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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. 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.

  3. 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.

  4. Electronic states of BP, BP +, BP -, B 2P 2, B2P2- and B2P2+

    NASA Astrophysics Data System (ADS)

    Linguerri, Roberto; Komiha, Najia; Oswald, Rainer; Mitrushchenkov, Alexander; Rosmus, Pavel

    2008-05-01

    Using augmented sextuple zeta basis sets and internally contracted multireference configuration interaction (MRCI) wavefunctions, potential energy, electric dipole and transition moments have been computed for the X 3Π, a 1Σ +, b 1Π and A 3Σ - states of BP, X 2Σ + and A 2Π states of BP - and X 4Σ - and A 4Π states of BP +. From these data spectroscopic constants, radiative transition probabilities and photoelectron spectra of BP - and BP have been evaluated. The non-vanishing spin-orbit coupling elements between the four low lying triplet and singlet states of the neutral BP have also been calculated from MRCI wavefunctions. The treatment of the corresponding perturbations in the manifold of dense rovibrational states in the three lowest states would require a precise knowledge of the electronic excitation energies. Our best singlet-triplet separations (X-a) are calculated to be 2412 cm -1 (MRCI) and 2482 cm -1 (restricted coupled cluster with perturbative triples (RCCSD(T))) with an estimated error bound of about ±200 cm -1. All three states have long radiative lifetimes with cascading among the rovibrational levels of different states. The ionization energy IE e of BP is calculated to be 9.22 eV (MRCI) and 9.48 eV (RCCSD(T)), the electron affinity EA e 2.51 eV (MRCI) and 2.74 eV (RCCSD(T)). The photoelectron spectra of BP and BP - have been obtained from the Franck-Condon factors of the MRCI potentials. For the UV spectroscopy the dipole allowed radiative transition probabilities are given for A 3Σ - ↔ X 3Π, b 1Π ↔ a 1Σ + of BP, A 2Π ↔ X 2Σ + of BP - and A 4Π ↔ X 4Σ - of BP +. The ionization energy IE e of B 2P 2 of 8.71 eV and the electron affinity EA e of 2.34 eV have been calculated by the RCCSD(T)/aVQZ approach. Also the harmonic vibrational wavenumbers for the electronic ground states of the ions B2P2+ and B2P2- are given.

  5. 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) .

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

    DOE PAGESBeta

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

    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

    DOE PAGESBeta

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

    2016-07-19

    Here, 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 temperaturemore » 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 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

  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. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Evolution of superconductivity and magnetism in La1-xYbxRu2P2

    NASA Astrophysics Data System (ADS)

    Roncaioli, Connor; Hodovanets, Halyna; Saha, Shanta; Paglione, Johnpierre

    LaRu2P2, with a 4.1 K transition, is the first known pnictide-based superconductor. Sharing structural and electronic elements similar to those of the unconventional Fe-pnictide superconductors, it is of interest to investigate the parameter space in which a superconducting ground state survives. We present preliminary indications of more interesting magnetic behavior and structural tuning behavior when paramagnetic Yb is substituted for La in La1-xYbxRu2P2, and investigate potential heavy fermion behavior in the Yb end-member of this series.

  15. 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).

  16. 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.

  17. A new barium titanium (III) pyrophosphate: BaTi 2(P 2O 7) 2

    NASA Astrophysics Data System (ADS)

    Wang, Shumin; Hwu, Shiou-Jyh

    1991-01-01

    The new barium titanium (III) pyrophosphate BaTi 2(P 2O 7) 2 has been prepared by conventional high temperature solid state reaction at 900°C in a fused silica tube. BaTi 2(P 2O 7) 2 crystallizes with four formula units in a cell with dimensions a = 10.680(3) Å, b = 10.564(4) Å, c = 9.834(4) Å/, β = 102.88(3)° and V = 1081.6(6) Å 3 in space group C 62h  C {2}/{c} (No. 15) of the monoclinic system. The single crystal structure refinement gives a final structure solution with R index on F2o of 0.018 for 99 variables and GOF = 1.05. BaTi 2(P 2O 7) 2 displays a new layered type structure which consists of layers of slightly distorted TiO 6 octahedra with (P 2O 7) and (BaO 10) polyhedra between the layers. The structural framework is built up from corner-sharing TiO 6 octahedra and P 2O 7 pyrophosphate groups, to give rise to [Ti 2(P 2O 7) 2] 2- units and to form tunnels where the barium cations reside. Magnetic susceptibility measurements on selected single crystals confirm the presence of Ti 3+ ( d1) ions with spin S = {1}/{2}. The high oxidative thermal stability of BaTi 2(P 2O 7) 2 versus the stabilities of other trivalent titanium cation-containing compounds, including Ti 2O 3, TiPO 4, and BaTi 2(PO 4) 3, owing to possible anion matrix effects are discussed.

  18. Wave mixing in nominally undoped Sn2P2S6 at high light intensities

    NASA Astrophysics Data System (ADS)

    Shumelyuk, A.; Wesner, M.; Imlau, M.; Odoulov, S.

    2009-06-01

    The intensity dependence of the photorefractive response of Sn2P2S6 is studied for the Kr+-laser wavelength of 647 nm and pump-beam intensities of up to 10 W/cm2. A considerable enhancement of the two-beam coupling gain factor with increasing intensity at a grating spacing of ≃1 μm is attributed to a light-induced increase of the effective trap density. The large gain reached at high intensities is applied for the build up of a double phase conjugate mirror with a sub-millisecond switch-on time.

  19. 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.

  20. Electron-phonon interaction and superconductivity in BaIr2P2.

    PubMed

    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 [Formula: see text] and the logarithmically averaged phonon frequency was [Formula: see text] K. From the Allen-Dynes formula, with [Formula: see text], the superconducting critical temperature was estimated to be [Formula: see text] 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.

  1. Electronic Structure and Phase Transition in Ferroelectic Sn2P2S6 Crystal

    PubMed Central

    Glukhov, Konstantin; Fedyo, Kristina; Banys, Juras; Vysochanskii, Yulian

    2012-01-01

    An analysis of the P2S6 cluster electronic structure and its comparison with the crystal valence band in the paraelectric and ferroelectric phases has been done by first-principles calculations for Sn2P2S6 ferroelectrics. The origin of ferroelectricity has been outlined. It was established that the spontaneous polarization follows from the stereochemical activity of the electron lone pair of tin cations, which is determined by hybridization with P2S6 molecular orbitals. The chemical bonds covalence increase and rearrangement are related to the valence band changes at transition from the paraelectric phase to the ferroelectric phase. PMID:23203069

  2. 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.

  3. Pressure Induced Enhancement of Superconductivity in LaRu2P2.

    PubMed

    Li, Baoxuan; Lu, Pengchao; 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

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. A Simple Pythagorean Interpretation of E2 = p2 c2 + (mc2)2

    NASA Astrophysics Data System (ADS)

    Tobar, J. A.; Guillen, C. I.; Vargas, E. L.; Andrianarijaona, V. M.

    2015-04-01

    We are considering the relationship between the relativistic energy, the momentum, and the rest energy, E2 =p2c2 + (mc2)2 , and using geometrical means to analyze each individual portion in a spatial setting. The aforementioned equation suggests that pc and mc2 could be thought of as the two axis of a plane. According to de Broglie's hypothesis λ = h / p therefore suggesting that the pc-axis is connected to the wave properties of a moving object, and subsequently, the mc2-axis is connected to the particle properties such as its moment of inertia. Consequently, these two axes could represent the particle (matter) and wave properties of the moving object. An overview of possible models and meaningful interpretations, which agree with Dirac's prediction of the electron's magnetic moment, will be presented. Authors wish to give special thanks to Pacific Union College Student Senate in Angwin, California, for their financial support.

  9. A Simple Pythagorean Interpretation of E2 = p2c2 + (mc2)2

    NASA Astrophysics Data System (ADS)

    Tobar, J. A.; Vargas, E. L.; Andrianarijaona, V. M.

    2015-03-01

    We are considering the relationship between the relativistic energy, the momentum, and the rest energy, E2 =p2c2 + (mc2)2 , and using geometrical means to analyze each individual portion in a spatial setting. The aforementioned equation suggests that pc and mc2 could be thought of as the two axis of a plane. According to de Broglie's hypothesis λ = h / p therefore suggesting that the pc-axis is connected to the wave properties of a moving object, and subsequently, the mc2-axis is connected to the particle properties. Consequently, these two axis could represent the particle and wave properties of the moving object. An overview of possible models and meaningful interpretations will be presented. Authors wish to give special thanks to Pacific Union College Student Senate in Angwin, California, for their financial support.

  10. Electron-phonon interaction and superconductivity in BaIr2P2.

    PubMed

    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 [Formula: see text] and the logarithmically averaged phonon frequency was [Formula: see text] K. From the Allen-Dynes formula, with [Formula: see text], the superconducting critical temperature was estimated to be [Formula: see text] 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. PMID:27494506

  11. Elastic and acoustooptic properties of Sn2P2S6 crystals: Effect of ferroelectric phase transition

    NASA Astrophysics Data System (ADS)

    Mys, O.; Zapeka, B.; Martynyuk-Lototska, I.; Vlokh, R.

    2012-12-01

    We report on the studies for temperature dependences of elastic stiffness coefficients in Sn2P2S6 crystals. Basing on the construction of acoustic velocity surfaces, we have determined the parameters of the slowest acoustic wave that propagates in Sn2P2S6 crystals. The acoustooptic figure of merit for the case of acoustooptic interaction with this wave is estimated as ˜0.8 × 10-12 s3/kg. We have shown that Sn2P2S6 is very close to the conditions of tricritical point on the (x, T)- and (p, T)-phase diagrams of the solid solutions Sn2P2(SexS1-x)6. The critical exponent α of the heat capacity for the Sn2P2S6 crystals is equal to 0.42 ± 0.03.

  12. Electron-phonon superconductivity in the ternary phosphides Ba M2P2 (M =Ni,Rh,and Ir)

    NASA Astrophysics Data System (ADS)

    Karaca, Ertuǧrul; Tütüncü, H. M.; Srivastava, G. P.; Uǧur, S.

    2016-08-01

    Ab initio plane-wave pseudopotential calculations of electronic and vibrational properties have been carried out for the ternary phosphides Ba M2P2 (M =Ni,Rh and Ir) with a ThCr2Si2 -type structure. The calculated electronic results show the metallic character of Ba M2P2 , and the plots of total and partial density of states of Ba M2P2 exhibit strong hybridization between the d states of the M atom and the p states of the P atom below the Fermi energy. Differences in the phonon spectrum and density of states both in the acoustical and optical ranges for these compounds are presented and discussed. The Eliashberg spectral function for these compounds has been calculated by using a linear response approach based on the density functional theory. By integrating the Eliashberg spectral function, the average electron-phonon coupling parameter (λ ) is determined to be 0.61 for BaNi2P2 , 0.55 for BaIr2P2 , and 0.43 for BaRh2P2 . Using the calculated values of λ and the logarithmically averaged phonon frequency ωln the superconducting critical temperature (Tc) values for BaNi2P2,BaIr2P2 , and BaRh2P2 are obtained to be 2.80, 1.97, and 0.70 K, respectively, which compare very well with their experimental values of 3.0, 2.1, and 1.0 K.

  13. Magnetic phase diagram of Sr1-xCaxCo2P2

    NASA Astrophysics Data System (ADS)

    Sugiyama, J.; Nozaki, H.; Umegaki, I.; Harada, M.; Higuchi, Y.; Ansaldo, E. J.; Brewer, J. H.; Imai, M.; Michioka, C.; Yoshimura, K.; Månsson, M.

    2014-12-01

    In order to study the phase diagram from a microscopic viewpoint, we have measured wTF- and ZF-μ+SR spectra for the Sr1-xCaxCo2P2 powder samples with x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1. Due to a characteristic time window and spatial resolution of μ+SR, the obtained phase diagram was found to be rather different from that determined by magnetization measurements. That is, as x increases from 0, a Pauli-paramagnetic phase is observed even at the lowest T measured (1.8 K) until x = 0.4, then, a spin-glass like phase appears at 0.5 <= x <= 0.6, and then, a phase with wide field distribution probably due to incommensurate AF order is detected for x = 0.8, and finally, a commensurate A-type AF ordered phase (for x = 1) is stabilized below TN ~ 80 K. Such change is most likely reasonable and connected to the shrink of the c-axis length with x, which naturally enhances the magnetic interaction between the two adjacent Co planes.

  14. 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.

  15. A Mo(V) Monophosphate with an Intersecting Tunnel Structure: K 2Mo 2P 2O 11

    NASA Astrophysics Data System (ADS)

    Gueho, C.; Borel, M. M.; Grandin, A.; Leclaire, A.; Raveau, B.

    1993-06-01

    A new molybdenum (V) monophosphate K 2Mo 2P 2O 11 has been isolated. The single crystal X-ray diffraction study of this phase has shown that it is isotypic with K 2Nb 2As 2O 11. It crystallizes in the P21/ c space group with a = 9.867 (2), b = 10.122 (1), c = 9.903 (2) Å, β = 97.95 (1)°. A new description of the structure is given, based on the existence of Mo 2P 2O 15 units formed of one Mo 2O 11 group sharing four of its corners with two PO 4 tetrahedra and leading to [Mo 2P 2O 13] ∞ chains running along c. The [Mo 2P 2O 11] 1 x framework forms two different intersecting tunnels running along c and <110>, respectively, where the K + cations are located. The existence of one free apex for each MoO 6 octahedron, which characterizes Mo(V), allows a great flexibility of the structure.

  16. Isonitrile iron(II) complexes with chiral N2P2 macrocycles in the enantioselective transfer hydrogenation of ketones.

    PubMed

    Bigler, Raphael; Mezzetti, Antonio

    2014-12-19

    Bis(isonitrile) iron(II) complexes bearing a C2-symmetric N2P2 macrocyclic ligand, which are easily prepared from the corresponding bis(acetonitrile) analogue, catalyze the asymmetric transfer hydrogenation (ATH) of a broad scope of ketones in excellent yields (up to 98%) and with high enantioselectivity (up to 91% ee).

  17. 2P2Idb v2: update of a structural database dedicated to orthosteric modulation of protein-protein interactions.

    PubMed

    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.

  18. 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

  19. Hydrostatic High-Pressure Studies to 25 GPA on the Model Superconducting Pnictide LaRu2P2

    NASA Astrophysics Data System (ADS)

    Lim, Jinhyuk; Forouzani, Neda; Schilling, James; Fotovat, Roxanna; Zheng, Chong; Hoffmann, Roald

    2014-03-01

    Prior to the discovery of the Fe-pnictides in 2008, the ruthenium phosphide LaRu2P2 possessed the highest value of the su- perconducting transition temperature, Tc ~ 4 K, in the entire pnictide family. Recently, there has been renewed interest in this compound in an effort to better understand why the Fe-pnictides have much higher values of Tc. In related phosphides superconductivity appears to only be present if the separation be- tween the phosphor ions dp-p in neigh- boring Ru2P2 planes is greater than the critical value 2.8 Å, too great for a P-P covalent bond to be formed. For example, in superconducting LaRu2P2, the value of dp-p is 3.0 Å. To test these ideas directly, we have carried out hydro- static high-pressure studies on single-crystalline LaRu2P2 in a diamond-anvil cell using He pressure medium to pres- sures as high as 25 GPa and temperatures as low as 1.5 K. We find that Tc initially increases under pressure, but suddenly disappears above 2.1 GPa. Since dp-p decreases under pressure, the sudden disappearance of superconductivity is likely due to the formation of a covalent P-P bond between adjacent Ru2P2 planes and a possible structural phase transition. Work at Washington University is supported by the NSF through Grant No. DMR-1104742 and by the Carnegie/DOE through NNSA/DOE Grant No. DE-FC52-08NA28554.

  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. Coralloid Co2P2O7 Nanocrystals Encapsulated by Thin Carbon Shells for Enhanced Electrochemical Water Oxidation.

    PubMed

    Chang, Yingxue; Shi, Nai-En; Zhao, Shulin; Xu, Dongdong; Liu, Chunyan; Tang, Yu-Jia; Dai, Zhihui; Lan, Ya-Qian; Han, Min; Bao, Jianchun

    2016-08-31

    Core-shell nanohybrids containing cheap inorganic nanocrystals and nanocarbon shells are promising electrocatalysts for water splitting or other renewable energy options. Despite that great progress has been achieved, biomimetic synthesis of metal phosphates@nanocarbon core-shell nanohybrids remains a challenge, and their use for electrocatalytic oxygen evolution reaction (OER) has not been explored. In this paper, novel nanohybrids composed of coralloid Co2P2O7 nanocrystal cores and thin porous nanocarbon shells are synthesized by combination of the structural merits of supramolecular polymer gels and a controllable thermal conversion technique, i.e., temperature programmable annealing of presynthesized supramolecular polymer gels that contain cobalt salt and phytic acid under a proper gas atmosphere. Electrocatalytic tests in alkaline solution show that such nanohybrids exhibit greatly enhanced electrocatalytic OER performance compared with that of Co2P2O7 nanostructure. At a current density of 10 mA cm(-2), their overpotential is 0.397 V, which is much lower than that of Co2P2O7 nanostructures, amorphous Co-Pi nanomaterials, Co(PO3)2 nanosheets, Pt/C, and some reported OER catalysts, and close to that of commercial IrO2. Most importantly, both of their current density at the overpotential over 0.40 V and durability are superior to those of IrO2 catalyst. As revealed by a series of spectroscopic and electrochemical analyses, their enhanced electrocatalytic performance results from the presence of thin porous nanocarbon shells, which not only improve interfacial electron penetration or transfer dynamics but also vary the coordination environment and increase the number of active 5-coordinated Co(2+) sites in Co2P2O7 cores. PMID:27500553

  2. Highly enantioselective transfer hydrogenation of ketones with chiral (NH)2 P2 macrocyclic iron(II) complexes.

    PubMed

    Bigler, Raphael; Huber, Raffael; Mezzetti, Antonio

    2015-04-20

    Bis(isonitrile) iron(II) complexes bearing a C2 -symmetric diamino (NH)2 P2 macrocyclic ligand efficiently catalyze the hydrogenation of polar bonds of a broad scope of substrates (ketones, enones, and imines) in high yield (up to 99.5 %), excellent enantioselectivity (up to 99 % ee), and with low catalyst loading (generally 0.1 mol %). The catalyst can be easily tuned by modifying the substituents of the isonitrile ligand.

  3. 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.

  4. 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

  5. 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

    2014-12-01

    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. PMID:25324009

  6. 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

    2014-12-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    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 = 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 B20 were calculated from the anisotropic paramagnetic θab and θc values and compared to theoretical trends across the rare earth series. 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.

  8. Deep red radioluminescence from a divalent bismuth doped strontium pyrophosphate Sr2P2O7:Bi2+

    NASA Astrophysics Data System (ADS)

    Li, Liyi; Viana, Bruno; Pauporté, Thierry; Peng, Mingying

    2014-03-01

    Scintillation materials have been used widely in either military or civil areas, but most of them emit lights in the spectral range of ultraviolet or visible. There are few candidates with an emission in the spectral range of 650 to 1200nm. Here, we report a Bi2+ doped phosphor of Sr2P2O7:Bi2+, which once exposed to X-ray can emit deep red peaking at ~700nm due to the typical 2P3/2 to 2P1/2 transition of Bi2+. Deep red radioluminescence manifests the potential application of the phosphor as implantable scintillator for instance or other sensor which can obtain real time dose information and reduce serious radiation accidents in the case of radiation therapy.

  9. 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.

  10. NMR study of crystallization in MgO-CaO-SiO 2-P 2O 5 glass-ceramics

    NASA Astrophysics Data System (ADS)

    Ren, Hai-Lan; Yue, Yong; Ye, Chao-Hui; Guo, Li-Ping; Lei, Jia-Heng

    1998-08-01

    29Si and 31P magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) measurements were employed to investigate crystallization in MgO-CaO-SiO 2-P 2O 5 bioglass-ceramics. The results suggest that wollastonite (β-CaSiO 3) is separated as a new crystalline phase, corresponding to the appearance of a sharp signal in the 29Si MAS NMR spectra, while oxyapatite (Ca 10(PO 4) 6O) forms in the process of the order of the phosphorus-rich phases increasing as a whole, corresponding to the gradual narrowing of 31P MAS NMR spectra. ZnO can make the glass stable and difficult to crystallize at a low temperature, while at a high temperature, ZnO can participate in the crystallization of β-CaSiO 3 and promote it.

  11. Structure of GeO(2)-P(2)O(5) glasses studied by x-ray and neutron diffraction.

    PubMed

    Hoppe, U; Brow, R K; Tischendorf, B C; Jóvári, P; Hannon, A C

    2006-02-15

    The structures of three xGeO(2)-(1- x)P(2)O(5) glasses, where x = 0.98,0.88, and 0.81, have been studied by neutron and x-ray diffraction experiments that yield well resolved P-O and Ge-O bond distances. The Ge-O coordination number (N(GeO)) increased from 4.0 ± 0.2 to 4.5 ± 0.2 with the decrease in x from 0.98 to 0.81. The increase in N(GeO) is consistent with a structural model that assumes that all oxygen form Ge-O-Ge and P-O-Ge linkages between Ge polyhedra and P tetrahedra and that new GeO(5) or GeO(6) polyhedra are formed with isolated PO(4) units when P(2)O(5) is added to GeO(2). The bond valencies in the P-O bonds of the PO(4) tetrahedra are greater than unity and are balanced in P-O-Ge bridges with underbonded Ge-O links in the GeO(5) or GeO(6) polyhedra. Mixed site connections are expected for the GeO(5) (or GeO(6)) and PO(4) units in glasses with relatively low (<20 mol%) P(2)O(5) content due to the overwhelming fraction of GeO(4) tetrahedra. The structural changes are compared with those reported for alkali germanate glasses. Several features indicate different characteristics for the compositional dependence of N(GeO) for the GeO(2)-P(2)O(5) and alkali germanate glasses. However, the distributions of the first-neighbour Ge-O distances are found to be nearly identical for the GeO(2)-P(2)O(5) and K(2)O-GeO(2) glasses of equimolar K(2)O and P(2)O(5) content.

  12. 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.

  13. Dielectric spectra of Li 2O-CaF 2-P 2O 5 glasses doped by silver ions

    NASA Astrophysics Data System (ADS)

    Sambasiva Rao, K.; Srinivasa Reddy, M.; Ravi Kumar, V.; Veeraiah, N.

    2007-06-01

    Dielectric constant ε‧, loss tan δ and a.c. conductivity σ( ω) Li 2O-CaF 2-P 2O 5 glasses doped with small concentrations of Ag 2O (ranging from 0 to 1.0 mol%) are studied as a function of frequency and temperature over moderately wide ranges. The variation of dielectric loss with temperature for these glasses has exhibited dielectric relaxation effects. The relaxation effects have been analyzed by a pseudo Cole-Cole plot method and the spreading of relaxation times has been established. The variation of a.c. conductivity with the concentration of Ag 2O pass through a minimum at 0.6 mol% Ag 2O. In the high-temperature region, the a.c. conduction seems to be connected with the mixed conduction, viz., electronic and ionic conduction. The low-temperature part of the a.c. conductivity which is observed to be nearly temperature independent has been explained on the basis of quantum mechanical-tunneling (QMT) model. The results have been further analyzed in detail with the aid of the data on optical absorption, IR and Raman spectral studies.

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

    DOE PAGESBeta

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

    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

  15. Measurement of the metastable lifetime for the 2s^2 2p^2 ^1So level in O^2+

    NASA Technical Reports Server (NTRS)

    Smith, S. J.; Cadez, I.; Chutjian, A.; Niimura, M.

    2004-01-01

    The radiative lifetime of the 1S0 level was found to be 540 +/- 27 ms. This is in good agreement with a previous measurement and with a number of theoretical calculations. Metastable lifetimes, when combined with collisional excitation rates, can provide a diagnostic for electron density Ne in a stellar or solar plasma.

  16. 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.

  17. 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.

  18. Synthesis and radiolabeling of (64)Cu-labeled 2-nitroimidazole derivative (64)Cu-BMS2P2 for hypoxia imaging.

    PubMed

    Luo, Zheng; Zhu, Hua; Lin, Xinfeng; Chu, Taiwei; Luo, Ruyi; Wang, Yunhua; Yang, Zhi

    2016-03-01

    The objective of this study was to develop a positron emission tomography (PET) probe with hypoxia targeting specificity and a relatively long half-life. The synthesis, (64)Cu-labeling in vitro and in vivo study of the novel 2-nitroimidazole complex (64)Cu-BMS2P2 is presented in this study. The hypoxia targeting capacity of (64)Cu-BMS2P2 in vitro was evaluated and compared with the (64)Cu-BMS181321, and confirmed by PET imaging in vivo and immunohistochemistry for carbonic anhydrase 9 (CA9) in a tumor mouse model. These results suggest that (64)Cu-BMS2P2 is a promising candidate for PET hypoxia imaging and worthy of further investigations in dynamic hypoxia imaging.

  19. 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

  20. 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.

  1. Bacteria Absorption-Based Mn2P2O7-Carbon@Reduced Graphene Oxides for High-Performance Lithium-Ion Battery Anodes.

    PubMed

    Yang, Yuhua; Wang, Bin; Zhu, Jingyi; Zhou, Jun; Xu, Zhi; Fan, Ling; Zhu, Jian; Podila, Ramakrishna; Rao, Apparao M; Lu, Bingan

    2016-05-24

    The development of freestanding flexible electrodes with high capacity and long cycle-life is a central issue for lithium-ion batteries (LIBs). Here, we use bacteria absorption of metallic Mn(2+) ions to in situ synthesize natural micro-yolk-shell-structure Mn2P2O7-carbon, followed by the use of vacuum filtration to obtain Mn2P2O7-carbon@reduced graphene oxides (RGO) papers for LIBs anodes. The Mn2P2O7 particles are completely encapsulated within the carbon film, which was obtained by carbonizing the bacterial wall. The resulting carbon microstructure reduces the electrode-electrolyte contact area, yielding high Coulombic efficiency. In addition, the yolk-shell structure with its internal void spaces is ideal for sustaining volume expansion of Mn2P2O7 during charge/discharge processes, and the carbon shells act as an ideal barrier, limiting most solid-electrolyte interphase formation on the surface of the carbon films (instead of forming on individual particles). Notably, the RGO films have high conductivity and robust mechanical flexibility. As a result of our combined strategies delineated in this article, our binder-free flexible anodes exhibit high capacities, long cycle-life, and excellent rate performance.

  2. Modulation of K2P2.1 and K2P10.1 K+ channel sensitivity to carvedilol by alternative mRNA translation initiation

    PubMed Central

    Kisselbach, J; Seyler, C; Schweizer, P A; Gerstberger, R; Becker, R; Katus, H A; Thomas, D

    2014-01-01

    Background and Purpose The β-receptor antagonist carvedilol blocks a range of ion channels. K2P2.1 (TREK1) and K2P10.1 (TREK2) channels are expressed in the heart and regulated by alternative translation initiation (ATI) of their mRNA, producing functionally distinct channel variants. The first objective was to investigate acute effects of carvedilol on human K2P2.1 and K2P10.1 channels. Second, we sought to study ATI-dependent modulation of K2P K+ current sensitivity to carvedilol. Experimental Approach Using standard electrophysiological techniques, we recorded currents from wild-type and mutant K2P2.1 and K2P10.1 channels in Xenopus oocytes and HEK 293 cells. Key Results Carvedilol concentration-dependently inhibited K2P2.1 channels (IC50,oocytes = 20.3 μM; IC50,HEK = 1.6 μM) and this inhibition was frequency-independent. When K2P2.1 isoforms generated by ATI were studied separately in oocytes, the IC50 value for carvedilol inhibition of full-length channels (16.5 μM) was almost 5-fold less than that for the truncated channel variant (IC50 = 79.0 μM). Similarly, the related K2P10.1 channels were blocked by carvedilol (IC50,oocytes = 24.0 μM; IC50,HEK = 7.6 μM) and subject to ATI-dependent modulation of drug sensitivity. Conclusions and Implications Carvedilol targets K2P2.1 and K2P10.1 K+ channels. This previously unrecognized mechanism supports a general role of cardiac K2P channels as antiarrhythmic drug targets. Furthermore, the work reveals that the sensitivity of the cardiac ion channels K2P2.1 and K2P10.1 to block was modulated by alternative mRNA translation initiation. PMID:25168769

  3. Peptide bond hydrolysis catalyzed by the Wells-Dawson Zr(α2-P2W17O61)2 polyoxometalate.

    PubMed

    Absillis, Gregory; Parac-Vogt, Tatjana N

    2012-09-17

    In this paper we report the first example of peptide hydrolysis catalyzed by a polyoxometalate complex. A series of metal-substituted Wells-Dawson polyoxometalates were synthesized, and their hydrolytic activity toward the peptide bond in glycylglycine (GG) was examined. Among these, the Zr(IV)- and Hf(IV)-substituted ones were the most reactive. Detailed kinetic studies were performed with the Zr(IV)-substituted Wells-Dawson type polyoxometalate K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O which was shown to act as a catalyst for the hydrolysis of the peptide bond in GG. The speciation of K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O which is highly dependent on the pD, concentration, and temperature of the solution, was fully determined with the help of (31)P NMR spectroscopy and its influence on the GG hydrolysis rate was examined. The highest reaction rate (k(obs) = 9.2 (±0.2) × 10(-5) min(-1)) was observed at pD 5.0 and 60 °C. A 10-fold excess of GG was hydrolyzed in the presence of K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O proving the principles of catalysis. (13)C NMR data suggested the coordination of GG to the Zr(IV) center in K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O via its N-terminal amine group and amide carbonyl oxygen. These findings were confirmed by the inactivity of K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O toward the N-blocked analogue acetamidoglycylglycinate and the inhibitory effect of oxalic, malic, and citric acid. Triglycine, tetraglycine, and pentaglycine were also fully hydrolyzed in the presence of K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O yielding glycine as the final product of hydrolysis. K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O also exhibited hydrolytic activity toward a series of other dipeptides.

  4. 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.

  5. 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.

  6. 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

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

  9. 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.

  10. 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.

  11. Ba2Cu2Te2P2O13: A new telluro-phosphate with S=1/2 Heisenberg chain

    NASA Astrophysics Data System (ADS)

    Xia, Mingjun; Shen, Shipeng; Lu, Jun; Sun, Young; Li, R. K.

    2015-10-01

    A new telluro-phosphate compound Ba2Cu2Te2P2O13 with S=1/2 Heisenberg chain has been successfully synthesized by solid state reaction and grown by flux method. Single crystal X-ray diffraction reveals that Ba2Cu2Te2P2O13 crystallizes into a monoclinic space group C2/c and cell parameters of a=17.647(3) Å, b=7.255(2) Å, c=9.191(2) Å and β=100.16 (3)°. In the structure of Ba2Cu2Te2P2O13, one dimensional [CuTePO7]3- chains are formed by tetrahedral PO4 and trigonal bi-pyramidal TeO4 joining square planar CuO4 groups. Those [CuTePO7]3- chains are inter-connected by sharing one oxygen atom from the TeO4 group to form two dimensional layers. Magnetic susceptibility and specific heat measurements confirm that the title compound is a model one dimensional Heisenberg antiferromagnetic chain system.

  12. 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.

  13. Doubly Excited States in Be III

    NASA Astrophysics Data System (ADS)

    Andersen, T.; Bentzen, S. M.; Poulsen, O.

    1980-01-01

    The triplet spectrum of doubly excited Be III has been studied in the wavelength region of 75-5000 Å in order to test the validity of the theoretical term values reported by Lipsky et al. The beam-foil excitation technique was applied to effectively populate the doubly excited states. The identified lower-lying, doubly excited states 2p2 3P, 2pnp 3P, or 3D, and 2pnd 3P, or 3D (n = 3, 4) show that the theoretical term values should be slightly modified.

  14. The α ↔ β phase transitions of Zn2P2O7 revisited: existence of an additional intermediate phase with an incommensurately modulated structure.

    PubMed

    Stöger, Berthold; Weil, Matthias; Dušek, Michal

    2014-06-01

    Zn2P2O7 crystallizes in a thortveitite-like structure and features temperature-dependent polymorphism. At high temperatures (T > 500 K), the aristotype phase β-Zn2P2O7 (C2/m, Z = 2, a ≃ 6.60, b ≃ 8.28, c ≃ 4.53 Å, β ≃ 105.4°) is stable. At lower temperatures the lock-in phase α1-Zn2P2O7 [at 350 K: I2/c, Z = 12, a = 20.1131 (13), b = 8.2769 (6), c = 9.109 (3) Å, β = 106.338 (16)°], a sixfold superstructure with commensurate modulation vector q = (1/3, 0, 1/2), is stable. Between the stability ranges of the α1- and β-phases exists the intermediate, incommensurately modulated α2-Zn2P2O7 phase with modulation wavevector q ≃ (0.33, 0, 0.40) and C2/m(α, 0, γ)0s superspace group symmetry. The α1 → α2 lock-in phase transition at TL = 408 K is of first-order and features virtually no hysteresis. It is immediately followed by the second-order α2 → β transition to the non-modulated phase at TI ≃ 430 K. This transformation is sluggish and even at T = 500 K very weak satellite reflections of the α2-phase were observed. Both phase transitions were analyzed with differential scanning calorimetry and high-temperature powder and single-crystal X-ray diffraction. The crystal structures of the α1- and α2-phases were refined from single crystal data collected at T = 350, 400, 405, 410, 415, 420, 425, 430, 450 and 500 K. Different models describing the slow transition from the incommensurately modulated α2- to the non-modulated β-phase were tested. In the model resulting in the best residuals, the bridging O atom of the [P2O7] group, which is located on a 2/m position in the basic structure, is described as an overlap of an atom ordered in internal space and one atom disordered around the mirror plane. The occupancy of the ordered atom decreases with temperature until at T = 500 K virtually only the disordered atom remains. Simultaneously, the amplitude of the modulation functions of the remaining atoms decreases, so that

  15. The α ↔ β phase transitions of Zn2P2O7 revisited: existence of an additional intermediate phase with an incommensurately modulated structure.

