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Sample records for 2p2 1sedouble excitation

  1. CCQE, 2p2h excitations and ν—energy reconstruction

    SciTech Connect

    Nieves, J.; Simo, I. Ruiz; Sánchez, F.; Vacas, M. J. Vicente

    2015-05-15

    We analyze the MiniBooNE muon neutrino CCQE-like dσ/dT{sub μ} d cos θ{sub μ} data using a theoretical model that, among other nuclear effects, includes RPA correlations and 2p2h (multinucleon) mechanisms. These corrections turn out to be essential for the description of the data. We find that MiniBooNE CCQE-like data are fully compatible with former determinations of the nucleon axial mass M{sub A} ∼ 1.05 GeV. This is in sharp contrast with several previous analysis where anomalously large values of M{sub A} ∼ 1.4 GeV have been suggested. We also show that because of the the multinucleon mechanism effects, the algorithm used to reconstruct the neutrino energy is not adequate when dealing with quasielastic-like events. Finally, we analyze the MiniBooNE unfolded cross section, and show that it exhibits an excess (deficit) of low (high) energy neutrinos, which is an artifact of the unfolding process that ignores 2p2h mechanisms.

  2. Blue-green luminescence in Hg free excited Sr2P2O7:Tb3+ pyrophosphate phosphor for NUV excited LEDs

    NASA Astrophysics Data System (ADS)

    Kohale, R. L.; Chimankar, O. P.; Dhoble, S. J.

    2015-02-01

    Tb3+ activated Sr2P2O7 phosphor was prepared by modified solid state diffusion technique at 700°C. The XRD pattern of Sr2P2O7 is in well argument with the standard ICDD File (24-1011) available. Surface morphology of the present phosphor has been studied by scanning electron microscope (SEM). In photoluminescence investigation, the excitation spectra of the phosphor extends from 200 to 400 nm gives optimum absorption at 352 nm, which is mercury free excitation and characteristics of NUV excited LED. Under the excitation of 352 nm, Sr2P2O7 doped with trivalent terbium ions produces weak blue emission between 400-500 nm owing to the 5D3 to the 7FJ transitions of Tb3+ and strong green emission in 500650 nm region of the visible spectrum due to the 4f-4f transitions from the 5D4 to 7FJ (J=6, 5, 4, 3) states of Tb3+. The entire study reveals that the present phosphor have promising applications in the lamp industry especially for solid state lighting (mercury free excited lamp phosphor) and NUV LEDs.

  3. Absolute cross sections for near-threshold electron-impact excitation of the 2s 2S-->2p 2P transition in C3+

    NASA Astrophysics Data System (ADS)

    Bannister, M. E.; Chung, Y.-S.; Djurić, N.; Wallbank, B.; Woitke, O.; Zhou, S.; Dunn, G. H.; Smith, A. C.

    1998-01-01

    Absolute total cross sections for electron-impact excitation of the 2s 2S-->2p 2P transition in C3+ were measured from 7.35 eV to 8.45 eV using the merged electron-ion-beams energy-loss technique. The results settle the discrepancy between two previous experiments using the crossed-beams fluorescence method, being in very good agreement with the older results [P. O. Taylor, D. Gregory, G. H. Dunn, R. A. Phaneuf, and D. H. Crandall, Phys. Rev. Lett. 39, 1256 (1977)] but less so with the more recent ones [D. W. Savin, L. D. Gardner, D. B. Reisenfeld, A. R. Young, and J. L. Kohl, Phys. Rev. A 51, 2162 (1995)]. The present measurements are also in good agreement with unitarized Coulomb-Born and close-coupling calculations.

  4. Absolute cross sections for excitation of the 2s 2S-->2p 2P transition in B2+ and for electron-impact single ionization of B2+

    NASA Astrophysics Data System (ADS)

    Woitke, O.; Djurić, N.; Dunn, G. H.; Bannister, M. E.; Smith, A. C.; Wallbank, B.; Badnell, N. R.; Pindzola, M. S.

    1998-12-01

    Absolute cross sections for electron-impact excitation of the 2s 2S-->2p 2P transition of B2+ measured between 5.4 and 7.0 eV are presented. The results are in good agreement with the R-matrix-with-pseudostates (RMPS) calculation of Marchalant et al. [J. Phys. B 30, L435 (1997)]. Also presented are cross sections for electron-impact single ionization of B2+, including measurements between 25 and 200 eV and calculations using the RMPS and time-dependent close-coupling methods. The measured ionization cross sections are about 14% higher near the peak than previous measurements by Crandall et al. [Phys. Rev. A 34, 1757 (1986)], but agree well with experimental data of Hofmann et al. [Z. Phys. D 16, 113 (1990)] and with the present and other theoretical predictions.

  5. 2p2 Team News

    NASA Astrophysics Data System (ADS)

    Jones, H.

    2000-06-01

    The 2p2 Team continued towards the implementation at the 2.2-m of the same BOB (Broker for Observation Blocks) observing interface as seen at other ESO telescopes. This requires an interface to be written between the existing BOB software and the non-VLT compatible control software for the Wide-Field Imager (WFI) and 2.2-m. Cristian Urrutia, Tatiana Paz and Eduardo Robledo are heading its development. With this software in place, observers can use the VLT Phase 2 Proposal Preparation System (P2PP) for definition of their exposures, whether they are for Visitor or Service Mode.

  6. EuCo2P2: A Model Molecular-Field Helical Heisenberg Antiferromagnet

    DOE PAGES

    Sangeetha, N. S.; Cuervo-Reyes, Eduardo; Pandey, Abhishek; ...

    2016-07-19

    The metallic compound EuCo2P2 with the body-centered tetragonal ThCr2Si2 structure containing Eu spins-7/2 was previously shown from single-crystal neutron diffraction measurements to exhibit a helical antiferromagnetic (AFM) structure below TN=66.5 K with the helix axis along the c axis and with the ordered moments aligned within the ab plane. Here we report crystallography, electrical resistivity, heat capacity, magnetization, and magnetic susceptibility measurements on single crystals of this compound. We demonstrate that EuCo2P2 is a model molecular-field helical Heisenberg antiferromagnet from comparisons of the anisotropic magnetic susceptibility χ, high-field magnetization, and magnetic heat capacity of EuCo2P2 single crystals at temperature T≤TNmore » with the predictions of our recent formulation of molecular-field theory. Values of the Heisenberg exchange interactions between the Eu spins are derived from the data. The low-T magnetic heat capacity ~T3 arising from spin-wave excitations with no anisotropy gap is calculated and found to be comparable to the lattice heat capacity. The density of states at the Fermi energy of EuCo2P2 and the related compound BaCo2P2 are found from the heat capacity data to be large, 10 and 16 states/eV per formula unit for EuCo2P2 and BaCo2P2, respectively. These values are enhanced by a factor of ~2.5 above those found from DFT electronic structure calculations for the two compounds. Additionally, the calculations also find ferromagnetic Eu–Eu exchange interactions within the ab plane and AFM interactions between Eu spins in nearest- and next-nearest planes, in agreement with the MFT analysis of χab(T≤TN).« less

  7. EuCo2P2 : A model molecular-field helical Heisenberg antiferromagnet

    NASA Astrophysics Data System (ADS)

    Sangeetha, N. S.; Cuervo-Reyes, Eduardo; Pandey, Abhishek; Johnston, D. C.

    2016-07-01

    The metallic compound EuCo2P2 with the body-centered tetragonal ThCr2Si2 structure containing Eu spins-7/2 was previously shown from single-crystal neutron diffraction measurements to exhibit a helical antiferromagnetic (AFM) structure below TN=66.5 K with the helix axis along the c axis and with the ordered moments aligned within the a b plane. Here we report crystallography, electrical resistivity, heat capacity, magnetization, and magnetic susceptibility measurements on single crystals of this compound. We demonstrate that EuCo2P2 is a model molecular-field helical Heisenberg antiferromagnet from comparisons of the anisotropic magnetic susceptibility χ , high-field magnetization, and magnetic heat capacity of EuCo2P2 single crystals at temperature T ≤TN with the predictions of our recent formulation of molecular-field theory. Values of the Heisenberg exchange interactions between the Eu spins are derived from the data. The low-T magnetic heat capacity ˜T3 arising from spin-wave excitations with no anisotropy gap is calculated and found to be comparable to the lattice heat capacity. The density of states at the Fermi energy of EuCo2P2 and the related compound BaCo2P2 are found from the heat capacity data to be large, 10 and 16 states/eV per formula unit for EuCo2P2 and BaCo2P2 , respectively. These values are enhanced by a factor of ˜2.5 above those found from DFT electronic structure calculations for the two compounds. The calculations also find ferromagnetic Eu-Eu exchange interactions within the a b plane and AFM interactions between Eu spins in nearest- and next-nearest planes, in agreement with the MFT analysis of χa b(T ≤TN) .

  8. Faraday effect in Sn2P2S6 crystals.

    PubMed

    Krupych, Oleh; Adamenko, Dmytro; Mys, Oksana; Grabar, Aleksandr; Vlokh, Rostyslav

    2008-11-10

    We have revealed a large Faraday rotation in tin thiohypodiphosphate (Sn(2)P(2)S(6)) crystals, which makes this material promising for magneto-optics. The effective Faraday tensor component and the Verdet constant for the direction of the optic axis have been determined by measuring the pure Faraday rotation in Sn(2)P(2)S(6) crystals with both the single-ray and small-angular polarimetric methods at the normal conditions and a wavelength of 632.8 nm. The effective Verdet constant is found to be equal to 115 rad/T x m.

  9. Mini Magnetospheric Plasma Propulsion (M2P2)

    NASA Technical Reports Server (NTRS)

    Gallagher, Dennis; Winglee, Robert

    2000-01-01

    The M2P2 concept is based on the transfer of momentum from the solar wind to an artificial magnetic field structure like that naturally occurs at all magnetized planets in the Solar System, called the magnetosphere. The objectives of this program include the following: (1) Demonstrate artificial magnetospheric inflation through cold plasma filling in vacuum; (2) Demonstrate deflection of a surrogate solar wind by an artificial magnetosphere in the laboratory vacuum chamber; (3) Compare theoretical calculations for thrust forces with laboratory measurements; (4) Develop flight control algorithms for planning mission specific trajectories; and (5) Develop M2P2 system concept.

  10. Energy calculation of 2s2 1S, 2p2 1D, 3s2 1S, 3p2 1D, 3d2 1G, 4p2 1D, 4d2 1D, 4f2 1I doubly excited states using a new wave function to four terms for 2 ≤ Z ≤ 15

    NASA Astrophysics Data System (ADS)

    Sow, B.; Sow, M.; Gning, Y.; Traore, A.; Ndao, A. S.; Wague, A.

    2016-06-01

    Calculation of the energy levels of atoms and ions with 2 ≤ Z ≤ 15 are carried out in this paper using a Hyllerass approximation. The method used is one of Screen Constant by Nuclear Charge Unit to calculate the total energy of two-electron atomic systems in ground and different doubly excited states. Employing a new wave function including correlation, we were able to calculate excited states (nl)2 (n ≤ 4). The Comparison of these results with the ones of other methods shows a good agreement.

  11. Time resolved nonlinear response of Sn2P2S6:Sb to nanosecond pulse excitation

    NASA Astrophysics Data System (ADS)

    Shumelyuk, A.; Skrypka, Y.; Odoulov, S.; Basun, S. A.; Halliburton, L. E.; Evans, D. R.

    2017-06-01

    The temporal variations of SPS:Sb transmission are measured within a 10 orders of magnitude time range (from a few nanoseconds to ten seconds) with a red diode laser beam, after illumination of the sample with a nanosecond pulse of green light. The measurements revealed a sequence of darkening and bleaching processes that are sensitive to the intensities of pre-illumination and testing beams, or the sample temperature, or both. This allowed for identifying particular nonlinear processes that manifest themselves in changes of transmission.

  12. Electron excitation cross sections for the 2s^2 2p ^2p^o-2s2p^2 ^4p and 2s2p^2 ^2D transitions in O^3+

    NASA Technical Reports Server (NTRS)

    Smith, S. J.; Lozano, J. A.; Tayal, S. S.; Chutjian, A.

    2003-01-01

    Comparison is made with results of new calculations in a 25-state R-matrix theory and with results in a previous eight-state R-matrix calculation. The presence of rich resonance structure is confirmed in both experiment and theory.

  13. α and 2 p 2 n emission in fast neutron-induced reactions on 60Ni

    NASA Astrophysics Data System (ADS)

    Fotiades, N.; Devlin, M.; Haight, R. C.; Nelson, R. O.; Kunieda, S.; Kawano, T.

    2015-06-01

    Background: The cross sections for populating the residual nucleus in the reaction ZAX(n,x) Z -2 A -4Y exhibit peaks as a function of incident neutron energy corresponding to the (n ,n'α ) reaction and, at higher energy, to the (n ,2 p 3 n ) reaction. The relative magnitudes of these peaks vary with the Z of the target nucleus. Purpose: Study fast neutron-induced reactions on 60Ni. Locate experimentally the nuclear charge region along the line of stability where the cross sections for α emission and for 2 p 2 n emission in fast neutron-induced reactions are comparable as a further test of reaction models. Methods: Data were taken by using the Germanium Array for Neutron-Induced Excitations. The broad-spectrum pulsed neutron beam of the Los Alamos Neutron Science Center's Weapons Neutron Research facility provided neutrons in the energy range from 1 to 250 MeV. The time-of-flight technique was used to determine the incident-neutron energies. Results: Absolute partial cross sections for production of seven discrete Fe γ rays populated in 60Ni (n ,α /2 p x n γ ) reactions with 2 ≤x ≤5 were measured for neutron energies 1 MeV2 p 2 n and 2 p 3 n emission at higher incident energies in the nuclear charge region around Fe.

  14. NMR study of heavy fermion compound EuNi2P2

    NASA Astrophysics Data System (ADS)

    Magishi, K.; Watanabe, R.; Hisada, A.; Saito, T.; Koyama, K.; Fujiwara, T.

    2015-03-01

    We report the results of 31P-nuclear magnetic resonance (NMR) measurements on heavy fermion compound EuNi2P2 in order to investigate the magnetic properties at low temperatures from a microscopic view point. The Knight shift has a negative value in an entire temperature range, and the absolute value increases with decreasing temperature but exhibits a broad maximum around 40 K, which is similar to the behavior of the magnetic susceptibility. Also, the nuclear spin-lattice relaxation rate 1/T1 is almost constant at high temperatures above 200 K, which is reminiscent of the relaxation mechanism dominated by the interaction of the 31P nucleus with fluctuating Eu-4f moments. Below 200 K, 1/T1 gradually decreases on cooling due to the change of the valence in the Eu ion. At low temperatures, 1/T1 does not obey the Korringa relation, in contrast to typical heavy fermion compounds. The nuclear spin-spin relaxation rate 1/T2 shows the similar behavior as 1/T1 at high temperatures. But, below 50 K, 1/T2 increases upon cooling due to the development of the magnetic excitation.

  15. Relativistic model of 2p-2h meson exchange currents in (anti)neutrino scattering

    NASA Astrophysics Data System (ADS)

    Ruiz Simo, I.; E Amaro, J.; Barbaro, M. B.; De Pace, A.; Caballero, J. A.; Donnelly, T. W.

    2017-06-01

    We develop a model of relativistic, charged meson-exchange currents (MEC) for neutrino-nucleus interactions. The two-body current is the sum of seagull, pion-in-flight, pion-pole and Δ-pole operators. These operators are obtained from the weak pion-production amplitudes for the nucleon derived in the nonlinear σ-model together with weak excitation of the {{Δ }}(1232) resonance and its subsequent decay into Nπ . With these currents we compute the five 2p-2h response functions contributing to ({ν }l,{l}-) and ({\\overline{ν }}l,{l}+) reactions in the relativistic Fermi gas model. The total current is the sum of vector and axial two-body currents. The vector current is related to the electromagnetic MEC operator that contributes to electron scattering. This allows one to check our model by comparison with the results of De Pace et al (2003 Nucl. Phys. A 726 303). Thus, our model is a natural extension of that model to the weak sector with the addition of the axial MEC operator. The dependences of the response functions on several ingredients of the approach are analyzed. Specifically we discuss relativistic effects, quantify the size of the direct-exchange interferences, and the relative importance of the axial versus vector current.

  16. /sup 90/Zr (p,n) and (n,p) distorted-wave impulse approximation cross sections in 2p2h random-phase approximation

    SciTech Connect

    Wambach, J.; Droz-dotdz-dot, S.; Schulte, A.; Speth, J.

    1988-03-01

    Within the distorted-wave impulse approximation and an extended random phase approximation theory which includes 1p 1h as well as 2p 2h excitations, we study (p,n) and (n,p) cross sections in /sup 90/Zr at 200 MeV. The inclusion of 2p2h excitations allows us to calculate spreading width effects microscopically without introduction of parameters. Given a fully microscopic description reasonable agreement between theory and experiment is found in the (p,n) channel. In the (n,p) channel at forward angles we find that the compact spin-dipole resonance predicted by 1p1h random-phase approximation calculations is not strongly effected by 2p2h mixing

  17. The effect of Tb+3 on α-Sr2P2O7 phosphor for green LED phosphor application

    NASA Astrophysics Data System (ADS)

    Patel, Nimesh P.; Srinivas, M.; Verma, Vishwnath; Modi, Dhaval

    2015-06-01

    A series of Tb+3 activated α-Sr2P2O7 (Strontium Pyrophosphate) phosphors were synthesized by high temperature combustion synthesis method. The structural analysis has been done by x-ray diffraction and FTIR (Fourier Transform Infrared Spectrum). The results obtained in structural characterization indicate that the doping concentration did not affect the crystal phase and structure of the phosphors. X-ray diffraction pattern reveals that the all samples were consistence with the JCPDS card No. 24-1011. The phosphor was excited at 232 nm wavelength, very intense PL green emission peak have been observed at 545 nm. This illustrates, that the phosphors could be efficiently excited because of the charge transfer band of the host as well as the energy transfer process occurred between host (Sr2P2O7) and activator (Tb+3). By increasing the doping concentration of Tb+3, the intensity of 545 nm emission peak has been increased predominantly and it suggest that the phosphor prepared has very good application in green LED phosphor.

  18. Raman spectroscopic study of (Ph 2P) 2CCH 2 and [(Ph 2P) 2CCH 2]W(CO) 4

    NASA Astrophysics Data System (ADS)

    Fickert, C.; Posset, U.; Kiefer, W.

    1997-06-01

    The Raman and IR spectra of 1,1-bis[diphenylphosphino]ethene (Ph 2P) 2CCH 2 (vdpp) and the tetracarbonyl tungsten complex (vdpp)W(CO) 4 have been recorded. Vibrational assignments are proposed based on local symmetry considerations. For the vinylidene stretching mode a coordination shift is observed from 1588 cm -1 in polycrystalline vdpp to 1581 cm -1 in its tetracarbonyl tungsten complex. From a comparison of the v(CO) splitting pattern with those of related complexes monoclinic structure with factor group C2h and four formula units per unit cell is concluded.

  19. Large-Scale Mini-Magnetosphere Plasma Propulsion (M2P2) Experiments

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.; Slough, J.; Ziemba, T.; Euripides, P.; Adrian, M. L.; Gallagher, D.; Craven, P.; Tomlinson, W.; Cravens, J.; Burch, J.; hide

    2001-01-01

    Mini-Magnetosphere Plasma Propulsion (M2P2) is an innovative plasma propulsion system that has the potential to propel spacecraft at unprecedented speeds of 50 to 80 km per second with a low-power requirement of approx. 1 kW per 100 kg of payload and approx. 1 kg of neutral gas [fuel] consumption per day of acceleration. Acceleration periods from several days to a few months are envisioned. High specific impulse and efficiency are achieved through coupling of the spacecraft to the 400 km per second solar wind through an artificial magnetosphere. The mini-magnetosphere or inflated magnetic bubble is produced by the injection of cold dense plasma into a spacecraft-generated magnetic field envelope. Magnetic bubble inflation is driven by electromagnetic processes thereby avoiding the material and deployment problems faced by mechanical solar sail designs, Here, we present the theoretical design of M2P2 as well as initial results from experimental testing of an M2P2 prototype demonstrating: 1) inflation of the dipole magnetic field geometry through the internal injection of cold plasma; and 2) deflection of and artificial solar wind by the prototype M2P2 system. In addition, we present plans for direct laboratory measurement of thrust imparted to a prototype M2P2 by an artificial solar wind during the summer of 2001.

  20. Large-Scale Mini-Magnetosphere Plasma Propulsion (M2P2) Experiments

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.; Slough, J.; Ziemba, T.; Euripides, P.; Gallagher, D.; Craven, P.; Adrian, M. L.; Tomlinson, W.; Cravens, J.; Burch, J.; hide

    2001-01-01

    Mini-Magnetosphere Plasma Propulsion (M2P2) is an innovative plasma propulsion system that has the potential to propel spacecraft at unprecedented speeds of 50 to 80 km/s, with a low power requirement of approx. 1 kW per 100 kg of payload and -1 kg of neutral gas [fuel] consumption per day of acceleration. Acceleration periods from several days to a few months are envisioned. High specific impulse and efficiency are achieved through coupling of the spacecraft to the 400 km/s. solar wind through an artificial magnetosphere. The mini-magnetosphere or inflated magnetic bubble is produced by the injection of cold dense plasma into a spacecraft-generated magnetic field envelope. Magnetic bubble inflation is driven by electromagnetic processes thereby avoiding the material and deployment problems faced by mechanical solar sail designs. Here, we present the theoretical design of M2P2 as well as initial results from experimental testing of an M2P2 prototype demonstrating: 1) inflation of the dipole magnetic field geometry through the internal injection of cold plasma; and 2) deflection of and artificial solar wind by the prototype M2P2 system. In addition, we present plans for direct laboratory measurement of thrust imparted to a prototype M2P2 by an artificial solar wind during the summer of 2001.

  1. Large-Scale Mini-Magnetosphere Plasma Propulsion (M2P2) Experiments

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.; Slough, J.; Ziemba, T.; Euripides, P.; Adrian, M. L.; Gallagher, D.; Craven, P.; Tomlinson, W.; Cravens, J.; Burch, J.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Mini-Magnetosphere Plasma Propulsion (M2P2) is an innovative plasma propulsion system that has the potential to propel spacecraft at unprecedented speeds of 50 to 80 km per second with a low-power requirement of approx. 1 kW per 100 kg of payload and approx. 1 kg of neutral gas [fuel] consumption per day of acceleration. Acceleration periods from several days to a few months are envisioned. High specific impulse and efficiency are achieved through coupling of the spacecraft to the 400 km per second solar wind through an artificial magnetosphere. The mini-magnetosphere or inflated magnetic bubble is produced by the injection of cold dense plasma into a spacecraft-generated magnetic field envelope. Magnetic bubble inflation is driven by electromagnetic processes thereby avoiding the material and deployment problems faced by mechanical solar sail designs, Here, we present the theoretical design of M2P2 as well as initial results from experimental testing of an M2P2 prototype demonstrating: 1) inflation of the dipole magnetic field geometry through the internal injection of cold plasma; and 2) deflection of and artificial solar wind by the prototype M2P2 system. In addition, we present plans for direct laboratory measurement of thrust imparted to a prototype M2P2 by an artificial solar wind during the summer of 2001.

  2. Large-Scale Mini-Magnetosphere Plasma Propulsion (M2P2) Experiments

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.; Slough, J.; Ziemba, T.; Euripides, P.; Gallagher, D.; Craven, P.; Adrian, M. L.; Tomlinson, W.; Cravens, J.; Burch, J.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Mini-Magnetosphere Plasma Propulsion (M2P2) is an innovative plasma propulsion system that has the potential to propel spacecraft at unprecedented speeds of 50 to 80 km/s, with a low power requirement of approx. 1 kW per 100 kg of payload and -1 kg of neutral gas [fuel] consumption per day of acceleration. Acceleration periods from several days to a few months are envisioned. High specific impulse and efficiency are achieved through coupling of the spacecraft to the 400 km/s. solar wind through an artificial magnetosphere. The mini-magnetosphere or inflated magnetic bubble is produced by the injection of cold dense plasma into a spacecraft-generated magnetic field envelope. Magnetic bubble inflation is driven by electromagnetic processes thereby avoiding the material and deployment problems faced by mechanical solar sail designs. Here, we present the theoretical design of M2P2 as well as initial results from experimental testing of an M2P2 prototype demonstrating: 1) inflation of the dipole magnetic field geometry through the internal injection of cold plasma; and 2) deflection of and artificial solar wind by the prototype M2P2 system. In addition, we present plans for direct laboratory measurement of thrust imparted to a prototype M2P2 by an artificial solar wind during the summer of 2001.

  3. Competing analysis of α and 2p2n-emission from compound nuclei formed in neutron induced reactions

    NASA Astrophysics Data System (ADS)

    Kaur, Amandeep; Sharma, Manoj K.

    2017-01-01

    The decay mechanism of compound system 61Ni* formed in fast neutron induced reactions is explored within the collective clusterization approach of the Dynamical Cluster-decay Model (DCM) in reference to a recent experiment over an energy spread of En = 1- 100 MeV. The excitation functions for the decay of the compound nucleus 61Ni* formed in the n +60Ni reaction show a double humped variation with incident beam energy where the peak at lower energy corresponds to α-emission while the one at higher energy originates from 2 p 2 n-emission. The experimentally observed transmutation of α-emission at lower energy into 2 p 2 n-emission at higher incident energies is explained on the basis of temperature dependence of the binding energies used within the framework of DCM. The cross-sections for the formation of the daughter nucleus 57Fe after emission of α-cluster from the 61Ni* nucleus are addressed by employing the neck length parameter (ΔR), finding decent agreement with the available experimental data. The calculations are done for non-sticking choice of moment of inertia (INS) in the centrifugal potential term, which forms the essential ingredient in DCM based calculations. In addition to this, the effect of mass (and charge) of the compound nucleus is exercised in view of α and 2 p 2 n emission and comparative study of the decay profiles of compound systems with mass A = 17-93 is employed to get better description of decay patterns.

  4. Highly efficient acousto-optic diffraction in Sn2P2S6 crystals.

    PubMed

    Martynyuk-Lototska, I Yu; Mys, O G; Grabar, A A; Stoika, I M; Vysochanskii, Yu M; Vlokh, R O

    2008-01-01

    We have studied the acousto-optic (AO) diffraction in Sn2P2S6 crystals and found that they manifest high values of an AO figure of merit. The above crystals may therefore be used as highly efficient materials in different AO applications.

  5. A study of a sector spectrophotometer and auroral O+(2P-2D) emissions

    NASA Technical Reports Server (NTRS)

    Swenson, G. R.

    1976-01-01

    The metastable O+(2P-2D) auroral emission was investigated. The neighboring OH contaminants and low intensity levels of the emission itself necessitated the evolution of an instrument capable of separating the emission from the contaminants and having a high sensitivity in the wavelength region of interest. A new type of scanning photometer was developed and its properties are discussed. The theoretical aspects of auroral electron interaction with atomic oxygen and the resultant O+(2P-2D) emissions were examined in conjunction with N2(+)1NEG emissions. Ground based measurements of O+(2P-2D) auroral emission intensities were made using the spatial scanning photometer (sector spectrophotometer). Simultaneous measurements of N2(+)1NEG sub 1,0 emission intensity were made in the same field of view using a tilting photometer. Time histories of the ratio of these two emissions made in the magnetic zenith during auroral breakup periods are given. Theories of I sub 7319/I sub 4278 of previous investigators were presented. A rocket measurement of N2(+)1NEG sub 0,0 and O+(2P-2D) emission in aurora was examined in detail and was found to agree with the ground based measurements. Theoretical examination resulted in the deduction of the electron impact efficiency generating O+(2P) and also suggests a large source of O+(2P) at low altitude. A possible source is charge exchange of N+(1S) with OI(3P).

  6. K2P2: Reduced data from campaigns 0-4 of the K2 mission

    NASA Astrophysics Data System (ADS)

    Handberg, R.; Lund, M. N.

    2017-01-01

    Context. After the loss of a second reaction wheel the Kepler mission was redesigned as the K2 mission, pointing towards the ecliptic and delivering data for new fields approximately every 80 days. The steady flow of data obtained with a reduced pointing stability calls for dedicated pipelines for extracting light curves and correcting these for use in, e.g., asteroseismic analysis. Aims: We provide corrected light curves for the K2 fields observed until now (campaigns 0-4), and provide a comparison with other pipelines for K2 data extraction/correction. Methods: Raw light curves are extracted from K2 pixel data using the "K2-pixel-photometry" (K2P2) pipeline, and corrected using the KASOC filter. Results: The use of K2P2 allows for the extraction of the order of 90 000 targets in addition to 70 000 targets proposed by the community - for these, other pipelines provide no data. We find that K2P2 in general performs as well as, or better than, other pipelines for the tested metrics of photometric quality. In addition to stars, pixel masks are properly defined using K2P2 for extended objects such as galaxies for which light curves are also extracted.

  7. Atomic Analysis of Protein-Protein Interfaces with Known Inhibitors: The 2P2I Database

    PubMed Central

    Bourgeas, Raphaël; Basse, Marie-Jeanne

    2010-01-01

    Background In the last decade, the inhibition of protein-protein interactions (PPIs) has emerged from both academic and private research as a new way to modulate the activity of proteins. Inhibitors of these original interactions are certainly the next generation of highly innovative drugs that will reach the market in the next decade. However, in silico design of such compounds still remains challenging. Methodology/Principal Findings Here we describe this particular PPI chemical space through the presentation of 2P2IDB, a hand-curated database dedicated to the structure of PPIs with known inhibitors. We have analyzed protein/protein and protein/inhibitor interfaces in terms of geometrical parameters, atom and residue properties, buried accessible surface area and other biophysical parameters. The interfaces found in 2P2IDB were then compared to those of representative datasets of heterodimeric complexes. We propose a new classification of PPIs with known inhibitors into two classes depending on the number of segments present at the interface and corresponding to either a single secondary structure element or to a more globular interacting domain. 2P2IDB complexes share global shape properties with standard transient heterodimer complexes, but their accessible surface areas are significantly smaller. No major conformational changes are seen between the different states of the proteins. The interfaces are more hydrophobic than general PPI's interfaces, with less charged residues and more non-polar atoms. Finally, fifty percent of the complexes in the 2P2IDB dataset possess more hydrogen bonds than typical protein-protein complexes. Potential areas of study for the future are proposed, which include a new classification system consisting of specific families and the identification of PPI targets with high druggability potential based on key descriptors of the interaction. Conclusions 2P2I database stores structural information about PPIs with known inhibitors and

  8. Vapor-phase synthesis of mesoporous SiO2-P2O5 thin films.

    PubMed

    Nishiyama, Norikazu; Kaihara, Junji; Nishiyama, Yuko; Egashira, Yasuyuki; Ueyama, Korekazu

    2007-04-24

    Mesoporous SiO2-P2O5 films were synthesized from the vapor phase onto a silicon substrate. First, a precursor solution of cetyltrimethylammonium bromide (C16TAB), H3PO4, ethanol, and water was deposited on a silicon substrate by a spin-coating method. Then, the C16TAB-H3PO4 composite film was treated with tetraethoxysilane (TEOS) vapor at 90-180 degrees C for 2.5 h. The H3PO4-C16TAB composite formed a hexagonal structure on the silicon substrate before vapor treatment. The TEOS molecules penetrated into the film without a phase transition. The periodic mesostructure of the SiO2-P2O5 films was retained after calcination. The calcined films showed a high proton conductivity of about 0.55 S/cm at room temperature. The molar ratio of P/Si in the SiO2-P2O5 film was as high as 0.43, a level that was not attained by a premixing sol-gel method. The high phosphate group content and the ordered periodic mesostructure contributed to the high proton conductivity.

  9. Pre-stimulus alpha power affects vertex N2-P2 potentials evoked by noxious stimuli.

    PubMed

    Babiloni, Claudio; Del Percio, Claudio; Brancucci, Alfredo; Capotosto, Paolo; Le Pera, Domenica; Marzano, Nicola; Valeriani, Massimiliano; Romani, Gian Luca; Arendt-Nielsen, Lars; Rossini, Paolo Maria

    2008-03-28

    It is well known that scalp potentials evoked by nonpainful visual and auditory stimuli are enhanced in amplitude when preceded by pre-stimulus low-amplitude alpha rhythms. This study tested the hypothesis that the same holds for the amplitude of vertex N2-P2 potentials evoked by brief noxious laser stimuli, an issue of interest for clinical perspective. EEG data were recorded in 10 subjects from 30 electrodes during laser noxious stimulation. The artifact-free vertex N2-P2 complex was spatially enhanced by surface Laplacian transformation. Pre-stimulus alpha power was computed at three alpha sub-bands according to subject's individual alpha frequency peak (i.e. about 6-8Hz for alpha 1, 8-10Hz for alpha 2 and 10-12Hz for alpha 3 sub-band). Individual EEG single trials were divided in two sub-groups. The strong-alpha sub-group (high band power) included halfway of all EEG single trials, namely those having the highest pre-stimulus alpha power. Weak-alpha sub-group (low band power) included the remaining trials. Averaging procedure provided laser evoked potentials for both trial sub-groups. No significant effect was found for alpha 1 and alpha 2 sub-bands. Conversely, compared to strong-alpha 3 sub-group, weak-alpha 3 sub-group showed vertex N2-P2 potentials having significantly higher amplitude (p<0.05). These results extend to the later phases of pain processing systems the notion that generation mechanisms of pre-stimulus alpha rhythms and (laser) evoked potentials are intrinsically related and subjected to fluctuating "noise". That "noise" could explain the trial-by-trial variability of laser evoked potentials and perception.

  10. Acoustic and elastic properties of Sn(2)P(2)S(6) crystals.

    PubMed

    Mys, O; Martynyuk-Lototska, I; Grabar, A; Vlokh, R

    2009-07-01

    We present the results concerned with acoustic and elastic properties of Sn(2)P(2)S(6) crystals. The complete matrices of elastic stiffness and compliance coefficients are determined in both the crystallographic coordinate system and the system associated with eigenvectors of the elastic stiffness tensor. The acoustic slowness surfaces are constructed and the propagation and polarization directions of the slowest acoustic waves promising for acousto-optic interactions are determined on this basis. The acoustic obliquity angle and the deviation of polarization of the acoustic waves from purely transverse or longitudinal states are quantitatively analysed.

  11. Pressure Induced Enhancement of Superconductivity in LaRu2P2

    PubMed Central

    Li, Baoxuan; Liu, Jianzhong; Sun, Jian; Li, Sheng; Zhu, Xiyu; Wen, Hai-Hu

    2016-01-01

    To explore new superconductors beyond the copper-based and iron-based systems is very important. The Ru element locates just below the Fe in the periodic table and behaves like the Fe in many ways. One of the common thread to induce high temperature superconductivity is to introduce moderate correlation into the system. In this paper, we report the significant enhancement of superconducting transition temperature from 3.8 K to 5.8 K by using a pressure only of 1.74 ± 0.05 GPa in LaRu2P2 which has an iso-structure of the iron-based 122 superconductors. The ab-initio calculation shows that the superconductivity in LaRu2P2 at ambient pressure can be explained by the McMillan’s theory with strong electron-phonon coupling. However, it is difficult to interpret the enhancement of Tc versus pressure within this picture. Detailed analysis of the pressure induced evolution of resistivity and upper critical field Hc2(T) reveals that the increase of Tc with pressure may be accompanied by the involvement of extra electron-boson interaction. This suggests that the Ru-based system has some commonality as the Fe-based superconductors. PMID:27086696

  12. Pressure Induced Enhancement of Superconductivity in LaRu2P2.

    PubMed

    Li, Baoxuan; Lu, Pengchao; Liu, Jianzhong; Sun, Jian; Li, Sheng; Zhu, Xiyu; Wen, Hai-Hu

    2016-04-18

    To explore new superconductors beyond the copper-based and iron-based systems is very important. The Ru element locates just below the Fe in the periodic table and behaves like the Fe in many ways. One of the common thread to induce high temperature superconductivity is to introduce moderate correlation into the system. In this paper, we report the significant enhancement of superconducting transition temperature from 3.8 K to 5.8 K by using a pressure only of 1.74 ± 0.05 GPa in LaRu2P2 which has an iso-structure of the iron-based 122 superconductors. The ab-initio calculation shows that the superconductivity in LaRu2P2 at ambient pressure can be explained by the McMillan's theory with strong electron-phonon coupling. However, it is difficult to interpret the enhancement of Tc versus pressure within this picture. Detailed analysis of the pressure induced evolution of resistivity and upper critical field Hc2(T) reveals that the increase of Tc with pressure may be accompanied by the involvement of extra electron-boson interaction. This suggests that the Ru-based system has some commonality as the Fe-based superconductors.

  13. Ferromagnetism in the Kondo-lattice compound CePd2P2.

    PubMed

    Tran, Vinh Hung; Bukowski, Zbigniew

    2014-06-25

    We report physical properties of CePd2P2 crystallizing in the tetragonal ThCr2Si2-type structure (space group I4/mmm). Dc-magnetic susceptibility, magnetization, specific heat, electrical resistivity and magnetoresistance measurements establish a ferromagnetic ordering below the Curie temperature TC = 28.4 ± 0.2 K. Critical analysis of isothermal and isofield magnetization yields critical exponents of β = 0.405 ± 0.005, γ = 1.11 ± 0.05 and δ = 3.74 ± 0.04. The ordered state is characterized by saturation moment Ms ∼ 0.98μB and magnon energy gap Δ/kB ∼25–35 K. The studied properties reflect a competing influence of the Kondo and crystalline electric field (CEF) interactions. The strength of the Kondo effect is assigned by a low-temperature Kondo scale TK ∼19 ± 10 K and a high-temperature Kondo scale TK ~ H 117 } 10 K. A model of the inelastic scattering of the conduction electrons with an exchanged CEF energy ΔCEF was applied to the magnetic resistivity. An average value ΔCEF = 260 ± 30 K is consistent in the relationships with TK and TK H. We argue that the CePd2P2 compound appears to be a new ferromagnetic Kondo-lattice among the Ce-based intermetallics.

  14. Pressure Induced Enhancement of Superconductivity in LaRu2P2

    NASA Astrophysics Data System (ADS)

    Li, Baoxuan; Lu, Pengchao; Liu, Jianzhong; Sun, Jian; Li, Sheng; Zhu, Xiyu; Wen, Hai-Hu

    2016-04-01

    To explore new superconductors beyond the copper-based and iron-based systems is very important. The Ru element locates just below the Fe in the periodic table and behaves like the Fe in many ways. One of the common thread to induce high temperature superconductivity is to introduce moderate correlation into the system. In this paper, we report the significant enhancement of superconducting transition temperature from 3.8 K to 5.8 K by using a pressure only of 1.74 ± 0.05 GPa in LaRu2P2 which has an iso-structure of the iron-based 122 superconductors. The ab-initio calculation shows that the superconductivity in LaRu2P2 at ambient pressure can be explained by the McMillan’s theory with strong electron-phonon coupling. However, it is difficult to interpret the enhancement of Tc versus pressure within this picture. Detailed analysis of the pressure induced evolution of resistivity and upper critical field Hc2(T) reveals that the increase of Tc with pressure may be accompanied by the involvement of extra electron-boson interaction. This suggests that the Ru-based system has some commonality as the Fe-based superconductors.

  15. Fermi Surface of the Pnictide Superconductor LaRu2 P 2 studied by quantum oscillations

    NASA Astrophysics Data System (ADS)

    Moll, Philip; Balakirev, Fedor; McDonald, Ross; Karpinski, Janusz; Bukowski, Zbigniew; Blaha, Peter; Schwarz, Karlheinz; Batlogg, Bertram

    2011-03-01

    LaRu 2 P2 is a stochiometric pnictide superconductor (Tc ~ 4.1 K) and crystallizes in the ThCr 2 Si 2 structure (the ``122'' pnictide family). We have mapped out its Fermi surface via the deHaas-vanAlphen effect in pulsed magnetic fields up to 60T (LANL/NHMFL). Pronounced oscillations were observed in the magnetic torque measured with a microcantilever setup. Two features are particularly noteworthy: The oscillations can be followed to surprisingly high temperatures beyond 20K, and the main frequency component at θ = 20circ; (θ = 0circ; at HIIc) is at 349T (α -peak), significantly lower than in the related compounds LaFe 2 P2 . A second frequency originating from a larger Fermi surface cross-section at 1921 T (β -peak) is identified. The temperature dependence of the amplitudes is well described by the Lifshitz- Kosevich formalism and gives low effective masses m*/m = 0.80 (α sheet) and 1.09 (β sheet). Therefore, most ``122'' metals appear to have similarly low effective masses.

  16. Electron-phonon interaction and superconductivity in BaIr2P2

    NASA Astrophysics Data System (ADS)

    Billington, D.

    2016-10-01

    Detailed calculations of the electronic structure, phonons and electron-phonon coupling of the superconducting compound BaIr2P2 were performed from first-principles. The electronic structure showed excellent agreement with the available experimental data. The total electron-phonon coupling constant was {λ\\text{ep}}=0.52 and the logarithmically averaged phonon frequency was \\hbar {ω\\text{log}}/{{k}\\text{B}}=168 K. From the Allen-Dynes formula, with {μ\\ast}=0.11 , the superconducting critical temperature was estimated to be {{T}\\text{c}}=2.05 K, which is in excellent agreement with the experiment. These results indicate that the electron-phonon coupling is of moderate strength and is easily capable of supporting the observed superconductivity.

  17. Optical Sensitizing of Photorefractive Sn2P2S6 With CW and Pulsed Pre-Exposure (Preprint)

    DTIC Science & Technology

    2015-06-16

    antimony doping. The second conclusion is in line with our published data on the identification of secondary centers in Sn2P2S6:Sb using the EPR...optical sensitizing of photorefraction in antimony doped Sn2P2S6 crystals. AKNOWLEDGMENTS The financial support of the European Office of

  18. Efficient Plasma Production in Low Background Neutral Pressures with the M2P2 Prototype

    NASA Technical Reports Server (NTRS)

    Ziemba, T.; Euripides, P.; Winglee, R.; Slough, J.; Giersch, L.

    2003-01-01

    Mini-Magnetospheric Plasma Propulsion (M2P2) seeks the creation of a large-scale (10 km radius) magnetic wall or bubble (i.e. a magnetosphere) by the electromagnetic inflation of a small-scale (20 cm radius) dipole magnet. The inflated magnetosphere will intercept the solar wind and thereby provide high-speed propulsion with modest power and fuel requirements due to the gain provided by the ambient medium. Magnetic field inflation is produced by the injection of plasma onto the dipole magnetic field eliminating the need for large mechanical structures and added material weight at launch. For successful inflation of the magnetic bubble a beta near unity must be achieved along the imposed dipole field. This is dependent on the plasma parameters that can be achieved with a plasma source that provide continuous operation at the desired power levels of 1 to 2 kilowatts. Over the last two years we have been developing a laboratory prototype to demonstrate the inflation of the magnetic field under space-like conditions. In this paper we will present some of the latest results from the prototype development at the University of Washington and show that the prototype can produce high ionization efficiencies while operating in near space like neutral background pressures producing electron temperatures of a few tens of electron volts. This allows for operation with propellant expenditures lower than originally estimated.

  19. A tetragonal polymorph of SrMn2P2 made under high pressure - theory and experiment in harmony.

    PubMed

    Xie, Weiwei; Winiarski, Michał J; Klimczuk, Tomasz; Cava, R J

    2017-05-30

    Following the predictions of total energy calculations, a tetragonal SrMn2P2 phase is proposed and successfully formed under high pressure. At ambient pressure, SrMn2P2 adopts the primitive trigonal La2O3 structure type (space group P3[combining macron]m1). However, the results of total energy calculations indicate that SrMn2P2 should be more stable in the tetragonal ThCr2Si2 structure type (space group I4/mmm) than in its known trigonal structure, thus motivating our synthetic experiments. Guided by these calculations, a new tetragonal polymorph of SrMn2P2 was found under the relatively mild conditions of 5 GPa applied pressure at a temperature of 900 °C through the transformation of the ambient pressure trigonal form. The new polymorph has the body centered tetragonal ThCr2Si2 structure type, as predicted. The electronic structure calculations indicate the likelihood of antiferromagnetic, semiconducting properties for the high pressure SrMn2P2 phase.

  20. Simulation of Mini-Magnetospheric Plasma Propulsion (M2P2) Interacting with an External Plasma Wind

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.; Euripides, P.; Ziemba, T.; Slough, J.; Giersch, L.

    2003-01-01

    Substantial progress has been made over the last year in the development of the laboratory Mini-Magnetospheric Plasma Propulsion (M2P2) prototype. The laboratory testing has shown that that the plasma can be produced at high neutral gas efficiency, at high temperatures (a few tens of eV) with excellent confinement up to the point where chamber wall interactions dominate the physics. This paper investigates the performance of the prototype as it is opposed by an external plasma acting as a surrogate for the solar wind. The experiments were performed in 5ft diameter by 6ft long vacuum chamber at the University of Washington. The solar wind source comprised of a 33 kWe arc jet attached to a 200 kWe inductively generated plasma source. The dual plasma sources allow the interaction to be studied for different power levels, shot duration and production method. It is shown that plasma from the solar wind source (SWS) is able to penetrate the field of the M2P2 magnetic when no plasma is present. With operation of the M2P2 plasma source at only 1.5 kWe, the penetration of the SWS even at the highest power of operation at 200 kWe is stopped. This deflection is shown to be greatly enhanced over that produced by the magnet alone. In addition it is shown that with the presence of the SWS, M2P2 is able to produce enhanced magnetized plasma production out to at least 10 magnet radii where the field strength is only marginally greater than the terrestrial field. The results are consistent with the initial predictions that kWe M2P2 systems would be able to deflect several hundred kWe plasma winds to produce enhanced propulsion for a spacecraft.

  1. 2P2Idb v2: update of a structural database dedicated to orthosteric modulation of protein–protein interactions

    PubMed Central

    Basse, Marie-Jeanne; Betzi, Stéphane; Morelli, Xavier; Roche, Philippe

    2016-01-01

    2P2Idb is a hand-curated structural database dedicated to protein–protein interactions with known small molecule orthosteric modulators. It compiles the structural information related to orthosteric inhibitors and their target [i.e. related 3D structures available in the RCSB Protein Data Bank (PDB)] and provides links to other useful databases. 2P2Idb includes all interactions for which both the protein–protein and protein–inhibitor complexes have been structurally characterized. Since its first release in 2010, the database has grown constantly and the current version contains 27 protein–protein complexes and 274 protein–inhibitor complexes corresponding to 242 unique small molecule inhibitors which represent almost a 5-fold increase compared to the previous version. A number of new data have been added, including new protein–protein complexes, binding affinities, molecular descriptors, precalculated interface parameters and links to other webservers. A new query tool has been implemented to search for inhibitors within the database using standard molecular descriptors. A novel version of the 2P2I-inspector tool has been implemented to calculate a series of physical and chemical parameters of the protein interfaces. Several geometrical parameters including planarity, eccentricity and circularity have been added as well as customizable distance cutoffs. This tool has also been extended to protein–ligand interfaces. The 2P2I database thus represents a wealth of structural source of information for scientists interested in the properties of protein–protein interactions and the design of protein–protein interaction modulators. Database URL: http://2p2idb.cnrs-mrs.fr PMID:26980515

  2. Unconventional magnetism in ThCr2Si2-type phosphides, La1 xNdxCo2P2

    SciTech Connect

    Thompson, Corey; Kovnir, Kirill; Garlea, Vasile O; Choi, E.; Zhou, Haidong; Shatruk, Michael

    2014-01-01

    Quaternary phases La1 xNdxCo2P2 (x = 0, 0.12, 0.25, 0.37, 0.50, 0.63, 0.75, 0.88, 1.0) have been synthesized from Sn flux to investigate the origins of drastic differences in properties between ferromagnetic LaCo2P2 and antiferromagnetic NdCo2P2. Powder and single-crystal X-ray diffraction indicate that all La1 xNdxCo2P2 samples are isostructural and crystallize in the ThCr2Si2 structure type. The unit cell parameters and volume change non-linearly with the Nd content (x), with the x < 0.50 10 samples being closer to LaCo2P2 and the ones with x > 0.50 being closer to NdCo2P2. These structural differences are also reflected in the magnetic behavior. The samples with lower Nd content are characterized by ferromagnetic ordering in the Co sublattice with the TC increasing from 132 K for x = 0 to 262 K for x = 0.50, while the samples with higher Nd content exhibit suppressed magnetization in the Co sublattice and canted antiferromagnetic ordering with TC ~ 270 K. Refinement of neutron powder 15 diffraction patterns for x = 0.50 and 0.75 reveals a gradual ordering of the Nd 4f moments under the influence of Co 3d moments below 100 K. At low temperatures and zero field, these samples exhibit antiferromagnetic ordering of both Nd and Co magnetic moments, but under applied field they demonstrate the stabilization of a ferrimagnetic state with antiparallel alignment of the 4f and 3d moments, as indicated by isothermal magnetization measurements. The re-entrant ferrimagnetic transition 20 is also observed in samples with x > 0.50 if the temperature is lowered below 5 K. The occurrence of this low-temperature magnetic transition was confirmed by alternating-current susceptibility measurements.

  3. Nqrs Data for C24H46I2N6O2P2Sn (Subst. No. 1589)

    NASA Astrophysics Data System (ADS)

    Chihara, H.; Nakamura, N.

    This document is part of Subvolume B 'Substances Containing C10H16 … Zn' of Volume 48 'Nuclear Quadrupole Resonance Spectroscopy Data' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains an extract of Section '3.2 Data tables' of the Chapter '3 Nuclear quadrupole resonance data' providing the NQRS data for C24H46I2N6O2P2Sn (Subst. No. 1589)

  4. Enhanced Superconductivity in Close Proximity to the Structural Phase Transition of Sr1-xBaxNi2P2

    NASA Astrophysics Data System (ADS)

    Kudo, Kazutaka; Kitahama, Yutaka; Iba, Keita; Takasuga, Masaya; Nohara, Minoru

    2017-03-01

    The structural evolution and superconductivity of a 122-type solid solution Sr1-xBaxNi2P2 were studied. We found that an orthorhombic-tetragonal structural phase transition takes place at x = 0.5, and is characterized by the P-P dimers breaking. The superconducting transition temperature exhibited its highest value of 2.85 K at x = 0.4.

  5. Synthesis of β-Ca2P2O7:Tb(3+) to gamma radiation detection by thermoluminescence.

    PubMed

    Roman-Lopez, J; Lozano, I B; Cruz-Zaragoza, E; Castañeda, J I Guzman; Díaz-Góngora, J A I

    2017-03-06

    In this work, luminescent emissions of beta-calcium pyrophosphate doped with terbium ions (β-Ca2P2O7:Tb(3+)) were studied. The Ca2P2O7:Tb(3+) powders were prepared by precipitation and annealed at 900°C for 2h was applied on the powders to observe the beta phase. Radioluminescence measurements showed emission bands related with (5)D3 ((5)D4)→(7)FJ transitions of Tb(3+) ions. Three overlapped peaks at 126, 165 and 220°C were observed in thermoluminescence response. A linear TL dose-response in the range of 0.2-10Gy and an acceptable TL reproducibility were showed by the β-Ca2P2O7:Tb(3+) samples exposed to (60)Co gamma radiation. The TL glow curves were analyzed by Initial Rise method and Computational Glow-Curve Deconvolution assuming a General Order Kinetic model to evaluate the kinetic parameters related with the TL peaks.

  6. Electronic structure and defect properties of selenophosphate Pb2P2Se6 for γ-ray detection

    NASA Astrophysics Data System (ADS)

    Kontsevoi, Oleg Y.; Im, Jino; Wessels, Bruce W.; Kanatzidis, Mercouri G.; Freeman, Arthur J.

    Heavy metal chalco-phosphate Pb2P2Se6 has shown a significant promise as an X-ray and γ-ray detector material. To assess the fundamental physical properties important for its performance as detector, theoretical calculations were performed for the electronic structure, band gaps, electron and hole effective masses, and static dielectric constants. The calculations were based on first-principles density functional theory (DFT) and employ the highly precise full potential linearized augmented plane wave method and the projector augmented wave method and include nonlocal exchange-correlation functionals to overcome the band gap underestimation in DFT calculations. The calculations show that Pb2P2Se6 is an indirect band gap material with the calculated band gap of 2.0 eV, has small effective masses, which could result in a good carrier mobility-lifetime product μτ , and a very high static dielectric constant, which could lead to high mobility of carriers by screening of charged scattering centers. We further investigated a large set of native defects in Pb2P2Se6 to determine the optimal growth conditions for application as γ-ray detectors. The results suggest that the prevalent intrinsic defects are selenium vacancies, followed by lead vacancies, then phosphorus vacancies and antisite defects. The effect of various chemical environments on defect properties was examined and the optimal conditions for material synthesis were suggested. Supported by DHS (Grant No. 2014-DN-077-ARI086-01).

  7. Estimation of a 2p2h effect on Gamow-Teller transitions within the second Tamm-Dancoff approximation

    NASA Astrophysics Data System (ADS)

    Minato, F.

    2016-04-01

    Two-particle two-hole (2p2h) effect on the Gamow-Teller (GT) transition for neutron-rich nuclei is studied by the second Tamm-Dancoff approximation (STDA) with the Skyrme interaction. Unstable 24O and 34Si and stable 48Ca nuclei are chosen to study the quenching and fragmentation of the GT strengths. Correlation of the 2p2h configurations causes about 20 % quenching and downward shift of GT giant resonances (GTGRs). The residual interaction changing relative angular momentum that appeared in the tensor force part gives a meaningful effect to the GT strength distributions. In this work, 17 - 26 % of the total GT strengths are brought to high-energy region above GTGRs. In particular, the tensor force brings strengths to high energy more than 50 MeV. STDA calculation within a small model space for 2p2h configuration is also performed and experimental data of 48Ca is reproduced reasonably.

  8. Metabolic and thermal stimuli control K2P2.1 (TREK-1) through modular sensory and gating domains

    PubMed Central

    Bagriantsev, Sviatoslav N; Clark, Kimberly A; Minor, Daniel L

    2012-01-01

    K2P2.1 (TREK-1) is a polymodal two-pore domain leak potassium channel that responds to external pH, GPCR-mediated phosphorylation signals, and temperature through the action of distinct sensors within the channel. How the various intracellular and extracellular sensory elements control channel function remains unresolved. Here, we show that the K2P2.1 (TREK-1) intracellular C-terminal tail (Ct), a major sensory element of the channel, perceives metabolic and thermal commands and relays them to the extracellular C-type gate through transmembrane helix M4 and pore helix 1. By decoupling Ct from the pore-forming core, we further demonstrate that Ct is the primary heat-sensing element of the channel, whereas, in contrast, the pore domain lacks robust temperature sensitivity. Together, our findings outline a mechanism for signal transduction within K2P2.1 (TREK-1) in which there is a clear crosstalk between the C-type gate and intracellular Ct domain. In addition, our findings support the general notion of the existence of modular temperature-sensing domains in temperature-sensitive ion channels. This marked distinction between gating and sensory elements suggests a general design principle that may underlie the function of a variety of temperature-sensitive channels. PMID:22728824

  9. Electromagnetic Moments of Radioactive 136Te and the Emergence of Collectivity 2p+2n outside of Double-Magic 132Sn

    SciTech Connect

    Allmond, James M; Stuchberry, A. E.; Danchev, M.; Baktash, Cyrus; Gargano, A.; Galindo-Uribarri, Alfredo {nmn}; Radford, David C; Bingham, C. R.; Brown, Alex; Coraggio, L.; Covello, A.; Gross, Carl J; Hausladen, Paul; Itaco, N.; Lagergren, Karin B; Padilla-Rodal, Elizabeth; Pavan, John R; Riley, Mark; Stone, N. J.; Stracener, Daniel W; Varner Jr, Robert L; Yu, Chang-Hong

    2017-01-01

    Radioactive 136Te has two valence protons and two valence neutrons outside of the 132Sn double shell closure, providing a simple laboratory for exploring the emergence of collectivity and nucleon- nucleon interactions. Coulomb excitation of 136Te on a titanium target was utilized to determine an extensive set of electromagnetic moments for the three lowest-lying states, including B(E2;0+1 2+1 ), Q(2+1 ), and g(2+1 ). The results indicate that the first-excited state, 2+1 , composed of the simple 2p 2n system, is prolate deformed, and its wavefunction is dominated by neutron degrees of freedom, but not to the extent previously suggested. It is demonstrated that extreme sensitivity of g(2+1 ) to the proton and neutron contributions to the wavefunction provides unique insight into the nature of emerging collectivity, and g(2+1 ) was used to differentiate among several state-of-the-art theoretical calculations. Our results are best described by the most recent shell model calculations.

