rejected, and pinhole-specific crystal-map projections were generated. Tomographic images then were reconstructed using a conventional pinhole SPECT

  18. Slow earthquakes coincident with episodic tremors and slow slip events.

    PubMed

    Ito, Yoshihiro; Obara, Kazushige; Shiomi, Katsuhiko; Sekine, Shutaro; Hirose, Hitoshi

    2007-01-26

    We report on the very-low-frequency earthquakes occurring in the transition zone of the subducting plate interface along the Nankai subduction zone in southwest Japan. Seismic waves generated by very-low-frequency earthquakes with seismic moment magnitudes of 3.1 to 3.5 predominantly show a long period of about 20 seconds. The seismicity of very-low-frequency earthquakes accompanies and migrates with the activity of deep low-frequency tremors and slow slip events. The coincidence of these three phenomena improves the detection and characterization of slow earthquakes, which are thought to increase the stress on updip megathrust earthquake rupture zones.

  19. CRF-PEPICO: Double velocity map imaging photoelectron photoion coincidence spectroscopy for reaction kinetics studies

    NASA Astrophysics Data System (ADS)

    Sztáray, Bálint; Voronova, Krisztina; Torma, Krisztián G.; Covert, Kyle J.; Bodi, Andras; Hemberger, Patrick; Gerber, Thomas; Osborn, David L.

    2017-07-01

    Photoelectron photoion coincidence (PEPICO) spectroscopy could become a powerful tool for the time-resolved study of multi-channel gas phase chemical reactions. Toward this goal, we have designed and tested electron and ion optics that form the core of a new PEPICO spectrometer, utilizing simultaneous velocity map imaging for both cations and electrons, while also achieving good cation mass resolution through space focusing. These optics are combined with a side-sampled, slow-flow chemical reactor for photolytic initiation of gas-phase chemical reactions. Together with a recent advance that dramatically increases the dynamic range in PEPICO spectroscopy [D. L. Osborn et al., J. Chem. Phys. 145, 164202 (2016)], the design described here demonstrates a complete prototype spectrometer and reactor interface to carry out time-resolved experiments. Combining dual velocity map imaging with cation space focusing yields tightly focused photoion images for translationally cold neutrals, while offering good mass resolution for thermal samples as well. The flexible optics design incorporates linear electric fields in the ionization region, surrounded by dual curved electric fields for velocity map imaging of ions and electrons. Furthermore, the design allows for a long extraction stage, which makes this the first PEPICO experiment to combine ion imaging with the unimolecular dissociation rate constant measurements of cations to detect and account for kinetic shifts. Four examples are shown to illustrate some capabilities of this new design. We recorded the threshold photoelectron spectrum of the propargyl and the iodomethyl radicals. While the former agrees well with a literature threshold photoelectron spectrum, we have succeeded in resolving the previously unobserved vibrational structure in the latter. We have also measured the bimolecular rate constant of the CH2I + O2 reaction and observed its product, the smallest Criegee intermediate, CH2OO. Finally, the second

  20. Cross-correlation in the auditory coincidence detectors of owls.

    PubMed

    Fischer, Brian J; Christianson, G Björn; Peña, José Luis

    2008-08-06

    Interaural time difference (ITD) plays a central role in many auditory functions, most importantly in sound localization. The classic model for how ITD is computed was put forth by Jeffress (1948). One of the predictions of the Jeffress model is that the neurons that compute ITD should behave as cross-correlators. Whereas cross-correlation-like properties of the ITD-computing neurons have been reported, attempts to show that the shape of the ITD response function is determined by the spectral tuning of the neuron, a core prediction of cross-correlation, have been unsuccessful. Using reverse correlation analysis, we demonstrate in the barn owl that the relationship between the spectral tuning and the ITD response of the ITD-computing neurons is that predicted by cross-correlation. Moreover, we show that a model of coincidence detector responses derived from responses to binaurally uncorrelated noise is consistent with binaural interaction based on cross-correlation. These results are thus consistent with one of the key tenets of the Jeffress model. Our work sets forth both the methodology to answer whether cross-correlation describes coincidence detector responses and a demonstration that in the barn owl, the result is that expected by theory.

  1. Cross-Correlation in the Auditory Coincidence Detectors of Owls

    PubMed Central

    Fischer, Brian J.; Christianson, G.Björn; Peña, José Luis

    2009-01-01

    Interaural time difference (ITD) plays a central role in many auditory functions, most importantly in sound localization. The classic model for how ITD is computed was put forth by Jeffress (1948). One of the predictions of the Jeffress model is that the neurons that compute ITD should behave as cross-correlators. Whereas cross-correlation-like properties of the ITD-computing neurons have been reported, attempts to show that the shape of the ITD response function is determined by the spectral tuning of the neuron, a core prediction of cross-correlation, have been unsuccessful. Using reverse correlation analysis, we demonstrate in the barn owl that the relationship between the spectral tuning and the ITD response of the ITD-computing neurons is that predicted by cross-correlation. Moreover, we show that a model of coincidence detector responses derived from responses to binaurally uncorrelated noise is consistent with binaural interaction based on cross-correlation. These results are thus consistent with one of the key tenets of the Jeffress model. Our work sets forth both the methodology to answer whether cross-correlation describes coincidence detector responses and a demonstration that in the barn owl, the result is that expected by theory. PMID:18685035

  2. Interacting quintessence, the coincidence problem, and cosmic acceleration

    NASA Astrophysics Data System (ADS)

    Huey, Greg; Wandelt, Benjamin D.

    2006-07-01

    Faced by recent evidence for a flat universe dominated by dark energy, cosmologists grapple with deep cosmic enigmas such as the cosmological constant problem, extreme fine-tuning and the cosmic coincidence problem. The extent to which we observe the dimming of distant supernovae suggests that the cosmic acceleration is as least as severe as in cosmological constant models. Extrapolating this to our cosmic future implies terrifying visions of either a cold and empty universe or an explosive demise in a “Big Rip.” We construct a class of dynamical scalar field models of dark energy and dark matter. Within this class we can explain why supernovae imply a cosmic equation of state w≲-1, address fine-tuning issues, protect the universe from premature acceleration and predict a constant fraction of dark energy to dark matter in the future (thus solving the coincidence problem), satisfy the dominant energy condition, and ensure that gravitationally bound objects remain so forever (avoid a Big Rip). This is achieved with a string theory inspired Lagrangian containing standard kinetic terms, exponential potentials and couplings, and parameters of order unity.

  3. Coincidence-anticipation timing requirements are different in racket sports.

    PubMed

    Akpinar, Selçuk; Devrilmez, Erhan; Kirazci, Sadettin

    2012-10-01

    The aim of this study was to compare the coincidence-anticipation timing accuracy of athletes of different racket sports with various stimulus velocity requirements. Ninety players (15 girls, 15 boys for each sport) from tennis (M age = 12.4 yr., SD = 1.4), badminton (M age = 12.5 yr., SD = 1.4), and table tennis (M age = 12.4 yr., SD = 1.2) participated in this study. Three different stimulus velocities, low, moderate, and high, were used to simulate the velocity requirements of these racket sports. Tennis players had higher accuracy when they performed under the low stimulus velocity compared to badminton and table tennis players. Badminton players performed better under the moderate speed comparing to tennis and table tennis players. Table tennis players had better performance than tennis and badminton players under the high stimulus velocity. Therefore, visual and motor systems of players from different racket sports may adapt to a stimulus velocity in coincidence-anticipation timing, which is specific to each type of racket sports.

  4. X-ray spectroscopy to determine line coincidences

    NASA Astrophysics Data System (ADS)

    Burkhalter, P. G.; Charatis, G.; Rockett, P.

    1983-01-01

    X-ray spectroscopy in the 12-15 A region of L-shell lines from selected transition elements was performed in a joint Naval Research Laboratory - KMS Fusion, Inc. experiment. The accurate wavelengths determined in this work will be utilized in selecting potential pumping candidates in future X-ray lasing schemes. Specifically, high-resolution X-ray spectra were collected under controlled geometric and target conditions using both red and green light laser excitation in the KMS Chroma laser. Three groups of X-ray spectra were collected with highly-dispersive X-ray crystals at wavelengths centered at 12.543, 13.781 and 14.458 A corresponding to He- and H-like lines from fluorine. Two specially-designed flat crystal spectrographs employing film shutters were used with pairs of beryl and TAP crystals. The spectra from potential lasant and pump candidates could be recorded on the same spectrogram to aid in identifying X-ray line coincidences. In cases where wavelengths were measured in both the red and green laser work, agreement within 1-3 mA was obtained for the L-series X-ray lines. Within this accuracy range, five L series X-ray lines, mostly 2p-3d transitions from the metals Cr, Mn, and Ni, had wavelength values coincident to K-series lines in fluorine.

  5. Alpha Coincidence Detection for the Assay of Actinides

    SciTech Connect

    Warren, Glen A.; Dion, Michael P.; Miller, Brian W.; Tatishvili, Gocha

    2013-11-15

    Abstract – Interferences in both decay counting and mass counting techniques limit their application for some environmental monitoring applications. For example, 238U interferes with 238Pu in mass spectrometry measurements, while in conventional alpha spectroscopy measurements it is nearly impossible to separate 238Pu from 241Am and 239Pu from 240Pu. These interferences are typically resolved by using chemical separation and/or different measurement techniques for different isotopes. We are investigating radiation detector concepts to simultaneously assay these four isotopes with minimal sample preparation by exploiting radiation signatures measured in coincidence with the typical alpha decays of these isotopes. Particles in coincidence with the alpha decay include conversion electrons, gamma rays, x-rays, and Auger electrons. Each decay has a unique energy distribution enabling the separation of the isotopes. We are exploring two basic detector concepts to achieve these goals: a silicon-based design and a gas-detector design. The silicon system provides the potential for higher energy resolution at the cost of lower efficiency compared to a gas detector. In this paper, we will describe our evaluation of the different detector concepts, which will include detection efficiency, ability to resolve the isotopes, sample preparation and equipment requirements.

  6. Improved β-γ Coincidence Detector For Radioxenon Detection

    SciTech Connect

    Cooper, Matthew W; Carman, April J; Hayes, James C; Heimbigner, Tom R; Hubbard, Charles W; Litke, Kevin E; McIntyre, Justin I; Morris, Scott J; Ripplinger, Michael D; Suarez, Reynold

    2005-08-31

    The Automated Radio-xenon Analyzer/Sampler (ARSA), built by Pacific Northwest National Laboratory (PNNL), can collect and detect several radioxenon isotopes. ARSA is very sensitive to 133Xe, 131mXe, 133mXe and 135Xe due to the compact high efficiency coincidence detector it uses. For this reason it is an excellent treaty monitoring and environmental sampling device. Although the system is shown to be both robust and reliable, based on several field tests, it is also complex due to a detailed photomultiplier tube gain matching regime. This complexity is a problem from a maintenance and quality assurance/quality control (QA/QC) standpoint. To reduce these issues a simplified coincident detector has been developed. A comparison of three different well detectors has been completed. In addition, a new plastic scintillator gas cell was constructed. The new simplified detector system has been demonstrated to equal or better performance compared with the original ARSA design in spectral resolution and efficiency and significantly easier to setup and calibrate.

  7. Performance of a coincidence based blood activity monitor

    SciTech Connect

    Moses, W.W.

    1989-12-01

    A new device has been constructed that measures the positron emitting radio-tracer concentration in arterial blood by extracting blood with a peristaltic pump, then measuring the activity concentration by detecting coincident pairs of 511 keV photons with a pair of heavy inorganic scintillators attached to photomultiplier tubes. The sensitivity of this device is experimentally determined to be 610 counts/second per {mu}Ci/ml, and has a paralyzing dead time of 1.2 {mu}s, so is capable of measuring blood activity concentration as high as 1 mCi/ml. Its performance is compared to two other blood monitoring methods: discrete blood samples counted with a well counter and device that uses a plastic scintillator to directly detect positrons. The positron detection efficiency of this device for {sup 18}F is greater than the plastic scintillation counter, and also eliminates the radioisotope dependent correction factors necessary to convert count rate to absolute concentration. Coincident photon detection also has the potential of reducing the background compared to direct positron detection, thereby increasing the minimum detectable isotope concentration. 10 refs., 6 figs.

  8. CSF biomarkers cutoffs: the importance of coincident neuropathological diseases

    PubMed Central

    Toledo, Jon B.; Brettschneider, Johannes; Grossman, Murray; Arnold, Steven E.; Hu, William T.; Xie, Sharon X.; Lee, Virginia M.-Y.; Shaw, Leslie M.

    2012-01-01

    The effects of applying clinical versus neuropathological diagnosis and the inclusion of cases with coincident neuropathological diagnoses have not been assessed specifically when studying cerebrospinal fluid (CSF) biomarker classification cutoffs for patients with neurodegenerative diseases that cause dementia. Thus, 142 neuropathologically diagnosed neurodegenerative dementia patients [71 Alzheimer’s disease (AD), 29 frontotemporal lobar degeneration (FTLD), 3 amyotrophic lateral sclerosis, 7 dementia with Lewy bodies, 32 of which cases also had coincident diagnoses] were studied. 96 % had enzyme-linked immunosorbant assay (ELISA) CSF data and 77 % had Luminex CSF data, with 43 and 46 controls for comparison, respectively. Aβ42, total, and phosphorylated tau181 were measured. Clinical and neuropathological diagnoses showed an 81.4 % overall agreement. Both assays showed high sensitivity and specificity to classify AD subjects against FTLD subjects and controls, and moderate sensitivity and specificity for classifying FTLD subjects against controls. However, among the cases with neuropathological diagnoses of AD plus another pathology (26.8 % of the sample), 69.4 % (ELISA) and 96.4 % (Luminex) were classified as AD according to their biomarker profiles. Use of clinical diagnosis instead of neuropathological diagnosis led to a 14–17 % underestimation of the biomarker accuracy. These results show that while CSF Aβ and tau assays are useful for diagnosis of AD and neurodegenerative diseases even at MCI stages, CSF diagnostic analyte panels that establish a positive diagnosis of Lewy body disease and FTLD are also needed, and must be established based on neuropathological rather than clinical diagnoses. PMID:22526019

  9. Instrumentation for coincidence imaging with multihead scintillation cameras.

    PubMed

    Patton, J A

    2000-10-01

    Positron emission tomography (PET) has been used as a tool by investigators for many years to study metabolic processes in the body primarily with the radiopharmaceutical 18-fluordeoxyglucose. However, use of this technology has not been widespread because of the high expense of the equipment and its limitation to the imaging of positron emitters only. Recent improvements in scintillation camera technology have now made it possible to produce hybrid multihead cameras that can function in a coincidence mode for the detection of the annihilation radiation from positron emitters and in the normal mode for routine single-photon imaging. Although still limited in sensitivity, these camera systems continue to be improved and the recent addition of iterative reconstruction algorithms and attenuation correction capability have resulted in significant improvements in image quality. The integration of a low resolution computed tomography (CT) scanner with a dualhead camera by 1 manufacturer now makes it possible to perform attenuation correction and image fusion of anatomy and function into 1 image to improve the anatomic localization of abnormalities detected with coincidence imaging. Investigators continue to work on improved electronics and new types of detectors to further improve the sensitivity of these systems. These developments coupled with continued improvements in PET technology have resulted in the availability of a broad spectrum of systems for the investigator to consider when purchasing a system with positron imaging capability.

  10. First principle active neutron coincidence counting measurements of uranium oxide

    NASA Astrophysics Data System (ADS)

    Goddard, Braden; Charlton, William; Peerani, Paolo

    2014-03-01

    Uranium is present in most nuclear fuel cycle facilities ranging from uranium mines, enrichment plants, fuel fabrication facilities, nuclear reactors, and reprocessing plants. The isotopic, chemical, and geometric composition of uranium can vary significantly between these facilities, depending on the application and type of facility. Examples of this variation are: enrichments varying from depleted (~0.2 wt% 235U) to high enriched (>20 wt% 235U); compositions consisting of U3O8, UO2, UF6, metallic, and ceramic forms; geometries ranging from plates, cans, and rods; and masses which can range from a 500 kg fuel assembly down to a few grams fuel pellet. Since 235U is a fissile material, it is routinely safeguarded in these facilities. Current techniques for quantifying the 235U mass in a sample include neutron coincidence counting. One of the main disadvantages of this technique is that it requires a known standard of representative geometry and composition for calibration, which opens up a pathway for potential erroneous declarations by the State and reduces the effectiveness of safeguards. In order to address this weakness, the authors have developed a neutron coincidence counting technique which uses the first principle point-model developed by Boehnel instead of the "known standard" method. This technique was primarily tested through simulations of 1000 g U3O8 samples using the Monte Carlo N-Particle eXtended (MCNPX) code. The results of these simulations showed good agreement between the simulated and exact 235U sample masses.

  11. Investigating Coincidence Techniques in Biomedical Applications of Neutron Activation Analysis

    NASA Astrophysics Data System (ADS)

    Chowdhury, P.; Gramer, R.; Tandel, S. K.; Reinhardt, C. J.

    2004-05-01

    While neutron activation analysis has been widely used in biomedical applications for some time, the use of non-radioactive tracer techniques, to monitor, for example, organ blood flow, is more recent. In these studies, pre-clinical animal models are injected with micro-spheres labeled with stable isotopes of elements that have a high neutron absorption cross-section. Subsequently, samples of blood and/or tissue from different locations in the body are subjected to neutron activation analysis to measure the propagation of the labeled micro-spheres through the body. Following irradiation, the counting (with high-resolution Ge detectors) is typically delayed by a few days to dissipate short-lived activity in the samples and improve signal-to-noise for the peaks of interest in the activation spectrum. The aim of the present study was to investigate whether coincidence techniques (for isotopes which decay via two-photon cascades) could improve signal-to-noise and turn-around times. The samples were irradiated at the 1 MW research reactor at the UMass Lowell Radiation Laboratory. The analysis of the multi-parameter coincidence data recorded in event-mode will be presented and compared with the standard method of recording singles spectra.

  12. TYPE III EXCITABILITY, SLOPE SENSITIVITY AND COINCIDENCE DETECTION

    PubMed Central

    Meng, Xiangying; Huguet, Gemma; Rinzel, John

    2013-01-01

    Some neurons in the nervous system do not show repetitive firing for steady currents. For time-varying inputs, they fire once if the input rise is fast enough. This property of phasic firing is known as Type III excitability. Type III excitability has been observed in neurons in the auditory brainstem (MSO), which show strong phase-locking and accurate coincidence detection. In this paper, we consider a Hodgkin-Huxley type model (RM03) that is widely-used for phasic MSO neurons and we compare it with a modification of it, showing tonic behavior. We provide insight into the temporal processing of these neuron models by means of developing and analyzing two reduced models that reproduce qualitatively the properties of the exemplar ones. The geometric and mathematical analysis of the reduced models allows us to detect and quantify relevant features for the temporal computation such as nearness to threshold and a temporal integration window. Our results underscore the importance of Type III excitability for precise coincidence detection. PMID:23667306

  13. 2012 DA14 and Chelyabinsk: Same Day Coincidence?

    NASA Astrophysics Data System (ADS)

    Chapman, Clark R.

    2013-10-01

    A long anticipated near-miss by near-Earth asteroid (NEA) 2012 DA14 on 15 February 2013 was upstaged 16 hours earlier by the impact and atmospheric explosion of a ~20 m NEA over Chelyabinsk, Russia. DA14 was earlier estimated to be 45 m across and passage at a distance under geosynchronous satellites was considered to be a record close approach by an object of that size, a once-in-40-years event. Actual Earth impact by a 20 m NEA had been estimated to be a once-in-200-years event. A simplistic calculation gives a probability of these happening on the same day of 1-in-a-billion. Within hours of the Chelyabinsk impact, it was recognized and widely reported that the two asteroids were in very different orbits and could not, at least in any readily understandable way, be physically related to each other (e.g. fragments of the same precursor body). Also, some early reports suggested that the two asteroids had very different compositions, further undermining the possibility they were pieces of the same body. (It seems unlikely, though certainly conceivable, that the two NEAs could have different compositions yet have some kind of causal connection resulting in the same-day events.) Nevertheless, incredibly tiny probabilities beg for an explanation. Here, with the benefit of hindsight, I re-examine issues that affect the probabilities, such as size, albedo, probable composition, and numbers of NEAs of these sizes. I also consider difficult issues of framing the apparent coincidence, which dominate other uncertainties. Updated information about the physical nature of the two asteroids somewhat modifies the original estimates of probabilities. Moreover, more proper ways of framing elements of the coincidence considerably reduce the improbability of the same-day events, but not nearly to the level (e.g. 1-in-1000 or perhaps 1-in-10,000) where we could rationalize dismissing the events as “just a coincidence.” The events of 15 February 2013 deserve more sophisticated

  14. IXO-XMS LVSID Anti-Coincidence Detector

    NASA Technical Reports Server (NTRS)

    Porter, Scott F.; Kilbourne, Caroline

    2010-01-01

    This document describes a high-TRL backup implementation of the anti-coincidence detector for the IXO/XMS instrument. The backup detector, hereafter referred to as the low-voltage silicon ionization detector (LVSID), has been successfully flown on Astro-E2 (Suzaku)/XRS and is currently being implemented, without significant changes, on the Astro-H/SXS instrument. The LVSID anti-coincidence detector on Astro-E2/XRS operated successfully for almost 2 years, and was not affected by the loss of liquid helium in that instrument. The LVSID continues to operate after almost 5 years on-orbit (LEO, 550 km) but with slightly increased noise following the expected depletion of solid Neon after 22 months. The noise of the device is increased after the loss of sNe due to thermally induced bias and readout noise. No radiation damage, or off-nominal affects have been observed with the LVSID on-orbit during the Astro-E2/XRS program. A detector die from the same fabrication run will be used on the Astro-H/SXS mission. The LVSID technology and cryogenic JFET readout system is thus TRL 9. The technology is described in detail in section 2. The IXO/XMS "backup-up" anti-coincidence detector is a small array of LVSID detectors that are almost identical to those employed for Astro -E2/XRS as described in this document. The readout system is identical and, infact would use the same design as the Astro -E2/XRS JFET amplifier module (19 channels) essentially without changes except for its mechanical mount. The changes required for the IXO/XMS LVSID array are limited to the mounting of the LVSID detectors, and the mechanical mounting of the JFET amplifier sub-assembly. There is no technical development needed for the IXO/XMS implementation and the technology is ready for detailed design-work leading to PDR. The TRL level is thus at least 6, and possibly higher. Characteristics of an IXO/XMS LVSID anti-co detector are given in Table 1 and described in detail in section 3.

  15. Geometric origin of coincidences and hierarchies in the landscape

    SciTech Connect

    Bousso, Raphael; Leichenauer, Stefan; Rosenhaus, Vladimir; Freivogel, Ben

    2011-10-15

    We show that the geometry of cutoffs on eternal inflation strongly constrains predictions for the time scales of vacuum domination, curvature domination, and observation. We consider three measure proposals: the causal patch, the fat geodesic, and the apparent horizon cutoff, which is introduced here for the first time. We impose neither anthropic requirements nor restrictions on landscape vacua. For vacua with positive cosmological constant, all three measures predict the double coincidence that most observers live at the onset of vacuum domination and just before the onset of curvature domination. The hierarchy between the Planck scale and the cosmological constant is related to the number of vacua in the landscape. These results require only mild assumptions about the distribution of vacua (somewhat stronger assumptions are required by the fat geodesic measure). At this level of generality, none of the three measures are successful for vacua with negative cosmological constant. Their applicability in this regime is ruled out unless much stronger anthropic requirements are imposed.

  16. Coincident-site lattice matching during van der Waals epitaxy

    PubMed Central

    Boschker, Jos E.; Galves, Lauren A.; Flissikowski, Timur; Lopes, Joao Marcelo J.; Riechert, Henning; Calarco, Raffaella

    2015-01-01

    Van der Waals (vdW) epitaxy is an attractive method for the fabrication of vdW heterostructures. Here Sb2Te3 films grown on three different kind of graphene substrates (monolayer epitaxial graphene, quasi freestanding bilayer graphene and the SiC (6√3 × 6√3)R30° buffer layer) are used to study the vdW epitaxy between two 2-dimensionally (2D) bonded materials. It is shown that the Sb2Te3 /graphene interface is stable and that coincidence lattices are formed between the epilayers and substrate that depend on the size of the surface unit cell. This demonstrates that there is a significant, although relatively weak, interfacial interaction between the two materials. Lattice matching is thus relevant for vdW epitaxy with two 2D bonded materials and a fundamental design parameter for vdW heterostructures. PMID:26658715

  17. Coincidence-Summing Corrections for Close Geometry Measurements

    SciTech Connect

    Gueray, R. Taygun

    2008-11-11

    For a given stellar temperature, nuclear reactions take place in the energy range of the Gamow window with the relatively low energies of the astrophysical interest for charged particle induced reactions. In order to measure the nuclear reaction cross sections with the activation method at projectile energies as low as possible, a gamma counting system that consists of Ge detectors and the irradiated target in close geometry is required. The presence of cascade transitions requires coincidence summing corrections that can not be ignored because of the very large solid angle. In this study, the determination of the summing correction factor and photopeak efficiency for a gamma spectrometer, as an example, composed of two Ge clover detectors in close geometry is briefly described.

  18. Serendipity in Cancer Drug Discovery: Rational or Coincidence?

    PubMed

    Prasad, Sahdeo; Gupta, Subash C; Aggarwal, Bharat B

    2016-06-01

    Novel drug development leading to final approval by the US FDA can cost as much as two billion dollars. Why the cost of novel drug discovery is so expensive is unclear, but high failure rates at the preclinical and clinical stages are major reasons. Although therapies targeting a given cell signaling pathway or a protein have become prominent in drug discovery, such treatments have done little in preventing or treating any disease alone because most chronic diseases have been found to be multigenic. A review of the discovery of numerous drugs currently being used for various diseases including cancer, diabetes, cardiovascular, pulmonary, and autoimmune diseases indicates that serendipity has played a major role in the discovery. In this review we provide evidence that rational drug discovery and targeted therapies have minimal roles in drug discovery, and that serendipity and coincidence have played and continue to play major roles. The primary focus in this review is on cancer-related drug discovery.

  19. Coincidence landscapes for three-channel linear optical networks

    NASA Astrophysics Data System (ADS)

    de Guise, Hubert; Tan, Si-Hui; Poulin, Isaac P.; Sanders, Barry C.

    2014-06-01

    We use permutation-group methods plus SU(3) group-theoretic methods to determine the action of a three-channel passive optical interferometer on controllably delayed single-photon pulse inputs to each channel. Permutation-group techniques allow us to relate directly expressions for rates and, in particular, investigate symmetries in the coincidence landscape. These techniques extend the traditional Hong-Ou-Mandel effect analysis for two-channel interferometry to valleys and plateaus in three-channel interferometry. Our group-theoretic approach is intuitively appealing because the calculus of Wigner D functions partially accounts for permutational symmetries and directly reveals the connections among D functions, partial distinguishability, and immanants.

  20. Coincident vortices in Antarctic wind fields and sea ice motion

    NASA Astrophysics Data System (ADS)

    Wassermann, S.; Schmitt, C.; Kottmeier, C.; Simmonds, I.

    2006-08-01

    This study introduces a method to examine the coincidence of rotational ice drift and winds caused by the forcing of ice motion by Antarctic cyclones. Vortices are automatically detected using the algorithm of Murray and Simmonds (1991) from both ECMWF surface pressures and SSM/I sea ice motions. For compatibility with this algorithm sea ice motion vectors are transformed to a scalar stream function. During a seven-day test period positions of pressure minima and stream function maxima (SFM) of ice drift are within 300 km in 96% of the cases. Lowest pressure minima are related to highest stream function maxima. The results promise the method to provide a complementary tool of detecting and localizing low-pressure systems over sea ice, adding to numerical pressure analyses.

  1. Pattern Recognition in Gamma-Gamma Coincidence Data sets

    NASA Astrophysics Data System (ADS)

    Manatt, D. R.; Barnes, F. L.; Becker, J. A.; Candy, J. V.; Henry, E. A.; Brinkman, M. J.

    1991-10-01

    Considerable amounts of tedious labor are required to manually scan high-resolution 1D slices of two dimensional γ-γ coincident matrices for relevant and exciting structures. This is particularly true when the interesting structures are of weak intensity. We are working on automated search methods for the detection of rotational band structures in the full 2D space using pattern recognition techniques. For nominal sized data sets (1024×1024), however, these techniques only become computationally feasible through the use of Fourier Transform methods. Furthermore the presentation of data matrices as images rather than series of 1D spectra has been shown to be useful. In this paper we will present the data manipulation techniques we have developed.

  2. Coincidence of GIST and pancreatic endocrine neoplasm in neurofibromatosis.

    PubMed

    Dominguez-Comesaña, Elias; Tome-Espiñeiro, Catherine; Ulla-Rocha, Jose L; Lorenzo-Lorenzo, Isabel; Lede-Fernandez, Angel; Portela-Serra, Jose L

    2011-09-01

    Carcinoids of the ampulla of Vater are infrequent tumors of which a quarter of cases have been detected in patients with type I neurofibromatosis. This hereditary disease is also associated with gastrointestinal stromal tumors (GIST). However, the coincidence of these three entities together have only been formerly detected in five cases. A 53 year-old female patient, diagnosed with type I neurofibromatosis, with a malignant carcinoid of ampulla of Vater and multiple gastrointestinal stromal tumors in the duodenum and jejunum, was treated with total pancreatectomy and the excision of her intestinal tumors. Five-years on, a follow-up showed the patient to be well, and free from tumor recurrence. The coexistence of an ampullary carcinoid tumor, GIST and neurofibramatosis is very rare. Radical curative surgical resection is a good treatment option, but the optimal management of this is not yet well established.

  3. Gamma Efficiency Simulations towards Coincidence Measurements for Fusion Cross Sections

    NASA Astrophysics Data System (ADS)

    Heine, M.; Courtin, S.; Fruet, G.; Jenkins, D. G.; Montanari, D.; Morris, L.; Regan, P. H.; Rudigier, M.; Symochko, D.

    2016-10-01

    With the experimental station STELLA (STELlar LAboratory) we will measure fusion cross sections of astrophysical relevance making use of the coincident detection of charged particles and gamma rays for background reduction. For the measurement of gamma rays from the de-excitation of fusion products a compact array of 36 UK FATIMA LaBr3 detectors is designed based on efficiency studies with Geant4. The photo peak efficiency in the region of interest compares to other gamma detection systems used in this field. The features of the internal decay of 138La is used in a background study to obtain an online calibration of the gamma detectors. Background data are fit to the Monte Carlo model of the self activity assuming crude exponential behavior of external background. Accuracy in the region of interest is of the order of some keV in this first study.

  4. Observations of ionospheric magnetospheric coupling - DE and Chatanika coincidences

    NASA Technical Reports Server (NTRS)

    Green, J. L.; Brace, L. H.; Waite, J. H.; Chappell, C. R.; Chandler, M. O.; Doupnik, J. R.; Richards, P. G.; Heelis, R.; Shawhan, S. D.

    1986-01-01

    Observations from several experiments on board the Dynamics Explorer 1 and 2 (DE 1 and 2) spacecraft and ground-based radar measurements from the Chatanika radar are combined in order to examine the details of ionospheric/magnetospheric coupling in the local evening sector. DE 1 and DE 2 were in coplanar polar orbits that provided measurements almost simultaneously in time and magnetically coincident with the Chatanika radar from L = 3 to L = 17. The coupling processes are inferred from the density, temperature, composition, and angular distributions of the low-energy plasma observed from the E region of the ionosphere to magnetospheric altitudes of 2.5 earth radii. Plasma characteristics of the plasmasphere, main trough, auroral zone, and polar cap can be studied in this data set. The observations imply that as L increases, the dominant coupling mechanism between the ionosphere and magnetosphere in the measured energy range changes from equilibrium diffusion to perpendicular acceleration and finally to parallel acceleration.

  5. Testable solution of the cosmological constant and coincidence problems

    SciTech Connect

    Shaw, Douglas J.; Barrow, John D.

    2011-02-15

    We present a new solution to the cosmological constant (CC) and coincidence problems in which the observed value of the CC, {Lambda}, is linked to other observable properties of the Universe. This is achieved by promoting the CC from a parameter that must be specified, to a field that can take many possible values. The observed value of {Lambda}{approx_equal}(9.3 Gyrs){sup -2}[{approx_equal}10{sup -120} in Planck units] is determined by a new constraint equation which follows from the application of a causally restricted variation principle. When applied to our visible Universe, the model makes a testable prediction for the dimensionless spatial curvature of {Omega}{sub k0}=-0.0056({zeta}{sub b}/0.5), where {zeta}{sub b}{approx}1/2 is a QCD parameter. Requiring that a classical history exist, our model determines the probability of observing a given {Lambda}. The observed CC value, which we successfully predict, is typical within our model even before the effects of anthropic selection are included. When anthropic selection effects are accounted for, we find that the observed coincidence between t{sub {Lambda}={Lambda}}{sup -1/2} and the age of the Universe, t{sub U}, is a typical occurrence in our model. In contrast to multiverse explanations of the CC problems, our solution is independent of the choice of a prior weighting of different {Lambda} values and does not rely on anthropic selection effects. Our model includes no unnatural small parameters and does not require the introduction of new dynamical scalar fields or modifications to general relativity, and it can be tested by astronomical observations in the near future.

  6. Glycine-activated currents are changed by coincident membrane depolarization in developing rat auditory brainstem neurones

    PubMed Central

    Backus, Kurt H; Deitmer, Joachim W; Friauf, Eckhard

    1998-01-01

    During early ontogeny, glycine receptors (GlyRs) exert depolarizing responses which may be of developmental relevance. We have used the gramicidin-perforated patch technique to elucidate the mechanism of glycine-activated currents in developing neurones of the rat lateral superior olive (LSO). When the holding potential was set to −60 mV, perforated-patch recordings revealed glycine-induced inward currents in 59%, outward currents in 5% and biphasic currents in 34% of the LSO neurones tested (n = 44). The biphasic currents were characterized by a transient outward phase which was followed by an inward phase. Ion substitution experiments showed that both Cl− and HCO3− contributed to the glycine- induced biphasic current responses. In the biphasic responses, the reversal potential of the glycine-induced current (Egly) depended on the response phase. A strong shift of Egly from a mean of −72 mV during the outward phase of the glycine response to a mean of −51 mV during the inward phase was observed, suggesting a shift of an ion gradient. When the membrane potential was depolarized, ‘tail’ currents were induced in the presence of glycine. An increased duration or amplitude of the evoked depolarizations resulted in a proportional enlargement of these tail currents, indicating that they were produced by a shift of an ion gradient. Since changes of the HCO3− gradient are negligible, because of the carbonic anhydrase activity, we suggest that these tail currents were caused by a shift of the Cl− gradient. We conclude that Cl− accumulates intracellularly during the activation of GlyRs and, consequently, Egly moves towards more positive values. Coincident depolarizing stimuli enhanced intracellular Cl− accumulation and the shift of Egly, thereby switching hyperpolarizing to depolarizing action. This change could assist in an activity-dependent strengthening and refinement of glycinergic synapses during the maturation of inhibitory connectivity. PMID

  7. Alpha and conversion electron spectroscopy of 238,239Pu and 241Am and alpha-conversion electron coincidence measurements

    NASA Astrophysics Data System (ADS)

    Dion, Michael P.; Miller, Brian W.; Warren, Glen A.

    2016-09-01

    A technique to determine the isotopic constituents of a mixed actinide sample has been proposed by a coincident alpha-conversion electron measurement. This presents a unique signature to allow the unfolding of isotopes that possess overlapping alpha particle energy and reduce backgrounds of an unseparated sample. The work presented here are results of conversion electron spectroscopy of 241Am, 238Pu and 239Pu using a dual-stage peltier-cooled 25 mm2 silicon drift detector and alpha spectroscopy with a passivated ion implanted planar silicon detector. The conversion electron spectra were evaluated from 20-55 keV based on fits to the dominant conversion electron emissions, which allowed the relative conversion electron emission intensities to be determined. These measurements provide crucial singles spectral information and calibration to aid in the coincident measurement approach. Furthermore, an alpha-conversion electron spectrometer was assembled using the silicon based detectors described and results of a coincident spectrum analysis is reported for 241Am.

  8. Neutron production in coincidence with fragments from the 4Ca+H reactions at Elab=357 and 565 A MeV

    NASA Astrophysics Data System (ADS)

    Tuvà, C.; Albergo, S.; Boemi, D.; Caccia, Z.; Chen, C.-X.; Costa, S.; Crawford, H. J.; Cronqvist, M.; Engelage, J.; Greiner, L.; Guzik, T. G.; Insolia, A.; Knott, C. N.; Lindstrom, P. J.; Mitchell, J. W.; Potenza, R.; Russo, G. V.; Soutoul, A.; Testard, O.; Tricomi, A.; Tull, C. E.; Waddington, C. J.; Webber, W. R.; Wefel, J. P.

    2000-04-01

    In the frame of the Transport Collaboration neutrons in coincidence with charged fragments produced in the 40Ca+H reaction at Elab=357 and 565 A MeV have been measured at the Heavy Ion Spectrometer System (HISS) facility of the Lawrence Berkeley National Laboratory, using the multifunctional neutron spectrometer MUFFINS. The detector covered a narrow angular range about the beam in the forward direction (0°-3.2°). In this contribution we report absolute neutron production cross sections in coincidence with charged fragments (10⩽Z⩽20). The neutron multiplicities have been estimated from the comparison between the neutron cross sections, in coincidence with the fragments, and the elemental cross sections. We have found evidence for a pre-equilibrium emission of prompt neutrons in superposition to a `slower' deexcitation of the equilibrated remnant by emission of nucleons and fragments, as already seen in the inclusive rapidity distributions.

  9. Neutron Production in Coincidence with Fragments from the {sup 40}Ca + H Reactions at E{sub lab} = 357 and 565 A MeV

    SciTech Connect

    Tuve, C.; Albergo, S.; Boemi, D.; Caccia, Z.; Chen, C.-X.; Costa, S.; Crawford, H.J.; Cronqvist, M.; Engelage, J.; Greiner, L.; Guzik, T.G.; Insolia, A.; Knott, C.N.; Lindstrom, P.J.; Mitchell, J.W.; Potenza, R.; Russo, G.V.; Soutoul, A.; Testard, O.; Tricomi, A.; Tull, C.E.; Waddington, C.J.; Webber, W.R.; Wefel, J.P.

    2000-12-31

    In the frame of the Transport Collaboration neutrons in coincidence with charged fragments produced in the {sup 40}Ca + H reaction at E{sub lab} = 357 and 565 AMeV have been measured at the Heavy Ion Spectrometer System (HISS) facility of the Lawrence Berkeley National Laboratory, using the multifunctional neutron spectrometer MUFFINS. The detector covered a narrow angular range about the beam in the forward direction (0? - 3.2?). In this contribution we report absolute neutron production cross sections in coincidence with charged fragments (10 {<=} Z {<=} 20). The neutron multiplicities have been estimated from the comparison between the neutron cross sections, in coincidence with the fragments, and the elemental cross sections. We have found evidence for a pre-equilibrium emission of prompt neutrons in superposition to a 'slower' deexcitation of the equilibrated remnant by emission of nucleons and fragments, as already seen in the inclusive rapidity distributions.

  10. Jovian Auroral X-ray Emission Coinciding with an Interplanetary Coronal Mass Ejection

    NASA Astrophysics Data System (ADS)

    Dunn, W.; Branduardi-Raymont, G.; Elsner, R.; Vogt, M.; Lamy, L.; Ford, P. G.; Coates, A. J.; Gladstone, R.; Jackman, C. M.; Nichols, J. D.; Rae, J.; Varsani, A.; Kimura, T.; Hansen, K. C.; Jasinski, J. M.

    2015-12-01

    The extent of the Solar Wind influence on Jupiter's X-ray aurora is yet to be understood. To probe this relationship, we compare two Chandra X-ray observations of Jupiter: one coinciding with the predicted arrival of an Interplanetary Coronal Mass Ejection (ICME) and another observation two days later. During the observation coincident with the ICME, we observe a bright auroral enhancement of a factor of 8 in a region normally absent of X-rays. This enhancement occurs ~1 hour before a burst of non-Io Decametric radio emission, believed to be associated with solar wind forward shocks [Hess et al. 2012, 2014]. We also find variation in X-ray auroral periodic behaviour, spatial and spectral distributions. We use magnetosphere-ionosphere mapping [Vogt et al. 2011] to identify the source of ions generating the X-rays and find that they originate from 10:30-18:00 magnetospheric local time (MLT) in regions of the outer magnetosphere close to the magnetopause. The model also maps some precipitation to open field lines. This suggests that X-rays may provide an excellent tool for analysing the Jovian outer magnetosphere and the processes occurring between the Jovian magnetopause and the solar wind. As discovered by Gladstone et al. [2002] discovery, we find an X-ray hot spot that pulses with quasi-periodicity. Measurements of this periodicity suggest 2 distinct ion populations generate the Jovian X-ray aurora: a sulphur/carbon dominated population from the middle to outer magnetosphere with a period of 26 minutes, and a combined oxygen and carbon/sulphur population from close to the magnetopause with a period of 12 minutes. The source region and periodicity support findings by Bunce et al. [2004] that pulsed dayside reconnection could energise the outer magnetosphere and drive X-ray emission To better understand the persistence of these features and/or their relationship to the ICME, we compare these 2011 observations with preliminary analysis of Chandra X-ray observations

  11. Line identification studies using traditional techniques and wavelength coincidence statistics

    NASA Technical Reports Server (NTRS)

    Cowley, Charles R.; Adelman, Saul J.

    1990-01-01

    Traditional line identification techniques result in the assignment of individual lines to an atomic or ionic species. These methods may be supplemented by wavelength coincidence statistics (WCS). The strength and weakness of these methods are discussed using spectra of a number of normal and peculiar B and A stars that have been studied independently by both methods. The present results support the overall findings of some earlier studies. WCS would be most useful in a first survey, before traditional methods have been applied. WCS can quickly make a global search for all species and in this way may enable identifications of an unexpected spectrum that could easily be omitted entirely from a traditional study. This is illustrated by O I. WCS is a subject to well known weakness of any statistical technique, for example, a predictable number of spurious results are to be expected. The danger of small number statistics are illustrated. WCS is at its best relative to traditional methods in finding a line-rich atomic species that is only weakly present in a complicated stellar spectrum.

  12. Super sub-wavelength patterns in photon coincidence detection.

    PubMed

    Liu, Ruifeng; Zhang, Pei; Zhou, Yu; Gao, Hong; Li, Fuli

    2014-02-17

    High-precision measurements implemented with light are desired in all fields of science. However, light acts as a wave, and the Rayleigh criterion in classical optics yields a diffraction limit that prevents obtaining a resolution smaller than the wavelength. Sub-wavelength interference has potential application in lithography because it beats the classical Rayleigh resolution limit. Here, we carefully study second-order correlation theory to establish the physics behind sub-wavelength interference in photon coincidence detection. A Young's double slit experiment with pseudo-thermal light is performed to test the second-order correlation pattern. The results show that when two point detectors are scanned in different ways, super sub-wavelength interference patterns can be obtained. We then provide a theoretical explanation for this surprising result, and demonstrate that this explanation is also suitable for the results found for entangled light. Furthermore, we discuss the limitations of these types of super sub-wavelength interference patterns in quantum lithography.

  13. Super sub-wavelength patterns in photon coincidence detection

    NASA Astrophysics Data System (ADS)

    Liu, Ruifeng; Zhang, Pei; Zhou, Yu; Gao, Hong; Li, Fuli

    2014-02-01

    High-precision measurements implemented with light are desired in all fields of science. However, light acts as a wave, and the Rayleigh criterion in classical optics yields a diffraction limit that prevents obtaining a resolution smaller than the wavelength. Sub-wavelength interference has potential application in lithography because it beats the classical Rayleigh resolution limit. Here, we carefully study second-order correlation theory to establish the physics behind sub-wavelength interference in photon coincidence detection. A Young's double slit experiment with pseudo-thermal light is performed to test the second-order correlation pattern. The results show that when two point detectors are scanned in different ways, super sub-wavelength interference patterns can be obtained. We then provide a theoretical explanation for this surprising result, and demonstrate that this explanation is also suitable for the results found for entangled light. Furthermore, we discuss the limitations of these types of super sub-wavelength interference patterns in quantum lithography.