    PubMed

    Stöger, Berthold; Weil, Matthias; Dušek, Michal

    2014-06-01

    Zn2P2O7 crystallizes in a thortveitite-like structure and features temperature-dependent polymorphism. At high temperatures (T > 500 K), the aristotype phase β-Zn2P2O7 (C2/m, Z = 2, a ≃ 6.60, b ≃ 8.28, c ≃ 4.53 Å, β ≃ 105.4°) is stable. At lower temperatures the lock-in phase α1-Zn2P2O7 [at 350 K: I2/c, Z = 12, a = 20.1131 (13), b = 8.2769 (6), c = 9.109 (3) Å, β = 106.338 (16)°], a sixfold superstructure with commensurate modulation vector q = (1/3, 0, 1/2), is stable. Between the stability ranges of the α1- and β-phases exists the intermediate, incommensurately modulated α2-Zn2P2O7 phase with modulation wavevector q ≃ (0.33, 0, 0.40) and C2/m(α, 0, γ)0s superspace group symmetry. The α1 → α2 lock-in phase transition at TL = 408 K is of first-order and features virtually no hysteresis. It is immediately followed by the second-order α2 → β transition to the non-modulated phase at TI ≃ 430 K. This transformation is sluggish and even at T = 500 K very weak satellite reflections of the α2-phase were observed. Both phase transitions were analyzed with differential scanning calorimetry and high-temperature powder and single-crystal X-ray diffraction. The crystal structures of the α1- and α2-phases were refined from single crystal data collected at T = 350, 400, 405, 410, 415, 420, 425, 430, 450 and 500 K. Different models describing the slow transition from the incommensurately modulated α2- to the non-modulated β-phase were tested. In the model resulting in the best residuals, the bridging O atom of the [P2O7] group, which is located on a 2/m position in the basic structure, is described as an overlap of an atom ordered in internal space and one atom disordered around the mirror plane. The occupancy of the ordered atom decreases with temperature until at T = 500 K virtually only the disordered atom remains. Simultaneously, the amplitude of the modulation functions of the remaining atoms decreases, so that

  16. Dielectric properties of Li2O-CaF2-P2O5 glass ceramic system doped with NiO

    NASA Astrophysics Data System (ADS)

    Krishna, G. Murali; Venkateswararao, G.; Srikumar, T.; Sambasiva Rao, K.; Ram Prasad, Ch

    2009-07-01

    Studies on various physical properties viz., dielectric properties (dielectric constant, loss tan δ, a.c conductivity σ) over a wide range of frequency and temperature, of Li2O-CaF2-P2O5: NiO glass ceramics have been reported. The dielectric constant and loss variation with the concentration of NiO have been explained on the basis of space charge polarization mechanism. The dielectric relaxation effects exhibited by these samples have been analyzed by a graphical method and the spreading of dielectric relaxation has been established. The a.c conductivity in the high temperature region seems to be connected both with electronic transfer and ionic movements.

  17. Degradation behaviour of a new bioceramic: Ca2P2O7 with addition of Na4P2O7.10H2O.

    PubMed

    Lin, F H; Liao, C J; Chen, K S; Sun, J S; Liu, H C

    1997-07-01

    A newly produced bioceramic, beta-Ca2P2O7 with addition of Na4P2O7.10H2O (SDCP), has been implanted into the femoral condyle of rabbits. Within 6 weeks after implantation, most of the bioceramic is replaced by new woven bone. On the contrary, block from hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP), which are osteoconductible, do not resorb within a short period of time. We believe that the biodegradable behaviour of SDCP may occur in two steps. The first and most important step is the digestion of particles and migration of the particles by phagocytosis. The object of this study is to examine the change in morphologies, chemical compositions and crystal structure of SDCP after soaking in distilled water for a certain period of time. The SDCP ceramic was also co-cultured with leucocytes to observe how the SDCP particles were digested by the leucocytes, so that the mechanism of biodegradable behaviour of SDCP ceramic in vivo might be clarified. Four types of sintered calcium phosphate ceramics were tested in the experiment: SDCP, pure beta-Ca2P2O7 (DCP), HA and beta-TCP. They wee soaked in distilled water at 37 degrees C for up to 30 days. The microstructure and morphology of crystals deposited on the surface were observed using scanning electron microscopy. Sodium, calcium and phosphorus ion contents in the supernatant solution were detected by atomic absorption analysis and ion coupled plasma. In summary, HA and DCP showed no significant evidence of dissolution in distilled water. In static distilled water, calcium ions may be released from beta-TCP into solution during the initial 7 days and then converted into HA by reprecipitation. The results showed that the SDCP was firstly dissolved into small grains or fragments by the solution. The small fragments should be so small as to be digested by the phagocytes in a physiological environment.

  18. Investigation of the system ThO 2-NpO 2-P 2O 5. Solid solutions of thorium-neptunium (IV) phosphate-diphosphate

    NASA Astrophysics Data System (ADS)

    Dacheux, N.; Thomas, A. C.; Brandel, V.; Genet, M.

    1998-11-01

    Considering that phosphate matrices could be potential candidates for the immobilization of actinides or for the final disposal of the excess plutonium from dismantled nuclear weapons, the chemistry of thorium phosphates has been re-examined. In the ThO 2-P 2O 5 system, the thorium phosphate-diphosphate Th 4(PO 4) 4P 2O 7 (TPD) can be synthesized by wet and dry chemical processes. The substitution of thorium by other tetravalent actinides like uranium or plutonium can be obtained for 0 < x < 3.0 and 0 < x < 1.63, respectively. In this work, we report the chemical conditions of synthesis of thorium-neptunium (IV) phosphate-diphosphate solid solutions Th 4- xNp x(PO 4) 4P 2O 7 (TNPD) with 0 < x < 1.6 from a mixture of thorium and neptunium (IV) nitrates and concentrated phosphoric acid. From the variation of the cell parameters and volume, the maximum substitution of Th 4+ by Np 4+ in the TPD structure is evaluated to 2.08 (which corresponds to about 52 mol% of thorium replaced by neptunium (IV)). The field of existence of solid solutions Th 4- xU- xNp- xPuU xUNp xNpPu xPu(PO 4)4P 2O 7 has been calculated. These solid solutions should be synthesized for 5 xU+7 xNp+9 xPu⩽15. In the NpO 2-P 2O 5 system, the unit cell parameters of Np 2O(PO 4) 2 were refined by analogy with U 2O(PO 4) 2 which crystallographic data have been published recently. For Np 2O(PO 4) 2 the unit cell is orthorhombic with the following cell parameters: a=7.033(2) Å, b=9.024(3) Å, c=12.587(6) Å and V=799(1) Å 3. The unit cell parameter obtained for α-NpP 2O 7 ( a=8.586(1) Å) is in good agreement with those already reported in literature.

  19. 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.

  20. 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.

  1. 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. PMID:24411365

  2. Mechanical properties and histological evaluation of sintered beta-Ca2P2O7 with Na4P2O7.10H2O addition.

    PubMed

    Lin, F H; Lin, C C; Lu, C M; Liu, H C; Sun, J S; Wang, C Y

    1995-07-01

    The ultimate goal of implantation of biomaterials in the skeleton is to reach full integration of the non-living implant with the living bone. The biomaterial can be used much as a bone graft, resorbing or dissolving as bone growth occurs, and the end result is a new remoulded bone. Calcium pyrophosphate, Ca2P2O7, is one of the intermediate products of bone mineralization. beta-Dicalcium pyrophosphate (beta-DCP) doped with certain amounts of Na4P2O7.10H2O was prepared as the developed material. Na4P2O7.10H2O was used as a liquid-phase additive to improve the sintering process and promote physiological bioresorbability. Compressive strength and four-point bending strength were measured by the Bionix test system 858. The mechanical strength of the sintered beta-DCP increased with the addition of Na4P2O7.10H2O up to 5 wt%, but thereafter decreased. The microstructure and crystal structure were analysed by the techniques of SEM, EPMA, TEM and XRD. The relationship between the mechanical strength of the sintered bioceramics and the Na4P2O7.10H2O dopant was examined in terms of the presence of NaCa(PO3)3, grain growth and abnormal grain coalescence while the dopant increased. Preliminary in vivo evaluation was studied by rabbit femur condyle implantation. There was no inflammation or any toxic sign during the experimental period. The histological section of intraosseous implantation revealed that the new bone deposited directly on the surface of the material in the fourth week after operation. The implant gradually decreased in volume and was replaced by the surrounding regenerated bone in the rabbit condyle in vivo environment. The results led us to conclude that the developed material has great potential as a biodegradable bone substitute.

  3. Beam-foil spectroscopical study of the 1s2s2p and 1s2p 2 quartet levels of Mg 9+ and Al 10+

    NASA Astrophysics Data System (ADS)

    Hellmann, H.; Träbert, E.

    1985-07-01

    Results of recent measurements of the fine structure and multiplet separation of the lowest quartet terms of doubly excited three-electron ions of Mg and Al are compared with other experiments and with theory. Preliminary results of lifetime measurements of 1s2p 24P 1/2.3/2 levels are presented. They confirm the recent calculation by Chen. Crasemann and Mark and contradict older calculations by Tunnell and Bhalla.

  4. Cryogenic exciter

    SciTech Connect

    Bray, James William; Garces, Luis Jose

    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.

  5. Structural variety in zinc telluro-phosphates: syntheses, crystal structures and characterizations of Sr2Zn3Te2P2O14, Pb2Zn3Te2P2O14 and Ba2Zn2TeP2O11.

    PubMed

    Xia, Mingjun; Li, R K

    2016-05-01

    Three new zinc telluro-phosphates, Sr2Zn3Te2P2O14 (1), Pb2Zn3Te2P2O14 (2) and Ba2Zn2TeP2O11 (3), were grown by flux method, and their crystal structures were solved by X-ray diffraction method. Although all three crystals crystallize into the same space group P21/c with similar chemical compositions, they exhibit different topology structure types. 1 features a two-dimensional layered structure with the connection of TeO4 and (Zn3TeP2O18)(16-) 12-membered rings (MRs), which are composed of planar square and tetrahedral configuration ZnO4 groups, tetrahedral PO4 and seesaw TeO4. Due to lone-pair Coulomb repulsion of Pb(2+), the structure of 2, which is also composed of unbalanced seesaw TeO4 and ZnO4 groups and distorted PO4 tetrahedra, is slightly different from that of its analog 1. Compound 3 exhibits a complicated three-dimensional network with (Zn2PO9)(9-) 6-MRs and (Zn2Te2O10)(8-) 8-MRs built from distorted tetrahedral ZnO4 and PO4 groups and trigonal pyramidal TeO3 units. According to UV-vis-NIR diffuse reflectance spectra, compounds 1, 2 and 3 are highly transparent in the range of 450 to 2500 nm with a UV cut-off of 275 nm, 330 nm and 278 nm, respectively. In addition, the characterizations, including thermal analyses, XPS measurement and dipole moment calculations, are also reported. PMID:27046132

  6. 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.

  7. Synthetic, Spectroscopic, and Electrochemical Studies of the Isomerically-Rich [M(CO)(2)(P(2)P')X](+/0) (M = Mn, Re; X = Cl, Br; P(2)P' = eta(3)-Ph(2)P(CH(2))(2)P(Ph)(CH(2))(2)PPh(2)) System: Structural Characterization of a Novel Pair of Diastereoisomers of cis,mer-Re(CO)(2)(P(2)P')Cl.

    PubMed

    Bond, Alan M.; Colton, Ray; Gable, Robert W.; Mackay, Maureen F.; Walter, Jacky N.

    1997-03-12

    Reaction of Mn(CO)(5)X (X = Cl, Br) with Ph(2)P(CH(2))(2)P(Ph)(CH(2))(2)PPh(2) (P(2)P') in refluxing xylene led to the formation of isomerically pure cis,mer-Mn(CO)(2)(eta(3)-P(2)P')X. Cyclic voltammograms in dichloromethane (0.1 M Bu(4)NPF(6)) show a reversible one-electron oxidation (process 1, E(1/2) = 0.142 V) to give cis,mer-[Mn(CO)(2)(P(2)P')X](+). However, in acetone (0.1 M Bu(4)NPF(6)) at room temperature, process 1 is not reversible and an additional redox process 4 (E(1/2) = 0.048 V) is observed. Process 4 is not observed at low temperatures, and at higher temperatures in acetone it merges with process 1 and also a new reversible redox couple (process 5, E(1/2) = -0.411 V) appears. A combination of electrolyses, chemical oxidation, and subsequent reduction, coupled with IR and (31)P NMR spectroscopies and electrospray mass spectrometry (ESMS), is used to show that processes 1, 4, and 5 are all associated with redox and interconversion reactions of different isomers of Mn(CO)(2)(P(2)P')X and [Mn(CO)(2)(P(2)P')X](+). Other irreversible processes due to oxidation of the different isomers of [Mn(CO)(2)(P(2)P')X](+) are observed at very positive potentials. Reaction between Re(CO)(5)X and P(2)P' in refluxing mesitylene gives a soluble product and a small amount of precipitate. The major soluble product was identified as cis,mer-Re(CO)(2)(P(2)P')X, and the oxidative chemistry is similar to that of the manganese analogues. The precipitate consists of five compounds, one of which was cis,mer-Re(CO)(2)(P(2)P')X. The new compounds A-D were identified as follows: A is cis,mer-{Re(CO)(2)(P(2)P')X}(2), a dimeric species with bridging P(2)P' ligands. The spectroscopic data for B indicated that it was a form of cis,mer-Re(CO)(2)(P(2)P')X, but not the same as the major product. Compound C is cis,fac-Re(CO)(2)(P(2)P')X, and compound D was shown to be fac-[Re(CO)(3)(P(2)P')]X. The crystal structures of cis,mer-Re(CO)(2)(P(2)P')Cl(I) and cis,mer-Re(CO)(2)(P(2)P')Cl(II) show

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

    PubMed

    Czakó, Gábor

    2013-04-01

    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

  9. Structure and physical properties of new iron hydrogenophosphates: K2Fe(HP2O7)(H2PO4)2, LiH3Fe2(P2O7)2, and FeH2P2O7.

    PubMed

    Pralong, V; Baies, R; Caignaert, V; Raveau, B

    2009-07-20

    The exploration of the systems Fe-H-P-O, Li-Fe-H-P-O, and K-Fe-H-P-O using soft chemistry methods has allowed three new hydrogenophosphates to be synthesized, whose structures have been determined by ab initio calculations. The structures of two of them--FeH(2)P(2)O(7) and LiH(3)Fe(P(2)O(7))(2)--exhibit close relationships: their 3D framework consists of [FeO(4)](infinity) and [LiFe(2)O(12)](infinity) chains of edge-sharing octahedra, respectively, interconnected through diphosphate groups. These two diphosphates exhibit a paramagnetic to antiferromagnetic transition at low temperatures. The former phase exhibits intrachain ferromagnetic interactions (theta(p) > 0) in competition with the antiferromagnetic interchain ordering, whereas for the second one, the ferromagnetic interactions have disappeared due to the presence of Li in the chains. Differently, the third phosphate, K(2)Fe(HP(2)O(7))(H(2)PO(4))(2), exhibits a chain structure, involving isolated FeO(6) octahedra, and consequently is paramagnetic in the whole temperature range (4-300 K). Among these three phosphates, only the latter exhibits ionic conductivity, which may originate from the proton mobility.

  10. 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.

  11. Reactivity of Hydrides FeH(2)(CO)(2)P(2) (P = Phosphites) with Aryldiazonium Cations: Preparation, Characterization, X-ray Crystal Structure, and Electrochemical Studies of Mono- and Binuclear Aryldiazenido Complexes.

    PubMed

    Albertin, Gabriele; Antoniutti, Stefano; Bacchi, Alessia; Barbera, Davide; Bordignon, Emilio; Pelizzi, Giancarlo; Ugo, Paolo

    1998-10-19

    Mono- and binuclear aryldiazenido complexes [Fe(ArN(2))(CO)(2)P(2)]BPh(4) (1-4) and [{Fe(CO)(2)P(2)}(2)(&mgr;-N(2)Ar-ArN(2))](BPh(4))(2) (5-8) [P = P(OEt)(3), PPh(OEt)(2), PPh(2)OEt, P(OPh)(3); Ar = C(6)H(5), 2-CH(3)C(6)H(4), 4-CH(3)C(6)H(4); Ar-Ar = 4,4'-C(6)H(4)-C(6)H(4), 4,4'-(2-CH(3))C(6)H(3)-C(6)H(3)(2-CH(3)), 4,4'-C(6)H(4)-CH(2)-C(6)H(4)] were prepared by allowing hydride species FeH(2)(CO)(2)P(2) to react with an excess of mono- (ArN(2))(BF(4)) or bis-aryldiazonium (N(2)Ar-ArN(2))(BF(4))(2) salts, respectively, at low temperature. A reaction path involving a hydride-aryldiazene intermediate [FeH(ArN=NH)(CO)(2)P(2)](+), which, through the loss of H(2), affords the final aryldiazenido complexes 1-8, is proposed. The compounds were characterized by (1)H and (31)P{(1)H} NMR spectroscopy (including (15)N isotopic substitution) and X-ray crystal structure determination. The complex [Fe(CO)(2){P(OEt)(3)}(2){&mgr;-4,4'-N(2)(2-CH(3))C(6)H(3)-C(6)H(3)(2-CH(3))N(2)}](BPh(4))(2) (5b) crystallizes in the space group P&onemacr; with a = 15.008(4) Å, b = 17.094(5) Å, c = 10.553(3) Å, alpha = 99.56(1) degrees, beta = 102.80(1) degrees, gamma = 65.30(1) degrees, and Z = 1. The structure is centrosymmetric and consists of binuclear cations with the two iron atoms in a quite regular trigonal bipyramidal environment, with the two CO in the equatorial and the two phosphites in the apical position, respectively. Aryldiazenido complexes 1-8 react with strong acids HX (X = Cl, CF(3)SO(3), CF(3)CO(2)) to give the corresponding aryldiazene derivatives, according to the equilibrium [Fe(ArN(2))(CO)(2)P(2)](+) + HX right harpoon over left harpoon [FeX(ArN=NH)(CO)(2)P(2)](+). Electrochemical studies of both mono- (1-4) and binuclear (5-8) compounds were undertaken, and a mechanism for oxidation and reduction processes is proposed.

  12. Preparation, electrochemistry and crystal structure of a derivative of 18-tungstophosphate with Dawson structure: K 16H[Yb(α-2-P 2W 17O 61) 2]·44H 2O

    NASA Astrophysics Data System (ADS)

    Niu, Jingyang; Zhao, Junwei; Guo, Dongjie; Wang, Jingping

    2004-04-01

    The heteropolyanion [Yb(α-2-P 2W 17O 61) 2] 17- has been isolated as a potassium salt in ˜30% yield by five-day decreasing temperature-programmed from 60 °C to room temperature, in a potassium acetate buffer, formed by reaction of K 6P 2W 18O 62·10H 2O with Yb(NO 3) 3 and characterized by IR, UV spectra. Single crystal X-ray structural analysis of K 16H[Yb(α-2-P 2W 17O 61) 2]·44H 2O (triclinic, space group PI a=14.499(3), b=22.433(5), c=24.505(5) Å, α=95.36(3), β=102.67(3), γ=100.06(3)°, Z=2, 24,089 independent reflections, R1=0.0497) reveals that two chemically identical [α-2-P 2W 17O 61] 10- moieties are connected through one Yb atom, which is in a square antiprismatic coordination environment with eight oxygen atoms, four from each of the two [α-2-P 2W 17O 61] 10- moieties. The Yb(III) ion substitutes for two [W=O] 4+ units in the 'cap' regions of the tungsten-oxygen frameworks of the two parent Wells-Dawson ions. The point group symmetry of the title polyanion is C 2. In the extensive pH region from 10.5 to 1.60, the cyclic voltammograms for the title compound in the presence of 0.5 M NaCl aqueous solution as supporting electrolyte mainly illustrate nearly reversible one-electron reduction processes. The results of the thermogravimetric analysis of the title compound show one one-step slow weight loss and the framework decomposition of the polyanion in the title compound is at 560.0 °C.

  13. Excited intruder states in {sup 32}Mg

    SciTech Connect

    Tripathi, Vandana; Tabor, S. L.; Bender, P.; Hoffman, C. R.; Lee, Sangjin; Pepper, K.; Perry, M.; Utsuno, Y.; Otsuka, T.; Mantica, P. F.; Pinter, J. S.; Stoker, J. B.; Cook, J. M.; Pereira, J.; Weisshaar, D.

    2008-03-15

    The low energy level structure of N=20 {sup 32}Mg obtained via {beta}-delayed {gamma} spectroscopy is reported. The level structure of {sup 32}Mg is found to be completely dominated by intruders. An inversion between the 1p-1h and 3p-3h states is observed for the negative parity states, similar to the 0p-0h and 2p-2h inversion for the positive parity states in these N{approx}20 nuclei. The intruder excited states, both positive and negative parity, are reasonably explained by Monte Carlo shell model calculations, which suggest a shrinking N=20 shell gap with decreasing Z.

  14. Sol-gel synthesis of Na4Fe3(PO4)2(P2O7)/C nanocomposite for sodium ion batteries and new insights into microstructural evolution during sodium extraction

    NASA Astrophysics Data System (ADS)

    Wu, Xuehang; Zhong, Guiming; Tang, Zheng; Yang, Yong

    2016-09-01

    A mixed polyanionic Na4Fe3(PO4)2(P2O7)/C nanocomposite is synthesized via a sol-gel route. The phosphate raw material is transformed to the mixed phosphate-pyrophosphate with high phase purity via a self-condensation reaction at 500 °C. Na4Fe3(PO4)2(P2O7)/C can deliver an initial capacity of 110 mAh g-1 at 0.05C with the average discharge voltage approaching 3.1 V. The nanocomposite shows excellent rate capability because of the presence of an in-situ formed 3-D network of carbon. At 10 C rate, the nanocomposite delivers a discharge capacity of 78 mAh g-1 at 25 mAh °C and 82 mAh g-1 at 55 °C. The nanocomposite has a good long-term cycling stability, retaining 89% of the initial discharge capacity after 300 cycles. In-situ XRD results demonstrate that the sodium insertion/extraction process in Na4Fe3(PO4)2(P2O7) is an imperfect solid-solution reaction with an obvious local lattice distortion instead of an ideal solid-solution reaction. Using a solid-state NMR technique, it is further found that the sodium extraction from the Na1, Na3, and Na4 sites causes an obvious change in local structure. However, the local structure of Na2 remains unchanged, which may aid the stability of the host structure.

  15. Synthis and Phisical And Chemical; Properties of SiO2 - B2O3 and SiO2 - P2O5 Thin Film Systems and Powders

    NASA Astrophysics Data System (ADS)

    Mal'chik, A. G.; Litovkin, S. V.; Seregin, V. I.; Rodionov, P. V.; Kryuchkova, S. O.

    2016-08-01

    The SiO2 - B2O3 and SiO2 - P2O5 films were synthesized by using film forming solutions having a P2O5 content of up to 30% and B2O3 up to 40%. Properties of the filmforming solutions and binary oxides were examined. The physical and chemical processes occurring in the solution during the heat treatment of films were examined. The conditions for producing films of different thicknesses were determined. The kinetic parameters were calculated.

  16. 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

  17. 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)

  18. Facile aqueous synthesis and electromagnetic properties of novel 3D urchin-like glass/Ni-Ni(3)P/Co(2)P(2)O(7) core/shell/shell composite hollow structures.

    PubMed

    An, Zhenguo; Zhang, Jingjie; Pan, Shunlong

    2010-04-14

    Novel 3D urchin-like glass/Ni-Ni(3)P/Co(2)P(2)O(7) core/shell/shell composite hollow structures are fabricated for the first time by controlled stepwise assembly of granular Ni-Ni(3)P alloy and ribbon-like Co(2)P(2)O(7) nanocrystals on hollow glass spheres in aqueous solutions at mild conditions. It is found that the shell structure and the overall morphology of the products can be tailored by properly tuning the annealing temperature. The as-obtained composite core/shell/shell products possess low density (ca. 1.18 g cm(-3)) and shape-dependent magnetic and microwave absorbing properties, and thus may have some promising applications in the fields of low-density magnetic materials, microwave absorbers, etc. Based on a series of contrast experiments, the probable formation mechanism of the core/shell/shell hierarchical structures is proposed. This work provides an additional strategy to prepare core/shell composite spheres with tailored shell morphology and electromagnetic properties. PMID:20379530

  19. 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. PMID:949223

  20. 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.

  1. 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.

  2. Unexpected formation of ruthenium(II) hydrides from a reactive dianiline precursor and 1,2-(Ph2P)2-1,2-closo-C2B10H10.

    PubMed

    Adams, Jeramie J; Del Negro, Andrew S; Arulsamy, Navamoney; Sullivan, B Patrick

    2008-03-17

    Reaction of the new precursor cis, trans-Ru(cod)(anln)2Cl2 with the diphosphine 1,2-bis(diphenylphosphino)-1,2-dicarba-closo-dodecaborane (o-dppc) unexpectedly results in two new ruthenium(II) hydrides, trans-Ru(o-dppc) 2(H)Cl and the neutral, five-coordinate complex Ru(o-dppc)(nido-dppc)(H), depending upon the reaction conditions [anln is aniline and nido-dppc is 7,8-(Ph2P)2C2B9H10(-)]. Chloride abstraction from trans-Ru(o-dppc)2(H)Cl leads to another five-coordinate hydride, [Ru(o-dppc)2(H)](+), which is isolated as either a triflate or hexafluorophosphate salt. On the basis of labeling and reactivity studies, the source of the hydride appears to be the cod ligand. PMID:18217750

  3. 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

    2014-02-01

    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.

  4. 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.

  5. 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.

  6. 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.

  7. Characterization and physical properties of Li 2O-CaF 2-P 2O 5 glass ceramics with Cr 2O 3 as a nucleating agent—Physical properties

    NASA Astrophysics Data System (ADS)

    Murali Krishna, G.; Anila Kumari, B.; Srinivasa Reddy, M.; Veeraiah, N.

    2007-10-01

    In this paper, studies on various physical properties, viz., dielectric properties (dielectric constant, loss tan δ, a.c. conductivity σ) over a wide range of frequency and temperature, optical absorption, ESR at liquid nitrogen temperature and magnetic susceptibility at room temperature of Li 2O-CaF 2-P 2O 5: Cr 2O 3 glass ceramics, have been reported. The optical absorption, ESR and magnetic susceptibility studies indicate that the chromium ions exist in Cr 5+, Cr 4+ and Cr 6+ states in addition to Cr 3+ state in these samples. The dielectric constant and loss variation with the concentration of Cr 2O 3 have been explained on the basis of space charge polarization mechanism. The dielectric relaxation effects exhibited by these samples have been analysed by a graphical method and the spreading of dielectric relaxation has been established. The a.c. conductivity in the high-temperature region seems to be connected both with electronic and ionic movements.

  8. 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.

  9. 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.

  10. Signature of triply excited Li-like V states in ion-solid collisions

    NASA Astrophysics Data System (ADS)

    Sharma, Gaurav; Haris, K.; Singh, G.; Kumar, B.; Karmakar, S.; Puri, N. K.; Mishra, Adya P.; Kumar, Pravin; Nandi, T.

    2016-10-01

    The transitions originating from triply excited, doubly autoionizing states of Li-like V formed in beam-foil experiments detected within a set of blended spectroscopic profiles have been assigned tentatively by the Hartree-Fock calculations including relativistic corrections and multi-configuration interactions as perturbations. The x-ray decay channels from the triply excited states such as 3p34S, 2p2 np4S (n ∼ 12) through radiative transitions to the ground state via two or more steps have been observed.

  11. 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

  12. Di- and tricobalt Dawson sandwich complexes: synthesis, spectroscopic characterization, and electrochemical behavior of Na(18)[(NaOH(2))(2)Co(2)(P(2)W(15)O(56))(2)] and Na(17)[(NaOH(2))Co(3)(H(2)O)(P(2)W(15)O(56))(2)].

    PubMed

    Ruhlmann, Laurent; Canny, Jacqueline; Contant, Roland; Thouvenot, René

    2002-07-29

    The reaction of the trivacant Dawson anion alpha-[P(2)W(15)O(56)](12-) and the divalent cations Co(2+) is known to form the tetracobalt sandwich complex [Co(4)(H(2)O)(2)(P(2)W(15)O(56))(2)](16-) (Co(4)P(4)W(30)). Two new complexes, with different Co/P(2)W(15) stoichiometry, [(NaOH(2))(2)Co(2)(P(2)W(15)O(56))(2)](18-) (Na(2)Co(2)P(4)W(30)) and [(NaOH(2))Co(3)(H(2)O)(P(2)W(15)O(56))(2)](17-) (NaCo(3)P(4)W(30)), have been synthesized as aqueous-soluble sodium salts, by a slight modification of the reaction conditions. Both compounds were characterized by IR, elemental analysis, and (31)P solution NMR spectroscopy. These species are "lacunary" sandwich complexes, which add Co(2+) cations according to Na(2)Co(2)P(4)W(30) + Co(2+) --> NaCo(3)P(4)W(30) + Na(+) followed by NaCo(3)P(4)W(30) + Co(2+) --> Co(4)P(4)W(30) + Na(+). A Li(+)/Na(+) exchange in the cavity was evidenced by (31)P dynamic NMR spectroscopy. The electrochemical behaviors of the sandwich complexes [(NaOH(2))Co(3)(H(2)O)(P(2)W(15)O(56))(2)](17-) and [(NaOH(2))(2)Co(2)(P(2)W(15)O(56))(2)](18-) were investigated in aqueous solutions and compared with that of [Co(4)(H(2)O)(2)(P(2)W(15)O(56))(2)](16-). These complexes showed an electrocatalytic effect on nitrite reduction.

  13. 16. EXCITERS, AND SYNCHROSCOPE GAUGE ON WALL. ACTIVE ELECTRIC EXCITER ...

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

    16. EXCITERS, AND SYNCHROSCOPE GAUGE ON WALL. ACTIVE ELECTRIC EXCITER AT REAR; UNUSED WATER-DRIVEN EXCITER IN FOREGROUND. VIEW TO SOUTH-SOUTHWEST. - Santa Ana River Hydroelectric System, SAR-2 Powerhouse, Redlands, San Bernardino County, CA

  14. 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.

  15. Decoherence at constant excitation

    NASA Astrophysics Data System (ADS)

    Torres, J. M.; Sadurní, E.; Seligman, T. H.

    2012-02-01

    We present a simple exactly solvable extension of the Jaynes-Cummings model by adding dissipation. This is done such that the total number of excitations is conserved. The Liouville operator in the resulting master equation can be reduced to blocks of 4×4 matrices.

  16. Excited states in hydrocarbons

    SciTech Connect

    Lipsky, S.

    1987-01-01

    In this brief review we first summarize some pertinent features of the photophysical properties of excited states of hydrocarbons and the mechanisms by which they transfer energy to solutes and then review their yields and their behavior under fast-electron irradiation conditions. 33 refs.

  17. 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.

  18. 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.

  19. 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.

  20. Aperture excited dielectric antennas

    NASA Technical Reports Server (NTRS)

    Crosswell, W. F.; Chatterjee, J. S.; Mason, V. B.; Tai, C. T.

    1974-01-01

    The results of a comprehensive experimental and theoretical study of the effect of placing dielectric objects over the aperture of waveguide antennas are presented. Experimental measurements of the radiation patterns, gain, impedance, near-field amplitude, and pattern and impedance coupling between pairs of antennas are given for various Plexiglas shapes, including the sphere and the cube, excited by rectangular, circular, and square waveguide feed apertures. The waveguide excitation of a dielectric sphere is modeled using the Huygens' source, and expressions for the resulting electric fields, directivity, and efficiency are derived. Calculations using this model show good overall agreement with experimental patterns and directivity measurements. The waveguide under an infinite dielectric slab is used as an impedance model. Calculations using this model agree qualitatively with the measured impedance data. It is concluded that dielectric loaded antennas such as the waveguide excited sphere, cube, or sphere-cylinder can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of 2 wavelengths or less. It is also shown that for certain configurations coupling between two antennas of this type is less than that for the same antennas without dielectric loading.

  1. 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.

  2. Measurements of defect structures by positron annihilation lifetime spectroscopy of the tellurite glass TeO2-P2O5-ZnO-LiNbO3 doped with ions of rare earth elements: Er3+, Nd3+ and Gd3+

    NASA Astrophysics Data System (ADS)

    Golis, E.; Yousef, El. S.; Reben, M.; Kotynia, K.; Filipecki, J.

    2015-12-01

    The objective of the study was the structural analysis of the TeO2-P2O5-ZnO-LiNbO3 tellurite glasses doped with ions of the rare-earth elements: Er3+, Nd3+ and Gd3+ based on the PALS (Positron Annihilation Lifetime Spectroscopy) method of measuring positron lifetimes. Values of positron lifetimes and the corresponding intensities may be connected with the sizes and number of structural defects, such as vacancies, mono-vacancies, dislocations or pores, the sizes of which range from a few angstroms to a few dozen nanometres. Experimental positron lifetime spectrum revealed existence of two positron lifetime components τ1 and τ2. Their interpretation was based on two-state positron trapping model where the physical parameters are the annihilation velocity and positron trapping rate.

  3. Reevaluation of experiments and new theoretical calculations for electron-impact excitation of C3+

    NASA Astrophysics Data System (ADS)

    Janzen, P. H.; Gardner, L. D.; Reisenfeld, D. B.; Savin, D. W.; Kohl, J. L.; Bartschat, K.

    1999-06-01

    Experimental absolute-rate coefficients for electron-impact excitation of C3+ (2s 2S1/2-->2p 2P1/2,3/2) near threshold [D. W. Savin, L. D. Gardner, D. B. Reisenfeld, A. R. Young, and J. L. Kohl, Phys. Rev. A 51, 2162 (1995)] have been reanalyzed to include a more accurate determination of optical efficiency and revised radiometric uncertainties which reduce the total systematic uncertainty of the results. Also, new R matrix with pseudostates (RMPS) calculations for this transition near threshold are presented. Comparison of the RMPS results to those of simpler close-coupling calculations indicates the importance of accounting for target continuum effects. The reanalyzed results of Savin et al. are in excellent agreement with the RMPS calculations; comparisons are also made to other measurements of this excitation. Agreement with the RMPS results is better for fluorescence technique measurements than for electron-energy-loss measurements.

  4. 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.

  5. 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.

  6. 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.

  7. Hydrological excitation of polar motion

    NASA Astrophysics Data System (ADS)

    Nastula, Y.; Kolaczek, B.

    2006-08-01

    Hydrological excitation of the polar motion (HAM) were computed from the available recently hydrological data series (NCEP, ECMWF, CPC water storage and LaD World simulations of global continental water) and compared. Time variable seasonal spectra of these hydrological excitation functions and of the geodetic excitation function of polar motion computed from the polar motion COMB03 data were compared showing big differences in their temporal characteristics and the necessity of the further improvement of the HAM models. Seasonal oscillations of the global geophysical excitation functions (AAM + OAM + HAM) and their time variations were compared also. These hydrological excitation functions do not close the budget of the global geophysical excitation function of polar motion.

  8. Neural Excitability and Singular Bifurcations.

    PubMed

    De Maesschalck, Peter; Wechselberger, Martin

    2015-12-01

    We discuss the notion of excitability in 2D slow/fast neural models from a geometric singular perturbation theory point of view. We focus on the inherent singular nature of slow/fast neural models and define excitability via singular bifurcations. In particular, we show that type I excitability is associated with a novel singular Bogdanov-Takens/SNIC bifurcation while type II excitability is associated with a singular Andronov-Hopf bifurcation. In both cases, canards play an important role in the understanding of the unfolding of these singular bifurcation structures. We also explain the transition between the two excitability types and highlight all bifurcations involved, thus providing a complete analysis of excitability based on geometric singular perturbation theory.