  10. 2P2IHUNTER: a tool for filtering orthosteric protein–protein interaction modulators via a dedicated support vector machine

    PubMed Central

    Hamon, Véronique; Bourgeas, Raphael; Ducrot, Pierre; Theret, Isabelle; Xuereb, Laura; Basse, Marie Jeanne; Brunel, Jean Michel; Combes, Sebastien; Morelli, Xavier; Roche, Philippe

    2014-01-01

    Over the last 10 years, protein–protein interactions (PPIs) have shown increasing potential as new therapeutic targets. As a consequence, PPIs are today the most screened target class in high-throughput screening (HTS). The development of broad chemical libraries dedicated to these particular targets is essential; however, the chemical space associated with this ‘high-hanging fruit’ is still under debate. Here, we analyse the properties of 40 non-redundant small molecules present in the 2P2I database (http://2p2idb.cnrs-mrs.fr/) to define a general profile of orthosteric inhibitors and propose an original protocol to filter general screening libraries using a support vector machine (SVM) with 11 standard Dragon molecular descriptors. The filtering protocol has been validated using external datasets from PubChem BioAssay and results from in-house screening campaigns. This external blind validation demonstrated the ability of the SVM model to reduce the size of the filtered chemical library by eliminating up to 96% of the compounds as well as enhancing the proportion of active compounds by up to a factor of 8. We believe that the resulting chemical space identified in this paper will provide the scientific community with a concrete support to search for PPI inhibitors during HTS campaigns. PMID:24196694

  11. Large negative thermal expansion in non-perovskite lead-free ferroelectric Sn2P2S6.

    PubMed

    Rong, Yangchun; Li, Menglei; Chen, Jun; Zhou, Mei; Lin, Kun; Hu, Lei; Yuan, Wenxia; Duan, Wenhui; Deng, Jinxia; Xing, Xianran

    2016-02-17

    Functional materials showing both negative thermal expansion (NTE) and physical performance, such as ferroelectricity and magnetism, have been extensively explored in the past decade. However, among ferroelectrics a remarkable NTE was only found in perovskite-type PbTiO3-based compounds. In this work, a large NTE of -4.7 × 10(-5) K(-1) is obtained in the non-perovskite lead-free ferroelectric Sn2P2S6 from 243 K to TC (338 K). Structure refinements and first-principle calculations reveal the effects of the Sn(ii) 5s-S 3p interaction on spontaneous polarization and its correlation with NTE. Then the mechanism of spontaneous volume ferroelectrostriction (SVFS) is verified and it could well elucidate the nature of NTE in ferroelectric Sn2P2S6. This is the first case to demonstrate the unusual NTE behavior by SVFS in a non-perovskite lead-free ferroelectric material.

  12. Application of Novel Molecular Field Theory to Helical Antiferromagnetic Ordering in EuCo2P2

    NASA Astrophysics Data System (ADS)

    Johnston, D. C.; Sangeetha, N. S.

    A formulation of Weiss molecular field theory (MFT) was recently advanced for antiferromagnetic (AFM) systems of identical crystallographically-equivalent local moments interacting by Heisenberg exchange that does not utilize the concept of magnetic sublattices.1 This formulation has the attractive feature that the magnetic and thermal properties in magnetic fields H --> 0 depend only on the interactions of a representative spin with its neighbors, and thus allows the properties of collinear and coplanar noncollinear AFM structures to be understood and modeled on the same footing. Neutron diffraction measurements showed that EuCo2P2 with the bct ThCr2Si2 -type structure undergoes an AFM transition to a coplanar noncollinear c-axis helical AFM structure below the ordering temperature TN = 66 . 5 K.2 Here we report the properties and apply our MFT to model the anisotropic magnetic susceptibility of single-crystal EuCo2P2 below TN. Research supported by U.S. Department of Energy, Division of Materials Science and Engineering, under Contract No. DE-AC02-07CH11358.

  13. NMR studies of the incommensurate helical antiferromagnet EuCo2P2 : Determination of antiferromagnetic propagation vector

    NASA Astrophysics Data System (ADS)

    Higa, Nonoka; Ding, Qing-Ping; Yogi, Mamoru; Sangeetha, N. S.; Hedo, Masato; Nakama, Takao; Ōnuki, Yoshichika; Johnston, D. C.; Furukawa, Yuji

    2017-07-01

    Recently, Q.-P. Ding et al. [Phys. Rev. B 95, 184404 (2017), 10.1103/PhysRevB.95.184404] reported that their nuclear magnetic resonance (NMR) study on EuCo2As2 successfully characterized the antiferromagnetic (AFM) propagation vector of the incommensurate helix AFM state, showing that NMR is a unique tool for determination of the spin structures in incommensurate helical AFMs. Motivated by this work, we have carried out 153Eu, 31P, and 59Co NMR measurements on the helical antiferromagnet EuCo2P2 with an AFM ordering temperature TN=66.5 K. An incommensurate helical AFM structure was clearly confirmed by 153Eu and 31P NMR spectra on single-crystalline EuCo2P2 in zero magnetic field at 1.6 K and its external magnetic field dependence. Furthermore, based on 59Co NMR data in both the paramagnetic and incommensurate AFM states, we have determined the model-independent value of the AFM propagation vector k =(0 ,0 ,0.73 ±0.09 )2 π /c , where c is the c -axis lattice parameter. The temperature dependence of k is also discussed.

  14. NMR studies of the incommensurate helical antiferromagnet EuCo2P2: Determination of antiferromagnetic propagation vector

    DOE PAGES

    Higa, Nonoka; Ding, Qing -Ping; Yogi, Mamoru; ...

    2017-07-06

    Recently, Q.-P. Ding et al. reported that their nuclear magnetic resonance (NMR) study on EuCo2As2 successfully characterized the antiferromagnetic (AFM) propagation vector of the incommensurate helix AFM state, showing that NMR is a unique tool for determination of the spin structures in incommensurate helical AFMs. Motivated by this work, we have carried out 153Eu, 31P, and 59Co NMR measurements on the helical antiferromagnet EuCo2P2 with an AFM ordering temperature TN = 66.5 K. An incommensurate helical AFM structure was clearly confirmed by 153Eu and 31P NMR spectra on single-crystalline EuCo2P2 in zero magnetic field at 1.6 K and its externalmore » magnetic field dependence. Furthermore, based on 59Co NMR data in both the paramagnetic and incommensurate AFM states, we have determined the model-independent value of the AFM propagation vector k = (0,0,0.73±0.09)2π/c, where c is the c-axis lattice parameter. As a result, the temperature dependence of k is also discussed.« less

  15. Formation and characterisation of the silver hydride nanocluster cation [Ag3H2((Ph2 P)2CH2)](+) and its release of hydrogen.

    PubMed

    Girod, Marion; Krstić, Marjan; Antoine, Rodolphe; MacAleese, Luke; Lemoine, Jérome; Zavras, Athanasios; Khairallah, George N; Bonačić-Koutecký, Vlasta; Dugourd, Philippe; O'Hair, Richard A J

    2014-12-08

    Multistage mass spectrometry and density functional theory (DFT) were used to characterise the small silver hydride nanocluster, [Ag3 H2 L](+) (where L=(Ph2 P)2 CH2 ) and its gas-phase unimolecular chemistry. Collision-induced dissociation (CID) yields [Ag2 HL](+) as the major product while laser-induced dissociation (LID) proceeds via H2 formation and subsequent release from [Ag3 H2 L](+) , giving rise to [Ag3 L](+) as the major product. Deuterium labelling studies on [Ag3 D2 L](+) prove that the source of H2 is from the hydrides and not from the ligand. Comparison of TD-DFT absorption patterns obtained for the optimised structures with action spectroscopy results, allows assignment of the measured features to structures of precursors and products. Molecular dynamics "on the fly" reveal that AgH loss is favoured in the ground state, but H2 formation and loss is preferred in the first excited state S1 , in agreement with CID and LID experimental findings. This indicates favourable photo-induced formation of H2 and subsequent release from [Ag3 H2 L](+) , an important finding in context of metal hydrides as a hydrogen storage medium, which can subsequently be released by heating or irradiation with light. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Magnetization and transport properties of single RPd2P2 (R=Y, La-Nd, Sm-Ho, Yb)

    NASA Astrophysics Data System (ADS)

    Drachuck, Gil; Boehmer, Anna; Bud'Ko, Sergey L.; Canfield, Paul

    Single crystals of RPd2P2 (R=Y, La-Nd, Sm-Ho, Yb) were grown using a self-flux method and were characterized by room-temperature powder X-ray diffraction, anisotropic temperature and field dependent magnetization and temperature dependent in-plane resistivity. Anisotropic magnetic properties, arising mostly from crystal electric field (CEF) effects, were observed for most magnetic rare earths. The experimentally estimated CEF parameters B02 were calculated from the anisotropic paramagnetic θab and θcvalues. Ordering temperatures, as well as the polycrystalline averaged paramagnetic Curie-Weiss temperature, θave, were extracted from magnetization and resistivity measurements. Work done at Ames Laboratory was supported by US Department of Energy, Basic Energy Sciences, Division of Materials Sciences and Engineering under Contract No. DE-AC02-07CH111358.

  17. Radiative lifetimes of the 2s2p2(4P) metastable levels of N III

    NASA Technical Reports Server (NTRS)

    Fang, Z.; Kwong, Victor H. S.; Parkinson, W. H.

    1993-01-01

    The radiative decay rates of N III 175 nm intersystem lines were measured in the laboratory by recording the time dependence of photon intensities emitted as the 2s2p2(4P) metastable term of N(2+) ions decay to the 2s22p(2P0) ground term. A cylindrical radio frequency ion trap was used to store the electron impact-produced N(2+) ions. The radiative decay signals were analyzed by multiexponential least-squares fits to the data. The measured radiative decay rates to the ground term are 1019(+/- 64)/s for 4P sub 1/2, 74.5(+/- 5.4)/s for 4P sub 3/2, and 308( +/- 22)/s for 4P sub 5/2. Comparisons of the measured values with theoretical values are presented.

  18. Radiative lifetimes of the 2s2p2(4P) metastable levels of N III

    NASA Technical Reports Server (NTRS)

    Fang, Z.; Kwong, Victor H. S.; Parkinson, W. H.

    1993-01-01

    The radiative decay rates of N III 175 nm intersystem lines were measured in the laboratory by recording the time dependence of photon intensities emitted as the 2s2p2(4P) metastable term of N(2+) ions decay to the 2s22p(2P0) ground term. A cylindrical radio frequency ion trap was used to store the electron impact-produced N(2+) ions. The radiative decay signals were analyzed by multiexponential least-squares fits to the data. The measured radiative decay rates to the ground term are 1019(+/- 64)/s for 4P sub 1/2, 74.5(+/- 5.4)/s for 4P sub 3/2, and 308( +/- 22)/s for 4P sub 5/2. Comparisons of the measured values with theoretical values are presented.

  19. Structural Investigation of Phosphorus in CaO-SiO2-P2O5 Ternary Glass

    NASA Astrophysics Data System (ADS)

    Wang, Zhanjun; Cai, Shengjia; Zhang, Mei; Guo, Min; Zhang, Zuotai

    2017-04-01

    The system of CaO-SiO2-P2O5 ternary glass is not only among the major constituents of steelmaking slags in iron and steel industry, but also play a significant role in other industrial process, such as chemical engineering and glass industry. In the present study, the structure of CaO-SiO2-P2O5 ternary glass with varying P2O5 content from 0 to 15 wt pct at a fixed CaO/SiO2 = 1.4 was investigated using molecular dynamics (MD) simulation combined with X-ray photoelectron spectroscopy and Raman spectra techniques. The results indicated that P5+ ions have a higher affinity to Ca2+ ions which are then stripped away from the silicate network with the addition of P2O5, resulting in the formation of Ca-O-P and Si-O-Si linkages. In addition, almost all P5+ ions displayed as {{Q}}_{{P}}0 ( {{Q}}_{{P}}n , n is the number of bridging oxygen in one [PO4]-tetrahedra units) and a small fraction of P5+ ions behave as {{Q}}_{{P}}1 (P-O-P) and P-O-Si. The enhanced degree of polymerization can be detected from the increase of {{X}}_{{Si}}3 and X_{{P}}1 /X_{{P}}0 (mole fraction of {{Q}}_{{Si}}i or {{Q}}_{{P}}i ). Furthermore, the ratio of Raman scattering coefficients for Q_{{Si}}i /Q_{{Si}}1 and Q_{{P}}i /Q_{{P}}1 were determined by combining MD simulated result with Raman spectra, which were considered to be suitable to the present study.

  20. Structural Investigation of Phosphorus in CaO-SiO2-P2O5 Ternary Glass

    NASA Astrophysics Data System (ADS)

    Wang, Zhanjun; Cai, Shengjia; Zhang, Mei; Guo, Min; Zhang, Zuotai

    2017-02-01

    The system of CaO-SiO2-P2O5 ternary glass is not only among the major constituents of steelmaking slags in iron and steel industry, but also play a significant role in other industrial process, such as chemical engineering and glass industry. In the present study, the structure of CaO-SiO2-P2O5 ternary glass with varying P2O5 content from 0 to 15 wt pct at a fixed CaO/SiO2 = 1.4 was investigated using molecular dynamics (MD) simulation combined with X-ray photoelectron spectroscopy and Raman spectra techniques. The results indicated that P5+ ions have a higher affinity to Ca2+ ions which are then stripped away from the silicate network with the addition of P2O5, resulting in the formation of Ca-O-P and Si-O-Si linkages. In addition, almost all P5+ ions displayed as Q_{P}0 ( Q_{P}n , n is the number of bridging oxygen in one [PO4]-tetrahedra units) and a small fraction of P5+ ions behave as Q_{P}1 (P-O-P) and P-O-Si. The enhanced degree of polymerization can be detected from the increase of X_{Si}3 and X_{P}1 /X_{P}0 (mole fraction of {Q}_{Si}i or {Q}_{P}i ). Furthermore, the ratio of Raman scattering coefficients for Q_{Si}i /Q_{Si}1 and Q_{P}i /Q_{P}1 were determined by combining MD simulated result with Raman spectra, which were considered to be suitable to the present study.

  1. Optical inter-satellite communication with dynamically reconfigurable optical device using Sn2P2S6 crystal

    NASA Astrophysics Data System (ADS)

    Nishimaki, Kaori; Okamoto, Atsushi; Fujita, Tomohiro; Grabar, Alexander A.; Takabayashi, Masanori; Uozumi, Jun; Tomita, Akihisa; Takayama, Yoshihisa

    2011-03-01

    Since the optical inter-satellite communication has attractive advantages such as high-speed transmission with high confidence, almost no electronic magnetic interference, and low power consumption, it has been activity investigated. However, directivity control of the laser beams requires a bulky and complicated system in satellite mobile communications. A more flexible and high accurate system with small and simple mechanism has been desired. In this study, we propose a new method of optical inter-satellite communication with a dynamically reconfigurable optical directional device in which diffraction gratings are automatically rewritten and reorganized in response of incident conditions by moving satellites. For realizing such a device, we have developed Sn2P2S6 crystals which have a high sensitive photorefractivity and dynamic reconfigurable property. Furthermore, this crystal has hundreds times faster response than conventional photorefractive materials such as BaTiO3. These features are extremely advantageous to construct a high-speed and flexible communication system with a large tolerance to displacement of moving satellites. To investigate the possibility of the dynamically reconfigurable optical inter-satellite communication system, we experimentally evaluate the temporal and spatial characteristics of Sn2P2S6 crystals for the variation of the beam incident angle. Moreover, the diffraction beam from the crystal has phase conjugate wavefronts of the beam entering from the counter direction. We try to utilize this behavior to suppress the beam spread and to reduce the background light such as sunlight with a spatial filtering technique that has sensitivity in wavefront differences of the signal and background light.

  2. Cross sections for production of H(2p, 2s, 1s) by electron collisional dissociation of H2

    NASA Technical Reports Server (NTRS)

    Ajello, J. M.; James, G. K.; Shemansky, D. E.

    1991-01-01

    The excitation function of H Ly-alpha from the astrophysically important dissociation of electron-excited H2 over the range 10-700 eV has been measured. The analysis predicts the cross section to energies higher than the present experimental limit, and it is found that the predicted shape is in close agreement with measured results. At 6 eV the cross section is dominated by the electric dipole first Born component, while at 100 eV the electric dipole component constitutes 73 percent of the total H(2p) cross section. The cross sections of the H(2s) and H(1s) components are calculated.

  3. Maltodextrin and fat preference deficits in "taste-blind" P2X2/P2X3 knockout mice.

    PubMed

    Sclafani, Anthony; Ackroff, Karen

    2014-07-01

    Adenosine triphosphate is a critical neurotransmitter in the gustatory response to the 5 primary tastes in mice. Genetic deletion of the purinergic P2X2/P2X3 receptor greatly reduces the neural and behavioral response to prototypical primary taste stimuli. In this study, we examined the behavioral response of P2X double knockout mice to maltodextrin and fat stimuli, which appear to activate additional taste channels. P2X double knockout and wild-type mice were given 24-h choice tests (vs. water) with ascending concentrations of Polycose and Intralipid. In Experiment 1, naive double knockout mice, unlike wild-type mice, were indifferent to dilute (0.5-4%) Polycose solutions but preferred concentrated (8-32%) Polycose to water. In a retest, the Polycose-experienced double knockout mice, like wild-type mice, preferred all Polycose concentrations. In Experiment 2, naive double knockout mice, unlike wild-type mice, were indifferent to dilute (0.313-2.5%) Intralipid emulsions but preferred concentrated (5-20%) Intralipid to water. In a retest, the fat-experienced double knockout mice, like wild-type mice, strongly preferred 0.313-5% Intralipid to water. These results indicate that the inherent preferences of mice for maltodextrin and fat are dependent upon adenosine triphosphate taste cell signaling. With experience, however, P2X double knockout mice develop strong preferences for the nontaste flavor qualities of maltodextrin and fat conditioned by the postoral actions of these nutrients.

  4. WN4 longitudinal structure in the O (5S - 3P) and O+ (2P - 2D) ionospheric emissions as simulated by the C-IAM

    NASA Astrophysics Data System (ADS)

    Martynenko, Oleg; Ward, William E.; Shepherd, Gordon; Cho, Young-Min; Namgaladze, Alexander; Fomichev, Victor; McConnell, John; Semeniuk, Kirill; Beagley, Stephen

    A newly developed Canadian Ionosphere and Atmosphere Model (C-IAM) is introduced. It is being developed on the basis of two existing first principle models: the extended Canadian Middle Atmosphere Model (CMAM) and the ionospheric part of the Upper Atmosphere Model (UAM). The model extends from the surface to the inner magnetosphere and hence, is able to describe in a self-consistent way how lower atmosphere dynamical variability propagates into and affects the upper atmosphere and ionosphere. The C-IAM was applied to model the spatial structure of two different ionospheric emissions: the nighttime 135.6 nm O ( (5) S - (3) P) and daytime 732 nm O (+) ( (2) P - (2) D) emissions. The IMAGE satellite observations showed a wave number 4 (WN4) longitudinal structure in the 135.6 nm ionospheric emission emanating from the equatorial ionization anomaly at 350-400 km near 20:00 local time at each longitude. C-IAM simulations are in a good agreement with the observations. Model result analysis reveals that the main mechanism for generating the WN4 structure in the 135.6 nm emission is a modification of the ionospheric dynamo field caused by longitudinal variation of the zonal wind due to waves penetrating from the lower atmosphere. It was also shown, that during geomagnetic storms and substorms the high-latitudinal electric field fully suppresses the dynamo, so that the emission intensity dramatically decreases and the WN4 structure does not appear. The 732 nm emission simulated with the C-IAM also reveals the WN4 structure. Similar to the 135.6 nm emission, this structure is caused by waves penetrating from the lower atmosphere. However, the mechanism of excitation is quite different. The 732 nm emission is produced by the instant local ionization and excitation, and, hence, its variation is caused by the neutral density variability in the F2 region (above 200 km) without any involvement of the electric field effects. Correspondingly, latitudinal distribution of this

  5. Tricritical Lifshitz point in the temperature-pressure-composition diagram for (PbySn1-y)2P2(SexS1-x)6 ferroelectrics

    NASA Astrophysics Data System (ADS)

    Andersson, O.; Chobal, O.; Rizak, I.; Rizak, V.

    2009-11-01

    The heat capacity of Sn2P2S6 ferroelectric crystals has been measured under quasihydrostatic pressures up to 0.7 GPa. The analysis of the heat-capacity and literature data for the birefringence shows that the tricritical point of Sn2P2S6 is in the 0.20-0.25 GPa range. Moreover, in the approximation of a linear change in the free-energy expansion coefficients, with respect to concentration and pressure, thermodynamic trajectories have been constructed for (PbySn1-y)2P2(SexS1-x)6 solid solutions. We have thereby identified the region of the T-p-y-x diagram for (PbySn1-y)2P2(SexS1-x)6 showing the tricritical Lifshitz point.

  6. Magnetization and transport properties of single crystalline RPd2P2 (R=Y, La–Nd, Sm–Ho, Yb)

    DOE PAGES

    Drachuck, Gil; Böhmer, Anna E.; Bud'ko, Sergey L.; ...

    2016-05-27

    Single crystals of RPd2P2 (R=Y, La–Nd, Sm–Ho, Yb) were grown out of a high temperature solution rich in Pd and P and characterized by room-temperature powder X-ray diffraction, anisotropic temperature- and field-dependent magnetization and temperature-dependent in-plane resistivity measurements. In this series, YPd2P2 and LaPd2P2 YbPd2P2 (with Yb2+) are non-local-moment bearing. Furthermore, YPd2P2 and LaPd2P2 are found to be superconducting with Tc≃0.75 and 0.96 K respectively. CePd2P2 and PrPd2P2 magnetically order at low temperature with a ferromagnetic component along the crystallographic c-axis. The rest of the series manifest low temperature antiferromagnetic ordering. EuPd2P2 has Eu2+ ions and both EuPd2P2 and GdPd2P2 have isotropic paramagnetic susceptibilities consistent with L =0 and J=S=more » $$\\frac{7}{2}$$ and exhibit multiple magnetic transitions. For R=Eu–Dy, there are multiple, T>1.8 K transitions in zero applied magnetic field and for R=Nd, Eu, Gd, Tb, and Dy there are clear metamagnetic transitions at T=2.0 K for H< 55 kOe. Strong anisotropies arising mostly from crystal electric field (CEF) effects were observed for most magnetic rare earths with L≠0. The experimentally estimated CEF parameters B$$_2^0$$ were calculated from the anisotropic paramagnetic θab and θc values and compared to theoretical trends across the rare earth series. Lastly, the ordering temperatures as well as the polycrystalline averaged paramagnetic Curie–Weiss temperature, θave, were extracted from magnetization and resistivity measurements, and compared to the de-Gennes factor.« less

  7. Crystal and electronic structure changes during the charge-discharge process of Na4Co3(PO4)2P2O7

    NASA Astrophysics Data System (ADS)

    Moriwake, Hiroki; Kuwabara, Akihide; Fisher, Craig A. J.; Nose, Masafumi; Nakayama, Hideki; Nakanishi, Shinji; Iba, Hideki; Ikuhara, Yuichi

    2016-09-01

    Sodium-ion batteries offer a potential solution to the problem of limited lithium resources, and the newly developed positive electrode material Na4Co3(PO4)2P2O7 is attracting significant attention due to its high rate, high capacity, and high voltage compared to other sodium-ion battery materials. However, details of its electronic structure and its charge/discharge behavior are still uncertain. Here we report detailed first-principles calculations of the desodiation behavior of Na4Co3(PO4)2P2O7 using the GGA + U formalism of density functional theory. Assuming a stepwise desodiation process, removal of Na down to NaCo3(PO4)2P2O7 is found to be accompanied by oxidation of Co2+ to Co3+. Further removal of Na to give Co3(PO4)2P2O7 requires oxidation of oxygen 2p orbitals in the P2O7 polyhedra instead of Co3+ being oxidized to Co4+. The holes thus formed are expected to be strongly self-trapped, rendering them immobile at room temperature. At the same time, a large volume shrinkage is observed during this last desodiation step, constricting the Na migration channels. These two factors may explain the difficulty encountered experimentally in removing all Na from Na4Co3(PO4)2P2O7.

  8. High-pressure synchrotron Mössbauer and X-ray diffraction studies: Exploring the structure-related valence fluctuation in EuNi2P2

    NASA Astrophysics Data System (ADS)

    Li, Chunyu; Yu, Zhenhai; Bi, Wenli; Zhao, Jiyong; Hu, Michael Y.; Zhao, Jinggeng; Wu, Wei; Luo, Jianlin; Yan, Hao; Alp, Esen E.; Liu, Haozhe

    2016-11-01

    The high-pressure effect on valence fluctuation of the ThCr2Si2-type intermetallic compound EuNi2P2 has been investigated using in situ synchrotron Mössbauer spectroscopy (SMS). The isomer shift of 151Eu in EuNi2P2 increases monotonically with increasing pressure up to 50 GPa, suggesting a valence transition of the Eu from mixed toward trivalent. The synchrotron angle-dispersive X-ray diffraction (AD-XRD) experiment shows that EuNi2P2 remains in the tetragonal structure up to 32.5 GPa at room temperature. We propose that the evolutions of bonding distance with pressure have an obvious effect on the valence fluctuation.

  9. Bulk Electronic Structure of Superconducting LaRu2P2 Single Crystals Measured by Soft-X-Ray Angle-Resolved Photoemission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Razzoli, E.; Kobayashi, M.; Strocov, V. N.; Delley, B.; Bukowski, Z.; Karpinski, J.; Plumb, N. C.; Radovic, M.; Chang, J.; Schmitt, T.; Patthey, L.; Mesot, J.; Shi, M.

    2012-06-01

    We present a soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) study of the stoichiometric pnictide superconductor LaRu2P2. The observed electronic structure is in good agreement with density functional theory (DFT) calculations. However, it is significantly different from its counterpart in high-temperature superconducting Fe pnictides. In particular, the bandwidth renormalization present in the Fe pnictides (˜2-3) is negligible in LaRu2P2 even though the mass enhancement is similar in both systems. Our results suggest that the superconductivity in LaRu2P2 has a different origin with respect to the iron pnictides. Finally, we demonstrate that the increased probing depth of SX-ARPES, compared to the widely used ultraviolet ARPES, is essential in determining the bulk electronic structure in the experiment.

  10. Residual Chemosensory Capabilities in Double P2X2/P2X3 Purinergic Receptor Null Mice: Intraoral or Postingestive Detection?

    PubMed Central

    Hallock, Robert M.; Tatangelo, Marco; Barrows, Jennell

    2009-01-01

    Mice lacking the purinergic receptors, P2X2 and P2X3 (P2X2/P2X3Dbl−/−), exhibit essentially no tastant-evoked activity in the chorda tympani and glossopharyngeal nerves and substantial loss of tastant-evoked behavior as measured in long-term intake experiments. To assess whether the residual chemically driven behaviors in these P2X2/P2X3Dbl−/− mice were attributable to postingestive detection or oropharyngeal detection of the compounds, we used brief access lickometer tests to assess the behavioral capabilities of the P2X2/P2X3Dbl−/− animals. The P2X2/P2X3Dbl−/− mice showed avoidance to high levels (10 mM quinine and 10–30 mM denatonium benzoate) of classical “bitter”-tasting stimuli in 24-h, 2-bottle preference tests but minimal avoidance of these substances in the lickometer tests, suggesting that the strong avoidance in the intake tests was largely mediated by post-oral chemosensors. Similarly, increases in consumption of 1 M sucrose by P2X2/P2X3Dbl−/− mice in long-term intake tests were not mirrored by increases in consumption of sucrose in lickometer tests, suggesting that sucrose detection in these mice is mediated by postingestive consequences. In contrast, in brief access tests, P2X2/P2X3Dbl−/− mice avoided citric acid and hydrochloric acid at the same concentrations as their wild-type counterparts, indicating that these weak acids activate oropharyngeal chemoreceptors. PMID:19833662

  11. Double P2X2/P2X3 Purinergic Receptor Knockout Mice Do Not Taste NaCl or the Artificial Sweetener SC45647

    PubMed Central

    Eddy, Meghan C.; Eschle, Benjamin K.; Barrows, Jennell; Hallock, Robert M.; Finger, Thomas E.

    2009-01-01

    The P2X ionotropic purinergic receptors, P2X2 and P2X3, are essential for transmission of taste information from taste buds to the gustatory nerves. Mice lacking both P2X2 and P2X3 purinergic receptors (P2X2/P2X3Dbl−/−) exhibit no taste-evoked activity in the chorda tympani and glossopharyngeal nerves when stimulated with taste stimuli from any of the 5 classical taste quality groups (salt, sweet, sour, bitter, and umami) nor do the mice show taste preferences for sweet or umami, or avoidance of bitter substances (Finger et al. 2005. ATP signaling is crucial for communication from taste buds to gustatory nerves. Science. 310[5753]:1495–1499). Here, we compare the ability of P2X2/P2X3Dbl−/− mice and P2X2/P2X3Dbl+/+ wild-type (WT) mice to detect NaCl in brief-access tests and conditioned aversion paradigms. Brief-access testing with NaCl revealed that whereas WT mice decrease licking at 300 mM and above, the P2X2/P2X3Dbl−/− mice do not show any change in lick rates. In conditioned aversion tests, P2X2/P2X3Dbl−/− mice did not develop a learned aversion to NaCl or the artificial sweetener SC45647, both of which are easily avoided by conditioned WT mice. The inability of P2X2/P2X3Dbl−/− mice to show avoidance of these taste stimuli was not due to an inability to learn the task because both WT and P2X2/P2X3Dbl−/− mice learned to avoid a combination of SC45647 and amyl acetate (an odor cue). These data suggest that P2X2/P2X3Dbl−/− mice are unable to respond to NaCl or SC45647 as taste stimuli, mirroring the lack of gustatory nerve responses to these substances. PMID:19833661

  12. NMR investigation of spin fluctuations in the itinerant-electron magnetic compound Sr1 -xCaxCo2P2

    NASA Astrophysics Data System (ADS)

    Imai, Masaki; Michioka, Chishiro; Ueda, Hiroaki; Yoshimura, Kazuyoshi

    2017-02-01

    We took P31 NMR measurements of mainly paramagnetic phase Sr1 -xCaxCo2P2 (0 ≤x ≤0.5 ) to reveal the itinerant-electron metamagnetic transition, and of its magnetically ordered phase (0.7 ≤x ≤1 ), and characterized their spin fluctuations by estimating the spin fluctuation parameter T0 corresponding to the width of the spin fluctuation in the spectrum in frequency space. SrCo2P2 has a quasi-two-dimensional uncollapsed tetragonal (ucT) cell without interlayer P-P bonds, whereas CaCo2P2 has a three-dimensional collapsed tetragonal (cT) cell with P-P bonds. The a b -in-plane component of T0 is much larger than the out-of-plane component in SrCo2P2 . As x increases from 0 to 0.5, the in-plane component of T0 decreases proportionally with the metamagnetic transition field. In the antiferromagnetic cT phase (0.7 ≤x ≤1 ), T0 is constant and spin fluctuations show an isotropic character in contrast to their behavior in the paramagnetic ucT phase (0 ≤x ≤0.5 ). These results indicate that the in-plane spin fluctuations due to the quasi-two-dimensional crystal structure play a significant role in the metamagnetic transition of this system.

  13. The splitting and oscillator strengths for the 2S/2/S-2p/2/P/0/ doublet in lithium-like sulfur. [during Skylab observed solar flares

    NASA Technical Reports Server (NTRS)

    Pegg, D. J.; Forester, J. P.; Elston, S. B.; Griffin, P. M.; Peterson, R. S.; Thoe, R. S.; Vane, C. R.; Sellin, I. A.; Groeneveld, K.-O.

    1977-01-01

    The beam-foil technique has been used to study the 2S(2)S-2p(2)P(0) doublet in S XIV. The results confirm the doublet splitting measured aboard Skylab during solar flare events. In addition, the oscillator strengths for the resonance transitions comprising this doublet have been measured and found to agree well with recent relativistic f-value calculations.

  14. The stimulation of proliferation and differentiation of periodontal ligament cells by the ionic products from Ca7Si2P2O16 bioceramics.

    PubMed

    Zhou, Yinghong; Wu, Chengtie; Xiao, Yin

    2012-07-01

    The ultimate goal of periodontal tissue engineering is to produce predictable regeneration of alveolar bone, root cementum, and periodontal ligament, which are lost as a result of periodontal diseases. To achieve this goal, it is of great importance to develop novel bioactive materials which could stimulate the proliferation, differentiation and osteogenic/cementogenic gene expression of periodontal ligament cells (PDLCs) for periodontal regeneration. In this study, we synthesized novel Ca(7)Si(2)P(2)O(16) ceramic powders for the first time by the sol-gel method and investigated the biological performance of PDLCs after exposure to different concentrations of Ca(7)Si(2)P(2)O(16) extracts. The original extracts were prepared at 200 mg ml(-1) and further diluted with serum-free cell culture medium to obtain a series of diluted extracts (100, 50, 25, 12.5 and 6.25 mg ml(-1)). Proliferation, alkaline phosphatase (ALP) activity, Ca deposition, and osteogenesis/cementogenesis-related gene expression (ALP, Col I, Runx2 and CEMP1) were assayed for PDLCs on days 7 and 14. The results showed that the ionic products from Ca(7)Si(2)P(2)O(16) powders significantly stimulated the proliferation, ALP activity, Ca deposition and osteogenesis/cementogenesis-related gene expression of PDLCs. In addition, it was found that Ca(7)Si(2)P(2)O(16) powders had excellent apatite-mineralization ability in simulated body fluids. This study demonstrated that Ca(7)Si(2)P(2)O(16) powders with such a specific composition possess the ability to stimulate the PDLC proliferation and osteoblast/cemenoblast-like cell differentiation, indicating that they are a promising bioactive material for periodontal tissue regeneration application.

  15. Fusion protein His-Hsp65-6IA2P2 prevents type 1 diabetes through nasal immunization in NOD Mice.

    PubMed

    Lu, Shiping; Li, Guoliang; Liu, Kunfeng; Yang, Xue; Cao, Rongyue; Zong, Li; Long, Jun; Jin, Liang; Wu, Jie

    2016-06-01

    Human heat shock protein 60 (Hsp60), is an endogenous β-cells autoantigen, it could postpone the onset of insulitis and sooner type 1 diabetes mellitus. P277 is one of Hsp65 determinants at position 437-469 of amino acids cascaded. Meanwhile, it's already well-known that there were several better anti-diabetic B epitopes, such as insulinoma antigen-2 (IA-2). Currently, fusion protein IA2P2 has constructed in order to enhance its pharmacological efficacy. In addition, added homologous bacterial-derived Hsp65 and His tag were beneficial to protein immunogenicity and purification separately. So, finally we examined a fusion protein His-Hsp65-6IA2P2 could regulate Th2 immune response and reduce natural diabetic incidence in NOD mice. We constructed two express vector pET28a-His-Hsp65-6P277 and pET28a-His-Hsp65-6IA2P2. After purification, we observed that triple intranasal administration of these two fusion protein in 4-week-old NOD mice maintained normal blood glucose and weight, with a lower diabetic or insulitis incidence. Consistent with induced splenic T cells proliferation and tolerance, His-Hsp65-6IA2P2-treated mice performed reduced IFN-γ and increased IL-10 level. In conclusion, we suggested that fusion protein His-Hsp65-6IA2P2 could be reconstructed and purified successively. Furthermore, nasal administration of this fusion protein could rebalance T cells population and prevent T1DM.

  16. K2M(H2P2O7)2.2H2O (M = Ni, Cu, Zn): orthorhombic forms and Raman spectra.

    PubMed

    Essehli, Rachid; El Bali, Brahim; Alaoui Tahiri, Aziz; Lachkar, Mohammed; Manoun, Bouchaib; Dusek, Michal; Fejfarova, Karla

    2005-12-01

    The crystal structures of three isotypic orthorhombic dihydrogendiphosphates, namely dipotassium copper(II)/nickel(II)/zinc(II) bis(dihydrogendiphosphate) dihydrate, K2M(H2P2O7)2.2H2O (M = Cu, Ni and Zn), have been refined from single-crystal data. The M2+ and K+ cations are located at sites of m symmetry, and the P atoms occupy general positions. These compounds also exist in triclinic forms with very similar structural features. The structures of both forms are compared, as well as the geometry of the MO6 octahedron, which is considerably elongated towards the water molecules for M = Ni and Cu. Such elongation has not been observed among the other representatives of the family. A Raman study of the whole series K2M(H2P2O7)2.2H2O (M = Mn, Co, Ni, Cu, Zn and Mg) is reported.

  17. Penta­cobalt(II) divanadium(III) tetrakis(diphosphate), Co5V2(P2O7)4

    PubMed Central

    Bronova, Anna; Glaum, Robert; Litterscheid, Christian

    2013-01-01

    Co5V2(P2O7)4 was crystallized by chemical vapour transport using HCl as transport agent. Its crystal structure is isotypic to that of FeII 5FeIII 2(P2O7)4 and can be regarded as a member of the thortveitite structure family with corrugated layers of metal–oxygen polyhedra extending parallel to (010). Significant occupational disorder between cobalt(II) and vanadium(III) is observed. Four of the five cation sites are occupied by both cobalt and vanadium. The fifth cation site (Co1) is occupied by cobalt only. Sites Co1, M3 and M4 are located on twofold axes. Sites Co1, M2, M3 and M4 show o­cta­hedral coordination by oxygen; M5 has a square-pyramidal environment. PMID:23723750

  18. Complex magnetic phase diagram with multistep spin-flop transitions in L a0.25P r0.75C o2P2

    NASA Astrophysics Data System (ADS)

    Tan, Xiaoyan; Garlea, V. Ovidiu; Kovnir, Kirill; Thompson, Corey M.; Xu, Tongshuai; Cao, Huibo; Chai, Ping; Tener, Zachary P.; Yan, Shishen; Xiong, Peng; Shatruk, Michael

    2017-01-01

    L a0.25P r0.75C o2P2 crystallizes in the tetragonal ThC r2S i2 structure type and shows multiple magnetic phase transitions driven by changes in temperature and magnetic field. The nature of these transitions was investigated by a combination of magnetic and magnetoresistance measurements and both single crystal and powder neutron diffraction. The Co magnetic moments order ferromagnetically (FM) parallel to the c axis at 282 K, followed by antiferromagnetic (AFM) ordering at 225 K. In the AFM structure, the Co magnetic moments align along the c axis with FM [C o2P2] layers arranged in an alternating sequence, ↑↑↓↓ , which leads to the doubling of the c axis in the magnetic unit cell. Another AFM transition is observed at 27 K, due to the ordering of a half of Pr moments in the a b plane. The other half of Pr moments undergoes AFM ordering along the c axis at 11 K, causing simultaneous reorientation of the previously ordered Pr moments into an AFM structure with the moments being canted with respect to the c axis. This AFM transition causes an abrupt decrease in electrical resistivity at 11 K. Under applied magnetic field, two metamagnetic transitions are observed in the Pr sublattice at 0.8 and 5.4 T. They correlate with two anomalies in magnetoresistance measurements at the same critical fields. A comparison of the temperature- and field-dependent magnetic properties of L a0.25P r0.75C o2P2 to the magnetic behavior of PrC o2P2 is provided.

  19. Experimental visualization of the diffusion pathway of sodium ions in the Na3[Ti2P2O10F] anode for sodium-ion battery.

    PubMed

    Ma, Zhaohui; Wang, Yuesheng; Sun, Chunwen; Alonso, J A; Fernández-Díaz, M T; Chen, Liquan

    2014-11-27

    Sodium-ion batteries have attracted considerable interest as an alternative to lithium-ion batteries for electric storage applications because of the low cost and natural abundance of sodium resources. The materials with an open framework are highly desired for Na-ion insertion/extraction. Here we report on the first visualization of the sodium-ion diffusion path in Na3[Ti2P2O10F] through high-temperature neutron powder diffraction experiments. The evolution of the Na-ion displacements of Na3[Ti2P2O10F] was investigated with high-temperature neutron diffraction (HTND) from room temperature to 600°C; difference Fourier maps were utilized to estimate the Na nuclear-density distribution. Temperature-driven Na displacements indicates that sodium-ion diffusion paths are established within the ab plane. As an anode for sodium-ion batteries, Na3[Ti2P2O10F] exhibits a reversible capacity of ~100 mAh g(-1) with lower intercalation voltage. It also shows good cycling stability and rate capability, making it promising applications in sodium-ion batteries.

  20. Experimental visualization of the diffusion pathway of sodium ions in the Na3[Ti2P2O10F] anode for sodium-ion battery

    PubMed Central

    Ma, Zhaohui; Wang, Yuesheng; Sun, Chunwen; Alonso, J. A.; Fernández-Díaz, M. T.; Chen, Liquan

    2014-01-01

    Sodium-ion batteries have attracted considerable interest as an alternative to lithium-ion batteries for electric storage applications because of the low cost and natural abundance of sodium resources. The materials with an open framework are highly desired for Na-ion insertion/extraction. Here we report on the first visualization of the sodium-ion diffusion path in Na3[Ti2P2O10F] through high-temperature neutron powder diffraction experiments. The evolution of the Na-ion displacements of Na3[Ti2P2O10F] was investigated with high-temperature neutron diffraction (HTND) from room temperature to 600°C; difference Fourier maps were utilized to estimate the Na nuclear-density distribution. Temperature-driven Na displacements indicates that sodium-ion diffusion paths are established within the ab plane. As an anode for sodium-ion batteries, Na3[Ti2P2O10F] exhibits a reversible capacity of ~100 mAh g−1 with lower intercalation voltage. It also shows good cycling stability and rate capability, making it promising applications in sodium-ion batteries. PMID:25427677

  1. Luminescence study and dosimetry approach of Ce on an α-Sr2 P2 O7 phosphor synthesized by a high-temperature combustion method.

    PubMed

    Patel, Nimesh P; Srinivas, M; Modi, Dhaval; Vishwnath, Verma; Murthy, K V R

    2015-06-01

    We report synthesis of a cerium-activated strontium pyrophosphate (Sr2 P2 O7 ) phosphor using a high-temperature combustion method. Samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and thermoluminescence (TL). The XRD pattern reveals that Sr2 P2 O7 has an α-phase with crystallization in the orthorhombic space group of Pnam. The IR spectrum of α-Sr2 P2 O7 displays characteristic bands at 746 and 1190 cm(-1) corresponding to the absorption of (P2 O7 )(-4) . PL emission spectra exhibit a broad emission band around 376 nm in the near-UV region due to the allowed 5d-4f transition of cerium and suggest its applications in a UV light-emitting diode (LED) source. PL also reveals that the emission originates from 5d-4f transition of Ce(3+) and intensity increases with doping concentration. TL measurements made after X-ray irradiation, manifest a single intense glow peak at around 192°C, which suggests that this is an outstanding candidate for dosimetry applications. The kinetic parameters, activation energy and frequency factor of the glow curve were calculated using different analysis methods. Copyright © 2014 John Wiley & Sons, Ltd.

  2. A novel pyrophosphate BaCr2(P2O7)2 as green pigment with high NIR solar reflectance and durable chemical stability

    NASA Astrophysics Data System (ADS)

    Tao, Zhengxu; Zhang, Wanqi; Huang, Yanlin; Wei, Donglei; Seo, Hyo Jin

    2014-08-01

    A novel pyrophosphate BaCr2(P2O7)2 was synthesized by the conventional solid-state reaction. The X-ray diffraction (XRD), FTIR spectrum, scanning electron microscopy (SEM) and ultraviolet-visible (UV-Vis) near infrared (NIR) reflectance spectra were applied to characterize the powders. The refractive indexes and nature of the VB and CB were determined. The structure, color properties and application were investigated. The results reveal that the anomalist bodies with smooth surfaces were obtained at 1200 °C with a mean size of 3 μm. A high reflectance peak at 535 nm was observed in the visible region, which is associated with the brilliant and deep green color of this pigment. With all the acids, alkali and deionized water treatment, the polycrystalline pigment BaCr2(P2O7)2 was found to be durable in chemical stability. The significantly high NIR solar reflectance of BaCr2(P2O7)2 is 90.0%, a higher cooling ability, so it has been selected to be tested as cool green pigment in ceramics. Moreover, this novel pyrophosphate pigment has great potential as cool pigment for surface coating applications.

  3. Crystal structure and vibrational spectra of tetrasodium dimagnesium dihydrogen diphosphate octahydrate Na 4Mg 2(H 2P 2O 7) 4·8H 2O

    NASA Astrophysics Data System (ADS)

    Harcharras, M.; Ennaciri, A.; Assaaoudi, H.; Mattei, G.; D'Orazio, V.; Moliterni, A. G. G.; Capitelli, F.

    2003-04-01

    A tetrasodium dimagnesium dihydrogen diphosphate octahydrate Na 4Mg 2(H 2P 2O 7) 4·8H 2O was synthesized. It crystallizes in the monoclinic system, space group P2 1/ m (no. 11), Z=4, and its unit-cell parameters are: a=8.0445(3) Å, b=11.5244(5) Å, c=9.0825(4) Å, β=113.1401(2)°, V=774.28(6) Å 3. The structure was determined by single-crystal X-ray diffractometry and refined to a R index of 0.0294 (w R=0.0727) for 1878 independent reflections with I>2 σ( I). The framework is made by the alternance of layers of MgO 6/NaO 6 octahedra and double tetrahedra PO 4 along b-axis. Such layers are characterized by the presence of strong hydrogen bonds. (H 2P 2O 7) 2- anions exhibit bent eclipsed conformation. Besides, the crystal was analyzed by FT-IR and micro-Raman vibrational spectroscopy. No coincidences of the majority of the Raman and infrared spectra bands of Na 4Mg 2(H 2P 2O 7) 4·8H 2O confirms a centrosymmetric structure of this material. The vibrational spectra confirm the bent POP configuration in this compound.

  4. 2p2 Team News

    NASA Astrophysics Data System (ADS)

    Jones, H.

    2001-03-01

    In December we welcomed Emanuel Galliano to our team. Emanuel is a French student at ESO Chile who is already familiar with La Silla, through his previous work with the DENIS group. He will be working primarily on operations at the 2.2-m. In February, however, we bade farewell to Emanuela Pompei after nearly two years with the team. Although Emanuela is leaving La Silla, she will remain with ESO in Chile, commencing work as a Staff Astronomer on Paranal in March. We wish her all the best in her move north.

  5. The Diphosphorus Complex [Cp2Mo2(CO)4(η(2)-P2)] as a Building Block for the Synthesis of Mixed-Hybrid Coordination Polymers.

    PubMed

    Moussa, Mehdi Elsayed; Attenberger, Bianca; Fleischmann, Martin; Schreiner, Andrea; Scheer, Manfred

    2016-10-01

    The three-component reaction of the tetrahedral diphosphorus complex [Cp2Mo2(CO)4(η(2)-P2)] (1), with Ag[BF4] (2) in the presence of 2,2'-bipyrimidine (3) leads to the formation of the two novel two-dimensional networks 4 and 5. Compound 4 is a new two-dimensional organometallic-organic hybrid polymer, while derivative 5 represents a unique two-dimensional organometallic-inorganic-organic hybrid polymer. These results show the possibility of synthesizing a new class of coordination polymers, which could not be obtained from two-component reactions with organic molecules in addition of metal ions.

  6. Magnetic phase transition of high-pressure phase (VO)2P2O7 studied by high-field ESR measurements

    NASA Astrophysics Data System (ADS)

    Hiraka, K.; Nagasaka, Y.; Kunimoto, T.; Inagaki, Y.; Okubo, S.; Ohta, H.; Saito, T.; Azuma, M.; Takano, M.

    2004-05-01

    The high-pressure phase of (VO)2P2O7 (HP-VOPO) is a S=1/2 Heisenberg antiferromagnetic alternating chain compound with one spin gap. The high-field ESR measurements of the HP-VOPO single crystal have been performed using the pulsed magnetic field up to 30T. Small anomaly is observed in ESR mode for both a- and b-axis. The linewidth became broad around Bc=20T when the field is applied along the a- and b-axis. The magnetic state of HP-VOPO above Bc will be discussed.

  7. Temporal Dynamics of Two Beam Coupling and the Origin of Compensation Photorefractive Gratings in Sn2P2S6:Sb (Postprint)

    DTIC Science & Technology

    2017-03-29

    Hypothiodiphosphate (Sn2P2S6, SPS) possesses impressive optical nonlinearities, especially a pronounced photorefractive effect in the red and near...saturates well before the slow grating develops in full (τf τs). The dashed gray lines and solid red line in Fig. 4 show the results of the best fits of...and τs , respectively. Half-filled ( red ) symbols are used for the antimony doped sample K33, while open symbols denote the nominally undoped

  8. Induction of MDM2-P2 Transcripts Correlates with Stabilized Wild-Type p53 in Betel- and Tobacco-Related Human Oral Cancer

    PubMed Central

    Ralhan, Ranju; Sandhya, Agarwal; Meera, Mathur; Bohdan, Wasylyk; Nootan, Shukla K.

    2000-01-01

    MDM2, a critical element of cellular homeostasis mechanisms, is involved in complex interactions with important cell-cycle and stress-response regulators including p53. The mdm2-P2 promoter is a transcriptional target of p53. The aim of this study was to determine the association between mdm2-P2 transcripts and the status of the p53 gene in betel- and tobacco-related oral squamous cell carcinomas (SCCs) to understand the mechanism of deregulation of MDM2 and p53 expression and their prognostic implications in oral tumorigenesis. Elevated levels of MDM2 proteins were observed in 11 of 25 (44%) oral hyperplastic lesions, nine of 15 (60%) dysplastic lesions, and 71 of 100 (71%) SCCs. The intriguing feature of the study was the identification and different subcellular localization of three isoforms of MDM2 (ie, 90 kd, 76 kd, and 57 kd) in oral SCCs and their correlation with p53 overexpression in each tumor. The hallmark of the study was the detection of mdm2-P2 transcripts in 12 of 20 oral SCCs overexpressing both MDM2 and p53 proteins while harboring wild-type p53 alleles. Furthermore, mdm2 amplification was an infrequent event in betel- and tobacco-associated oral tumorigenesis. The differential compartmentalization of the three isoforms of MDM2 suggests that each has a distinct function, potentially in the regulation of p53 and other gene products implicated in oral tumorigenesis. In conclusion, we report herein the first evidence suggesting that enhanced translation of mdm2-P2 transcripts (S-mdm2) may represent an important mechanism of overexpression and consequent stabilization and functional inactivation of wild-type p53 serving as an adverse prognosticator in betel- and tobacco-related oral cancer. The clinical significance of the functional inactivation of wild-type p53 by MDM2 is underscored by the significantly shorter median disease-free survival time (16 months) observed in p53/MDM2-positive cases as compared to those which did not show co-expression of

  9. Crystal structure of Rb2Mn3(H2O)2[P2O7]2, a new representative of the family of hydrated diphosphates

    NASA Astrophysics Data System (ADS)

    Kiriukhina, G. V.; Yakubovich, O. V.; Dimitrova, O. V.; Volkov, A. S.

    2016-09-01

    The crystal structure of Rb2Mn3(H2O)2[P2O7]2, a new phase obtained in the form of single crystals under hydrothermal conditions in the MnCl2-Rb3PO4-H2O system, is determined by X-ray diffraction (Xcalibur-S-CCD diffractometer, R = 0.0270): a = 9.374(2), b = 8.367(2), c = 9.437(2) Å, ß = 99.12(2)°, space group P21/ c, Z = 2, D x = 3.27 g/cm3. A correlation between the unit-cell parameters and the size of cations forming the crystal structures of isostructural A2M3(H2O)2[P2O7]2 diphosphates ( A = K, NH4, Rb, or Na; M = Mn, Fe, Co, or Ni) is revealed. It is shown that, due to the topological similarity, the structures of diphosphates and orthophosphates of the farringtonite structural type can undergo mutual transformations.

  10. Heavy-metal extraction from sewage sludge using phosphorous-based salts: optimization process with Na2H2P2O7.

    PubMed

    Navarro-González, Milagros; Ortega-López, Vanesa; Lópéz-Fernández, Juana I; Amo-Salas, Mariano; González-Carcedo, Salvador

    2016-11-24

    Land application is one of the important disposal alternatives for sewage sludge, but availability of potential toxic metals often restricts its uses. Three phosphorous-based salts (Na2H2P2O7, K4P2O7, KH2PO4) were studied as potential metal extractants. The conclusions of the research were that greater extractive efficiency is achieved through a 30-min process of vertical shaking with disodium diacid pyrophosphate - Na2H2P2O7 - at a concentration of 0.2 M at pH 2. Alternatively, the optimized process with oscillating shaking equipment would require 60 min. In both cases the average of set of extracted metals is around 50%. A second extraction process with potassium pyrophosphate - K4P2O7 at pH 6 achieved the reduction of further total amounts of metal, upper 65% with respect to the initial content. In this way the sludge could be used in land applications, with restrictions on each soil, according to the limit values specified in the future regulations.

  11. Structure of the calcium pyrophosphate monohydrate phase (Ca2P2O7·H2O): towards understanding the dehydration process in calcium pyrophosphate hydrates.

    PubMed

    Gras, Pierre; Ratel-Ramond, Nicolas; Teychéné, Sébastien; Rey, Christian; Elkaim, Erik; Biscans, Béatrice; Sarda, Stéphanie; Combes, Christèle

    2014-09-01

    Calcium pyrophosphate hydrate (CPP, Ca(2)P(2)O(7) · nH2O) and calcium orthophosphate compounds (including apatite, octacalcium phosphate etc.) are among the most prevalent pathological calcifications in joints. Even though only two dihydrated forms of CPP (CPPD) have been detected in vivo (monoclinic and triclinic CPPD), investigations of other hydrated forms such as tetrahydrated or amorphous CPP are relevant to a further understanding of the physicochemistry of those phases of biological interest. The synthesis of single crystals of calcium pyrophosphate monohydrate (CPPM; Ca(2)P(2)O(7) · H2O) by diffusion in silica gel at ambient temperature and the structural analysis of this phase are reported in this paper. Complementarily, data from synchrotron X-ray diffraction on a CPPM powder sample have been fitted to the crystal parameters. Finally, the relationship between the resolved structure for the CPPM phase and the structure of the tetrahydrated calcium pyrophosphate β phase (CPPT-β) is discussed.

  12. 2P2I HUNTER: a tool for filtering orthosteric protein-protein interaction modulators via a dedicated support vector machine.

    PubMed

    Hamon, Véronique; Bourgeas, Raphael; Ducrot, Pierre; Theret, Isabelle; Xuereb, Laura; Basse, Marie Jeanne; Brunel, Jean Michel; Combes, Sebastien; Morelli, Xavier; Roche, Philippe

    2014-01-06

    Over the last 10 years, protein-protein interactions (PPIs) have shown increasing potential as new therapeutic targets. As a consequence, PPIs are today the most screened target class in high-throughput screening (HTS). The development of broad chemical libraries dedicated to these particular targets is essential; however, the chemical space associated with this 'high-hanging fruit' is still under debate. Here, we analyse the properties of 40 non-redundant small molecules present in the 2P2I database (http://2p2idb.cnrs-mrs.fr/) to define a general profile of orthosteric inhibitors and propose an original protocol to filter general screening libraries using a support vector machine (SVM) with 11 standard Dragon molecular descriptors. The filtering protocol has been validated using external datasets from PubChem BioAssay and results from in-house screening campaigns. This external blind validation demonstrated the ability of the SVM model to reduce the size of the filtered chemical library by eliminating up to 96% of the compounds as well as enhancing the proportion of active compounds by up to a factor of 8. We believe that the resulting chemical space identified in this paper will provide the scientific community with a concrete support to search for PPI inhibitors during HTS campaigns.

  13. Quantum oscillations of the superconductor LaRu2P2: Comparable mass enhancement λ≈1 in Ru and Fe phosphides

    NASA Astrophysics Data System (ADS)

    Moll, Philip J. W.; Kanter, Jakob; McDonald, Ross D.; Balakirev, Fedor; Blaha, Peter; Schwarz, Karlheinz; Bukowski, Zbigniew; Zhigadlo, Nikolai D.; Katrych, Sergiy; Mattenberger, Kurt; Karpinski, Janusz; Batlogg, Bertram

    2011-12-01

    We have studied the angular-dependent de Haas-van Alphen oscillations of LaRu2P2 using magnetic torque in pulsed magnetic fields up to 60 T. The observed oscillation frequencies are in excellent agreement with the geometry of the calculated Fermi surface. The temperature dependence of the oscillation amplitudes reveals effective masses m*(α)=0.71 and m*(β)=0.99 me, which are enhanced over the calculated band mass by λcyc of 0.8. We find a similar enhancement of λγ≈1 in comparing the measured electronic specific heat (γ=11.5 mJ/mol K2) with the total density of states from band-structure calculations. Remarkably, very similar mass enhancements have been reported in other pnictides, LaFe2P2, LaFePO (Tc≈4K), and LaRuPO, independent of whether they are superconducting or not. This is contrary to the common perceptions that the normal-state quasiparticle renormalizations reflect the strength of the superconducting pairing mechanism and leads to new questions about pairing in isostructural and isoelectronic Ru- and Fe-pnictide superconductors.

  14. Fully gapped superconductivity in Ni-pnictide superconductors BaNi2As2 and SrNi2P2

    NASA Astrophysics Data System (ADS)

    Kurita, N.; Ronning, F.; Miclea, C. F.; Tokiwa, Y.; Bauer, E. D.; Subedi, A.; Singh, D. J.; Sakai, H.; Thompson, J. D.; Movshovich, R.

    2011-01-01

    We have performed low-temperature specific heat C and thermal conductivity κ measurements on the Ni-pnictide superconductors BaNi2As2 (Tc = 0.7K) and SrNi2P2 (Tc = 1.4K). The temperature dependences C(T) and κ(T) of the two compounds are similar to the results of a number of s-wave superconductors. Furthermore, the concave field responses of the residual κ for BaNi2As2 rules out the presence of nodes on the Fermi surfaces. We postulate that fully gapped superconductivity could be universal for Ni-pnictide superconductors. Specific heat data on Ba0.6La0.4Ni2As2 shows a mild suppression of Tc and Hc2 relative to BaNi2As2.

  15. Measurements of radiative-decay rates of the 2s22p(2P°)-2s2p2(4P) intersystem transitions of C+

    NASA Astrophysics Data System (ADS)

    Fang, Z.; Kwong, Victor H. S.; Wang, Jiebing; Parkinson, W. H.

    1993-08-01

    The radiative-decay rates of the 2s22p(2P0)-2s2p2(4P) intersystem transitions of C+ ions have been measured by recording the time dependence of the ~233-nm emission. A cylindrical radio-frequency ion trap was used to store electron-impact-produced C+ ions. The time-dependent signals were analyzed by multiexponential least-squares fits to the data. The measured radiative-decay rates to the ground term are 146.4(+8.3,-9.2) s-1 for 4P1/2, 11.6(+0.8,-1.7) s-1 for 4P3/2, and 51.2(+2.6,-3.5) s-1 for 4P5/2. Comparison of the measured values with theoretical values is presented.