  14. Intrinsic coincident full-Stokes polarimeter using stacked organic photovoltaics.

    PubMed

    Yang, Ruonan; Sen, Pratik; O'Connor, B T; Kudenov, M W

    2017-02-20

    An intrinsic coincident full-Stokes polarimeter is demonstrated by using strain-aligned polymer-based organic photovoltaics (OPVs) that can preferentially absorb certain polarized states of incident light. The photovoltaic-based polarimeter is capable of measuring four Stokes parameters by cascading four semitransparent OPVs in series along the same optical axis. This in-line polarimeter concept potentially ensures high temporal and spatial resolution with higher radiometric efficiency as compared to the existing polarimeter architecture. Two wave plates were incorporated into the system to modulate the S3 Stokes parameter so as to reduce the condition number of the measurement matrix and maximize the measured signal-to-noise ratio. Radiometric calibration was carried out to determine the measurement matrix. The polarimeter presented in this paper demonstrated an average RMS error of 0.84% for reconstructed Stokes vectors after normalized to S0. A theoretical analysis of the minimum condition number of the four-cell OPV design showed that for individually optimized OPV cells, a condition number of 2.4 is possible.

  15. Analytical model of coincidence resolving time in TOF-PET.

    PubMed

    Wieczorek, H; Thon, A; Dey, T; Khanin, V; Rodnyi, P

    2016-06-21

    The coincidence resolving time (CRT) of scintillation detectors is the parameter determining noise reduction in time-of-flight PET. We derive an analytical CRT model based on the statistical distribution of photons for two different prototype scintillators. For the first one, characterized by single exponential decay, CRT is proportional to the decay time and inversely proportional to the number of photons, with a square root dependence on the trigger level. For the second scintillator prototype, characterized by exponential rise and decay, CRT is proportional to the square root of the product of rise time and decay time divided by the doubled number of photons, and it is nearly independent of the trigger level. This theory is verified by measurements of scintillation time constants, light yield and CRT on scintillator sticks. Trapping effects are taken into account by defining an effective decay time. We show that in terms of signal-to-noise ratio, CRT is as important as patient dose, imaging time or PET system sensitivity. The noise reduction effect of better timing resolution is verified and visualized by Monte Carlo simulation of a NEMA image quality phantom.

  16. Coincidence and awareness of oral parafunctions in college students.

    PubMed

    Panek, H; Nawrot, P; Mazan, M; Bielicka, B; Sumisławska, M; Pomianowski, R

    2012-03-01

    The aim of the study was to determine the prevalence and awareness of particular types of oral parafunctions in young healthy students and any association with temporomandibular disorders (TMD). The study was performed in a randomly selected group of 303 healthy students (mean age 18.8 years) from the vocational technical school in Wrocław, Poland, who underwent a routine clinical examination and functional analysis of the mouth. On taking the history all subjects were asked about their awareness of various forms of parafunctional activity in their mouth. Almost all subjects revealed various oral parafunctions such as: bruxism, nail and pen biting, chewing gum, and biting the mucosa of lip or cheek. These habits were present singly or as double, triple or even fourfold coincidences in a single person. The most frequent oral parafunctions were habitual gum chewing and bruxism. Subjects were very seldom aware of the last parafunction. TMDs were more prevalent in the presence of bruxism than in other oral parafunctions. The studied students revealed various types of oral parafunctions, however most of them were not aware of clenching and grinding their teeth.

  17. Nonlinear Dynamics of Neuronal Excitability, Oscillations, and Coincidence Detection

    PubMed Central

    RINZEL, JOHN; HUGUET, GEMMA

    2014-01-01

    We review some widely studied models and firing dynamics for neuronal systems, both at the single cell and network level, and dynamical systems techniques to study them. In particular, we focus on two topics in mathematical neuroscience that have attracted the attention of mathematicians for decades: single-cell excitability and bursting. We review the mathematical framework for three types of excitability and onset of repetitive firing behavior in single-neuron models and their relation with Hodgkin’s classification in 1948 of repetitive firing properties. We discuss the mathematical dissection of bursting oscillations using fast/slow analysis and demonstrate the approach using single-cell and mean-field network models. Finally, we illustrate the properties of Type III excitability in which case repetitive firing for constant or slow inputs is absent. Rather, firing is in response only to rapid enough changes in the stimulus. Our case study involves neuronal computations for sound localization for which neurons in the auditory brain stem perform extraordinarily precise coincidence detection with submillisecond temporal resolution. PMID:25392560

  18. A high-efficiency HPGe coincidence system for environmental analysis.

    PubMed

    Britton, R; Davies, A V; Burnett, J L; Jackson, M J

    2015-08-01

    The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is supported by a network of certified laboratories which must meet certain sensitivity requirements for CTBT relevant radionuclides. At the UK CTBT Radionuclide Laboratory (GBL15), a high-efficiency, dual-detector gamma spectroscopy system has been developed to improve the sensitivity of measurements for treaty compliance, greatly reducing the time required for each sample. Utilising list-mode acquisition, each sample can be counted once, and processed multiple times to further improve sensitivity. For the 8 key radionuclides considered, Minimum Detectable Activities (MDA's) were improved by up to 37% in standard mode (when compared to a typical CTBT detector system), with the acquisition time required to achieve the CTBT sensitivity requirements reduced from 6 days to only 3. When utilising the system in coincidence mode, the MDA for (60) Co in a high-activity source was improved by a factor of 34 when compared to a standard CTBT detector, and a factor of 17 when compared to the dual-detector system operating in standard mode. These MDA improvements will allow the accurate and timely quantification of radionuclides that decay via both singular and cascade γ emission, greatly enhancing the effectiveness of CTBT laboratories. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

  19. Coincident Phosphatidic Acid Interaction Restrains Drp1 in Mitochondrial Division.

    PubMed

    Adachi, Yoshihiro; Itoh, Kie; Yamada, Tatsuya; Cerveny, Kara L; Suzuki, Takamichi L; Macdonald, Patrick; Frohman, Michael A; Ramachandran, Rajesh; Iijima, Miho; Sesaki, Hiromi

    2016-09-15

    Mitochondria divide to control their size, distribution, turnover, and function. Dynamin-related protein 1 (Drp1) is a critical mechanochemical GTPase that drives constriction during mitochondrial division. It is generally believed that mitochondrial division is regulated during recruitment of Drp1 to mitochondria and its oligomerization into a division apparatus. Here, we report an unforeseen mechanism that regulates mitochondrial division by coincident interactions of Drp1 with the head group and acyl chains of phospholipids. Drp1 recognizes the head group of phosphatidic acid (PA) and two saturated acyl chains of another phospholipid by penetrating into the hydrophobic core of the membrane. The dual phospholipid interactions restrain Drp1 via inhibition of oligomerization-stimulated GTP hydrolysis that promotes membrane constriction. Moreover, a PA-producing phospholipase, MitoPLD, binds Drp1, creating a PA-rich microenvironment in the vicinity of a division apparatus. Thus, PA controls the activation of Drp1 after the formation of the division apparatus.

  20. The alpha-gamma coincidence spectrometer and its application

    SciTech Connect

    Shengzhong Qiao )

    1991-01-01

    In this paper the author describes the structure and properties of the high-resolution {alpha}-{gamma} coincidence spectrometer and its applications in determining heavy nuclides qualitatively and quantitatively. The energy resolution of the spectrometer is 0.25% (full-width at half-maximum is 13.8 keV for 5.486-MeV alpha particles); the energy shift of the peak is 0.05% in 8 h; non-linearity is < 0.2% for the 4- to 8-MeV energy region. the uncertainty in the quantitative measurement is better than {plus minus}1%. The spectrometer is being applied to some important measurements of specific cases. It can resolve some complex and difficult measurements problems because of its high accuracy, sensitivity, selectivity, and ability to remove interferences. The paper describes results with determination of {sup 242}Pu in plutonium samples; determination of the {sup 241}Am content in the presence of {sup 242}Cm and fission products; determination of the {sup 241}Am in plutonium samples; determination of the {sup 241}Am and {sup 243}Cm in irradiated plutonium solutions; and other applications.

  1. Coincident loss of consciousness and ventricular tachycardia during +GZ stress.

    PubMed

    Whinnery, J E; Laughlin, M H; Uhl, G S

    1980-08-01

    The environment of the advanced fighter aircraft represents a unique combination of stressful factors. Each of the individual stresses is hazardous, with the summation of these factors possibly resulting in an additional risk for sudden in-flight incapacitation. Advanced fighter aircraft are capabble of producing both rapid onset and high sustained +GZ forces which, on occasion, can exceed the tolerance limits of the pilot. The +GZ forces encountered during aerial combat maneuvering are physiologically stressful and have a profound effect on the regulatory mechanisms of the body. The influence of these stresses, including +GZ stress, on the autonomic nervous system is complex. The overall normal regulation of the cardiovascular system depends on a balance between both branches of the autonomic nervous system. An imbalance between sympathetic and parasympathetic tone can result in cardiac dysrhythmias and symptoms not conducive to safe and effective flight. An episode of ventricular tachycardia, coincident with an episode of loss of consciousness, was observed in an apparently healthy aircrewman during +GZ stress on the USAF School of Aerospace Medicine human centrifuge. The implications of autonomic imbalance in the production of similar potentially hazardous dysrhythmias and symptoms in the multistress environment deserve more in-depth investigation.

  2. Performance of Down syndrome subjects during a coincident timing task

    PubMed Central

    2013-01-01

    Background The time synchronization is a very important ability for the acquisition and performance of motor skills that generate the need to adapt the actions of body segments to external events of the environment that are changing their position in space. Down Syndrome (DS) individuals may present some deficits to perform tasks with synchronization demand. We aimed to investigate the performance of individuals with DS in a simple Coincident Timing task. Method 32 individuals were divided into 2 groups: the Down syndrome group (DSG) comprised of 16 individuals with average age of 20 (+/− 5 years old), and a control group (CG) comprised of 16 individuals of the same age. All individuals performed the Simple Timing (ST) task and their performance was measured in milliseconds. The study was conducted in a single phase with the execution of 20 consecutive trials for each participant. Results There was a significant difference in the intergroup analysis for the accuracy adjustment - Absolute Error (Z = 3.656, p = 0.001); and for the performance consistence - Variable Error (Z = 2.939, p = 0.003). Conclusion DS individuals have more difficulty in integrating the motor action to an external stimulus and they also present more inconsistence in performance. Both groups presented the same tendency to delay their motor responses. PMID:23618314

  3. Dubin-Johnson syndrome coinciding with colon cancer and atherosclerosis.

    PubMed

    Sticova, Eva; Elleder, Milan; Hulkova, Helena; Luksan, Ondrej; Sauer, Martin; Wunschova-Moudra, Irena; Novotny, Jan; Jirsa, Milan

    2013-02-14

    Hyperbilirubinemia has been presumed to prevent the process of atherogenesis and cancerogenesis mainly by decreasing oxidative stress. Dubin-Johnson syndrome is a rare, autosomal recessive, inherited disorder characterized by biphasic, predominantly conjugated hyperbilirubinemia with no progression to end-stage liver disease. The molecular basis in Dubin-Johnson syndrome is absence or deficiency of human canalicular multispecific organic anion transporter MRP2/cMOAT caused by homozygous or compound heterozygous mutation(s) in ABCC2 located on chromosome 10q24. Clinical onset of the syndrome is most often seen in the late teens or early adulthood. In this report, we describe a case of previously unrecognized Dubin-Johnson syndrome caused by two novel pathogenic mutations (c.2360_2366delCCCTGTC and c.3258+1G>A), coinciding with cholestatic liver disease in an 82-year-old male patient. The patient, suffering from advanced atherosclerosis with serious involvement of coronary arteries, developed colorectal cancer with nodal metastases. The subsequent findings do not support the protective role of Dubin-Johnson type hyperbilirubinemia.

  4. Analytical model of coincidence resolving time in TOF-PET

    NASA Astrophysics Data System (ADS)

    Wieczorek, H.; Thon, A.; Dey, T.; Khanin, V.; Rodnyi, P.

    2016-06-01

    The coincidence resolving time (CRT) of scintillation detectors is the parameter determining noise reduction in time-of-flight PET. We derive an analytical CRT model based on the statistical distribution of photons for two different prototype scintillators. For the first one, characterized by single exponential decay, CRT is proportional to the decay time and inversely proportional to the number of photons, with a square root dependence on the trigger level. For the second scintillator prototype, characterized by exponential rise and decay, CRT is proportional to the square root of the product of rise time and decay time divided by the doubled number of photons, and it is nearly independent of the trigger level. This theory is verified by measurements of scintillation time constants, light yield and CRT on scintillator sticks. Trapping effects are taken into account by defining an effective decay time. We show that in terms of signal-to-noise ratio, CRT is as important as patient dose, imaging time or PET system sensitivity. The noise reduction effect of better timing resolution is verified and visualized by Monte Carlo simulation of a NEMA image quality phantom.

  5. The Structure of the Cubic Coincident Site Lattice Rotation Group

    SciTech Connect

    Reed, B W; Minich, R W; Rudd, R E; Kumar, M

    2004-01-13

    This work is intended to be a mathematical underpinning for the field of grain boundary engineering and its relatives. The interrelationships within the set of rotations producing coincident site lattices in cubic crystals are examined in detail. Besides combining previously established but widely scattered results into a unified context, the present work details newly developed representations of the group structure in terms of strings of generators (based on quaternionic number theory, and including uniqueness proofs and rules for algebraic manipulation) as well as an easily visualized topological network model. Important results that were previously obscure or not universally understood (e.g. the {Sigma} combination rule governing triple junctions) are clarified in these frameworks. The methods also facilitate several general observations, including the very different natures of twin-limited structures in two and three dimensions, the inadequacy of the {Sigma} combination rule to determine valid quadruple nodes, and a curious link between allowable grain boundary assignments and the four-color map theorem. This kind of understanding is essential to the generation of realistic statistical models of grain boundary networks (particularly in twin-dominated systems) and is especially applicable to the field of grain boundary engineering.

  6. Coincident Observations of Surface Ozone and NMVOCs over Abu Dhabi

    NASA Astrophysics Data System (ADS)

    Abbasi, Naveed; Majeed, Tariq; Iqbal, Mazhar; Tarasick, David; Davies, Jonathan; Riemer, Daniel; Apel, Eric

    2016-07-01

    The vertical profiles of ozone are measured coincidently with non-methane volatile organic compounds (NMVOCs) at the meteorological site located at the Abu Dhabi international airport (latitude 24.45N; longitude 54.22E) during the years 2012 - 2014. Some of the profiles show elevated surface ozone >95 ppbv during the winter months (December, January and February). The ground-level NMVOCs obtained from the gas chromatography-flame ionization detection/mass spectrometry system also show elevated values of acetylene, ethane, propane, butane, pentane, benzene, and toluene. NMVOCs and ozone abundances in other seasons are much lower than the values in winter season. NMVOCs are emitted from an extensive number of sources in urban environments including fuel production, distribution, and consumption, and serve as precursor of ozone. Transport sources contribute a substantial portion of the NMVOC burden to the urban atmosphere in developed regions. Abu Dhabi is located at the edge of the Arabian Gulf and is highly affected by emissions from petrochemical industries in the neighboring Gulf region. The preliminary results indicate that wintertime enhancement in ozone is associated with large values of NMVOCs at Abu Dhabi. The domestic production of surface ozone is estimated from the combination of oxygen recombination and NMVOCs and compared with the data. It is estimated that about 40-50% of ozone in Abu Dhabi is transported from the neighbouring petrochemical industries. We will present ozone sounding and NMVOCs data and our model estimates of surface ozone, including a discussion on the high levels of the tropospheric ozone responsible for contaminating the air quality in the UAE. This work is supported by National Research Foundation, UAE.

  7. Near coincidence site lattice misorientations in monoclinic zirconia

    SciTech Connect

    Gertsman, V.Y. |; Zhilyaev, A.P. |; Szpunar, J.

    1996-12-01

    Zirconium dioxide, ZrO{sub 2}, exists in three crystalline phases: monoclinic, tetragonal, and cubic. Calculations of the coincidence site lattice (CSL) misorientations for the last two lattices and for hexagonal ones using the methods developed represent little difficulty. However, no procedure for the determination of the CSL misorientations in the monoclinic system has been reported so far. Monoclinic zirconia has the crystallographic space group P2{sub 1}/c and the following parameters of the unit cell (e.g., 5, 6): a = 5.1490 {angstrom}, b = 5.2133 {angstrom}, c = 5.3161 {angstrom}, and {beta} = 99.228{degree}. Before discussing possible CSL misorientations in zirconia, consider a simple example based on geometric considerations. In any monoclinic crystal (with any lattice parameters) the two symmetrical boundaries along the (001) and (100) planes must have highly ordered atomic structure. The misorientation of the first boundary is descried as a rotation of either 180{degree} around the [100] direction or 180{degree} around the normal to the (001) plane. The misorientation of the second boundary is 180{degree} [001] or 180{degree} around the normal to the (100) plane. It can be shown that three-dimensional CSLs will exist in both cases if (c/a)cos{beta} is a rational number. This example justifies the following approximation of the unit cell in the monoclinic zirconia: a = b = c and cos{beta} = {minus}1/6 (i.e., {beta} = 99.594{degree}). Consider the following prismatic cell in the monoclinic crystal structure: ([1 0 1], [{bar 1} 0 1], [0 1 0]). With the above approximation, this cell is orthogonal with the ratios of the squares of the edge lengths expressed as 5:7:3. Therefore, one can apply the algorithm for calculations of the CSL misorientations in orthorhombic lattices with rational ratios of squares of the lattice periods, which is based on the general vector-quaternion method of misorientation representation.

  8. Measurement of the coincidence response of very thin BGO crystals

    SciTech Connect

    Murthy, K.; Thompson, C.J. . Montreal Neurological Inst.); Weinberg, I.N. Johns Hopkins Univ., Baltimore, MD . Dept. of Radiology); Mako, F.M. )

    1994-08-01

    More then half the 511 keV photons in BGO crystals undergo Compton scattering at least once prior to photo-electric interaction within the detector. In a PET scanner, this can result in mis-positioning of annihilation events. As crystal dimensions are made smaller, the fraction of mispositioned events increases. The authors have studied the coincidence aperture function (CAF) of 25 mm [times] 10 mm BGO crystals with thicknesses varying from 1 mm to 3 mm in steps of 0.5 mm. By sandwiching the active crystal between two other BGO crystals not in contact with the photomultiplier, the authors have studied the effect of Compton scatter upon CAF. By allowing the annihilation photons to be incident along the 25 mm axis and the 10 mm axis, the authors have studied the effect of detector depth upon the CAF, with and without Compton Scatter. The CAF increases linearly with crystal width, ranging from 1.3 mm for the 1 mm wide crystal to 2.15 for 3 mm crystal. The lines joining the FWHM of the CAFs as a function of crystal width appear to converge indicating that no further improvement in resolution can be achieved by reducing crystal width. The CAFs for 10 mm and 25 mm long crystals without Compton scatter is essentially the same. The presence of neighboring crystals results in an increase in the CAF which is greater for long crystals compared with short ones of the same width. Using 1 mm wide and 10 mm long crystals sandwiched between two uncoupled BGO crystals, the authors have achieved spatial resolution of 1.64 mm FWHM for a PMT separation of 34 cm. Recent experiments with PMT separation of 11.5 cm have yielded 1.23 mm FWHM CAF in the same setup.

  9. The optimum choice of gate width for neutron coincidence counting

    NASA Astrophysics Data System (ADS)

    Croft, S.; Henzlova, D.; Favalli, A.; Hauck, D. K.; Santi, P. A.

    2014-11-01

    In the measurement field of international nuclear safeguards, passive neutron coincidence counting is used to quantify the spontaneous fission rate of certain special nuclear materials. The shift register autocorrelation analysis method is the most commonly used approach. However, the Feynman-Y technique, which is more commonly applied in reactor noise analysis, provides an alternative means to extract the correlation information from a pulse train. In this work we consider how to select the optimum gate width for each of these two time-correlation analysis techniques. The optimum is considered to be that which gives the lowest fractional precision on the net doublets rate. Our theoretical approach is approximate but is instructional in terms of revealing the key functional dependence. We show that in both cases the same performance figure of merit applies so that common design criteria apply to the neutron detector head. Our prediction is that near optimal results, suitable for most practical applications, can be obtained from both techniques using a common gate width setting. The estimated precision is also comparable in the two cases. The theoretical expressions are tested experimentally using 252Cf spontaneous fission sources measured in two thermal well counters representative of the type in common use by international inspectorates. Fast accidental sampling was the favored method of acquiring the Feynman-Y data. Our experimental study confirmed the basic functional dependences predicted although experimental results when available are preferred. With an appropriate gate setting Feynman-Y analysis provides an alternative to shift register analysis for safeguards applications which is opening up new avenues of data collection and data reduction to explore.

  10. Digital coincidence counting (DCC) and its use in the corrections for out-of-channel gamma events in 4pi beta-gamma coincidence counting.

    PubMed

    Keightle, J D; Watt, G C

    2002-01-01

    The digital coincidence counting system developed by NPL and ANSTO is briefly described along with its benefits in the data collection and processing for the 4pi beta-gamma coincidence counting technique of radionuclide standardization. One of these benefits is the automatic detection of and correction for out-of-channel coincidences in the Computer Discrimination method. Where the criteria for the use of the Cox-Isham/Smith correction formulae for dead times and resolving times are not met, a generalized approximation based on the work of Campion is suggested.

  11. Elemental PGNAA analysis using gamma-gamma coincidence counting with the library least-squares approach

    NASA Astrophysics Data System (ADS)

    Metwally, Walid A.; Gardner, Robin P.; Mayo, Charles W.

    2004-01-01

    An accurate method for determining elemental analysis using gamma-gamma coincidence counting is presented. To demonstrate the feasibility of this method for PGNAA, a system of three radioisotopes (Na-24, Co-60 and Cs-134) that emit coincident gamma rays was used. Two HPGe detectors were connected to a system that allowed both singles and coincidences to be collected simultaneously. A known mixture of the three radioisotopes was used and data was deliberately collected at relatively high counting rates to determine the effect of pulse pile-up distortion. The results obtained, with the library least-squares analysis, of both the normal and coincidence counting are presented and compared to the known amounts. The coincidence results are shown to give much better accuracy. It appears that in addition to the expected advantage of reduced background, the coincidence approach is considerably more resistant to pulse pile-up distortion.

  12. Characterization of Alpha Contamination in Lanthanum Trichloride Scintillators Using Coincidence Measurements

    SciTech Connect

    Milbrath, Brian D.; Runkle, Robert C.; Hossbach, Todd W.; Kaye, William R.; Lepel, Elwood A.; McDonald, Benjamin S.; Smith, Leon E.

    2005-08-01

    The commercial availability of LaCl3:Ce scintillators has been much anticipated due to their significantly lower resolution relative to NaI(Tl). Our investigation of these scintillators in regards to the effect of their improved resolution for coincidence gamma-ray measurement applications revealed that the scintillators had a large, internal alpha contamination affecting the gamma-ray energy range from 1700-3000 keV. One passive method of identifying contaminants relies on exploiting coincident signatures. Aided by a coincidence lookup library developed at PNNL, we determined that the parent contaminant is Ac-227 via an alpha-gamma coincidence measurement. In this paper, we characterize the level of contamination and describe our coincidence measurement technique. The Ac-227 concentration was approximately 0.13 ppt. We demonstrate that this coincidence technique measures minimum detectable activities much lower than singles gamma-ray spectroscopy. We also discuss gamma- and beta-contamination in these scintillators.

  13. Coincident observations of ionospheric troughs and the equatorial plasmapause

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Maynard, N. C.; Tulunay, Y. K.; Lanzerotti, L. J.

    1976-01-01

    Electron-density observations made in the topside ionosphere by the Ariel 4 and Isis 2 satellites are examined in conjunction with results obtained by Explorer 45 when it traversed the near-equatorial plasmapause with one hour (both UT and MLT) of the Ariel and Isis traversals of the same L coordinate. Both dusk and night observations are analyzed, and an attempt is made to show that depressions in ionospheric electron density occur in the vicinity of the plasmapause field line. It is concluded that the electron distributions observed in the electron-density troughs at 550 km near dusk by Ariel and at 1400 km near midnight by Isis do not always parallel variations in the light-ion distribution inferred from the Explorer plasmapause traversals and that there appears to be no specific feature of the main ionospheric trough which can be used to identify the plasmapause field line except in a statistical sense.

  14. Description and performance characteristics for the neutron Coincidence Collar for the verification of reactor fuel assemblies

    SciTech Connect

    Menlove, H.O.

    1981-08-01

    An active neutron interrogation method has been developed for the measurement of /sup 235/U content in fresh fuel assemblies. The neutron Coincidence Collar uses neutron interrogation with an AmLi neutron source and coincidence counting the induced fission reaction neutrons from the /sup 235/U. This manual describes the system components, operation, and performance characteristics. Applications of the Coincidence Collar to PWR and BWR types of reactor fuel assemblies are described.

  15. Automated QA/QC Check for Beta-Gamma Coincidence Detector

    DTIC Science & Technology

    2007-09-01

    a Β/Γ Coincidence Spectrometer for Automated Radioxenon Analysis. Nuclear Instruments and Methods in Physics Research . Section A , Accelerators , Spectrometers , Detectors and Associated Equipment 521

  16. Coincidence-anticipation timing and reaction time in youth tennis and table tennis players.

    PubMed

    Ak, Emre; Koçak, Settar

    2010-06-01

    The purpose of this study was to compare the coincidence-anticipation timing and reaction times (RT) of 10- to 14-year-old tennis and table tennis players and examine possible sex differences. 107 (51.4%) tennis and 101 (48.6%) table tennis players participated in this study. Players were compared on coincidence-anticipation timing and reaction time. Tennis players performed with less error in the coincidence-anticipation timing task than table tennis players, whereas table tennis players had lower mean reaction time than tennis players. It was also found that male players made fewer errors in the coincidence-anticipation timing task than their female counterparts.

  17. Monte Carlo investigation and optimization of coincidence prompt gamma-ray neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Wang, Jiaxin; Calderon, Adan; Peeples, Cody R.; Ai, Xianyun; Gardner, Robin P.

    2011-10-01

    Normal Prompt Gamma-Ray Neutron Activation Analysis (PGNAA) suffers from a large inherent noise or background. The coincidence PGNAA approach is being investigated for eliminating almost all of the interfering backgrounds and thereby significantly improving the signal-to-noise ratio (SNR). This can be done since almost all of the prompt gamma rays from elements of interest are emitted in coincidence except hydrogen. However, it has been found previously that while the use of two normal NaI detectors greatly reduces the background, the signal is also greatly reduced so that very little improvement in standard deviation is obtained. With the help of MCNP5, the general-purpose Monte Carlo N-Particle code, and CEARCPG, the specific purpose Monte Carlo code for Coincidence PGNAA, further optimization of the proposed coincidence system is being accomplished. The idea pursued here is the use of a large area plastic scintillation detector as the trigger for coincidence events together with a normal large NaI detector. In this approach the detection solid angle is increased greatly, which directly increases the probability of coincidence detection. The 2D-coincidence spectrum obtained can then be projected to the axis representing the NaI detector to overcome the drawback of low energy resolution and photopeak intensity of the plastic scintillation detector and utilize the overall higher coincidence counting rate. To reach the best coincidence detection, the placement of detectors, sample, and the moderator of the neutron source have been optimized through Monte Carlo simulation.

  18. Ion source

    DOEpatents

    Leung, Ka-Ngo; Ehlers, Kenneth W.

    1984-01-01

    A magnetic filter for an ion source reduces the production of undesired ion species and improves the ion beam quality. High-energy ionizing electrons are confined by the magnetic filter to an ion source region, where the high-energy electrons ionize gas molecules. One embodiment of the magnetic filter uses permanent magnets oriented to establish a magnetic field transverse to the direction of travel of ions from the ion source region to the ion extraction region. In another embodiment, low energy 16 eV electrons are injected into the ion source to dissociate gas molecules and undesired ion species into desired ion species.

  19. Ion-Ion Neutralization.

    DTIC Science & Technology

    1980-12-31

    ion flow tube (SIFT) experiments have been given in previous publications and so only the essential features and tho.;e detail:. specific to the present...rapidly, essentially at the gas kinetic limiting rate within the accuracy of the experimental data (1 30% on the measured rate coefficients). The...the various negative ions remained essentially invariant along the length of the plasma column. The data in Table C show that ". for all of the

  20. Coincident particle observations from AE-C and ATS 6 during the October 28, 1977, geomagnetic storm

    SciTech Connect

    Zanetti, L.J.; Potemra, T.A.; Doering, J.P.; Lee, J.S.; Arnoldy, R.L.; Hoffman, R.A.

    1980-09-01

    Ion and electron energy spectra (<30 keV) were recorded simultaneously by the AE-C (at approx.400-km altitude) and ATS 6 (at 6.63 R/sub E/) spacecraft during the intense geomagnetic strom of October 28, 1977 (Kp..-->..7+). Observations were acquired in the evening sector, when the two spacecraft were nearly on the same L shell. The orbit of AE-C provides wide longitudinal coverage of the auroral oval, whereas ATS 6 remains relatively stationary near the equatorial plane. An unusual particle injection event that was characterized by a series of periodic (approx.12 min) bursts of electrons was observed by ATS 6. During this time a variety of phenomena could be identified in the AE-C particle data, including a widespread low-energy ''inverted V'' that extended over 1-1/2 hours of locaL time. Distinct from this region are precipitating electrons which have monoenergetic peaks of variable intensity. These electron spectra are similar to those normally observed coincident with discrete arc aurora. The coincident electron energy spectra acquired by AE-C and ATS 6 match well above 5 keV. The spectra of electrons peak near 1 keV at ionospheric altitudes (typical of this event), whereas no peaks in energy appear at syncthronous altitude.

  1. It takes two—coincidence coding within the dual olfactory pathway of the honeybee

    PubMed Central

    Brill, Martin F.; Meyer, Anneke; Rössler, Wolfgang

    2015-01-01

    To rapidly process biologically relevant stimuli, sensory systems have developed a broad variety of coding mechanisms like parallel processing and coincidence detection. Parallel processing (e.g., in the visual system), increases both computational capacity and processing speed by simultaneously coding different aspects of the same stimulus. Coincidence detection is an efficient way to integrate information from different sources. Coincidence has been shown to promote associative learning and memory or stimulus feature detection (e.g., in auditory delay lines). Within the dual olfactory pathway of the honeybee both of these mechanisms might be implemented by uniglomerular projection neurons (PNs) that transfer information from the primary olfactory centers, the antennal lobe (AL), to a multimodal integration center, the mushroom body (MB). PNs from anatomically distinct tracts respond to the same stimulus space, but have different physiological properties, characteristics that are prerequisites for parallel processing of different stimulus aspects. However, the PN pathways also display mirror-imaged like anatomical trajectories that resemble neuronal coincidence detectors as known from auditory delay lines. To investigate temporal processing of olfactory information, we recorded PN odor responses simultaneously from both tracts and measured coincident activity of PNs within and between tracts. Our results show that coincidence levels are different within each of the two tracts. Coincidence also occurs between tracts, but to a minor extent compared to coincidence within tracts. Taken together our findings support the relevance of spike timing in coding of olfactory information (temporal code). PMID:26283968

  2. Manganese-56 coincidence-counting facility precisely measures neutron-source strength

    NASA Technical Reports Server (NTRS)

    De Volpi, A.; Larsen, R. N.; Porges, K. G. A.

    1969-01-01

    Precise measurement of neutron-source strength is provided by a manganese 56 coincidence-counting facility using the manganese-bath technique. This facility combines nuclear instrumentation with coincidence-counting techniques to handle a wide variety of radioisotope-counting requirements.

  3. The search for coincidences of rare events using LVD and BUST detectors

    NASA Astrophysics Data System (ADS)

    Agafonova, N. Yu.; Ashikhmin, V. V.; Boliev, M. M.; Volchenko, V. V.; Dadykin, V. L.; Dzaparova, I. M.; Dobrynina, E. A.; Enikeev, R. I.; Kochkarov, M. M.; Novoseltsev, Yu. F.; Novoseltseva, R. V.; Mal'gin, A. S.; Petkov, V. B.; Ryazhskaya, O. G.; Shakiryanova, I. R.; Yakushev, V. F.; Yanin, A. F.; LVD Collaboration

    2016-06-01

    The results of the time coincidences of rare events in the LVD and BUST detectors are presented. The rare events could be caused by neutrino interaction in the experimental setup. The distributions of the coincidence number per day for 4-year period are obtained.

  4. Standardisation of 124SB and 152EU using software coincidence counting system.

    PubMed

    Havelka, Miroslav; Sochorová, Jana

    2010-01-01

    Activities of the radionuclides (124)Sb and (152)Eu were determined by the efficiency extrapolation method applied to 4pi(PC)-gamma coincidence counting. The (124)Sb sources were prepared from a solution with the chemical form of 50 microg g(-1) SbCl(3) in 2 M HCl. To inhibit the volatility of antimony chlorides, the sources were slowly dried in a H(2)S atmosphere with relative humidity of 76% for about 48 h. This procedure increased the beta detection efficiency up to 0.98, which simplified the standardisation. In the (152)Eu standardisation, the optimal gamma-ray energy window setting to achieve a linear dependency and the correct slope of the extrapolation curve were derived by means of software coincidence counting system using offline evaluation of data with different coincidence parameter settings. The results obtained by the software coincidence counting system were compared with those obtained by the conventional coincidence method.

  5. Ionic dissociation dynamics and energetics of hexamethyldigermanium, (CH3)6Ge2, by threshold photoelectron-photoion coincidence spectroscopy

    NASA Astrophysics Data System (ADS)

    Dávalos, Juan Z.; Baer, Tomas; Blancas, Carlos

    2017-09-01

    Threshold Photoelectron-Photoion Coincidence Spectroscopy (TPEPICO) has been used to study the ionic dissociation dynamics and energetics of Me6Ge2 (Me = CH3). Ions are energy-selected and the 0 K dissociation onsets for methyl and Me3Ge loss are obtained from the breakdown diagram and mass spectra distributions, both of them analyzed and modeled with statistical SSACM theory and quantum chemical (DFT, MP2) calculations. An updated value for the enthalpy of formation, ΔfHm0 (g) of Me6Ge2, is used to derive Δf Hm0 (Me3Ge,g) = 70.8 ± 8.9 kJ·mol-1. The bond dissociation enthalpies, BDE (Gesbnd X), of Me3Gesbnd X (X = Me, GeMe3, Cl and Br) were also derived in this study.

  6. Position-sensitive coincidence detection of nuclear reaction products at the Prague Van-de-Graaff accelerator

    NASA Astrophysics Data System (ADS)

    Granja, Carlos; Kraus, Vaclav; Pugatch, Valery; Kohout, Zdenek

    2017-06-01

    In low-energy nuclear reactions of astrophysical interest or fusion studies the spatial- and time-correlated detection of two and more reaction products can be a valuable tool in studies of reaction mechanisms, resolving reaction channels and measuring angular distributions of reaction products. For this purpose we constructed a configurable array of position-sensitive detectors based on the hybrid semiconductor pixel detector Timepix. Additional analog-signal electronics provide self-trigger together with extended multi-device control and synchronized readout electronics by a customized control and coincidence unit. The instrumentation, developed and used for detection of fission fragments in spontaneous and neutron induced fission as well as in charged particle detection in neutron induced reactions, is being implemented for low-energy light-ion induced nuclear reactions. Application and demonstration of the technique with two Timepix detectors on p+p elastic scattering at the Van-de-Graaff (VdG) accelerator in Prague is given.

  7. Development and Testing of the Positron Identification By Coincident Annihilation Photons (PICAP) System

    NASA Astrophysics Data System (ADS)

    Tran, D.; Connell, J. J.; Lopate, C.; Bickford, B.

    2014-12-01

    Moderate energy positrons (~few to 10 MeV) have seldom been observed in the Heliosphere, due primarily to there not having been dedicated instruments for such measurements. Their detection would have implications in the study of Solar energetic particle events and the transport and modulation of the Solar wind and Galactic cosmic rays. The Positron Identification by Coincident Annihilation Photons (PICAP) system is designed specifically to measure these moderate energy positrons by simultaneously detecting the two 511-keV γ-ray photons that result from a positron stopping in the instrument and the subsequent electron-positron annihilation. This method is also expected to effectively discriminate positrons from protons by measuring the amount of energy deposited in the detectors (dE/dx versus residual energy). PICAP offers a low-mass, low-power option for measuring positrons, electrons, and ions in space. Following Monte Carlo modeling, a PICAP laboratory prototype, adaptable to a space-flight design, was designed, built, and tested. This instrument is comprised of (Si) solid-state detectors, plastic scintillation detectors, and high-Z BGO crystal scintillator suitable for detecting the 511-keV γ rays. The prototype underwent preliminary laboratory testing and calibration using radioactive sources for the purpose of establishing functionality. It has since been exposed to beams of energetic protons (up to ~200 MeV) at Massachusetts General Hospital's Francis H. Burr Proton Beam Therapy Center and positrons and electrons (up to ~10 MeV) at Idaho State University's Idaho Accelerator Center. The goal is to validate modeling and determine the performance of the instrument concept. We will present a summary of modeling calculations and analysis of data taken at the accelerator tests. This work is 95% supported by NASA Grant NNX10AC10G.

  8. Triple coincidence experiment to explore the two-electron continuum states of the projectile resulting from mutual ionization in 100-keV He0 + He collisions.

    PubMed

    Sarkadi, László; Orbán, Andrea

    2008-04-04

    The existence of the two-electron cusp in atomic collisions, i.e., the enhanced emission of two electrons in the forward direction with velocities equal to that of the projectile, has been investigated experimentally. Using a time-of-flight technique, the energies of the two electrons resulting from the simultaneous target and projectile ionization in 100-keV He(0)+He collisions have been measured by detecting triple coincidence between the electrons and the outgoing He(+) ion. The coincidence yield clearly shows a peak as a function of the electron energies at the expected cusp position. Furthermore, a strong correlation was found between the energies of the two electrons, which is traced back to an angular correlation of 180 degrees in the projectile-centered reference system.

  9. Tight bounds for the Pearle-Braunstein-Caves chained inequality without the fair-coincidence assumption

    NASA Astrophysics Data System (ADS)

    Jogenfors, Jonathan; Larsson, Jan-Åke

    2017-08-01

    In any Bell test, loopholes can cause issues in the interpretation of the results, since an apparent violation of the inequality may not correspond to a violation of local realism. An important example is the coincidence-time loophole that arises when detector settings might influence the time when detection will occur. This effect can be observed in many experiments where measurement outcomes are to be compared between remote stations because the interpretation of an ostensible Bell violation strongly depends on the method used to decide coincidence. The coincidence-time loophole has previously been studied for the Clauser-Horne-Shimony-Holt and Clauser-Horne inequalities, but recent experiments have shown the need for a generalization. Here, we study the generalized "chained" inequality by Pearle, Braunstein, and Caves (PBC) with N ≥2 settings per observer. This inequality has applications in, for instance, quantum key distribution where it has been used to reestablish security. In this paper we give the minimum coincidence probability for the PBC inequality for all N ≥2 and show that this bound is tight for a violation free of the fair-coincidence assumption. Thus, if an experiment has a coincidence probability exceeding the critical value derived here, the coincidence-time loophole is eliminated.

  10. A Maximum NEC Criterion for Compton Collimation to Accurately Identify True Coincidences in PET

    PubMed Central

    Chinn, Garry; Levin, Craig S.

    2013-01-01

    In this work, we propose a new method to increase the accuracy of identifying true coincidence events for positron emission tomography (PET). This approach requires 3-D detectors with the ability to position each photon interaction in multi-interaction photon events. When multiple interactions occur in the detector, the incident direction of the photon can be estimated using the Compton scatter kinematics (Compton Collimation). If the difference between the estimated incident direction of the photon relative to a second, coincident photon lies within a certain angular range around colinearity, the line of response between the two photons is identified as a true coincidence and used for image reconstruction. We present an algorithm for choosing the incident photon direction window threshold that maximizes the noise equivalent counts of the PET system. For simulated data, the direction window removed 56%–67% of random coincidences while retaining > 94% of true coincidences from image reconstruction as well as accurately extracted 70% of true coincidences from multiple coincidences. PMID:21317079

  11. A multievent study of the coincidence of heliospheric current sheet and stream interface

    NASA Astrophysics Data System (ADS)

    Huang, Jia; Liu, Yong C.-M.; Qi, Zhaohui; Klecker, Berndt; Marghitu, Octav; Galvin, Antoinette B.; Farrugia, Charles J.; Li, Xiaoyu

    2016-11-01

    Generally, the heliospheric current sheet (HCS) is separated from the stream interface (SI) at about 1 AU. A recent study found an event where the HCS coincides with the SI, and in which the HCS is separated from the true sector boundary (TSB), defined by the switch of suprathermal electron pitch angle distributions. We present a multievent study by using STEREO, ACE, and Wind data during 2007 to 2010 to investigate whether other classes of such coincidence cases exist, as well as their stability. We find coincidence cases related to ideal HCSs, separated TSB and HCS, or heat flux dropouts in the vicinity; therefore, we define them as types I, II, and III. Among the nine coincidence cases, there are seven type I, one type II, and one type III. For each type, a possible schematic origin is presented. We also compared the observations on different spacecraft. Only two out of nine cases are observed by several spacecraft with a large separation, indicating that the coincidence structures are usually unstable. The study also shows that the coincidence cases have a variable connection with pseudostreamers. Interchange reconnection and pseudostreamers could play a role in forming these coincidence cases and lead to different configurations in different situations.

  12. Towards component-based validation of GATE: aspects of the coincidence processor.

    PubMed

    Moraes, Eder R; Poon, Jonathan K; Balakrishnan, Karthikayan; Wang, Wenli; Badawi, Ramsey D

    2015-02-01

    GATE is public domain software widely used for Monte Carlo simulation in emission tomography. Validations of GATE have primarily been performed on a whole-system basis, leaving the possibility that errors in one sub-system may be offset by errors in others. We assess the accuracy of the GATE PET coincidence generation sub-system in isolation, focusing on the options most closely modeling the majority of commercially available scanners. Independent coincidence generators were coded by teams at Toshiba Medical Research Unit (TMRU) and UC Davis. A model similar to the Siemens mCT scanner was created in GATE. Annihilation photons interacting with the detectors were recorded. Coincidences were generated using GATE, TMRU and UC Davis code and results compared to "ground truth" obtained from the history of the photon interactions. GATE was tested twice, once with every qualified single event opening a time window and initiating a coincidence check (the "multiple window method"), and once where a time window is opened and a coincidence check initiated only by the first single event to occur after the end of the prior time window (the "single window method"). True, scattered and random coincidences were compared. Noise equivalent count rates were also computed and compared. The TMRU and UC Davis coincidence generators agree well with ground truth. With GATE, reasonable accuracy can be obtained if the single window method option is chosen and random coincidences are estimated without use of the delayed coincidence option. However in this GATE version, other parameter combinations can result in significant errors. Copyright © 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  13. Application of length vernier in phase coincidence detection and precision frequency measurement.

    PubMed

    Miao, Miao; Wei, Zhou; Bin, Wang

    2012-02-01

    For comparison of arbitrary frequency signals, the paper proposed two levels of length vernier based on the time-space relationship are used in three levels of phase coincidence detecting circuits to extract the phase coincidence information by proper logic calculation. The length∕phase of each vernier is respectively corresponding to the accuracy and the resolution of detecting circuit. The time-space relationship is based on high-stability, high-accuracy, and high-speed of signal transmission. The method is effective to reduce the fuzzy region in the phase coincidence information and reach a higher measuring precision.

  14. Testing the cosmic coincidence problem and the nature of dark energy.

    PubMed

    Dalal, N; Abazajian, K; Jenkins, E; Manohar, A V

    2001-10-01

    Dark energy models which alter the relative scaling behavior of dark energy and matter could provide a natural solution to the cosmic coincidence problem-why the densities of dark energy and dark matter are comparable today. A generalized class of dark energy models is introduced which allows noncanonical scaling of the ratio of dark matter and dark energy with the Robertson-Walker scale factor a(t). We show that determining whether there is a coincidence problem, and the extent of cosmic coincidence, can be addressed by several forthcoming experiments.

  15. The IAEA neutron coincidence counting (INCC) and the DEMING least-squares fitting programs

    SciTech Connect

    Krick, M.S.; Harker, W.C.; Rinard, P.M.; Wenz, T.R.; Lewis, W.; Pham, P.; Ridder, P. de

    1998-12-01

    Two computer programs are described: (1) the INCC (IAEA or International Neutron Coincidence Counting) program and (2) the DEMING curve-fitting program. The INCC program is an IAEA version of the Los Alamos NCC (Neutron Coincidence Counting) code. The DEMING program is an upgrade of earlier Windows{reg_sign} and DOS codes with the same name. The versions described are INCC 3.00 and DEMING 1.11. The INCC and DEMING codes provide inspectors with the software support needed to perform calibration and verification measurements with all of the neutron coincidence counting systems used in IAEA inspections for the nondestructive assay of plutonium and uranium.

