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Sample records for excitation functions

  1. 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.

  2. 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.

  3. 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.

  4. Excitability of motor cortices as a function of emotional sounds.

    PubMed

    Komeilipoor, Naeem; Pizzolato, Fabio; Daffertshofer, Andreas; Cesari, Paola

    2013-01-01

    We used transcranial magnetic stimulation (TMS) to clarify how non-verbal emotionally-characterized sounds modulate the excitability of the corticospinal motor tract (CST). While subjects were listening to sounds (monaurally and binaurally), single TMS pulses were delivered to either left or right primary motor cortex (M1), and electromyographic activities were recorded from the contralateral abductor pollicis brevis muscle. We found a significant increase in CST excitability in response to unpleasant as compared to neutral sounds. The increased excitability was lateralized as a function of stimulus valence: Unpleasant stimuli resulted in a significantly higher facilitation of motor potentials evoked in the left hemisphere, while pleasant stimuli yielded a greater CST excitability in the right one. Furthermore, TMS induced higher motor evoked potentials when listening to unpleasant sounds with the left than with the right ear. Taken together, our findings provide compelling evidence for an asymmetric modulation of CST excitability as a function of emotional sounds along with ear laterality.

  5. Excitation Spectra of Nucleobases with Multiconfigurational Density Functional Theory.

    PubMed

    Hubert, Mickaël; Jensen, Hans Jørgen Aa; Hedegård, Erik D

    2016-01-14

    Range-separated hybrid methods between wave function theory and density functional theory (DFT) can provide high-accuracy results, while correcting some of the inherent flaws of both the underlying wave function theory and DFT. We here assess the accuracy for excitation energies of the nucleobases thymine, uracil, cytosine, and adenine, using a hybrid between complete active space self-consistent field (CASSCF) and DFT methods. The method is based on range separation, thereby avoiding all double-counting of electron correlation and is denoted long-range CASSCF short-range DFT (CAS-srDFT). Using a linear response extension of CAS-srDFT, we compare the first 7-8 excited states of the nucleobases with perturbative multireference approaches as well as coupled cluster based methods. Our results show that the CAS-srDFT method can provide accurate excitation energies in good correspondence with the computationally more expensive methods. PMID:26669578

  6. Excitations and benchmark ensemble density functional theory for two electrons

    SciTech Connect

    Pribram-Jones, Aurora; Burke, Kieron; Yang, Zeng-hui; Ullrich, Carsten A.; Trail, John R.; Needs, Richard J.

    2014-05-14

    A new method for extracting ensemble Kohn-Sham potentials from accurate excited state densities is applied to a variety of two-electron systems, exploring the behavior of exact ensemble density functional theory. The issue of separating the Hartree energy and the choice of degenerate eigenstates is explored. A new approximation, spin eigenstate Hartree-exchange, is derived. Exact conditions that are proven include the signs of the correlation energy components and the asymptotic behavior of the potential for small weights of the excited states. Many energy components are given as a function of the weights for two electrons in a one-dimensional flat box, in a box with a large barrier to create charge transfer excitations, in a three-dimensional harmonic well (Hooke's atom), and for the He atom singlet-triplet ensemble, singlet-triplet-singlet ensemble, and triplet bi-ensemble.

  7. Band Excitation in Scanning Probe Microscopy: Recognition and Functional Imaging

    SciTech Connect

    Jesse, Stephen; Vasudevan, Dr. Rama; Collins, Liam; Strelcov, Evgheni; Okatan, Mahmut B; Belianinov, Alex; Baddorf, Arthur P; Proksch, Roger; Kalinin, Sergei V

    2014-01-01

    Field confinement at the junction between a biased scanning probe microscope s (SPM) tip and solid surface enables local probing of various bias-induced transformations such as polarization switching, ionic motion, or electrochemical reactions to name a few. The nanoscale size of the biased region is smaller or comparable to features like grain boundaries and dislocations, potentially allows for the study of kinetics and thermodynamics at the level of a single defect. In contrast to classical statistically averaged approaches, this allows one to link structure to functionality and deterministically decipher associated mesoscopic and atomistic mechanisms. Furthermore, this type of information can serve as a fingerprint of local material functionality, allowing for local recognition imaging. Here, current progress in multidimensional SPM techniques based on band-excitation time and voltage spectroscopies is illustrated, including discussions on data acquisition, dimensionality reduction, and visualization along with future challenges and opportunities for the field.

  8. Excitation function calculations for α + 93Nb nuclear reactions

    NASA Astrophysics Data System (ADS)

    Yiǧit, M.; Tel, E.; Sarpün, İ. H.

    2016-10-01

    In this study, the excitation functions of alpha-induced reactions on the 93Nb target nucleus were calculated by using ALICE-ASH code. The hybrid model, Weisskopf-Ewing model and geometry dependent hybrid model in this code were used to understand the alpha-niobium interaction. The contribution on the nuclear interaction of compound and pre-compound processes, with variation of the incident alpha particle energy, was presented. Furthermore, the reaction cross sections were calculated by using different level density models such as Superfluid nuclear model, Fermi gas model and Kataria-Ramamurthy Fermi gas model. Obtaining a good agreement between the calculated and the measured cross sections, the exciton numbers and the nuclear level density models were varied. Finally, the proper choice of the exciton numbers and the nuclear level density models was found to be quite important in order to obtain the more realistic cross section values.

  9. Functional Assessment of Corticospinal System Excitability in Karate Athletes

    PubMed Central

    Moscatelli, Fiorenzo; Messina, Giovanni; Valenzano, Anna; Monda, Vincenzo; Viggiano, Andrea; Messina, Antonietta; Petito, Annamaria; Triggiani, Antonio Ivano; Ciliberti, Michela Anna Pia; Monda, Marcellino; Capranica, Laura; Cibelli, Giuseppe

    2016-01-01

    Objectives To investigate the involvement of the primary motor cortex (M1) in the coordination performance of karate athletes through transcranial magnetic stimulation (TMS). Methods Thirteen right-handed male karate athletes (25.0±5.0 years) and 13 matched non-athlete controls (26.7±6.2 years) were enrolled. A single-pulse TMS was applied using a figure-eight coil stimulator. Resting motor threshold (rMT) was determined. Surface electromyography was recorded from the first dorsal interosseous muscle. Motor evoked potential (MEP) latencies and amplitudes at rMT, 110%, and 120% of rMT were considered. Functional assessment of the coordination performance was assessed by in-phase (IP) and anti-phase (AP) homolateral hand and foot coordination tasks performed at 80, 120, and 180 bpm. Results Compared to controls, athletes showed lower rMT (p<0.01), shorter MEP latency (p<0.01) and higher MEP amplitude (p<0.01), with a significant correlation (r = 0.50, p<0.01) between rMT and MEP latency. Coordination decreased with increasing velocity, and better IP performances emerged compared to AP ones (p<0.001). In general, a high correlation between rMT and coordination tasks was found for both IP and AP conditions. Conclusion With respect to controls, karate athletes present a higher corticospinal excitability indicating the presence of an activity-dependent alteration in the balance and interactions between inhibitory and facilitatory circuits determining the final output from the M1. Furthermore, the high correlation between corticospinal excitability and coordination performance could support sport-specific neurophysiological arrangements. PMID:27218465

  10. Some light-ion excitation-function measurements on titanium, yttrium, and europium, and associated results

    SciTech Connect

    West, H.I. Jr.; Lanier, R.G.; Mustafa, M.G.; Nuckolls, R.M.; Nagle, R.J.; O`Brien, H.; Frehaut, J.; Adam, A.; Philis, C.

    1993-11-01

    This report discusses: Fabrication of Plastic-Matrix-Encapsulated Accelerator Targets and Their Use in Measuring Nuclear Excitation Functions; Correcting Excitation Function Data in the Low Energy Region for Finite Thickness of the Target Foils, Including Effects of Straggling; Excitation Functions for the Nuclear Reactions on Titanium Leading to the Production {sup 48}V, {sup 44}Sc and {sup 47}Sc by Proton, Deuteron and Triton Irradiations at 0--35 MeV; Some Excitation Functions of Proton and Deuteron Induced Reactions on {sup 89}Y; Measurements of the Excitation Functions of the Isobaric Chain {sup 87}Y, {sup 87}Y{sup m}, {sup 87}Y{sup g} and {sup 87}Sr{sup m}; Levels in {sup 87}Y Observed in the Decay of {sup 87}Zr; and Nuclear Reaction Excitation Functions from the Irradiation of {sup 151,153}Eu with Protons And deuterons up to 35 MeV.

  11. Excitation Control: Balancing PSD-95 Function at the Synapse

    PubMed Central

    Keith, Dove; El-Husseini, Alaa

    2008-01-01

    Excitability of individual neurons dictates the overall excitation in specific brain circuits. This process is thought to be regulated by molecules that regulate synapse number, morphology and strength. Neuronal excitation is also influenced by the amounts of neurotransmitter receptors and signaling molecules retained at particular synaptic sites. Recent studies revealed a key role for PSD-95, a scaffolding molecule enriched at glutamatergic synapses, in modulation of clustering of several neurotransmitter receptors, adhesion molecules, ion channels, cytoskeletal elements and signaling molecules at postsynaptic sites. In this review we will highlight mechanisms that control targeting of PSD-95 at the synapse, and discuss how this molecule influences the retention and clustering of diverse synaptic proteins to regulate synaptic structure and strength. We will also discuss how PSD-95 may maintain a balance between excitation and inhibition in the brain and how alterations in this balance may contribute to neuropsychiatric disorders. PMID:18946537

  12. Is There a Linear Building Transfer Function for Small Excitation?

    NASA Astrophysics Data System (ADS)

    Clinton, J. F.; Heaton, T. H.

    2003-12-01

    In the absence of actual building accelerometer data, the linear response of a structure to strong ground motion is estimated by the convolution of the dynamic response of the structure with an input ground motion. The input motion is usually provided by a local `reference' station record. In this study, we look at whether actual recorded ground motion at two instrumented buildings with well studied dynamic properties can be satisfactorily modeled using a local ground station. All stations record continuous 24-bit data streams on the CISN network, so analysis of a variety of weak earthquake motions, as well as ambient noise, is possible. Our buildings are the 9-story reinforced concrete Millikan Library (CISN Station MIK) and the 3-story braced steel frame Broad Center (CBC), both on the Caltech Campus. Motions recorded on their upper floors are compared with motions from ground stations located in the basement of a lightweight wood-frame house (GSA), and in a subsurface vault (CRP). All stations are within 200m of each other. Recent work using the new continuous datastream indicates that the natural frequencies of these structures can vary by up to 5% during normal ambient conditions, due to such factors as changing building usage, diurnal temperature variation, and wind/rainfall events. These shifts can be sudden, and models of building motions are sensitive to these previously un-documented changes. Further, during stronger motions, such as forced vibration testing, and minor earthquake shaking, natural frequencies are shown to drop by up to 10% (2003 M5.4 Big Bear Earthquake, Δ = 119km), with near-instantaneous recovery once the excitation is over. Moderate earthquakes can temporarily reduce frequencies by up to 30% with no apparent structural damage (1971 M6.6 San Fernando Earthquake, Δ = 31km). Post-event permanent reductions of about 10% have been observed. The ability to monitor these evolving dynamic characteristics makes a re-evaluation of the

  13. Dissociative excitation of the N(+)(5S) state by electron impact on N2 - Excitation function and quenching

    NASA Technical Reports Server (NTRS)

    Erdman, P. W.; Zipf, E. C.

    1986-01-01

    Metastable N(+)(5S) ions were produced in the laboratory by dissociative excitation of N2 with energetic electrons. The resulting radiative decay of the N(+)(5S) state was observed with sufficient resolution to completely resolve the doublet from the nearby N2 molecular radiation. The excitation function was measured from threshold to 500 eV. The cross section peaks at a high electron energy and also exhibits a high threshold energy both of which are typical of dissociative excitation-ionization processes. This finding complicates the explanation of electron impact on N2 as the mechanism for the source of the 2145 A 'auroral mystery feature' by further increasing the required peak cross section. It is suggested that the apparent N(+)(5S) quenching in auroras may be an artifact due to the softening of the electron energy spectrum in the auroral E region.

  14. Validation of local hybrid functionals for TDDFT calculations of electronic excitation energies

    NASA Astrophysics Data System (ADS)

    Maier, Toni M.; Bahmann, Hilke; Arbuznikov, Alexei V.; Kaupp, Martin

    2016-02-01

    The first systematic evaluation of local hybrid functionals for the calculation of electronic excitation energies within linear-response time-dependent density functional theory (TDDFT) is reported. Using our recent efficient semi-numerical TDDFT implementation [T. M. Maier et al., J. Chem. Theory Comput. 11, 4226 (2015)], four simple, thermochemically optimized one-parameter local hybrid functionals based on local spin-density exchange are evaluated against a database of singlet and triplet valence excitations of organic molecules, and against a mixed database including also Rydberg, intramolecular charge-transfer (CT) and core excitations. The four local hybrids exhibit comparable performance to standard global or range-separated hybrid functionals for common singlet valence excitations, but several local hybrids outperform all other functionals tested for the triplet excitations of the first test set, as well as for relative energies of excited states. Evaluation for the combined second test set shows that local hybrids can also provide excellent Rydberg and core excitations, in the latter case rivaling specialized functionals optimized specifically for such excitations. This good performance of local hybrids for different excitation types could be traced to relatively large exact-exchange (EXX) admixtures in a spatial region intermediate between valence and asymptotics, as well as close to the nucleus, and lower EXX admixtures in the valence region. In contrast, the tested local hybrids cannot compete with the best range-separated hybrids for intra- and intermolecular CT excitation energies. Possible directions for improvement in the latter category are discussed. As the used efficient TDDFT implementation requires essentially the same computational effort for global and local hybrids, applications of local hybrid functionals to excited-state problems appear promising in a wide range of fields. Influences of current-density dependence of local kinetic

  15. One-electron and multi-electron transitions observed in the excitation function of the dissociative photoionization excitation of ?

    NASA Astrophysics Data System (ADS)

    Kitajima, Masashi; Ukai, Masatoshi; Machida, Shuntaro; Kameta, Kosei; Ehresmann, Arno; Kouchi, Noriyuki; Hatano, Yoshihiko; Hayaishi, Tatsuji; Shigemasa, Eiji; Ito, Kenji

    1996-05-01

    The excitation function of the dissociative photoionization excitation ( DIE) of 0953-4075/29/9/017/img14 has been measured with the detection technique of coincidence between photoion 0953-4075/29/9/017/img15 and a fluorescence photon emitted from an excited atom N* using extreme- UV synchrotron radiation ( SR) as an excitation source in the energy region of 35 - 65 eV. The axis of the detection system was set at two angles, parallel or perpendicular with respect to the major axis of the elliptically polarized SR, in the present measurement. The coincidence spectra obtained in this energy region show at least two qualitatively different structures originating from two different DIE processes. The major components of the DIE in the present energy region are ascribed to the dissociation of the 0953-4075/29/9/017/img16 state which is strongly coupled with correlation states in the 0953-4075/29/9/017/img17 symmetry. In addition, DIE from other precursor states in the 0953-4075/29/9/017/img18 symmetry or dissociative photo-double ionization excitation ( DDIE) was also observed.

  16. Self-Consistent Optimization of Excited States within Density-Functional Tight-Binding.

    PubMed

    Kowalczyk, Tim; Le, Khoa; Irle, Stephan

    2016-01-12

    We present an implementation of energies and gradients for the ΔDFTB method, an analogue of Δ-self-consistent-field density functional theory (ΔSCF) within density-functional tight-binding, for the lowest singlet excited state of closed-shell molecules. Benchmarks of ΔDFTB excitation energies, optimized geometries, Stokes shifts, and vibrational frequencies reveal that ΔDFTB provides a qualitatively correct description of changes in molecular geometries and vibrational frequencies due to excited-state relaxation. The accuracy of ΔDFTB Stokes shifts is comparable to that of ΔSCF-DFT, and ΔDFTB performs similarly to ΔSCF with the PBE functional for vertical excitation energies of larger chromophores where the need for efficient excited-state methods is most urgent. We provide some justification for the use of an excited-state reference density in the DFTB expansion of the electronic energy and demonstrate that ΔDFTB preserves many of the properties of its parent ΔSCF approach. This implementation fills an important gap in the extended framework of DFTB, where access to excited states has been limited to the time-dependent linear-response approach, and affords access to rapid exploration of a valuable class of excited-state potential energy surfaces.

  17. Functional patterned multiphoton excitation deep inside scattering tissue

    NASA Astrophysics Data System (ADS)

    Papagiakoumou, Eirini; Bègue, Aurélien; Leshem, Ben; Schwartz, Osip; Stell, Brandon M.; Bradley, Jonathan; Oron, Dan; Emiliani, Valentina

    2013-04-01

    Stochastic distortion of light beams in scattering samples makes in-depth photoexcitation in brain tissue a major challenge. A common solution for overcoming scattering involves adaptive pre-compensation of the unknown distortion. However, this requires long iterative searches for sample-specific optimized corrections, which is a problem when applied to optical neurostimulation where typical timescales in the system are in the millisecond range. Thus, photoexcitation in scattering media that is independent of the properties of a specific sample would be an ideal solution. Here, we show that temporally focused two-photon excitation with generalized phase contrast enables photoexcitation of arbitrary spatial patterns within turbid tissues with remarkable robustness to scattering. We demonstrate three-dimensional confinement of tailored photoexcitation patterns >200 µm in depth, both in numerical simulations and through brain slices combined with patch-clamp recording of photoactivated channelrhodopsin-2.

  18. Multiple-Resonance Local Wave Functions for Accurate Excited States in Quantum Monte Carlo.

    PubMed

    Zulfikri, Habiburrahman; Amovilli, Claudio; Filippi, Claudia

    2016-03-01

    We introduce a novel class of local multideterminant Jastrow-Slater wave functions for the efficient and accurate treatment of excited states in quantum Monte Carlo. The wave function is expanded as a linear combination of excitations built from multiple sets of localized orbitals that correspond to the bonding patterns of the different Lewis resonance structures of the molecule. We capitalize on the concept of orbital domains of local coupled-cluster methods, which is here applied to the active space to select the orbitals to correlate and construct the important transitions. The excitations are further grouped into classes, which are ordered in importance and can be systematically included in the Jastrow-Slater wave function to ensure a balanced description of all states of interest. We assess the performance of the proposed wave function in the calculation of vertical excitation energies and excited-state geometry optimization of retinal models whose π → π* state has a strong intramolecular charge-transfer character. We find that our multiresonance wave functions recover the reference values of the total energies of the ground and excited states with only a small number of excitations and that the same expansion can be flexibly used at very different geometries. Furthermore, significant computational saving can also be gained in the orbital optimization step by selectively mixing occupied and virtual orbitals based on spatial considerations without loss of accuracy on the excitation energy. Our multiresonance wave functions are therefore compact, accurate, and very promising for the calculation of multiple excited states of different character in large molecules.

  19. Core and valence excitations in resonant X-ray spectroscopy using restricted excitation window time-dependent density functional theory

    PubMed Central

    Zhang, Yu; Biggs, Jason D.; Healion, Daniel; Govind, Niranjan; Mukamel, Shaul

    2012-01-01

    We report simulations of X-ray absorption near edge structure (XANES), resonant inelastic X-ray scattering (RIXS) and 1D stimulated X-ray Raman spectroscopy (SXRS) signals of cysteine at the oxygen, nitrogen, and sulfur K and \\documentclass[12pt]{minimal}\\begin{document}$\\textrm {L}_{2,3}$\\end{document}L2,3 edges. Comparison of the simulated XANES signals with experiment shows that the restricted window time-dependent density functional theory is more accurate and computationally less expensive than the static exchange method. Simulated RIXS and 1D SXRS signals give some insights into the correlation of different excitations in the molecule. PMID:23181305

  20. Core and Valence Excitations in Resonant X-ray Spectroscopy using Restricted Excitation Window Time-dependent Density Functional Theory

    SciTech Connect

    Zhang, Yu; Biggs, Jason D.; Healion, Daniel; Govind, Niranjan; Mukamel, Shaul

    2012-11-21

    We report simulations of X-ray absorption near edge structure (XANES), resonant inelastic X-ray scattering (RIXS) and 1D stimulated X-ray Raman spectroscopy (SXRS) signals of cysteine at the oxygen, nitrogen and sulfur K and L2,3 edges. The simulated XANES signals from the restricted window time-dependent density functional theory (REW-TDDFT) and the static exchange (STEX) method are compared with experiments, showing that REW-TDDFT is more accurate and computationally less expensive than STEX. Simulated RIXS and 1D SXRS signals from REW-TDDFT give some insights on the correlation of different excitations in the molecule.

  1. Comparison of the hydrological excitation functions HAM of polar motion for the period 1980.0-2007.0

    NASA Astrophysics Data System (ADS)

    Nastula, J.; Pasnicka, M.; Kolaczek, B.

    2011-10-01

    In this study we compared contributions of polar motion excitation determined from hydrological models and harmonic coefficients of the Earth gravity field obtained from Gravity Recovery and Climate Experiment (GRACE). Hydrological excitation function (hydrological angular momentum - HAM) has been estimated from models of global hydrology, based on the observed distribution of surface water, snow, ice and soil moisture. All of them were compared with observed Geodetic Angular Momentum (GAM), excitations of polar motion. The spectra of these excitation functions of polar motion and residual geodetic excitation function G-A-O obtained from GAM by elimination of atmospheric and oceanic excitation functions were computed too. Phasor diagrams of the seasonal components of the polar motion excitation functions of all HAM excitation functions as well as of two GRACE solutions: CSR, CNES were determined and discussed.

  2. Linearity condition for orbital energies in density functional theory (V): Extension to excited state calculations

    NASA Astrophysics Data System (ADS)

    Imamura, Yutaka; Suzuki, Kensei; Iizuka, Takeshi; Nakai, Hiromi

    2015-01-01

    A new scheme is proposed for constructing an orbital-specific (OS) exchange-correlation functional that satisfies multiple linearity conditions for orbital energies (LCOEs). The Hartree-Fock exchange portions in the OS exchange-correlation functional, based on a multiply range-separated functional, are set so as to satisfy the multiple LCOEs. The current scheme has also been extended to calculations of core, valence, and Rydberg excitations. Numerical assessments on ionization potentials, electron affinities and excitation energies have confirmed accurate descriptions of core, valence, and Rydberg orbitals by the OS hybrid functional.

  3. Fragment-based configuration interaction wave function to calculate environmental effect on excited states in proteins and solutions

    NASA Astrophysics Data System (ADS)

    Hasegawa, Jun-ya

    2013-05-01

    Solvatochromic effect in proteins and solutions was described by a configuration interaction singles (CIS) wave function with fragment-localized molecular orbitals. Coarse-grained analysis indicated that the CI wave function can be described by local excitations and charge-transfer (CT) excitations between the chromophore and the environment. We developed an atomic-orbital direct runcated CIS code and applied the excited states of retinal chromophore in bacteriorhodopsin and MeOH environments, and those of s-trans-acrolein in water. Number of excitation operators was significantly reduced by eliminating the CT excitations between the environmental fragments. The truncated CIS wave functions reproduced the original excitation energies very well.

  4. Multiconfiguration Pair-Density Functional Theory Is as Accurate as CASPT2 for Electronic Excitation.

    PubMed

    Hoyer, Chad E; Ghosh, Soumen; Truhlar, Donald G; Gagliardi, Laura

    2016-02-01

    A correct description of electronically excited states is critical to the interpretation of visible-ultraviolet spectra, photochemical reactions, and excited-state charge-transfer processes in chemical systems. We have recently proposed a theory called multiconfiguration pair-density functional theory (MC-PDFT), which is based on a combination of multiconfiguration wave function theory and a new kind of density functional called an on-top density functional. Here, we show that MC-PDFT with a first-generation on-top density functional performs as well as CASPT2 for an organic chemistry database including valence, Rydberg, and charge-transfer excitations. The results are very encouraging for practical applications. PMID:26794241

  5. Excited State Absorption from Real-Time Time-Dependent Density Functional Theory.

    PubMed

    Fischer, Sean A; Cramer, Christopher J; Govind, Niranjan

    2015-09-01

    The optical response of excited states is a key property used to probe photophysical and photochemical dynamics. Additionally, materials with a large nonlinear absorption cross-section caused by two-photon (TPA) and excited state absorption (ESA) are desirable for optical limiting applications. The ability to predict the optical response of excited states would help in the interpretation of transient absorption experiments and aid in the search for and design of optical limiting materials. We have developed an approach to obtain excited state absorption spectra by combining real-time (RT) and linear-response (LR) time-dependent density functional theory (TDDFT). Being based on RT-TDDFT, our method is aimed at tackling larger molecular complexes and materials systems where excited state absorption is predominantly seen and many time-resolved experimental efforts are focused. To demonstrate our method, we have calculated the ground and excited state spectra of H₂⁺ and H₂ due to the simplicity in the interpretation of the spectra. We have validated our new approach by comparing our results for butadiene with previously published results based on quadratic response (QR). We also present results for oligofluorenes, where we compare our results with both QR-TDDFT and experimental measurements. Because our method directly measures the response of an excited state, stimulated emission features are also captured; although, these features are underestimated in energy which could be attributed to a change of the reference from the ground to the excited state.

  6. Relativistic Energy Density Functionals: Exotic modes of excitation

    SciTech Connect

    Vretenar, D.; Paar, N.; Marketin, T.

    2008-11-11

    The framework of relativistic energy density functionals has been applied to the description of a variety of nuclear structure phenomena, not only in spherical and deformed nuclei along the valley of {beta}-stability, but also in exotic systems with extreme isospin values and close to the particle drip-lines. Dynamical aspects of exotic nuclear structure have been investigated with the relativistic quasiparticle random-phase approximation. We present results for the evolution of low-lying dipole (pygmy) strength in neutron-rich nuclei, and charged-current neutrino-nucleus cross sections.

  7. Assessing Accuracy of Exchange-Correlation Functionals for the Description of Atomic Excited States

    NASA Astrophysics Data System (ADS)

    Makowski, Marcin; Hanas, Martyna

    2016-09-01

    The performance of exchange-correlation functionals for the description of atomic excitations is investigated. A benchmark set of excited states is constructed and experimental data is compared to Time-Dependent Density Functional Theory (TDDFT) calculations. The benchmark results show that for the selected group of functionals good accuracy may be achieved and the quality of predictions provided is competitive to computationally more demanding coupled-cluster approaches. Apart from testing the standard TDDFT approaches, also the role of self-interaction error plaguing DFT calculations and the adiabatic approximation to the exchange-correlation kernels is given some insight.

  8. Communication: Exciton analysis in time-dependent density functional theory: How functionals shape excited-state characters.

    PubMed

    Mewes, Stefanie A; Plasser, Felix; Dreuw, Andreas

    2015-11-01

    Excited-state descriptors based on the one-particle transition density matrix referring to the exciton picture have been implemented for time-dependent density functional theory. State characters such as local, extended ππ(∗), Rydberg, or charge transfer can be intuitively classified by simple comparison of these descriptors. Strong effects of the choice of the exchange-correlation kernel on the physical nature of excited states can be found and decomposed in detail leading to a new perspective on functional performance and the design of new functionals.

  9. Communication: Exciton analysis in time-dependent density functional theory: How functionals shape excited-state characters

    NASA Astrophysics Data System (ADS)

    Mewes, Stefanie A.; Plasser, Felix; Dreuw, Andreas

    2015-11-01

    Excited-state descriptors based on the one-particle transition density matrix referring to the exciton picture have been implemented for time-dependent density functional theory. State characters such as local, extended ππ∗, Rydberg, or charge transfer can be intuitively classified by simple comparison of these descriptors. Strong effects of the choice of the exchange-correlation kernel on the physical nature of excited states can be found and decomposed in detail leading to a new perspective on functional performance and the design of new functionals.

  10. Gravimetric excitation function of polar motion from the GRACE RL05 solution

    NASA Astrophysics Data System (ADS)

    Nastula, Y.

    2014-12-01

    Impact of land hydrosphere on polar motion excitation is still not as well known as the impact of the angular momentum of the atmosphere and ocean. Satellite mission Gravity Recovery and Climate Experiment (GRACE) from 2002 provides additional information about mass distribution of the land hydrosphere. However, despite the use of similar computational procedures, the differences between GRACE data series made available by the various centers of computations are still considerable. In the paper we compare three series of gravimetric excitation functions of polar motion determined from Rl05 GRACE solution from the Center for Space Research (CSR), the Jet Propulsion Laboratory (JPL) and the GeoForschungsZentrum (GFZ). These data are used to determine the gravimetric polar motion excitation function. Gravimetric signal is compared also with the geodetic residuals computed by subtracting atmospheric and oceanic signals from geodetic excitation functions of polar motion. Gravimetric excitation functions obtained on the basis of JPL data differ significantly from the geodetic residuals while and the series obtained from CSR and GFZ are more compatible.

  11. Thick-target transmission method for excitation functions of interaction cross sections

    NASA Astrophysics Data System (ADS)

    Aikawa, M.; Ebata, S.; Imai, S.

    2016-09-01

    We propose a method, called as thick-target transmission (T3) method, to obtain an excitation function of interaction cross sections. In an ordinal experiment to measure the excitation function of interaction cross sections by the transmission method, we need to change the beam energy for each cross section. In the T3 method, the excitation function is derived from the beam attenuations measured at the targets of different thicknesses without changing the beam energy. The advantage of the T3 method is the simplicity and availability for radioactive beams. To confirm the availability, we perform a simulation for the 12C + 27Al system with the PHITS code instead of actual experiments. Our results have large uncertainties but well reproduce the tendency of the experimental data.

  12. Detection of time-frequency relations between geodetic and geophysical excitation functions of polar motion

    NASA Astrophysics Data System (ADS)

    Rzeszotko, A.; Kosek, W.; Popinski, W.

    2009-09-01

    The redistribution of mass in the atmosphere, oceans and hydrology and the changes of the wind and ocean currents velocities are important sources of polar motion excitation. Relations between the geodetic excitation function and the effective angular momentum functions of the atmosphere, oceans and hydrology are examined in the time-frequency domain by means of coherence and phase synchronization. Coherence may be interpreted as a correlation coefficient between oscillations with the same frequencies present in two time series whereas phase synchronization allow to investigate the phase agreement between these oscillations.

  13. Assessment of the ΔSCF density functional theory approach for electronic excitations in organic dyes

    SciTech Connect

    Kowalczyk, T.; Yost, S. R.; Van Voorhis, T.

    2010-01-01

    This paper assesses the accuracy of the ΔSCF method for computing low-lying HOMO→LUMO transitions in organic dye molecules. For a test set of vertical excitation energies of 16 chromophores, surprisingly similar accuracy is observed for time-dependent density functional theory and for ΔSCF density functional theory. In light of this performance, we reconsider the ad hoc ΔSCF prescription and demonstrate that it formally obtains the exact stationary density within the adiabatic approximation, partially justifying its use. The relative merits and future prospects of ΔSCF for simulating individual excited states are discussed.

  14. Excitation functions for actinides produced in the interactions of sup 31 P with sup 248 Cm

    SciTech Connect

    Leyba, J.D.; Henderson, R.A.; Hall, H.L.; Czerwinski, K.R.; Kadkhodayan, B.A.; Kreek, S.A.; Brady, E.K.; Gregorich, K.E.; Lee, D.M.; Nurmia, M.J.; Hoffman, D.C. Nuclear Science Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California )

    1991-11-01

    Excitation functions have been measured for the production of various isotopes of Bk, Cf, Es, and Fm from the interactions of 174- and 239-MeV {sup 31}P projectiles with {sup 248}Cm. The isotopic distributions were symmetric and displayed full widths at half maximum of 2.5, 2.5, and 2.25 mass units for Bk, Cf, and Fm, respectively. The maxima of the isotopic distributions occur for those reaction channels which involve the exchange of the fewest number of nucleons between the target and projectile for which the calculated excitation energy is a positive quantity. The maxima of the excitation functions occur at those projectile energies which are consistent with the calculated reaction barriers based upon a binary reaction mechanism. The effects of the odd proton in the {sup 31}P projectile on the final isotopic distributions are discussed.

  15. Employment of sawtooth-shaped-function excitation signal and oversampling for improving resistance measurement accuracy

    NASA Astrophysics Data System (ADS)

    Lin, Ling; Li, Shujuan; Yan, Wenjuan; Li, Gang

    2016-10-01

    In order to achieve higher measurement accuracy of routine resistance without increasing the complexity and cost of the system circuit of existing methods, this paper presents a novel method that exploits a shaped-function excitation signal and oversampling technology. The excitation signal source for resistance measurement is modulated by the sawtooth-shaped-function signal, and oversampling technology is employed to increase the resolution and the accuracy of the measurement system. Compared with the traditional method of using constant amplitude excitation signal, this method can effectively enhance the measuring accuracy by almost one order of magnitude and reduce the root mean square error by 3.75 times under the same measurement conditions. The results of experiments show that the novel method can attain the aim of significantly improve the measurement accuracy of resistance on the premise of not increasing the system cost and complexity of the circuit, which is significantly valuable for applying in electronic instruments.

  16. Analysis of Real Ship Rolling Dynamics under Wave Excitement Force Composed of Sums of Cosine Functions

    SciTech Connect

    Zhang, Y. S.; Cai, F.; Xu, W. M.

    2011-09-28

    The ship motion equation with a cosine wave excitement force describes the slip moments in regular waves. A new kind of wave excitement force model, with the form as sums of cosine functions was proposed to describe ship rolling in irregular waves. Ship rolling time series were obtained by solving the ship motion equation with the fourth-order-Runger-Kutta method. These rolling time series were synthetically analyzed with methods of phase-space track, power spectrum, primary component analysis, and the largest Lyapunove exponent. Simulation results show that ship rolling presents some chaotic characteristic when the wave excitement force was applied by sums of cosine functions. The result well explains the course of ship rolling's chaotic mechanism and is useful for ship hydrodynamic study.

  17. Plasmon excitations in sodium atomic planes: a time-dependent density functional theory study.

    PubMed

    Wang, Bao-Ji; Xu, Yuehua; Ke, San-Huang

    2012-08-01

    The collective electronic excitation in planar sodium clusters is studied by time-dependent density functional theory calculations. The formation and development of the resonances in photoabsorption spectra are investigated in terms of the shape and size of the two-dimensional (2D) systems. The nature of these resonances is revealed by the frequency-resolved induced charge densities present on a real-space grid. For long double chains, the excitation is similar to that in long single atomic chains, showing longitudinal modes, end and central transverse modes. However, for 2D planes consisting of (n × n) atoms with n being up to 16, new 2D characteristic modes emerge regardless of the symmetries considered. For in-plane excitations, besides the equivalent end mode, mixed modes with contrary polarity occur. The relation between the frequency of the primary modes and the system size is similar to the case of a 2D electron gas but with a correction due to the realistic atomic structure. For excitations perpendicular to the plane there are corner, side center, bulk center, and circuit modes. Our calculation reveals the importance of dimensionality for plasmon excitation and how it evolves from 1D to 2D.