  9. 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. PMID:21895014

  10. Pattern Formation in Excitable Media

    NASA Astrophysics Data System (ADS)

    Reynolds, William Nash

    1992-01-01

    The phenomenon of excitability is observed in a wide variety of physical and biological systems. In this work, spatially extended excitable systems are examined from several different perspectives. First, a pedagogical introduction is used to motivate the derivation of the dynamics of one dimensional excitable pulses. In the second part, coupled map techniques for numerical simulation of excitable media and other interfacial systems are described. Examples are given for both excitable media and crystal growth. The third chapter addresses the phenomenon of spiral formation in excitable media. Exact rotating solutions are found for a class of models of excitable media. The solutions consist of two regions: an outer region, consisting of the spiral proper, which exhibits a singularity at its tip, and the core region, obtained by rescaling space in the vicinity of the tip. The tip singularity is resolved in the core region, leading to a consistent solution in all of space. The stability of both the spiral and the core is investigated, with the result that the spiral is found to be stable, and the core unstable. Finally, the stability of excitable waves of the chemical cAMP traveling over aggregating colonies of the slime mold Dictyostelium discoideum is examined by coupling the excitable dynamics of the cAMP signalling system to a simple model of chemotaxis, with result that cellular motion is found to destabilize the waves, causing the initially uniform field of cells to break up into streams.

  11. 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.

  12. Coulomb excitation of 31Mg

    NASA Astrophysics Data System (ADS)

    Seidlitz, M.; Mücher, D.; Reiter, P.; Bildstein, V.; Blazhev, A.; Bree, N.; Bruyneel, B.; Cederkäll, J.; Clement, E.; Davinson, T.; Van Duppen, P.; Ekström, A.; Finke, F.; Fraile, L. M.; Geibel, K.; Gernhäuser, R.; Hess, H.; Holler, A.; Huyse, M.; Ivanov, O.; Jolie, J.; Kalkühler, M.; Kotthaus, T.; Krücken, R.; Lutter, R.; Piselli, E.; Scheit, H.; Stefanescu, I.; Van de Walle, J.; Voulot, D.; Warr, N.; Wenander, F.; Wiens, A.

    2011-06-01

    The ground state properties of 31Mg indicate a change of nuclear shape at N = 19 with a deformed Jπ = 1 /2+ intruder state as a ground state, implying that 31Mg is part of the "island of inversion". The collective properties of excited states were the subject of a Coulomb excitation experiment at REX-ISOLDE, CERN, employing a radioactive 31Mg beam. De-excitation γ-rays were detected by the MINIBALL γ-spectrometer in coincidence with scattered particles in a segmented Si-detector. The level scheme of 31Mg was extended. Spin and parity assignment of the 945 keV state yielded 5 /2+ and its de-excitation is dominated by a strong collective M1 transition. Comparison of the transition probabilities of 30,31,32Mg establishes that for the N = 19 magnesium isotope not only the ground state but also excited states are largely dominated by a deformed pf intruder configuration.

  13. 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.

  14. 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.

  15. Coulomb excitation of 107In

    NASA Astrophysics Data System (ADS)

    DiJulio, D. D.; Cederkall, J.; Fahlander, C.; Ekström, A.; Hjorth-Jensen, M.; Albers, M.; Bildstein, V.; Blazhev, A.; Darby, I.; Davinson, T.; De Witte, H.; Diriken, J.; Fransen, Ch.; Geibel, K.; Gernhäuser, R.; Görgen, A.; Hess, H.; Heyde, K.; Iwanicki, J.; Lutter, R.; Reiter, P.; Scheck, M.; Seidlitz, M.; Siem, S.; Taprogge, J.; Tveten, G. M.; Van de Walle, J.; Voulot, D.; Warr, N.; Wenander, F.; Wimmer, K.

    2013-01-01

    The radioactive isotope 107In was studied using sub-barrier Coulomb excitation at the REX-ISOLDE facility at CERN. Two γ rays were observed during the experiment, corresponding to the low-lying 11/2+ and 3/2- states. The reduced transition probability of the 11/2+ state was determined with the semiclassical Coulomb excitation code gosia2. The result is discussed in comparison to large-scale shell-model calculations, previous unified-model calculations, and earlier Coulomb excitation measurements in the odd-mass In isotopes.

  16. Isotope effects and Born-Oppenheimer breakdown in excited singlet states of the lithium dimer.

    PubMed

    Adohi-Krou, A; Martin, F; Ross, A J; Linton, C; Le Roy, R J

    2004-10-01

    Observation of infrared electronic transitions involving the 1 (1)Deltag state of 7Li2 has instigated an investigation of Born-Oppenheimer breakdown in four singlet electronic states correlating with (2s+2s), (2s+2p), and (2p+2p) lithium atoms. The 1 (1)Deltag state, which correlates at long range with (2p+2p) atoms, has been observed in emission from the (5p) (1)Piu Rydberg state and in 1 (1)Deltag-B (1)Piu bands, in both instances following optical-optical double-resonance excitation. The latter transition was observed previously for the lighter isotopomer, 6Li2 [C. Linton, F. Martin, P. Crozet, A. J. Ross, and R. Bacis, J. Mol. Spectrosc. 158, 445 (1993)]. By analyzing multiple-isotopomer data for several electronic systems simultaneously, we have determined the electronic isotope shifts and the leading vibrational and/or rotational Born-Oppenheimer breakdown terms for the X (1)Sigmag+, A (1)Sigmau+, B (1)Piu, and 1 (1)Deltag states of the lithium dimer. This paper also reports Fourier transform measurements of the B-X absorption spectra of 6Li2 and 7Li2, which were required to better define the bottom portion of the B (1)Piu state potential.

  17. Resonance Radiation and Excited Atoms

    NASA Astrophysics Data System (ADS)

    Mitchell, Allan C. G.; Zemansky, Mark W.

    2009-06-01

    1. Introduction; 2. Physical and chemical effects connected with resonance radiation; 3. Absorption lines and measurements of the lifetime of the resonance state; 4. Collision processes involving excited atoms; 5. The polarization of resonance radiation; Appendix; Index.

  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. 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.

  20. Exciting Polaritons with Quantum Light.

    PubMed

    López Carreño, J C; Sánchez Muñoz, C; Sanvitto, D; del Valle, E; Laussy, F P

    2015-11-01

    We discuss the excitation of polaritons-strongly coupled states of light and matter-by quantum light, instead of the usual laser or thermal excitation. As one illustration of the new horizons thus opened, we introduce "Mollow spectroscopy"-a theoretical concept for a spectroscopic technique that consists of scanning the output of resonance fluorescence onto an optical target-from which weak nonlinearities can be read with high precision even in strongly dissipative environments. PMID:26588401

  1. 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.

  2. 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.

  3. 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

  4. Probable nonexistence of a 3Pe metastable excited state of the positronium negative ion

    NASA Astrophysics Data System (ADS)

    Mills, Allen P., Jr.

    1981-12-01

    The H- ion is known to have a metastable 2p2 3Pe triplet excited state. To see if an analog of this state is present in the positronium negative ion Ps- the Coulomb binding energy Eb of the lowest-energy even-parity L=1 configuration of two identical-charge -e fermions of mass m1 plus one spinless particle of mass m2 and charge +e is calculated. We find a value of Eb below the n=2 level of the neutral atom for 0<=m2M<=0.17 and 0.90

  5. 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

  6. Indirect excitation of ultrafast demagnetization.

    PubMed

    Vodungbo, Boris; Tudu, Bharati; 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

  7. Indirect excitation of ultrafast demagnetization

    DOE PAGESBeta

    Vodungbo, Boris; Tudu, Bahrati; Perron, Jonathan; Delaunay, Renaud; Müller, Leonard; Berntsen, Magnus H.; Grübel, Gerhard; Malinowski, Grégory; Weier, Christian; Gautier, Julien; et al

    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

  8. 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.

  9. 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.

  10. Pair Excitations in Fermi Fluids

    NASA Astrophysics Data System (ADS)

    Böhm, Helga M.; Krotscheck, Eckhard; Schörkhuber, Karl; Springer, Josef

    2006-09-01

    We present a theory of multi-pair excitations in strongly interacting Fermi systems. Based on an equations-of-motion approach for time-dependent pair correlations it leads to a qualitatively new structure of the density-density response function. Our theory reduces to both, i) the "correlated" random-phase approximation (RPA) for fermions if the two-pair excitations are ignored, and ii) the correlated Brillouin-Wigner perturbation theory for bosons in the appropriate limit. The theory preserves the two first energy-weighted sum rules. A familiar problem of the standard RPA is that its zero-sound mode is energetically much higher than found in experiments. The popular cure of introducing an average effective mass in the Lindhard function violates sum rules and describes the physics incorrectly. We demonstrate that the inclusion of correlated pair excitations gives the correct dispersion. As in 4He, a modification of the effective mass is unnecessary also in 3He.

  11. Calculation of molecular excitation rates

    NASA Astrophysics Data System (ADS)

    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

  12. Magnetically induced pulser laser excitation

    SciTech Connect

    Taylor, R.S.; Leopold, K.E.

    1985-02-15

    A novel excitation scheme has been developed for excimer discharge lasers. The technique uses pulse transformer technology to induce a fast, high voltage pulse directly onto a ground potential laser electrode resulting in the breakdown of the laser gas mix. Saturation of the pulse transformer core inductance then permits efficient energy transfer from the main energy storage circuit into the discharge. When this excitation technique was used in a XeCl laser an output energy density of 2.5 J/l and an overall electrical to optical efficiency of 2% were obtained. The technique appears promising for the development of high energy, high average power excimer lasers.

  13. Autoresonant excitation of antiproton plasmas.

    PubMed

    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

    2011-01-14

    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.

  14. Autoresonant Excitation of Antiproton Plasmas

    SciTech Connect

    Andresen, G. B.; Bowe, P. D.; Hangst, J. S.; Ashkezari, M. D.; Hayden, M. E.; Baquero-Ruiz, M.; Chapman, S.; Fajans, J.; Povilus, A.; So, C.; Bertsche, W.; Butler, E.; Charlton, M.; Humphries, A. J.; Madsen, N.; Werf, D. P. van der; Carpenter, P. T.; Hurt, J. L.; Robicheaux, F.; Cesar, C. L.

    2011-01-14

    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.

  15. 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.

  16. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... (incorporated by reference; see 46 CFR 110.10-1), except that those for mobile offshore drilling units must meet... 46 CFR 110.10-1). In particular, no static exciter may be used for excitation of an emergency... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must...

  17. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... (incorporated by reference; see 46 CFR 110.10-1), except that those for mobile offshore drilling units must meet... 46 CFR 110.10-1). In particular, no static exciter may be used for excitation of an emergency... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must...

  18. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... (incorporated by reference; see 46 CFR 110.10-1), except that those for mobile offshore drilling units must meet... 46 CFR 110.10-1). In particular, no static exciter may be used for excitation of an emergency... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must...

  19. 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)

  20. 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).

  1. Collisional excitation of interstellar water

    NASA Technical Reports Server (NTRS)

    Palma, Amedeo; Green, Sheldon; Defrees, D. J.; Mclean, A. D.

    1988-01-01

    Rates for rotational excitation of water molecules in collisions with He atoms have been obtained from a new, accurate theoretical interaction potential. Rates among the lowest 40 ortho levels are given for kinetic temperatures to 1400 K and among the lowest 29 para levels for kinetic temperatures to 800 K.

  2. 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…

  3. 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.

  4. 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).

  5. 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…

  6. Band excitation Kelvin probe force microscopy utilizing photothermal excitation

    SciTech Connect

    Collins, Liam E-mail: liq1@ORNL.gov; Rodriguez, Brian J.; Jesse, Stephen; Balke, Nina; Kalinin, Sergei; Li, Qian E-mail: liq1@ORNL.gov

    2015-03-09

    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. Finally, PthBE-KPFM data contain information relating to local dielectric properties and electronic dissipation between tip and sample unattainable using conventional single frequency KPFM approaches.

  7. Dipole excitations in 96Ru

    NASA Astrophysics Data System (ADS)

    Linnemann, A.; Fransen, C.; Gorska, M.; Jolie, J.; Kneissl, U.; Knoch, P.; Mücher, D.; Pitz, H. H.; Scheck, M.; Scholl, C.; Brentano, P. Von

    2005-12-01

    Candidates for the two-phonon quadrupole-octupole 1- state and the two-phonon mixed-symmetry 1+ms state have been identified in the N=52 isotope 96Ru using the nuclear resonance fluorescence technique at the bremsstrahlung facility of the Stuttgart Dynamitron accelerator. Detailed information on energies, spins, branching ratios, and transition strengths of four new dipole excitations in 96Ru have been obtained. The observed dipole excitations are nearly at the same energies as in 94Mo, and the transition probabilities are comparable to those for the decay of the (2+1⊗3-1)1- and the (2+1⊗2+ms)1+ms states in 94Mo.

  8. Excitation energies from ensemble DFT

    NASA Astrophysics Data System (ADS)

    Borgoo, Alex; Teale, Andy M.; Helgaker, Trygve

    2015-12-01

    We study the evaluation of the Gross-Oliveira-Kohn expression for excitation energies E1-E0=ɛ1-ɛ0+∂E/xc,w[ρ] ∂w | ρ =ρ0. This expression gives the difference between an excitation energy E1 - E0 and the corresponding Kohn-Sham orbital energy difference ɛ1 - ɛ0 as a partial derivative of the exchange-correlation energy of an ensemble of states Exc,w[ρ]. Through Lieb maximisation, on input full-CI density functions, the exchange-correlation energy is evaluated accurately and the partial derivative is evaluated numerically using finite difference. The equality is studied numerically for different geometries of the H2 molecule and different ensemble weights. We explore the adiabatic connection for the ensemble exchange-correlation energy. The latter may prove useful when modelling the unknown weight dependence of the exchange-correlation energy.

  9. Collisional excitation of interstellar cyclopropenylidene

    NASA Technical Reports Server (NTRS)

    Green, Sheldon; Defrees, D. J.; Mclean, A. D.

    1987-01-01

    Theoretical rotational excitation rates were computed for C3H2 in collisions with He atoms at temperatures from 30 to 120 K. The intermolecular forces were obtained from accurate self-consistent field and perturbation theory calculations, and collision dynamics were treated within the infinite-order sudden approximation. The accuracy of the latter was examined by comparing with the more exact coupled states approximation.

  10. Excitation rates of heavy quarks

    NASA Astrophysics Data System (ADS)

    Canal, C. A.; Santangelo, E. M.; Ducati, M. B.

    1985-06-01

    We obtain the production rates for c, b, and t quarks in deep-inelastic neutrino- (antineutrino-) nucleon interactions, in the standard six-quark model with left-handed couplings. The results are obtained with the most recent mixing parameters and we include a comparison between quark parametrizations. The excitations are calculated separately for each flavor, allowing the understanding of the role of threshold effects when considered through different rescaling variables.

  11. 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.

  12. 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.

  13. Local Optical Excitations in Metals

    NASA Astrophysics Data System (ADS)

    Gibbs, Laurence Kay Doon

    Core spectra of p('6) (--->) p('5)s excitations of rare gas, halogen, and alkali impurities located on the surface and in the bulk of host alkali and Mg metals are presented. The data were obtained by means of differential reflectance spectroscopy in the energy range 5-20 eV using synchrotron radiation. In striking contrast to the absorption profiles of the pure alkalis, linear redshifted profiles are observed at dilution for rare gas adsorbates on alkali surfaces, for Cs adsorbed on Mg, and for Cs dispersed in bulk Na as an alloy. When Cs is dispersed in bulk K the sharp edge characteristic of the pure alkalis is observed. The spectra of Cs and Rb adsorbates on alkali surfaces mirror these same trends, but retain a distinct atomic character. A central result of the present research is that the linear profile may be associated with strong coupling of the excitation to the conduction electrons. A criterion for strong coupling is given which depends on the degree to which the excited impurity level mixes with the host conduction band. There is not at present any theory which can explain these observations. Spectra of halogen adsorbates on alkali and Mg surfaces are also presented; it is found that the ground configuration of isolated halogen atoms on these surfaces is ionic. All the impurity-metal complexes are studied at high concentration when impurity-impurity interactions are important.

  14. Entanglement entropy of electronic excitations.

    PubMed

    Plasser, Felix

    2016-05-21

    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.

  15. 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

  16. 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

  17. 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.

  18. Convective Excitation of Internal Waves

    NASA Astrophysics Data System (ADS)

    Lecoanet, Daniel; Le Bars, Michael; Burns, Keaton; Vasil, Geoffrey; Quataert, Eliot; Brown, Benjamin; Oishi, Jeffrey

    2015-11-01

    We will present a joint experimental & computational study of internal wave generation by convection. First we describe an experiment using the peculiar property of water that its density maximum is at 4° C . A tank of water cooled from below and heated from above develops a cold, convective layer near 4° C at the bottom of the tank, adjacent to a hot stably stratified layer at the top of the tank. We simulate this setup in 2D using the open-source Dedalus code (dedalus-project.org). Our simulations show that waves are excited from within the convection zone, opposed to at the interface between the convective and stably stratified regions. Finally, we will present 3D simulations of internal wave excitation by convection in a fully compressible atmosphere with multiple density scaleheights. These simulations provide greater freedom in choosing the thermal equilibrium of the system, and are run at higher Rayleigh number. The simulated waves are then compared to analytic predictions of the bulk excitation model.

  19. 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.

  20. Spurious Excitations in Semiclassical Scattering Theory.

    ERIC Educational Resources Information Center

    Gross, D. H. E.; And Others

    1980-01-01

    Shows how through proper handling of the nonuniform motion of semiclassical coordinates spurious excitation terms are eliminated. An application to the problem of nuclear Coulomb excitation is presented as an example. (HM)

  1. Discovering work excitement among navy nurses.

    PubMed

    Savage, S; Simms, L M; Williams, R A; Erbin-Roesemann, M

    1993-01-01

    An interest in what makes work exciting among Navy Nurse Corps officers led to the use of Simms' work excitement data collection protocol in Navy Medical Centers. Significant levels of work excitement were found among Navy nurses when compared to civilian nurses in non-military settings. Overall, results indicated that Navy nurses are excited about the variety, the leadership/management experiences, and the opportunities for teaching and learning--elements that are the very essence of Navy nursing practice. PMID:8345880

  2. Two-photon excitation of aluminium phthalocyanines

    SciTech Connect

    Meshalkin, Yu P; Alfimov, E E; Makukha, V K; Vasil'ev, N E; Denisov, A N; Ogirenko, A P

    1999-12-31

    A demonstration is given of the feasibility of two-photon excitation of aluminium phthalocyanine and of the pharmaceutical preparation 'Fotosens', used in photodynamic therapy. The excitation source was an Nd:YAG laser emitting at the 1064 nm wavelength. The spectra of the two-photon-excited luminescence were obtained and the two-photon absorption cross sections were determined. (lasers in medicine)

  3. 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)

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. Nucleon resonance excitation with CLAS

    SciTech Connect

    R. De Vita; CLAS Collaboration

    2004-09-01

    The study of the baryon spectrum is a fundamental part of the scientific program in Hall B at Jefferson Laboratory. The so called N* program indeed concerns the measurement of the electromagnetic production of exclusive hadronic final states, with the purpose of extracting information on baryon excited states. CLAS, the CEBAF Large Acceptance Spectrometer, is explicitly designed for conducting a broad experimental program in hadronic physics, using the continuous electron beam provided by the laboratory. An overview of the most recent results is presented.

  9. Volumetric Light-Field Excitation.

    PubMed

    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

  10. Mechanically-Excited Sessile Drops

    NASA Astrophysics Data System (ADS)

    Chang, Chun-Ti; Bostwick, Joshua; Daniel, Susan; Steen, Paul

    2010-11-01

    The volume and contact-line mobility of a sessile drop determine the frequency response of the drop to mechanical excitation. A useful signature of the drop is its response to a sweep of frequency. At particular frequencies the drop exhibits standing wave patterns of different mode numbers and/or azimuthal, spinning motion. We report observations of the spectrum of standing wave patterns and compare to predictions of a linear stability theory. On the side of application, the results suggest how to tune the pinning-unpinning of a sessile drop in order to maximize its translation.

  11. [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. PMID:9658699

  12. Volumetric Light-Field Excitation.

    PubMed

    Schedl, David C; Bimber, Oliver

    2016-07-01

    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.

  13. [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.

  14. Volumetric Light-Field Excitation

    NASA Astrophysics Data System (ADS)

    Schedl, David C.; Bimber, Oliver

    2016-07-01

    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.

  15. 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.

  16. 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.

  17. 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.

  18. Dual excitation multiphase electrostatic drive

    SciTech Connect

    Niino, Toshiki; Higuchi, Toshiro |; Egawa, Saku

    1995-12-31

    A novel electrostatic drive technology named Dual Excitation Multiphase Electrostatic Drive (DEMED) was presented. A basic DEMED consisted of two plastic films in which 3-phase parallel electrodes were embedded and was driven by a 3-phase ac excitation to the electrodes. Static characteristics of DEMED were calculated and tested and the results agreed very well. Three prototype motors of DEMED were fabricated using commercially available technique. The first prototype consisted of a single slider and stator and generated a linear motion with a slider`s motion range of about 5mm. It weighed 7g and generated a power of 1.6W and a thrust force of 4.4N. The second prototype consisted of 50 layer stack of linear motors, summing their outputs. It weighed 3.6kg and generated a propulsive force of 310N being powered with boosted commercial 3-phase electricity. The third prototype consisted of a rotor and a stator in which electrodes were arranged radially and generated rotational motion. The maximum power of 36mW was generated by the prototype weighing only 260mg for its rotor and stator. From the results of the numerical calculation, a practical design methodology for the motor was determined. An optimal design for a motor employing currently available material and fabrication techniques is provided as an example. Analyses predict that force generation over the interfacial area between the slider and stator of this motor would be 3,900N/m{sup 2}.

  19. Coulomb excitation of Ga73

    NASA Astrophysics Data System (ADS)

    Diriken, J.; Stefanescu, I.; Balabanski, D.; Blasi, N.; Blazhev, A.; Bree, N.; Cederkäll, J.; Cocolios, T. E.; Davinson, T.; Eberth, J.; Ekström, A.; Fedorov, D. V.; Fedosseev, V. N.; Fraile, L. M.; Franchoo, S.; Georgiev, G.; Gladnishki, K.; Huyse, M.; Ivanov, O. V.; Ivanov, V. S.; Iwanicki, J.; Jolie, J.; Konstantinopoulos, T.; Kröll, Th.; Krücken, R.; Köster, U.; Lagoyannis, A.; Lo Bianco, G.; Maierbeck, P.; Marsh, B. A.; Napiorkowski, P.; Patronis, N.; Pauwels, D.; Reiter, P.; Seliverstov, M.; Sletten, G.; van de Walle, J.; van Duppen, P.; Voulot, D.; Walters, W. B.; Warr, N.; Wenander, F.; Wrzosek, K.

    2010-12-01

    The B(E2;Ii→If) values for transitions in 3171Ga40 and 3173Ga42 were deduced from a Coulomb excitation experiment at the safe energy of 2.95 MeV/nucleon using post-accelerated beams of Ga71,73 at the REX-ISOLDE on-line isotope mass separator facility. The emitted γ rays were detected by the MINIBALL γ-detector array, and B(E2;Ii→If) values were obtained from the yields normalized to the known strength of the 2+→0+ transition in the Sn120 target. The comparison of these new results with the data of less neutron-rich gallium isotopes shows a shift of the E2 collectivity toward lower excitation energy when adding neutrons beyond N=40. This supports conclusions from previous studies of the gallium isotopes, which indicated a structural change in this isotopic chain between N=40 and 42. Combined with recent measurements from collinear laser spectroscopy showing a 1/2- spin and parity for the ground state, the extracted results revealed evidence for a 1/2-,3/2- doublet near the ground state in 3173Ga42 differing by at most 0.8 keV in energy.

  20. New Insights in 4f(12)5d(1) Excited States of Tm(2+) through Excited State Excitation Spectroscopy.

    PubMed

    de Jong, Mathijs; Biner, Daniel; Krämer, Karl W; Barandiarán, Zoila; Seijo, Luis; Meijerink, Andries

    2016-07-21

    Optical excitation of ions or molecules typically leads to an expansion of the equilibrium bond lengths in the excited electronic state. However, for 4f(n-1)5d(1) excited states in lanthanide ions both expansion and contraction relative to the 4f(n) ground state have been reported, depending on the crystal field and nature of the 5d state. To probe the equilibrium distance offset between different 4f(n-1)5d(1) excited states, we report excited state excitation (ESE) spectra for Tm(2+) doped in CsCaBr3 and CsCaCl3 using two-color excited state excitation spectroscopy. The ESE spectra reveal sharp lines at low energies, confirming a similar distance offset for 4f(n-1)5d(t2g)(1) states. At higher energies, broader bands are observed, which indicate the presence of excited states with a different offset. On the basis of ab initio embedded-cluster calculations, the broad bands are assigned to two-photon d-d absorption from the excited state. In this work, we demonstrate that ESE is a powerful spectroscopic tool, giving access to information which cannot be obtained through regular one-photon spectroscopy. PMID:27347766

  1. New Insights in 4f(12)5d(1) Excited States of Tm(2+) through Excited State Excitation Spectroscopy.

    PubMed

    de Jong, Mathijs; Biner, Daniel; Krämer, Karl W; Barandiarán, Zoila; Seijo, Luis; Meijerink, Andries

    2016-07-21

    Optical excitation of ions or molecules typically leads to an expansion of the equilibrium bond lengths in the excited electronic state. However, for 4f(n-1)5d(1) excited states in lanthanide ions both expansion and contraction relative to the 4f(n) ground state have been reported, depending on the crystal field and nature of the 5d state. To probe the equilibrium distance offset between different 4f(n-1)5d(1) excited states, we report excited state excitation (ESE) spectra for Tm(2+) doped in CsCaBr3 and CsCaCl3 using two-color excited state excitation spectroscopy. The ESE spectra reveal sharp lines at low energies, confirming a similar distance offset for 4f(n-1)5d(t2g)(1) states. At higher energies, broader bands are observed, which indicate the presence of excited states with a different offset. On the basis of ab initio embedded-cluster calculations, the broad bands are assigned to two-photon d-d absorption from the excited state. In this work, we demonstrate that ESE is a powerful spectroscopic tool, giving access to information which cannot be obtained through regular one-photon spectroscopy.

  2. 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.

  3. Coulomb excitation of 107Sn

    NASA Astrophysics Data System (ADS)

    DiJulio, D. D.; Cederkall, J.; Fahlander, C.; Ekström, A.; Hjorth-Jensen, M.; Albers, M.; Bildstein, V.; Blazhev, A.; Darby, I.; Davinson, T.; De Witte, H.; Diriken, J.; Fransen, Ch.; Geibel, K.; Gernhäuser, R.; Görgen, A.; Hess, H.; Iwanicki, J.; Lutter, R.; Reiter, P.; Scheck, M.; Seidlitz, M.; Siem, S.; Taprogge, J.; Tveten, G. M.; Van de Walle, J.; Voulot, D.; Warr, N.; Wenander, F.; Wimmer, K.

    2012-07-01

    The radioactive isotope 107Sn was studied using Coulomb excitation at the REX-ISOLDE facility at CERN. This is the lightest odd-Sn nucleus examined using this technique. The reduced transition probability of the lowest-lying 3/2+ state was measured and is compared to shell-model predictions based on several sets of single-neutron energies relative to 100Sn . Similar to the transition probabilities for the 2+ states in the neutron-deficient even-even Sn nuclei, the measured value is underestimated by shell-model calculations. Part of the strength may be recovered by considering the ordering of the d_{5/2} and g_{7/2} single-neutron states.

  4. Collective excitations of supersymmetric plasma

    SciTech Connect

    Czajka, Alina; Mrowczynski, Stanislaw

    2011-02-15

    Collective excitations of N=1 supersymmetric electromagnetic plasma are studied. Since the Keldysh-Schwinger approach is used, not only equilibrium but also nonequilibrium plasma, which is assumed to be ultrarelativistic, is under consideration. The dispersion equations of photon, photino, electron, and selectron modes are written down and the self-energies, which enter the equations, are computed in the hard loop approximation. The self-energies are discussed in the context of effective action which is also given. The photon modes and electron ones appear to be the same as in the usual ultrarelativistic plasma of electrons, positrons, and photons. The photino modes coincide with the electron ones and the selectron modes are as of a free relativistic massive particle.

  5. 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.

  6. 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 .

  7. 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.

  8. 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

  9. Circadian regulation of human cortical excitability.

    PubMed

    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

    2016-06-24

    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.

  10. A Hamiltonian approach to the parametric excitation

    NASA Astrophysics Data System (ADS)

    Leroy, V.; Bacri, J.-C.; Hocquet, T.; Devaud, M.

    2006-05-01

    We propose a solution of the parametrically excited oscillator problem using the Hamiltonian formalism introduced by Glauber. The main advantage is that, within the framework of this formalism, the different possible approximations appear much more naturally than in the standard textbook presentation. Experiments on adiabatic and resonant parametric excitations of a pendulum are presented as an illustration, with particular attention being paid to the role played by the phase of the excitation.

  11. The Dynamics of Small Excitable Systems

    NASA Astrophysics Data System (ADS)

    Jung, Peter; Shuai, Jian-Wei

    2005-03-01

    We consider clusters of sodium ion channels similar as found in the nodes of Ranvier in myelinated neurons. The cluster behaves like excitable systems in the limit of large numbers of ion channels. Small clusters of channels, i.e. small excitable systems, exhibit spontaneous action potentials. We show that small excitable systems exhibit maxima of the spontaneous firing rate and of the response to external stimuli at multiple specific cluster sizes that are universally determined by arithmetic properties of small numbers.

  12. Two-photon excitation fluorescence bioassays.

    PubMed

    Hänninen, Pekka; Soukka, Jori; Soini, Juhani T

    2008-01-01

    Application of two-photon excitation of fluorescence in microscopy is one of the major discoveries of the "renaissance" of light microscopy that started in the 1980s. The technique derives its advantages from the biologically "smooth" wavelength of the excitation light and the confinement of the excitation. Difficult, and seemingly nontransparent, samples may be imaged with the technique with good resolution. Although the bioresearch has been concentrating mostly on the positive properties of the technique for imaging, the same properties may be applied successfully to nonimaging bioassays. This article focuses on the development path of two-photon excitation-based assay system. PMID:18596366

  13. 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.

  14. 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

  15. Multi-photon excitation microscopy.

    PubMed

    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.

  16. Multi-photon excitation microscopy.

    PubMed

    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

  17. 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.

  18. The Excited State Spectrum of QCD

    SciTech Connect

    Robert Edwards

    2010-08-01

    The determination of the highly excited state spectrum of baryons within QCD is a major theoretical and experimental challenge. I will present recent results from lattice QCD that give some indications on the structure of these highly excited states, and outline on-going and future work needed for a full determination of the spectrum, including strong decays.

  19. Vibrationally excited molecular hydrogen near Herschel 36

    SciTech Connect

    Rachford, Brian L.; Snow, Theodore P.; Ross, Teresa L.

    2014-05-10

    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 rovibrational excitation of molecular hydrogen in material at a single velocity or very small range of velocities, with this component presumably lying near the star system and undergoing fluorescent excitation. The overall H{sub 2} excitation is similar to, but apparently larger than, that seen toward HD 37903 which previously showed the largest vibrationally excited H{sub 2} column densities seen in UV absorption spectra. While the velocities of the highly excited H{sub 2} lines are consistent within each observation, it appears that they underwent a ∼60 km s{sup –1} redshift during the 3.6 yr 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{sup +} lines and several unusually broad diffuse interstellar bands toward Herschel 36. Along with the H{sub 2} excitation, all of these findings appear to be related to the extreme environment within ∼0.1 pc of the massive young stellar system.

  20. 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. PMID:24727909

  1. 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…

  2. 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.

  3. 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.

  4. 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

  5. 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.

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

    PubMed

    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.

  7. 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.

  8. Impact of ground- and excited-state aromaticity on cyclopentadiene and silole excitation energies and excited-state polarities.

    PubMed

    Jorner, Kjell; Emanuelsson, Rikard; Dahlstrand, Christian; Tong, Hui; Denisova, Aleksandra V; Ottosson, Henrik

    2014-07-21

    A new qualitative model for estimating the properties of substituted cyclopentadienes and siloles in their lowest ππ* excited states is introduced and confirmed through quantum chemical calculations, and then applied to explain earlier reported experimental excitation energies. According to our model, which is based on excited-state aromaticity and antiaromaticity, siloles and cyclopentadienes are cross-hyperconjugated "aromatic chameleons" that adapt their electronic structures to conform to the various aromaticity rules in different electronic states (Hückel's rule in the π(2) electronic ground state (S0) and Baird's rule in the lowest ππ* excited singlet and triplet states (S1 and T1)). By using pen-and-paper arguments, one can explain polarity changes upon excitation of substituted cyclopentadienes and siloles, and one can tune their lowest excitation energies by combined considerations of ground- and excited-state aromaticity/antiaromaticity effects. Finally, the "aromatic chameleon" model can be extended to other monocyclic compound classes of potential use in organic electronics, thereby providing a unified view of the S0, T1, and S1 states of a range of different cyclic cross-π-conjugated and cross-hyperconjugated compound classes. PMID:25043523

  9. Zero Degree Target Electron Spectroscopy: Double Excitation-Autoionization of Helium in Fast Electron, Hydrogen Ion, HELIUM(+) Ion and HELIUM(+2) Ion Collisions

    NASA Astrophysics Data System (ADS)

    Wang, Houle

    The purpose of this work is to investigate few -body dynamical effects in fast ion-atom and electron-atom collisions using zero-degree high-resolution Auger electron spectroscopy. In this study we report the first zero degree high-resolution spectra and double differential cross sections (DDCS) measurement for double excitation-autoionization of He target atoms. We also measured direct ionization DDCS at zero degree observation angle. All of our cross sections are absolutely calibrated. The projectiles used in this work are energetic electrons in the energy range 150 to 1000eV, 100KeV to 1.5MeV protons, 400KeV to 1.5MeV He^+ and 400KeV to 1.6MeV He ^{2+}. The zero degree observation angle provide a unique opportunity to maximize interaction between the emitted electron, the ionized target atom and the charged projectile particle. Using an equal or better than 0.2% instrumental energy resolution allows us to study the autoionization line profiles. In particular the doubly excited autoionizing (2lnl') states of He have been observed as a function of the collision conditions such as impact velocity, projectile charge sign and type of projectile, specifically for dominating (2p^2)^1 Dto(1sepsilon d) and (2s2p)^1P ^circto(1sepsilon p) channels. The results of our measurement clearly indicate that the three-body Coulomb interaction in the final state (CIFS) not only affect autoionizing resonance energies and line widths but also strongly influences the interference of the transition amplitudes between competing processes such as direct ionization and autoionization. We found that the Fano or Shore parametrization generally fails for zero degree autoionization by positive ion impact at medium to high projectile energy. Therefore a new post collisional three-body CIFS model has been developed as a parametrization procedure. This model has been successfully applied to double excitation processes to study single differential cross sections of the (2p^2) ^1D and (2s2p)^1P

  10. 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

  11. Slow excited state phototautomerization in 3-hydroxyisoquinoline.

    PubMed

    Joshi, Neeraj Kumar; Arora, Priyanka; Pant, Sanjay; Joshi, Hem Chandra

    2014-06-01

    In the present work we report the spectral and photophysical properties of 3-hydroxyisoquinoline in various protic/aprotic solvents. Our steady state and time resolved fluorescence data indicates that in the monomer form of 3HIQ phototautomerization can take place in the excited state through excited state intramolecular proton, while as per earlier suggestions phototautomerization in 3HIQ occurs in dimer or complex (in the presence of acetic acid) form. Moreover, we find rather slow tautomerization (occurring on the nanosecond scale). It is found that proton transfer occurs both in the ground as well as excited states and is controlled by the polarity of the solvent.