  16. Comparison of satellite reflectance algorithms for estimating chlorophyll-a in a temperate reservoir using coincident hyperspectral aircraft imagery and dense coincident surface observations

    EPA Science Inventory

    We analyzed 10 established and 4 new satellite reflectance algorithms for estimating chlorophyll-a (Chl-a) in a temperate reservoir in southwest Ohio using coincident hyperspectral aircraft imagery and dense water truth collected within one hour of image acquisition to develop si...

  17. Comparison of satellite reflectance algorithms for estimating chlorophyll-a in a temperate reservoir using coincident hyperspectral aircraft imagery and dense coincident surface observations

    EPA Science Inventory

    We analyzed 10 established and 4 new satellite reflectance algorithms for estimating chlorophyll-a (Chl-a) in a temperate reservoir in southwest Ohio using coincident hyperspectral aircraft imagery and dense water truth collected within one hour of image acquisition to develop si...

  18. A photoelectron-photoion coincidence imaging apparatus for femtosecond time-resolved molecular dynamics with electron time-of-flight resolution of {sigma}=18 ps and energy resolution {delta}E/E=3.5%

    SciTech Connect

    Vredenborg, Arno; Roeterdink, Wim G.; Janssen, Maurice H. M.

    2008-06-15

    We report on the construction and performance of a novel photoelectron-photoion coincidence machine in our laboratory in Amsterdam to measure the full three-dimensional momentum distribution of correlated electrons and ions in femtosecond time-resolved molecular beam experiments. We implemented sets of open electron and ion lenses to time stretch and velocity map the charged particles. Time switched voltages are operated on the particle lenses to enable optimal electric field strengths for velocity map focusing conditions of electrons and ions separately. The position and time sensitive detectors employ microchannel plates (MCPs) in front of delay line detectors. A special effort was made to obtain the time-of-flight (TOF) of the electrons at high temporal resolution using small pore (5 {mu}m) MCPs and implementing fast timing electronics. We measured the TOF distribution of the electrons under our typical coincidence field strengths with a temporal resolution down to {sigma}=18 ps. We observed that our electron coincidence detector has a timing resolution better than {sigma}=16 ps, which is mainly determined by the residual transit time spread of the MCPs. The typical electron energy resolution appears to be nearly laser bandwidth limited with a relative resolution of {delta}E{sub FWHM}/E=3.5% for electrons with kinetic energy near 2 eV. The mass resolution of the ion detector for ions measured in coincidence with electrons is about {delta}m{sub FWHM}/m=1/4150. The velocity map focusing of our extended source volume of particles, due to the overlap of the molecular beam with the laser beams, results in a parent ion spot on our detector focused down to {sigma}=115 {mu}m.

  19. X-ray fluorescence/Auger-electron coincidence spectroscopy of vacancy cascades in atomic argon

    SciTech Connect

    Arp, U.; LeBrun, T.; Southworth, S.H.; Jung, M.; MacDonald, M.A.

    1996-12-01

    Argon L{sub 2.3}-M{sub 2.3}M{sub 2.3} Auger-electron spectra were measured in coincidence with K{alpha} fluorescent x-rays in studies of Ar K-shell vacancy decays at several photon energies above the K-threshold and on the 1s-4p resonance in atomic argon. The complex spectra recorded by conventional electron spectroscopy are greatly simplified when recorded in coincidence with fluorescent x-rays, allowing a more detailed analysis of the vacancy cascade process. The resulting coincidence spectra are compared with Hartree-Fock calculations which include shake-up transitions in the resonant case. Small energy shifts of the coincidence electron spectra are attributed to post-collision interaction with 1s photoelectrons.

  20. Required conditions for and coincident 1/1-mode activity associated with the nonlocal electron heat transport effect on TFTR

    SciTech Connect

    Kissick, M.W.; Callen, J.D.; Fredrickson, E.D.

    1997-08-01

    A database of 71 distinct and randomly collected cold pulse cases from TFTR is analyzed. Observations show a striking parameter regime cutoff for the presence of nonlocal transient transport and coincident MHD (1/1-mode) activity as well as for changes in the radial speed of the nonlocal transport effect and changes in the sawtooth period. A nontrivial link is demonstrated between electron heat transport and MHD properties through observation of a common cutoff in the parameter n{sub e}(0)/T{sub e}(0){sup 1/2} and a common threshold in injection size for radial speed and sawtooth period changes. Auxiliary heating (via energetic neutral beams) destroys whatever process is responsible for the nonlocal transport effect, unless the discharge contains significant amounts of injected tritium. These observations are preliminary, but they represent important circumstantial evidence for mysterious propagation of changes in some MHD-related phenomenon as being responsible for a large fraction of electron heat transport. This propagation is then probably a function of n{sub e}(0)/T{sub e}(0){sup 1/2}, ion mass, and possibly beam power. An analysis of Ohmic cases shows that the cutoff in n{sub e}(0)/T{sub e}{sup 1/2} indicates the nonlocal transport effects may occur when the electrons are collisionally thermally decoupled from the ions.

  1. Shift Register Clock Rate Effects on Coincidence Collection 50MHz versus 4MHz Comparison Tests

    SciTech Connect

    Newell, Matthew R.; Bourret, Steven C.; Swinhoe, Martyn Thomas

    2015-11-03

    The following report identifies and quantifies the timing differences between the older slower Shift Register Coincidence/Multiplicity modules and today’s modern higher speed devices. Modern high speed Shift Register Coincidence/Multiplicity instruments employ high speed internal clocks that run at frequencies more than ten times the older units, typically 50MHz. These higher speed clocks allow for a finer time resolution when recording input pulses.

  2. Multiple tests based on a gaussian approximation of the unitary events method with delayed coincidence count.

    PubMed

    Tuleau-Malot, Christine; Rouis, Amel; Grammont, Franck; Reynaud-Bouret, Patricia

    2014-07-01

    The unitary events (UE) method is one of the most popular and efficient methods used over the past decade to detect patterns of coincident joint spike activity among simultaneously recorded neurons. The detection of coincidences is usually based on binned coincidence count (Grün, 1996 ), which is known to be subject to loss in synchrony detection (Grün, Diesmann, Grammont, Riehle, & Aertsen, 1999 ). This defect has been corrected by the multiple shift coincidence count (Grün et al., 1999 ). The statistical properties of this count have not been further investigated until this work, the formula being more difficult to deal with than the original binned count. First, we propose a new notion of coincidence count, the delayed coincidence count, which is equal to the multiple shift coincidence count when discretized point processes are involved as models for the spike trains. Moreover, it generalizes this notion to nondiscretized point processes, allowing us to propose a new gaussian approximation of the count. Since unknown parameters are involved in the approximation, we perform a plug-in step, where unknown parameters are replaced by estimated ones, leading to a modification of the approximating distribution. Finally the method takes the multiplicity of the tests into account via a Benjamini and Hochberg approach (Benjamini & Hochberg, 1995 ), to guarantee a prescribed control of the false discovery rate. We compare our new method, MTGAUE (multiple tests based on a gaussian approximation of the unitary events) and the UE method proposed in Grün et al. ( 1999 ) over various simulations, showing that MTGAUE extends the validity of the previous method. In particular, MTGAUE is able to detect both profusion and lack of coincidences with respect to the independence case and is robust to changes in the underlying model. Furthermore MTGAUE is applied on real data.

  3. Standardisation of 54Mn and 65Zn using a software coincidence counting system.

    PubMed

    Havelka, Miroslav; Auerbach, Pavel; Sochorová, Jana

    2006-01-01

    The activities of 54Mn and 65Zn have been determined by 4pi(PC)-gamma coincidence counting, with efficiency variation performed by the conventional method of altering the self-absorption in the sources as well as by the computer discrimination method. The standardisation of 65Zn presents some complications requiring optimisation of the gamma-ray energy window settings to achieve a linear efficiency-extrapolation curve. Determination of these optimal settings by the conventional coincidence method is a tedious task. These difficulties have been reduced by the utilisation of a software coincidence counting system that records time and amplitude information of individual pulses from coincidence measurements, where the coincidence parameters are set after the data collection process has completed, facilitating multiple data evaluations on a single data set. The optimal gamma-ray energy window settings for the 65Zn standardisation were derived from the results of the 54Mn standardisation, as well as from studies of the 65Zn data itself. The setting of the PC channel thresholds for K and both (K+L) electrons is also discussed. The results are compared with those attained using conventional coincidence counting.

  4. A hybrid approach to the fusion of partially coinciding alarms from asynchronous or specialized detectors

    NASA Astrophysics Data System (ADS)

    Smock, Brandon; Wilson, Joseph; Glenn, Taylor

    2014-06-01

    The accurate detection of a diverse set of targets often requires the use of multiple sensor modalities and algorithms. Fusion approaches can be used to combine information from multiple sensors or detectors. But typical fusion approaches are not suitable when detectors do not operate on all of the same locations of interest, or when detectors are specialized to detect disjoint sets of target types. Run Packing is an algorithm we developed previously to optimally combine detectors when their output never coincides, which can be expected when the detectors are specialized to detect different target types. But when asynchronous detectors sometimes coincide, or specialized detectors sometimes detect the same target, Run Packing ignores this coincidence information and thus may be suboptimal in certain cases. In this paper, we show how multi-detector fusion involving partially­ coinciding alarms can be re-framed as an equivalent fusion problem that is optimally addressed by Run Packing. This amounts to a hierarchical or hybrid approach involving fusion methods to join coinciding alarms at the same location into a single unified alarm and then using Run Packing to optimally fuse the resulting set of non­ coinciding alarms. We report preliminary results of applying the method in a few typical landmine detection scenarios to demonstrate its potential utility.

  5. Observations of energetic ions near the Venus ionopause

    NASA Technical Reports Server (NTRS)

    Kasprzak, W. T.; Taylor, H. A.; Brace, L. H.; Niemann, H. B.; Scarf, F. L.

    1982-01-01

    Ions (primarily O/+/) with spacecraft rest frame energies greater than 40 eV have been observed by the Pioneer Venus Neutral Mass Spectrometer. The signature occurs in about 13% of the 700 orbits examined, primarily near the ionopause and at all solar zenith angles. The energetic ions coincide in location with superthermal ions observed by the Ion Mass Spectrometer and more rarely occur in some of the plasma clouds observed by the Electron Temperature Probe. These observations in conjunction with measurements by the Plasma Wave Instrument near the ionopause suggest that the ions are accelerated out of ionospheric plasma by the shocked solar wind through plasma wave-particle interactions.

  6. Clonal integration of Fragaria orientalis in reciprocal and coincident patchiness resources: cost-benefit analysis.

    PubMed

    Zhang, Yunchun; Zhang, Qiaoying

    2013-01-01

    Clonal growth allows plants to spread horizontally and to experience different levels of resources. If ramets remain physiologically integrated, clonal plants can reciprocally translocate resources between ramets in heterogeneous environments. But little is known about the interaction between benefits of clonal integration and patterns of resource heterogeneity in different patches, i.e., coincident patchiness or reciprocal patchiness. We hypothesized that clonal integration will show different effects on ramets in different patches and more benefit to ramets under reciprocal patchiness than to those under coincident patchiness, as well as that the benefit from clonal integration is affected by the position of proximal and distal ramets under reciprocal or coincident patchiness. A pot experiment was conducted with clonal fragments consisting of two interconnected ramets (proximal and distal ramet) of Fragaria orientalis. In the experiment, proximal and distal ramets were grown in high or low availability of resources, i.e., light and water. Resource limitation was applied either simultaneously to both ramets of a clonal fragment (coincident resource limitation) or separately to different ramets of the same clonal fragment (reciprocal resource limitation). Half of the clonal fragments were connected while the other half were severed. From the experiment, clonal fragments growing under coincident resource limitation accumulated more biomass than those under reciprocal resource limitation. Based on a cost-benefit analysis, the support from proximal ramets to distal ramets was stronger than that from distal ramets to proximal ramets. Through division of labour, clonal fragments of F. orientalis benefited more in reciprocal patchiness than in coincident patchiness. While considering biomass accumulation and ramets production, coincident patchiness were more favourable to clonal plant F. orientalis.

  7. Analysis of calibration data for the uranium active neutron coincidence counting collar with attention to errors in the measured neutron coincidence rate

    NASA Astrophysics Data System (ADS)

    Croft, Stephen; Burr, Tom; Favalli, Andrea; Nicholson, Andrew

    2016-03-01

    The declared linear density of 238U and 235U in fresh low enriched uranium light water reactor fuel assemblies can be verified for nuclear safeguards purposes using a neutron coincidence counter collar in passive and active mode, respectively. The active mode calibration of the Uranium Neutron Collar - Light water reactor fuel (UNCL) instrument is normally performed using a non-linear fitting technique. The fitting technique relates the measured neutron coincidence rate (the predictor) to the linear density of 235U (the response) in order to estimate model parameters of the nonlinear Padé equation, which traditionally is used to model the calibration data. Alternatively, following a simple data transformation, the fitting can also be performed using standard linear fitting methods. This paper compares performance of the nonlinear technique to the linear technique, using a range of possible error variance magnitudes in the measured neutron coincidence rate. We develop the required formalism and then apply the traditional (nonlinear) and alternative approaches (linear) to the same experimental and corresponding simulated representative datasets. We find that, in this context, because of the magnitude of the errors in the predictor, it is preferable not to transform to a linear model, and it is preferable not to adjust for the errors in the predictor when inferring the model parameters.

  8. Digital Pulse Shape Analysis with Phoswich Detectors to Simplify Coincidence Measurements of Radioactive Xenon

    SciTech Connect

    Hennig, Wolfgang; Tan, Hui; Warburton, William K.; McIntyre, Justin I.

    2005-08-31

    The Comprehensive Nuclear-Test-Ban Treaty establishes a network of monitoring stations to detect radioactive Xenon in the atmosphere from nuclear weapons testing. One such monitoring system is the Automated Radio-xenon Sampler/Analyzer (ARSA) developed at Pacific Northwest National Laboratory, which uses a complex arrangement of separate beta and gamma detectors to detect beta-gamma coincidences from the Xe isotopes of interest. The coincidence measurement is very sensitive, but the large number of detectors and photomultiplier tubes require careful calibration which makes the system hard to use. It has been suggested that beta-gamma coincidences could be detected with only a single photomultiplier tube and electronics channel by using a phoswich detector consisting of optically coupled beta and gamma detectors (Ely, 2003). In that work, rise time analysis of signals from a phoswich detector was explored as a method to determine if interactions occurred in either the beta or the gamma detector or in both simultaneously. However, this approach was not able to detect coincidences with the required sensitivity or to measure the beta and gamma energies with sufficient precision for Xenon monitoring. In this paper, we present a new algorithm to detect coincidences by pulse shape analysis of the signals from a BC-404/CsI(Tl) phoswich detector. Implemented on fast digital readout electronics, the algorithm achieves clear separation of beta only, gamma only and coincidence events, accurate measurement of both beta and gamma energies, and has an error rate for detecting coincidences of less than 0.1%. Monte Carlo simulations of radiation transport and light collection were performed to optimize design parameters for a replacement detector module for the ARSA system, obtaining an estimated coincidence detection efficiency of 82-92% and a background rejection rate better than 99%. The new phoswich/pulse shape analysis method is thus suitable to simplify the existing ARSA

  9. Passive neutron coincidence counting with plastic scintillators for the characterization of radioactive waste drums

    SciTech Connect

    Deyglun, C.; Simony, B.; Perot, B.; Carasco, C.; Saurel, N.; Colas, S.; Collot, J.

    2015-07-01

    The quantification of radioactive material is essential in the fields of safeguards, criticality control of nuclear processes, dismantling of nuclear facilities and components, or radioactive waste characterization. The Nuclear Measurement Laboratory (LMN) of CEA is involved in the development of time-correlated neutron detection techniques using plastic scintillators. Usually, 3He proportional counters are used for passive neutron coincidence counting owing to their high thermal neutron capture efficiency and gamma insensitivity. However, the global {sup 3}He shortage in the past few years has made these detectors extremely expensive. In addition, contrary to {sup 3}He counters for which a few tens of microseconds are needed to thermalize fast neutrons, in view to maximize the {sup 3}He(n,p){sup 3}H capture cross section, plastic scintillators are based on elastic scattering and therefore the light signal is formed within a few nanoseconds, correlated pulses being detected within a few dozen- or hundred nanoseconds. This time span reflects fission particles time of flight, which allows reducing accordingly the duration of the coincidence gate and thus the rate of random coincidences, which may totally blind fission coincidences when using {sup 3}He counters in case of a high (α,n) reaction rate. However, plastic scintillators are very sensitive to gamma rays, requiring the use of a thick metallic shield to reduce the corresponding background. Cross talk between detectors is also a major issue, which consists on the detection of one particle by several detectors due to elastic or inelastic scattering, leading to true but undesired coincidences. Data analysis algorithms are tested to minimize cross-talk in simultaneously activated detectors. The distinction between useful fission coincidences and the correlated background due to cross-talk, (α,n) and induced (n,2n) or (n,n'γ) reactions, is achieved by measuring 3-fold coincidences. The performances of a passive

  10. Recovering the triple coincidence of non-pure positron emitters in preclinical PET

    NASA Astrophysics Data System (ADS)

    Lin, Hsin-Hon; Chuang, Keh-Shih; Chen, Szu-Yu; Jan, Meei-Ling

    2016-03-01

    Non-pure positron emitters, with their long half-lives, allow for the tracing of slow biochemical processes which cannot be adequately examined by the commonly used short-lived positron emitters. Most of these isotopes emit high-energy cascade gamma rays in addition to positron decay that can be detected and create a triple coincidence with annihilation photons. Triple coincidence is discarded in most scanners, however, the majority of the triple coincidence contains true photon pairs that can be recovered. In this study, we propose a strategy for recovering triple coincidence events to raise the sensitivity of PET imaging for non-pure positron emitters. To identify the true line of response (LOR) from a triple coincidence, a framework utilizing geometrical, energy and temporal information is proposed. The geometrical criterion is based on the assumption that the LOR with the largest radial offset among the three sub pairs of triple coincidences is least likely to be a true LOR. Then, a confidence time window is used to test the valid LOR among those within triple coincidence. Finally, a likelihood ratio discriminant rule based on the energy probability density distribution of cascade and annihilation gammas is established to identify the true LOR. An Inveon preclinical PET scanner was modeled with GATE (GEANT4 application for tomographic emission) Monte Carlo software. We evaluated the performance of the proposed method in terms of identification fraction, noise equivalent count rates (NECR), and image quality on various phantoms. With the inclusion of triple coincidence events using the proposed method, the NECR was found to increase from 11% to 26% and 19% to 29% for I-124 and Br-76, respectively, when 7.4-185 MBq of activity was used. Compared to the reconstructed images using double coincidence, this technique increased the SNR by 5.1-7.3% for I-124 and 9.3-10.3% for Br-76 within the activity range of 9.25-74 MBq, without compromising the spatial resolution or

  11. The effect of deadtime and electronic transients on the predelay bias in neutron coincidence counting

    DOE PAGES

    Croft, Stephen; Favalli, Andrea; Swinhoe, Martyn T.; ...

    2016-01-13

    In neutron coincidence counting using the shift register autocorrelation technique, a predelay is inserted before the opening of the (R+A)-gate. Operationally the purpose of the predelay is to ensure that the (R+A)- and A-gates have matched effectiveness, otherwise a bias will result when the difference between the gates is used to calculate the accidentals corrected net reals coincidence rate. The necessity for the predelay was established experimentally in the early practical development and deployment of the coincidence counting method. The choice of predelay for a given detection system is usually made experimentally, but even today long standing traditional values (e.g.,more » 4.5 µs) are often used. This, at least in part, reflects the fact that a deep understanding of why a finite predelay setting is needed and how to control the underlying influences has not been fully worked out. We attempt, in this paper, to gain some insight into the problem. One aspect we consider is the slowing down, thermalization, and diffusion of neutrons in the detector moderator. The other is the influence of deadtime and electronic transients. These may be classified as non-ideal detector behaviors because they are not included in the conventional model used to interpret measurement data. From improved understanding of the effect of deadtime and electronic transients on the predelay bias in neutron coincidence counting, the performance of both future and current coincidence counters may be improved.« less

  12. The effect of deadtime and electronic transients on the predelay bias in neutron coincidence counting

    SciTech Connect

    Croft, Stephen; Favalli, Andrea; Swinhoe, Martyn T.; Goddard, Braden; Stewart, Scott

    2016-01-13

    In neutron coincidence counting using the shift register autocorrelation technique, a predelay is inserted before the opening of the (R+A)-gate. Operationally the purpose of the predelay is to ensure that the (R+A)- and A-gates have matched effectiveness, otherwise a bias will result when the difference between the gates is used to calculate the accidentals corrected net reals coincidence rate. The necessity for the predelay was established experimentally in the early practical development and deployment of the coincidence counting method. The choice of predelay for a given detection system is usually made experimentally, but even today long standing traditional values (e.g., 4.5 µs) are often used. This, at least in part, reflects the fact that a deep understanding of why a finite predelay setting is needed and how to control the underlying influences has not been fully worked out. We attempt, in this paper, to gain some insight into the problem. One aspect we consider is the slowing down, thermalization, and diffusion of neutrons in the detector moderator. The other is the influence of deadtime and electronic transients. These may be classified as non-ideal detector behaviors because they are not included in the conventional model used to interpret measurement data. From improved understanding of the effect of deadtime and electronic transients on the predelay bias in neutron coincidence counting, the performance of both future and current coincidence counters may be improved.

  13. Light-particle-complex-fragment coincidence cross sections from intermediate energy nucleus-nucleus collisions

    SciTech Connect

    Hasselquist, B.E.; Crawley, G.M.; Jacak, B.V.; Koenig, Z.M.; Westfall, G.D.; Yurkon, J.E.; Tickle, R.S.; Dufour, J.P.; Symons, T.J.M.

    1985-07-01

    Light-particle (Zcoincidence spectra have been measured for the reactions 30 MeV/nucleon /sup 12/C+Al and /sup 12/C+Au and 92 MeV/nucleon /sup 40/Ar+Au at angles from 45/sup 0/ to 90/sup 0/. Coincidence triggers for the light-particle spectra were intermediate rapidity fragments (3coincidence data. The coincidence spectra are compared with a model based on the moving source model but incorporating momentum conservation to account for kinematical biases. Little difference between inclusive and complex-fragment-triggered coincidence cross sections is observed, indicating that all the fragments have a common source.

  14. Simulations of Lithium-Based Neutron Coincidence Counter for Gd-Loaded Fuel

    SciTech Connect

    Cowles, Christian C.; Kouzes, Richard T.; Siciliano, Edward R.

    2014-10-01

    The Department of Energy Office of Nuclear Safeguards and Security (NA-241) is supporting the project Lithium-Based Alternative Neutron Detection Technology Coincidence Counting for Gd-loaded Fuels at Pacific Northwest National Laboratory for the development of a lithium-based neutron coincidence counter for nondestructively assaying Gd loaded nuclear fuel. This report provides results from MCNP simulations of a lithium-based coincidence counter for the possible measurement of Gd-loaded nuclear fuel. A comparison of lithium-based simulations and UNCL-II simulations with and without Gd loaded fuel is provided. A lithium-based model, referred to as PLNS3A-R1, showed strong promise for assaying Gd loaded fuel.

  15. Two-dimensional diagonal summing of coincidence spectra for bulk PGNAA applications

    NASA Astrophysics Data System (ADS)

    Metwally, W. A.; Gardner, R. P.; Mayo, C. W.

    2004-06-01

    In the past 10 years, new electronic devices have been developed that allow fast coincidence measurements to be performed that are capable of simultaneously recording the individual spectra as well as the coincidence spectra of multiple detectors. Utilizing these devices with computer software allows multiparameter data acquisition which adds much more flexibility in data analysis. One of the capabilities that is enabled is that of obtaining two-dimensional spectra. In this work, the use of this equipment and the two-dimensional spectra obtained with it are used to allow two-dimensional diagonal summing. The main advantages of this approach are improved peak resolution and very low background (Compton continuum). Possible uses of the two-dimensional diagonal summing are identifying coincidence schemes, performing elemental analysis, and identifying trace elements in bulk samples. The spectra obtained are very promising for these applications.

  16. The Monte Carlo code CEARCPG for coincidence prompt gamma-ray neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Han, Xiaogang; Gardner, Robin P.

    2007-10-01

    Prompt gamma-ray neutron activation analysis (PGNAA) is widely used to determine the elemental composition of bulk samples. The detection sensitivities of PGNAA are often restricted by the inherent poor signal-to-noise ratio (SNR). There are many sources of noise (background) including the natural background, neutron activation of the detector, gamma-rays associated with the neutron source and prompt gamma-rays from the structural materials of the analyzer. Results of the prompt gamma-ray coincidence technique show that it could greatly improve the SNR by removing almost all of the background interferences. The first specific Monte Carlo code (CEARCPG) for coincidence PGNAA has been developed at the Center for Engineering Application of Radioisotopes (CEAR) to explore the capabilities of this technique. Benchmark bulk sample experiments have been performed with coal, sulfur, and mercury samples and indicate that the code is accurate and will be very useful in the design of coincidence PGNAA devices.

  17. Moisture corrections in neutron coincidence counting of PuO/sub 2/

    SciTech Connect

    Stewart, J.E.; Menlove, H.O.

    1987-01-01

    Passive neutron coincidence counting is capable of 1% assay accuracy for pure, well-characterized PuO/sub 2/ samples that contain plutonium masses from a few tens of grams to several kilograms. Moisture in the sample can significantly bias the assay high by changing the (..cap alpha..,n) neutron production, the sample multiplication, and the detection efficiency. Monte Carlo calculations and an analytical model of coincidence counting have been used to quantify the individual and cumulative effects of moisture biases for two PuO/sub 2/ sample sizes and a range of moisture levels from 0 to 9 wt %. Results of the calculations suggest a simple correction procedure for moisture bias that is effective from 0 to 3 wt % H/sub 2/O. The procedure requires that the moisture level in the sample be known before the coincidence measurement.

  18. Standardization of 241Am by digital coincidence counting, liquid scintillation counting and defined solid angle counting.

    PubMed

    Balpardo, C; Capoulat, M E; Rodrigues, D; Arenillas, P

    2010-01-01

    The nuclide (241)Am decays by alpha emission to (237)Np. Most of the decays (84.6%) populate the excited level of (237)Np with energy of 59.54 keV. Digital coincidence counting was applied to standardize a solution of (241)Am by alpha-gamma coincidence counting with efficiency extrapolation. Electronic discrimination was implemented with a pressurized proportional counter and the results were compared with two other independent techniques: Liquid scintillation counting using the logical sum of double coincidences in a TDCR array and defined solid angle counting taking into account activity inhomogeneity in the active deposit. The results show consistency between the three methods within a limit of a 0.3%. An ampoule of this solution will be sent to the International Reference System (SIR) during 2009. Uncertainties were analysed and compared in detail for the three applied methods.

  19. Coincident orientation of objects and viewpoint-dependence in scene recognition.

    PubMed

    Li, Jing; Zhang, Kan

    2012-02-01

    Viewpoint-dependence is a well-known phenomenon in which participants' spatial memory is better for previously experienced points of view than for novel ones. In the current study, partial-scene-recognition was used to examine the effect of coincident orientation of all the objects on viewpoint-dependence in spatial memory. When objects in scenes had no clear orientations (e.g., balls), participants' recognition of experienced directions was better than that of novel ones, indicating that there was viewpoint-dependence. However, when the objects in scenes were toy bears with clear orientations, the coincident orientation of objects (315 degrees), which was not experienced, shared the advantage of the experienced direction (0 degrees), and participants were equally likely to choose either direction when reconstructing the spatial representation in memory. These findings suggest that coincident orientation of objects may affect egocentric representations in spatial memory.

  20. A theoretical basis for the analysis of multiversion software subject to coincident errors

    NASA Technical Reports Server (NTRS)

    Eckhardt, D. E., Jr.; Lee, L. D.

    1985-01-01

    Fundamental to the development of redundant software techniques (known as fault-tolerant software) is an understanding of the impact of multiple joint occurrences of errors, referred to here as coincident errors. A theoretical basis for the study of redundant software is developed which: (1) provides a probabilistic framework for empirically evaluating the effectiveness of a general multiversion strategy when component versions are subject to coincident errors, and (2) permits an analytical study of the effects of these errors. An intensity function, called the intensity of coincident errors, has a central role in this analysis. This function describes the propensity of programmers to introduce design faults in such a way that software components fail together when executing in the application environment. A condition under which a multiversion system is a better strategy than relying on a single version is given.

  1. CoINcIDE: A framework for discovery of patient subtypes across multiple datasets.

    PubMed

    Planey, Catherine R; Gevaert, Olivier

    2016-03-09

    Patient disease subtypes have the potential to transform personalized medicine. However, many patient subtypes derived from unsupervised clustering analyses on high-dimensional datasets are not replicable across multiple datasets, limiting their clinical utility. We present CoINcIDE, a novel methodological framework for the discovery of patient subtypes across multiple datasets that requires no between-dataset transformations. We also present a high-quality database collection, curatedBreastData, with over 2,500 breast cancer gene expression samples. We use CoINcIDE to discover novel breast and ovarian cancer subtypes with prognostic significance and novel hypothesized ovarian therapeutic targets across multiple datasets. CoINcIDE and curatedBreastData are available as R packages.

  2. Measurement of beta-gamma coincidence with a multi-parameter analyzer system

    NASA Astrophysics Data System (ADS)

    Yazdanpanah-Kejani, M.; Abbasi, F.; Lamehi-Rachti, M.; Doost-Mohammadi, V.

    2017-01-01

    A new version of the Iranian Noble Gas Analyzing System (INGAS) has been improved to facilitate measurement of beta-gamma coincidence events. It employs a new prototype list-mode multi-parameter data analyzer system, MPA4300. In order to test the new version performance, it has used to obtain energy spectra from radioxenon isotopes using the detector assembly of the Iranian Noble Gas Analyzing System. The MPA4300 is able to set the coinciding parameters, extract the corresponding spectrum, and through the use of event by event list file, can replay the measurement in offline mode. A great novelty of this work is the use of internal timing circuit in MPA4300 instead of using standard pick up time modules to identify coincidence events of detectors. A detailed description of the measuring 222Rn and 131mXe is presented.

  3. Convergent input from brainstem coincidence detectors onto delay-sensitive neurons in the inferior colliculus.

    PubMed

    McAlpine, D; Jiang, D; Shackleton, T M; Palmer, A R

    1998-08-01

    Responses of low-frequency neurons in the inferior colliculus (IC) of anesthetized guinea pigs were studied with binaural beats to assess their mean best interaural phase (BP) to a range of stimulating frequencies. Phase plots (stimulating frequency vs BP) were produced, from which measures of characteristic delay (CD) and characteristic phase (CP) for each neuron were obtained. The CD provides an estimate of the difference in travel time from each ear to coincidence-detector neurons in the brainstem. The CP indicates the mechanism underpinning the coincidence detector responses. A linear phase plot indicates a single, constant delay between the coincidence-detector inputs from the two ears. In more than half (54 of 90) of the neurons, the phase plot was not linear. We hypothesized that neurons with nonlinear phase plots received convergent input from brainstem coincidence detectors with different CDs. Presentation of a second tone with a fixed, unfavorable delay suppressed the response of one input, linearizing the phase plot and revealing other inputs to be relatively simple coincidence detectors. For some neurons with highly complex phase plots, the suppressor tone altered BP values, but did not resolve the nature of the inputs. For neurons with linear phase plots, the suppressor tone either completely abolished their responses or reduced their discharge rate with no change in BP. By selectively suppressing inputs with a second tone, we are able to reveal the nature of underlying binaural inputs to IC neurons, confirming the hypothesis that the complex phase plots of many IC neurons are a result of convergence from simple brainstem coincidence detectors.

  4. LIGO Triggered Search for Coincidence with High Energy Photon Survey Missions

    NASA Technical Reports Server (NTRS)

    Camp, Jordan

    2009-01-01

    LIGO is about to begin a new, higher sensitivity science run, where gravitational detection is plausible. A possible candidate for detection is a compact binary merger, which would also be likely to emit a high energy electromagnetic signal. Coincident observation of the gw signal from a compact merger with an x-ray or gamma-ray signal would add considerable weight to the claim for gw detection. In this talk I will consider the possibility of using LIGO triggers with time and sky position to perform a coincident analysis of EM signals from the RXTE, SWIFT, and FERMI missions.

  5. Boron-Coated Straw Collar for Uranium Neutron Coincidence Collar Replacement

    SciTech Connect

    Hu, Jianwei; Croft, Stephen; McElroy, Robert Dennis

    2017-01-01

    The objective of this project was to design and optimize, in simulation space, an active neutron coincidence counter (or collar) using boron-coated straws (BCSs) as a non-3He replacement to the Uranium Neutron Coincidence Collar (UNCL). UNCL has been used by the International Atomic Energy Agency (IAEA) and European Atomic Energy Community (Euratom) since the 1980s to verify the 235U content in fresh light water reactor fuel assemblies for safeguards purposes. This report documents the design and optimization of the BCS collar.

  6. Line-on-Line Coincidence: A New Type of Epitaxy Found in Organic-Organic Heterolayers

    NASA Astrophysics Data System (ADS)

    Mannsfeld, Stefan C.; Leo, Karl; Fritz, Torsten

    2005-02-01

    We propose a new type of epitaxy, line-on-line coincidence (LOL), which explains the ordering in the organic-organic heterolayer system PTCDA on HBC on graphite. LOL epitaxy is similar to point-on-line coincidence (POL) in the sense that all overlayer molecules lie on parallel, equally spaced lines. The key difference to POL is that these lines are not restricted to primitive lattice lines of the substrate lattice. Potential energy calculations demonstrate that this new type of epitaxy is indeed characterized by a minimum in the overlayer-substrate interaction potential.

  7. Standardization of (99m)Tc by means of a software coincidence system.

    PubMed

    Brito, A B; Koskinas, M F; Litvak, F; Toledo, F; Dias, M S

    2012-09-01

    The procedure followed by the Nuclear Metrology Laboratory, at IPEN, for the primary standardization of (99m)Tc is described. The primary standardization has been accomplished by the coincidence method. The beta channel efficiency was varied by electronic discrimination using a software coincidence counting system. Two windows were selected for the gamma channel: one at 140 keV gamma-ray and the other at 20 keV X-ray total absorption peaks. The experimental extrapolation curves were compared with Monte Carlo simulations by means of code ESQUEMA. Copyright © 2012 Elsevier Ltd. All rights reserved.

  8. Monte Carlo simulations of the response of a plastic scintillator and an HPGe spectrometer in coincidence.

    PubMed

    Joković, D R; Dragić, A; Udovicić, V; Banjanac, R; Puzović, J; Anicin, I

    2009-05-01

    A simulation programme based on the Geant4 toolkit has been developed to simulate the coincident responses of a plastic scintillator and an HPGe detector to the cosmic-ray muons. The detectors are situated in a low-level underground laboratory (25 m.w.e). Primary positions, momentum directions and energies of the muons are sampled from the angular and energy distributions of the cosmic-ray muons at the shallow underground level. Obtained coincident spectra of both detectors are presented and discussed.

  9. Development of Monte Carlo code for coincidence prompt gamma-ray neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Han, Xiaogang

    Prompt Gamma-Ray Neutron Activation Analysis (PGNAA) offers a non-destructive, relatively rapid on-line method for determination of elemental composition of bulk and other samples. However, PGNAA has an inherently large background. These backgrounds are primarily due to the presence of the neutron excitation source. It also includes neutron activation of the detector and the prompt gamma rays from the structure materials of PGNAA devices. These large backgrounds limit the sensitivity and accuracy of PGNAA. Since most of the prompt gamma rays from the same element are emitted in coincidence, a possible approach for further improvement is to change the traditional PGNAA measurement technique and introduce the gamma-gamma coincidence technique. It is well known that the coincidence techniques can eliminate most of the interference backgrounds and improve the signal-to-noise ratio. A new Monte Carlo code, CEARCPG has been developed at CEAR to simulate gamma-gamma coincidence spectra in PGNAA experiment. Compared to the other existing Monte Carlo code CEARPGA I and CEARPGA II, a new algorithm of sampling the prompt gamma rays produced from neutron capture reaction and neutron inelastic scattering reaction, is developed in this work. All the prompt gamma rays are taken into account by using this new algorithm. Before this work, the commonly used method is to interpolate the prompt gamma rays from the pre-calculated gamma-ray table. This technique works fine for the single spectrum. However it limits the capability to simulate the coincidence spectrum. The new algorithm samples the prompt gamma rays from the nucleus excitation scheme. The primary nuclear data library used to sample the prompt gamma rays comes from ENSDF library. Three cases are simulated and the simulated results are benchmarked with experiments. The first case is the prototype for ETI PGNAA application. This case is designed to check the capability of CEARCPG for single spectrum simulation. The second

  10. LIGO Triggered Search for Coincidence with High Energy Photon Survey Missions

    NASA Technical Reports Server (NTRS)

    Camp, Jordan

    2009-01-01

    LIGO is about to begin a new, higher sensitivity science run, where gravitational detection is plausible. A possible candidate for detection is a compact binary merger, which would also be likely to emit a high energy electromagnetic signal. Coincident observation of the gw signal from a compact merger with an x-ray or gamma-ray signal would add considerable weight to the claim for gw detection. In this talk I will consider the possibility of using LIGO triggers with time and sky position to perform a coincident analysis of EM signals from the RXTE, SWIFT, and FERMI missions.

  11. Molecular Isomer Identification of Titan's Tholins Organic Aerosols by Photoelectron/Photoion Coincidence Spectroscopy Coupled to VUV Synchrotron Radiation.

    PubMed

    Cunha de Miranda, Barbara; Garcia, Gustavo A; Gaie-Levrel, François; Mahjoub, Ahmed; Gautier, Thomas; Fleury, Benjamin; Nahon, Laurent; Pernot, Pascal; Carrasco, Nathalie

    2016-08-25

    The chemical composition of Titan organic haze is poorly known. To address this issue, laboratory analogues named tholins are synthesized and analyzed by methods often requiring an extraction process in a carrier solvent. These methods exclude the analysis of the insoluble tholins' fraction and assume a hypothetical chemical equivalence between soluble and insoluble fractions. In this work, we present a powerful complementary analysis method recently developed on the DESIRS VUV synchrotron beamline at SOLEIL. It involves soft pyrolysis of tholins at ∼230 °C and electron/ion coincidence analysis of the emitted volatile compounds photoionized by tunable synchrotron radiation. By comparison with reference photoelectron spectra (PES), the spectral information collected on the detected molecules yields their isomeric structure. The method is more readily applied to light species (m/z ≤ 69), while for heavier ones, the number of possibilities and the lack of PES reference spectra in the literature limit its analysis. A notable pattern in the analyzed tholins is the presence of species containing adjacent doubly bonded N atoms, which might be a signature of heterogeneous incorporation of N2 in tholins.

  12. The super-cooling agent icilin reveals a mechanism of coincidence detection by a temperature-sensitive TRP channel.

    PubMed

    Chuang, Huai-hu; Neuhausser, Werner M; Julius, David

    2004-09-16

    TRPM8, a member of the transient receptor potential family of ion channels, depolarizes somatosensory neurons in response to cold. TRPM8 is also activated by the cooling agents menthol and icilin. When exposed to menthol or cold, TRPM8 behaves like many ligand-gated channels, exhibiting rapid activation followed by moderate Ca(2+)-dependent adaptation. In contrast, icilin activates TRPM8 with extremely variable latency followed by extensive desensitization, provided that calcium is present. Here, we show that, to achieve full efficacy, icilin requires simultaneous elevation of cytosolic Ca2+, either via permeation through TRPM8 channels or by release from intracellular stores. Thus, two stimuli must be paired to elicit full channel activation, illustrating the potential for coincidence detection by TRP channels. Determinants of icilin sensitivity map to a region of TRPM8 that corresponds to the capsaicin binding site on the noxious heat receptor TRPV1, suggesting a conserved molecular logic for gating of these thermosensitive channels by chemical agonists.

  13. The Design, Implementation, and Performance of the Astro-H SXS Calorimeter Array and Anti-Coincidence Detector

    NASA Technical Reports Server (NTRS)

    Kilbourne, Caroline A.; Adams, Joseph S.; Brekosky, Regis P.; Chiao, Meng P.; Chervenak, James A.; Eckart, Megan E.; Figueroa-Feliciano, Enectali; Galeazzi, Masimilliano; Grein, Christoph; Jhabvala, Christine A.; hide

    2016-01-01

    The calorimeter array of the JAXA Astro-H (renamed Hitomi) Soft X-ray Spectrometer (SXS) was designed to provide unprecedented spectral resolution of spatially extended cosmic x-ray sources and of all cosmic x-ray sources in the Fe-K band around 6 keV, enabling essential plasma diagnostics. The SXS has a square array of 36 microcalorimeters at the focal plane. These calorimeters consist of ion-implanted silicon thermistors and HgTe thermalizing x-ray absorbers. These devices have demonstrated a resolution of better than 4.5 eV at 6 keV when operated at a heat-sink temperature of 50 mK. We will discuss the basic physical parameters of this array, including the array layout, thermal conductance of the link to the heat sink, resistance function, absorber details, and means of attaching the absorber to the thermistor-bearing element. We will also present the thermal characterization of the whole array, including thermal conductance and crosstalk measurements and the results of pulsing the frame temperature via alpha particles, heat pulses, and the environmental background. A silicon ionization detector is located behind the calorimeter array and serves to reject events due to cosmic rays. We will briefly describe this anti-coincidence detector and its performance.

  14. The design, implementation, and performance of the Atro-H SXS calorimeter array and anti-coincidence detector

    NASA Astrophysics Data System (ADS)

    Kilbourne, Caroline A.; Adams, Joseph S.; Brekosky, Regis P.; Chervenak, James A.; Chiao, Meng P.; Eckart, Megan E.; Figueroa-Feliciano, Enectali; Galeazzi, Massimiliano; Grein, Christoph; Jhabvala, Christine A.; Kelley, Richard L.; Kelly, Daniel P.; Leutenegger, Maurice A.; McCammon, Dan; Porter, F. S.; Szymkowiak, Andrew E.; Watanabe, Tomomi; Zhao, Jun

    2016-07-01

    The calorimeter array of the JAXA Astro-H (renamed Hitomi) Soft X-ray Spectrometer (SXS) was designed to provide unprecedented spectral resolution of spatially extended cosmic x-ray sources and of all cosmic x-ray sources in the Fe-K band around 6 keV, enabling essential plasma diagnostics. The SXS has a square array of 36 microcalorimeters at the focal plane. These calorimeters consist of ion-implanted silicon thermistors and HgTe thermalizing x-ray absorbers. These devices have demonstrated a resolution of better than 4.5 eV at 6 keV when operated at a heat-sink temperature of 50 mK. We will discuss the basic physical parameters of this array, including the array layout, thermal conductance of the link to the heat sink, resistance function, absorber details, and means of attaching the absorber to the thermistorbearing element. We will also present the thermal characterization of the whole array, including thermal conductance and crosstalk measurements and the results of pulsing the frame temperature via alpha particles, heat pulses, and the environmental background. A silicon ionization detector is located behind the calorimeter array and serves to reject events due to cosmic rays. We will briefly describe this anti-coincidence detector and its performance.

  15. Ion colliders

    SciTech Connect

    Fischer, W.

    2011-12-01

    Ion colliders are research tools for high-energy nuclear physics, and are used to test the theory of Quantum Chromo Dynamics (QCD). The collisions of fully stripped high-energy ions create matter of a temperature and density that existed only microseconds after the Big Bang. Ion colliders can reach higher densities and temperatures than fixed target experiments although at a much lower luminosity. The first ion collider was the CERN Intersecting Storage Ring (ISR), which collided light ions [77Asb1, 81Bou1]. The BNL Relativistic Heavy Ion Collider (RHIC) is in operation since 2000 and has collided a number of species at numerous energies. The CERN Large Hadron Collider (LHC) started the heavy ion program in 2010. Table 1 shows all previous and the currently planned running modes for ISR, RHIC, and LHC. All three machines also collide protons, which are spin-polarized in RHIC. Ion colliders differ from proton or antiproton colliders in a number of ways: the preparation of the ions in the source and the pre-injector chain is limited by other effects than for protons; frequent changes in the collision energy and particle species, including asymmetric species, are typical; and the interaction of ions with each other and accelerator components is different from protons, which has implications for collision products, collimation, the beam dump, and intercepting instrumentation devices such a profile monitors. In the preparation for the collider use the charge state Z of the ions is successively increased to minimize the effects of space charge, intrabeam scattering (IBS), charge change effects (electron capture and stripping), and ion-impact desorption after beam loss. Low charge states reduce space charge, intrabeam scattering, and electron capture effects. High charge states reduce electron stripping, and make bending and acceleration more effective. Electron stripping at higher energies is generally more efficient. Table 2 shows the charge states and energies in the

  16. Active neutron coincidence counting for the assay of MTR fuel elements

    SciTech Connect

    Sher, R.