  16. Dichloro-Cycloazatriphosphane: The Missing Link between N2 P2 and P4 Ring Systems in the Systematic Development of NP Chemistry.

    PubMed

    Bresien, Jonas; Hinz, Alexander; Schulz, Axel; Suhrbier, Tim; Thomas, Max; Villinger, Alexander

    2017-09-12

    A dichloro-cycloazatriphosphane that incorporates a cyclic NP3 backbone could be synthesized using knowledge gained from the chemistry of N2 P2 and P4 ring systems. It fills the gap between the congeneric compounds [ClP(μ-NR)]2 and [ClP(μ-PR)]2 (R=sterically demanding substituent), and thus contributes to the systematic development of nitrogen-phosphorus chemistry in general. The title compound was studied with respect to its formation via a labile aminodiphosphene, which readily underwent different rearrangement reactions depending on the solvent. All compounds were fully characterized by experimental and computational methods. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Modification of magnetic anisotropy through 3d-4f coupling in La0.75Pr0.25Co2P2

    NASA Astrophysics Data System (ADS)

    Kovnir, Kirill; Thompson, Corey M.; Garlea, V. Ovidiu; Haskel, Daniel; Polyanskii, Anatolii A.; Zhou, Haidong; Shatruk, Michael

    2013-09-01

    Magnetic behavior of La0.75Pr0.25Co2P2 was investigated by a combination of magnetic measurements, magneto-optical imaging, neutron diffraction, and x-ray absorption spectroscopy, including x-ray magnetic circular dichroism. The material crystallizes in the ThCr2Si2 structure type and exhibits three consecutive magnetic phase transitions. At 167 K, the Co magnetic moments order ferromagnetically in the ab plane of the tetragonal crystal structure. At 66 K, a ferromagnetic ordering of Pr(4f) moments parallel to the c axis causes a rotation of the Co(3d) moments towards the c axis in the direction opposite to the Pr moments, thus forming a noncollinear ferrimagnetically ordered structure and switching the direction of the total magnetization from the ab plane to the c axis. The third magnetic transition observed at 35 K is likely associated with the establishment of the collinear ferrimagnetic order along the c axis.

  18. Hyperbolic decay of photo-created Sb2+ ions in Sn2P2S6:Sb crystals detected with electron paramagnetic resonance

    NASA Astrophysics Data System (ADS)

    Basun, S. A.; Halliburton, L. E.; Evans, D. R.

    2017-01-01

    In this paper, we employed a method that overcomes the known limitations of electron paramagnetic resonance (EPR) to monitor charge trap dynamics over a broad temperature range not normally accessible due to the lifetime broadening of the EPR lines at higher temperatures. This was achieved by measuring the decay of the EPR intensity after thermal annealing by rapid cycling back to low temperatures for the EPR measurement. This technique was used to experimentally demonstrate interesting physics in the form of a direct measurement of the hyperbolic decay 1/(1+t) of a charge trap population, which previously was only considered theoretically. The nontrivial effects of bimolecular recombination are demonstrated in the Sn2S2P6:Sb crystals, providing an explanation of the optical sensitization process observed in photorefractive Sn2P2S6:Sb used for dynamic holography.

  19. Measurement of electron-impact excitation in boronlike carbon

    NASA Technical Reports Server (NTRS)

    Lafyatis, G. P.; Kohl, J. L.

    1987-01-01

    The cross section for the electron-impact excitation of C(+) (2s2 2p 2P0)-(2s2p2 2D) is measured in a colliding-beams apparatus for several collision energies near the threshold for the process. A cross section of (1.1 + or - 0.3) x 10 to the -16th sq cm at threshold is found. Reasonable agreement is found with close-coupling calculations.

  20. Sn vacancies in photorefractive Sn2P2S6 crystals: An electron paramagnetic resonance study of an optically active hole trap

    NASA Astrophysics Data System (ADS)

    Golden, E. M.; Basun, S. A.; Evans, D. R.; Grabar, A. A.; Stoika, I. M.; Giles, N. C.; Halliburton, L. E.

    2016-10-01

    Electron paramagnetic resonance (EPR) is used to identify the singly ionized charge state of the Sn vacancy ( VSn - ) in single crystals of Sn2P2S6 (often referred to as SPS). These vacancies, acting as a hole trap, are expected to be important participants in the photorefractive effect observed in undoped SPS crystals. In as-grown crystals, the Sn vacancies are doubly ionized ( VSn 2 - ) with no unpaired spins. They are then converted to a stable EPR-active state when an electron is removed (i.e., a hole is trapped) during an illumination below 100 K with 633 nm laser light. The resulting EPR spectrum has g-matrix principal values of 2.0079, 2.0231, and 1.9717. There are resolved hyperfine interactions with two P neighbors and one Sn neighbor. The isotropic portions of these hyperfine matrices are 167 and 79 MHz for the two 31P neighbors and 8504 MHz for the one Sn neighbor (this latter value is the average for 117Sn and 119Sn). These VSn - vacancies are shallow acceptors with the hole occupying a diffuse wave function that overlaps the neighboring Sn2+ ion and (P2S6)4- anionic unit. Using a general-order kinetics approach, an analysis of isothermal decay curves of the VSn - EPR spectrum in the 107-115 K region gives an activation energy of 283 meV.

  1. In vivo evaluation of CaO-SiO2-P2O5-B2O3 glass-ceramics coating on Steinman pins.

    PubMed

    Lee, Jae Hyup; Hong, Kug Sun; Baek, Hae-Ri; Seo, Jun-Hyuk; Lee, Kyung Mee; Ryu, Hyun-Seung; Lee, Hyun-Kyung

    2013-07-01

    Surface coating using ceramics improves the bone bonding strength of an implant. We questioned whether a new type of glass-ceramics (BGS-7) coating (CaO-SiO2 -P2 O5 -B2 O3 ) would improve the osseointegration of Steinman pins (S-pins) both biomechanically and histomorphometrically. An in vivo study was performed using rabbits by inserting three S-pins into each iliac bone. The pins were 2.2-mm S-pins with a coating of 30-μm-thick BGS-7 and 550-nm-thick hydroxyapatite (HA), as opposed to an S-pin without coating. A tensile strength test and histomorphometrical evaluation was performed. In the 2-week group, the BGS-7 implant showed a significantly higher tensile strength than the S-pin. In the 4- and 8-week groups, the BGS-7 implants had significantly higher tensile strengths than the S-pins and HA implants. The histomorphometrical study revealed that the BGS-7 implant had a significantly higher contact ratio than the S-pin and HA implants in the 4-week group. The biomechanical and histomorphometrical tests showed that the BGS-7 coating had superior bone bonding properties than the groups without the coating from the initial stage of insertion. The BGS-7 coating of an S-pin will enhance the bone bonding strength, and there might also be an advantage in human bone bonding.

  2. Critical behavior near the Lifshitz point in Sn(2)P(2)(S(1 - x)Se(x))(6) ferroelectric semiconductors from thermal diffusivity measurements.

    PubMed

    Oleaga, A; Salazar, A; Kohutych, A A; Vysochanskii, Yu M

    2011-01-19

    The thermal diffusivity of the ferroelectric family Sn(2)P(2)(Se(x)S(1 - x))(6) (0 ≤ x ≤ 1) has been measured by a high-resolution ac photopyroelectric technique, using single crystals, with the aim of studying the evolution of the ferroelectric transition with Se doping. Its change from second order character to first order while passing the Lifshitz point (x approximately 0.28) has been evaluated, as well as the splitting of the transition at high Se concentrations. The critical behavior of the ferroelectric transition in terms of the different universality classes and their underlying physical dominant effects (tricriticality, long-range dipole interactions, Lifshitz point) has been discussed using thermal diffusivity measurements in the very close vicinity of the critical temperature. This study reveals that for Se concentrations around the Lifshitz point, long-range dipole interactions do not play a significant role and that the critical parameters are close to those predicted for the Lifshitz universality class.

  3. Cryogenic exciter

    DOEpatents

    Bray, James William [Niskayuna, NY; Garces, Luis Jose [Niskayuna, NY

    2012-03-13

    The disclosed technology is a cryogenic static exciter. The cryogenic static exciter is connected to a synchronous electric machine that has a field winding. The synchronous electric machine is cooled via a refrigerator or cryogen like liquid nitrogen. The static exciter is in communication with the field winding and is operating at ambient temperature. The static exciter receives cooling from a refrigerator or cryogen source, which may also service the synchronous machine, to selected areas of the static exciter and the cooling selectively reduces the operating temperature of the selected areas of the static exciter.

  4. Observations of the O+ (2P-2D) 732 and 733 nm Thermospheric Airglow Emissions with the Wind Imaging Interferometer Leading to Atomic Oxygen Concentrations and ionospheric Winds

    NASA Astrophysics Data System (ADS)

    Shepherd, G. G.; Cho, Y. M.

    2014-12-01

    Remote sensing of airglow emission provides a powerful approach to the measurement of composition, temperature and winds in the thermosphere, on short and long time scales, including the responses to magnetic storms. Of the available emissions, one that has not been exploited to its full potential is the O+ (2P-2D) pair of doublets at 732.0 and 733.0 nm wavelength. This presentation is of recently analyzed results from WINDII, the Wind Imaging Interferometer on NASA's Upper Atmosphere Research Satellite, launched in 1991. WINDII is a Doppler Michelson interferometer with the capacity to measure airglow emission rates, Doppler temperatures from line widths and winds from Doppler shifts. One of the filters used to select specific airglow emissions was intended for measurement of the P1(2) line of the (8,3) Meinel band of OH at 731.63 nm but it also transmitted the O+ lines of interest. These have recently been retrieved from the data and are the basis of this presentation. The O+ emission is produced in the daytime, primarily from the photo-ionization of atomic oxygen and so knowing the solar flux the concentration of atomic oxygen can be determined. As a first step the variation of the emission rate on solar flux, solar zenith angle and conjugate photoelectron flux has been investigated, and preliminary results on atomic oxygen concentration are presented. In addition, ion winds can be determined from the Doppler shifts of the emission, which may be compared with the neutral winds obtained with WINDII from the atomic oxygen O(1S) and O(1D) emissions at 557.7 nm and 630.0 nm respectively. This possibility will allow the study of the interactions between the thermosphere and ionosphere for a wide range of conditions.

  5. Preparation of 3-D scaffolds in the SiO2-P2O5 system with tailored hierarchical meso-macroporosity.

    PubMed

    García, Ana; Izquierdo-Barba, Isabel; Colilla, Montserrat; de Laorden, Carlos López; Vallet-Regí, María

    2011-03-01

    Herein we report for the first time the synthesis of three-dimensional scaffolds in the binary system SiO2-P2O5 exhibiting different scales of porosity: (i) highly ordered mesopores with diameters of ca. 4 nm; (ii) macropores with diameters in the 30-80 μm range with interconnections of ca. 2-4 and 8-9 μm; and (iii) ultra-large macropores of ca. 400 μm. The hierarchical porosity of the resulting scaffolds makes them suitable for bone tissue engineering applications. The chemical nature and mesoporosity of these matrices would allow these scaffolds to act as local controlled delivery systems of biologically active molecules, such as certain drugs to treat bone pathologies. The synthetic method consists of the combination of a single-step sol-gel route in the presence of a surfactant as the mesostructure directing agent and a biomacromolecular polymer such as methylcellulose as the macrostructure template followed by rapid prototyping technique. An exhaustive study of the aging process as well as of the rheological properties of the slurry after methylcellulose addition has been carried out to obtain hierarchical meso-macroporosity. This study allows the establishment of the time period in which the slurry presents appropriate viscosity to be extruded during the rapid prototyping once the ink is prepared. The setting up of this manufacture process at the laboratory level is important from the industrial point of view when the large-scale production of scaffolds for bone tissue repair and regeneration is targeted. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  6. Structural and thermal characterization of CaO-MgO-SiO2-P2O5-CaF2 glasses

    SciTech Connect

    Kansal, Ishu; Goel, Ashutosh; Tulyaganov, Dilshat U.; Rajagopal, Raghu R.; Ferreira, Jose M.

    2012-08-01

    The paper presents the influence of varying CaO/MgO ratio on the structure and thermal properties of CaO-MgO-SiO2-P2O5-CaF2 glasses. A series of eight glass compositions in the glass forming region of diopside (CaMgSi2O6) - fluorapatite [Ca5(PO4)3F] - wollastonite (CaSiO3) ternary system have been designed and synthesized by varying diopside/wollastonite ratio in glasses. The as prepared melt-quenched glasses have been characterized for their structure by infrared spectroscopy (FTIR) and magic angle spinning (MAS)-nuclear magnetic resonance (NMR) spectroscopy. Silicon is predominantly present as Q2 (Si) species, while phosphorus tends to coordinate in orthophosphate environment in all the investigated glasses. The change in CaO/MgO ratio had an insignificant affect on the structure of glasses. The thermal sintering and crystallization parameters for the studied glasses have been obtained from differential thermal analysis (DTA) while crystalline phase fractions in the sintered glass-ceramics have been analyzed by X-ray diffraction adjoined with Rietveld refinement. Diopside, fluorapatite, wollastonite and pseudowollastonite have crystallized as the main crystalline phases in all the glass-ceramics with their content varying with respect to variation in CaO/MgO ratio in glasses. Scanning electron microscopy (SEM) has been used to shed light on the microstructure of glass-ceramics. The possible implications of structure and sintering behaviour of glasses on their bioactivity have been discussed.

  7. Influence of fluoride additions on biological and mechanical properties of Na2O-CaO-SiO2-P2O5 glass-ceramics.

    PubMed

    Li, H C; Wang, D G; Hu, J H; Chen, C Z

    2014-02-01

    Two series of Na2O-CaO-SiO2-P2O5 glass-ceramics doped with NH4HF2 (G-NH4HF2) or CaF2 (G-CaF2) have been prepared by sol-gel method. The glass-ceramic phase composition and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). The mechanical properties and thermal expansion coefficient were measured by a microhardness tester, an electronic tensile machine and a thermal expansion coefficient tester. The structure difference between these two glass-ceramics was investigated by Fourier transform infrared spectroscopy (FTIR), and the in vitro bioactivity of the glass-ceramics was determined by in vitro simulated body fluid (SBF) immersion test. The hemolysis test, in vitro cytotoxicity test, systemic toxicity test and the implanted experiment in animals were used to evaluate the biocompatibility of the glass-ceramics. The mechanical properties of sample G-NH4HF2 are lower than that of sample G-CaF2, and the bioactivity of sample G-NH4HF2 is better than that of sample G-CaF2. The thermal expansion coefficients of these two glass-ceramics are all closer to that of Ti6Al4V. After 7 days of SBF immersion, apatites were induced on glass-ceramic surface, indicating that the glass-ceramics have bioactivity. The hemolysis test, in vitro cytotoxicity test and systemic toxicity test demonstrate that the glass-ceramics do not cause hemolysis reaction, and have no toxicity to cell and living animal. The implanted experiment in animals shows that bone tissue can form a good osseointegration with the implant after implantation for two months, indicating that the glass-ceramics are safe to serve as implants.

  8. Determination of the 1s2{\\ell }2{{\\ell }}^{\\prime } state production ratios {{}^{4}P}^{o}/{}^{2}P, {}^{2}D/{}^{2}P and {{}^{2}P}_{+}/{{}^{2}P}_{-} from fast (1{s}^{2},1s2s\\,{}^{3}S) mixed-state He-like ion beams in collisions with H2 targets

    NASA Astrophysics Data System (ADS)

    Benis, E. P.; Zouros, T. J. M.

    2016-12-01

    New results are presented on the ratio {R}m={σ }{T2p}( {}4P)/{σ }{T2p}({}2P) concerning the production cross sections of Li-like 1s2s2p quartet and doublet P states formed in energetic ion-atom collisions by single 2p electron transfer to the metastable 1s2s {}3S component of the He-like ion beam. Spin statistics predict a value of R m = 2 independent of the collision system in disagreement with most reported measurements of {R}m≃ 1{--}9. A new experimental approach is presented for the evaluation of R m having some practical advantages over earlier approaches. It also allows for the determination of the separate contributions of ground- and metastable-state beam components to the measured spectra. Applying our technique to zero-degree Auger projectile spectra from 4.5 MeV {{{B}}}3+ (Benis et al 2002 Phys. Rev. A 65 064701) and 25.3 MeV {{{F}}}7+ (Zamkov et al 2002 Phys. Rev. A 65 062706) mixed state (1{s}2 {}1S,1s2s {}3S) He-like ion collisions with H2 targets, we report new values of {R}m=3.5+/- 0.4 for boron and {R}m=1.8+/- 0.3 for fluorine. In addition, the ratios of {}2D/{}2P and {{}2P}+/{{}2P}- populations from either the metastable and/or ground state beam component, also relevant to this analysis, are evaluated and compared to previously reported results for carbon collisions on helium (Strohschein et al 2008 Phys. Rev. A 77 022706) including a critical comparison to theory.

  9. Relativistic electron-correlation on the 2p-2s transitions in Li-like to F-like Xe ions

    NASA Astrophysics Data System (ADS)

    Hao, Liang-huan; Liu, Jing-jing; Kang, Xiao-ping

    2016-06-01

    Energy levels, wavelengths, transition rates and line strengths are reported for transitions in Li-like to F-like Xe ions, Xe LII-XLVI. For the calculations, a fully relativistic GRASP2k code based on the multiconfiguration Dirac-Hartree-Fock (MCDHF) method has been adopted, Valence and core-Valence correlation effects were accounted for through single- and double-excitation expansions to increasing sets of active orbitals. The fine-structure energy levels and wavelengths are compared with experimental data and with values from other calculations. The calculated values including core-valence correlation are found to be similar and compare very well with other theoretical and experimental values for Xe ions. Our calculated wavelengths for Li-, Be- and B-like ions are much more precise than some available theoretical data and reveal significant shortcomings of the various theoretical predictions.

  10. Chirp excitation

    NASA Astrophysics Data System (ADS)

    Khaneja, Navin

    2017-09-01

    The paper describes the design of broadband chirp excitation pulses. We first develop a three stage model for understanding chirp excitation in NMR. We then show how a chirp π pulse can be used to refocus the phase of the chirp excitation pulse. The resulting magnetization still has some phase dispersion in it. We show how a combination of two chirp π pulses instead of one can be used to eliminate this dispersion, leaving behind a small residual phase dispersion. The excitation pulse sequence presented here allows exciting arbitrary large bandwidths without increasing the peak rf-amplitude. Experimental excitation profiles for the residual HDO signal in a sample of 99.5 % D2O are displayed as a function of resonance offset. Although methods presented in this paper have appeared elsewhere, we present complete analytical treatment that elucidates the working of these methods.

  11. Proton Environments in Biomimetic Calcium Phosphates Formed from Mesoporous Bioactive CaO-SiO2-P2O5 Glasses in Vitro: Insights from Solid-State NMR.

    PubMed

    Mathew, Renny; Turdean-Ionescu, Claudia; Yu, Yang; Stevensson, Baltzar; Izquierdo-Barba, Isabel; García, Ana; Arcos, Daniel; Vallet-Regí, María; Edén, Mattias

    2017-06-22

    When exposed to body fluids, mesoporous bioactive glasses (MBGs) of the CaO-SiO2-P2O5 system develop a bone-bonding surface layer that initially consists of amorphous calcium phosphate (ACP), which transforms into hydroxy-carbonate apatite (HCA) with a very similar composition as bone/dentin mineral. Information from various (1)H-based solid-state nuclear magnetic resonance (NMR) experiments was combined to elucidate the evolution of the proton speciations both at the MBG surface and within each ACP/HCA constituent of the biomimetic phosphate layer formed when each of three MBGs with distinct Ca, Si, and P contents was immersed in a simulated body fluid (SBF) for variable periods between 15 min and 30 days. Directly excited magic-angle-spinning (MAS) (1)H NMR spectra mainly reflect the MBG component, whose surface is rich in water and silanol (SiOH) moieties. Double-quantum-single-quantum correlation (1)H NMR experimentation at fast MAS revealed their interatomic proximities. The comparatively minor H species of each ACP and HCA component were probed selectively by heteronuclear (1)H-(31)P NMR experimentation. The initially prevailing ACP phase comprises H2O and "nonapatitic" HPO4(2-)/PO4(3-) groups, whereas for prolonged MBG soaking over days, a well-progressed ACP → HCA transformation was evidenced by a dominating O(1)H resonance from HCA. We show that (1)H-detected (1)H → (31)P cross-polarization NMR is markedly more sensitive than utilizing powder X-ray diffraction or (31)P NMR for detecting the onset of HCA formation, notably so for P-bearing (M)BGs. In relation to the long-standing controversy as to whether bone mineral comprises ACP and/or forms via an ACP precursor, we discuss a recently accepted structural core-shell picture of both synthetic and biological HCA, highlighting the close relationship between the disordered surface layer and ACP.

  12. Exciter switch

    NASA Technical Reports Server (NTRS)

    Mcpeak, W. L.

    1975-01-01

    A new exciter switch assembly has been installed at the three DSN 64-m deep space stations. This assembly provides for switching Block III and Block IV exciters to either the high-power or 20-kW transmitters in either dual-carrier or single-carrier mode. In the dual-carrier mode, it provides for balancing the two drive signals from a single control panel located in the transmitter local control and remote control consoles. In addition to the improved switching capabilities, extensive monitoring of both the exciter switch assembly and Transmitter Subsystem is provided by the exciter switch monitor and display assemblies.

  13. Accurate ab initio potential energy surface, thermochemistry, and dynamics of the Br(2P, 2P3/2) + CH4 → HBr + CH3 reaction

    NASA Astrophysics Data System (ADS)

    Czakó, Gábor

    2013-04-01

    Chemically accurate full-dimensional non-spin-orbit and spin-orbit (SO) ground-state potential energy surfaces (PESs) are obtained for the Br + CH4 → HBr + CH3 reaction by fitting 21 574 composite ab initio energy points. The composite method considers electron correlation methods up to CCSD(T), basis sets up to aug-cc-pwCVTZ-PP, correlation of the core electrons, scalar relativistic effects via an effective core potential (ECP), and SO corrections, thereby achieving an accuracy better than 0.5 kcal/mol. Benchmark structures and relative energies are computed for the stationary points using the ab initio focal-point analysis (FPA) scheme based on both ECP and Douglas-Kroll approaches providing all-electron relativistic CCSDT(Q)/complete-basis-set quality energies. The PESs accurately describe the saddle point of the abstraction reaction and the van der Waals complexes in the entrance and product channels. The SO-corrected PES provides a classical barrier height of 7285(7232 ± 50) cm-1, De values of 867(799 ± 10) and 399(344 ± 10) cm-1 for the complexes CH3-HBr and CH3-BrH, respectively, and reaction endothermicity of 7867(7857 ± 50) cm-1, in excellent agreement with the new, FPA-based benchmark data shown in parentheses. The difference between the Br + CH4 asymptotes of the non-SO and SO PESs is 1240 cm-1, in good agreement with the experiment (1228 cm-1). Quasiclassical trajectory calculations based on more than 13 million trajectories for the late-barrier Br + CH4(vk = 0, 1) [k = 1, 2, 3, 4] reactions show that the vibrational energy, especially the excitation of the stretching modes, activates the reaction much more efficiently than translational energy, in agreement with the extended Polanyi rules. Angular distributions show dominant backward scattering for the ground-state reaction and forward scattering for the stretching-excited reactions. The reactivity on the non-SO PES is about 3-5 times larger than that on the SO PES in a wide collision energy

  14. Accurate ab initio potential energy surface, thermochemistry, and dynamics of the Br(2P, 2P(3∕2)) + CH4 → HBr + CH3 reaction.

    PubMed

    Czakó, Gábor

    2013-04-07

    Chemically accurate full-dimensional non-spin-orbit and spin-orbit (SO) ground-state potential energy surfaces (PESs) are obtained for the Br + CH4 → HBr + CH3 reaction by fitting 21 574 composite ab initio energy points. The composite method considers electron correlation methods up to CCSD(T), basis sets up to aug-cc-pwCVTZ-PP, correlation of the core electrons, scalar relativistic effects via an effective core potential (ECP), and SO corrections, thereby achieving an accuracy better than 0.5 kcal∕mol. Benchmark structures and relative energies are computed for the stationary points using the ab initio focal-point analysis (FPA) scheme based on both ECP and Douglas-Kroll approaches providing all-electron relativistic CCSDT(Q)∕complete-basis-set quality energies. The PESs accurately describe the saddle point of the abstraction reaction and the van der Waals complexes in the entrance and product channels. The SO-corrected PES provides a classical barrier height of 7285(7232 ± 50) cm(-1), De values of 867(799 ± 10) and 399(344 ± 10) cm(-1) for the complexes CH3-HBr and CH3-BrH, respectively, and reaction endothermicity of 7867(7857 ± 50) cm(-1), in excellent agreement with the new, FPA-based benchmark data shown in parentheses. The difference between the Br + CH4 asymptotes of the non-SO and SO PESs is 1240 cm(-1), in good agreement with the experiment (1228 cm(-1)). Quasiclassical trajectory calculations based on more than 13 million trajectories for the late-barrier Br + CH4(vk = 0, 1) [k = 1, 2, 3, 4] reactions show that the vibrational energy, especially the excitation of the stretching modes, activates the reaction much more efficiently than translational energy, in agreement with the extended Polanyi rules. Angular distributions show dominant backward scattering for the ground-state reaction and forward scattering for the stretching-excited reactions. The reactivity on the non-SO PES is about 3-5 times larger than that on the SO PES in a wide

  15. Optical phase conjugation of picosecond pulses at 1.06 mum in Sn(2)P(2)S(6):Te for wavefront correction in high-power Nd-doped amplifier systems.

    PubMed

    Bach, Tobias; Nawata, Kouji; Jazbinsek, Mojca; Omatsu, Takashige; Günter, Peter

    2010-01-04

    We report, for the first time to our knowledge, on picosecondpulse optical phase conjugation using photorefractive Sn(2)P(2)S(6) crystals. For 7.2-ps pulses at 1.06 mum, we have achieved phase-conjugate reflectivities of up to 45% with very fast build-up times, about 15 ms at an intensity of 23 W/cm(2) using Te-doped Sn(2)P(2)S(6). We furthermore demonstrate aberration-free 5 W optical output of 8-ps pulses at 1.06 mum from a side pumped Nd:YVO(4) amplifier using the Sn(2)P(2)S(6)-based phase-conjugate feedback.

  16. One-pot carbanionic synthesis of P1,P2-diglycosyl, P1,P1,P2-triglycosyl, and P1,P1,P2,P2-tetraribosyl methylenediphosphonates.

    PubMed

    Grison, Claude; Chibli, Hicham; Barthès, Nicolas; Coutrot, Philippe

    2006-10-13

    Novel lithiated carbanions derived from ethyl glycosyl- and diglycosyl methylphosphonates were used in a direct and convenient synthesis of P1,P2-diglycosyl, P1,P1,P2-triglycosyl, and P1,P1,P2,P2-tetraribosyl methylenediphosphonates involving a one-pot methylidenediphosphonylation of sugars.

  17. Exciting Pools

    ERIC Educational Resources Information Center

    Wright, Bradford L.

    1975-01-01

    Advocates the creation of swimming pool oscillations as part of a general investigation of mechanical oscillations. Presents the equations, procedure for deriving the slosh modes, and methods of period estimation for exciting swimming pool oscillations. (GS)

  18. Ekectron-Impact Excitation of C+

    NASA Astrophysics Data System (ADS)

    Pearce, A. J.; Ballance, C. P.; Loch, S. D.; Pindzola, M. S.

    2015-05-01

    Electron-impact excitation cross sections are calculated for ground and excited states of C+ using the R-matrix with pseudo-states method. We used the configurations 1s2 2s2 nl (3 s <= nl <= 12 g) , 1s2 2 s 2 pnl (2 p <= nl <= 12 g) , 1s2 2p2 nl (2 p <= nl <= 12 g) , 1s2 2 s 3s2 , and 1s2 2 s 3d2 , resulting in 890 LS terms and 2048 LSJ levels. Excitation cross sections for the 1s2 2s2 2 p2 P -->4 P,2 D,2 S transitions are in good agreement with experiment. Combined with previous calculations for C and Cq+ (q = 2- 5), sufficient excitation, ionization, and recombination atomic data is now available to generate high quality collisional-radiative coefficients for the entire C isonuclear sequence. Work supported in part by grants from NASA, NSF, and DOE.

  19. [Co(η5-P5){η2-P2H(mes)}]2-: a phospha-organometallic complex obtained by the transition-metal-mediated activation of the heptaphosphide trianion.

    PubMed

    Knapp, Caroline M; Westcott, Bethan H; Raybould, Melissa A C; McGrady, John E; Goicoechea, Jose M

    2012-09-03

    A carbon copy: The chemical activation of the heptaphosphide trianion with [Co(PEt(2)Ph)(2)(mes)(2)] (see picture; 1) yields the novel phospha-organometallic complex [Co(η(5)-P(5)){η(2)-P(2)H(mes)}](2-) (2). The reaction product maintains the nuclearity of the parent cluster, but extensive cage fragmentation takes place to yield a diamagnetic "inorganometallic" cobalt complex. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Excited Delirium

    PubMed Central

    Takeuchi, Asia; Ahern, Terence L.; Henderson, Sean O.

    2011-01-01

    Excited (or agitated) delirium is characterized by agitation, aggression, acute distress and sudden death, often in the pre-hospital care setting. It is typically associated with the use of drugs that alter dopamine processing, hyperthermia, and, most notably, sometimes with death of the affected person in the custody of law enforcement. Subjects typically die from cardiopulmonary arrest, although the cause is debated. Unfortunately an adequate treatment plan has yet to be established, in part due to the fact that most patients die before hospital arrival. While there is still much to be discovered about the pathophysiology and treatment, it is hoped that this extensive review will provide both police and medical personnel with the information necessary to recognize and respond appropriately to excited delirium. PMID:21691475

  1. Voiced Excitations

    DTIC Science & Technology

    2004-12-01

    for purposes of vocoding in high noise environments: Task 1: Estimation of voiced excitation functions using skin surface vibration...High Noise Environments. The work on “ Voiced Excitations” shows that the surface vibrations of neck skin, during voicing , carry a great deal of...5 in this report). For field use, it may be better to obtain data from another location on the neck or face. A pressure function of voiced speech is

  2. Excited baryons

    SciTech Connect

    Mukhopadhyay, N.C.

    1986-01-01

    The status of the theory of the low-energy approach to hadron structure is reviewed briefly by surveying a few relevant models. A few examples of tests needed to sort out the predictions of different models pertaining to the quark-gluon structure of hadrons are discussed, and given the resulting physics objectives, a few experimental options for excited baryon research at CFBAF are suggested. (LEW)

  3. Synthesis and characterization of fac-[M(CO)3(P)(OO)] and cis-trans-[M(CO)2(P)2(OO)] complexes (M = Re, (99m)Tc) with acetylacetone and curcumin as OO donor bidentate ligands.

    PubMed

    Triantis, Charalampos; Tsotakos, Theodoros; Tsoukalas, Charalampos; Sagnou, Marina; Raptopoulou, Catherine; Terzis, Aris; Psycharis, Vassilis; Pelecanou, Maria; Pirmettis, Ioannis; Papadopoulos, Minas

    2013-11-18

    The synthesis and characterization of neutral mixed ligand complexes fac-[M(CO)3(P)(OO)] and cis-trans-[M(CO)2(P)2(OO)] (M = Re, (99m)Tc), with deprotonated acetylacetone or curcumin as the OO donor bidentate ligands and a phosphine (triphenylphosphine or methyldiphenylphosphine) as the monodentate P ligand, is described. The complexes were synthesized through the corresponding fac-[M(CO)3(H2O)(OO)] (M = Re, (99m)Tc) intermediate aqua complex. In the presence of phosphine, replacement of the H2O molecule of the intermediate complex at room temperature generates the neutral tricarbonyl monophosphine fac-[Re(CO)3(P)(OO)] complex, while under reflux conditions further replacement of the trans to the phosphine carbonyl generates the new stable dicarbonyl bisphosphine complex cis-trans-[Re(CO)2(P)2(OO)]. The Re complexes were fully characterized by elemental analysis, spectroscopic methods, and X-ray crystallography showing a distorted octahedral geometry around Re. Both the monophosphine and the bisphosphine complexes of curcumin show selective binding to β-amyloid plaques of Alzheimer's disease. At the (99m)Tc tracer level, the same type of complexes, fac-[(99m)Tc(CO)3(P)(OO)] and cis-trans-[(99m)Tc(CO)2(P)2(OO)], are formed introducing new donor combinations for (99m)Tc(I). Overall, β-diketonate and phosphine constitute a versatile ligand combination for Re(I) and (99m)Tc(I), and the successful employment of the multipotent curcumin as β-diketone provides a solid example of the pharmacological potential of this system.

  4. The IL4-VNTR P1 Allele, IL4-VNTR P2P2 Genotype, and IL4-VNTR_IL6-174CG P2P1-GG Genotype Are Associated with an Increased Risk of Brucellosis.

    PubMed

    Gunal, Ozgur; Yigit, Serbulent; Yalcın, Arzu Didem; Celik, Betul; Barut, Sener; Demir, Osman; Ates, Omer; Duygu, Fazilet; Kaya, Safak; Rustemoglu, Aydin; Sezer, Ozlem

    2017-01-24

    In this study, associations between IL-4, IL-6, and macrophage migration inhibitory factor (MIF) polymorphisms and susceptibility to brucellosis were investigated. Consecutive adult patients with no known treatment against brucellosis and who did not have any other autoimmune and/or chronic disorders, were included in this study (n = 120, Group I). Age and sex-matched controls who had no other autoimmune and/or chronic disorders were also included (n = 120, healthy volunteers, Group II). The IL4_P2P2 genotype, IL4_P1 allele, and IL4_variable number of tandem repeats (VNTR)_IL6-174CG compound genotype were found to be more frequent in the patient group than in control subjects. There were significant differences between the patients and controls with respect to the frequencies of the IL4_P2P2 genotype (77.5% versus 87.5%; p = 0.001; OR, 0.36; 95% confidence interval [CI], 0.21-0.62) and the IL4_P1 allele (12.1% versus 6.7%; p = 0.030; OR, 0.92; CI, 1.02-3.64). The IL4-VNTR_IL6-174CG compound genotype was also present at a significantly higher frequency in the patient group than in control subjects (11.7% versus 4.2%; p = 0.027, OR, 3.04; CI, 1.06-8.68). No statistically significant differences in the frequencies of the IL-6-174, MIF-173, IL-4_P1P1, and IL4_P2P1 genotypes were observed between patients and control subjects. The IL4_VNTR P1 allele, P2P2 genotypes, and IL4-VNTR_IL6-174CG P2P1-GG genotypes are common in southern Turkey, and carriers of these polymorphisms are susceptible to brucellosis.

  5. Comparison of fusion rate and clinical results between CaO-SiO2-P2O5-B2O3 bioactive glass ceramics spacer with titanium cages in posterior lumbar interbody fusion.

    PubMed

    Lee, Jae Hyup; Kong, Chang-Bae; Yang, Jae Jun; Shim, Hee-Jong; Koo, Ki-Hyoung; Kim, Jeehyoung; Lee, Choon-Ki; Chang, Bong-Soon

    2016-11-01

    The CaO-SiO2-P2O5-B2O3 glass ceramics spacer generates chemical bonding to adjacent bones with high mechanical stability to produce a union with the end plate, and ultimately stability. The authors aimed to compare the clinical efficacy and safety of CaO-SiO2-P2O5-B2O3 glass ceramics with a titanium cage that is widely used for posterior lumbar interbody fusion (PLIF) surgery in the clinical field. This is a prospective, stratified randomized, multicenter, single-blinded, comparator-controlled non-inferiority trial. The present study was conducted in four hospitals and enrolled a total of 86 patients between 30 and 80 years of age who required one-level PLIF due to severe spinal stenosis, spondylolisthesis, or huge disc herniation. The Oswestry Disability Index (ODI), Short Form-36 Health Survey (SF-36), and pain visual analog scale (VAS) were assessed before surgery and at 3, 6, and 12 months after surgery. The spinal fusion rate was assessed at 6 and 12 months after surgery. The spinal fusion rate and the area of fusion, subsidence of each CaO-SiO2-P2O5-B2O3 glass ceramics and titanium cage, and the extent of osteolysis were evaluated using a dynamic plain radiography and a three-dimensional computed tomography at 12 months after surgery. The present study was supported by BioAlpha, and some authors (JHL, C-KL, and B-SC) have stock ownership (<10,000 US dollars). From the plain radiography results, the 6-month fusion rates for the bioactive glass ceramics group and the titanium group were 89.7% and 91.4%, respectively. In addition, the 12-month fusion rates based on CT scan were 89.7% and 91.2%, respectively, showing no significant difference. However, the bone fusion area directly attached to the end plate of either bioactive glass ceramics or the titanium cage was significantly higher in the bioactive glass ceramics group than in the titanium group. The ODI, SF-36, back pain, and lower limb pain in both groups significantly improved after surgery, with no

  6. Relativistic electron correlation, quantum electrodynamics, and the lifetime of the 1s(2)2s(2)2p2p0(3/2) level in boronlike argon.

    PubMed

    Lapierre, A; Jentschura, U D; Crespo López-Urrutia, J R; Braun, J; Brenner, G; Bruhns, H; Fischer, D; González Martínez, A J; Harman, Z; Johnson, W R; Keitel, C H; Mironov, V; Osborne, C J; Sikler, G; Soria Orts, R; Shabaev, V; Tawara, H; Tupitsyn, I I; Ullrich, J; Volotka, A

    2005-10-28

    The lifetime of the Ar13+ 1s(2)2s(2)2p2p0(3/2) metastable level was determined at the Heidelberg Electron Beam Ion Trap to be 9.573(4)(5). The accuracy level of one per thousand makes this measurement sensitive to quantum electrodynamic effects like the electron anomalous magnetic moment (EAMM) and to relativistic electron-electron correlation effects like the frequency-dependent Breit interaction. Theoretical predictions, adjusted for the EAMM, cluster about a lifetime that is approximately shorter than our experimental result.

  7. Sexual excitement.

    PubMed

    Stoller, R J

    1976-08-01

    Sexual excitement depends on a scenario the person to be aroused has been writing since childhood. The story is an adventure, an autobiography disguised as fiction, in which the hero/heroine hides crucial intrapsychic conflicts, mysteries, screen memories of actual traumatic events and the resolution of these elements into a happy ending, best celebrated by orgasm. The function of the fantasy is to take these painful experiences and convert them to pleasure-triumph. In order to sharpen excitement-the vibration between the fear of original traumas repeating and the hope of a pleasurable conclusion this time-one introduces into the story elements of risk (approximations of the trauma) meant to prevent boredom and safety factors (sub-limnal signals to the storyteller that the risk are not truly dangerous). Sexual fantasy can be studied by means of a person's daydreams (including those chosen in magazines, books, plays, television, movies, and outright pornography), masturbatory behavior, object choice, foreplay, techniques of intercourse, or postcoital behavior.

  8. Viscosity and Structure of CaO-SiO2-P2O5-FetO System with Varying P2O5 and FeO Content

    NASA Astrophysics Data System (ADS)

    Diao, Jiang; Gu, Pan; Liu, De-Man; Jiang, Lu; Wang, Cong; Xie, Bing

    2017-10-01

    A rotary viscosimeter and Raman spectrum were employed to measure the viscosity and structural information of the CaO-SiO2-P2O5-FetO system at 1673 K. The experimental data have been compared with the calculated results using different viscosity models. It shows that the National Physical Laboratory (NPL) and Pal models fit the CaO-SiO2-P2O5-FeOt system better. With the P2O5 content increasing from 5% to 14%, the viscosity increases from 0.12 Pa s to 0.27 Pa s. With the FeO content increasing from 30% to 40%, the viscosity decreases from 0.21 Pa s to 0.12 Pa s. Increasing FeO content makes the complicated molten melts become simple, and increasing P2O5 content will complicate the molten melts. The linear relation between viscosity and structure parameter Q(Si + P) was obtained by regression analysis. The calculated viscosity by using the optimized NPL and Pal model are almost identical with the fitted values.

  9. Viscosity and Structure of CaO-SiO2-P2O5-FetO System with Varying P2O5 and FeO Content

    NASA Astrophysics Data System (ADS)

    Diao, Jiang; Gu, Pan; Liu, De-Man; Jiang, Lu; Wang, Cong; Xie, Bing

    2017-07-01

    A rotary viscosimeter and Raman spectrum were employed to measure the viscosity and structural information of the CaO-SiO2-P2O5-FetO system at 1673 K. The experimental data have been compared with the calculated results using different viscosity models. It shows that the National Physical Laboratory (NPL) and Pal models fit the CaO-SiO2-P2O5-FeOt system better. With the P2O5 content increasing from 5% to 14%, the viscosity increases from 0.12 Pa s to 0.27 Pa s. With the FeO content increasing from 30% to 40%, the viscosity decreases from 0.21 Pa s to 0.12 Pa s. Increasing FeO content makes the complicated molten melts become simple, and increasing P2O5 content will complicate the molten melts. The linear relation between viscosity and structure parameter Q(Si + P) was obtained by regression analysis. The calculated viscosity by using the optimized NPL and Pal model are almost identical with the fitted values.

  10. Conductance simulation of the purinergic P2X2, P2X4, and P2X7 ionic channels using a combined Brownian dynamics and molecular dynamics approach.

    PubMed

    Turchenkov, Dmitry A; Bystrov, Vladimir S

    2014-08-07

    This paper investigates the application of an original combined approach of molecular and Brownian dynamic methods with quantum chemistry calculations for modeling the process of conductance of ion channels using purinergic P2X family receptors P2X2, P2X4, and P2X7 as a case study. A simplified model of the ionic channel in the lipid bilayer has been developed. A high level of conductance (30 pS) of P2X2 ionic channel together with the key role of Asp349 in forming the selectivity filter of P2X2 has been shown by using this approach. Calculated P2X2 permeability to monovalent cations Li(+), Na(+), and K(+) conforms to the free diffusion coefficient of these ions, which shows the low selectivity of P2X2 ionic channel.

  11. Effects of Substitution of K2O for Na2O on the Bioactivity of CaO-Na2O-SiO2-P2O5 glasses

    NASA Astrophysics Data System (ADS)

    Kim, Taehee; Hwang, Chawon; Gwoo, Donggun; Park, Hoyyul; Ryu, Bong-Ki

    2012-10-01

    The compositional dependences of bioactivity, thermal properties, atomic structure, and surface morphology have been investigated in the CaO-Na2O-SiO2-P2O5 system; this system is known as a bioglass. 45S5 Bioglass® is known to be a general and highly bioactive material. However, the bioactivity of this glassy material is expected to be improved by modifying the alkali-metal composition. Thermal properties, density, and molar volume were measured to investigate the structural packing. FT-IR spectra and X-ray diffraction were used to confirm the structures of these glasses. The morphology was examined using field emission electron microscopy, and the formation of a Ca-P layer was studied using an energy-dispersive system. This study shows that the tendency to form a calcium phosphate layer is increased with the substitution of K2O for Na2O.

  12. pH-Dependent solution dynamics of a manganese(II) polyoxometalate, [Mn4(H2O)2(P2W15O56)2](16-), and [Mn(H2O)6](2+).

    PubMed

    Sharma, Rupali; Zhang, Jie; Ohlin, C André

    2015-11-28

    The aqueous reaction dynamics of the manganese(II)-functionalised Wells-Dawson polyoxometalate [Mn4(H2O)2(P2W15O56)2](16-) has been determined as a function of pH using variable temperature (17)O NMR, and compared with that of the well-studied monomeric manganese(II) hexa-aqua ion, [Mn(H2O)6](2+). While the rate of aquo-ligand exchange on the hexa-aqua ion remains independent of pH in the range 3.2-6.0, the rate of water exchange of the polyoxometalate ion varies by a factor of fifteen, from 1.98 × 10(7) s(-1) at pH 3.2 to 1.3 × 10(6) s(-1) at pH 6.0. This decrease in the rate of exchange correlates with the deprotonation of the polyoxometalate framework.

  13. Effect of ZnO addition on bioactive CaO-SiO2-P2O5-CaF2 glass-ceramics containing apatite and wollastonite.

    PubMed

    Kamitakahara, M; Ohtsuki, C; Inada, H; Tanihara, M; Miyazaki, T

    2006-07-01

    Some ceramics show bone-bonding ability, i.e. bioactivity. Apatite formation on ceramics is an essential condition to bring about direct bonding to living bone when implanted into bony defects. A controlled surface reaction of the ceramic is an important factor governing the bioactivity and biodegradation of the implanted ceramic. Among bioactive ceramics, glass-ceramic A-W containing apatite and wollastonite shows high bioactivity, as well as high mechanical strength. In this study, glass-ceramics containing zinc oxide were prepared by modification of the composition of the glass-ceramic A-W. Zinc oxide was selected to control the reactivity of the glass-ceramics since zinc is a trace element that shows stimulatory effects on bone formation. Glass-ceramics were prepared by heat treatment of glasses with the general composition: xZnOx(57.0-x)CaOx35.4SiO(2)x7.2P(2)O(5)x0.4CaF(2) (where x=0-14.2mol.%). Addition of ZnO increased the chemical durability of the glass-ceramics, resulting in a decrease in the rate of apatite formation in a simulated body fluid. On the other hand, the release of zinc from the glass-ceramics increased with increasing ZnO content. Addition of ZnO may provide bioactive CaO-SiO(2)-P(2)O(5)-CaF(2) glass-ceramics with the capacity for appropriate biodegradation, as well as enhancement of bone formation.

  14. Mechanical and biological properties of two types of bioactive bone cements containing MgO-CaO-SiO2-P2O5-CaF2 glass and glass-ceramic powder.

    PubMed

    Tamura, J; Kawanabe, K; Kobayashi, M; Nakamura, T; Kokubo, T; Yoshihara, S; Shibuya, T

    1996-01-01

    In this study two types of bioactive bone cement containing either MgO-CaO-SiO2-P2O5-CaF2 glass (type A) or glass-ceramic powder (type B) were made to evaluate the effect of the crystalline phases on their mechanical and biological properties. Type A bone cement was produced from glass powder and bisphenol-a-glycidyl methacrylate (BIS-GMA) resin, and type B from glass-ceramic powder containing apatite and wollastonite crystals and BIS-GMA resin. Glass or glass-ceramic powder (30, 50, 70, and 80 by wt %) was added to the cement. The compressive strength of type A (153-180 MPa) and B (167-194 MPa) cement were more than twice that of conventional polymethylmethacrylate (PMMA) cement (68 MPa). Histological examination of rat tibiae showed that all the bioactive cements formed direct contact with the bone. A reactive layer was seen at the bone-cement interface. In specimens with type A cement the reactive layer consisted of two layers, a radiopaque outer layer (Ca-P-rich layer) and a relatively radiolucent inner layer (low-calcium-level layer). With type B cement, although the Ca-P-rich layer was seen, the radiolucent inner layer was absent. Up to 26 weeks there was progressive bone formation around each cement (70 wt %) and no evidence of biodegradation. The mechanical and biological properties of the cements were compared with those of a previously reported bone cement containing MgO-free CaO-SiO2-P2O5-CaF2 glass powder (designated type C).

  15. Dicobalt-μ-oxo polyoxometalate compound, [(α(2)-P2W17O61Co)2O](14-): a potent species for water oxidation, C-H bond activation, and oxygen transfer.

    PubMed

    Barats-Damatov, Delina; Shimon, Linda J W; Weiner, Lev; Schreiber, Roy E; Jiménez-Lozano, Pablo; Poblet, Josep M; de Graaf, Coen; Neumann, Ronny

    2014-02-03

    High-valent oxo compounds of transition metals are often implicated as active species in oxygenation of hydrocarbons through carbon-hydrogen bond activation or oxygen transfer and also in water oxidation. Recently, several examples of cobalt-catalyzed water oxidation have been reported, and cobalt(IV) species have been suggested as active intermediates. A reactive species, formally a dicobalt(IV)-μ-oxo polyoxometalate compound [(α2-P2W17O61Co)2O](14-), [(POMCo)2O], has now been isolated and characterized by the oxidation of a monomeric [α2-P2W17O61Co(II)(H2O)](8-), [POMCo(II)H2O], with ozone in water. The crystal structure shows a nearly linear Co-O-Co moiety with a Co-O bond length of ∼1.77 Å. In aqueous solution [(POMCo)2O] was identified by (31)P NMR, Raman, and UV-vis spectroscopy. Reactivity studies showed that [(POMCo)2O]2O] is an active compound for the oxidation of H2O to O2, direct oxygen transfer to water-soluble sulfoxides and phosphines, indirect epoxidation of alkenes via a Mn porphyrin, and the selective oxidation of alcohols by carbon-hydrogen bond activation. The latter appears to occur via a hydrogen atom transfer mechanism. Density functional and CASSCF calculations strongly indicate that the electronic structure of [(POMCo)2O]2O] is best defined as a compound having two cobalt(III) atoms with two oxidized oxygen atoms.

  16. Methanocarba Modification of Uracil and Adenine Nucleotides: High Potency of Northern Ring Conformation at P2Y1, P2Y2, P2Y4, and P2Y11 but Not P2Y6 Receptors

    PubMed Central

    Kim, Hak Sung; Ravi, R. Gnana; Marquez, Victor E.; Maddileti, Savitri; Wihlborg, Anna-Karin; Erlinge, David; Malmsjö, Malin; Boyer, José L.; Harden, T. Kendall; Jacobson, Kenneth A.

    2016-01-01

    The potency of nucleotide antagonists at P2Y1 receptors was enhanced by replacing the ribose moiety with a constrained carbocyclic ring (Nandanan, et al. J. Med. Chem. 2000, 43, 829—842). We have now synthesized ring-constrained methanocarba analogues (in which a fused cyclopropane moiety constrains the pseudosugar ring) of adenine and uracil nucleotides, the endogenous activators of P2Y receptors. Methanocarba-adenosine 5′-triphosphate (ATP) was fixed in either a Northern (N) or a Southern (S) conformation, as defined in the pseudorotational cycle. (N)-Methanocarba-uridine was prepared from the 1-amino-pseudosugar ring by treatment with β-ethoxyacryloyl cyanate and cyclization to form the uracil ring. Phosphorylation was carried out at the 5′-hydroxyl group through a multistep process: Reaction with phosphoramidite followed by oxidation provided the 5′-monophosphates, which then were treated with 1,1′-carbonyldiimidazole for condensation with additional phosphate groups. The ability of the analogues to stimulate phospholipase C through activation of turkey P2Y1 or human P2Y1, P2Y2, P2Y4, P2Y6, and P2Y11 receptors stably expressed in astrocytoma cells was measured. At recombinant human P2Y1 and P2Y2 receptors, (N)-methanocarba-ATP was 138- and 41-fold, respectively, more potent than racemic (S)-methanocarba-ATP as an agonist. (N)-methanocarba-ATP activated P2Y11 receptors with a potency similar to ATP. (N)-Methanocarba-uridine 5′-triphosphate (UTP) was equipotent to UTP as an agonist at human P2Y2 receptors and also activated P2Y4 receptors with an EC50 of 85 nM. (N)-Methanocarba-uridine 5′-diphosphate (UDP) was inactive at the hP2Y6 receptor. The vascular effects of (N)-methanocarba-UTP and (N)-methanocarba-UDP were studied in a model of the rat mesenteric artery. The triphosphate was more potent than UTP in inducing a dilatory P2Y4 response (pEC50 = 6.1 ± 0.2), while the diphosphate was inactive as either an agonist or antagonist in a P2Y6

  17. Bone bonding behavior of MgO-CaO-SiO2-P2O5-CaF2 glass (mother glass of A.W-glass-ceramics).

    PubMed

    Kitsugi, T; Yamamuro, T; Nakamura, T; Kokubo, T

    1989-06-01

    In this study, it was found that a Ca-P layer and a Si layer were formed on the interface of the mother glass of apatite-wollastonite containing glass-ceramics (designated AW) and bone tissue. The dissolution of Si, Ca, and P from glass (MgO-CaO-SiO2-P2O5-CaF2) is necessary to form a chemical film (a Si layer and a Ca-P layer). The three kinds of glasses used were 1) a mirror surface of the mother glass (MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, CaF 0.5 weight ratio) of AW (designated G-AW (mirror], 2) an abraded surface of G-AW (designated G-AW (#2000)), 3) a mirror surface SiO2 glass (designated G-Si, 100% SiO2). The glass plates (15 mm x 10 mm x 2 mm) were implanted into the metaphysis of tibia of mature male rabbits for 10 and 25 weeks. The failure load, when an implant detached from the bone or when the bone itself broke, was measured by a detaching test and the interface of glass/bone was observed by SEM-EPMA. Failure loads in G-Si, G-AW (mirror), and G-AW (#2000) 10 weeks after implantation were 0.18 +/- 0.24, 3.06 +/- 1.29, and 2.94 +/- 1.77 kg, respectively. Those in G-Si, G-AW (mirror), and G-AW (#2000) 25 weeks after implantation were 1.30 +/- 1.18, 3.88 +/- 1.06, and 3.55 +/- 1.51, respectively. The failure loads in G-Si vs. G-AW (mirror) and those in G-Si vs. G-AW (#2000) differed significantly (P less than 0.01). There were no significant differences in the failure load according to the surface roughness of G-AW. As shown by SEM-EPMA observation, a Si layer next to G was adjacent to a Ca-P layer next to the bone. The chemical film showed no increase in thickness as time passed. A Ca-P layer did not form on the interface of Si-G and bone.

  18. Influence of heat treatments upon the mechanical properties and in vitro bioactivity of ZrO2-toughened MgO-CaO-SiO2-P2O5-CaF2 glass-ceramics.

    PubMed

    Li, Huan-Cai; Wang, Dian-Gang; Meng, Xiang-Guo; Chen, Chuan-Zhong

    2014-09-01

    Zirconia-toughened MgO-CaO-SiO2-P2O5-CaF2 glass-ceramics are prepared using sintering techniques, and a series of heat treatment procedures are designed to obtain a glass-ceramic with improved properties. The crystallization behavior, phase composition, and morphology of the glass-ceramics are characterized. The bending strength, elastic modulus, fracture toughness, and microhardness of the glass-ceramics are investigated, and the effect mechanism of heat treatments upon the mechanical properties is discussed. The bioactivity of glass-ceramics is then evaluated using the in vitro simulated body fluid (SBF) soaking test, and the mechanism whereby apatite forms on the glass-ceramic surfaces in the SBF solution is discussed. The results indicate that the main crystal phase of the G-24 sample undergoing two heat treatment procedures is Ca5(PO4)3F (fluorapatite), and those of the G-2444 sample undergoing four heat treatment procedures are Ca5(PO4)3F and β-CaSiO3 (β-wollastonite). The heat treatment procedures are found to greatly influence the mechanical properties of the glass-ceramic, and an apatite layer is induced on the glass-ceramic surface after soaking in the SBF solution.

  19. Effects of sodium and potassium ions on a novel SeO2-B2O3-SiO2-P2O5-CaO bioactive system

    NASA Astrophysics Data System (ADS)

    Trandafir, D. L.; Ponta, O.; Ciceo-Lucacel, R.; Simon, V.

    2015-01-01

    The study is focused on Na2O and/or K2O influence on a new sol-gel derived SeO2-B2O3-SiO2-P2O5-CaO bioactive system. The structural changes induced by Na2O and/or K2O addition were correlated with the samples behavior in simulated biological media. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the structure and the type of the chemical bonds. The morphology of the samples was characterized through scanning electron microscopy (SEM). XRD results pointed out a prevalent vitreous structure with an incipient hydroxyapatite (HA) crystalline phase. FTIR results revealed a complex network consisting of silicate, phosphate and borate units, as well as the development of both A- and B-type of carbonate-substituted HA. The bioactivity of the samples was tested in vitro following the evolution of the apatite layers self-assembled on the samples surface in simulated body fluid. Their biocompatibility was investigated after samples surface functionalization with protein. The results indicate that sodium and potassium addition improves the biocompatibility by enhancement of protein adherence on samples surface and without to prevent the samples bioactivity.

  20. Effect of ZrO(2) additions on the crystallization, mechanical and biological properties of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics.

    PubMed

    Li, H C; Wang, D G; Meng, X G; Chen, C Z

    2014-06-01

    A series of ZrO(2) doped MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics were obtained by sintering method. The crystallization behavior, phase composition, morphology and structure of glass-ceramics were characterized. The bending strength, elastic modulus, fracture toughness, micro-hardness and thermal expansion coefficient (TEC) of glass-ceramics were investigated. The in vitro bioactivity and cytotoxicity tests were used to evaluate the bioactivity and biocompatibility of glass-ceramics. The sedimentation mechanism and growth process of apatites on sample surface were discussed. The results showed that the mainly crystalline phases of glass-ceramics were Ca(5)(PO4)3F (fluorapatite) and β-CaSiO(3). (β-wollastonite). m-ZrO(2) (monoclinic zirconia) declined the crystallization temperatures of glasses. t-ZrO(2) (tetragonal zirconia) increased the crystallization temperature of Ca(5)(PO4)(3)F and declined the crystallization temperature of β-CaSiO(3). t-ZrO(2) greatly increased the fracture toughness, bending strength and micro-hardness of glass-ceramics. The nanometer apatites were induced on the surface of glass-ceramic after soaking 28 days in SBF (simulated body fluid), indicating the glass-ceramic has good bioactivity. The in vitro cytotoxicity test demonstrated the glass-ceramic has no toxicity to cell.

  1. Disappearance of superconductivity in the solid solution between (Ca4Al2O6)(Fe2As2) and (Ca4Al2O6)(Fe2P2) superconductors.