  18. Vertical Singlet Excitations on Adenine Dimer: A Time Dependent Density Functional Study

    NASA Astrophysics Data System (ADS)

    Crespo-Hernández, Carlos E.; Marai, Christopher N. J.

    2007-12-01

    The condense phase, excited state dynamics of the adenylyl(3'→5')adenine (ApA) dinucleotide has been previously studied using transient absorption spectroscopy with femtosecond time resolution (Crespo-Hernández et al. Chem. Rev. 104, 1977-2019 (2004)). An ultrafast and a long-lived component were observed with time constants of <1 ps and 60±16 ps, respectively. Comparison of the time constants measured for the dinucleotide with that for the adenine nucleotide suggested that the fast component observed in ApA could be assigned to monomer dynamics. The long-lived component observed in ApA was assigned to an excimer state that originates from a fraction of base stacked conformations present at the time of excitation. In this contribution, supermolecule calculations using the time dependent implementation of density functional theory is used to provide more insights on the origin of the initial Franck-Condon excitations. Monomer-like, localized excitations are observed for conformations having negligible base stacking interactions, whereas delocalized excitations are predicted for conformations with significant vertical base-base overlap.

  19. Measurement of fusion excitation functions in the system {sup 78}Kr + {sup 100}Mo

    SciTech Connect

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

    1995-08-01

    Earlier measurements of fusion reactions involving {sup 78}Kr and {sup 100}Mo projectiles and Ni-targets showed surprisingly large fusion yields at low energies which could not be explained by coupled-channels calculations. The main difference to similar measurements involving the neighboring {sup 86}Kr and {sup 92}Mo isotopes was the different slope of the excitation functions at sub-barrier energies. An analysis of a variety of experiments showed a correlation between the nuclear structure and the slope of the excitation functions, with the {open_quotes}soft{close_quotes} transitional nuclei ({sup 78}Kr, {sup 100}Mo) exhibiting shallower slopes than the {open_quotes}stiff{close_quotes} nuclei ({sup 86}Kr, {sup 92}Mo) measured at the same energies with respect to the barrier. In this experiment we studied the fusion excitation function involving two transitional nuclei {sup 78}Kr + {sup 100}Mo. The measurements were performed with {sup 78}Kr beams from the ECR source at energies between 285-370 MeV. Separation of the evaporation nucleus from the elastically scattered particles was achieved by measuring time-of-flight and magnetic rigidity in the gas-filled spectrograph. The data were completely analyzed. A comparison of the cross sections with measurements for the system {sup 86}Kr + {sup 92}Mo populating the same compound nucleus {sup 178}Pt. It shows good agreement at the highest energies, but quite different falloffs of the excitation functions toward lower energies. Coupled-channels calculations, including multi-phonon excitation for the two systems, are being performed.

  20. A relativistic time-dependent density functional study of the excited states of the mercury dimer.

    PubMed

    Kullie, Ossama

    2014-01-14

    In previous works on Zn2 and Cd2 dimers we found that the long-range corrected CAMB3LYP gives better results than other density functional approximations for the excited states, especially in the asymptotic region. In this paper, we use it to present a time-dependent density functional (TDDFT) study for the ground-state as well as the excited states corresponding to the (6s(2) + 6s6p), (6s(2) + 6s7s), and (6s(2) + 6s7p) atomic asymptotes for the mercury dimer Hg2. We analyze its spectrum obtained from all-electron calculations performed with the relativistic Dirac-Coulomb and relativistic spinfree Hamiltonian as implemented in DIRAC-PACKAGE. A comparison with the literature is given as far as available. Our result is excellent for the most of the lower excited states and very encouraging for the higher excited states, it shows generally good agreements with experimental results and outperforms other theoretical results. This enables us to give a detailed analysis of the spectrum of the Hg2 including a comparative analysis with the lighter dimers of the group 12, Cd2, and Zn2, especially for the relativistic effects, the spin-orbit interaction, and the performance of CAMB3LYP and is enlightened for similar systems. The result shows, as expected, that spinfree Hamiltonian is less efficient than Dirac-Coulomb Hamiltonian for systems containing heavy elements such as Hg2.

  1. A relativistic time-dependent density functional study of the excited states of the mercury dimer

    NASA Astrophysics Data System (ADS)

    Kullie, Ossama

    2014-01-01

    In previous works on Zn2 and Cd2 dimers we found that the long-range corrected CAMB3LYP gives better results than other density functional approximations for the excited states, especially in the asymptotic region. In this paper, we use it to present a time-dependent density functional (TDDFT) study for the ground-state as well as the excited states corresponding to the (6s2 + 6s6p), (6s2 + 6s7s), and (6s2 + 6s7p) atomic asymptotes for the mercury dimer Hg2. We analyze its spectrum obtained from all-electron calculations performed with the relativistic Dirac-Coulomb and relativistic spinfree Hamiltonian as implemented in DIRAC-PACKAGE. A comparison with the literature is given as far as available. Our result is excellent for the most of the lower excited states and very encouraging for the higher excited states, it shows generally good agreements with experimental results and outperforms other theoretical results. This enables us to give a detailed analysis of the spectrum of the Hg2 including a comparative analysis with the lighter dimers of the group 12, Cd2, and Zn2, especially for the relativistic effects, the spin-orbit interaction, and the performance of CAMB3LYP and is enlightened for similar systems. The result shows, as expected, that spinfree Hamiltonian is less efficient than Dirac-Coulomb Hamiltonian for systems containing heavy elements such as Hg2.

  2. Measurement of excitation functions in alpha induced reactions on natCu

    NASA Astrophysics Data System (ADS)

    Shahid, Muhammad; Kim, Kwangsoo; Kim, Guinyun; Zaman, Muhammad; Nadeem, Muhammad

    2015-09-01

    The excitation functions of 66,67,68Ga, 62,63,65Zn, 61,64Cu, and 58,60Co radionuclides in the natCu(α, x) reaction were measured in the energy range from 15 to 42 MeV by using a stacked-foil activation method at the MC-50 cyclotron of the Korean Institute of Radiological and Medical Sciences. The measured results were compared with the literature data as well as the theoretical values obtained from the TENDL-2013 and TENDL-2014 libraries based on the TALYS-1.6 code. The integral yields for thick targets of the produced radionuclides were also determined from the measured excitation functions and the stopping power of natural copper.

  3. Measurement of the 208Pb(52Cr, n)259Sg Excitation Function

    SciTech Connect

    Folden III, C.M.; Dragojevic, I.; Dullmann, Ch.E.; Eichler, R.; Garcia, M.A.; Gates, J.M.; Nelson, S.L.; Sudowe, R.; Gregorich, K.E.; Hoffman, D.C.; Nitsche, H.

    2010-03-19

    The excitation function for the 208Pb(52Cr, n)259Sg reaction has been measured using the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. The maximum cross section of pb is observed at a center-of-target laboratory-frame energy of 253.0 MeV. In total, 25 decay chains originating from 259Sg were observed and the measured decay properties are in good agreement with previous reports. In addition, a partial excitation function for the 208Pb(52Cr, 2n)258Sg reaction was obtained, and an improved 258Sg half-life of ms was calculated by combining all available experimental data.

  4. Generating functions and stability study of multivariate self-excited epidemic processes

    NASA Astrophysics Data System (ADS)

    Saichev, A. I.; Sornette, D.

    2011-09-01

    We present a stability study of the class of multivariate self-excited Hawkes point processes, that can model natural and social systems, including earthquakes, epileptic seizures and the dynamics of neuron assemblies, bursts of exchanges in social communities, interactions between Internet bloggers, bank network fragility and cascading of failures, national sovereign default contagion, and so on. We present the general theory of multivariate generating functions to derive the number of events over all generations of various types that are triggered by a mother event of a given type. We obtain the stability domains of various systems, as a function of the topological structure of the mutual excitations across different event types. We find that mutual triggering tends to provide a significant extension of the stability (or subcritical) domain compared with the case where event types are decoupled, that is, when an event of a given type can only trigger events of the same type.

  5. Communication: Excited states, dynamic correlation functions and spectral properties from full configuration interaction quantum Monte Carlo.

    PubMed

    Booth, George H; Chan, Garnet Kin-Lic

    2012-11-21

    In this communication, we propose a method for obtaining isolated excited states within the full configuration interaction quantum Monte Carlo framework. This method allows for stable sampling with respect to collapse to lower energy states and requires no uncontrolled approximations. In contrast with most previous methods to extract excited state information from quantum Monte Carlo methods, this results from a modification to the underlying propagator, and does not require explicit orthogonalization, analytic continuation, transient estimators, or restriction of the Hilbert space via a trial wavefunction. Furthermore, we show that the propagator can directly yield frequency-domain correlation functions and spectral functions such as the density of states which are difficult to obtain within a traditional quantum Monte Carlo framework. We demonstrate this approach with pilot applications to the neon atom and beryllium dimer.

  6. The transfer function method for gear system dynamics applied to conventional and minimum excitation gearing designs

    NASA Technical Reports Server (NTRS)

    Mark, W. D.

    1982-01-01

    A transfer function method for predicting the dynamic responses of gear systems with more than one gear mesh is developed and applied to the NASA Lewis four-square gear fatigue test apparatus. Methods for computing bearing-support force spectra and temporal histories of the total force transmitted by a gear mesh, the force transmitted by a single pair of teeth, and the maximum root stress in a single tooth are developed. Dynamic effects arising from other gear meshes in the system are included. A profile modification design method to minimize the vibration excitation arising from a pair of meshing gears is reviewed and extended. Families of tooth loading functions required for such designs are developed and examined for potential excitation of individual tooth vibrations. The profile modification design method is applied to a pair of test gears.

  7. Two-photon excitation of porphyrin-functionalized porous silicon nanoparticles for photodynamic therapy.

    PubMed

    Secret, Emilie; Maynadier, Marie; Gallud, Audrey; Chaix, Arnaud; Bouffard, Elise; Gary-Bobo, Magali; Marcotte, Nathalie; Mongin, Olivier; El Cheikh, Khaled; Hugues, Vincent; Auffan, Mélanie; Frochot, Céline; Morère, Alain; Maillard, Philippe; Blanchard-Desce, Mireille; Sailor, Michael J; Garcia, Marcel; Durand, Jean-Olivier; Cunin, Frédérique

    2014-12-01

    Porous silicon nanoparticles (pSiNPs) act as a sensitizer for the 2-photon excitation of a pendant porphyrin using NIR laser light, for imaging and photodynamic therapy. Mannose-functionalized pSiNPs can be vectorized to MCF-7 human breast cancer cells through a mannose receptor-mediated endocytosis mechanism to provide a 3-fold enhancement of the 2-photon PDT effect.

  8. Comparison of polar motion excitation functions computed from different sets of gravimetric coefficients

    NASA Astrophysics Data System (ADS)

    Nastula, J.; Winska, M.; Birylo, M.

    2015-08-01

    Since its launch in February, the Gravity Recovery and Climate Experiment (GRACE) has been source of data of temporal changes in Earth's gravity field. These gravity fields can be used to determine the changing mass field of the Earth caused by redistribution of the geophysical fluids, and from that excitations of polar motion. The so-called Level 2 gravity field product are available, in the form of changes in the coefficients: C_{nm}, S_{nm}. Since 2002 until the present time there are still attempts to better process these data. In this study we estimate gravimetric excitation of polar motion using a recent series of C_{21}, S_{21} coefficients. In our calculations we use several series developed by different centers. Firstly, we compare these gravimetric functions with each other. Then we examine the compatibility of these functions with hydrological signal in observed geodetic excitation function. We focus on seasonal and subseasonal time scales. The main purpose is to explore which from these several solutions are closed.

  9. Influence of the excited states on the electron-energy distribution function in low-pressure microwave argon plasmas

    SciTech Connect

    Yanguas-Gil, A.; Cotrino, J.; Gonzalez-Elipe, A.R.

    2005-07-01

    In this work the influence of the excited states on the electron-energy distribution function has been determined for an argon microwave discharge at low pressure. A collisional-radiative model of argon has been developed taking into account the most recent experimental and theoretical values of argon-electron-impact excitation cross sections. The model has been solved along with the electron Boltzmann equation in order to study the influence of the inelastic collisions from the argon excited states on the electron-energy distribution function. Results show that under certain conditions the excited states can play an important role in determining the shape of the distribution function and the mean kinetic energy of the electrons, deplecting the high-energy tail due to inelastic processes from the excited states, especially from the 4s excited configuration. It has been found that from the populations of the excited states an excitation temperature can be defined. This excitation temperature, which can be experimentally determined by optical emission spectroscopy, is lower than the electron kinetic temperature obtained from the electron-energy distribution function.

  10. Measurement of the fusion excitation function for 19O + 12C at near barrier energies

    NASA Astrophysics Data System (ADS)

    Singh, Varinderjit; Steinbach, T. K.; Vadas, J.; Wiggins, B. B.; Hudan, S.; Desouza, R. T.; Baby, L. T.; Tripathi, V.; Kuvin, S. A.; Wiedenhover, I.

    2015-10-01

    Fusion of neutron-rich light nuclei in the outer crust of an accreting neutron star has been proposed as responsible for triggering X-ray super-bursts. The underlying hypothesis in this proposition is that the fusion of neutron-rich nuclei is enhanced as compared to stable nuclei. To investigate this hypothesis, an experiment has been performed to measure the fusion excitation function for 18O and 19O nuclei incident on a 12C target. A beam of 19O was produced by the 18O(d,p) reaction at Florida State University and separated using the RESOLUT mass spectrometer. The resulting 19O beam bombarded a 100 μg/cm2 12C target at an intensity of 2-4 × 103 p/s. Evaporation residues resulting from the de-excitation of the fusion product were distinguished by measuring their energy and time-of-flight. Using silicon detectors, micro-channel plate detectors, and an ionization chamber, evaporation residues were detected in the angular range θlab <= 23° with high efficiency. Initial experimental results including measurement of the fusion cross-section to approximately the 100 mb level will be presented. The measured excitation function will be compared to theoretical predictions. Supported by the US DOE under Grand No. DEFG02-88ER-40404.

  11. A closer look at the apparent correlation of structural and functional connectivity in excitable neural networks

    NASA Astrophysics Data System (ADS)

    Messé, Arnaud; Hütt, Marc-Thorsten; König, Peter; Hilgetag, Claus C.

    2015-01-01

    The relationship between the structural connectivity (SC) and functional connectivity (FC) of neural systems is a central focus in brain network science. It is an open question, however, how strongly the SC-FC relationship depends on specific topological features of brain networks or the models used for describing excitable dynamics. Using a basic model of discrete excitable units that follow a susceptible - excited - refractory dynamic cycle (SER model), we here analyze how functional connectivity is shaped by the topological features of a neural network, in particular its modularity. We compared the results obtained by the SER model with corresponding simulations by another well established dynamic mechanism, the Fitzhugh-Nagumo model, in order to explore general features of the SC-FC relationship. We showed that apparent discrepancies between the results produced by the two models can be resolved by adjusting the time window of integration of co-activations from which the FC is derived, providing a clearer distinction between co-activations and sequential activations. Thus, network modularity appears as an important factor shaping the FC-SC relationship across different dynamic models.

  12. Measurement of fusion excitation function for 7Li+64Ni near the barrier

    NASA Astrophysics Data System (ADS)

    Moin Shaikh, Md.; Roy, Subinit; Rajbanshi, S.; Mukherjee, A.; Pradhan, M. K.; Basu, P.; Pal, S.; Nanal, V.; Shrivastava, A.; Saha, S.; Pillay, R. G.

    2016-05-01

    Total fusion (TF) excitation function has been measured for the system 7Li + 64Ni at the energies near the Coulomb barrier of the system. The evaporation residue (ER) cross sections have been estimated through the online detection of characteristic γ-rays of the ERs. The summed ER cross sections yielding the experimental TF cross section have been compared with the theoretical one dimensional barrier penetration model (1DBPM) prediction. The measured and the model cross sections are very close to each other at above barrier energies. However, an enhancement of the experimental TF cross section with respect to the 1DBPM prediction is observed at below barrier energies. Coupled channels (CC) calculation with inelastic excitations alone could not explain the enhancement. The origin of the enhancement is identified as due to the enhanced population of the αxn channels.

  13. A developmental switch in the excitability and function of the starburst network in the mammalian retina.

    PubMed

    Zheng, Ji-Jian; Lee, Seunghoon; Zhou, Z Jimmy

    2004-12-01

    Dual patch-clamp recording and Ca2+ uncaging revealed Ca2+-dependent corelease of ACh and GABA from, and the presence of reciprocal nicotinic and GABAergic synapses between, starburst cells in the perinatal rabbit retina. With maturation, the nicotinic synapses between starburst cells dramatically diminished, whereas the GABAergic synapses remained and changed from excitatory to inhibitory, indicating a coordinated conversion of the starburst network excitability from an early hyperexcitatory to a mature nonepileptic state. We show that this transition allows the starburst cells to use their neurotransmitters for two completely different functions. During early development, the starburst network mediates recurrent excitation and spontaneous retinal waves, which are important for visual system development. After vision begins, starburst cells release GABA in a prolonged and Ca2+-dependent manner and inhibit each other laterally via direct GABAergic synapses, which may be important for visual integration, such as the detection of motion direction.

  14. A relativistic time-dependent density functional study of the excited states of the mercury dimer

    SciTech Connect

    Kullie, Ossama E-mail: ossama.kullie@unistra.fr

    2014-01-14

    In previous works on Zn{sub 2} and Cd{sub 2} dimers we found that the long-range corrected CAMB3LYP gives better results than other density functional approximations for the excited states, especially in the asymptotic region. In this paper, we use it to present a time-dependent density functional (TDDFT) study for the ground-state as well as the excited states corresponding to the (6s{sup 2} + 6s6p), (6s{sup 2} + 6s7s), and (6s{sup 2} + 6s7p) atomic asymptotes for the mercury dimer Hg{sub 2}. We analyze its spectrum obtained from all-electron calculations performed with the relativistic Dirac-Coulomb and relativistic spinfree Hamiltonian as implemented in DIRAC-PACKAGE. A comparison with the literature is given as far as available. Our result is excellent for the most of the lower excited states and very encouraging for the higher excited states, it shows generally good agreements with experimental results and outperforms other theoretical results. This enables us to give a detailed analysis of the spectrum of the Hg{sub 2} including a comparative analysis with the lighter dimers of the group 12, Cd{sub 2}, and Zn{sub 2}, especially for the relativistic effects, the spin-orbit interaction, and the performance of CAMB3LYP and is enlightened for similar systems. The result shows, as expected, that spinfree Hamiltonian is less efficient than Dirac-Coulomb Hamiltonian for systems containing heavy elements such as Hg{sub 2}.

  15. Excited-state nuclear forces on adiabatic potential-energy surfaces by time-dependent density-functional theory

    NASA Astrophysics Data System (ADS)

    Haruyama, Jun; Suzuki, Takahiro; Hu, Chunping; Watanabe, Kazuyuki

    2012-01-01

    We present a simple and computationally efficient method to calculate excited-state nuclear forces on adiabatic potential-energy surfaces (APES) from linear-response time-dependent density-functional theory within a real-space framework. The Casida ansatz, which has been validated for computing first-order nonadiabatic couplings in previous studies, was applied to the calculation of the excited-state forces. Our method is validated by the consistency of results in the lower excited states, which reproduce well those obtained by the numerical derivative of each APES. We emphasize the usefulness of this technique by demonstrating the excited-state molecular-dynamics simulation.

  16. Beyond Time-Dependent Density Functional Theory Using Only Single Excitations: Methods for Computational Studies of Excited States in Complex Systems.

    PubMed

    Herbert, John M; Zhang, Xing; Morrison, Adrian F; Liu, Jie

    2016-05-17

    Single-excitation methods, namely, configuration interaction singles and time-dependent density functional theory (TDDFT), along with semiempirical versions thereof, represent the most computationally affordable electronic structure methods for describing electronically excited states, scaling as [Formula: see text] absent further approximations. This relatively low cost, combined with a treatment of electron correlation, has made TDDFT the most widely used excited-state quantum chemistry method over the past 20+ years. Nevertheless, certain inherent problems (beyond just the accuracy of this or that exchange-correlation functional) limit the utility of traditional TDDFT. For one, it affords potential energy surfaces whose topology is incorrect in the vicinity of any conical intersection (CI) that involves the ground state. Since CIs are the conduits for transitions between electronic states, the TDDFT description of photochemistry (internal conversion and intersystem crossing) is therefore suspect. Second, the [Formula: see text] cost can become prohibitive in large systems, especially those that involve multiple electronically coupled chromophores, for example, the antennae structures of light-harvesting complexes or the conjugated polymers used in organic photovoltaics. In such cases, the smallest realistic mimics might already be quite large from the standpoint of ab initio quantum chemistry. This Account describes several new computational methods that address these problems. Topology around a CI can be rigorously corrected using a "spin-flip" version of TDDFT, which involves an α → β spin-flipping transition in addition to occupied → virtual excitation of one electron. Within this formalism, singlet states are generated via excitation from a high-spin triplet reference state, doublets from a quartet, etc. This provides a more balanced treatment of electron correlation between ground and excited states. Spin contamination is problematic away from the

  17. Electronic excitation spectra from time-dependent density functional response theory using plane-wave methods

    NASA Astrophysics Data System (ADS)

    Doltsinis, Nikos L.; Sprik, Michiel

    2000-11-01

    The time-dependent density functional response theory method for the computation of electronic excitation spectra has been implemented in a plane-wave basis set/pseudo-potential formalism. We compare our test results for N2 and H2CO to literature atomic basis set calculations and find good agreement. We also discuss some of the technical complications specific to the use of plane-wave basis sets. As an application, the thermally broadened photoabsorption spectrum of formamide at room temperature is computed by averaging over a number of vibrational configurations sampled from an ab initio molecular dynamics run and compared to experiment.

  18. Finding Limit Cycles in self-excited oscillators with infinite-series damping functions

    NASA Astrophysics Data System (ADS)

    Das, Debapriya; Banerjee, Dhruba; Bhattacharjee, Jayanta K.

    2015-03-01

    In this paper we present a simple method for finding the location of limit cycles of self excited oscillators whose damping functions can be represented by some infinite convergent series. We have used standard results of first-order perturbation theory to arrive at amplitude equations. The approach has been kept pedagogic by first working out the cases of finite polynomials using elementary algebra. Then the method has been extended to various infinite polynomials, where the fixed points of the corresponding amplitude equations cannot be found out. Hopf bifurcations for systems with nonlinear powers in velocities have also been discussed.

  19. Green's functions for analysis of dynamic response of wheel/rail to vertical excitation

    NASA Astrophysics Data System (ADS)

    Mazilu, Traian

    2007-09-01

    An analytical model to simulate wheel/rail interaction using the Green's functions method is proposed in this paper. The model consists of a moving wheel on a discretely supported rail. Particularly for this model of rail, the bending and the longitudinal displacement are coupled due to the rail pad and a complex model of the rail pad is adopted. An efficient method for solving a time-domain analysis for wheel/rail interaction is presented. The method is based on the properties of the rail's Green functions and starting to these functions, a track's Green matrix is assembled for the numerical simulations of wheel/rail response due to three kinds of vertical excitations: the steady-state interaction, the rail corrugation and the wheel flat. The study points to influence of the worn rail—rigid contact—on variation in the wheel/rail contact force. The concept of pinned-pinned inhibitive rail pad is also presented.

  20. Charge asymmetry in rovibrationally excited HD{sup +} determined using explicitly correlated all-particle Gaussian functions

    SciTech Connect

    Kirnosov, Nikita; Sharkey, Keeper L.; Adamowicz, Ludwik

    2013-11-28

    Very accurate non-Born-Oppenheimer quantum-mechanical calculations are performed to determine the average values of the interparticle distances and the proton-deuteron density function for the rovibrationally excited HD{sup +} ion. The states corresponding to excitations to all bound vibrational states (v = 0, …, 22) and simultaneously excited to the first excited rotational state (N = 1) are considered. To describe each state up to 8000 explicitly correlated all-particle Gaussian functions are used. The nonlinear parameters of the Gaussians are variationally optimized using a procedure that employs the analytical energy gradient determined with respect to these parameters. The results show an increasing asymmetry in the electron distribution with the vibrational excitation as the electron density shifts towards deuteron and away from the proton.

  1. Neuropeptides function in a homeostatic manner to modulate excitation-inhibition imbalance in C. elegans.

    PubMed

    Stawicki, Tamara M; Takayanagi-Kiya, Seika; Zhou, Keming; Jin, Yishi

    2013-05-01

    Neuropeptides play crucial roles in modulating neuronal networks, including changing intrinsic properties of neurons and synaptic efficacy. We previously reported a Caenorhabditis elegans mutant, acr-2(gf), that displays spontaneous convulsions as the result of a gain-of-function mutation in a neuronal nicotinic acetylcholine receptor subunit. The ACR-2 channel is expressed in the cholinergic motor neurons, and acr-2(gf) causes cholinergic overexcitation accompanied by reduced GABAergic inhibition in the locomotor circuit. Here we show that neuropeptides play a homeostatic role that compensates for this excitation-inhibition imbalance in the locomotor circuit. Loss of function in genes required for neuropeptide processing or release of dense core vesicles specifically modulate the convulsion frequency of acr-2(gf). The proprotein convertase EGL-3 is required in the cholinergic motor neurons to restrain convulsions. Electrophysiological recordings of neuromuscular junctions show that loss of egl-3 in acr-2(gf) causes a further reduction of GABAergic inhibition. We identify two neuropeptide encoding genes, flp-1 and flp-18, that together counteract the excitation-inhibition imbalance in acr-2(gf) mutants. We further find that acr-2(gf) causes an increased expression of flp-18 in the ventral cord cholinergic motor neurons and that overexpression of flp-18 reduces the convulsion of acr-2(gf) mutants. The effects of these peptides are in part mediated by two G-protein coupled receptors, NPR-1 and NPR-5. Our data suggest that the chronic overexcitation of the cholinergic motor neurons imposed by acr-2(gf) leads to an increased production of FMRFamide neuropeptides, which act to decrease the activity level of the locomotor circuit, thereby homeostatically modulating the excitation and inhibition imbalance.

  2. Can we improve the calculation of some excitation functions for deuteron-induced reactions?

    NASA Astrophysics Data System (ADS)

    Pierre Chau, Huu-Tai

    2015-12-01

    In this paper, we propose to use the CDCC* approach to calculate (d,p) excitation functions. Starting from the CDCC* results, we derive some (d,p) differential and integrated cross sections, then using a simple semi-phenomenological model, we calculate the excitation functions for this process. We compare our calculations with the experimental cross sections for the 27Al (d, p)28Al, 58Fe(d, p)59Fe, 59Co(d, p)60Co, 75As(d, p)76As, 81Br(d, p)82Br, 84Kr(d, p)85Kr, 86Kr(d, p)87Kr, 108Pd (d, p)109Pd, 140Ce(d, p)141Ce, 142Ce(d, p)143Ce, 141Pr(d, p)142Pr, 165Ho(d, p)166Ho, and 180Hf (d, p)181Hf reactions. We plan to include these cross sections into evaluations of d-induced reactions and this could be a first step for improving of the quality of the next decade cross sections libraries.

  3. Comparison between Theoretical Calculation and Experimental Results of Excitation Functions for Production of Relevant Biomedical Radionuclides

    SciTech Connect

    Menapace, E.; Birattari, C.; Bonardi, M.L.; Groppi, F.; Morzenti, S.; Zona, C.

    2005-05-24

    The radionuclide production for biomedical applications has been brought up in the years, as a special nuclear application, at INFN LASA Laboratory, particularly in co-operation with the JRC-Ispra of EC. Mainly scientific aspects concerning radiation detection and the relevant instruments, the measurements of excitation functions of the involved nuclear reactions, the requested radiochemistry studies and further applications have been investigated. On the side of the nuclear data evaluations, based on nuclear model calculations and critically selected experimental data, the appropriate competence has been developed at ENEA Division for Advanced Physics Technologies. A series of high specific activity accelerator-produced radionuclides in no-carrier-added (NCA) form, for uses in metabolic radiotherapy and for PET radiodiagnostics, are investigated. In this work, last revised measurements and model calculations are reviewed for excitation functions of natZn(d,X)64Cu, 66Ga reactions, referring to irradiation experiments at K=38 variable energy Cyclotron of JRC-Ispra. Concerning the reaction data for producing 186gRe and 211At/211gPo (including significant emission spectra) and 210At, most recent and critically selected experimental results are considered and discussed in comparison with model calculations paying special care to pre-equilibrium effects estimate and to the appropriate overall parameterization. Model calculations are presented for 226Ra(p,2n)225Ac reaction, according to the working program of the ongoing IAEA CRP on the matter.

  4. Visualization of molecular fluorescence point spread functions via remote excitation switching fluorescence microscopy

    PubMed Central

    Su, Liang; Lu, Gang; Kenens, Bart; Rocha, Susana; Fron, Eduard; Yuan, Haifeng; Chen, Chang; Van Dorpe, Pol; Roeffaers, Maarten B. J.; Mizuno, Hideaki; Hofkens, Johan; Hutchison, James A.; Uji-i, Hiroshi

    2015-01-01

    The enhancement of molecular absorption, emission and scattering processes by coupling to surface plasmon polaritons on metallic nanoparticles is a key issue in plasmonics for applications in (bio)chemical sensing, light harvesting and photocatalysis. Nevertheless, the point spread functions for single-molecule emission near metallic nanoparticles remain difficult to characterize due to fluorophore photodegradation, background emission and scattering from the plasmonic structure. Here we overcome this problem by exciting fluorophores remotely using plasmons propagating along metallic nanowires. The experiments reveal a complex array of single-molecule fluorescence point spread functions that depend not only on nanowire dimensions but also on the position and orientation of the molecular transition dipole. This work has consequences for both single-molecule regime-sensing and super-resolution imaging involving metallic nanoparticles and opens the possibilities for fast size sorting of metallic nanoparticles, and for predicting molecular orientation and binding position on metallic nanoparticles via far-field optical imaging. PMID:25687887

  5. Visualization of molecular fluorescence point spread functions via remote excitation switching fluorescence microscopy.

    PubMed

    Su, Liang; Lu, Gang; Kenens, Bart; Rocha, Susana; Fron, Eduard; Yuan, Haifeng; Chen, Chang; Van Dorpe, Pol; Roeffaers, Maarten B J; Mizuno, Hideaki; Hofkens, Johan; Hutchison, James A; Uji-I, Hiroshi

    2015-01-01

    The enhancement of molecular absorption, emission and scattering processes by coupling to surface plasmon polaritons on metallic nanoparticles is a key issue in plasmonics for applications in (bio)chemical sensing, light harvesting and photocatalysis. Nevertheless, the point spread functions for single-molecule emission near metallic nanoparticles remain difficult to characterize due to fluorophore photodegradation, background emission and scattering from the plasmonic structure. Here we overcome this problem by exciting fluorophores remotely using plasmons propagating along metallic nanowires. The experiments reveal a complex array of single-molecule fluorescence point spread functions that depend not only on nanowire dimensions but also on the position and orientation of the molecular transition dipole. This work has consequences for both single-molecule regime-sensing and super-resolution imaging involving metallic nanoparticles and opens the possibilities for fast size sorting of metallic nanoparticles, and for predicting molecular orientation and binding position on metallic nanoparticles via far-field optical imaging. PMID:25687887

  6. SLEEPLESS is a bi-functional regulator of excitability and cholinergic synaptic transmission

    PubMed Central

    Wu, Meilin; Robinson, James E.; Joiner, William J.

    2014-01-01

    Summary Background Although sleep is conserved throughout evolution, the molecular basis of its control is still largely a mystery. We previously showed that the quiver/sleepless (qvr/sss) gene encodes a membrane-tethered protein that is required for normal sleep in Drosophila. SLEEPLESS (SSS) protein functions, at least in part, by upregulating the levels and open probability of Shaker (Sh) potassium channels to suppress neuronal excitability and enable sleep. Consistent with this proposed mechanism, loss-of-function mutations in Sh phenocopy qvr/sss null mutants. However, sleep is more genetically modifiable in Sh than in qvr/sss mutants, suggesting that sss may regulate additional molecules to influence sleep. Results Here we show that SSS also antagonizes nicotinic acetylcholine receptors (nAChRs) to reduce synaptic transmission and promote sleep. Mimicking this antagonism with the nAChR inhibitor mecamylamine or by RNAi knockdown of specific nAChR subunits is sufficient to restore sleep to qvr/sss mutants. Regulation of nAChR activity by SSS occurs post-transcriptionally since the levels of nAChR mRNAs are unchanged in qvr/sss mutants. Regulation of nAChR activity by SSS may in fact be direct, since SSS forms a stable complex with and antagonizes fly nAChR function in transfected cells. Intriguingly, lynx1, a mammalian homolog of SSS, can partially restore normal sleep to qvr/sss mutants, and lynx1 can form stable complexes with Shaker-type channels and nAChRs. Conclusions Together, our data point to an evolutionarily conserved, bi-functional role for SSS and its homologs in controlling excitability and synaptic transmission in fundamental processes of the nervous system such as sleep. PMID:24613312

  7. Excitation spectra and correlation functions of quantum Su-Schrieffer-Heeger models

    NASA Astrophysics Data System (ADS)

    Weber, Manuel; Assaad, Fakher F.; Hohenadler, Martin

    2015-06-01

    We study one-dimensional Su-Schrieffer-Heeger (SSH) models with quantum phonons using a continuous-time quantum Monte Carlo method. Within statistical errors, we obtain identical results for the SSH model with acoustic phonons, and a related model with a coupling to an optical bond phonon mode. Based on this agreement, we first study the Peierls metal-insulator transition of the spinless SSH model, and relate it to the Kosterlitz-Thouless transition of a spinless Luttinger liquid. In the Peierls phase, the spectral functions reveal the single-particle and charge gap, and a central peak related to long-range order. For the spinful SSH model, which has a dimerized ground state for any nonzero coupling, we reveal a symmetry-related degeneracy of spin and charge excitations, and the expected spin and charge gaps as well as a central peak. Finally, we study the SSH-U V model with electron-phonon and electron-electron interaction. We observe a Mott phase with critical spin and bond correlations at weak electron-phonon coupling, and a Peierls phase with gapped spin excitations at strong coupling. We relate our findings to the extended Hubbard model, and discuss the physical origin of the agreement between optical and acoustic phonons.