    1983-02-01

    The active well coincidence counter (AWCC) and the neutron coincidence collar (CC) were investigated for their suitability to assay materials testing reactor (MTR) fuel elements. The AWCC was used with its special insert to hold the fuel element and interrogation source. The CC was modified by the addition of polyethylene liners 2.5 cm (1 in.) thick on the sides. For a typical MTR element (approx. 220 g /sup 235/U) and 1000-s count times, statistical errors were approx. 1.6% for the CC and approx. 0.6% for AWCC. For either instrument, the change in count rate corresponding to the removal or addition of one fuel plate (with an 18-plate element) was approx. 3.8%; thus, either instrument can detect removal of one plate. The AWCC can also detect removal of one plate in count times that are considerably less than 1000 s. Various functions were investigated to fit the coincidence count rate vs /sup 235/U mass curve for the AWCC. Programs have been written for the Hewlett-Packard HP-97 calculator to calculate the calibration constants of these functions by a least-squares technique. Coincidence count rates in the AWCC depend on the orientation of the plates of the fuel elements because of the counting efficiency variation in the insert. To lessen this dependence, the MTR element should be counted with its plates positioned vertically, that is, parallel to the radius of the device. For the collar, the effect of plate orientation is much smaller.

  17. Changes in Sensory Evoked Responses Coincide with Rapid Improvement in Speech Identification Performance

    ERIC Educational Resources Information Center

    Alain, Claude; Campeanu, Sandra; Tremblay, Kelly

    2010-01-01

    Perceptual learning is sometimes characterized by rapid improvements in performance within the first hour of training (fast perceptual learning), which may be accompanied by changes in sensory and/or response pathways. Here, we report rapid physiological changes in the human auditory system that coincide with learning during a 1-hour test session…

  18. Active Well Coincidence Counter measurements of enriched uranium fuel assemblies in scanning and stationary modes

    SciTech Connect

    Krick, M.S.; Cowder, L. ); Maltsev, V.; Chernikov, A.; Mokeenko, P.; D'yadkov, K.; Ivanov, V. Nuclear Power Plant, Zarechnyy ); Lagattu, A.; Lopatin, Y.; Czock, K.; Rundquist, D.; Pedraza, L. )

    1991-01-01

    Enriched uranium fuel assemblies were measured with an Active Well Coincidence Counter (AWCC) at the Beloyarskaya Nuclear Power Plant. Special AWCC inserts, electronics, and software were used. Stationary and scanning measurements were performed to establish calibrations and performance specifications for the assay of {sup 235}U and {sub 235}U/cm for BN600 fuel. 6 refs., 7 figs., 2 tabs.

  19. Coincidence of Homophone Spelling Errors and Attention Problems in Schoolchildren: A Survey Study

    ERIC Educational Resources Information Center

    Tsai, Li-Hui; Meng, Ling-Fu; Hung, Li-Yu; Chen, Hsin-Yu; Lu, Chiu-Ping

    2011-01-01

    This article examines the relationship between writing and attention problems and hypothesizes that homophone spelling errors coincide with attention deficits. We analyze specific types of attention deficits, which may contribute to Attention Deficits Hyperactivity Disorder (ADHD); rather than studying ADHD, however, we focus on the inattention…

  20. New 1-k PROM for the coincidence-counter electronics package

    SciTech Connect

    Swansen, J.E.

    1982-02-01

    A new programmable read-only memory (PROM) for the Los Alamos-designed neutron coincidence electronics package is described. The new 1-k PROM allows remote control of the electronics by a computer or a remote terminal through an RS-232 serial data port. No modifications of the existing unit are required.

  1. Pre-coincidence brain activity predicts the perceptual outcome of streaming/bouncing motion display.

    PubMed

    Zhao, Song; Wang, Yajie; Jia, Lina; Feng, Chengzhi; Liao, Yu; Feng, Wenfeng

    2017-08-18

    When two identical visual discs move toward each other on a two-dimensional visual display, they can be perceived as either "streaming through" or "bouncing off" each other after their coincidence. Previous studies have observed a strong bias toward the streaming percept. Additionally, the incidence of the bouncing percept in this ambiguous display could be increased by various factors, such as a brief sound at the moment of coincidence and a momentary pause of the two discs. The streaming/bouncing bistable motion phenomenon has been studied intensively since its discovery. However, little is known regarding the neural basis underling the perceptual ambiguity in the classic version of the streaming/bouncing motion display. The present study investigated the neural basis of the perception disambiguating underling the processing of the streaming/bouncing bistable motion display using event-related potential (ERP) recordings. Surprisingly, the amplitude of frontal central P2 (220-260 ms) that was elicited by the moving discs ~200 ms before the coincidence of the two discs was observed to be predictive of subsequent streaming or bouncing percept. A larger P2 amplitude was observed for streaming percept than the bouncing percept. These findings suggest that the streaming/bouncing bistable perception may have been disambiguated unconsciously ~200 ms before the coincidence of the two discs.

  2. Developing Coincident Timing Skill in Children: A Comparison of Training Methods.

    ERIC Educational Resources Information Center

    Wrisberg, Craig A.; Mead, Barbara J.

    1983-01-01

    A study assessed whether the nature of training experiences influences development of coincident timing skills in young children, using a task involving eye-hand coordination. Researchers concluded that such training should emphasize slower speed stimuli and blocking of additional speeds which are more rapid. (Authors/PP)

  3. Coincidence of Homophone Spelling Errors and Attention Problems in Schoolchildren: A Survey Study

    ERIC Educational Resources Information Center

    Tsai, Li-Hui; Meng, Ling-Fu; Hung, Li-Yu; Chen, Hsin-Yu; Lu, Chiu-Ping

    2011-01-01

    This article examines the relationship between writing and attention problems and hypothesizes that homophone spelling errors coincide with attention deficits. We analyze specific types of attention deficits, which may contribute to Attention Deficits Hyperactivity Disorder (ADHD); rather than studying ADHD, however, we focus on the inattention…

  4. Towards a possible solution for the coincidence problem: f(G) gravity as background

    NASA Astrophysics Data System (ADS)

    Rudra, Prabir

    2015-12-01

    In this paper, we address the well-known cosmic coincidence problem in the framework of the f(G) gravity. In order to achieve this, an interaction between dark energy and dark matter is considered. A set-up is designed and a constraint equation is obtained, which generates the f(G) models that do not suffer from the coincidence problem. Due to the absence of a universally accepted interaction term introduced by a fundamental theory, the study is conducted over three different forms of logically chosen interaction terms. To illustrate the set-up three widely known models of f(G) gravity are taken into consideration and the problem is studied under the designed set-up. The study reveals that the popular f(G) gravity models do not approve of a satisfactory solution of the long standing coincidence problem, thus proving to be a major setback for them as successful models of universe. Finally, two nonconventional models of f(G) gravity have been proposed and studied in the framework of the designed set-up. It is seen that a complete solution of the coincidence problem is achieved for these models. The study also reveals that the b-interaction term is much more preferable compared to the other interactions, due to its greater compliance with the recent observational data.

  5. Towards a possible solution for the coincidence problem: f(G) gravity as background

    NASA Astrophysics Data System (ADS)

    Rudra, Prabir

    2016-07-01

    In this article we address the well-known cosmic coincidence problem in the framework of the f(G) gravity. In order to achieve this, an interaction between dark energy and dark matter is considered. A set-up is designed and a constraint equation is obtained which generates the f(G) models that do not suffer from the coincidence problem. Due to the absence of a universally accepted interaction term introduced by a fundamental theory, the study is conducted over three different forms of logically chosen interaction terms. To illustrate the set-up three widely known models of f(G) gravity are taken into consideration and the problem is studied under the designed set-up. The study reveals that the popular f(G) gravity models does not approve of a satisfactory solution of the long standing coincidence problem, thus proving to be a major setback for them as successful models of universe. Finally, two non-conventional models of f(G) gravity have been proposed and studied in the framework of the designed set-up. It is seen that a complete solution of the coincidence problem is achieved for these models. The study also reveals that the 'b-interaction' term is much more preferable compared to the other interactions, due to its greater compliance with the recent observational data.

  6. ION SOURCE

    DOEpatents

    Martina, E.F.

    1958-04-22

    An improved ion source particularly adapted to provide an intense beam of ions with minimum neutral molecule egress from the source is described. The ion source structure includes means for establishing an oscillating electron discharge, including an apertured cathode at one end of the discharge. The egress of ions from the source is in a pencil like beam. This desirable form of withdrawal of the ions from the plasma created by the discharge is achieved by shaping the field at the aperture of the cathode. A tubular insulator is extended into the plasma from the aperture and in cooperation with the electric fields at the cathode end of the discharge focuses the ions from the source,

  7. Ion mixing

    NASA Technical Reports Server (NTRS)

    Matteson, S.; Nicolet, M.-A.

    1983-01-01

    Recent experimental studies of the ion-mixing phenomenon are summarized. Ion mixing is differentiated from ion implantation and shown to be a useful technique for overcoming the sputter-dependent limitations of implantation processes. The fundamental physical principles of ion/solid interactions are explored. The basic experimental configurations currently in use are characterized: bilayered samples, multilayered samples, and samples with a thin marker layer. A table listing the binary systems (metal-semiconductor or metal-metal) which have been investigated using each configuration is presented. Results are discussed, and some sample data are plotted. The prospects for future application of ion mixing to the alteration of solid surface properties are considered. Practical applications are seen as restricted by economic considerations to the production of small, expensive components or to fields (such as the semiconductor industry) which already have facilities for ion implantation.

  8. A simple and versatile data acquisition system for software coincidence and pulse-height discrimination in 4πβ-γ coincidence experiments.

    PubMed

    Kawada, Y; Yamada, T; Unno, Y; Yunoki, A; Sato, Y; Hino, Y

    2012-09-01

    A simple but versatile data acquisition system for software coincidence experiments is described, in which any time stamping and live time controller are not provided. Signals from β- and γ-channels are fed to separately two fast ADCs (16 bits, 25 MHz clock maximum) via variable delay circuits and pulse-height stretchers, and also to pulse-height discriminators. The discriminating level was set to just above the electronic noise. Two ADCs were controlled with a common clock signal, and triggered simultaneously by the logic OR pulses from both discriminators. Paired digital signals for each sampling were sent to buffer memories connected to main PC with a FIFO (First-In, First-Out) pipe via USB. After data acquisition in list mode, various processing including pulse-height analyses was performed using MS-Excel (version 2007 and later). The usefulness of this system was demonstrated for 4πβ(PS)-4πγ coincidence measurements of (60)Co, (134)Cs and (152)Eu. Possibilities of other extended applications will be touched upon. Copyright © 2012 Elsevier Ltd. All rights reserved.

  9. Ion Sources

    NASA Astrophysics Data System (ADS)

    Haseroth, Helmut; Hora, Heinrich

    1993-03-01

    Ion sources for accelerators are based on plasma configurations with an extraction system in order to gain a very high number of ions within an appropriately short pulse and of sufficiently high charge number Z for advanced research. Beginning with the duoplasmatron, all established ion sources are based on low-density plasmas, of which the electron beam ionization source (EBIS) and the electron cyclotron resonance (ECR) source are the most advanced; for example they result in pulses of nearly 6 × 108 fully stripped sulfur ions per pulse in the Super Proton Synchrotron (SPS) at CERN with energies of 200 GeV/u. As an example of a forthcoming development, we are reporting about the lead ion source for the same purpose. Contrary to these cases of low-density plasmas, where a rather long time is always necessary to generate sufficiently high charge states, the laser ion source uses very high density plasmas and therefore produced, for example in 1983, single shots of Au51+ ions of high directivity with energies above 300 MeV within 2 ns irradiation time of a gold target with a medium-to-large CO2 laser. Experiments at Dubna and Moscow, using small-size lasers, produced up to one million shots with 1 Hz sequence. After acceleration by a linac or otherwise, ion pulses of up to nearly 5 × 1010 ions of C4+ or Mg12+ with energies in the synchrotrons of up to 2 GeV/u were produced. The physics of the laser generation of the ions is most complex, as we know from laser fusion studies, including non-linear dynamic and dielectric effects, resonances, self-focusing, instabilities, double layers, and an irregular pulsation in the 20 ps range. This explains not only what difficulties are implied with the laser ion source, but also why it opens up a new direction of ion sources.

  10. Coinciding development of winter wheat and leaf beetles along an Alpine transect

    NASA Astrophysics Data System (ADS)

    Bechini, Luca; Morlacchi, Pablo; Baumgärtner, Johann

    2013-02-01

    The degree of temporal coincidence in the development of winter wheat (Triticum aestivum L.) and the cereal leaf beetles Oulema melanopus (L.) and Oulema duftschmidi (Redtenbacher, 1874) was studied by means of explanatory phenology models. Temperature and photoperiod control crop development, whereas oviposition and development of eggs and larvae of the two beetles depend on temperature and crop phases. The models parametrized with literature data satisfactorily represented crop and prepupal insect development at several Swiss and Italian locations. The successfully validated models were used for representing multiannual crop and insect development at seven locations on a European transect between the Danube river in the North and the Po River in the South. Depending on temperature and photoperiod, the crop phases occurred at different time periods but were generally of similar durations. The shifting of the crop phases exposed the cereal leaf beetles to environmental conditions which were similar during oviposition and slightly different as the growing season progressed. The simulated oviposition and prepupal survivorship was much higher for O. melanopus than for O. duftschmidi but did not differ between the locations. The crop phase-dependent mortality (Mc) was consistently higher for O. duftschmidi than for O. melanopus, whose Mc increased with increasing altitude. The extent of coinciding development was investigated by means of the summed larval development rates divided by the summed wheat development rate. During the oviposition period the insect development was coincident with wheat development. With time progression, however, the temperature difference between the locations increased causing an incomplete coincidence in the development of wheat and cereal leaf beetles. These results support the hypothesis that the extent of coinciding development of the three species is largely controlled by temperature and photoperiodic conditions.

  11. Detecting gravitational waves from inspiraling binaries with a network of detectors: Coherent versus coincident strategies

    SciTech Connect

    Mukhopadhyay, Himan; Dhurandhar, Sanjeev; Sago, Norichika; Tagoshi, Hideyuki; Takahashi, Hirotaka; Kanda, Nobuyuki

    2006-10-15

    We compare two strategies of multidetector detection of compact binary inspiral signals, namely, the coincidence and the coherent. For simplicity we consider here two identical detectors having the same power spectral density of noise, that of initial LIGO, located in the same place and having the same orientation. We consider the cases of independent noise as well as that of correlated noise. The coincident strategy involves separately making two candidate event lists, one for each detector, and from these choosing those pairs of events from the two lists which lie within a suitable parameter window, which then are called coincidence detections. The coherent strategy on the other hand involves combining the data phase coherently, so as to obtain a single network statistic which is then compared with a single threshold. Here we attempt to shed light on the question as to which strategy is better. We compare the performances of the two methods by plotting the receiver operating characteristics (ROC) for the two strategies. Several of the results are obtained analytically in order to gain insight. Further we perform numerical simulations in order to determine certain parameters in the analytic formulae and thus obtain the final complete results. We consider here several cases from the relatively simple to the astrophysically more relevant in order to establish our results. The bottom line is that the coherent strategy although more computationally expensive in general than the coincidence strategy, is superior to the coincidence strategy--considerably less false dismissal probability for the same false alarm probability in the viable false alarm regime.

  12. Development of a method for activity measurements of 232Th daughters with a multidetector gamma-ray coincidence spectrometer.

    PubMed

    Antovic, N; Svrkota, N

    2009-06-01

    The method for activity measurements of the (232)Th daughters, developed at the six-crystal gamma-ray coincidence spectrometer PRIPYAT-2M and based on coincidence counting of the 583 and 2615 keV photons from cascade transitions which follow beta(-)-decay of (208)Tl, as well as on counting the 911 keV photons which follow beta(-)-decay of (228)Ac in the integral and non-coincidence mode of counting, is presented.

  13. Ion Chromatography.

    ERIC Educational Resources Information Center

    Mulik, James D.; Sawicki, Eugene

    1979-01-01

    Accurate for the analysis of ions in solution, this form of analysis enables the analyst to directly assay many compounds that previously were difficult or impossible to analyze. The method is a combination of the methodologies of ion exchange, liquid chromatography, and conductimetric determination with eluant suppression. (Author/RE)

  14. Ion Chromatography.

    ERIC Educational Resources Information Center

    Mulik, James D.; Sawicki, Eugene

    1979-01-01

    Accurate for the analysis of ions in solution, this form of analysis enables the analyst to directly assay many compounds that previously were difficult or impossible to analyze. The method is a combination of the methodologies of ion exchange, liquid chromatography, and conductimetric determination with eluant suppression. (Author/RE)

  15. Highly charged ion based time of flight emission microscope

    DOEpatents

    Barnes, Alan V.; Schenkel, Thomas; Hamza, Alex V.; Schneider, Dieter H.; Doyle, Barney

    2001-01-01

    A highly charged ion based time-of-flight emission microscope has been designed, which improves the surface sensitivity of static SIMS measurements because of the higher ionization probability of highly charged ions. Slow, highly charged ions are produced in an electron beam ion trap and are directed to the sample surface. The sputtered secondary ions and electrons pass through a specially designed objective lens to a microchannel plate detector. This new instrument permits high surface sensitivity (10.sup.10 atoms/cm.sup.2), high spatial resolution (100 nm), and chemical structural information due to the high molecular ion yields. The high secondary ion yield permits coincidence counting, which can be used to enhance determination of chemical and topological structure and to correlate specific molecular species.

  16. An (e, 2e + ion) investigation of dissociative ionization of methane.

    PubMed

    Xu, Shenyue; Ma, Xinwen; Ren, Xueguang; Senftleben, Arne; Pflüger, Thomas; Yan, Shuncheng; Zhang, Pengju; Yang, Jie; Ullrich, Joachim; Dorn, Alexander

    2013-04-07

    We present in this paper an (e, 2e + ion) investigation of the dissociative ionization of methane by 54 eV electron impact employing the advanced reaction microscope. By measuring two electrons and the ion in the final state in triple coincidence, the species of the ions are identified and the energies deposited into the target are determined. The species and the kinetic energies of the fragmented ion show strong dependence on the intermediate states of the parent ion. Possible decay pathways for the production of different species of ions are analyzed.

  17. Coincidence Measurements of Core-Excited Molecules and Clusters Using TOF Fragment-Mass Spectroscopy

    SciTech Connect

    Tabayashi, Kiyohiko; Maruyama, Tomoe; Tanaka, Kenichiro; Namatame, Hirofumi; Taniguchi, Masaki

    2007-01-19

    In order to investigate photo-induced processes and dynamics of photochemical reactions involving molecular complexes and clusters in the vacuum ultraviolet and soft X-ray region, a cluster beam-photoreactive scattering apparatus has been designed and constructed at the HiSOR facility in Hiroshima University. The apparatus has a basic arrangement of a cluster beam source and a linear time-of-flight mass spectrometer, where it was designed to give strong cluster beam intensity enough to perform a variety of photoelectron and photoion coincidence measurements. Here, we present spectroscopic and coincidence measurements of the photo-induced processes of atomic and molecular clusters in the soft X-ray region to make a fundamental assessment for the present cluster beam-photoreactive scattering apparatus.

  18. Safeguards Technology Factsheet 3He-free Neutron Coincidence Counter

    SciTech Connect

    Henzlova, Daniela; Menlove, Howard Olsen

    2016-04-21

    A full scale thermal neutron coincidence counter (High Level Neutron Counter – Boron: HLNB) based on 3He alternative detection technology was designed and built at LANL and field tested at Plutonium Conversion Development Facility (PCDF) of Japan Atomic Energy Agency (JAEA) during FY15. HLNB is based on boron-lined proportional plates that replace the traditional 3He proportional tubes and was designed as a direct alternative to 3He-based High Level Neutron Coincidence Counter (HLNC-II). During the JAEA field trial the HLNB demonstrated comparable performance to HLNC-II, which represents a key development in the area of 3He alternative technologies and provides a complete demonstration of the technology for nuclear safeguards applications including high mass MOX samples.

  19. Nuclear-state population transfer by a train of coincident pulses

    NASA Astrophysics Data System (ADS)

    Nedaee-Shakarab, B.; Saadati-Niari, M.; Zolfagharpour, F.

    2016-11-01

    Population transfer of three-level Λ -like nuclei interacting with x-ray free electron lasers (XFEL) via a train of coincident pulses has been investigated theoretically. This study uses copropagating beams in which the frequency of the pump laser is different from that of the Stokes laser. We calculate the required laser intensities for each step which satisfy the condition of coincident-pulse technique in different nuclei. By employing the master equation and considering the effect of spontaneous emission, we show that complete nuclear population transfer occurs by choosing the appropriate number of pulse pairs. It is shown that the effect of laser intensity fluctuation is suppressed by increasing the number of pulse pairs. In this scheme, after each step, the populations of system are in stable states and the time delays between the neighboring pulses do not affect the transmission efficiency.

  20. Coincident site lattice-matched growth of semiconductors on substrates using compliant buffer layers

    DOEpatents

    Norman, Andrew

    2016-08-23

    A method of producing semiconductor materials and devices that incorporate the semiconductor materials are provided. In particular, a method is provided of producing a semiconductor material, such as a III-V semiconductor, on a silicon substrate using a compliant buffer layer, and devices such as photovoltaic cells that incorporate the semiconductor materials. The compliant buffer material and semiconductor materials may be deposited using coincident site lattice-matching epitaxy, resulting in a close degree of lattice matching between the substrate material and deposited material for a wide variety of material compositions. The coincident site lattice matching epitaxial process, as well as the use of a ductile buffer material, reduce the internal stresses and associated crystal defects within the deposited semiconductor materials fabricated using the disclosed method. As a result, the semiconductor devices provided herein possess enhanced performance characteristics due to a relatively low density of crystal defects.

  1. A Coincident Search for Radio and Gravitational Waves from Binary Neutron Star Mergers

    NASA Astrophysics Data System (ADS)

    Cardena, Brett

    2011-05-01

    The merger of neutron star-neutron star binary pairs may be accompanied by the prompt emission of a coherent low-frequency radio pulse. This radio transient is produced as synchrotron radiation caused by the spin and rotation of the surface charge density of a pulsar through the magnetosphere of a larger neutron star, usually referred to as a Magnetar . This type of merger event would also result in the release of a gravitational coalescence wave-form. We will discuss a coincident radio transient and gravitational wave search. This search is being conducted by two radio telescope arrays: The Long Wave Array (LWA) and the Eight-meter-wavelength Transient Array (ETA) in coordination with the Laser Interferometer Gravitational-Wave Observatory (LIGO). We will outline this ongoing coincident search and discuss some preliminary results.

  2. Application of Triple Coincidence for the Detection of Small Amounts of Special Nuclear Materials

    SciTech Connect

    DIOSZEGI, I.; Salwen, C.; and Forman, L.

    2011-06-12

    We constructed a device that measures two {gamma}-rays and one neutron from spontaneous fission and any resulting multiplication chains. It extends the associated particle technique based upon correlated counting of the multiplicity of gamma-rays and neutrons released in spontaneous- or neutron-induced fission. There are two advantages in incorporating a third detector in the design over the standard two-detector version. First, we found that random uncorrelated events dominate the background of coincident counting with a gamma-ray- and neutron-detector. These might be suppressed by requiring an additional coincidence. Second, the time history of gamma-ray emission between the two gamma-ray detectors is related to multiplication in the target media. Multiplication in highly enriched uranium is much greater than in depleted uranium.

  3. A feasibility study of a coincidence counting approach for PGNAA applications

    PubMed

    Gardner; Mayo; El-Sayyed; Metwally; Zheng; Poezart

    2000-10-01

    Prompt gamma-ray nutron activation analysis (PGNAA) has an inherently low signal-to-noise (S/N) ratio primarily because of the large background (noise) associated with it. Most elements emit a significant fraction of their prompt gamma rays in coincidence with one or more other prompt gamma rays. This paper reports on initial efforts to use coincidence counting in PGNAA to significantly reduce the several sources of background and thereby increase the S/N ratio. An added benefit is the elimination of the often dominant hydrogen prompt gamma-ray spectrum which emits only a single prompt gamma ray with an energy of 2.223 MeV. Preliminary results are given for both in situ bulk analysis applications with a 252Cf neutron source and for nuclear reactor thermal neutron beam applications for small laboratory samples.

  4. Application of Triple Coincidence for the Detection of Small Amounts of Special Nuclear Materials

    NASA Astrophysics Data System (ADS)

    Dioszegi, I.; Salwen, C.; Forman, L.

    2011-12-01

    We constructed a device that measures two γ-rays and one neutron from spontaneous fission and any resulting multiplication chains. It extends the associated particle technique based upon correlated counting of the multiplicity of gamma-rays and neutrons released in spontaneous- or neutron-induced fission. There are two advantages in incorporating a third detector in the design over the standard two-detector version. First, we found that random uncorrelated events dominate the background of coincident counting with a gamma-ray and neutron detector. These might be suppressed by requiring an additional coincidence. Second, the time history of gamma-ray emission between the two gamma-ray detectors is related to multiplication in the target media. Multiplication in highly enriched uranium is much greater than in depleted uranium.

  5. Non-coincident Inter-instrument Comparisons of Ozone Measurements Using Quasi-conservative Coordinates

    NASA Technical Reports Server (NTRS)

    Lait, L. R.; Newman, P. A.; Schoeberl, M. R.; McGee, T.; Twigg, T.; Browell, E.; Bevilacqua, R.; Andersen, S. B.; DeBacker, H.; Benesova, A.

    2004-01-01

    Ozone measurements from ozonesondes, AROTAL, DIAL, and POAM III instruments during the SOLVE-2/VINTERSOL period are composited in a time-varying, flow-following quasi-conservative (PV-6) coordinate space; the resulting composites from each instrument are mapped onto the other instruments locations and times. The mapped data are then used to intercompare data from the different instruments. Overall, the four data sets are found to be in good agreement. AROTAL shows somewhat lower values below 16 km, and DIAL has a positive bias at the upper limits of its altitude range. These intercomparisons are consistent with those obtained from more conventional near-coincident profiles, where available. Although the PV-theta mapping technique entails larger uncertainties of individual profile differences compared to direct near-coincident comparisons, the ability to include much larger numbers of comparisons can make this technique advantageous.

  6. Learning words in space and time: probing the mechanisms behind the suspicious-coincidence effect.

    PubMed

    Spencer, John P; Perone, Sammy; Smith, Linda B; Samuelson, Larissa K

    2011-08-01

    A major debate in the study of word learning centers on the extension of categories to new items. The rational approach assumes that learners make structured inferences about category membership, whereas the mechanistic approach emphasizes the attentional and memory processes that form the basis of generalization behaviors. Recent support for the rational view comes from observations of the suspicious-coincidence effect: People generalize category membership narrowly when presented with three subordinate-level exemplars that share the same label and generalize category membership broadly when presented with one exemplar. Across three experiments, we examined the mechanistic basis of this effect. Results showed that the presentation of multiple subordinate-level exemplars led to narrow generalization only when the exemplars were presented simultaneously, even when the number of exemplars was increased from three to six. These data demonstrate that the suspicious-coincidence effect is firmly grounded in the general cognitive processes of attention, memory, and visual comparison.

  7. Coincident retrievals of CO and CO2 from high resolution solar absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Keppel-Aleks, G.; Wennberg, P. O.; Wunch, D.; Toon, G. C.; Roehl, C. M.; Deutscher, N. M.; Griffith, D. W.

    2009-12-01

    The Total Carbon Column Observing Network (TCCON) is a global network of ground-based high-resolution spectrometers. We obtain coincident retrievals of the vertically integrated mass of atmospheric trace species including CH4, N2O, CO, CO2 from near-infrared direct solar absorption spectra. Here, we focus on coincident retrievals of CO and CO2 made at three TCCON sites: Park Falls, Wisconsin; Darwin, Australia; and Pasadena, California. First, we present results that calibrate the retrieved CO total column against aircraft profiles of CO obtained over the observatories and compare to satellite observations of CO from MOPITT. Second, we explore the co-variation between CO and CO2 at each site and use the observations to derive emission ratios for individual fire plumes observed at the sites. Third, we examine the utility of combined total column CO and CO2 observations to constrain regional fluxes of CO2.

  8. Precise measurement and calculation of coincidence summing corrections for point and linear sources.

    PubMed

    Sima, Octavian; Arnold, Dirk

    2012-09-01

    Point sources of (60)Co, (133)Ba, (134)Cs and (152)Eu, calibrated at Physikalisch-Technische Bundesanstalt were measured in 13 positions on the axis of a 50% relative efficiency p-type detector. The peak and total efficiencies were calibrated using single photon emitting nuclides. Precise experimental values of the coincidence summing corrections were evaluated in each geometry. Synthetic linear source data, as well as the corresponding peak and total efficiency curves, were prepared using the dependence of the count rates on the position of the emitting point. The coincidence summing corrections for the linear sources were computed, analyzed with respect to different approximations and compared with simulations carried out with GESPECOR. Copyright © 2012 Elsevier Ltd. All rights reserved.

  9. Coincident Site Lattice Matched InGaN on (111) Spinel Substrates

    SciTech Connect

    Norman, A. G.; Dippo, P. C.; Moutinho, H. R.; Simon, J.; Ptak, A. J.

    2012-04-09

    Coincident site lattice-matched wurtzite (0001) In{sub 0.31}Ga{sub 0.69}N, emitting in the important green wavelength region, is demonstrated by molecular beam epitaxy on a cubic (111) MgAl{sub 2}O{sub 4} spinel substrate. The coincident site lattice matching condition involves a 30{sup o} rotation between the lattice of the InGaN epitaxial layer and the lattice of the spinel. This work describes an alternative approach towards realizing more compositionally homogenous InGaN films with low dislocation density emitting in the 'green gap' of low efficiency currently observed for semiconductor light emitting diodes (LEDs). This approach could lead to higher efficiency green LEDs presently of great interest for solid-state lighting applications.

  10. Coincident site lattice-matched InGaN on (111) spinel substrates

    SciTech Connect

    Norman, A. G.; Dippo, P. C.; Moutinho, H. R.; Simon, J.; Ptak, A. J.

    2012-04-09

    Coincident site lattice-matched wurtzite (0001) In{sub 0.31}Ga{sub 0.69}N, emitting in the important green wavelength region, is demonstrated by molecular beam epitaxy on a cubic (111) MgAl{sub 2}O{sub 4} spinel substrate. The coincident site lattice matching condition involves a 30 deg. rotation between the lattice of the InGaN epitaxial layer and the lattice of the spinel. This work describes an alternative approach towards realizing more compositionally homogenous InGaN films with low dislocation density emitting in the ''green gap'' of low efficiency currently observed for semiconductor light emitting diodes (LEDs). This approach could lead to higher efficiency green LEDs presently of great interest for solid-state lighting applications.

  11. Development of a coincidence system for the measurement of X-ray emission atomic parameters

    NASA Astrophysics Data System (ADS)

    Martínez, Filiberto; Miranda, Javier

    2013-07-01

    Preliminary results obtained in experiments carried out with an x-ray spectrometer built at the Instituto de Física for Atomic Physics and environmental sciences studies are presented. The experiments are based on a coincidence method for signals produced by LEGe and Si(Li) detectors. The x-ray fluorescence yields (ωLi) and Coster-Kronig transition probabilities (fij) for elements with 55 ≤ Z ≤ 60 are among the quantities of interest. The method is based on the simultaneous detection of K x-rays with the LEGe detector and the L x-rays with the Si(Li) detector. The primary radiation source is an x-ray tube with Rh anode. The system was tested with the coincidence of the L x-rays from Ce with its K line, demonstrating the feasibility of the experiments.

  12. Flowering time and seed dormancy control use external coincidence to generate life history strategy.

    PubMed

    Springthorpe, Vicki; Penfield, Steven

    2015-03-31

    Climate change is accelerating plant developmental transitions coordinated with the seasons in temperate environments. To understand the importance of these timing advances for a stable life history strategy, we constructed a full life cycle model of Arabidopsis thaliana. Modelling and field data reveal that a cryptic function of flowering time control is to limit seed set of winter annuals to an ambient temperature window which coincides with a temperature-sensitive switch in seed dormancy state. This coincidence is predicted to be conserved independent of climate at the expense of flowering date, suggesting that temperature control of flowering time has evolved to constrain seed set environment and therefore frequency of dormant and non-dormant seed states. We show that late flowering can disrupt this bet-hedging germination strategy. Our analysis shows that life history modelling can reveal hidden fitness constraints and identify non-obvious selection pressures as emergent features.

  13. Detection of coincident radiations in a single transducer by pulse shape analysis

    DOEpatents

    Warburton, William K.; Tan, Hui; Hennig, Wolfgang

    2008-03-11

    Pulse shape analysis determines if two radiations are in coincidence. A transducer is provided that, when it absorbs the first radiation produces an output pulse that is characterized by a shorter time constant and whose area is nominally proportional to the energy of the absorbed first radiation and, when it absorbs the second radiation produces an output pulse that is characterized by a longer time constant and whose area is nominally proportional to the energy of the absorbed second radiation. When radiation is absorbed, the output pulse is detected and two integrals are formed, the first over a time period representative of the first time constant and the second over a time period representative of the second time constant. The values of the two integrals are examined to determine whether the first radiation, the second radiation, or both were absorbed in the transducer, the latter condition defining a coincident event.

  14. Electron-photon coincidence technique for the absolute calibration of VUV detectors

    NASA Technical Reports Server (NTRS)

    Mcadams, R.; Srivastava, S. K.

    1983-01-01

    A method is described whereby VUV photon detectors can be accurately calibrated. This method is illustrated by taking the 58.4-nm transition of He as an example. The technique consists of crossing a monoenergetic electron beam with a beam of He atoms. When inelastically scattered electrons which have excited the 2 1P state are detected in coincidence with the 58.4-nm photons emitted in the decay of the excited state, the interaction volume formed by the crossed beams constitutes a standard source of photons. By comparing the number of detected coincidences with the predicted number the calibration can be made. A total detector efficiency of 0.024 + or - 0.003 is obtained for a Galileo 4830 channeltron.

  15. A comparison of cloud motion winds from ATS 6 images with coinciding SMS 1 winds

    NASA Technical Reports Server (NTRS)

    Kuhlow, W. W.; Chatters, G. C.

    1978-01-01

    A methodology is developed for accurate measurement of cloud motion winds from the geosynchronous ATS 6 image data. Attitude changes between consecutive images (as a function of scan-line number) are accounted for in wind computations through measurement of the earth-edge displacements between the successive infrared images. Also, an image matching procedure is used to remove obvious and distracting image distortions. The availability of SMS imagery coinciding with ATS 6 imagery makes SMS an excellent reference against which the quality of ATS 6 winds can be tested. The resulting winds inferred from cloud displacement measurements taken from a sequence of the corrected images are found to agree better than 2 m/sec rms with winds measured from coincident SMS 1 imagery.

  16. SPADnet: Embedded coincidence in a smart sensor network for PET applications

    NASA Astrophysics Data System (ADS)

    Bruschini, C.; Charbon, E.; Veerappan, C.; Braga, L. H. C.; Massari, N.; Perenzoni, M.; Gasparini, L.; Stoppa, D.; Walker, R.; Erdogan, A.; Henderson, R. K.; East, S.; Grant, L.; Jatekos, B.; Ujhelyi, F.; Erdei, G.; Lörincz, E.; André, L.; Maingault, L.; Reboud, V.; Verger, L.; Gros d'Aillon, E.; Major, P.; Papp, Z.; Németh, G.

    2014-01-01

    In this paper we illustrate the core technologies at the basis of the European SPADnet project (www.spadnet.eu), and present the corresponding first results. SPADnet is aimed at a new generation of MRI-compatible, scalable large area image sensors, based on CMOS technology, that are networked to perform gamma-ray detection and coincidence to be used primarily in (Time-of-Flight) Positron Emission Tomography (PET). The project innovates in several areas of PET systems, from optical coupling to single-photon sensor architectures, from intelligent ring networks to reconstruction algorithms. In addition, SPADnet introduced the first computational model enabling study of the full chain from gamma photons to network coincidence detection through scintillation events, optical coupling, etc.

  17. PLUMEX I: Coincident Radar and Rocket Observations of Equatorial Spread-F.

    DTIC Science & Technology

    1980-03-17

    provide signatures of its bottomuide source domin and estinate of average maximum vertical drift velocity. For long4lved depletion, molecular - Ion... molecular ions usually more abundant inside the bite- out. Brinton et al. (1975) and McClure et al. (1977) have found O depleted by as much as a...factor of 10 to a concentration below that of NO+. The molecular ion NO4 was found to be dominant in the O+ depleted region, with the bite-outs varying

  18. Heavy Ion Radiation Effects Studies With Ion Photon Emission Microscopy

    SciTech Connect

    Branson, J. V.; Hattar, K.; Vizkelethy, G.; Powell, C. J.; Doyle, B. L.; Rossi, P.

    2011-06-01

    The development of a new radiation effects microscopy (REM) technique is crucial as emerging semiconductor technologies demonstrate smaller feature sizes and thicker back end of line (BEOL) layers. To penetrate these materials and still deposit sufficient energy into the device to induce single event effects, high energy heavy ions are required. Ion photon emission microscopy (IPEM) is a technique that utilizes coincident photons, which are emitted from the location of each ion impact to map out regions of radiation sensitivity in integrated circuits and devices, circumventing the obstacle of focusing high-energy heavy ions. Several versions of the IPEM have been developed and implemented at Sandia National Laboratories (SNL). One such instrument has been utilized on the microbeam line of the 6 MV tandem accelerator at SNL. Another IPEM was designed for ex-vacu use at the 88'' cyclotron at Lawrence Berkeley National Laboratory (LBNL). Extensive engineering is involved in the development of these IPEM systems, including resolving issues with electronics, event timing, optics, phosphor selection, and mechanics. The various versions of the IPEM and the obstacles, as well as benefits associated with each will be presented. In addition, the current stage of IPEM development as a user instrument will be discussed in the context of recent results.

  19. Heavy ion radiation effects studies with ion photon emission microscopy.

    SciTech Connect

    Doyle, Barney Lee; Rossi, Paolo; Powell, Cody Joseph; Hattar, Khalid Mikhiel; Vizkelethy, Gyorgy; Branson, Janelle Villone

    2010-08-01

    The development of a new radiation effects microscopy (REM) technique is crucial as emerging semiconductor technologies demonstrate smaller feature sizes and thicker back end of line (BEOL) layers. To penetrate these materials and still deposit sufficient energy into the device to induce single event effects, high energy heavy ions are required. Ion photon emission microscopy (IPEM) is a technique that utilizes coincident photons, which are emitted from the location of each ion impact to map out regions of radiation sensitivity in integrated circuits and devices, circumventing the obstacle of focusing high-energy heavy ions. Several versions of the IPEM have been developed and implemented at Sandia National Laboratories (SNL). One such instrument has been utilized on the microbeam line of the 6 MV tandem accelerator at SNL. Another IPEM was designed for ex-vacu use at the 88 cyclotron at Lawrence Berkeley National Laboratory (LBNL). Extensive engineering is involved in the development of these IPEM systems, including resolving issues with electronics, event timing, optics, phosphor selection, and mechanics. The various versions of the IPEM and the obstacles, as well as benefits associated with each will be presented. In addition, the current stage of IPEM development as a user instrument will be discussed in the context of recent results.

  20. The matching theorems and coincidence theorems for generalized R-KKM mapping in topological spaces

    NASA Astrophysics Data System (ADS)

    Huang, Jianhua

    2005-12-01

    In this paper we present some new matching theorems with open cover and closed cover by using the generalized R-KKM theorems [L. Deng, X. Xia, Generalized R-KKM theorem in topological space and their applications, J. Math. Anal. Appl. 285 (2003) 679-690] in the topological spaces with property (H). As applications, some coincidence theorems are established in topological spaces. Our results extend and generalize some known results.

  1. Fluorescent atom coincidence spectroscopy of extremely neutron-deficient barium isotopes

    NASA Astrophysics Data System (ADS)

    Wells, S. A.; Evans, D. E.; Griffith, J. A. R.; Eastham, D. A.; Groves, J.; Smith, J. R. H.; Tolfree, D. W. L.; Warner, D. D.; Billowes, J.; Grant, I. S.; Walker, P. M.

    1988-09-01

    Fluorescent atom coincidence spectroscopy (FACS) has been used to measure the nuclear mean square radii and moments of the extremely neutron-deficient isotopes 120-124Ba. At N=65 an abrupt change in nuclear mean square charge radii is observed which can be understood in terms of the occupation of the spin-orbit partner g7/25/2[413] neutron and g9/29/2[404] proton orbitals and the consequent enhancement of the n-p interaction.

  2. Sizeable acquired subglottic cyst in a baby with Williams-Beuren syndrome: association or coincidence?

    PubMed

    Christoforidis, Athanasios; Tsakalides, Christos; Chatziavramidis, Angelos; Karagianni, Paraskevi; Dimitriadou, Meropi; Konstantinidis, Iordanis

    2013-10-15

    We describe a case of an acquired subglottic cyst presented with persistent stridor and voice hoarsening in a baby diagnosed with Williams-Beuren syndrome that was born premature and required intubation during neonatal period. We also comment on whether this is a coincidence or there can be an association between impaired elastogenesis, a feature of patients with the syndrome and the formation of a subglottic cyst. © 2013 Elsevier B.V. All rights reserved.

  3. Mass Measurement of 80Y by β-γ Coincidence Spectroscopy

    NASA Astrophysics Data System (ADS)

    Brenner, D. S.; Barton, C. J.; Zamfir, N. V.; Caprio, M. A.; Aprahamian, A.; Beausang, C. W.; Berant, Z.; Casten, R. F.; Cooper, J. R.; Gill, R. L.; Kruecken, R.; Novak, J. R.; Pietralla, N.; Shawcross, M.; Teymurazyan, A.; Wolf, A.; Wiescher, M.

    2003-06-01

    The QEC value of 80Y has been measured by β-γ coincidence spectroscopy to be ≥8929(83) keV. Combing this result with the adopted mass excess of the daughter 80Sr gives a mass excess for 80Y of ≥ -61376(83) keV. Results are compared with other measurements, with Audi-Wapstra systematics, and with predictions of mass formulas. Implications for rp-process simulations are considered.

  4. Mass measurement of 80Y by β-γ coincidence spectroscopy

    NASA Astrophysics Data System (ADS)

    Barton, C. J.; Brenner, D. S.; Zamfir, N. V.; Caprio, M. A.; Aprahamian, A.; Wiescher, M. C.; Beausang, C. W.; Berant, Z.; Casten, R. F.; Cooper, J. R.; Gill, R. L.; Krücken, R.; Novak, J. R.; Pietralla, N.; Shawcross, M.; Teymurazyan, A.; Wolf, A.

    2003-03-01

    The QEC value of 80Y has been measured by β-γ coincidence spectroscopy to be ⩾8929(83) keV. Combining this result with the adopted mass excess of the daughter 80Sr gives a mass excess for 80Y of ⩾-61 376(83) keV. Results are compared with other measurements, with Audi-Wapstra systematics, and with predictions of mass formulas. Implications of this measurement are considered for the rp process.

  5. Test and evaluation of the dual-range coincidence counter at the Savannah River Plant

    SciTech Connect

    Ensslin, N.; Gibbs, A.; Denard, C.; Deason, P.

    1981-04-01

    This report describes the test and evaluation of a Los Alamos National Laboratory-designed dual-range neutron coincidence counter at the Savannah River Plant Separations Area. A variety of incoming plutonium metal and oxide shipments were assayed with the counter. Assay accuracies were 2% l sigma for pure metal, about 10% l sigma for impure metal, and 3% l sigma for oxide that was analyzed on a batch-by-batch basis.