    PubMed

    Shirage, Parasharam M; Kihou, Kunihiro; Lee, Chul-Ho; Takeshita, Nao; Eisaki, Hiroshi; Iyo, Akira

    2012-09-19

    The effect of alloying the two perovskite-type iron-based superconductors (Ca(4)Al(2)O(6))(Fe(2)As(2)) and (Ca(4)Al(2)O(6))(Fe(2)P(2)) was examined. While the two stoichiometric compounds possess relatively high T(c)'s of 28 and 17 K, respectively, their solid solutions of the form (Ca(4)Al(2)O(6))(Fe(2)(As(1-x)P(x))(2)) do not show superconductivity over a wide range from x = 0.50 to 0.95. The resultant phase diagram is thus completely different from those of other typical iron-based superconductors such as BaFe(2)(As,P)(2) and LaFe(As,P)O, in which superconductivity shows up when P is substituted for As in the non-superconducting "parent" compounds. Notably, the solid solutions in the non-superconducting range exhibit resistivity anomalies at temperatures of 50-100 K. The behavior is reminiscent of the resistivity kink commonly observed in various non-superconducting parent compounds that signals the onset of antiferromagnetic/orthorhombic long-range order. The similarity suggests that the suppression of the superconductivity in the present case also has a magnetic and/or structural origin.

  2. Electron Impact Excitation Of Ti XIX

    NASA Astrophysics Data System (ADS)

    Aggarwal, Kanti M.; Keenan, F. P.

    2012-05-01

    Emission lines of Ti XIX are important for the modeling and diagnostics of lasing, fusion and astrophysical plasmas, for which atomic data are required for a variety of parameters, such as energy levels, radiative rates (A- values), and excitation rates or equivalently the effective collision strengths (Υ), which are obtained from the electron impact collision strengths (Ω). Experimentally, energy levels are available for Ti XIX on the NIST website, but there is paucity for accurate collisional atomic data. Therefore, here we report a complete set of results (namely energy levels, radiative rates, and effective collision strengths) for all transitions among the lowest 98 levels of Ti XIX. These levels belong to the (1s2) 2s2, 2s2p, 2p2, 2s3l, 2p3l, 2s4l, and 2p4l configurations. Finally, we also report the A- values for four types of transitions, namely electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1), and magnetic quadrupole (M2), because these are also required for plasma modeling. For our calculations of wavefunctions, we have adopted the fully relativistic GRASP code, and for the calculations of Ω, the Dirac atomic R-matrix code (DARC) of PH Norrington and IP Grant. Additionally, parallel calculations have also been performed with the Flexible Atomic Code (FAC) of Gu, so that all atomic parameters can be rigorously assessed for accuracy.

  3. Neuropharmacology of Purinergic Receptors in Human Submucous Plexus: Involvement of P2X1, P2X2, P2X3 Channels, P2Y and A3 Metabotropic Receptors in Neurotransmission

    PubMed Central

    Liñán-Rico, A.; Wunderlich, JE.; Enneking, JT.; Tso, DR.; Grants, I.; Williams, KC.; Otey, A.; Michel, K.; Schemann, M.; Needleman, B.; Harzman, A.; Christofi, FL.

    2015-01-01

    Rationale The role of purinergic signaling in the human ENS is not well understood. We sought to further characterize the neuropharmacology of purinergic receptors in human ENS and test the hypothesis that endogenous purines are critical regulators of neurotransmission. Experimental Approach LSCM-Fluo-4-(Ca2+)-imaging of postsynaptic Ca2+ transients (PSCaTs) was used as a reporter of neural activity. Synaptic transmission was evoked by fiber tract electrical stimulation in human SMP surgical preparations. Pharmacological analysis of purinergic signaling was done in 1,556 neurons from 234 separate ganglia 107 patients; immunochemical labeling for P2XRs of neurons in ganglia from 19 patients. Real-time MSORT (Di-8-ANEPPS) imaging was used to test effects of adenosine on fast excitatory synaptic potentials (fEPSPs). Results Synaptic transmission is sensitive to pharmacological manipulations that alter accumulation of extracellular purines. Apyrase blocks PSCaTs in a majority of neurons. An ecto-NTPDase-inhibitor 6-N,N-diethyl-D-β,γ-dibromomethyleneATP or adenosine deaminase augments PSCaTs. Blockade of reuptake/deamination of eADO inhibits PSCaTs. Adenosine inhibits fEPSPs and PSCaTs (IC50=25μM), sensitive to MRS1220-antagonism (A3AR). A P2Y agonist ADPβS inhibits PSCaTs (IC50=111nM) in neurons without stimulatory ADPβS responses (EC50=960nM). ATP or a P2X1,2,2/3 (α,β-MeATP) agonist evokes fast, slow, biphasic Ca2+ transients or Ca2+ oscillations (EC50=400μM). PSCaTs are sensitive to P2X1 antagonist NF279. Low (20nM) or high (5μM) concentrations of P2X antagonist TNP-ATP block PSCaTs in different neurons; proportions of neurons with P2XR-ir follow the order P2X2>P2X1≫P2X3; P2X1+ P2X2 and P2X3+P2X2 are co-localized. RT-PCR identified mRNA-transcripts for P2X1-7,P2Y1,2,12-14R. Responsive neurons were also identified by HuC/D-ir. Conclusions Purines are critical regulators of neurotransmission in the human enteric nervous system. Purinergic signaling involves

  4. RESONANT CAVITY EXCITATION SYSTEM

    DOEpatents

    Baker, W.R.; Kerns, Q.A.; Riedel, J.

    1959-01-13

    An apparatus is presented for exciting a cavity resonator with a minimum of difficulty and, more specifically describes a sub-exciter and an amplifier type pre-exciter for the high-frequency cxcitation of large cavities. Instead of applying full voltage to the main oscillator, a sub-excitation voltage is initially used to establish a base level of oscillation in the cavity. A portion of the cavity encrgy is coupled to the input of the pre-exciter where it is amplified and fed back into the cavity when the pre-exciter is energized. After the voltage in the cavity resonator has reached maximum value under excitation by the pre-exciter, full voltage is applied to the oscillator and the pre-exciter is tunned off. The cavity is then excited to the maximum high voltage value of radio frequency by the oscillator.

  5. Accurate ab initio potential energy surface, thermochemistry, and dynamics of the Cl(2P, 2P3/2) + CH4 → HCl + CH3 and H + CH3Cl reactions

    NASA Astrophysics Data System (ADS)

    Czakó, Gábor; Bowman, Joel M.

    2012-01-01

    We report a high-quality, ab initio, full-dimensional global potential energy surface (PES) for the Cl(2P, 2P3/2) + CH4 reaction, which describes both the abstraction (HCl + CH3) and substitution (H + CH3Cl) channels. The analytical PES is a least-squares fit, using a basis of permutationally invariant polynomials, to roughly 16 000 ab initio energy points, obtained by an efficient composite method, including counterpoise and spin-orbit corrections for the entrance channel. This composite method is shown to provide accuracy almost equal to all-electron CCSD(T)/aug-cc-pCVQZ results, but at much lower computational cost. Details of the PES, as well as additional high-level benchmark characterization of structures and energetics are reported. The PES has classical barrier heights of 2650 and 15 060 cm-1 (relative to Cl(2P3/2) + CH4(eq)), respectively, for the abstraction and substitution reactions, in good agreement with the corresponding new computed benchmark values, 2670 and 14 720 cm-1. The PES also accurately describes the potential wells in the entrance and exit channels for the abstraction reaction. Quasiclassical trajectory calculations using the PES show that (a) the inclusion of the spin-orbit corrections in the PES decreases the cross sections by a factor of 1.5-2.5 at low collision energies (Ecoll); (b) at Ecoll ≈ 13 000 cm-1 the substitution channel opens and the H/HCl ratio increases rapidly with Ecoll; (c) the maximum impact parameter (bmax) for the abstraction reaction is ˜6 bohr; whereas bmax is only ˜2 bohr for the substitution; (d) the HCl and CH3 products are mainly in the vibrational ground state even at very high Ecoll; and (e) the HCl rotational distributions are cold, in excellent agreement with experiment at Ecoll = 1280 cm-1.

  6. Role of G-protein beta gamma subunits in the augmentation of P2Y2 (P2U)receptor-stimulated responses by neuropeptide Y Y1 Gi/o-coupled receptors.

    PubMed Central

    Selbie, L A; King, N V; Dickenson, J M; Hill, S J

    1997-01-01

    Neuropeptide Y (NPY) significantly potentiates the constrictor actions of noradrenaline and ATP on blood vessels via a pertussis toxin (PTX)-sensitive mechanism involving Gi/o (alpha beta gamma) protein subunits (Gi/o, GTP-binding proteins sensitive to PTX). In Chinese hamster ovary K1 (CHO K1) cells expressing specific receptors for these neurotransmitters, stimulation of Gi/o protein-coupled receptors for NPY and other neurotransmitters can augment the Gq/11-coupled (Gq/11, GTP-binding proteins insensitive to PTX) alpha 1B adrenoceptor- or ATP receptor-induced arachidonic acid (AA) release and inositol phosphate (IP) production (early events which may precede vasoconstriction). In this study, we have assessed the role of G beta gamma subunits in the synergistic interaction between Gi/o- (NPY Y1, 5-hydroxytryptamine 5-HT1B, adenosine A1) and Gq/11- [ATP P2Y2 (P2U)]-coupled receptors on AA release by using the specific abilities of regions of the beta-adrenergic receptor kinase (beta ARK1 residues 495-689) and the transducin alpha subunit to associate with G-protein beta gamma subunit dimers and to act as G beta gamma subunit scavengers. Transient expression of beta ARK1(495-689) in CHO K1 cells heterologously expressing NPY Y1 receptors had no significant effect on the PTX-insensitive ability of ATP to stimulate AA release. Stimulation of NPY Y1 receptors (as well as the endogenous 5-hydroxytryptamine 5-HT1B receptor and the transiently expressed human adenosine A1 receptor) resulted in a PTX-sensitive augmentation of ATP-stimulated AA release, which was inhibited by expression of both G beta gamma subunit scavengers. Expression of beta ARK1(495-689) similarly inhibited NPY Y1 receptor augmentation of ATP-stimulated IP production (a measure of phospholipase C activity), a step thought to precede the NPY Y1 receptor-augmented protein kinase C-dependent AA release previously observed in these cells. These experiments demonstrate that G beta gamma subunits, as

  7. Fabrication and evaluation of osteoblastic differentiation of human mesenchymal stem cells on novel CaO-SiO2-P2O5-B2O3 glass-ceramics.

    PubMed

    Lee, Jae Hyup; Seo, Jun-Hyuk; Lee, Kyung Mee; Ryu, Hyun-Seung; Baek, Hae-Ri

    2013-07-01

    Apatite-wollastonite glass-ceramics have high mechanical strength, and CaO-SiO2 -B2 O3 glass-ceramics showed excellent bioactivity and high biodegradability. A new type of CaO-SiO2 -P2 O5 -B2 O3 system of bioactive glass-ceramics (BGS-7) was fabricated, and the effect and usefulness was evaluated via bioactivity using simulated body fluid and human mesenchymal stem cells (hMSCs). The purpose of this study was to compare BGS-7 and hydroxyapatite (HA) using hMSCs in order to evaluate the bioactivity of BGS-7 and its possibility as a bone graft extender. Alkaline phosphatase (ALP) staining, ALP activity, cell proliferation 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay, Alizarin Red-S (AR-S) staining, calcium levels, the mRNA expression of ALP, osteocalcin, osteopontin, and runt-related transcription factor 2 (runx-2) using reverse-transcription polymerase chain reaction (RT-PCR) and the protein expression of osteocalcin and runx-2 using Western blot were measured by transplanting hMSC onto a tissue culture plate, HA, and BGS-7. The ALP staining and AR-S staining of BGS-7 was greater than that of HA and control. The ALP value of BGS-7 was significantly higher than that of HA and control. The MTS results showed that BGS-7 had a higher value than the groups transplanted onto HA and control on day 15. The calcium level was higher than the control in both HA and BGS-7, and was especially high in BGS-7. There were more mineral products on BGS-7 than on the HA when analyzed by scanning electron microscopy. The mRNA expression of ALP, osteopontin, osteocalcin, and runx-2 were higher on BGS-7 than on HA and the control when analyzed by RT-PCR. The relative gene expression of osteopontin and runx-2 were found to be higher on BGS-7 than on HA and the control by Western blot. Accordingly, it is predicted that BGS-7 would have high biocompatibility and good osteoconductivity, and presents a possibility as a new

  8. Ground- and excited-state impurity bands in quantum wells

    NASA Astrophysics Data System (ADS)

    Ghazali, A.; Gold, A.; Serre, J.

    1989-02-01

    The density of states and the spectral density of electrons in quantum wells with charged impurities are calculated with use of a multiple-scattering method. The impurity-density-dependent broadening and the gradual merging of the ground (1s) and excited (2p+/-,2s) impurity levels into impurity bands are investigated. At low density the shapes of the 1s, 2p+/-, and 2s spectral densities are found to be in excellent agreement with the analytical results obtained for the ideal two-dimensional Coulomb problem.

  9. Portable vibration exciter

    NASA Technical Reports Server (NTRS)

    Beecher, L. C.; Williams, F. T.

    1970-01-01

    Gas-driven vibration exciter produces a sinusoidal excitation function controllable in frequency and in amplitude. It allows direct vibration testing of components under normal loads, removing the possibility of component damage due to high static pressure.

  10. Excited charmed mesons

    SciTech Connect

    Butler, J.N.; Shukla, S.

    1995-05-01

    The experimental status of excited charmed mesons is reviewed and is compared to theoretical expectations. Six states have been observed and their properties are consistent with those predicted for excited charmed states with orbital angular momentum equal to one.

  11. Reactivity of the anionic diphosphorus complex [Mo2Cp2(μ-PCy2)(μ-κ(2):κ(2)-P2)(CO)2]- toward phosphorus- and transition metal-based electrophiles.

    PubMed

    Alvarez, M Angeles; García, M Esther; García-Vivó, Daniel; Lozano, Raquel; Ramos, Alberto; Ruiz, Miguel A

    2013-08-05

    The reactions of the Li(+) salt of the title anion with chlorophosphines PR2Cl (R = Cy, Ph, (t)Bu) led in all cases to products of formula [Mo2Cp2(μ-PCy2)(μ-κ(2)(P,P)':κ(2)(P,P″)-P2PR2)(CO)2], with the PR2 group inserted in one of the Mo-P(basal) bonds of the anion to give novel tridentate phosphinodiphosphenyl ligands, as confirmed by the solid-state structure of the PCy2 compound. When R was the bulky (t)Bu group, this product was in equilibrium with an isomer of formula [Mo2Cp2(μ-PCy2)(μ-κ(2)(P,P)':κ(2)(P,P')-P2P(t)Bu2)(CO)2], in which the diphosphorus ligand of the anion binds the P(t)Bu2 group through the lone pair of electrons at the basal P atom in an "end-on" fashion (computed P-P-P(t)Bu2 = 114.7°); the latter isomer was more stable than the former, according to the NMR data and density functional theory (DFT) calculations. The title anion reacted with halide complexes of the type [MXLn] (MLn = FeCp(CO)2, MoCp(CO)3, ZrCpCl, Mn(CO)5, Re(CO)5) to give compounds of formula [Mo2MCp2(μ-PCy2)(μ-κ(2):κ(2):κ(1)-P2)(CO)2Ln] incorporating the organometallic fragment MLn also in an "end-on" position at the basal P atom of the anion, as confirmed by the solid-state structure of the Fe compound (P-P = 2.089(2) Å; P-P-Fe = 124.6(1)°). All these complexes, except the Zr compound, underwent a fluxional process in solution involving a swing of the P2 ligand around the Mo-Mo axis with concomitant exchange of the MLn fragment between the P atoms of the diphosphorus ligand, as revealed by variable-temperature NMR experiments. Thermal decarbonylation of the Mn and Re compounds gave hexanuclear derivatives of formula [Mo4M2Cp4(μ-PCy2)2(μ4-κ(1):κ(2):κ(2):κ(1)-P2)2(CO)12] (M = Mn, Re) as a mixture of two isomers derived from the different assembly of the asymmetric Mo2P2 subunits, as confirmed through X-ray analyses of both compounds. Each of the P2 ligands in these two complexes bind two Mo and two M atoms (M = Mn, Re), with the latter defining central P4M

  12. Acoustically excited heated jets. 1: Internal excitation

    NASA Technical Reports Server (NTRS)

    Lepicovsky, J.; Ahuja, K. K.; Brown, W. H.; Salikuddin, M.; Morris, P. J.

    1988-01-01

    The effects of relatively strong upstream acoustic excitation on the mixing of heated jets with the surrounding air are investigated. To determine the extent of the available information on experiments and theories dealing with acoustically excited heated jets, an extensive literature survey was carried out. The experimental program consisted of flow visualization and flowfield velocity and temperature measurements for a broad range of jet operating and flow excitation conditions. A 50.8-mm-diam nozzle was used for this purpose. Parallel to the experimental study, an existing theoretical model of excited jets was refined to include the region downstream of the jet potential core. Excellent agreement was found between theory and experiment in moderately heated jets. However, the theory has not yet been confirmed for highly heated jets. It was found that the sensitivity of heated jets to upstream acoustic excitation varies strongly with the jet operating conditions and that the threshold excitation level increases with increasing jet temperature. Furthermore, the preferential Strouhal number is found not to change significantly with a change of the jet operating conditions. Finally, the effects of the nozzle exit boundary layer thickness appear to be similar for both heated and unheated jets at low Mach numbers.

  13. SiO2-P2O5-HfO2-Al2O3-Na2O glasses activated by Er3+ ions: From bulk sample to planar waveguide fabricated by rf-sputtering

    NASA Astrophysics Data System (ADS)

    Chiasera, A.; Vasilchenko, I.; Dorosz, D.; Cotti, M.; Varas, S.; Iacob, E.; Speranza, G.; Vaccari, A.; Valligatla, S.; Zur, L.; Lukowiak, A.; Righini, G. C.; Ferrari, M.

    2017-01-01

    0.4 Er3+-doped 90.7 SiO2 - 4.4 P2O5 - 2.3 HfO2 - 1.7 Al2O3 - 0.7 Na2O planar waveguide was fabricated by multi-target rf-sputtering technique starting by massive Er3+-activated P2O5-SiO2-Al2O3-Na2O glass. The optical parameters were measured by m-line apparatus operating at 632.8, 1319 and 1542 nm. The waveguide compositions were investigated by Energy Dispersive X-ray Spectroscopy and its morphology analyzed by Atomic Force Microscopy. The waveguide exhibits a single propagation mode at 1319 and 1542 nm with an attenuation coefficient of 0.2 dB/cm in the infrared. The emission of 4I13/2 → 4I15/2 transition of Er3+ ion, with a 28.5 nm bandwidth was observed upon TE0 mode excitation at 514.5 nm. The optical and spectroscopic features of the Er3+-activated parent P2O5-SiO2-Al2O3-Na2O glass were also investigated.

  14. RESONANT CAVITY EXCITATION SYSTEM

    DOEpatents

    Baker, W.R.

    1959-08-01

    A cavity excitation circuit is described for rapidly building up and maintaining high-level oscillations in a resonant cavity. The circuit overcomes oscillation buildup slowing effects such as ion locking in the cavity by providing for the selective application of an amplified accelerating drive signal to the main cavity exciting oscillator during oscillation buildup and a direct drive signal to the oscillator thereafter.

  15. 8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER No. 2., AND GENERATOR UNITS BEHIND EXCITER No. 2 IN BACKGROUND. EXCITER No. 1 GENERATOR HAS A COVER OVER TOP HALF OF COMMUTATOR ELEMENT. VIEW TO NORTHWEST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  16. Excitability dependent pattern formation

    NASA Astrophysics Data System (ADS)

    Prabhakara, Kaumudi; Gholami, Azam; Bodenschatz, Eberhard

    2014-03-01

    On starvation, the amoebae Dictyostelium discoideum emit the chemo-attractant cyclic adenosine monophosphate (cAMP) at specific frequencies. The neighboring amoebae sense cAMP through membrane receptors and produce their own cAMP. Soon the cells synchronize and move via chemotaxis along the gradient of cAMP. The response of the amoebae to the emission of cAMP is seen as spiral waves or target patterns under a dark field microscope. The causal reasons for the selection of one or the other patterns are still unclear. Here we present a possible explanation based on excitability. The excitability of the amoebae depends on the starvation time because the gene expression changes with starvation. Cells starved for longer times are more excitable. In this work, we mix cells of different excitabilities to study the dependence of the emergent patterns on the excitability. Preliminary results show a transition from spirals to target patterns for specific excitabilities. A phase map of the patterns for different combinations of excitability and number densities is obtained. We compare our findings with numerical simulations of existing theoretical models.

  17. 15. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 WITH EXCITER No. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 WITH EXCITER No. 1 BEHIND. OVERHEAD CRANE DANGLES AT TOP OF PHOTO. VIEW TO NORTHEAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  18. Geomagnetic excitation of nutation

    NASA Astrophysics Data System (ADS)

    Ron, C.; Vondrák, J.

    2015-08-01

    We tested the hypothesis of Malkin (2013), who demonstrated that the observed changes of Free Core Nutation parameters (phase, amplitude) occur near the epochs of geomagnetic jerks. We found that if the numerical integration of Brzeziński broad-band Liouville equations of atmospheric/oceanic excitations is re-initialized at the epochs of geomagnetic jerks, the agreement between the integrated and observed celestial pole offsets is improved (Vondrák & Ron, 2014). Nevertheless, this approach assumes that the influence of geomagnetic jerks leads to a stepwise change in the position of celestial pole, which is physically not acceptable. Therefore we introduce a simple continuous excitation function that hypothetically describes the influence of geomagnetic jerks, and leads to rapid but continuous changes of pole position. The results of numerical integration of atmospheric/oceanic excitations and this newly introduced excitation are then compared with the observed celestial pole offsets, and prove that the agreement is improved significantly.

  19. Excitation by rockets

    NASA Technical Reports Server (NTRS)

    Tammadge, C. E.

    1975-01-01

    Standard methods of excitation are not always practical when a single mode of known frequency requires investigation. This form of investigation is often required on a modified aircraft. A new method of excitation was developed and proved in flight, which consists of firing small rocket charges attached to the aircraft structure. Damping values at gradually increasing airspeeds are obtained, as in Stick Jerk tests, and flutter speeds predicted.

  20. Electron Impact Excitation of Ti XVIII

    NASA Astrophysics Data System (ADS)

    Zhong, Jia Yong; Zeng, Jiao Long; Zhao, Gang; Bari, Muhanmmud Abbas; Zhang, Jie

    2005-10-01

    Two different methods were used to calculate the collision strengths of boron-like titanium. One was a close-coupling way using the Dirac Atomic R-matrix Code (DARC) of P. H. Norrington and I. P. Grant (private communication), and the other was based on a relativistic distorted-wave (RDW) approximation with a Flexible Atomic Code (FAC) by Gu (2003). For DARC, the lowest 125 fine-structure levels belonging to the (1s2) 2s22p, 2s2p2, 2p3, 2s23l, 2s2p3l, and 2p23l (l=s, p, and d) configurations were included in the calculations. The target model space encompassed the lowest 15 levels, and all 105Δn=0 transitions together with 40 partial waves were included in calculations of the collision strengths. For FAC, the configuration interactions included in the calculations of atomic structure and excitation were among the same configurations of DARC. The collision strengths for all 125 levels were calculated at 10 scattered electron energies (10-10000eV). The effective collision strengths, obtained after integrating the collision strengths of two codes over a Maxwellian distribution of electron energies, were also calculated for the electron temperatures in the range (50-500eV). For application to spectral modeling or diagnostics, we report a complete set of data for the energy levels, radiative rates, and effective collision strengths (only FAC) for all transitions.

  1. Excitation Methods for Bridge Structures

    SciTech Connect

    Farrar, C.R.; Duffy, T.A.; Cornwell, P.J.; Doebling, S.W.

    1999-02-08

    This paper summarizes the various methods that have been used to excited bridge structures during dynamic testing. The excitation methods fall into the general categories of ambient excitation methods and measured-input excitation methods. During ambient excitation the input to the bridge is not directly measured. In contrast, as the category label implies, measured-input excitations are usually applied at a single location where the force input to the structure can be monitored. Issues associated with using these various types of measurements are discussed along with a general description of the various excitation methods.

  2. Spin waves and magnetic excitations

    SciTech Connect

    Borovik-Romanov, A.S.; Sinha, S.K.

    1988-01-01

    This book describes both simple spin waves (magnons) and complicated excitations in magnetic systems. The following subjects are covered: - various methods of magnetic excitation investigations such as neutron scattering on magnetic excitations, spin-wave excitation by radio-frequency, power light scattering on magnons and magnetic excitation observation within the light-absorption spectrum; - oscillations of magnetic electron systems coupled with phonons, nuclear spin systems and localized impurity modes: - low-dimensional magnetics, amorphous magnetics and spin glasses.

  3. Positron excitation of neon

    NASA Technical Reports Server (NTRS)

    Parcell, L. A.; Mceachran, R. P.; Stauffer, A. D.

    1990-01-01

    The differential and total cross section for the excitation of the 3s1P10 and 3p1P1 states of neon by positron impact were calculated using a distorted-wave approximation. The results agree well with experimental conclusions.

  4. Proteins of Excitable Membranes

    PubMed Central

    Nachmansohn, David

    1969-01-01

    Excitable membranes have the special ability of changing rapidly and reversibly their permeability to ions, thereby controlling the ion movements that carry the electric currents propagating nerve impulses. Acetylcholine (ACh) is the specific signal which is released by excitation and is recognized by a specific protein, the ACh-receptor; it induces a conformational change, triggering off a sequence of reactions resulting in increased permeability. The hydrolysis of ACh by ACh-esterase restores the barrier to ions. The enzymes hydrolyzing and forming ACh and the receptor protein are present in the various types of excitable membranes. Properties of the two proteins directly associated with electrical activity, receptor and esterase, will be described in this and subsequent lectures. ACh-esterase has been shown to be located within the excitable membranes. Potent enzyme inhibitors block electrical activity demonstrating the essential role in this function. The enzyme has been recently crystallized and some protein properties will be described. The monocellular electroplax preparation offers a uniquely favorable material for analyzing the properties of the ACh-receptor and its relation to function. The essential role of the receptor in electrical activity has been demonstrated with specific receptor inhibitors. Recent data show the basically similar role of ACh in the axonal and junctional membranes; the differences of electrical events and pharmacological actions are due to variations of shape, structural organization, and environment. PMID:19873642

  5. Energies and E1, M1, E2, M2 transition rates for states of the 2s{sup 2}2p, 2s2p{sup 2}, and 2p{sup 3} configurations in boron-like ions between N III and Zn XXVI

    SciTech Connect

    Rynkun, P.; Joensson, P.; Gaigalas, G.; Froese Fischer, C.

    2012-07-15

    Energies, E1, M1, E2, M2 transition rates, line strengths, oscillator strengths, and lifetimes from relativistic configuration interaction calculations are reported for the states of the (1s{sup 2})2s{sup 2}2p, 2s2p{sup 2}, and 2p{sup 3} configurations in all boron-like ions between N III and Zn XXVI. Valence, core-valence, and core-core correlation effects were accounted for through single-double multireference (SD-MR) expansions to increasing sets of active orbitals.

  6. Adsorption of the cis-[Pt(NH3)2(P2O7)](2-) (phosphaplatin) on hydroxyapatite nanocrystals as a smart way to selectively release activated cis-[Pt(NH3)2Cl2] (cisplatin) in tumor tissues.

    PubMed

    Benedetti, Michele; De Castro, Federica; Romano, Alessandro; Migoni, Danilo; Piccinni, Barbara; Verri, Tiziano; Lelli, Marco; Roveri, Norberto; Fanizzi, Francesco P

    2016-04-01

    The relevant adsorption of cis-[Pt(NH3)2(P2O7)](2-) (phosphaplatin) on hydroxyapatite nanocrystals (nHAP) was observed and studied in water suspension. Phosphaplatin cytotoxicity, which is very low for HeLa, MCF-7 and HS-5 cell lines could be enhanced, reaching that of cisplatin, by interaction with solid nHAP. This effect stems from nHAP ability to catalyze the phosphaplatin hydrolysis, producing the same hydrolytic species responsible for cisplatin antitumor activity.

  7. Experiments on excitation waves

    NASA Astrophysics Data System (ADS)

    Müller, S. C.

    Recent trends in the experimentation on chemical and biochemical excitation waves are presented. In the Belousov-Zhabotinsky reaction, which is the most suitable chemical laboratory system for the study of wave propagation in excitable medium, the efficient control of wave dynamics by electrical fields and by light illumination is illustrated. In particular, the effects of a feedback control are shown. Further new experiments in this system are concerned with three-dimensional topologies and boundary effects. Important biological applications are found in the aggregation of slime mould amoebae, in proton waves during oscillatory glycolysis, and in waves of spreading depression in neuronal tissue as studied by experiments in chicken retina. Numerical simulations with appropriate reaction-diffusion models complement a large number of these experimental findings.

  8. Magnetostrictive resonance excitation

    DOEpatents

    Schwarz, Ricardo B.; Kuokkala, Veli-Tapani

    1992-01-01

    The resonance frequency spectrum of a magnetostrictive sample is remotely determined by exciting the magnetostrictive property with an oscillating magnetic field. The permeability of a magnetostrictive material and concomitant coupling with a detection coil varies with the strain in the material whereby resonance responses of the sample can be readily detected. A suitable sample may be a magnetostrictive material or some other material having at least one side coated with a magnetostrictive material. When the sample is a suitable shape, i.e., a cube, rectangular parallelepiped, solid sphere or spherical shell, the elastic moduli or the material can be analytically determined from the measured resonance frequency spectrum. No mechanical transducers are required and the sample excitation is obtained without contact with the sample, leading to highly reproducible results and a measurement capability over a wide temperature range, e.g. from liquid nitrogen temperature to the Curie temperature of the magnetostrictive material.

  9. Excitable scale free networks

    NASA Astrophysics Data System (ADS)

    Copelli, M.; Campos, P. R. A.

    2007-04-01

    When a simple excitable system is continuously stimulated by a Poissonian external source, the response function (mean activity versus stimulus rate) generally shows a linear saturating shape. This is experimentally verified in some classes of sensory neurons, which accordingly present a small dynamic range (defined as the interval of stimulus intensity which can be appropriately coded by the mean activity of the excitable element), usually about one or two decades only. The brain, on the other hand, can handle a significantly broader range of stimulus intensity, and a collective phenomenon involving the interaction among excitable neurons has been suggested to account for the enhancement of the dynamic range. Since the role of the pattern of such interactions is still unclear, here we investigate the performance of a scale-free (SF) network topology in this dynamic range problem. Specifically, we study the transfer function of disordered SF networks of excitable Greenberg-Hastings cellular automata. We observe that the dynamic range is maximum when the coupling among the elements is critical, corroborating a general reasoning recently proposed. Although the maximum dynamic range yielded by general SF networks is slightly worse than that of random networks, for special SF networks which lack loops the enhancement of the dynamic range can be dramatic, reaching nearly five decades. In order to understand the role of loops on the transfer function we propose a simple model in which the density of loops in the network can be gradually increased, and show that this is accompanied by a gradual decrease of dynamic range.

  10. Harmonically excited orbital variations

    SciTech Connect

    Morgan, T.

    1985-08-06

    Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In this formulation the equations of motion adopt the form of a damped harmonic oscillator when torques are applied to the orbit in a variationally prescribed manner. The frequencies of the oscillator equation are in some ways unexpected but can nonetheless be exploited through resonant forcing functions to achieve large secular variations in the orbital elements. Two cases are discussed using a circular orbit as the control case: (1) large changes in orbital inclination achieved by harmonic excitation rather than one impulsive velocity change, and (2) periodic and secular changes to the longitude of the ascending node using both stable and unstable excitation strategies. The implications of these equations are also discussed for both artificial satellites and natural satellites. For the former, two utilitarian orbits are suggested, each exploiting a form of harmonic excitation. 5 refs.

  11. Pulse excitation of bolometer bridges

    NASA Technical Reports Server (NTRS)

    Rusk, S. J.

    1972-01-01

    Driving bolometer bridge by appropriately phased excitation pulses increases signal-to-noise ratio of bolometer sensor which operates on a chopped light beam. Method allows higher applied voltage than is possible by conventional ac or dc excitation.

  12. Apparatus for photon excited catalysis

    NASA Technical Reports Server (NTRS)

    Saffren, M. M. (Inventor)

    1977-01-01

    An apparatus is described for increasing the yield of photonically excited gas phase reactions by extracting excess energy from unstable, excited species by contacting the species with the surface of a finely divided solid.

  13. Get excited: reappraising pre-performance anxiety as excitement.

    PubMed

    Brooks, Alison Wood

    2014-06-01

    Individuals often feel anxious in anticipation of tasks such as speaking in public or meeting with a boss. I find that an overwhelming majority of people believe trying to calm down is the best way to cope with pre-performance anxiety. However, across several studies involving karaoke singing, public speaking, and math performance, I investigate an alternative strategy: reappraising anxiety as excitement. Compared with those who attempt to calm down, individuals who reappraise their anxious arousal as excitement feel more excited and perform better. Individuals can reappraise anxiety as excitement using minimal strategies such as self-talk (e.g., saying "I am excited" out loud) or simple messages (e.g., "get excited"), which lead them to feel more excited, adopt an opportunity mind-set (as opposed to a threat mind-set), and improve their subsequent performance. These findings suggest the importance of arousal congruency during the emotional reappraisal process.

  14. Search for Gluonic Excitations

    SciTech Connect

    Eugenio, Paul

    2007-10-26

    Studies of meson spectra via strong decays provide insight regarding QCD at the confinement scale. These studies have led to phenomenological models for QCD such as the constituent quark model. However, QCD allows for a much richer spectrum of meson states which include extra states such as exotics, hybrids, multi-quarks, and glueballs. First discussion of the status of exotic meson searches is given followed by a discussion of plans at Jefferson Lab to double the energy of the machine to 12 GeV, which will allow us to access photoproduction of mesons in search for gluonic excited states.

  15. Search for Gluonic Excitations

    SciTech Connect

    Paul Eugenio

    2007-10-01

    Studies of meson spectra via strong decays provide insight regarding QCD at the confinement scale. These studies have led to phenomenological models for QCD such as the constituent quark model. However, QCD allows for a much richer spectrum of meson states which include extra states such as exotics, hybrids, multi-quarks, and glueballs. First discussion of the status of exotic meson searches is given followed by a discussion of plans at Jefferson Lab to double the energy of the machine to 12 GeV, which will allow us to access photoproduction of mesons in search for gluonic excited states.

  16. Metastable Interactions: Dissociative Excitation.

    DTIC Science & Technology

    1985-05-01

    participate. The mercuric halide compounds HgBr2 , HgCl 2 , and HgI2 are of recent interest because of laser output achieved on the B2 E - X2 E transition in...the * respective mercuric halide radicals in the range of 400-600 nm. Population inversion has been obtained by photodissociation and electron impact...excitation in mixtures o the mercuric - halide compounds and the rare gases. Chang and -* Burnham (3) have noted Improved laser efficiency and improved

  17. SHOCK-EXCITED OSCILLATOR

    DOEpatents

    Creveling, R.

    1957-12-17

    S> A shock-excited quartz crystal oscillator is described. The circuit was specifically designed for application in micro-time measuring work to provide an oscillator which immediately goes into oscillation upon receipt of a trigger pulse and abruptly ceases oscillation when a second pulse is received. To achieve the instant action, the crystal has a prestressing voltage applied across it. A monostable multivibrator receives the on and off trigger pulses and discharges a pulse through the crystal to initiate or terminate oscillation instantly.

  18. Many-electron aspects of molecular promotion in ion-atom collisions - Production of core-excited states of Li in Li/+/-He collisions

    NASA Technical Reports Server (NTRS)

    Elston, S. B.; Vane, C. R.; Schumann, S.

    1979-01-01

    Production of core-excited autoionizing states of neutral Li having configurations of the form 1snln(prime)l(prime) has been observed over the impact-energy range from 10-50 keV. Although the results for production of all such states is remarkably consistent with a quasi-molecular-excitation model proposed by Stolterfoht and Leithaeuser (1976), production of individual lines in the observed spectra exhibits collision-velocity dependencies indicative of considerably more complex processes, including processes which appear to be inherently two-electron in nature. Excitation functions are presented for (1s2s/2/)/2/S, 1s(2s2p/3/P)/2/P, 1s(2s2p/1/P)/2/P, and (1s2p/2/)/2/D core-excited state of Li and for total core excitation.

  19. Many-electron aspects of molecular promotion in ion-atom collisions - Production of core-excited states of Li in Li/+/-He collisions

    NASA Technical Reports Server (NTRS)

    Elston, S. B.; Vane, C. R.; Schumann, S.

    1979-01-01

    Production of core-excited autoionizing states of neutral Li having configurations of the form 1snln(prime)l(prime) has been observed over the impact-energy range from 10-50 keV. Although the results for production of all such states is remarkably consistent with a quasi-molecular-excitation model proposed by Stolterfoht and Leithaeuser (1976), production of individual lines in the observed spectra exhibits collision-velocity dependencies indicative of considerably more complex processes, including processes which appear to be inherently two-electron in nature. Excitation functions are presented for (1s2s/2/)/2/S, 1s(2s2p/3/P)/2/P, 1s(2s2p/1/P)/2/P, and (1s2p/2/)/2/D core-excited state of Li and for total core excitation.

  20. Excitability in Dictyostelium development

    NASA Astrophysics Data System (ADS)

    Schwab, David

    2013-03-01

    Discovering how populations of cells reliably develop into complex multi-cellular structures is a key challenge in modern developmental biology. This requires an understanding of how networks at the single-cell level, when combined with intercellular signaling and environmental cues, give rise to the collective behaviors observed in cellular populations. I will present work in collaboration with the Gregor lab, showing that the signal-relay response of starved cells of the amoebae Dictyostelium discoideum can be well modeled as an excitable system. This is in contrast to existing models of the network that postulate a feed-forward cascade. I then extend the signal-relay model to describe how spatial gradient sensing may be achieved via excitability. One potential advantage of relying on feedback for gradient sensing is in preventing ``cheaters'' that do not produce signals from taking over the population. I then combine these models of single-cell signaling and chemotaxis to perform large-scale agent-based simulations of aggregating populations. This allows direct study of how variations in single-cell dynamics modify population behavior. In order to further test this model, I use the results of a screen for mutant cell lines that exhibit altered collective patterns. Finally, I use an existing FRET movie database of starved cell populations at varying cell densities and dilution rates to study heterogeneity in repeated spatio-temporal activity patterns.

  1. Structures, energies, and spin-spin coupling constants of fluoro-substituted 1,3-diborata-2,4-diphosphoniocyclobutanes: four-member B-P-B-P rings B2P2F(n)H(8-n) with n = 0, 1, 2, 4.

    PubMed

    Del Bene, Janet E; Alkorta, Ibon; Elguero, José

    2011-05-05

    An ab initio study has been carried out to determine the structures, relative stabilities, and spin-spin coupling constants of a set of 15 fluoro-substituted 1,3-diborata-2,4-diphosphoniocyclobutanes B(2)P(2)F(n)H(8-n), for n = 0, 1, 2, 4, with four-member B-P-B-P rings. Except for B(2)P(2)F(4)H(4) with four fluorines bonded to two borons, these rings are puckered in a butterfly conformation. For a fixed number of fluorines, the isomers with B-F bonds are significantly more stable than those with P-F bonds. As the number of fluorines increases, the energy difference between the most stable isomer and the other isomers increases. Transition structures which interconvert axial and equatorial positions present relatively small inversion barriers. Coupling constants involving (31)P, namely, (1)J(B-P), (1)J(P-F), (2)J(P-P), (2)J(P-F), and (3)J(P-F) are large and are capable of providing structural information. They are sensitive to the number of fluorines present and can discriminate between axial, equatorial, and geminal B-F and P-F bonds, although not all do this to the same extent. (1)J(B-P) and (2)J(P-P) are similar in equilibrium and transition structures. Although transition structures no longer discriminate between axial and equatorial bonds, (1)J(P-F) and (3)J(P-F) remain sensitive to the number of fluorine atoms present.

  2. Length of excitable knots

    NASA Astrophysics Data System (ADS)

    Maucher, Fabian; Sutcliffe, Paul

    2017-07-01

    In this paper, we present extensive numerical simulations of an excitable medium to study the long-term dynamics of knotted vortex strings for all torus knots up to crossing number 11. We demonstrate that FitzHugh-Nagumo evolution preserves the knot topology for all the examples presented, thereby providing a field theory approach to the study of knots. Furthermore, the evolution yields a well-defined minimal length for each knot that is comparable to the ropelength of ideal knots. We highlight the role of the medium boundary in stabilizing the length of the knot and discuss the implications beyond torus knots. We also show that there is not a unique attractor within a given knot topology.

  3. CINE: Comet INfrared Excitation

    NASA Astrophysics Data System (ADS)

    de Val-Borro, Miguel; Cordiner, Martin A.; Milam, Stefanie N.; Charnley, Steven B.

    2017-08-01

    CINE calculates infrared pumping efficiencies that can be applied to the most common molecules found in cometary comae such as water, hydrogen cyanide or methanol. One of the main mechanisms for molecular excitation in comets is the fluorescence by the solar radiation followed by radiative decay to the ground vibrational state. This command-line tool calculates the effective pumping rates for rotational levels in the ground vibrational state scaled by the heliocentric distance of the comet. Fluorescence coefficients are useful for modeling rotational emission lines observed in cometary spectra at sub-millimeter wavelengths. Combined with computational methods to solve the radiative transfer equations based, e.g., on the Monte Carlo algorithm, this model can retrieve production rates and rotational temperatures from the observed emission spectrum.

  4. Excited states of boron isoelectronic series from explicitly correlated wave functions.

    PubMed

    Gálvez, F J; Buendía, E; Sarsa, A

    2005-04-15

    The ground state and some low-lying excited states arising from the 1s2 2s2p2 configuration of the boron isoelectronic series are studied starting from explicitly correlated multideterminant wave functions. One- and two-body densities in position space have been calculated and different expectation values such as , , , , , and , where r, r12, and R stand for the electron-nucleus, interelectronic, and two electron center of mass coordinates, respectively, have been obtained. The energetic ordering of the excited states and the fulfillment of the Hund's rules is analyzed systematically along the isoelectronic series in terms of the electron-electron and electron-nucleus potential energies. The effects of electronic correlations have been systematically studied by comparing the correlated results with the corresponding noncorrelated ones. All the calculations have been done by using the variational Monte Carlo method.

  5. Front interaction induces excitable behavior

    NASA Astrophysics Data System (ADS)

    Parra-Rivas, P.; Matías, M. A.; Colet, P.; Gelens, L.; Walgraef, D.; Gomila, D.

    2017-02-01

    Spatially extended systems can support local transient excitations in which just a part of the system is excited. The mechanisms reported so far are local excitability and excitation of a localized structure. Here we introduce an alternative mechanism based on the coexistence of two homogeneous stable states and spatial coupling. We show the existence of a threshold for perturbations of the homogeneous state. Subthreshold perturbations decay exponentially. Superthreshold perturbations induce the emergence of a long-lived structure formed by two back to back fronts that join the two homogeneous states. While in typical excitability the trajectory follows the remnants of a limit cycle, here reinjection is provided by front interaction, such that fronts slowly approach each other until eventually annihilating. This front-mediated mechanism shows that extended systems with no oscillatory regimes can display excitability.

  6. Optically excited states in positronium

    NASA Technical Reports Server (NTRS)

    Howell, R. H.; Ziock, Klaus P.; Magnotta, F.; Dermer, Charles D.; Failor, R. A.; Jones, K. M.

    1990-01-01

    Optical excitation are reported of the 1 3S-2 3P transition in positronium, and a second excitation from n=2 to higher n states. The experiment used light from two pulsed dye lasers. Changes in the positronium annihilation rate during and after the laser pulse were used to deduce the excited state populations. The n=2 level was found to be saturable and excitable to a substantial fraction of n=2 positronium to higher levels. Preliminary spectroscopic measurements were performed on n=14 and n=15 positronium.

  7. Fission fragment excited laser system

    DOEpatents

    McArthur, David A.; Tollefsrud, Philip B.

    1976-01-01

    A laser system and method for exciting lasing action in a molecular gas lasing medium which includes cooling the lasing medium to a temperature below about 150 K and injecting fission fragments through the lasing medium so as to preferentially excite low lying vibrational levels of the medium and to cause population inversions therein. The cooled gas lasing medium should have a mass areal density of about 5 .times. 10.sup.-.sup.3 grams/square centimeter, relaxation times of greater than 50 microseconds, and a broad range of excitable vibrational levels which are excitable by molecular collisions.

  8. The Excitable Membrane

    PubMed Central

    Offner, Franklin F.

    1972-01-01

    The model of the excitable membrane assumes common channels for Na+ and K+; the two ion species interact within the pores through their electrostatic forces. The electric field varies across the membrane and with time, as a result of ionic redistribution. Ionic flow is primarily controlled by energy barriers at the two interfaces and by Ca++ adsorption at the external interface. When the membrane is polarized, the high electric field at the external interface acting on the membrane fixed charge keeps the effective channel diameter small, so that only dihydrated ions can cross the interface. The higher energy required to partially dehydrate Na+ accounts for its lower permeability when polarized. Depolarized, the channel entrance can expand, permitting quadrihydrated ions to pass; the large initial Na+ flow is the result of the large concentration ratio across the interface. The effect at the internal interface is symmetric; Na+ crosses with greater difficulty when the membrane is depolarized. Na+ inactivation occurs when the ion distribution within the membrane has assumed its new steady-state value. Calculations based on parameters consistent with physicochemical data agree generally with a wide range of experiments. The model does not obey the two fundamental Hodgkin-Huxley (HH) postulates (independence principle, ion flow proportional to thermodynamic potential). In several instances the model predicts experimental results which are not predicted by the HH equations. ImagesFIGURE 12 PMID:4655662

  9. Double excitations in finite systems.

    PubMed

    Romaniello, P; Sangalli, D; Berger, J A; Sottile, F; Molinari, L G; Reining, L; Onida, G

    2009-01-28

    Time-dependent density-functional theory (TDDFT) is widely used in the study of linear response properties of finite systems. However, there are difficulties in properly describing excited states, which have double- and higher-excitation characters, which are particularly important in molecules with an open-shell ground state. These states would be described if the exact TDDFT kernel were used; however, within the adiabatic approximation to the exchange-correlation (xc) kernel, the calculated excitation energies have a strict single-excitation character and are fewer than the real ones. A frequency-dependent xc kernel could create extra poles in the response function, which would describe states with a multiple-excitation character. We introduce a frequency-dependent xc kernel, which can reproduce, within TDDFT, double excitations in finite systems. In order to achieve this, we use the Bethe-Salpeter equation with a dynamically screened Coulomb interaction W(omega), which can describe these excitations, and from this we obtain the xc kernel. Using a two-electron model system, we show that the frequency dependence of W does indeed introduce the double excitations that are instead absent in any static approximation of the electron-hole screening.

  10. Excited waves in shear layers

    NASA Technical Reports Server (NTRS)

    Bechert, D. W.

    1982-01-01

    The generation of instability waves in free shear layers is investigated. The model assumes an infinitesimally thin shear layer shed from a semi-infinite plate which is exposed to sound excitation. The acoustical shear layer excitation by a source further away from the plate edge in the downstream direction is very weak while upstream from the plate edge the excitation is relatively efficient. A special solution is given for the source at the plate edge. The theory is then extended to two streams on both sides of the shear layer having different velocities and densities. Furthermore, the excitation of a shear layer in a channel is calculated. A reference quantity is found for the magnitude of the excited instability waves. For a comparison with measurements, numerical computations of the velocity field outside the shear layer were carried out.

  11. Structures, energies, and spin-spin coupling constants of methyl-substituted 1,3-diborata-2,4-diphosphoniocyclobutanes: four-member B-P-B-P rings B2P2(CH3)(n)H(8-n), with n = 0, 1, 2, 4.

    PubMed

    Del Bene, Janet E; Alkorta, Ibon; Elguero, José

    2011-09-29

    An ab initio study has been carried out to determine the structures, relative stabilities, and spin-spin coupling constants of a set of 17 methyl-substituted 1,3-diborata-2,4-diphosphoniocyclobutanes B(2)P(2)(CH(3))(n)H(8-n), for n = 0, 1, 2, 4, with four-member B-P-B-P rings. The B-P-B-P rings are puckered in a butterfly conformation, in agreement with experimental data for related molecules. Isomers with the CH(3) group bonded to P are more stable than those with CH(3) bonded to B. If there is only one methyl group or if two methyl groups are bonded to two different P or B atoms, isomers with equatorial bonds are more stable than those with axial bonds. However, when two methyl groups are present, the gem isomers are the most stable for molecules B(2)P(2)(CH(3))(2)H(6) with P-C and B-C bonds, respectively. Transition structures present barriers to the interconversion of two equilibrium structures or to the interchange of axial and equatorial positions in the same isomer. These barriers are very low for the isomer with two methyl groups bonded to B in axial positions for the isomer with four axial bonds and for the isomer with geminal B-C bonds at both B atoms. Coupling constants (1)J(B-P), (1)J(P-C), (1)J(B-C), (2)J(P-P), and (3)J(P-C) are capable of providing structural information. They are sensitive to the number of methyl groups present and can discriminate between axial, equatorial, and geminal bonds, although not all do this to the same extent. The one-bond coupling constants (1)J(B-P), (1)J(P-C), and (1)J(B-C) are similar in equilibrium and transition structures, but (3)J(P-C) and (2)J(P-P) are not. These coupling constants and those of the corresponding fluoro-derivatives of the 1,3-diborata-2,4-diphosphoniocyclobutanes demonstrate the great sensitivity of phosphorus coupling to structural and electronic effects.

  12. Vibrational excitation induces double reaction.

    PubMed

    Huang, Kai; Leung, Lydie; Lim, Tingbin; Ning, Zhanyu; Polanyi, John C

    2014-12-23

    Electron-induced reaction at metal surfaces is currently the subject of extensive study. Here, we broaden the range of experimentation to a comparison of vibrational excitation with electronic excitation, for reaction of the same molecule at the same clean metal surface. In a previous study of electron-induced reaction by scanning tunneling microscopy (STM), we examined the dynamics of the concurrent breaking of the two C-I bonds of ortho-diiodobenzene physisorbed on Cu(110). The energy of the incident electron was near the electronic excitation threshold of E0=1.0 eV required to induce this single-electron process. STM has been employed in the present work to study the reaction dynamics at the substantially lower incident electron energies of 0.3 eV, well below the electronic excitation threshold. The observed increase in reaction rate with current was found to be fourth-order, indicative of multistep reagent vibrational excitation, in contrast to the first-order rate dependence found earlier for electronic excitation. The change in mode of excitation was accompanied by altered reaction dynamics, evidenced by a different pattern of binding of the chemisorbed products to the copper surface. We have modeled these altered reaction dynamics by exciting normal modes of vibration that distort the C-I bonds of the physisorbed reagent. Using the same ab initio ground potential-energy surface as in the prior work on electronic excitation, but with only vibrational excitation of the physisorbed reagent in the asymmetric stretch mode of C-I bonds, we obtained the observed alteration in reaction dynamics.

  13. Effect of temperature of Li2O-Al2O3-TiO2-P2O5 solid-state electrolyte coating process on the performance of LiNi0.5Mn1.5O4 cathode materials

    NASA Astrophysics Data System (ADS)

    Deng, Yu-Feng; Zhao, Shi-Xi; Xu, Ya-Hui; Nan, Ce-Wen

    2015-11-01

    Electrochemical performance of spinel LiNi0.5Mn1.5O4 (LNMO) at elevated temperature is improved by solid-state electrolyte Li2O-Al2O3-TiO2-P2O5 (LATP) coating. Crystallinity and thickness of coatings are controlled by adjusting the coating process at two different temperatures (550 and 650 °C). 2.0 wt.% LATP-modified LNMO cathode materials obtained at 650 °C exhibits remarkably promoted electrochemical performance compared to that of the pristine one in terms of cycling and rate ability at 55 °C. The enhanced performance of the surface-modified samples can be accounted for the suppressed side reactions between the cathode materials and electrolyte solution. What is more important is that LATP cannot only protect the active materials from electrolyte solution but also improve Li+ mobility. The higher crystallinity of glass-ceramic LATP coating layer with thinner thickness implies more unobstructed, stable and shorter diffusion path of Li+ transport. It is found that the coating process is in favor of the disordered to ordered phase transition, implying that the heating process of coating plays a role of anneal as well.

  14. Complex-scaling treatment for quantum entanglement in doubly excited helium atom

    NASA Astrophysics Data System (ADS)

    Lin, Chien-Hao; Ho, Yew Kam

    2015-05-01

    Recently, we have investigated entanglement measures in natural atomic systems that involve two highly correlated indistinguishable spin-1/2 fermions (electrons). Linear entropy and von Neumann entropy were calculated for spatial (electron-electron orbital) entanglement measures for ground and singly excited bound states in two-electron atomic systems, such as He, H- and Ps-. In our present work, we carry out an investigation on entanglement in doubly excited resonance states of helium. Since resonance states are lying in the scattering continuum, their energies are no longer bound by the variational theorem; we apply the complex scaling method to solve the complex energy pole with which the resonance energy and resonance width are deduced. Hylleraas-type wave functions are used to consider correlation effects. Once the wave function for a doubly excited state is obtained, we apply the Schmidt decomposition method to calculate the linear entropy and von Neumann entropy for the doubly excited 2s2, 2 s3 s, 2p2, 3s2, and 3p21Se resonance states in the helium atom. Work supported by the Ministry of Science and Technology of Taiwan.

  15. Coulomb excitations of monolayer germanene

    NASA Astrophysics Data System (ADS)

    Shih, Po-Hsin; Chiu, Yu-Huang; Wu, Jhao-Ying; Shyu, Feng-Lin; Lin, Ming-Fa

    2017-01-01

    The feature-rich electronic excitations of monolayer germanene lie in the significant spin-orbit coupling and the buckled structure. The collective and single-particle excitations are diversified by the magnitude and direction of transferred momentum, the Fermi energy and the gate voltage. There are four kinds of plasmon modes, according to the unique frequency- and momentum-dependent phase diagrams. They behave as two-dimensional acoustic modes at long wavelength. However, for the larger momenta, they might change into another kind of undamped plasmons, become the seriously suppressed modes in the heavy intraband e–h excitations, keep the same undamped plasmons, or decline and then vanish in the strong interband e–h excitations. Germanene, silicene and graphene are quite different from one another in the main features of the diverse plasmon modes.

  16. Coulomb excitations of monolayer germanene

    PubMed Central

    Shih, Po-Hsin; Chiu, Yu-Huang; Wu, Jhao-Ying; Shyu, Feng-Lin; Lin, Ming-Fa

    2017-01-01

    The feature-rich electronic excitations of monolayer germanene lie in the significant spin-orbit coupling and the buckled structure. The collective and single-particle excitations are diversified by the magnitude and direction of transferred momentum, the Fermi energy and the gate voltage. There are four kinds of plasmon modes, according to the unique frequency- and momentum-dependent phase diagrams. They behave as two-dimensional acoustic modes at long wavelength. However, for the larger momenta, they might change into another kind of undamped plasmons, become the seriously suppressed modes in the heavy intraband e–h excitations, keep the same undamped plasmons, or decline and then vanish in the strong interband e–h excitations. Germanene, silicene and graphene are quite different from one another in the main features of the diverse plasmon modes. PMID:28091555

  17. Excitations of strange bottom baryons

    NASA Astrophysics Data System (ADS)

    Woloshyn, R. M.

    2016-09-01

    The ground-state and first-excited-state masses of Ωb and Ω_{bb} baryons are calculated in lattice QCD using dynamical 2 + 1 flavour gauge fields. A set of baryon operators employing different combinations of smeared quark fields was used in the framework of the variational method. Results for radial excitation energies were confirmed by carrying out a supplementary multiexponential fitting analysis. Comparison is made with quark model calculations.

  18. Collisional excitation of interstellar formaldehyde

    NASA Technical Reports Server (NTRS)

    Green, S.; Garrison, B. J.; Lester, W. A., Jr.; Miller, W. H.

    1978-01-01

    Previous calculations for rates of excitation of ortho-H2CO by collisions with He have been extended to higher rotational levels and kinetic temperatures to 80 K. Rates for para-H2CO have also been computed. Pressure-broadening widths for several spectral lines have been obtained from these calculations and are found to agree with recent data within the experimental uncertainty of 10%. Excitation of formaldehyde by collisions with H2 molecules is also discussed.

  19. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  20. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  1. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  2. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  3. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  4. Redox Control of Cardiac Excitability

    PubMed Central

    Aggarwal, Nitin T.

    2013-01-01

    Abstract Reactive oxygen species (ROS) have been associated with various human diseases, and considerable attention has been paid to investigate their physiological effects. Various ROS are synthesized in the mitochondria and accumulate in the cytoplasm if the cellular antioxidant defense mechanism fails. The critical balance of this ROS synthesis and antioxidant defense systems is termed the redox system of the cell. Various cardiovascular diseases have also been affected by redox to different degrees. ROS have been indicated as both detrimental and protective, via different cellular pathways, for cardiac myocyte functions, electrophysiology, and pharmacology. Mostly, the ROS functions depend on the type and amount of ROS synthesized. While the literature clearly indicates ROS effects on cardiac contractility, their effects on cardiac excitability are relatively under appreciated. Cardiac excitability depends on the functions of various cardiac sarcolemal or mitochondrial ion channels carrying various depolarizing or repolarizing currents that also maintain cellular ionic homeostasis. ROS alter the functions of these ion channels to various degrees to determine excitability by affecting the cellular resting potential and the morphology of the cardiac action potential. Thus, redox balance regulates cardiac excitability, and under pathological regulation, may alter action potential propagation to cause arrhythmia. Understanding how redox affects cellular excitability may lead to potential prophylaxis or treatment for various arrhythmias. This review will focus on the studies of redox and cardiac excitation. Antioxid. Redox Signal. 18, 432–468. PMID:22897788

  5. Electron-excited molecule interactions

    SciTech Connect

    Christophorou, L.G. Tennessee Univ., Knoxville, TN . Dept. of Physics)

    1991-01-01

    In this paper the limited but significant knowledge to date on electron scattering from vibrationally/rotationally excited molecules and electron scattering from and electron impact ionization of electronically excited molecules is briefly summarized and discussed. The profound effects of the internal energy content of a molecule on its electron attachment properties are highlighted focusing in particular on electron attachment to vibrationally/rotationally and to electronically excited molecules. The limited knowledge to date on electron-excited molecule interactions clearly shows that the cross sections for certain electron-molecule collision processes can be very different from those involving ground state molecules. For example, optically enhanced electron attachment studies have shown that electron attachment to electronically excited molecules can occur with cross sections 10{sup 6} to 10{sup 7} times larger compared to ground state molecules. The study of electron-excited molecule interactions offers many experimental and theoretical challenges and opportunities and is both of fundamental and technological significance. 54 refs., 15 figs.