  12. Surface and bulk excitations in condensed matter

    SciTech Connect

    Ritchie, R.H.

    1988-01-01

    In this lecture collective and single-particle electron excitations of solids will be discussed with emphasis on the properties of metallic and semiconducting materials. However, some of the general properties of long-wavelength collective modes to be discussed are valid for insulators as well, and some considerations apply to nuclear excitations such as optical or acoustical phonons, dipolar plasmons, etc. The concept of elementary excitations in solids, pioneered by Bohm and Pines almost 4 decades ago, has proved to be extremely useful in understanding the properties of systems of many particles, especially in respect to the response to the action of external probes. 32 refs., 12 figs.

  13. 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.

  14. Helicon wave excitation with helical antennas

    SciTech Connect

    Light, M.; Chen, F.F.

    1995-04-01

    Components of the wave magnetic field in a helicon discharge have been measured with a single-turn, coaxial magnetic probe. Left- and right-handed helical antennas, as well as plane-polarized antennas, were used; and the results were compared with the field patterns computed for a nonuniform plasma. The results show that the right-hand circularly polarized mode is preferentially excited with all antennas, even those designed to excite the left-hand mode. For right-hand excitation, the radial amplitude profiles are in excellent agreement with computations. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  15. Materials Data on Hg2P2H4O9 (SG:2) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-10-02

    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 Li2Bi2P2O9 (SG:4) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-10-02

    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

  17. Materials Data on Ca2P2H8O11 (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

  18. Materials Data on CsZn2P2HO8 (SG:64) 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

  19. 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...

  20. 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. PMID:27219844

  1. 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.

  2. Materials Data on Tb(Ni2P)2 (SG:136) by Materials Project

    DOE Data Explorer

    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

  3. 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.

  4. Materials Data on CaV2P2O9 (SG:62) by Materials Project

    SciTech Connect

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

    DOE PAGESBeta

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

    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.

  6. Materials Data on K2P2H2O7 (SG:2) 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

  7. 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.

  8. 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

  9. 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

  10. Materials Data on NaZn2P2HO8 (SG:2) by Materials Project

    SciTech Connect

    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

  11. Materials Data on U(Ni2P)2 (SG:136) by Materials Project

    SciTech Connect

    Kristin Persson

    2015-02-09

    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

  12. Materials Data on ZnAg2P2O7 (SG:136) by Materials Project

    SciTech Connect

    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

  13. 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

  14. 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

  15. Materials Data on Fe2P2O7 (SG:2) by Materials Project

    SciTech Connect

    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 Hf2P2O9 (SG:12) 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

  17. Materials Data on Mo2P2O11 (SG:62) 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

  18. 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

  19. 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

  20. 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

  1. Materials Data on Sm(Ni2P)2 (SG:58) 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

  2. Materials Data on Ti2P2H4O11 (SG:2) 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

  3. Materials Data on RbB2P2HO9 (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

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. Broadband single-molecule excitation spectroscopy

    NASA Astrophysics Data System (ADS)

    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.

  9. 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.

  10. Geophysical excitation of nutation and geomagnetic jerks

    NASA Astrophysics Data System (ADS)

    Vondrák, Jan; Ron, Cyril

    2014-05-01

    Recently Zinovy Malkin (2013) proposed that the observed changes of Free Core Nutation parameters (phase, amplitude) might be related to geomagnetic jerks (rapid changes of the secular variations of geomagnetic field). We tested this hypothesis and found that if the numerical integration of Brzezinski 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 significantly. This approach however tacitly assumes that the influence of geomagnetic jerks has a stepwise character, which is physically not acceptable. The present study continues in this effort by introducing a simple continuous excitation function (hypothetically due to geomagnetic jerks). The results of numerical integration of atmospheric/oceanic excitations plus this newly introduced excitation are then compared with the observed celestial pole offsets.

  11. 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.

  12. 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.

  13. Faraday Waves under Time-Reversed Excitation

    NASA Astrophysics Data System (ADS)

    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 , Phys. Rev. E 78, 036218 (2008)PLEEE81539-3755]. 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.

  14. Probing the excitation spectrum of polariton condensates

    SciTech Connect

    Wouters, Michiel; Carusotto, Iacopo

    2009-03-15

    We propose a four-wave mixing experiment to probe the elementary excitation spectrum of a nonequilibrium Bose-Einstein condensate of exciton-polaritons under nonresonant pumping. Analytical calculations based on mean-field theory show that this method is able to reveal the characteristic negative energy feature of the Bogoliubov dispersion. Numerical simulations including the finite spatial profile of the excitation laser spot and a weak disorder confirm the practical utility of the method for realistic condensates.

  15. Plasmoelectronics: coupling plasmonic excitation with electron flow.

    PubMed

    Warren, Scott C; Walker, David A; Grzybowski, Bartosz A

    2012-06-19

    Explorations of the coupling of light and charge via localized surface plasmons have led to the discovery that plasmonic excitation can influence macroscopic flows of charge and, conversely, that charging events can change the plasmonic excitation. We discuss recent theory and experiments in the emerging field of plasmoelectronics, with particular emphasis on the application of these materials to challenges in nanotechnology, energy use, and sensing. PMID:22385329

  16. 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.

  17. Tailoring dye-sensitized upconversion nanoparticle excitation bands towards excitation wavelength selective imaging

    SciTech Connect

    Wu, Xiang; Lee, Hyungseok; Bilsel, Osman; Zhang, Yuanwei; Li, Zhanjun; Chen, Teresa; Liu, Yi; Duan, Chunying; Shen, Jie; Punjabi, Amol; Han, Gang

    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.

  18. Tailoring Dye-sensitized Upconversion Nanoparticles Excitation Bands towards Excitation Wavelength Selective Imaging

    PubMed Central

    Wu, Xiang; Lee, Hyungseok; Bilsel, Osman; Zhang, Yuanwei; Li, Zhanjun; Chen, Teresa; Liu, Yi; Duan, Chunying; Shen, Jie; Punjabi, Amol; Han, Gang

    2015-01-01

    One of 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. 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. PMID:26499208

  19. 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.

  20. 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.

  1. 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

    2009-01-01

    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)].

  2. Electron impact excitation of Kr XXXII

    SciTech Connect

    Aggarwal, K.M. Keenan, F.P.; Lawson, K.D.

    2009-09-15

    Collision strengths ({omega}) have been calculated for all 7750 transitions among the lowest 125 levels belonging to the 2s{sup 2}2p,2s2p{sup 2},2p{sup 3},2s{sup 2}3l,2s2p3l, and 2p{sup 2}3l configurations of boron-like krypton, Kr XXXII, for which the Dirac Atomic R-matrix Code has been adopted. All partial waves with angular momentum J{<=}40 have been included, sufficient for the convergence of {omega} for forbidden transitions. For allowed transitions, a top-up has been included in order to obtain converged values of {omega} up to an energy of 500 Ryd. Resonances in the thresholds region have been resolved in a narrow energy mesh, and results for effective collision strengths (Y) have been obtained after averaging the values of {omega} over a Maxwellian distribution of electron velocities. Values of Y are reported over a wide temperature range below 10{sup 7.3}K, and the accuracy of the results is assessed. Values of Y are also listed in the temperature range 7.3{<=}logT{sub e}(K){<=}9.0, obtained from the nonresonant collision strengths from the Flexible Atomic Code.

  3. "Safe" Coulomb excitation of 30Mg.

    PubMed

    Niedermaier, O; Scheit, H; Bildstein, V; Boie, H; Fitting, J; von Hahn, R; Köck, F; Lauer, M; Pal, U K; Podlech, H; Repnow, R; Schwalm, D; Alvarez, C; Ames, F; Bollen, G; Emhofer, S; Habs, D; Kester, O; Lutter, R; Rudolph, K; Pasini, M; Thirolf, P G; Wolf, B H; Eberth, J; Gersch, G; Hess, H; Reiter, P; Thelen, O; Warr, N; Weisshaar, D; Aksouh, F; Van den Bergh, P; Van Duppen, P; Huyse, M; Ivanov, O; Mayet, P; Van de Walle, J; Aystö, J; Butler, P A; Cederkäll, J; Delahaye, P; Fynbo, H O U; Fraile, L M; Forstner, O; Franchoo, S; Köster, U; Nilsson, T; Oinonen, M; Sieber, T; Wenander, F; Pantea, M; Richter, A; Schrieder, G; Simon, H; Behrens, T; Gernhäuser, R; Kröll, T; Krücken, R; Münch, M; Davinson, T; Gerl, J; Huber, G; Hurst, A; Iwanicki, J; Jonson, B; Lieb, P; Liljeby, L; Schempp, A; Scherillo, A; Schmidt, P; Walter, G

    2005-05-01

    We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient gamma spectrometer MINIBALL. Using 30Mg ions accelerated to an energy of 2.25 MeV/u together with a thin (nat)Ni target, Coulomb excitation of the first excited 2+ states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative deexcitation gamma-ray yields the B(E2;0(+)gs-->2(+)1) value of 30Mg was determined to be 241(31)e2 fm4. Our result is lower than values obtained at projectile fragmentation facilities using the intermediate-energy Coulomb excitation method, and confirms the theoretical conjecture that the neutron-rich magnesium isotope 30Mg resides outside the "island of inversion."

  4. Bernoulli excitation and detection of gas bubbles.

    PubMed

    Telling, R H; Walton, A J

    2001-10-01

    A simple method is proposed for detecting and sizing bubbles in pipeline fluid flow. This is based on changing the pressure of the fluid, which in turn excites volume oscillations in the bubble. If the change in pressure is of sufficient brevity and magnitude, the transient distortion results in excitation of the bubble into radiative oscillation at its natural frequency. In a moving fluid, the Bernoulli equation predicts that such a pressure change can be achieved through a suitable gradient in the flow velocity. In the experiments described here, this is achieved by altering the cross-sectional area of the pipe in which the fluid is flowing. We demonstrate the efficacy of this excitation method and, by detecting the radiated sound using a nearby hydrophone, determine the size of individual bubbles from their characteristic oscillation frequency.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Excitation of gravity waves in common envelopes

    NASA Technical Reports Server (NTRS)

    Soker, Noam

    1992-01-01

    We study the excitation of gravity waves by a low-mass companion orbiting inside the envelope of a giant star, concentrating on brown dwarfs inside the envelope of asymptotic giant branch stars. Efficient g-wave excitations occur only after the brown dwarf has spiraled-in to the radiative zone, well inside the envelope, of the asymptotic giant branch star. The brown dwarf excites g-waves when its orbital radius is about 3-10 solar radii. At this stage of the evolution the envelope mass is below 0.1 solar mass. The g-waves propagate inward from the secondary orbit, carrying angular momentum and energy. We find that the angular momentum transport leads to an efficient spin-up of the inner envelopes. The differential rotation between the envelope and core and nonlinear wave effects, can cause a mixing of heavy elements from the core to the envelope.

  12. 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

  13. Excitation spectrum of the attractive Hubbard model

    SciTech Connect

    Micnas, R.; Pedersen, M.H.; Schafroth, S.; Schneider, T.; Rodriguez-Nunez, J.J.; Beck, H.

    1995-12-01

    We study excitation-spectrum and normal-state properties of the two-dimensional attractive Hubbard model using the conserving, self-consistent {ital T}-matrix formalism in the intermediate coupling regime and at low electron concentration. Numerical results are presented for one-particle and two-particle excitation spectra, the one-particle momentum distribution, the chemical potential, and the static spin susceptibility. For a coupling strength of {ital U}/{ital t}=4.0, the one-particle spectral function, {ital A}(k,{omega}), shows two peaks of different weights. One peak can be associated with pair formation, whereas the other corresponds to renormalized quasiparticle excitation. It turns out that the two-band feature is reasonably well described by an ansatz for {ital A}(k,{omega}), which satisfies the first four frequency moments.

  14. 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.

  15. 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.

  16. 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

  17. Electron-impact vibrational excitation of cyclopropane.

    PubMed

    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° to 180° 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 ν4 of A1 (″) symmetry by the 5.5 eV A2 (') 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 A2 (') symmetry which causes excitation of the non-symmetric HCH twisting mode ν4 of the A1 (″) symmetry and departs in p- and f-waves of A2 (″) symmetry. PMID:25877583

  18. Optical Excitation and Probing of Bottle Microresonators

    NASA Astrophysics Data System (ADS)

    Murugan, G. Senthil; Wilkinson, J. S.; Zervas, M. N.

    2010-11-01

    Fiber bottle microresonators supporting helical whispering gallery modes and exhibiting field maxima symmetrically located on either side of the neck of the bottle have been demonstrated. Channel dropping characteristics have been studied experimentally for the first time in this type of microresonator, using tapered excitation and probe fibers symmetrically placed on both sides of the bottle microresonator. Selective excitation on one side of the bottle microresonator leads to symmetrically located turning points and power localization on both sides of the bottle, leading to the potential to construct add-drop filters.

  19. 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.

  20. 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.

  1. Selective form of an excitable membrane plasticity.

    PubMed

    Tsitolovsky, L E; Babkina, N V

    1992-11-01

    This work describes the change in an active electrogenesis of the command neurons responsible for defensive closure of a snail's pneumostome during elaborating, extinction and restoration of a classical conditioned defensive reflex to a tactile stimulus. Tactile stimulations applied to different parts of a snail's body served as a differential stimulus. As the biological value of a conditioned stimulus increases due to learning, the excitability of command neurons in response to conditioned stimulus rises. At the same time the neurons demonstrated a reduced excitability in response to a differentiating stimulus.

  2. Wave instabilities in an excitable electrochemical system

    NASA Astrophysics Data System (ADS)

    Otterstedt, R. D.; Jaeger, N. I.; Plath, P. J.; Hudson, J. L.

    1998-11-01

    Spatiotemporal pattern formation under potentiostatic control in the excitable potential range at the active/passive transition of cobalt in buffered phosphoric acid has been investigated in a ribbon electrode geometry. The propagation of an active area with modulation and wave splitting has been observed, depending on the parameters potential and time of passivation prior to excitation. The modulation and wave splitting are influenced both by the kinetics of repassivation on the electrode surface and by long-range coupling and positive feedback through the electric field. Modulation in the vicinity of the system boundary gives rise to an apparent reflection of the active area at the boundary.

  3. Collective charge excitations along cell membranes

    NASA Astrophysics Data System (ADS)

    Manousakis, E.

    2005-07-01

    A significant part of the thin layers of counter-ions adjacent to the exterior and interior surfaces of a cell membrane form quasi-two-dimensional (2D) layers of mobile charge. Collective charge density oscillations, known as plasmon modes, in these 2D charged systems of counter-ions are predicted in the present paper. This is based on a calculation of the self-consistent response of this system to a fast electric field fluctuation. The possibility that the membrane channels might be using these excitations to carry out fast communication is suggested and experiments are proposed to reveal the existence of such excitations.

  4. Exciting Baryons: now and in the future

    SciTech Connect

    Michael Pennington

    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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. Optimal Parametric Feedback Excitation of Nonlinear Oscillators

    NASA Astrophysics Data System (ADS)

    Braun, David J.

    2016-01-01

    An optimal parametric feedback excitation principle is sought, found, and investigated. The principle is shown to provide an adaptive resonance condition that enables unprecedentedly robust movement generation in a large class of oscillatory dynamical systems. Experimental demonstration of the theory is provided by a nonlinear electronic circuit that realizes self-adaptive parametric excitation without model information, signal processing, and control computation. The observed behavior dramatically differs from the one achievable using classical parametric modulation, which is fundamentally limited by uncertainties in model information and nonlinear effects inevitably present in real world applications.

  10. Optimal Parametric Feedback Excitation of Nonlinear Oscillators.

    PubMed

    Braun, David J

    2016-01-29

    An optimal parametric feedback excitation principle is sought, found, and investigated. The principle is shown to provide an adaptive resonance condition that enables unprecedentedly robust movement generation in a large class of oscillatory dynamical systems. Experimental demonstration of the theory is provided by a nonlinear electronic circuit that realizes self-adaptive parametric excitation without model information, signal processing, and control computation. The observed behavior dramatically differs from the one achievable using classical parametric modulation, which is fundamentally limited by uncertainties in model information and nonlinear effects inevitably present in real world applications. PMID:26871336

  11. 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.

  12. Theory and computation of the attosecond dynamics of pairs of electrons excited by high-frequency short light pulses

    SciTech Connect

    Mercouris, Th.; Komninos, Y.; Nicolaides, C.A.

    2004-03-01

    By defining and solving from first principles, using the state-specific expansion approach, a time-dependent pump-probe problem with real atomic states, we show computationally that, if time resolution reaches the attosecond regime, strongly correlated electronic ''motion'' can be probed and can manifest itself in terms of time-dependent mixing of symmetry-adapted configurations. For the system that was chosen in this study, these configurations, the He 2s2p,2p3d, and 3s3p P{sup o1}, whose radials are computed by solving multiconfigurational Hartree-Fock equations, label doubly excited states (DES) of He inside the 1s{epsilon}p P{sup o1} scattering continuum and act as nonstationary states that mix, and simultaneously decay exponentially to 1s{epsilon}p P{sup o1} via the atomic Hamiltonian, H{sub A}. The herein presented theory and analysis permitted the computation of attosecond snapshots of pairs of electrons in terms of time-dependent probability distributions of the angle between the position vectors of the two electrons. The physical processes were determined by solving ab initio the time-dependent Schroedinger equation, using as initial states either the He 1s{sup 2} or the 1s2s S{sup 1} discrete states and two femtosecond Gaussian pulses of 86 fs full width at half-maximum, having frequencies in resonance with the energies of the correlated states represented by the 2s2p and 2p3d configurations. We calculated the probability of photoabsorption and of two-photon resonance ionization and of the simultaneous oscillatory mixing of the configurations 2s2p,2p3d,3s3p, and 1s{epsilon}p P{sup o1}, within the attosecond scale, via the interactions present in H{sub A}. Among the possible channels for observing the attosecond oscillations of the occupation probabilities of the DES, is the de-excitation path of the transition to the He 1s3d D{sup 1} discrete state, which emits at 6680 A.

  13. 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.

  14. 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.

  15. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the... GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL... (incorporated by reference; see 46 CFR 110.10-1), except that those for mobile offshore drilling units must...

  16. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the... GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL... (incorporated by reference; see 46 CFR 110.10-1), except that those for mobile offshore drilling units must...

  17. Contemporary continuum QCD approaches to excited hadrons

    NASA Astrophysics Data System (ADS)

    El-Bennich, Bruno; Rojas, Eduardo

    2016-03-01

    Amongst the bound states produced by the strong interaction, radially excited meson and nucleon states offer an important phenomenological window into the long-range behavior of the coupling constant in Quantum Chromodynamics. We here report on some technical details related to the computation of the bound state's eigenvalue spectrum in the framework of Bethe-Salpeter and Faddeev equations.

  18. 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.

  19. 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.

  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. 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.

  2. Spectroscopy of Optical Excitations in Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Ma, Yingzhong

    2006-03-01

    Understanding the optical spectra and electronic excited state dynamics of carbon naotubes is important both for fundamental research and a wide variety of potential applications. In this presentation, we will report the results of a systematic study on semiconducting single-walled carbon nanotubes (SWNTs) obtained by utilizing complementary femtosecond spectroscopic techniques, including fluorescence up-conversion, frequency-resolved transient absorption, and three-pulse photon echo peakshift (3PEPS) spectroscopy. Our efforts have focused on optically selective detection of the spectra and dynamics associated with structurally distinct semiconducting SWNT species. Using individual nanotube enriched micelle-dispersed SWNT preparations, in combination with resonant excitation and detection, has enabled us to independently access selected species, such as the (8,3), (6,5), (7,5), (11,0), (7,6) and (9,5) nanotubes. We will discuss the following topics: (1) the excitonic nature of the elementary excitation and its unambiguous identification from direct determination of the exciton binding energy for a selected semiconducting nanotube, the (8,3) tube; (2) the spectroscopic and dynamical signatures of exciton-exciton annihilation and its predominant role in governing ultrafast excited state relaxation; (3) the annihilation-concomitant exciton dissociation and the spectroscopic and dynamic features of the resulting electron-hole continuum; (4) timescales characterizing the ultrafast thermalization processes. In addition, we will demonstrate the power of 3PEPS spectroscopy to elucidate the spectral properties and dynamics of SWNTs. This work was supported by the NSF.

  3. 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…

  4. Hexadecapolar excitation in sup 100 Ru

    SciTech Connect

    Sirota, S.; Duarte, J.L.M.; Horodynski-Matsushigue, L.B.; Borello-Lewin, T. )

    1989-09-01

    Attention is drawn to the strong collective {ital L}=4 direct excitation of the state at 2.367 MeV in {sup 100}Ru by inelastic scattering of 16 MeV protons characterized by a deformation parameter {beta}{sub 4}=0.10, one of the highest reported for any region of the mass table.

  5. 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.

  6. 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.

  7. The excited random walk in one dimension

    NASA Astrophysics Data System (ADS)

    Antal, T.; Redner, S.

    2005-03-01

    We study the excited random walk, in which a walk that is at a site that contains cookies eats one cookie and then hops to the right with probability p and to the left with probability q = 1 - p. If the walk hops onto an empty site, there is no bias. For the 1-excited walk on the half-line (one cookie initially at each site), the probability of first returning to the starting point at time t scales as t-(2-p). Although the average return time to the origin is infinite for all p, the walk eats, on average, only a finite number of cookies until this first return when p < 1/2. For the infinite line, the probability distribution for the 1-excited walk has an unusual anomaly at the origin. The positions of the leftmost and rightmost uneaten cookies can be accurately estimated by probabilistic arguments and their corresponding distributions have power-law singularities. The 2-excited walk on the infinite line exhibits peculiar features in the regime p > 3/4, where the walk is transient, including a mean displacement that grows as tν, with \

  8. Excited Random Walk in One Dimension

    NASA Astrophysics Data System (ADS)

    Antal, Tibor

    2005-03-01

    We study the k-excited random walk, in which each site initially contains k cookies, and a random walk that is at a site that contains at least one cookie eats a cookie and then hops to the right with probability p and to the left with probability q=1-p. If the walk hops from an empty site, there is no bias. For the 1-excited walk on the half-line (each site initially contains one cookie), the probability of first returning to the starting point at time t scales as t-1-q. We also derive the probability distribution of the position of the leftmost uneaten cookie in the large time limit. For the infinite line, the probability distribution of the position of the 1-excited walk has an unusual anomaly at the origin and the distributions of positions for the leftmost and rightmost uneaten cookie develop a power-law singularity at the origin. The 2-excited walk on the infinite line exhibits peculiar features in the regime p>3/4, where the walk is transient, including a mean displacement that grows as t^ν, with ν>12 dependent on p, and a breakdown of scaling for the probability distribution of the walk.

  9. 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.

  10. Human Cortical Excitability Increases with Time Awake

    PubMed Central

    Huber, Reto; Mäki, Hanna; Rosanova, Mario; Casarotto, Silvia; Canali, Paola; Casali, Adenauer G.; Tononi, Giulio

    2013-01-01

    Prolonged wakefulness is associated not only with obvious changes in the way we feel and perform but also with well-known clinical effects, such as increased susceptibility to seizures, to hallucinations, and relief of depressive symptoms. These clinical effects suggest that prolonged wakefulness may be associated with significant changes in the state of cortical circuits. While recent animal experiments have reported a progressive increase of cortical excitability with time awake, no conclusive evidence could be gathered in humans. In this study, we combine transcranial magnetic stimulation (TMS) and electroencephalography (EEG) to monitor cortical excitability in healthy individuals as a function of time awake. We observed that the excitability of the human frontal cortex, measured as the immediate (0–20 ms) EEG reaction to TMS, progressively increases with time awake, from morning to evening and after one night of total sleep deprivation, and that it decreases after recovery sleep. By continuously monitoring vigilance, we also found that this modulation in cortical responsiveness is tonic and not attributable to transient fluctuations of the level of arousal. The present results provide noninvasive electrophysiological evidence that wakefulness is associated with a steady increase in the excitability of human cortical circuits that is rebalanced during sleep. PMID:22314045

  11. 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.

  12. 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.

  13. 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.

  14. 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…

  15. "Fast excitation" CID in a quadrupole ion trap mass spectrometer.

    PubMed

    Murrell, J; Despeyroux, D; Lammert, S A; Stephenson, J L; Goeringer, D E

    2003-07-01

    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(4)/b(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)(17+) of horse heart myoglobin is also shown to illustrate the application of "fast excitation" CID to proteins.

  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. Accelerating slow excited state proton transfer.

    PubMed

    Stewart, David J; Concepcion, Javier J; Brennaman, M Kyle; Binstead, Robert A; Meyer, Thomas J

    2013-01-15

    Visible light excitation of the ligand-bridged assembly [(bpy)(2)Ru(a)(II)(L)Ru(b)(II)(bpy)(OH(2))(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(-•))Ru(b)(III)-OH(2) with an excited-state lifetime of 13 ± 1 ns. Near-diffusion-controlled quenching of the emission occurs with added HPO(4)(2-) 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 k(q) = 4.1 × 10(8) M(-1) • s(-1) and an estimated pK(a)* value of ~5 ± 1 for the [(bpy)(2)Ru(a)(II)(L(•-))Ru(b)(III)(bpy)(OH(2))(4+)]* excited state. Following proton loss and rapid excited-state decay to give [(bpy)(2)Ru(a)(II)(L)Ru(b)(II)(bpy)(OH)(3+)] in a H(2)PO(4)(-)/HPO(4)(2-) buffer, back proton transfer occurs from H(2)PO(4)(-) to give [(bpy)(2)Ru(a)(II)(L)Ru(b)(bpy)(OH(2))(4+)] with k(PT,2) = 4.4 × 10(8) M(-1) • s(-1). From the intercept of a plot of k(obs) vs. [H(2)PO(4)(-)], k = 2.1 × 10(6) s(-1) for reprotonation by water providing a dramatic illustration of kinetically limiting, slow proton transfer for acids and bases with pK(a) values intermediate between pK(a)(H(3)O(+)) = -1.74 and pK(a)(H(2)O) = 15.7. PMID:23277551

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. Dielectronic recombination and resonant transfer excitation processes for helium-like krypton

    NASA Astrophysics Data System (ADS)

    Hu, Xiao-Li; Qu, Yi-Zhi; Zhang, Song-Bin; Zhang, Yu

    2012-10-01

    The relativistic configuration interaction method is employed to calculate the dielectronic recombination (DR) cross sections of helium-like krypton via the 1s2lnl' (n = 2, 3, ..., 15) resonances. Then, the resonant transfer excitation (RTE) processes of Kr34+ colliding with H, He, H2, and CHx (x = 0-4) targets are investigated under the impulse approximation. The needed Compton profiles of targets are obtained from the Hartree—Fock wave functions. The RTE cross sections are strongly dependent on DR resonant energies and strengths, and the electron momentum distributions of the target. For H2 and H targets, the ratio of their RTE cross sections changes from 1.85 for the 1s2l2l' to 1.88 for other resonances, which demonstrates the weak molecular effects on the Compton profiles of H2. For CHx (x = 0-4) targets, the main contribution to the RTE cross section comes from the carbon atom since carbon carries 6 electrons; as the number of hydrogen increases in CHx, the RTE cross section almost increases by the same value, displaying the strong separate atom character for the hydrogen. However, further comparison of the individual orbital contributions of C(2p, 2s, 1s) and CH4(1t2, 2a1, 1a1) to the RTE cross sections shows that the molecular effects induce differences of about 25.1%, 19.9%, and 0.2% between 2p-1t2, 2s-2a1, and 1s-1a1 orbitals, respectively.

  3. Electron excitations in solids and novel materials

    NASA Astrophysics Data System (ADS)

    Spataru, Catalin-Dan

    Several applications of the use of ab initio many-body methods in condensed matter theory are presented. In particular, these methods are used for the study of electronic excitations in various kinds of materials, ranging from bulk to low dimensional systems, and from metals to semiconductors. Two types of electron excitations are considered: quasiparticle excitations and electron-hole excitations. The work is organized in five chapters as follows: (1) The first chapter gives an introduction to the concept of quasiparticle and electron-hole excitations, as well as to the many-body framework underlying the theoretical formalism used in this work. (2) Chapter two presents the calculation of quasiparticle lifetimes in graphite. The inverse lifetime of low energy quasi-electrons shows significant deviations from the quadratic behavior naively expected from Fermi liquid theory. The deviations are explained in terms of the unique features of the band structure of this material. (3) In chapter three, the real and imaginary parts of the quasiparticle self-energy in jellium and crystalline Al are calculated at high electron temperatures. We find a decrease in the electron lifetime and an increase in the valence and conduction band widths as the temperature is increased. Calculation of the spectral function suggests that the quasiparticle concept may still be reasonable at high electron temperatures. (4) Chapter four presents calculations of the quasiparticle spectrum of highly irradiated crystalline GaAs. Our results indicate that the valence-conduction band gap is a sensitive function of the amount of electrons excited above the ground state. However, contrary to previous results, we find that it is not possible to induce a complete band gap closure by purely electronic means. (5) In chapter five we present calculations of the electron-hole interaction effects on the optical spectra of several single-walled carbon nanotubes. We show that the optical spectra of both

  4. Excitation strengths in 109Sn: Single-neutron and collective excitations near 100Sn

    NASA Astrophysics Data System (ADS)

    DiJulio, D. D.; Cederkall, J.; Fahlander, C.; Ekström, A.; Hjorth-Jensen, M.; Albers, M.; Bildstein, V.; Blazhev, A.; Darby, I.; Davinson, T.; De Witte, H.; Diriken, J.; Fransen, Ch.; Geibel, K.; Gernhäuser, R.; Görgen, A.; Hess, H.; Iwanicki, J.; Lutter, R.; Reiter, P.; Scheck, M.; Seidlitz, M.; Siem, S.; Taprogge, J.; Tveten, G. M.; Van de Walle, J.; Voulot, D.; Warr, N.; Wenander, F.; Wimmer, K.

    2012-09-01

    A set of B(E2) values for the low-lying excited states in the radioactive isotope 109Sn were deduced from a Coulomb excitation experiment. The 2.87-MeV/u radioactive beam was produced at the REX-ISOLDE facility at CERN and was incident on a secondary 58Ni target. The B(E2) values were determined using the known 2+→0+ reduced transition probability in 58Ni as normalization with the semiclassical Coulomb excitation code gosia2. The transition probabilities are compared to shell-model calculations based on a realistic nucleon-nucleon interaction and the predictions of a simple core-excitation model. This measurement represents the first determination of multiple B(E2) values in a light Sn nucleus using the Coulomb excitation technique with low-energy radioactive beams. The results provide constraints for the single-neutron states relative to 100Sn and also indicate the importance of both single-neutron and collective excitations in the light Sn isotopes.

  5. A scalable piezoelectric impulse-excited energy harvester for human body excitation

    NASA Astrophysics Data System (ADS)

    Pillatsch, P.; Yeatman, E. M.; Holmes, A. S.

    2012-11-01

    Harvesting energy from low-frequency and non-harmonic excitations typical of human motion presents specific challenges. While resonant devices do have an advantage in environments where the excitation frequency is constant, and while they can make use of the entire proof mass travel range in the case of excitation amplitudes that are smaller than the internal displacement limit, they are not suitable for body applications since the frequencies are random and the amplitudes tend to be larger than the device size. In this paper a piezoelectric, impulse-excited approach is presented. A cylindrical proof mass actuates an array of piezoelectric bi-morph beams through magnetic attraction. After the initial excitation these transducers are left to vibrate at their natural frequency. This increases the operational frequency range as well as the electromechanical coupling. The principle of impulse excitation is discussed and a centimetre-scale functional model is introduced as a proof of concept. The obtained data show the influence of varying the frequency, acceleration and proof mass. Finally, a commercially available integrated circuit for voltage regulation is tested. At a frequency of 2 Hz and an acceleration of 2.7 m s-2 a maximal power output of 2.1 mW was achieved.

  6. 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.

  7. 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.

  8. From membrane excitability to metazoan psychology.

    PubMed

    Cook, Norman D; Carvalho, Gil B; Damasio, Antonio

    2014-12-01

    Unlike the nonexcitable cell membranes that are ubiquitous in all domains of life, excitable membranes are found almost exclusively in animal organisms (Protozoa and Metazoa). Their transient permeability to ion flow makes possible the rapid detection of, and response to, external stimuli, and results in the phenomena that most clearly distinguish fauna from flora: perception, cognition, and motor activity. Interestingly, all known forms of membrane excitability are a consequence of one unique mechanism: the influx of positively charged ions into the normally alkaline cytoplasm. Here, we suggest that the sudden reversal of the membrane potential during the sensory potential and the action potential is an electrostatic disturbance of homeostasis that is the necessary first step in the processes of 'sentience' and 'irritability'. PMID:25176475

  9. CHARMONIUM EXCITED STATES FROM LATTICE QCD

    SciTech Connect

    Jozef Dudek; Robert Edwards; Nilmani Mathur; David Richards

    2007-11-20

    We apply the variational method with a large basis of interpolating operators to demonstrate the feasibility of extracting multiple excited states in charmonium from lattice QCD. The calculation is performed in the quenched approximation to QCD, using the clover fermion action on an anisotropic lattice. A crucial element of our approach is a knowledge of the continuum limit of the interpolating operators, providing important additional information on the spin assignment of the states, even at a single value of the lattice spacing. Though we find excited-state masses that are systematically high with respect to the quark potential model, and the experimental masses where known, we attribute this as most likely an artifact of the quenched approximation.

  10. Liquid storage tanks under vertical excitation

    SciTech Connect

    Philippacopoulos, A.J.

    1985-01-01

    Until recently, the hydrodynamic effects on liquid storage tanks induced by an earthquake excitation were basically treated for the horizontal component of the earthquake. Recent studies, however, showed that the hydrodynamic effects due to the vertical component of an earthquake may be significant. In these studies the tank is assumed to be fixed at the bottom. This paper is concerned with the hydrodynamic behavior of liquid storage tanks induced by vertical earthquake input excitation. First, the fluid-tank system is treated as a fixed-base system and a simple formula is obtained for the coupled fluid-structure natural frequency. Second, additional interaction effects due to the foundation flexibility on the fluid-tank system are investigated. It is concluded that the foundation flexibility may have a significant effect on the hydrodynamic behavior of the liquid storage tanks under a vertical ground shaking.

  11. The excitation of O2 in auroras.

    NASA Technical Reports Server (NTRS)

    Cartwright, D. C.; Trajmar, S.; Williams, W.

    1972-01-01

    Newly measured electron impact cross sections for excitation of the a super 1 Delta sub g and b super 1 Sigma (plus) sub g electronic states of O2 have been employed to predict the absolute volume emission rates from these states under auroral conditions. A secondary electron flux typical of an IBC II nighttime aurora was used, and the most important quenching processes were included in the calculations. The new excitation cross sections for the a super 1 Delta sub g and b super 1 Sigma (plus) sub g states are more than an order of magnitude larger than previous estimates and lead to correspondingly greater intensities in the atmospheric and IR atmospheric band systems. The calculated intensity ratios of the volume emission rates of 7621 A and 1.27 micron to that for 3914 A are smaller than those obtained from aircraft observations and recent rocket experiments.

  12. Electrical Excitation of Surface Plasmon Polaritons

    NASA Astrophysics Data System (ADS)

    van Loon, R. V. A.