  8. Spin contamination-free N-electron wave functions in the excitation-based configuration interaction treatment

    NASA Astrophysics Data System (ADS)

    Alcoba, Diego R.; Torre, Alicia; Lain, Luis; Massaccesi, Gustavo E.; Oña, Ofelia B.; Capuzzi, Pablo

    2016-07-01

    This work deals with the spin contamination in N-electron wave functions provided by the excitation-based configuration interaction methods. We propose a procedure to ensure a suitable selection of excited N-electron Slater determinants with respect to a given reference determinant, required in these schemes. The procedure guarantees the construction of N-electron wave functions which are eigenfunctions of the spin-squared operator S ˆ 2 , avoiding any spin contamination. Our treatment is based on the evaluation of the excitation level of the determinants by means of the expectation value of an excitation operator formulated in terms of spin-free replacement operators. We report numerical determinations of energies and < S ˆ 2 > expectation values, arising from our proposal as well as from traditional configuration interaction methods, in selected open-shell systems, in order to compare the behavior of these procedures and their computational costs.

  9. Calculation of vibrational and electronic excited state absorption spectra of arsenic-water complexes using density functional theory

    NASA Astrophysics Data System (ADS)

    Huang, L.; Lambrakos, S. G.; Shabaev, A.; Massa, L.

    2016-05-01

    Calculations are presented of vibrational and electronic excited-state absorption spectra for As-H2O complexes using density function theory (DFT) and time-dependent density functional theory (TD-DFT). DFT and TD-DFT can provide interpretation of absorption spectra with respect to molecular structure for excitation by electromagnetic waves at frequencies within the IR and UV-visible ranges. The absorption spectrum corresponding to excitation states of As-H2O complexes consisting of relatively small numbers of water molecules should be associated with response features that are intermediate between that of isolated molecules and that of a bulk system. DFT and TD-DFT calculated absorption spectra represent quantitative estimates that can be correlated with additional information obtained from laboratory measurements and other types of theory based calculations. The DFT software GAUSSIAN was used for the calculations of excitation states presented here.

  10. Multiconfiguration Pair-Density Functional Theory Outperforms Kohn-Sham Density Functional Theory and Multireference Perturbation Theory for Ground-State and Excited-State Charge Transfer.

    PubMed

    Ghosh, Soumen; Sonnenberger, Andrew L; Hoyer, Chad E; Truhlar, Donald G; Gagliardi, Laura

    2015-08-11

    The correct description of charge transfer in ground and excited states is very important for molecular interactions, photochemistry, electrochemistry, and charge transport, but it is very challenging for Kohn-Sham (KS) density functional theory (DFT). KS-DFT exchange-correlation functionals without nonlocal exchange fail to describe both ground- and excited-state charge transfer properly. We have recently proposed a theory called multiconfiguration pair-density functional theory (MC-PDFT), which is based on a combination of multiconfiguration wave function theory with a new type of density functional called an on-top density functional. Here we have used MC-PDFT to study challenging ground- and excited-state charge-transfer processes by using on-top density functionals obtained by translating KS exchange-correlation functionals. For ground-state charge transfer, MC-PDFT performs better than either the PBE exchange-correlation functional or CASPT2 wave function theory. For excited-state charge transfer, MC-PDFT (unlike KS-DFT) shows qualitatively correct behavior at long-range with great improvement in predicted excitation energies.

  11. Efficient evaluation of dielectric response functions and calculations of ground and excited state properties beyond local Density Functional approaches

    NASA Astrophysics Data System (ADS)

    Lu, Deyu; Li, Yan; Rocca, Dario; Viet Nguyen, H.; Gygi, Francois; Galli, Giulia

    2010-03-01

    A recently developed technique to diagonalize iteratively dielectric matrices [1], is used to carry out efficient, ab-initio calculations of dispersion interactions, and excited state properties of nanostructures. In particular, we present results for the binding energies of weakly bonded molecular crystals [2], obtained at the EXX/RPA level of theory, and for absorption spectra of semiconducting clusters, obtained by an iterative solution of the Bethe-Salpeter equations [3]. We show that the ability to obtain the eigenmodes of dielectric matrices from Density Functional perturbation theory, without computing single particle excited states, greatly improves the efficiency of both EXX/RPA and many body perturbation theory [3,4] calculations and opens the way to large scale computations. [1] H. Wilson, F. Gygi and G. Galli, Phys. Rev. B , 78, 113303, 2008; and H. Wilson, D. Lu, F. Gygi and G. Galli, Phys. Rev. B, 79, 245106, 2009. [2] D. Lu, Y. Li, D. Rocca and G. Galli, Phys. Rev. Lett, 102, 206411, 2009; and Y. Li, D. Lu, V. Nguyen and G. Galli, J. Phys. Chem. C (submitted) [3] D. Rocca, D. Lu and G. Galli, submitted. [4] D. Lu, F. Gygi and G. Galli, Phys. Rev. Lett. 100, 147601, 2008. Work was funded by DOE/Scidac DE-FC02-06ER25794 and DOE/BES DE-FG02-06ER46262.

  12. The use of coherence functions to determine dynamic excitation sources on launch vehicle payloads

    NASA Technical Reports Server (NTRS)

    Barrett, S.; Halvorson, R. M.

    1979-01-01

    The problem of determining the relative contribution of simultaneous acoustic and mechanical inputs to the response of structures under combined dynamic loads was studied. An analytical technique developed by Bendat for calculating ordinary, partial, and multiple coherence functions, using an iterative nonmatrix approach was applied to data obtained from laboratory tests on a complex structural assembly. Testing was performed in an acoustically 'live' room. Up to three random inputs, having similar spectral content and varying degrees of mutual coherence, and a single output were used. Stationary and nonstationary inputs were used. It was concluded that the technique provided an effective method of identifying sources of dynamic excitation and evaluating their relative contributions to the measured output at structural resonances, for stationary random inputs. An attempt to apply the technique to nonstationary inputs did not yield consistent results.

  13. A multireference density functional approach to the calculation of the excited states of uranium ions

    NASA Astrophysics Data System (ADS)

    Beck, Eric V.

    An accurate and efficient hybrid Density Functional Theory (DFT) and Multireference Configuration Interaction (MRCI) model for computing electronic excitation energies in atoms and molecules was developed. The utility of a hybrid method becomes apparent when ground and excited states of large molecules, clusters of molecules, or even moderately sized molecules containing heavy element atoms are desired. In the case of large systems of lighter elements, the hybrid method brings to bear the numerical efficiency of the DFT method in computing the electron-electron dynamic correlation, while including non-dynamical electronic correlation via the Configuration Interaction (CI) calculation. Substantial reductions in the size of the CI expansion necessary to obtain accurate spectroscopic results are possible in the hybrid method. Where heavy element compounds are of interest, fully relativistic calculations based upon the Dirac Hamiltonian rapidly become computationally prohibitive, as the basis set requirements in four-component calculations increase by a factor of two or more in order to satisfy kinetic balance between the large electronic components and small positronic components, while the size of the MRCI Hamiltonian quadruples with respect to a non-relativistic calculation. In this hybrid method, applications to heavy element compounds such as bromine and uranium were accomplished through the use of relativistic effective core potentials, allowing for the first time both scalar relativistic and spin-orbit effect treatment necessary for the accurate calculation of electronic excitation energies in heavy elements in a Density Functional Theory Multireference Configuration Interaction Hybrid Model (DFT/MRCI) method. This implementation of the original hybrid method, developed by Grimme and Waletzke, was modified to remove inherent spin-multiplicity limitations, as well as reduce the number of free parameters used in the method from five to three. The DFT portion of

  14. Comparison of hydrological and GRACE-based excitation functions of polar motion in the seasonal spectral band

    NASA Astrophysics Data System (ADS)

    Nastula, J.; Kolaczek, B.; Salstein, D. A.

    2008-04-01

    Understanding changes in the global balance of the Earths angular momentum due to the mass redistribution of geophysical fluids is needed to explain the observed polar motion. The impact of continental hydrologic signals, from land water, snow, and ice, on polar motion excitation (hydrological angular momentum-HAM), is still inadequately known. Although estimates of HAM have been made from several models of global hydrology based upon the observed distribution of surface water, snow, and soil moisture, the relatively sparse observation network and the presence of errors in the data and the geophysical fluid models preclude a full understanding of the HAM influence on polar motion variations. Recently the GRACE mission monitoring Earths time variable gravity field has allowed us to determine the mass term of polar motion excitation functions and compare them with the mass term derivable as a residual from the geodetic excitation functions and geophysical fluid motion terms on seasonal time scales. Differences between these mass terms in the years 2004 - 2005.5 are still on the order of 20 mas. Besides the overall mass excitation of polar motion comparisons with GRACE (RL04-release), we also intercompare the non-atmospheric, non-oceanic signals in the mass term of geodetic polar motion excitation with hydrological excitation of polar motion.

  15. Obtaining Hartree-Fock and density functional theory doubly excited states with Car-Parrinello density matrix search

    NASA Astrophysics Data System (ADS)

    Liang, Wenkel; Isborn, Christine M.; Li, Xiaosong

    2009-11-01

    The calculation of doubly excited states is one of the major problems plaguing the modern day excited state workhorse methodology of linear response time dependent Hartree-Fock (TDHF) and density function theory (TDDFT). We have previously shown that the use of a resonantly tuned field within real-time TDHF and TDDFT is able to simultaneously excite both the α and β electrons to achieve the two-electron excited states of minimal basis H2 and HeH+ [C. M. Isborn and X. Li, J. Chem. Phys. 129, 204107 (2008)]. We now extend this method to many electron systems with the use of our Car-Parrinello density matrix search (CP-DMS) with a first-principles fictitious mass method for wave function optimization [X. Li, C. L. Moss, W. Liang, and Y. Feng, J. Chem. Phys. 130, 234115 (2009)]. Real-time TDHF/TDDFT is used during the application of the laser field perturbation, driving the electron density toward the doubly excited state. The CP-DMS method then converges the density to the nearest stationary state. We present these stationary state doubly excited state energies and properties at the HF and DFT levels for H2, HeH+, lithium hydride, ethylene, and butadiene.

  16. A New Method To Evaluate Excited States Lifetimes Based on Green's Function: Application to Dye-Sensitized Solar Cells.

    PubMed

    Sulzer, David; Iuchi, Satoru; Yasuda, Koji

    2016-07-12

    Dye-sensitized solar cell (DSSCs) are the promising device for electricity generation. However, the initial stage in which an electron is injected from a dye to the semiconductor has not been precisely understood. Standard quantum chemistry methods cannot handle infinite number of orbitals coming from the band structure of the semiconductor, whereas solid state calculations cannot handle many excited states at a reasonable computational cost. In this regard, we propose a new method to evaluate lifetimes of many excited states of a molecule on a semi-infinite surface. On the basis of the theory of resonance state, the effect of the semi-infinite semiconductor is encoded into the complex self-energy from surface Green's function. The lifetimes of excited states are evaluated through the imaginary part of the self-energy, and the self-energy correction is included into excitation energies obtained from time-dependent density functional theory calculations. This new method is applied to a DSSC system composed of black dye attached to the TiO2 semiconductor, and the computed lifetimes are linked to the natures of excited states and to the surface properties. The present method provides the firm ground for analysis of interplay between many excited states of the dye and band structure of the semiconductor. PMID:27310524

  17. A New Method To Evaluate Excited States Lifetimes Based on Green's Function: Application to Dye-Sensitized Solar Cells.

    PubMed

    Sulzer, David; Iuchi, Satoru; Yasuda, Koji

    2016-07-12

    Dye-sensitized solar cell (DSSCs) are the promising device for electricity generation. However, the initial stage in which an electron is injected from a dye to the semiconductor has not been precisely understood. Standard quantum chemistry methods cannot handle infinite number of orbitals coming from the band structure of the semiconductor, whereas solid state calculations cannot handle many excited states at a reasonable computational cost. In this regard, we propose a new method to evaluate lifetimes of many excited states of a molecule on a semi-infinite surface. On the basis of the theory of resonance state, the effect of the semi-infinite semiconductor is encoded into the complex self-energy from surface Green's function. The lifetimes of excited states are evaluated through the imaginary part of the self-energy, and the self-energy correction is included into excitation energies obtained from time-dependent density functional theory calculations. This new method is applied to a DSSC system composed of black dye attached to the TiO2 semiconductor, and the computed lifetimes are linked to the natures of excited states and to the surface properties. The present method provides the firm ground for analysis of interplay between many excited states of the dye and band structure of the semiconductor.

  18. Calculation of excitation functions of proton, alpha and deuteron induced reactions for production of medical radioisotopes 122-125I

    NASA Astrophysics Data System (ADS)

    Artun, Ozan; Aytekin, Hüseyin

    2015-02-01

    In this work, the excitation functions for production of medical radioisotopes 122-125I with proton, alpha, and deuteron induced reactions were calculated by two different level density models. For the nuclear model calculations, the Talys 1.6 code were used, which is the latest version of Talys code series. Calculations of excitation functions for production of the 122-125I isotopes were carried out by using the generalized superfluid model (GSM) and Fermi-gas model (FGM). The results have shown that generalized superfluid model is more successful than Fermi-gas model in explaining the experimental results.

  19. Functional imaging of living Paramecium by means of confocal and two-photon excitation fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Diaspro, Alberto; Fronte, Paola; Raimondo, Marco; Fato, Marco; DeLeo, Gianluca; Beltrame, Francesco; Cannone, Fabio; Chirico, Giberto; Ramoino, Paola

    2002-05-01

    Confocal and Two-photon excitation laser scanning microscopy allow gathering three-dimensional and temporal information from biological systems exploiting fluorescence labeling and autofluorescence properties. In this work we study biological events linked to functionality in Paramecium primaurelia. The internalization of material in ciliated one-celled organisms (protozoa) occurs via different mechanisms, even if most of nutrients, particulate or not, is taken up by food vacuoles formed at the bottom of the oral cavity. The endocytosis of small-sized molecules occurs at the parasomal sacs, located next the ciliar basal bodies. Vital fluorescent dyes (BSA-FITC, WGA-FITC, dextran-Texas Red, cholesteryl-Bodipy) and autofluorescence were used to study formation, movement, and fusion of vesicles during endocytosis and phagocytosis of Paramecium primaurelia. By immobilizing living cells pulsed with food vacuole and endosome markers at successive times after chasing in unlabeled medium, the intracellular movement and fusion of food vacuoles and of endosomes were visualized. A temporal analysis of fluorescence images and the false-color technique were used. Starting from time series or 3D data sets composite images were generated by associating with each originally acquired image a different color corresponding to each sampling point in time and along the z-axis. Second Harmonic Generation Imaging attempts are also outlined.

  20. Measuring excitation functions needed to interpret cosmogenic nuclide production in lunar rocks

    NASA Technical Reports Server (NTRS)

    Sisterson, J. M.; Kim, K.; Beverding, A.; Englert, P. A. J.; Caffee, M. W.; Vincent, J.; Castaneda, C.; Reedy, R. C.

    1997-01-01

    Radionuclides produced in lunar rocks by cosmic ray interactions are measured using Accelerator Mass Spectrometry or gamma-ray spectroscopy. From these measurements, estimates of the solar proton flux over time periods characterized by the half-life of the isotope under study can be made, if all the cross sections for all the reactions of all cosmic ray particles with all elements found in lunar rocks are known. Proton production cross sections are very important because (approximately) 98% of solar cosmic rays and (approximately) 87% of galactic cosmic rays are protons in the lunar environment. Many of the needed cross sections have never been measured. Targets of C, Al, Si, SiO2, mg, K, Ca, Fe and Ni have been irradiated using three accelerators to cover a proton energy range of 25-500 MeV. Excitation functions for Be-7, Be-10, Na-22, and Al-26 production from Mg and Al will be reported, and the consequences of using these new cross section values to estimate solar proton fluxes discussed.

  1. Sub-barrier fusion excitation function data and energy dependent Woods-Saxon potential

    NASA Astrophysics Data System (ADS)

    Gautam, Manjeet Singh

    2016-07-01

    This paper analyzed the role of intrinsic degrees of freedom of colliding nuclei in the enhancement of sub-barrier fusion cross-section data of various heavy ion fusion reactions. The influences of inelastic surface vibrations of colliding pairs are found to be dominant and their couplings result in the significantly larger fusion enhancement over the predictions of the one dimensional barrier penetration model at sub-barrier energies. The theoretical calculations are performed by using energy dependent Woods-Saxon potential model (EDWSP model) in conjunction with the one dimensional Wong formula. The effects of dominant intrinsic channels are entertained within framework of the coupled channel calculations obtained by using the code CCFULL. It is quite interesting to note that the energy dependence in Woods-Saxon potential simulates the effects of inelastic surface vibrational states of reactants wherein significantly larger value of diffuseness parameter ranging from a = 0.85 fm to a = 0.95 fm is required to address the observed fusion excitation function data of the various heavy ion fusion reactions.

  2. Design and optimization for variable rate selective excitation using an analytic RF scaling function.

    PubMed

    Gai, Neville D; Zur, Yuval

    2007-11-01

    At higher B(0) fields, specific absorption rate (SAR) deposition increases. Due to maximum SAR limitation, slice coverage decreases and/or scan time increases. Conventional selective RF pulses are played out in conjunction with a time independent field gradient. Variable rate selective excitation (VERSE) is a technique that modifies the original RF and gradient waveforms such that slice profile is unchanged. The drawback is that the slice profile for off-resonance spins is distorted. A new VERSE algorithm based on modeling the scaled waveforms as a Fermi function is introduced. It ensures that system related constraints of maximum gradient amplitude and slew rate are not exceeded. The algorithm can be used to preserve the original RF pulse duration while minimizing SAR and peak b1 or to minimize the RF pulse duration. The design is general and can be applied to any symmetrical or asymmetrical RF waveform. The algorithm is demonstrated by using it to (a) minimize the SAR of a linear phase RF pulse, (b) minimize SAR of a hyperbolic secant RF pulse, and (c) minimize the duration of a linear phase RF pulse. Images with a T1-FLAIR (T1 FLuid Attenuated Inversion Recovery) sequence using a conventional and VERSE adiabatic inversion RF pulse are presented. Comparison of images and scan parameters for different anatomies and coils shows increased scan coverage and decreased SAR with the VERSE inversion RF pulse, while image quality is preserved.

  3. The excitation functions of 187Re(n,2n) 186m,gRe reactions

    NASA Astrophysics Data System (ADS)

    Huang, Xiao-Long; Kang, Meng-Xiao; Liu, Li-Le; Wang, Ji-Min; Chen, Xiong-Jun

    2016-08-01

    A new value for the emission probability of 137.144 keV γ-rays from 186gRe decay is recommended to be (9.47±0.03)/%. Using this value the measured cross sections for 187Re(n,2n)186mRe and 187Re(n,2n)186gRe reactions around 14 MeV are analyzed, and the cross section for 187Re(n,2n)186m+gRe reaction at 14.8 MeV is (2213±116) mb. The UNF code was adopted to calculate the cross sections for the 187Re(n,2n)186m+gRe reaction below 20 MeV, fitting to the value (2213±116) mb at 14.8 MeV using a set of optimum neutron optical potential parameters which were obtained based on the relevant experimental data of rhenium. The isomeric cross section ratio for the 187Re(n,2n)186m,gRe reaction was analyzed using the V-H method based on nuclear statistical theory. Combining these calculated results, the excitation functions for the 187Re(n,2n)186mRe and 187Re(n,2n)186gRe reactions were obtained. The obtained results are in good agreement with the available experimental data.

  4. Channels Active in the Excitability of Nerves and Skeletal Muscles across the Neuromuscular Junction: Basic Function and Pathophysiology

    ERIC Educational Resources Information Center

    Goodman, Barbara E.

    2008-01-01

    Ion channels are essential for the basic physiological function of excitable cells such as nerve, skeletal, cardiac, and smooth muscle cells. Mutations in genes that encode ion channels have been identified to cause various diseases and disorders known as channelopathies. An understanding of how individual ion channels are involved in the…

  5. A Preliminary Transcranial Magnetic Stimulation Study of Cortical Inhibition and Excitability in High-Functioning Autism and Asperger Disorder

    ERIC Educational Resources Information Center

    Enticott, Peter G.; Rinehart, Nicole J.; Tonge, Bruce J.; Bradshaw, John L.; Fitzgerald, Paul B.

    2010-01-01

    Aim: Controversy surrounds the distinction between high-functioning autism (HFA) and Asperger disorder, but motor abnormalities are associated features of both conditions. This study examined motor cortical inhibition and excitability in HFA and Asperger disorder using transcranial magnetic stimulation (TMS). Method: Participants were diagnosed by…

  6. Aromatic Lateral Substituents Influence the Excitation Energies of Hexaaza Lanthanide Macrocyclic Complexes: A Wave Function Theory and Density Functional Study.

    PubMed

    Rabanal-León, Walter A; Murillo-López, Juliana A; Páez-Hernández, Dayán; Arratia-Pérez, Ramiro

    2015-09-24

    The high interest in lanthanide chemistry, and particularly in their luminescence, has been encouraged by the need of understanding the lanthanide chemical coordination and how the design of new luminescent materials can be affected by this. This work is focused on the understanding of the electronic structure, bonding nature, and optical properties of a set of lanthanide hexaaza macrocyclic complexes, which can lead to potential optical applications. Here we found that the DFT ground state of the open-shell complexes are mainly characterized by the manifold of low lying f states, having small HOMO-LUMO energy gaps. The results obtained from the wave function theory calculations (SO-RASSI) put on evidence the multiconfigurational character of their ground state and it is observed that the large spin-orbit coupling and the weak crystal field produce a strong mix of the ground and the excited states. The electron localization function (ELF) and the energy decomposition analysis (EDA) support the idea of a dative interaction between the macrocyclic ligand and the lanthanide center for all the studied systems; noting that, this interaction has a covalent character, where the d-orbital participation is evidenced from NBO analysis, leaving the f shell completely noninteracting in the chemical bonding. From the optical part we observed in all cases the characteristic intraligand (IL) (π-π*) and ligand to metal charge-transfer (LMCT) bands that are present in the ultraviolet and visible regions, and for the open-shell complexes we found the inherent f-f electronic transitions on the visible and near-infrared region. PMID:26325624

  7. Excitation function of the 60Ni(p ,γ )61Cu reaction from threshold to 16 MeV

    NASA Astrophysics Data System (ADS)

    Uddin, M. S.; Sudár, S.; Spahn, I.; Shariff, M. A.; Qaim, S. M.

    2016-04-01

    Excitation function of the reaction 60Ni(p ,γ )61Cu was measured via the activation technique in the energy range of 1.3-16.0 MeV using a low-energy accelerator and a small cyclotron. The results are comparable to those previously obtained via prompt γ counting. In addition excitation functions of the more common competing 60Ni(p ,n )60Cu and 60Ni(p ,α )57Co reactions were also measured. Theoretical calculations on proton-induced reactions on 60Ni were performed using the nuclear model code talys. The results suggest that near the threshold of the reaction the compound nucleus mechanism dominates. Thereafter the contribution of direct interactions becomes rather strong, especially between 4 and 6 MeV, i.e., just below the threshold of the 60Ni(p ,n )60Cu reaction. The cross section at the maximum of the excitation function of each of the three reactions, namely, 60Ni(p ,γ )61Cu,60Ni(p ,n )60Cu , and 60Ni(p ,α )57Co , amounts to 2, 320, and 85 mb, respectively. The (p ,n ) reaction is thus the most commonly occurring process, and the (p ,γ ) reaction is the weakest, possibly due to higher probability of particle emission than γ-ray emission from the highly excited intermediate nucleus 61Cu formed in the interaction of a proton with the target nucleus 60Ni.

  8. Excited-State Absorption from Real-Time Time-Dependent Density Functional Theory: Optical Limiting in Zinc Phthalocyanine.

    PubMed

    Fischer, Sean A; Cramer, Christopher J; Govind, Niranjan

    2016-04-01

    Optical-limiting materials are capable of attenuating light to protect delicate equipment from high-intensity light sources. Phthalocyanines have attracted a lot of attention for optical-limiting applications due to their versatility and large nonlinear absorption. With excited-state absorption (ESA) being the primary mechanism for optical limiting behavior in phthalocyanines, the ability to tune the optical absorption of ground and excited states in phthalocyanines would allow for the development of advanced optical limiters. We recently developed a method for the calculation of ESA based on real-time time-dependent density functional theory propagation of an excited-state density. In this work, we apply the approach to zinc phthalocyanine, demonstrating the ability of our method to efficiently identify the optical limiting potential of a molecular complex.

  9. Hydrogen sulfide regulates cardiovascular function by influencing the excitability of subfornical organ neurons.

    PubMed

    Kuksis, Markus; Smith, Pauline M; Ferguson, Alastair V

    2014-01-01

    Hydrogen sulfide (H2S), a gasotransmitter endogenously found in the central nervous system, has recently been suggested to act as a signalling molecule in the brain having beneficial effects on cardiovascular function. This study was thus undertaken to investigate the effect of NaHS (an H2S donor) in the subfornical organ (SFO), a central nervous system site important to blood pressure regulation. We used male Sprague-Dawley rats for both in vivo and in vitro experiments. We first used RT-PCR to confirm our previous microarray analyses showing that mRNAs for the enzymes required to produce H2S are expressed in the SFO. We then used microinjection techniques to investigate the physiological effects of NaHS in SFO, and found that NaHS microinjection (5 nmol) significantly increased blood pressure (mean AUC = 853.5±105.7 mmHg*s, n = 5). Further, we used patch-clamp electrophysiology and found that 97.8% (88 of 90) of neurons depolarized in response to NaHS. This response was found to be concentration dependent with an EC50 of 35.6 µM. Coupled with the depolarized membrane potential, we observed an overall increase in neuronal excitability using an analysis of rheobase and action potential firing patterns. This study has provided the first evidence of NaHS and thus H2S actions and their cellular correlates in SFO, implicating this brain area as a site where H2S may act to control blood pressure.

  10. Hydrogen Sulfide Regulates Cardiovascular Function by Influencing the Excitability of Subfornical Organ Neurons

    PubMed Central

    Kuksis, Markus; Smith, Pauline M.; Ferguson, Alastair V.

    2014-01-01

    Hydrogen sulfide (H2S), a gasotransmitter endogenously found in the central nervous system, has recently been suggested to act as a signalling molecule in the brain having beneficial effects on cardiovascular function. This study was thus undertaken to investigate the effect of NaHS (an H2S donor) in the subfornical organ (SFO), a central nervous system site important to blood pressure regulation. We used male Sprague-Dawley rats for both in vivo and in vitro experiments. We first used RT-PCR to confirm our previous microarray analyses showing that mRNAs for the enzymes required to produce H2S are expressed in the SFO. We then used microinjection techniques to investigate the physiological effects of NaHS in SFO, and found that NaHS microinjection (5 nmol) significantly increased blood pressure (mean AUC = 853.5±105.7 mmHg*s, n = 5). Further, we used patch-clamp electrophysiology and found that 97.8% (88 of 90) of neurons depolarized in response to NaHS. This response was found to be concentration dependent with an EC50 of 35.6 µM. Coupled with the depolarized membrane potential, we observed an overall increase in neuronal excitability using an analysis of rheobase and action potential firing patterns. This study has provided the first evidence of NaHS and thus H2S actions and their cellular correlates in SFO, implicating this brain area as a site where H2S may act to control blood pressure. PMID:25144759

  11. Analytical approach for the excited-state Hessian in time-dependent density functional theory: Formalism, implementation, and performance

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Liang, WanZhen

    2011-11-01

    The paper presents the formalism, implementation, and performance of the analytical approach for the excited-state Hessian in the time-dependent density functional theory (TDDFT) that extends our previous work [J. Liu and W. Z. Liang, J. Chem. Phys. 135, 014113 (2011)] on the analytical Hessian in TDDFT within Tamm-Dancoff approximation (TDA) to full TDDFT. In contrast to TDA-TDDFT, an appreciable advantage of full TDDFT is that it maintains the oscillator strength sum rule, and therefore yields more precise results for the oscillator strength and other related physical quantities. For the excited-state harmonic vibrational frequency calculation, however, full TDDFT does not seem to be advantageous since the numerical tests demonstrate that the accuracy of TDDFT with and without TDA are comparable to each other. As a common practice, the computed harmonic vibrational frequencies are scaled by a suitable scale factor to yield good agreement with the experimental fundamental frequencies. Here we apply both the optimized ground-state and excited-state scale factors to scale the calculated excited-state harmonic frequencies and find that the scaling decreases the root-mean-square errors. The optimized scale factors derived from the excited-state calculations are slightly smaller than those from the ground-state calculations.

  12. exciting: a full-potential all-electron package implementing density-functional theory and many-body perturbation theory

    NASA Astrophysics Data System (ADS)

    Gulans, Andris; Kontur, Stefan; Meisenbichler, Christian; Nabok, Dmitrii; Pavone, Pasquale; Rigamonti, Santiago; Sagmeister, Stephan; Werner, Ute; Draxl, Claudia

    2014-09-01

    Linearized augmented planewave methods are known as the most precise numerical schemes for solving the Kohn-Sham equations of density-functional theory (DFT). In this review, we describe how this method is realized in the all-electron full-potential computer package, exciting. We emphasize the variety of different related basis sets, subsumed as (linearized) augmented planewave plus local orbital methods, discussing their pros and cons and we show that extremely high accuracy (microhartrees) can be achieved if the basis is chosen carefully. As the name of the code suggests, exciting is not restricted to ground-state calculations, but has a major focus on excited-state properties. It includes time-dependent DFT in the linear-response regime with various static and dynamical exchange-correlation kernels. These are preferably used to compute optical and electron-loss spectra for metals, molecules and semiconductors with weak electron-hole interactions. exciting makes use of many-body perturbation theory for charged and neutral excitations. To obtain the quasi-particle band structure, the GW approach is implemented in the single-shot approximation, known as G0W0. Optical absorption spectra for valence and core excitations are handled by the solution of the Bethe-Salpeter equation, which allows for the description of strongly bound excitons. Besides these aspects concerning methodology, we demonstrate the broad range of possible applications by prototypical examples, comprising elastic properties, phonons, thermal-expansion coefficients, dielectric tensors and loss functions, magneto-optical Kerr effect, core-level spectra and more.

  13. Exciting: a full-potential all-electron package implementing density-functional theory and many-body perturbation theory.

    PubMed

    Gulans, Andris; Kontur, Stefan; Meisenbichler, Christian; Nabok, Dmitrii; Pavone, Pasquale; Rigamonti, Santiago; Sagmeister, Stephan; Werner, Ute; Draxl, Claudia

    2014-09-10

    Linearized augmented planewave methods are known as the most precise numerical schemes for solving the Kohn-Sham equations of density-functional theory (DFT). In this review, we describe how this method is realized in the all-electron full-potential computer package, exciting. We emphasize the variety of different related basis sets, subsumed as (linearized) augmented planewave plus local orbital methods, discussing their pros and cons and we show that extremely high accuracy (microhartrees) can be achieved if the basis is chosen carefully. As the name of the code suggests, exciting is not restricted to ground-state calculations, but has a major focus on excited-state properties. It includes time-dependent DFT in the linear-response regime with various static and dynamical exchange-correlation kernels. These are preferably used to compute optical and electron-loss spectra for metals, molecules and semiconductors with weak electron-hole interactions. exciting makes use of many-body perturbation theory for charged and neutral excitations. To obtain the quasi-particle band structure, the GW approach is implemented in the single-shot approximation, known as G(0)W(0). Optical absorption spectra for valence and core excitations are handled by the solution of the Bethe-Salpeter equation, which allows for the description of strongly bound excitons. Besides these aspects concerning methodology, we demonstrate the broad range of possible applications by prototypical examples, comprising elastic properties, phonons, thermal-expansion coefficients, dielectric tensors and loss functions, magneto-optical Kerr effect, core-level spectra and more. PMID:25135665

  14. Ghost-interaction correction in ensemble density-functional theory for excited states with and without range separation

    NASA Astrophysics Data System (ADS)

    Alam, Md. Mehboob; Knecht, Stefan; Fromager, Emmanuel

    2016-07-01

    Ensemble density-functional theory (eDFT) suffers from the so-called "ghost-interaction" error when approximate exchange-correlation functionals are used. In this work, we present a rigorous ghost-interaction correction (GIC) scheme in the context of range-separated eDFT. The method relies on an exact decomposition of the ensemble short-range exchange-correlation energy into a multideterminantal exact exchange term, which involves the long-range interacting ensemble density matrix, instead of the Kohn-Sham (KS) one, and a complementary density-functional correlation energy. A generalized adiabatic connection formula is derived for the latter. In order to perform practical calculations, the complementary correlation functional is simply modeled by its ground-state local density approximation (LDA), while long-range interacting ground- and excited-state wave functions are obtained self-consistently by combining a long-range configuration-interaction calculation with a short-range LDA potential. We show that the GIC reduces the curvature of approximate range-separated ensemble energies drastically while providing considerably more accurate excitation energies, even for charge-transfer and double excitations. Interestingly, the method performs well also in the context of standard KS-eDFT, which is recovered when the range-separation parameter is set to 0.

  15. A simplified Tamm-Dancoff density functional approach for the electronic excitation spectra of very large molecules

    NASA Astrophysics Data System (ADS)

    Grimme, Stefan

    2013-06-01

    Two approximations in the Tamm-Dancoff density functional theory approach (TDA-DFT) to electronically excited states are proposed which allow routine computations for electronic ultraviolet (UV)- or circular dichroism (CD) spectra of molecules with 500-1000 atoms. Speed-ups compared to conventional time-dependent DFT (TD-DFT) treatments of about two to three orders of magnitude in the excited state part at only minor loss of accuracy are obtained. The method termed sTDA ("s" for simplified) employs atom-centered Löwdin-monopole based two-electron repulsion integrals with the asymptotically correct 1/R behavior and perturbative single excitation configuration selection. It is formulated generally for any standard global hybrid density functional with given Fock-exchange mixing parameter ax. The method performs well for two standard benchmark sets of vertical singlet-singlet excitations for values of ax in the range 0.2-0.6. The mean absolute deviations from reference data are only 0.2-0.3 eV and similar to those from standard TD-DFT. In three cases (two dyes and one polypeptide), good mutual agreement between the electronic spectra (up to 10-11 eV excitation energy) from the sTDA method and those from TD(A)-DFT is obtained. The computed UV- and CD-spectra of a few typical systems (e.g., C60, two transition metal complexes, [7]helicene, polyalanine, a supramolecular aggregate with 483 atoms and about 7000 basis functions) compare well with corresponding experimental data. The method is proposed together with medium-sized double- or triple-zeta type atomic-orbital basis sets as a quantum chemical tool to investigate the spectra of huge molecular systems at a reliable DFT level.