  6. Electrostatic Tuning of Cellular Excitability

    PubMed Central

    Börjesson, Sara I.; Parkkari, Teija; Hammarström, Sven; Elinder, Fredrik

    2010-01-01

    Abstract Voltage-gated ion channels regulate the electric activity of excitable tissues, such as the heart and brain. Therefore, treatment for conditions of disturbed excitability is often based on drugs that target ion channels. In this study of a voltage-gated K channel, we propose what we believe to be a novel pharmacological mechanism for how to regulate channel activity. Charged lipophilic substances can tune channel opening, and consequently excitability, by an electrostatic interaction with the channel's voltage sensors. The direction of the effect depends on the charge of the substance. This was shown by three compounds sharing an arachidonyl backbone but bearing different charge: arachidonic acid, methyl arachidonate, and arachidonyl amine. Computer simulations of membrane excitability showed that small changes in the voltage dependence of Na and K channels have prominent impact on excitability and the tendency for repetitive firing. For instance, a shift in the voltage dependence of a K channel with −5 or +5 mV corresponds to a threefold increase or decrease in K channel density, respectively. We suggest that electrostatic tuning of ion channel activity constitutes a novel and powerful pharmacological approach with which to affect cellular excitability. PMID:20141752

  7. Performance seeking control excitation mode

    NASA Technical Reports Server (NTRS)

    Schkolnik, Gerard

    1995-01-01

    Flight testing of the performance seeking control (PSC) excitation mode was successfully completed at NASA Dryden on the F-15 highly integrated digital electronic control (HIDEC) aircraft. Although the excitation mode was not one of the original objectives of the PSC program, it was rapidly prototyped and implemented into the architecture of the PSC algorithm, allowing valuable and timely research data to be gathered. The primary flight test objective was to investigate the feasibility of a future measurement-based performance optimization algorithm. This future algorithm, called AdAPT, which stands for adaptive aircraft performance technology, generates and applies excitation inputs to selected control effectors. Fourier transformations are used to convert measured response and control effector data into frequency domain models which are mapped into state space models using multiterm frequency matching. Formal optimization principles are applied to produce an integrated, performance optimal effector suite. The key technical challenge of the measurement-based approach is the identification of the gradient of the performance index to the selected control effector. This concern was addressed by the excitation mode flight test. The AdAPT feasibility study utilized the PSC excitation mode to apply separate sinusoidal excitation trims to the controls - one aircraft, inlet first ramp (cowl), and one engine, throat area. Aircraft control and response data were recorded using on-board instrumentation and analyzed post-flight. Sensor noise characteristics, axial acceleration performance gradients, and repeatability were determined. Results were compared to pilot comments to assess the ride quality. Flight test results indicate that performance gradients were identified at all flight conditions, sensor noise levels were acceptable at the frequencies of interest, and excitations were generally not sensed by the pilot.

  8. Excitation with quantum light. I. Exciting a harmonic oscillator

    NASA Astrophysics Data System (ADS)

    Carreño, J. C. López; Laussy, F. P.

    2016-12-01

    We present a two-part study of the excitation of an optical target by quantum light. In this first part, we introduce the problematic and address the first case of interest, that of exciting the quantum harmonic oscillator, corresponding to, e.g., a single-mode passive cavity or a noninteracting bosonic field. We introduce a mapping of the Hilbert space that allows to chart usefully the accessible regions. We then consider the quantum excitation from single-photon sources in the form of a two-level system under various regimes of (classical) pumping: incoherent, coherent, and in the Mollow triplet regime. We close this first part with an overview of the material to be covered in the subsequent work.

  9. Sadomasochism, sexual excitement, and perversion.

    PubMed

    Kernberg, O F

    1991-01-01

    Sadomasochism, an ingredient of infantile sexuality, is an essential part of normal sexual functioning and love relations, and of the very nature of sexual excitement. Sadomasochistic elements are also present in all sexual perversions. Sadomasochism starts out as the potential for erotic masochism in both sexes, and represents a very early capacity to link aggression with the libidinal elements of sexual excitement. Sexual excitement may be considered a basic affect that overcomes primitive splitting of love and hatred. Erotic desire is a more mature form of sexual excitement. Psychoanalytic exploration makes it possible to uncover the unconscious components of sexual excitement: wishes for symbiotic fusion and for aggressive penetration and intermingling; bisexual identifications; the desire to transgress oedipal prohibitions and the secretiveness of the primal scene, and to violate the boundaries of a teasing and withholding object. The relation between these wishes and the development of erotic idealization processes in both sexes is explored in the context of a critical review of the pertinent psychoanalytic literature.

  10. Modeling excitable systems: Reentrant tachycardia

    NASA Astrophysics Data System (ADS)

    Lancaster, Jarrett L.; Hellen, Edward H.; Leise, Esther M.

    2010-01-01

    Excitable membranes are an important type of nonlinear dynamical system, and their study can be used to provide a connection between physical and biological circuits. We discuss two models of excitable membranes important in cardiac and neural tissues. One model is based on the Fitzhugh-Nagumo equations, and the other is based on a three-transistor excitable circuit. We construct a circuit that simulates reentrant tachycardia and its treatment by surgical ablation. This project is appropriate for advanced undergraduates as a laboratory capstone project or as a senior thesis or honors project and can also be a collaborative project, with one student responsible for the computational predictions and another for the circuit construction and measurements.

  11. Recurrent Excitation in Neocortical Circuits

    NASA Astrophysics Data System (ADS)

    Douglas, Rodney J.; Koch, Christof; Mahowald, Misha; Martin, Kevan A. C.; Suarez, Humbert H.

    1995-08-01

    The majority of synapses in the mammalian cortex originate from cortical neurons. Indeed, the largest input to cortical cells comes from neighboring excitatory cells. However, most models of cortical development and processing do not reflect the anatomy and physiology of feedback excitation and are restricted to serial feedforward excitation. This report describes how populations of neurons in cat visual cortex can use excitatory feedback, characterized as an effective "network conductance," to amplify their feedforward input signals and demonstrates how neuronal discharge can be kept proportional to stimulus strength despite strong, recurrent connections that threaten to cause runaway excitation. These principles are incorporated into models of cortical direction and orientation selectivity that emphasize the basic design principles of cortical architectures.

  12. Indirect excitation of ultrafast demagnetization

    DOE PAGES

    Vodungbo, Boris; Tudu, Bahrati; Perron, Jonathan; ...

    2016-01-06

    Does the excitation of ultrafast magnetization require direct interaction between the photons of the optical pump pulse and the magnetic layer? Here, we demonstrate unambiguously that this is not the case. For this we have studied the magnetization dynamics of a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon excitation with an intense femtosecond-short IR laser pulse, the film exhibits the classical ultrafast demagnetization phenomenon although only a negligible number of IR photons penetrate the aluminum layer. In comparison with an uncapped cobalt/palladium reference film, the initial demagnetization of the capped film occurs with a delayed onset andmore » at a slower rate. Both observations are qualitatively in line with energy transport from the aluminum layer into the underlying magnetic film by the excited, hot electrons of the aluminum film. As a result, our data thus confirm recent theoretical predictions.« less

  13. Indirect excitation of ultrafast demagnetization

    PubMed Central

    Vodungbo, Boris; Tudu, Bahrati; Perron, Jonathan; Delaunay, Renaud; Müller, Leonard; Berntsen, Magnus H.; Grübel, Gerhard; Malinowski, Grégory; Weier, Christian; Gautier, Julien; Lambert, Guillaume; Zeitoun, Philippe; Gutt, Christian; Jal, Emmanuelle; Reid, Alexander H.; Granitzka, Patrick W.; Jaouen, Nicolas; Dakovski, Georgi L.; Moeller, Stefan; Minitti, Michael P.; Mitra, Ankush; Carron, Sebastian; Pfau, Bastian; von Korff Schmising, Clemens; Schneider, Michael; Eisebitt, Stefan; Lüning, Jan

    2016-01-01

    Does the excitation of ultrafast magnetization require direct interaction between the photons of the optical pump pulse and the magnetic layer? Here, we demonstrate unambiguously that this is not the case. For this we have studied the magnetization dynamics of a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon excitation with an intense femtosecond-short IR laser pulse, the film exhibits the classical ultrafast demagnetization phenomenon although only a negligible number of IR photons penetrate the aluminum layer. In comparison with an uncapped cobalt/palladium reference film, the initial demagnetization of the capped film occurs with a delayed onset and at a slower rate. Both observations are qualitatively in line with energy transport from the aluminum layer into the underlying magnetic film by the excited, hot electrons of the aluminum film. Our data thus confirm recent theoretical predictions. PMID:26733106

  14. Indirect excitation of ultrafast demagnetization

    SciTech Connect

    Vodungbo, Boris; Tudu, Bahrati; Perron, Jonathan; Delaunay, Renaud; Müller, Leonard; Berntsen, Magnus H.; Grübel, Gerhard; Malinowski, Grégory; Weier, Christian; Gautier, Julien; Lambert, Guillaume; Zeitoun, Philippe; Gutt, Christian; Jal, Emmanuelle; Reid, Alexander H.; Granitzka, Patrick W.; Jaouen, Nicolas; Dakovski, Georgi L.; Moeller, Stefan; Minitti, Michael P.; Mitra, Ankush; Carron, Sebastian; Pfau, Bastian; von Korff Schmising, Clemens; Schneider, Michael; Eisebitt, Stefan; Lüning, Jan

    2016-01-06

    Does the excitation of ultrafast magnetization require direct interaction between the photons of the optical pump pulse and the magnetic layer? Here, we demonstrate unambiguously that this is not the case. For this we have studied the magnetization dynamics of a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon excitation with an intense femtosecond-short IR laser pulse, the film exhibits the classical ultrafast demagnetization phenomenon although only a negligible number of IR photons penetrate the aluminum layer. In comparison with an uncapped cobalt/palladium reference film, the initial demagnetization of the capped film occurs with a delayed onset and at a slower rate. Both observations are qualitatively in line with energy transport from the aluminum layer into the underlying magnetic film by the excited, hot electrons of the aluminum film. As a result, our data thus confirm recent theoretical predictions.

  15. Stochastic excitation of stellar oscillations

    NASA Astrophysics Data System (ADS)

    Samadi, Reza

    2001-05-01

    Since more than about thirty years, solar oscillations are thought to be excited stochastically by the turbulent motions in the solar convective zone. It is currently believed that oscillations of stars lower than 2 solar masses - which possess an upper convective zone - are excited stochastically by turbulent convection in their outer layers. Providing that accurate measurements of the oscillation amplitudes and damping rates are available it is possible to evaluate the power injected into the modes and thus - by comparison with the observations - to constrain current theories. A recent theoretical work (Samadi & Goupil, 2001; Samadi et al., 2001) supplements and reinforces the theory of stochastic excitation of star vibrations. This process was generalized to a global description of the turbulent state of their convective zone. The comparison between observation and theory, thus generalized, will allow to better know the turbulent spectrum of stars, and this in particular thanks to the COROT mission.

  16. Excitation optimization for damage detection

    SciTech Connect

    Bement, Matthew T; Bewley, Thomas R

    2009-01-01

    A technique is developed to answer the important question: 'Given limited system response measurements and ever-present physical limits on the level of excitation, what excitation should be provided to a system to make damage most detectable?' Specifically, a method is presented for optimizing excitations that maximize the sensitivity of output measurements to perturbations in damage-related parameters estimated with an extended Kalman filter. This optimization is carried out in a computationally efficient manner using adjoint-based optimization and causes the innovations term in the extended Kalman filter to be larger in the presence of estimation errors, which leads to a better estimate of the damage-related parameters in question. The technique is demonstrated numerically on a nonlinear 2 DOF system, where a significant improvement in the damage-related parameter estimation is observed.

  17. First excited states in doubly-odd {sup 110}Sb: Smooth band termination in the A {approx} 110 region

    SciTech Connect

    Lane, G.J.; Fossan, D.B.; Thorslund, I.

    1996-11-01

    Excited states have been identified for the first time in {sup 110}Sb in a comprehensive series of {gamma}-spectroscopy experiments, including recoil-mass and neutron-field measurements. Three high-spin decoupled bands with configurations based on 2p-2h excitations across the Z = 50 shell gap, are observed to show the features of smooth band termination, the first such observation in an odd-odd nucleus. The yrast intruder band has been connected to the low spin levels and is tentatively identified up to its predicred termination at I{sup {pi}} = (45{sup +}). Detailed configuration assignments are made through comparison with configuration-dependent cranked Nilsson-Strutinsky calculations; excellent agreement with experiment is obtained. The systematic occurrence of smoothly terminating bands in the neighboring isotopes is discussed.

  18. Calculation of molecular excitation rates

    NASA Technical Reports Server (NTRS)

    Flynn, George

    1993-01-01

    State-to-state collisional excitation rates for interstellar molecules observed by radio astronomers continue to be required to interpret observed line intensities in terms of local temperatures and densities. A problem of particular interest is collisional excitation of water which is important for modeling the observed interstellar masers. In earlier work supported by a different NASA Grant, excitation of water in collisions with He atoms was studied; after many years of successively more refined calculations that problem now seems to be well understood, and discrepancies with earlier experimental data for related (pressure broadening) phenomena are believed to reflect experimental errors. Because of interstellar abundances, excitation by H2, the dominant interstellar species, is much more important than excitation by He, although it has been argued that rates for excitation by these are similar. Under the current grant theoretical study of this problem has begun which is greatly complicated by the additional degrees of freedom which must be included both in determining the interaction potential and also in the molecular scattering calculation. We have now computed the interaction forces for nearly a thousand molecular geometries and are close to having an acceptable global fit to these points which is necessary for the molecular dynamics calculations. Also, extensive modifications have been made to the molecular scattering code, MOLSCAT. These included coding the rotational basis sets and coupling matrix elements required for collisions of an asymmetric top with a linear rotor. A new method for numerical solution of the coupled equations has been incorporated. Because of the long-ranged nature of the water-hydrogen interaction it is necessary to integrate the equations to rather large intermolecular separations, and the integration methods previously available in MOLSCAT are not ideal for such cases. However, the method used by Alexander in his HIBRIDON code is

  19. Excited-to-excited-state scattering using weak measurements

    NASA Astrophysics Data System (ADS)

    U, Satya Sainadh; Narayanan, Andal

    2015-11-01

    Weak measurements are a subset of measurement processes in quantum mechanics wherein the system, which is being measured, interacts very weakly with the measuring apparatus. Measurement values of observables undergoing a weak interaction and their amplification are concepts that have sharpened our understanding of interaction processes in quantum mechanics. Recent experiments show that naturally occurring processes such as resonance fluorescence from excited states of an atom can exhibit weak value amplification effect. In this paper we theoretically analyze the process of elastic resonance fluorescence from a V -type three-level atomic system, using the well-known Weiskopff-Wigner (WW) theory of spontaneous emission. Within this theory we show that a weak interaction regime can be identified and for suitable choices of initial and final excited states the mean scattering time between these states show an amplification effect during interaction with the vacuum bath modes of the electromagnetic field. We thus show that a system-bath interaction can show weak value amplification. Using our theory we reproduce the published experimental results carried out in such a system. More importantly, our theory can calculate scattering time scales in elastic resonance scattering between multiple excited states of a single atom or between common excited state configurations of interacting multiatom systems.

  20. Autoresonant Excitation of Antiproton Plasmas

    NASA Astrophysics Data System (ADS)

    Andresen, G. B.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Bowe, P. D.; Butler, E.; Carpenter, P. T.; Cesar, C. L.; Chapman, S.; Charlton, M.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Hangst, J. S.; Hardy, W. N.; Hayden, M. E.; Humphries, A. J.; Hurt, J. L.; Hydomako, R.; Jonsell, S.; Madsen, N.; Menary, S.; Nolan, P.; Olchanski, K.; Olin, A.; Povilus, A.; Pusa, P.; Robicheaux, F.; Sarid, E.; Silveira, D. M.; So, C.; Storey, J. W.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.; Yamazaki, Y.

    2011-01-01

    We demonstrate controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense, and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination.

  1. Directional excitation without breaking reciprocity

    NASA Astrophysics Data System (ADS)

    Ramezani, Hamidreza; Dubois, Marc; Wang, Yuan; Shen, Y. Ron; Zhang, Xiang

    2016-09-01

    We propose a mechanism for directional excitation without breaking reciprocity. This is achieved by embedding an impedance matched parity-time symmetric potential in a three-port system. The amplitude distribution within the gain and loss regions is strongly influenced by the direction of the incoming field. Consequently, the excitation of the third port is contingent on the direction of incidence while transmission in the main channel is immune. Our design improves the four-port directional coupler scheme, as there is no need to implement an anechoic termination to one of the ports.

  2. Decentralized nonlinear optimal excitation control

    SciTech Connect

    Lu, Q.; Sun, Y.; Xu, Z.; Mochizuki, T.

    1996-11-01

    A design method to lay emphasis on differential geometric approach for decentralized nonlinear optimal excitation control of multimachine systems is suggested in this paper. The control law achieved is implemented via purely local measurements. Moreover, it is independent of the parameters of power networks. Simulations are performed on a six-machine system. It has been demonstrated that the nonlinear optimal excitation control could adapt to the conditions under large disturbances. Besides, this paper has verified that the optimal control in the sense of LQR principle for the linearized system is equivalent to an optimal control in the sense of a quasi-quadratic performance index for the primitive nonlinear control system.

  3. Electron impact cross sections for the 2,2P state excitation of lithium

    NASA Technical Reports Server (NTRS)

    Vuskovic, L.; Trajmar, S.; Register, D. F.

    1982-01-01

    Electron impact excitation of the 2p 2P state of Li was studied at 10, 20, 60, 100, 150 and 200 eV. Relative differential cross sections in the angular range 3-120 deg were measured and then normalized to the absolute scale by using the optical f value. Integral and momentum transfer cross sections were obtained by extrapolating the differential cross sections to 0 deg and to 180 deg. The question of normalizing electron-metal-atom collision cross sections in general was examined and the method of normalization to optical f values in particular was investigated in detail. It has been concluded that the extrapolation of the apparent generalized oscillator strength (obtained from the measured differential cross sections) to the zero momentum transfer limit with an expression using even powers of the momentum transfer and normalization of the limit to the optical f value yields reliable absolute cross sections.

  4. Launch Excitement with Water Rockets

    ERIC Educational Resources Information Center

    Sanchez, Juan Carlos; Penick, John

    2007-01-01

    Explosions and fires--these are what many students are waiting for in science classes. And when they do occur, students pay attention. While we can't entertain our students with continual mayhem, we can catch their attention and cater to their desires for excitement by saying, "Let's make rockets." In this activity, students make simple, reusable…

  5. Elementary Excitations in Quantum Liquids.

    ERIC Educational Resources Information Center

    Pines, David

    1981-01-01

    Discusses elementary excitations and their role in condensed matter physics, focusing on quantum plasma, helium liquids, and superconductors. Considers research primarily conducted in the 1950s and concludes with a brief survey of some closely related further developments. (Author/JN)

  6. Pseudorandom selective excitation in NMR

    NASA Astrophysics Data System (ADS)

    Walls, Jamie D.; Coomes, Alexandra

    2011-09-01

    In this work, average Hamiltonian theory is used to study selective excitation under a series of small flip-angle θ-pulses θ ≪ {π}/{3} applied either periodically [corresponding to the DANTE pulse sequence] or aperiodically to a spin-1/2 system. First, an average Hamiltonian description of the DANTE pulse sequence is developed that is valid for frequencies either at or very far from integer multiples of {1}/{τ}, where τ is the interpulse delay. For aperiodic excitation, a single resonance, νsel, can be selectively excited if the θ-pulse phases are modulated in concert with the interpulse delays. The conditions where average Hamiltonian theory can be accurately applied to describe the dynamics under aperiodic selective pulses, which are referred to as pseudorandom-DANTE or p-DANTE sequences, are similar to those found for the DANTE sequence. Signal averaging over different p-DANTE sequences improves the apparent selectivity at νsel by reducing the excitations at other frequencies. Experimental demonstrations of p-DANTE sequences and comparisons with the theory are presented.

  7. Exciting cytoskeleton-membrane waves

    NASA Astrophysics Data System (ADS)

    Shlomovitz, R.; Gov, N. S.

    2008-10-01

    Propagating waves on the surface of cells, over many micrometers, involve active forces. We investigate here the mechanical excitation of such waves when the membrane is perturbed by an external oscillatory force. The external perturbation may trigger the propagation of such waves away from the force application. This scheme is then suggested as a method to probe the properties of the excitable medium of the cell, and learn about the mechanisms that drive the wave propagation. We then apply these ideas to a specific model of active cellular membrane waves, demonstrating how the response of the system to the external perturbation depends on the properties of the model. The most outstanding feature that we find is that the excited waves exhibit a resonance phenomenon at the frequency corresponding to the tendency of the system to develop a linear instability. Mechanical excitation of membrane waves in cells at different frequencies can therefore be used to characterize the properties of the mechanism underlying the existence of these waves.

  8. Communicating the Excitement of Science

    ScienceCinema

    Michael Turner

    2016-07-12

    In this talk (which will include some exciting science) I will discuss some lessons I have learned about communicating science to scientists (in my own field and others), students, the public, the press, and policy makers in giving 500+ colloquia and seminars, 300+ public lectures and many informal presentations (including cocktail parties).

  9. Predictions for Excited Strange Baryons

    SciTech Connect

    Fernando, Ishara P.; Goity, Jose L.

    2016-04-01

    An assessment is made of predictions for excited hyperon masses which follow from flavor symmetry and consistency with a 1/N c expansion of QCD. Such predictions are based on presently established baryonic resonances. Low lying hyperon resonances which do not seem to fit into the proposed scheme are discussed.

  10. Pattern Formation in Excitable Media

    NASA Astrophysics Data System (ADS)

    Mikhailov, Alexander S.

    1997-03-01

    In this talk I give a short review of the history and the current state of theoretical research on spiral wave patterns in excitable media. I start with the theoretical model of wave propagation in excitable media proposed in 1946 by Wiener and Rosenblueth(N. Wiener and A. Rosenblueth, The mathematical formulation of the problem of conduction of impulses in a network of connected excitable elements, specifically in cardiac muscle, Arch. Inst. Cardiol. Mexico 16 (1946) 205). This model describes spiral waves rotating around obstacles. I show how, by taking additionally into account curvature effects and gradual recovery of the medium after passage of an excitation wave, the model is generalized to describe freely rotating spiral waves and the breakup which produces spirals. In the context of this kinematic model, complex dynamics of spiral waves, i.e. their meandering, drift and resonance, is discussed. Instabilities of spiral waves in confined geometries, i.e. inside a circular region and on a sphere, are analyzed. At the end, I show how spiral waves in such systems can be efficiently controlled by application of a delayed global feedback. The talk is based on the review paper(A. S. Mikhailov, V. A. Davydov, and V. S. Zykov, Complex dynamics of spiral waves and motion of curves, Physica D 70 (1994) 1) and the monograph(A. S. Mikhailov, Foundations of Synergetics I, 2nd revised edition (Springer, Berlin, 1994)).

  11. Elementary Excitations in Quantum Liquids.

    ERIC Educational Resources Information Center

    Pines, David

    1981-01-01

    Discusses elementary excitations and their role in condensed matter physics, focusing on quantum plasma, helium liquids, and superconductors. Considers research primarily conducted in the 1950s and concludes with a brief survey of some closely related further developments. (Author/JN)

  12. Launch Excitement with Water Rockets

    ERIC Educational Resources Information Center

    Sanchez, Juan Carlos; Penick, John

    2007-01-01

    Explosions and fires--these are what many students are waiting for in science classes. And when they do occur, students pay attention. While we can't entertain our students with continual mayhem, we can catch their attention and cater to their desires for excitement by saying, "Let's make rockets." In this activity, students make simple, reusable…

  13. Excitation processes in cometary comae

    NASA Astrophysics Data System (ADS)

    Singh, P. D.

    The excitation of cometary NH and S2 molecules is discussed. Particular attention is given to emission bands due to a specific S2 transition in the range of 2829-3058 A observed in the UV spectra of comet IRAS Araki-Alcock (1983). It is suggested that photodissociation and dissociative electron recombination processes may be sources of metastable nitrogen atoms in comets.

  14. Perceptual Load Alters Visual Excitability

    ERIC Educational Resources Information Center

    Carmel, David; Thorne, Jeremy D.; Rees, Geraint; Lavie, Nilli

    2011-01-01

    Increasing perceptual load reduces the processing of visual stimuli outside the focus of attention, but the mechanism underlying these effects remains unclear. Here we tested an account attributing the effects of perceptual load to modulations of visual cortex excitability. In contrast to stimulus competition accounts, which propose that load…

  15. High Excitation Gas and ISM

    NASA Technical Reports Server (NTRS)

    Peeters, E.; Martin-Hernandez, N. L.; Rodriguez-Fernandez, N. J.; Tielens, A. G. G. M.

    2004-01-01

    An overview is given of ISO results on regions of high excitation ISM and gas, i.e. HII regions, the Galactic Centre and Supernovae Remnants. IR emission due to fine-structure lines, molecular hydrogen, silicates, polycyclic aromatic hydrocarbons and dust are summarized, their diagnostic capabilities illustrated and their implications highlighted.

  16. Dynamics of excited molecular states

    NASA Astrophysics Data System (ADS)

    Meyer, Hans-Dieter

    2005-01-01

    The photo-excitation or photo-ionization of a polyatomic molecule is typically accompanied by a strong excitation of the vibrational modes. In particular when a conical intersection of the electronic potential energy surfaces involved lies within or close to the Frank-Condon zone, the nuclear motion becomes very complicated, often chaotic, and the spectra become irregular and dense. An accurate simulation of the dynamics of such excited molecules requires firstly that the multi-dimensional and multi-state potential energy surface - or a reliable model thereof - can be determined. Secondly, the multi-dimensional quantum dynamics have to be solved. This is a very difficult task, because of the high dimensionality of the problem (6 to 30 degrees of freedom, say). The multi-configuration time-dependent Hartree (MCTDH) method has proven to be very useful for the study of such problems. In fact, an accurate treatment of the quantal dynamics of molecules like the allene cation (C3 H+4, 15D), the butatriene cation (C4 H+4, 18D), or the pyrazine molecule (C4N2H4, 24D) in their full dimensionality, is - up to date - only possible with MCTDH. (The acronym n D denotes the dimensionality.) The construction of the vibronic model Hamiltonian and the MCTDH method will be briefly discussed. After this, the excited state dynamics of the butatriene and pyrazine molecules will be discussed.

  17. Fast excitation variable period wiggler

    SciTech Connect

    van Steenbergen, A.; Gallardo, J.; Romano, T.; Woodle, M.

    1991-01-01

    The design of an easily stackable, variable period length, fast excitation driven wiggler, making use of geometrically alternating substacks of Vanadium Permandur ferromagnetic laminations, interspaced with conductive, non magnetic, laminations which act as eddy current induced field reflectors,'' is discussed and experimental results obtained with short wiggler models are presented.

  18. Fast excitation variable period wiggler

    SciTech Connect

    van Steenbergen, A.; Gallardo, J.; Romano, T.; Woodle, M.

    1991-12-31

    The design of an easily stackable, variable period length, fast excitation driven wiggler, making use of geometrically alternating substacks of Vanadium Permandur ferromagnetic laminations, interspaced with conductive, non magnetic, laminations which act as eddy current induced ``field reflectors,`` is discussed and experimental results obtained with short wiggler models are presented.

  19. Communicating the Excitement of Science

    SciTech Connect

    Michael Turner

    2009-06-05

    In this talk (which will include some exciting science) I will discuss some lessons I have learned about communicating science to scientists (in my own field and others), students, the public, the press, and policy makers in giving 500+ colloquia and seminars, 300+ public lectures and many informal presentations (including cocktail parties).

  20. Band Excitation Kelvin probe force microscopy utilizing photothermal excitation

    DOE PAGES

    Collins, Liam; Jesse, Stephen; Balke, Nina; ...

    2015-03-13

    A multifrequency open loop Kelvin probe force microscopy (KPFM) approach utilizing photothermal as opposed to electrical excitation is developed. Photothermal band excitation (PthBE)-KPFM is implemented here in a grid mode on a model test sample comprising a metal-insulator junction with local charge-patterned regions. Unlike the previously described open loop BE-KPFM, which relies on capacitive actuation of the cantilever, photothermal actuation is shown to be highly sensitive to the electrostatic force gradient even at biases close to the contact potential difference (CPD). PthBE-KPFM is further shown to provide a more localized measurement of true CPD in comparison to the gold standardmore » ambient KPFM approach, amplitude modulated KPFM. In conclusion, PthBE-KPFM data contain information relating to local dielectric properties and electronic dissipation between tip and sample unattainable using conventional single frequency KPFM approaches.« less

  1. Band Excitation Kelvin probe force microscopy utilizing photothermal excitation

    SciTech Connect

    Collins, Liam; Jesse, Stephen; Balke, Nina; Rodriguez, Brian J.; Kalinin, Sergei; Li, Qian

    2015-03-13

    A multifrequency open loop Kelvin probe force microscopy (KPFM) approach utilizing photothermal as opposed to electrical excitation is developed. Photothermal band excitation (PthBE)-KPFM is implemented here in a grid mode on a model test sample comprising a metal-insulator junction with local charge-patterned regions. Unlike the previously described open loop BE-KPFM, which relies on capacitive actuation of the cantilever, photothermal actuation is shown to be highly sensitive to the electrostatic force gradient even at biases close to the contact potential difference (CPD). PthBE-KPFM is further shown to provide a more localized measurement of true CPD in comparison to the gold standard ambient KPFM approach, amplitude modulated KPFM. In conclusion, PthBE-KPFM data contain information relating to local dielectric properties and electronic dissipation between tip and sample unattainable using conventional single frequency KPFM approaches.

  2. Mean excitation energies for molecular ions

    NASA Astrophysics Data System (ADS)

    Jensen, Phillip W. K.; Sauer, Stephan P. A.; Oddershede, Jens; Sabin, John R.

    2017-03-01

    The essential material constant that determines the bulk of the stopping power of high energy projectiles, the mean excitation energy, is calculated for a range of smaller molecular ions using the RPA method. It is demonstrated that the mean excitation energy of both molecules and atoms increase with ionic charge. However, while the mean excitation energies of atoms also increase with atomic number, the opposite is the case for mean excitation energies for molecules and molecular ions. The origin of these effects is explained by considering the spectral representation of the excited state contributing to the mean excitation energy.

  3. Receiver-exciter controller design

    NASA Technical Reports Server (NTRS)

    Jansma, P. A.

    1982-01-01

    A description of the general design of both the block 3 and block 4 receiver-exciter controllers for the Deep Space Network (DSN) Mark IV-A System is presented along with the design approach. The controllers are designed to enable the receiver-exciter subsystem (RCV) to be configured, calibrated, initialized and operated from a central location via high level instructions. The RECs are designed to be operated under the control of the DMC subsystem. The instructions are in the form of standard subsystem blocks (SSBs) received via the local area network (LAN). The centralized control provided by RECs and other DSCC controllers in Mark IV-A is intended to reduce DSN operations costs from the Mark III era.

  4. Light baryons and their excitations

    NASA Astrophysics Data System (ADS)

    Eichmann, Gernot; Fischer, Christian S.; Sanchis-Alepuz, Hèlios

    2016-11-01

    We study ground states and excitations of light octet and decuplet baryons within the framework of Dyson-Schwinger and Faddeev equations. We improve upon similar approaches by explicitly taking into account the momentum-dependent dynamics of the quark-gluon interaction that leads to dynamical chiral symmetry breaking. We perform calculations in both the three-body Faddeev framework and the quark-diquark approximation in order to assess the impact of the latter on the spectrum. Our results indicate that both approaches agree well with each other. The resulting spectra furthermore agree one-to-one with experiment, provided well-known deficiencies of the rainbow-ladder approximation are compensated for. We also discuss the mass evolution of the Roper and the excited Δ with varying pion mass and analyze the internal structure in terms of their partial wave decompositions.

  5. Electron impact excitation of Hg/+/

    NASA Technical Reports Server (NTRS)

    Crandall, D. H.; Phaneuf, R. A.; Dunn, G. H.

    1974-01-01

    A crossed charged beam technique was employed in the investigation reported. The ion beam was crossed at right angles by a magnetically confined electron beam. Cross sections were determined as a function of electron impact energy. Considerable structure in the excitation cross section appears immediately above the threshold. It is pointed out that a primary application of cross sections is related to the calculation of plasma rate coefficients.

  6. Self-excited multifractal dynamics

    NASA Astrophysics Data System (ADS)

    Filimonov, V.; Sornette, D.

    2011-05-01

    We introduce the self-excited multifractal (SEMF) model, defined such that the amplitudes of the increments of the process are expressed as exponentials of a long memory of past increments. The principal novel feature of the model lies in the self-excitation mechanism combined with exponential nonlinearity, i.e. the explicit dependence of future values of the process on past ones. The self-excitation captures the microscopic origin of the emergent endogenous self-organization properties, such as the energy cascade in turbulent flows, the triggering of aftershocks by previous earthquakes and the "reflexive" interactions of financial markets. The SEMF process has all the standard stylized facts found in financial time series, which are robust to the specification of the parameters and the shape of the memory kernel: multifractality, heavy tails of the distribution of increments with intermediate asymptotics, zero correlation of the signed increments and long-range correlation of the squared increments, the asymmetry (called "leverage" effect) of the correlation between increments and absolute value of the increments and statistical asymmetry under time reversal.

  7. Entanglement entropy of electronic excitations

    NASA Astrophysics Data System (ADS)

    Plasser, Felix

    2016-05-01

    A new perspective into correlation effects in electronically excited states is provided through quantum information theory. The entanglement between the electron and hole quasiparticles is examined, and it is shown that the related entanglement entropy can be computed from the eigenvalue spectrum of the well-known natural transition orbital (NTO) decomposition. Non-vanishing entanglement is obtained whenever more than one NTO pair is involved, i.e., in the case of a multiconfigurational or collective excitation. An important implication is that in the case of entanglement it is not possible to gain a complete description of the state character from the orbitals alone, but more specific analysis methods are required to decode the mutual information between the electron and hole. Moreover, the newly introduced number of entangled states is an important property by itself giving information about excitonic structure. The utility of the formalism is illustrated in the cases of the excited states of two interacting ethylene molecules, the conjugated polymer para-phenylene vinylene, and the naphthalene molecule.

  8. Synaptic Control of Motoneuronal Excitability

    PubMed Central

    Rekling, Jens C.; Funk, Gregory D.; Bayliss, Douglas A.; Dong, Xiao-Wei; Feldman, Jack L.

    2016-01-01

    Movement, the fundamental component of behavior and the principal extrinsic action of the brain, is produced when skeletal muscles contract and relax in response to patterns of action potentials generated by motoneurons. The processes that determine the firing behavior of motoneurons are therefore important in understanding the transformation of neural activity to motor behavior. Here, we review recent studies on the control of motoneuronal excitability, focusing on synaptic and cellular properties. We first present a background description of motoneurons: their development, anatomical organization, and membrane properties, both passive and active. We then describe the general anatomical organization of synaptic input to motoneurons, followed by a description of the major transmitter systems that affect motoneuronal excitability, including ligands, receptor distribution, pre- and postsynaptic actions, signal transduction, and functional role. Glutamate is the main excitatory, and GABA and glycine are the main inhibitory transmitters acting through ionotropic receptors. These amino acids signal the principal motor commands from peripheral, spinal, and supraspinal structures. Amines, such as serotonin and norepinephrine, and neuropeptides, as well as the glutamate and GABA acting at metabotropic receptors, modulate motoneuronal excitability through pre- and postsynaptic actions. Acting principally via second messenger systems, their actions converge on common effectors, e.g., leak K+ current, cationic inward current, hyperpolarization-activated inward current, Ca2+ channels, or presynaptic release processes. Together, these numerous inputs mediate and modify incoming motor commands, ultimately generating the coordinated firing patterns that underlie muscle contractions during motor behavior. PMID:10747207

  9. Channelopathies of skeletal muscle excitability

    PubMed Central

    Cannon, Stephen C.

    2016-01-01

    Familial disorders of skeletal muscle excitability were initially described early in the last century and are now known to be caused by mutations of voltage-gated ion channels. The clinical manifestations are often striking, with an inability to relax after voluntary contraction (myotonia) or transient attacks of severe weakness (periodic paralysis). An essential feature of these disorders is fluctuation of symptoms that are strongly impacted by environmental triggers such as exercise, temperature, or serum K+ levels. These phenomena have intrigued physiologists for decades, and in the past 25 years the molecular lesions underlying these disorders have been identified and mechanistic studies are providing insights for therapeutic strategies of disease modification. These familial disorders of muscle fiber excitability are “channelopathies” caused by mutations of a chloride channel (ClC-1), sodium channel (NaV1.4), calcium channel (CaV1.1) and several potassium channels (Kir2.1, Kir2.6, Kir3.4). This review provides a synthesis of the mechanistic connections between functional defects of mutant ion channels, their impact on muscle excitability, how these changes cause clinical phenotypes, and approaches toward therapeutics. PMID:25880512

  10. Wedding ring shaped excitation coil

    DOEpatents

    MacLennan, Donald A.; Tsai, Peter

    2001-01-01

    A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and/or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency.

  11. Cross sections and rate coefficients for excitation of Δn = 1 transitions in Li-like ions with 6 < Z < 42.

    NASA Astrophysics Data System (ADS)

    Safronova, U. I.; Safronova, M. S.; Kato, T.

    Excitation cross sections and rate coefficients by electron impact were calculated for the 1s22s - 1s2s2p, 1s22s - 1s2s2 and 1s22s - 1s2p2 transitions of the Li-like ions (C IV, N V, O VI, Ne VIII, Mg X, Al XI, Si XII, S XIV, Ar XVI, Ca XVIII, Ti XX, Fe XXIV, Ni XXVI, Zn XXVIII, Ge XXX, Se XXXII, Kr XXXIIV and Mo XXXX) by a Coulomb-Born approximation with exchange and including relativistic effects and configuration interactions. Level energies, mixing coefficients and transition wavelengths and probabilities were also computed.

  12. On Diversity of Configurations Generated by Excitable Cellular Automata with Dynamical Excitation Intervals

    NASA Astrophysics Data System (ADS)

    Adamatzky, Andrew

    2012-11-01

    Excitable cellular automata with dynamical excitation interval exhibit a wide range of space-time dynamics based on an interplay between propagating excitation patterns which modify excitability of the automaton cells. Such interactions leads to formation of standing domains of excitation, stationary waves and localized excitations. We analyzed morphological and generative diversities of the functions studied and characterized the functions with highest values of the diversities. Amongst other intriguing discoveries we found that upper boundary of excitation interval more significantly affects morphological diversity of configurations generated than lower boundary of the interval does and there is no match between functions which produce configurations of excitation with highest morphological diversity and configurations of interval boundaries with highest morphological diversity. Potential directions of future studies of excitable media with dynamically changing excitability may focus on relations of the automaton model with living excitable media, e.g. neural tissue and muscles, novel materials with memristive properties and networks of conductive polymers.

  13. Control of excitation in the fluorescence microscope.

    PubMed

    Lea, D J; Ward, D J

    1979-01-01

    In fluorescence microscopy image brightness and contrast and the rate of fading depend upon the intensity of illumination of the specimen. An iris diaphragm or neutral density filters may be used to reduce fluorescence excitation. Also the excitation bandwidth may be varied by using a broad band exciter filter with a set of interchangeable yellow glass filters at the lamphouse.

  14. Resource Paper: Molecular Excited State Relaxation Processes.

    ERIC Educational Resources Information Center

    Rhodes, William

    1979-01-01

    Develops the concept of oscillatory v dissipative limits as it applies to electronic excited state processes in molecular systems. Main emphasis is placed on the radiative and nonradiative dynamics of the excited state of a molecule prepared by interaction with light or some other excitation source. (BT)

  15. Turbulent swirling jets with excitation

    NASA Technical Reports Server (NTRS)

    Taghavi, Rahmat; Farokhi, Saeed

    1988-01-01

    An existing cold-jet facility at NASA Lewis Research Center was modified to produce swirling flows with controllable initial tangential velocity distribution. Two extreme swirl profiles, i.e., one with solid-body rotation and the other predominated by a free-vortex distribution, were produced at identical swirl number of 0.48. Mean centerline velocity decay characteristics of the solid-body rotation jet flow exhibited classical decay features of a swirling jet with S - 0.48 reported in the literature. However, the predominantly free-vortex distribution case was on the verge of vortex breakdown, a phenomenon associated with the rotating flows of significantly higher swirl numbers, i.e., S sub crit greater than or equal to 0.06. This remarkable result leads to the conclusion that the integrated swirl effect, reflected in the swirl number, is inadequate in describing the mean swirling jet behavior in the near field. The relative size (i.e., diameter) of the vortex core emerging from the nozzle and the corresponding tangential velocity distribution are also controlling factors. Excitability of swirling jets is also investigated by exciting a flow with a swirl number of 0.35 by plane acoustic waves at a constant sound pressure level and at various frequencies. It is observed that the cold swirling jet is excitable by plane waves, and that the instability waves grow about 50 percent less in peak r.m.s. amplitude and saturate further upstream compared to corresponding waves in a jet without swirl having the same axial mass flux. The preferred Strouhal number based on the mass-averaged axial velocity and nozzle exit diameter for both swirling and nonswirling flows is 0.4.

  16. Peculiarities of collisional excitation transfer with excited screened energy levels of atoms

    SciTech Connect

    Gerasimov, V. A.; Gerasimov, V. V.; Pavlinskiy, A. V.

    2007-09-15

    We report an experimental discovery of deviations from the known regularities in collisional excitation transfer processes for metal atoms. The collisional excitation transfer with excited screened energy levels of thulium and dysprosium atoms is studied. The selecting role of the screening 6s shell in collisional excitation transfer is shown.

  17. Volumetric Light-Field Excitation

    PubMed Central

    Schedl, David C.; Bimber, Oliver

    2016-01-01

    We explain how to concentrate light simultaneously at multiple selected volumetric positions by means of a 4D illumination light field. First, to select target objects, a 4D imaging light field is captured. A light field mask is then computed automatically for this selection to avoid illumination of the remaining areas. With one-photon illumination, simultaneous generation of complex volumetric light patterns becomes possible. As a full light-field can be captured and projected simultaneously at the desired exposure and excitation times, short readout and lighting durations are supported. PMID:27363565

  18. Excited states in 129I

    NASA Astrophysics Data System (ADS)

    Deleanu, D.; Balabanski, D. L.; Venkova, Ts.; Bucurescu, D.; Mărginean, N.; Ganioǧlu, E.; Căta-Danil, Gh.; Atanasova, L.; Căta-Danil, I.; Detistov, P.; Filipescu, D.; Ghiţă, D.; Glodariu, T.; Ivaşcu, M.; Mărginean, R.; Mihai, C.; Negret, A.; Pascu, S.; Sava, T.; Stroe, L.; Suliman, G.; Zamfir, N. V.

    2013-01-01

    Excited states in 129I were populated with the 124Sn(7Li,2n) reaction at 23 MeV. In-beam measurements of γ-ray coincidences were performed with an array of eight HPGe detectors and five LaBr3(Ce) scintillation detectors. Based on the γγ coincidence data, a positive parity band structure built on the 7/2+ ground state was established and the πg7/2 configuration at oblate deformation was assigned to it. The results are compared to interacting Boson-Fermion model (IBFM) and total Routhian surface (TRS) calculations.

  19. [Neurosteroids. Neuromodulators of cerebral excitability].

    PubMed

    Calixto González, E; Brailowsky, S

    1998-01-01

    Steroids which are produced by the brain are called neurosteroids, and they are able to modulate neurotransmissions: GABAergic; glutamatergic; glycinergic, and cholinergic (nicotine receptor). These effects are of short latency and duration, and do not implicate the cellular genome. The interaction of these neurosteroids with membrane receptors contribute to the regulation of neuronal excitability, and their study has allowed a better understanding of cognitive, hormonal, and epileptic phenomena as well as the development of new drugs with anxiolytic, antidepressive, anesthetic and anti-epileptic effects.

  20. Multiarmed Spirals in Excitable Media

    NASA Astrophysics Data System (ADS)

    Vasiev, Bakthier; Siegert, Florian; Weijer, Cornelis

    1997-03-01

    Numerical studies of the properties of multiarmed spirals show that they can form spontaneously in low excitability media. The maximum number of arms in a multiarmed spiral is proportional to the ratio of the single spiral period to the refractoriness of the medium. Multiarmed spirals are formed due to attraction of single spirals if these spirals rotate in the same direction and their tips are less than one wavelength apart, i.e., a spiral broken not far from its tip can evolve into a 2-armed spiral. We propose this mechanism to be responsible for the formation of multiarmed spirals in mounds of the slime mold Dictyostelium discoideum.

  1. Collective excitations in the continuum

    SciTech Connect

    Dussel, G. G.; Betan, R. Id; Liotta, R. J.; Vertse, T.

    2009-12-15

    Pairing (particle-particle) giant resonances are analyzed within a shell-model formalism in the complex energy plane with the aim of understanding why they have not been observed so far. A comparison is made with the equivalent particle-hole mode by applying the formalism to the analysis of the well-understood particle-hole giant resonance. It is found that because of the proper treatment of the continuum intrinsic to the formalism, giant pairing resonances lie much higher than previously predicted and that some of them may be too wide to be observed, whereas others are meaningful excitations. For these, new experimental searches are proposed.

  2. Multi-Band Excitation Vocoder.

    DTIC Science & Technology

    1987-03-01

    to random. Vocoder Clean speechb 715 Noe Uncoded WA 0. eiard: 2400 bps 36.5 71.4 B elgard: Noise Excitation 36.4 66.3 I Ta~ble 1.1: DI ? Bem I Another...estimation. Chapter 4 dis - cumes methods for synthesizing speech from these model parameters. In Chapter 5, we apply the MBE Model to the problem of bit-rate...expensive problem. However, we note that for a given pitch period, the best spectral envelope parameters can be easily estimated. To show this, we di - I

  3. High Frequency Chandler Wobble Excitation

    NASA Astrophysics Data System (ADS)

    Seitz, F.; Stuck, J.; Thomas, M.

    2003-04-01

    Variations of Earth rotation on sub-daily to secular timescales are caused by mass redistributions in the Earth system as a consequence of geophysical processes and gravitational influences. Forced oscillations of polar motion are superposed by free oscillations of the Earth, i.e. the Chandler wobble and the free core nutation. In order to study the interactions between externally induced polar motion and the Earth's free oscillations, a non-linear gyroscopic model has been developed. In most of the former investigations on polar motion, the Chandler wobble is introduced as a damped oscillation with predetermined frequency and amplitude. However, as the effect of rotational deformation is a backcoupling mechanism of polar motion on the Earth's rotational dynamics, both period and amplitude of the Chandler wobble are time-dependent when regarding additional excitations from, e.g., atmospheric or oceanic mass redistributions. The gyroscopic model is free of any explicit information concerning amplitude, phase, and period of free oscillations. The characteristics of the Earth's free oscillation is reproduced by the model from rheological and geometrical parameters and rotational deformation is taken into account. This enables to study the time variable Chandler oscillation when the gyro is forced with atmospheric and oceanic angular momentum from the global atmospheric ECHAM3-T21 general circulation model together with the ocean model for circulation and tides OMCT driven by ECHAM including surface pressure. Besides, mass redistributions in the Earth's body due to gravitational and loading deformations are regarded and external torques exerted by Moon and Sun are considered. The numerical results of the gyro are significantly related with the geodetically observed time series of polar motion published by the IERS. It is shown that the consistent excitation is capable to counteract the damping and thus to maintain the Chandler amplitude. Spectral analyses of the ECHAM

  4. Theoretical studies of electronically excited states

    SciTech Connect

    Besley, Nicholas A.

    2014-10-06

    Time-dependent density functional theory is the most widely used quantum chemical method for studying molecules in electronically excited states. However, excited states can also be computed within Kohn-Sham density functional theory by exploiting methods that converge the self-consistent field equations to give excited state solutions. The usefulness of single reference self-consistent field based approaches for studying excited states is demonstrated by considering the calculation of several types of spectroscopy including the infrared spectroscopy of molecules in an electronically excited state, the rovibrational spectrum of the NO-Ar complex, core electron binding energies and the emission spectroscopy of BODIPY in water.

  5. Gene circuit designs for noisy excitable dynamics.

    PubMed

    Rué, Pau; Garcia-Ojalvo, Jordi

    2011-05-01

    Certain cellular processes take the form of activity pulses that can be interpreted in terms of noise-driven excitable dynamics. Here we present an overview of different gene circuit architectures that exhibit excitable pulses of protein expression, when subject to molecular noise. Different types of excitable dynamics can occur depending on the bifurcation structure leading to the specific excitable phase-space topology. The bifurcation structure is not, however, linked to a particular circuit architecture. Thus a given gene circuit design can sustain different classes of excitable dynamics depending on the system parameters.

  6. Three-photon excitation in fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Hell, Stefan W.; Bahlmann, Karsten; Schrader, Martin; Soini, Aleksi; Malak, Henryk; Gryczynski, Ignacy; Lakowicz, Joseph R.

    1996-01-01

    We show experiments proving the feasibility of scanning fluorescence microscopy by three-photon excitation. Three-photon excitation fluorescence axial images are shown of polystyrene beads stained with the fluorophore 2,5- bis(4-biphenyl)oxazole (BBO). Three-photon excitation is performed at an excitation wavelength of 900 nm and with pulses of 130 fs duration provided by a mode-locked titanium-sapphire laser. Fluorescence is collected between 350 and 450 nm. The fluorescence image signal features a third-order dependence on the excitation power, also providing intrinsic 3-D imaging. The resolution of a three-photon excitation microscope is increased over that of a comparable two-photon excitation microscope.

  7. Transfer Excitation Processes Observed in N3+-He and O3+-He Collisions at Elab = 33 eV

    NASA Astrophysics Data System (ADS)

    Itoh, Yoh

    2016-09-01

    We measured the relative state-selective differential cross sections (DCSs) for one-electron capture reactions using a crossed-beam apparatus. The scattering angle θlab studied in the laboratory frame ranged from -3.0 to 22° and the laboratory collision energy Elab was 33 eV. Only the transfer excitation processes, i.e., the electron capture reactions with the simultaneous excitation of the projectile, were observed. The DCSs were determined for the following reactions: N3+ (1s2 2s2 1S) + He (1s2 1S) → N2+ (1s2 2s2p2 2D) + He+ (1s 2S) + 10.3 eV, O3+ (1s2 2s2 2p 2P) + He (1s2 1S) → O2+ (1s2 2s 2p3 3P) + He+ (1s 2S) + 12.7 eV, and O3+ (1s2 2s2 2p 2P) + He (1s2 1S) → O2+ (1s2 2s 2p3 3D) + He+ (1s 2S) + 15.5 eV. In the N3+-He system, the DCSs for the reaction are zero at the center-of-mass angle θcm = 0 and show a peak at a certain angle and a shoulder at a larger angle. In the O3+-He system, the DCSs are again zero at θcm = 0. The capture process to the O2+ (1s2 2s 2p3 3P) state is mainly observed at smaller scattering angles, and the reaction to the O2+ (1s2 2s 2p3 3D) state becomes dominant with increasing scattering angle. A classical trajectory analysis within the two-state approximation based on the ab initio potentials for (NHe)3+ revealed that the transfer excitation of a two-electron process takes place through a single crossing of the relevant potentials.

  8. Multiphoton excitation of fluorescent DNA base analogs.

    PubMed

    Katilius, Evaldas; Woodbury, Neal W

    2006-01-01

    Multiphoton excitation was used to investigate properties of the fluorescent DNA base analogs, 2-aminopurine (2AP) and 6-methylisoxanthopterin (6MI). 2-aminopurine, a fluorescent analog of adenine, was excited by three-photon absorption. Fluorescence correlation measurements were attempted to evaluate the feasibility of using three-photon excitation of 2AP for DNA-protein interaction studies. However, high excitation power and long integration times needed to acquire high signal-to-noise fluorescence correlation curves render three-photon excitation FCS of 2AP not very useful for studying DNA base dynamics. The fluorescence properties of 6-methylisoxanthopterin, a guanine analog, were investigated using two-photon excitation. The two-photon absorption cross-section of 6MI was estimated to be about 2.5 x 10(-50) cm(4)s (2.5 GM units) at 700 nm. The two-photon excitation spectrum was measured in the spectral region from 700 to 780 nm; in this region the shape of the two-photon excitation spectrum is very similar to the shape of single-photon excitation spectrum in the near-UV spectral region. Two-photon excitation of 6MI is suitable for fluorescence correlation measurements. Such measurements can be used to study DNA base dynamics and DNA-protein interactions over a broad range of time scales.

  9. Excited Baryons in Holographic QCD

    SciTech Connect

    de Teramond, Guy F.; Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins

    2011-11-08

    The light-front holographic QCD approach is used to describe baryon spectroscopy and the systematics of nucleon transition form factors. Baryon spectroscopy and the excitation dynamics of nucleon resonances encoded in the nucleon transition form factors can provide fundamental insight into the strong-coupling dynamics of QCD. The transition from the hard-scattering perturbative domain to the non-perturbative region is sensitive to the detailed dynamics of confined quarks and gluons. Computations of such phenomena from first principles in QCD are clearly very challenging. The most successful theoretical approach thus far has been to quantize QCD on discrete lattices in Euclidean space-time; however, dynamical observables in Minkowski space-time, such as the time-like hadronic form factors are not amenable to Euclidean numerical lattice computations.

  10. Microwave Excitation In ECRIS plasmas

    SciTech Connect

    Ciavola, G.; Celona, L.; Consoli, F.; Gammino, S.; Maimone, F.; Barbarino, S.; Catalano, R. S.; Mascali, D.; Tumino, L.

    2007-09-28

    A number of phenomena related to the electron cyclotron resonance ion sources (ECRIS) has been better understood recently by means of the improvement of comprehension of the coupling mechanism between microwave generators and ECR plasma. In particular, the two frequency heating and the frequency tuning effect, that permit a remarkable increase of the current for the highest charge states ions, can be explained in terms of modes excitation in the cylindrical cavity of the plasma chamber. Calculations based on this theoretical approach have been performed, and the major results will be presented. It will be shown that the electric field pattern completely changes for a few MHz frequency variations and the changes in ECRIS performances can be correlated to the efficiency of the power transfer between electromagnetic field and plasma.

  11. Propagation failure in excitable media

    SciTech Connect

    Hagberg, A.; Meron, E.

    1998-01-01

    We study a mechanism of pulse propagation failure in excitable media where stable traveling pulse solutions appear via a subcritical pitchfork bifurcation. The bifurcation plays a key role in that mechanism. Small perturbations, externally applied or from internal instabilities, may cause pulse propagation failure (wave breakup) provided the system is close enough to the bifurcation point. We derive relations showing how the pitchfork bifurcation is unfolded by weak curvature or advective field perturbations and use them to demonstrate wave breakup. We suggest that the recent observations of wave breakup in the Belousov-Zhabotinsky reaction induced by either an electric field [J.J. Taboada {ital et al.}. Chaos {bold 4}, 519 (1994)] or a transverse instability [M. Markus, G. Kloss, and I. Kusch, Nature (London) {bold 371}, 402 (1994)] are manifestations of this mechanism. {copyright} {ital 1998} {ital The American Physical Society}

  12. Statistical dynamo theory: Mode excitation.

    PubMed

    Hoyng, P

    2009-04-01

    We compute statistical properties of the lowest-order multipole coefficients of the magnetic field generated by a dynamo of arbitrary shape. To this end we expand the field in a complete biorthogonal set of base functions, viz. B= summation operator_{k}a;{k}(t)b;{k}(r) . The properties of these biorthogonal function sets are treated in detail. We consider a linear problem and the statistical properties of the fluid flow are supposed to be given. The turbulent convection may have an arbitrary distribution of spatial scales. The time evolution of the expansion coefficients a;{k} is governed by a stochastic differential equation from which we infer their averages a;{k} , autocorrelation functions a;{k}(t)a;{k *}(t+tau) , and an equation for the cross correlations a;{k}a;{l *} . The eigenfunctions of the dynamo equation (with eigenvalues lambda_{k} ) turn out to be a preferred set in terms of which our results assume their simplest form. The magnetic field of the dynamo is shown to consist of transiently excited eigenmodes whose frequency and coherence time is given by Ilambda_{k} and -1/Rlambda_{k} , respectively. The relative rms excitation level of the eigenmodes, and hence the distribution of magnetic energy over spatial scales, is determined by linear theory. An expression is derived for |a;{k}|;{2}/|a;{0}|;{2} in case the fundamental mode b;{0} has a dominant amplitude, and we outline how this expression may be evaluated. It is estimated that |a;{k}|;{2}/|a;{0}|;{2} approximately 1/N , where N is the number of convective cells in the dynamo. We show that the old problem of a short correlation time (or first-order smoothing approximation) has been partially eliminated. Finally we prove that for a simple statistically steady dynamo with finite resistivity all eigenvalues obey Rlambda_{k}<0 .