  6. Coincident frequencies and relative phases among brain activity and hormonal signals.

    PubMed

    Solís-Ortíz, Silvia; Campos, Rafael G; Félix, Julián; Obregón, Octavio

    2009-03-14

    Fourier transform is a basic tool for analyzing biological signals and is computed for a finite sequence of data sample. The electroencephalographic (EEG) signals analyzed with this method provide only information based on the frequency range, for short periods. In some cases, for long periods it can be useful to know whether EEG signals coincide or have a relative phase between them or with other biological signals. Some studies have evidenced that sex hormones and EEG signals show oscillations in their frequencies across a period of 28 days; so it seems of relevance to seek after possible patterns relating EEG signals and endogenous sex hormones, assumed as long time-periodic functions to determine their typical periods, frequencies and relative phases. In this work we propose a method that can be used to analyze brain signals and hormonal levels and obtain frequencies and relative phases among them. This method involves the application of a discrete Fourier Transform on previously reported datasets of absolute power of brain signals delta, theta, alpha1, alpha2, beta1 and beta2 and the endogenous estrogen and progesterone levels along 28 days. Applying the proposed method to exemplary datasets and comparing each brain signal with both sex hormones signals, we found a characteristic profile of coincident periods and typical relative phases. For the corresponding coincident periods the progesterone seems to be essentially in phase with theta, alpha1, alpha2 and beta1, while delta and beta2 go oppositely. For the relevant coincident periods, the estrogen goes in phase with delta and theta and goes oppositely with alpha2. Findings suggest that the procedure applied here provides a method to analyze typical frequencies, or periods and phases between signals with the same period. It generates specific patterns for brain signals and hormones and relations among them.

  7. Coincidence of Incomplete Pentalogy of Cantrell and Meningomyelocele in a Dizygotic Twin Pregnancy

    PubMed Central

    Timur, Hakan; Bayram, Hatice; Şükran Çakar, Esra; Danışman, Nuri

    2015-01-01

    Pentalogy of Cantrell is an extremely rare and lethal syndrome. Ectopia cordis is frequently found in fetuses with POC but not required for incomplete forms. Likewise, meningomyelocele is a relatively uncommon neural tube defect affecting central nervous system and associated with neurological problems. Herein, we presented a woman with dizygotic twin pregnancy having coincidence of incomplete POC and MMC in each individual fetus, which has never been reported previously. PMID:26421202

  8. Interacting models may be key to solve the cosmic coincidence problem

    SciTech Connect

    Campo, Sergio del; Herrera, Ramon; Pavon, Diego E-mail: ramon.herrera@ucv.cl

    2009-01-15

    It is argued that cosmological models that feature a flow of energy from dark energy to dark matter may solve the coincidence problem of late acceleration (i.e., ''why the energy densities of both components are of the same order precisely today?{sup )}. However, much refined and abundant observational data of the redshift evolution of the Hubble factor are needed to ascertain whether they can do the job.

  9. Coincident frequencies and relative phases among brain activity and hormonal signals

    PubMed Central

    Solís-Ortíz, Silvia; Campos, Rafael G; Félix, Julián; Obregón, Octavio

    2009-01-01

    Background Fourier transform is a basic tool for analyzing biological signals and is computed for a finite sequence of data sample. The electroencephalographic (EEG) signals analyzed with this method provide only information based on the frequency range, for short periods. In some cases, for long periods it can be useful to know whether EEG signals coincide or have a relative phase between them or with other biological signals. Some studies have evidenced that sex hormones and EEG signals show oscillations in their frequencies across a period of 28 days; so it seems of relevance to seek after possible patterns relating EEG signals and endogenous sex hormones, assumed as long time-periodic functions to determine their typical periods, frequencies and relative phases. Methods In this work we propose a method that can be used to analyze brain signals and hormonal levels and obtain frequencies and relative phases among them. This method involves the application of a discrete Fourier Transform on previously reported datasets of absolute power of brain signals delta, theta, alpha1, alpha2, beta1 and beta2 and the endogenous estrogen and progesterone levels along 28 days. Results Applying the proposed method to exemplary datasets and comparing each brain signal with both sex hormones signals, we found a characteristic profile of coincident periods and typical relative phases. For the corresponding coincident periods the progesterone seems to be essentially in phase with theta, alpha1, alpha2 and beta1, while delta and beta2 go oppositely. For the relevant coincident periods, the estrogen goes in phase with delta and theta and goes oppositely with alpha2. Conclusion Findings suggest that the procedure applied here provides a method to analyze typical frequencies, or periods and phases between signals with the same period. It generates specific patterns for brain signals and hormones and relations among them. PMID:19284671

  10. Development of a TES-Based Anti-Coincidence Detector for Future X-Ray Observations

    NASA Technical Reports Server (NTRS)

    Bailey, Catherine N.; Adams, J. S.; Bandler, S. R.; Eckart, M. E.; Ewin, A. J.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. S.; Sadleir, J. E.; hide

    2012-01-01

    Microcalorimeters onboard future x-ray observatories require an anticoincidence detector to remove environmental backgrounds. In order to most effectively integrate this anti-coincidence detector with the main microcalorimeter array, both instruments should use similar read-out technology. The detectors used in the Cryogenic Dark Matter Search (CDMS) use a phonon measurement technique that is well suited for an anti-coincidence detector with a microcalorimeter array using SQUID readout. This technique works by using a transition-edge sensor (TES) connected to superconducting collection fins to measure the athermal phonon signal produced when an event occurs in the substrate crystal. Energy from the event propagates through the crystal to the superconducting collection fins, creating quasiparticles, which are then trapped as they enter the TES where they produce a signal. We are currently developing a prototype anti-coincidence detector for future x-ray missions and have recently fabricated test devices with Mo/Au TESs and Al collection fins. We present results from the first tests of these devices which indicate a proof of concept that quasiparticle trapping is occurring in these materials.

  11. Cognitive and motor aspects of a coincidence-timing task in Cerebral Palsy children.

    PubMed

    Olivier, I; Baker, C; Cordier, J; Thomann, G; Nougier, V

    2015-08-18

    Cerebral Palsy (CP) is a clinical syndrome involving postural and motor deficits. CP children are less accurate than healthy ones when trying to reach a target. Thus, it is difficult for CP children to perform anticipation-coincidence tasks requiring temporal and/or spatial accuracy to reach the target at the good place in the right time. The purpose of the present experiment was to further investigate CP children's ability to perform anticipation-coincidence tasks, by dissociating the cognitive from the motor aspects of the task. 11 CP children aged 6-14 years, 51 healthy children aged 6-13 years, and 13 healthy adults performed, as accurately as possible, a coincidence-timing in response to a specific sound of a musical sequence. Two experimental conditions were manipulated: In the verbal condition, temporal estimation occurred through a simple verbal response whereas in the motor condition, temporal estimation was performed by reaching a target at a self-paced velocity. In the verbal condition, CP children made similar temporal errors than their healthy counterpart. However, even though all participants underestimated stimulus occurrence, CP children also exhibited greater and more variable temporal errors when they provided a motor response for estimating stimulus occurrence. These data suggested that CP children were able to anticipate stimulus occurrence and to partially take into account their sensory-motor deficits to reach the target at this time occurrence.

  12. New approach to calculate the true-coincidence effect of HpGe detector

    SciTech Connect

    Alnour, I. A. E-mail: ibrahim.elnour@yahoo.com; Wagiran, H.; Ibrahim, N.; Hamzah, S.; Elias, M. S.; Siong, W. B.

    2016-01-22

    The corrections for true-coincidence effects in HpGe detector are important, especially at low source-to-detector distances. This work established an approach to calculate the true-coincidence effects experimentally for HpGe detectors of type Canberra GC3018 and Ortec GEM25-76-XLB-C, which are in operation at neutron activation analysis lab in Malaysian Nuclear Agency (NM). The correction for true-coincidence effects was performed close to detector at distances 2 and 5 cm using {sup 57}Co, {sup 60}Co, {sup 133}Ba and {sup 137}Cs as standard point sources. The correction factors were ranged between 0.93-1.10 at 2 cm and 0.97-1.00 at 5 cm for Canberra HpGe detector; whereas for Ortec HpGe detector ranged between 0.92-1.13 and 0.95-100 at 2 and 5 cm respectively. The change in efficiency calibration curve of the detector at 2 and 5 cm after correction was found to be less than 1%. Moreover, the polynomial parameters functions were simulated through a computer program, MATLAB in order to find an accurate fit to the experimental data points.

  13. Development of a TES-Based Anti-Coincidence Detector for Future X-ray Observatories

    NASA Technical Reports Server (NTRS)

    Bailey, Catherine

    2011-01-01

    Microcalorimeters onboard future x-ray observatories require an anti-coincidence detector to remove environmental backgrounds. In order to most effectively integrate this anticoincidence detector with the main microcalorimeter array, both instruments should use similar read-out technology. The detectors used in the Cryogenic Dark Matter Search (CDMS) use a phonon measurement technique that is well suited for an anti-coincidence detector with a microcalorimeter array using SQUID readout. This technique works by using a transition-edge sensor (TES) connected to superconducting collection fins to measure the athermal phonon signal produced when an event occurs in the substrate crystal. Energy from the event propagates through the crystal to the superconducting collection fins, creating quasiparticles, which are then trapped as they enter the TES where they produce a signal. We are currently developing a prototype anti-coincidence detector for future x-ray missions and have recently fabricated test devices with Mo/Au TESs and Al collection fins. We will present results from the first tests of these devices which indicate a proof of concept that quasiparticle trapping is occurring in these materials.

  14. Diversification of C(4) grasses (Poaceae) does not coincide with their ecological dominance.

    PubMed

    Bouchenak-Khelladi, Yanis; Slingsby, Jasper A; Verboom, G Anthony; Bond, William J

    2014-02-01

    The radiation of a lineage and its rise to ecological dominance are distinct phenomena and driven by different processes. For example, paleoecological data has been used to show that the Cretaceous angiosperm radiation did not coincide with their rise to dominance. Using a phylogenetic approach, we here explored the evolution of C4 grasses and evaluated whether the diversification of this group and its rise to ecological dominance in the late Miocene were decoupled. We assembled a matrix including 675 grass species of the PACMAD clade and 2784 characters (ITS and ndhF) to run a molecular dating analysis using three fossils as reference calibrations. We coded species as C3 vs. C4 and reconstructed ancestral states under maximum likelihood. We used the program BiSSE to test whether rates of diversification are correlated with photosynthetic pathway and whether the radiation of C4 lineages preceded or coincided with their rise to ecological dominance from ∼10 Ma. C4 grass lineages first originated around 35 Ma at the time of the Eocene-Oligocene transition. Accelerated diversification of C4 lineages did not coincide with their rise to ecological dominance. C4-dominated grasslands have expanded only since the Late Miocene and Pliocene. The initial diversification of their biotic elements can be tracked back as far as the Eocene-Oligocene transition. We suggest that shifts in taxonomic diversification and ecological dominance were stimulated by different factors, as in the case of the early angiosperms in the Cretaceous.

  15. Functional brain abnormalities localized in 55 chronic tinnitus patients: fusion of SPECT coincidence imaging and MRI.

    PubMed

    Farhadi, Mohammad; Mahmoudian, Saeid; Saddadi, Fariba; Karimian, Ali Reza; Mirzaee, Mohammad; Ahmadizadeh, Majid; Ghasemikian, Khosro; Gholami, Saeid; Ghoreyshi, Esmaeel; Beyty, Saeid; Shamshiri, Ahmadreza; Madani, Sedighe; Bakaev, Valery; Moradkhani, Seddighe; Raeisali, Gholamreza

    2010-04-01

    Tinnitus is often defined as the perception of sounds or noise in the absence of any external auditory stimuli. The pathophysiology of subjective idiopathic tinnitus remains unclear. The aim of this study was to investigate the functional brain activities and possible involved cerebral areas in subjective idiopathic tinnitus patients by means of single photon emission computerized tomography (SPECT) coincidence imaging, which was fused with magnetic resonance imaging (MRI). In this cross-sectional study, 56 patients (1 subject excluded) with subjective tinnitus and 8 healthy controls were enrolled. After intravenous injection of 5 mCi F18-FDG (fluorodeoxyglucose), all subjects underwent a brain SPECT coincidence scan, which was then superimposed on their MRIs. In the eight regions of interest (middle temporal, inferotemporal, medial temporal, lateral temporal, temporoparietal, frontal, frontoparietal, and parietal areas), the more pronounced values were represented in medial temporal, inferotemporal, and temporoparietal areas, which showed more important proportion of associative auditory cortices in functional attributions of tinnitus than primary auditory cortex. Brain coincidence SPECT scan, when fused on MRI is a valuable technique in the assessment of patients with tinnitus and could show the significant role of different regions of central nervous system in functional attributions of tinnitus.

  16. Functional brain abnormalities localized in 55 chronic tinnitus patients: fusion of SPECT coincidence imaging and MRI

    PubMed Central

    Farhadi, Mohammad; Mahmoudian, Saeid; Saddadi, Fariba; Karimian, Ali Reza; Mirzaee, Mohammad; Ahmadizadeh, Majid; Ghasemikian, Khosro; Gholami, Saeid; Ghoreyshi, Esmaeel; Beyty, Saeid; Shamshiri, Ahmadreza; Madani, Sedighe; Bakaev, Valery; Moradkhani, Seddighe; Raeisali, Gholamreza

    2010-01-01

    Tinnitus is often defined as the perception of sounds or noise in the absence of any external auditory stimuli. The pathophysiology of subjective idiopathic tinnitus remains unclear. The aim of this study was to investigate the functional brain activities and possible involved cerebral areas in subjective idiopathic tinnitus patients by means of single photon emission computerized tomography (SPECT) coincidence imaging, which was fused with magnetic resonance imaging (MRI). In this cross-sectional study, 56 patients (1 subject excluded) with subjective tinnitus and 8 healthy controls were enrolled. After intravenous injection of 5 mCi F18-FDG (fluorodeoxyglucose), all subjects underwent a brain SPECT coincidence scan, which was then superimposed on their MRIs. In the eight regions of interest (middle temporal, inferotemporal, medial temporal, lateral temporal, temporoparietal, frontal, frontoparietal, and parietal areas), the more pronounced values were represented in medial temporal, inferotemporal, and temporoparietal areas, which showed more important proportion of associative auditory cortices in functional attributions of tinnitus than primary auditory cortex. Brain coincidence SPECT scan, when fused on MRI is a valuable technique in the assessment of patients with tinnitus and could show the significant role of different regions of central nervous system in functional attributions of tinnitus. PMID:20068582

  17. Action-sound coincidence-related attenuation of auditory ERPs is not modulated by affordance compatibility.

    PubMed

    Horváth, János

    2013-04-01

    A couple of studies showed that auditory processing of sounds presented concurrently with one's own actions is attenuated. Because in these studies actions were key-presses, it was hypothesized that attenuation might be caused by robust key-press-effect associations formed by long-term interactions with everyday devices. Key-pressing may be special because most everyday devices are designed to comply with the perceived affordance that a key/button should be pressed to trigger an effect. Therefore, key-presses would attenuate auditory processing, but key-releases would not. In the present experiment, participants marked time intervals by pressing or releasing a key. Independently, a random sequence of tones was presented. Tones coinciding with a key-press or -release elicited similarly attenuated Tb, vertex N1, and P2 ERPs, suggesting that coincidence-related auditory attenuation is not brought about by special key-press-effect associations. Whereas Tb and P2 attenuations were pure amplitude modulations, vertex N1 was attenuated (partly) by an overlapping coincidence-related ERP.

  18. Triple-color coincidence analysis: one step further in following higher order molecular complex formation.

    PubMed

    Heinze, Katrin G; Jahnz, Michael; Schwille, Petra

    2004-01-01

    Confocal fluorescence spectroscopy is a versatile method for studying dynamics and interactions of biomolecules in their native environment with minimal interference with the observed system. Analyzing coincident fluctuations induced by single molecule movement in spectrally distinct detection channels, dual-color fluorescence cross-correlation, and coincidence analysis have proven most powerful for probing the formation or cleavage of molecular bonds in real time. The similarity of the optical setup with those used for laser scanning microscopy, as well as the non-invasiveness of the methods, make them easily adaptive for intracellular measurements, to observe the association and dissociation of biomolecules in situ. However, in contrast to standard fluorescence microscopy, where multiple fluorophores can be spectrally resolved, single molecule detection has so far been limited to dual-color detection systems due to the harsh requirements on detection sensitivity. In this study, we show that under certain experimental conditions, employing simultaneous two-photon excitation of three distinct dye species, their successful discrimination indeed becomes possible even on a single molecule level. This enables the direct observation of higher order molecular complex formation in the confocal volume. The theoretical concept of triple-color coincidence analysis is outlined in detail, along with an experimental demonstration of its principles utilizing a simple nucleic acid reaction system.

  19. Measuring the radium-226 activity using a multidetector gamma-ray coincidence spectrometer.

    PubMed

    Antovic, N; Svrkota, N

    2009-10-01

    The method is based on coincidence counting of the 609 keV photons from two-, three- and four-step cascade transitions which follow beta(-)-decay of (214)Bi, developed on the six-crystal spectrometer PRIPYAT-2M. As regards the determination of the activity of (226)Ra and its decay products, the double coincidences mode of counting is the optimum one because of the highest spectrometer sensitivity. Minimum detectable radium activity concentration in that mode of counting in a soil sample is estimated to be 0.68 Bq kg(-1) for live measuring time of 897.4s, while it was 2.03 Bq kg(-1) over 10 002.9s in the case of the HPGe spectrometer. Using the double coincidences method, the (226)Ra activity was determined in soil and sand samples from the Coastal region of Montenegro. The measurements were performed much faster than when an HPGe spectrometer is used, and the results showed relatively low level of the radium activity concentration.

  20. Modelling Random Coincidences in Positron Emission Tomography by Using Singles and Prompts: A Comparison Study

    PubMed Central

    2016-01-01

    Random coincidences degrade the image in Positron Emission Tomography, PET. To compensate for their degradation effects, the rate of random coincidences should be estimated. Under certain circumstances, current estimation methods fail to provide accurate results. We propose a novel method, “Singles–Prompts” (SP), that includes the information conveyed by prompt coincidences and models the pile–up. The SP method has the same structure than the well-known “Singles Rate” (SR) approach. Hence, SP can straightforwardly replace SR. In this work, the SP method has been extensively assessed and compared to two conventional methods, SR and the delayed window (DW) method, in a preclinical PET scenario using Monte–Carlo simulations. SP offers accurate estimates for the randoms rates, while SR and DW tend to overestimate the rates (∼10%, and 5%, respectively). With pile-up, the SP method is more robust than SR (but less than DW). At the image level, the contrast is overestimated in SR-corrected images, +16%, while SP produces the correct value. Spill–over is slightly reduced using SP instead of SR. The DW images values are similar to those of SP except for low-statistic scenarios, where DW behaves as if randoms were not compensated for. In particular, the contrast is reduced, −16%. In general, the better estimations of SP translate into better image quality. PMID:27603143

  1. Fast neutron detection with coincidence counting of recoil tracks in CR-39

    NASA Astrophysics Data System (ADS)

    Lengar, I.; Skvarč, J.; Ilić, R.

    2002-06-01

    Unpredictable background is often the major drawback in the assessment of low fluences of fast neutrons with solid state nuclear track detectors. The problem can be effectively solved by counting coincidence tracks in two detector foils that are in close contact during the irradiation. The detection of fast neutrons performed with a pair of CR-39 detector foils, subsequent chemical etching and evaluation of the etched tracks by an automatic track counting system was studied. After counting, only tracks produced by the same recoil nuclei in the surface layers of both detector foils were taken into account. In this way, the background due to objects that cannot be separated from tracks by an automatic counting system was drastically reduced. Emphasis was given to determining the properties of such a coincidence fast neutron detector based on utilisation of CR-39. The response of the coincidence detector was found to be 3×10 -5 tracks/neutron and is comparable with a detector based on counting tracks in a single foil of CR-39. The lower neutron detection limit was found to be 2×10 4 cm -2 with a counting area of 10 cm 2, and is two orders of magnitude lower than that obtained with a detector based on counting tracks in a single foil of CR-39.

  2. Development of a TES-Based Anti-Coincidence Detector for Future X-Ray Observations

    NASA Technical Reports Server (NTRS)

    Bailey, Catherine N.; Adams, J. S.; Bandler, S. R.; Eckart, M. E.; Ewin, A. J.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. S.; Sadleir, J. E.; Smith, S. J.; Sultana, M.

    2012-01-01

    Microcalorimeters onboard future x-ray observatories require an anticoincidence detector to remove environmental backgrounds. In order to most effectively integrate this anti-coincidence detector with the main microcalorimeter array, both instruments should use similar read-out technology. The detectors used in the Cryogenic Dark Matter Search (CDMS) use a phonon measurement technique that is well suited for an anti-coincidence detector with a microcalorimeter array using SQUID readout. This technique works by using a transition-edge sensor (TES) connected to superconducting collection fins to measure the athermal phonon signal produced when an event occurs in the substrate crystal. Energy from the event propagates through the crystal to the superconducting collection fins, creating quasiparticles, which are then trapped as they enter the TES where they produce a signal. We are currently developing a prototype anti-coincidence detector for future x-ray missions and have recently fabricated test devices with Mo/Au TESs and Al collection fins. We present results from the first tests of these devices which indicate a proof of concept that quasiparticle trapping is occurring in these materials.

  3. A theoretical basis for the analysis of redundant software subject to coincident errors

    NASA Technical Reports Server (NTRS)

    Eckhardt, D. E., Jr.; Lee, L. D.

    1985-01-01

    Fundamental to the development of redundant software techniques fault-tolerant software, is an understanding of the impact of multiple-joint occurrences of coincident errors. A theoretical basis for the study of redundant software is developed which provides a probabilistic framework for empirically evaluating the effectiveness of the general (N-Version) strategy when component versions are subject to coincident errors, and permits an analytical study of the effects of these errors. The basic assumptions of the model are: (1) independently designed software components are chosen in a random sample; and (2) in the user environment, the system is required to execute on a stationary input series. The intensity of coincident errors, has a central role in the model. This function describes the propensity to introduce design faults in such a way that software components fail together when executing in the user environment. The model is used to give conditions under which an N-Version system is a better strategy for reducing system failure probability than relying on a single version of software. A condition which limits the effectiveness of a fault-tolerant strategy is studied, and it is posted whether system failure probability varies monotonically with increasing N or whether an optimal choice of N exists.

  4. A model of spike-timing dependent plasticity: one or two coincidence detectors?

    PubMed

    Karmarkar, Uma R; Buonomano, Dean V

    2002-07-01

    In spike-timing dependent plasticity (STDP), synapses exhibit LTD or LTP depending on the order of activity in the presynaptic and postsynaptic cells. LTP occurs when a single presynaptic spike precedes a postsynaptic one (a positive interspike interval, or ISI), while the reverse order of activity (a negative ISI) produces LTD. A fundamental question is whether the "standard model" of plasticity in which moderate increases in Ca(2+) influx through the N-methyl-D-aspartate (NMDA) channels induce LTD and large increases induce LTP, can account for the order and interval sensitivity of STDP. To examine this issue we developed a model that captures postsynaptic Ca(2+) influx dynamics and the associativity of the NMDA receptors. While this model can generate both LTD and LTP, it predicts that LTD will be observed at both negative and positive ISIs. This is because longer and longer positive ISIs induce monotonically decreasing levels of Ca(2+), which eventually fall into the same range that produced LTD at negative ISIs. A second model that incorporated a second coincidence detector in addition to the NMDA receptor generated LTP at positive intervals and LTD only at negative ones. Our findings suggest that a single coincidence detector model based on the standard model of plasticity cannot account for order-specific STDP, and we predict that STDP requires two coincidence detectors.

  5. ION SWITCH

    DOEpatents

    Cook, B.

    1959-02-10

    An ion switch capable of transferring large magnitudes of power is described. An ion switch constructed in accordance with the invention includes a pair of spaced control electrodes disposed in a highly evacuated region for connection in a conventional circuit to control the passing of power therethrough. A controllable ionic conduction path is provided directiy between the control electrodes by a source unit to close the ion switch. Conventional power supply means are provided to trigger the source unit and control the magnitude, durations and pulse repetition rate of the aforementioned ionic conduction path.

  6. Effect of inter-crystal scatter on estimation methods for random coincidences and subsequent correction.

    PubMed

    Torres-Espallardo, I; Rafecas, M; Spanoudaki, V; McElroy, D P; Ziegler, S I

    2008-05-07

    Random coincidences can contribute substantially to the background in positron emission tomography (PET). Several estimation methods are being used for correcting them. The goal of this study was to investigate the validity of techniques for random coincidence estimation, with various low-energy thresholds (LETs). Simulated singles list-mode data of the MADPET-II small animal PET scanner were used as input. The simulations have been performed using the GATE simulation toolkit. Several sources with different geometries have been employed. We evaluated the number of random events using three methods: delayed window (DW), singles rate (SR) and time histogram fitting (TH). Since the GATE simulations allow random and true coincidences to be distinguished, a comparison between the number of random coincidences estimated using the standard methods and the number obtained using GATE was performed. An overestimation in the number of random events was observed using the DW and SR methods. This overestimation decreases for LETs higher than 255 keV. It is additionally reduced when the single events which have undergone a Compton interaction in crystals before being detected are removed from the data. These two observations lead us to infer that the overestimation is due to inter-crystal scatter. The effect of this mismatch in the reconstructed images is important for quantification because it leads to an underestimation of activity. This was shown using a hot-cold-background source with 3.7 MBq total activity in the background region and a 1.59 MBq total activity in the hot region. For both 200 keV and 400 keV LET, an overestimation of random coincidences for the DW and SR methods was observed, resulting in approximately 1.5% or more (at 200 keV LET: 1.7% for DW and 7% for SR) and less than 1% (at 400 keV LET: both methods) underestimation of activity within the background region. In almost all cases, images obtained by compensating for random events in the reconstruction

  7. USING A PHENOMENOLOGICAL MODEL TO TEST THE COINCIDENCE PROBLEM OF DARK ENERGY

    SciTech Connect

    Chen Yun; Zhu Zonghong; Alcaniz, J. S.; Gong Yungui

    2010-03-01

    By assuming a phenomenological form for the ratio of the dark energy and matter densities rho{sub X} {proportional_to} rho{sub m} a {sup x}i, we discuss the cosmic coincidence problem in light of current observational data. Here, xi is a key parameter to denote the severity of the coincidence problem. In this scenario, xi = 3 and xi = 0 correspond to LAMBDACDM and the self-similar solution without the coincidence problem, respectively. Hence, any solution with a scaling parameter 0 < xi < 3 makes the coincidence problem less severe. In addition, the standard cosmology without interaction between dark energy and dark matter is characterized by xi + 3omega{sub X} = 0, where omega{sub X} is the equation of state of the dark energy component, whereas the inequality xi + 3omega{sub X} {ne} 0 represents non-standard cosmology. We place observational constraints on the parameters (OMEGA{sub X,0}, omega{sub X}, xi) of this model, where OMEGA{sub X,0} is the present value of density parameter of dark energy OMEGA{sub X}, by using the Constitution Set (397 supernovae of type Ia data, hereafter SNeIa), the cosmic microwave background shift parameter from the five-year Wilkinson Microwave Anisotropy Probe and the Sloan Digital Sky Survey baryon acoustic peak. Combining the three samples, we get OMEGA{sub X,0} = 0.72 +- 0.02, omega{sub X} = -0.98 +- 0.07, and xi = 3.06 +- 0.35 at 68.3% confidence level. The result shows that the LAMBDACDM model still remains a good fit to the recent observational data, and the coincidence problem indeed exists and is quite severe, in the framework of this simple phenomenological model. We further constrain the model with the transition redshift (deceleration/acceleration). It shows that if the transition from deceleration to acceleration happens at the redshift z > 0.73, within the framework of this model, we can conclude that the interaction between dark energy and dark matter is necessary.

  8. Background Count Rates and the Anti-Coincidence Detector on the Instrument on Astro-E2

    NASA Technical Reports Server (NTRS)

    Kilbourne, C. A.

    2004-01-01

    Minimum ionizing particles incident on the XRS microcalorimeter array will deposit energy in the pixels on the same scale as an x-ray photon and would be confused with x-rays without an anti-coincidence detector. The XRS anti-coincidence detector is a silicon ionization detector placed directly behind the calorimeter array. Given an isotropic particle flux, 98% of those particles that pass through a calorimeter pixel will also deposit energy in the anti-coincidence detector. Particle events that are not rejected by coincidence are those that pass through at small angles relative to the plane of the array, and thus deposit more energy. Modeling with GEANT4 showed that only 0.1% of all protons incident on the array miss the anti-coincidence detector yet deposit less than 10 keV in a pixel. The unrejected background will thus be dominated by secondary events; we will provide an estimate of this rate. Protons incident on the thick silicon frame around the active area of the array deposit enough energy t o heat the whole chip slightly. This results in small simultaneous pulses on multiple pixels. These can be easily rejected by pixel-to-pixel coincidence. We will discuss the impact of these events on the instrument dead time and will present the expected rate. We will present laboratory background data demonstrating the performance of the anti-coincidence detector and the effectiveness of coincidence analysis in the laboratory environment.

  9. Walther Bothe and Bruno Rossi: The birth and development of coincidence methods in cosmic-ray physics

    NASA Astrophysics Data System (ADS)

    Bonolis, Luisa

    2011-11-01

    In 1924, Walther Bothe and Hans Geiger applied a coincidence method to the study of Compton scattering with Geiger needle counters. Their experiment confirmed the existence of radiation quanta and established the validity of conservation principles in elementary processes. At the end of the 1920s, Bothe and Werner Kolhörster coupled the coincidence technique with the new Geiger-Müller counter to study cosmic rays, marking the start of cosmic-ray research as a branch of physics. The coincidence method was further refined by Bruno Rossi, who developed a vacuum-tube device capable of registering the simultaneous occurrence of electrical pulses from any number of counters with a tenfold improvement in time resolution. The electronic coincidence circuit bearing Rossi's name was instrumental in his research on the corpuscular nature and the properties of cosmic radiation during the early 1930s, a period characterized by a lively debate between Millikan and followers of the corpuscular interpretation. The Rossi coincidence circuit was also at the core of the counter-controlled cloud chamber developed by Patrick Blackett and Giuseppe Occhialini, and became one of the important ingredients of particle and nuclear physics. During the late 1930s and 1940s, coincidences, anti-coincidences and delayed coincidences played a crucial role in a series of experiments on the decay of the muon, which inaugurated the current era of particle physics.

  10. Ion focusing

    DOEpatents

    Cooks, Robert Graham; Baird, Zane; Peng, Wen-Ping

    2017-01-17

    The invention generally relates to apparatuses for focusing ions at or above ambient pressure and methods of use thereof. In certain embodiments, the invention provides an apparatus for focusing ions that includes an electrode having a cavity, at least one inlet within the electrode configured to operatively couple with an ionization source, such that discharge generated by the ionization source is injected into the cavity of the electrode, and an outlet. The cavity in the electrode is shaped such that upon application of voltage to the electrode, ions within the cavity are focused and directed to the outlet, which is positioned such that a proximal end of the outlet receives the focused ions and a distal end of the outlet is open to ambient pressure.

  11. ION SOURCE

    DOEpatents

    Leland, W.T.

    1960-01-01

    The ion source described essentially eliminater the problem of deposits of nonconducting materials forming on parts of the ion source by certain corrosive gases. This problem is met by removing both filament and trap from the ion chamber, spacing them apart and outside the chamber end walls, placing a focusing cylinder about the filament tip to form a thin collimated electron stream, aligning the cylinder, slits in the walls, and trap so that the electron stream does not bombard any part in the source, and heating the trap, which is bombarded by electrons, to a temperature hotter than that in the ion chamber, so that the tendency to build up a deposit caused by electron bombardment is offset by the extra heating supplied only to the trap.

  12. ION SOURCE

    DOEpatents

    Blue, C.W.; Luce, J.S.

    1960-07-19

    An ion source is described and comprises an arc discharge parallel to the direction of and inside of a magnetic field. an accelerating electrode surrounding substantially all of the discharge except for ion exit apertures, and means for establishing an electric field between that electrode and the arc discharge. the electric field being oriented at an acute angle to the magnetic field. Ions are drawn through the exit apertures in the accelrating electrcde in a direction substantially divergent to the direction of the magnetic field and so will travel in a spiral orbit along the magnetic field such that the ions will not strike the source at any point in their orbit within the magnetic field.

  13. Ion focusing

    SciTech Connect

    Cooks, Robert Graham; Baird, Zane; Peng, Wen-Ping

    2015-11-10

    The invention generally relates to apparatuses for focusing ions at or above ambient pressure and methods of use thereof. In certain embodiments, the invention provides an apparatus for focusing ions that includes an electrode having a cavity, at least one inlet within the electrode configured to operatively couple with an ionization source, such that discharge generated by the ionization source is injected into the cavity of the electrode, and an outlet. The cavity in the electrode is shaped such that upon application of voltage to the electrode, ions within the cavity are focused and directed to the outlet, which is positioned such that a proximal end of the outlet receives the focused ions and a distal end of the outlet is open to ambient pressure.

  14. Mössbauer spectra obtained using β - γ coincidence method after 57Mn implantation into LiH and LiD

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Kobayashi, Y.; Yamada, Y.; Kubo, M. K.; Mihara, M.; Nagatomo, T.; Sato, W.; Miyazaki, J.; Tanigawa, S.; Natori, D.; Sato, S.; Kitagawa, A.

    2016-12-01

    Highly energetic 57Mn ( T 1/2 = 1.45 m) was generated by nuclear projectile fragmentation in a heavy-ion accelerator, and implanted into lithium hydride (LiH) and lithium deuteride (LiD) at 578 K. Mössbauer spectroscopy with β - γ coincidence detection was then carried out on the 57Fe obtained from β -decay of the 57Mn to study the time dependence of the site distributions and coordination environments of dilute Fe atoms implanted in the LiH and LiD. The results suggest that the Fe atoms can substitute for either the Li and H or D atoms within 100 ns. Additionally, the displacement behavior of the substitutional 57Fe atoms on the lattice sites is discussed.

  15. Dissociative Ionization Mechanism and Appearance Energies in Adipic Acid Revealed by Imaging Photoelectron Photoion Coincidence, Selective Deuteration, and Calculations.

    PubMed

    Heringa, Maarten F; Slowik, Jay G; Prévôt, André S H; Baltensperger, Urs; Hemberger, Patrick; Bodi, Andras

    2016-05-26

    Adipic acid, a model compound for oxygenated organic aerosol, has been studied at the VUV beamline of the Swiss Light Source. Internal energy selected cations were prepared by threshold photoionization using vacuum ultraviolet synchrotron radiation and imaging photoelectron photoion coincidence spectroscopy (iPEPICO). The threshold photoelectron spectrum yields a vertical ionization energy (IE) of 10.5 eV, significantly above the calculated adiabatic IE of 8.6 eV. The cationic minimum is accessible after vertical ionization by H-transfer from one of the γ-carbons to a carbonyl oxygen and is sufficiently energetic to decay by water loss at the ionization onset. The slope of the breakdown curves, quantum chemical calculations, and selective deuteration of the carboxylic hydrogens establish the dissociative photoionization mechanism. After ionization, one γ-methylene hydrogen and the two carboxylic hydrogens are randomized prior to H2O loss. On the basis of the deuteration degree in the H2O + CO-loss product at higher energies, a direct water-loss channel without complete randomization also exists. The breakdown diagram and center of gravity of the H2O + CO-loss peak were modeled to obtain 0 K appearance energies of 10.77, 10.32, and 11.53 eV for H2O + CO loss, CH2COOH loss, and H2O + CH2COOH loss from adipic acid. These agree well with the CBS-QB3 calculated values of 10.68, 10.45, and 11.57 eV, respectively, which shows that threshold photoionization can yield energetics data as long as the dissociation is statistical, even when the parent ion cannot be observed. The results can be used as a starting point for a deeper understanding of the ionization and low-energy fragmentation of organic aerosol components.

  16. Coincidence Lattices and Interlayer Twist in van der Waals Heterostructures: Application of the Coincidence Lattice Method on \\hbox {hBN/MoSe}_2 Heterobilayer Systems

    NASA Astrophysics Data System (ADS)

    Koda, Daniel S.; Bechstedt, Friedhelm; Marques, Marcelo; Teles, Lara K.

    2017-07-01

    Van der Waals heterostructures have great potential in large-scale integration devices and exploration of new physics. Experimental investigations allow flexible combinations of two-dimensional crystals in device fabrications. Theory, however, has limitations of supercell sizes and commensurability, translated into computational effort. In this work, we demonstrate the application of the coincidence lattice method to simulate two \\hbox {hBN/MoSe}_2 heterobilayers taking interlayer twist effects into account. We predict that both systems are stable upon contact and interact via van der Waals dispersions. We found that electronic properties of \\hbox {MoSe}_2 are preserved for both simulated systems, but hBN suffers from the increase of interface interactions, as evidenced by band structures and density of states calculations. Finally, band discontinuities are obtained and charge transfer arguments explain small shifts in band offsets with respect to natural alignments. We conclude that hBN is a reasonable substrate for preserving useful properties of \\hbox {MoSe}_2 for application in electronic and optoelectronic devices, and that interlayer twist angles play a significant role in the physics of van der Waals heterostructures.

  17. Coincidence detection of convergent perforant path and mossy fibre inputs by CA3 interneurons

    PubMed Central

    Calixto, Eduardo; Galván, Emilio J; Card, J Patrick; Barrionuevo, Germán

    2008-01-01

    We performed whole-cell recordings from CA3 s. radiatum (R) and s. lacunosum-moleculare (L-M) interneurons in hippocampal slices to examine the temporal aspects of summation of converging perforant path (PP) and mossy fibre (MF) inputs. PP EPSPs were evoked from the s. lacunosum-moleculare in area CA1. MF EPSPs were evoked from the medial extent of the suprapyramidal blade of the dentate gyrus. Summation was strongly supralinear when examining PP EPSP with MF EPSP in a heterosynaptic pair at the 10 ms ISI, and linear to sublinear at longer ISIs. This pattern of nonlinearities suggests that R and L-M interneurons act as coincidence detectors for input from PP and MF. Summation at all ISIs was linear in voltage clamp mode demonstrating that nonlinearities were generated by postsynaptic voltage-dependent conductances. Supralinearity was not detected when the first EPSP in the pair was replaced by a simulated EPSP injected into the soma, suggesting that the conductances underlying the EPSP boosting were located in distal dendrites. Supralinearity was selectively eliminated with either Ni2+ (30 μm), mibefradil (10 μm) or nimodipine (15 μm), but was unaffected by QX-314. This pharmacological profile indicates that supralinearity is due to recruitment of dendritic T-type Ca2+channels by the first subthreshold EPSP in the pair. Results with the hyperpolarization-activated (Ih) channel blocker ZD 7288 (50 μm) revealed that Ih restricted the time course of supralinearity for coincidently summed EPSPs, and promoted linear to sublinear summation for asynchronous EPSPs. We conclude that coincidence detection results from the counterbalanced activation of T-type Ca2+ channels and inactivation of Ih. PMID:18388134

  18. Coincidence detection of convergent perforant path and mossy fibre inputs by CA3 interneurons.

    PubMed

    Calixto, Eduardo; Galván, Emilio J; Card, J Patrick; Barrionuevo, Germán

    2008-06-01

    We performed whole-cell recordings from CA3 s. radiatum (R) and s. lacunosum-moleculare (L-M) interneurons in hippocampal slices to examine the temporal aspects of summation of converging perforant path (PP) and mossy fibre (MF) inputs. PP EPSPs were evoked from the s. lacunosum-moleculare in area CA1. MF EPSPs were evoked from the medial extent of the suprapyramidal blade of the dentate gyrus. Summation was strongly supralinear when examining PP EPSP with MF EPSP in a heterosynaptic pair at the 10 ms ISI, and linear to sublinear at longer ISIs. This pattern of nonlinearities suggests that R and L-M interneurons act as coincidence detectors for input from PP and MF. Summation at all ISIs was linear in voltage clamp mode demonstrating that nonlinearities were generated by postsynaptic voltage-dependent conductances. Supralinearity was not detected when the first EPSP in the pair was replaced by a simulated EPSP injected into the soma, suggesting that the conductances underlying the EPSP boosting were located in distal dendrites. Supralinearity was selectively eliminated with either Ni2+ (30 microm), mibefradil (10 microm) or nimodipine (15 microm), but was unaffected by QX-314. This pharmacological profile indicates that supralinearity is due to recruitment of dendritic T-type Ca2+channels by the first subthreshold EPSP in the pair. Results with the hyperpolarization-activated (Ih) channel blocker ZD 7288 (50 microm) revealed that Ih restricted the time course of supralinearity for coincidently summed EPSPs, and promoted linear to sublinear summation for asynchronous EPSPs. We conclude that coincidence detection results from the counterbalanced activation of T-type Ca2+ channels and inactivation of Ih.

  19. Phasic Firing and Coincidence Detection by Subthreshold Negative Feedback: Divisive or Subtractive or, Better, Both

    PubMed Central

    Huguet, Gemma; Meng, Xiangying; Rinzel, John

    2017-01-01

    Phasic neurons typically fire only for a fast-rising input, say at the onset of a step current, but not for steady or slow inputs, a property associated with type III excitability. Phasic neurons can show extraordinary temporal precision for phase locking and coincidence detection. Exemplars are found in the auditory brain stem where precise timing is used in sound localization. Phasicness at the cellular level arises from a dynamic, voltage-gated, negative feedback that can be recruited subthreshold, preventing the neuron from reaching spike threshold if the voltage does not rise fast enough. We consider two mechanisms for phasicness: a low threshold potassium current (subtractive mechanism) and a sodium current with subthreshold inactivation (divisive mechanism). We develop and analyze three reduced models with either divisive or subtractive mechanisms or both to gain insight into the dynamical mechanisms for the potentially high temporal precision of type III-excitable neurons. We compare their firing properties and performance for a range of stimuli. The models have characteristic non-monotonic input-output relations, firing rate vs. input intensity, for either stochastic current injection or Poisson-timed excitatory synaptic conductance trains. We assess performance according to precision of phase-locking and coincidence detection by the models' responses to repetitive packets of unitary excitatory synaptic inputs with more or less temporal coherence. We find that each mechanism contributes features but best performance is attained if both are present. The subtractive mechanism confers extraordinary precision for phase locking and coincidence detection but only within a restricted parameter range when the divisive mechanism of sodium inactivation is inoperative. The divisive mechanism guarantees robustness of phasic properties, without compromising excitability, although with somewhat less precision. Finally, we demonstrate that brief transient inhibition if

  20. A near-infrared SETI experiment: probability distribution of false coincidences

    NASA Astrophysics Data System (ADS)

    Maire, Jérôme; Wright, Shelley A.; Werthimer, Dan; Treffers, Richard R.; Marcy, Geoffrey W.; Stone, Remington P. S.; Drake, Frank; Siemion, Andrew

    2014-07-01

    A Search for Extraterrestrial Life (SETI), based on the possibility of interstellar communication via laser signals, is being designed to extend the search into the near-infrared spectral region (Wright et al, this conference). The dedicated near-infrared (900 to 1700 nm) instrument takes advantage of a new generation of avalanche photodiodes (APD), based on internal discrete amplification. These discrete APD (DAPD) detectors have a high speed response (< 1 GHz) and gain comparable to photomultiplier tubes, while also achieving significantly lower noise than previous APDs. We are investigating the use of DAPD detectors in this new astronomical instrument for a SETI search and transient source observations. We investigated experimentally the advantages of using a multiple detector device operating in parallel to remove spurious signals. We present the detector characterization and performance of the instrument in terms of false positive detection rates both theoretically and empirically through lab measurements. We discuss the required criteria that will be needed for laser light pulse detection in our experiment. These criteria are defined to optimize the trade between high detection efficiency and low false positive coincident signals, which can be produced by detector dark noise, background light, cosmic rays, and astronomical sources. We investigate experimentally how false coincidence rates depend on the number of detectors in parallel, and on the signal pulse height and width. We also look into the corresponding threshold to each of the signals to optimize the sensitivity while also reducing the false coincidence rates. Lastly, we discuss the analytical solution used to predict the probability of laser pulse detection with multiple detectors.