  16. Radial and angular correlations of two excited electrons. IV. Comparison of configuration-interaction wave functions with the group-theoretical basis functions

    NASA Astrophysics Data System (ADS)

    Lin, C. D.; Macek, J. H.

    1984-05-01

    Doubly-excited-state basis (DESB) functions of Herrick and Sinanoǧlu are compared with the large-scale configuration-interaction (CI) wave functions of Lipsky et al., and with the adiabatic channel functions in hyperspherical coordinates. It is shown that DESB functions will represent those states where the mean value of θ12 is large. Owing to the absence of intershell correlations, and a consequent underestimation of radial correlations, the DESB functions give excessive concentrations near θ12=0 for other, less sharply correlated in angle, states.

  17. Nonlinear electronic excitations in crystalline solids using meta-generalized gradient approximation and hybrid functional in time-dependent density functional theory.

    PubMed

    Sato, Shunsuke A; Taniguchi, Yasutaka; Shinohara, Yasushi; Yabana, Kazuhiro

    2015-12-14

    We develop methods to calculate electron dynamics in crystalline solids in real-time time-dependent density functional theory employing exchange-correlation potentials which reproduce band gap energies of dielectrics; a meta-generalized gradient approximation was proposed by Tran and Blaha [Phys. Rev. Lett. 102, 226401 (2009)] (TBm-BJ) and a hybrid functional was proposed by Heyd, Scuseria, and Ernzerhof [J. Chem. Phys. 118, 8207 (2003)] (HSE). In time evolution calculations employing the TB-mBJ potential, we have found it necessary to adopt the predictor-corrector step for a stable time evolution. We have developed a method to evaluate electronic excitation energy without referring to the energy functional which is unknown for the TB-mBJ potential. For the HSE functional, we have developed a method for the operation of the Fock-like term in Fourier space to facilitate efficient use of massive parallel computers equipped with graphic processing units. We compare electronic excitations in silicon and germanium induced by femtosecond laser pulses using the TB-mBJ, HSE, and a simple local density approximation (LDA). At low laser intensities, electronic excitations are found to be sensitive to the band gap energy: they are close to each other using TB-mBJ and HSE and are much smaller in LDA. At high laser intensities close to the damage threshold, electronic excitation energies do not differ much among the three cases. PMID:26671367

  18. Nonlinear electronic excitations in crystalline solids using meta-generalized gradient approximation and hybrid functional in time-dependent density functional theory

    SciTech Connect

    Sato, Shunsuke A.; Taniguchi, Yasutaka; Shinohara, Yasushi; Yabana, Kazuhiro

    2015-12-14

    We develop methods to calculate electron dynamics in crystalline solids in real-time time-dependent density functional theory employing exchange-correlation potentials which reproduce band gap energies of dielectrics; a meta-generalized gradient approximation was proposed by Tran and Blaha [Phys. Rev. Lett. 102, 226401 (2009)] (TBm-BJ) and a hybrid functional was proposed by Heyd, Scuseria, and Ernzerhof [J. Chem. Phys. 118, 8207 (2003)] (HSE). In time evolution calculations employing the TB-mBJ potential, we have found it necessary to adopt the predictor-corrector step for a stable time evolution. We have developed a method to evaluate electronic excitation energy without referring to the energy functional which is unknown for the TB-mBJ potential. For the HSE functional, we have developed a method for the operation of the Fock-like term in Fourier space to facilitate efficient use of massive parallel computers equipped with graphic processing units. We compare electronic excitations in silicon and germanium induced by femtosecond laser pulses using the TB-mBJ, HSE, and a simple local density approximation (LDA). At low laser intensities, electronic excitations are found to be sensitive to the band gap energy: they are close to each other using TB-mBJ and HSE and are much smaller in LDA. At high laser intensities close to the damage threshold, electronic excitation energies do not differ much among the three cases.

  19. Nonlinear electronic excitations in crystalline solids using meta-generalized gradient approximation and hybrid functional in time-dependent density functional theory

    NASA Astrophysics Data System (ADS)

    Sato, Shunsuke A.; Taniguchi, Yasutaka; Shinohara, Yasushi; Yabana, Kazuhiro

    2015-12-01

    We develop methods to calculate electron dynamics in crystalline solids in real-time time-dependent density functional theory employing exchange-correlation potentials which reproduce band gap energies of dielectrics; a meta-generalized gradient approximation was proposed by Tran and Blaha [Phys. Rev. Lett. 102, 226401 (2009)] (TBm-BJ) and a hybrid functional was proposed by Heyd, Scuseria, and Ernzerhof [J. Chem. Phys. 118, 8207 (2003)] (HSE). In time evolution calculations employing the TB-mBJ potential, we have found it necessary to adopt the predictor-corrector step for a stable time evolution. We have developed a method to evaluate electronic excitation energy without referring to the energy functional which is unknown for the TB-mBJ potential. For the HSE functional, we have developed a method for the operation of the Fock-like term in Fourier space to facilitate efficient use of massive parallel computers equipped with graphic processing units. We compare electronic excitations in silicon and germanium induced by femtosecond laser pulses using the TB-mBJ, HSE, and a simple local density approximation (LDA). At low laser intensities, electronic excitations are found to be sensitive to the band gap energy: they are close to each other using TB-mBJ and HSE and are much smaller in LDA. At high laser intensities close to the damage threshold, electronic excitation energies do not differ much among the three cases.

  20. Measurement of the {sup 208}Pb({sup 52}Cr,n){sup 259}Sg excitation function

    SciTech Connect

    Folden III, C. M.; Dragojevic, I.; Garcia, M. A.; Gates, J. M.; Nelson, S. L.; Hoffman, D. C.; Nitsche, H.; Duellmann, Ch. E.; Sudowe, R.; Gregorich, K. E.; Eichler, R.

    2009-02-15

    The excitation function for the {sup 208}Pb({sup 52}Cr,n){sup 259}Sg reaction has been measured using the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. The maximum cross section of 320{sub -100}{sup +110} pb is observed at a center-of-target laboratory-frame energy of 253.0 MeV. In total, 25 decay chains originating from {sup 259}Sg were observed and the measured decay properties are in good agreement with previous reports. In addition, a partial excitation function for the {sup 208}Pb({sup 52}Cr,2n){sup 258}Sg reaction was obtained, and an improved {sup 258}Sg half-life of 2.6{sub -0.4}{sup +0.6} ms was calculated by combining all available experimental data.

  1. Excitation functions of (nat)Zn(p,x) nuclear reactions with proton beam energy below 18 MeV.

    PubMed

    Asad, Ali H; Chan, Sun; Morandeau, Laurence; Cryer, David; Smith, Suzanne V; Price, Roger I

    2014-12-01

    We measured the excitation functions of (nat)Zn (p,x) reactions up to 17.6MeV, using the stacked-foils activation technique. High-purity natural zinc (and copper) foils were irradiated with proton beams generated by an 18MeV isochronous cyclotron. Activated foils were measured using high-purity Ge gamma spectroscopy to quantify the radionuclides (61)Cu, (66)Ga, (67)Ga, and (65)Zn produced from the reactions. Thick-target integral yields were also deduced from the measured excitation functions of the produced radioisotopes. These results were compared with the published literature and were found to be in good agreement with most reports, particularly those most recently compiled.

  2. Excitation functions for (d,x) reactions on (133)Cs up to Ed=40MeV.

    PubMed

    Tárkányi, F; Ditrói, F; Takács, S; Hermanne, A; Baba, M; Ignatyuk, A V

    2016-04-01

    In the frame of a systematic study of excitation functions of deuteron induced reactions the excitation functions of the (133)Cs(d,x)(133m,133mg,131mg)Ba,(134,)(132)Cs and (12)(9m)Xe nuclear reactions were measured up to 40MeV deuteron energies by using the stacked foil irradiation technique and γ-ray spectroscopy of activated samples. The results were compared with calculations performed with the theoretical nuclear reaction codes ALICE-IPPE-D, EMPIRE II-D and TALYS calculation listed in the TENDL-2014 library. A moderate agreement was obtained. Based on the integral yields deduced from our measured cross sections, production of (131)Cs via the (133)Cs(d,4n)(131)Ba→(131)Cs reaction and (133)Ba via (133)Cs(d,2n) reactions is discussed in comparison with other charged particle production routes. PMID:26773822

  3. Excitation functions for {sup 208-211}Fr produced in the {sup 18}O+{sup 197}Au fusion reaction

    SciTech Connect

    Corradi, L.; Behera, B.R.; Fioretto, E.; Gadea, A.; Latina, A.; Stefanini, A.M.; Szilner, S.; Trotta, M.; Wu, Y.; Beghini, S.; Montagnoli, G.; Scarlassara, F.; Sagaidak, R.N.; Atutov, S.N.; Mai, B.; Stancari, G.; Tomassetti, L.; Mariotti, E.; Khanbekyan, A.; Veronesi, S.

    2005-01-01

    Excitation functions for {sup 208-211}Fr isotopes produced in the {sup 18}O+{sup 197}Au fusion-evaporation reaction have been measured at E{sub lab}=75-130 MeV via characteristic {alpha} decays by means of an electrostatic deflector and a semiconductor detector. Data have been compared with calculations giving barrier-passing (capture) cross sections and probabilities of the compound nucleus decay into different channels according to the standard statistical model.

  4. Variation of excited-state dynamics in trifluoromethyl functionalized C60 fullerenes.

    PubMed

    Park, Jaehong; Ramirez, Jessica J; Clikeman, Tyler T; Larson, Bryon W; Boltalina, Olga V; Strauss, Steven H; Rumbles, Garry

    2016-08-17

    We report on electronically excited-state dynamics of three different trifluoromethyl C60 fullerenes (TMFs, C60(CF3)n: C60/4-1, C60/6-2, and C60/10-1, featuring four, six, and ten trifluoromethyl groups, respectively) using steady-state and time-resolved optical spectroscopy as well as ultrafast pump/probe transient absorption spectroscopy. C60/4-1 and C60/6-2 dissolved in toluene solvent show near-unity S1 → T1 intersystem crossing quantum yield (ΦISC), ca. 1 ns S1-state lifetimes, and microsecond-timescale T1-state lifetimes, which are typical of the fullerene class. On the other hand, C60/10-1 exhibits a dominant sub-nanosecond nonradiative S1 → S0 relaxation mechanism and negligible ΦISC, therefore decreasing the average excited-state lifetime (τavg) by about 5 orders of magnitude compared to that of C60/4-1 and C60/6-2 (τavg ≈ 17 μs and 54 μs for C60/4-1 and C60/6-2, respectively, whereas τavg ≈ 100 ps for C60/10-1). These excited-state characteristics of C60/4-1 and C60/6-2 are preserved in polymer matrix, suggesting that fullerene/polymer interactions do not modulate intrinsic photophysics of trifluoromethyl-substituted fullerenes. The contrasting excited-state study results of C60/4-1 and C60/6-2 to that of C60/10-1 infer that intrinsic optical properties and excited-state dynamics can be affected by the substitution on the fullerene. PMID:27485768

  5. Variation of excited-state dynamics in trifluoromethyl functionalized C60 fullerenes.

    PubMed

    Park, Jaehong; Ramirez, Jessica J; Clikeman, Tyler T; Larson, Bryon W; Boltalina, Olga V; Strauss, Steven H; Rumbles, Garry

    2016-08-17

    We report on electronically excited-state dynamics of three different trifluoromethyl C60 fullerenes (TMFs, C60(CF3)n: C60/4-1, C60/6-2, and C60/10-1, featuring four, six, and ten trifluoromethyl groups, respectively) using steady-state and time-resolved optical spectroscopy as well as ultrafast pump/probe transient absorption spectroscopy. C60/4-1 and C60/6-2 dissolved in toluene solvent show near-unity S1 → T1 intersystem crossing quantum yield (ΦISC), ca. 1 ns S1-state lifetimes, and microsecond-timescale T1-state lifetimes, which are typical of the fullerene class. On the other hand, C60/10-1 exhibits a dominant sub-nanosecond nonradiative S1 → S0 relaxation mechanism and negligible ΦISC, therefore decreasing the average excited-state lifetime (τavg) by about 5 orders of magnitude compared to that of C60/4-1 and C60/6-2 (τavg ≈ 17 μs and 54 μs for C60/4-1 and C60/6-2, respectively, whereas τavg ≈ 100 ps for C60/10-1). These excited-state characteristics of C60/4-1 and C60/6-2 are preserved in polymer matrix, suggesting that fullerene/polymer interactions do not modulate intrinsic photophysics of trifluoromethyl-substituted fullerenes. The contrasting excited-state study results of C60/4-1 and C60/6-2 to that of C60/10-1 infer that intrinsic optical properties and excited-state dynamics can be affected by the substitution on the fullerene.

  6. Double excitations and state-to-state transition dipoles in π-π∗ excited singlet states of linear polyenes: Time-dependent density-functional theory versus multiconfigurational methods

    NASA Astrophysics Data System (ADS)

    Mikhailov, Ivan A.; Tafur, Sergio; Masunov, Artëm E.

    2008-01-01

    The effect of static and dynamic electron correlation on the nature of excited states and state-to-state transition dipole moments is studied with a multideterminant wave function approach on the example of all-trans linear polyenes ( C4H6 , C6H8 , and C8H10 ). Symmetry-forbidden singlet nAg states were found to separate into three groups: purely single, mostly single, and mostly double excitations. The excited-state absorption spectrum is dominated by two bright transitions: 1Bu-2Ag and 1Bu-mAg , where mAg is the state, corresponding to two-electron excitation from the highest occupied to lowest unoccupied molecular orbital. The richness of the excited-state absorption spectra and strong mixing of the doubly excited determinants into lower- nAg states, reported previously at the complete active space self-consistent field level of theory, were found to be an artifact of the smaller active space, limited to π orbitals. When dynamic σ-π correlation is taken into account, single- and double-excited states become relatively well separated at least at the equilibrium geometry of the ground state. This electronic structure is closely reproduced within time-dependent density-functional theory (TD DFT), where double excitations appear in a second-order coupled electronic oscillator formalism and do not mix with the single excitations obtained within the linear response. An extension of TD DFT is proposed, where the Tamm-Dancoff approximation (TDA) is invoked after the linear response equations are solved (a posteriori TDA). The numerical performance of this extension is validated against multideterminant-wave-function and quadratic-response TD DFT results. It is recommended for use with a sum-over-states approach to predict the nonlinear optical properties of conjugated molecules.

  7. Evaporation residue excitation function measurements in 50Ti- and 54Cr-induced reactions with lanthanide targets

    NASA Astrophysics Data System (ADS)

    Mayorov, D. A.; Werke, T. A.; Alfonso, M. C.; Tereshatov, E. E.; Bennett, M. E.; Frey, M. M.; Folden, C. M.

    2015-11-01

    Cross sections for the production of shell-stabilized evaporation residues in the 50Ti+Gd160 , 159Tb, 162Dy , and 54Cr+Dy162 reactions are reported. The compound nucleus excitation energy range considered principally covers the 4 n evaporation channel with segments of the 3 n and 5 n channels also measured. The resultant production cross sections are for nuclides with Z =86 -90 . From an analysis based on a statistical model, it is concluded that a larger fission probability than that predicted by the Bohr-Wheeler transition-state theory is needed to describe the data. This outcome is attributed to the influence of collective nuclear excitations. Subsequently, the expected stability enhancement against fission due to the influence of the magic N =126 shell is not evident. The x n excitation functions measured in previous experiments in the reactions 48Ca+Gd154 , 159Tb,Dy162 , and 165Ho are combined with the present data for Z >20 projectiles to illustrate systematic behavior of measured cross sections as a function of the difference in fission barrier and neutron separation energy.

  8. Photosensitized Singlet Oxygen Production upon Two-Photon Excitation of Single-Walled Carbon Nanotubes and Their Functionalized Analogs

    PubMed Central

    Gandra, Naveen; Chiu, Pui Lam; Li, Wenbing; Anderson, Yolanda R.; Mitra, Somenath; He, Huixin; Gao, Ruomei

    2009-01-01

    Single-walled carbon nanotubes (SWNTs) functionalized with -COOH (along with some sulphonation and nitration), and/or modified with chitosan were prepared and tested for their singlet oxygen (1O2) production. The emission from 1O2 observed upon SWNT irradiation at 532 nm was due to a two-photon process, while 1O2 production via excitation at 355 nm occurred through a conventional one-photon pathway. The relative quantum yield of 1O2 production at excitation wavelength of 532 nm was found to be 0.00, 0.07-0.13 and 0.24-0.54 for highly-functionalized, partially-functionalized and non-functionalized SWNT samples respectively. The nanotube-mediated generation of 1O2 may find applications in both targeted destruction of tumor cells and selective degradation of drug molecules. Our research provides a practical approach to modulate the production of reactive oxygen species from SWNTs via surface functionalization/modification. PMID:20046942

  9. Motor cortex maturation is associated with reductions in recurrent connectivity among functional subpopulations and increases in intrinsic excitability.

    PubMed

    Biane, Jeremy S; Scanziani, Massimo; Tuszynski, Mark H; Conner, James M

    2015-03-18

    Behavior is derived from the configuration of synaptic connectivity among functionally diverse neurons. Fine motor behavior is absent at birth in most mammals but gradually emerges during subsequent postnatal corticospinal system maturation; the nature of circuit development and reorganization during this period has been largely unexplored. We investigated connectivity and synaptic signaling among functionally distinct corticospinal populations in Fischer 344 rats from postnatal day 18 through 75 using retrograde tracer injections into specific spinal cord segments associated with distinct aspects of forelimb function. Primary motor cortex slices were prepared enabling simultaneous patch-clamp recordings of up to four labeled corticospinal neurons and testing of 3489 potential synaptic connections. We find that, in immature animals, local connectivity is biased toward corticospinal neurons projecting to the same spinal cord segment; this within-population connectivity significantly decreases through maturation until connection frequency is similar between neurons projecting to the same (within-population) or different (across-population) spinal segments. Concomitantly, postnatal maturation is associated with a significant reduction in synaptic efficacy over time and an increase in intrinsic neuronal excitability, altering how excitation is effectively transmitted across recurrent corticospinal networks. Collectively, the postnatal emergence of fine motor control is associated with a relative broadening of connectivity between functionally diverse cortical motor neurons and changes in synaptic properties that could enable the emergence of smaller independent networks, enabling fine motor movement. These changes in synaptic patterning and physiological function provide a basis for the increased capabilities of the mature versus developing brain.

  10. Role of physiological ClC-1 Cl− ion channel regulation for the excitability and function of working skeletal muscle

    PubMed Central

    Riisager, Anders; de Paoli, Frank Vincenzo; Chen, Tsung-Yu; Nielsen, Ole Bækgaard

    2016-01-01

    Electrical membrane properties of skeletal muscle fibers have been thoroughly studied over the last five to six decades. This has shown that muscle fibers from a wide range of species, including fish, amphibians, reptiles, birds, and mammals, are all characterized by high resting membrane permeability for Cl− ions. Thus, in resting human muscle, ClC-1 Cl− ion channels account for ∼80% of the membrane conductance, and because active Cl− transport is limited in muscle fibers, the equilibrium potential for Cl− lies close to the resting membrane potential. These conditions—high membrane conductance and passive distribution—enable ClC-1 to conduct membrane current that inhibits muscle excitability. This depressing effect of ClC-1 current on muscle excitability has mostly been associated with skeletal muscle hyperexcitability in myotonia congenita, which arises from loss-of-function mutations in the CLCN1 gene. However, given that ClC-1 must be drastically inhibited (∼80%) before myotonia develops, more recent studies have explored whether acute and more subtle ClC-1 regulation contributes to controlling the excitability of working muscle. Methods were developed to measure ClC-1 function with subsecond temporal resolution in action potential firing muscle fibers. These and other techniques have revealed that ClC-1 function is controlled by multiple cellular signals during muscle activity. Thus, onset of muscle activity triggers ClC-1 inhibition via protein kinase C, intracellular acidosis, and lactate ions. This inhibition is important for preserving excitability of working muscle in the face of activity-induced elevation of extracellular K+ and accumulating inactivation of voltage-gated sodium channels. Furthermore, during prolonged activity, a marked ClC-1 activation can develop that compromises muscle excitability. Data from ClC-1 expression systems suggest that this ClC-1 activation may arise from loss of regulation by adenosine nucleotides and

  11. Role of physiological ClC-1 Cl- ion channel regulation for the excitability and function of working skeletal muscle.

    PubMed

    Pedersen, Thomas Holm; Riisager, Anders; de Paoli, Frank Vincenzo; Chen, Tsung-Yu; Nielsen, Ole Bækgaard

    2016-04-01

    Electrical membrane properties of skeletal muscle fibers have been thoroughly studied over the last five to six decades. This has shown that muscle fibers from a wide range of species, including fish, amphibians, reptiles, birds, and mammals, are all characterized by high resting membrane permeability for Cl(-) ions. Thus, in resting human muscle, ClC-1 Cl(-) ion channels account for ∼80% of the membrane conductance, and because active Cl(-) transport is limited in muscle fibers, the equilibrium potential for Cl(-) lies close to the resting membrane potential. These conditions-high membrane conductance and passive distribution-enable ClC-1 to conduct membrane current that inhibits muscle excitability. This depressing effect of ClC-1 current on muscle excitability has mostly been associated with skeletal muscle hyperexcitability in myotonia congenita, which arises from loss-of-function mutations in the CLCN1 gene. However, given that ClC-1 must be drastically inhibited (∼80%) before myotonia develops, more recent studies have explored whether acute and more subtle ClC-1 regulation contributes to controlling the excitability of working muscle. Methods were developed to measure ClC-1 function with subsecond temporal resolution in action potential firing muscle fibers. These and other techniques have revealed that ClC-1 function is controlled by multiple cellular signals during muscle activity. Thus, onset of muscle activity triggers ClC-1 inhibition via protein kinase C, intracellular acidosis, and lactate ions. This inhibition is important for preserving excitability of working muscle in the face of activity-induced elevation of extracellular K(+) and accumulating inactivation of voltage-gated sodium channels. Furthermore, during prolonged activity, a marked ClC-1 activation can develop that compromises muscle excitability. Data from ClC-1 expression systems suggest that this ClC-1 activation may arise from loss of regulation by adenosine nucleotides and

  12. Two-photon excited fluorescence of intrinsic fluorophores enables label-free assessment of adipose tissue function

    PubMed Central

    Alonzo, Carlo Amadeo; Karaliota, Sevasti; Pouli, Dimitra; Liu, Zhiyi; Karalis, Katia P.; Georgakoudi, Irene

    2016-01-01

    Current methods for evaluating adipose tissue function are destructive or have low spatial resolution. These limit our ability to assess dynamic changes and heterogeneous responses that occur in healthy or diseased subjects, or during treatment. Here, we demonstrate that intrinsic two-photon excited fluorescence enables functional imaging of adipocyte metabolism with subcellular resolution. Steady-state and time-resolved fluorescence from intracellular metabolic co-factors and lipid droplets can distinguish the functional states of excised white, brown, and cold-induced beige fat. Similar optical changes are identified when white and brown fat are assessed in vivo. Therefore, these studies establish the potential of non-invasive, high resolution, endogenous contrast, two-photon imaging to identify distinct adipose tissue types, monitor their functional state, and characterize heterogeneity of induced responses. PMID:27491409

  13. Two-photon excited fluorescence of intrinsic fluorophores enables label-free assessment of adipose tissue function

    NASA Astrophysics Data System (ADS)

    Alonzo, Carlo Amadeo; Karaliota, Sevasti; Pouli, Dimitra; Liu, Zhiyi; Karalis, Katia P.; Georgakoudi, Irene

    2016-08-01

    Current methods for evaluating adipose tissue function are destructive or have low spatial resolution. These limit our ability to assess dynamic changes and heterogeneous responses that occur in healthy or diseased subjects, or during treatment. Here, we demonstrate that intrinsic two-photon excited fluorescence enables functional imaging of adipocyte metabolism with subcellular resolution. Steady-state and time-resolved fluorescence from intracellular metabolic co-factors and lipid droplets can distinguish the functional states of excised white, brown, and cold-induced beige fat. Similar optical changes are identified when white and brown fat are assessed in vivo. Therefore, these studies establish the potential of non-invasive, high resolution, endogenous contrast, two-photon imaging to identify distinct adipose tissue types, monitor their functional state, and characterize heterogeneity of induced responses.

  14. Apelin acts in the subfornical organ to influence neuronal excitability and cardiovascular function.

    PubMed

    Dai, Li; Smith, Pauline M; Kuksis, Markus; Ferguson, Alastair V

    2013-07-01

    Apelin is an adipocyte-derived hormone involved in the regulation of water balance, food intake and the cardiovascular system partially through actions in the CNS. The subfornical organ (SFO) is a circumventricular organ with identified roles in body fluid homeostasis, cardiovascular control and energy balance. The SFO lacks a normal blood-brain barrier, and is thus able to detect circulating signalling molecules such as angiotensin II and leptin. In this study, we investigated actions of apelin-13, the predominant apelin isoform in brain and circulatory system, on the excitability of dissociated SFO neurons using electrophysiological approaches, and determined the cardiovascular consequences of direct administration into the SFO of anaesthetized rats. Whole cell current clamp recording revealed that bath-applied 100 nm apelin-13 directly influences the excitability of the majority of SFO neurons by eliciting either depolarizing (31.8%, mean 7.0 ± 0.8 mV) or hyperpolarizing (28.6%, mean -10.4 ± 1.8 mV) responses. Using voltage-clamp techniques, we also identified modulatory actions of apelin-13 on specific ion channels, demonstrating that apelin-13 activates a non-selective cationic conductance to depolarize SFO neurons while activation of the delayed rectifier potassium conductance underlies hyperpolarizing effects. In anaesthetized rats, microinjection of apelin into SFO decreased both blood pressure (BP) (mean area under the curve -1492.3 ± 357.1 mmHg.s, n = 5) and heart rate (HR) (-32.4 ± 10.39 beats, n = 5). Our data suggest that circulating apelin can directly affect BP and HR as a consequence of the ability of this peptide to modulate the excitability of SFO neurons.

  15. Apelin acts in the subfornical organ to influence neuronal excitability and cardiovascular function

    PubMed Central

    Dai, Li; Smith, Pauline M; Kuksis, Markus; Ferguson, Alastair V

    2013-01-01

    Apelin is an adipocyte-derived hormone involved in the regulation of water balance, food intake and the cardiovascular system partially through actions in the CNS. The subfornical organ (SFO) is a circumventricular organ with identified roles in body fluid homeostasis, cardiovascular control and energy balance. The SFO lacks a normal blood–brain barrier, and is thus able to detect circulating signalling molecules such as angiotensin II and leptin. In this study, we investigated actions of apelin-13, the predominant apelin isoform in brain and circulatory system, on the excitability of dissociated SFO neurons using electrophysiological approaches, and determined the cardiovascular consequences of direct administration into the SFO of anaesthetized rats. Whole cell current clamp recording revealed that bath-applied 100 nm apelin-13 directly influences the excitability of the majority of SFO neurons by eliciting either depolarizing (31.8%, mean 7.0 ± 0.8 mV) or hyperpolarizing (28.6%, mean −10.4 ± 1.8 mV) responses. Using voltage-clamp techniques, we also identified modulatory actions of apelin-13 on specific ion channels, demonstrating that apelin-13 activates a non-selective cationic conductance to depolarize SFO neurons while activation of the delayed rectifier potassium conductance underlies hyperpolarizing effects. In anaesthetized rats, microinjection of apelin into SFO decreased both blood pressure (BP) (mean area under the curve −1492.3 ± 357.1 mmHg.s, n= 5) and heart rate (HR) (−32.4 ± 10.39 beats, n= 5). Our data suggest that circulating apelin can directly affect BP and HR as a consequence of the ability of this peptide to modulate the excitability of SFO neurons. PMID:23629509

  16. Nanoscale visualization of functional adhesion/excitability nodes at the intercalated disc

    PubMed Central

    Leo-Macias, Alejandra; Agullo-Pascual, Esperanza; Sanchez-Alonso, Jose L.; Keegan, Sarah; Lin, Xianming; Arcos, Tatiana; Feng-Xia-Liang; Korchev, Yuri E.; Gorelik, Julia; Fenyö, David; Rothenberg, Eli; Delmar, Mario

    2016-01-01

    Intercellular adhesion and electrical excitability are considered separate cellular properties. Studies of myelinated fibres, however, show that voltage-gated sodium channels (VGSCs) aggregate with cell adhesion molecules at discrete subcellular locations, such as the nodes of Ranvier. Demonstration of similar macromolecular organization in cardiac muscle is missing. Here we combine nanoscale-imaging (single-molecule localization microscopy; electron microscopy; and ‘angle view' scanning patch clamp) with mathematical simulations to demonstrate distinct hubs at the cardiac intercalated disc, populated by clusters of the adhesion molecule N-cadherin and the VGSC NaV1.5. We show that the N-cadherin-NaV1.5 association is not random, that NaV1.5 molecules in these clusters are major contributors to cardiac sodium current, and that loss of NaV1.5 expression reduces intercellular adhesion strength. We speculate that adhesion/excitability nodes are key sites for crosstalk of the contractile and electrical molecular apparatus and may represent the structural substrate of cardiomyopathies in patients with mutations in molecules of the VGSC complex. PMID:26787348

  17. Modeling Spin Fluctuations and Magnetic Excitations from Time-Dependent Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Gorni, Tommaso; Timrov, Iurii; Dal Corso, Andrea; Baroni, Stefano

    Harnessing spin fluctuations and magnetic excitations in materials is key in many fields of technology, spanning from memory devices to information transfer and processing, to name but a few. A proper understanding of the interplay between collective and single-particle spin excitations is still lacking, and it is expected that first-principle simulations based on TDDFT may shed light on this interplay, as well as on the role of important effects such as relativistic ones and related magnetic anisotropies. All the numerical approaches proposed so far to tackle this problem are based on the computationally demanding solution of the Sternheimer equations for the response orbitals or the even more demanding solution of coupled Dyson equations for the spin and charge susceptibilities. The Liouville-Lanczos approach to TDDFT has already proven to be a valuable alternative, the most striking of its features being the avoidance of sums over unoccupied single-particle states and the frequency-independence of the main numerical bottleneck. In this work we present an extension of this methodology to magnetic systems and its implementation in the Quantum ESPRESSO distribution, together with a few preliminary results on the magnon dispersions in bulk Fe.

  18. Electronically Excited States of Higher Acenes up to Nonacene: A Density Functional Theory/Multireference Configuration Interaction Study.

    PubMed

    Bettinger, Holger F; Tönshoff, Christina; Doerr, Markus; Sanchez-Garcia, Elsa

    2016-01-12

    While the optical spectra of the acene series up to pentacene provide textbook examples for the annulation principle, the spectra of the larger members are much less understood. The present work provides an investigation of the optically allowed excited states of the acene series from pentacene to nonacene, the largest acene observed experimentally, using the density functional based multireference configuration method (DFT/MRCI). For this purpose, the ten lowest energy states of the B2u and B3u irreducible representations were computed. In agreement with previous computational investigations, the electronic wave functions of the acenes acquire significant multireference character with increasing acene size. The HOMO → LUMO excitation is the major contributor to the (1)La state (p band, B2u) also for the larger acenes. The oscillator strength decreases with increasing length. The (1)Lb state (α band, B3u), so far difficult to assign for the larger acenes due to overlap with photoprecursor bands, becomes almost insensitive to acene length. The (1)Bb state (β band, B3u) also moves only moderately to lower energy with increasing acene size. Excited states of B3u symmetry that formally result from double excitations involving HOMO, HOMO-1, LUMO, and LUMO+1 decrease in energy much faster with system size. One of them (D1) has very small oscillator strength but becomes almost isoenergetic with the (1)La state for nonacene. The other (D2) also has low oscillator strength as long as it is higher in energy than (1)Bb. Once it is lower in energy than the (1)Bb state, both states interact strongly resulting in two states with large oscillator strengths. The emergence of two strongly absorbing states is in agreement with experimental observations. The DFT/MRCI computations reproduce experimental excitation energies very well for pentacene and hexacene (within 0.1 eV). For the larger acenes deviations are larger (up to 0.2 eV), but qualitative agreement is observed. PMID

  19. [Density functional theory study of surface-enhanced raman spectra and excited state of 1,4-benzenedithiol].

    PubMed

    Shao, Yang-Fan; Li, Chong-Yang; Feng, Yuan-Ming; Lin, Wang

    2014-02-01

    Raman scattering spectra and optimized geometries of the 1,4-benzenedithiol molecule and complexes have been calculated using density functional theory (DFT) with B3LYP functional at the level of 6-311G+(d) basis set for C, H, S atoms and LanL2DZ for Ag, Au atoms, respectively. The optimized 1,4-benzenedithiol molecule was non-planar structure and the angle between benzene ring plane and S-H is 20.20. By means of the simulation of molecule adsorbed on gold and silver cluster, we concluded that gold clusters are nearly parallel to the benzenedithiol molecule and silver clusters are almost perpendicular to the molecular surface. The authors studied the interaction between Raman intensity and molecular properties, such as static polarizablity and charge distribution. The Raman intensity of 1,4-BDT-Au2, 1,4-BDT-Ag2 and Ag2-1,4-BDT-Au2 were in good agreement with static polarizability. The excited states of Ag2-1,4-BDT-Au2 complex were calculated using time-dependent density functional theory (TDDFT). And the simulated absorption spectra and several allowed singlet excited states were analyzed to investigate the surface-enhanced Raman chemical enhancement mechanism. PMID:24822413

  20. Measurement of excitation function for 63Cu(n, p) 63Ni reaction up to En=15 MeV

    NASA Astrophysics Data System (ADS)

    Shibata, S.; Shibata, T.; Imamura, M.; Ohkubo, T.; Satoh, S.; Uwamino, Y.; Nogawa, N.; Baba, M.; Matsuyama, S.; Iwasaki, S.

    1999-01-01

    The excitation function for the 63Cu(n, p) 63Ni reaction were measured using neutrons produced by the T(p, n) reaction at En=˜1.5 MeV, D(d, n) at En=˜6.5 MeV and T(d, n) at En=˜14 MeV, respectively. Irradiations were performed using the dynamitron accelerator at the Fast Neutron Laboratory of Tohoku University. After irradiation, the nickel was separated by anion-exchange and solvent extraction. The 63Ni was measured by liquid scintillation method. The cross sections obtained were compared with the calculated values of JENDL-3.