  13. Excitation of interstellar hydrogen chloride

    NASA Technical Reports Server (NTRS)

    Neufild, David A.; Green, Sheldon

    1994-01-01

    We have computed new rate coefficients for the collisional excitation of HCl by He, in the close-coupled formalism and using an interaction potential determined recently by Willey, Choong, & DeLucia. Results have been obtained for temperatures between 10 K and 300 K. With the use of the infinite order sudden approximation, we have derived approximate expressions of general applicability which may be used to estimate how the rate constant for a transition (J to J prime) is apportioned among the various hyperfine states F prime of the final state J prime. Using these new rate coefficients, we have obtained predictions for the HCl rotational line strengths expected from a dense clump of interstellar gas, as a function of the HCl fractional abundance. Over a wide range of HCl abundances, we have found that the line luminosities are proportional to abundance(exp 2/3), a general result which can be explained using a simple analytical approximation. Our model for the excitation of HCl within a dense molecular cloud core indicates that the J = 1 goes to 0 line strengths measured by Blake, Keene, & Phillips toward the Orion Molecular Cloud (OMC-1) imply a fractional abundance n(HCl)/n(H2) approximately 2 x 10(exp -9), a value which amounts to only approximately 0.3% of the cosmic abundance of chlorine nuclei. Given a fractional abundance of 2 x 10(exp -9), the contribution of HCl emission to the total radiative cooling of a dense clump is small. For Orion, we predict a flux approximately 10(exp -19) W/sq cm for the HCl J = 3 goes to 2 line near 159.8 micrometers, suggesting that the strength of this line could be measured using the Infrared Space Observatory.

  14. Circadian regulation of human cortical excitability

    PubMed Central

    Ly, Julien Q. M.; Gaggioni, Giulia; Chellappa, Sarah L.; Papachilleos, Soterios; Brzozowski, Alexandre; Borsu, Chloé; Rosanova, Mario; Sarasso, Simone; Middleton, Benita; Luxen, André; Archer, Simon N.; Phillips, Christophe; Dijk, Derk-Jan; Maquet, Pierre; Massimini, Marcello; Vandewalle, Gilles

    2016-01-01

    Prolonged wakefulness alters cortical excitability, which is essential for proper brain function and cognition. However, besides prior wakefulness, brain function and cognition are also affected by circadian rhythmicity. Whether the regulation of cognition involves a circadian impact on cortical excitability is unknown. Here, we assessed cortical excitability from scalp electroencephalography (EEG) responses to transcranial magnetic stimulation in 22 participants during 29 h of wakefulness under constant conditions. Data reveal robust circadian dynamics of cortical excitability that are strongest in those individuals with highest endocrine markers of circadian amplitude. In addition, the time course of cortical excitability correlates with changes in EEG synchronization and cognitive performance. These results demonstrate that the crucial factor for cortical excitability, and basic brain function in general, is the balance between circadian rhythmicity and sleep need, rather than sleep homoeostasis alone. These findings have implications for clinical applications such as non-invasive brain stimulation in neurorehabilitation. PMID:27339884

  15. 1s22p3 and 1s22s23l, l = s,p,d, excited states of boron isoelectronic series from explicitly correlated wave functions.

    PubMed

    Gálvez, F J; Buendía, E; Sarsa, A

    2005-07-15

    For some members of the boron isoelectronic series and starting from explicitly correlated wave functions, six low-lying excited states have been studied. Three of them arise from the 1s(2)2p(3) configuration, and the other three from the 1s(2)2s(2)3l, l = s,p,d, configurations. This work follows a previous one on both the 1s(2)2s(2)2p-(2)P ground state and the four excited states coming from the 1s(2)2s2p(2) configuration. Energies, one- and two-body densities in position space and some other two-body properties in position and momentum spaces have been obtained. A systematic analysis of the energetic ordering of the states as a function of the total orbital angular momentum and spin is performed in terms of the electron-nucleus and electron-electron potential energies and the role of the angular correlation is discussed. All calculations have been carried out by using the Monte Carlo algorithm.

  16. Collisional energy transfer from excited nitrogen dioxide

    SciTech Connect

    Patten, K.O.

    1991-05-01

    The radiative lifetimes of gaseous nitrogen dioxide excited by pulsed, tunable dye laser radiation are determined for excitation wavelengths ranging from 400 to 750 nm. When the data are expressed in the form of zero-pressure radiative rate constants (k{sub 0}/s{sup {minus}1}), they fit a linear equation with respect to excitation energy. This fit predicts a radiative lifetime of 64 {mu}s for 400 nm excitation and 102 {mu}s at 750 nm. The effects of pressure, observation delay time, and wavelength range of the fluorescence detection apparatus are determined for both radiative lifetime and quenching constant. Dispersed fluorescence spectra from excited nitrogen dioxide are analyzed into three-parameter functions that approximate the corresponding excited state population distributions. Energy transfer from nitrogen dioxide excited at 532 nm and colliding with thirteen buffer gases is studied by this population deconvolution method. The energy removal rate constants increase in the order Ne < Ar < Kr < Xe < He < CO < N{sub 2} < O{sub 2} < NO < NO{sub 2} < CO{sub 2} < SF{sub 6} < SO{sub 2}. The energy transfer rate constant is strongly correlated with the number of degrees of freedom of the buffer molecule and with low vibrational frequencies of the buffer molecule. Population deconvolution from excited nitrogen dioxide fluorescence spectra is again employed to find energy removal rate constants for the NO {sub 2}{sup *}-NO{sub 2} collisions, excited by dye laser at 475.34, 435.04, and 400.00 nm. The energy transfer rate constant increases with decreasing excitation wavelength. The energy removal rate constant between 400 and 532 nm excitation increases as the (3.6 {plus minus} 0.4) power of the excitation photon energy. 76 refs., 67 figs., 16 tabs.

  17. Excitement in shame: the price we pay.

    PubMed

    Aledort, Stewart L

    2014-01-01

    This paper explores the role of excitement in shame, extending the theoretical underpinnings of my work (Aledort, 2002, 2003, 2008, 2009) on narcissism and the omnipotent child syndrome. Shame, excitement, and early narcissistic self-states are complexly intermingled, each influencing the other. Empathy alone is insufficient; the passion connected to shame can be easily hidden. Detailed case studies describe a model for working with the excitement in shame, how it functions, and how it gets resolved.

  18. Spatially encoded multiple-quantum excitation.

    PubMed

    Ridge, Clark D; Borvayeh, Leila; Walls, Jamie D

    2013-05-28

    In this work, we present a simple method to spatially encode the transition frequencies of nuclear spin transitions and to read out these frequencies within a single scan. The experiment works by combining pulsed field gradients with an excitation sequence that selectively excites spin transitions within certain sample regions. After the initial excitation, imaging the resulting ẑ-magnetization is used to determine the locations where the excitations occurred, from which the corresponding transition frequencies are determined. Simple experimental demonstrations of this technique on one- and two-spin systems are presented.

  19. Laser Excited Fluorescence Studies Of Black Liquor

    NASA Astrophysics Data System (ADS)

    Horvath, J. J.; Semerjian, H. G.

    1986-10-01

    Laser excited fluorescence of black liquor was investigated as a possible monitoring technique for pulping processes. A nitrogen pumped dye laser was used to examine the fluorescence spectrum of black liquor solutions. Various excitation wavelengths were used between 290 and 403 nm. Black liquor fluorescence spectra were found to vary with both excitation wavelength and black liquor concentration. Laser excited fluorescence was found to be a sensitive technique for measurement of black liquor with good detection limits and linear response over a large dynamic range.

  20. Single determinant calculations of excited state polarizabilities

    NASA Astrophysics Data System (ADS)

    Jonsson, Dan; Norman, Patrick; Ågren, Hans

    1997-12-01

    We apply response theory to simulate excited state polarizabilities emphasizing the possibility to do so by means of optimization of a ground state single determinant only. The excited state polarizabilities are given by the double residues of the cubic response functions. A set of molecules with varying ground state configurations and properties have been considered: water, ozone, formaldehyde, ethylene, butadiene, cyclobutadiene, pyridine, pyrazine and s-tetrazine. The results have been compared to excited state experiments where available and with linear response calculations of the multi-determinant optimized excited state. It is shown that calculations of excited state polarizabilities based on a ground state optimized single determinant work well for most of the cases investigated. This contention is exemplified by the fact the gas phase value from an electrochromism experiment for the polarizability of the 1 1B2 excited state of formaldehyde is better reproduced by ground state cubic response theory than by the corresponding separate state linear response function calculation, and by that the calculations call for an experimental reinvestigation of the excited state polarizabilities of s-tetrazine. A few prerequisites are given: The excited state should be isolated in energy, the ordering of the main contributing states should be reproduced, and the geometric conformation of the excited state in question should not be very different from the ground state geometry. The computational and formal advantages of the approach are discussed.

  1. Quasiparticle excitations in superdeformed [sup 192]Hg

    SciTech Connect

    Fallon, P. ); Lauritsen, T.; Ahmad, I.; Carpenter, M.P. ); Cederwall, B.; Clark, R.M. ); Crowell, B. ); Deleplanque, M.A.; Diamond, R.M. ); Gall, B.; Hannachi, F. ); Henry, R.G.; Janssens, R.V.F.; Khoo, T.L. ); Korichi, A. ); Lee, I.Y.; Macchiavelli, A.O. (Nuclear Science Division, Lawrence

    1995-04-01

    For the first time, two excited superdeformed (SD) bands have been observed in the double closed shell superdeformed nucleus [sup 192]Hg. One of the SD bands exhibits a pronounced peak in the dynamic moment of inertia which is interpreted as a crossing between two excited SD configurations involving the [ital N]=7 intruder and the [512]5/2 orbitals. This is only the second occurrence of such a crossing in a SD nucleus around [ital A]=190. The second excited SD band has near identical transition energies to an excited SD band in [sup 191]Hg.

  2. Local pair natural orbitals for excited states

    NASA Astrophysics Data System (ADS)

    Helmich, Benjamin; Hättig, Christof

    2011-12-01

    We explore how in response calculations for excitation energies with wavefunction based (e.g., coupled cluster) methods the number of double excitation amplitudes can be reduced by means of truncated pair natural orbital (PNO) expansions and localized occupied orbitals. Using the CIS(D) approximation as a test model, we find that the number of double excitation amplitudes can be reduced dramatically with minor impact on the accuracy if the excited state wavefunction is expanded in state-specific PNOs generated from an approximate first-order guess wavefunction. As for ground states, the PNO truncation error can also for excitation energies be controlled by a single threshold related to generalized natural occupation numbers. The best performance is found with occupied orbitals which are localized by the Pipek-Mezey localization. For a large test set of excited states we find with this localization that already a PNO threshold of 10-8-10-7, corresponding to an average of only 40-80 PNOs per pair, is sufficient to keep the PNO truncation error for vertical excitation energies below 0.01 eV. This is a significantly more rapid convergence with the number doubles amplitudes than in domain-based local response approaches. We demonstrate that the number of significant excited state PNOs scales asymptotically linearly with the system size in the worst case of completely delocalized excitations and sub-linearly whenever the chromophore does not increase with the system size. Moreover, we observe that the flexibility of state-specific PNOs to adapt to the character of an excitation allows for an almost unbiased treatment of local, delocalized and charge transfer excited states.

  3. Local pair natural orbitals for excited states.

    PubMed

    Helmich, Benjamin; Hättig, Christof

    2011-12-07

    We explore how in response calculations for excitation energies with wavefunction based (e.g., coupled cluster) methods the number of double excitation amplitudes can be reduced by means of truncated pair natural orbital (PNO) expansions and localized occupied orbitals. Using the CIS(D) approximation as a test model, we find that the number of double excitation amplitudes can be reduced dramatically with minor impact on the accuracy if the excited state wavefunction is expanded in state-specific PNOs generated from an approximate first-order guess wavefunction. As for ground states, the PNO truncation error can also for excitation energies be controlled by a single threshold related to generalized natural occupation numbers. The best performance is found with occupied orbitals which are localized by the Pipek-Mezey localization. For a large test set of excited states we find with this localization that already a PNO threshold of 10(-8)-10(-7), corresponding to an average of only 40-80 PNOs per pair, is sufficient to keep the PNO truncation error for vertical excitation energies below 0.01 eV. This is a significantly more rapid convergence with the number doubles amplitudes than in domain-based local response approaches. We demonstrate that the number of significant excited state PNOs scales asymptotically linearly with the system size in the worst case of completely delocalized excitations and sub-linearly whenever the chromophore does not increase with the system size. Moreover, we observe that the flexibility of state-specific PNOs to adapt to the character of an excitation allows for an almost unbiased treatment of local, delocalized and charge transfer excited states.

  4. Multi-photon excitation microscopy

    PubMed Central

    Diaspro, Alberto; Bianchini, Paolo; Vicidomini, Giuseppe; Faretta, Mario; Ramoino, Paola; Usai, Cesare

    2006-01-01

    Multi-photon excitation (MPE) microscopy plays a growing role among microscopical techniques utilized for studying biological matter. In conjunction with confocal microscopy it can be considered the imaging workhorse of life science laboratories. Its roots can be found in a fundamental work written by Maria Goeppert Mayer more than 70 years ago. Nowadays, 2PE and MPE microscopes are expected to increase their impact in areas such biotechnology, neurobiology, embryology, tissue engineering, materials science where imaging can be coupled to the possibility of using the microscopes in an active way, too. As well, 2PE implementations in noninvasive optical bioscopy or laser-based treatments point out to the relevance in clinical applications. Here we report about some basic aspects related to the phenomenon, implications in three-dimensional imaging microscopy, practical aspects related to design and realization of MPE microscopes, and we only give a list of potential applications and variations on the theme in order to offer a starting point for advancing new applications and developments. PMID:16756664

  5. Multi-photon excitation microscopy.

    PubMed

    Diaspro, Alberto; Bianchini, Paolo; Vicidomini, Giuseppe; Faretta, Mario; Ramoino, Paola; Usai, Cesare

    2006-06-06

    Multi-photon excitation (MPE) microscopy plays a growing role among microscopical techniques utilized for studying biological matter. In conjunction with confocal microscopy it can be considered the imaging workhorse of life science laboratories. Its roots can be found in a fundamental work written by Maria Goeppert Mayer more than 70 years ago. Nowadays, 2PE and MPE microscopes are expected to increase their impact in areas such biotechnology, neurobiology, embryology, tissue engineering, materials science where imaging can be coupled to the possibility of using the microscopes in an active way, too. As well, 2PE implementations in noninvasive optical bioscopy or laser-based treatments point out to the relevance in clinical applications. Here we report about some basic aspects related to the phenomenon, implications in three-dimensional imaging microscopy, practical aspects related to design and realization of MPE microscopes, and we only give a list of potential applications and variations on the theme in order to offer a starting point for advancing new applications and developments.

  6. Magnetic excitations in plutonium monoantimonide

    SciTech Connect

    Lander, G.H.; Stirling, W.G.; Mignod, J.R.; Spirlet, J.C.; Rebezant, J.; Vogt, O.

    1985-01-01

    Neutron inelastic scattering studies of uranium compounds have illustrated the complexity of the interactions in this part of periodic table. Recently, large crystals of plutonium compounds have been grown at the Transuranium Institute, and we report here the first neutron inelastic scattering on PuSb. A monodomain sample of ferromagnetic PuSb was prepared by cooling in a field with H vector parallel to (001). We observe an almost dispersionless magnetic transition, assigned to arise within the GAMMA/sub 8/ ground state, with an energy of 4.3 THz. Surprisingly, the lowest frequency (3.5 THz) excitation occurs at the zone boundary, with a polarization along the wavevector. Theoretical predictions give the spin-wave gap and GAMMA/sub 8/-GAMMA/sub 7/ crystal field splitting (> 12 THz experimentally), but are presently unable to explain the lifting of the degeneracy of the longitudinal and transverse modes and the minimum of the former at the zone boundary. 7 refs., 3 figs.

  7. Nuclear excitations and reaction mechanisms

    SciTech Connect

    Fallieros, S.; Levin, F.S.

    1990-08-01

    The main theme of this report is the study and interpretation of the sequence of events that occur during the collisions of nuclear particles. Some of the processes discussed in parts A and B involve short range interactions; others involve interactions of long range. In most of part A one of the particles in the initial or in the final state (or in both) is a photon, which serves as a probe of the second particle, which may be a nucleus, a proton, a pion or any other hadron. The complexity of the processes taking place during the collisions makes it necessary to simplify some aspects of the physical problem. This leads to the introduction of modals which are used to describe a limited number of features in as much detail as possible. The main interest is the understanding of the hadronic excitations which result from the absorption of a photon and the determination of the fundamental structure constants of the target particle. In part B, all the particles are hadrons. The purpose here is to develop and apply optimal quantal methods appropriate for describing the interacting systems. Of particular interest are three-particle collision systems in which the final state consists of three free particles. Part B also considers the process of nuclear fusion as catalyzed by bound muons.

  8. Excitation-scanning hyperspectral imaging microscope.

    PubMed

    Favreau, Peter F; Hernandez, Clarissa; Heaster, Tiffany; Alvarez, Diego F; Rich, Thomas C; Prabhat, Prashant; Leavesley, Silas J

    2014-04-01

    Hyperspectral imaging is a versatile tool that has recently been applied to a variety of biomedical applications, notably live-cell and whole-tissue signaling. Traditional hyperspectral imaging approaches filter the fluorescence emission over a broad wavelength range while exciting at a single band. However, these emission-scanning approaches have shown reduced sensitivity due to light attenuation from spectral filtering. Consequently, emission scanning has limited applicability for time-sensitive studies and photosensitive applications. In this work, we have developed an excitation-scanning hyperspectral imaging microscope that overcomes these limitations by providing high transmission with short acquisition times. This is achieved by filtering the fluorescence excitation rather than the emission. We tested the efficacy of the excitation-scanning microscope in a side-by-side comparison with emission scanning for detection of green fluorescent protein (GFP)-expressing endothelial cells in highly autofluorescent lung tissue. Excitation scanning provided higher signal-to-noise characteristics, as well as shorter acquisition times (300  ms/wavelength band with excitation scanning versus 3  s/wavelength band with emission scanning). Excitation scanning also provided higher delineation of nuclear and cell borders, and increased identification of GFP regions in highly autofluorescent tissue. These results demonstrate excitation scanning has utility in a wide range of time-dependent and photosensitive applications.

  9. What Gets a Cell Excited? Kinky Curves

    ERIC Educational Resources Information Center

    Kay, Alan R.

    2014-01-01

    Hodgkin and Huxley's (5) revealing the origins of cellular excitability is one of the great triumphs of physiology. In an extraordinarily deft series of papers, they were able to measure the essential electrical characteristics of neurons and synthesize them into a quantitative model that accounts for the excitability of neurons and other…

  10. Multimode optical fibers: steady state mode exciter.

    PubMed

    Ikeda, M; Sugimura, A; Ikegami, T

    1976-09-01

    The steady state mode power distribution of the multimode graded index fiber was measured. A simple and effective steady state mode exciter was fabricated by an etching technique. Its insertion loss was 0.5 dB for an injection laser. Deviation in transmission characteristics of multimode graded index fibers can be avoided by using the steady state mode exciter.

  11. Excitation of helium ion by positron impact

    SciTech Connect

    Khan, P.; Ghosh, A.S.

    1986-01-01

    Three (1s,2s,2p) and five (1s,2s,2p,3s-bar,3p-bar) -state close-coupling methods have been employed to calculate the n = 2 excitation cross sections of helium ion by positron impact. The effect of pseudostate is found to be very pronounced in the case of 1s-2s excitation.

  12. Coulomb excitation of radioactive {sup 79}Pb

    SciTech Connect

    Lister, C.J.; Blumenthal, D.; Davids, C.N.

    1995-08-01

    The technical challenges expected in experiments with radioactive beams can already be explored by using ions produced in primary reactions. In addition, the re-excitation of these ions by Coulomb excitation allows a sensitive search for collective states that are well above the yrast line. We are building an experiment to study Coulomb excitation of radioactive ions which are separated from beam particles by the Fragment Mass Analyzer. An array of gamma detectors will be mounted at the focal plane to measure the gamma radiation following re-excitation. Five Compton-suppressed Ge detectors and five planar LEPS detectors will be used. The optimum experiment of this type appears to be the study of {sup 79}Rb following the {sup 24}Mg ({sup 58}Ni,3p) reaction. We calculate that about 5 x 10{sup 5} {sup 79}Rb nuclei/second will reach the excitation foil. This rubidium isotope was selected for study as it is strongly produced and is highly deformed, so easily re-excited. The use of a {sup 58}Ni re-excitation foil offers the best yields. After re-excitation the ions will be subsequently transported into a shielded beamdump to prevent the accumulation of activity.

  13. Excitations in Topological Superfluids and Superconductors

    NASA Astrophysics Data System (ADS)

    Wu, Hao

    In this thesis I present the theoretical work on Fermionic surface states, and %the bulk Bosonic collective excitations in topological superfluids and superconductors. Broken symmetries %Bulk-edge correspondence in topological condensed matter systems have implications for the spectrum of Fermionic excitations confined on surfaces or topological defects. (Abstract shortened by ProQuest.).

  14. Excitation-scanning hyperspectral imaging microscope

    PubMed Central

    Favreau, Peter F.; Hernandez, Clarissa; Heaster, Tiffany; Alvarez, Diego F.; Rich, Thomas C.; Prabhat, Prashant; Leavesley, Silas J.

    2014-01-01

    Abstract. Hyperspectral imaging is a versatile tool that has recently been applied to a variety of biomedical applications, notably live-cell and whole-tissue signaling. Traditional hyperspectral imaging approaches filter the fluorescence emission over a broad wavelength range while exciting at a single band. However, these emission-scanning approaches have shown reduced sensitivity due to light attenuation from spectral filtering. Consequently, emission scanning has limited applicability for time-sensitive studies and photosensitive applications. In this work, we have developed an excitation-scanning hyperspectral imaging microscope that overcomes these limitations by providing high transmission with short acquisition times. This is achieved by filtering the fluorescence excitation rather than the emission. We tested the efficacy of the excitation-scanning microscope in a side-by-side comparison with emission scanning for detection of green fluorescent protein (GFP)-expressing endothelial cells in highly autofluorescent lung tissue. Excitation scanning provided higher signal-to-noise characteristics, as well as shorter acquisition times (300  ms/wavelength band with excitation scanning versus 3  s/wavelength band with emission scanning). Excitation scanning also provided higher delineation of nuclear and cell borders, and increased identification of GFP regions in highly autofluorescent tissue. These results demonstrate excitation scanning has utility in a wide range of time-dependent and photosensitive applications. PMID:24727909

  15. What Gets a Cell Excited? Kinky Curves

    ERIC Educational Resources Information Center

    Kay, Alan R.

    2014-01-01

    Hodgkin and Huxley's (5) revealing the origins of cellular excitability is one of the great triumphs of physiology. In an extraordinarily deft series of papers, they were able to measure the essential electrical characteristics of neurons and synthesize them into a quantitative model that accounts for the excitability of neurons and other…

  16. Study of excited nucleons and their structure

    SciTech Connect

    Burkert, Volker D.

    2014-01-01

    Recent advances in the study of excited nucleons are discussed. Much of the progress has been achieved due to the availability of high precision meson production data in the photoproduction and electroproduction sectors, the development of multi-channel partial wave analysis techniques, and advances in Lattice QCD with predictions of the full excitation spectrum.

  17. Multiphoton excited fluorescence spectroscopy of biomolecular systems

    NASA Astrophysics Data System (ADS)

    Birch, David J. S.

    2001-09-01

    Recent work on the emerging application of multiphoton excitation to fluorescence studies of biomolecular dynamics and structure is reviewed. The fundamental principles and experimental techniques of multiphoton excitation are outlined, fluorescence lifetimes, anisotropy and spectra in membranes, proteins, hydrocarbons, skin, tissue and metabolites are featured, and future opportunities are highlighted.

  18. Ensemble density functional theory method correctly describes bond dissociation, excited state electron transfer, and double excitations

    SciTech Connect

    Filatov, Michael; Huix-Rotllant, Miquel; Burghardt, Irene

    2015-05-14

    State-averaged (SA) variants of the spin-restricted ensemble-referenced Kohn-Sham (REKS) method, SA-REKS and state-interaction (SI)-SA-REKS, implement ensemble density functional theory for variationally obtaining excitation energies of molecular systems. In this work, the currently existing version of the SA-REKS method, which included only one excited state into the ensemble averaging, is extended by adding more excited states to the averaged energy functional. A general strategy for extension of the REKS-type methods to larger ensembles of ground and excited states is outlined and implemented in extended versions of the SA-REKS and SI-SA-REKS methods. The newly developed methods are tested in the calculation of several excited states of ground-state multi-reference systems, such as dissociating hydrogen molecule, and excited states of donor–acceptor molecular systems. For hydrogen molecule, the new method correctly reproduces the distance dependence of the lowest excited state energies and describes an avoided crossing between the doubly excited and singly excited states. For bithiophene–perylenediimide stacked complex, the SI-SA-REKS method correctly describes crossing between the locally excited state and the charge transfer excited state and yields vertical excitation energies in good agreement with the ab initio wavefunction methods.

  19. Excited States of Non-Isolated Chromophores

    NASA Astrophysics Data System (ADS)

    Matsika, S.; Kozak, C.; Kistler, K.

    2009-06-01

    The photophysical and photochemical behavior of nucleobases is very important because of their biological role as the building blocks in DNA and RNA. Great progress has been made in understanding the excited-state properties of single bases. In order to understand the photophysical properties of nucleobases in complex environments we have investigated their excited states (a) in aqueous solutions and (b) as π-stacked dimers in DNA. The solvatochromic shifts of the excited states of pyrimidine nucleobases in aqueous solution have been investigated using a combined QM/MM procedure where the quantum mechanical solute is described using high level multireference configuration interaction methods while molecular dynamics simulations are used to obtain the structure of the solvent around the solute in an average way. The excited states of π-stacked nucleobases have also been investigated using various ab initio methods. The effect of the environment on the excited states and conical intersections is investigated.

  20. Numerical simulation of excited jet mixing layers

    NASA Astrophysics Data System (ADS)

    Scott, J. N.; Hankey, W. L.

    1987-01-01

    A numerical simulation of unsteady flow in jet mixing layers, both with and without external excitation, has been performed by solving the time-dependent compressible Navier-Stokes equations. Computations were performed on a CRAY X-MP computer using MacCormick's explicit finite difference algorithm. Different excitation methods were investigated and were shown to be very effective in controlling the well organized periodic production, shedding and pairing of large scale vortex structures. It is found that pressure excitation was generally more effective than temperature excitation, and that grid refinement results in substantial improvement in the resolution of unsteady features. The location and orientation, in addition to the frequency, of the excitation source are shown to have a significant influence on the production and interaction of large scale vortex structures in the jet mixing layer.

  1. NMR with excitation modulated by Frank sequences

    NASA Astrophysics Data System (ADS)

    Blümich, Bernhard; Gong, Qingxia; Byrne, Eimear; Greferath, Marcus

    2009-07-01

    Miniaturized NMR is of growing importance in bio-, chemical, and -material sciences. Other than the magnet, bulky components are the radio-frequency power amplifier and the power supply or battery pack. We show that constant flip-angle excitation with phase modulation following a particular type of polyphase perfect sequences results in low peak excitation power at high response peak power. It has ideal power distribution in both the time domain and the frequency domain. A savings in peak excitation power of six orders of magnitude has been realized compared to conventionally pulsed excitation. Among others, the excitation promises to be of use for button-cell operated miniature NMR devices as well as for complying with specific-absorption-rate regulations in high-field medical imaging.

  2. Effects of core turbulence on jet excitability

    NASA Technical Reports Server (NTRS)

    Mankbadi, Reda R.; Raman, Ganesh; Rice, Edward J.

    1989-01-01

    The effects of varying freestream core turbulence on the evolution of a circular jet with and without tonal excitation are examined. Measurements are made on an 8.8 cm diameter jet at a Mach number of 0.3. The jet is excitated by plane waves at Strouhal number 0.5. For the excited and unexcited cases the turbulence level is varied by screens and grids placed upstream of the nozzle exit. The experiment results are compared with a theoretical model which incorporates a variable core turbulence and considers the energy interactions between the mean flow, the turbulence and the forced component. Both data and theory indicate that increasing the freestream turbulence diminishes the excitability of the jet and reduces the effect of excitation on the spreading rate of the jet.

  3. Loss of excitation of synchronous generator

    NASA Astrophysics Data System (ADS)

    Krištof, Vladimír; Mešter, Marián

    2017-01-01

    This paper presents results of study of loss-of-excitation phenomena simulations. Loss of excitation is a very common fault in synchronous machine operating and can be caused by short circuit of the field winding, unexpected field breaker open or loss-of-excitation relay mal-operation. According to the statistic [1], the generator failure due to loss-of-excitation accounts for 69% of all generator failures. There has been concern over possible incorrect operation of the relay when operating the generator in the under-excited region, during stable transient swings and during major system disturbances. This article can serve as inputs for system operators in preparation of operation area or protection relaying area.

  4. Localization of electrons and excitations

    NASA Astrophysics Data System (ADS)

    Larsson, Sven

    2006-07-01

    Electrons, electron holes, or excitations in finite or infinite 'multimer systems' may be localized or delocalized. In the theory of Hush, localization depends on the ratio Δ/ λ ( Δ/2 = coupling; λ = reorganization energy). The latter theory has been extended to the infinite system [S. Larsson, A. Klimkāns, Mol. Cryst. Liq. Cryst. 355 (2000) 217]. The metal/insulator transition often takes place abruptly as a function of Δ/ λ. It is argued that localization in a system with un-filled bands cannot be determined on the basis of Mott-Hubbard U alone, but depends on the number of accessible valence states, reorganization energy λ and coupling Δ (=2t). In fact U = 0 does not necessarily imply delocalization. The analysis here shows that there are many different situations for an insulator to metal transition. Charge transfer in doped NiO is characterized by Ni 2+ - Ni 3+ exchange while charge transfer in pure NiO is characterized by a disproportionation 2Ni 2+ → Ni + + Ni 3+. In spite of the great differences between these two cases, U has been applied without discrimination to both. The relevant localization parameters appear to be Δ and λ in the first case, with only two oxidation states, and U, Δ and λ in the second case with three oxidation states. The analysis is extended to insulator-metal transitions, giant magnetic resistance (GMR) and high Tc superconductivity (SC). λ and Δ can be determined quite accurately in quantum mechanical calculations involving only one and two monomers, respectively.

  5. Excited Delirium: A Systematic Review.

    PubMed

    Gonin, Philippe; Beysard, Nicolas; Yersin, Bertrand; Carron, Pierre-Nicolas

    2017-10-09

    We aimed to clarify the definition, epidemiology, and pathophysiology of excited delirium syndrome (ExDS) and to summarize evidence-based treatment recommendations. We conducted a systematic literature search of MEDLINE, Ovid, Web of Knowledge, and Cochrane Library for articles published to March 18, 2017. We also searched the grey literature (Google Scholar) and official police or medical expert reports to complete specific epidemiological data. Search results and full-text articles were independently assessed by two investigators and agreements between reviewers assessed with K statistics. We classified articles by study type, setting, and evidence level. After reviewing the title and abstract of 3604 references, we fully reviewed 284 potentially relevant references, from which 66 were selected for final review. Six contributed to the definition of ExDS, 24 to its epidemiology, 38 to its pathophysiology, and 27 to its management. The incidence of ExDS varies widely with medical or medico-legal context. Mortality is estimated to be as much as 8.3 to 16.5%. Patients are predominantly male. Male gender, young age, African-American race, and being overweight are independent risk factors. Pathophysiology hypotheses mostly implicate dopaminergic pathways. Most cases occur with psychostimulant use or among psychiatric patients, or both. Proposed treatments are symptomatic, often with rapid sedation with benzodiazepines or antipsychotic agents. Ketamine is suggested as an alternative. The overall quality of studies was poor. A universally recognized definition is lacking, remaining mostly syndromic and based on clinical subjective criteria. High mortality rate may be due to definition inconsistency and reporting bias. Our results suggest that ExDS is a real clinical entity, that still kills people and that has probably specific mechanisms and risk factors. No comparative study has been done to conclude whether one treatment approach is preferable to another in the case

  6. Chirp excitation of ultrasonic guided waves.

    PubMed

    Michaels, Jennifer E; Lee, Sang Jun; Croxford, Anthony J; Wilcox, Paul D

    2013-01-01

    Most ultrasonic guided wave methods require tone burst excitations to achieve some degree of mode purity while maintaining temporal resolution. In addition, it is often desirable to acquire data using multiple frequencies, particularly during method development when the best frequency for a specific application is not known. However, this process is inconvenient and time-consuming, particularly if extensive signal averaging at each excitation frequency is required to achieve a satisfactory signal-to-noise ratio. Both acquisition time and data storage requirements may be prohibitive if responses from many narrowband tone burst excitations are measured. Here chirp excitations are utilized to address the need to both test at multiple frequencies and achieve a high signal-to-noise ratio to minimize acquisition time. A broadband chirp is used to acquire data at a wide range of frequencies, and deconvolution is applied to extract multiple narrowband responses. After optimizing the frequency and duration of the desired tone burst excitation, a long-time narrowband chirp is used as the actual excitation, and the desired tone burst response is similarly extracted during post-processing. Results are shown that demonstrate the efficacy of both broadband and narrowband chirp excitations.

  7. Inclination Excitation in Compact Extrasolar Planetary Systems

    NASA Astrophysics Data System (ADS)

    Becker, Juliette; Adams, Fred C.

    2015-05-01

    The Kepler Mission has detected dozens of compact planetary systems with more than four transiting planets. This sample provides a collection of close-packed planetary systems with relatively little spread in the inclination angles of the inferred orbits. We have explored the effectiveness of dynamical mechanisms in exciting orbital inclination in this class of solar systems. The two mechanisms we discuss are self-excitation of orbital inclination in initially (nearly) coplanar planetary systems and perturbations by additional unseen larger bodies in the outer regions of the solar systems. For both of these scenarios, we determine the regimes of parameter space for which orbital inclination can be effectively excited. For compact planetary systems with the observed architectures, we find that the orbital inclination angles are not spread out appreciably through self-excitation, resulting in a negligible scatter in impact parameter and a subsequently stable transiting system. In contrast, companions in the outer solar system can be effective in driving variations of the inclination angles of the inner planetary orbits, leading to significant scatter in impact parameter and resultantly non-transiting systems. We present the results of our study, the regimes in which each excitation method - self-excitation of inclination and excitation by a perturbing secondary - are relevant, and the magnitude of the effects.

  8. Seismic excitation by space shuttles

    USGS Publications Warehouse

    Kanamori, H.; Mori, J.; Sturtevant, B.; Anderson, D.L.; Heaton, T.

    1992-01-01

    Shock waves generated by the space shuttles Columbia (August 13, 1989), Atlantis (April 11, 1991) and Discovery (September 18, 1991) on their return to Edwards Air Force Base, California, were recorded by TERRAscope (Caltech's broadband seismic network), the Caltech-U.S.G.S Southern California Seismic Network (SCSN), and the University of Southern California (USC) Los Angeles Basin Seismic Network. The spatial pattern of the arrival times exhibits hyperbolic shock fronts from which the path, velocity and altitude of the space shuttle could be determined. The shock wave was acoustically coupled to the ground, converted to a seismic wave, and recorded clearly at the broadband TERRAscope stations. The acoustic coupling occurred very differently depending on the conditions of the Earth's surface surrounding the station. For a seismic station located on hard bedrock, the shock wave (N wave) was clearly recorded with little distortion. Aside from the N wave, very little acoustic coupling of the shock wave energy to the ground occurred at these sites. The observed N wave record was used to estimate the overpressure of the shock wave accurately; a pressure change of 0.5 to 2.2 mbars was obtained. For a seismic station located close to the ocean or soft sedimentary basins, a significant amount of shock wave energy was transferred to the ground through acoustic coupling of the shock wave and the oceanic Rayleigh wave. A distinct topography such as a mountain range was found effective to couple the shock wave energy to the ground. Shock wave energy was also coupled to the ground very effectively through large man made structures such as high rise buildings and offshore oil drilling platforms. For the space shuttle Columbia, in particular, a distinct pulse having a period of about 2 to 3 seconds was observed, 12.5 s before the shock wave, with a broadband seismograph in Pasadena. This pulse was probably excited by the high rise buildings in downtown Los Angeles which were

  9. Ionization of excited xenon atoms by electrons

    NASA Astrophysics Data System (ADS)

    Erwin, Daniel A.; Kunc, Joseph A.

    2004-08-01

    Measured cross sections for electron-impact ionization of excited Xe atoms are not presently available. Therefore, we combine in this work the formalisms of the binary encounter approximation and Sommerfeld’s quantization of atomic orbits and derive from first-principles cross sections for ionization of excited atoms by electrons of low and moderate energies (up to a few hundred eV ). The approach of this work can be used to calculate the cross sections for electron-impact ionization of excited atoms and atomic ions other than xenon.

  10. Pulse Vector-Excitation Speech Encoder

    NASA Technical Reports Server (NTRS)

    Davidson, Grant; Gersho, Allen

    1989-01-01

    Proposed pulse vector-excitation speech encoder (PVXC) encodes analog speech signals into digital representation for transmission or storage at rates below 5 kilobits per second. Produces high quality of reconstructed speech, but with less computation than required by comparable speech-encoding systems. Has some characteristics of multipulse linear predictive coding (MPLPC) and of code-excited linear prediction (CELP). System uses mathematical model of vocal tract in conjunction with set of excitation vectors and perceptually-based error criterion to synthesize natural-sounding speech.

  11. Pulse Vector-Excitation Speech Encoder

    NASA Technical Reports Server (NTRS)

    Davidson, Grant; Gersho, Allen

    1989-01-01

    Proposed pulse vector-excitation speech encoder (PVXC) encodes analog speech signals into digital representation for transmission or storage at rates below 5 kilobits per second. Produces high quality of reconstructed speech, but with less computation than required by comparable speech-encoding systems. Has some characteristics of multipulse linear predictive coding (MPLPC) and of code-excited linear prediction (CELP). System uses mathematical model of vocal tract in conjunction with set of excitation vectors and perceptually-based error criterion to synthesize natural-sounding speech.

  12. Vibrational excitation of CO by blackbody radiation

    NASA Astrophysics Data System (ADS)

    Arriola, L.; Wilson, J. W.

    1985-09-01

    Lasers excited by blackbody radiation are of interest for power beaming applications in space. In such a system sunlight is collected and focused into a blackbody cavity, heating it to approximately 2000 K. An appropriate absorbing molecule is vibrationally heated but not translationally heated when passed through the blackbody cavity. The vibrationally excited gas is then mixed with a lasant resulting in laser emission. The number density of CO molecules within a blackbody radiation field of a given temperature and pressure is calculated. Such calculations show the degree of excitation achievable, under ideal conditions, from blackbody pumping.

  13. Broadband single-molecule excitation spectroscopy

    PubMed Central

    Piatkowski, Lukasz; Gellings, Esther; van Hulst, Niek F.

    2016-01-01

    Over the past 25 years, single-molecule spectroscopy has developed into a widely used tool in multiple disciplines of science. The diversity of routinely recorded emission spectra does underpin the strength of the single-molecule approach in resolving the heterogeneity and dynamics, otherwise hidden in the ensemble. In early cryogenic studies single molecules were identified by their distinct excitation spectra, yet measuring excitation spectra at room temperature remains challenging. Here we present a broadband Fourier approach that allows rapid recording of excitation spectra of individual molecules under ambient conditions and that is robust against blinking and bleaching. Applying the method we show that the excitation spectra of individual molecules exhibit an extreme distribution of solvatochromic shifts and distinct spectral shapes. Importantly, we demonstrate that the sensitivity and speed of the broadband technique is comparable to that of emission spectroscopy putting both techniques side-by-side in single-molecule spectroscopy. PMID:26794035

  14. Magnetic Excitation for Spin Vibration Testing

    NASA Technical Reports Server (NTRS)

    Johnson, Dexter; Mehmed, Oral; Brown, Gerald V.

    1997-01-01

    The Dynamic Spin Rig Laboratory (DSRL) at the NASA Lewis Research Center is a facility used for vibration testing of structures under spinning conditions. The current actuators used for excitation are electromagnetic shakers which are configured to apply torque to the rig's vertical rotor. The rotor is supported radially and axially by conventional bearings. Current operation is limited in rotational speed, excitation capability, and test duration. In an effort to enhance its capabilities, the rig has been initially equipped with a radial magnetic bearing which provides complementary excitation and shaft support. The new magnetic feature has been used in actual blade vibration tests and its performance has been favorable. Due to the success of this initial modification further enhancements are planned which include making the system fully magnetically supported. This paper reports on this comprehensive effort to upgrade the DSRL with an emphasis on the new magnetic excitation capability.

  15. The DSS-14 C-band exciter

    NASA Technical Reports Server (NTRS)

    Rowan, D. R.

    1989-01-01

    The development and implementation of a C-band exciter for use with the Block IV Receiver-Exciter Subsystem at Deep Space Station 14 (DSS-14) has been completed. The exciter supplements the standard capabilities of the Block IV system by providing a drive signal for the C-band transmitter while generating coherent translation frequencies for C-band (5-GHz) to S-band (2.2- to 2.3-GHz) Doppler extraction, C-band to L-band (1.6-GHz) zero delay measurements, and a level calibrated L-band test signal. Exciter functions are described, and a general explanation and description of the C-band uplink controller is presented.

  16. Ultrafast optical excitation of magnetic skyrmions

    PubMed Central

    Ogawa, N.; Seki, S.; Tokura, Y.

    2015-01-01

    Magnetic skyrmions in an insulating chiral magnet Cu2OSeO3 were studied by all-optical spin wave spectroscopy. The spins in the conical and skyrmion phases were excited by the impulsive magnetic field from the inverse-Faraday effect, and resultant spin dynamics were detected by using time-resolved magneto-optics. Clear dispersions of the helimagnon were observed, which is accompanied by a distinct transition into the skyrmion phase, by sweeping temperature and magnetic field. In addition to the collective excitations of skyrmions, i.e., rotation and breathing modes, several spin precession modes were identified, which would be specific to optical excitation. The ultrafast, nonthermal, and local excitation of the spin systems by photons would lead to the efficient manipulation of nano-magnetic structures. PMID:25897634

  17. Aeroacoustic characteristics of acoustically excited jets

    NASA Astrophysics Data System (ADS)

    Vlasov, E. V.; Ginevskii, A. S.; Karavosov, R. K.

    The effect of acoustic excitation on the aerodynamic and acoustic characteristics of air jets at Reynolds numbers of (0.5-4) x 10 to the 5th was studied experimentally. It is shown that high-frequency excitation (Sh sub s not greater than 1) causes a reduction in the range of the jet and an increase in broadband noise generated by the jet. High-frequency excitation (Sh sub s = 3-5) produces the opposite effect. These effects were observed for both laminar and turbulent boundary layers on the nozzle wall in the exit section. An analysis is made of the parameters of the far acoustic field of the jet as it is excited by gas-jet radiators.

  18. Acoustics of Excited Jets: A Historical Perspective

    NASA Technical Reports Server (NTRS)

    Brown, Cliffard A.

    2005-01-01

    The idea that a jet may be excited by external forcing is not new. The first published demonstration of a jet responding to external pressure waves occurred in the mid-1800's. It was not, however, until the 1950's, with the advent of commercial jet aircraft, that interest in the subject greatly increased. Researchers first used excited jets to study the structure of the jet and attempt to determine the nature of the noise sources. The jet actuators of the time limited the range (Reynolds and Mach numbers) of jets that could be excited. As the actuators improved, more realistic jets could be studied. This has led to a better understanding of how jet excitation may be used not only as a research tool to understand the flow properties and noise generation process, but also as a method to control jet noise.

  19. Nonlinear excited waves on the interventricular septum

    NASA Astrophysics Data System (ADS)

    Bekki, Naoaki; Harada, Yoshifumi; Kanai, Hiroshi

    2012-11-01

    Using a novel ultrasonic noninvasive imaging method, we observe some phase singularities in propagating excited waves on a human cardiac interventricular septum (IVS) for a healthy young male. We present a possible physical model explaining one-dimensional dynamics of phase singularities in nonlinearly excited waves on the IVS. We show that at least one of the observed phase singularities in the excited waves on the IVS can be explained by the Bekki-Nozaki hole solution of the complex Ginzburg-Landau equation without any adjustable parameters. We conclude that the complex Ginzburg-Landau equation is such a suitable model for one-dimensional dynamics of cardiac phase singularities in nonlinearly excited waves on the IVS.

  20. Faraday waves under time-reversed excitation.

    PubMed

    Pietschmann, Dirk; Stannarius, Ralf; Wagner, Christian; John, Thomas

    2013-03-01

    Do parametrically driven systems distinguish periodic excitations that are time mirrors of each other? Faraday waves in a Newtonian fluid are studied under excitation with superimposed harmonic wave forms. We demonstrate that the threshold parameters for the stability of the ground state are insensitive to a time inversion of the driving function. This is a peculiarity of some dynamic systems. The Faraday system shares this property with standard electroconvection in nematic liquid crystals [J. Heuer et al., Phys. Rev. E 78, 036218 (2008)]. In general, time inversion of the excitation affects the asymptotic stability of a parametrically driven system, even when it is described by linear ordinary differential equations. Obviously, the observed symmetry has to be attributed to the particular structure of the underlying differential equation system. The pattern selection of the Faraday waves above threshold, on the other hand, discriminates between time-mirrored excitation functions.

  1. The aeronomy of vibrationally excited ozone

    NASA Technical Reports Server (NTRS)

    Frederick, J. E.; Allen, J. E., Jr.

    1980-01-01

    Theoretical calculations show that above 80 km in the earth's atmosphere the production of vibrationally excited ozone by chemical processes leads to number densities which are usually larger than those expected for local thermodynamic equilibrium. Quenching of highly excited molecules produced in O+O2+M, O3+M provided a significant source of the lower lying states above the mesopause while the 9.6 microns emission of O3 (0,0,1) was a major sink. Analysis of available laboratory results implied that reactions involving excited ozone play a significant role in the global ozone balance despite the relatively small abundance of the molecule. However, this effect is implicit in many of the rate coefficients currently used in stratospheric calculations. In the upper mesosphere and lower thermosphere, where the excited state populations differ from those for thermal equilibrium, published reaction rate data are not necessarily applicable to aeronomic calculations.

  2. Hydrogen Bonds in Excited State Proton Transfer

    NASA Astrophysics Data System (ADS)

    Horke, D. A.; Watts, H. M.; Smith, A. D.; Jager, E.; Springate, E.; Alexander, O.; Cacho, C.; Chapman, R. T.; Minns, R. S.

    2016-10-01

    Hydrogen bonding interactions between biological chromophores and their surrounding protein and solvent environment significantly affect the photochemical pathways of the chromophore and its biological function. A common first step in the dynamics of these systems is excited state proton transfer between the noncovalently bound molecules, which stabilizes the system against dissociation and principally alters relaxation pathways. Despite such fundamental importance, studying excited state proton transfer across a hydrogen bond has proven difficult, leaving uncertainties about the mechanism. Through time-resolved photoelectron imaging measurements, we demonstrate how the addition of a single hydrogen bond and the opening of an excited state proton transfer channel dramatically changes the outcome of a photochemical reaction, from rapid dissociation in the isolated chromophore to efficient stabilization and ground state recovery in the hydrogen bonded case, and uncover the mechanism of excited state proton transfer at a hydrogen bond, which follows sequential hydrogen and charge transfer processes.

  3. Magnetic Excitation for Spin Vibration Testing

    NASA Technical Reports Server (NTRS)

    Johnson, Dexter; Mehmed, Oral; Brown, Gerald V.

    1997-01-01

    The Dynamic Spin Rig Laboratory (DSRL) at the NASA Lewis Research Center is a facility used for vibration testing of structures under spinning conditions. The current actuators used for excitation are electromagnetic shakers which are configured to apply torque to the rig's vertical rotor. The rotor is supported radially and axially by conventional bearings. Current operation is limited in rotational speed, excitation capability, and test duration. In an effort to enhance its capabilities, the rig has been initially equipped with a radial magnetic bearing which provides complementary excitation and shaft support. The new magnetic feature has been used in actual blade vibration tests and its performance has been favorable. Due to the success of this initial modification further enhancements are planned which include making the system fully magnetically supported. This paper reports on this comprehensive effort to upgrade the DSRL with an emphasis on the new magnetic excitation capability.

  4. Inclination Excitation in Extrasolar Planetary Systems

    NASA Astrophysics Data System (ADS)

    Becker, Juliette; Adams, Fred C.

    2015-01-01

    The Kepler Mission has detected dozens of planetary systems with more than four transiting planets. This sample provides a collection of planetary systems with little or no excited inclination between the inferred orbits. This present study examines the magnitude and efficacy of three potential mechanisms for exciting orbital inclination in these systems: self-excitation of orbital inclination in initially coplanar planetary systems, perturbations by larger bodies within the planetary systems, and perturbations by massive bodies external to the systems. For each of these mechanisms, we determine the regime(s) of parameter space for which orbital inclination excitation is effective. This work provides constraints on the properties (masses and orbital elements) of possible additional bodies in observed planetery systems, and on their dynamical history. One interesting application is to consider the relative size of the external perturbations both in and out of clusters.

  5. How to excite a rogue wave

    SciTech Connect

    Akhmediev, N.; Ankiewicz, A.; Soto-Crespo, J. M.

    2009-10-15

    We propose initial conditions that could facilitate the excitation of rogue waves. Understanding the initial conditions that foster rogue waves could be useful both in attempts to avoid them by seafarers and in generating highly energetic pulses in optical fibers.

  6. Mode Selective Excitation Using Coherent Control Spectroscopy

    SciTech Connect

    Singh, Ajay K.; Konradi, Jakow; Materny, Arnulf; Sarkar, Sisir K.

    2008-11-14

    Femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) gives access to ultrafast molecular dynamics. However, femtosecond laser pulses are spectrally broad and therefore coherently excite several molecular modes. While the temporal resolution is high, usually no mode-selective excitation is possible. This paper demonstrates the feasibility of selectively exciting specific molecular vibrations in solution phase with shaped fs laser excitation using a feedback-controlled optimization technique guided by an evolutionary algorithm. This approach is also used to obtain molecule-specific CARS spectra from a mixture of different substances. The optimized phase structures of the fs pulses are characterized to get insight into the control process. Possible applications of the spectrum control are discussed.

  7. Students Excited by Stellar Discovery

    NASA Astrophysics Data System (ADS)

    2011-02-01

    In the constellation of Ophiuchus, above the disk of our Milky Way Galaxy, there lurks a stellar corpse spinning 30 times per second -- an exotic star known as a radio pulsar. This object was unknown until it was discovered last week by three high school students. These students are part of the Pulsar Search Collaboratory (PSC) project, run by the National Radio Astronomy Observatory (NRAO) in Green Bank, WV, and West Virginia University (WVU). The pulsar, which may be a rare kind of neutron star called a recycled pulsar, was discovered independently by Virginia students Alexander Snider and Casey Thompson, on January 20, and a day later by Kentucky student Hannah Mabry. "Every day, I told myself, 'I have to find a pulsar. I better find a pulsar before this class ends,'" said Mabry. When she actually made the discovery, she could barely contain her excitement. "I started screaming and jumping up and down." Thompson was similarly expressive. "After three years of searching, I hadn't found a single thing," he said, "but when I did, I threw my hands up in the air and said, 'Yes!'." Snider said, "It actually feels really neat to be the first person to ever see something like that. It's an uplifting feeling." As part of the PSC, the students analyze real data from NRAO's Robert C. Byrd Green Bank Telescope (GBT) to find pulsars. The students' teachers -- Debra Edwards of Sherando High School, Leah Lorton of James River High School, and Jennifer Carter of Rowan County Senior High School -- all introduced the PSC in their classes, and interested students formed teams to continue the work. Even before the discovery, Mabry simply enjoyed the search. "It just feels like you're actually doing something," she said. "It's a good feeling." Once the pulsar candidate was reported to NRAO, Project Director Rachel Rosen took a look and agreed with the young scientists. A followup observing session was scheduled on the GBT. Snider and Mabry traveled to West Virginia to assist in the

  8. Electron impact vibrational excitation of methyl chloride

    NASA Astrophysics Data System (ADS)

    Sakaamini, Ahmad; Hargreaves, Leigh; Khakoo, Murtadha

    2016-05-01

    Low energy differential cross sections and excitation functions for vibrational excitation of CH3 Cl are presented for five vibrational features in the electron energy loss spectrum of this molecule. Electron energies range from 1 eV to 15 eV and scattering angles from 10o to 125o. Results will be compared to existing data for CH3 Cl in the literature. Funded by a NSF-AMOP-RUI Grant.

  9. Feedback Error Learning with Insufficient Excitation

    NASA Astrophysics Data System (ADS)

    Alali, Basel; Hirata, Kentaro; Sugimoto, Kenji

    This letter studies the tracking error in Multi-input Multi-output Feedback Error Learning (MIMO-FEL) system having insufficient excitation. It is shown that the error converges to zero exponentially even if the reference signal lacks the persistently excitation (PE) condition. Furthermore, by making full use of this fast convergence, we estimate the plant parameter while in operation based on frequency response. Simulation results show the effectiveness of the proposed method compared to a conventional approach.

  10. Fast pulsed excitation wiggler or undulator

    DOEpatents

    van Steenbergen, Arie

    1990-01-01

    A fast pulsed excitation, electromagnetic undulator or wiggler, employing geometrically alternating substacks of thin laminations of ferromagnetic material, together with a single turn current loop excitation of the composite assembly, of such shape and configuration that intense, spatially alternating, magnetic fields are generated; for use as a pulsed mode undulator or wiggler radiator, for use in a Free Electron Laser (FEL) type radiation source or, for use in an Inverse Free Electron Laser (IFEL) charged particle accelerator.

  11. Intrinsic asymmetry of polar motion excitation

    NASA Astrophysics Data System (ADS)

    Bizouard, C.

    2012-12-01

    Anisotropy of the pole tide and Earth triaxiality make the polar motion excitation asymmetric with respect to and y pole coordinates (Okamoto and Sasao 1977). After having proposed a general description of these non isotropic effects, we show that there are significant in light of the contemporaneous accuracy of the pole coordinates and cannot be cast aside in the interpretation of the Chandler wobble excitation

  12. Reactions and Spectroscopy of Excited Nitrenes

    DTIC Science & Technology

    1992-10-05

    34- Reactions and Spectroscopy of Excited Nitrenes 12. PERSONAL AUTHORIS) Robert D. Coombe 13.. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORT IYr.. Mo...reversee iftnecei •ry and identify by block numanbers FIELD GROUP SUB. G. chernical lasers, reactions, energy transfer, haloý:en nitrenes , iodine laser...THIS PACE INTRODUCTION This report describes progress made on the research program "Reactions and Spectroscopy of Excited Nitrenes " during the eighteen

  13. Care of the patient in excited delirium.

    PubMed

    Gordon, Cheryl; Schmelzer, Marilee

    2013-03-01

    Patients with excited delirium present a challenge to both law enforcement and health care personnel because handcuffs, the traditional method used to keep persons from harming themselves and others, may be fatal. The patient's survival depends upon rapid recognition and treatment, including chemical sedation, decreased environmental stimulation, intravenous fluids, and other supportive interventions. Excited delirium protocols should be established to ensure rapid and appropriate treatment to ensure patient survival and the safety of those caring for them.

  14. K2P2— A Photometry Pipeline for the K2 Mission

    NASA Astrophysics Data System (ADS)

    Lund, Mikkel N.; Handberg, Rasmus; Davies, Guy R.; Chaplin, William J.; Jones, Caitlin D.

    2015-06-01

    With the loss of a second reaction wheel, resulting in the inability to point continuously and stably at the same field of view, the NASA Kepler satellite recently entered a new mode of observation known as the K2 mission. The data from this redesigned mission present a specific challenge; the targets systematically drift in position on an ∼6 hr timescale, inducing a significant instrumental signal in the photometric time series—this greatly impacts the ability to detect planetary signals and perform asteroseismic analysis. Here we detail our version of a reduction pipeline for K2 target pixel data, which automatically defines masks for all targets in a given frame; extracts the target’s flux and position time series; corrects the time series based on the apparent movement on the CCD (either in 1D or 2D), combined with the correction of instrumental and/or planetary signals via the Kepler Asteroseismic Science Operations Center (KASOC) filter, thus rendering the time series ready for asteroseismic analysis; computes power spectra for all targets and identifies potential contaminations between targets. From a test of our pipeline on a sample of targets from the K2 campaign 0, the recovery of data for multiple targets increases the amount of potential light curves by a factor of ≥slant 10. Our pipeline could be applied to the upcoming TESS and PLATO 2.0 missions.

  15. Materials Data on MgFe2P2(HO)18 (SG:2) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  16. Materials Data on MnAl2P2(HO)18 (SG:2) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  17. Materials Data on MgAl2P2(HO)18 (SG:2) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  18. Materials Data on Al2P2O11F (SG:19) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-10

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  19. Materials Data on KAl2P2H5O11 (SG:14) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-04

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  20. Materials Data on Al2P2H9NO11 (SG:14) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-05

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  1. Materials Data on KAl2P2H4O11 (SG:19) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-10

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  2. Materials Data on Zr2P2O9 (SG:12) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-05-13

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  3. Materials Data on KAl2P2H5O11 (SG:19) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  4. Materials Data on KFe2P2H5O11 (SG:14) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-04-22

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  5. Materials Data on Mo2P2O11 (SG:11) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-04-22

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  6. Protein-Protein Interaction Inhibition (2P2I)-Oriented Chemical Library Accelerates Hit Discovery.