    2009-02-01

    A surface plasmon polariton (SPP) is an electromagnetic wave propagating at the interface between a metal and a dielectric material. The two-dimensional confinement of SPPs and the tunability of their dispersion enable optical functionality that cannot be achieved with regular dielectrics. Several novel concepts for sensing and opto-electronic integration based on SPPs have been proposed. In nearly all applications, as well as experiments based on SPPs, far-field excitation of SPPs is used, leading to bulky device designs. This thesis presents an electrically excitable source for SPPs that can be integrated in small, chip-size devices to enable the full application potential of SPPs. The device is based on a dielectric/metal geometry in which silicon quantum dots are placed in the near-field of the SPP mode. The quantum dots are electrically excited and decay by the generation of SPPs. Silicon quantum dots in silica are made by a magnetron sputtering technique, followed by annealing. From photoluminescence spectra as well as lifetime measurements we conclude that well-passivated Si quantum dots with quantum confined luminescence around 800 nm can be made. An electrical injection geometry is presented and electroluminescence is observed around 650 nm under a bias of 15-30 V. Strong bleaching of the quantum dot luminescence is observed under 0.5-20 keV electron beam irradiation, which has a potential consequence for the use of electron beam lithography in nanofabrication of structures with Si quantum dots. We describe the design and the fabrication of an electrically excitable plasmon source based on an insulator-metal-insulator (IMI) geometry. The coupling of quantum dots to the SPP mode was studied theoretically. For quantum dots spaced 20-200 nm away from the metal surface, more than 50% of the decay is into SPPs. An IMI SPP geometry for electrical excitation was fabricated using gold and silica doped with Si quantum dots as dielectric material. An IMI SPP source

  13. Excitation and Characterization of Chladni Plate Patterns

    NASA Astrophysics Data System (ADS)

    Bourke, Shannon; Behringer, Ernest

    2011-04-01

    When a thin metal plate with a small amount of sand on it is made to vibrate, aesthetically pleasing sand patterns can form along the nodal lines of the plate. These symmetric patterns are called Chladni Patterns. Students taking PHY 101 Physical Science in the Arts at Eastern Michigan University create these patterns by pulling a violin bow across the edge of a plate, or by using a mechanical oscillator to drive the center of a plate. These two methods only allow a small subset of all possible points on the plate to be excited. We designed and built an electronic device that allows its user to excite the plate at any point. We present patterns created with this electronic device and other methods, and describe ways to model the observed patterns.

  14. Edge Magnon Excitation in Spin Dimer Systems

    NASA Astrophysics Data System (ADS)

    Sakaguchi, Ryo; Matsumoto, Masashige

    2016-10-01

    Magnetic excitation in a spin dimer system on a bilayer honeycomb lattice is investigated in the presence of a zigzag edge, where disordered and ordered phases can be controlled by a quantum phase transition. In analogy with the case of graphene with a zigzag edge, a flat edge magnon mode appears in the disordered phase. In an ordered phase, a finite magnetic moment generates a mean-field potential to the magnon. Since the potential is nonuniform on the edge and bulk sites, it affects the excitation, and the dispersion of the edge mode deviates from the flat shape. We investigate how the edge magnon mode evolves when the phase changes through the quantum phase transition and discuss the similarities to ordered spin systems on a monolayer honeycomb lattice.

  15. Time resolved excitation dynamics in emeraldine base

    NASA Astrophysics Data System (ADS)

    Menšík, Miroslav; Rais, David; Pfleger, Jiří

    2015-07-01

    Using femtosecond pump-probe transient absorption spectroscopy (wavelengths 330-800 nm), we observed and explained excited state, charge transfer and polaron state dynamics in emeraldine base form of polyaniline in dimethyl sulfoxide solution. The excited state created by a pump pulse (700 nm) in the quinoid absorption Q-band loses its initial symmetry by subsequent energy transition to a charge transfer state within 50 fs. The hot charge transfer state either recombines non-radiatively into the ground state with decay time constant 0.55 ps or transfers into a relaxed state corresponding to the relaxed phenyl geometry during ca 2.1 ps. This relaxed state shows a prolonged lifetime of about 6.5 ps before its recombination to the ground state. However, a small amount of long-lived polarons with lifetime of about 2 ns in air and with lifetime longer than 6 ns in the solution bubbled with dry N2 was detected.

  16. Diversity improves performance in excitable networks

    PubMed Central

    Copelli, Mauro; Roberts, James A.

    2016-01-01

    As few real systems comprise indistinguishable units, diversity is a hallmark of nature. Diversity among interacting units shapes properties of collective behavior such as synchronization and information transmission. However, the benefits of diversity on information processing at the edge of a phase transition, ordinarily assumed to emerge from identical elements, remain largely unexplored. Analyzing a general model of excitable systems with heterogeneous excitability, we find that diversity can greatly enhance optimal performance (by two orders of magnitude) when distinguishing incoming inputs. Heterogeneous systems possess a subset of specialized elements whose capability greatly exceeds that of the nonspecialized elements. We also find that diversity can yield multiple percolation, with performance optimized at tricriticality. Our results are robust in specific and more realistic neuronal systems comprising a combination of excitatory and inhibitory units, and indicate that diversity-induced amplification can be harnessed by neuronal systems for evaluating stimulus intensities. PMID:27168961

  17. Edge excitations in fractional Chern insulators

    NASA Astrophysics Data System (ADS)

    Luo, Wei-Wei; Chen, Wen-Chao; Wang, Yi-Fei; Gong, Chang-De

    2013-10-01

    Recent theoretical papers have demonstrated the realization of fractional quantum anomalous Hall states (also called fractional Chern insulators) in topological flat band lattice models without an external magnetic field. Such newly proposed lattice systems play a vital role in obtaining a large class of fractional topological phases. Here we report the exact numerical studies of edge excitations for such systems in a disk geometry loaded with hard-core bosons, which will serve as a more viable experimental probe for such topologically ordered states. We find convincing numerical evidence of a series of edge excitations characterized by the chiral Luttinger liquid theory for the bosonic fractional Chern insulators in both the honeycomb disk Haldane model and the kagome-lattice disk model. We further verify these current-carrying chiral edge states by inserting a central flux to test their compressibility.

  18. Excited charmonium physics from lattice QCD

    SciTech Connect

    Jozef Dudek

    2009-12-01

    Properties of excited mesons are studied using a lattice QCD simulation of a system comparable to charmonium. We extract a spectrum of states, including those with manifestly exotic quantum numbers. Radiative transition form-factors are also computed, in particular the transition from exotic ·c1 to J /È ³ which is found to be large on the usual scale of magnetic dipole transitions.

  19. Collisional excitation of interstellar methyl cyanide

    NASA Technical Reports Server (NTRS)

    Green, Sheldon

    1986-01-01

    Theoretical calculations are used to determine the collisional excitation rates of methyl cyanide under interstellar molecular cloud conditions. The required Q(L,M) as a function of kinetic temperature were determined by averaging fixed energy IOS (infinite order sudden) results over appropriate Boltzmann distributions of collision energies. At a kinetic temperature of 40 K, rates within a K ladder were found to be accurate to generally better than about 30 percent.

  20. Dynamical analysis of highly excited molecular spectra

    SciTech Connect

    Kellman, M.E.

    1993-12-01

    The goal of this program is new methods for analysis of spectra and dynamics of highly excited vibrational states of molecules. In these systems, strong mode coupling and anharmonicity give rise to complicated classical dynamics, and make the simple normal modes analysis unsatisfactory. New methods of spectral analysis, pattern recognition, and assignment are sought using techniques of nonlinear dynamics including bifurcation theory, phase space classification, and quantization of phase space structures. The emphasis is chaotic systems and systems with many degrees of freedom.

  1. Spiral core in singly diffusive excitable media

    SciTech Connect

    Kessler, D.A. ); Levine, H.; Reynolds, W.N. )

    1992-01-20

    We formulate the problem of finding the spiral core which smoothly matches onto the asymptotic rotating solution of the FitzHugh-Nagumo model. We prove that the inner problem (with scale {epsilon}, the ratio of the reaction rates) has a solution for all possible outer solutions on scale {epsilon}{sup 2/3}; furthermore, we explicitly determine this solution via a simple numerical procedure. This completes the rigorous demonstration of the existence of rotating spiral solutions in singly diffusive excitable systems.

  2. Excitation of terahertz nanoantennas by Rabi waves

    SciTech Connect

    Slepyan, G. Ya.; Yerchak, Y. D.; Maksimenko, S. A.; Hoffmann, A.; Bass, F. G.

    2011-10-03

    Theoretical model of quantum dot ring, strongly coupled with classical electromagnetic field, is developed. We demonstrate, that tunnel current in the QD-ring has low-frequency component, excited by Rabi waves, propagating into the ring, and the ring can be considered as a candidate for role of terahertz magnetic loop antenna. The low-frequency current is inspired by the asymmetry of electron tunneling.

  3. STIRAP on helium: Excitation to Rydberg states

    NASA Astrophysics Data System (ADS)

    Yuan, Deqian

    Research in optically induced transitions between dierent atomic levels has a long history. For transitions between states driven by a coherent optical eld, the theoretical eciency could be ideally high as 100% but there could be many factors preventing this. In the three state helium atom excitation process, i.e. 23S→33P→nL , the stimulated emission from intermediate state makes it hard to achieve ecient population transfer to the nal state through an intuitive excitation order. One technique to achieve a higher eciency is Stimulated Raman Adiabatic Passage (STIRAP) which is being studied and under research in our lab. Unlike traditional three level excitation processes, STIRAP actually uses a counter intuitive pulsed laser beams timing arrangement. The excitation objects are metastable helium atoms traveling in a vacuum system with a longitudinal velocity of ~ 1070 m/s. We are using a 389 nm UV laser to connect the 23S and the 33P state and a frequency tunable ~790 nm IR laser to connect the 33P state and the dierent Rydberg states. A third 1083 nm wavelength laser beam drives the 23S → 23P transition to transversely separate the residual metastable atoms and the Rydberg atoms for eciency measurements. The data is taken by a stainless steel detector in the vacuum system. As the Rydberg atoms will get ionized by blackbody radiation under room temperature, we can utilize this for their detection. An ion detector sitting on the eld plate is capable to collect the ion signals of the Rydberg atoms for detection. So far the whole system has not been ready for data collection and measurement, so here we are using data and results from previous theses for discussions. The highest transition frequency that has ever been achieved in our lab is around 70% after corrections.

  4. Novel methods of copper vapor laser excitation

    SciTech Connect

    McColl, W.B.; Ching, H.; Bosch, R.; Brake, M.; Gilgenbach, R.

    1990-12-31

    Microwave and intense electron beam excitation of copper vapor are being investigated to be used in copper vapor lasers for isotope separation. Both methods use copper chloride vapor by heating copper chloride. Helium was used as the buffer gas at 2 to 100 torr. In the microwave system, intense copperlines at 510 nm and 578 nm were observed. Initial electron beam results indicate that light emission follows the beam current.

  5. Multiphonon excitations in boson quantum films

    SciTech Connect

    Clements, B.E. |; Krotscheck, E. |; Tymczak, C.J.

    1996-05-01

    Dynamical excitations in thin liquid films of {sup 4}He adsorbed to a substrate are investigated by using a microscopic theory of excitations that includes multiple-phonon scattering. We study the dispersion relation, excitation mechanisms, transition densities, and particle currents as a function of surface coverage. A primary new result is that we have included three-phonon scattering processes in the calculation of the dynamic structure function and the one-body current densities. With the exception that our ground state is determined by our variational theory, rather than taken from experiment, our work on the dynamic structure function is the generalization of that of Jackson [Phys. Rev. A {bold 4}, 2386 (1971)] to inhomogeneous systems (films). Using sum rules for the dynamic structure function as a guide, we suggest a simple scaling argument for improving the agreement between our dynamic structure function and the experimental one. The addition of three-phonon contributions bring about the following changes. First, the energy of most modes is lowered by a non-negligible amount for finite momentum excitations. Second, the film{close_quote}s surface mode is the exception; it is only slightly affected. Third, for monolayer films there is large scattering at high energies at intermediate values of momenta. This scattering can be traced back to an anomalously large contribution to the two-particle density of states. Fourth, all modes with energy above a critical energy decay, and the associated peaks of the dynamic structure function are broadened. Fifth, the maxonlike character is enhanced in the bulklike modes. {copyright} {ital 1996 The American Physical Society.}

  6. Excitation of a slow wave structure

    SciTech Connect

    Zhang Peng; Lau, Y. Y.; Hoff, Brad; French, D. M.; Luginsland, J. W.

    2012-12-15

    The Green's function on a slow wave structure is constructed. The Green's function includes all radial modes, and for each radial mode, all space harmonics. We compare the analytic solution of the frequency response on the slow wave structure with that obtained from a particle-in-cell code. Favorable comparison is obtained when the first few lower order modes are resonantly excited. This gives some confidence in the prediction of converting a pulse train into radiation using a slow wave structure.

  7. Excitation of ``monotron'' oscillations in klystrons

    NASA Astrophysics Data System (ADS)

    Nusinovich, Gregory; Read, Michael; Song, Liqun

    2004-11-01

    A general method for calculations of starting currents of modes in klystron cavities is developed. This method allows one to determine the threshold for excitation of so-called monotron oscillations in klystrons having an arbitrary geometry of cavities and an arbitrary cross section of an electron beam. The method is used for evaluating the starting currents of monotron oscillations in a sheet beam, X-band klystron, which is currently in the design state at Calabazas Creek Research Inc.

  8. Love waves excited by a moving source

    NASA Astrophysics Data System (ADS)

    Zaslavskii, Yu. M.

    2016-01-01

    The study analyzes the characteristics of surface Love waves excited by the moment of an oscillating torsional force with a point of action that moves uniformly and rectilinearly along the free flat boundary of a medium having the structure of a "layer on a half-space." The azimuthal-angular distribution of the amplitude and Doppler shift in frequency of the wave modes is studied as a function of the motion velocity of a vibrating source and the parameters of the medium.

  9. New photocalorimetric references for UV excitation

    NASA Astrophysics Data System (ADS)

    Murgida, D. H.; Erra-Balsells, R.; Bilmes, G. M.

    1996-02-01

    A set of calorimetric references for excitation at λ = 266 nm in acetonitrile solutions is proposed. Theophylline and several purinic compounds (purine, 6-methylpurine, 6-methoxypurine, 6-chloropurine, and 6-aminopurine) were investigated using pulsed laser optoacoustic spectroscopy with resolution times between 150 ns and 1 μs and compared with 2-hydroxybenzophenone. At room temperature, all these compounds show no fluorescence, good stability and no photochemical processes as photodegradation or multiphotonic effects below fluences of 1000 J/m 2.

  10. Asymmetric magnon excitation by spontaneous toroidal ordering

    DOE PAGESBeta

    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 latticemore » 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.« less

  11. Excitation energy transfer in the photosystem I

    SciTech Connect

    Webber, Andrew N

    2012-09-25

    Photosystem I is a multimeric pigment protein complex in plants, green alage and cyanobacteria that functions in series with Photosystem II to use light energy to oxidize water and reduce carbon dioxide. The Photosystem I core complex contains 96 chlorophyll a molecules and 22 carotenoids that are involved in light harvesting and electron transfer. In eucaryotes, PSI also has a peripheral light harvesting complex I (LHCI). The role of specific chlorophylls in excitation and electron transfer are still unresolved. In particular, the role of so-called bridging chlorophylls, located between the bulk antenna and the core electron transfer chain, in the transfer of excitation energy to the reaction center are unknown. During the past funding period, site directed mutagenesis has been used to create mutants that effect the physical properties of these key chlorophylls, and to explore how this alters the function of the photosystem. Studying these mutants using ultrafast absorption spectroscopy has led to a better understanding of the process by which excitation energy is transferred from the antenna chlorophylls to the electron transfer chain chlorophylls, and what the role of connecting chlorophylls and A_0 chlorophylls is in this process. We have also used these mutants to investigate whch of the central group of six chlorophylls are involved in the primary steps of charge separation and electron transfer.

  12. Experiments on shells under base excitation

    NASA Astrophysics Data System (ADS)

    Pellicano, Francesco; Barbieri, Marco; Zippo, Antonio; Strozzi, Matteo

    2016-05-01

    The aim of the present paper is a deep experimental investigation of the nonlinear dynamics of circular cylindrical shells. The specific problem regards the response of circular cylindrical shells subjected to base excitation. The shells are mounted on a shaking table that furnishes a vertical vibration parallel to the cylinder axis; a heavy rigid disk is mounted on the top of the shells. The base vibration induces a rigid body motion, which mainly causes huge inertia forces exerted by the top disk to the shell. In-plane stresses due to the aforementioned inertias give rise to impressively large vibration on the shell. An extremely violent dynamic phenomenon suddenly appears as the excitation frequency varies up and down close to the linear resonant frequency of the first axisymmetric mode. The dynamics are deeply investigated by varying excitation level and frequency. Moreover, in order to generalise the investigation, two different geometries are analysed. The paper furnishes a complete dynamic scenario by means of: (i) amplitude frequency diagrams, (ii) bifurcation diagrams, (iii) time histories and spectra, (iv) phase portraits and Poincaré maps. It is to be stressed that all the results presented here are experimental.

  13. Electrically Excited Plasmonic Nanoruler for Biomolecule Detection.

    PubMed

    Dathe, André; Ziegler, Mario; Hübner, Uwe; Fritzsche, Wolfgang; Stranik, Ondrej

    2016-09-14

    Plasmon-based sensors are excellent tools for a label-free detection of small biomolecules. An interesting group of such sensors are plasmonic nanorulers that rely on the plasmon hybridization upon modification of their morphology to sense nanoscale distances. Sensor geometries based on the interaction of plasmons in a flat metallic layer together with metal nanoparticles inherit unique advantages but need a special optical excitation configuration that is not easy to miniaturize. Herein, we introduce the concept of nanoruler excitation by direct, electrically induced generation of surface plasmons based on the quantum shot noise of tunneling currents. An electron tunneling junction consisting of a metal-dielectric-semiconductor heterostructure is directly incorporated into the nanoruler basic geometry. With the application of voltage on this modified nanoruler, the plasmon modes are directly excited without any additional optical component as a light source. We demonstrate via several experiments that this electrically driven nanoruler possesses similar properties as an optically exited one and confirm its sensing capabilities by the detection of the binding of small biomolecules such as antibodies. This new sensing principle could open the way to a new platform of highly miniaturized, integrated plasmonic sensors compatible with monolithic integrated circuits.

  14. Spin-flavor composition of excited baryons

    NASA Astrophysics Data System (ADS)

    Fernando, Ishara; Goity, Jose

    2015-10-01

    The excited baryon masses are analyzed in the framework of the 1 /Nc expansion using the available physical masses and also the masses obtained in lattice QCD for different quark masses. The baryon states are organized into irreducible representations of SU (6) × O (3) , where the [ 56 ,lP =0+ ] ground state and excited baryons, and the [ 56 ,2+ ] and [ 70 ,1- ] excited states are analyzed. The analyses are carried out to O 1 /Nc and first order in the quark masses. The issue of state identifications is discussed. Numerous parameter independent mass relations result at those orders, among them the well known Gell-Mann-Okubo and Equal Spacing relations, as well as additional relations involving baryons with different spins. It is observed that such relations are satisfied at the expected level of precision. Predictions for physically unknown states for each multiplet are obtained. From the quark-mass dependence of the coefficients in the baryon mass formulas an increasingly simpler picture of the spin-flavor composition of the baryons is observed with increasing pion mass (equivalently, increasing mu , d masses), as measured by the number of significant mass operators. This work was supported in part by DOE Contract No. DE-AC05-06OR23177 under which JSA operates the Thomas Jefferson National Accelerator Facility (J. L. G.), and by the NSF (USA) through Grant PHY-0855789 and PHY-1307413 (I. P. F and J. L. G).

  15. Excitable Pattern Formation in Inhomogeneous Systems

    NASA Astrophysics Data System (ADS)

    Prabhakara, Kaumudi; Gholami, Azam; Zykov, Vladimir; Bodenschatz, Eberhard

    2015-03-01

    On starvation, the amoebae Dictyostelium discoideum signal via the chemo-attractant cyclic adenosine monophosphate (cAMP). The amoebae sense cAMP through membrane receptors and produce their own cAMP. Simultaneously they produce a basal level of Phosphodiesterase, an enzyme that degrades cAMP. Soon a pattern of rotating spiral waves or circular waves is formed at the multi-cellular level. The causal reasons for the selection of one or the other pattern are still unclear. Here we report experimental and theoretical investigations of the pattern-formation of mixtures of cells starved for different times. The excitability of the amoebae depends on the starvation time due to time dependent gene expressions. Cells starved for longer times are known to exhibit increased excitability. We report phase maps of the patterns for mixtures of different combinations of excitability. Numerical simulations of a modified Kessler-Levine model allow us to explain the experimental results and provide new insights into the dynamical behavior of the system. This work is supported by the Max Planck Society.

  16. Doubly excited states in some light atoms

    SciTech Connect

    Berry, H.G.; Brooks, R.L.; Hardis, J.E.; Ray, W.J.

    1981-01-01

    We have identified a singlet transition in doubly excited helium: 2p/sup 2/ /sup 1/D - 2p3d /sup 1/D, at 3298 +- 2A with a full width of 54A or 0.061 +- 0.005 eV. This width is in good agreement with a previous measurement and theory for the width of the 2p/sup 2/ /sup 1/D/sub 2/ state. We have remeasured the decay rate of 1s/sup 2/2p/sup 2/P - 1s2p/sup 2/ /sup 2/P in Li I and find it is in good agreement with theory. Several transitions in doubly excited Li II have been identified in the 1000A region. No evidence was found for doubly excited quartet transitions in Li I in the vacuum ultraviolet. We present measurements of wavelengths and fine structure of the 1s2s2p/sup 2/ /sup 5/P - 1s2p/sup 3/ /sup 5/S transitions in C III, N IV and O V.

  17. Nematic electroconvection under time-reversed excitation

    NASA Astrophysics Data System (ADS)

    Pietschmann, Dirk; John, Thomas; Stannarius, Ralf

    2010-10-01

    We study nematic electrohydrodynamic convection (EHC) under excitation with superimposed harmonic wave forms. Within the standard model for EHC, a time reversal of the excitation does not affect threshold voltages and pattern wavelengths obtained in a linear stability analysis. This was confirmed in experiments with superimposed square waves [Heuer , Phys. Rev. E 78, 036218 (2008)10.1103/PhysRevE.78.036218]. We show here that this symmetry with respect to time reversal of the excitation breaks down close to the transition from the conduction regime to the dielectric regime. The EHC standard model without flexoelectric terms fails to predict quantitatively correct threshold curves and wavelengths in a certain parameter range below the transition. This is an indication that a more elaborate description of the EHC mechanism is necessary in this range. We suggest that the weak electrolyte model has to be employed for a correct description. This is in accordance with observations of traveling rolls and of localized structures at onset of the convection in earlier experiments described in literature.

  18. Excited States of {sup 11}Be

    SciTech Connect

    Cappuzzello, F.; Cunsolo, A.; Fortier, S.; Foti, A.; Laurent, H.; Lenske, H.; Maison, J.M.; Melita, A.L.; Nociforo, C.; Rosier, L.; Stephan, C.; Tassan-Got, L.; Winfield, J.S.; Wolter, H.H.

    2000-12-31

    The {sup 11}B({sup 7}Li,{sup 7}Be){sup 11}Be reaction at 57 MeV incident energy was used to explore the {sup 11}Be excitation energy spectrum at forward angles. Angular distributions were extracted for the transitions to the ground and to the states of {sup 11}Be at excitation energies of E*=0.32, 1.78, 2.69, 3.41, 3.89, 3.96, 6.05 MeV combined with the ground and the first excited state of {sup 7}Be. Also the SDR [1][2] oscillation mode was observed at E*=9.5 MeV and FWHM{approx}9 MeV and a new peak at E*=6.05 MeV and FWHM{approx}0.3 MeV was observed. QRPA calculations in the G-matrix representation are in progress in order to describe the continuum structure of {sup 11}Be. DWBA calculations have been started to evaluate transferred angular momenta both in the one step and in the two steps dynamical framework.

  19. Plasmons and optical excitations in graphene rings.

    PubMed

    Wang, Weihua

    2012-10-10

    A simple semiclassical drude-like conductivity of graphene is employed to describe plasmon excitations of graphene in the ring structures. A quasi-static self-consistent integral equation approach is performed, allowing the calculation of all the plasmon modes with different angular momentum l. Among them only the dipole modes (l = 1) will couple out to the radiation modes, which in turn can be excited optically by the plane waves, and the excitation energies as a function of the ratio of the radius of the inner hole to that of the outer ring have also been investigated. It is demonstrated that the energy of symmetric modes will monotonically decrease as the ratio rises, and the energy of antisymmetric modes does not exhibit a monotonically increasing behavior as in a three-dimensional metallic ring, but first reduces and then increases. These predictions are tested by full-wave simulations using the optical conductivity of graphene that was obtained from the random phase approximation (RPA). PMID:22971520

  20. Excitation equilibria in plasmas; a classification

    NASA Astrophysics Data System (ADS)

    van der Mullen, J. A. M.

    1990-07-01

    This review gives a classification of the excitation kinetics ruled by electrons in plasmas. It is a study on the atomic state distribution function (ASDF) and its relation with underlying processes, which, for the case of an electron excitation kinetics (EEK) plasma, is merely a competition between free and bound electrons, the same particles in different circumstances. In a quasi steady state the population density of an atomic state results from production-destruction balances in equilibrium. If all balances are proper, i.e., consist of each other's inverse processes, then the ASDF is described by the Boltzmann-Saha relation. In other cases the balance will be denoted as improper, the ASDF will deviate from the equilibrium shape, but reflecting the underlying improper balances, it may give information about the plasma. Four improper balances and their impact on the ASDF are dealt with. An important feature is that improper balances are associated with particle transport. Special attention is paid to the distribution function of the excitation saturation balance in which the overpopulated bound electrons are subjected to frequent interactions with free electrons and the energy distribution of the free electrons is taken over. This distribution, denoted as the bound Maxwell distribution, is experimentally found in several ionizing plasmas. Its recombining counterpart, the deexcitation saturation balance, creates under certain conditions inversion in the ASDF, the basis for the recombination laser.

  1. Experimental Overview of the Excited Baryon Program

    NASA Astrophysics Data System (ADS)

    Crede, Volker

    2011-05-01

    High-energy electrons and photons are a remarkably clean probe of hadronic matter, essentially providing a microscope for examining atomic nuclei and the strong nuclear force. For more than a decade, laboratories worldwide have accumulated data for such investigations, resulting in a number of surprising discoveries and contributing to our understanding of the nucleon, its underlying quark structure, and the dynamics of the strong interaction. One notable discovery has been the unexpected Q2 variation of the ratio of the proton elastic form-factors GEp/GMp, which suggests an important contribution from quark orbital angular momentum to the spin of the nucleon. Moreover, the spectrum of excited hadrons can serve as an excellent probe of Quantum Chromodynamics (QCD), the fundamental theory of strong interactions. Since nucleons are complex systems of confined quarks, they exhibit the characteristic spectra of excited states. Highly excited nucleon states are sensitive to details of quark confinement which is poorly understood within QCD. The current effort at facilities worldwide studying the systematics of hadron spectra is to utilize highly-polarized frozen-spin (butanol) and deuterium targets in combination with polarized photon beams. These are important steps toward complete experiments that allow us to unambiguously determine the scattering amplitude in the underlying reactions and to identify resonance contributions.

  2. Excitation picture of an interacting Bose gas

    SciTech Connect

    Kira, M.

    2014-12-15

    Atomic Bose–Einstein condensates (BECs) can be viewed as macroscopic objects where atoms form correlated atom clusters to all orders. Therefore, the presence of a BEC makes the direct use of the cluster-expansion approach–lucrative e.g. in semiconductor quantum optics–inefficient when solving the many-body kinetics of a strongly interacting Bose. An excitation picture is introduced with a nonunitary transformation that describes the system in terms of atom clusters within the normal component alone. The nontrivial properties of this transformation are systematically studied, which yields a cluster-expansion friendly formalism for a strongly interacting Bose gas. Its connections and corrections to the standard Hartree–Fock–Bogoliubov approach are discussed and the role of the order parameter and the Bogoliubov excitations are identified. The resulting interaction effects are shown to visibly modify number fluctuations of the BEC. Even when the BEC has a nearly perfect second-order coherence, the BEC number fluctuations can still resolve interaction-generated non-Poissonian fluctuations. - Highlights: • Excitation picture expresses interacting Bose gas with few atom clusters. • Semiconductor and BEC many-body investigations are connected with cluster expansion. • Quantum statistics of BEC is identified in terms of atom clusters. • BEC number fluctuations show extreme sensitivity to many-body correlations. • Cluster-expansion friendly framework is established for an interacting Bose gas.

  3. Unravelling the Excitation Spectrum of the Nucleon

    SciTech Connect

    Sandorfi, Andrew M.

    2013-03-01

    The low-energy structure of QCD lies encoded in the excited states of the nucleon, a complicated overlap of many resonances. Recent Lattice calculations have confirmed the longstanding quark model predictions of many more excited states than have been identified. Reactions that probe the spectrum are clouded by effects that dress the interactions and complicate the identification of excited levels and the interpretation of their structure. Recent theoretical work has exposed dramatic effects from such dressings. On the experimental side, new complete measurements of pseudoscalar meson photo-production are being pursued at several laboratories, where here the designation of complete refers to measurements of most if not all of the 16 possible reaction observables. This has been the focus of a series of experiments at Jefferson Lab culminating in the recently completed g9/FROST and g14/HDice runs which are now under analysis. With realistic errors, the number of observables needed to constrain the production amplitude is many more than required of a mathematical solution.

  4. Magnesium induces neuronal apoptosis by suppressing excitability

    PubMed Central

    Dribben, W H; Eisenman, L N; Mennerick, S

    2010-01-01

    In clinical obstetrics, magnesium sulfate (MgSO4) use is widespread, but effects on brain development are unknown. Many agents that depress neuronal excitability increase developmental neuroapoptosis. In this study, we used dissociated cultures of rodent hippocampus to examine the effects of Mg++ on excitability and survival. Mg++-induced caspase-3-associated cell loss at clinically relevant concentrations. Whole-cell patch-clamp techniques measured Mg++ effects on action potential threshold, action potential peak amplitude, spike number and changes in resting membrane potential. Mg++ depolarized action potential threshold, presumably from surface charge screening effects on voltage-gated sodium channels. Mg++ also decreased the number of action potentials in response to fixed current injection without affecting action potential peak amplitude. Surprisingly, Mg++ also depolarized neuronal resting potential in a concentration-dependent manner with a +5.2 mV shift at 10 mM. Voltage ramps suggested that Mg++ blocked a potassium conductance contributing to the resting potential. In spite of this depolarizing effect of Mg++, the net inhibitory effect of Mg++ nearly completely silenced neuronal network activity measured with multielectrode array recordings. We conclude that although Mg++ has complex effects on cellular excitability, the overall inhibitory influence of Mg++ decreases neuronal survival. Taken together with recent in vivo evidence, our results suggest that caution may be warranted in the use of Mg++ in clinical obstetrics and neonatology. PMID:21364668

  5. Thermal Excitation System for Shearography (TESS)

    NASA Technical Reports Server (NTRS)

    Lansing, Matthew D.; Bullock, Michael W.

    1996-01-01

    One of the most convenient and effective methods of stressing a part or structure for shearographic evaluation is thermal excitation. This technique involves heating the part, often convectively with a heat gun, and then monitoring with a shearography device the deformation during cooling. For a composite specimen, unbonds, delaminations, inclusions, or matrix cracking will deform during cooling differently than other more structurally sound regions and thus will appear as anomalies in the deformation field. However, one of the difficulties that cause this inspection to be dependent on the operator experience is the conventional heating process. Fanning the part with a heat gun by hand introduces a wide range of variability from person to person and from one inspection to the next. The goal of this research effort was to conduct research in the methods of thermal excitation for shearography inspection. A computerized heating system was developed for inspection of 0.61 m (24 in.) square panels. The Thermal Excitation System for Shearography (TESS) provides radiant heating with continuous digital measurement of the surface temperature profile to ensure repeatability. The TESS device functions as an accessory to any electronic shearography device.

  6. Seismic Excitation of the Polar Motion

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin Fong; Gross, Richard S.; Han, Yan-Ben

    1996-01-01

    The mass redistribution in the earth as a result of an earthquake faulting changes the earth's inertia tensor, and hence its rotation. Using the complete formulae developed by Chao and Gross (1987) based on the normal mode theory, we calculated the earthquake-induced polar motion excitation for the largest 11,015 earthquakes that occurred during 1977.0-1993.6. The seismic excitations in this period are found to be two orders of magnitude below the detection threshold even with today's high precision earth rotation measurements. However, it was calculated that an earthquake of only one tenth the size of the great 1960 Chile event, if happened today, could be comfortably detected in polar motion observations. Furthermore, collectively these seismic excitations have a strong statistical tendency to nudge the pole towards approx. 140 deg E, away from the actually observed polar drift direction. This non-random behavior, similarly found in other earthquake-induced changes in earth rotation and low-degree gravitational field by Chao and Gross (1987), manifests some geodynamic behavior yet to be explored.

  7. Laser cooling via excitation of localized electrons

    NASA Astrophysics Data System (ADS)

    Emin, David

    2007-07-01

    Under appropriate conditions, absorption of light by a solid can initiate a process by which it is cooled. In particular, energy is extracted from a material when its absorption of a photon is followed by emission of a photon of higher energy. This up-conversion requires some of the solid’s electrons to garner energy from atomic vibrations. Here, two schemes for laser cooling via localized electronic states are addressed. The first scheme utilizes the ground state and an excited state of a localized center. In this two-level scheme, the cooling process is initiated with photon absorption in the extreme low-energy tail of a localized state’s vibrationally broadened absorption spectrum. The subsequent atomic relaxation transfers energy of especially large vibratory atomic strains into electrical energy that is then extracted via photon emission. The second scheme involves the ground state and two excited states of a localized center. Cooling is facilitated when (i) the photoexcitation of an electron from its ground state to the lower excited level is followed by (ii) electron-phonon-induced promotion to the uppermost level and the subsequent (iii) return of the electron to its ground state with emission of a photon of higher energy than that of the absorbed photon. However, competing relaxation processes contribute to heating. The net cooling power per unit volume is maximized for both schemes, thereby determining characteristics of localized electronic systems that foster optical cooling. The cooling power per unit volume is greatest at high temperatures and falls rapidly as the thermal energy is reduced below each system’s luminescence Stokes shift. Moreover, cooling via the three-level scheme is most effective when (i) the energy separation between excited states is smaller than the thermal energy and (ii) the degeneracy of the highest-lying excited state is much larger than that of the center’s middle level. These restrictive conditions appear to be

  8. Charge transfer excitations from excited state Hartree-Fock subsequent minimization scheme

    NASA Astrophysics Data System (ADS)

    Theophilou, Iris; Tassi, M.; Thanos, S.