  1. Excitation functions for production of heavy actinides from interactions of /sup 16/O with /sup 249/Cf

    SciTech Connect

    Chasteler, R.M.; Henderson, R.A.; Lee, D.; Gregorich, K.E.; Nurmia, M.J.; Welch, R.B.; Hoffman, D.C.

    1987-11-01

    Excitation functions have been measured for the production of isotopes of Bk through Fm in bombardments of /sup 249/Cf with 90- to 150-MeV /sup 16/O ions. A comparison of the maxima of the mass-yield curves measured in this experiment with those for the reactions of /sup 18/O ions with /sup 249/Cf shows different shifts from those that have been measured for reactions of the /sup 16,18/O and /sup 20,22/Ne ion pairs with /sup 248/Cm. However, the shifts appear similar to those recently measured for reactions of these ion pairs with /sup 254/Es.

  2. Multiphoton excitation microscopy of in vivo human skin. Functional and morphological optical biopsy based on three-dimensional imaging, lifetime measurements and fluorescence spectroscopy.

    PubMed

    Masters, B R; So, P T; Gratton, E

    1998-02-01

    Two-photon excitation microscopy has the potential as an effective, noninvasive, diagnostic tool for in vivo examination of human deep tissue structure at the subcellular level. By using infrared photons as the excitation source in two-photon microscopy, a significant improvement in penetration depth can be achieved because of the much lower tissue scattering and absorption coefficients in the infrared wavelengths. Two-photon absorption occurs primarily at the focal point and provides the physical basis for optical sectioning. Multiphoton excitation microscopy at 730 nm was used to image in vivo human skin autofluorescence from the surface to a depth of about 200 microns. The spectroscopic data suggest that reduced pyridine nucleotides, NAD(P)H, are the primary source of the skin autofluorescence using 730 nm excitation. This study demonstrates the use of multiphoton excitation microscopy for functional imaging of the metabolic states of in vivo human skin cells and provides a functional and morphological optical biopsy.

  3. Functional testing of space flight induced changes in tonic motor control by using limb-attached excitation and load devices

    NASA Astrophysics Data System (ADS)

    Gallasch, Eugen; Kozlovskaya, Inessa

    2007-02-01

    Long term space flights induce atrophy and contractile changes on postural muscles such effecting tonic motor control. Functional testing of tonic motor control structures is a challenge because of the difficulties to deliver appropriate test forces on crew members. In this paper we propose two approaches for functional testing by using limb attached loading devices. The first approach is based on a frequency and amplitude controllable moving magnet exciter to deliver sinusoidal test forces during limb postures. The responding limb deflection is recorded by an embedded accelerometer to obtain limb impedance. The second approach is based on elastic limb loading to evoke self-excited oscillations during arm extensions. Here the contraction force at the oscillation onset provides information about limb stiffness. The rationale for both testing approaches is based on Feldman's λ-model. An arm expander based on the second approach was probed in a 6-month MIR space flight. The results obtained from the load oscillations, confirmed that this device is well suited to capture space flight induced neuromuscular changes.

  4. New excitation functions for proton induced reactions on natural titanium, nickel and copper up to 70 MeV

    NASA Astrophysics Data System (ADS)

    Garrido, E.; Duchemin, C.; Guertin, A.; Haddad, F.; Michel, N.; Métivier, V.

    2016-09-01

    New excitation functions for proton induced nuclear reactions on natural titanium, nickel and copper were measured, using the stacked-foil technique and gamma spectrometry, up to 70 MeV. The experimental cross sections were measured using the Ti-nat(p,x) V-48, Ni-nat(p,x) Ni-57 and Cu-nat(p,x) Zn-62,Co-56 monitor reactions recommended by the International Atomic Energy Agency (IAEA), depending on the investigated energy range. Data have been extracted for the Ti-nat(p,x) Sc-43,44m,46,47,48, V-48, K-42,43, Ni-nat(p,x) Ni-56,57, Co-55,56,57,58, Mn-52,54, Cu-nat(p,x) Cu-61,64, Ni-57, Co-56,57,58,60, Zn-62,65, Mn-54 reactions. Our results are discussed and compared to the existing ones as well as with the TALYS code version 1.6 calculations using default models. Our experimental data are in overall good agreement with the literature. TALYS is able to reproduce, in most cases, the experimental trend. Our new experimental results allow to expand our knowledge on these excitation functions, to confirm the existing trends and to give additional values on a large energy range. This work is in line with the new Coordinated Research Project (CRP) launched by the IAEA to expand the database of monitor reactions.

  5. Genetic Inhibition of CaMKII in Dorsal Striatal Medium Spiny Neurons Reduces Functional Excitatory Synapses and Enhances Intrinsic Excitability

    PubMed Central

    Klug, Jason R.; Mathur, Brian N.; Kash, Thomas L.; Wang, Hui-Dong; Matthews, Robert T.; Robison, A. J.; Anderson, Mark E.; Deutch, Ariel Y.; Lovinger, David M.; Colbran, Roger J.; Winder, Danny G.

    2012-01-01

    Ca2+/calmodulin-dependent protein kinase II (CaMKII) is abundant in striatal medium spiny neurons (MSNs). CaMKII is dynamically regulated by changes in dopamine signaling, as occurs in Parkinson's disease as well as addiction. Although CaMKII has been extensively studied in the hippocampus where it regulates excitatory synaptic transmission, relatively little is known about how it modulates neuronal function in the striatum. Therefore, we examined the impact of selectively overexpressing an EGFP-fused CaMKII inhibitory peptide (EAC3I) in striatal medium spiny neurons (MSNs) using a novel transgenic mouse model. EAC3I-expressing cells exhibited markedly decreased excitatory transmission, indicated by a decrease in the frequency of spontaneous excitatory postsynaptic currents (sEPSCs). This decrease was not accompanied by changes in the probability of release, levels of glutamate at the synapse, or changes in dendritic spine density. CaMKII regulation of the AMPA receptor subunit GluA1 is a major means by which the kinase regulates neuronal function in the hippocampus. We found that the decrease in striatal excitatory transmission seen in the EAC3I mice is mimicked by deletion of GluA1. Further, while CaMKII inhibition decreased excitatory transmission onto MSNs, it increased their intrinsic excitability. These data suggest that CaMKII plays a critical role in setting the excitability rheostat of striatal MSNs by coordinating excitatory synaptic drive and the resulting depolarization response. PMID:23028932

  6. Parallel transmit excitation at 1.5 T based on the minimization of a driving function for device heating

    SciTech Connect

    Gudino, N.; Sonmez, M.; Nielles-Vallespin, S.; Faranesh, A. Z.; Lederman, R. J.; Balaban, R. S.; Hansen, M. S.; Yao, Z.; Baig, T.; Martens, M.; Griswold, M. A.

    2015-01-15

    Purpose: To provide a rapid method to reduce the radiofrequency (RF) E-field coupling and consequent heating in long conductors in an interventional MRI (iMRI) setup. Methods: A driving function for device heating (W) was defined as the integration of the E-field along the direction of the wire and calculated through a quasistatic approximation. Based on this function, the phases of four independently controlled transmit channels were dynamically changed in a 1.5 T MRI scanner. During the different excitation configurations, the RF induced heating in a nitinol wire immersed in a saline phantom was measured by fiber-optic temperature sensing. Additionally, a minimization of W as a function of phase and amplitude values of the different channels and constrained by the homogeneity of the RF excitation field (B{sub 1}) over a region of interest was proposed and its results tested on the benchtop. To analyze the validity of the proposed method, using a model of the array and phantom setup tested in the scanner, RF fields and SAR maps were calculated through finite-difference time-domain (FDTD) simulations. In addition to phantom experiments, RF induced heating of an active guidewire inserted in a swine was also evaluated. Results: In the phantom experiment, heating at the tip of the device was reduced by 92% when replacing the body coil by an optimized parallel transmit excitation with same nominal flip angle. In the benchtop, up to 90% heating reduction was measured when implementing the constrained minimization algorithm with the additional degree of freedom given by independent amplitude control. The computation of the optimum phase and amplitude values was executed in just 12 s using a standard CPU. The results of the FDTD simulations showed similar trend of the local SAR at the tip of the wire and measured temperature as well as to a quadratic function of W, confirming the validity of the quasistatic approach for the presented problem at 64 MHz. Imaging and heating

  7. Parallel transmit excitation at 1.5 T based on the minimization of a driving function for device heating

    PubMed Central

    Gudino, N.; Sonmez, M.; Yao, Z.; Baig, T.; Nielles-Vallespin, S.; Faranesh, A. Z.; Lederman, R. J.; Martens, M.; Balaban, R. S.; Hansen, M. S.; Griswold, M. A.

    2015-01-01

    Purpose: To provide a rapid method to reduce the radiofrequency (RF) E-field coupling and consequent heating in long conductors in an interventional MRI (iMRI) setup. Methods: A driving function for device heating (W) was defined as the integration of the E-field along the direction of the wire and calculated through a quasistatic approximation. Based on this function, the phases of four independently controlled transmit channels were dynamically changed in a 1.5 T MRI scanner. During the different excitation configurations, the RF induced heating in a nitinol wire immersed in a saline phantom was measured by fiber-optic temperature sensing. Additionally, a minimization of W as a function of phase and amplitude values of the different channels and constrained by the homogeneity of the RF excitation field (B1) over a region of interest was proposed and its results tested on the benchtop. To analyze the validity of the proposed method, using a model of the array and phantom setup tested in the scanner, RF fields and SAR maps were calculated through finite-difference time-domain (FDTD) simulations. In addition to phantom experiments, RF induced heating of an active guidewire inserted in a swine was also evaluated. Results: In the phantom experiment, heating at the tip of the device was reduced by 92% when replacing the body coil by an optimized parallel transmit excitation with same nominal flip angle. In the benchtop, up to 90% heating reduction was measured when implementing the constrained minimization algorithm with the additional degree of freedom given by independent amplitude control. The computation of the optimum phase and amplitude values was executed in just 12 s using a standard CPU. The results of the FDTD simulations showed similar trend of the local SAR at the tip of the wire and measured temperature as well as to a quadratic function of W, confirming the validity of the quasistatic approach for the presented problem at 64 MHz. Imaging and heating

  8. Can we Predict Quantum Yields Using Excited State Density Functional Theory for New Families of Fluorescent Dyes?

    NASA Astrophysics Data System (ADS)

    Kohn, Alexander W.; Lin, Zhou; Shepherd, James J.; Van Voorhis, Troy

    2016-06-01

    For a fluorescent dye, the quantum yield characterizes the efficiency of energy transfer from the absorbed light to the emitted fluorescence. In the screening among potential families of dyes, those with higher quantum yields are expected to have more advantages. From the perspective of theoreticians, an efficient prediction of the quantum yield using a universal excited state electronic structure theory is in demand but still challenging. The most representative examples for such excited state theory include time-dependent density functional theory (TDDFT) and restricted open-shell Kohn-Sham (ROKS). In the present study, we explore the possibility of predicting the quantum yields for conventional and new families of organic dyes using a combination of TDDFT and ROKS. We focus on radiative (kr) and nonradiative (knr) rates for the decay of the first singlet excited state (S_1) into the ground state (S_0) in accordance with Kasha's rule. M. Kasha, Discuss. Faraday Soc., 9, 14 (1950). For each dye compound, kr is calculated with the S_1-S_0 energy gap and transition dipole moment obtained using ROKS and TDDFT respectively at the relaxed S_1 geometry. Our predicted kr agrees well with the experimental value, so long as the order of energy levels is correctly predicted. Evaluation of knr is less straightforward as multiple processes are involved. Our study focuses on the S_1-T_1 intersystem crossing (ISC) and the S_1-S_0 internal conversion (IC): we investigate the properties that allow us to model the knr value using a Marcus-like expression, such as the Stokes shift, the reorganization energy, and the S_1-T_1 and S_1-S_0 energy gaps. Taking these factors into consideration, we compare our results with those obtained using the actual Marcus theory and provide explanation for discrepancy. T. Kowalczyk, T. Tsuchimochi, L. Top, P.-T. Chen, and T. Van Voorhis, J. Chem. Phys., 138, 164101 (2013). M. Kasha, Discuss. Faraday Soc., 9, 14 (1950).

  9. Time-dependent density functional theory study of cobalt corrinoids: Electronically excited states of coenzyme B12

    NASA Astrophysics Data System (ADS)

    Andruniów, Tadeusz; Jaworska, Maria; Lodowski, Piotr; Zgierski, Marek Z.; Dreos, Renata; Randaccio, Lucio; Kozlowski, Pawel M.

    2009-09-01

    The analysis of the electronic spectra of adenosylcobalamin (AdoCbl) and its derivative in which the trans axial base was replaced by a water molecule (AdoCbi-H2O) has been performed by means of time-dependent density functional theory (TDDFT). The latter corresponds to the situation encountered in strongly acidic conditions. The TDDFT electronic transitions and oscillator strengths were calculated at the optimized B3LYP and BP86 ground state equilibrium geometries. A comparison of the orbital energy diagrams obtained with the B3LYP and BP86 functionals reveals a different orbital order and composition of the highest occupied and lowest unoccupied molecular orbitals. In B3LYP the lowest-energy transitions are of π /d→π*, π /d→σ*, and π /d→d characters while in the case of BP86 they are mainly d /π→π* and d →π*. The long range charge transfer transitions involving excitations from adenine π orbitals to antibonding corrin π* orbital can be observed at low energies, especially in BP86 results. Calculated electronic excitations were used to simulate the absorption spectra for a direct comparison with the absorption spectra recorded for AdoCbl at different pH values. As previously found for methylcobalamin [see Andruniów et al., J. Chem. Phys. 129, 085101 (2008)] also for AdoCbl the two-parameter scaling technique is required to obtain a satisfactory agreement between theoretical and experimental spectra. Both functionals correctly predict the shifting of the lowest intense transition toward blue by approximately 13nm upon changing pH from 7 to 1.

  10. Density Relaxation in Time-Dependent Density Functional Theory: Combining Relaxed Density Natural Orbitals and Multireference Perturbation Theories for an Improved Description of Excited States.

    PubMed

    Ronca, Enrico; Angeli, Celestino; Belpassi, Leonardo; De Angelis, Filippo; Tarantelli, Francesco; Pastore, Mariachiara

    2014-09-01

    Making use of the recently developed excited state charge displacement analysis [E. Ronca et al., J. Chem. Phys. 140, 054110 (2014)], suited to quantitatively characterize the charge fluxes coming along an electronic excitation, we investigate the role of the density relaxation effects in the overall description of electronically excited states of different nature, namely, valence, ionic, and charge transfer (CT), considering a large set of prototypical small and medium-sized molecular systems. By comparing the response densities provided by time-dependent density functional theory (TDDFT) and the corresponding relaxed densities obtained by applying the Z-vector postlinear-response approach [N. C. Handy and H. F. Schaefer, J. Chem. Phys. 81, 5031 (1984)] with those obtained by highly correlated state-of-the-art wave function calculations, we show that the inclusion of the relaxation effects is imperative to get an accurate description of the considered excited states. We also examine what happens at the quality of the response function when an increasing amount of Hartree-Fock (HF) exchange is included in the functional, showing that the usually improved excitation energies in the case of CT states are not always the consequence of an improved description of their overall properties. Remarkably, we find that the relaxation of the response densities is always able to reproduce, independently of the extent of HF exchange in the functional, the benchmark wave function densities. Finally, we propose a novel and computationally convenient strategy, based on the use of the natural orbitals derived from the relaxed TDDFT density to build zero-order wave function for multireference perturbation theory calculations. For a significant set of different excited states, the proposed approach provided accurate excitation energies, comparable to those obtained by computationally demanding ab initio calculations.

  11. Unrestricted density functional theory based on the fragment molecular orbital method for the ground and excited state calculations of large systems

    SciTech Connect

    Nakata, Hiroya; Fedorov, Dmitri G.; Yokojima, Satoshi; Kitaura, Kazuo; Sakurai, Minoru; Nakamura, Shinichiro

    2014-04-14

    We extended the fragment molecular orbital (FMO) method interfaced with density functional theory (DFT) into spin unrestricted formalism (UDFT) and developed energy gradients for the ground state and single point excited state energies based on time-dependent DFT. The accuracy of FMO is evaluated in comparison to the full calculations without fragmentation. Electronic excitations in solvated organic radicals and in the blue copper protein, plastocyanin (PDB code: 1BXV), are reported. The contributions of solvent molecules to the electronic excitations are analyzed in terms of the fragment polarization and quantum effects such as interfragment charge transfer.

  12. Unrestricted density functional theory based on the fragment molecular orbital method for the ground and excited state calculations of large systems.

    PubMed

    Nakata, Hiroya; Fedorov, Dmitri G; Yokojima, Satoshi; Kitaura, Kazuo; Sakurai, Minoru; Nakamura, Shinichiro

    2014-04-14

    We extended the fragment molecular orbital (FMO) method interfaced with density functional theory (DFT) into spin unrestricted formalism (UDFT) and developed energy gradients for the ground state and single point excited state energies based on time-dependent DFT. The accuracy of FMO is evaluated in comparison to the full calculations without fragmentation. Electronic excitations in solvated organic radicals and in the blue copper protein, plastocyanin (PDB code: 1BXV), are reported. The contributions of solvent molecules to the electronic excitations are analyzed in terms of the fragment polarization and quantum effects such as interfragment charge transfer.

  13. Excitation functions of alpha particle induced reactions on natTi up to 40 MeV

    NASA Astrophysics Data System (ADS)

    Uddin, M. S.; Scholten, B.

    2016-08-01

    Excitation functions of the reactions natTi(α,x)48Cr, natTi(α,x)48V and natTi(α,x)46,48Sc were determined by the stacked-foil activation technique up to 40 MeV. The radioactivities produced in the natTi target were measured by γ-ray spectrometry using HPGe detector. The reaction natTi(α,x)51Cr was used to determine the beam parameters. New experimental values for the above reactions have been obtained. An intercomparison of our data with the available literature values has been done. The cross section results obtained in this work could be useful in defining new monitor reactions, radiation safety and isotope production.

  14. Converging genetic and functional brain imaging evidence links neuronal excitability to working memory, psychiatric disease, and brain activity

    PubMed Central

    Heck, A.; Fastenrath, M.; Ackermann, S.; Auschra, B.; Bickel, H.; Coynel, D.; Gschwind, L.; Jessen, F.; Kaduszkiewicz, H.; Maier, W.; Milnik, A.; Pentzek, M.; Riedel-Heller, S.G.; Ripke, S.; Spalek, K.; Sullivan, P.; Vogler, C.; Wagner, M.; Weyerer, S.; Wolfsgruber, S.; de Quervain, D.; Papassotiropoulos, A.

    2014-01-01

    Summary Working memory, the capacity of actively maintaining task-relevant information during a cognitive task, is a heritable trait. Working memory deficits are characteristic for many psychiatric disorders. We performed genome-wide gene-set enrichment analyses in multiple independent data sets of young and aged cognitively healthy subjects (n = 2’824), and in a large schizophrenia case-control sample (n = 32’143). The voltage-gated cation channel activity gene-set, consisting of genes related to neuronal excitability, was robustly linked to performance in working memory-related tasks across ages, and to schizophrenia. Functional brain imaging in 707 healthy participants linked this gene-set also to working memory-related activity in the parietal cortex and the cerebellum. Gene-set analyses may help to dissect the molecular underpinnings of cognitive dimensions, brain activity and psychopathology. PMID:24529980

  15. Near and Above Ionization Electronic Excitations with Non-Hermitian Real-Time Time-Dependent Density Functional Theory

    SciTech Connect

    Lopata, Kenneth A.; Govind, Niranjan

    2013-11-12

    We present a real-time time-dependent density functional theory (RT-TDDFT) prescription for capturing near and post-ionization excitations based on non-Hermitian von Neumann density matrix propagation with atom-centered basis sets, tuned range-separated DFT, and a phenomenological imaginary molecular orbital-based absorbing potential to mimic coupling to the continuum. The computed extreme ultraviolet absorption spectra for acetylene (C2H2), water (H2O), and Freon 12 (CF2Cl2) agree well with electron energy loss spectroscopy (EELS) data over the range 0 to 50 eV. The absorbing potential removes spurious high energy finite basis artifacts, yielding correct bound to bound transitions, metastable (autoionizing) resonance states, and consistent overall absorption shapes.

  16. Near and Above Ionization Electronic Excitations with Non-Hermitian Real-Time Time-Dependent Density Functional Theory.

    PubMed

    Lopata, Kenneth; Govind, Niranjan

    2013-11-12

    We present a real-time time-dependent density functional theory (RT-TDDFT) prescription for capturing near and post-ionization excitations based on non-Hermitian von Neumann density matrix propagation with atom-centered basis sets, tuned range-separated DFT, and a phenomenological imaginary molecular orbital-based absorbing potential to mimic coupling to the continuum. The computed extreme ultraviolet absorption spectra for acetylene (C2H2), water (H2O), and Freon 12 (CF2Cl2) agree well with electron energy loss spectroscopy (EELS) data over the range of 0-50 eV. The absorbing potential removes spurious high-energy finite basis artifacts, yielding correct bound-to-bound transitions, metastable (autoionizing) resonance states, and consistent overall absorption shapes. PMID:26583412

  17. Comparative assessment of density functional methods for evaluating essential parameters to simulate SERS spectra within the excited state energy gradient approximation

    NASA Astrophysics Data System (ADS)

    Mohammadpour, Mozhdeh; Jamshidi, Zahra

    2016-05-01

    The prospect of challenges in reproducing and interpretation of resonance Raman properties of molecules interacting with metal clusters has prompted the present research initiative. Resonance Raman spectra based on the time-dependent gradient approximation are examined in the framework of density functional theory using different methods for representing the exchange-correlation functional. In this work the performance of different XC functionals in the prediction of ground state properties, excitation state energies, and gradients are compared and discussed. Resonance Raman properties based on time-dependent gradient approximation for the strongly low-lying charge transfer states are calculated and compared for different methods. We draw the following conclusions: (1) for calculating the binding energy and ground state geometry, dispersion-corrected functionals give the best performance in comparison to ab initio calculations, (2) GGA and meta GGA functionals give good accuracy in calculating vibrational frequencies, (3) excited state energies determined by hybrid and range-separated hybrid functionals are in good agreement with EOM-CCSD calculations, and (4) in calculating resonance Raman properties GGA functionals give good and reasonable performance in comparison to the experiment; however, calculating the excited state gradient by using the hybrid functional on the hessian of GGA improves the results of the hybrid functional significantly. Finally, we conclude that the agreement of charge-transfer surface enhanced resonance Raman spectra with experiment is improved significantly by using the excited state gradient approximation.

  18. Calculations of Excitation Functions of Some Structural Fusion Materials for ( n, t) Reactions up to 50 MeV Energy

    NASA Astrophysics Data System (ADS)

    Tel, E.; Durgu, C.; Aktı, N. N.; Okuducu, Ş.

    2010-06-01

    Fusion serves an inexhaustible energy for humankind. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. Tritium self-sufficiency must be maintained for a commercial power plant. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. So, the working out the systematics of ( n, t) reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at different energies. In this study, ( n, t) reactions for some structural fusion materials such as 27Al, 51V, 52Cr, 55Mn, and 56Fe have been investigated. The new calculations on the excitation functions of 27Al( n, t)25Mg, 51V( n, t)49Ti, 52Cr( n, t)50V, 55Mn( n, t)53Cr and 56Fe( n, t)54Mn reactions have been carried out up to 50 MeV incident neutron energy. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. The pre-equilibrium calculations involve the new evaluated the geometry dependent hybrid model, hybrid model and the cascade exciton model. Equilibrium effects are calculated according to the Weisskopf-Ewing model. Also in the present work, we have calculated ( n, t) reaction cross-sections by using new evaluated semi-empirical formulas developed by Tel et al. at 14-15 MeV energy. The calculated results are discussed and compared with the experimental data taken from the literature.

  19. Investigation of effect of excitation frequency on electron energy distribution functions in low pressure radio frequency bounded plasmas

    SciTech Connect

    Bhattacharjee, Sudeep; Lafleur, Trevor; Charles, Christine; Boswell, Rod

    2011-07-15

    Particle in cell (PIC) simulations are employed to investigate the effect of excitation frequency {omega} on electron energy distribution functions (EEDFs) in a low pressure radio frequency (rf) discharge. The discharge is maintained over a length of 0.10 m, bounded by two infinite parallel plates, with the coherent heating field localized at the center of the discharge over a distance of 0.05 m and applied perpendicularly along the y and z directions. On varying the excitation frequency f (={omega}/2{pi}) in the range 0.01-50 MHz, it is observed that for f {<=} 5 MHz the EEDF shows a trend toward a convex (Druyvesteyn-like) distribution. For f > 5 MHz, the distribution resembles more like a Maxwellian with the familiar break energy visible in most of the distributions. A prominent ''hot tail'' is observed at f{>=} 20 MHz and the temperature of the tail is seen to decrease with further increase in frequency (e.g., at 30 MHz and 50 MHz). The mechanism for the generation of the ''hot tail'' is considered to be due to preferential transit time heating of energetic electrons as a function of {omega}, in the antenna heating field. There exists an optimum frequency for which high energy electrons are maximally heated. The occurrence of the Druyvesteyn-like distributions at lower {omega} may be explained by a balance between the heating of the electrons in the effective electric field and elastic cooling due to electron neutral collision frequency {nu}{sub en}; the transition being dictated by {omega} {approx} 2{pi}{nu}{sub en}.

  20. Investigation of effect of excitation frequency on electron energy distribution functions in low pressure radio frequency bounded plasmas

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Sudeep; Lafleur, Trevor; Charles, Christine; Boswell, Rod

    2011-07-01

    Particle in cell (PIC) simulations are employed to investigate the effect of excitation frequency ω on electron energy distribution functions (EEDFs) in a low pressure radio frequency (rf) discharge. The discharge is maintained over a length of 0.10 m, bounded by two infinite parallel plates, with the coherent heating field localized at the center of the discharge over a distance of 0.05 m and applied perpendicularly along the y and z directions. On varying the excitation frequency f (=ω/2π) in the range 0.01-50 MHz, it is observed that for f ≤ 5 MHz the EEDF shows a trend toward a convex (Druyvesteyn-like) distribution. For f > 5 MHz, the distribution resembles more like a Maxwellian with the familiar break energy visible in most of the distributions. A prominent "hot tail" is observed at f ≥ 20 MHz and the temperature of the tail is seen to decrease with further increase in frequency (e.g., at 30 MHz and 50 MHz). The mechanism for the generation of the "hot tail" is considered to be due to preferential transit time heating of energetic electrons as a function of ω, in the antenna heating field. There exists an optimum frequency for which high energy electrons are maximally heated. The occurrence of the Druyvesteyn-like distributions at lower ω may be explained by a balance between the heating of the electrons in the effective electric field and elastic cooling due to electron neutral collision frequency νen; the transition being dictated by ω ˜ 2πνen.

  1. Comparison of polar motion excitation function derived from equivalent water thickness data, obtained from filtered stokes coefficients

    NASA Astrophysics Data System (ADS)

    Nagalski, T.

    2012-12-01

    It is known that the estimates of the Earth's gravity field produced by the Gravity Recovery and Climate Experiment (GRACE) satellite mission can be used to infer changes in equivalent water thickness (EWT). However, inadequately smoothed GRACE satellite mission EWT data contain significant striping and thus ought to be filtered to improve signal to noise ratio. We used Stokes coefficients data from GFZ (GeoForschungsZentrum), JPL (Jet Propulsion Laboratory) and CSR (Center for Space Research), filtered by decorrelation anisotropic filters: DDK3, DDK2 and DDK1 (Kusche et al., 2009) and made available in the ICGEM (International Center for Global Earth Models). To determine gravimetric excitation function of polar motion for the entire globe or selected areas, we convert gravity coefficients into Equivalent Water Thickness fields. To eliminate stripes from the maps of the EWT, one uses anisotropic filters (Kusche et al., 2009) that are smoothing the EWT data. In this study we investigate the influence of decorrelation anisotropic DDK filters used to process the GRACE EWT fields on the determined polar motion gravimetric excitation functions. We investigate the effect of these filters for four regions: 1) entire Earth, 2) ocean area, 3) land area and 4) Tibetan Plateau area (a rectangle bounded by 4 points A(37.N,78.E), B(37.N,102.E), C(28.N,78.E), D(28.N,102.E). Stokes coefficients are made available on the ICGEM web site. The data contain spherical harmonic coefficients delivered by three research centers: CSR, GFZ, JPL. The time span of the data is 2002 - 2010. The time resolution is 30 days. The ICGEM delivers either the raw Stokes coefficients or filtered Stokes coefficients after application of the anisotropic filters. Computation were based on the following equations

  2. Investigations of the potential functions of weakly bound diatomic molecules and laser-assisted excitive Penning ionization

    SciTech Connect

    Goble, J.H. Jr.

    1982-05-01

    Three variations on the Dunham series expansion function of the potential of a diatomic molecule are compared. The differences among these expansions lie in the choice of the expansion variable, lambda. The functional form of these variables are lambda/sub s/ = l-r/sub e//r for the Simon-Parr-Finlan version, lambda/sub T/ - 1-(r/sub e//r)/sup p/ for that of Thakkar, and lambda/sub H/ = 1-exp(-rho(r/r/sub e/-1) for that of Huffaker. A wide selection of molecular systems are examined. It is found that, for potentials in excess of thirty kcal/mole, the Huffaker expansion provides the best description of the three, extrapolating at large internuclear separation to a value within 10% of the true dissociation energy. For potentials that result from the interaction of excited states, all series expansions show poor behavior away from the equilibrium internuclear separation of the molecule. The series representation of the potentials of weakly bound molecules are examined in more detail. The ground states of BeAr/sup +/, HeNe/sup +/, NaAr, and Ar/sub 2/ and the excited states of HeNe+, NaNe, and NaAr are best described by the Thakkar expansion. Finally, the observation of laser-assisted excitive Penning ionization in a flowing afterglow is reported. The reaction Ar(/sup 3/P/sub 2/) + Ca + h nu ..-->.. Ar + Ca/sup +/(5p /sup 2/P/sub J/) + e/sup -/ occurs when the photon energy, h nu, is approximately equal to the energy difference between the metastable argon and one of the fine structure levels of the ion's doublet. By monitoring the cascade fluorescence of the above reaction and comparing it to the flourescence from the field-free process Ar(/sup 3/P/sub 2/) + Ca ..-->.. Ar + Ca/sup +/(4p /sup 2/P/sub J/) + e/sup -/ a surprisingly large cross section of 6.7 x 10/sup 3/ A/sup 2/ is estimated.

  3. Ground- and excited-state diatomic bond lengths, vibrational levels, and potential-energy curves from conventional and localized Hartree-Fock-based density-functional theory

    NASA Astrophysics Data System (ADS)

    Teale, Andrew M.; Tozer, David J.

    2005-01-01

    Ground- and excited-state diatomic bond lengths, vibrational levels, and potential-energy curves are determined using conventional and localized Hartree-Fock (LHF)-based density-functional theory. Exchange only and hybrid functionals (with various fractions of exchange) are considered, together with a standard generalized gradient approximation (GGA). Ground-state bond lengths and vibrational wave numbers are relatively insensitive to whether orbital exchange is treated using the conventional or LHF approach. Excited-state calculations are much more sensitive. For a standard fraction of orbital exchange, N2 and CO vertical excitation energies at experimental bond lengths are accurately described by both conventional and LHF-based approaches, providing an asymptotic correction is present. Excited-state bond lengths and vibrational levels are more accurate with the conventional approach. The best quality, however, is obtained with an asymptotically corrected GGA functional. For the ground and lowest four singlet excited states, the GGA mean absolute errors in bond lengths are 0.006 Å (0.5%) and 0.011 Å (0.8%) for N2 and CO, respectively. Mean absolute errors in fundamental vibrational wavenumbers are 49 cm-1 (2.7%) and 68 cm-1 (5.0%), respectively. The GGA potential-energy curves are compared with near-exact Rydberg-Klein-Rees curves. Agreement is very good for the ground and first excited state, but deteriorates for the higher states.

  4. Density functional investigation of the electronic structure and charge transfer excited states of a multichromophoric antenna

    NASA Astrophysics Data System (ADS)

    Basurto, Luis; Zope, Rajendra R.; Baruah, Tunna

    2016-05-01

    We report an electronic structure study of a multichromophoric molecular complex containing two of each borondipyrromethane dye, Zn-tetraphenyl-porphyrin, bisphenyl anthracene and a fullerene. The snowflake shaped molecule behaves like an antenna capturing photon at different frequencies and transferring the photon energy to the porphyrin where electron transfer occurs from the porphyrin to the fullerene. The study is performed within density functional formalism using large polarized Guassian basis sets (12,478 basis functions in total). The energies of the HOMO and LUMO states in the complex, as adjudged by the ionization potential and the electron affinity values, show significant differences with respect to their values in participating subunits in isolation. These differences are also larger than the variations of the ionization potential and electron affinity values observed in non-bonded C60-ZnTPP complexes in co-facial arrangement or end-on orientations. An understanding of the origin of these differences is obtained by a systematic study of the effect of structural strain, the presence of ligands, the effect of orbital delocalization on the ionization energy and the electron affinity. Finally, a few lowest charge transfer energies involving electronic transitions from the porphyrin component to the fullerene subunit of the complex are predicted.

  5. Rapid homeostatic plasticity of intrinsic excitability in a central pattern generator network stabilizes functional neural network output.

    PubMed

    Ransdell, Joseph L; Nair, Satish S; Schulz, David J

    2012-07-11

    Neurons and networks undergo a process of homeostatic plasticity that stabilizes output by integrating activity levels with network and cellular properties to counter longer-term perturbations. Here we describe a rapid compensatory interaction among a pair of potassium currents, I(A) and I(KCa), that stabilizes both intrinsic excitability and network function in the cardiac ganglion of the crab, Cancer borealis. We determined that mRNA levels in single identified neurons for the channels which encode I(A) and I(KCa) are positively correlated, yet the ionic currents themselves are negatively correlated, across a population of motor neurons. We then determined that these currents are functionally coupled; decreasing levels of either current within a neuron causes a rapid increase in the other. This functional interdependence results in homeostatic stabilization of both the individual neuronal and the network output. Furthermore, these compensatory increases are mechanistically independent, suggesting robustness in the maintenance of neural network output that is critical for survival. Together, we generate a complete model for homeostatic plasticity from mRNA to network output where rapid post-translational compensatory mechanisms acting on a reservoir of channels proteins regulated at the level of gene expression provide homeostatic stabilization of both cellular and network activity. PMID:22787050

  6. Dual effect of local anesthetics on the function of excitable rod outer segment disk membrane

    SciTech Connect

    Mashimo, T.; Abe, K.; Yoshiya, I.