    PubMed

    Milhas, Sabine; Raux, Brigitt; Betzi, Stéphane; Derviaux, Carine; Roche, Philippe; Restouin, Audrey; Basse, Marie-Jeanne; Rebuffet, Etienne; Lugari, Adrien; Badol, Marion; Kashyap, Rudra; Lissitzky, Jean-Claude; Eydoux, Cécilia; Hamon, Véronique; Gourdel, Marie-Edith; Combes, Sébastien; Zimmermann, Pascale; Aurrand-Lions, Michel; Roux, Thomas; Rogers, Catherine; Müller, Susanne; Knapp, Stefan; Trinquet, Eric; Collette, Yves; Guillemot, Jean-Claude; Morelli, Xavier

    2016-08-19

    Protein-protein interactions (PPIs) represent an enormous source of opportunity for therapeutic intervention. We and others have recently pinpointed key rules that will help in identifying the next generation of innovative drugs to tackle this challenging class of targets within the next decade. We used these rules to design an oriented chemical library corresponding to a set of diverse "PPI-like" modulators with cores identified as privileged structures in therapeutics. In this work, we purchased the resulting 1664 structurally diverse compounds and evaluated them on a series of representative protein-protein interfaces with distinct "druggability" potential using homogeneous time-resolved fluorescence (HTRF) technology. For certain PPI classes, analysis of the hit rates revealed up to 100 enrichment factors compared with nonoriented chemical libraries. This observation correlates with the predicted "druggability" of the targets. A specific focus on selectivity profiles, the three-dimensional (3D) molecular modes of action resolved by X-ray crystallography, and the biological activities of identified hits targeting the well-defined "druggable" bromodomains of the bromo and extraterminal (BET) family are presented as a proof-of-concept. Overall, our present study illustrates the potency of machine learning-based oriented chemical libraries to accelerate the identification of hits targeting PPIs. A generalization of this method to a larger set of compounds will accelerate the discovery of original and potent probes for this challenging class of targets.

  7. Materials Data on Ca2P2O7 (SG:14) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2016-02-04

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  8. Materials Data on CaSn2P2O9 (SG:62) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-11

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  9. Materials Data on Hg2P2S7 (SG:5) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-04

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  10. Materials Data on CeTl2P2S7 (SG:14) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  11. Materials Data on K2P2H2O7 (SG:11) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-05

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  12. THE SYNTHESIS OF LEAD PYROPHOSPHATE, PB2P2O7, IN WATER

    EPA Science Inventory

    Polyphosphates are used in the drinking water to prevent the precipitation of cations such as calcium and iron. The possible negative impact of using polyphosphates is the undesirable complexation of lead which could result in elevated lead levels in consumer’s tap water. Altho...

  13. Experimental study of the 2p-2h band in {sup 111}Sn

    SciTech Connect

    Ganguly, S.; Banerjee, P.; Ray, I.; Kshetri, R.; Raut, R.; Bhattacharya, S.; Saha-Sarkar, M.; Goswami, A.; Basu, S. K.

    2008-09-15

    The {delta}I=2 intruder band in {sup 111}Sn, built upon the 4074.3 keV state, was studied. The states were populated in the {sup 100}Mo({sup 20}Ne, {alpha}5n) reaction at a beam energy of 136 MeV. Mean lifetimes of five states up to 8737.2 keV (spin 43/2{sup -}) have been measured for the first time using the Doppler shift attenuation method. In addition, an upper limit of mean lifetime has been estimated for the 9860.0 keV (spin 47/2{sup -}) state. The B(E2) values, derived from the present lifetime results, indicate a quadrupole deformation of {beta}{sub 2}=0.28{+-}0.02 for the 31/2{sup -} state and decrease progressively with spin, suggesting a reduction in collectivity. The dynamic moment of inertia for the band also decreases continuously up to the highest observed frequencies. These results, along with the predictions of a total Routhian surface calculation, suggest that the {delta}I=2 band in {sup 111}Sn undergoes a change of shape from collective prolate to triaxial with increase in spin and possibly terminates in a noncollective oblate state at a high spin.

  14. Materials Data on K2In2P2HO10 (SG:19) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-04-23

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  15. Materials Data on Ca(Cu2P)2 (SG:136) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2016-02-11

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  16. Materials Data on K2P2H2O7 (SG:2) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-04

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  17. Materials Data on Re2P2O11 (SG:62) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-10

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  18. 2p2h effects on the weak pion production cross section

    SciTech Connect

    Mariano, A.; Barbero, C.

    2015-05-15

    The ν{sub l}n → l{sup −}p QE reaction on the A-target is used as a signal event or/and to reconstruct the neutrino energy, using two-body kinematics. Competition of another processes could lead to misidentification of the arriving neutrinos, being important the fake events coming from the CC1π background. A precise knowledge of cross sections is a prerequisite in order to make simulations in event generators to substract the fake ones from the QE countings, and in this contribution we analyze the different nuclear effects on the CC1π channel. Our calculations also can be extended for the NC case.

  19. Radiative transitions involving the (2p2)(3 Pe) metastable autodetaching of H(-)

    NASA Technical Reports Server (NTRS)

    Jacobs, V. L.; Bhatia, A. K.; Temkin, A.

    1974-01-01

    The absorption coefficient for the free-bound transition H (ls) + e(-)+ h omega yields H(-)(2 sq p,(3)P(e)) is calculated (together with the differential emission rate for the inverse process) using ls - 2s - 2p close coupling continuum wave functions and a Hylleraas bound state wave function. A maximum in the absorption and emission spectra is found to occur at a photon wavelength of 1219.5 A, which is 2 A closer to the Lyman alpha line than predicted by the calculations of Drake, and is in closer agreement with the stellar absorption feature identified by Heap and Stecher. The free-bound absorption process appears to be a significant source of continuous ultraviolet opacity.

  20. Materials Data on As2P2S7 (SG:14) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-04

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  1. α and 2p2n emission in fast neutron-induced reactions on Ni60

    DOE PAGES

    Fotiades, N.; Devlin, M.; Haight, R. C.; ...

    2015-06-19

    The cross sections for populating the residual nucleus in the reaction AZX(n,x)A-4Z-2Y exhibit peaks as a function of incident neutron energy corresponding to the (n,n'α) reaction and, at higher energy, to the (n,2p3n) reaction. In addition, the relative magnitudes of these peaks vary with the Z of the target nucleus.

  2. Materials Data on Sn2P2O7 (SG:14) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-07-14

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  3. Materials Data on ZnCr2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  4. Materials Data on ZnCo2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  5. Materials Data on CaMo2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  6. Materials Data on CaFe2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  7. Materials Data on Mn2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  8. Materials Data on MgCr2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  9. Materials Data on ZnSn2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  10. Materials Data on MgFe2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  11. Materials Data on CaMn2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  12. Materials Data on CaCr2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  13. Materials Data on MgMo2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  14. Materials Data on MgMn2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  15. Materials Data on Cr2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  16. Materials Data on Mo2P2O9 (SG:62) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-09-30

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  17. Materials Data on LiV2P2O9 (SG:62) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-10-28

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  18. Materials Data on LiCr2P2O9 (SG:62) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-10-28

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  19. Materials Data on LiCo2P2O9 (SG:62) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-10-29

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  20. Materials Data on LiNi2P2O9 (SG:62) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-10-31

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  1. Materials Data on LiMo2P2O9 (SG:62) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-10-15

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  2. Materials Data on LiTi2P2O9 (SG:62) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-10-27

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  3. Materials Data on LiFe2P2O9 (SG:62) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-10-28

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  4. Materials Data on NaMo2P2O9 (SG:62) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-10-28

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  5. Materials Data on Al2P2H4O11 (SG:61) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-05-31

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  6. Materials Data on KV2P2H4O13 (SG:2) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-04-23

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  7. Materials Data on Fe2P2H4NO8 (SG:15) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  8. Electron excitation from ground state to first excited state: Bohmian mechanics method

    NASA Astrophysics Data System (ADS)

    Yang, Song; Shuang, Zhao; Fu-Ming, Guo; Yu-Jun, Yang; Su-Yu, Li

    2016-03-01

    The excitation process of electrons from the ground state to the first excited state via the resonant laser pulse is investigated by the Bohmian mechanics method. It is found that the Bohmian particles far away from the nucleus are easier to be excited and are excited firstly, while the Bohmian particles in the ground state is subject to a strong quantum force at a certain moment, being excited to the first excited state instantaneously. A detailed analysis for one of the trajectories is made, and finally we present the space and energy distribution of 2000 Bohmian particles at several typical instants and analyze their dynamical process at these moments. Project supported by the Doctoral Research Start-up Funding of Northeast Dianli University, China (Grant No. BSJXM-201332), the National Natural Science Foundation of China (Grant Nos. 11547114, 11534004, 11474129, 11274141, 11447192, and 11304116), and the Graduate Innovation Fund of Jilin University, China (Grant No. 2015091).

  9. How much double excitation character do the lowest excited states of linear polyenes have?

    NASA Astrophysics Data System (ADS)

    Starcke, Jan Hendrik; Wormit, Michael; Schirmer, Jochen; Dreuw, Andreas

    2006-10-01

    Doubly excited states play important roles in the low-energy region of the optical spectra of polyenes and their investigation has been subject of theoretical and experimental studies for more than 30 years now and still is in the focus of ongoing research. In this work, we address the question why doubly excited states play a role in the low-energy region of the optical spectrum of molecular systems at all, since from a naive point of view one would expect their excitation energy approximately twice as large as the one of the corresponding single excitation. Furthermore, we show that extended-ADC(2) is well suited for the balanced calculation of the low-lying excited 21Ag-, 11Bu- and 11Bu+ states of long all- trans polyenes, which are known to possess substantial double excitation character. A careful re-investigation of the performance of TDDFT calculations for these states reveals that the previously reported good performance for the 21Ag- state relies heavily on fortuitous cancellation of errors. Finally, the title question is answered such that for short polyenes the lowest excited 21Ag- and 11Bu- states can clearly be classified as doubly excited, whereas the 11Ag- ground state is essentially represented by the (ground-state) HF determinant. For longer polyenes, in addition to increasing double excitation contributions in the 21Ag- and 11Bu- states, the ground state itself aquires substantial double excitation character (45% in C 22H 24), so that the transition from the ground state to these excited states should not be addressed as the excitation of two electrons relative to the 11Ag- ground state.

  10. Tailoring dye-sensitized upconversion nanoparticle excitation bands towards excitation wavelength selective imaging

    DOE PAGES

    Wu, Xiang; Lee, Hyungseok; Bilsel, Osman; ...

    2015-01-01

    One of the key roadblocks in UCNP development is its extremely limited choices of excitation wavelengths. We report a generic design to program UCNPs to possess highly tunable dye characteristic excitation bands. Using such distinctive properties, we were able to develop a new excitation wavelength selective security imaging. Finally, this work unleashed the greater freedom of the excitation wavelengths of the upconversion nanoparticles and we believe it is a game-changer in the field and this method will enable numerous applications that are currently limited by existing UCNPs.

  11. Electronic excitations in long polyenes revisited.

    PubMed

    Schmidt, Maximilian; Tavan, Paul

    2012-03-28

    We apply the valence shell model OM2 [W. Weber and W. Thiel, Theor. Chem. Acc. 103, 495, (2000)] combined with multireference configuration interaction (MRCI) to compute the vertical excitation energies and transition dipole moments of the low-energy singlet excitations in the polyenes with 4 ≤ N ≤ 22π-electrons. We find that the OM2/MRCI descriptions closely resemble those of Pariser-Parr-Pople (PPP) π-electron models [P. Tavan and K. Schulten, Phys. Rev. B 36, 4337, (1987)], if equivalent MRCI procedures and regularly alternating model geometries are used. OM2/MRCI optimized geometries are shown to entail improved descriptions particularly for smaller polyenes (N ≤ 12), for which sizeable deviations from the regular model geometries are found. With configuration interaction active spaces covering also the σ- in addition to the π-electrons, OM2/MRCI excitation energies turn out to become smaller by at most 0.35 eV for the ionic and 0.15 eV for the covalent excitations. The particle-hole (ph) symmetry, which in Pariser-Parr-Pople models arises from the zero-differential overlap approximation, is demonstrated to be only weakly broken in OM2 such that the oscillator strengths of the covalent 1B(u)(-) states, which artificially vanish in ph-symmetric models, are predicted to be very small. According to OM2/MRCI and experimental data the 1B(u)(-) state is the third excited singlet state for N < 12 and becomes the second for N ≥ 14. By comparisons with results of other theoretical approaches and experimental evidence we argue that deficiencies of the particular MRCI method employed by us, which show up in a poor size consistency of the covalent excitations for N > 12, are caused by its restriction to at most doubly excited references.

  12. Electronic excitations in long polyenes revisited

    NASA Astrophysics Data System (ADS)

    Schmidt, Maximilian; Tavan, Paul

    2012-03-01

    We apply the valence shell model OM2 [W. Weber and W. Thiel, Theor. Chem. Acc. 103, 495, (2000), 10.1007/s002149900083] combined with multireference configuration interaction (MRCI) to compute the vertical excitation energies and transition dipole moments of the low-energy singlet excitations in the polyenes with 4 ⩽ N ⩽ 22π-electrons. We find that the OM2/MRCI descriptions closely resemble those of Pariser-Parr-Pople (PPP) π-electron models [P. Tavan and K. Schulten, Phys. Rev. B 36, 4337, (1987)], if equivalent MRCI procedures and regularly alternating model geometries are used. OM2/MRCI optimized geometries are shown to entail improved descriptions particularly for smaller polyenes (N ⩽ 12), for which sizeable deviations from the regular model geometries are found. With configuration interaction active spaces covering also the σ- in addition to the π-electrons, OM2/MRCI excitation energies turn out to become smaller by at most 0.35 eV for the ionic and 0.15 eV for the covalent excitations. The particle-hole (ph) symmetry, which in Pariser-Parr-Pople models arises from the zero-differential overlap approximation, is demonstrated to be only weakly broken in OM2 such that the oscillator strengths of the covalent 1B_u^- states, which artificially vanish in ph-symmetric models, are predicted to be very small. According to OM2/MRCI and experimental data the 1B_u^- state is the third excited singlet state for N < 12 and becomes the second for N ⩾ 14. By comparisons with results of other theoretical approaches and experimental evidence we argue that deficiencies of the particular MRCI method employed by us, which show up in a poor size consistency of the covalent excitations for N > 12, are caused by its restriction to at most doubly excited references.

  13. Atmospheric Excitation of Planetary Normal Modes

    NASA Technical Reports Server (NTRS)

    Tanimoto, Toshiro

    2001-01-01

    The objectives of this study were to: (1) understand the phenomenon of continuous free oscillations of the Earth and (2) examine the idea of using this phenomenon for planetary seismology. We first describe the results on (1) and present our evaluations of the idea (2) in the final section. In 1997, after almost forty years since the initial attempt by Benioff et al, continuous free oscillations of the Earth were discovered. Spheroidal fundamental modes between 2 and 7 millihertz are excited continuously with acceleration amplitudes of about 0.3-0.5 nanogals. The signal is now commonly found in virtually all data recorded by STS-1 type broadband seismometers at quiet sites. Seasonal variation in amplitude and the existence of two coupled modes between the atmosphere and the solid Earth support that these oscillations are excited by the atmosphere. Stochastic excitation due to atmospheric turbulence is a favored mechanism, providing a good match between theory and data. The atmosphere has ample energy to support this theory because excitation of these modes require only 500-10000 W whereas the atmosphere contains about 117 W of kinetic energy. An application of this phenomenon includes planetary seismology, because other planets may be oscillating due to atmospheric excitation. The interior structure of planets could be learned by determining the eigenfrequencies in the continuous free oscillations. It is especially attractive to pursue this idea for tectonically quiet planets, since quakes may be too infrequent to be recorded by seismic instruments.

  14. Theory of elementary excitations in quasiperiodic structures

    NASA Astrophysics Data System (ADS)

    Albuquerque, E. L.; Cottam, M. G.

    2003-03-01

    The aim of this work is to present a comprehensive and up-to-date review of the main physical properties (such as energy profiles, localization, scale laws, multifractal analysis, transmission spectra, transmission fingerprints, electronic structures, magnetization curves and thermodynamic properties) of the elementary excitations that can propagate in multilayered structures with constituents arranged in a quasiperiodic fashion. These excitations include plasmon-polaritons, spin waves, light waves and electrons, among others. A complex fractal or multifractal profile of the energy spectra is the common feature among these excitations. The quasiperiodic property is formed by the incommensurate arrangement of periodic unit cells and can be of the type referred to as deterministic (or controlled) disorder. The resulting excitations are characterized by the nature of their Fourier spectrum, which can be dense pure point (as for the Fibonacci sequence) or singular continuous (as for the Thue-Morse and double-period sequences). These sequences are described in terms of a series of generations that obey particular recursion relations, and they can be considered as intermediate systems between a periodic crystal and the random amorphous solids, thus defining a novel description of disorder. A discussion is also included of some spectroscopic techniques used to probe the excitations, emphasizing Raman and Brillouin light scattering.

  15. Nuclear Excitation via Auger Transitions (NEAT)

    NASA Astrophysics Data System (ADS)

    Ward, Thomas; Emery, Guy; Rasmussen, John; Karwowski, Hugon; Castaneda, Carlos

    2008-10-01

    Triggering (prompt de-excitation) of isomeric states produced in a process of coupling nuclear excitations to atomic shells via Auger transitions (NEAT) is studied. In this resonant process the nuclear transition energy between the two states must be less than the Auger transition energy. This requires the emitted Auger electron energy and the exact on-resonance nuclear excitation share the Auger transition energy. NEAT is compared to other proposed processes of nuclear excitation produced by x-rays (NEET), by electron capture (NEEC) and bound internal conversion (BIC), all of which suffer from off-resonance nuclear excitation except in those accidental cases where the energies may coincide. Estimates of the total resonance strength will be given for the case of ^182mHf which has been extensively studied theoretically. A second case, ^189Os, where NEAT processes may contribute to the nuclear resonance fluorescence (NRF) of the ground state to the 5.8hr isomeric state will also be examined as a good case for experimental verification of the NEAT process.

  16. Targeting individual excited states in DMRG.

    NASA Astrophysics Data System (ADS)

    Dorando, Jonathan; Hachmann, Johannes; Kin-Lic Chan, Garnet

    2007-03-01

    The low-lying excited states of π-conjugated molecules are important for the development of novel devices such as lasers, light-emitting diodes, photovoltaic cells, and field-effect transistors [1,2]. The ab-intio Density Matrix Renormalization Group (DMRG) provides a powerful way to explore the electronic structure of quasi-one-dimensional systems such as conjugated organic oligomers. However, DMRG is limited to targeting only low-lying excited states through state-averaged DMRG (SDMRG). There are several drawbacks; state-averaging degrades the accuracy of the excited states and is limited to at most a few of the low-lying states [3]. In this study, we present a new method for targeting higher individual excited states. Due to progress in the field of numerical analysis presented by Van Der Horst and others [4], we are able to target individual excited states of the Hamiltonian. This is accomplished by modifying the Jacobi-Davidson algorithm via a ``Harmonic Ritz'' procedure. We will present studies of oligoacenes and polyenes that compare the accuracy of SDMRG and Harmonic Davidson DMRG. [1] Burroughes, et al. , Nature 347, 539 (1990). [2] Shirota, J. Mater. Chem. 10, 1, (2000). [3] Ramasesha, Pati, Krishnamurthy, Shuai, Bredas, Phys. Rev. B. 54, 7598, (1997). [4] Bai, Demmel, Dongarra, Ruhe, Van Der Horst, Templates for the Solution of Algebraic Eigenvalue Problems, SIAM, 2000.

  17. Tone-excited jet: Theory and experiments

    NASA Technical Reports Server (NTRS)

    Ahuja, K. K.; Lepicovsky, J.; Tam, C. K. W.; Morris, P. J.; Burrin, R. H.

    1982-01-01

    A detailed study to understand the phenomenon of broadband jet-noise amplification produced by upstream discrete-tone sound excitation has been carried out. This has been achieved by simultaneous acquisition of the acoustic, mean velocity, turbulence intensities, and instability-wave pressure data. A 5.08 cm diameter jet has been tested for this purpose under static and also flight-simulation conditions. An open-jet wind tunnel has been used to simulate the flight effects. Limited data on heated jets have also been obtained. To improve the physical understanding of the flow modifications brought about by the upstream discrete-tone excitation, ensemble-averaged schlieren photographs of the jets have also been taken. Parallel to the experimental study, a mathematical model of the processes that lead to broadband-noise amplification by upstream tones has been developed. Excitation of large-scale turbulence by upstream tones is first calculated. A model to predict the changes in small-scale turbulence is then developed. By numerically integrating the resultant set of equations, the enhanced small-scale turbulence distribution in a jet under various excitation conditions is obtained. The resulting changes in small-scale turbulence have been attributed to broadband amplification of jet noise. Excellent agreement has been found between the theory and the experiments. It has also shown that the relative velocity effects are the same for the excited and the unexcited jets.

  18. [Pre-excitation syndrome in monozygotic twins].

    PubMed

    Mispireta, J L; Cárdenas, M; Attié, F; Martínez-Ríos, M A; Medrano, G A

    1976-01-01

    A family group of seven members is presented, two of which have pre-excitation syndrome. These subjects are identical twin brothers. One of them has the W-P-W syndrome tipe B, and the other has L-G-L syndrome. The latter had an associated atrial-septal defect, and the other twin had no associated cardiovascular lesions. Both underwent electrocardiographic and vectorcardiographic studies, as well as His bundle electrograms. In the case with W-P-W, the diagnosis was made by electrocardiography, and was confirmed by vertocardiography. The His bundle electrogram showed the habitual findings in this type of pre-excitation. The His bundle potential was preceded by the beginning of the delta wave. The patient with W-P-W had episodes of supraventricular paroxysmal tachycardia, some of these with antegrade conduction through the normal pathway, and others with conduction through the anomalous pathway. The other had a L-G-L syndrome, demonstrated by electrocardiography and vectorcardiography. During the register of the His bundle electrogram, he did not present pre-excitation, the tracings in basal conditions as well as during atrial stimulation were normal. The conclusion is that many factors exist which back up the hypothesis that the pre-excitation syndromes occur because of anomalous pathways, and that this type of alteration might have a sex linked genetic basis. This presumption appears to be confirmed by the presence of pre-excitation in identical twin brothers. Other possibilities are also discussed.

  19. Asymptotic properties of mathematical models of excitability.

    PubMed

    Biktasheva, I V; Simitev, R D; Suckley, R; Biktashev, V N

    2006-05-15

    We analyse small parameters in selected models of biological excitability, including Hodgkin-Huxley (Hodgkin & Huxley 1952 J. Physiol.117, 500-544) model of nerve axon, Noble (Noble 1962 J. Physiol.160, 317-352) model of heart Purkinje fibres and Courtemanche et al. (Courtemanche et al. 1998 Am. J. Physiol.275, H301-H321) model of human atrial cells. Some of the small parameters are responsible for differences in the characteristic time-scales of dynamic variables, as in the traditional singular perturbation approaches. Others appear in a way which makes the standard approaches inapplicable. We apply this analysis to study the behaviour of fronts of excitation waves in spatially extended cardiac models. Suppressing the excitability of the tissue leads to a decrease in the propagation speed, but only to a certain limit; further suppression blocks active propagation and leads to a passive diffusive spread of voltage. Such a dissipation may happen if a front propagates into a tissue recovering after a previous wave, e.g. re-entry. A dissipated front does not recover even when the excitability restores. This has no analogy in FitzHugh-Nagumo model and its variants, where fronts can stop and then start again. In two spatial dimensions, dissipation accounts for breakups and self-termination of re-entrant waves in excitable media with Courtemanche et al. kinetics.

  20. Excited-state imaging of cold atoms

    NASA Astrophysics Data System (ADS)

    Sheludko, David V.; Bell, Simon C.; Vredenbregt, Edgar J. D.; Scholten, Robert E.

    2007-09-01

    We have investigated state-selective diffraction contrast imaging (DCI) of cold 85Rb atoms in the first excited (52P3/2) state. Excited-state DCI requires knowledge of the complex refractive index of the atom cloud, which was calculated numerically using a semi-classical model. The Autler-Townes splitting predicted by the model was verified experimentally, showing excellent agreement. 780 nm lasers were used to cool and excite atoms within a magneto-optical trap, and the atoms were then illuminated by a 776 nm imaging laser. Several excited-state imaging techniques, including blue cascade fluorescence, on-resonance absorption, and DCI have been demonstrated. Initial results show that improved signal-to-noise ratio (SNR) will be required to accurately determine the excited state fraction. We have demonstrated magnetic field gradient compression of the cold atom cloud, and expect that further progress on compression and additional cooling will achieve sufficient diffraction contrast for quantitative state-selective imaging.

  1. Vibrationally Excited Molecular Hydrogen Near Herschel 36

    NASA Astrophysics Data System (ADS)

    Rachford, Brian L.; Snow, T. P.; Ross, T.

    2014-01-01

    We present the first high resolution UV spectra toward Herschel 36, a Trapezium-like system of high-mass stars contained within the Lagoon Nebula (M8, NGC 6523). The spectra reveal extreme ro-vibrational excitation of molecular hydrogen in material at a single velocity or very small range of velocities, most likely the largest ever seen in UV absorption spectra. While the velocities of the highly excited H2 lines are consistent within each observation, it appears that they underwent a ≈60 km s-1 redshift during the 3.6 years between observations. In neither case does the velocity of the highly excited material match the velocity of the bulk of the line-of-sight material which appears to mostly be in the foreground of M8. Recent work shows unusually excited CH and CH+ lines and several unusually broad Diffuse Interstellar Bands (DIBs) towards Herschel 36. Along with the H2 excitation, all of these findings appear to be related to the extreme environment within ˜0.1 pc of the massive young stellar system.

  2. Patterns of conductivity in excitable automata with updatable intervals of excitations

    NASA Astrophysics Data System (ADS)

    Adamatzky, Andrew

    2012-11-01

    We define a cellular automaton where a resting cell excites if number of its excited neighbors belong to some specified interval and boundaries of the interval change depending on ratio of excited and refractory neighbors in the cell's neighborhood. We calculate excitability of a cell as a number of possible neighborhood configurations that excite the resting cell. We call cells with maximal values of excitability conductive. In exhaustive search of functions of excitation interval updates we select functions which lead to formation of connected configurations of conductive cells. The functions discovered are used to design conductive, wirelike, pathways in initially nonconductive arrays of cells. We demonstrate that by positioning seeds of growing conductive pathways it is possible to implement a wide range of routing operations, including reflection of wires, stopping wires, formation of conductive bridges, and generation of new wires in the result of collision. The findings presented may be applied in designing conductive circuits in excitable nonlinear media, reaction-diffusion chemical systems, neural tissue, and assemblies of conductive polymers.

  3. Multiple proton decays of 6Be, 8C, 8B(IAS) and excited states in 10C

    NASA Astrophysics Data System (ADS)

    Sobotka, Lee

    2011-10-01

    Recent technical advances have allowed for high-order correlation experiments to be done. We have primarily focused on experiments in which the final channels are composed of only alphas and protons. Four cases we have studied are: 6Be, 10C*, 8C, and 8B*(IAS) via 3, 4, 5, and 3-particle correlation measurements, respectively. While the first case had been studied before, our work presents very high statistics in the full Jacobi coordinates (the coordinates needed to describe 3-body decay.) Our study of 10C excited states provides isolatable examples of: correlated 2p decay, from one state, and the decay of another which is unusually highly correlated, a ``ménage a quatre.'' 8C decay presents the only case of sequential 3-body 2p decay steps (i.e. 2p-2p.) The intermediate in this 2-step process is the first example (6Be) mentioned above. Unlike the well-studied second step (6Be decay), the first step in this 2p-2p process provides another example of correlated 2p emission. The decay of 8B(IAS), the isobaric analog of 8C, also decays overwhelmingly by 2p emission, in this case to 6Li(IAS). This IAS-to-IAS 2p decay is one for which decay to the potential 1p intermediates is energetically allowed but isospin forbidden. This represents an expansion, over that originally envisioned by Goldanski, of the conceivable nuclear territory for 2p decay.

  4. Self-excitation of surface plasmon polaritons

    NASA Astrophysics Data System (ADS)

    Bordo, V. G.

    2016-04-01

    The novel effect of self-excitation of surface plasmons (SESP) in a plasmonic nanocavity is predicted, and its theory is developed from first principles. It is assumed that the cavity is formed by a nanogap between two metals and contains polarizable inclusions. Basing on the dyadic Green's function of the structure, the equations for the field in the cavity are investigated. It is shown that under certain conditions the field becomes unstable that leads to its self-excitation. The threshold criterion for self-excitation as well as the frequency of self-oscillation are derived in an analytical form. The SESP effect is explained in terms of a positive feedback for the polarization of inclusions provided by the field reflected from the cavity walls. These findings suggest a principally new avenue to surface plasmon generation which does not employ stimulated emission and is different from SPASER or plasmon laser.

  5. Asymmetric Magnon Excitation by Spontaneous Toroidal Ordering

    NASA Astrophysics Data System (ADS)

    Hayami, Satoru; Kusunose, Hiroaki; Motome, Yukitoshi

    2016-05-01

    The effects of spontaneous toroidal ordering on magnetic excitation are theoretically investigated for a localized spin model that includes a staggered Dzyaloshinsky-Moriya interaction and anisotropic exchange interactions, which arise from the antisymmetric spin-orbit coupling and the multiorbital correlation effect. We show that the model exhibits a Néel-type antiferromagnetic order, which simultaneously accompanies a ferroic toroidal order. We find that the occurrence of toroidal order modulates the magnon dispersion in an asymmetric way with respect to the wave number: a toroidal dipole order on the zigzag chain leads to a band-bottom shift, while a toroidal octupole order on the honeycomb lattice gives rise to a valley splitting. These asymmetric magnon excitations could be a source of unusual magnetic responses, such as nonreciprocal magnon transport. A variety of modulations are discussed while changing the lattice and magnetic symmetries. The implications regarding candidate materials for asymmetric magnon excitations are presented.

  6. Localized excitations from localized unitary operators

    NASA Astrophysics Data System (ADS)

    Sivaramakrishnan, Allic

    2017-06-01

    Localized unitary operators are basic probes of locality and causality in quantum systems: localized unitary operators create localized excitations in entangled states. Working with an explicit form, we explore properties of these operators in quantum mechanics and quantum field theory. We show that, unlike unitary operators, local non-unitary operators generically create non-local excitations. We present a local picture for quantum systems in which localized experimentalists can only act through localized Hamiltonian deformations, and therefore localized unitary operators. We demonstrate that localized unitary operators model certain quantum quenches exactly. We show how the Reeh-Schlieder theorem follows intuitively from basic properties of entanglement, non-unitary operators, and the local picture. We show that a recent quasi-particle picture for excited-state entanglement entropy in conformal field theories is not universal for all local operators. We prove a causality relation for entanglement entropy and connect our results to the AdS/CFT correspondence.

  7. Shear layer excitation, experiment versus theory

    NASA Technical Reports Server (NTRS)

    Bechert, D. W.; Stahl, B.

    1984-01-01

    The acoustical excitation of shear layers is investigated. Acoustical excitation causes the so-called orderly structures in shear layers and jets. Also, the deviations in the spreading rate between different shear layer experiments are due to the same excitation mechanism. Measurements in the linear interaction region close to the edge from which the shear layer is shed are examined. Two sets of experiments (Houston 1981 and Berlin 1983/84) are discussed. The measurements were carried out with shear layers in air using hot wire anemometers and microphones. The agreement between these measurements and the theory is good. Even details of the fluctuating flow field correspond to theoretical predictions, such as the local occurrence of negative phase speeds.

  8. Resonance Raman excitation profiles of lycopene

    NASA Astrophysics Data System (ADS)

    Hoskins, L. C.

    1981-01-01

    The resonance Raman spectrum of lycopene has been examined in acetone solvent and excitation profiles of the three fundamentals ν1, ν2, and ν3 have been determined. The excitation data and the visible spectrum have been analyzed using two-mode and three-mode vibrational models, with the two-mode model involving virtual states of ν1 and ν2 giving the best fit to the data. This mode mixing or Duskinsky effect was not observed for β-carotene. The single-mode and three-mode theories which have been used to explain the corresponding data for β-carotene are shown to be inconsistent with the experimental data of lycopene. Equations for calculating excitation profiles and visible spectra are given.

  9. On modulations of the Chandler wobble excitation

    NASA Astrophysics Data System (ADS)

    Zotov, L.; Bizouard, C.

    2012-12-01

    We derive the Chandler wobble excitation from the polar motion (PM) observations by using the Panteleev corrective filtering. The latter method is based on inversion of the Euler-Liouville equation, with additional filtering in the Chandler frequency band. The excitation reconstruction reveals amplitude changes different from the one observed in the Chandler wobble itself. Their main feature, well observable over the length of the day (LOD), is the presence of a 18.6-year amplitude modulation synchronous with the lunar orbital precession cycle and tidal effects. The filtering of oceanic and atmospheric excitation in the Chandler frequency band also reveals a coherent 18.6-year oceanic pattern. Most probably the ocean provide a channel for the tidal energy transfer.

  10. Chandler wobble excitation reconstruction and analysis

    NASA Astrophysics Data System (ADS)

    Zotov, Leonid

    2010-05-01

    Different methods of geodetic excitation reconstruction from observations of the polar motion are compared. Among them Wilson-Jeffreys filter, Tikhonov regularization, Panteleev corrective smoothing. Reconstruction of Chandler excitation is an inverse problem, aggravated by the strong annual oscillation, which is nearby in frequency band. Special attempts to filter annual oscillation out were undertaken, among them the harmonic model subtraction, Singular Spectrum Analysis (SSA) and Panteleev smoothing. Obtained results compared one with another and with geophysical excitations, such as atmospheric and oceanic angular momentum, El Nino event, solar and lunar tides. Amplitude and phase correlation analysis was performed. Phase change of the Chandler oscillation in the 30-th of the XX century found a partial explanation. This work is supported by grant of the President of Russia MK-4234.2009.5

  11. Charge-displacement analysis for excited states

    SciTech Connect

    Ronca, Enrico Tarantelli, Francesco; Pastore, Mariachiara Belpassi, Leonardo; De Angelis, Filippo; Angeli, Celestino; Cimiraglia, Renzo

    2014-02-07

    We extend the Charge-Displacement (CD) analysis, already successfully employed to describe the nature of intermolecular interactions [L. Belpassi et al., J. Am. Chem. Soc. 132, 13046 (2010)] and various types of controversial chemical bonds [L. Belpassi et al., J. Am. Chem. Soc. 130, 1048 (2008); N. Salvi et al., Chem. Eur. J. 16, 7231 (2010)], to study the charge fluxes accompanying electron excitations, and in particular the all-important charge-transfer (CT) phenomena. We demonstrate the usefulness of the new approach through applications to exemplary excitations in a series of molecules, encompassing various typical situations from valence, to Rydberg, to CT excitations. The CD functions defined along various spatial directions provide a detailed and insightful quantitative picture of the electron displacements taking place.

  12. Minimizing broadband excitation under dissipative conditions

    NASA Astrophysics Data System (ADS)

    Gelman, David; Kosloff, Ronnie

    2005-12-01

    Optimal control theory is employed for the task of minimizing the excited-state population of a dye molecule in solution. The spectrum of the excitation pulse is contained completely in the absorption band of the molecule. Only phase control is studied which is equivalent to optimizing the transmission of the pulse through the medium. The molecular model explicitly includes two electronic states and a single vibrational mode. The other degrees of freedom are classified as bath modes. The surrogate Hamiltonian method is employed to incorporate these bath degrees of freedom. Their influence can be classified as electronic dephasing and vibrational relaxation. In accordance with experimental results, minimal excitation is associated with a negatively chirped pulses. Optimal pulses with more complex transient structure are found to be superior to linearly chirped pulses. The difference is enhanced when the fluence is increased. The improvement degrades when dissipative effects become more dominant.

  13. Exciting dynamic anapoles with electromagnetic doughnut pulses

    NASA Astrophysics Data System (ADS)

    Raybould, Tim; Fedotov, Vassili A.; Papasimakis, Nikitas; Youngs, Ian; Zheludev, Nikolay I.

    2017-08-01

    As was predicted in 1995 by Afanasiev and Stepanovsky, a superposition of electric and toroidal dipoles can lead to a non-trivial non-radiating charge current-configuration, the dynamic anapole. The dynamic anapoles were recently observed first in microwave metamaterials and then in dielectric nanodisks. However, spectroscopic studies of toroidal dipole and anapole excitations are challenging owing to their diminishing coupling to transverse electromagnetic waves. Here, we show that anapoles can be excited by electromagnetic Flying Doughnut (FD) pulses. First described by Helwarth and Nouchi in 1996, FD pulses (also known as "Flying Toroids") are space-time inseparable exact solutions to Maxwell's equations that have toroidal topology and propagate in free-space at the speed of light. We argue that FD pulses can be used as a diagnostic and spectroscopic tool for the dynamic anapole excitations in matter.

  14. Asymmetric magnon excitation by spontaneous toroidal ordering

    SciTech Connect

    Hayami, Satoru; Kusunose, Hiroaki; Motome, Yukitoshi

    2016-04-12

    The effects of spontaneous toroidal ordering on magnetic excitation are theoretically investigated for a localized spin model that includes a staggered Dzyaloshinsky–Moriya interaction and anisotropic exchange interactions, which arise from the antisymmetric spin–orbit coupling and the multiorbital correlation effect. We show that the model exhibits a Néel-type antiferromagnetic order, which simultaneously accompanies a ferroic toroidal order. We find that the occurrence of toroidal order modulates the magnon dispersion in an asymmetric way with respect to the wave number: a toroidal dipole order on the zigzag chain leads to a band-bottom shift, while a toroidal octupole order on the honeycomb lattice gives rise to a valley splitting. These asymmetric magnon excitations could be a source of unusual magnetic responses, such as nonreciprocal magnon transport. A variety of modulations are discussed while changing the lattice and magnetic symmetries. Furthermore, the implications regarding candidate materials for asymmetric magnon excitations are presented.

  15. Elementary excitations in single-chain magnets

    NASA Astrophysics Data System (ADS)

    Lutz, Philipp; Aguilà, David; Mondal, Abhishake; Pinkowicz, Dawid; Marx, Raphael; Neugebauer, Petr; Fâk, Björn; Ollivier, Jacques; Clérac, Rodolphe; van Slageren, Joris

    2017-09-01

    Single-chain magnets (SCMs) are one-dimensional coordination polymers or spin chains that display slow relaxation of the magnetization. Typically their static magnetic properties are described by the Heisenberg model, while the description of their dynamic magnetic properties is based on an Ising-like model. The types of excitations predicted by these models (collective vs localized) are quite different. Therefore we probed the nature of the elementary excitations for two SCMs abbreviated Mn2Ni and Mn2Fe , as well as a mononuclear derivative of the Mn2Fe chain, by means of high-frequency electron paramagnetic resonance spectroscopy (HFEPR) and inelastic neutron scattering (INS). We find that the HFEPR spectra of the chains are clearly distinct from those of the monomer. The momentum transfer dependence of the INS intensity did not reveal significant dispersion, indicating an essentially localized nature of the excitations. At the lowest temperatures these are modified by the occurrence of short-range correlations.

  16. Artificial Excitation of Schumann Resonance with HAARP

    NASA Astrophysics Data System (ADS)

    Streltsov, A. V.; Chang, C. L.

    2014-12-01

    We report results from the experiment aimed at the artificial excitation of extremely-low-frequency (ELF) electromagnetic waves with frequencies corresponding to the frequency of Schumann resonance (typically, 7.5 - 8.0 Hz frequency range). Electromagnetic waves with these frequencies can form a standing pattern inside the spherical cavity formed by the surface of the earth and the ionosphere. In the experiment the ELF waves were excited by heating the ionosphere with X-mode HF electromagnetic waves generated by the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. The experiment demonstrates that heating of the ionosphere can excite relatively large-amplitude electromagnetic waves with frequencies in the range of the Schumann resonance, when the ionosphere has a strong F-layer and an electric field greater than 5 mV/m is present in the E-region.

  17. Asymptotic wave propagation in excitable media.

    PubMed

    Bernus, Olivier; Vigmond, Edward

    2015-07-01

    Wave shape and velocity are important issues in reaction-diffusion systems, and are often the result of competition in media with heterogeneous conduction properties. Asymptotic wave front propagation at maximal conduction velocity has been previously reported in the context of anisotropic cardiac tissue, but it is unknown whether this is a universal property of excitable tissues where conduction velocity can be locally modulated by mechanisms other than anisotropy. Here, we investigate the impact of conduction heterogeneities and boundary effects on wave propagation in excitable media. Following a theoretical analysis, we find that wave-front cusps occur where local velocity is reduced and that asymptotic wave fronts propagate at the maximal translational conduction velocity. Simulations performed in different reaction-diffusion systems, including cardiac tissue, confirm our theoretical findings. We conclude that this property can be found in a wide range of reaction-diffusion systems with excitable dynamics and that asymptotic wave-front shapes can be predicted.

  18. Excited light meson spectroscopy from lattice QCD

    SciTech Connect

    Christopher Thomas, Hadron Spectrum Collaboration

    2012-04-01

    I report on recent progress in calculating excited meson spectra using lattice QCD, emphasizing results and phenomenology. With novel techniques we can now extract extensive spectra of excited mesons with high statistical precision, including spin-four states and those with exotic quantum numbers. As well as isovector meson spectra, I will present new calculations of the spectrum of excited light isoscalar mesons, something that has up to now been a challenge for lattice QCD. I show determinations of the flavor content of these mesons, including the eta-eta' mixing angle, providing a window on annihilation dynamics in QCD. I will also discuss recent work on using lattice QCD to map out the energy-dependent phase shift in pi-pi scattering and future applications of the methodology to the study of resonances and decays.

  19. Vibrational and electronic excitations in gold nanocrystals

    NASA Astrophysics Data System (ADS)

    Bayle, Maxime; Combe, Nicolas; Sangeetha, Neralagatta M.; Viau, Guillaume; Carles, Robert

    2014-07-01

    An experimental analysis of all elementary excitations - phonons and electron-holes - in gold nanocrystals has been performed using plasmon resonance Raman scattering. Assemblies of monodisperse, single-crystalline gold nanoparticles, specific substrates and specific experimental configurations have been used. Three types of excitations are successively analyzed: collective quasi-acoustical vibrations of the particles (Lamb's modes), electron-hole excitations (creating the so-called ``background'' in surface-enhanced Raman scattering) and ensembles of atomic vibrations (``bulk'' phonons). The experimental vibrational density of states extracted from the latter contribution is successfully compared with theoretical estimations performed using atomic simulations. The dominant role of surface atoms over the core ones on lattice dynamics is clearly demonstrated. Consequences on the thermodynamic properties of nanocrystals such as the decrease of the characteristic Debye temperature are also considered.

  20. Charge-displacement analysis for excited states

    NASA Astrophysics Data System (ADS)

    Ronca, Enrico; Pastore, Mariachiara; Belpassi, Leonardo; De Angelis, Filippo; Angeli, Celestino; Cimiraglia, Renzo; Tarantelli, Francesco

    2014-02-01

    We extend the Charge-Displacement (CD) analysis, already successfully employed to describe the nature of intermolecular interactions [L. Belpassi et al., J. Am. Chem. Soc. 132, 13046 (2010)] and various types of controversial chemical bonds [L. Belpassi et al., J. Am. Chem. Soc. 130, 1048 (2008); N. Salvi et al., Chem. Eur. J. 16, 7231 (2010)], to study the charge fluxes accompanying electron excitations, and in particular the all-important charge-transfer (CT) phenomena. We demonstrate the usefulness of the new approach through applications to exemplary excitations in a series of molecules, encompassing various typical situations from valence, to Rydberg, to CT excitations. The CD functions defined along various spatial directions provide a detailed and insightful quantitative picture of the electron displacements taking place.

  1. Excitation of atomic nitrogen by electron impact

    NASA Technical Reports Server (NTRS)

    Stone, E. J.; Zipf, E. C.

    1972-01-01

    Absolute cross sections were measured for the excitation of the N I(1134, 1164, 1168, 1200, 1243, and 1743 A) multiplets by electron impact on atomic nitrogen. The presence of vibrationally excited molecular nitrogen in the discharged gas was confirmed, and its effect on the measurements is discussed. The ratio of the oscillator strengths of the 1200 and 1134 A resonance transitions is presented, as well as the branching ratio for the N I(1311/1164 A) multiplets. Striking differences in the distribution of intensity between the spectra of atomic nitrogen and molecular nitrogen excited by energetic electrons suggest an optical method for measuring the density of atomic nitrogen in the upper atmosphere.

  2. Stationary Phonon Squeezing by Optical Polaron Excitation

    NASA Astrophysics Data System (ADS)

    Papenkort, T.; Axt, V. M.; Kuhn, T.

    2017-03-01

    We demonstrate that a stationary squeezed phonon state can be prepared by a pulsed optical excitation of a semiconductor quantum well. Unlike previously discussed scenarios for generating squeezed phonons, the corresponding uncertainties become stationary after the excitation and do not oscillate in time. The effect is caused by two-phonon correlations within the excited polaron. We demonstrate by quantum kinetic simulations and by a perturbation analysis that the energetically lowest polaron state comprises two-phonon correlations which, after the pulse, result in an uncertainty of the lattice momentum that is continuously lower than in the ground state of the semiconductor. The simulations show the dynamics of the polaron formation process and the resulting time-dependent lattice uncertainties.

  3. Photothermal measurements using a localized excitation source

    NASA Astrophysics Data System (ADS)

    Aamodt, L. C.; Murphy, J. C.

    1981-08-01

    Optical-beam deflection (OBD) photothermal imaging uses spatially localized excitation to observe spatial variations in the sample surface temperature. This paper analyzes OBD signals produced by localized excitation in terms of three-dimensional thermal diffusion in the sample and in the fluid region in contact with the sample. The dependence of the signals on the local optical absorption coefficient, on gas/sample thermal properties, on modulation frequency, and on the probe/excitation beam radii are discussed with special attention being given to determining the spatial resolution possible for OBD imaging. A criterion for photothermal ''saturation'' appropriate to localized optical absorption is developed. Finally, a new variant of the OBD technique is introduced, which is especially adapted to studying optical and thermal boundaries in the plane of the sample. Some comparisons between theory and experiment are provided which illustrate transverse thermal diffusion.

  4. Nanoscale control of phonon excitations in graphene

    PubMed Central

    Kim, Hyo Won; Ko, Wonhee; Ku, JiYeon; Jeon, Insu; Kim, Donggyu; Kwon, Hyeokshin; Oh, Youngtek; Ryu, Seunghwa; Kuk, Young; Hwang, Sung Woo; Suh, Hwansoo

    2015-01-01

    Phonons, which are collective excitations in a lattice of atoms or molecules, play a major role in determining various physical properties of condensed matter, such as thermal and electrical conductivities. In particular, phonons in graphene interact strongly with electrons; however, unlike in usual metals, these interactions between phonons and massless Dirac fermions appear to mirror the rather complicated physics of those between light and relativistic electrons. Therefore, a fundamental understanding of the underlying physics through systematic studies of phonon interactions and excitations in graphene is crucial for realising graphene-based devices. In this study, we demonstrate that the local phonon properties of graphene can be controlled at the nanoscale by tuning the interaction strength between graphene and an underlying Pt substrate. Using scanning probe methods, we determine that the reduced interaction due to embedded Ar atoms facilitates electron–phonon excitations, further influencing phonon-assisted inelastic electron tunnelling. PMID:26109454

  5. Excited baryons in the 1/Nc expansion

    NASA Astrophysics Data System (ADS)

    Matagne, N.; Stancu, Fl.

    2012-04-01

    We briefly describe the 1/Nc expansion method for studying baryon masses. Two approaches of the large Nc excited baryons have been proposed so far. The first one, based on the Hartree picture, treats the baryon as a ground state core and an excited quark and the second one, suggested recently, considers the baryon globally, without decoupling the system. The masses of excited states of mixed orbital symmetry of nonstrange and strange baryons belonging to the lowest [70, -] multiplet are calculated in the 1/Nc expansion to order 1/Nc with the new method which allows to considerably reduce the number of linearly independent operators entering the mass formula. The status of the resonance Λ(1405) is discussed.

  6. Measurement of excited layer thickness in highly photo-excited GaAs

    NASA Astrophysics Data System (ADS)

    Liang, Lingliang; Tian, Jinshou; Wang, Tao; Wu, Shengli; Li, Fuli; Gao, Guilong

    2016-10-01

    Highly photo-excited layer thickness in GaAs is measured using a pump probe arrangement. A normally incident pump illumination spatially modulated by a mask will induce a corresponding refractive index change distribution in the depth direction due to edge scattering and attenuation absorption effect, which can deflect the probe beam passing through this excited region. Maximum deflection of the probe beam will be limited by the thickness of excited layer, and thus can also be employed to measure the thickness of the photo-excited layer of the material. Theoretical calculation confirms the experimental results. This method can find its application in measurements of photo-excited layer thickness of many kinds of materials and be significant to study the characteristics of materials in laser machining, grating and waveguide fabricating.

  7. Influence of excitation and deexcitation processes on the dynamics of laser-excited argon clusters

    NASA Astrophysics Data System (ADS)

    Moll, M.; Schlanges, M.; Bornath, Th.; Krainov, V. P.

    2015-03-01

    The excitation of atomic clusters by intense infrared laser pulses leads to the creation of highly charged ions and to the emission of energetic photons. These phenomena, which follow from ionization processes occurring in the cluster, depend significantly on the population of ground states and excited states in the laser-produced nanoplasma. This makes it necessary to account for collisional excitation and deexcitation processes. We investigate the interaction of femtosecond laser pulses with argon clusters by means of a nanoplasma model. Considering laser excitation with single and double pulses, we analyze the role of excitation and deexcitation processes in detail and calculate the yield of highly charged ions and of energetic photons in different wavelength regimes.

  8. Electron-impact vibrational excitation of cyclopropane

    SciTech Connect

    Čurík, R. Čársky, P.; Allan, M.

    2015-04-14

    We report a very detailed test of the ab initio discrete momentum representation (DMR) method of calculating vibrational excitation of polyatomic molecules by electron impact, by comparison of its results with an extensive set of experimental data, covering the entire range of scattering angles from 10{sup ∘} to 180{sup ∘} and electron energies from 0.4 to 20 eV. The DMR calculations were carried out by solving the two-channel Lippmann-Schwinger equation in the momentum space, and the interaction between the scattered electron and the target molecule was described by exact static-exchange potential corrected by a density functional theory (DFT) correlation-polarization interaction that models target’s response to the field of incoming electron. The theory is found to quantitatively reproduce the measured spectra for all normal modes, even at the difficult conditions of extreme angles and at low energies, and thus provides full understanding of the excitation mechanism. It is shown that the overlap of individual vibrational bands caused by limited experimental resolution and rotational excitation must be properly taken into account for correct comparison of experiment and theory. By doing so, an apparent discrepancy between published experimental data could be reconciled. A substantial cross section is found for excitation of the non-symmetric HCH twisting mode ν{sub 4} of A{sub 1}{sup ″} symmetry by the 5.5 eV A{sub 2}{sup ′} resonance, surprisingly because the currently accepted selection rules predict this process to be forbidden. The DMR theory shows that the excitation is caused by an incoming electron in an f-wave of A{sub 2}{sup ′} symmetry which causes excitation of the non-symmetric HCH twisting mode ν{sub 4} of the A{sub 1}{sup ″} symmetry and departs in p- and f-waves of A{sub 2}{sup ″} symmetry.

  9. Elliptic polarisation of the polar motion excitation

    NASA Astrophysics Data System (ADS)

    Bizouard, Christian

    2016-02-01

    Because of its geophysical interpretation, Earth's polar motion excitation is generally decomposed into prograde (counter-clockwise) and retrograde (clockwise) circular terms at fixed frequency. Yet, these later are commonly considered as specific to the frequency and to the underlying geophysical process, and no study has raised the possibility that they could share features independent from frequency. Complex Fourier Transform permits to determine retrograde and prograde circular terms of the observed excitation and of its atmospheric, oceanic and hydrological counterparts. The total prograde and retrograde parts of these excitations are reconstructed in time domain. Then, complex linear correlation between retrograde and conjugate prograde parts is observed for both the geodetic excitation and the matter term of the hydro-atmospheric excitation. In frequency domain, the ratio of the retrograde circular terms with their corresponding conjugate prograde terms favours specific values: the amplitude ratio follows a probabilistic gamma distribution centred around 1.5 (maximum for 1), and the argument ratio obeys a distribution close to a normal law centred around 2 α = 160°. These frequency and time domain characteristics mean an elliptical polarisation towards α ={˜ } 80° East with an ellipticity of 0.8, mostly resulting from the matter term of the hydro-atmospheric excitation. Whatsoever the frequency band above 0.4 cpd, the hydro-atmospheric matter term tends to be maximal in the geographic areas surrounding the great meridian circle of longitude {˜ }80° or {˜ } 260° East. The favoured retrograde/prograde amplitude ratio around 1.5 or equivalently the ellipticity of 0.8 can result from the amplification of pressure waves propagating towards the west by the normal atmospheric mode Ψ _3^1 around 10 days.

  10. BROADBAND EXCITATION IN NUCLEAR MAGNETIC RESONANCE

    SciTech Connect

    Tycko, R.

    1984-10-01

    Theoretical methods for designing sequences of radio frequency (rf) radiation pulses for broadband excitation of spin systems in nuclear magnetic resonance (NMR) are described. The sequences excite spins uniformly over large ranges of resonant frequencies arising from static magnetic field inhomogeneity, chemical shift differences, or spin couplings, or over large ranges of rf field amplitudes. Specific sequences for creating a population inversion or transverse magnetization are derived and demonstrated experimentally in liquid and solid state NMR. One approach to broadband excitation is based on principles of coherent averaging theory. A general formalism for deriving pulse sequences is given, along with computational methods for specific cases. This approach leads to sequences that produce strictly constant transformations of a spin system. The importance of this feature in NMR applications is discussed. A second approach to broadband excitation makes use of iterative schemes, i.e. sets of operations that are applied repetitively to a given initial pulse sequences, generating a series of increasingly complex sequences with increasingly desirable properties. A general mathematical framework for analyzing iterative schemes is developed. An iterative scheme is treated as a function that acts on a space of operators corresponding to the transformations produced by all possible pulse sequences. The fixed points of the function and the stability of the fixed points are shown to determine the essential behavior of the scheme. Iterative schemes for broadband population inversion are treated in detail. Algebraic and numerical methods for performing the mathematical analysis are presented. Two additional topics are treated. The first is the construction of sequences for uniform excitation of double-quantum coherence and for uniform polarization transfer over a range of spin couplings. Double-quantum excitation sequences are demonstrated in a liquid crystal system. The

  11. Band excitation method applicable to scanning probe microscopy

    DOEpatents

    Jesse, Stephen; Kalinin, Sergei V.

    2017-01-03

    Scanning probe microscopy may include a method for generating a band excitation (BE) signal and simultaneously exciting a probe at a plurality of frequencies within a predetermined frequency band based on the excitation signal. A response of the probe is measured across a subset of frequencies of the predetermined frequency band and the excitation signal is adjusted based on the measured response.

  12. Band excitation method applicable to scanning probe microscopy

    DOEpatents

    Jesse, Stephen; Kalinin, Sergei V.

    2015-08-04

    Scanning probe microscopy may include a method for generating a band excitation (BE) signal and simultaneously exciting a probe at a plurality of frequencies within a predetermined frequency band based on the excitation signal. A response of the probe is measured across a subset of frequencies of the predetermined frequency band and the excitation signal is adjusted based on the measured response.

  13. Laser Excited Fluorescence For Forensic Diagnostics

    NASA Astrophysics Data System (ADS)

    McKinney, Robert E.

    1986-07-01

    The application of laser excited fluorescence to the detection and identification of latent fingerprints was first accomplished ten years ago. The development of the technology has progressed rapidly with the introduction of commercial equipment by several manufacturers. Systems based on Argon-ion, Copper-vapor, and frequency-doubled Nd:YAG lasers are compared. The theoretical basis of detection by fluorescence is discussed along with the more useful techniques of dye staining. Other applications of the laser excited fluorescence in forensic investigation include gunshot residue analysis, serology, collection of trace evidence, and document examination.

  14. Mexican waves in an excitable medium.

    PubMed

    Farkas, I; Helbing, D; Vicsek, T

    2002-09-12

    The Mexican wave, or La Ola, which rose to fame during the 1986 World Cup in Mexico, surges through the rows of spectators in a stadium as those in one section leap to their feet with their arms up, and then sit down again as the next section rises to repeat the motion. To interpret and quantify this collective human behaviour, we have used a variant of models that were originally developed to describe excitable media such as cardiac tissue. Modelling the reaction of the crowd to attempts to trigger the wave reveals how this phenomenon is stimulated, and may prove useful in controlling events that involve groups of excited people.

  15. Computing correct truncated excited state wavefunctions

    NASA Astrophysics Data System (ADS)

    Bacalis, N. C.; Xiong, Z.; Zang, J.; Karaoulanis, D.

    2016-12-01

    We demonstrate that, if a wave function's truncated expansion is small, then the standard excited states computational method, of optimizing one "root" of a secular equation, may lead to an incorrect wave function - despite the correct energy according to the theorem of Hylleraas, Undheim and McDonald - whereas our proposed method [J. Comput. Meth. Sci. Eng. 8, 277 (2008)] (independent of orthogonality to lower lying approximants) leads to correct reliable small truncated wave functions. The demonstration is done in He excited states, using truncated series expansions in Hylleraas coordinates, as well as standard configuration-interaction truncated expansions.

  16. Charmonium excited state spectrum in lattice QCD

    SciTech Connect

    Jozef Dudek; Robert Edwards; Nilmani Mathur; David Richards

    2008-02-01

    Working with a large basis of covariant derivative-based meson interpolating fields we demonstrate the feasibility of reliably extracting multiple excited states using a variational method. The study is performed on quenched anisotropic lattices with clover quarks at the charm mass. We demonstrate how a knowledge of the continuum limit of a lattice interpolating field can give additional spin-assignment information, even at a single lattice spacing, via the overlap factors of interpolating field and state. Excited state masses are systematically high with respect to quark potential model predictions and, where they exist, experimental states. We conclude that this is most likely a result of the quenched approximation.