  1. Coinciding exercise with peak serum caffeine does not improve cycling performance.

    PubMed

    Skinner, Tina L; Jenkins, David G; Taaffe, Dennis R; Leveritt, Michael D; Coombes, Jeff S

    2013-01-01

    To investigate whether coinciding peak serum caffeine concentration with the onset of exercise enhances subsequent endurance performance. Randomised, double-blind, crossover. In this randomised, placebo-controlled, double-blind crossover study, 14 male trained cyclists and triathletes (age 31±5year, body mass 75.4±5.7 kg, VO₂max 69.5±6.1 mL kg⁻¹ min⁻¹ and peak power output 417±35W, mean±SD) consumed 6 mg kg(-1) caffeine or a placebo either 1h (C(1h)) prior to completing a 40 km time trial or when the start of exercise coincided with individual peak serum caffeine concentrations (C(peak)). C(peak) was determined from a separate 'caffeine profiling' session that involved monitoring caffeine concentrations in the blood every 30 min over a 4h period. Following caffeine ingestion, peak serum caffeine occurred 120 min in 12 participants and 150 min in 2 participants. Time to complete the 40 km time trial was significantly faster (2.0%; p=0.002) in C(1h) compared to placebo. No statistically significant improvement in performance was noted in the C(peak) trial versus placebo (1.1%; p=0.240). Whilst no differences in metabolic markers were found between C(peak) and placebo conditions, plasma concentrations of glucose (p=0.005), norepinephrine and epinephrine (p≤0.002) were higher in the C(1h) trial 6 min post-exercise versus placebo. In contrast to coinciding peak serum caffeine concentration with exercise onset, caffeine consumed 60 min prior to exercise resulted in significant improvements in 40 km time trial performance. The ergogenic effect of caffeine was not found to be related to peak caffeine concentration in the blood at the onset of endurance exercise. Copyright © 2012 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  2. Preliminary study for the development of a tweezers-type coincidence detector for tumor detection

    NASA Astrophysics Data System (ADS)

    Yamamoto, Seiichi; Higashi, Tatsuya; Matsumoto, Keiichi; Senda, Michio

    2005-08-01

    We have conducted a preliminary study for development of a tweezer-type coincidence detector for tumor detection in procedures such as FDG-guided surgery. The detector consists of a pair of LSO scintillators, optical fibers, a pair of photo-multiplier tubes (PMTs), and a coincidence circuit. Because the LSO scintillators are located on the tips of tweezers, a target organ such as a lymph node or the colon can be positioned between them. The size of a single LSO was 3.7 mm×3.7 mm×10 mm, and the scintillation photons are transferred to the PMTs via 2-mm-diameter, 1-m long optical fibers. The results show that the light loss due to the fiber was significant but there was sufficient light to observe the photo-peak of the 511-keV gamma photons. Sensitivity response function perpendicular to the detector has a full-width at half-maximum (FWHM) of 2.5 mm, while that parallel to the detector has a FWHM of 5.5 mm. Background counts due to the natural radioisotope in 176Lu can be observed when the distance between these two scintillators is small. Results also show that the absolute sensitivity was 0.057% at the center of the detector when the two LSOs were 10 mm apart and that the optical fiber was insensitive to bending up to a radius of 10 cm. From these results, we conclude that the proposed tweezers-type coincidence detector could be some interest for tumor detection using FDG, such as that in radio-guided surgery.

  3. A simultaneous beta and coincidence-gamma imaging system for plant leaves.

    PubMed

    Ranjbar, Homayoon; Wen, Jie; Mathews, Aswin J; Komarov, Sergey; Wang, Qiang; Li, Ke; O'Sullivan, Joseph A; Tai, Yuan-Chuan

    2016-05-07

    Positron emitting isotopes, such as (11)C, (13)N, and (18)F, can be used to label molecules. The tracers, such as (11)CO2, are delivered to plants to study their biological processes, particularly metabolism and photosynthesis, which may contribute to the development of plants that have a higher yield of crops and biomass. Measurements and resulting images from PET scanners are not quantitative in young plant structures or in plant leaves due to poor positron annihilation in thin objects. To address this problem we have designed, assembled, modeled, and tested a nuclear imaging system (simultaneous beta-gamma imager). The imager can simultaneously detect positrons ([Formula: see text]) and coincidence-gamma rays (γ). The imaging system employs two planar detectors; one is a regular gamma detector which has a LYSO crystal array, and the other is a phoswich detector which has an additional BC-404 plastic scintillator for beta detection. A forward model for positrons is proposed along with a joint image reconstruction formulation to utilize the beta and coincidence-gamma measurements for estimating radioactivity distribution in plant leaves. The joint reconstruction algorithm first reconstructs beta and gamma images independently to estimate the thickness component of the beta forward model and afterward jointly estimates the radioactivity distribution in the object. We have validated the physics model and reconstruction framework through a phantom imaging study and imaging a tomato leaf that has absorbed (11)CO2. The results demonstrate that the simultaneously acquired beta and coincidence-gamma data, combined with our proposed joint reconstruction algorithm, improved the quantitative accuracy of estimating radioactivity distribution in thin objects such as leaves. We used the structural similarity (SSIM) index for comparing the leaf images from the simultaneous beta-gamma imager with the ground truth image. The jointly reconstructed images yield SSIM indices of 0

  4. A simultaneous beta and coincidence-gamma imaging system for plant leaves

    NASA Astrophysics Data System (ADS)

    Ranjbar, Homayoon; Wen, Jie; Mathews, Aswin J.; Komarov, Sergey; Wang, Qiang; Li, Ke; O'Sullivan, Joseph A.; Tai, Yuan-Chuan

    2016-05-01

    Positron emitting isotopes, such as 11C, 13N, and 18F, can be used to label molecules. The tracers, such as 11CO2, are delivered to plants to study their biological processes, particularly metabolism and photosynthesis, which may contribute to the development of plants that have a higher yield of crops and biomass. Measurements and resulting images from PET scanners are not quantitative in young plant structures or in plant leaves due to poor positron annihilation in thin objects. To address this problem we have designed, assembled, modeled, and tested a nuclear imaging system (simultaneous beta-gamma imager). The imager can simultaneously detect positrons ({β+} ) and coincidence-gamma rays (γ). The imaging system employs two planar detectors; one is a regular gamma detector which has a LYSO crystal array, and the other is a phoswich detector which has an additional BC-404 plastic scintillator for beta detection. A forward model for positrons is proposed along with a joint image reconstruction formulation to utilize the beta and coincidence-gamma measurements for estimating radioactivity distribution in plant leaves. The joint reconstruction algorithm first reconstructs beta and gamma images independently to estimate the thickness component of the beta forward model and afterward jointly estimates the radioactivity distribution in the object. We have validated the physics model and reconstruction framework through a phantom imaging study and imaging a tomato leaf that has absorbed 11CO2. The results demonstrate that the simultaneously acquired beta and coincidence-gamma data, combined with our proposed joint reconstruction algorithm, improved the quantitative accuracy of estimating radioactivity distribution in thin objects such as leaves. We used the structural similarity (SSIM) index for comparing the leaf images from the simultaneous beta-gamma imager with the ground truth image. The jointly reconstructed images yield SSIM indices of 0.69 and 0.63, whereas the

  5. Convex Optimization of Coincidence Time Resolution for a High-Resolution PET System

    PubMed Central

    Reynolds, Paul D.; Olcott, Peter D.; Pratx, Guillem; Lau, Frances W. Y.

    2013-01-01

    We are developing a dual panel breast-dedicated positron emission tomography (PET) system using LSO scintillators coupled to position sensitive avalanche photodiodes (PSAPD). The charge output is amplified and read using NOVA RENA-3 ASICs. This paper shows that the coincidence timing resolution of the RENA-3 ASIC can be improved using certain list-mode calibrations. We treat the calibration problem as a convex optimization problem and use the RENA-3’s analog-based timing system to correct the measured data for time dispersion effects from correlated noise, PSAPD signal delays and varying signal amplitudes. The direct solution to the optimization problem involves a matrix inversion that grows order (n3) with the number of parameters. An iterative method using single-coordinate descent to approximate the inversion grows order (n). The inversion does not need to run to convergence, since any gains at high iteration number will be low compared to noise amplification. The system calibration method is demonstrated with measured pulser data as well as with two LSO-PSAPD detectors in electronic coincidence. After applying the algorithm, the 511 keV photopeak paired coincidence time resolution from the LSO-PSAPD detectors under study improved by 57%, from the raw value of 16.3 ± 0.07 ns full-width at half-maximum (FWHM) to 6.92 ± 0.02 ns FWHM (11.52 ± 0.05 ns to 4.89 ± 0.02 ns for unpaired photons). PMID:20876008

  6. Utilization of coincidence criteria in absolute length measurements by optical interferometry in vacuum and air

    NASA Astrophysics Data System (ADS)

    Schödel, R.

    2015-08-01

    Traceability of length measurements to the international system of units (SI) can be realized by using optical interferometry making use of well-known frequencies of monochromatic light sources mentioned in the Mise en Pratique for the realization of the metre. At some national metrology institutes, such as Physikalisch-Technische Bundesanstalt (PTB) in Germany, the absolute length of prismatic bodies (e.g. gauge blocks) is realized by so-called gauge-block interference comparators. At PTB, a number of such imaging phase-stepping interference comparators exist, including specialized vacuum interference comparators, each equipped with three highly stabilized laser light sources. The length of a material measure is expressed as a multiple of each wavelength. The large number of integer interference orders can be extracted by the method of exact fractions in which the coincidence of the lengths resulting from the different wavelengths is utilized as a criterion. The unambiguous extraction of the integer interference orders is an essential prerequisite for correct length measurements. This paper critically discusses coincidence criteria and their validity for three modes of absolute length measurements: 1) measurements under vacuum in which the wavelengths can be identified with the vacuum wavelengths, 2) measurements under air in which the air refractive index is obtained from environmental parameters using an empirical equation, and 3) measurements under air in which the air refractive index is obtained interferometrically by utilizing a vacuum cell placed along the measurement pathway. For case 3), which corresponds to PTB’s Kösters-Comparator for long gauge blocks, the unambiguous determination of integer interference orders related to the air refractive index could be improved by about a factor of ten when an ‘overall dispersion value,’ suggested in this paper, is used as coincidence criterion.

  7. Pathological α-synuclein Distribution in Subjects with Coincident Alzheimer’s and Lewy Body Pathology

    PubMed Central

    Toledo, Jon B.; Gopal, Pallavi; Raible, Kevin; Irwin, David J.; Brettschneider, Johannes; Sedor, Samantha; Watts, Kayla; Boluda, Susana; Grossman, Murray; Van Deerlin, Vivianna M.; Lee, Edward B.; Arnold, Steven E.; Duda, John E.; Hurtig, Howard; Lee, Virginia M-Y; Adler, Charles H.; Beach, Thomas G.; Trojanowski, John Q.

    2016-01-01

    We investigated the distribution patterns of Lewy body related pathology (LRP) and the effect of coincident Alzheimer disease (AD) pathology using a data-driven clustering approach that identified groups with different LRP pathology distributions without any diagnostic or researcher’s input in two cohorts including: Parkinson disease patients without (PD, n=141) and with AD (PD-AD, n=80), dementia with Lewy bodies subjects without AD (DLB, n=13) and demented subjects with AD and LRP pathology (Dem-AD-LB, n=308). This latter group presented two LRP patterns, olfactory-amygdala and limbic LRP with negligible brainstem pathology, that were absent in the PD groups, are not currently included in the DLB staging system and lacked extracranial LRP as opposed to the PD group. The Dem-AD-LB individuals showed relative preservation of substantia nigra cells and dopamine active transporter in putamen. PD cases with AD pathology showed increased LRP. The cluster with occipital LRP was associated with non-AD type dementia clinical diagnosis in the Dem-AD-LB group and a faster progression to dementia in the PD groups. We found that 1) LRP pathology in Dem-AD-LB shows a distribution that differs from PD, without significant brainstem or extracranial LRP in initial phases, 2) coincident AD pathology is associated with increased LRP in PD indicating an interaction, 3) LRP and coincident AD pathology independently predict progression to dementia in PD, and 4) evaluation of LRP needs to acknowledge different LRP spreading patterns and evaluate substantia nigra integrity in the neuropathological assessment and consider the implications of neuropathological heterogeneity for clinical and biomarker characterization. PMID:26721587

  8. Search for Coincidences in Time and Arrival Direction of Auger Data with Astrophysical Transients

    SciTech Connect

    Anchordoqui, Luis; Collaboration, for the Pierre Auger

    2007-06-01

    The data collected by the Pierre Auger Observatory are analyzed to search for coincidences between the arrival directions of high-energy cosmic rays and the positions in the sky of astrophysical transients. Special attention is directed towards gamma ray observations recorded by NASA's Swift mission, which have an angular resolution similar to that of the Auger surface detectors. In particular, we check our data for evidence of a signal associated with the giant flare that came from the soft gamma repeater 1806-20 on December 27, 2004.

  9. Experimental studies in vortex pair motion coincident with a liquid reaction

    NASA Technical Reports Server (NTRS)

    Karagozian, A. R.; Suganuma, Y.; Strom, B. D.

    1988-01-01

    An experimental examination of the coincidence of a liquid reaction (acid/base) with the formation of a vortex pair structure is described in which emphasis is placed on the evolution of the strained diffusion layer and reacted core structures. Flow visualization of the reaction process is achieved via the technique of chemically sensitive LIF. The observed growth of reacted core structures associated with each vortex is compared with theoretically predicted behavior (Marble, 1983; Karagozian and Marble, 1986). Vortex pair separation is also compared with theoretical correlations, and the relevance of the analogy between a fast liquid reaction and a gaseous reaction is discussed.

  10. Reseau astrometry with Palomar Schmidt plates - Position-coincidence optical identification of radio sources

    SciTech Connect

    Mitchell, K.J.; Condon, J.J.; Warnock, A., III

    1981-10-01

    The simple, inexpensive method for determining celestial coordinates on original Palomar Schmidt plates developed previously is here inverted and shown to be a useful way of finding and identifying objects with known celestial coordinates. The method is especially suited for rapidly identifying large numbers of radio sources having accurate radio positions which are found in surveys made with large aperture-synthesis instruments. The average position error (approximately 0.9 arc sec) for stellar objects, galaxies, and faint objects near the plate limit is sufficient for making reliable optical identifications of objects as faint as J magnitude +24 on the basis of position coincidence alone, without regard to color or morphology.

  11. Optimization of a coincidence system using plastic scintillators in 4pi geometry.

    PubMed

    Dias, M S; Piuvezam-Filho, H; Koskinas, M F

    2008-01-01

    Improvements recently developed at the Nuclear Metrology Laboratory of IPEN-CNEN/SP in São Paulo were performed in order to increase the detector efficiency of a 4pibeta-gamma coincidence primary system using plastic scintillators in 4pi geometry. Measurements were undertaken and compared to the original system and Monte Carlo simulations of the extrapolation curves were calculated for this new system and compared to experimental results. For this purpose, the code Penelope was applied for calculating response functions for each detector and the code Esquema, developed at LMN, was used for simulating the decay scheme processes.

  12. Radiative corrections to elastic proton-electron scattering measured in coincidence

    NASA Astrophysics Data System (ADS)

    Gakh, G. I.; Konchatnij, M. I.; Merenkov, N. P.; Tomasi-Gustafsson, E.

    2017-05-01

    The differential cross section for elastic scattering of protons on electrons at rest is calculated, taking into account the QED radiative corrections to the leptonic part of interaction. These model-independent radiative corrections arise due to emission of the virtual and real soft and hard photons as well as to vacuum polarization. We analyze an experimental setup when both the final particles are recorded in coincidence and their energies are determined within some uncertainties. The kinematics, the cross section, and the radiative corrections are calculated and numerical results are presented.

  13. Silicon PIN diode based electron-gamma coincidence detector system for Noble Gases monitoring.

    PubMed

    Khrustalev, K; Popov, V Yu; Popov, Yu S

    2017-08-01

    We present a new second generation SiPIN based electron-photon coincidence detector system developed by Lares Ltd. for use in the Noble Gas measurement systems of the International Monitoring System and the On-site Inspection verification regimes of the Comprehensive Nuclear-Test Ban Treaty (CTBT). The SiPIN provide superior energy resolution for electrons. Our work describes the improvements made in the second generation detector cells and the potential use of such detector systems for other applications such as In-Situ Kr-85 measurements for non-proliferation purposes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Interesting coincidence of atypical TSH-secreting pituitary adenoma and chronic lymphocytic leukemia.

    PubMed

    Bolanowski, Marek; Zieliński, Grzegorz; Jawiarczyk-Przybyłowska, Aleksandra; Maksymowicz, Maria; Potoczek, Stanisław; Syrycka, Joanna; Podgórski, Jan K

    2014-01-01

    Thyrotropin-secreting adenomas (TSH-oma) are very rare pituitary tumours. They are macroadenomas usually presenting with signs and symptoms of hyperthyroidism, and mass effects. They can co-secrete other hormones such as growth hormone or prolactin. Different malignancies, including haematological ones, are reported in patients with pituitary diseases. Chronic lymphocytic leukemia (CLL) occurs mostly in older patients, more often in males. CLL is associated with increased risk of second malignancies such as other blood neoplasms, skin and solid tumours. We present a successful neurosurgical outcome in a patient with an interesting coincidence of atypical TSH-oma and asymptomatic CLL.

  15. Coincidence measurement of the fully differential cross section for atomic-field bremsstrahlung

    NASA Technical Reports Server (NTRS)

    Faulk, J. D.; Quarles, C. A.

    1974-01-01

    A coincidence measurement was made of the absolute cross section for electron-atomic-field bremsstrahlung, differential in photon energy, photon-emission angle, and electron scattering angle. The incident electron energy was 140 keV and the scattering materials were thin films of aluminum and gold. The data are compared to the theoretical calculations of Elwert and Haug and of Bethe and Heitler. Both theories give generally satisfactory agreement for aluminum. The Elwert-Haug theory is somewhat more accurate for gold.

  16. Deconvolution of 2D coincident Doppler broadening spectroscopy using the Richardson Lucy algorithm

    NASA Astrophysics Data System (ADS)

    Zhang, J. D.; Zhou, T. J.; Cheung, C. K.; Beling, C. D.; Fung, S.; Ng, M. K.

    2006-05-01

    Coincident Doppler Broadening Spectroscopy (CDBS) measurements are popular in positron solid-state studies of materials. By utilizing the instrumental resolution function obtained from a gamma line close in energy to the 511 keV annihilation line, it is possible to significantly enhance the quality of the CDBS spectra using deconvolution algorithms. In this paper, we compare two algorithms, namely the Non-Negativity Least Squares (NNLS) regularized method and the Richardson-Lucy (RL) algorithm. The latter, which is based on the method of maximum likelihood, is found to give superior results to the regularized least-squares algorithm and with significantly less computer processing time.

  17. Synchrotron threshold photoelectron photoion coincidence spectroscopy of radicals produced in a pyrolysis source: The methyl radical

    NASA Astrophysics Data System (ADS)

    Zhu, Yupeng; Wu, Xiangkun; Tang, Xiaofeng; Wen, Zuoying; Liu, Fuyi; Zhou, Xiaoguo; Zhang, Weijun

    2016-11-01

    We present here a flash pyrolysis source coupled with a threshold photoelectron photoion coincidence (TPEPICO) spectrometer and vacuum ultraviolet synchrotron radiation to investigate the spectroscopy and photochemistry of free radicals. The radicals are produced from pyrolysis in a heated silicon carbide tube, and the TPEPICO scheme provides a strategy to obtain pure spectra of the radicals without contamination from other byproducts. As a representative example, the methyl radical was studied, and its threshold photoelectron spectrum shows a series of umbrella vibrational transitions. The adiabatic ionization energy of the methyl radical was determined to be 9.84 ± 0.01 eV.

  18. Elemental analysis of positron affinitive site in materials by coincidence Doppler broadening spectroscopy

    NASA Astrophysics Data System (ADS)

    Nagai, Y.; Tang, Z.; Ohkubo, H.; Takadate, K.; Hasegawa, M.

    2003-10-01

    Elemental analysis study of the positron affinitive nano-structures in materials by coincidence Doppler broadening method are presented: (1) defect free Cu nano-clusters embedded in Fe, (2) nano-voids in Fe covered with Cu atoms, and (3) solute clusters (GP zones) in Al alloys (Al-Ag and Al-Zn). By utilizing positron trapping not only in vacancy-type defects but also positron affinitive, defect-free nano-clusters embedded in materials, unique and exclusive information, such as defect structure, coherency, chemical composition, and so on, on the trapping sites can be obtained.

  19. Geometric bias and time coincidence in 3-dimensional laser Doppler velocimeter systems

    NASA Technical Reports Server (NTRS)

    Brown, J. L.

    1989-01-01

    The measurement by a three-dimensional laser Doppler velocimeter of a turbulent flow has been numerically simulated. Errors associated with the probe volume geometry and the coincidence time window concept are revealed. One type of error occurs for high system data rates when multiple particles lead to system realizations. Another error occurs associated with a geometric bias discovered in the present study. This three-dimensional ldv geometric bias exists even for single-particle realizations and regardless of the system data rate. A technique for the elimination of the geometric bias is presented.

  20. IMPLEMENTING THE STANDARD SPECTRUM METHOD FOR ANALYSIS OF β-γ COINCIDENCE SPECTRA

    SciTech Connect

    Biegalski, S.; Flory, Adam E.; Schrom, Brian T.; Ely, James H.; Haas, Derek A.; Bowyer, Ted W.; Hayes, James C.

    2011-09-14

    The standard deconvolution analysis tool (SDAT) algorithms were developed and tested at the University of Texas at Austin. These algorithms utilize the standard spectrum technique for spectral analysis of {beta}-{gamma} coincidence spectra for nuclear explosion monitoring. Work has been conducted under this contract to implement these algorithms into a useable scientific software package with a graphical user interface. Improvements include the ability to read in PHD formatted data, gain matching, and data visualization. New auto-calibration algorithms were developed and implemented based on 137Cs spectra for assessment of the energy vs. channel calibrations. Details on the user tool and testing are included.

  1. Coincidence measurement of the fully differential cross section for atomic-field bremsstrahlung

    NASA Technical Reports Server (NTRS)

    Faulk, J. D.; Quarles, C. A.

    1974-01-01

    A coincidence measurement was made of the absolute cross section for electron-atomic-field bremsstrahlung, differential in photon energy, photon-emission angle, and electron scattering angle. The incident electron energy was 140 keV and the scattering materials were thin films of aluminum and gold. The data are compared to the theoretical calculations of Elwert and Haug and of Bethe and Heitler. Both theories give generally satisfactory agreement for aluminum. The Elwert-Haug theory is somewhat more accurate for gold.

  2. Summing-coincidence corrections with Geant4 in routine measurements by γ spectrometry of environmental samples.

    PubMed

    Quintana, B; Montes, C

    2014-05-01

    In this work, we describe a method to quantitatively evaluate true-coincidence-summing effects by making use of the Geant4 toolkit, which incorporates an emulation of the radionuclide disintegration scheme. To check the capabilities of the method, we firstly validated the simulated corrections using the ones obtained experimentally for radionuclides such as (60)Co, (152)Eu and (133)Ba. Secondly, we evaluated the effect of summing corrections of some radionuclides included in two intercomparison exercises to conclude that the results were improved when utilising the method described here. © 2013 Published by Elsevier Ltd.

  3. Development of a Body Shield for Small Animal PET System to Reduce Random and Scatter Coincidences

    NASA Astrophysics Data System (ADS)

    Wada, Yasuhiro; Yamamoto, Seiichi; Watanabe, Yasuyoshi

    2015-02-01

    For small animal positron emission tomography (PET) research using high radioactivity, such as dynamic studies, the resulting high random coincidence rate of the system degrades image quality. The random coincidence rate is increased not only by the gamma photons from inside the axial-field-of-view (axial-FOV) of the PET system but also by those from outside the axial-FOV. For brain imaging in small animal studies, significant interference is observed from gamma photons emitted from the body. Single gamma photons from the body enter the axial-FOV and increase the random and scatter coincidences. Shielding against the gamma photons from outside the axial-FOV would improve the image quality. For this purpose, we developed a body shield for a small animal PET system, the microPET Primate 4-ring system, and evaluated its performance. The body shield is made of 9-mm-thick lead and it surrounds most of a rat's body. We evaluated the effectiveness of the body shield using a head phantom and a body phantom with a radioactivity concentration ratio of 1:2 and a maximum total activity of approximately 250 MBq. The random coincidence rate was dramatically decreased to 1/10, and the noise equivalent count rate (NECR) was increased 6 times with an activity of 7 MBq in the head phantom. The true count rate was increased to 35% due to the decrease in system deadtime. The average scatter fraction was decreased to 1/2.5 with the body shield. Count rate measurements of rat were also conducted with an injection activity of approximately 25 MBq of [C-11]N,N-dimethyl-2-(2-amino-4-cyanophenylthio) benzylamine ([C-11]DASB) and approximately 70 and 310 MBq of 2-deoxy-2-(F-18)fluoro-D-glucose ([F-18]FDG). Using the body shield, [F-18]FDG images of rats were improved by increasing the amount of radioactivity injected. The body shield designed for small animal PET systems is a promising tool for improving image quality and quantitation accuracy in small animal molecular imaging research.

  4. In Situ Measurements of Meteoric Ions. Chapter 8

    NASA Technical Reports Server (NTRS)

    Grebowsky, Joseph M.; Aikin, Arthur C.; Vondrak, Richard R. (Technical Monitor)

    2001-01-01

    Metal ions found in the atmosphere above 60 km are the result of incoming meteoroid atmospheric ablation. Layers of metal ions are detected by sounding rocket in situ mass spectrometric sampling in the 80 to 130 km region, which coincides with the altitude region where meteors are observed. Enhancements of metal ion concentrations occur during meteor showers. Even outside of shower periods, the metal ion altitude profiles vary from measurement to measurement. Double layers are frequent at middle latitudes. More than 40 different meteoric atomic and molecular ions, including isotopes, have been detected. Atmospheric metal ions on average have an abundance that matches chrondritic material, the same composition as the early solar system. However there are frequently local departures from this composition due to differential ablation, species dependent chemistry and mass dependent ion transport. Metal ions react with atmospheric O2, O, O3, H2O and H2O2 to form oxygenated and hydrogenated ionic compounds. Metal atomic ions at high altitudes have long lifetimes. As a result, these ions, in the presence of Earth's magnetic field, are transported over long distances by upper atmospheric winds and ionospheric electric fields. Satellite measurements have detected metal ions as high as, approximately 1000 km and have revealed circulation of the ions on a global scale.

  5. Performance demonstration of 4πβ(LS)-γ coincidence counting system for standardization of radionuclides with complex decay scheme.

    PubMed

    Kulkarni, D B; Anuradha, R; Joseph, Leena; Kulkarni, M S; Tomar, B S

    2016-02-01

    A standardization of (134)Cs and (131)I was carried out in order to demonstrate the performance and applicability of the 4πβ(LS)-γ coincidence counting system for standardization of radionuclides with complex decay scheme. The coincidence analyzer, capable of analyzing coincidence between beta and two gamma windows simultaneously, was developed and used for the standardization. The use of this dual coincidence analyzer has reduced the total experimental time by half. The activity concentrations obtained using the 4πβ(LS)-γ coincidence counting system, a 4πβ(PC)-γ coincidence counting system, and the CIEMAT/NIST method are in excellent agreement with each other within uncertainty limits and hence demonstrates its performance for standardization of radionuclides decaying with complex decay scheme. Hence use of this 4πβ(LS)-γ coincidence counting system can be an alternative method suitable to standardize radionuclides with complex decay scheme with acceptable precision. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. ION SOURCE

    DOEpatents

    Bell, W.A. Jr.; Love, L.O.; Prater, W.K.

    1958-01-28

    An ion source is presented capable of producing ions of elements which vaporize only at exceedingly high temperatures, i.e.,--1500 degrees to 3000 deg C. The ion source utilizes beams of electrons focused into a first chamber housing the material to be ionized to heat the material and thereby cause it to vaporize. An adjacent second chamber receives the vaporized material through an interconnecting passage, and ionization of the vaporized material occurs in this chamber. The ionization action is produced by an arc discharge sustained between a second clectron emitting filament and the walls of the chamber which are at different potentials. The resultant ionized material egresses from a passageway in the second chamber. Using this device, materials which in the past could not be processed in mass spectometers may be satisfactorily ionized for such applications.

  7. Obtaining coincident image observations for Mission to Planet Earth science data return

    NASA Technical Reports Server (NTRS)

    Newman, Lauri Kraft; Folta, David C.; Farrell, James P.

    1994-01-01

    One objective of the Mission to Planet Earth (MTPE) program involves comparing data from various instruments on multiple spacecraft to obtain a total picture of the Earth's systems. To correlate image data from instruments on different spacecraft, these spacecraft must be able to image the same location on the Earth at approximately the same time. Depending on the orbits of the spacecraft involved, complicated operational details must be considered to obtain such observations. If the spacecraft are in similar orbits, close formation flying or synchronization techniques may be used to assure coincident observations. If the orbits are dissimilar, the launch time of the second satellite may need to be restricted in order to align its orbit with that of the first satellite launched. This paper examines strategies for obtaining coincident observations for spacecraft in both similar and dissimilar orbits. Although these calculations may be performed easily for coplanar spacecraft, the non-coplanar case involves additional considerations which are incorporated into the algorithms presented herein.

  8. A novel phoswich imaging detector for simultaneous beta and coincidence-gamma imaging of plant leaves.

    PubMed

    Wu, Heyu; Tai, Yuan-Chuan

    2011-09-07

    To meet the growing demand for functional imaging technology for use in studying plant biology, we are developing a novel technique that permits simultaneous imaging of escaped positrons and coincidence gammas from annihilation of positrons within an intake leaf. The multi-modality imaging system will include two planar detectors: one is a typical PET detector array and the other is a phoswich imaging detector that detects both beta and gamma. The novel phoswich detector is made of a plastic scintillator, a lutetium oxyorthosilicate (LSO) array, and a position sensitive photomultiplier tube (PS-PMT). The plastic scintillator serves as a beta detector, while the LSO array serves as a gamma detector and light guide that couples scintillation light from the plastic detector to the PMT. In our prototype, the PMT signal was fed into the Siemens QuickSilver electronics to achieve shaping and waveform sampling. Pulse-shape discrimination based on the detectors' decay times (2.1 ns for plastic and 40 ns for LSO) was used to differentiate beta and gamma events using the common PMT signals. Using our prototype phoswich detector, we simultaneously measured a beta image and gamma events (in single mode). The beta image showed a resolution of 1.6 mm full-width-at-half-maximum using F-18 line sources. Because this shows promise for plant-scale imaging, our future plans include development of a fully functional simultaneous beta-and-coincidence-gamma imager with sub-millimeter resolution imaging capability for both modalities.

  9. Classical signal model reproducing quantum probabilities for single and coincidence detections

    NASA Astrophysics Data System (ADS)

    Khrennikov, Andrei; Nilsson, Börje; Nordebo, Sven

    2012-05-01

    We present a simple classical (random) signal model reproducing Born's rule. The crucial point of our approach is that the presence of detector's threshold and calibration procedure have to be treated not as simply experimental technicalities, but as the basic counterparts of the theoretical model. We call this approach threshold signal detection model (TSD). The experiment on coincidence detection which was done by Grangier in 1986 [22] played a crucial role in rejection of (semi-)classical field models in favour of quantum mechanics (QM): impossibility to resolve the wave-particle duality in favour of a purely wave model. QM predicts that the relative probability of coincidence detection, the coefficient g(2) (0), is zero (for one photon states), but in (semi-)classical models g(2)(0) >= 1. In TSD the coefficient g(2)(0) decreases as 1/ɛ2d, where ɛd > 0 is the detection threshold. Hence, by increasing this threshold an experimenter can make the coefficient g(2) (0) essentially less than 1. The TSD-prediction can be tested experimentally in new Grangier type experiments presenting a detailed monitoring of dependence of the coefficient g(2)(0) on the detection threshold. Structurally our model has some similarity with the prequantum model of Grossing et al. Subquantum stochasticity is composed of the two counterparts: a stationary process in the space of internal degrees of freedom and the random walk type motion describing the temporal dynamics.

  10. Coincidence of homophone spelling errors and attention problems in schoolchildren: a survey study.

    PubMed

    Tsai, Li-Hui; Meng, Ling-Fu; Hung, Li-Yu; Chen, Hsin-Yu; Lu, Chiu-Ping

    2011-01-01

    This article examines the relationship between writing and attention problems and hypothesizes that homophone spelling errors coincide with attention deficits. We analyze specific types of attention deficits, which may contribute to Attention Deficits Hyperactivity Disorder (ADHD); rather than studying ADHD, however, we focus on the inattention dimension of behavior. Our methodology was to develop a survey study for exploring the coincidence of homophone errors and attention problems in schoolchildren. Two sets of parent-questionnaires characterizing individually types of Chinese handwriting errors and behavioral problems in schoolchildren were developed by the research team. Our participants were 491 Taiwanese children from the first to fifth grades in an elementary school in Taipei; they all used traditional Chinese as their primary written language of communication. Based on the ratings of the parent-questionnaires, two groups with proficient and non-proficient homophonic writing were formed. One consisted of children known to have made heterographic homophone errors (words with correct pronunciation but different spellings). The other (control group) consisted of children known to be proficient in Chinese homophone spellings. In each group, there were 54 boy and girl pupils, matched by gender, age, school and grade. A significant correlation was found between attention deficits and homophone errors. This survey study confirms our hypothesis and strengthens a currently underdeveloped theory in the literature of handwriting that attention impairments play an important role in the production of homophone errors. Copyright © 2010 Elsevier Ltd. All rights reserved.

  11. Coincidences in analysis: Sigmund Freud and the strange case of Dr Forsyth and Herr von Vorsicht.

    PubMed

    Pierri, Maria

    2010-08-01

    Freud's interest in thought transference opens the possibility for psychoanalytic research on the primary preverbal language and the maternal function, which the emphasis on verbal and paternal communication had hidden in the background of the setting. The author advances a new interpretation of coincidences in analysis and of the psychopathology of everyday life of the setting. Starting from a strange coincidence, new hypotheses are submitted following additional readings of the unpublished manuscript of the 'Forsyth case', recovered by the author, in regard to a significant moment of transformation, both in Freud and in psychoanalysis, at the end of the war. This phase corresponds first to a change of language, from German to English, as well as to the foundation of the International Journal of Psychoanalysis by Ernest Jones. In particular, the roots of the metapsychological turn of the 1920s are explored, together with the opening of private and productive thoughts in the area of 'telepathy' that joined Freud, Ferenczi, and Anna Freud in a true 'dialogue of unconsciouses'. The free association between A Child Is Being Beaten, Beyond the Pleasure Principle, and the clinical experience with 'Herr B.' is outlined in order to understand Freud's heroic self-analysis at the time when he was treating his daughter Anna and grieving the death of his beloved Sophie.

  12. Technical basis for the use of a correlated neutron source in the uranium neutron coincidence collar

    DOE PAGES

    Root, Margaret A.; Menlove, Howard Olsen; Lanza, Richard C.; ...

    2017-01-16

    Active neutron coincidence systems are commonly used by international inspectorates to verify a material balance across the various stages of the nuclear fuel cycle. The Uranium Neutron Coincidence Collar (UNCL) is one such instrument; it is used to measure the linear density of 235U (g 235U/cm of active length in assembly) in fresh light water reactor fuel in nuclear fuel fabrication facilities. The UNCL and other active neutron interrogation detectors have historically relied on americium lithium (241AmLi) sources to induce fission within the sample in question. Californium-252 is under consideration as a possible alternative to the traditional 241AmLi source. Finally,more » this work relied upon a combination of experiments and Monte Carlo simulations to demonstrate the technical basis for the replacement of 241AmLi sources with 252Cf sources by evaluating the statistical uncertainty in the measurements incurred by each source and assessing the penetrability of neutrons from each source for the UNCL.« less

  13. Ionospheric disturbances observed coincident with the 2006 and 2009 North Korean underground nuclear tests

    NASA Astrophysics Data System (ADS)

    Yang, Yu-Ming; Garrison, James L.; Lee, See-Chen

    2012-01-01

    Acoustic-Gravity Waves (AGWs) in the neutral atmosphere can induce disturbances in the ionosphere that are subsequently observable in trans-ionospheric Global Navigation Satellite System (GNSS) measurements. Disruptive events on the Earth's surface, such as earthquakes, tsunamis and large explosions are one source of these disturbances. In this study, we apply wavelet analysis to enhance a cross-correlation technique for detecting the presence of ionospheric disturbances in dual frequency GNSS time series collected from the GEONET (Japan) during the North Korean Underground Nuclear Tests (UGTs) conducted on 9 October 2006 and 25 May 2009. Through use of the wavelet coherence analysis, we are able to find significant wave trains in the Integrated Electron Content (IEC) data collected from the network. Low frequency disturbances, with periods between 3 and 12 min and horizontal propagation speeds between 75 and 453 m/s were found coincident with both the 2006 and 2009 events. High frequency disturbances, with periods between 2 and 5 min and horizontal speeds between 297 and 1322 m/s were found only after the 2009 event. The disturbances extracted from these signals showed propagation speeds, directions, and times of arrival coincident with the reported geographic location and times of the UGTs.

  14. Prognostic significance of increased serum bilirubin levels coincident with cardiac decompensation in chronic heart failure.

    PubMed

    Shinagawa, Hisahito; Inomata, Takayuki; Koitabashi, Toshimi; Nakano, Hironari; Takeuchi, Ichiro; Naruke, Takashi; Ohsaka, Tsutomu; Nishii, Mototsugu; Takehana, Hitoshi; Izumi, Tohru

    2008-03-01

    The aim of this study was to analyze the relationship between abnormal liver function tests (LFTs) coincident with heart failure (HF) exacerbation and subsequent long-term outcome in patients with chronic HF. The study population consisted of 183 consecutive patients admitted for HF exacerbation with left ventricular ejection fraction < or =40%. Cox proportional hazard analysis revealed that serum total bilirubin (T-Bil) levels on admission (hazard ratio 1.896, p<0.001, 95% confidence interval 1.323-2.717), but not T-Bil at discharge or other LFTs, was an independent predictor of subsequent cardiac events after hospital discharge (cardiac death or readmission for HF exacerbation) The cardiac-event-free rates significantly decreased according to increasing tertiles of T-Bil stratified by the level of 0.7 and 1.2 mg/dl (p<0.001). T-Bil on admission had significant correlations with simultaneously-measured central venous pressure (CVP) (r=0.42, p<0.01) and cardiac index (CI) (r= -0.50, p<0.01). The patients demonstrating high CVP together with low CI showed significantly increased T-Bil compared with any other group. Increased T-Bil coincident with cardiac decompensation predicts a worse long-term prognosis of CHF, presumably through the potential liability to both congestion and tissue hypoperfusion simultaneously when HF deteriorates.

  15. Hydrogen analysis for granite using proton-proton elastic recoil coincidence spectrometry.

    PubMed

    Komatsubara, T; Sasa, K; Ohshima, H; Kimura, H; Tajima, Y; Takahashi, T; Ishii, S; Yamato, Y; Kurosawa, M

    2008-07-01

    In an effort to develop DS02, a new radiation dosimetry system for the atomic bomb survivors of Hiroshima and Nagasaki, measurements of neutron-induced activities have provided valuable information to reconstruct the radiation situation at the time of the bombings. In Hiroshima, the depth profile of (152)Eu activity measured in a granite pillar of the Motoyasu Bridge (128 m from the hypocenter) was compared with that calculated using the DS02 methodology. For calculation of the (152)Eu production due to the thermal-neutron activation reaction, (151)Eu(n,gamma)(152)Eu, information on the hydrogen content in granite is important because the transport and slowing-down process of neutrons penetrating into the pillar is strongly affected by collisions with the protons of hydrogen. In this study, proton-proton elastic recoil coincidence spectrometry has been used to deduce the proton density in the Motoyasu pillar granite. Slices of granite samples were irradiated by a 20 MeV proton beam, and the energies of scattered and recoil protons were measured with a coincidence method. The water concentration in the pillar granite was evaluated to be 0.30 +/- 0.07%wt. This result is consistent with earlier data on adsorptive water (II) and bound water obtained by the Karl Fisher method.

  16. Physiology of Layer 5 Pyramidal Neurons in Mouse Primary Visual Cortex: Coincidence Detection through Bursting

    PubMed Central

    Shai, Adam S.; Anastassiou, Costas A.; Larkum, Matthew E.; Koch, Christof

    2015-01-01

    L5 pyramidal neurons are the only neocortical cell type with dendrites reaching all six layers of cortex, casting them as one of the main integrators in the cortical column. What is the nature and mode of computation performed in mouse primary visual cortex (V1) given the physiology of L5 pyramidal neurons? First, we experimentally establish active properties of the dendrites of L5 pyramidal neurons of mouse V1 using patch-clamp recordings. Using a detailed multi-compartmental model, we show this physiological setup to be well suited for coincidence detection between basal and apical tuft inputs by controlling the frequency of spike output. We further show how direct inhibition of calcium channels in the dendrites modulates such coincidence detection. To establish the singe-cell computation that this biophysics supports, we show that the combination of frequency-modulation of somatic output by tuft input and (simulated) calcium-channel blockage functionally acts as a composite sigmoidal function. Finally, we explore how this computation provides a mechanism whereby dendritic spiking contributes to orientation tuning in pyramidal neurons. PMID:25768881

  17. Effect of expertise on coincident-timing accuracy in a fast ball game.

    PubMed

    Ripoll, H; Latiri, I

    1997-12-01

    The aim of this study was to examine the effect of intensive practice in table tennis on perceptual coincident timing. The main question was whether the perceptual demands encountered in fast ball sports produce modifications of the perceptual visual system. Expert table tennis players and novices were compared in a perceptual task which consisted of estimating, by pressing a key, the arrival of a moving stimulus at a target. The stimulus, which was presented either at constant velocity or at constant deceleration, reproduced as closely as possible the natural visual demands encountered in table tennis. The difference between the time of response and the time of arrival of the stimulus at a target position was measured over 40 trials for each of the 16 participants. The results showed no effect of expertise under the constant-velocity condition but an effect under the decelerative condition, indicating that experts were less trajectory-dependent than novices. This result was interpreted as reflecting a better adaptation of the perceptual system of experts to the constraints encountered during table tennis and specifically to the perceptual demands resulting from varied and decelerated ball trajectories. Finally, some limitations of the coincidence anticipation procedure are highlighted, concerning its use in practical settings for evaluating athletes or detecting sport talents, and the need for the simulation conditions during testing to reproduce as closely as possible the perceptual demands of real life is discussed.

  18. DIVERSE ACTIVE WELL NEUTRON COINCIDENCE COUNTER UTILITY AT THE SAVANNAH RIVER NATIONAL LABORATORY

    SciTech Connect

    Dewberry, R; Saleem Salaymeh, S

    2007-01-08

    In this paper we describe use of the Aquila active well neutron coincidence counter for nuclear material assays of {sup 235}U in multiple analytical techniques at Savannah River Site (SRS), at the Savannah River National Laboratory (SRNL), and at Argonne West National Laboratory (AWNL). The uses include as a portable passive neutron counter for field measurements searching for evidence of {sup 252}Cf deposits and storage; as a portable active neutron counter using an external activation source for field measurements searching for trace {sup 235}U deposits and holdup; for verification measurements of U-Al reactor fuel elements; for verification measurements of uranium metal; and for verification measurements of process waste of impure uranium in a challenging cement matrix. The wide variety of uses described demonstrate utility of the technique for neutron coincidence verification measurements over the dynamic ranges of 100 g-5000 g for U metal, 200 g-1300 g for U-Al, and 8 g-35 g for process waste. In addition to demonstrating use of the instrument in both the passive and active modes, we also demonstrate its use in both the fast and thermal neutron modes.

  19. Performance of coincidence-based PSD on LiF/ZnS Detectors for Multiplicity Counting

    SciTech Connect

    Robinson, Sean M.; Stave, Sean C.; Lintereur, Azaree; Siciliano, Edward R.; Cowles, Christian C.; Kouzes, Richard T.; Behling, Richard S.

    2016-10-06

    Abstract: Mass accountancy measurement is a nuclear nonproliferation application which utilizes coincidence and multiplicity counters to verify special nuclear material declarations. With a well-designed and efficient detector system, several relevant parameters of the material can be verified simultaneously. 6LiF/ZnS scintillating sheets may be used for this purpose due to a combination of high efficiency and short die-away times in systems designed with this material, but involve choices of detector geometry and exact material composition (e.g., the addition of Ni-quenching in the material) that must be optimized for the application. Multiplicity counting for verification of declared nuclear fuel mass involves neutron detection in conditions where several neutrons arrive in a short time window, with confounding gamma rays. This paper considers coincidence-based Pulse-Shape Discrimination (PSD) techniques developed to work under conditions of high pileup, and the performance of these algorithms with different detection materials. Simulated and real data from modern LiF/ZnS scintillator systems are evaluated with these techniques and the relationship between the performance under pileup and material characteristics (e.g., neutron peak width and total light collection efficiency) are determined, to allow for an optimal choice of detector and material.