    1986-04-01

    The effects of local anesthetics and a divalent cation, Ca2+, on the function of rhodopsin were estimated from the measurements of light-induced proton uptake. The light-induced proton uptake by rhodopsin in the rod outer segment disk membrane was enhanced at lower pH (4) but depressed at higher pHs (6 to 8) by the tertiary amine local anesthetics lidocaine, bupivacaine, tetracaine, and dibucaine. The order of local anesthetic-induced depression of the proton uptake followed that of their clinical anesthetic potencies. The depression of the proton uptake versus the concentration of the uncharged form of local anesthetic nearly describes the same curve for small and large dose of added anesthetic. Furthermore, a neutral local anesthetic, benzocaine, depressed the proton uptake at all pHs between 4 and 7. These results indicate that the depression of the proton uptake is due to the effect of only the uncharged form. It is hypothesized that the uncharged form of local anesthetics interacts hydrophobically with the rhodopsin in the disk membrane. The dual effect of local anesthetics on the proton uptake, on the other hand, suggests that the activation of the function of rhodopsin may be caused by the charged form. There was no significant change in the light-induced proton uptake by rhodopsin when 1 mM of Ca2+ was introduced into the disk membrane at varying pHs in the absence or presence of local anesthetics. This fact indicates that Ca2+ ion does not influence the diprotonating process of metarhodopsin; neither does it interfere with the local anesthetic-induced changes in the rhodopsin molecule.

  7. Rapid development of Purkinje cell excitability, functional cerebellar circuit, and afferent sensory input to cerebellum in zebrafish.

    PubMed

    Hsieh, Jui-Yi; Ulrich, Brittany; Issa, Fadi A; Wan, Jijun; Papazian, Diane M

    2014-01-01

    The zebrafish has significant advantages for studying the morphological development of the brain. However, little is known about the functional development of the zebrafish brain. We used patch clamp electrophysiology in live animals to investigate the emergence of excitability in cerebellar Purkinje cells, functional maturation of the cerebellar circuit, and establishment of sensory input to the cerebellum. Purkinje cells are born at 3 days post-fertilization (dpf). By 4 dpf, Purkinje cells spontaneously fired action potentials in an irregular pattern. By 5 dpf, the frequency and regularity of tonic firing had increased significantly and most cells fired complex spikes in response to climbing fiber activation. Our data suggest that, as in mammals, Purkinje cells are initially innervated by multiple climbing fibers that are winnowed to a single input. To probe the development of functional sensory input to the cerebellum, we investigated the response of Purkinje cells to a visual stimulus consisting of a rapid change in light intensity. At 4 dpf, sudden darkness increased the rate of tonic firing, suggesting that afferent pathways carrying visual information are already active by this stage. By 5 dpf, visual stimuli also activated climbing fibers, increasing the frequency of complex spiking. Our results indicate that the electrical properties of zebrafish and mammalian Purkinje cells are highly conserved and suggest that the same ion channels, Nav1.6 and Kv3.3, underlie spontaneous pacemaking activity. Interestingly, functional development of the cerebellum is temporally correlated with the emergence of complex, visually-guided behaviors such as prey capture. Because of the rapid formation of an electrically-active cerebellum, optical transparency, and ease of genetic manipulation, the zebrafish has great potential for functionally mapping cerebellar afferent and efferent pathways and for investigating cerebellar control of motor behavior.

  8. Cell adhesion molecule L1 contributes to neuronal excitability regulating the function of voltage-gated Na+ channels.

    PubMed

    Valente, Pierluigi; Lignani, Gabriele; Medrihan, Lucian; Bosco, Federica; Contestabile, Andrea; Lippiello, Pellegrino; Ferrea, Enrico; Schachner, Melitta; Benfenati, Fabio; Giovedì, Silvia; Baldelli, Pietro

    2016-05-01

    L1 (also known as L1CAM) is a trans-membrane glycoprotein mediating neuron-neuron adhesion through homophilic and heterophilic interactions. Although experimental evidence has implicated L1 in axonal outgrowth, fasciculation and pathfinding, its contribution to voltage-gated Na(+) channel function and membrane excitability has remained unknown. Here, we show that firing rate, single cell spiking frequency and Na(+) current density are all reduced in hippocampal excitatory neurons from L1-deficient mice both in culture and in slices owing to an overall reduced membrane expression of Na(+) channels. Remarkably, normal firing activity was restored when L1 was reintroduced into L1-deficient excitatory neurons, indicating that abnormal firing patterns are not related to developmental abnormalities, but are a direct consequence of L1 deletion. Moreover, L1 deficiency leads to impairment of action potential initiation, most likely due to the loss of the interaction of L1 with ankyrin G that produces the delocalization of Na(+) channels at the axonal initial segment. We conclude that L1 contributes to functional expression and localization of Na(+) channels to the neuronal plasma membrane, ensuring correct initiation of action potential and normal firing activity. PMID:26985064

  9. Damage detection of metro tunnel structure through transmissibility function and cross correlation analysis using local excitation and measurement

    NASA Astrophysics Data System (ADS)

    Feng, Lei; Yi, Xiaohua; Zhu, Dapeng; Xie, Xiongyao; Wang, Yang

    2015-08-01

    In a modern metropolis, metro rail systems have become a dominant mode for mass transportation. The structural health of a metro tunnel is closely related to public safety. Many vibration-based techniques for detecting and locating structural damage have been developed in the past several decades. However, most damage detection techniques and validation tests are focused on bridge and building structures; very few studies have been reported on tunnel structures. Among these techniques, transmissibility function and cross correlation analysis are two well-known diagnostic approaches. The former operates in frequency domain and the latter in time domain. Both approaches can be applied to detect and locate damage through acceleration data obtained from sensor arrays. Furthermore, the two approaches can directly utilize structural response data without requiring excitation measurement, which offers advantages in field testing on a large structure. In this research, a numerical finite element model of a metro tunnel is built and different types of structural defects are introduced at multiple locations of the tunnel. Transmissibility function and cross correlation analysis are applied to perform structural damage detection and localization, based on simulated structural vibration data. Numerical results demonstrate that the introduced defects can be successfully identified and located. The sensitivity and feasibility of the two approaches have been verified when sufficient distribution of measurement locations is available. Damage detection results of the two different approaches are compared and discussed.

  10. How Bond Length Alternation and Thermal Disorder Affect the Optical Excitation Energies of π-Conjugated Chains: A Combined Density Functional Theory and Molecular Dynamics Study.

    PubMed

    Bois, Juliana; Körzdörfer, Thomas

    2016-04-12

    We dissect the sources of error leading to inaccuracies in the description of the geometry and optical excitation energies of π-conjugated polymers. While the ground-state bond length alternation is shown to be badly reproduced by standard functionals, the recently adapted functionals PBEh* and ωPBE* as well as the double hybrid functional XYGJ-OS manage to replicate results obtained at the CCSD(T) level. By analysis of the bond length alternation in the excited state, a sensitive dependence of the exciton localization on the long-range behavior of the functional and the amount of Hartree-Fock exchange present is shown. Introducing thermal disorder through molecular dynamics simulations allows the consideration of a range of thermally accessible configurations of each oligomer, including trans to cis rotations, which break the conjugation of the backbone. Thermal disorder has a considerable effect when combined with functionals that overestimate the delocalization of the excitation, such as B3LYP. For functionals with a larger amount of exact exchange such as our PBEh* and ωPBE*, however, the effect is small, as excitations are often localized enough to fit between twists in the chain. PMID:26960057

  11. Multiresolution quantum chemistry in multiwavelet bases: excited states from time-dependent Hartree–Fock and density functional theory via linear response

    DOE PAGES

    Yanai, Takeshi; Fann, George I.; Beylkin, Gregory; Harrison, Robert J.

    2015-02-25

    Using the fully numerical method for time-dependent Hartree–Fock and density functional theory (TD-HF/DFT) with the Tamm–Dancoff (TD) approximation we use a multiresolution analysis (MRA) approach to present our findings. From a reformulation with effective use of the density matrix operator, we obtain a general form of the HF/DFT linear response equation in the first quantization formalism. It can be readily rewritten as an integral equation with the bound-state Helmholtz (BSH) kernel for the Green's function. The MRA implementation of the resultant equation permits excited state calculations without virtual orbitals. Moreover, the integral equation is efficiently and adaptively solved using amore » numerical multiresolution solver with multiwavelet bases. Our implementation of the TD-HF/DFT methods is applied for calculating the excitation energies of H2, Be, N2, H2O, and C2H4 molecules. The numerical errors of the calculated excitation energies converge in proportion to the residuals of the equation in the molecular orbitals and response functions. The energies of the excited states at a variety of length scales ranging from short-range valence excitations to long-range Rydberg-type ones are consistently accurate. It is shown that the multiresolution calculations yield the correct exponential asymptotic tails for the response functions, whereas those computed with Gaussian basis functions are too diffuse or decay too rapidly. Finally, we introduce a simple asymptotic correction to the local spin-density approximation (LSDA) so that in the TDDFT calculations, the excited states are correctly bound.« less

  12. Multiresolution quantum chemistry in multiwavelet bases: excited states from time-dependent Hartree–Fock and density functional theory via linear response

    SciTech Connect

    Yanai, Takeshi; Fann, George I.; Beylkin, Gregory; Harrison, Robert J.

    2015-02-25

    Using the fully numerical method for time-dependent Hartree–Fock and density functional theory (TD-HF/DFT) with the Tamm–Dancoff (TD) approximation we use a multiresolution analysis (MRA) approach to present our findings. From a reformulation with effective use of the density matrix operator, we obtain a general form of the HF/DFT linear response equation in the first quantization formalism. It can be readily rewritten as an integral equation with the bound-state Helmholtz (BSH) kernel for the Green's function. The MRA implementation of the resultant equation permits excited state calculations without virtual orbitals. Moreover, the integral equation is efficiently and adaptively solved using a numerical multiresolution solver with multiwavelet bases. Our implementation of the TD-HF/DFT methods is applied for calculating the excitation energies of H2, Be, N2, H2O, and C2H4 molecules. The numerical errors of the calculated excitation energies converge in proportion to the residuals of the equation in the molecular orbitals and response functions. The energies of the excited states at a variety of length scales ranging from short-range valence excitations to long-range Rydberg-type ones are consistently accurate. It is shown that the multiresolution calculations yield the correct exponential asymptotic tails for the response functions, whereas those computed with Gaussian basis functions are too diffuse or decay too rapidly. Finally, we introduce a simple asymptotic correction to the local spin-density approximation (LSDA) so that in the TDDFT calculations, the excited states are correctly bound.

  13. 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.

  14. Excitation function shape and neutron spectrum of the 7Li(p ,n )7Be reaction near threshold

    NASA Astrophysics Data System (ADS)

    Martín-Hernández, Guido; Mastinu, Pierfrancesco; Maggiore, Mario; Pranovi, Lorenzo; Prete, Gianfranco; Praena, Javier; Capote-Noy, Roberto; Gramegna, Fabiana; Lombardi, Augusto; Maran, Luca; Scian, Carlo; Munaron, Enrico

    2016-09-01

    The forward-emitted low energy tail of the neutron spectrum generated by the 7Li(p ,n )7Be reaction on a thick target at a proton energy of 1893.6 keV was measured by time-of-flight spectroscopy. The measurement was performed at BELINA (Beam Line for Nuclear Astrophysics) of the Laboratori Nazionali di Legnaro. Using the reaction kinematics and the proton on lithium stopping power the shape of the excitation function is calculated from the measured neutron spectrum. Good agreement with two reported measurements was found. Our data, along with the previous measurements, are well reproduced by the Breit-Wigner single-resonance formula for s -wave particles. The differential yield of the reaction is calculated and the widely used neutron spectrum at a proton energy of 1912 keV was reproduced. Possible causes regarding part of the 6.5% discrepancy between the 197Au(n ,γ ) cross section measured at this energy by Ratynski and Kappeler [Phys. Rev. C 37, 595 (1988), 10.1103/PhysRevC.37.595] and the one obtained using the Evaluated Nuclear Data File version B-VII.1 are given.

  15. Validation of Earth orientation parameters (EOP), geophysical excitation functions ( EF) and the second degree gravity field coefficients (GFC)

    NASA Astrophysics Data System (ADS)

    Heiker, A.; Schmidt, M.

    2012-04-01

    The project P9 of the research group "Earth rotation and geophysical processes" aims at the combined analysis and validation of Earth rotation observations and models (see Göttl et al. EGU 2012 poster). The EOP, EF and GFC are linked by the Earth tensor of inertia. This link is used for a sophisticated mutual validation. A least squares adjustment model which estimate the unknown tensor of inertia was developed for this purpose. Additionally variance and covariance components are estimated. The results of the adjustment model are the residuals for each data series and the adjusted tensor of inertia. It is assumed that the residuals contain the inconsistencies between the various time series. A thorough analysis of the residuals in the time and frequency domain reveals the systematic effects within the residuals. The adjusted variance and covariance components allow to check the standard deviations and in some cases the correlations given by the data centers. We present the results obtained from the combined analysis of IERS EOP, two different atmospheric and oceanic excitation functions (NCEP/ECCO from the Jet Propulsion Laboratory and ERAInterim/OMCT from the GeoForschungsZentrum (GFZ) Potsdam) and six different gravity field solutions (five GRACE solutions and one SLR solution).

  16. Electronic bands and excited states of III-V semiconductor polytypes with screened-exchange density functional calculations

    SciTech Connect

    Akiyama, Toru; Nakamura, Kohji; Ito, Tomonori; Freeman, Arthur J.

    2014-03-31

    The electronic band structures and excited states of III-V semiconductors such as GaP, AlP, AlAs, and AlSb for various polytypes are determined employing the screened-exchange density functional calculations implemented in the full-potential linearized augmented plane-wave methods. We demonstrate that GaP and AlSb in the wurtzite (WZ) structure have direct gap while III-V semiconductors in the zinc blende, 4H, and 6H structures considered in this study exhibit an indirect gap. Furthermore, we find that inclusion of Al atoms less than 17% and 83% in the hexagonal Al{sub x}Ga{sub 1−x}P and Al{sub x}Ga{sub 1−x}As alloys, respectively, leads to a direct transition with a gap energy of ∼2.3 eV. The feasibility of III-V semiconductors with a direct gap in WZ structure offers a possible crystal structure engineering to tune the optical properties of semiconductor materials.

  17. 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

  18. 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.

  19. New evolution equations for the joint response-excitation probability density function of stochastic solutions to first-order nonlinear PDEs

    SciTech Connect

    Venturi, D.; Karniadakis, G.E.

    2012-08-30

    By using functional integral methods we determine new evolution equations satisfied by the joint response-excitation probability density function (PDF) associated with the stochastic solution to first-order nonlinear partial differential equations (PDEs). The theory is presented for both fully nonlinear and for quasilinear scalar PDEs subject to random boundary conditions, random initial conditions or random forcing terms. Particular applications are discussed for the classical linear and nonlinear advection equations and for the advection-reaction equation. By using a Fourier-Galerkin spectral method we obtain numerical solutions of the proposed response-excitation PDF equations. These numerical solutions are compared against those obtained by using more conventional statistical approaches such as probabilistic collocation and multi-element probabilistic collocation methods. It is found that the response-excitation approach yields accurate predictions of the statistical properties of the system. In addition, it allows to directly ascertain the tails of probabilistic distributions, thus facilitating the assessment of rare events and associated risks. The computational cost of the response-excitation method is order magnitudes smaller than the one of more conventional statistical approaches if the PDE is subject to high-dimensional random boundary or initial conditions. The question of high-dimensionality for evolution equations involving multidimensional joint response-excitation PDFs is also addressed.

  20. Benchmarking DFT and TD-DFT Functionals for the Ground and Excited States of Hydrogen-Rich Peptide Radicals.

    PubMed

    Riffet, Vanessa; Jacquemin, Denis; Cauët, Emilie; Frison, Gilles

    2014-08-12

    We assess the pros and cons of a large panel of DFT exchange-correlation functionals for the prediction of the electronic structure of hydrogen-rich peptide radicals formed after electron attachment on a protonated peptide. Indeed, despite its importance in the understanding of the chemical changes associated with the reduction step, the question of the attachment site of an electron and, more generally, of the reduced species formed in the gas phase through electron-induced dissociation (ExD) processes in mass spectrometry is still a matter of debate. For hydrogen-rich peptide radicals in which several positive groups and low-lying π* orbitals can capture the incoming electron in ExD, inclusion of full Hartree-Fock exchange at long-range interelectronic distance is a prerequisite for an accurate description of the electronic states, thereby excluding several popular exchange-correlation functionals, e.g., B3LYP, M06-2X, or CAM-B3LYP. However, we show that this condition is not sufficient by comparing the results obtained with asymptotically correct range-separated hybrids (M11, LC-BLYP, LC-BPW91, ωB97, ωB97X, and ωB97X-D) and with reference CASSCF-MRCI and EOM-CCSD calculations. The attenuation parameter ω significantly tunes the spin density distribution and the excited states vertical energies. The investigated model structures, ranging from methylammonium to hexapeptide, allow us to obtain a description of the nature and energy of the electronic states, depending on (i) the presence of hydrogen bond(s) around the cationic site(s), (ii) the presence of π* molecular orbitals (MOs), and (iii) the selected DFT approach. It turns out that, in the present framework, LC-BLYP and ωB97 yields the most accurate results.

  1. A comprehensive study of sensorimotor cortex excitability in chronic cocaine users: Integrating TMS and functional MRI data☆

    PubMed Central

    Hanlon, Colleen A.; DeVries, William; Dowdle, Logan T.; West, Julia A.; Siekman, Bradley; Li, Xingbao; George, Mark S.

    2016-01-01

    Background Disruptions in motor control are often overlooked features of chronic cocaine users. During a simple sensorimotor integration task, for example, cocaine users activate a larger area of cortex than controls but have lower functional connectivity between the cortex and dorsal striatum, which is further correlated with poor performance. The purpose of this study was to determine whether abnormal cortical excitability in cocaine users was related to disrupted inhibitory or excitatory mechanisms, as measured by transcranial magnetic stimulation (TMS). Methods A battery of TMS measures were acquired from 87 individuals (50 cocaine dependent, 37 controls). Functional MRI data were acquired from a subset of 28 individuals who performed a block-design finger tapping task. Results TMS measures revealed that cocaine users had significantly higher resting motor thresholds and higher intracortical cortical facilitation (ICF) than controls. There was no between-group difference in either measure of cortical inhibition. Task-evoked BOLD signal in the motor cortex was significantly correlated with ICF in the cocaine users. There was no significant difference in brain-skull distance between groups. Conclusion These data demonstrated that cocaine users have disrupted cortical facilitation (as measured with TMS), which is related to elevated BOLD signal. Cortical inhibition, however, is largely intact. Given the relationship between ICF and glutamatergic agents, this may be a potentially fruitful and treatable target in addiction. Finally, among controls the distance from the scalp to the cortex was correlated with the motor threshold which may be a useful parameter to integrate into therapeutic TMS protocols in the future. PMID:26541870

  2. Preparation and functionalization of a visible-light-excited europium complex-modified luminescent protein for cell imaging applications.

    PubMed

    Tian, Lu; Dai, Zhichao; Ye, Zhiqiang; Song, Bo; Yuan, Jingli

    2014-03-01

    Lanthanide complex-based luminescent bioprobes have shown great utility in a variety of time-resolved luminescence bioassays, but these bioprobes often require UV excitation and suffer from problems related to bioaffinity and biocompatibility for in vivo applications. In this work, a new visible-light-excited europium(III) complex with the maximum excitation wavelength over 400 nm, BHHBB-Eu(3+)-BPT {BHHBB: 1,2-bis[4'-(1'',1'',1'',2'',2'',3'',3''-heptafluoro-4'',6''-hexanedion-6''-yl)-benzyl]-benzene; BPT: 2-(N,N-diethylanilin-4-yl)-4,6-bis(pyrazol-1-yl)-1,3,5-triazine}, has been synthesized for the preparation of an artificial luminescent protein that can be used as a visible-light-excited luminescent bioprobe for cell imaging. By encapsulating BHHBB-Eu(3+)-BPT into apoferritin with a simple dissociation-reassembly method, the luminescent protein, Eu@AFt, with a maximum excitation peak at 420 nm and a long luminescence lifetime of 365 μs was fabricated and successfully used for visible-light-excited time-resolved luminescence cell imaging. Moreover, by conjugating a mitochondria-targeting molecule, (5-N-succinimidoxy-5-oxopentyl)-triphenylphosphonium bromide (SPTPP), onto the surface of Eu@AFt, a mitochondria-specifically-tracking luminescent probe, Eu@AFt-SPTPP, was further prepared and used for visible-light-excited confocal luminescence microscopy imaging to visualize the mitochondria of living cells.

  3. Synthesis and functionalization of monodisperse near-ultraviolet and visible excitable multifunctional Eu(3+), Bi(3+):REVO4 nanophosphors for bioimaging and biosensing applications.

    PubMed

    Escudero, Alberto; Carrillo-Carrión, Carolina; Zyuzin, Mikhail V; Ashraf, Sumaira; Hartmann, Raimo; Núñez, Nuria O; Ocaña, Manuel; Parak, Wolfgang J

    2016-06-16

    Near-ultraviolet and visible excitable Eu- and Bi-doped NPs based on rare earth vanadates (REVO4, RE = Y, Gd) have been synthesized by a facile route from appropriate RE precursors, europium and bismuth nitrate, and sodium orthovanadate, by homogeneous precipitation in an ethylene glycol/water mixture at 120 °C. The NPs can be functionalized either by a one-pot synthesis with polyacrylic acid (PAA) or by a Layer-by-Layer approach with poly(allylamine hydrochloride) (PAH) and PAA. In the first case, the particle size can also be tuned by adjusting the amount of PAA. The Eu- Bi-doped REVO4 based nanophosphors show the typical red luminescence of Eu(iii), which can be excited through an energy transfer process from the vanadate anions, resulting in a much higher luminescence intensity in comparison to the direct excitation of the europium cations. The incorporation of Bi into the REVO4 structure shifts the original absorption band of the vanadate anions towards longer wavelengths, giving rise to nanophosphors with an excitation maximum at 342 nm, which can also be excited in the visible range. The suitability of such nanophosphors for bioimaging and biosensing applications, as well as their colloidal stability in different buffer media of biological interest, their cytotoxicity, their degradability at low pH, and their uptake by HeLa cells have been evaluated. Their suitability for bioimaging and biosensing applications is also demonstrated. PMID:27253384

  4. Atomic, Molecular, and Optical Physics: Optical Excitation Function of H(1s-2p) Produced by electron Impact from Threshold to 1.8 keV

    NASA Technical Reports Server (NTRS)

    James, G. K.; Slevin, J. A.; Shemansky, D. E.; McConkey, J. W.; Bray, I.; Dziczek, D.; Kanik, I.; Ajello, J. M.

    1997-01-01

    The optical excitation function of prompt Lyman-Alpha radiation, produced by electron impact on atomic hydrogen, has been measured over the extended energy range from threshold to 1.8 keV. Measurements were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source. A vacuum-ultraviolet mono- chromator system was used to measure the emitted Lyman-Alpha radiation. The absolute H(1s-2p) electron impact excitation cross section was obtained from the experimental optical excitation function by normalizing to the accepted optical oscillator strength, with corrections for polarization and cascade. Statistical and known systematic uncertainties in our data range from +/- 4% near threshold to +/- 2% at 1.8 keV. Multistate coupling affecting the shape of the excitation function up to 1 keV impact energy is apparent in both the present experimental data and present theoretical results obtained with convergent close- coupling (CCC) theory. This shape function effect leads to an uncertainty in absolute cross sections at the 10% level in the analysis of the experimental data. The derived optimized absolute cross sections are within 7% of the CCC calculations over the 14 eV-1.8 keV range. The present CCC calculations converge on the Bethe- Fano profile for H(1s-2p) excitation at high energy. For this reason agreement with the CCC values to within 3% is achieved in a nonoptimal normalization of the experimental data to the Bethe-Fano profile. The fundamental H(1s-2p) electron impact cross section is thereby determined to an unprecedented accuracy over the 14 eV - 1.8 keV energy range.

  5. Tight-binding approximations to time-dependent density functional theory — A fast approach for the calculation of electronically excited states

    NASA Astrophysics Data System (ADS)

    Rüger, Robert; van Lenthe, Erik; Heine, Thomas; Visscher, Lucas

    2016-05-01

    We propose a new method of calculating electronically excited states that combines a density functional theory based ground state calculation with a linear response treatment that employs approximations used in the time-dependent density functional based tight binding (TD-DFTB) approach. The new method termed time-dependent density functional theory TD-DFT+TB does not rely on the DFTB parametrization and is therefore applicable to systems involving all combinations of elements. We show that the new method yields UV/Vis absorption spectra that are in excellent agreement with computationally much more expensive TD-DFT calculations. Errors in vertical excitation energies are reduced by a factor of two compared to TD-DFTB.

  6. Ground- and excited-state properties of inorganic solids from full-potential density-functional calculations

    NASA Astrophysics Data System (ADS)

    Ravindran, P.; Vidya, R.; Vajeeston, P.; Kjekshus, A.; Fjellvåg, H.

    2003-12-01

    The development in theoretical condensed-matter science based on density-functional theory (DFT) has reached a level where it is possible, from "parameter-free" quantum mechanical calculations to obtain total energies, forces, vibrational frequencies, magnetic moments, mechanical and optical properties and so forth. The calculation of such properties are important in the analyses of experimental data and they can be predicted with a precision that is sufficient for comparison with experiments. It is almost impossible to do justice to all developments achieved by DFT because of its rapid growth. Hence, it has here been focused on a few advances, primarily from our laboratory. Unusual bonding behaviors in complex materials are conveniently explored using the combination of charge density, charge transfer, and electron-localization function along with crystal-orbital Hamilton-population analyses. It is indicated that the elastic properties of materials can reliably be predicted from DFT calculations if one takes into account the structural relaxations along with gradient corrections in the calculations. Experimental techniques have their limitations in studies of the structural stability and pressure-induced structural transitions in hydride materials whereas the present theoretical approach can be applied to reliably predict properties under extreme pressures. From the spin-polarized, relativistic full-potential calculations one can study novel materials such as ruthenates, quasi-one-dimensional oxides, and spin-, charge-, and orbital-ordering in magnetic perovskite-like oxides. The importance of orbital-polarization correction to the DFT to predict the magnetic anisotropy in transition-metal compounds and magnetic moments in lanthanides and actinides are emphasized. Apart from the full-potential treatment, proper magnetic ordering as well as structural distortions have to be taken into account to predict correctly the insulating behavior of transition-metal oxides

  7. Excited-State Electronic Structure with Configuration Interaction Singles and Tamm–Dancoff Time-Dependent Density Functional Theory on Graphical Processing Units

    PubMed Central

    2011-01-01

    Excited-state calculations are implemented in a development version of the GPU-based TeraChem software package using the configuration interaction singles (CIS) and adiabatic linear response Tamm–Dancoff time-dependent density functional theory (TDA-TDDFT) methods. The speedup of the CIS and TDDFT methods using GPU-based electron repulsion integrals and density functional quadrature integration allows full ab initio excited-state calculations on molecules of unprecedented size. CIS/6-31G and TD-BLYP/6-31G benchmark timings are presented for a range of systems, including four generations of oligothiophene dendrimers, photoactive yellow protein (PYP), and the PYP chromophore solvated with 900 quantum mechanical water molecules. The effects of double and single precision integration are discussed, and mixed precision GPU integration is shown to give extremely good numerical accuracy for both CIS and TDDFT excitation energies (excitation energies within 0.0005 eV of extended double precision CPU results). PMID:21687784

  8. Modeling laser induced molecule excitation using real-time time-dependent density functional theory: application to 5- and 6-benzyluracil.

    PubMed

    Bende, Attila; Toşa, Valer

    2015-02-28

    The fully propagated real time-dependent density functional theory method has been applied to study the laser-molecule interaction in 5- and 6-benzyluracil (5BU and 6BU). The molecular geometry optimization and the time-dependent electronic dynamics propagation were carried out using the M11-L local meta-NGA (nonseparable gradient approximations) exchange-correlation functional together with the def2-TZVP basis set. Different laser field parameters like direction, strength, and wavelength have been varied in order to estimate the conditions for an efficient excitation of the molecules. The results show that the two molecules respond differently to the applied laser field and therefore specific laser field parameters have to be chosen for each of them in order to get efficient and selective excitation behavior. It was also found that from the molecular excitation point of view not only the magnitude of the transition dipoles between the involved orbitals but also their orientation with respect to the laser field is important. On the other hand, it was shown that the molecular excitation is a very complex overlapping of different one-electron orbital depopulation-population processes of the occupied and virtual orbitals.

  9. Numerical simulation of the transient photoconductivity in a-Si:H as a function of excitation density

    SciTech Connect

    Feist, H.; Kunst, M.

    1997-07-01

    The dependence of the transient photoconductivity induced by pulsed excitation (TPC) on the excitation density is discussed with the help of numerical simulations. It is shown that recombination between excess mobile electrons and all excess holes (mainly localized) can explain the excitation density dependence of the TPC amplitude of standard a-Si:H at room temperature using a rate parameter k{sub BB} of 10{sup {minus}8} cm{sup 3}/s. This model leads to a decay faster than experimentally observed in the time range from 40 ns to 1 {micro}s. A variation of the recombination model is presented that gives short time range. Moreover comparison of the simulations with experimental data yields limits for the parameters of the conduction band tail. In particular, the time necessary to establish a dynamic equilibrium of excess electrons between delocalized states in the conduction band and localized states in the tail appears to be very informative.

  10. Lowest excited states and optical absorption spectra of donor-acceptor copolymers for organic photovoltaics: a new picture emerging from tuned long-range corrected density functionals.

    PubMed

    Pandey, Laxman; Doiron, Curtis; Sears, John S; Brédas, Jean-Luc

    2012-11-01

    Polymers with low optical gaps are of importance to the organic photovoltaics community due to their potential for harnessing a large portion of the solar energy spectrum. The combination along their backbones of electron-rich and electron-deficient fragments contributes to the presence of low-lying excited states that are expected to display significant charge-transfer character. While conventional hybrid functionals are known to provide unsatisfactory results for charge-transfer excitations at the time-dependent DFT level, long-range corrected (LRC) functionals have been reported to give improved descriptions in a number of systems. Here, we use such LRC functionals, considering both tuned and default range-separation parameters, to characterize the absorption spectra of low-optical-gap systems of interest. Our results indicate that tuned LRC functionals lead to simulated optical-absorption properties in good agreement with experimental data. Importantly, the lowest-lying excited states (excitons) are shown to present a much more localized nature than initially anticipated.

  11. Effect of Peruvosid (CD412) on excitability and functional refractory period of atrial and ventricular tissues in cardiomyopathy caused by Trypanosoma cruzi

    PubMed Central

    Moleiro, Frederico; Anselmi, Alfonso; Suárez, Régulo; Suárez, José Angel; Drayer, Alberto

    1970-01-01

    Attempts were made to produce myocarditis by Trypanosoma cruzi inoculation in healthy dog puppies 6 to 8 weeks old. Significant electrocardiographic abnormalities were produced, coinciding with interstitial inflammatory processes in the cardiac tissue and with degenerative changes in the myocardial fibres. In puppies showing these changes, profound changes in the excitability and the functional refractory period of the atrial and ventricular muscular tissue were observed. The administration of Peruvosid in doses of 0·0240 to 0·0647 mg./kg. tended to diminish the excitability, previously increased by the inflammatory process, at the same time increasing the functional refractory period duration which had previously been shortened. The fact that Peruvosid corrects these fundamental factors in the genesis of cardiac arrhythmias suggests that the drug may be useful in the treatment of cardiac insufficiency produced by Chagas' myocardiopathy, in which arrhythmias are one of the basic characteristics. Images PMID:4985863

  12. Measurements and analyses of principal dynamic parameters of building structures as a function of type of vibration excitation

    NASA Astrophysics Data System (ADS)

    Bartmański, Cezary; Bochenek, Wojciech; Passia, Henryk; Szade, Adam

    2006-06-01

    The methods of direct measurement and analysis of the dynamic response of a building structure through real-time recording of the amplitude of low-frequency vibration (tilt) have been presented. Subject to analyses was the reaction induced either by kinematic excitation (road traffic and mining-induced vibration) or controlled action of solid-fuel rocket micro-engines installed on the building. The forces were analysed by means of a set of transducers installed both in the ground and on the structure. After the action of excitation forces has been stopped, the system (structure) makes damped vibration around the static equilibrium position. It has been shown that the type of excitation affects the accuracy of evaluation of principal dynamic parameters of the structure. In the authors opinion these are the decrement of damping and natural vibration frequency. Positive results of tests with the use of excitation by means of short-action (0.6 second) rocket micro-engines give a chance to develop a reliable method for periodical assessment of acceptable loss of usability characteristics of building structures heavily influenced by environmental effects.

  13. Time-dependent density functional theory study on the electronic excited-state hydrogen bonding of the chromophore coumarin 153 in a room-temperature ionic liquid.

    PubMed

    Wang, Dandan; Hao, Ce; Wang, Se; Dong, Hong; Qiu, Jieshan

    2012-03-01

    In the present work, in order to investigate the electronic excited-state intermolecular hydrogen bonding between the chromophore coumarin 153 (C153) and the room-temperature ionic liquid N,N-dimethylethanolammonium formate (DAF), both the geometric structures and the infrared spectra of the hydrogen-bonded complex C153-DAF(+) in the excited state were studied by a time-dependent density functional theory (TDDFT) method. We theoretically demonstrated that the intermolecular hydrogen bond C(1) = O(1)···H(1)-O(3) in the hydrogen-bonded C153-DAF(+) complex is significantly strengthened in the S(1) state by monitoring the spectral shifts of the C=O group and O-H group involved in the hydrogen bond C(1) = O(1)···H(1)-O(3). Moreover, the length of the hydrogen bond C(1) = O(1)···H(1)-O(3) between the oxygen atom and hydrogen atom decreased from 1.693 Å to 1.633 Å upon photoexcitation. This was also confirmed by the increase in the hydrogen-bond binding energy from 69.92 kJ mol(-1) in the ground state to 90.17 kJ mol(-1) in the excited state. Thus, the excited-state hydrogen-bond strengthening of the coumarin chromophore in an ionic liquid has been demonstrated theoretically for the first time.