  17. The resonance Raman excitation profile of lutein

    NASA Astrophysics Data System (ADS)

    Hoskins, L. C.

    The resonance Raman excitation profiles for the ν 1, ν 2 and ν 3 vibrations of lutein in acetone, toluene and carbon disulfide solvents have been measured. The results are interpreted in terms of a three-mode vibrational theory which includes both homogeneous and inhomogeneous broadening effects. Excellent agreement between calculated and observed excitation profiles and visible spectra was found in acetone and toluene, but the results in carbon disulfide indicate a possible breakdown in the three-mode model. The major broadening mechanism is homogeneous, with about a 25% contribution from inhomogeneous broadening.

  18. The resonance Raman excitation profile of fucoxanthin

    NASA Astrophysics Data System (ADS)

    Ballard, L. J.; Glasgow, L. A.; Hoskins, L. C.; Krohe, T.

    1989-01-01

    The resonance Raman excitation profiles (RREPs) of the ν 1 and ν 2 vibrations of fucoxanthin in acetone and toluene solvents have been studied. Fucoxanthin, which is a predominant pigment in marine seaweed and phytoplankton, has several structural differences from carotenoids for which excitation profiles have been determined. The RREPs for fucoxanthin are interpreted in terms of a two-mode model and show a B2 value which is approximately 20% lower than for carotenoids like β-carotene and lutein which occur in higher plants. Excellent fits between experimental data and the theoretical model were observed in both solvents.

  19. Boundary layer control by acoustic excitation

    NASA Technical Reports Server (NTRS)

    Papathanasiou, A. G.; Nagel, R. T.

    1986-01-01

    An experimental program in which the effectiveness of a single large eddy break-up device (LEBU) blade is enhanced by proper acoustic excitation is described. An acoustic pulse, phase-locked to the incident large eddies and directed at the LEBU can enhance the large eddy cancellation process and can in effect lead to a decrease in the skin friction coefficient. Cross-correlation data and turbulence intensity measurements show that this acoustic excitation causes eddy cancellation at the trailing edge of the manipulator plate. It is concluded that both reduced turbulent boundary layer mixing and significant drag reduction can be achieved upon proper acoustic input to a LEBU.

  20. Elementary spin excitations in ultrathin itinerant magnets

    NASA Astrophysics Data System (ADS)

    Zakeri, Khalil

    2014-12-01

    Elementary spin excitations (magnons) play a fundamental role in condensed matter physics, since many phenomena e.g. magnetic ordering, electrical (as well as heat) transport properties, ultrafast magnetization processes, and most importantly electron/spin dynamics can only be understood when these quasi-particles are taken into consideration. In addition to their fundamental importance, magnons may also be used for information processing in modern spintronics. Here the concept of spin excitations in ultrathin itinerant magnets is discussed and reviewed. Starting with a historical introduction, different classes of magnons are introduced. Different theoretical treatments of spin excitations in solids are outlined. Interaction of spin-polarized electrons with a magnetic surface is discussed. It is shown that, based on the quantum mechanical conservation rules, a magnon can only be excited when a minority electron is injected into the system. While the magnon creation process is forbidden by majority electrons, the magnon annihilation process is allowed instead. These fundamental quantum mechanical selection rules, together with the strong interaction of electrons with matter, make the spin-polarized electron spectroscopies as appropriate tools to excite and probe the elementary spin excitations in low-dimensional magnets e.g ultrathin films and nanostructures. The focus is put on the experimental results obtained by spin-polarized electron energy loss spectroscopy and spin-polarized inelastic tunneling spectroscopy. The magnon dispersion relation, lifetime, group and phase velocity measured using these approaches in various ultrathin magnets are discussed in detail. The differences and similarities with respect to the bulk excitations are addressed. The role of the temperature, atomic structure, number of atomic layers, lattice strain, electronic complexes and hybridization at the interfaces are outlined. A possibility of simultaneous probing of magnons and phonons

  1. Double Photoionization of excited Lithium and Beryllium

    SciTech Connect

    Yip, Frank L.; McCurdy, C. William; Rescigno, Thomas N.

    2010-05-20

    We present total, energy-sharing and triple differential cross sections for one-photon, double ionization of lithium and beryllium starting from aligned, excited P states. We employ a recently developed hybrid atomic orbital/ numerical grid method based on the finite-element discrete-variable representation and exterior complex scaling. Comparisons with calculated results for the ground-state atoms, as well as analogous results for ground-state and excited helium, serve to highlight important selection rules and show some interesting effects that relate to differences between inter- and intra-shell electron correlation.

  2. Deciphering Nonlinear Waves in Excitable Media

    NASA Astrophysics Data System (ADS)

    Jung, Peter; Zhou, Yin; Gailey, Paul

    2000-03-01

    The analysis of dynamics in spatially extended systems is often hampered by only partially accessible information. Prominent examples are the electric excitation waves in cardiac tissue. In many cases, however, projected data streams, presenting integrated measures of the entire system, are available. In the case of cardiac tissue such an integrated measure can be the heart-dipole vector. EEG's are examples of integrated measures of organized spatiotemporal activity in brain tissue. As an example we consider nonlinear waves in noisy excitable media. We discuss the fingerprints of their spatiotemporal properties burried in data streams of integrated measures.

  3. When inhibition not excitation synchronizes neural firing.

    PubMed

    Van Vreeswijk, C; Abbott, L F; Ermentrout, G B

    1994-12-01

    Excitatory and inhibitory synaptic coupling can have counter-intuitive effects on the synchronization of neuronal firing. While it might appear that excitatory coupling would lead to synchronization, we show that frequently inhibition rather than excitation synchronizes firing. We study two identical neurons described by integrate-and-fire models, general phase-coupled models or the Hodgkin-Huxley model with mutual, non-instantaneous excitatory or inhibitory synapses between them. We find that if the rise time of the synapse is longer than the duration of an action potential, inhibition not excitation leads to synchronized firing.

  4. Increased Excitability of Acidified Skeletal Muscle

    PubMed Central

    Pedersen, Thomas H.; de Paoli, Frank; Nielsen, Ole B.

    2005-01-01

    Generation of the action potentials (AP) necessary to activate skeletal muscle fibers requires that inward membrane currents exceed outward currents and thereby depolarize the fibers to the voltage threshold for AP generation. Excitability therefore depends on both excitatory Na+ currents and inhibitory K+ and Cl− currents. During intensive exercise, active muscle loses K+ and extracellular K+ ([K+]o) increases. Since high [K+]o leads to depolarization and ensuing inactivation of voltage-gated Na+ channels and loss of excitability in isolated muscles, exercise-induced loss of K+ is likely to reduce muscle excitability and thereby contribute to muscle fatigue in vivo. Intensive exercise, however, also leads to muscle acidification, which recently was shown to recover excitability in isolated K+-depressed muscles of the rat. Here we show that in rat soleus muscles at 11 mM K+, the almost complete recovery of compound action potentials and force with muscle acidification (CO2 changed from 5 to 24%) was associated with reduced chloride conductance (1731 ± 151 to 938 ± 64 μS/cm2, P < 0.01) but not with changes in potassium conductance (405 ± 20 to 455 ± 30 μS/cm2, P < 0.16). Furthermore, acidification reduced the rheobase current by 26% at 4 mM K+ and increased the number of excitable fibers at elevated [K+]o. At 11 mM K+ and normal pH, a recovery of excitability and force similar to the observations with muscle acidification could be induced by reducing extracellular Cl− or by blocking the major muscle Cl− channel, ClC-1, with 30 μM 9-AC. It is concluded that recovery of excitability in K+-depressed muscles induced by muscle acidification is related to reduction in the inhibitory Cl− currents, possibly through inhibition of ClC-1 channels, and acidosis thereby reduces the Na+ current needed to generate and propagate an AP. Thus short term regulation of Cl− channels is important for maintenance of excitability in working muscle. PMID:15684096

  5. Direct transient stability assessment with excitation control

    SciTech Connect

    Fouad, A.A.; Vittal, V.; Ni, Y.X.; Pota, H.R.; Nodehi, K.; Zein-Eldin, H.M.; Vaahedi, E.; Kim

    1989-02-01

    Recently the authors incorporated the effect of excitation control on the transient energy of a multi-machine power system during the first swing. The models used are: the generator represented by the two-axis model and the exciter represented by one gain, one time constant and one limiter. In this paper the parameters of the newly developed transient energy function, which assumes a constant average internal EMF, are computed. The critical value of this transient energy is determined and its use in transient stability assessment is investigated. A procedure for transient stability assessment using the new energy function has been developed and successfully applied to fault disturbances in two test networks.

  6. Chemical waves in inhomogeneous excitable media

    NASA Astrophysics Data System (ADS)

    Maselko, Jerzy; Showalter, Kenneth

    1991-04-01

    Propagating chemical waves are typically studied in homogeneous, excitable reaction mixtures. Chemical waves in an inhomogeneous excitable medium are examined in this paper. Cation exchange beads, loaded with ferroin, are bathed in Belousov-Zhabotinsky reaction mixtures containing no catalyst. Spiral waves are spontaneously initiated above a critical bromate concentration, which is dependent on the size of the ferroin-loaded beads. At high bromate concentrations, irregular patterns are formed due to an overcrowding of spirals. An upper limit in the number of individual waves is exhibited, which is independent on the bead size. Regular and irregular patterns are analyzed by calculating spatial correlation functions from digital images.

  7. Reactions and Spectroscopy of Excited Nitrenes

    DTIC Science & Technology

    1994-01-28

    NIT Boiling AFB, DIC 20332-0001 ELEMENT NO. No. NO. NO. 11. TITLE fi’Icludd SeCudPlY CZI4dIficatiOnt Reactions and Snectosc v ofExited Nitrenes 12...publi0 release dist ribut ion unl imited. The electronically excited singlet states of halogen nitrenes have been of interest for a number of years...excited singlet nitrenes have drawn significant interest from the basic science community, since these species are isoelectronic to the well studied

  8. Two-photon excitation fluorescence microscopy.

    PubMed

    So, P T; Dong, C Y; Masters, B R; Berland, K M

    2000-01-01

    Two-photon fluorescence microscopy is one of the most important recent inventions in biological imaging. This technology enables noninvasive study of biological specimens in three dimensions with submicrometer resolution. Two-photon excitation of fluorophores results from the simultaneous absorption of two photons. This excitation process has a number of unique advantages, such as reduced specimen photodamage and enhanced penetration depth. It also produces higher-contrast images and is a novel method to trigger localized photochemical reactions. Two-photon microscopy continues to find an increasing number of applications in biology and medicine.

  9. Exciting baryons: Now and in the future

    NASA Astrophysics Data System (ADS)

    Pennington, M. R.

    2012-04-01

    This is the final talk of NSTAR2011 conference. It is not a summary talk, but rather a looking forward to what still needs to be done in excited baryon physics. In particular, we need to hone our tools connecting experimental inputs with QCD. At present we rely on models that often have doubtful connections with the underlying theory, and this needs to be dramatically improved, if we are to reach definitive conclusions about the relevant degrees of freedom of excited baryons. Conclusions that we want to have by NSTAR2021.

  10. The photodissociation and reaction dynamics of vibrationally excited molecules

    SciTech Connect

    Not Available

    1993-01-01

    We have used combined vibrational overtone excitation and laser induced fluorescence detection to study dissociation dynamics of hydroxylamine (NH[sub 2]OH), have performed our first laser induced grating experiments on water, and have begun assembling a new apparatus for preparing vibrationally excited molecules with simulated Raman excitation. We study role of vibrational excitation in photodissociation dynamics by using a vibrational state preparation technique, such as vibrational overtone excitation or stimulated Raman excitation, to create molecules with particular nuclear motions and then to excite that molecule to a dissociative electronic state.

  11. Structural responses to arbitrarily coherent stationary random excitations

    NASA Astrophysics Data System (ADS)

    Lin, Jia-Hao; Zhang, Wen-Shou; Li, Jian-Jun

    1994-03-01

    The pseudo-excitation or fast CQC method for a single excitation problem is extended to deal with general MIMO (multi-input, multi-output) problems in which the excitations can be fully or partially coherent, i.e. the excitation PSD matrices are more general Hermitian matrices. This extension makes the analyses of structural responses to general stationary multipoint excitations computationally more efficient and convenient.

  12. Relaxation channels of multi-photon excited xenon clusters

    SciTech Connect

    Serdobintsev, P. Yu.; Melnikov, A. S.; Rakcheeva, L. P. Murashov, S. V.; Khodorkovskii, M. A.; Lyubchik, S.; Timofeev, N. A.; Pastor, A. A.

    2015-09-21

    The relaxation processes of the xenon clusters subjected to multi-photon excitation by laser radiation with quantum energies significantly lower than the thresholds of excitation of atoms and ionization of clusters were studied. Results obtained by means of the photoelectron spectroscopy method showed that desorption processes of excited atoms play a significant role in the decay of two-photon excited xenon clusters. A number of excited states of xenon atoms formed during this process were discovered and identified.

  13. Relaxation channels of multi-photon excited xenon clusters.

    PubMed

    Serdobintsev, P Yu; Rakcheeva, L P; Murashov, S V; Melnikov, A S; Lyubchik, S; Timofeev, N A; Pastor, A A; Khodorkovskii, M A

    2015-09-21

    The relaxation processes of the xenon clusters subjected to multi-photon excitation by laser radiation with quantum energies significantly lower than the thresholds of excitation of atoms and ionization of clusters were studied. Results obtained by means of the photoelectron spectroscopy method showed that desorption processes of excited atoms play a significant role in the decay of two-photon excited xenon clusters. A number of excited states of xenon atoms formed during this process were discovered and identified.

  14. Relaxation channels of multi-photon excited xenon clusters

    NASA Astrophysics Data System (ADS)

    Serdobintsev, P. Yu.; Rakcheeva, L. P.; Murashov, S. V.; Melnikov, A. S.; Lyubchik, S.; Timofeev, N. A.; Pastor, A. A.; Khodorkovskii, M. A.

    2015-09-01

    The relaxation processes of the xenon clusters subjected to multi-photon excitation by laser radiation with quantum energies significantly lower than the thresholds of excitation of atoms and ionization of clusters were studied. Results obtained by means of the photoelectron spectroscopy method showed that desorption processes of excited atoms play a significant role in the decay of two-photon excited xenon clusters. A number of excited states of xenon atoms formed during this process were discovered and identified.

  15. First in-beam observation of excited states in {sup 156}{sub 72}Hf{sub 84} using the recoul-decay tagging method

    SciTech Connect

    Seweryniak, D.; Ahmad, H.; Amro, D.J.

    1996-12-31

    Excited states in the proton rich nuclide {sup 156}{sub 72}Hf{sub 84} were observed for the first time using the {sup 102}({sup 58}Ni, 2p2n){sup 156}Hf reaction at 270 MeV. Gamma rays were detected with the AYEBALL array of Compton suppressed Ge detectors, placed in front of the Fragment Mass Analyzer, and were assigned to individual reaction charmers using the Recoil-Decay Tagging Method. Prompt {gamma}-ray cascades were associated with the alpha decay of both the ground state and the 8{sup +} isomeric state in {sup 156}Hf. The level scheme constructed for {sup 156}Hf is compared with level schemes of lighter even-even N=84 isotones and is discussed within the framework of the Shell Model.

  16. "Fast Excitation" CID in Quadrupole Ion Trap Mass Spectrometer

    SciTech Connect

    Murrell, J.; Despeyroux, D.; Lammert, Stephen {Steve} A; Stephenson Jr, James {Jim} L; Goeringer, Doug

    2003-01-01

    Collision-induced dissociation (CID) in a quadrupole ion trap mass spectrometer is usually performed by applying a small amplitude excitation voltage at the same secular frequency as the ion of interest. Here we disclose studies examining the use of large amplitude voltage excitations (applied for short periods of time) to cause fragmentation of the ions of interest. This process has been examined using leucine enkephalin as the model compound and the motion of the ions within the ion trap simulated using ITSIM. The resulting fragmentation information obtained is identical with that observed by conventional resonance excitation CID. ''Fast excitation'' CID deposits (as determined by the intensity ratio of the a{sub 4}/b{sub 4} ion of leucine enkephalin) approximately the same amount of internal energy into an ion as conventional resonance excitation CID where the excitation signal is applied for much longer periods of time. The major difference between the two excitation techniques is the higher rate of excitation (gain in kinetic energy) between successive collisions with helium atoms with ''fast excitation'' CID as opposed to the conventional resonance excitation CID. With conventional resonance excitation CID ions fragment while the excitation voltage is still being applied whereas for ''fast excitation'' CID a higher proportion of the ions fragment in the ion cooling time following the excitation pulse. The fragmentation of the (M + 17H){sup 17+} of horse heart myoglobin is also shown to illustrate the application of ''fast excitation'' CID to proteins.

  17. Two-color temporal focusing multiphoton excitation imaging with tunable-wavelength excitation

    NASA Astrophysics Data System (ADS)

    Lien, Chi-Hsiang; Abrigo, Gerald; Chen, Pei-Hsuan; Chien, Fan-Ching

    2017-02-01

    Wavelength tunable temporal focusing multiphoton excitation microscopy (TFMPEM) is conducted to visualize optical sectioning images of multiple fluorophore-labeled specimens through the optimal two-photon excitation (TPE) of each type of fluorophore. The tunable range of excitation wavelength was determined by the groove density of the grating, the diffraction angle, the focal length of lenses, and the shifting distance of the first lens in the beam expander. Based on a consideration of the trade-off between the tunable-wavelength range and axial resolution of temporal focusing multiphoton excitation imaging, the presented system demonstrated a tunable-wavelength range from 770 to 920 nm using a diffraction grating with groove density of 830 lines/mm. TPE fluorescence imaging examination of a fluorescent thin film indicated that the width of the axial confined excitation was 3.0±0.7 μm and the shifting distance of the temporal focal plane was less than 0.95 μm within the presented wavelength tunable range. Fast different wavelength excitation and three-dimensionally rendered imaging of Hela cell mitochondria and cytoskeletons and mouse muscle fibers were demonstrated. Significantly, the proposed system can improve the quality of two-color TFMPEM images through different excitation wavelengths to obtain higher-quality fluorescent signals in multiple-fluorophore measurements.

  18. An Artificial Ising System with Phononic Excitations

    NASA Astrophysics Data System (ADS)

    Ghaffari, Hamed; Griffith, W. Ashley; Benson, Philip; Nasseri, M. H. B.; Young, R. Paul

    Many intractable systems and problems can be reduced to a system of interacting spins. Here, we report mapping collective phononic excitations from different sources of crystal vibrations to spin systems. The phononic excitations in our experiments are due to micro and nano cracking (yielding crackling noises due to lattice distortion). We develop real time mapping of the multi-array senores to a network-space and then mapping the excitation- networks to spin-like systems. We show that new mapped system satisfies the quench (impulsive) characteristics of the Ising model in 2D classical spin systems. In particular, we show that our artificial Ising system transits between two ground states and approaching the critical point accompanies with a very short time frozen regime, inducing formation of domains separated by kinks. For a cubic-test under a true triaxial test (3D case), we map the system to a 6-spin ring under a transversal-driving field where using functional multiplex networks, the vector components of the spin are inferred (i.e., XY model). By visualization of spin patterns of the ring per each event, we demonstrate that ``kinks'' (as defects) proliferate when system approach from above to its critical point. We support our observations with employing recorded acoustic excitations during distortion of crystal lattices in nano-indentation tests on different crystals (silicon and graphite), triaxial loading test on rock (poly-crystal) samples and a true 3D triaxial test.

  19. Extracting excited mesons from the finite volume

    SciTech Connect

    Doring, Michael

    2014-12-01

    As quark masses come closer to their physical values in lattice simulations, finite volume effects dominate the level spectrum. Methods to extract excited mesons from the finite volume are discussed, like moving frames in the presence of coupled channels. Effective field theory can be used to stabilize the determination of the resonance spectrum.

  20. Excitation system for rotating synchronous machines

    DOEpatents

    Umans, Stephen D.; Driscoll, David J.

    2002-01-01

    A system for providing DC current to a rotating superconducting winding is provided. The system receives current feedback from the superconducting winding and determines an error signal based on the current feedback and a reference signal. The system determines a control signal corresponding to the error signal and provides a positive and negative superconducting winding excitation voltage based on the control signal.

  1. Contour Line Portraits: Excited about Artistic Abilities

    ERIC Educational Resources Information Center

    Neal, Kari Gertz

    2012-01-01

    In this article, the author describes a self-portrait project that encouraged students, boosted their self-confidence, and got them excited about their artistic abilities--while producing amazing results. This lesson effectively develops artistic ability by compelling students to see that drawing is quite simply breaking down objects into the…

  2. Supersolitons: Solitonic Excitations in Atomic Soliton Chains

    SciTech Connect

    Novoa, David; Michinel, Humberto; Perez-Garcia, Victor M.

    2008-10-03

    We show that, by tuning interactions in nonintegrable vector nonlinear Schroedinger equations modeling Bose-Einstein condensates and other relevant physical systems, it is possible to achieve a regime of elastic particlelike collisions between solitons. This would allow one to construct a Newton's cradle with solitons and supersolitons: localized collective excitations in solitary-wave chains.

  3. Nuclear excitation and precompound nuclear reactions

    SciTech Connect

    De, A.; Ray, S.; Ghosh, S.K.

    1988-06-01

    The angular distribution of nucleons emitted in nucleon-induced precompound nuclear reactions are calculated taking into account the effect of excitation on the kinematics of nucleon-nucleon scattering inside the target-plus-projectile system. The results are compared with quantum mechanical calculations and those of reaction models based on a pure nucleon-nucleon collision picture.

  4. Synthesis of laughter by modifying excitation characteristics.

    PubMed

    Thati, Sathya Adithya; Kumar K, Sudheer; Yegnanarayana, B

    2013-05-01

    In this paper, a method to synthesize laughter by modifying the excitation source information is presented. The excitation source information is derived by extracting epoch locations and instantaneous fundamental frequency using zero frequency filtering approach. The zero frequency filtering approach is modified to capture the rapidly varying instantaneous fundamental frequency in natural laugh signals. The nature of variation of excitation features in natural laughter is examined to determine the features to be incorporated in the synthesis of a laugh signal. Features such as pitch period and strength of excitation are modified in the utterance of vowel /a/ or /i/ to generate the laughter signal. Frication is also incorporated wherever appropriate. Laugh signal is generated by varying parameters at both call level and bout level. Experiments are conducted to determine the significance of different features in the perception of laughter. Subjective evaluation is performed to determine the level of acceptance and quality of synthesis of the synthesized laughter signal for different choices of parameter values and for different input types.

  5. Ionic electrostatic excitations along biological membranes

    NASA Astrophysics Data System (ADS)

    Moradi, Afshin

    2011-02-01

    A theoretical analysis of ionic electrostatic excitations of a charged biological membrane is presented within the framework of the fluid theory for surface ions inside and outside the cell, in conjunction with the Poisson's equation. General expressions of dispersion relations are obtained for electrostatic oscillations of intrinsic cellular with different shapes and symmetries.

  6. On the Electronically Excited States of Uracil

    SciTech Connect

    Epifanovsky, Evgeny; Kowalski, Karol; Fan, Peng-Dong; Valiev, Marat; Matsika, Spiridoula; Krylov, Anna

    2008-10-09

    Vertical excitation energies in uracil in the gas phase and in water solution are investigated by the equation-of-motion coupled-cluster and multi-reference configuration interaction methods. Basis set effects are found to be important for converged results. The analysis of electronic wave functions reveals that the lowest singlet states are predominantly of a singly excited character and are therefore well described by single-reference equation-of-motion methods augmented by a perturbative triples correction to account for dynamical correlation. Our best estimates for the vertical excitation energies for the lowest singlet n and are 5.0±0.1 eV and 5.3±0.1 eV, respectively. The solvent effects for these states are estimated to be +0.5 eV and ±0.1 eV, respectively. We attribute the difference between the computed vertical excitations and the maximum of the experimental absorption to strong vibronic interaction between the lowest A00 and A0 states leading to intensity borrowing by the forbidden transition.

  7. Dipolar excitation in the third stability region.

    PubMed

    Konenkov, Nikolai V; Chernyak, Eugenii Ya; Stepanov, Vladimir A

    2016-01-01

    Dipole resonant excitation of ions creates instability bands which follow iso-β lines where β is the characteristic exponent (stability parameter). Instability bands are exited most effectively on the fundamental frequency π= βΩ/2. Here π is the angle resonance frequency of the dipolar voltage applied to x or y pair rods of the analyzer, and Ω is the angle frequency of the main drive voltage. Our goal is to study the mass peak shape in the third stability region with dipolar resonance excitation of the instability band with respect to the resonance frequency π and the dipolar potential amplitude. Numerical integration of the ion motion equations with a given ion source emittance is used to investigate peak shapes and ion transmission. We show that it is possible to vary the resolution power at any part of the third stability region. A change of the dipolar potential phase leads to a periodical variation of the resolution with period π.The most effective dipolar excitation in the y direction is along βy near the stability boundary. The mass peak shape is calculated also for a quadrupole with round rods. The best peak shape (small tails and high resolution) takes place for the rod set with r/r0=1.130. Dipolar excitation increases the transmission by approximately 5-10% at a given resolution.

  8. Contextual fear conditioning depresses infralimbic excitability.

    PubMed

    Soler-Cedeño, Omar; Cruz, Emmanuel; Criado-Marrero, Marangelie; Porter, James T

    2016-04-01

    Patients with posttraumatic stress disorder (PTSD) show hypo-active ventromedial prefrontal cortices (vmPFC) that correlate with their impaired ability to discriminate between safe and dangerous contexts and cues. Previously, we found that auditory fear conditioning depresses the excitability of neurons populating the homologous structure in rodents, the infralimbic cortex (IL). However, it is undetermined if IL depression was mediated by the cued or contextual information. The objective of this study was to examine whether contextual information was sufficient to depress IL neuronal excitability. After exposing rats to context-alone, pseudoconditioning, or contextual fear conditioning, we used whole-cell current-clamp recordings to examine the excitability of IL neurons in prefrontal brain slices. We found that contextual fear conditioning reduced IL neuronal firing in response to depolarizing current steps. In addition, neurons from contextual fear conditioned animals showed increased slow afterhyperpolarization potentials (sAHPs). Moreover, the observed changes in IL excitability correlated with contextual fear expression, suggesting that IL depression may contribute to the encoding of contextual fear.

  9. New Logic Circuit with DC Parametric Excitation

    NASA Astrophysics Data System (ADS)

    Sugahara, Masanori; Kaneda, Hisayoshi

    1982-12-01

    It is shown that dc parametric excitation is possible in a circuit named JUDO, which is composed of two resistively-connected Josephson junctions. Simulation study proves that the circuit has large gain and properties suitable for the construction of small, high-speed logic circuits.

  10. Engage and Excite Students with Educational Games

    ERIC Educational Resources Information Center

    Petsche, Jennifer

    2011-01-01

    Using educational games to learn or reinforce lessons engages students and turns a potentially boring subject into something exciting and desirable to know! Games offer teachers and parents a new way to grab students' attention so that they will retain information. Games have become a teaching tool, an invaluable resource for reaching students in…

  11. Coherent Rydberg Excitation in Thermal Microcells

    NASA Astrophysics Data System (ADS)

    Loew, Robert

    2011-05-01

    In order to create quantum devices based on the Rydberg blockade mechanism, it is necessary to have a confinement of the excitation volume to less than the blockade radius in a frozen gas of atoms; i.e. the excitation times need to be shorter than the timescales of the respective dephasing mechanisms. While ultracold gases seem to be the obvious choice, our approach utilizes thermal atomic vapor in small glass cells which offer multiple advantages like good optical access and scalability. Such a system can be realized by confining the atoms to geometries in the micron regime. Decoherence effects like resonant interactions of the Rydberg atoms with polaritonic excitations in the glass have been studied and can be minimized by the appropriate choice of Rydberg states. Using a bandwidth-limited pulsed laser system for the Rydberg excitation we observe coherent Rabi oscillations on the nanosecond timescale. In collaboration with Renate Daschner, Harald Kuebler, Bernhard Huber, Thomas Baluktsian, Andreas Koelle, James Shaffer, and Tilman Pfau.

  12. On the excitation of Goodwin's oscillations

    NASA Astrophysics Data System (ADS)

    Antonova, A. O.; Reznik, S. N.; Todorov, M. D.

    2014-11-01

    We consider the necessary condition for excitation of long-periodic Goodwin's oscillations and short-periodic sawtooth oscillations in the Goodwin model with fixed delay in the induced investment. Also, using the method of equivalent linearization we evaluate the amplitude of steady-state oscillation.

  13. Multipurpose exciter with low phase noise

    NASA Technical Reports Server (NTRS)

    Conroy, B.; Le, D.

    1989-01-01

    Results of an effort to develop a lower-cost exciter with high stability, low phase noise, and controllable phase and frequency for use in Deep Space Network and Goldstone Solar System Radar applications are discussed. Included is a discussion of the basic concept, test results, plans, and concerns.

  14. Does intrinsic motivation enhance motor cortex excitability?

    PubMed

    Radel, Rémi; Pjevac, Dusan; Davranche, Karen; d'Arripe-Longueville, Fabienne; Colson, Serge S; Lapole, Thomas; Gruet, Mathieu

    2016-11-01

    Intrinsic motivation (IM) is often viewed as a spontaneous tendency for action. Recent behavioral and neuroimaging evidence indicate that IM, in comparison to extrinsic motivation (EM), solicits the motor system. Accordingly, we tested whether IM leads to greater excitability of the motor cortex than EM. To test this hypothesis, we used two different tasks to induce the motivational orientation using either words representing each motivational orientation or pictures previously linked to each motivational orientation through associative learning. Single-pulse transcranial magnetic stimulation over the motor cortex was applied when viewing the stimuli. Electromyographic activity was recorded on the contracted first dorsal interosseous muscle. Two indexes of corticospinal excitability (the amplitude of motor-evoked potential and the length of cortical silent period) were obtained through unbiased automatic detection and analyzed using a mixed model that provided both statistical power and a high level of control over all important individual, task, and stimuli characteristics. Across the two tasks and the two indices of corticospinal excitability, the exposure to IM-related stimuli did not lead to a greater corticospinal excitability than EM-related stimuli or than stimuli with no motivational valence (ps > .20). While these results tend to dismiss the advantage of IM at activating the motor cortex, we suggest alternative hypotheses to explain this lack of effect, which deserves further research.

  15. Excitation of atmospheric oscillations by volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Kanamori, Hiroo; Mori, Jim; Harkrider, David G.

    1994-11-01

    We investigated the mechanism of atmospheric oscillations with periods of about 300 s which were observed for the 1991 Pinatubo and the 1982 El Chichon eruptions. Two distinct spectral peaks, at T = 270 and 230 s for the Pinatubo eruption and at T = 195 and 266 s for the El Chichon eruptions, have been reported. We found similar oscillations for the 1980 Mount St. Helens and the 1883 Krakatoa eruptions. To explain these observations, we investigated excitation problems for two types of idealized sources, 'mass injection' and 'energy injection' sources, placed in an isothermal atmosphere. In general, two modes of oscillations, 'acoustic' and 'gravity' modes, can be excited. For realistic atmospheric parameters, the acoustic and gravity modes have a period of 275 and 304 s, respectively. For a realistic time history of eruption, atmospheric oscillations with an amplitude of 50 to 100 Pa (0.5 to 1 mbar) can be excited by an energy injection source with a total energy of 10(exp 17) J. This result is consistent with the observations and provides a physical basis for interpretation of atmospheric oscillations excited by volcanic eruptions.

  16. Propagation of Localized Excitations in Desoxyribonucleic Acid

    NASA Astrophysics Data System (ADS)

    Yang, Xian-jun; Zhuo, Yi-zhong; Wu, Xi-zhen

    1997-12-01

    The result that the process by which the pulses, initially distributed in desoxyribonucleic acid(DNA) molecules can resume its form to localize the large amplitude excitations is proposed. This process may play an important role in the dynamics of localized thermal bubble for the transcription of DNA molecules.

  17. Magnetic Excitations from Stripes in Cuprate Superconductors

    NASA Astrophysics Data System (ADS)

    Tranquada, J. M.; Woo, H.; Perring, T. G.; Goka, H.; Gu, G. D.; Xu, G.; Fujita, M.; Yamada, K.

    2004-03-01

    While it is generally believed that antiferromagnetic spin excitations play a significant role in the pairing mechanism of copper-oxide superconductors [1], the nature of the magnetic excitations themselves remains a matter of controversy. Recent measurements of the dispersion of spin excitations in superconducting YBa_2Cu_3O_6+x (YBCO) have attracted much attention. Here we present the results of comprehensive inelastic neutron scattering measurements of the momentum- and energy-dependent spectra of the magnetic fluctuations in La_0.875Ba_0.125CuO_4, which exhibits inhomogeneous, charge-stripe order. We will also point out universalities and differences in the magnetic excitation spectra compared to related charge-stripe ordered compounds and high-temperature superconductors, including La_2-xSr_xNiO4 and YBCO. JMT, HW, GDG and GX are supported by U.S. Department of Energy contract # DE-AC02-98CH1088 [1] J. Orenstein and A. J. Millis, Science 288, 468 (2000).

  18. The CLAS Excited Baryon Program at JLab

    SciTech Connect

    Crede, Volker

    2007-10-26

    Nucleons are complex systems of confined quarks and exhibit characteristic spectra of excited states. Highly excited nucleon states are sensitive to details of quark confinement which is poorly understood within Quantum Chromodynamics (QCD), the fundamental theory of strong interactions. Thus, measurements of excited states and the corresponding determination of their properties are needed to come to a better understanding of how confinement works in nucleons. However, the excited states of the nucleon cannot simply be inferred from cleanly separated spectral lines. Quite the contrary, a spectral analysis in nucleon resonance physics is challenging because of the fact that the resonances are broadly overlapping states which decay into a multitude of final states involving mesons and baryons. To provide a consistent and complete picture of an individual nucleon resonance, the various possible production and decay channels must be treated in a multichannel framework that permits separating resonance from background contributions. Very often, resonances reveal themselves more clearly through interference with dominant amplitudes. These interference terms can be isolated via polarization observables. The current CLAS effort is to utilize highly-polarized hydrogen and deuterium targets as well as polarized photon beams toward a complete measurement of a large number of reaction channels.

  19. The CLAS Excited Baryon Program at Jlab

    SciTech Connect

    Volker Crede

    2007-10-01

    Nucleons are complex systems of confined quarks and exhibit characteristic spectra of excited states. Highly excited nucleon states are sensitive to details of quark confinement which is poorly understood within Quantum Chromodynamics (QCD), the fundamental theory of strong interactions. Thus, measurements of excited states and the corresponding determination of their properties are needed to come to a better understanding of how confinement works in nucleons. However, the excited states of the nucleon cannot simply be inferred from cleanly separated spectral lines. Quite the contrary, a spectral analysis in nucleon resonance physics is challenging because of the fact that the resonances are broadly overlapping states which decay into a multitude of final states involving mesons and baryons. To provide a consistent and complete picture of an individual nucleon resonance, the various possible production and decay channels must be treated in a multichannel framework that permits separating resonance from background contributions. Very often, resonances reveal themselves more clearly through interference with dominant amplitudes. These interference terms can be isolated via polarization observables. The current CLAS effort is to utilize highly-polarized hydrogen and deuterium targets as well as polarized photon beams toward a complete measurement of a large number of reaction channels.

  20. Excitation modes in non-axial nuclei

    SciTech Connect

    Leviatan, A.; Ginnochio, J.N.

    1990-01-01

    Excitation modes of non-axial quadrupole shapes are investigated in the framework of interacting boson models. Both {gamma}-unstable and {gamma}-rigid nuclear shapes are considered for systems with one type of boson as well as with proton-neutron bosons. 6 refs.

  1. Nuclear Excitation by Electronic Transition - NEET

    SciTech Connect

    Becker, J.A.

    2002-06-10

    Experiments seeking to demonstrate nuclear excitation induced by synchrotron radiation have been enabled by the development of intense synchrotron radiation. The phenomena has been demonstrated in {sup 197}Au, while realistic upper limits for {sup 189}Os have been established. A new experiment in {sup 189}Os is described. The experimental claim of NEET in isomeric {sup 178}Hf is not credible.

  2. Residual Excitation and Ego-Defensive Attributions.

    ERIC Educational Resources Information Center

    Gollwitzer, Peter M.; Earle, Walter B.

    It has been suggested that egotistical attributions for success and failure are mediated by the affective reactions resulting from achievement outcomes. To establish the motivational impact of failure-related affect on subsequent ego-defensive attributions, an excitation transfer paradigm was used to manipulate the negative feelings elicited by…

  3. Contour Line Portraits: Excited about Artistic Abilities

    ERIC Educational Resources Information Center

    Neal, Kari Gertz

    2012-01-01

    In this article, the author describes a self-portrait project that encouraged students, boosted their self-confidence, and got them excited about their artistic abilities--while producing amazing results. This lesson effectively develops artistic ability by compelling students to see that drawing is quite simply breaking down objects into the…

  4. How to Generate Student Excitement in Science

    ERIC Educational Resources Information Center

    Ediger, Marlow

    2005-01-01

    To successfully generate student excitement in science, teachers need to be flexible regarding their curriculums. Students also need to be open to novel, hands-on experiences. This article describes a student teacher (ST) who taught a science unit on "Our Environment." She had already prepared her lesson and unit thoroughly but she changed the…

  5. Engage and Excite Students with Educational Games

    ERIC Educational Resources Information Center

    Petsche, Jennifer

    2011-01-01

    Using educational games to learn or reinforce lessons engages students and turns a potentially boring subject into something exciting and desirable to know! Games offer teachers and parents a new way to grab students' attention so that they will retain information. Games have become a teaching tool, an invaluable resource for reaching students in…

  6. Saturated excitation of fluorescence to quantify excitation enhancement in aperture antennas.

    PubMed

    Aouani, Heykel; Hostein, Richard; Mahboub, Oussama; Devaux, Eloïse; Rigneault, Hervé; Ebbesen, Thomas W; Wenger, Jérôme

    2012-07-30

    Fluorescence spectroscopy is widely used to probe the electromagnetic intensity amplification on optical antennas, yet measuring the excitation intensity amplification is a challenge, as the detected fluorescence signal is an intricate combination of excitation and emission. Here, we describe a novel approach to quantify the electromagnetic amplification in aperture antennas by taking advantage of the intrinsic non linear properties of the fluorescence process. Experimental measurements of the fundamental f and second harmonic 2f amplitudes of the fluorescence signal upon excitation modulation are used to quantify the electromagnetic intensity amplification with plasmonic aperture antennas.

  7. Reactions of R(2)P-P(SiMe(3))Li with [(R'(3)P)(2)PtCl(2)]. A general and efficient entry to phosphanylphosphinidene complexes of platinum. Syntheses and structures of [(eta(2)-P=(i)Pr(2))Pt(p-Tol(3)P)(2)], [(eta(2)-P=(t)Bu(2))Pt(p-Tol(3)P)(2)], [{eta(2)-P=(N(i)Pr(2))(2)}Pt(p-Tol(3)P)(2)] and [{(Et(2)PhP)(2)Pt}(2)P(2)].

    PubMed

    Domańska-Babul, Wioleta; Chojnacki, Jaroslaw; Matern, Eberhard; Pikies, Jerzy

    2009-01-07

    The reactions of lithium derivatives of diphosphanes R(2)P-P(SiMe(3))Li (R = (t)Bu, (i)Pr, Et(2)N and (i)Pr(2)N) with [(R'(3)P)(2)PtCl(2)] (R'(3)P = Et(3)P, Et(2)PhP, EtPh(2)P and p-Tol(3)P) proceed in a facile manner to afford side-on bonded phosphanylphosphinidene complexes of platinum [(eta(2)-P=R(2))Pt(PR'(3))(2)]. The related reactions of Ph(2)P-P(SiMe(3))Li with [(R'(3)P)(2)PtCl(2)] did not yield [(eta(2)-P=PPh(2))Pt(PR'(3))(2)] and resulted mainly in the formation of [{(R'(3)P)(2)Pt}(2)P(2)], Ph(2)P-PLi-PPh(2), (Me(3)Si)(2)PLi and (Me(3)Si)(3)P. Crystallographic data are reported for the compounds [(eta(2)-P=R(2))Pt(p-Tol(3)P)(2)] (R = (t)Bu, (i)Pr, ((i)Pr(2)N)(2)P) and for [{(Et(2)PhP)(2)Pt}(2)P(2)].

  8. Excitation mechanism of non-migrating tides

    NASA Astrophysics Data System (ADS)

    Miyoshi, Yasunobu; Pancheva, Dora; Mukhtarov, Plamen; Jin, Hidekatsu; Fujiwara, Hitoshi; Shinagawa, Hiroyuki

    2017-04-01

    Using an atmosphere-ionosphere coupled model, the excitation source and temporal (seasonal and interannual) variations in non-migrating tides are investigated in this study. We first focus our attention on temporal variations in eastward moving diurnal tide with zonal wavenumber 3 (DE3), which is the largest of all the non-migrating tides in the mesosphere and lower thermosphere (MLT). Our simulation results indicate that upward propagation of the DE3 excited in the troposphere is sensitive to the zonal mean zonal wind in the stratosphere and mesosphere. The DE3 amplitude is enhanced in the region where the vertical shear of the zonal mean zonal wind is positive (westerly shear). Quasi-2-year variation in the DE3 amplitude in the MLT region is generated by quasi-2-year variation in the zonal mean zonal wind between 40 and 70 km, which is modulated by the stratospheric QBO. The excitation mechanisms of SW3 (westward moving semidiurnal tide with zonal wavenumber 3) and SW1 (westward moving semidiurnal tide with zonal wavenumber 1) are also investigated. During equinoxes, the SW3 and SW1 are excited by tropospheric heating (latent heat release and solar radiative heating) associated with cumulus convection in the tropics, and propagate upward into the MLT region. On the other hand, during solstices, SW3 and SW1 are generated in the winter stratosphere and mesosphere through the nonlinear interaction between the stationary planetary wave and migrating semidiurnal tide, and propagate upward to the lower thermosphere. The excitation sources of other non-migrating tides are also discussed.

  9. Accelerating slow excited state proton transfer

    PubMed Central

    Stewart, David J.; Concepcion, Javier J.; Brennaman, M. Kyle; Binstead, Robert A.; Meyer, Thomas J.

    2013-01-01

    Visible light excitation of the ligand-bridged assembly [(bpy)2RuaII(L)RubII(bpy)(OH2)4+] (bpy is 2,2′-bipyridine; L is the bridging ligand, 4-phen-tpy) results in emission from the lowest energy, bridge-based metal-to-ligand charge transfer excited state (L−•)RubIII-OH2 with an excited-state lifetime of 13 ± 1 ns. Near–diffusion-controlled quenching of the emission occurs with added HPO42− and partial quenching by added acetate anion (OAc−) in buffered solutions with pH control. A Stern–Volmer analysis of quenching by OAc− gave a quenching rate constant of kq = 4.1 × 108 M−1⋅s−1 and an estimated pKa* value of ∼5 ± 1 for the [(bpy)2RuaII(L•−)RubIII(bpy)(OH2)4+]* excited state. Following proton loss and rapid excited-state decay to give [(bpy)2RuaII(L)RubII(bpy)(OH)3+] in a H2PO4−/HPO42− buffer, back proton transfer occurs from H2PO4− to give [(bpy)2RuaII(L)Rub(bpy)(OH2)4+] with kPT,2 = 4.4 × 108 M−1⋅s−1. From the intercept of a plot of kobs vs. [H2PO4−], k = 2.1 × 106 s−1 for reprotonation by water providing a dramatic illustration of kinetically limiting, slow proton transfer for acids and bases with pKa values intermediate between pKa(H3O+) = −1.74 and pKa(H2O) = 15.7. PMID:23277551

  10. Self-excitation of single nanomechanical pillars

    NASA Astrophysics Data System (ADS)

    Kim, Hyun S.; Qin, Hua; Blick, Robert H.

    2010-03-01

    Self-excitation is a mechanism that is ubiquitous for electromechanical power devices such as electrical generators. This is conventionally achieved by making use of the magnetic field component in electrical generators (Nedic and Lipo 2000 IEEE/IAS Conf. Records (Rome, Italy) vol 1 pp 51-6), a good and widely visible example of which is the wind turbine farm (Muljadi et al 2005 J. Sol. Energy Eng. 127 581-7). In other words, a static force, such as the wind acting on rotor blades, can generate a resonant excitation at a certain mechanical frequency. For nanomechanical systems (Craighead 2000 Science 290 1532-5 Roukes 2001 Phys. World 14 25-31 Cleland 2003 Foundations of Nanomechanics (Berlin: Springer); Ayari et al 2007 Nano Lett. 7 2252-7 Koenig et al 2008 Nat. Nanotechnol. 3 482-4) such a self-excitation (SE) mechanism is also highly desirable, because it can generate mechanical oscillations at radio frequencies by simply applying a dc bias voltage. This is of great importance for low-power signal communication devices and detectors, as well as for mechanical computing elements. For a particular nanomechanical system—the single electron shuttle—this effect was predicted some time ago by Gorelik et al (Phys. Rev. Lett. 80 4526-9). Here, we use a nanoelectromechanical single electron transistor (NEMSET) to demonstrate self-excitation for both the soft and hard regimes, respectively. The ability to use self-excitation in nanomechanical systems may enable the detection of quantum mechanical backaction effects (Naik et al 2006 Nature 443 193-6) in direct tunneling, macroscopic quantum tunneling (Savelev et al 2006 New J. Phys. 8 105-15) and rectification (Pistolesi and Fazio 2005 Phys. Rev. Lett. 94 036806-4). All these effects have so far been overshadowed by the large driving voltages that had to be applied.

  11. Cascadable excitability in optically injected microdisks

    NASA Astrophysics Data System (ADS)

    Van Vaerenbergh, Thomas; Alexander, Koen; Fiers, Martin; Mechet, Pauline; Dambre, Joni; Bienstman, Peter

    2014-05-01

    All-optical spiking neural networks would allow high speed parallelized processing of time-encoded information, using the same energy efficient computational principles as our brain. As the neurons in these networks need to be able to process pulse trains, they should be excitable. Using simulations, we demonstrate Class 1 excitability in optically injected microdisk lasers, and propose a cascadable optical spiking neuron design. The neuron has a clear threshold and an integrating behavior. In addition, we show that the optical phase of the input pulses can be used to create inhibitory, as well as excitatory perturbations. Furthermore, we incorporate our optical neuron design in a topology that allows a disk to react on excitations from other disks. Phase tuning of the intermediate connections allows to control the disk response. Additionally, we investigate the sensitivity of the disk circuit to deviations in driving current and locking signal wavelength detuning. Using state-of-the-art fabrication techniques for microdisk laser, the standard deviation of the lasing wavelength is still about one order of magnitude too large. Finally, as the dynamical behavior of the microdisks is identical to the behavior in Semiconductor Ring Lasers (SRL), we compare the excitability mechanism due to optically injection with the previously proposed excitability due to asymmetry in the intermodal coupling in SRLs, as the latter mechanism can also be induced in disks due to, e.g., asymmetry in the external reaction. In both cases, the symmetry between the two counter-propagating modes of the cavity needs to be broken to prevent switching to the other mode, and allow the system to relax to its initial state after a perturbation. However, the asymmetry due to optical injection results in an integrating spiking neuron, whereas the asymmetry in the intermodal coupling is known to result in a resonating spiking neuron.

  12. Peroxyacetyl radical: Electronic excitation energies, fundamental vibrational frequencies, and symmetry breaking in the first excited state

    SciTech Connect

    Copan, Andreas V.; Wiens, Avery E.; Nowara, Ewa M.; Schaefer, Henry F.; Agarwal, Jay

    2015-02-07

    Peroxyacetyl radical [CH{sub 3}C(O)O{sub 2}] is among the most abundant peroxy radicals in the atmosphere and is involved in OH-radical recycling along with peroxyacetyl nitrate formation. Herein, the ground (X{sup ~}) and first (A{sup ~}) excited state surfaces of cis and trans peroxyacetyl radical are characterized using high-level ab initio methods. Geometries, anharmonic vibrational frequencies, and adiabatic excitation energies extrapolated to the complete basis-set limit are reported from computations with coupled-cluster theory. Excitation of the trans conformer is found to induce a symmetry-breaking conformational change due to second-order Jahn-Teller interactions with higher-lying excited states. Additional benchmark computations are provided to aid future theoretical work on peroxy radicals.

  13. Coulomb excitation of states in 238U

    NASA Astrophysics Data System (ADS)

    McGowan, F. K.; Milner, W. T.

    1994-05-01

    Twenty-two states in 238U have been observed with 18 MeV 4He ions on a thick target. Eight 2 + states between 966 and 1782 keV and three 3 - states are populated by direct E2 and E3, respectively. The remaining states are either weakly excited by multiple Coulomb excitation and /or populated by the γ-ray decay of the directly excited states. Spin assignments are based on γ-ray angular distributions. Reduced transition probabilities have been deduced from the γ-ray yields. The B(E2) values for excitation of the 2 + states range from 0.10 to 3.0 W.u. (281 W.u. for the first 2 + state). For the 3 states, the B(E3, 0 → 3 -) values are 7.1, 7.8, and 24.2 W.u. Several of the 2 + states have decay branches to the one-phonon states with B(E2) values between 27 and 56 W.u. which are an order of magnitude larger than the B(E2) values between the one- and zero-phonon states. This disagrees with our present understanding of collectivity in nuclei if these 2 + states are considered to be collective two-phonon excitations. However, the excitation energies of these 2 + states with respect to the one-phonon states are only 1.3 to 1.6. The B(E1) values for 17 transitions between the positive- and negative-parity states range between 10 -3 and 10 -7 W.u. The B(E1) branching ratios for many of these transitions have large deviations from the Alaga-rule predictions. These deviations can be understood by the strong Coriolis coupling between the states of the one-phonon octupole quadruplet in deformed nuclei. The general features of the experimental results for the B(E3) values are reproduced by the microscopic calculations of Neergård and Vogel when the Coriolis coupling between the states of the octupole quadruplet is included.

  14. Coulomb excitation of states in 232Th

    NASA Astrophysics Data System (ADS)

    McGowan, F. K.; Milner, W. T.

    1993-09-01

    Twenty-five states in 232Th have been observed with 18 MeV 4He ions on a thick target. Eleven 2 + states between 774 and 1554 keV and three 3 - states are populated by direct E2 and E3, respectively. The remaining states are either weakly excited by multiple Coulomb excitation and/or populated by the decay of the directly excited states. Spin assignments are based on γ-ray angular distributions. Reduced transition probabilities have been deduced from the γ-ray yields. The B(E2) values for excitation of the 2 + states range from 0.024 to 3.5 W.u. (222 W.u. for the first 2 + state). For the 3 - states, the B(E3,0 → 3 -) values are 1.7, 11, and 24 W.u. A possible two-phonon state at 1554 keV, which is nearly harmonic, decays to four members of the one-phonon states, to the ground-state band, and to the K = 0 - octupole band. The B(E2) value for excitation of this state is 0.66 ± 0.05 W.u. and the B(E1) values for decay of this state are (2 and 6)×10 -4 W.u. The B(E2) values between two- and one-phonon vibrational states range between 16 and 53 W.u. which are an order of magnitude larger than the B(E2) values between the one- and zero-phonon states. This disagrees with our present understanding of collectivity in nuclei if this 2 + state is considered to be a collective two-phonon excitation. The 2 + states at 1477 and 1387 keV, which are also nearly harmonic, are possible candidates with two-phonon structure. The agreement between the experimental results and the microscopic calculations by Neergård and Vogel of the B(E3,0 → 3) for the 3 - members of the one-phonon octupole quadruplet is satisfactory when the Coriolis coupling between the states with K and K ± 1 is included. The B(E1) branching ratios for transitions from the 3 - and 1 - states to the ground-state band have large deviations from the Alaga-rule predictions. These deviations can be understood by the strong Coriolis coupling between the states of the octupole quadruplet in deformed nuclei.

  15. Direct excitation of microwave-spin dressed states using a laser-excited resonance Raman interaction

    NASA Astrophysics Data System (ADS)

    Shahriar, M. S.; Hemmer, P. R.

    1990-10-01

    We have used a laser-induced resonance Raman transition between the ground-state hyperfine sublevels in a sodium atomic beam to excite individual dressed states of the microwave-spin hyperfine transition. In addition, we have used the microwave interaction to excite the Raman trapped state. Extension of this technique to mm waves or to the far infrared may lead to applications such as mm-wave-beam steering and holographic image conversion.

  16. Solution phase isomerization of vibrationally excited singlet nitrenes to vibrationally excited 1,2-didehydroazepine.

    PubMed

    Burdzinski, Gotard T; Middleton, Chris T; Gustafson, Terry L; Platz, Matthew S

    2006-11-22

    Photolysis of phenyl and o-biphenylyl azide (at 270 nm) releases vibrationally excited singlet nitrene which isomerizes to the corresponding hot 1,2-didehydroazepine at a rate competitive with thermal relaxation. Using ultrafast vibrational spectroscopy we observe the formation of vibrationally excited 1,2-4,6-azacycloheptatetraene (1,2-didehydroazepine) in picoseconds following photolysis of phenyl azide in chloroform and o-biphenylyl azide in acetonitrile at ambient temperature.

  17. Search for intrinsic collective excitations in Sm152

    NASA Astrophysics Data System (ADS)

    Kulp, W. D.; Wood, J. L.; Garrett, P. E.; Wu, C. Y.; Cline, D.; Allmond, J. M.; Bandyopadhyay, D.; Dashdorj, D.; Choudry, S. N.; Hayes, A. B.; Hua, H.; Mynk, M. G.; McEllistrem, M. T.; McKay, C. J.; Orce, J. N.; Teng, R.; Yates, S. W.

    2008-06-01

    The 685 keV excitation energy of the first excited 0+ state in Sm152 makes it an attractive candidate to explore expected two-phonon excitations at low energy. Multiple-step Coulomb excitation and inelastic neutron scattering studies of Sm152 are used to probe the E2 collectivity of excited 0+ states in this “soft” nucleus and the results are compared with model predictions. No candidates for two-phonon Kπ=0+quadrupole vibrational states are found. A 2+,K=2 state with strong E2 decay to the first excited Kπ=0+ band and a probable 3+ band member are established.

  18. Resonance Raman and photoluminescence excitation profiles and excited-state dynamics in CdSe nanocrystals

    NASA Astrophysics Data System (ADS)

    Baker, Joshua A.; Kelley, David F.; Kelley, Anne Myers

    2013-07-01

    Resonance Raman excitation profiles for the longitudinal optical (LO) phonon fundamental and its first overtone have been measured for organic ligand capped, wurtzite form CdSe nanocrystals of ˜3.2 nm diameter dissolved in chloroform. The absolute differential Raman cross-section for the fundamental is much larger when excited at 532 or 543 nm, on the high-frequency side of the lowest-wavelength absorption maximum, than for excitation in the 458-476 nm range although the absorbance is higher at the shorter wavelengths. That is, the quantum yield for resonance Raman scattering is reduced for higher-energy excitation. In contrast, the photoluminescence quantum yield is relatively constant with wavelength. The optical absorption spectrum and the resonance Raman excitation profiles and depolarization dispersion curves are reproduced with a model for the energies, oscillator strengths, electron-phonon couplings, and dephasing rates of the multiple low-lying electronic excitations. The Huang-Rhys factor for LO phonon in the lowest excitonic transition is found to lie in the range S = 0.04-0.14. The strong, broad absorption feature about 0.5 eV above the lowest excitonic peak, typically labeled as the 1P3/21Pe transition, is shown to consist of at least two significant components that vary greatly in the magnitude of their electron-phonon coupling.

  19. Two-Photon Excitation of Conjugated Molecules in Solution: Spectroscopy and Excited-State Dynamics

    NASA Astrophysics Data System (ADS)

    Elles, Christopher G.; Houk, Amanda L.; de Wergifosse, Marc; Krylov, Anna

    2017-06-01

    We examine the two-photon absorption (2PA) spectroscopy and ultrafast excited-state dynamics of several conjugated molecules in solution. By controlling the relative wavelength and polarization of the two photons, the 2PA measurements provide a more sensitive means of probing the electronic structure of a molecule compared with traditional linear absorption spectra. We compare experimental spectra of trans-stilbene, cis-stilbene, and phenanthrene in solution with the calculated spectra of the isolated molecules using EOM-EE-CCSD. The calculated spectra show good agreement with the low-energy region of the experimental spectra (below 6 eV) after suppressing transitions with strong Rydberg character and accounting for solvent and method-dependent shifts of the valence transitions. We also monitor the excited state dynamics following two-photon excitation to high-lying valence states of trans-stilbene up to 6.5 eV. The initially excited states rapidly relax to the lowest singlet excited state and then follow the same reaction path as observed following direct one-photon excitation to the lowest absorption band at 4.0 eV.

  20. Excitation of millimeter and submillimeter water masers

    NASA Technical Reports Server (NTRS)

    Neufeld, David A.; Melnick, Gary J.

    1991-01-01

    The excitation of maser emission in millimeter and submillimeter transitions of interstellar and circumstellar water is considered. An escape probability method is used to determine the equilibrium populations in 349 rotational states of both ortho- and para-water under varying conditions of gas temperature, density, water abundance, and radiation field. It is shown that, under those conditions believed to prevail around late-type stars and within star-forming regions, strong millimeter and submillimeter water maser emission can be generated by collisional excitations by H2. Several maser transitions can have strengths close to that of the 22 GHz line. The water maser line which can be observed from mountaintop facilities and those which will require air- or space-borne platforms are indicated. The exact portion of parameter space in which each maser transition exhibits peak emission is shown.