    2014-04-01

    Photoinduced charge-transfer processes play a key role for novel photovoltaic phenomena and devices. Thus, the development of ab initio methods that allow for an accurate and computationally inexpensive treatment of charge-transfer excitations is a topic that nowadays attracts a lot of scientific attention. In this paper we extend an approach recently introduced for the description of single and double excitations [M. Tassi, I. Theophilou, and S. Thanos, Int. J. Quantum Chem. 113, 690 (2013); M. Tassi, I. Theophilou, and S. Thanos, J. Chem. Phys. 138, 124107 (2013)] to allow for the description of intermolecular charge-transfer excitations. We describe an excitation where an electron is transferred from a donor system to an acceptor one, keeping the excited state orthogonal to the ground state and avoiding variational collapse. These conditions are achieved by decomposing the space spanned by the Hartree-Fock (HF) ground state orbitals into four subspaces: The subspace spanned by the occupied orbitals that are localized in the region of the donor molecule, the corresponding for the acceptor ones and two more subspaces containing the virtual orbitals that are localized in the neighborhood of the donor and the acceptor, respectively. Next, we create a Slater determinant with a hole in the subspace of occupied orbitals of the donor and a particle in the virtual subspace of the acceptor. Subsequently we optimize both the hole and the particle by minimizing the HF energy functional in the corresponding subspaces. Finally, we test our approach by calculating the lowest charge-transfer excitation energies for a set of tetracyanoethylene-hydrocarbon complexes that have been used earlier as a test set for such kind of excitations.

  9. Charge transfer excitations from excited state Hartree-Fock subsequent minimization scheme

    SciTech Connect

    Theophilou, Iris; Tassi, M.; Thanos, S.

    2014-04-28

    Photoinduced charge-transfer processes play a key role for novel photovoltaic phenomena and devices. Thus, the development of ab initio methods that allow for an accurate and computationally inexpensive treatment of charge-transfer excitations is a topic that nowadays attracts a lot of scientific attention. In this paper we extend an approach recently introduced for the description of single and double excitations [M. Tassi, I. Theophilou, and S. Thanos, Int. J. Quantum Chem. 113, 690 (2013); M. Tassi, I. Theophilou, and S. Thanos, J. Chem. Phys. 138, 124107 (2013)] to allow for the description of intermolecular charge-transfer excitations. We describe an excitation where an electron is transferred from a donor system to an acceptor one, keeping the excited state orthogonal to the ground state and avoiding variational collapse. These conditions are achieved by decomposing the space spanned by the Hartree-Fock (HF) ground state orbitals into four subspaces: The subspace spanned by the occupied orbitals that are localized in the region of the donor molecule, the corresponding for the acceptor ones and two more subspaces containing the virtual orbitals that are localized in the neighborhood of the donor and the acceptor, respectively. Next, we create a Slater determinant with a hole in the subspace of occupied orbitals of the donor and a particle in the virtual subspace of the acceptor. Subsequently we optimize both the hole and the particle by minimizing the HF energy functional in the corresponding subspaces. Finally, we test our approach by calculating the lowest charge-transfer excitation energies for a set of tetracyanoethylene-hydrocarbon complexes that have been used earlier as a test set for such kind of excitations.

  10. Combined effect of cascade through circular orbits and Stark quenching on the decay of n=2→n=1 transition of H-like Fe in beam-foil excitation

    NASA Astrophysics Data System (ADS)

    Kumar, Yogesh; Mishra, Adya P.; Nandi, T.

    2014-11-01

    Recently Mishra et al. (Mishra AP, et al. J Quant Spectrosc Radiat Transf 2013;120:114-9), while analyzing the effects of cascading through circular orbits (l=n-1)on the decay of unresolved 2p,2s→1s transitions of H-like Fe, neglected the effect of electric field at the exit surface of foil on the lifetime of the 2s state. In the present work we have considered the combined effect of cascading through circular orbits and the Stark mixing on the decay of the 2p,2s→1s transitions of H-like Fe in beam-foil excitation. It is observed that the natural lifetime of the 2s state (350.6 ps) is reduced to 221.8±22.4 ps due to Stark mixing of the long-lived 2s2S1/2 state with the very close and short-lived 2p P1/2o2 state. The strength of the electric field responsible for such mixing comes out to be 7.09±0.37×106 V/cm. The results of the present work for cascading of circular orbits through the 2p state are in good agreement (within the error bars) with those obtained earlier by Mishra et al.

  11. Strong decays of excited baryons in Large Nc QCD

    SciTech Connect

    Goity, J. L.; Scoccola, N. N.

    2007-02-12

    We present the analysis of the strong decays widths of excited baryons in the framework of the 1/Nc expansion of QCD. These studies are performed up to order 1/Nc and include both positive and negative parity excited baryons.

  12. Strong decays of excited baryons in Large Nc QCD

    SciTech Connect

    Goity, Jose; Scoccola, Norberto

    2007-02-01

    We present the analysis of the strong decays widths of excited baryons in the framework of the 1/Nc expansion of QCD. These studies are performed up to order 1/Nc and include both positive and negative parity excited baryons.

  13. 12. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 SMALL PELTONDOBLE IMPULSE ...

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

    12. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 SMALL PELTON-DOBLE IMPULSE WHEEL, HAND-CONTROLLED GATE VALVE, AND NOZZLE. VIEW TO SOUTHWEST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  14. 6. POWERHOUSE INTERIOR SHOWING EXCITER No. 1. HANDCONTROLLED GATE VALVE ...

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

    6. POWERHOUSE INTERIOR SHOWING EXCITER No. 1. HAND-CONTROLLED GATE VALVE SHOWN ON NOZZLE TO PELTON-DOBLE IMPULSE WHEEL. VIEW TO NORTHEAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  15. 69. Credit TCL. Housing of Pelton exciter impulse wheel and ...

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

    69. Credit TCL. Housing of Pelton exciter impulse wheel and attached General Electric 60 kW exciter generator. - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

  16. 10. POWERHOUSE INTERIOR, DETAIL OF EXCITER No. 2 GENERAL ELECTRIC ...

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

    10. POWERHOUSE INTERIOR, DETAIL OF EXCITER No. 2 GENERAL ELECTRIC GENERATOR SHOWING CABLING FROM ARMATURE TO COMMUTATOR. VIEW TO NORTHEAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  17. 11. POWERHOUSE INTERIOR, DETAIL OF EXCITER No. 2 GENERAL ELECTRIC ...

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

    11. POWERHOUSE INTERIOR, DETAIL OF EXCITER No. 2 GENERAL ELECTRIC GENERATOR SHOWING COPPER COMMUTATOR AND CARBON BRUSHES. VIEW TO NORTHEAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  18. 13. POWERHOUSE INTERIOR, DETAIL OF EXCITER No. 2 GENERAL ELECTRIC ...

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

    13. POWERHOUSE INTERIOR, DETAIL OF EXCITER No. 2 GENERAL ELECTRIC INDUCTION MOTOR NAMEPLATE. VIEW TO EAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  19. 14. POWERHOUSE INTERIOR, EXCITER No. 2 SHOWING GENERAL ELECTRIC INDUCTION ...

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

    14. POWERHOUSE INTERIOR, EXCITER No. 2 SHOWING GENERAL ELECTRIC INDUCTION MOTOR IN SERIES BETWEEN PELTON-DOBLE IMPULSE WHEEL AND GENERAL ELECTRIC GENERATOR. VIEW TO EAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  20. Simultaneous two-photon excitation of photodynamic therapy agents

    SciTech Connect

    Wachter, E.A.; Fisher, W.G. |; Partridge, W.P.; Dees, H.C.; Petersen, M.G.

    1998-01-01

    The spectroscopic and photochemical properties of several photosensitive compounds are compared using conventional single-photon excitation (SPE) and simultaneous two-photon excitation (TPE). TPE is achieved using a mode-locked titanium:sapphire laser, the near infrared output of which allows direct promotion of non-resonant TPE. Excitation spectra and excited state properties of both type 1 and type 2 photodynamic therapy (PDT) agents are examined.

  1. Excited-State Dynamics in Folic Acid and 6-CARBOXYPTERIN upon Uva Excitation

    NASA Astrophysics Data System (ADS)

    Huang, Huijuan; Vogt, R. Aaron; Crespo-Hernandez, Carlos E.

    2013-06-01

    The excited-state dynamics of folic acid (FA) and 6-carboxypterin (6CP) are poorly understood and work is needed to uncover the relaxation pathways that ultimately lead to their oxidative damage of DNA. In our approach, broad-band transient absorption spectroscopy was used to monitor the evolution of the excited states in FA and 6CP in basic aqueous solution upon excitation at 350 nm. In addition, quantum-chemical calculations were performed to assist in the interpretation of the experimental results and in the postulation of kinetic mechanisms. The combined experimental and computational results support a kinetic model where excitation of FA results in ultrafast charge separation (τ = 0.6 ps), which decays back to the ground state primarily by charge recombination with a lifetime of 2.2 ps. A small fraction of the charge transfer state undergoes intersystem crossing to populate the lowest-energy triplet state with a lifetime of 200 ps. On the other hand, a large fraction of the initially excited singlet state in 6CP decays by fluorescence emission with a lifetime of 100 ps, while intersystem crossing to the triplet state occurs with a lifetime of 4.4 ns. The potential implications of these results to the oxidative damage of DNA by FA and 6CP will be discussed. Funding from the National Science Foundation is gratefully acknowledged (CHE-1255084).

  2. Excitation Spectra and Brightness Optimization of Two-Photon Excited Probes

    PubMed Central

    Mütze, Jörg; Iyer, Vijay; Macklin, John J.; Colonell, Jennifer; Karsh, Bill; Petrášek, Zdeněk; Schwille, Petra; Looger, Loren L.; Lavis, Luke D.; Harris, Timothy D.

    2012-01-01

    Two-photon probe excitation data are commonly presented as absorption cross section or molecular brightness (the detected fluorescence rate per molecule). We report two-photon molecular brightness spectra for a diverse set of organic and genetically encoded probes with an automated spectroscopic system based on fluorescence correlation spectroscopy. The two-photon action cross section can be extracted from molecular brightness measurements at low excitation intensities, while peak molecular brightness (the maximum molecular brightness with increasing excitation intensity) is measured at higher intensities at which probe photophysical effects become significant. The spectral shape of these two parameters was similar across all dye families tested. Peak molecular brightness spectra, which can be obtained rapidly and with reduced experimental complexity, can thus serve as a first-order approximation to cross-section spectra in determining optimal wavelengths for two-photon excitation, while providing additional information pertaining to probe photostability. The data shown should assist in probe choice and experimental design for multiphoton microscopy studies. Further, we show that, by the addition of a passive pulse splitter, nonlinear bleaching can be reduced—resulting in an enhancement of the fluorescence signal in fluorescence correlation spectroscopy by a factor of two. This increase in fluorescence signal, together with the observed resemblance of action cross section and peak brightness spectra, suggests higher-order photobleaching pathways for two-photon excitation. PMID:22385865

  3. Dynamic analysis of parametrically excited system under uncertainties and multi-frequency excitations

    NASA Astrophysics Data System (ADS)

    Wei, Sha; Han, Qinkai; Peng, Zhike; Chu, Fulei

    2016-05-01

    Some system parameters in mechanical systems are always uncertain due to uncertainties in geometric and material properties, lubrication condition and wear. For a more reasonable estimation of dynamic analysis of the parametrically excited system, the effect of uncertain parameters should be taken into account. This paper presents a new non-probabilistic analysis method for solving the dynamic responses of parametrically excited systems under uncertainties and multi-frequency excitations. By using the multi-dimensional harmonic balance method (MHBM) and the Chebyshev inclusion function (CIF), an interval multi-dimensional harmonic balance method (IMHBM) is obtained. To illustrate the accuracy of the proposed method, a time-varying geared system of wind turbine with different kinds of uncertainties is demonstrated. By comparing with the results of the scanning method, it is shown that the presented method is valid and effective for the parametrically excited system with uncertainties and multi-frequency excitations. The effects of some uncertain system parameters including uncertain mesh stiffnesses and uncertain bearing stiffnesses on the frequency responses of the system are also discussed in detail. It is shown that the dynamic responses of the system are insensitive to the uncertain mesh stiffness and bearing stiffnesses of the planetary gear stage. The uncertain bearing stiffnesses of the intermediate and high-speed stages will lead to relatively large uncertainties in the dynamic responses around resonant regions. It will provide valuable guidance for the optimal design and condition monitoring of wind turbine gearboxes.

  4. Radiative transitions of excited ions moving slowly in plasmas

    SciTech Connect

    Hu, Hongwei Chen, Wencong; Li, Peng; Zhao, Yongtao; Zhou, Xianming; Li, Zhen; Li, Fuli; Dong, Chenzhong

    2014-12-15

    The electric dipole transitions of excited ions moving slowly in plasmas are studied. The results show that some transitions forbidden for excited ions at rest become allowed for moving excited ions. The transition rates change with varying speed of the ions. Forbidden transitions are strongly influenced by the speed, non-forbidden transitions are weakly influenced.

  5. Nuclear excitation by electronic transition of 235U

    DOE PAGESBeta

    Chodash, P. A.; Norman, E. B.; Burke, J. T.; Casperson, R. J.; Fisher, S. E.; Holliday, K. S.; Jeffries, J. R.; Wakeling, M. A.; Wilks, S. C.

    2016-03-11

    Here, nuclear excitation by electronic transition (NEET) is a rare nuclear excitation that can occur in isotopes containing a low-lying nuclear excited state. Over the past 40 yr, several experiments have attempted to measure NEET of 235U and those experiments have yielded conflicting results.

  6. Chain of excitation spot generation by aperture engineering

    NASA Astrophysics Data System (ADS)

    Mondal, Partha Pratim

    2010-04-01

    An optical technique is proposed for obtaining multiple excitation spots. Phase-matched counter propagating extended depth-of-focus fields were superimposed along the optical axis for generating multiple localized excitation spots. Moreover, the filtering effect due to the optical mask increases the lateral resolution. Proposed technique introduces the concept of simultaneous multiplane excitation and improves three-dimensional resolution.

  7. LASERS IN MEDICINE: Two-photon excitation of aluminium phthalocyanines

    NASA Astrophysics Data System (ADS)

    Meshalkin, Yu P.; Alfimov, E. E.; Vasil'ev, N. E.; Denisov, A. N.; Makukha, V. K.; Ogirenko, A. P.

    1999-12-01

    A demonstration is given of the feasibility of two-photon excitation of aluminium phthalocyanine and of the pharmaceutical preparation 'Fotosens', used in photodynamic therapy. The excitation source was an Nd:YAG laser emitting at the 1064 nm wavelength. The spectra of the two-photon-excited luminescence were obtained and the two-photon absorption cross sections were determined.

  8. Two-versus one photon excitation laser scanning microscopy: Critical importance of excitation wavelength

    PubMed Central

    Bush, Peter G.; Wokosin, David L.; Hall, Andrew C.

    2008-01-01

    It is often anticipated that two-photon excitation (TPE) laser scanning microscopy should improve cell survival and tissue penetration relative to conventional one-photon excitation (OPE) confocal scanning laser microscopy (CLSM). However few studies have directly compared live cell imaging using one- vs two-photon laser scanning microscopy. We have used calcein-loaded in situ chondrocytes within cartilage as a model for quantitatively comparing these techniques. TPE reduced photo-bleaching and improved cell viability compared to OPE. Using improved detection sensitivity coupled with increased tissue penetration of the near infra-red TPE laser, it was possible to capture images deeper within the cartilage. However, the advantages of TPE vs OPE were strongly dependent on excitation wavelength. We conclude that optimising TPE conditions is essential if the full benefits of this approach are to be realised. PMID:17127269

  9. Lifetime and g-factor measurements of excited states using Coulomb excitation and alpha transfer reactions

    NASA Astrophysics Data System (ADS)

    Guevara, Z. E.; Torres, D. A.

    2016-07-01

    In this contribution the challenges in the use of a setup to simultaneously measure lifetimes and g-factor values will be presented. The simultaneous use of the transient field technique and the Doppler Shift Attenuation Method, to measure magnetic moments and lifetimes respectively, allows to obtain a complete characterization of the currents of nucleons and the deformation in excited states close to the ground state. The technique is at the moment limited to Coulomb excitation and alpha-transfer reactions, what opens an interesting perspective to consider this type of experiments with radioactive beams. The use of deep-inelastic and fusion-evaporation reactions will be discussed. An example of a setup that makes use of a beam of 106Cd to study excited states of 110Sn and the beam nuclei itself will be presented.

  10. Electron-impact excitation and ionization cross sections for ground state and excited helium atoms

    SciTech Connect

    Ralchenko, Yu. Janev, R.K.; Kato, T.; Fursa, D.V.; Bray, I.; Heer, F.J. de

    2008-07-15

    Comprehensive and critically assessed cross sections for the electron-impact excitation and ionization of ground state and excited helium atoms are presented. All states (atomic terms) with n{<=}4 are treated individually, while the states with n{>=}5 are considered degenerate. For the processes involving transitions to and from n{>=}5 levels, suitable cross section scaling relations are presented. For a large number of transitions, from both ground and excited states, convergent close coupling calculations were performed to achieve a high accuracy of the data. The evaluated/recommended cross section data are presented by analytic fit functions, which preserve the correct asymptotic behavior of the cross sections. The cross sections are also displayed in graphical form.

  11. Excitability of the squid giant axon revisited.

    PubMed

    Clay, J R

    1998-08-01

    The electrical properties of the giant axon from the common squid Loligo pealei have been reexamined. The primary motivation for this work was the observation that the refractoriness of the axon was significantly greater than the predictions of the standard model of nerve excitability. In particular, the axon fired only once in response to a sustained, suprathreshold stimulus. Similarly, only a single action potential was observed in response to the first pulse of a train of 1-ms duration current pulses, when the pulses were separated in time by approximately 10 ms. The axon was refractory to all subsequent pulses in the train. The underlying mechanisms for these results concern both the sodium and potassium ion currents INa and IK. Specifically, Na+ channel activation has long been known to be coupled to inactivation during a depolarizing voltage-clamp step. This feature appears to be required to simulate the pulse train results in a revised model of nerve excitability. Moreover, the activation curve for IK has a significantly steeper voltage dependence, especially near its threshold (approximately -60 mV), than in the standard model, which contributes to reduced excitability, and the fully activated current-voltage relation for IK has a nonlinear, rather than a linear, dependence on driving force. An additional aspect of the revised model is accumulation/depeletion of K+ in the space between the axon and the glial cells surrounding the axon, which is significant even during a single action potential and which can account for the 15-20 mV difference between the potassium equilibrium potential EK and the maximum afterhyperpolarization of the action potential. The modifications in IK can also account for the shape of voltage changes near the foot of the action potential.

  12. Tilted excitation implies odd periodic resonances

    NASA Astrophysics Data System (ADS)

    Depetri, G. I.; Sartorelli, J. C.; Marin, B.; Baptista, M. S.

    2016-07-01

    Our aim is to unveil how resonances of parametric systems are affected when symmetry is broken. We showed numerically and experimentally that odd resonances indeed come about when the pendulum is excited along a tilted direction. Applying the Melnikov subharmonic function, we not only determined analytically the loci of saddle-node bifurcations delimiting resonance regions in parameter space but also explained these observations by demonstrating that, under the Melnikov method point of view, odd resonances arise due to an extra torque that appears in the asymmetric case.

  13. Internal waves excited by the marangoni effect

    PubMed

    Wierschem; Linde; Velarde

    2000-11-01

    Traveling periodic internal wave trains are generated in liquid layers during the absorption process of a miscible surface-active substance out of the vapor phase. In our nonstationary experimental runs, internal waves are excited by surface waves, which had been previously generated by a surface-tension-gradient-driven instability. The internal wave trains adjust their wave number by an Eckhaus instability. Close to the instability threshold narrow and extended pulses are observed. Furthermore, the wave trains can alter their traveling direction, i.e., one wave train traveling in one direction yields to another train, in general of different wave number, traveling in the opposite direction. PMID:11101989

  14. Paramagnetic excited vortex states in superconductors

    NASA Astrophysics Data System (ADS)

    Gomes, Rodolpho Ribeiro; Doria, Mauro M.; Romaguera, Antonio R. de C.

    2016-06-01

    We consider excited vortex states, which are vortex states left inside a superconductor once the external applied magnetic field is switched off and whose energy is lower than of the normal state. We show that this state is paramagnetic and develop here a general method to obtain its Gibbs free energy through conformal mapping. The solution for any number of vortices in any cross-section geometry can be read off from the Schwarz-Christoffel mapping. The method is based on the first-order equations used by Abrikosov to discover vortices.

  15. Quasiparticle excitations of adsorbates on doped graphene

    NASA Astrophysics Data System (ADS)

    Lischner, Johannes; Wickenburg, Sebastian; Wong, Dillon; Karrasch, Christoph; Wang, Yang; Lu, Jiong; Omrani, Arash A.; Brar, Victor; Tsai, Hsin-Zon; Wu, Qiong; Corsetti, Fabiano; Mostofi, Arash; Kawakami, Roland K.; Moore, Joel; Zettl, Alex; Louie, Steven G.; Crommie, Mike

    Adsorbed atoms and molecules can modify the electronic structure of graphene, but in turn it is also possible to control the properties of adsorbates via the graphene substrate. In my talk, I will discuss the electronic structure of F4-TCNQ molecules on doped graphene and present a first-principles based theory of quasiparticle excitations that captures the interplay of doping-dependent image charge interactions between substrate and adsorbate and electron-electron interaction effects on the molecule. The resulting doping-dependent quasiparticle energies will be compared to experimental scanning tunnelling spectra. Finally, I will also discuss the effects of charged adsorbates on the electronic structure of doped graphene.

  16. Excitation of solar p-modes

    NASA Technical Reports Server (NTRS)

    Goldreich, Peter; Murray, Norman; Kumar, Pawan

    1994-01-01

    We investigate the rates at which energy is supplied to individual p-modes as a function of their frequencies nu and angular degrees l. The observationally determined rates are compared with those calculated on the hypothesis that the modes are stochastically excited by turbulent convection. The observationally determined excitation rate is assumed to be equal to the product of the mode's energy E and its (radian) line width Gamma. We obtain E from the mode's mean square surface velocity with the aid of its velocity eigenfuction. We assume that Gamma measures the mode's energy decay rate, even though quasi-elastic scattering may dominate true absorption. At fixed l, E(Gamma) arises as nu(exp 7) at low nu, reaches a peak at nu approximately equal 3.5 mHz, and then declines as nu(exp 4.4) at higher nu . At fixed nu, E(Gamma) exhibits a slow decline with increasing l. To calculate energy input rates, P(sub alpha), we rely on the mixing-length model of turbulent convection. We find entropy fluctuations to be about an order of magnitude more effective than the Reynolds stress in exciting p-modes . The calculated P(sub alpha) mimic the nu(exp 7) dependence of E(Gamma) at low nu and the nu(exp -4.4) dependence at high nu. The break of 11.4 powers in the nu-dependence of E(Gamma) across its peak is attributed to a combination of (1) the reflection of high-frequency acoustic waves just below the photosphere where the scale height drops precipitously and (2) the absence of energy-bearing eddies with short enough correlation times to excite high-frequency modes. Two parameters associated with the eddy correlation time are required to match the location and shape of the break. The appropriate values of these parameters, while not unnatural, are poorly constrained by theory. The calculated P(sub alpha) can also be made to fit the magnitude of E(Gamma) with a reasonable value for the eddy aspect ratio. Our resutls suggest a possible explanation for the decline of mode energy

  17. Rydberg Excitation of a Single Trapped Ion.

    PubMed

    Feldker, T; Bachor, P; Stappel, M; Kolbe, D; Gerritsma, R; Walz, J; Schmidt-Kaler, F

    2015-10-23

    We demonstrate excitation of a single trapped cold (40)Ca(+) ion to Rydberg levels by laser radiation in the vacuum ultraviolet at a wavelength of 122 nm. Observed resonances are identified as 3d(2)D(3/2) to 51F, 52F and 3d(2)D(5/2) to 64F. We model the line shape and our results imply a large state-dependent coupling to the trapping potential. Rydberg ions are of great interest for future applications in quantum computing and simulation, in which large dipolar interactions are combined with the superb experimental control offered by Paul traps. PMID:26551109

  18. Spike Bursts from an Excitable Optical System

    NASA Astrophysics Data System (ADS)

    Rios Leite, Jose R.; Rosero, Edison J.; Barbosa, Wendson A. S.; Tredicce, Jorge R.

    Diode Lasers with double optical feedback are shown to present power drop spikes with statistical distribution controllable by the ratio of the two feedback times. The average time between spikes and the variance within long time series are studied. The system is shown to be excitable and present bursting of spikes created with specific feedback time ratios and strength. A rate equation model, extending the Lang-Kobayashi single feedback for semiconductor lasers proves to match the experimental observations. Potential applications to construct network to mimic neural systems having controlled bursting properties in each unit will be discussed. Brazilian Agency CNPQ.

  19. Collective Excitations in Electron-Hole Bilayers

    SciTech Connect

    Kalman, G. J.; Hartmann, P.; Donko, Z.; Golden, K. I.

    2007-06-08

    We report a combined analytic and molecular dynamics analysis of the collective mode spectrum of a bipolar (electron-hole) bilayer in the strong coupling classical limit. A robust, isotropic energy gap is identified in the out-of-phase spectra, generated by the combined effect of correlations and of the excitation of the bound dipoles. In the in-phase spectra we identify longitudinal and transverse acoustic modes wholly maintained by correlations. Strong nonlinear generation of higher harmonics of the fundamental dipole oscillation frequency and the transfer of harmonics between different modes is observed.

  20. Coherent motion in excited free shear flows

    NASA Technical Reports Server (NTRS)

    Wygnanski, Israel J.; Petersen, Robert A.

    1987-01-01

    The application of the inviscid instability approach to externally excited turbulent free shear flows at high Reynolds numbers is explored. Attention is given to the cases of a small-deficit plane turbulent wake, a plane turbulent jet, an axisymmetric jet, the nonlinear evolution of instabilities in free shear flows, the concept of the 'preferred mode', vortex pairing in turbulent mixing layers, and experimental results for the control of free turbulent shear layers. The special features often attributed to pairing or to the preferred mode are found to be difficult to comprehend; the concept of feedback requires further substantiation in the case of incompressible flow.

  1. Rabi resonances in the {lambda} excitation scheme

    SciTech Connect

    Godone, Aldo; Micalizio, Salvatore; Levi, Filippo

    2002-12-01

    We consider the interaction of a three-level system with phase-modulated resonant fields in the {lambda} excitation scheme. We treat theoretically the case of a sinusoidal phase modulation, a phase step perturbation, and a stochastic phase modulation. The appearance of a Rabi resonance both in the spectrum of the optical transmitted signal (electromagnetically induced transparency) and in the spectrum of the microwave emission (coherent population trapping maser) is considered in detail. All the theoretical results are compared with the analogous ones reported for the two-level system and with our experimental observations obtained for the case of rubidium in a buffer gas.

  2. Automatic cytometric device using multiple wavelength excitations

    NASA Astrophysics Data System (ADS)

    Rongeat, Nelly; Ledroit, Sylvain; Chauvet, Laurence; Cremien, Didier; Urankar, Alexandra; Couderc, Vincent; Nérin, Philippe

    2011-05-01

    Precise identification of eosinophils, basophils, and specific subpopulations of blood cells (B lymphocytes) in an unconventional automatic hematology analyzer is demonstrated. Our specific apparatus mixes two excitation radiations by means of an acousto-optics tunable filter to properly control fluorescence emission of phycoerythrin cyanin 5 (PC5) conjugated to antibodies (anti-CD20 or anti-CRTH2) and Thiazole Orange. This way our analyzer combining techniques of hematology analysis and flow cytometry based on multiple fluorescence detection, drastically improves the signal to noise ratio and decreases the spectral overlaps impact coming from multiple fluorescence emissions.

  3. Two photon excitation of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Pindzola, M. S.

    1977-01-01

    A standard perturbation expansion in the atom-radiation field interaction is used to calculate the two photon excitation cross section for 1s(2) 2s(2) 2p(4) p3 to 1s(2) 2s(2) 2p(3) (s4) 3p p3 transition in atomic oxygen. The summation over bound and continuum intermediate states is handled by solving the equivalent inhomogeneous differential equation. Exact summation results differ by a factor of 2 from a rough estimate obtained by limiting the intermediate state summation to one bound state. Higher order electron correlation effects are also examined.

  4. Recent Theoretical Studies On Excitation and Recombination

    NASA Technical Reports Server (NTRS)

    Pradhan, Anil K.

    2000-01-01

    New advances in the theoretical treatment of atomic processes in plasmas are described. These enable not only an integrated, unified, and self-consistent treatment of important radiative and collisional processes, but also large-scale computation of atomic data with high accuracy. An extension of the R-matrix work, from excitation and photoionization to electron-ion recombination, includes a unified method that subsumes both the radiative and the di-electronic recombination processes in an ab initio manner. The extensive collisional calculations for iron and iron-peak elements under the Iron Project are also discussed.

  5. Dynamics of excitation energy transfer in phycobiliproteins

    NASA Astrophysics Data System (ADS)

    Zheng, Xiguang; Wang, He Z.; Zhao, Fuli; Gao, Zhaolan; Yu, Zhenxin

    1994-08-01

    Theoretical descriptions of excitation energy transfer between chromophores in allophycocyanin are presented, including bilateral energy transfer paths between chromophores, and are expressed, based on Foster interaction mechanism, as Pauli master equations. Group analysis in C3 symmetry is performed to carry out analytic expressions for fluorescence decays which is generally of triexponential with effects of chromophore coupling and exciton splitting taken account. It is pointed out that the time constant of each decay component contains mixed information of different energy transfer paths, and therefore show its dependence on subtle configuration of chromophores, probably related to site heterogeneity and thus to inhomogeneous broadening previously observed.

  6. Excited light isoscalar mesons from lattice QCD

    SciTech Connect

    Christopher Thomas

    2011-07-01

    I report a recent lattice QCD calculation of an excited spectrum of light isoscalar mesons, something that has up to now proved challenging for lattice QCD. With novel techniques we extract an extensive spectrum with high statistical precision, including spin-four states and, for the first time, light isoscalars with exotic quantum numbers. In addition, the hidden flavour content of these mesons is determined, providing a window on annihilation dynamics in QCD. I comment on future prospects including applications to the study of resonances.

  7. Tilted excitation implies odd periodic resonances.

    PubMed

    Depetri, G I; Sartorelli, J C; Marin, B; Baptista, M S

    2016-07-01

    Our aim is to unveil how resonances of parametric systems are affected when symmetry is broken. We showed numerically and experimentally that odd resonances indeed come about when the pendulum is excited along a tilted direction. Applying the Melnikov subharmonic function, we not only determined analytically the loci of saddle-node bifurcations delimiting resonance regions in parameter space but also explained these observations by demonstrating that, under the Melnikov method point of view, odd resonances arise due to an extra torque that appears in the asymmetric case. PMID:27575118

  8. Semiempirical Modeling of Ag Nanoclusters: New Parameters for Optical Property Studies Enable Determination of Double Excitation Contributions to Plasmonic Excitation.

    PubMed

    Gieseking, Rebecca L; Ratner, Mark A; Schatz, George C

    2016-07-01

    Quantum mechanical studies of Ag nanoclusters have shown that plasmonic behavior can be modeled in terms of excited states where collectivity among single excitations leads to strong absorption. However, new computational approaches are needed to provide understanding of plasmonic excitations beyond the single-excitation level. We show that semiempirical INDO/CI approaches with appropriately selected parameters reproduce the TD-DFT optical spectra of various closed-shell Ag clusters. The plasmon-like states with strong optical absorption comprise linear combinations of many singly excited configurations that contribute additively to the transition dipole moment, whereas all other excited states show significant cancellation among the contributions to the transition dipole moment. The computational efficiency of this approach allows us to investigate the role of double excitations at the INDO/SDCI level. The Ag cluster ground states are stabilized by slight mixing with doubly excited configurations, but the plasmonic states generally retain largely singly excited character. The consideration of double excitations in all cases improves the agreement of the INDO/CI absorption spectra with TD-DFT, suggesting that the SDCI calculation effectively captures some of the ground-state correlation implicit in DFT. These results provide the first evidence to support the commonly used assumption that single excitations are in many cases sufficient to describe the optical spectra of plasmonic excitations quantum mechanically.

  9. The photodissociation and reaction dynamics of vibrationally excited molecules

    SciTech Connect

    Crim, F.F.

    1993-12-01

    This research determines the nature of highly vibrationally excited molecules, their unimolecular reactions, and their photodissociation dynamics. The goal is to characterize vibrationally excited molecules and to exploit that understanding to discover and control their chemical pathways. Most recently the author has used a combination of vibrational overtone excitation and laser induced fluorescence both to characterize vibrationally excited molecules and to study their photodissociation dynamics. The author has also begun laser induced grating spectroscopy experiments designed to obtain the electronic absorption spectra of highly vibrationally excited molecules.

  10. Seeded excitation avalanches in off-resonantly driven Rydberg gases

    NASA Astrophysics Data System (ADS)

    Simonelli, C.; Valado, M. M.; Masella, G.; Asteria, L.; Arimondo, E.; Ciampini, D.; Morsch, O.

    2016-08-01

    We report an experimental investigation of the facilitated excitation dynamics in off-resonantly driven Rydberg gases by separating the initial off-resonant excitation phase from the facilitation phase, in which successive facilitation events lead to excitation avalanches. We achieve this by creating a controlled number of initial seed excitations. Greater insight into the avalanche mechanism is obtained from an analysis of the full counting distributions. We also present simple mathematical models and numerical simulations of the excitation avalanches that agree well with our experimental results.

  11. Standoff alpha radiation detection via excited state absorption of air

    SciTech Connect

    Yao, Jimmy; Yin, Stuart Shizhuo; Brenizer, Jack; Hui, Rongqing

    2013-06-24

    A standoff alpha radiation detection technique based on the physical mechanism of excited state absorption of air molecules was explored and is presented in this paper. Instead of directly detecting the radiation via measuring the intensity of radiation induced air fluorescence, the radiation is detected via the excited state absorption of alpha radiation excited/ionized air molecules. Both theoretical analyses and experimental verifications were conducted. The experimental results confirmed that the radiation could be detected via excited state absorption of radiation excited/ionized air molecules at a 10 m standoff distance, which was consistent with the theoretical analyses.

  12. Investigation of Nanoscale Interactions by Means of Subharmonic Excitation.

    PubMed

    Chiesa, Matteo; Gadelrab, Karim; Stefancich, Marco; Armstrong, Peter; Li, Guang; Souier, Tewfik; Thomson, Neil H; Barcons, Victor; Font, Josep; Verdaguer, Albert; Phillips, Michael A; Santos, Sergio

    2012-08-16

    Multifrequency atomic force microscopy holds promise as a method to provide qualitative and quantitative information about samples with high spatial resolution. Here, we provide experimental evidence of the excitation of subharmonics in ambient conditions in the regions where capillary interactions are predicted to be the mechanism of excitation. We also experimentally decouple a second mechanism for subharmonic excitation that is highly independent of environmental conditions such as relative humidity. This implies that material properties could be mapped. Subharmonic excitation could lead to experimental determination of surface water affinity in the nanoscale whenever water interactions are the mechanism of excitation.