  14. Highly efficient implementation of pseudospectral time-dependent density-functional theory for the calculation of excitation energies of large molecules.

    PubMed

    Cao, Yixiang; Hughes, Thomas; Giesen, Dave; Halls, Mathew D; Goldberg, Alexander; Vadicherla, Tati Reddy; Sastry, Madhavi; Patel, Bhargav; Sherman, Woody; Weisman, Andrew L; Friesner, Richard A

    2016-06-15

    We have developed and implemented pseudospectral time-dependent density-functional theory (TDDFT) in the quantum mechanics package Jaguar to calculate restricted singlet and restricted triplet, as well as unrestricted excitation energies with either full linear response (FLR) or the Tamm-Dancoff approximation (TDA) with the pseudospectral length scales, pseudospectral atomic corrections, and pseudospectral multigrid strategy included in the implementations to improve the chemical accuracy and to speed the pseudospectral calculations. The calculations based on pseudospectral time-dependent density-functional theory with full linear response (PS-FLR-TDDFT) and within the Tamm-Dancoff approximation (PS-TDA-TDDFT) for G2 set molecules using B3LYP/6-31G*(*) show mean and maximum absolute deviations of 0.0015 eV and 0.0081 eV, 0.0007 eV and 0.0064 eV, 0.0004 eV and 0.0022 eV for restricted singlet excitation energies, restricted triplet excitation energies, and unrestricted excitation energies, respectively; compared with the results calculated from the conventional spectral method. The application of PS-FLR-TDDFT to OLED molecules and organic dyes, as well as the comparisons for results calculated from PS-FLR-TDDFT and best estimations demonstrate that the accuracy of both PS-FLR-TDDFT and PS-TDA-TDDFT. Calculations for a set of medium-sized molecules, including Cn fullerenes and nanotubes, using the B3LYP functional and 6-31G(**) basis set show PS-TDA-TDDFT provides 19- to 34-fold speedups for Cn fullerenes with 450-1470 basis functions, 11- to 32-fold speedups for nanotubes with 660-3180 basis functions, and 9- to 16-fold speedups for organic molecules with 540-1340 basis functions compared to fully analytic calculations without sacrificing chemical accuracy. The calculations on a set of larger molecules, including the antibiotic drug Ramoplanin, the 46-residue crambin protein, fullerenes up to C540 and nanotubes up to 14×(6,6), using the B3LYP functional and 6-31G

  15. Highly efficient implementation of pseudospectral time-dependent density-functional theory for the calculation of excitation energies of large molecules.

    PubMed

    Cao, Yixiang; Hughes, Thomas; Giesen, Dave; Halls, Mathew D; Goldberg, Alexander; Vadicherla, Tati Reddy; Sastry, Madhavi; Patel, Bhargav; Sherman, Woody; Weisman, Andrew L; Friesner, Richard A

    2016-06-15

    We have developed and implemented pseudospectral time-dependent density-functional theory (TDDFT) in the quantum mechanics package Jaguar to calculate restricted singlet and restricted triplet, as well as unrestricted excitation energies with either full linear response (FLR) or the Tamm-Dancoff approximation (TDA) with the pseudospectral length scales, pseudospectral atomic corrections, and pseudospectral multigrid strategy included in the implementations to improve the chemical accuracy and to speed the pseudospectral calculations. The calculations based on pseudospectral time-dependent density-functional theory with full linear response (PS-FLR-TDDFT) and within the Tamm-Dancoff approximation (PS-TDA-TDDFT) for G2 set molecules using B3LYP/6-31G*(*) show mean and maximum absolute deviations of 0.0015 eV and 0.0081 eV, 0.0007 eV and 0.0064 eV, 0.0004 eV and 0.0022 eV for restricted singlet excitation energies, restricted triplet excitation energies, and unrestricted excitation energies, respectively; compared with the results calculated from the conventional spectral method. The application of PS-FLR-TDDFT to OLED molecules and organic dyes, as well as the comparisons for results calculated from PS-FLR-TDDFT and best estimations demonstrate that the accuracy of both PS-FLR-TDDFT and PS-TDA-TDDFT. Calculations for a set of medium-sized molecules, including Cn fullerenes and nanotubes, using the B3LYP functional and 6-31G(**) basis set show PS-TDA-TDDFT provides 19- to 34-fold speedups for Cn fullerenes with 450-1470 basis functions, 11- to 32-fold speedups for nanotubes with 660-3180 basis functions, and 9- to 16-fold speedups for organic molecules with 540-1340 basis functions compared to fully analytic calculations without sacrificing chemical accuracy. The calculations on a set of larger molecules, including the antibiotic drug Ramoplanin, the 46-residue crambin protein, fullerenes up to C540 and nanotubes up to 14×(6,6), using the B3LYP functional and 6-31G

  16. Critical Assessment of Time-Dependent Density Functional Theory for Excited States of Open-Shell Systems: II. Doublet-Quartet Transitions.

    PubMed

    Li, Zhendong; Liu, Wenjian

    2016-06-14

    Compared with closed-shell systems, open-shell systems place three additional challenges to time-dependent density functional theory (TD-DFT) for electronically excited states: (a) the spin-contamination problem is a serious issue; (b) the exchange-correlation (XC) kernel may be numerically instable; and (c) the single-determinant description of open-shell ground states readily becomes energetically instable. Confined to flip-up single excitations, the spin-contamination problem can largely be avoided by using the spin-flip TD-DFT (SF-TD-DFT) formalism, provided that a noncollinear XC kernel is employed. As for the numerical instabilities associated with such a kernel, only an ad hoc scheme has been proposed so far, viz., the ALDA0 kernel, which amounts to setting the divergent components (arising from density gradients and kinetic energy density) simply to zero. The ground-state instability problem can effectively be avoided by introducing the Tamm-Dancoff approximation (TDA) to TD-DFT. Therefore, on a general basis, the SF-TDA/ALDA0 Ansatz is so far the only promising means within the TD-DFT framework for flip-up single excitations of open-shell systems. To assess systematically the performance of SF-TDA/ALDA0, in total 61 low-lying quartet excited states of the benchmark set of 11 small radicals [J. Chem. Theory Comput. 2016, 12, 238] are investigated with various XC functionals. Taking the MRCISD+Q (multireference configuration interaction with singles and doubles plus the Davidson correction) results as benchmark, it is found that the mean absolute errors of SF-TDA/ALDA0 with the SAOP (statistical averaging of model orbital potentials), global hybrid, and range-separated hybrid functionals are in the range of 0.2-0.4 eV. This is in line not only with the typical accuracy of TD-DFT for singlet and triplet excited states of closed-shell systems but also with the gross accuracy of spin-adapted TD-DFT for spin-conserving excited states of open-shell systems. PMID

  17. Critical Assessment of Time-Dependent Density Functional Theory for Excited States of Open-Shell Systems: II. Doublet-Quartet Transitions.

    PubMed

    Li, Zhendong; Liu, Wenjian

    2016-06-14

    Compared with closed-shell systems, open-shell systems place three additional challenges to time-dependent density functional theory (TD-DFT) for electronically excited states: (a) the spin-contamination problem is a serious issue; (b) the exchange-correlation (XC) kernel may be numerically instable; and (c) the single-determinant description of open-shell ground states readily becomes energetically instable. Confined to flip-up single excitations, the spin-contamination problem can largely be avoided by using the spin-flip TD-DFT (SF-TD-DFT) formalism, provided that a noncollinear XC kernel is employed. As for the numerical instabilities associated with such a kernel, only an ad hoc scheme has been proposed so far, viz., the ALDA0 kernel, which amounts to setting the divergent components (arising from density gradients and kinetic energy density) simply to zero. The ground-state instability problem can effectively be avoided by introducing the Tamm-Dancoff approximation (TDA) to TD-DFT. Therefore, on a general basis, the SF-TDA/ALDA0 Ansatz is so far the only promising means within the TD-DFT framework for flip-up single excitations of open-shell systems. To assess systematically the performance of SF-TDA/ALDA0, in total 61 low-lying quartet excited states of the benchmark set of 11 small radicals [J. Chem. Theory Comput. 2016, 12, 238] are investigated with various XC functionals. Taking the MRCISD+Q (multireference configuration interaction with singles and doubles plus the Davidson correction) results as benchmark, it is found that the mean absolute errors of SF-TDA/ALDA0 with the SAOP (statistical averaging of model orbital potentials), global hybrid, and range-separated hybrid functionals are in the range of 0.2-0.4 eV. This is in line not only with the typical accuracy of TD-DFT for singlet and triplet excited states of closed-shell systems but also with the gross accuracy of spin-adapted TD-DFT for spin-conserving excited states of open-shell systems.

  18. Synthesis and functionalization of monodisperse near-ultraviolet and visible excitable multifunctional Eu3+, Bi3+:REVO4 nanophosphors for bioimaging and biosensing applications

    NASA Astrophysics Data System (ADS)

    Escudero, Alberto; Carrillo-Carrión, Carolina; Zyuzin, Mikhail V.; Ashraf, Sumaira; Hartmann, Raimo; Núñez, Nuria O.; Ocaña, Manuel; Parak, Wolfgang J.

    2016-06-01

    Near-ultraviolet and visible excitable Eu- and Bi-doped NPs based on rare earth vanadates (REVO4, RE = Y, Gd) have been synthesized by a facile route from appropriate RE precursors, europium and bismuth nitrate, and sodium orthovanadate, by homogeneous precipitation in an ethylene glycol/water mixture at 120 °C. The NPs can be functionalized either by a one-pot synthesis with polyacrylic acid (PAA) or by a Layer-by-Layer approach with poly(allylamine hydrochloride) (PAH) and PAA. In the first case, the particle size can also be tuned by adjusting the amount of PAA. The Eu- Bi-doped REVO4 based nanophosphors show the typical red luminescence of Eu(iii), which can be excited through an energy transfer process from the vanadate anions, resulting in a much higher luminescence intensity in comparison to the direct excitation of the europium cations. The incorporation of Bi into the REVO4 structure shifts the original absorption band of the vanadate anions towards longer wavelengths, giving rise to nanophosphors with an excitation maximum at 342 nm, which can also be excited in the visible range. The suitability of such nanophosphors for bioimaging and biosensing applications, as well as their colloidal stability in different buffer media of biological interest, their cytotoxicity, their degradability at low pH, and their uptake by HeLa cells have been evaluated. Their suitability for bioimaging and biosensing applications is also demonstrated.Near-ultraviolet and visible excitable Eu- and Bi-doped NPs based on rare earth vanadates (REVO4, RE = Y, Gd) have been synthesized by a facile route from appropriate RE precursors, europium and bismuth nitrate, and sodium orthovanadate, by homogeneous precipitation in an ethylene glycol/water mixture at 120 °C. The NPs can be functionalized either by a one-pot synthesis with polyacrylic acid (PAA) or by a Layer-by-Layer approach with poly(allylamine hydrochloride) (PAH) and PAA. In the first case, the particle size can also be

  19. On the truncation of the number of excited states in density functional theory sum-over-states calculations of indirect spin spin coupling constants

    NASA Astrophysics Data System (ADS)

    Zarycz, M. Natalia C.; Provasi, Patricio F.; Sauer, Stephan P. A.

    2015-12-01

    It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCCs), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections of the Polarization Propagator (IPPP-CLOPPA) approach to analyzing SSCCs in terms of localized orbitals. As a test set we have studied the nine simple compounds, CH4, NH3, H2O, SiH4, PH3, SH2, C2H2, C2H4, and C2H6. The excited (pseudo)states were obtained from time-dependent density functional theory (TD-DFT) calculations with the B3LYP exchange-correlation functional and the specialized core-property basis set, aug-cc-pVTZ-J. We investigated both how the calculated coupling constants depend on the number of (pseudo)states included in the summation and whether the summation can be truncated in a systematic way at a smaller number of states and extrapolated to the total number of (pseudo)states for the given one-electron basis set. We find that this is possible and that for some of the couplings it is sufficient to include only about 30% of the excited (pseudo)states.

  20. Excitation functions for production of heavy actinides from interactions of /sup 40/Ca and /sup 48/Ca ions with /sup 248/Cm

    SciTech Connect

    Hoffman, D.C.; Fowler, M.M.; Daniels, W.R.; von Gunten, H.R.; Lee, D.; Moody, K.J.; Gregorich, K.; Welch, R.; Seaborg, G.T.; Bruechle, W.

    1985-05-01

    Excitation functions have been measured for production of isotopes of Bk through Fm in bombardments of /sup 248/Cm with 234- to 294-MeV /sup 40/Ca ions and with 239- to 318-MeV /sup 48/Ca ions. The maxima of the isotopic distributions for these elements occur at only 2 to 3 mass numbers larger for /sup 48/Ca than for /sup 40/Ca reactions. The shapes of the distributions and the half-widths of about 2.5 mass numbers are quite similar to those observed previously for reactions of /sup 16/O, /sup 18/O, /sup 20/Ne, and /sup 22/Ne with /sup 248/Cm. In general, the excitation functions for /sup 40/Ca show maxima near the Coulomb barrier while those for /sup 48/Ca are about 20 MeV above the barrier. The cross sections decrease rather slowly with increasing projectile energy over the energy range studied, indicating that the additional projectile energy is not manifested as excitation energy of these actinide products.

  1. On the truncation of the number of excited states in density functional theory sum-over-states calculations of indirect spin spin coupling constants

    SciTech Connect

    Zarycz, M. Natalia C. Provasi, Patricio F.; Sauer, Stephan P. A.

    2015-12-28

    It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCCs), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections of the Polarization Propagator (IPPP-CLOPPA) approach to analyzing SSCCs in terms of localized orbitals. As a test set we have studied the nine simple compounds, CH{sub 4}, NH{sub 3}, H{sub 2}O, SiH{sub 4}, PH{sub 3}, SH{sub 2}, C{sub 2}H{sub 2}, C{sub 2}H{sub 4}, and C{sub 2}H{sub 6}. The excited (pseudo)states were obtained from time-dependent density functional theory (TD-DFT) calculations with the B3LYP exchange-correlation functional and the specialized core-property basis set, aug-cc-pVTZ-J. We investigated both how the calculated coupling constants depend on the number of (pseudo)states included in the summation and whether the summation can be truncated in a systematic way at a smaller number of states and extrapolated to the total number of (pseudo)states for the given one-electron basis set. We find that this is possible and that for some of the couplings it is sufficient to include only about 30% of the excited (pseudo)states.

  2. In Vitro Assessment Reveals Parameters-Dependent Modulation on Excitability and Functional Connectivity of Cerebellar Slice by Repetitive Transcranial Magnetic Stimulation

    PubMed Central

    Tang, Rongyu; Zhang, Guanghao; Weng, Xiechuan; Han, Yao; Lang, Yiran; Zhao, Yuwei; Zhao, Xiaobo; Wang, Kun; Lin, Qiuxia; Wang, Changyong

    2016-01-01

    Repetitive transcranial magnetic stimulation (rTMS) is an increasingly common technique used to selectively modify neural excitability and plasticity. There is still controversy concerning the cortical response to rTMS of different frequencies. In this study, a novel in vitro paradigm utilizing the Multi-Electrodes Array (MEA) system and acute cerebellar slicing is described. In a controllable environment that comprises perfusion, incubation, recording and stimulation modules, the spontaneous single-unit spiking activity in response to rTMS of different frequencies and powers was directly measured and analyzed. Investigation using this in vitro paradigm revealed frequency-dependent modulation upon the excitability and functional connectivity of cerebellar slices. The 1-Hz rTMS sessions induced short-term inhibition or lagged inhibition, whereas 20-Hz sessions induced excitation. The level of modulation is influenced by the value of power. However the long-term response fluctuated without persistent direction. The choice of evaluation method may also interfere with the interpretation of modulation direction. Furthermore, both short-term and long-term functional connectivity was strengthened by 1-Hz rTMS and weakened by 20-Hz rTMS. PMID:27000527

  3. Excited protein states of human tear lipocalin for low- and high-affinity ligand binding revealed by functional AB loop motion.

    PubMed

    Gasymov, Oktay K; Abduragimov, Adil R; Glasgow, Ben J

    2010-06-01

    Human tear lipocalin (TL), a prominent member of lipocalin family, exhibits functional and structural promiscuity. The plasticity of loop regions modulates entry to the ligand pocket at the "open" end of the eight-stranded beta-barrel. Site-directed multi-distance measurements using fluorescence resonance energy transfer between functional loops register two excited protein states for low- and high-affinity ligand binding. At low pH, the longest loop AB adopts the conformation of the low-affinity excited protein state that matches the crystal structure of holo-TL at pH 8. A "crankshaft" like movement is detected for the loop AB in a low pH transition. At pH 7.3 the holo-protein assumes a high-affinity excited protein state, in which the loop AB is more compact (RMS=3.1A). In the apo-holo transition, the reporter Trp 28 moves about 4.5A that reflects a decrease in distance between Glu27 and Lys108. This interaction fixes the loop AB conformation for the high-affinity mode. No such movement is detected at low pH, where Glu27 is protonated. Data strongly indicate that the protonation state of Glu27 modulates the conformation of the loop AB for high- and low-affinity binding. PMID:20439130

  4. On the truncation of the number of excited states in density functional theory sum-over-states calculations of indirect spin spin coupling constants.

    PubMed

    Zarycz, M Natalia C; Provasi, Patricio F; Sauer, Stephan P A

    2015-12-28

    It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCCs), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections of the Polarization Propagator (IPPP-CLOPPA) approach to analyzing SSCCs in terms of localized orbitals. As a test set we have studied the nine simple compounds, CH4, NH3, H2O, SiH4, PH3, SH2, C2H2, C2H4, and C2H6. The excited (pseudo)states were obtained from time-dependent density functional theory (TD-DFT) calculations with the B3LYP exchange-correlation functional and the specialized core-property basis set, aug-cc-pVTZ-J. We investigated both how the calculated coupling constants depend on the number of (pseudo)states included in the summation and whether the summation can be truncated in a systematic way at a smaller number of states and extrapolated to the total number of (pseudo)states for the given one-electron basis set. We find that this is possible and that for some of the couplings it is sufficient to include only about 30% of the excited (pseudo)states.

  5. 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.

  6. Ultrafast dynamics of the dielectric functions of ZnO and BaTiO{sub 3} thin films after intense femtosecond laser excitation

    SciTech Connect

    Acharya, S.; Seifert, G.; Chouthe, S.; Graener, H.; Böntgen, T.; Sturm, C.; Schmidt-Grund, R.; Grundmann, M.

    2014-02-07

    The ultrafast carrier dynamics of epitaxial ZnO and BaTiO{sub 3} thin films after intense excitation at 3.10 eV and 4.66 eV photon energy has been studied by femtosecond absorption spectroscopy. Modelling the transient transmission changes on the basis of spectroscopic ellipsometry data and pertinent equilibrium model dielectric functions extended by additional terms for the effects at high carrier density (P-band luminescence and stimulated emission from electron-hole-plasma), a self-consistent parameterized description was obtained for both materials. Excited carrier lifetimes in the range of ≈2 to ≈60 ps and long-lived thermal effects after several hundred ps have been identified in both materials. These findings form a reliable basis to quantitatively describe future femtosecond studies on ZnO/BaTiO{sub 3} heterolayer systems.

  7. Source mechanism of long-period events at Kusatsu-Shirane Volcano, Japan, inferred from waveform inversion of the effective excitation functions

    USGS Publications Warehouse

    Nakano, M.; Kumagai, H.; Chouet, B.A.

    2003-01-01

    We investigate the source mechanism of long-period (LP) events observed at Kusatsu-Shirane Volcano, Japan, based on waveform inversions of their effective excitation functions. The effective excitation function, which represents the apparent excitation observed at individual receivers, is estimated by applying an autoregressive filter to the LP waveform. Assuming a point source, we apply this method to seven LP events the waveforms of which are characterized by simple decaying and nearly monochromatic oscillations with frequency in the range 1-3 Hz. The results of the waveform inversions show dominant volumetric change components accompanied by single force components, common to all the events analyzed, and suggesting a repeated activation of a sub-horizontal crack located 300 m beneath the summit crater lakes. Based on these results, we propose a model of the source process of LP seismicity, in which a gradual buildup of steam pressure in a hydrothermal crack in response to magmatic heat causes repeated discharges of steam from the crack. The rapid discharge of fluid causes the collapse of the fluid-filled crack and excites acoustic oscillations of the crack, which produce the characteristic waveforms observed in the LP events. The presence of a single force synchronous with the collapse of the crack is interpreted as the release of gravitational energy that occurs as the slug of steam ejected from the crack ascends toward the surface and is replaced by cooler water flowing downward in a fluid-filled conduit linking the crack and the base of the crater lake. ?? 2003 Elsevier Science B.V. All rights reserved.

  8. Application of recent double-hybrid density functionals to low-lying singlet-singlet excitation energies of large organic compounds

    NASA Astrophysics Data System (ADS)

    Meo, F. Di; Trouillas, P.; Adamo, C.; Sancho-García, J. C.

    2013-10-01

    The present work assesses some recently developed double-hybrid density functionals (B2π-PLYP, PBE0-DH, and PBE0-2) using linear-response Tamm-Dancoff Time-Dependent Density Functional Theory. This assessment is achieved against experimentally derived low-lying excitation energies of large organic dyes of recent interest, including some excitations dominated by charge-transfer transitions. Comparisons are made with some of the best-performing methods established from the literature, such as PBE0 or B3LYP hybrid or the recently proposed B2-PLYP and B2GP-PLYP double-hybrid models, to ascertain their quality and robustness on equal footing. The accuracy of parameter-free or empirical forms of double-hybrid functionals is also briefly discussed. Generally speaking, it turns out that double-hybrid expressions always provide more accurate estimates than corresponding hybrid methods. Double-hybrid functionals actually reach averaged accuracies of 0.2 eV, that can be admittedly considered close to any intended accuracy limit within the present theoretical framework.

  9. Free electrons and ionic liquids: study of excited states by means of electron-energy loss spectroscopy and the density functional theory multireference configuration interaction method.

    PubMed

    Regeta, Khrystyna; Bannwarth, Christoph; Grimme, Stefan; Allan, Michael

    2015-06-28

    The technique of low energy (0-30 eV) electron impact spectroscopy, originally developed for gas phase molecules, is applied to room temperature ionic liquids (IL). Electron energy loss (EEL) spectra recorded near threshold, by collecting 0-2 eV electrons, are largely continuous, assigned to excitation of a quasi-continuum of high overtones and combination vibrations of low-frequency modes. EEL spectra recorded by collecting 10 eV electrons show predominantly discrete vibrational and electronic bands. The vibrational energy-loss spectra correspond well to IR spectra except for a broadening (∼0.04 eV) caused by the liquid surroundings, and enhanced overtone activity indicating a contribution from resonant excitation mechanism. The spectra of four representative ILs were recorded in the energy range of electronic excitations and compared to density functional theory multireference configuration interaction (DFT/MRCI) calculations, with good agreement. The spectra up to about 8 eV are dominated by π-π* transitions of the aromatic cations. The lowest bands were identified as triplet states. The spectral region 2-8 eV was empty in the case of a cation without π orbitals. The EEL spectrum of a saturated solution of methylene green in an IL band showed the methylene green EEL band at 2 eV, indicating that ILs may be used as a host to study nonvolatile compounds by this technique in the future.

  10. Electronic Excitations in Push-Pull Oligomers and Their Complexes with Fullerene from Many-Body Green's Functions Theory with Polarizable Embedding.

    PubMed

    Baumeier, Björn; Rohlfing, Michael; Andrienko, Denis

    2014-08-12

    We present a comparative study of excited states in push-pull oligomers of PCPDTBT and PSBTBT and prototypical complexes with a C60 acceptor using many-body Green's functions theory within the GW approximation and the Bethe-Salpeter equation. We analyze excitations in oligomers up to a length of 5 nm and find that for both materials the absorption energy practically saturates for structures larger than two repeat units due to the localized nature of the excitation. In the bimolecular complexes with C60, the transition from Frenkel to charge transfer excitons is generally exothermic and strongly influenced by the acceptor's position and orientation. The high CT binding energy of the order of 2 eV results from the lack of an explicit molecular environment. External polarization effects are then modeled in a GW-BSE based QM/MM approach by embedding the donor-acceptor complex into a polarizable lattice. The lowest charge transfer exciton is energetically stabilized by about 0.5 eV, while its binding energy is reduced to about 0.3 eV. We also identify a globally unbound charge transfer state with a more delocalized hole at higher energy while still within the absorption spectrum, which opens another potential pathway for charge separation. For both PCPDTBT and PSBTBT, the energetics are largely similar with respect to absorption and the driving force to form intermediate charge transfer excitations for free charge generation. These results support that the higher power conversion efficiency observed for solar cells using PSBTBT as donor material is a result of molecular packing rather than of the electronic structure of the polymer.

  11. Solvent effects on optical excitations of poly para phenylene ethynylene studied by QM/MM simulations based on many-body Green's functions theory

    NASA Astrophysics Data System (ADS)

    Bagheri, B.; Karttunen, M.; Baumeier, B.

    2016-07-01

    Electronic excitations in dilute solutions of poly para phenylene ethynylene (poly-PPE) are studied using a QM/MM approach combining many-body Green's functions theory within the GW approximation and the Bethe-Salpeter equation with polarizable force field models. Oligomers up to a length of 7.5 nm (10 repeat units) functionalized with nonyl side chains are solvated in toluene and water, respectively. After equilibration using atomistic molecular dynamics (MD), the system is partitioned into a quantum region (backbone) embedded into a classical (side chains and solvent) environment. Optical absorption properties are calculated solving the coupled QM/MM system self-consistently and special attention is paid to the effects of solvents. The model allows to differentiate the influence of oligomer conformation induced by the solvation from electronic effects related to local electric fields and polarization. It is found that the electronic environment contributions are negligible compared to the conformational dynamics of the conjugated PPE. An analysis of the electron-hole wave function reveals a sensitivity of energy and localization characteristics of the excited states to bends in the global conformation of the oligomer rather than to the relative of phenyl rings along the backbone.

  12. Angular distribution, kinetic energy distributions, and excitation functions of fast metastable oxygen fragments following electron impact of CO2

    NASA Technical Reports Server (NTRS)

    Misakian, M.; Mumma, M. J.; Faris, J. F.

    1975-01-01

    Dissociative excitation of CO2 by electron impact was studied using the methods of translational spectroscopy and angular distribution analysis. Earlier time of flight studies revealed two overlapping spectra, the slower of which was attributed to metastable CO(a3 pi) fragments. The fast peak is the focus of this study. Threshold energy, angular distribution, and improve time of flight measurements indicate that the fast peak actually consists of five overlapping features. The slowest of the five features is found to consist of metastable 0(5S) produced by predissociation of a sigma u + state of CO2 into 0(5S) + CO(a3 pi). Oxygen Rydberg fragments originating directly from a different sigma u + state are believed to make up the next fastest feature. Mechanisms for producing the three remaining features are discussed.

  13. The discrepant kinematics of recombination and collisionally excited lines in NGC 7009 as a function of ionization structure

    NASA Astrophysics Data System (ADS)

    Torres-Peimbert, S.; Richer, M. R.; Georgiev, L.; Arrieta, A.

    2014-10-01

    We have analyzed the kinematics of emission of the planetary nebula NGC 7009 from long slit spectroscopy from the UVES spectrograph at the VLT of ESO. In particular we are interested in comparing lines excited by recombination and collisions with electrons to determine whether similarities or differences could be useful in elucidating the well-known abundance discrepancy derived from them. We construct position-velocity maps for recombination, fluorescence, charge transfer, and collisionally excited lines.We find a plasma component emitting in the C II, N II, O II, and Ne II recombination lines whose kinematics are discrepant: they are incompatible with the ionization structure derived from all other evidence and the kinematics derived from all of these lines are unexpectedly very similar. We found direct evidence for a recombination contribution to [N II] λ5755. Once taken into account, the electron temperatures from [N II], [O III], and [Ne III] agree at a given position and velocity. The electron densities derived from [O II] and [Ar IV] are consistent with direct imaging and the distribution of hydrogen emission. The kinematics of the C II, N II, O II, and Ne II lines does not coincide with the kinematics of the [O III] and [Ne III] forbidden emission, indicating that there is an additional plasma component to the recombination emission that arises from a different volume from that giving rise to the forbidden emission from the parent ions within NGC 7009. Thus, the chemical abundances derived from either type of line are correct only for the plasma component from which they arise. Apart from [N II] λ5755, we find no anomaly with the forbidden lines usually used to determine chemical abundances in ionized nebulae, so the abundances derived from them should be reliable for the medium from which they arise.

  14. Description of electron transfer in the ground and excited states of organic donor–acceptor systems by single-reference and multi-reference density functional methods

    SciTech Connect

    Filatov, Michael

    2014-09-28

    Electron transfer in the ground and excited states of a model donor–acceptor (D–A) system is investigated using the single-reference and multi-reference density functional theory (DFT) methods. To analyze the results of the calculations, a simple two-site multi-reference model was derived that predicts a stepwise electron transfer in the S{sub 0} state and a wave-like dependence of the S{sub 1} electron transfer on the external stimulus. The standard single-reference Kohn-Sham (KS) DFT approach and the time-dependent DFT (TDDFT) method failed to describe the correct dependence of the S{sub 0} and S{sub 1} electron transfer on the external electric field applied along the donor–acceptor system. The multi-reference DFT approach, the spin-restricted ensemble-referenced KS (REKS) method, was able to successfully reproduce the correct behavior of the S{sub 0} and S{sub 1} electron transfer on the applied field. The REKS method was benchmarked against experimentally measured gas phase charge transfer excitations in a series of organic donor–acceptor complexes and displayed its ability to describe this type of electronic transitions with a very high accuracy, mean absolute error of 0.05 eV with the use of the standard range separated density functionals. On the basis of the calculations undertaken in this work, it is suggested that the non-adiabatic coupling between the S{sub 0} and S{sub 1} states may interfere with the electron transfer in a weakly coupled donor–acceptor system. It is also suggested that the electronic excitation of a D{sup +}–A{sup −} system may play a dual role by assisting the further electron transfer at certain magnitudes of the applied electric field and causing the backward transfer at lower electric field strengths.

  15. Excitation function for 63Cu(n,p)63Ni reaction in neutron energy range up to 15 MeV.

    PubMed

    Takamiya, K; Ota, Y; Akamine, M; Shibata, S; Shibata, T; Ito, Y; Imamura, M; Uwamino, Y; Nogawa, N; Baba, M; Iwasaki, S; Matsuyama, S

    2008-10-01

    The excitation function for the (63)Cu(n,p)(63)Ni reaction has been measured by activation method using the 4.5 MV Dynamitron accelerator of the Fast Neutron Laboratory of Tohoku University. Copper plates and hollow spherical copper shells were irradiated by neutrons of various energy up to 14.9 MeV produced by the T(p,n), D(d,n), and T(d,n) reactions. The (63)Ni produced in the irradiated copper target was chemically separated. The beta-rays emitted from the extracted (63)Ni were measured by a liquid scintillation method. The cross sections obtained were compared with the evaluated data files of JENDL-3.3, ENDF/B-VI and FENDL/A-2.0. Consequently, it is found that FENDL/A-2.0 is consistent with our experimental data in the energy range studied in this work. The effect of proton shell appeared in the excitation function obtained is also discussed.

  16. Complete and incomplete fusion reactions in the {sup 16}O+{sup 169}Tm system: Excitation functions and recoil range distributions

    SciTech Connect

    Sharma, Manoj Kumar; Unnati,; Sharma, B.K.; Singh, B.P.; Prasad, R.; Bhardwaj, H.D.; Kumar, Rakesh; Golda, K.S.

    2004-10-01

    With the view to study complete and incomplete fusion in heavy ion induced reactions, experiments have been carried out for measuring excitation functions for several reactions in the system {sup 16}O+{sup 169}Tm at energies near the Coulomb barrier to well above it, using an activation technique. The measured excitation functions have been compared with those calculated theoretically using three different computer codes viz., ALICE-91, CASCADE and PACE2. The enhancement of experimentally measured cross sections for alpha emission channels over their theoretical prediction has been attributed to the fact that these residues are formed not only by complete fusion but also through incomplete fusion. In order to separate out the relative contributions of complete and incomplete fusion, the recoil range distributions of eight residues produced in the interaction of {sup 16}O with {sup 169}Tm at {approx_equal}87 MeV have been measured. The recoil range distributions indicate significant contributions from incomplete fusion at {approx_equal}87 MeV for some of the channels.

  17. Testing time-dependent density functional theory with depopulated molecular orbitals for predicting electronic excitation energies of valence, Rydberg, and charge-transfer states and potential energies near a conical intersection

    SciTech Connect

    Li, Shaohong L.; Truhlar, Donald G.

    2014-09-14

    Kohn-Sham (KS) time-dependent density functional theory (TDDFT) with most exchange-correlation functionals is well known to systematically underestimate the excitation energies of Rydberg and charge-transfer excited states of atomic and molecular systems. To improve the description of Rydberg states within the KS TDDFT framework, Gaiduk et al. [Phys. Rev. Lett. 108, 253005 (2012)] proposed a scheme that may be called HOMO depopulation. In this study, we tested this scheme on an extensive dataset of valence and Rydberg excitation energies of various atoms, ions, and molecules. It is also tested on a charge-transfer excitation of NH{sub 3}-F{sub 2} and on the potential energy curves of NH{sub 3} near a conical intersection. We found that the method can indeed significantly improve the accuracy of predicted Rydberg excitation energies while preserving reasonable accuracy for valence excitation energies. However, it does not appear to improve the description of charge-transfer excitations that are severely underestimated by standard KS TDDFT with conventional exchange-correlation functionals, nor does it perform appreciably better than standard TDDFT for the calculation of potential energy surfaces.

  18. 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

  19. 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)

  20. The discrepant kinematics of recombination and collisionally-excited in NGC7009 as a function of ionization structure

    NASA Astrophysics Data System (ADS)

    Arrieta, A.; Richer, M.; Georgiev, L. N.; Torres-Peimbert, S.