  20. A new MCNPX PTRAC coincidence capture file capability: a tool for neutron detector design

    SciTech Connect

    Evans, Louise G; Schear, Melissa A; Hendricks, John S; Swinhoe, Martyn T; Tobin, Stephen J; Croft, Stephen

    2011-02-16

    The existing Monte Carlo N-Particle (MCNPX) particle tracking (PTRAC) coincidence capture file allows a full list of neutron capture events to be recorded in any simulated detection medium. The originating event history number (e.g. spontaneous fission events), capture time, location and source particle number are tracked and output to file for post-processing. We have developed a new MCNPX PTRAC coincidence capture file capability to aid detector design studies. New features include the ability to track the nuclides that emitted the detected neutrons as well as induced fission chains in mixed samples before detection (both generation number and nuclide that underwent induced fission). Here, the power of this tool is demonstrated using a detector design developed for the non-destructive assay (NDA) of spent nuclear fuel. Individual capture time distributions have been generated for neutrons originating from Curium-244 source spontaneous fission events and induced fission events in fissile nuclides of interest: namely Plutonium-239, Plutonium-241, and Uranium-235. Through this capability, a full picture for the attribution of neutron capture events in the detector can be simulated.

  1. Design of a coincidence processing board for a dual-head PET scanner for breast imaging

    NASA Astrophysics Data System (ADS)

    Martínez, J. D.; Toledo, J.; Esteve, R.; Sebastiá, A.; Mora, F. J.; Benlloch, J. M.; Fernández, M. M.; Giménez, M.; Giménez, E. N.; Lerche, Ch. W.; Pavón, N.; Sánchez, F.

    2005-07-01

    This paper describes the design of a coincidence processing board for a dual-head Positron Emission Tomography (PET) scanner for breast imaging. The proposed block-oriented data acquisition system relies on a high-speed DSP processor for fully digital trigger and on-line event processing that surpasses the performance of traditional analog coincidence detection systems. A mixed-signal board has been designed and manufactured. The analog section comprises 12 coaxial inputs (six per head) which are digitized by means of two 8-channel 12-bit 40-MHz ADCs in order to acquire the scintillation pulse, the charge division signals and the depth of interaction within the scintillator. At the digital section, a state-of-the-art FPGA is used as deserializer and also implements the DMA interface to the DSP processor by storing each digitized channel into a fast embedded FIFO memory. The system incorporates a high-speed USB 2.0 interface to the host computer.

  2. Sensitive neutron detection method using delayed coincidence transitions in existing iodine-containing detectors

    NASA Astrophysics Data System (ADS)

    Yakushev, E.; Rozov, S.; Drokhlyansky, A.; Filosofov, D.; Kalaninova, Z.; Timkin, V.; Ponomarev, D.

    2017-03-01

    This work explains a new, highly sensitive method for the detection of neutrons, which uses the T1/2 = 845 ns delay in the decay of 128I at the 137.8 keV energy level, resulting from the capture of thermal neutrons by iodine nuclei in NaI and CsI scintillation detectors. The use of delayed coincidence techniques with a several μs delay time window for delayed events allows for the highly effective discrimination of neutron events from any existing background signals. A comparison of ambient neutron measurements between those identified through the suggested method from a cylindrical, ø 63 mm × 63 mm NaI(Tl) scintillator and those from a low-background proportional 3He counter experimentally demonstrates the efficacy of this neutron detection method. For an isotropic, 4 π , thermal neutron flux of 1 ncm-2s-1 , the absolute sensitivity of the NaI detector was found to be 6.5 ± 1 countss-1 with an accidental coincidence background of 0.8 eventsday-1 for any delay time window of Δt = 1 μs . The proposed method can provide low-background experiments, using NaI or CsI, with measurements of the rate and stability of incoming neutron flux to a greater accuracy than 10-8 ncm-2s-1 .

  3. Fluorescence coincidence spectroscopy for single-molecule fluorescence resonance energy-transfer measurements.

    PubMed

    Orte, Angel; Clarke, Richard W; Klenerman, David

    2008-11-15

    Single-molecule fluorescence resonance energy transfer (FRET) is commonly used to probe different conformations and conformational dynamics of single biomolecules. However, the analysis of raw burst traces is not always straightforward. The presence of a "zero peak" and the skewness of peaks at high and low FRET efficiencies in proximity ratio histograms make the accurate evaluation of the histogram a challenging task. This is further compounded by the difficulty associated with siting two fluorophores in optimal range of each other. Here we present an alternative method of analysis, based on handling coincident FRET photon bursts, that addresses these problems. In addition, we demonstrate methods to enhance coincidence levels and thus the accuracy of FRET determination: the use of dual-color excitation, including direct excitation of the acceptor fluorophore; the addition of a remote dye to the biomolecule, not involved in the FRET process; or a combination of the two. We show the advantages of dual excitation by studying several labeled double-stranded DNA samples as FRET models. This method extends the application of single-molecule FRET to more complicated biological systems where only a small fraction of complexes are fully assembled.

  4. Cerebellar Dysfunction and Ataxia in Patients with Epilepsy: Coincidence, Consequence, or Cause?

    PubMed

    Marcián, Václav; Filip, Pavel; Bareš, Martin; Brázdil, Milan

    2016-01-01

    Basic epilepsy teachings assert that seizures arise from the cerebral cortex, glossing over infratentorial structures such as the cerebellum that are believed to modulate rather than generate seizures. Nonetheless, ataxia and other clinical findings in epileptic patients are slowly but inevitably drawing attention to this neural node. Tracing the evolution of this line of inquiry from the observed coincidence of cerebellar atrophy and cerebellar dysfunction (most apparently manifested as ataxia) in epilepsy to their close association, this review considers converging clinical, physiological, histological, and neuroimaging evidence that support incorporating the cerebellum into epilepsy pathology. We examine reports of still controversial cerebellar epilepsy, studies of cerebellar stimulation alleviating paroxysmal epileptic activity, studies and case reports of cerebellar lesions directly associated with seizures, and conditions in which ataxia is accompanied by epileptic seizures. Finally, the review substantiates the role of this complex brain structure in epilepsy whether by coincidence, as a consequence of deleterious cortical epileptic activity or antiepileptic drugs, or the very cause of the disease.

  5. Cerebellar Dysfunction and Ataxia in Patients with Epilepsy: Coincidence, Consequence, or Cause?

    PubMed Central

    Marcián, Václav; Filip, Pavel; Bareš, Martin; Brázdil, Milan

    2016-01-01

    Basic epilepsy teachings assert that seizures arise from the cerebral cortex, glossing over infratentorial structures such as the cerebellum that are believed to modulate rather than generate seizures. Nonetheless, ataxia and other clinical findings in epileptic patients are slowly but inevitably drawing attention to this neural node. Tracing the evolution of this line of inquiry from the observed coincidence of cerebellar atrophy and cerebellar dysfunction (most apparently manifested as ataxia) in epilepsy to their close association, this review considers converging clinical, physiological, histological, and neuroimaging evidence that support incorporating the cerebellum into epilepsy pathology. We examine reports of still controversial cerebellar epilepsy, studies of cerebellar stimulation alleviating paroxysmal epileptic activity, studies and case reports of cerebellar lesions directly associated with seizures, and conditions in which ataxia is accompanied by epileptic seizures. Finally, the review substantiates the role of this complex brain structure in epilepsy whether by coincidence, as a consequence of deleterious cortical epileptic activity or antiepileptic drugs, or the very cause of the disease. PMID:27375960

  6. Triple coincidence beam spin asymmetry measurements in Deeply Virtual Compton Scattering

    NASA Astrophysics Data System (ADS)

    Canan, Mustafa

    2011-12-01

    The Generalized Parton Distributions (GPDs) provides hitherto the most complete information about the quark structure of hadron. GPDs are accessible through hard-exclusive reactions, among which Deeply Virtual Compton Scattering (DVCS) is the cleanest reaction. A dedicated DVCS experiment on Hydrogen (E00-110) ran in the Hall A at Jefferson Laboratory in Fall 2004. I present here Beam Spin Asymmetry (BSA) results for the ep → epgamma reaction studied in the E00-110 experiment with fully exclusive triple coincidence H(e, e'gammap ) detection. I present a re-calibration of the electromagnetic calorimeter used to detect the high energy photon. This calibration is necessary to account for the effects of pile-up. The results show a 1-sigma disagreement with the double coincidence H(e, e'gamma )p results, I also presents a feasibility study for measurements of neutron GPDs via the 3He ? (e, e'gamma)ppn reaction on a polarized 3He target with JLab at 12 GeV. These measurements offer the prospect of a determination of all four GPDs.

  7. Beyond contact-based transmission networks: the role of spatial coincidence.

    PubMed

    Richardson, Thomas O; Gorochowski, Thomas E

    2015-10-06

    Animal societies rely on interactions between group members to effectively communicate and coordinate their actions. To date, the transmission properties of interaction networks formed by direct physical contacts have been extensively studied for many animal societies and in all cases found to inhibit spreading. Such direct interactions do not, however, represent the only viable pathways. When spreading agents can persist in the environment, indirect transmission via 'same-place, different-time' spatial coincidences becomes possible. Previous studies have neglected these indirect pathways and their role in transmission. Here, we use rock ant colonies, a model social species whose flat nest geometry, coupled with individually tagged workers, allowed us to build temporally and spatially explicit interaction networks in which edges represent either direct physical contacts or indirect spatial coincidences. We show how the addition of indirect pathways allows the network to enhance or inhibit the spreading of different types of agent. This dual-functionality arises from an interplay between the interaction-strength distribution generated by the ants' movement and environmental decay characteristics of the spreading agent. These findings offer a general mechanism for understanding how interaction patterns might be tuned in animal societies to control the simultaneous transmission of harmful and beneficial agents. © 2015 The Author(s).

  8. Quark seesaw mechanism, dark U (1 ) symmetry, and the baryon-dark matter coincidence

    NASA Astrophysics Data System (ADS)

    Gu, Pei-Hong; Mohapatra, Rabindra N.

    2017-09-01

    We attempt to understand the baryon-dark matter coincidence problem within the quark seesaw extension of the standard model where parity invariance is used to solve the strong C P problem. The S U (2 )L×S U (2 )R×U (1 )B -L gauge symmetry of this model is extended by a dark U (1 )X group plus inclusion of a heavy neutral vector-like fermion χL ,R charged under the dark group which plays the role of dark matter. All fermions are Dirac type in this model. Decay of heavy scalars charged under U (1 )X leads to simultaneous asymmetry generation of the dark matter and baryons after sphaleron effects are included. The U (1 )X group not only helps to stabilize the dark matter but also helps in the elimination of the symmetric part of the dark matter via χ -χ ¯ annihilation. For dark matter mass near the proton mass, it explains why the baryon and dark matter abundances are of similar magnitude (the baryon-dark matter coincidence problem). This model is testable in low threshold (sub-keV) direct dark matter search experiments.

  9. Synthesis of fast qudit gates by a train of coincident pulses

    NASA Astrophysics Data System (ADS)

    Amniat-Talab, Mahdi; Saadati-Niari, Maghsoud

    2015-09-01

    We propose an exact analytical method for the production of fast quantum gates in a system of d degenerate states, using a technique of a train of coincident pulses. It is an alternative to the adiabatic passage technique. This study exploits the Morris-Shore transformation and generalized quantum Householder reflection in which each of Householder reflection is implemented by n + m (n and m are arbitrary integers) sets of coincident pulses. Decoherence due to the population of the upper state is efficiently suppressed as the number of pulse sets (n and m) increases. It is remarkable that the upper state population is damped considerably, even for a small number of pulse sets, despite the fact that all the fields applied were on resonance with their transitions. In this method, simple Gaussian pulses with minimal pulse areas were used, which is easy to achieve experimentally. As a case study to validate the method, we implement the quantum Fourier transform in qutrit and ququad by a proper pulse train.

  10. A consistent but non-coincident visual pattern facilitates the learning of spatial relations among locations.

    PubMed

    Katz, Scott S; Brown, Michael F; Sturz, Bradley R

    2014-02-01

    Human participants searched in a dynamic three-dimensional computer-generated virtual-environment open-field search task for four hidden goal locations arranged in a diamond configuration located in a 5 × 5 matrix of raised bins. Participants were randomly assigned to one of two groups: visual pattern or visual random. All participants experienced 30 trials in which four goal locations maintained the same spatial relations to each other (i.e., a diamond pattern), but this diamond pattern moved to random locations within the 5 × 5 matrix from trial to trial. For participants in the visual pattern group, four locations were marked in a distinct color and arranged in a diamond pattern that moved to a random location independent of the hidden spatial pattern from trial to trial throughout the experimental session. For participants in the visual random group, four random locations were marked with a distinct color and moved to random locations independent from the hidden spatial pattern from trial to trial throughout the experimental session. As a result, the visual cues for the visual pattern group were consistent but not coincident with the hidden spatial pattern, whereas the visual cues for the visual random group were neither consistent nor coincident with the hidden spatial pattern. Results indicated that participants in both groups learned the spatial configuration of goal locations and that the presence of consistent but noncoincident visual cues facilitated the learning of spatial relations among locations.

  11. The LVV Auger line shape of sulfur on copper studied by Auger photoelectron coincidence spectroscopy.

    PubMed

    Di Filippo, G; Trioni, M I; Fratesi, G; Schumann, F O; Wei, Z; Li, C H; Behnke, L; Patil, S; Kirschner, J; Stefani, G

    2015-03-04

    We have studied the line shapes of Cu(0 0 1)-p (2 × 2)S L2VV and L3VV Auger decay by means of Auger photoelectron coincidence spectroscopy. Measuring the LVV Auger spectrum in coincidence with S 2p1/2 and 2p3/2 photoelectrons respectively, we have been able to separate the two overlapping Auger spectra and determine their intrinsic line shapes. The two Auger transitions, though shifted in energy, display an identical line shape whose main features can be qualitatively understood considering a single particle approximation but are better described within a Cini-Sawatzky (CS) approach. Comparison between the experimental and the CS calculated spectra confirms that a substantial part of the Auger lines (∼20%) can be ascribed to decay events accompanied by the excitation of one additional electron-hole pair in the valence band. For the first time, the locality of the Auger process combined with the surface sensitivity of the APECS technique and its ability to separate overlapping structures are used to study Auger transitions taking place at the the surface states of a S/noble-metal interface.

  12. A novel phoswich imaging detector for simultaneous beta and coincidence-gamma imaging of plant leaves

    NASA Astrophysics Data System (ADS)

    Wu, Heyu; Tai, Yuan-Chuan

    2011-09-01

    To meet the growing demand for functional imaging technology for use in studying plant biology, we are developing a novel technique that permits simultaneous imaging of escaped positrons and coincidence gammas from annihilation of positrons within an intake leaf. The multi-modality imaging system will include two planar detectors: one is a typical PET detector array and the other is a phoswich imaging detector that detects both beta and gamma. The novel phoswich detector is made of a plastic scintillator, a lutetium oxyorthosilicate (LSO) array, and a position sensitive photomultiplier tube (PS-PMT). The plastic scintillator serves as a beta detector, while the LSO array serves as a gamma detector and light guide that couples scintillation light from the plastic detector to the PMT. In our prototype, the PMT signal was fed into the Siemens QuickSilver electronics to achieve shaping and waveform sampling. Pulse-shape discrimination based on the detectors' decay times (2.1 ns for plastic and 40 ns for LSO) was used to differentiate beta and gamma events using the common PMT signals. Using our prototype phoswich detector, we simultaneously measured a beta image and gamma events (in single mode). The beta image showed a resolution of 1.6 mm full-width-at-half-maximum using F-18 line sources. Because this shows promise for plant-scale imaging, our future plans include development of a fully functional simultaneous beta-and-coincidence-gamma imager with sub-millimeter resolution imaging capability for both modalities.

  13. A mechanism for detecting coincidence of auditory and visual spatial signals.

    PubMed

    Orchard-Mills, Emily; Leung, Johahn; Burr, David; Morrone, Maria Concetta; Wufong, Ella; Carlile, Simon; Alais, David

    2013-01-01

    Information about the world is captured by our separate senses, and must be integrated to yield a unified representation. This raises the issue of which signals should be integrated and which should remain separate, as inappropriate integration will lead to misrepresentation and distortions. One strong cue suggesting that separate signals arise from a single source is coincidence, in space and in time. We measured increment thresholds for discriminating spatial intervals defined by pairs of simultaneously presented targets, one flash and one auditory sound, for various separations. We report a 'dipper function', in which thresholds follow a 'U-shaped' curve, with thresholds initially decreasing with spatial interval, and then increasing for larger separations. The presence of a dip in the audiovisual increment-discrimination function is evidence that the auditory and visual signals both input to a common mechanism encoding spatial separation, and a simple filter model with a sigmoidal transduction function simulated the results well. The function of an audiovisual spatial filter may be to detect coincidence, a fundamental cue guiding whether to integrate or segregate.

  14. Development of Simultaneous Beta-and-Coincidence-Gamma Imager for Plant Imaging Research

    SciTech Connect

    Tai, Yuan-Chuan

    2016-09-30

    The goal of this project is to develop a novel imaging system that can simultaneously acquire beta and coincidence gamma images of positron sources in thin objects such as leaves of plants. This hybrid imager can be used to measure carbon assimilation in plants quantitatively and in real-time after C-11 labeled carbon-dioxide is administered. A better understanding of carbon assimilation, particularly under the increasingly elevated atmospheric CO2 level, is extremely critical for plant scientists who study food crop and biofuel production. Phase 1 of this project is focused on the technology development with 3 specific aims: (1) develop a hybrid detector that can detect beta and gamma rays simultaneously; (2) develop an imaging system that can differentiate these two types of radiation and acquire beta and coincidence gamma images in real-time; (3) develop techniques to quantify radiotracer distribution using beta and gamma images. Phase 2 of this project is to apply technologies developed in phase 1 to study plants using positron-emitting radionuclide such as 11C to study carbon assimilation in biofuel plants.

  15. Flowering time and seed dormancy control use external coincidence to generate life history strategy

    PubMed Central

    Springthorpe, Vicki; Penfield, Steven

    2015-01-01

    Climate change is accelerating plant developmental transitions coordinated with the seasons in temperate environments. To understand the importance of these timing advances for a stable life history strategy, we constructed a full life cycle model of Arabidopsis thaliana. Modelling and field data reveal that a cryptic function of flowering time control is to limit seed set of winter annuals to an ambient temperature window which coincides with a temperature-sensitive switch in seed dormancy state. This coincidence is predicted to be conserved independent of climate at the expense of flowering date, suggesting that temperature control of flowering time has evolved to constrain seed set environment and therefore frequency of dormant and non-dormant seed states. We show that late flowering can disrupt this bet-hedging germination strategy. Our analysis shows that life history modelling can reveal hidden fitness constraints and identify non-obvious selection pressures as emergent features. DOI: http://dx.doi.org/10.7554/eLife.05557.001 PMID:25824056

  16. Transient receptor potential channels function as a coincidence signal detector mediating phosphatidylserine exposure.

    PubMed

    Harper, Matthew T; Londoño, Juan E Camacho; Quick, Kathryn; Londoño, Julia Camacho; Flockerzi, Veit; Philipp, Stephan E; Birnbaumer, Lutz; Freichel, Marc; Poole, Alastair W

    2013-06-25

    Blood platelet aggregation must be tightly controlled to promote clotting at injury sites but avoid inappropriate occlusion of blood vessels. Thrombin, which cleaves and activates Gq-coupled protease-activated receptors, and collagen-related peptide, which activates the receptor glycoprotein VI, stimulate platelets to aggregate and form thrombi. Coincident activation by these two agonists synergizes, causing the exposure of phosphatidylserine on the cell surface, which is a marker of cell death in many cell types. Phosphatidylserine exposure is also essential to produce additional thrombin on platelet surfaces, which contributes to thrombosis. We found that activation of either thrombin receptors or glycoprotein VI alone produced a calcium signal that was largely dependent only on store-operated Ca(2+) entry. In contrast, experiments with platelets from knockout mice showed that the presence of both ligands activated nonselective cation channels of the transient receptor potential C (TRPC) family, TRPC3 and TRPC6. These channels principally allowed entry of Na(+), which coupled to reverse-mode Na(+)/Ca(2+) exchange to allow calcium influx and thereby contribute to Ca(2+) signaling and phosphatidylserine exposure. Thus, TRPC channels act as coincidence detectors to coordinate responses to multiple signals in cells, thereby indirectly mediating in platelets an increase in intracellular calcium concentrations and exposure of prothrombotic phosphatidylserine.

  17. Fast Neutron Dose Evaluation Using CR39 by Coincidence Counting Process

    SciTech Connect

    Vilela, Eudice; Freitas, F. F. de; Brandao, J. O. C.; Santos, J. A. L.

    2008-08-07

    The solid state nuclear tracks detection (SSNTD) technique is widely used in the area of radiation dosimetry. Different materials can be used applying this technique as glass and the most used in the dosimetry field that are the polycarbonates, CR39 and Makrofol-DE. Both are very rich in hydrogenous, that enables the SSNTD to detect fast neutrons through recoils of protons in the own detector material, without need of converters. The low reproducibility of its backgroundhas often been the major drawback in the assessment of low fluences of fast neutrons with SSNTDs. This problem can be effectively solved by counting coincidence of tracks in two detectors foils irradiated in close contact. After processing and counting only tracks produced by the same recoil nuclei on the surfaces of both detectors are considered as a track. This procedure enables the reduction of the background counts in the response of the detectors. In this work a preliminary study on the application of the coincidence technique for neutron dosimetry is presented. The CR39 material was investigated aiming to achieve the personal dose equivalent for fast neutrons. Using this method of analysis a significant reduction on the lower detectable dose was observed resulting even one order of magnitude smaller value. Reading, however, needs to be automated due to the large areas necessary to achieve a satisfactory number of tracks for statistical significance of results.

  18. Beyond contact-based transmission networks: the role of spatial coincidence

    PubMed Central

    Richardson, Thomas O.; Gorochowski, Thomas E.

    2015-01-01

    Animal societies rely on interactions between group members to effectively communicate and coordinate their actions. To date, the transmission properties of interaction networks formed by direct physical contacts have been extensively studied for many animal societies and in all cases found to inhibit spreading. Such direct interactions do not, however, represent the only viable pathways. When spreading agents can persist in the environment, indirect transmission via ‘same-place, different-time’ spatial coincidences becomes possible. Previous studies have neglected these indirect pathways and their role in transmission. Here, we use rock ant colonies, a model social species whose flat nest geometry, coupled with individually tagged workers, allowed us to build temporally and spatially explicit interaction networks in which edges represent either direct physical contacts or indirect spatial coincidences. We show how the addition of indirect pathways allows the network to enhance or inhibit the spreading of different types of agent. This dual-functionality arises from an interplay between the interaction-strength distribution generated by the ants' movement and environmental decay characteristics of the spreading agent. These findings offer a general mechanism for understanding how interaction patterns might be tuned in animal societies to control the simultaneous transmission of harmful and beneficial agents. PMID:26400200

  19. Means and method for calibrating a photon detector utilizing electron-photon coincidence

    NASA Technical Reports Server (NTRS)

    Srivastava, S. K. (Inventor)

    1984-01-01

    An arrangement for calibrating a photon detector particularly applicable for the ultraviolet and vacuum ultraviolet regions is based on electron photon coincidence utilizing crossed electron beam atom beam collisions. Atoms are excited by electrons which lose a known amount of energy and scatter with a known remaining energy, while the excited atoms emit photons of known radiation. Electrons of the known remaining energy are separated from other electrons and are counted. Photons emitted in a direction related to the particular direction of scattered electrons are detected to serve as a standard. Each of the electrons is used to initiate the measurements of a time interval which terminates with the arrival of a photon exciting the photon detector. Only the number of time intervals related to the coincidence correlation and of electrons scattered in the particular direction with the known remaining energy and photons of a particular radiation level emitted due to the collisions of such scattered electrons are counted. The detector calibration is related to the number of counted electrons and photons.

  20. Simulating γ-γ coincidences of β-delayed γ-rays from fission product nuclei

    NASA Astrophysics Data System (ADS)

    Padgett, Stephen; Wang, Tzu-Fang

    2015-01-01

    Analyzing radiation from material that has undergone neutron induced fission is important for fields such as nuclear forensics, reactor physics, and nonproliferation monitoring. The γ-ray spectroscopy of fission products is a major part of the characterization of a material's fissile inventory and the energy of incident neutrons inducing fission. Cumulative yields and γ-ray intensities from nuclear databases are inputs into a GEANT4 simulation to create expected γ-ray spectra from irradiated 235U. The simulations include not only isotropically emitted γ-rays but also γ-γ cascades from certain fission products, emitted with their appropriate angular correlations. Here γ singles spectra as well as γ-γ coincidence spectra are simulated in detectors at both 90° and 180° pairings. The ability of these GEANT4 Monte Carlo simulations to duplicate experimental data is explored in this work. These simulations demonstrate potential in exploiting angular correlations of γ-γ cascades in fission product decays to determine isotopic content. Analyzing experimental and simulated γ-γ coincidence spectra as opposed to singles spectra should improve the ability to identify fission product nuclei since such spectra are cleaner and contain more resolved peaks when compared to γ singles spectra.

  1. Studies of transitional Gadolinium nuclei by particle-gamma coincidence techniques

    NASA Astrophysics Data System (ADS)

    Ross, T. J.; Hughes, R. O.; Beausang, C. W.; Allmond, J. M.; Burke, J. T.; Escher, J. E.; Phair, L. W.; Scielzo, N.; Angell, C. T.; Basunia, M. S.; Bleuel, D. L.; Casperson, R. J.; Fallon, P.; Hatarik, R.; Munson, J.; Paschalis, S.; Petri, M.; Ressler, J. J.; Stars-Liberace Collaboration

    2011-10-01

    Nuclei in the N = 90 transitional region have been the focus of intense study for a number of years. In spite of this, recent particle-gamma coincidence studies of 155Gd revealed inconsistencies in the present single particle assignments. Expanding on these findings, an experiment was performed using the STARS-LIBERACE array at the 88-Inch Cyclotron in Lawrence Berkeley National Laboratory. A 25 MeV proton beam incident on 154Gd and 158Gd targets was used to populate states in 152 , 153 , 156 , 157Gd via (p,d) and (p,t) reactions. The silicon telescope STARS provided particle identification, residual nucleus energy and angular information. Coincident gamma rays were detected using the LIBERACE clover array. Details of new states identified in 153Gd and 157Gd will be presented as well as a method of extracting the spin distribution imparted to the nucleus via transfer reactions. This work supported in part by U.S. DOE grant numbers DE-FG02-05 ER41379 & DE-FG52-06 NA26206(University of Richmond), DE-AC52 07NA27344(LLNL) and DE-AC02 05CH11231(LBNL).

  2. A coincidence between a hydrocarbon plasma absorption spectrum and the λ5450 DIB

    NASA Astrophysics Data System (ADS)

    Linnartz, H.; Wehres, N.; van Winckel, H.; Walker, G. A. H.; Bohlender, D. A.; Tielens, A. G. G. M.; Motylewski, T.; Maier, J. P.

    2010-02-01

    Aims: The aim of this work is to link the broad λ5450 diffuse interstellar band (DIB) to a laboratory spectrum recorded through expanding acetylene plasma. Methods: Cavity ring-down direct absorption spectra and astronomical observations of HD 183143 with the HERMES spectrograph on the Mercator Telescope on La Palma and the McKellar spectrograph on the DAO 1.2 m Telescope are compared. Results: In the 543-547 nm region a broad band is measured with a band maximum at 545 nm and FWHM of 1.03(0.1) nm coinciding with a well-known diffuse interstellar band at λ5450 with an FWHM of 0.953 nm. Conclusions: A coincidence is found between the laboratory and the two independent observational studies obtained at higher spectral resolution. This result is important, as a match between a laboratory spectrum and a - potentially lifetime broadened - DIB is found. A series of additional experiments were performed in order to unambiguously identify the laboratory carrier of this band, but this was not successful. The laboratory results, however, restrict the carrier to a molecular transient, consisting of carbon and hydrogen.

  3. Ferritin Protein Nanocage Ion Channels

    PubMed Central

    Tosha, Takehiko; Behera, Rabindra K.; Ng, Ho-Leung; Bhattasali, Onita; Alber, Tom; Theil, Elizabeth C.

    2012-01-01

    Ferritin protein nanocages, self-assembled from four-α-helix bundle subunits, use Fe2+ and oxygen to synthesize encapsulated, ferric oxide minerals. Ferritin minerals are iron concentrates stored for cell growth. Ferritins are also antioxidants, scavenging Fenton chemistry reactants. Channels for iron entry and exit consist of helical hairpin segments surrounding the 3-fold symmetry axes of the ferritin nanocages. We now report structural differences caused by amino acid substitutions in the Fe2+ ion entry and exit channels and at the cytoplasmic pores, from high resolution (1.3–1.8 Å) protein crystal structures of the eukaryotic model ferritin, frog M. Mutations that eliminate conserved ionic or hydrophobic interactions between Arg-72 and Asp-122 and between Leu-110 and Leu-134 increase flexibility in the ion channels, cytoplasmic pores, and/or the N-terminal extensions of the helix bundles. Decreased ion binding in the channels and changes in ordered water are also observed. Protein structural changes coincide with increased Fe2+ exit from dissolved, ferric minerals inside ferritin protein cages; Fe2+ exit from ferritin cages depends on a complex, surface-limited process to reduce and dissolve the ferric mineral. High concentrations of bovine serum albumin or lysozyme (protein crowders) to mimic the cytoplasm restored Fe2+ exit in the variants to wild type. The data suggest that fluctuations in pore structure control gating. The newly identified role of the ferritin subunit N-terminal extensions in gating Fe2+ exit from the cytoplasmic pores strengthens the structural and functional analogies between ferritin ion channels in the water-soluble protein assembly and membrane protein ion channels gated by cytoplasmic N-terminal peptides. PMID:22362775

  4. Absolute 108Agm characterization based on gamma-gamma coincident detection by two NaI(Tl) detectors.

    PubMed

    Volkovitsky, Peter

    2010-01-01

    A two-dimensional analysis of three coincident gamma-rays in (108)Ag(m) decay, detected by two NaI(Tl) scintillation detectors, allows a direct measurement of the source activity. A modification of the Eldridge-Crowther formulas derived originally for (125)I was done recently for the case of two coincident gamma-rays in (60)Co decay (Volkovitsky and Naudus, 2009). A similar approach is applied to a more complicated case of three coincident gamma-rays in the (108)Ag(m) decay. The large number of experimental quantities, measured both in coincidence and anticoincidence modes, allows the determination of both detector efficiencies for all three gamma-ray photopeaks and to find the source activity. Results are compared with measurements of the activity of the same source with HPGe detectors. Published by Elsevier Ltd.

  5. A new coincidence model for single particle counters, Part II: Advances and applications.

    PubMed

    Knapp, J Z; Lieberman, A; Abramson, L R

    1994-01-01

    Accuracy, acceptance limits and methods for U.S.P. (788) contaminating particle assays published in the XXII Revision are refined in U.S.P. XXIII. In both Revisions, although different numerical values and methods are employed, particle contamination limits remain constants for all S.V.I. container volumes. The effect of this quality standard is high particle concentration acceptance limits in the smallest S.V.I. container sizes. The effect of these high concentrations is to introduce both undercount errors and false counts into U.S.P. (788) SVI contaminating particle assays. There is general agreement that the count of high concentrations of particles by a single particle light extinction counter result in an increase of the average size of the distribution of particles reported and a decrease in their total number. The error mechanism is termed "signal coincidence." Understanding and control of both these problems is unified with the introduction of the count efficiency parameter. Part I of this paper makes available two core concepts with which evaluation and control of coincidence error in single particle counters can be accurately quantified. These two core concepts are the "Particle Triggered Poisson Model," a new more accurate statistical model of the particle counting process and a concentration measure that includes the effect of particle size on the counting capability of a detector. Use of these concepts make it possible to evaluate particle detector count efficiency capability from experimental data of the coincidence effect. This is an application paper. It combines the theory in the Part I paper with the replicability of particle counters into a simple test protocol. The test results can be used to calculate a contour of particle size and count within which both undercount errors and the introduction of false counts into U.S.P. (788) particle assays are controlled. From the data analyzed it can be seen that any single particle size test cannot

  6. Feynman variance-to-mean in the context of passive neutron coincidence counting

    NASA Astrophysics Data System (ADS)

    Croft, S.; Favalli, A.; Hauck, D. K.; Henzlova, D.; Santi, P. A.

    2012-09-01

    Passive Neutron Coincidence Counting (PNCC) based on shift register autocorrelation time analysis of the detected neutron pulse train is an important Nondestructive Assay (NDA) method. It is used extensively in the quantification of plutonium and other spontaneously fissile materials for purposes of nuclear materials accountancy. In addition to the totals count rate, which is also referred to as the singles, gross or trigger rate, a quantity known as the reals coincidence rate, also called the pairs or doubles, is obtained from the difference between the measured neutron multiplicities in two measurement gates triggered by the incoming events on the pulse train. The reals rate is a measure of the number of time correlated pairs present on the pulse train and this can be related to the fission rates (and hence material mass) since fissions emit neutrons in bursts which are also detected in characteristic clusters. A closely related measurement objective is the determination of the reactivity of systems as they approach criticality. In this field an alternative autocorrelation signature is popular, the so called Feynman variance-to-mean technique which makes use of the multiplicity histogram formed the periodic, or clock-triggered opening of a coincidence gate. Workers in these two application areas share common challenges and improvement opportunities but are often separated by tradition, problem focus and technical language. The purpose of this paper is to recognize the close link between the Feynman variance-to-mean metric and traditional PNCC using shift register logic applied to correlated pulse trains. We, show using relationships for the late-gate (or accidentals) histogram recorded using a multiplicity shift register, how the Feynman Y-statistic, defined as the excess variance-to-mean ratio, can be expressed in terms of the singles and doubles rates familiar to the safeguards and waste assay communities. These two specialisms now have a direct bridge between

  7. Effects of Calcium Spikes in the Layer 5 Pyramidal Neuron on Coincidence Detection and Activity Propagation.

    PubMed

    Chua, Yansong; Morrison, Abigail

    2016-01-01

    The role of dendritic spiking mechanisms in neural processing is so far poorly understood. To investigate the role of calcium spikes in the functional properties of the single neuron and recurrent networks, we investigated a three compartment neuron model of the layer 5 pyramidal neuron with calcium dynamics in the distal compartment. By performing single neuron simulations with noisy synaptic input and occasional large coincident input at either just the distal compartment or at both somatic and distal compartments, we show that the presence of calcium spikes confers a substantial advantage for coincidence detection in the former case and a lesser advantage in the latter. We further show that the experimentally observed critical frequency phenomenon, in which action potentials triggered by stimuli near the soma above a certain frequency trigger a calcium spike at distal dendrites, leading to further somatic depolarization, is not exhibited by a neuron receiving realistically noisy synaptic input, and so is unlikely to be a necessary component of coincidence detection. We next investigate the effect of calcium spikes in propagation of spiking activities in a feed-forward network (FFN) embedded in a balanced recurrent network. The excitatory neurons in the network are again connected to either just the distal, or both somatic and distal compartments. With purely distal connectivity, activity propagation is stable and distinguishable for a large range of recurrent synaptic strengths if the feed-forward connections are sufficiently strong, but propagation does not occur in the absence of calcium spikes. When connections are made to both the somatic and the distal compartments, activity propagation is achieved for neurons with active calcium dynamics at a much smaller number of neurons per pool, compared to a network of passive neurons, but quickly becomes unstable as the strength of recurrent synapses increases. Activity propagation at higher scaling factors can be

  8. Effects of Calcium Spikes in the Layer 5 Pyramidal Neuron on Coincidence Detection and Activity Propagation

    PubMed Central

    Chua, Yansong; Morrison, Abigail

    2016-01-01

    The role of dendritic spiking mechanisms in neural processing is so far poorly understood. To investigate the role of calcium spikes in the functional properties of the single neuron and recurrent networks, we investigated a three compartment neuron model of the layer 5 pyramidal neuron with calcium dynamics in the distal compartment. By performing single neuron simulations with noisy synaptic input and occasional large coincident input at either just the distal compartment or at both somatic and distal compartments, we show that the presence of calcium spikes confers a substantial advantage for coincidence detection in the former case and a lesser advantage in the latter. We further show that the experimentally observed critical frequency phenomenon, in which action potentials triggered by stimuli near the soma above a certain frequency trigger a calcium spike at distal dendrites, leading to further somatic depolarization, is not exhibited by a neuron receiving realistically noisy synaptic input, and so is unlikely to be a necessary component of coincidence detection. We next investigate the effect of calcium spikes in propagation of spiking activities in a feed-forward network (FFN) embedded in a balanced recurrent network. The excitatory neurons in the network are again connected to either just the distal, or both somatic and distal compartments. With purely distal connectivity, activity propagation is stable and distinguishable for a large range of recurrent synaptic strengths if the feed-forward connections are sufficiently strong, but propagation does not occur in the absence of calcium spikes. When connections are made to both the somatic and the distal compartments, activity propagation is achieved for neurons with active calcium dynamics at a much smaller number of neurons per pool, compared to a network of passive neurons, but quickly becomes unstable as the strength of recurrent synapses increases. Activity propagation at higher scaling factors can be

  9. Coincidence and coherent data analysis methods for gravitational wave bursts in a network of interferometric detectors

    NASA Astrophysics Data System (ADS)

    Arnaud, Nicolas; Barsuglia, Matteo; Bizouard, Marie-Anne; Brisson, Violette; Cavalier, Fabien; Davier, Michel; Hello, Patrice; Kreckelbergh, Stephane; Porter, Edward K.

    2003-11-01

    Network data analysis methods are the only way to properly separate real gravitational wave (GW) transient events from detector noise. They can be divided into two generic classes: the coincidence method and the coherent analysis. The former uses lists of selected events provided by each interferometer belonging to the network and tries to correlate them in time to identify a physical signal. Instead of this binary treatment of detector outputs (signal present or absent), the latter method involves first the merging of the interferometer data and looks for a common pattern, consistent with an assumed GW waveform and a given source location in the sky. The thresholds are only applied later, to validate or not the hypothesis made. As coherent algorithms use more complete information than coincidence methods, they are expected to provide better detection performances, but at a higher computational cost. An efficient filter must yield a good compromise between a low false alarm rate (hence triggering on data at a manageable rate) and a high detection efficiency. Therefore, the comparison of the two approaches is achieved using so-called receiving operating characteristics (ROC), giving the relationship between the false alarm rate and the detection efficiency for a given method. This paper investigates this question via Monte Carlo simulations, using the network model developed in a previous article. Its main conclusions are the following. First, a three-interferometer network such as Virgo-LIGO is found to be too small to reach good detection efficiencies at low false alarm rates: larger configurations are suitable to reach a confidence level high enough to validate as true GW a detected event. In addition, an efficient network must contain interferometers with comparable sensitivities: studying the three-interferometer LIGO network shows that the 2-km interferometer with half sensitivity leads to a strong reduction of performances as compared to a network of three

  10. Polarisation-based coincidence event discrimination: an in silico study towards a feasible scheme for Compton-PET.

    PubMed

    Toghyani, M; Gillam, J E; McNamara, A L; Kuncic, Z

    2016-08-07

    Current positron emission tomography (PET) systems use temporally localised coincidence events discriminated by energy and time-of-flight information. The two annihilation photons are in an entangled polarisation state and, in principle, additional information from the polarisation correlation of photon pairs could be used to improve the accuracy of coincidence classification. In a previous study, we demonstrated that in principle, the polarisation correlation information could be transferred to an angular correlation in the distribution of scattered photon pairs in a planar Compton camera system. In the present study, we model a source-phantom-detector system using Geant4 and we develop a coincidence classification scheme that exploits the angular correlation of scattered annihilation quanta to improve the accuracy of coincidence detection. We find a [Formula: see text] image quality improvement in terms of the peak signal-to-noise ratio when scattered coincidence events are discriminated solely by their angular correlation, thus demonstrating the feasibility of this novel classification scheme. By integrating scatter events (both single-single and single-only) with unscattered coincidence events discriminated using conventional methods, our results suggest that Compton-PET may be a promising candidate for optimal emission tomographic imaging.

  11. Polarisation-based coincidence event discrimination: an in silico study towards a feasible scheme for Compton-PET

    NASA Astrophysics Data System (ADS)

    Toghyani, M.; Gillam, J. E.; McNamara, A. L.; Kuncic, Z.

    2016-08-01

    Current positron emission tomography (PET) systems use temporally localised coincidence events discriminated by energy and time-of-flight information. The two annihilation photons are in an entangled polarisation state and, in principle, additional information from the polarisation correlation of photon pairs could be used to improve the accuracy of coincidence classification. In a previous study, we demonstrated that in principle, the polarisation correlation information could be transferred to an angular correlation in the distribution of scattered photon pairs in a planar Compton camera system. In the present study, we model a source-phantom-detector system using Geant4 and we develop a coincidence classification scheme that exploits the angular correlation of scattered annihilation quanta to improve the accuracy of coincidence detection. We find a 22% image quality improvement in terms of the peak signal-to-noise ratio when scattered coincidence events are discriminated solely by their angular correlation, thus demonstrating the feasibility of this novel classification scheme. By integrating scatter events (both single-single and single-only) with unscattered coincidence events discriminated using conventional methods, our results suggest that Compton-PET may be a promising candidate for optimal emission tomographic imaging.

  12. Sav1 Loss Induces Senescence and Stat3 Activation Coinciding with Tubulointerstitial Fibrosis.

    PubMed

    Leung, Janet Y; Wilson, Harper L; Voltzke, Kristin J; Williams, Lindsay A; Lee, Hyo Jin; Wobker, Sara E; Kim, William Y

    2017-06-15

    Tubulointerstitial fibrosis (TIF) is recognized as a final phenotypic manifestation in the transition from chronic kidney disease (CKD) to end-stage renal disease (ESRD). Here we show that conditional inactivation of Sav1 in the mouse renal epithelium resulted in upregulated expression of profibrotic genes and TIF. Loss of Sav1 induced Stat3 activation and a senescence-associated secretory phenotype (SASP) that coincided with the development of tubulointerstitial fibrosis. Treatment of mice with the YAP inhibitor verteporfin (VP) inhibited activation of genes associated with senescence, SASPs, and activation of Stat3 as well as impeded the development of fibrosis. Collectively, our studies offer novel insights into molecular events that are linked to fibrosis development from Sav1 loss and implicate VP as a potential pharmacological inhibitor to treat patients at risk for developing CKD and TIF. Copyright © 2017 American Society for Microbiology.

  13. Sparse Auto-Calibration for Radar Coincidence Imaging with Gain-Phase Errors

    PubMed Central

    Zhou, Xiaoli; Wang, Hongqiang; Cheng, Yongqiang; Qin, Yuliang

    2015-01-01

    Radar coincidence imaging (RCI) is a high-resolution staring imaging technique without the limitation of relative motion between target and radar. The sparsity-driven approaches are commonly used in RCI, while the prior knowledge of imaging models needs to be known accurately. However, as one of the major model errors, the gain-phase error exists generally, and may cause inaccuracies of the model and defocus the image. In the present report, the sparse auto-calibration method is proposed to compensate the gain-phase error in RCI. The method can determine the gain-phase error as part of the imaging process. It uses an iterative algorithm, which cycles through steps of target reconstruction and gain-phase error estimation, where orthogonal matching pursuit (OMP) and Newton’s method are used, respectively. Simulation results show that the proposed method can improve the imaging quality significantly and estimate the gain-phase error accurately. PMID:26528981

  14. Energy and coincidence time resolution measurements of CdTe detectors for PET

    PubMed Central

    Ariño, G.; Chmeissani, M.; De Lorenzo, G.; Puigdengoles, C.; Cabruja, E.; Calderón, Y.; Kolstein, M.; Macias-Montero, J.G.; Martinez, R.; Mikhaylova, E.; Uzun, D.