  13. New laser excitation method for modal analysis of microstructure

    NASA Astrophysics Data System (ADS)

    Xiong, Liangcai; Zhou, Quansheng; Wu, You; Chen, Peng

    2015-01-01

    A novel impulse laser excitation technique to determine the dynamic response of micro-electro-mechanical systems (MEMS) has been investigated. During the laser excitation experiments, MEMS structures are excited by the wide-band impact force created by the laser-target interaction, and Laser Doppler Vibrometer (LDV) is introduced to measure the vibration velocity of MEMS structures. A distinguishing characteristic of the methodology is that both the excitation and measurement are non-contact, which is especially suitable for the testing of MEMS microstructures that are not easily accessible. This novel excitation method and MEMS modal analysis system are verified by experiments on various cantilever beams. The results show that the laser excitation is capable of exciting the first three modes of cantilevers.

  14. Fusion excitation functions involving transitional nuclei

    SciTech Connect

    Rehm, K.E.; Jiang, C.L.; Esbensen, H.

    1995-08-01

    Measurements of fusion excitation functions involving transitional nuclei {sup 78}Kr and {sup 100}Mo showed a different behavior at low energies, if compared to measurements with {sup 86}Kr and {sup 92}Mo. This points to a possible influence of nuclear structure on the fusion process. One way to characterize the structure of vibrational nuclei is via their restoring force parameters C{sub 2} which can be calculated from the energy of the lowest 2{sup +} state and the corresponding B(E2) value. A survey of the even-even nuclei between A = 28-150 shows strong variations in C{sub 2} values spanning two orders of magnitude. The lowest values for C{sub 2} are observed for {sup 78}Kr, {sup 104}Ru and {sup 124}Xe followed by {sup 74,76}Ge, {sup 74,76}Se, {sup 100}Mo and {sup 110}Pd. In order to learn more about the influence of {open_quotes}softness{close_quotes} on the sub-barrier fusion enhancement, we measured cross sections for evaporation residue production for the systems {sup 78}Kr + {sup 104}Ru and {sup 78}Kr + {sup 76}Ge with the gas-filled magnet technique. For both systems, fusion excitation functions involving the closed neutron shell nucleus {sup 86}Kr were measured previously. The data are presently being analyzed.

  15. Dual excitation acoustic paramagnetic logging tool

    DOEpatents

    Vail, III, William B.

    1989-01-01

    New methods and apparatus are disclosed which allow measurement of the presence of oil and water in gelogical formations using a new physical effect called the Acoustic Paramagnetic Logging Effect (APLE). The presence of petroleum in formation causes a slight increase in the earth's magnetic field in the vicinity of the reservoir. This is the phenomena of paramagnetism. Application of an acoustic source to a geological formation at the Larmor frequency of the nucleous present causes the paramagnetism of the formation to disappear. This results in a decrease in the earth's magnetic field in the vicinity of the oil bearing formation. Repetitively frequency sweeping the acoustic source through the Larmor frequency of the nucleons present (approx. 2 kHz) causes an amplitude modulation of the earth's magnetic field which is a consequence of the APLE. The amplitude modulation of the earth's magnetic field is measured with an induction coil gradiometer and provides a direct measure of the amount of oil and water in the excitation zone of the formation. The phase of the signal is used to infer the longitudinal relaxation times of the fluids present, which results in the ability in general to separate oil and water and to measure the viscosity of the oil present. Such measurements may be preformed in open boreholes and in cased well bores. The Dual Excitation Acoustic Paramagnetic Logging Tool employing two acoustic sources is also described.

  16. Low-lying excitations in 72Ni

    NASA Astrophysics Data System (ADS)

    Morales, A. I.; Benzoni, G.; Watanabe, H.; Nishimura, S.; Browne, F.; Daido, R.; Doornenbal, P.; Fang, Y.; Lorusso, G.; Patel, Z.; Rice, S.; Sinclair, L.; Söderström, P.-A.; Sumikama, T.; Wu, J.; Xu, Z. Y.; Yagi, A.; Yokoyama, R.; Baba, H.; Avigo, R.; Bello Garrote, F. L.; Blasi, N.; Bracco, A.; Camera, F.; Ceruti, S.; Crespi, F. C. L.; de Angelis, G.; Delattre, M.-C.; Dombradi, Zs.; Gottardo, A.; Isobe, T.; Kojouharov, I.; Kurz, N.; Kuti, I.; Matsui, K.; Melon, B.; Mengoni, D.; Miyazaki, T.; Modamio-Hoyborg, V.; Momiyama, S.; Napoli, D. R.; Niikura, M.; Orlandi, R.; Sakurai, H.; Sahin, E.; Sohler, D.; Shaffner, H.; Taniuchi, R.; Taprogge, J.; Vajta, Zs.; Valiente-Dobón, J. J.; Wieland, O.; Yalcinkaya, M.

    2016-03-01

    Low-lying excited states in 72Ni have been investigated in an in-flight fission experiment at the RIBF facility of the RIKEN Nishina Center. The combination of the state-of-the-art BigRIPS and EURICA setups has allowed for a very accurate study of the β decay from 72Co to 72Ni, and has provided first experimental information on the decay sequence 72Fe→72Co→72Ni and on the delayed neutron-emission branch 73Co→72Ni . Accordingly, we report nearly 60 previously unobserved γ transitions which deexcite 21 new levels in 72Ni. Evidence for the location of the so-sought-after (42+) ,(62+) , and (81+) seniority states is provided. As well, the existence of a low-spin β -decaying isomer in odd-odd neutron-rich Co isotopes is confirmed for mass A =72 . The new experimental information is compared to simple shell-model calculations including only neutron excitations across the f p g shells. It is shown that, in general, the calculations reproduce well the observed states.

  17. Parametric excitation of magnetization by electric field

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Jin; Lee, Han Kyu; Verba, Roman; Katine, Jordan; Tiberkevich, Vasil; Slavin, Andrei; Barsukov, Igor; Krivorotov, Ilya

    Manipulation of magnetization by electric field is of primary importance for development of low-power spintronic devices. We present the first experimental demonstration of parametric generation of magnetic oscillations by electric field. We realize the parametric generation in CoFeB/MgO/SAF nanoscale magnetic tunnel junctions (MTJs). The magnetization of the free layer is perpendicular to the sample plane while the magnetizations of the synthetic antiferromagnet (SAF) lie in the plane. We apply microwave voltage to the MTJ at 2 f, where f is the ferromagnetic resonance frequency of the free layer. In this configuration, the oscillations can only be driven parametrically via voltage-controlled magnetic anisotropy (VCMA) whereby electric field across the MgO barrier modulates the free layer anisotropy. The parametrically driven oscillations are detected via microwave voltage from the MTJ near f and show resonant character, observed only in a narrow range of drive frequencies near 2 f. The excitation also exhibits a well-pronounced threshold drive voltage of approximately 0.1 Volts. Our work demonstrates a low threshold for parametric excitation of magnetization by VCMA that holds promise for the development of energy-efficient nanoscale spin wave devices.

  18. Spatiotemporal Patterns in Excitable and Self - Media

    NASA Astrophysics Data System (ADS)

    Zou, Xiaoqin

    The formation of spatiotemporal patterns is studied in excitable and self-oscillatory media. Two systems are considered in detail: oxidation of CO over catalyst surfaces and propagation of cardiac action potentials. In the first case, several wave patterns are investigated, including traveling waves and spiral waves on a polycrystalline substrate at atmospheric pressure, and standing waves on a single crystal surface at low pressure. Specifically, the dispersion relation and linear stability are analyzed for traveling waves, and selection rules of frequency and wavelength are obtained for spirals. A possible mechanism for the formation of standing waves is also proposed, that of a self-induced parametric driving. In the cardiac case, reentrant spiral waves are examined from two different perspectives. First, the interaction between a drifting spiral and defects is studied numerically by modeling the myocardium as a simple excitable medium. Here, trapping by defects will sustain a permanent reentrant spiral. Second, the instability of spiral waves is analyzed indirectly by investigating electrical wave propagation along a ring. A coupled discrete map reduced from a electrophyiological model shows that a 1D (almost) period-doubling instability is closely related to 2D spiral breakup.

  19. Lifetime of the Excited State In Vivo

    PubMed Central

    Govindjee; Hammond, J. H.; Merkelo, H.

    1972-01-01

    Lifetime of the excited state (τ) of bacteriochlorophyll (BChl) in photosynthetic bacteria, measured with a mode-locked argon laser (oscillating at 488 nm; mode locked at 56 MHz) as light source, ranged from 0.3 to 2.5 nsec. These τ values are reported with a precision of ±0.1 nsec. The value of τ at high exciting light intensity (I) was two to three times that at low intensity. For young cultures of green bacterium Chloropseudomonas ethylicum, τ ranged from 0.5 (low I) to 1.0 nsec (high I); for those of the purple bacterium Rhodospirillum rubrum, from 0.4 (low I) to 1.0 nsec (high I); and for those of the BChl b-containing Rhodopseudomonas viridis, from 1.0 (low I) to 2.5 nsec (high I). These data provide information regarding the efficiencies of the photochemical process in these bacteria. Quantum yield (ø) of BChl fluorescence, calculated from ø = τ/τ0 (where τ0 is the intrinsic lifetime of fluorescence), ranges from 2-6% at low intensities to 6-14% at high intensities. PMID:4624833

  20. VIBRATIONALLY EXCITED C{sub 6}H

    SciTech Connect

    Gottlieb, C. A.; McCarthy, M. C.; Thaddeus, P.

    2010-08-15

    Rotational spectra of the linear carbon chain radical C{sub 6}H in two low-lying excited vibrational states were observed both at millimeter wavelengths in a low-pressure glow discharge and at centimeter wavelengths in a supersonic molecular beam. Two series of harmonically related lines with rotational constants within 0.3% of the {sup 2{Pi}} ground state were assigned to the {sup 2{Sigma}} and {sup 2{Delta}} vibronic components of an excited bending vibrational level. Measurements of the intensities of the lines in the glow discharge indicate that the {sup 2{Sigma}} component lies very close to ground, but the {sup 2{Delta}} component is much higher in energy. The standard Hamiltonian for an isolated {sup 2{Delta}} state with five spectroscopic constants reproduces the observed rotational spectrum, but several high-order distortion terms in the spin-rotation interaction are needed to reproduce the spectrum of the {sup 2{Sigma}} component in C{sub 6}H and C{sub 6}D. The derived spectroscopic constants allow astronomers to calculate the rotational spectra of the {sup 2{Sigma}} and {sup 2{Delta}} states up to 260 GHz to within 0.1 km s{sup -1} or better in equivalent radial velocity.

  1. Imaging Cracks by Laser Excited Thermography

    NASA Astrophysics Data System (ADS)

    Schlichting, J.; Kervalishvili, G. N.; Maierhofer, Ch.; Kreutzbruck, M.

    2010-02-01

    During the last years active thermography is increasingly used in a number of NDT problems in production and maintenance. In this work we focus on the detection of vertical cracks starting at the surface, which is an important indication of structural failure. By using local thermal excitation it is possible to image anisotropies in the lateral diffusivity by recording the temporal temperature data with an infrared camera. The regional transient behaviour of temperature distribution then can provide quantitative information of the crack parameter. In doing so, we present an advanced technique for the determination of the crack depth. The experimental set-up is based on an Nd:YAG laser. The beam is focused on the test sample by using an optical scanner to create the required lateral heat flow. The time resolved temperature distribution is recorded with an infrared camera (InSb FPA, 3 to 5 μm) providing a frame rate of up to 500 Hz. In addition we report on numerical simulation to investigate the concept of local heat excitation for a quantitative estimation of crack parameters. The modeling also includes the influence of surface to surface radiation inside the crack. We obtained a good consistency between experimental and theoretical data.

  2. Vertical Distribution of Vibrationally Excited Hydroxyl

    NASA Astrophysics Data System (ADS)

    Grygalashvyly, Mykhaylo; Becker, Erich; Sonnemann, Gerd

    2016-04-01

    Knowledge about the vertical distribution of the vibrationally excited states of hydroxyl (OH*) is important for the interpretation of airglow measurements with respect to dynamical processes in the mesopause region. We derive an approximate analytical expression for the distribution of OH* that highlights the dependence on atomic oxygen and temperature. In addition, we use an advanced numerical model for the formation and relaxation of OH* and investigate the distributions of the different vibrationally exited states of OH*. For the production of OH*, the model includes the reaction of atomic hydrogen with ozone, as well as the reaction of atomic oxygen with hydroperoxy radicals. As loss processes we include 1) deactivation by atomic oxygen, molecular oxygen, and molecular nitrogen, 2) spontaneous emission, and 3) loss due to chemical reaction with atomic oxygen. All these processes take the dependence on the vibrational number into account. The quenching by molecular and atomic oxygen is parameterized by a multi-quantum relaxation scheme. This diagnostic model for OH* has been implemented as part of a chemistry-transport model that is driven by the dynamics simulated with the KMCM (Kühlungsborn Mechanistic general Circulation Model). Numerical results confirm that emission from excited states with higher vibrational number is weaker and emanates from higher altitudes. In addition we find that the OH*-peak altitudes depend significantly on season and latitude. This behavior is mainly controlled by the corresponding variations of atomic oxygen and temperature, as is also confirmed by the aforementioned approximate theory.

  3. Motor cortex excitability in vascular depression.

    PubMed

    Bella, Rita; Ferri, Raffaele; Cantone, Mariagiovanna; Pennisi, Manuela; Lanza, Giuseppe; Malaguarnera, Giulia; Spampinato, Concetto; Giordano, Daniela; Raggi, Alberto; Pennisi, Giovanni

    2011-12-01

    The aim of this study was to evaluate excitatory/inhibitory intracortical circuit changes in patients with vascular depression, and whether there are any interhemispheric differences of motor cortical excitability. Fifteen vascular depressed elderly (VD), ten nondepressed subcortical vascular disease patients (SVD) and ten age-matched controls underwent bilateral motor threshold and paired-pulse studies. They were also assessed for their brain vascular burden at MRI and neuropsychological profile. Executive dysfunction and apathy were significantly higher in VD; we were unable to find significant differences in resting motor threshold, cortical silent period and paired-pulse curves between VD, SVD and controls, and between the two hemispheres in the VD group. Our findings might suggest that neurophysiological mechanisms underlying VD differ from those previously reported in Major Depression (reduced excitability in the left hemisphere) and seem to be similar to those of patients with SVD. Our findings also, support the "vascular depression" hypothesis, suggesting that in VD patients the depressive syndrome is not the primary disease but can be considered as one of the clinical manifestations in the wide symptom spectrum of the cerebral small vessel disease.

  4. Dissociative excitation study of iron pentacarbonyl molecule

    NASA Astrophysics Data System (ADS)

    Ribar, Anita; Danko, Marián; Országh, Juraj; Ferreira da Silva, Filipe; Utke, Ivo; Matejčík, Štefan

    2015-04-01

    The processes of dissociative excitation (DE) and dissociative ionisation with excitation (DIE) of iron pentacarbonyl, Fe(CO)5, have been studied using a crossed electron-molecule beam experimental apparatus (Electron Induced Fluorescence Apparatus, EIFA). Using EIFA we were able to record the emission spectrum of the molecule in the UV-VIS range, as well as the photon efficiency curves initiated by electron impact. The emission spectrum of Fe(CO)5 initiated by impact of 50 eV electrons was recorded in the spectral range between 200 nm and 470 nm. It shows a high density of emission lines and bands (mainly iron lines and carbonyl bands). Additionally, we have measured photon efficiency curves (PECs) as a function of the electron impact energy for several lines and bands. On the basis of the PECs we have discussed the reaction mechanism and the energetics of the reactions associated with the DE and DIE processes. Contribution to the Topical Issue "Elementary Processes with Atoms and Molecules in Isolated and Aggregated States", edited by Friedrich Aumayr, Bratislav Marinkovic, Štefan Matejčík, John Tanis and Kurt H. Becker.

  5. Two-photon excitation energy transfer microscopy

    NASA Astrophysics Data System (ADS)

    Periasamy, Ammasi

    2000-04-01

    Fluorescence resonance energy transfer (FRET) imaging is a unique tool used to visualize the spaciotemporal dynamics of protein-protein interactions in living cells. We used FRET to study the dimerization of the pituitary-specific transcription factor of Pit-1 fused with blue flourescent protein and green fluorescent protein. Transcriptional activity of the GFP- and BFP-Pit-1 fusion proteins was demonstrated by their ability to activate the prolactin gene promoter. The energy transfer in the conventional fluorescence microscopy was less efficient due to photobleaching of the BFP-Pit-1 donor molecules. In our studies we developed two-photon excitation energy transfer microscopy, where the photobleaching of blue flourescent protein was considerably reduced. This 2p-FRET imaging system was used to acquire the donor and acceptor images for a living HeLa cell nucleus. We selected 732 nm from the tunable Verdi pumped ti:sapphire laser, in a way that only excites the BFP-Pit-1 and not the GFP-Pit-1 proteins. The efficiency of the 2p-FRET signal increased to 30 percent compared to the conventional FRET imaging, which clearly demonstrates that there is considerable reduction in photobleaching of donor molecules in the 2p-FRET microscopy.

  6. Dual excitation acoustic paramagnetic logging tool

    DOEpatents

    Vail, W.B. III.

    1989-02-14

    New methods and apparatus are disclosed which allow measurement of the presence of oil and water in geological formations using a new physical effect called the Acoustic Paramagnetic Logging Effect (APLE). The presence of petroleum in formation causes a slight increase in the earth's magnetic field in the vicinity of the reservoir. This is the phenomena of paramagnetism. Application of an acoustic source to a geological formation at the Larmor frequency of the nucleons present causes the paramagnetism of the formation to disappear. This results in a decrease in the earth's magnetic field in the vicinity of the oil bearing formation. Repetitively frequency sweeping the acoustic source through the Larmor frequency of the nucleons present (approx. 2 kHz) causes an amplitude modulation of the earth's magnetic field which is a consequence of the APLE. The amplitude modulation of the earth's magnetic field is measured with an induction coil gradiometer and provides a direct measure of the amount of oil and water in the excitation zone of the formation. The phase of the signal is used to infer the longitudinal relaxation times of the fluids present, which results in the ability in general to separate oil and water and to measure the viscosity of the oil present. Such measurements may be performed in open boreholes and in cased well bores. The Dual Excitation Acoustic Paramagnetic Logging Tool employing two acoustic sources is also described. 6 figs.

  7. Solvation of electronically excited I2 -

    NASA Astrophysics Data System (ADS)

    Maslen, P. E.; Papanikolas, J. M.; Faeder, J.; Parson, R.; ONeil, S. V.

    1994-10-01

    The interaction potentials between the six lowest electronic states of I-2 and an arbitrary discrete charge distribution are calculated approximately using a one-electron model. The model potentials are much easier to calculate than ab initio potentials, with the cost of a single energy point scaling linearly with the number of solvent molecules, enabling relatively large systems to be studied. Application of the model to simulation of electronically excited I-2 in liquids and CO2 clusters is discussed. In a preliminary application, solvent effects are approximated by a uniform electric field. If electronically excited (2Πg,1/2) I-2 undergoes dissociation in the presence of a strong electric field, the negative charge localizes so as to minimize the total potential energy. However, in a weak field the negative charge localizes in the opposite direction, maximizing the potential energy. Based on a study of the field-dependent potential surfaces, a solvent-transfer mechanism is proposed for the electronic relaxation of 2Πg,1/2I-2, in contrast to the conventional view of relaxation via electron transfer.

  8. Force Sensor Characterization Under Sinusoidal Excitations

    PubMed Central

    Medina, Nieves; de Vicente, Jesús

    2014-01-01

    The aim in the current work is the development of a method to characterize force sensors under sinusoidal excitations using a primary standard as the source of traceability. During this work the influence factors have been studied and a method to minimise their contributions, as well as the corrections to be performed under dynamic conditions have been established. These results will allow the realization of an adequate characterization of force sensors under sinusoidal excitations, which will be essential for its further proper use under dynamic conditions. The traceability of the sensor characterization is based in the direct definition of force as mass multiplied by acceleration. To do so, the sensor is loaded with different calibrated loads and is maintained under different sinusoidal accelerations by means of a vibration shaker system that is able to generate accelerations up to 100 m/s2 with frequencies from 5 Hz up to 2400 Hz. The acceleration is measured by means of a laser vibrometer with traceability to the units of time and length. A multiple channel data acquisition system is also required to simultaneously acquire the electrical output signals of the involved instrument in real time. PMID:25290287

  9. Electromagnetic excitation of the Delta(1232) resonance

    SciTech Connect

    V. Pascalutsa; M. Vanderhaeghen; Shin Nan Yang

    2006-09-05

    We review the description of the lowest-energy nucleon excitation--the Delta(1232)-resonance. Much of the recent effort has been focused on the precision measurements of the nucleon to Delta transition by means of electromagnetic probes. We review the results of those measurements and confront them with the state-of-the-art calculations based on chiral effective-field theories (EFT), lattice QCD, and QCD-inspired models. Some of the theoretical approaches are reviewed in detail. In particular, we describe the chiral EFT of QCD in the energy domain of the Delta-resonance, and its applications to the electromagnetic nucleon-to-Delta transition (gamma N Delta). We also describe the recent dynamical and unitary-isobar models of pion electroproduction which are extensively used in the extraction of the gamma* N Delta form factors from experiment. Furthermore, we discuss the link of the gamma* N Delta form factors to generalized parton distributions (GPDs), as well as the predictions of perturbative QCD for these transition form factors. The present status of understanding the Delta-resonance properties and the nature of its excitation is summarized.

  10. Spin excitations of weakly coupled magnetic atoms

    NASA Astrophysics Data System (ADS)

    Goldberg, E. C.; Flores, F.

    2015-04-01

    A theoretical description of the measured differential conductance through magnetic atoms on a C u2N /Cu ( 100 ) substrate is presented [Otte et al., Phys. Rev. Lett. 103, 107203 (2009), 10.1103/PhysRevLett.103.107203]. In particular, we analyze the case of a weakly coupled Co/ Fe dimer. The starting point of our model is an ionic Hamiltonian which describes the inelastic electron tunneling excitations and the Kondo resonances as due to atomic spin fluctuations associated with electron cotunneling processes in the tip-atom-surface system. The interaction terms of this Hamiltonian are written in the basis set of the eigenstates of the atomic part, which in the present case includes the crystalline and Zeeman fields and also, a Heisenberg exchange coupling between the two spins. The appropriate Green's functions that define the differential conductance spectra are calculated by means of the equation-of-motion method. We obtain, in this form, a very satisfactory description of the overall experimental findings related to the behavior of the spin state excitations and Kondo resonance structures in the presence of an applied magnetic field.

  11. Ocean tidal excitation of polar motion

    NASA Technical Reports Server (NTRS)

    Sanchez, B. V.

    1979-01-01

    An investigation was conducted to ascertain the response of the rotational motion of the earth to forcing functions produced by the water mass redistribution due to the ocean tides. In particular, the components of displacement of the rotation axis at the surface of the Earth were obtained. The investigation also addressed the larger question concerning the possibility of excitation of the Chandler wobble of the earth. In general, the results show the existence of a polar wobble as a response to each of the components of the ocean tides. The magnitude of the polar displacement depends on two factors: the amplitude of the tidal component and its period. The maximum periodic contributions are: the Doodson's component number 055.565 with a period of 18.613 years and 50 cm of polar displacement, the annual component 056.544 with 37 cm of polar displacement and the semi-annual 057.555 with 32 cm. The tidal components with daily and semi-daily periods yield very small polar displacements of the order of 0.01 cm. The combined effect of all the periodic components can yield as much as 90 cm of pole displacements. The changes produced by the ocean tides in the products of inertia are periodic and regular, therefore, they cannot be the source of excitation of the Chandler wobble.

  12. Improved Underwater Excitation-Emission Matrix Fluorometer

    NASA Technical Reports Server (NTRS)

    Moore, Casey; daCunha, John; Rhoades, Bruce; Twardowski, Michael

    2007-01-01

    A compact, high-resolution, two-dimensional excitation-emission matrix fluorometer (EEMF) has been designed and built specifically for use in identifying and measuring the concentrations of organic compounds, including polluting hydrocarbons, in natural underwater settings. Heretofore, most EEMFs have been designed and built for installation in laboratories, where they are used to analyze the contents of samples collected in the field and brought to the laboratories. Because the present EEMF can be operated in the field, it is better suited to measurement of spatially and temporally varying concentrations of substances of interest. In excitation-emission matrix (EEM) fluorometry, fluorescence is excited by irradiating a sample at one or more wavelengths, and the fluorescent emission from the sample is measured at multiple wavelengths. When excitation is provided at only one wavelength, the technique is termed one-dimensional (1D) EEM fluorometry because the resulting matrix of fluorescence emission data (the EEM) contains only one row or column. When excitation is provided at multiple wavelengths, the technique is termed two-dimensional (2D) EEM fluorometry because the resulting EEM contains multiple rows and columns. EEM fluorometry - especially the 2D variety - is well established as a means of simultaneously detecting numerous dissolved and particulate compounds in water. Each compound or pool of compounds has a unique spectral fluorescence signature, and each EEM is rich in information content, in that it can contain multiple fluorescence signatures. By use of deconvolution and/or other mixture-analyses techniques, it is often possible to isolate the spectral signature of compounds of interest, even when their fluorescence spectra overlap. What distinguishes the present 2D EEMF over prior laboratory-type 2D EEMFs are several improvements in packaging (including a sealed housing) and other aspects of design that render it suitable for use in natural underwater

  13. Low-Pressure Microwave Excited Microplasmas as Sources of VUV Photons and Metastable Excited Atoms: Modeling

    NASA Astrophysics Data System (ADS)

    Kushner, Mark; Cooley, James; Xue, Jun; Urdhal, Randall

    2011-10-01

    Low pressure plasmas sustained in rare gases and rare gas mixtures can be efficient sources of VUV light from resonant optical transitions. Many applications would benefit from having small, inexpensive sources of plasma produced VUV light. To address this need, microwave wave excited microplasma sources in rare gases operating at pressures of <10 Torr are being developed. The microplasmas are sustained in ceramic cavities having cross sectional dimensions of <=1 mm, excited by a split-ring resonator antenna operated at 2.45 GHz. Power deposition is a few W. Hybrid computer modeling of microplasmas sustained in Ar has been performed to develop scaling laws for increasing the efficiency of VUV light production. The model includes a Monte Carlo simulation for the electron energy distribution and for radiation transport. Results from those studies will be discussed for plasma densities, electron energy distributions, VUV light production and excited state densities as a function of power, pressure and aspect ratio of the microplasma cavities. Modeling results will be compared to laser absorption spectroscopy of Ar excited state densities. Work supported by Agilent Technologies.

  14. Excitation rate dependence of Auger recombination in silicon

    NASA Astrophysics Data System (ADS)

    Hopkins, Patrick E.; Barnat, Edward V.; Cruz-Campa, Jose L.; Grubbs, Robert K.; Okandan, Murat; Nielson, Gregory N.

    2010-03-01

    This work reports on measurements of the Auger recombination coefficients in silicon wafers with pump-probe thermoreflectance techniques operating at two different excitation rates: 250 kHz (low repetition rate) and 80 MHz (high repetition rate). The different excitation frequencies give rise to different thermoreflectance signals in the Si samples, which is ascribed to the excited number density in the conduction band. In the low repetition rate case, the excited carriers recombine via Auger processes before the next pump excitation is absorbed. However, in the high repetition rate case, the rate in which the pump excitations are absorbed at the sample surface is higher than the Auger recombination rate, indicating that the excited carrier densities in the high repetition rate experiments are much higher than in the low repetition rate measurements even though the pump fluences are comparable. This is ascribed to pulse accumulation in the high repetition rate measurements, and is quantified with rate equation and thermoreflectance models fit to the experimental data. Comparing the data taken at the two different excitation modulations gives insight into the excited carrier density when recombination rate are on the same order as excitation frequencies.

  15. Unstable resonators with excited converging wave

    SciTech Connect

    Hodgson, N. ); Weber, H. )

    1990-04-01

    This paper reports the properties of unstable resonators with an additional mirror inside or outside the resonator investigated, both experimentally and theoretically. The additional mirror excites the converging wave, and by this, output coupling is decreased without affecting beam quality. Experiments were performed with a pulsed Nd:YAG system. The theoretical model was based on the coupled Kirchhoff integrals and solved numerically. Agreement between theory and experiments indicates that this kind of resonator provides high focusability and maximum extraction efficiency simultaneously, even with low-gain media. This enables one to apply unstable resonators to solid-state lasers with low small-signal gain, like alexandrite or CW-pumped Nd:YAG.

  16. Small massless excitations against a nontrivial background

    NASA Astrophysics Data System (ADS)

    Khariton, N. G.; Svetovoy, V. B.

    1994-03-01

    We propose a systematic approach for finding bosonic zero modes of nontrivial classical solutions in a gauge theory. The method allows us to find all the modes connected with the broken space-time and gauge symmetries. The ground state is supposed to be dependent on some space coordinates yα and independent of the rest of the coordinates xi. The main problem which is solved is how to construct the zero modes corresponding to the broken xiyα rotations in vacuum and which boundary conditions specify them. It is found that the rotational modes are typically singular at the origin or at infinity, but their energy remains finite. They behave as massless vector fields in x space. We analyze local and global symmetries affecting the zero modes. An algorithm for constructing the zero mode excitations is formulated. The main results are illustrated in the Abelian Higgs model with the string background.

  17. Excited state baryon spectroscopy from lattice QCD

    DOE PAGESBeta

    Robert G. Edwards; Dudek, Jozef J.; Richards, David G.; Wallace, Stephen J.

    2011-10-31

    Here, we present a calculation of the Nucleon and Delta excited state spectrum on dynamical anisotropic clover lattices. A method for operator construction is introduced that allows for the reliable identification of the continuum spins of baryon states, overcoming the reduced symmetry of the cubic lattice. Using this method, we are able to determine a spectrum of single-particle states for spins up to and including $J = 7/2$, of both parities, the first time this has been achieved in a lattice calculation. We find a spectrum of states identifiable as admixtures of $SU(6) Ⓧ O(3)$ representations and a counting ofmore » levels that is consistent with the non-relativistic $qqq$ constituent quark model. This dense spectrum is incompatible with quark-diquark model solutions to the "missing resonance problem" and shows no signs of parity doubling of states.« less

  18. Independent optical excitation of distinct neural populations.

    PubMed

    Klapoetke, Nathan C; Murata, Yasunobu; Kim, Sung Soo; Pulver, Stefan R; Birdsey-Benson, Amanda; Cho, Yong Ku; Morimoto, Tania K; Chuong, Amy S; Carpenter, Eric J; Tian, Zhijian; Wang, Jun; Xie, Yinlong; Yan, Zhixiang; Zhang, Yong; Chow, Brian Y; Surek, Barbara; Melkonian, Michael; Jayaraman, Vivek; Constantine-Paton, Martha; Wong, Gane Ka-Shu; Boyden, Edward S

    2014-03-01

    Optogenetic tools enable examination of how specific cell types contribute to brain circuit functions. A long-standing question is whether it is possible to independently activate two distinct neural populations in mammalian brain tissue. Such a capability would enable the study of how different synapses or pathways interact to encode information in the brain. Here we describe two channelrhodopsins, Chronos and Chrimson, discovered through sequencing and physiological characterization of opsins from over 100 species of alga. Chrimson's excitation spectrum is red shifted by 45 nm relative to previous channelrhodopsins and can enable experiments in which red light is preferred. We show minimal visual system-mediated behavioral interference when using Chrimson in neurobehavioral studies in Drosophila melanogaster. Chronos has faster kinetics than previous channelrhodopsins yet is effectively more light sensitive. Together these two reagents enable two-color activation of neural spiking and downstream synaptic transmission in independent neural populations without detectable cross-talk in mouse brain slice.

  19. Interchange mode excited by trapped energetic ions

    SciTech Connect

    Nishimura, Seiya

    2015-07-15

    The kinetic energy principle describing the interaction between ideal magnetohydrodynamic (MHD) modes with trapped energetic ions is revised. A model is proposed on the basis of the reduced ideal MHD equations for background plasmas and the bounce-averaged drift-kinetic equation for trapped energetic ions. The model is applicable to large-aspect-ratio toroidal devices. Specifically, the effect of trapped energetic ions on the interchange mode in helical systems is analyzed. Results show that the interchange mode is excited by trapped energetic ions, even if the equilibrium states are stable to the ideal interchange mode. The energetic-ion-induced branch of the interchange mode might be associated with the fishbone mode in helical systems.

  20. Excited state baryon spectroscopy from lattice QCD

    SciTech Connect

    Edwards, Robert G.; Richards, David G.; Dudek, Jozef J.; Wallace, Stephen J.

    2011-10-01

    We present a calculation of the Nucleon and Delta excited state spectra on dynamical anisotropic clover lattices. A method for operator construction is introduced that allows for the reliable identification of the continuum spins of baryon states, overcoming the reduced symmetry of the cubic lattice. Using this method, we are able to determine a spectrum of single-particle states for spins up to and including J=(7/2), of both parities, the first time this has been achieved in a lattice calculation. We find a spectrum of states identifiable as admixtures of SU(6) x O(3) representations and a counting of levels that is consistent with the nonrelativistic qqq constituent quark model. This dense spectrum is incompatible with quark-diquark model solutions to the 'missing resonance problem' and shows no signs of parity doubling of states.

  1. Excited state baryon spectroscopy from lattice QCD

    SciTech Connect

    Robert G. Edwards; Dudek, Jozef J.; Richards, David G.; Wallace, Stephen J.

    2011-10-31

    Here, we present a calculation of the Nucleon and Delta excited state spectrum on dynamical anisotropic clover lattices. A method for operator construction is introduced that allows for the reliable identification of the continuum spins of baryon states, overcoming the reduced symmetry of the cubic lattice. Using this method, we are able to determine a spectrum of single-particle states for spins up to and including $J = 7/2$, of both parities, the first time this has been achieved in a lattice calculation. We find a spectrum of states identifiable as admixtures of $SU(6) Ⓧ O(3)$ representations and a counting of levels that is consistent with the non-relativistic $qqq$ constituent quark model. This dense spectrum is incompatible with quark-diquark model solutions to the "missing resonance problem" and shows no signs of parity doubling of states.

  2. Chemical composition of high-excitation planetaries.

    PubMed

    Aller, L H; Czyzak, S J

    1981-09-01

    Nebular spectral line intensities measured mostly in the optical region, but also in the IR and satellite UV (where possible), are used to derive plasma diagnostics and ionic concentrations n (X(i))/n(H(+)). Then, we use theoretical nebular models to represent as closely as possible certain excitation-sensitive line ratios of HeII/HeI, [OIII]/[OII], and [NeIII]/[NeV]. Also, we try to reproduce the line intensities themselves. These models are used as devices to allow for unobserved ionization stages. Although He, C, and N show significant variations among different nebulae, heavier elements such as O, and probably Ne, S, Cl, and Ar are more nearly constant, suggesting that progenitor stars underwent nuclear transformations in their interiors that affected C and N but not heavier elements. PMID:16593076

  3. Photonic simulation of topological excitations in metamaterials.

    PubMed

    Tan, Wei; Sun, Yong; Chen, Hong; Shen, Shun-Qing

    2014-01-23

    Condensed matter systems with topological order and metamaterials with left-handed chirality have attracted recently extensive interests in the fields of physics and optics. So far the topological order and chirality of electromagnetic wave are two independent concepts, and there is no work to address their connection. Here we propose to establish the relation between the topological order in condensed matter systems and the chirality in metamaterials, by mapping explicitly Maxwell's equations to the Dirac equation in one dimension. We report an experimental implement of the band inversion in the Dirac equation, which accompanies change of chirality of electromagnetic wave in metamaterials, and the first microwave measurement of topological excitations and topological phases in one dimension. Our finding provides a proof-of-principle example that electromagnetic wave in the metamaterials can be used to simulate the topological order in condensed matter systems and quantum phenomena in relativistic quantum mechanics in a controlled laboratory environment.