    2013-01-01

    We report on the characterization of 2 mm thick CdTe diode detector with Schottky contacts to be employed in a novel conceptual design of PET scanner. Results at −8°C with an applied bias voltage of −1000 V/mm show a 1.2% FWHM energy resolution at 511 keV. Coincidence time resolution has been measured by triggering on the preamplifier output signal to improve the timing resolution of the detector. Results at the same bias and temperature conditions show a FWHM of 6 ns with a minimum acceptance energy of 500 keV. These results show that pixelated CdTe Schottky diode is an excellent candidate for the development of next generation nuclear medical imaging devices such as PET, Compton gamma cameras, and especially PET-MRI hybrid systems when used in a magnetic field immune configuration. PMID:23750177

  15. Energy and coincidence time resolution measurements of CdTe detectors for PET

    NASA Astrophysics Data System (ADS)

    Ariño, G.; Chmeissani, M.; De Lorenzo, G.; Puigdengoles, C.; Cabruja, E.; Calderón, Y.; Kolstein, M.; Macias-Montero, J. G.; Martinez, R.; Mikhaylova, E.; Uzun, D.

    2013-02-01

    We report on the characterization of 2 mm thick CdTe diode detector with Schottky contacts to be employed in a novel conceptual design of PET scanner. Results at -8°C with an applied bias voltage of -1000 V/mm show a 1.2% FWHM energy resolution at 511 keV. Coincidence time resolution has been measured by triggering on the preamplifier output signal to improve the timing resolution of the detector. Results at the same bias and temperature conditions show a FWHM of 6 ns with a minimum acceptance energy of 500 keV. These results show that pixelated CdTe Schottky diode is an excellent candidate for the development of next generation nuclear medical imaging devices such as PET, Compton gamma cameras, and especially PET-MRI hybrid systems when used in a magnetic field immune configuration.

  16. Direct fissile assay of enriched uranium using random self-interrogation and neutron coincidence response

    DOEpatents

    Menlove, H.O.; Stewart, J.E.

    1985-02-04

    Apparatus and method for the direct, nondestructive evaluation of the /sup 235/U nuclide content of samples containing UF/sub 6/, UF/sub 4/, or UO/sub 2/ utilizing the passive neutron self-interrogation of the sample resulting from the intrinsic production of neutrons therein. The ratio of the emitted neutron coincidence count rate to the total emitted neutron count rate is determined and yields a measure of the bulk fissile mass. The accuracy of the method is 6.8% (1sigma) for cylinders containing UF/sub 6/ with enrichments ranging from 6% to 98% with measurement times varying from 3-6 min. The samples contained from below 1 kg to greater than 16 kg. Since the subject invention relies on fast neutron self-interrogation, complete sampling of the UF/sub 6/ takes place, reducing difficulties arising from inhomogeneity of the sample which adversely affects other assay procedures. 4 figs., 1 tab.

  17. Direct fissile assay of enriched uranium using random self-interrogation and neutron coincidence response

    DOEpatents

    Menlove, Howard O.; Stewart, James E.

    1986-01-01

    Apparatus and method for the direct, nondestructive evaluation of the .sup.235 U nuclide content of samples containing UF.sub.6, UF.sub.4, or UO.sub.2 utilizing the passive neutron self-interrogation of the sample resulting from the intrinsic production of neutrons therein. The ratio of the emitted neutron coincidence count rate to the total emitted neutron count rate is determined and yields a measure of the bulk fissile mass. The accuracy of the method is 6.8% (1.sigma.) for cylinders containing UF.sub.6 with enrichments ranging from 6% to 98% with measurement times varying from 3-6 min. The samples contained from below 1 kg to greater than 16 kg. Since the subject invention relies on fast neutron self-interrogation, complete sampling of the UF.sub.6 takes place, reducing difficulties arising from inhomogeneity of the sample which adversely affects other assay procedures.

  18. Dislocation generation at near-coincidence site lattice grain boundaries during silicon directional solidification

    NASA Astrophysics Data System (ADS)

    Autruffe, Antoine; Stenhjem Hagen, Vegard; Arnberg, Lars; Di Sabatino, Marisa

    2015-02-01

    Bi-crystal silicon ingots separated by near-coincident site lattice (near-CSL) grain boundaries (GBs), namely Σ9 and Σ27a, have been grown in a small scale Bridgman-type furnace at 3 μm/s. Surface observations show different microstructure developments, depending on the nature of the seed GB and initial deviation from the low energy configuration. Grain boundary structure evolution and dislocation emission sources have been assessed for both types of GBs. Topological imperfections forming at the near - Σ9 and Σ27 GBs during the growth have been found to be the major source of defect generation. These imperfections are the result of the re-arrangement of the GBs during the growth due to the seed GBs deviation from low energy configurations - i.e. Σ9{221}1/{221}2 and Σ27a{511}1/{511}2.

  19. Cessation of feline calicivirus shedding coincident with resolution of chronic gingivostomatitis in a cat.

    PubMed

    Addie, D D; Radford, A; Yam, P S; Taylor, D J

    2003-04-01

    Feline calicivirus (FCV) shedding and oral bacterial flora were monitored over a period of 22 months in a case of feline gingivostomatitis (FGS). The cat was treated daily with 50 mg thalidomide capsules by mouth, and 200 mg lactoferrin powder was applied directly to the lesions. Clinical signs began to resolve after 11 months when, in addition to treatment, the diet had been changed to an additive-free cat food supplemented with antioxidant vitamins A, D3 and E. Resolution of clinical signs of FGS coincided with the cessation of FCV shedding, and this is the first report documenting such an association. Which part of the treatment, if any, contributed to the cure requires further investigation.

  20. When the Gomory-Chvatal Closure Coincides with the Integer Hull

    DTIC Science & Technology

    2016-03-01

    n and b̃ ∈ Zm, can be obtained in polynomial time from the vectors v1, v2, · · · , vn+ 3 . We can see from the coordinates of v1, v2, · · · , vn and vn... 3 that P is a n- dimensional polyhedron. Let i be a counter looping through n, n + 1 and n + 2. For every i vectors of v1, v2, · · · , vn+ 3 , check if...Closure Coincides with the Integer Hull 3 A negative result proved by Eisenbrand [10] is that GC-Sep is NP-hard, which implies the NP-hardness of GC-Opt as

  1. Growth of coincident site lattice matched semiconductor layers and devices on crystalline substrates

    DOEpatents

    Norman, Andrew G; Ptak, Aaron J

    2013-08-13

    Methods of fabricating a semiconductor layer or device and said devices are disclosed. The methods include but are not limited to providing a substrate having a crystalline surface with a known lattice parameter (a). The method further includes growing a crystalline semiconductor layer on the crystalline substrate surface by coincident site lattice matched epitaxy, without any buffer layer between the crystalline semiconductor layer and the crystalline surface of the substrate. The crystalline semiconductor layer will be prepared to have a lattice parameter (a') that is related to the substrate lattice parameter (a). The lattice parameter (a') maybe related to the lattice parameter (a) by a scaling factor derived from a geometric relationship between the respective crystal lattices.

  2. True coincidence summing corrections for an extended energy range HPGe detector

    SciTech Connect

    Venegas-Argumedo, Y.; Montero-Cabrera, M. E.

    2015-07-23

    True coincidence summing (TCS) effect for natural radioactive families of U-238 and Th-232 represents a problem when an environmental sample with a close source-detector geometry measurement is performed. By using a certified multi-nuclide standard source to calibrate an energy extended range (XtRa) HPGe detector, it is possible to obtain an intensity spectrum slightly affected by the TCS effect with energies from 46 to 1836 keV. In this work, the equations and some other considerations required to calculate the TCS correction factor for isotopes of natural radioactive chains are described. It is projected a validation of the calibration, performed with the IAEA-CU-2006-03 samples (soil and water)

  3. Synaptic diversity enables temporal coding of coincident multi-sensory inputs in single neurons

    PubMed Central

    Chabrol, François P.; Arenz, Alexander; Wiechert, Martin T.; Margrie, Troy W.; DiGregorio, David A.

    2015-01-01

    The ability of the brain to rapidly process information from multiple pathways is critical for reliable execution of complex sensory-motor behaviors, yet the cellular mechanisms underlying a neuronal representation of multimodal stimuli are poorly understood. Here we explored the possibility that the physiological diversity of mossy fiber (MF) to granule cell (GC) synapses within the mouse vestibulocerebellum may contribute to the processing of coincident multisensory information at the level of individual GCs. We found that the strength and short-term dynamics of individual MF-GC synapses can act as biophysical signatures for primary vestibular, secondary vestibular and visual input pathways. The majority of GCs receive inputs from different modalities, which when co-activated, produced enhanced GC firing rates and distinct first spike latencies. Thus, pathway-specific synaptic response properties permit temporal coding of correlated multisensory input by single GCs, thereby enriching sensory representation and facilitating pattern separation. PMID:25821914

  4. Frequent floods in the European Alps coincide with cooler periods of the past 2500 years.

    PubMed

    Glur, Lukas; Wirth, Stefanie B; Büntgen, Ulf; Gilli, Adrian; Haug, Gerald H; Schär, Christoph; Beer, Jürg; Anselmetti, Flavio S

    2013-09-26

    Severe floods triggered by intense precipitation are among the most destructive natural hazards in Alpine environments, frequently causing large financial and societal damage. Potential enhanced flood occurrence due to global climate change would thus increase threat to settlements, infrastructure, and human lives in the affected regions. Yet, projections of intense precipitation exhibit major uncertainties and robust reconstructions of Alpine floods are limited to the instrumental and historical period. Here we present a 2500-year long flood reconstruction for the European Alps, based on dated sedimentary flood deposits from ten lakes in Switzerland. We show that periods with high flood frequency coincide with cool summer temperatures. This wet-cold synchronism suggests enhanced flood occurrence to be triggered by latitudinal shifts of Atlantic and Mediterranean storm tracks. This paleoclimatic perspective reveals natural analogues for varying climate conditions, and thus can contribute to a better understanding and improved projections of weather extremes under climate change.

  5. Frequent floods in the European Alps coincide with cooler periods of the past 2500 years

    PubMed Central

    Glur, Lukas; Wirth, Stefanie B.; Büntgen, Ulf; Gilli, Adrian; Haug, Gerald H.; Schär, Christoph; Beer, Jürg; Anselmetti, Flavio S.

    2013-01-01

    Severe floods triggered by intense precipitation are among the most destructive natural hazards in Alpine environments, frequently causing large financial and societal damage. Potential enhanced flood occurrence due to global climate change would thus increase threat to settlements, infrastructure, and human lives in the affected regions. Yet, projections of intense precipitation exhibit major uncertainties and robust reconstructions of Alpine floods are limited to the instrumental and historical period. Here we present a 2500-year long flood reconstruction for the European Alps, based on dated sedimentary flood deposits from ten lakes in Switzerland. We show that periods with high flood frequency coincide with cool summer temperatures. This wet-cold synchronism suggests enhanced flood occurrence to be triggered by latitudinal shifts of Atlantic and Mediterranean storm tracks. This paleoclimatic perspective reveals natural analogues for varying climate conditions, and thus can contribute to a better understanding and improved projections of weather extremes under climate change. PMID:24067733

  6. A network of coincidence detector neurons with periodic and chaotic dynamics.

    PubMed

    Watanabe, Masataka; Aihara, Kazuyuki

    2004-09-01

    We propose a simple neural network model to understand the dynamics of temporal pulse coding. The model is composed of coincidence-detector neurons with uniform synaptic efficacies and random pulse propagation delays. We also assume a global negative feedback mechanism which controls the network activity, leading to a fixed number of neurons firing within a certain time window. Due to this constraint, the network state becomes well defined and the dynamics equivalent to a piecewise nonlinear map. Numerical simulations of the model indicate that the latency of neuronal firing is crucial to the global network dynamics; when the timing of postsynaptic firing is less sensitive to perturbations in timing of presynaptic spikes, the network dynamics become stable and periodic, whereas increased sensitivity leads to instability and chaotic dynamics. Furthermore, we introduce a learning rule which decreases the Lyapunov exponent of an attractor and enlarges the basin of attraction.

  7. Using gamma gamma coincidence measurements to validate Monte Carlo generated detector response functions

    NASA Astrophysics Data System (ADS)

    Metwally, W. A.; Gardner, R. P.; Sood, A.

    2007-10-01

    Monte Carlo simulation of gamma-ray transport for the purpose of performing elemental analysis of bulk samples requires the tracking of gamma rays in the sample and also in the detector(s) used. Detector response functions (DRF's) are an efficient and accurate variance reduction technique that greatly decreases the simulation time by substituting the tracking of gamma rays inside the detector by predefined single energy gamma-ray spectra. These spectra correspond to the average response of the detector for incident gamma rays. DRF's are generated by Monte Carlo methods and are benchmarked with experimental data. In this work, prompt gamma-gamma coincidence measurements are presented as a way to validate DRF's for high-energy gamma rays.

  8. A Recurrent Network in the Lateral Amygdala: A Mechanism for Coincidence Detection

    PubMed Central

    Johnson, Luke R.; Hou, Mian; Ponce-Alvarez, Adrian; Gribelyuk, Leo M.; Alphs, Hannah H.; Albert, Ladislau; Brown, Bruce L.; LeDoux, Joseph E.; Doyère, Valerie

    2008-01-01

    Synaptic changes at sensory inputs to the dorsal nucleus of the lateral amygdala (LAd) play a key role in the acquisition and storage of associative fear memory. However, neither the temporal nor spatial architecture of the LAd network response to sensory signals is understood. We developed a method for the elucidation of network behavior. Using this approach, temporally patterned polysynaptic recurrent network responses were found in LAd (intra-LA), both in vitro and in vivo, in response to activation of thalamic sensory afferents. Potentiation of thalamic afferents resulted in a depression of intra-LA synaptic activity, indicating a homeostatic response to changes in synaptic strength within the LAd network. Additionally, the latencies of thalamic afferent triggered recurrent network activity within the LAd overlap with known later occurring cortical afferent latencies. Thus, this recurrent network may facilitate temporal coincidence of sensory afferents within LAd during associative learning. PMID:19104668

  9. Coincidence Doppler broadening study of Eurofer 97 irradiated in spallation environment

    NASA Astrophysics Data System (ADS)

    Sabelová, V.; Kršjak, V.; Kuriplach, J.; Dai, Y.; Slugeň, V.

    2015-03-01

    The behavior of transmutation helium during isochronal annealing of irradiated Eurofer 97 was investigated using coincidence Doppler broadening spectroscopy (CDBS). The investigated ferritic martensitic steel was irradiated in 2000 and 2001 in the frame of the STIP-II project at the Swiss neutron spallation source (SINQ) (irradiation with neutrons and protons) at the Paul Scherrer Institute (PSI). During isochronal annealing experiment, coarsening of vacancy clusters and/or growth of helium bubbles was observed at T ⩾ 500 °C. This process causes an increase of low-momentum annihilation events and related increase of the S parameter during thermal treatment of material. On the other hand, the maximum concentration of helium in small vacancy clusters (Vn) was observed after annealing at 400 °C, where an excellent correlation with the calculated CDBS profiles of Vn + Hem clusters was found.

  10. The anti-coincidence detector for the GLAST large area telescope

    NASA Astrophysics Data System (ADS)

    Moiseev, A. A.; Hartman, R. C.; Ormes, J. F.; Thompson, D. J.; Amato, M. J.; Johnson, T. E.; Segal, K. N.; Sheppard, D. A.

    2007-06-01

    This paper describes the design, fabrication and testing of the Anti-Coincidence Detector (ACD) for the Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT). The ACD is LATs first-level defense against the charged cosmic ray background that outnumbers the gamma rays by 3 5 orders of magnitude. The ACD covers the top and four sides of the LAT tracking detector, requiring a total active area of ˜8.3 m2. The ACD detector utilizes plastic scintillator tiles with wavelength shifting fiber readout. In order to suppress self-veto by shower particles at high gamma-ray energies, the ACD is segmented into 89 tiles of different sizes. The overall ACD efficiency for detection of singly charged relativistic particles entering the tracking detector from the top or sides of the LAT exceeds the required 0.9997.

  11. Subducting slab ultra-slow velocity layer coincident with silent earthquakes in southern Mexico.

    PubMed

    Song, Teh-Ru Alex; Helmberger, Donald V; Brudzinski, Michael R; Clayton, Robert W; Davis, Paul; Pérez-Campos, Xyoli; Singh, Shri K

    2009-04-24

    Great earthquakes have repeatedly occurred on the plate interface in a few shallow-dipping subduction zones where the subducting and overriding plates are strongly locked. Silent earthquakes (or slow slip events) were recently discovered at the down-dip extension of the locked zone and interact with the earthquake cycle. Here, we show that locally observed converted SP arrivals and teleseismic underside reflections that sample the top of the subducting plate in southern Mexico reveal that the ultra-slow velocity layer (USL) varies spatially (3 to 5 kilometers, with an S-wave velocity of approximately 2.0 to 2.7 kilometers per second). Most slow slip patches coincide with the presence of the USL, and they are bounded by the absence of the USL. The extent of the USL delineates the zone of transitional frictional behavior.

  12. Do climate extreme events foster violent civil conflicts? A coincidence analysis

    NASA Astrophysics Data System (ADS)

    Schleussner, Carl-Friedrich; Donges, Jonathan F.; Donner, Reik V.

    2014-05-01

    Civil conflicts promoted by adverse environmental conditions represent one of the most important potential feedbacks in the global socio-environmental nexus. While the role of climate extremes as a triggering factor is often discussed, no consensus is yet reached about the cause-and-effect relation in the observed data record. Here we present results of a rigorous statistical coincidence analysis based on the Munich Re Inc. extreme events database and the Uppsala conflict data program. We report evidence for statistically significant synchronicity between climate extremes with high economic impact and violent conflicts for various regions, although no coherent global signal emerges from our analysis. Our results indicate the importance of regional vulnerability and might aid to identify hot-spot regions for potential climate-triggered violent social conflicts.

  13. Calculation of true coincidence summing corrections for extended sources with EFFTRAN.

    PubMed

    Vidmar, Tim; Kanisch, Günter; Vidmar, Gaj

    2011-06-01

    A deterministic code was developed for the calculation of true coincidence summing correction factors and has been incorporated into the EFFTRAN tool. The approach is aimed at the analysis of extended samples measured on p-type HPGe detectors in environmental gamma-ray spectrometry and was verified against the results of a state-of-the-art full Monte Carlo code. The two sets of results matched on average within 1%. Our code requires no measurements in addition to a standard full-energy-peak calibration, has a very short run time and takes into account the spatial variation of the efficiency across the sample volume. The EFFTRAN code is free software, available from the authors on request.

  14. Evaluation of MISR Land Surface BRF Measurements: Intercomparison with Coincident Airborne and Ground Field Measurements

    NASA Technical Reports Server (NTRS)

    Abdou, Wedad A.; Helmlinger, Mark C.; Jovanovic, Veljko M.; Martonchik, John V.; Diner, David J.; Gatebe, Charles K.; King, Michael D.

    2005-01-01

    The bidirectional reflectance factor, BRF, retrieved by the Multiangle Imaging SpectroRadiometer, MISR, is compared with those coincidently measured from aircraft, by the Cloud Absorption Radiometer, CAR, and MISR airborne simulator, AirMISR, and on the ground, by the Portable Apparatus for Rabid Acquisition of Bidirectional Observations of Land and Atmosphere, PARABOLA Ill. The intercomparisons are made for six types of surfaces: bright desert, salt pans, grassland, forests, snow and the Dismal Swamp. The results show that MISR BRF values are mostly within +/- 10% in agreement with the corresponding airborne and ground measurements, independent of the surface types This study is part of an effort to evaluate and validate MISR surface products.

  15. Coincidence theorem for the direct correlation function of hard-particle fluids

    NASA Astrophysics Data System (ADS)

    Wertheim, M. S.

    1988-09-01

    The Mayer f-function for purely hard particles of arbitrary shape satisfies f 2(1, 2)=- f(1, 2). This relation can be introduced into the graphical expansion of the direct correlation function c(1, 2) to obtain a graphical expression for the case of exact coincidence, in position and orientation, of two identical hard cores. The resulting expression for c(1, 1)+1 contains only graphs G from c(1), the sum of irreducible graphs with one labeled point. Relative to its coefficient in c(1), G occurs in c(1, 1) with an additional factor R c which is 1 for the leading graph in the expansion and of the form 2-2 L( G) for all other graphs. Here L( G)=0, 1, 2,..., is a nonnegative integer. Topological analysis is used to derive an expression for L( G) in terms of the connectivity properties of G.

  16. Coincidence, historical repetition, and self-knowledge: Jung, Vico, and Joyce.

    PubMed

    Verene, Donald Phillip

    2002-07-01

    Jung develops synchronicity as an a causal principle of connection by recounting various examples of meaningful coincidence from experience and by analysing various systems of divination, notably the I Ching. Philosophical theory of causality has given no significant attention to synchronicity; the events of synchronicity are regarded as chance. The Neapolitan philosopher Giambattista Vico (1668-1744) developed a doctrine of historical experience and of self-knowledge that grounds the phenomenon of synchronicity in a metaphysics. James Joyce employed Vico's conception of language and historical cycles as the basis of Joyce's final literary work, Finnegans Wake. Vico's metaphysical sense of synchronicity and Joyce's literary formulation offer a grounding of this principle in non-divinatory sources in modern Western thought, something which Jung's discussion does not provide. These philosophical and literary perspectives complement Jung's to offer an expanded context in which to recognize synchronicity and to make sense of it.

  17. Field test and evaluation of the passive neutron coincidence collar for prototype fast reactor fuel subassemblies

    SciTech Connect

    Menlove, H.O.; Keddar, A.

    1982-08-01

    The passive neutron Coincidence Collar, which was developed for the verification of plutonium content in fast reactor fuel subassemblies, has been field tested using Prototype Fast Reactor fuel. For passive applications, the system measures the /sup 240/Pu-effective mass from the spontaneous fission rate, and in addition, a self-interrogation technique is used to determine the fissile content in the subassembly. Both the passive and active modes were evaluated at the Windscale Works in the United Kingdom. The results of the tests gave a standard deviation 0.75% for the passive count and 3 to 7% for the active measurement for a 1000-s counting time. The unit will be used in the future for the verification of plutonium in fresh fuel assemblies.

  18. Nothing can be coincidence: synaptic inhibition and plasticity in the cerebellar nuclei

    PubMed Central

    Pugh, Jason R.; Raman, Indira M.

    2009-01-01

    Many cerebellar neurons fire spontaneously, generating 10–100 action potentials per second even without synaptic input. This high basal activity correlates with information-coding mechanisms that differ from those of cells that are quiescent until excited synaptically. For example, in the deep cerebellar nuclei, Hebbian patterns of coincident synaptic excitation and postsynaptic firing fail to induce long-term increases in the strength of excitatory inputs. Instead, excitatory synaptic currents are potentiated by combinations of inhibition and excitation that resemble the activity of Purkinje and mossy fiber afferents that is predicted to occur during cerebellar associative learning tasks. Such results indicate that circuits with intrinsically active neurons have rules for information transfer and storage that distinguish them from other brain regions. PMID:19178955

  19. Coincidence detection of spatially correlated photon pairs with a monolithic time-resolving detector array.

    PubMed

    Unternährer, Manuel; Bessire, Bänz; Gasparini, Leonardo; Stoppa, David; Stefanov, André

    2016-12-12

    We demonstrate coincidence measurements of spatially entangled photons by means of a multi-pixel based detection array. The sensor, originally developed for positron emission tomography applications, is a fully digital 8×16 silicon photomultiplier array allowing not only photon counting but also per-pixel time stamping of the arrived photons with an effective resolution of 265 ps. Together with a frame rate of 500 kfps, this property exceeds the capabilities of conventional charge-coupled device cameras which have become of growing interest for the detection of transversely correlated photon pairs. The sensor is used to measure a second-order correlation function for various non-collinear configurations of entangled photons generated by spontaneous parametric down-conversion. The experimental results are compared to theory.

  20. Characterizations of double pulsing in neutron multiplicity and coincidence counting systems

    NASA Astrophysics Data System (ADS)

    Koehler, Katrina E.; Henzl, Vladimir; Croft, Stephen S.; Henzlova, Daniela; Santi, Peter A.

    2016-10-01

    Passive neutron coincidence/multiplicity counters are subject to non-ideal behavior, such as double pulsing and dead time. It has been shown in the past that double-pulsing exhibits a distinct signature in a Rossi-alpha distribution, which is not readily noticed using traditional Multiplicity Shift Register analysis. However, it has been assumed that the use of a pre-delay in shift register analysis removes any effects of double pulsing. In this work, we use high-fidelity simulations accompanied by experimental measurements to study the effects of double pulsing on multiplicity rates. By exploiting the information from the double pulsing signature peak observable in the Rossi-alpha distribution, the double pulsing fraction can be determined. Algebraic correction factors for the multiplicity rates in terms of the double pulsing fraction have been developed. We discuss the role of these corrections across a range of scenarios.

  1. Exact solutions for rate and synchrony in recurrent networks of coincidence detectors.

    PubMed

    Mikula, Shawn; Niebur, Ernst

    2008-11-01

    We provide analytical solutions for mean firing rates and cross-correlations of coincidence detector neurons in recurrent networks with excitatory or inhibitory connectivity, with rate-modulated steady-state spiking inputs. We use discrete-time finite-state Markov chains to represent network state transition probabilities, which are subsequently used to derive exact analytical solutions for mean firing rates and cross-correlations. As illustrated in several examples, the method can be used for modeling cortical microcircuits and clarifying single-neuron and population coding mechanisms. We also demonstrate that increasing firing rates do not necessarily translate into increasing cross-correlations, though our results do support the contention that firing rates and cross-correlations are likely to be coupled. Our analytical solutions underscore the complexity of the relationship between firing rates and cross-correlations.

  2. Insight on hole-hole interaction and magnetic order from dichroic auger-photoelectron coincidence spectra.

    PubMed

    Cini, M; Perfetto, E; Gotter, R; Offi, F; Ruocco, A; Stefani, G

    2011-11-18

    The absence of sharp structures in the Auger line shapes of partially filled bands has severely limited the use of electron spectroscopy in magnetic crystals and other correlated materials. By a novel interplay of experimental and theoretical techniques we achieve a combined understanding of the photoelectron, Auger, and Auger-photoelectron coincidence spectra (APECS) of the antiferromagnetic CoO. A recently discovered dichroic effect in angle resolved (DEAR) APECS reveals a complex pattern in the Auger line shape, which is here explained in detail, labeling the final states by their total spin. Since the dichroic effect exists in the antiferromagnetic state but vanishes at the Néel temperature, the DEAR-APECS technique detects the phase transition from its local effects, thus providing a unique tool to observe and understand magnetic correlations where the usual methods are not applicable.

  3. Intrinsically disordered tau protein in Alzheimer's tangles: a coincidence or a rule?

    PubMed

    Skrabana, R; Skrabanova, M; Csokova, N; Sevcik, J; Novak, M

    2006-01-01

    Tau protein, the major constituent of neurofibrillary tangles in Alzheimer's disease (AD) and related tauopathies, is classified as intrinsically disordered protein (IDP). IDPs in contrast to globular proteins contain high proportion of polar and charged amino acids in their sequence, which results in the absence of a well-defined three-dimensional structure of the free protein. Structural flexibility of IDPs is required to perform their important role in many cellular processes. In the course of tauopathies, highly soluble disordered tau protein acquires rigid fold and forms highly insoluble filaments. Beneficial intrinsic disorder transforms into a fatal order: is it a coincidence, or is there an underlying reason for preferential IDPs assembly? In this review we present the structural characteristics of tau protein filamentous lesions in AD and discuss the tendency of IDPs to assembly and to form amyloid deposits (Ref: 65).

  4. Characterizations of double pulsing in neutron multiplicity and coincidence counting systems

    DOE PAGES

    Koehler, Katrina E.; Henzl, Vladimir; Croft, Stephen; ...

    2016-06-29

    Passive neutron coincidence/multiplicity counters are subject to non-ideal behavior, such as double pulsing and dead time. It has been shown in the past that double-pulsing exhibits a distinct signature in a Rossi-alpha distribution, which is not readily noticed using traditional Multiplicity Shift Register analysis. But, it has been assumed that the use of a pre-delay in shift register analysis removes any effects of double pulsing. Here, we use high-fidelity simulations accompanied by experimental measurements to study the effects of double pulsing on multiplicity rates. By exploiting the information from the double pulsing signature peak observable in the Rossi-alpha distribution, themore » double pulsing fraction can be determined. Algebraic correction factors for the multiplicity rates in terms of the double pulsing fraction have been developed. We also discuss the role of these corrections across a range of scenarios.« less

  5. The Anti-Coincidence Detector for the GLAST Large Area Telescope

    SciTech Connect

    Moiseev, A.A.; Hartman, R.C.; Ormes, J.F.; Thompson, D.J.; Amato, M.J.; Johnson, T.E.; Segal, K.N.; Sheppard, D.A.

    2007-03-23

    This paper describes the design, fabrication and testing of the Anti-Coincidence Detector (ACD) for the Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT). The ACD is LAT's first-level defense against the charged cosmic ray background that outnumbers the gamma rays by 3-5 orders of magnitude. The ACD covers the top and 4 sides of the LAT tracking detector, requiring a total active area of {approx}8.3 square meters. The ACD detector utilizes plastic scintillator tiles with wave-length shifting fiber readout. In order to suppress self-veto by shower particles at high gamma-ray energies, the ACD is segmented into 89 tiles of different sizes. The overall ACD efficiency for detection of singly charged relativistic particles entering the tracking detector from the top or sides of the LAT exceeds the required 0.9997.

  6. Catalyzing Transdisciplinarity: A Systems Ethnography of Cancer-Obesity Comorbidity and Risk Coincidence.

    PubMed

    Graham, S Scott; Harley, Amy; Kessler, Molly M; Roberts, Laura; DeVasto, Dannielle; Card, Daniel J; Neuner, Joan M; Kim, Sang-Yeon

    2017-05-01

    Effectively addressing wicked health problems, that is, those arising from complex multifactorial biological and socio-economic causes, requires transdisciplinary action. However, a significant body of research points toward substantial difficulties in cultivating transdisciplinary collaboration. Accordingly, this article presents the results of a study that adapts Systems Ethnography and Qualitative Modeling (SEQM) in response to wicked health problems. SEQM protocols were designed to catalyze transdisciplinary responses to national defense concerns. We adapted these protocols to address cancer-obesity comorbidity and risk coincidence. In so doing, we conducted participant-observations and interviews with a diverse range of health care providers, community health educators, and health advocacy professionals who target either cancer or obesity. We then convened a transdisciplinary conference designed to catalyze a coordinated response. The findings offer productive insights into effective ways of catalyzing transdisciplinarity in addressing wicked health problems action and demonstrate the promise of SEQM for continued use in health care contexts.

  7. Antidepressant-coincident mania in children and adolescents treated with selective serotonin reuptake inhibitors

    PubMed Central

    Joseph, Megan F; Youngstrom, Eric A; Soares, Jair C

    2009-01-01

    Several factors have amplified concern about the possibility that antidepressant medication may contribute to induction of pediatric mania. These include the high rate of antidepressant medication prescription, the recent surge in the rate of diagnosis of pediatric bipolar disorder in the USA, and a growing number of case reports and clinical studies showing coincidence of manic symptoms with antidepressant pharmacotherapy in both youths and adults. However, the question of how medications and manic symptoms might be related is complicated, and decisive research studies with rigorous designs for evaluating the issues have not been published. The situation makes it difficult for practitioners to make good, evidence-based decisions. The scientific literature is ambiguous, and the stakes are high. We review the extant literature, offer seven different conceptual models of how medication and mania might be related, and comment on the evidence and clinical implications of each. PMID:19884978

  8. Time-and-frequency-gated photon coincidence counting; a novel multidimensional spectroscopy tool

    NASA Astrophysics Data System (ADS)

    Dorfman, Konstantin E.; Mukamel, Shaul

    2016-08-01

    Coherent multidimensional optical spectroscopy is broadly applied across the electromagnetic spectrum ranging from NMR to UV. These techniques reveal the properties of matter through the correlation plots of signal fields generated in response to sequences of short pulses with variable delays. Here we discuss a new class of multidimensional techniques obtained by the time-and-frequency-resolved photon coincidence counting measurements of N photons, which constitute a 2N dimensional spectrum. A compact description of these signals is developed based on time-ordered superoperators rather than the normally ordered ordinary operators used in Glauber's photon counting formalism. The independent control of the time and frequency gate parameters reveals fine details of matter dynamics not available otherwise. These signal are illustrated for application to an anharmonic oscillator model with fluctuating energy and anharmonicity.

  9. Pressure oscillations on the surface of Gale Crater and coincident observations of global circulation patterns.

    NASA Astrophysics Data System (ADS)

    De La Torre Juarez, M.; Kass, D. M.; Haberle, R. M.; Gómez-Elvira, J.; Harri, A. M.; Kleinboehl, A.; Kahanpää, H.; Kahre, M. A.; Lemmon, M. T.; Martín-Torres, J.; Newman, C. E.; Rafkin, S. C.; Rodriguez-Manfredi, J. A.; Peinado, V.; Vasavada, A. R.; Zorzano, M. P.

    2014-12-01

    The annual cycle of mean diurnal surface pressures observed by Curiosity's Rover Environmental Monitoring Station (REMS) has shown oscillations after two Southern Hemispheric storms that occurred before the annual pressure maxima and minima of the dusty season (Ls~250 and 330). The oscillations had a period of ~7 sols and were less visible or absent during the dust free seasons (Ls ~ 0). Martian airborne dust alters the atmosphere's response to solar radiation and the resulting heating profiles. Since the atmospheric circulation responds to thermal forcing by the Sun, atmospheric dust can alter the large-scale circulation. We use coincident global observations by the Mars Climate Sounder (MCS) to examine the global circulation. We find that the observed surface pressure oscillations relate to oscillations of the Hadley cell. We also analyze the potential impacts of these coupled oscillations especially as related to traveling waves and thermal tides.

  10. Adult onset Still's disease diagnosed concomitantly with occult papillary thyroid cancer: paraneoplastic manifestation or coincidence?

    PubMed

    Ahn, Joong Kyong; Oh, Ji-Min; Lee, Jaejoon; Kim, Sun Wook; Cha, Hoon-Suk; Koh, Eun-Mi

    2010-02-01

    Adult onset Still's disease (AOSD) is an inflammatory disease of unknown etiology, characterized by spiking fever, evanescent salmon pink maculopapular rash, arthritis, and leukocytosis with neutrophilia. Malignant lymphoma is one of the most important differential diagnoses of AOSD. AOSD has been reported as one of paraneoplastic syndromes associated with breast cancer. We report a rare case of occult papillary thyroid cancer (PTC) diagnosed coincidently with AOSD. A 32-year-old woman was diagnosed with AOSD according to the diagnostic criteria of Yamaguchi as follows: leukocytosis with neutrophilia, high fever with 39 degrees C and above, arthralgia/arthritis, sore throat, liver dysfunctions, and lymphadenopathy. Excisional biopsy of cervical lymph node showed metastatic papillary carcinoma, and immunohistochemical staining for thyroglobulin and thyroid transcription factor-1 was strongly positive. There was no evidence of focal lesion in the thyroid glands. To our knowledge, this is the first report of adult onset Still's disease diagnosed concomitantly with occult PTC.

  11. The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) Front Anti-Coincidence Counter (FACC) Testing

    NASA Astrophysics Data System (ADS)

    Chen, Mingqian

    The searching for proton decay (PDK) is going on current Water Cherenkov (WCh) detectors such as Super-Kamiokande. However, PDK-like backgrounds produced by the neutrino interactions will limit the sensitivity of the detectors. The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) is going to measure the neutron yield of neutrino interactions in gadolinium-loaded water by the Booster Neutrino Beam (BNB) with known characteristics. In this thesis, neutrino, neutrino oscillations, Dirac neutrino and Majorana neutrino and neutrino interactions are introduced. ANNIE experiment is also introduced. And two modes of proton decays are discussed. The ANNIE experiment requires detection of the neutrons produced by the BNB interactions with water. However, dirt muons produced by the interaction of the BNB with the rock and dirt upstream of the ANNIE hall will cause a correlated background. Therefore, the Front Anti-Coincidence Counter (FACC) was built to measure the rock muons. This thesis details the design, installation, and commissioning of the ANNIE FACC.

  12. Characterizations of double pulsing in neutron multiplicity and coincidence counting systems

    SciTech Connect

    Koehler, Katrina E.; Henzl, Vladimir; Croft, Stephen; Henzlova, Daniela; Santi, Peter A.

    2016-06-29

    Passive neutron coincidence/multiplicity counters are subject to non-ideal behavior, such as double pulsing and dead time. It has been shown in the past that double-pulsing exhibits a distinct signature in a Rossi-alpha distribution, which is not readily noticed using traditional Multiplicity Shift Register analysis. But, it has been assumed that the use of a pre-delay in shift register analysis removes any effects of double pulsing. Here, we use high-fidelity simulations accompanied by experimental measurements to study the effects of double pulsing on multiplicity rates. By exploiting the information from the double pulsing signature peak observable in the Rossi-alpha distribution, the double pulsing fraction can be determined. Algebraic correction factors for the multiplicity rates in terms of the double pulsing fraction have been developed. We also discuss the role of these corrections across a range of scenarios.

  13. Calculation of Coincidence Summing Correction Factors for an HPGe detector using GEANT4.

    PubMed

    Giubrone, G; Ortiz, J; Gallardo, S; Martorell, S; Bas, M C

    2016-07-01

    The aim of this paper was to calculate the True Coincidence Summing Correction Factors (TSCFs) for an HPGe coaxial detector in order to correct the summing effect as a result of the presence of (88)Y and (60)Co in a multigamma source used to obtain a calibration efficiency curve. Results were obtained for three volumetric sources using the Monte Carlo toolkit, GEANT4. The first part of this paper deals with modeling the detector in order to obtain a simulated full energy peak efficiency curve. A quantitative comparison between the measured and simulated values was made across the entire energy range under study. The True Summing Correction Factors were calculated for (88)Y and (60)Co using the full peak efficiencies obtained with GEANT4. This methodology was subsequently applied to (134)Cs, and presented a complex decay scheme. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Threshold-photoelectron-spectroscopy-coincidence study of the double photoionization of HBr.

    PubMed

    Alagia, Michele; Brunetti, Brunetto G; Candori, Pietro; Falcinelli, Stefano; Teixidor, Marc Moix; Pirani, Fernando; Richter, Robert; Stranges, Stefano; Vecchiocattivi, Franco

    2004-04-15

    A threshold-photoelectron-coincidence spectrum of HBr has been recorded in the 32.2-35.8 eV photon energy range, with a resolution of approximately 0.01 eV, using a synchrotron radiation source. The X (3)Sigma(-) and a (1)Delta(2) states of the HBr(2+) dication are clearly observed in the spectrum, while there is no clear evidence for the formation of the b (1)Sigma(+) electronic state. For the first two states, the vibrational states v=0-3 have been resolved, while for the ground X (3)Sigma(-) state also spin-orbit splitting has been detected. The results appear in good agreement with previous experimental observations. A comparison with theoretical predictions indicates the role of "noncovalent" contributions to the interaction between the two atomic partners for the formation of metastable states.

  15. Uncertainties in calculated correction factors for true coincidence-summing (TCS).

    PubMed

    Kastlander, J; De Geer, L-E; Jonsson, S; Ramebäck, H

    2017-04-01

    The aim of this work was to estimate the uncertainties in Monte Carlo calculated correction factors for true coincidence summing (TCS). In this work TCS-factors and their uncertainties were calculated for (134)Cs and then the corrected activities compared to empirical data. The study was carried out using a close-end coaxial p-type detector (Ø80mm×54.5mm, 80% relative efficiency) and a cylindrical glass fiber sample (Ø60mm×14mm). It was shown that the uncertainty in the calculated correction factor for the primary gamma ray was below 0.5%, which means it will not contribute significantly to the combined uncertainty in an activity measurement for e.g. environmental monitoring.

  16. EMRIs and the relativistic loss-cone: The curious case of the fortunate coincidence

    NASA Astrophysics Data System (ADS)

    Alexander, Tal

    2017-05-01

    Extreme mass ratio inspiral (EMRI) events are vulnerable to perturbations by the stellar background, which can abort them prematurely by deflecting EMRI orbits to plunging ones that fall directly into the massive black hole (MBH), or to less eccentric ones that no longer interact strongly with the MBH. A coincidental hierarchy between the collective resonant Newtonian torques due to the stellar background, and the relative magnitudes of the leading-order post-Newtonian precessional and radiative terms of the general relativistic 2-body problem, allows EMRIs to decouple from the background and produce semi-periodic gravitational wave signals. I review the recent theoretical developments [1] that confirm this conjectured fortunate coincidence [2], and briefly discuss the implications for EMRI rates, and show how these dynamical effects can be probed locally by stars near the Galactic MBH.

  17. Albright's hereditary osteodystrophy associated with cerebellar pilocytic astrocytoma: coincidence or genetic relationship?

    PubMed

    Sobottka, S B; Huebner, A; Haase, M; Ahrens, W; Rupprecht, E; Schackert, H K; Schackert, G

    2001-01-01

    Albright's hereditary osteodystrophy (AHO) is a rare inherited disease characterized by skeletal abnormalities, short stature, and, in some cases, resistance to parathyroid hormone, resulting in pseudohypoparathyroidism (PHP). Heterozygous inactivating mutations of the GNAS1 gene are responsible for reduced activity of the alpha subunit of the Gs protein (G(Salpha)), a protein that mediates hormone signal transduction across cell membranes. G(salpha) is also known to have oncogenic potentials, leading to the development of human pituitary tumors and Leydig cell tumors. Here, we report the 1st case, a 3.5-year-old girl, with classic AHO phenotype and PHP type 1A associated with a cerebellar pilocytic astrocytoma. Coincidence or genetic relationships of both diseases are discussed according to molecular findings and current literature. Copyright 2001 S. Karger AG, Basel

  18. Performance of the Anti-Coincidence Detector on the GLAST Large Area Telescope

    SciTech Connect

    Thompson, D.J.; Charles, E.; Hartman, R.C.; Moiseev, A.A.; Ormes, J.F.; /NASA, Goddard /Denver U.

    2007-10-22

    The Anti-Coincidence Detector (ACD), the outermost detector layer in the Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT), is designed to detect and veto incident cosmic ray charged particles, which outnumber cosmic gamma rays by 3-4 orders of magnitude. The challenge in ACD design is that it must have high (0.9997) detection efficiency for singly-charged relativistic particles, but must also have a low probability for self-veto of high-energy gammas by backsplash radiation from interactions in the LAT calorimeter. Simulations and tests demonstrate that the ACD meets its design requirements. The performance of the ACD has remained stable through stand-alone environmental testing, shipment across the U.S., installation onto the LAT, shipment back across the U.S., LAT environmental testing, and shipment to Arizona. As part of the fully-assembled GLAST observatory, the ACD is being readied for final testing before launch.

  19. The ability of the Coincidence Doppler Broadening Spectroscopy to characterize polymers containing different chemical elements

    NASA Astrophysics Data System (ADS)

    Yang, J.; Zhang, T.; Han, L. A.; Cao, X. Z.; Yu, R. S.; Wang, B. Y.

    2017-04-01

    Hydrocarbon polymers, O-containing, F-containing and Cl-containing polymers are comprehensively studied by Coincidence Doppler Broadening Spectroscopy (CDBS). It is shown that for polymers with different chemical structure, CDBS results can effectively distinguish polar groups C dbnd O, Csbnd Cl, and Csbnd F. For polymers with similar chemical structure, the intensity of the element-specific peak in the CDBS ratio curve is dependent not only on the fraction of free positrons, but also on the content of characteristic atom in polymer repeated unit, and the polarity of the polymer molecule. For polymers containing several different polar groups, such as PCTFE (Csbnd F & Csbnd Cl) and PFA (Csbnd F & C dbnd O), whether the element-specific peak appears or not depends on the amount of the polar groups and its positron capture ability. This work may provide insights into potential applications of CDBS for studying complex polymer systems.

  20. The underwater coincidence counter for plutonium measurements in mixed-oxide fuel assemblies manual

    SciTech Connect

    G. W. Eccleston; H. O. Menlove; M. Abhold; M. Baker; J. Pecos

    1999-05-01

    This manual describes the Underwater Coincidence Counter (UWCC) that has been designed for the measurement of plutonium in mixed-oxide (MOX) fuel assemblies prior to irradiation. The UWCC uses high-efficiency {sup 3}He neutron detectors to measure the spontaneous-fission and induced-fission rates in the fuel assembly. Measurements can be made on MOX fuel assemblies in air or underwater. The neutron counting rate is analyzed for singles, doubles, and triples time correlations to determine the {sup 240}Pu effective mass per unit length of the fuel assembly. The system can verify the plutonium loading per unit length to a precision of less than 1% in a measurement time of 2 to 3 minutes. System design, components, performance tests, and operational characteristics are described in this manual.