  4. Photonic simulation of topological excitations in metamaterials

    PubMed Central

    Tan, Wei; Sun, Yong; Chen, Hong; Shen, Shun-Qing

    2014-01-01

    Condensed matter systems with topological order and metamaterials with left-handed chirality have attracted recently extensive interests in the fields of physics and optics. So far the topological order and chirality of electromagnetic wave are two independent concepts, and there is no work to address their connection. Here we propose to establish the relation between the topological order in condensed matter systems and the chirality in metamaterials, by mapping explicitly Maxwell's equations to the Dirac equation in one dimension. We report an experimental implement of the band inversion in the Dirac equation, which accompanies change of chirality of electromagnetic wave in metamaterials, and the first microwave measurement of topological excitations and topological phases in one dimension. Our finding provides a proof-of-principle example that electromagnetic wave in the metamaterials can be used to simulate the topological order in condensed matter systems and quantum phenomena in relativistic quantum mechanics in a controlled laboratory environment. PMID:24452532

  5. Collective excitations and dust particles in space

    NASA Technical Reports Server (NTRS)

    Gilra, D. P.

    1972-01-01

    It is shown that observed bands at 2200 A and in the 10 micron region are most probably due to collective excitations of dust particles. The following specific conclusions are drawn: (1) the 2200 A interstellar band is very likely due to graphite particles; (2) these graphite particles should be very small, approximately spherical, and should have no coating whatsoever; (3) the identification of circumstellar and interstellar silicates from the observations in the 10 micron region does not seem to be correct; (4) very valuable information about the shape of the circumstellar and interstellar dust particles can be obtained directly from observations; and (5) narrow band polarization measurements in the spectral regions of these bands will be very helpful in determining the shape of the particles.

  6. Photoacoustic excitation profiles of gold nanoparticles.

    PubMed

    Feis, Alessandro; Gellini, Cristina; Salvi, Pier Remigio; Becucci, Maurizio

    2014-03-01

    The wavelength dependence of the laser-induced photoacoustic signal amplitude has been measured for water dispersions of 10, 61, and 93 nm diameter gold nanospheres. The whole region of the localized surface plasmon resonance has been covered. This "photoacoustic excitation profile" can be overlayed with the extinction spectrum between 450 nm and 600 nm in the case of the smallest nanoparticles. At variance, the larger-sized nanoparticles display a progressive deviation from the extinction spectrum at longer wavelength, where the photoacoustic signal becomes relatively smaller. Considering that photoacoustics is intrinsically insensitive to light scattering, at least for optically thin samples, the results are in agreement with previous theoretical work predicting (i) an increasing contribution of scattering to extinction when the nanoparticle size increases and (ii) a larger scattering component at longer wavelengths. Therefore, the method has a general validity and can be applied to selectively determine light absorption by plasmonic systems.

  7. The decay of highly excited open strings

    NASA Technical Reports Server (NTRS)

    Mitchell, D.; Turok, N.; Wilkinson, R.; Jetzer, P.

    1988-01-01

    The decay rates of leading edge Regge trajectory states are calculated for very high level number in open bosonic string theories, ignoring tachyon final states. The optical theorem simplifies the analysis while enabling identification of the different mass level decay channels. The main result is that (in four dimensions) the greatest single channel is the emission of a single photon and a state of the next mass level down. A simple asymptotic formula for arbitrarily high level number is given for this process. Also calculated is the total decay rate exactly up to N=100. It shows little variation over this range but appears to decrease for larger N. The formalism is checked in examples and the decay rate of the first excited level calculated for open superstring theories. The calculation may also have implications for high spin meson resonances.

  8. Chemotaxis to Excitable Waves in Dictyostelium Discoideum

    NASA Astrophysics Data System (ADS)

    Bhowmik, Arpan; Rappel, Wouter-Jan; Levine, Herbert

    In recent years, there have been significant advances in our understanding of the mechanisms underlying chemically directed motility by eukaryotic cells such as Dictyostelium. In particular, the LEGI model has proven capable of providing a framework for quantitatively explaining many experiments that present Dictyostelium cells with tailored chemical stimuli and monitor their subsequent polarization. Here, we couple the LEGI approach to an excitable medium model of the cAMP wave-field that is self-generated by the cells and investigate the extent to which this class of models enables accurate chemotaxis to the cAMP waveforms expected in vivo. Our results indicate that the ultra-sensitive version of the model does an excellent job in providing natural wave rectification, thereby providing a compelling solution to the ``back-of-the-wave paradox'' during cellular aggregation. This work was supported by National Institutes of Health Grant P01 GM078586.

  9. Photoionization from excited states of helium

    NASA Technical Reports Server (NTRS)

    Jacobs, V. L.

    1973-01-01

    The cross sections for photoionization from the 2 1S, 2 3S, 2 1P and 2 3P excited states of helium are calculated for photoelectron energies below the n = 2 threshold of He(+) using Hylleraas bound state wave functions and 1s-2s-2p close coupling final state wave functions. The resonant structures associated with the lowest-lying 1S, 1P, 3P, and 1D autoionizing states of helium are found to be characterized by large values of the line profile parameter q. The cross sections and the photoelectron angular distribution asymmetry parameters for the P-states are calculated for various polarization states of the target atom and the incident photon. Experiments which would lead to the separate determinations of the S- and D- wave partial photoionization cross sections are discussed.

  10. Fission dynamics at low excitation energy

    NASA Astrophysics Data System (ADS)

    Aritomo, Y.; Chiba, S.; Ivanyuk, F.

    2014-11-01

    The mass asymmetry in the fission of 236U at low excitation energy is clarified by the analysis of the trajectories obtained by solving the Langevin equations for the shape degrees of freedom. It is demonstrated that the position of the peaks in the mass distribution of fission fragments is determined mainly by the saddle point configuration originating from the shell correction energy. The width of the peaks, on the other hand, results from the shape fluctuations close to the scission point caused by the random force in the Langevin equation. We have found out that the fluctuations between elongated and compact shapes are essential for the fission process. According to our results the fission does not occur with continuous stretching in the prolate direction, similarly to that observed in starch syrup, but is accompanied by the fluctuations between elongated and compact shapes. This picture presents a new viewpoint of fission dynamics and the splitting mechanism.

  11. Microtaper fiber excitation effects in bottle microresonators

    NASA Astrophysics Data System (ADS)

    Mohd Nasir, M. Narizee; Ding, Ming; Murugan, G. Senthil; Zervas, Michalis N.

    2013-03-01

    We have carried out a systematic study of the effect of microtaper diameter on the spectral characteristics of bottle microresonators. By increasing the microtaper-diameter (Dt) from 2μm to 10μm results in progressively cleaner spectra. The transmission depth at resonance varies from ~15dB (@Dt=2μm) to >3dB (@Dt=10μm). The loaded Q factors were measured to be >10+6 in all cases. However, with microtaper Dt=10μm clearly-resolved single resonance peaks could be observed and free-spectral ranges could be easily identified. At some transmission resonances, we have observed LP01-->LP11 mode transformation at the excitation microtaper waist, for the first time, as the resonance is scanned.

  12. Excitation of turbulence by density waves

    NASA Technical Reports Server (NTRS)

    Tichen, C. M.

    1985-01-01

    A nonlinear system describes the microdynamical state of turbulence that is excited by density waves. It consists of an equation of propagation and a master equation. A group-scaling generates the scaled equations of many interacting groups of distribution functions. The two leading groups govern the transport processes of evolution and eddy diffusivity. The remaining sub-groups represent the relaxation for the approach of diffusivity to equilibrium. In strong turbulence, the sub-groups disperse themselves and the ensemble acts like a medium that offers an effective damping to close the hierarchy. The kinetic equation of turbulence is derived. It calculates the eddy viscosity and identifies the effective damping of the assumed medium self-consistently. It formulates the coupling mechanism for the intensification of the turbulent energy at the expense of the wave energy, and the transfer mechanism for the cascade. The spectra of velocity and density fluctuations find the power law k sup-2 and k sup-4, respectively.

  13. Nanoparticles inside nanodishes for plasmon excitations

    NASA Astrophysics Data System (ADS)

    Wi, Jung-Sub; Son, Jin Gyeong; Han, Sang Woo; Lee, Tae Geol

    2015-11-01

    We demonstrate a simple route to hybridize two different nanomaterials by using three-dimensional nanodishes that can serve as small plasmonic containers to host guest nanoparticles. The nanodishes were fabricated using nanoimprint lithography and oblique-angle film deposition, and the guest nanoparticles were drop-cast onto the host nanodishes. Based on the proposed method, colloidal Au nanoparticles were assembled inside the Au nanodishes in the form of a labyrinth. These Au nanoparticle-nanodish hybrids excited a strong surface plasmon resonance, as verified by a numerical simulation of the local field enhancement and by direct observation of both the enhanced Raman signals and photochemical reactions. Our results point to the potential of the nanodishes as a useful platform for combining diverse nanomaterials and their functionalities.

  14. Photoacoustic excitation profiles of gold nanoparticles☆

    PubMed Central

    Feis, Alessandro; Gellini, Cristina; Salvi, Pier Remigio; Becucci, Maurizio

    2014-01-01

    The wavelength dependence of the laser-induced photoacoustic signal amplitude has been measured for water dispersions of 10, 61, and 93 nm diameter gold nanospheres. The whole region of the localized surface plasmon resonance has been covered. This “photoacoustic excitation profile” can be overlayed with the extinction spectrum between 450 nm and 600 nm in the case of the smallest nanoparticles. At variance, the larger-sized nanoparticles display a progressive deviation from the extinction spectrum at longer wavelength, where the photoacoustic signal becomes relatively smaller. Considering that photoacoustics is intrinsically insensitive to light scattering, at least for optically thin samples, the results are in agreement with previous theoretical work predicting (i) an increasing contribution of scattering to extinction when the nanoparticle size increases and (ii) a larger scattering component at longer wavelengths. Therefore, the method has a general validity and can be applied to selectively determine light absorption by plasmonic systems. PMID:25302155

  15. Hadron collider potential for excited bosons search

    NASA Astrophysics Data System (ADS)

    Chizhov, M. V.; Boyko, I. R.; Bednyakov, V. A.; Budagov, J. A.

    2014-05-01

    The e + e - and μ+μ- dilepton final states are the most clear channels for a new heavy neutral resonance search. Their advantage is that usually in the region of expected heavy-mass resonance peak the main irreducible background, from the Standard Model Drell-Yan process, contributes two orders of magnitude smaller than the signal. In this paper we consider the future prospects for search for the excited neutral Z*-bosons. The bosons can be observed as a Breit-Wigner resonance peak in the dilepton invariant mass distributions in the same way as the well-known extra gauge Z' bosons. However, the Z* bosons have unique signatures in transverse momentum, angular and pseudorapidity distributions of the final leptons, which allow to distinguish them from the other heavy neutral resonances. At present only the ATLAS Collaboration has looked for such new excitations at the Large Hadron Collider and has published its results for 7 TeV collision energy. After successful comparison of our evaluation with these official results we present our estimations for the discovery potential and the exclusion limits on the Z*-boson search in pp collisions at higher centre-of-mass energies and different luminosities. In particular, LHC Run 2 can discover Z*-boson with its mass up to 5.3 TeV, while the High Luminosity LHC can extend that reach to 6.2 TeV. The High Energy LHC (with collision energy of 33 TeV) will be able to probe two times heavier resonance masses at the same integrated luminosities.

  16. Molecular excitation in the Eagle nebula's fingers

    NASA Astrophysics Data System (ADS)

    Schuller, F.; Leurini, S.; Hieret, C.; Menten, K. M.; Philipp, S. D.; Güsten, R.; Schilke, P.; Nyman, L.-Å.

    2006-08-01

    Context: .The M 16 nebula is a relatively nearby Hii region, powered by O stars from the open cluster NGC 6611, which borders to a Giant Molecular Cloud. Radiation from these hot stars has sculpted columns of dense obscuring material on a few arcmin scales. The interface between these pillars and the hot ionised medium provides a textbook example of a Photodissociation Region (PDR). Aims: .To constrain the physical conditions of the atomic and molecular material with submillimeter spectroscopic observations. Methods: .We used the APEX submillimeter telescope to map a ˜ 3'×3' region in the CO J= 3-2, 4-3 and 7-6 rotational lines, and a subregion in atomic carbon lines. We also observed C18O(3-2) and CO(7-6) with longer integrations on five peaks found in the CO(3-2) map. The large scale structure of the pillars is derived from the molecular lines' emission distribution. We estimate the magnitude of the velocity gradient at the tips of the pillars and use LVG modelling to constrain their densities and temperatures. Excitation temperatures and carbon column densities are derived from the atomic carbon lines. Results: .The atomic carbon lines are optically thin and excitation temperatures are of order 60 K to 100 K, well consistent with observations of other Hii region-molecular cloud interfaces. We derive somewhat lower temperatures from the CO line ratios, of order 40 K. The Ci/CO ratio is around 0.1 at the fingers tips.

  17. VIBRATIONALLY EXCITED C{sub 4}H

    SciTech Connect

    Cooksy, Andrew L.; Gottlieb, C. A.; Thaddeus, P.; Patel, Nimesh A.; Young, Ken H.; McCarthy, M. C.; Killian, T. C.

    2015-02-01

    Rotational spectra in four new excited vibrational levels of the linear carbon chain radical C{sub 4}H were observed in the millimeter band between 69 and 364 GHz in a low pressure glow discharge, and two of these were observed in a supersonic molecular beam between 19 and 38 GHz. All have rotational constants within 0.4% of the X{sup 2}Σ{sup +} ground vibrational state of C{sub 4}H and were assigned to new bending vibrational levels, two each with {sup 2}Σ and {sup 2}Π vibrational symmetry. The new levels are tentatively assigned to the 1ν{sub 6} and 1ν{sub 5} bending vibrational modes (both with {sup 2}Π symmetry), and the 1ν{sub 6}+1ν{sub 7} and 1ν{sub 5}+1ν{sub 6} combination levels ({sup 2}Σ symmetry) on the basis of the derived spectroscopic constants, relative intensities in our discharge source, and published laser spectroscopic and quantum calculations. Prior spectroscopic constants in the 1ν{sub 7} and 2ν{sub 7} levels were refined. Also presented are interferometric maps of the ground state and the 1ν{sub 7} level obtained with the Submillimeter Array (SMA) near 257 GHz which show that C{sub 4}H is present near the central star in IRC+10216. We found no evidence with the SMA for the new vibrationally excited levels of C{sub 4}H at a peak flux density averaged over a 3{sup ′′} synthesized beam of ⩾0.15 Jy/beam in the 294–296 and 304–306 GHz range, but it is anticipated that rotational lines in the new levels might be observed in IRC+10216 when ALMA attains its full design capability.

  18. Intramolecular energy transfer and excitation coupling in metal-to-ligand charge transfer (MLCT) excited states

    NASA Astrophysics Data System (ADS)

    Riesen, Hans; Krausz, Elmars

    1995-02-01

    Several new spectroscopic studies relating to the coupling and dynamics in the spin-forbidden 3MLCT excited states of the chromophores [Ru(bpy)3]2+ and [Os(bpy)3]2+ (bpy equals 2,2'-bipyridine) in the racemic crystal lattices [Ru(bpy)3](PF6)2, [Ru(bpy)3](ClO4)2 and [Zn(bpy)3](ClO4)2 are presented. In the first of these lattices there are three closely related chromophoric sites at low temperatures, each with trigonal (C3) symmetry. In the two, isomorphic perchlorate salts there is a single chromophoric site, which has C2 symmetry. Using time resolved luminescence line narrowing, we have been able to directly measure the excitation transfer rate between two equivalent metal-ligand units in the [Ru(bpy)3]2+ chromophore doped in the [Zn(bpy)3](ClO4)2 lattice. The rate obtained (approximately equals 1 X 108 sec-1) is in excellent accord with estimates made from the observed linewidth in Stark swept transient hole-burning experiments made on the same system and confirm the single ligand, localized nature of the lowest emitting excited states and thus the very weak intramolecular coupling between metal ligand sub-units within this chromophore. The corresponding coupling in the [Os(bpy)3]2+ system is stronger and, in contrast to the ruthenium analogue, gives rise to additional features in the optical spectra in the origin region of the lowest 3MLCT excited states. The magnitude of the coupling can be probed and assessed by preparing modified chromophoric materials, in which one or two of the bpy ligands are perdeuterated (bpy-d8). This selective deuteration breaks the (near) degeneracy of excitations involving crystallographically equivalent ligands by approximately equals 30 - 40 cm-1 and this competes with or completely overrides the exciton coupling process. The exciton coupling is found to be approximately equals 2.4 cm-1 for [Os(bpy)3]2+ doped in [Ru(bpy)3](PF6)2 and can be understood within a mini-exciton description. Stronger couplings for the same chromophore in

  19. Some simple mechanisms of multiphoton excitation in many - level systems

    NASA Astrophysics Data System (ADS)

    Donley, E. A.; Marquardt, R.; Quack, M.; Stohner, J.; Thanopulos, I.; Wallenborn, E.-U.

    Results are reported on coherent monochromatic multiphoton excitation in many-level systems, which are representative for some of the basic mechanisms for atomic and molecular multiphoton processes. Numerical solutions are discussed that use the Floquet and quasiresonant approximations in the framework of the URIMIR program package. The excitation schemes include direct three-photon excitation, two-photon excitation with diagonal coupling, Göppert-Mayer-type two-photon processes, multiphoton excitation with off-resonant intermediates, and practically irreversible coherent excitation into dense spectral structures. Several interesting phenomena are observed, such as nonlinear line shifts and broadenings of multiphoton resonances of relevance for multiphoton spectroscopy and almost constant intermediate population inversions, potentially useful for laser design. The accurate numerical results are compared with approximate solutions from perturbation theory, and with simple analytical solutions from Rabi-type formulae.

  20. Search for intrinsic collective excitations in {sup 152}Sm

    SciTech Connect

    Kulp, W. D.; Wood, J. L.; Allmond, J. M.; Garrett, P. E.; Wu, C. Y.; Cline, D.; Hayes, A. B.; Hua, H.; Teng, R.; Bandyopadhyay, D.; Choudry, S. N.; McEllistrem, M. T.; McKay, C. J.; Orce, J. N.; Dashdorj, D.; Mynk, M. G.; Yates, S. W.

    2008-06-15

    The 685 keV excitation energy of the first excited 0{sup +} state in {sup 152}Sm makes it an attractive candidate to explore expected two-phonon excitations at low energy. Multiple-step Coulomb excitation and inelastic neutron scattering studies of {sup 152}Sm are used to probe the E2 collectivity of excited 0{sup +} states in this 'soft' nucleus and the results are compared with model predictions. No candidates for two-phonon K{sup {pi}}=0{sup +}quadrupole vibrational states are found. A 2{sup +},K=2 state with strong E2 decay to the first excited K{sup {pi}}=0{sup +} band and a probable 3{sup +} band member are established.

  1. Proton release from Stentor photoreceptors in the excited states.

    PubMed Central

    Song, P S; Walker, E B; Auerbach, R A; Robinson, G W

    1981-01-01

    Steady-state and picosecond pulse excitations of the photophobic-phototactic receptors isolated from Stentor coeruleus produced anionic species predominantly in the excited singlet state, although neutral photoreceptors in the ground state were exclusively excited. The same photoreceptor in vivo also emits fluorescence from the excited state of its anionic species, with an excitation spectrum identical to the absorption spectrum of the neutral species in the ground state. The excited state dissociation of protons from the photoreceptor chromophore (stentorin; hypericin covalently linked to protein) efficiently occurs in less than 10 ps. A possible role of the transient-proton release from the photoreceptor, in the signal transduction photoresponse of Stentor, is briefly discussed. PMID:6791722

  2. Excitation of parametric instabilities by radio waves in the ionosphere.

    NASA Technical Reports Server (NTRS)

    Fejer, J. A.; Leer, E.

    1972-01-01

    The excitation of parametric instabilities by radio waves in a magnetoplasma is discussed. A uniform medium is assumed and linear approximations are used. Excitation by a pump wave of ordinary polarization is hardly affected by the magnetic field. Low or zero frequency ion waves and high frequency Langmuir waves are excited simultaneously. For an extraordinary pump wave, the excited high frequency electrostatic waves are in the Bernstein mode. The threshold is slightly higher and excitation can occur only within certain 'allowed' frequency bands. A new type of parametric instability in which the excited waves are electromagnetic in nature and which is more strongly affected by the inhomogeneous nature of the medium is discussed qualitatively.

  3. Systematics of α -decay transitions to excited states

    NASA Astrophysics Data System (ADS)

    Delion, D. S.; Dumitrescu, A.

    2015-08-01

    We systematize the available experimental material concerning α -decay transitions to low-lying excited states in even-even and odd-mass emitters. We generalize our previous theoretical prediction concerning the linear dependence between hindrance factors and the excitation energy for transitions in even-even α emitters. Thus, we show that α intensities for transitions to excited states depend linearly upon the excitation energy for all known even-even and odd-mass α emitters. It turns out that the well-known Viola-Seaborg law for α -decay transitions between ground states can be generalized for transitions to excited states. This rule can be used to predict any α -decay half-life to a low-lying excited state.

  4. Effects of abnormal excitation on the dynamics of spiral waves

    NASA Astrophysics Data System (ADS)

    Min-Yi, Deng; Xue-Liang, Zhang; Jing-Yu, Dai

    2016-01-01

    The effect of physiological and pathological abnormal excitation of a myocyte on the spiral waves is investigated based on the cellular automaton model. When the excitability of the medium is high enough, the physiological abnormal excitation causes the spiral wave to meander irregularly and slowly. When the excitability of the medium is low enough, the physiological abnormal excitation leads to a new stable spiral wave. On the other hand, the pathological abnormal excitation destroys the spiral wave and results in the spatiotemporal chaos, which agrees with the clinical conclusion that the early after depolarization is the pro-arrhythmic mechanism of some anti-arrhythmic drugs. The mechanisms underlying these phenomena are analyzed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11365003 and 11165004).

  5. Two-Photon Excitation of trans-Stilbene: Spectroscopy and Dynamics of Electronically Excited States above S1.

    PubMed

    Houk, Amanda L; Zheldakov, Igor L; Tommey, Tyler A; Elles, Christopher G

    2015-07-23

    The photoisomerization dynamics of trans-stilbene have been well studied in the lowest excited state, but much less is known about the behavior following excitation to higher-lying electronically excited states. This contribution reports a combined study of the spectroscopy and dynamics of two-photon accessible states above S1. Two-photon absorption (2PA) measurements using a broadband pump-probe technique reveal distinct bands near 5.1 and 6.4 eV. The 2PA bands have absolute cross sections of 40 ± 16 and 270 ± 110 GM, respectively, and a pump-probe polarization dependence that suggests both of the transitions access Ag-symmetry excited states. Separate transient absorption measurements probe the excited-state dynamics following two-photon excitation into each of the bands using intense pulses of 475 and 380 nm light, respectively. The initially excited states rapidly relax via internal conversion, leading to the formation of an S1 excited-state absorption band that is centered near 585 nm and evolves on a time scale of 1-2 ps due to intramolecular vibrational relaxation. The subsequent evolution of the S1 excited-state absorption is identical to the behavior following direct one-photon excitation of the lowest excited state at 4.0 eV. The complementary spectroscopy and dynamics measurements provide new benchmarks for computational studies of the electronic structure and dynamics of this model system on excited states above S1. Probing the dynamics of molecules in their higher-lying excited states is an important frontier in chemical reaction dynamics.

  6. Electronic excitations in fast ion-solid collisions

    SciTech Connect

    Burgdoerfer, J. . Dept. of Physics and Astronomy Oak Ridge National Lab., TN )

    1990-01-01

    We review recent developments in the study of electronic excitation of projectiles in fast ion-solid collisions. Our focus will be primarily on theory but experimental advances will also be discussed. Topics include the evidence for velocity-dependent thresholds for the existence of bound states, wake-field effects on excited states, the electronic excitation of channeled projectiles, transport phenomena, and the interaction of highly charged ions with surfaces. 44 refs., 14 figs.

  7. Excitation and Ionization-Excitation of Helium in Fast Ion-Atom Collisions.

    NASA Astrophysics Data System (ADS)

    Fuelling, Stephan R. K.

    1991-02-01

    The purpose of this work is to investigate several aspects of many-body effects in fast ion-atom collisions using the target gas helium where the projectile velocities are above the Bohr velocity. The method of high resolution extreme ultraviolet (EUV) spectroscopy has been applied in order to measure absolute state selective cross sections of emitted light from excited HeI and HeII target states. We have performed a relative intensity calibration of our 1.5 m spectrometer by comparing 1MeV C^+ + Ne spectra with those examined from a wavelength-calibrated 2.2 m grazing incidence monochromator installed at the Dynamitron Tandem Laboratory at the University of Bochum, Germany. The absolute calibration of our instrument has been accomplished with a single measurement of the Ly_alpha transition of He^+ from 200 eV e-He collisions, where the absolute cross section is known. A comparison between the two-electron processes of ionization-excitation and the one-electron process of excitation of helium following e^-, H^+ and C^{6+ } impact is made for projectile Bohr velocities (v_0) ranging between 1.5 and 9.6. Therefore, the Lyman series of He^+(np) ^2P to (1s) ^2S for n = 2 to 5 and the Rydberg series of He (1snp) ^1P to (1s^2) ^1 S for n = 2 to 5 have been measured. We have been the first to report such extensive absolute state selective cross section measurements. The absolute EUV emission cross sections for ionization-excitation show a significant difference in magnitude for projectiles e^ -, H^+ and C^ {6+} when compared at equal velocities. These differences are possibly due to interference effects between different collision processes. These differences can also be considered as interference between first and second order Born expansions terms. The cross section for electron impact at projectile velocities between 1.5 and 8 v _0 exceeds that for protons by a factor of up to about 3. The H^+ and C ^{6+} cross sections scale approximately as Z_sp{p}{3}. Finally, cross

  8. Properties of chrysene in the higher triplet excited state

    NASA Astrophysics Data System (ADS)

    Cai, Xichen; Hara, Michihiro; Kawai, Kiyohiko; Tojo, Sachiko; Majima, Tetsuro

    2003-01-01

    Properties of chrysene in the higher triplet excited state were studied by the two-color two-laser flash photolysis method. Triplet energy transfers from chrysene in the higher triplet excited state to quenchers such as biphenyl and naphthalene, and from the quenchers in the triplet excited state back to chrysene in the ground state were observed to proceed at the diffusion-controlled rate. From dependence of the quenching efficiency on the quencher concentration, the lifetime of chrysene in the higher triplet excited state was estimated to be 60 ps with considering the time-dependent quenching.

  9. Excited state quantum phase transitions in many-body systems

    SciTech Connect

    Caprio, M.A. Cejnar, P.; Iachello, F.

    2008-05-15

    Phenomena analogous to ground state quantum phase transitions have recently been noted to occur among states throughout the excitation spectra of certain many-body models. These excited state phase transitions are manifested as simultaneous singularities in the eigenvalue spectrum (including the gap or level density), order parameters, and wave function properties. In this article, the characteristics of excited state quantum phase transitions are investigated. The finite-size scaling behavior is determined at the mean-field level. It is found that excited state quantum phase transitions are universal to two-level bosonic and fermionic models with pairing interactions.

  10. The excitation of plasma lines in blanketing sporadic E

    NASA Technical Reports Server (NTRS)

    Gordon, W. E.; Carlson, H. C.

    1976-01-01

    Enhanced plasma lines in blanketing sporadic E have been excited by a powerful HF radio wave illuminating the E region over the Arecibo Observatory. The plasma lines are observed by the incoherent scatter radar at the observatory. They originate in the sporadic E layer when the blanketing frequency exceeds the exciting frequency, a result which confirms that the plasma is overdense for the exciting frequency. Around the time when the blanketing frequency falls through the exciting frequency, large fluctuations in the plasma line intensities are observed, and thus the possibility of overdense patches drifting through the sampled volume is suggested.

  11. Block 3 X-band receiver-exciter

    NASA Technical Reports Server (NTRS)

    Johns, C. E.

    1987-01-01

    The development of an X-band exciter, for use in the X-Band Uplink Subsystem, was completed. The exciter generates the drive signal for the X-band transmitter and also generates coherent test signals for the S- and X-band Block 3 translator and a Doppler reference signal for the Doppler extractor system. In addition to the above, the exciter generates other reference signals that are described. Also presented is an overview of the exciter design and some test data taken on the prototype. A brief discussion of the Block 3 Doppler extractor is presented.

  12. Excitation of coherent terahertz radiation by stimulated Raman scatterings

    SciTech Connect

    Liu, Z. J.; He, X. T.; Zheng, C. Y.; Zhu Shaoping; Cao, L. H.; Wang Yugang

    2010-02-15

    The excitation of terahertz radiation by stimulated Raman scattering is considered. Vlasov-Maxwell numerical simulations show that powerful terahertz radiation can be produced by cascade Raman scatterings.

  13. 51. Credit JTL. View of Doble wheel housing, exciter, generator, ...

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

    51. Credit JTL. View of Doble wheel housing, exciter, generator, switchboard with overhead field rheostat (above). - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

  14. Laser Excitation of a Fracture Source for Elastic Waves

    SciTech Connect

    Blum, Thomas E.; Wijk, Kasper van; Snieder, Roel; Willis, Mark E.

    2011-12-30

    We show that elastic waves can be excited at a fracture inside a transparent sample by focusing laser light directly onto this fracture. The associated displacement field, measured by a laser interferometer, has pronounced waves that are diffracted at the fracture tips. We confirm that these are tip diffractions from direct excitation of the fracture by comparing them with tip diffractions from scattered elastic waves excited on the exterior of the sample. Being able to investigate fractures - in this case in an optically transparent material - via direct excitation opens the door to more detailed studies of fracture properties in general.

  15. Finite-element simulation of myocardial electrical excitation

    NASA Astrophysics Data System (ADS)

    Vasserman, I. N.; Matveenko, V. P.; Shardakov, I. N.; Shestakov, A. P.

    2014-01-01

    Based on a single-domain model of myocardial conduction, isotropic and anisotropic finite element models of the myocardium are developed allowing excitation wave propagation to be studied. The Aliev-Panfilov phenomenological equations were used as the relations between the transmembrane current and the transmembrane potential. Interaction of an additional source of initial excitation with an excitation wave that passed and the spread of the excitation wave are studied using heart tomograms. A numerical solution is obtained using a splitting algorithm that allows the nonlinear boundary-value problem to be reduced to a sequence of simpler problems: ordinary differential equations and linear boundary-value problems in partial derivatives.

  16. Vibrationally excited molecular hydrogen in the upper atmosphere of Jupiter

    NASA Astrophysics Data System (ADS)

    Cravens, T. E.

    1987-10-01

    Experiments on the Voyager 1 and 2 spacecraft and observations made by the International Ultraviolet Explorer (IUE) have provided evidence for the existence of energetic particle precipitation into the upper atmosphere of Jupiter from the magnetosphere. This auroral precipitation has been shown to generate large ionization and dissociation rates, to excite auroral emissions, and also to vibrationally excite molecular hydrogen. A theoretical model of vibrationally excited H2 in the upper atmosphere of Jupiter is presented in this paper. Models are considered for both the auroral region and also for lower latitudes, where H2 is vibrationally excited owing to processes associated with the absorption of solar ultraviolet radiation.

  17. NASA and Mary J. Blige Encourage Exciting Careers For Women

    NASA Video Gallery

    NASA is collaborating with award-winning recording artist Mary J. Blige to encourage young women to pursue exciting experiences and career choices through studying science, technology, engineering ...

  18. Computing electronic structures: A new multiconfiguration approach for excited states

    SciTech Connect

    Cances, Eric . E-mail: cances@cermics.enpc.fr; Galicher, Herve . E-mail: galicher@cermics.enpc.fr; Lewin, Mathieu . E-mail: lewin@cermic.enpc.fr

    2006-02-10

    We present a new method for the computation of electronic excited states of molecular systems. This method is based upon a recent theoretical definition of multiconfiguration excited states [due to one of us, see M. Lewin, Solutions of the multiconfiguration equations in quantum chemistry, Arch. Rat. Mech. Anal. 171 (2004) 83-114]. Our algorithm, dedicated to the computation of the first excited state, always converges to a stationary state of the multiconfiguration model, which can be interpreted as an approximate excited state of the molecule. The definition of this approximate excited state is variational. An interesting feature is that it satisfies a non-linear Hylleraas-Undheim-MacDonald type principle: the energy of the approximate excited state is an upper bound to the true excited state energy of the N-body Hamiltonian. To compute the first excited state, one has to deform paths on a manifold, like this is usually done in the search for transition states between reactants and products on potential energy surfaces. We propose here a general method for the deformation of paths which could also be useful in other settings. We also compare our method to other approaches used in Quantum Chemistry and give some explanation of the unsatisfactory behaviours which are sometimes observed when using the latter. Numerical results for the special case of two-electron systems are provided: we compute the first singlet excited state potential energy surface of the H {sub 2} molecule.

  19. Excited-State Effective Masses in Lattice QCD

    SciTech Connect

    George Fleming, Saul Cohen, Huey-Wen Lin

    2009-10-01

    We apply black-box methods, i.e. where the performance of the method does not depend upon initial guesses, to extract excited-state energies from Euclidean-time hadron correlation functions. In particular, we extend the widely used effective-mass method to incorporate multiple correlation functions and produce effective mass estimates for multiple excited states. In general, these excited-state effective masses will be determined by finding the roots of some polynomial. We demonstrate the method using sample lattice data to determine excited-state energies of the nucleon and compare the results to other energy-level finding techniques.

  20. Excited-state dynamics of 3-hydroxyflavone anion in alcohols.

    PubMed

    Dereka, Bogdan; Letrun, Romain; Svechkarev, Denis; Rosspeintner, Arnulf; Vauthey, Eric

    2015-02-12

    The electronic absorption spectrum of 3-hydroxyflavone (3HF) in various solvents exhibits a long-wavelength (LW) band, whose origin has been debated. The excited-state dynamics of neutral and basic solutions of 3HF in alcohols upon excitation in this LW band has been investigated using a combination of fluorescence up-conversion and transient electronic and vibrational absorption spectroscopies. The ensemble of results reveals that, in neutral solutions, LW excitation results in the population of two excited species with similar fluorescence spectra but very different lifetimes, namely 40-100 ps and 2-3 ns, depending on the solvent. In basic solutions, the relative concentrations of these species change considerably in favor of that with the short-lived excited state. On the basis of the spectroscopic data and quantum chemistry calculations, the short lifetime is attributed to the excited state of 3HF anion, whereas the long one is tentatively assigned to an excited hydrogen-bonded complex with the solvent. Excited-state intermolecular proton transfer from the solvent to the anion yielding the tautomeric form of 3HF is not operative, as the excited anion decays to the ground state via an efficient nonradiative transition.