    2014-04-01

    We present spatially- and velocity-resolved echelle spectroscopy for NGC 7009 obtained with the UVES spectrograph at the ESO VLT. We construct position-velocity maps for recombination, fluorescence, charge transfer, and collisionally excited lines. We find a plasma component emitting in the C II, N II, O II, and Ne II recombination lines whose kinematics are discrepant: They are incompatible with the ionization structure derived from all other evidence and the kinematics derived from all of these lines are unexpectedly very similar. We find direct evidence for a recombination contribution to [N II] 5755. Once taken into account, the electron temperatures from [N II], [O III], and [Ne III] agree at a given position and velocity, even though both the [N II] and [O III] temperatures clearly vary. The electron densities derived from [O II] and [Ar IV] are consistent with direct imaging and the distribution of hydrogen emission. The kinematics of the C II, N II, O II, and Ne II lines does not coincide with the kinematics of the [O III] and [Ne III] forbidden emission, indicating that there is an additional plasma component to the recombination emission that arises from a different volume from that giving rise to the forbidden emission from the parent ions within NGC 7009. Thus, the chemical abundances derived from either type of line are correct only for the plasma component from which they arise. Apart from [N II] 5755, we find no anomaly with the forbidden lines usually used to determine chemical abundances in ionized nebulae, so the abundances derived from them should be reliable for the medium from which they arise.

  1. Simulating One-Photon Absorption and Resonance Raman Scattering Spectra Using Analytical Excited State Energy Gradients within Time-Dependent Density Functional Theory

    SciTech Connect

    Silverstein, Daniel W.; Govind, Niranjan; van Dam, Hubertus J. J.; Jensen, Lasse

    2013-12-10

    A parallel implementation of analytical time-dependent density functional theory gradients is presented for the quantum chemistry program NWChem. The implementation is based on the Lagrangian approach developed by Furche and Ahlrichs. To validate our implementation, we first calculate the Stokes shifts for a range of organic dye molecules using a diverse set of exchange-correlation functionals (traditional density functionals, global hybrids, and range-separated hybrids) followed by simulations of the one-photon absorption and resonance Raman scattering spectrum of the phenoxyl radical, the well-studied dye molecule rhodamine 6G, and a molecular host–guest complex (TTFcCBPQT4+). The study of organic dye molecules illustrates that B3LYP and CAM-B3LYP generally give the best agreement with experimentally determined Stokes shifts unless the excited state is a charge transfer state. Absorption, resonance Raman, and fluorescence simulations for the phenoxyl radical indicate that explicit solvation may be required for accurate characterization. For the host–guest complex and rhodamine 6G, it is demonstrated that absorption spectra can be simulated in good agreement with experimental data for most exchange-correlation functionals. Finally, however, because one-photon absorption spectra generally lack well-resolved vibrational features, resonance Raman simulations are necessary to evaluate the accuracy of the exchange-correlation functional for describing a potential energy surface.

  2. Reduced L-type Ca2+ current and compromised excitability induce loss of skeletal muscle function during acute cooling in locust.

    PubMed

    Findsen, Anders; Overgaard, Johannes; Pedersen, Thomas Holm

    2016-08-01

    Low temperature causes most insects to enter a state of neuromuscular paralysis, termed chill coma. The susceptibility of insect species to chill coma is tightly correlated to their distribution limits and for this reason it is important to understand the cellular processes that underlie chill coma. It is known that muscle function is markedly depressed at low temperature and this suggests that chill coma is partly caused by impairment in the muscle per se. To find the cellular mechanism(s) underlying muscle dysfunction at low temperature, we examined the effect of low temperature (5°C) on several events in excitation-contraction coupling in the migratory locust (Locusta migratoria). Intracellular membrane potential recordings during single nerve stimulations showed that 70% of fibers at 20°C produced an action potential (AP), while only 55% of fibers were able to fire an AP at 5°C. Reduced excitability at low temperature was caused by an ∼80% drop in L-type Ca(2+) current and a depolarizing shift in its activation of around 20 mV, which means that a larger endplate potential would be needed to activate the muscle AP at low temperature. In accordance, we showed that intracellular Ca(2+) transients were largely absent at low temperature following nerve stimulation. In contrast, maximum contractile force was unaffected by low temperature in chemically skinned muscle bundles, which demonstrates that the function of the contractile filaments is preserved at low temperature. These findings demonstrate that reduced L-type Ca(2+) current is likely to be the most important factor contributing to loss of muscle function at low temperature in locust. PMID:27247315

  3. Nonadiabatic coupling vectors for excited states within time-dependent density functional theory in the Tamm-Dancoff approximation and beyond

    NASA Astrophysics Data System (ADS)

    Tavernelli, Ivano; Curchod, Basile F. E.; Laktionov, Andrey; Rothlisberger, Ursula

    2010-11-01

    Recently, we have proposed a scheme for the calculation of nonadiabatic couplings and nonadiabatic coupling vectors within linear response time-dependent density functional theory using a set of auxiliary many-electron wavefunctions [I. Tavernelli, E. Tapavicza, and U. Rothlisberger, J. Chem. Phys. 130, 124107 (2009)]. As demonstrated in a later work [I. Tavernelli, B. F. E. Curchod, and U. Rothlisberger, J. Chem. Phys. 131, 196101 (2009)], this approach is rigorous in the case of the calculation of nonadiabatic couplings between the ground state and any excited state. In this work, we extend this formalism to the case of coupling between pairs of singly excited states with the same spin multiplicity. After proving the correctness of our formalism using the electronic oscillator approach by Mukamel and co-workers [S. Tretiak and S. Mukamel, Chem. Rev. (Washington, D.C.) 102, 3171 (2002)], we tested the method on a model system, namely, protonated formaldimine, for which we computed S1/S2 nonadiabatic coupling vectors and compared them with results from high level (MR-CISD) electronic structure calculations.

  4. Nonadiabatic coupling vectors for excited states within time-dependent density functional theory in the Tamm-Dancoff approximation and beyond.

    PubMed

    Tavernelli, Ivano; Curchod, Basile F E; Laktionov, Andrey; Rothlisberger, Ursula

    2010-11-21

    Recently, we have proposed a scheme for the calculation of nonadiabatic couplings and nonadiabatic coupling vectors within linear response time-dependent density functional theory using a set of auxiliary many-electron wavefunctions [I. Tavernelli, E. Tapavicza, and U. Rothlisberger, J. Chem. Phys. 130, 124107 (2009)]. As demonstrated in a later work [I. Tavernelli, B. F. E. Curchod, and U. Rothlisberger, J. Chem. Phys. 131, 196101 (2009)], this approach is rigorous in the case of the calculation of nonadiabatic couplings between the ground state and any excited state. In this work, we extend this formalism to the case of coupling between pairs of singly excited states with the same spin multiplicity. After proving the correctness of our formalism using the electronic oscillator approach by Mukamel and co-workers [S. Tretiak and S. Mukamel, Chem. Rev. (Washington, D.C.) 102, 3171 (2002)], we tested the method on a model system, namely, protonated formaldimine, for which we computed S(1)/S(2) nonadiabatic coupling vectors and compared them with results from high level (MR-CISD) electronic structure calculations. PMID:21090851

  5. Intersystem Crossing Pathway in Quinoline-Pyrazole Isomerism: A Time-Dependent Density Functional Theory Study on Excited-State Intramolecular Proton Transfer.

    PubMed

    Liu, Yu-Hui; Lan, Sheng-Cheng; Zhu, Chaoyuan; Lin, Sheng-Hsien

    2015-06-18

    The dynamics of the excited-state intramolecular proton-transfer (ESIPT) reaction of quinoline-pyrazole (QP) isomers, designated as QP-I and QP-II, has been investigated by means of time-dependent density functional theory (TDDFT). A lower barrier has been found in the potential energy curve for the lowest singlet excited state (S1) along the proton-transfer coordinate of QP-II compared with that of QP-I; however, this is at variance with a recent experimental report [J. Phys. Chem. A 2010, 114, 7886-7891], in which the authors proposed that the ESIPT reaction would only proceed in QP-I due to the absence of a PT emission for QP-II. Therefore, several deactivating pathways have been investigated to determine whether fluorescence quenching occurs in the PT form of QP-II (PT-II). The S1 state of PT-II has nπ* character, which is a well-known dark state. Moreover, the energy gap between the S1 and T2 states is only 0.29 eV, implying that an intersystem crossing (ISC) process would occur rapidly following the ESIPT reaction. Therefore, it is demonstrated that the ESIPT could successfully proceed in QP-II and that the PT emission would be quenched by the ISC process.

  6. Subsystem density-functional theory as an effective tool for modeling ground and excited states, their dynamics and many-body interactions

    NASA Astrophysics Data System (ADS)

    Krishtal, Alisa; Sinha, Debalina; Genova, Alessandro; Pavanello, Michele

    2015-05-01

    Subsystem density-functional theory (DFT) is an emerging technique for calculating the electronic structure of complex molecular and condensed phase systems. In this topical review, we focus on some recent advances in this field related to the computation of condensed phase systems, their excited states, and the evaluation of many-body interactions between the subsystems. As subsystem DFT is in principle an exact theory, any advance in this field can have a dual role. One is the possible applicability of a resulting method in practical calculations. The other is the possibility of shedding light on some quantum-mechanical phenomenon which is more easily treated by subdividing a supersystem into subsystems. An example of the latter is many-body interactions. In the discussion, we present some recent work from our research group as well as some new results, casting them in the current state-of-the-art in this review as comprehensively as possible.

  7. Excitation functions for production of heavy actinides from interactions of /sup 18/O with /sup 248/Cm and /sup 249/Cf

    SciTech Connect

    Lee, D.; Moody, K.J.; Nurmia, M.J.; Seaborg, G.T.; von Gunten, H.R.; Hoffman, D.C.

    1983-06-01

    Excitation functions have been measured for the production of isotopes of Bk through Fm in bombardments of /sup 248/Cm with 97- to 122-MeV /sup 18/O ions and of isotopes of Bk through No in bombardments of /sup 249/Cf with 91- to 150-MeV /sup 18/O ions. The cross sections and widths of the mass distributions for the actinides produced in these reactions are very similar for transfer of the same numbers of nucleons. A semiquantitative comparison of the experimental results with calculations based on a simple model shows that calculations of this type are helpful in selection of projectile-target systems and optimum energies for production of specific actinide isotopes and for synthesis of as yet unknown heavy isotopes and elements. Comparisons of experimental results with calculations show that, in general, about half of the kinetic energy of the projectile is transferred to the actinide product.

  8. Total Reaction Cross Section Excitation Function Studies for 6He Interaction with 181Ta, 59Co, natSi, 9Be Nuclei

    NASA Astrophysics Data System (ADS)

    Sobolev, Yu. G.; Penionzhkevich, Yu. E.; Borcea, C.; Demekhina, N. A.; Eshanov, A. G.; Ivanov, M. P.; Kabdrakhimova, G. D.; Kabyshev, A. M.; Kugler, A.; Kuterbekov, K. A.; Lukyanov, K. V.; Maj, A.; Maslov, V. A.; Negret, A.; Skobelev, N. K.; Testov, D.; Trzaska, W. H.; Voskobojnik, E. I.; Zemlyanaya, E. V.

    2015-06-01

    Total reaction cross section excitation functions σR(E) were measured for 6He secondary beam particles on 181Ta, 59Co, natSi and 9Be targets in a wide energy range by direct and model-independent method. This experimental method was based on prompt n-γ 4π-technique applied in event-by event mode. A high efficiency CsI(Tl) γ-spectrometer was used for the detection of reaction products (prompt γ-quanta and neutrons) accompanying each reaction event. Using the ACCULINNA fragment-separator 6He fragments (produced by 11B primary beam with 9Be target) are separated and transported to n-γ shielded experimental cave at FLNR JINR. The measured total reaction cross section data σR(E) for the above mentioned reactions are compared with a theoretical calculation based on the optical potential with the real part having the double-folding form.

  9. Excitation functions for 7Be, 22,24Na production in Mg and Al by deuteron irradiations up to 50 MeV.

    PubMed

    Hermanne, A; Takács, S; Tárkányi, F; Adam-Rebeles, R; Ignatyuk, A

    2012-12-01

    New experimental data for production of (7)Be and (22,24)Na in deuteron irradiation of (nat)Mg and Al up to 50 MeV are presented. The induced activity, measured with HPGe spectroscopy, allows us to determine excitation functions of (nat)Mg(d,x) and (27)Al(d,x) reactions involved in the activation process with reference to (nat)Ti(d,x)(48)V monitor cross sections. A comparison with experimental literature values and results from updated theoretical codes is discussed. Thick target yields were derived from fits to our cross-sections and integrated personnel dose was calculated for different irradiation cycles and exposure scenarios around high power deuteron accelerator facilities. PMID:23044286

  10. Extension of excitation functions up to 50 MeV for activation products in deuteron irradiations of Pr and Tm targets

    NASA Astrophysics Data System (ADS)

    Hermanne, A.; Tárkányi, F.; Takács, S.; Ditrói, F.

    2016-09-01

    Extension up to 50 MeV incident deuteron energy is presented for excitation functions of activation products formed in monoisotopic Tm (169Tm) and Pr (141Pr). By stacked foil irradiations direct and/or cumulative production of 140,139m,138Nd, 138mPr, 141,139,137m,135Ce on Pr and 166,169Yb, 166,167,168Tm on Tm targets were measured. Confirmation of earlier experimental results for all investigated radionuclides is found and the influence of the higher energy on thick target yields and batch production of medically relevant radionuclides (140Nd, 139Pr (as decay product of 139mNd), 166,169Yb, 167Tm) is discussed. A comparison of experimental values with TALYS1.6 code results (predicted values from TENDL-2015 on-line library) shows a better description of the (d,pxn) reactions than older ones.

  11. Excitation function for deuteron induced nuclear reactions on natural ytterbium for production of high specific activity 177g Lu in no-carrier-added form for metabolic radiotherapy.

    PubMed

    Manenti, Simone; Groppi, Flavia; Gandini, Andrea; Gini, Luigi; Abbas, Kamel; Holzwarth, Uwe; Simonelli, Federica; Bonardi, Mauro

    2011-01-01

    Deuteron-induced nuclear reactions for generation of no-carrier-added Lu radionuclides were investigated using the stacked-foil activation technique on natural Yb targets at energies up to E(d)=18.18 MeV. Excitation functions of the reactions (nat)Yb(d,xn)(169,170,171,172,173,174g,174m,176m,177g)Lu and (nat)Yb(d,pxn)(169,175,177)Yb have been measured, among them three ((169)Lu, (174m)Lu and (176m)Lu) are reported for the first time. The upper limit of the contamination from the long-lived metastable level (177m)Lu was evaluated too. Thick-target yields for all investigated radionuclides are calculated.

  12. Measurements of Excitation Functions and Line Polarizations for Electron Impact Excitation of the n = 2, 3 States of Atomic Hydrogen in the Energy Range 11 - 2000 eV

    NASA Technical Reports Server (NTRS)

    James, G. K.; Ajello, J. M.; Kanik, I.; Slevin, J.; Franklin, B.; Shemansky, D.

    1993-01-01

    The electron-atomic hydrogen scattering system is an important testing ground for theoretical models and has received a great deal of attention from experimentalists and theoreticians alike over the years. A complete description of the excitation process requires a knowledge of many different parameters, and experimental measurements of these parameters have been performed in various laboratories around the world. As far as total cross section data are concerned it has been noted that the discrepancy between the data of Long et al. and Williams for n = 2 excitations needs to be resolved in the interests of any further refinement of theory. We report new measurements of total cross sections and atomic line polarizations for both n=2 and n=3 excitations at energies from threshold to 2000 eV...

  13. Electronic states of thiophene/phenylene co-oligomers: Extreme-ultra violet excited photoelectron spectroscopy observations and density functional theory calculations

    SciTech Connect

    Kawaguchi, Yoshizo; Sasaki, Fumio; Mochizuki, Hiroyuki; Ishitsuka, Tomoaki; Tomie, Toshihisa; Ootsuka, Teruhisa; Watanabe, Shuji; Shimoi, Yukihiro; Yamao, Takeshi; Hotta, Shu

    2013-02-28

    We have investigated electronic states in the valence electron bands for the thin films of three thiophene/phenylene co-oligomer (TPCO) compounds, 2,5-bis(4-biphenylyl)thiophene (BP1T), 1,4-bis(5-phenylthiophen-2-yl)benzene (AC5), and 1,4-bis{l_brace}5-[4-(trifluoromethyl)phenyl]thiophen-2-yl{r_brace}benzene (AC5-CF{sub 3}), by using extreme-UV excited photoelectron spectroscopy (EUPS). By comparing both EUPS spectra and secondary electron spectra between AC5 and AC5-CF{sub 3}, we confirm that CF{sub 3} substitution to AC5 deepens valence states by 2 eV, and increases the ionization energy by 3 eV. From the cut-off positions of secondary electron spectra, the work functions of AC5, AC5-CF{sub 3}, and BP1T are evaluated to be 3.8 eV, 4.8 eV, and 4.0 eV, respectively. We calculate molecular orbital (MO) energy levels by the density functional theory and compare results of calculations with those of experiments. Densities of states obtained by broadening MO levels well explain the overall features of experimental EUPS spectra of three TPCOs.

  14. Time-dependent density functional theory (TD-DFT) study on the excited-state intramolecular proton transfer (ESIPT) in 2-hydroxybenzoyl compounds: Significance of the intramolecular hydrogen bonding

    NASA Astrophysics Data System (ADS)

    Lan, Xin; Yang, Dapeng; Sui, Xiao; Wang, Dandan

    2013-02-01

    The excited-state properties of intramolecular hydrogen bonding (IMHB) in methyl salicylate (MS) and its effects on the excited-state intramolecular proton transfer (ESIPT) have been investigated using theoretical methods. From the geometric optimization and IR spectra in the ground and excited states calculated by density functional theory (DFT) and time-dependent DFT (TD-DFT) methods respectively, the IMHB is demonstrated to be significantly strengthened upon excitation to excited state S1. Thereby, the ESIPT is facilitated by the excited-state IMHB strengthening since ESIPT takes place through IMHB. In addition, the absorption and fluorescence peaks of the S1 state are also calculated using the TD-DFT method. It is noted that the calculated spectra are in good agreement with the experimental results, which has confirmed the ESIPT mechanism of MS first proposed by Weller. Moreover, other four 2-hydroxybenzoyl compounds forming strong IMHB are investigated to understand the effect of substituent R on the ESIPT process. We find that the hydrogen bond strength can be controlled by the inductive field effect of the substituent. Thus it is inferred that the ESIPT reaction can be facilitated by the inductive effect of electron-donating substituent.

  15. Experimental and calculated excitation functions for discrete-line gamma-ray production due to 1-40 MeV neutron interactions with sup 56 Fe

    SciTech Connect

    Dickens, J.K.; Fu, C.Y.; Hetrick, D.M.; Larson, D.C.; Todd, J.H.

    1991-01-01

    Measuring cross sections for gamma-ray production from tertiary reactions is one of the ways to gain experimental information about these reactions. To this end, inelastic and other nonelastic neutron interactions with {sup 56}Fe have been studied for incident neutron energies between 0.8 and 41 MeV. An iron sample isotopically enriched in the mass 56 isotope was used. Gamma rays representing 70 transitions among levels in residual nuclei were identified, and production cross sections were deduced. The reactions studies were {sup 56}Fe(n,n{prime}){sup 56}Fe, {sup 56}Fe(n,p){sup 56}Mn, {sup 56}Fe(n,2n){sup 55}Fe, {sup 56}Fe(n,d + n,np){sup 55}Mn, {sup 56}Fe(n, t + n, nd + n,2np){sup 54}Mn, {sup 56}Fe(n,{alpha}){sup 53}Cr, {sup 56}Fe(n,n{alpha}){sup 52}Cr, and {sup 56}Fe(n,3n){sup 54}Fe. Experimental excitation functions have been compared with cross sections calculated using the nuclear reaction model code TNG, with generally favorable results. 24 refs., 2 figs.

  16. Excitation function for the production of {sup 262}Bh (Z=107) in the odd-Z-projectile reaction {sup 208}Pb({sup 55}Mn, n)

    SciTech Connect

    Folden, C.M. III; Nelson, S.L.; Duellmann, Ch.E.; Schwantes, J.M.; Zielinski, P.M.; Nitsche, H.; Hoffman, D.C.; Sudowe, R.; Gregorich, K.E.

    2006-01-15

    The excitation function for production of {sup 262}Bh in the odd-Z-projectile reaction {sup 208}Pb({sup 55}Mn, n) has been measured at three projectile energies using the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. In total, 33 decay chains originating from {sup 262}Bh and 2 decay chains originating from {sup 261}Bh were observed. The measured decay properties are in good agreement with previous reports. The maximum cross section of 540{sub -150}{sup +180} pb is observed at a lab-frame center-of-target energy of 264.0 MeV and is more than five times larger than that expected based on previously reported results for production of {sup 262}Bh in the analogous even-Z-projectile reaction {sup 209}Bi({sup 54}Cr, n). Our results indicate that the optimum beam energy in one-neutron-out heavy-ion fusion reactions can be estimated simply using the optimum energy rule proposed by SwiaPtecki, Siwek-Wilczynska, and Wilczynski.

  17. Excitation function for the production of 262Bh (Z = 107) in theodd-Z projectile reaction 208Pb(55Mn, n)

    SciTech Connect

    Folden III, C.M.; Nelson, S.L.; Dullmann, Ch.E.; Schwantes, J.M.; Sudowe, R.; Zielinski, P.M.; Gregorich, K.E.; Nitsche, H.; Hoffman, D.C.

    2005-05-16

    The excitation function for production of 262Bh in the odd-Z-projectile reaction 208Pb(55Mn,n) has been measured at three projectile energies using the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. In total, 33 decay chains originating from 262Bh and 2 decay chains originating from 261Bh were observed. The measured decay properties are in good agreement with previous reports. The maximum cross section of 540 +180 - 150 pb is observed at a lab-frame center-of-target energy of 264.0 MeV and is more than fives times larger than that expected based on previously reported results for production of 262Bh in the analogous even-Z-projectile reaction 209Bi(54Cr,n). Our results indicate that the optimum beam energy in one-neutron-out heavy-ion fusion reactions can be estimated simply using the ''Optimum Energy Rule'' proposed by Swiatecki, Siwek-Wilczynska, and Wilczynski.

  18. Molecular orbital studies (hardness, chemical potential, electrophilicity, and first electron excitation), vibrational investigation and theoretical NBO analysis of 2-hydroxy-5-bromobenzaldehyde by density functional method

    NASA Astrophysics Data System (ADS)

    Nataraj, A.; Balachandran, V.; Karthick, T.

    2013-01-01

    In this work, the vibrational spectral analysis was carried out using Raman and infrared spectroscopy in the range 4000-400 cm-1 and 3500-100 cm-1, respectively, for the 2-hydroxy-5-bromobenzaldehyde (HBB). The experimental spectra were recorded in the solid phase. The fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) with the standard B3LYP/6-311G++(d,p) method and basis set. Normal co-ordinate calculations were performed with the DFT force field corrected by a recommended set of scaling factors yielding fairly good agreement between observed and calculated frequencies. Simulation of infrared and Raman spectra utilizing the results of these calculations led to excellent overall agreement with the observed spectral patterns. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The optimized geometric parameters (bond lengths and bond angles) were compared with experimental values of related compound. The stability of the molecule arising from hyper conjugative interactions and the charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The directly calculated ionization potential (IP), electron affinity (EA), electronegativity (χ), electrophilicity index (ω), hardness (η), chemical potential (μ), and first electron excitation (τ) are all correlated with the HOMO and LUMO energies with their molecular properties. These show that charge transfer occurs within the molecule. Furthermore, molecular electrostatic potential maps (MESP) of the molecule have been calculated.

  19. Reversed Effects of Intermittent Theta Burst Stimulation following Motor Training That Vary as a Function of Training-Induced Changes in Corticospinal Excitability

    PubMed Central

    Stöckel, Tino; Summers, Jeffery J.; Hinder, Mark R.

    2015-01-01

    Intermittent theta burst stimulation (iTBS) has the potential to enhance corticospinal excitability (CSE) and subsequent motor learning. However, the effects of iTBS following motor learning are unknown. The purpose of the present study was to explore the effect of iTBS on CSE and performance following motor learning. Therefore twenty-four healthy participants practiced a ballistic motor task for a total of 150 movements. iTBS was subsequently applied to the trained motor cortex (STIM group) or the vertex (SHAM group). Performance and CSE were assessed before motor learning and before and after iTBS. Training significantly increased performance and CSE in both groups. In STIM group participants, subsequent iTBS significantly reduced motor performance with smaller reductions in CSE. CSE changes as a result of motor learning were negatively correlated with both the CSE changes and performance changes as a result of iTBS. No significant effects of iTBS were found for SHAM group participants. We conclude that iTBS has the potential to degrade prior motor learning as a function of training-induced CSE changes. That means the expected LTP-like effects of iTBS are reversed following motor learning. PMID:26167305

  20. Description of excited states in [Re(Imidazole)(CO)3 (Phen)](+) including solvent and spin-orbit coupling effects: Density functional theory versus multiconfigurational wavefunction approach.

    PubMed

    Fumanal, Maria; Daniel, Chantal

    2016-10-15

    The low-lying electronic excited states of [Re(imidazole)(CO)3 (phen)](+) (phen = 1,10-phenanthroline) ranging between 420 nm and 330 nm have been calculated by means of relativistic spin-orbit time-dependent density functional theory (TD-DFT) and wavefunction approaches (state-average-CASSCF/CASPT2). A direct comparison between the theoretical absorption spectra obtained with different methods including SOC and solvent corrections for water points to the difficulties at describing on the same footing the bands generated by metal-to-ligand charge transfer (MLCT), intraligand (IL) transition, and ligand-to-Ligand- charge transfer (LLCT). While TD-DFT and three-roots-state-average CASSCF (10,10) reproduce rather well the lowest broad MLCT band observed in the experimental spectrum between 420 nm and 330 nm, more flexible wavefunctions enlarged either by the number of roots or by the number of active orbitals and electrons destabilize the MLCT states by introducing IL and LLCT character in the lowest part of the absorption spectrum. © 2016 Wiley Periodicals, Inc. PMID:27510636

  1. Linker mutations dissociate the function of synaptotagmin I during evoked and spontaneous release and reveal membrane penetration as a step during excitation-secretion coupling

    PubMed Central

    Liu, Huisheng; Bai, Hua; Xue, Renhao; Takahashi, Hirohide; Edwardson, J. Michael; Chapman, Edwin R.

    2014-01-01

    The Ca2+ sensor for rapid synaptic vesicle exocytosis, synaptotagmin I (syt), is largely composed of two Ca2+-sensing C2-domains, C2A and C2B. We have investigated the apparent synergy between the tandem C2 domains by altering the length and rigidity of the linker that connects them. The behavior of the linker mutants revealed a correlation between the ability of the C2-domains to penetrate membranes in response to Ca2+ and to drive evoked neurotransmitter release in cultured mouse neurons, uncovering a step in excitation-secretion coupling. Atomic force microscopy experiments indicate that the synergy between these C2-domains involves intra-molecular interactions between them. Thus, syt function is profoundly affected by changes in the physical nature of the linker that connects its tandem C2-domains. Moreover, the linker mutations uncoupled syt-mediated regulation of evoked and spontaneous release, revealing that syt also acts as a fusion clamp prior to the Ca2+ trigger. PMID:24657966

  2. Reaction mechanism in the {sup 16}O+{sup 27}Al system: Measurements and analysis of excitation functions and angular distributions

    SciTech Connect

    Sharma, Manoj Kumar; Unnati,; Singh, Devendra P.; Singh, Pushpendra P.; Singh, B. P.; Prasad, R.; Bhardwaj, H. D.

    2007-06-15

    To study the dynamics of heavy ion fusion reactions in the lower mass region, experiments were carried out to measure the cross sections of radioactive residues produced in the interaction of the {sup 16}O ion with {sup 27}Al target nucleus at 19 different energies in very close intervals covering the energy range from {approx_equal}58 to 94 MeV, using the well-known recoil catcher off-line {gamma}-ray spectroscopy technique. The simulation of experimental data was performed using statistical-model-based computer codes, viz., CASCADE, PACE2, and ALICE-91. The analysis of measured excitation functions indicates that these residues are likely to be produced by complete fusion, incomplete fusion, and direct reaction processes. Furthermore, to confirm the contribution of different reaction channels, a complementary experiment was performed that measured the angular distributions of the residues produced in the {sup 16}O+{sup 27}Al system at 85 MeV beam energy. The analysis of the results of both experiments indicates that at these energies, the direct reactions compete with complete fusion and incomplete fusion reaction processes.

  3. Excitation function of the alpha particle induced nuclear reactions on enriched 116Cd, production of the theranostic isotope 117mSn

    NASA Astrophysics Data System (ADS)

    Ditrói, F.; Takács, S.; Haba, H.; Komori, Y.; Aikawa, M.; Szűcs, Z.; Saito, M.

    2016-10-01

    117mSn is one of the radioisotopes can be beneficially produced through alpha particle irradiation. The targets were prepared by deposition of 116Cd metal onto high purity 12 μm thick Cu backing. The average deposited thickness was 21.9 μm. The beam energy was thoroughly measured by Time of Flight (TOF) methods and proved to be 51.2 MeV. For the experiment the well-established stacked foil technique was used. In addition to the Cd targets, Ti foils were also inserted into the stacks for energy and intensity monitoring. The Cu backings were also used for monitoring and as recoil catcher of the reaction products from the cadmium layer. The activities of the irradiated foils were measured with HPGe detector for gamma-ray spectrometry and cross section values were determined. As a result excitation functions for the formation of 117mSn, 117m,gIn, 116mIn, 115mIn and 115m,gCd from enriched 116Cd were deduced and compared with the available literature data and with the results of the nuclear reaction model code calculations EMPIRE 3.2 and TALYS 1.8. Yield curves were also deduced for the measured nuclear reactions and compared with the literature.

  4. Description of excited states in [Re(Imidazole)(CO)3 (Phen)](+) including solvent and spin-orbit coupling effects: Density functional theory versus multiconfigurational wavefunction approach.

    PubMed

    Fumanal, Maria; Daniel, Chantal

    2016-10-15

    The low-lying electronic excited states of [Re(imidazole)(CO)3 (phen)](+) (phen = 1,10-phenanthroline) ranging between 420 nm and 330 nm have been calculated by means of relativistic spin-orbit time-dependent density functional theory (TD-DFT) and wavefunction approaches (state-average-CASSCF/CASPT2). A direct comparison between the theoretical absorption spectra obtained with different methods including SOC and solvent corrections for water points to the difficulties at describing on the same footing the bands generated by metal-to-ligand charge transfer (MLCT), intraligand (IL) transition, and ligand-to-Ligand- charge transfer (LLCT). While TD-DFT and three-roots-state-average CASSCF (10,10) reproduce rather well the lowest broad MLCT band observed in the experimental spectrum between 420 nm and 330 nm, more flexible wavefunctions enlarged either by the number of roots or by the number of active orbitals and electrons destabilize the MLCT states by introducing IL and LLCT character in the lowest part of the absorption spectrum. © 2016 Wiley Periodicals, Inc.

  5. 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.

  6. 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

  7. Raptor ablation in skeletal muscle decreases Cav1.1 expression and affects the function of the excitation-contraction coupling supramolecular complex.

    PubMed

    Lopez, Rubén J; Mosca, Barbara; Treves, Susan; Maj, Marcin; Bergamelli, Leda; Calderon, Juan C; Bentzinger, C Florian; Romanino, Klaas; Hall, Michael N; Rüegg, Markus A; Delbono, Osvaldo; Caputo, Carlo; Zorzato, Francesco

    2015-02-15

    The protein mammalian target of rapamycin (mTOR) is a serine/threonine kinase regulating a number of biochemical pathways controlling cell growth. mTOR exists in two complexes termed mTORC1 and mTORC2. Regulatory associated protein of mTOR (raptor) is associated with mTORC1 and is essential for its function. Ablation of raptor in skeletal muscle results in several phenotypic changes including decreased life expectancy, increased glycogen deposits and alterations of the twitch kinetics of slow fibres. In the present paper, we show that in muscle-specific raptor knockout (RamKO), the bulk of glycogen phosphorylase (GP) is mainly associated in its cAMP-non-stimulated form with sarcoplasmic reticulum (SR) membranes. In addition, 3[H]-ryanodine and 3[H]-PN200-110 equilibrium binding show a ryanodine to dihydropyridine receptors (DHPRs) ratio of 0.79 and 1.35 for wild-type (WT) and raptor KO skeletal muscle membranes respectively. Peak amplitude and time to peak of the global calcium transients evoked by supramaximal field stimulation were not different between WT and raptor KO. However, the increase in the voltage sensor-uncoupled RyRs leads to an increase of both frequency and mass of elementary calcium release events (ECRE) induced by hyper-osmotic shock in flexor digitorum brevis (FDB) fibres from raptor KO. The present study shows that the protein composition and function of the molecular machinery involved in skeletal muscle excitation-contraction (E-C) coupling is affected by mTORC1 signalling.

  8. Electronic structure and optical properties of CdS{sub x}Se{sub 1−x} solid solution nanostructures from X-ray absorption near edge structure, X-ray excited optical luminescence, and density functional theory investigations

    SciTech Connect

    Murphy, M. W.; Yiu, Y. M. Sham, T. K.; Ward, M. J.; Liu, L.; Hu, Y.; Zapien, J. A.; Liu, Yingkai

    2014-11-21

    The electronic structure and optical properties of a series of iso-electronic and iso-structural CdS{sub x}Se{sub 1−x} solid solution nanostructures have been investigated using X-ray absorption near edge structure, extended X-ray absorption fine structure, and X-ray excited optical luminescence at various absorption edges of Cd, S, and Se. It is found that the system exhibits compositions, with variable local structure in-between that of CdS and CdSe accompanied by tunable optical band gap between that of CdS and CdSe. Theoretical calculation using density functional theory has been carried out to elucidate the observations. It is also found that luminescence induced by X-ray excitation shows new optical channels not observed previously with laser excitation. The implications of these observations are discussed.

  9. 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.

  10. Functional Network Overlap as Revealed by fMRI Using sICA and Its Potential Relationships with Functional Heterogeneity, Balanced Excitation and Inhibition, and Sparseness of Neuron Activity

    PubMed Central

    Xu, Jiansong; Calhoun, Vince D.; Worhunsky, Patrick D.; Xiang, Hui; Li, Jian; Wall, John T.; Pearlson, Godfrey D.; Potenza, Marc N.

    2015-01-01

    Functional magnetic resonance imaging (fMRI) studies traditionally use general linear model-based analysis (GLM-BA) and regularly report task-related activation, deactivation, or no change in activation in separate brain regions. However, several recent fMRI studies using spatial independent component analysis (sICA) find extensive overlap of functional networks (FNs), each exhibiting different task-related modulation (e.g., activation vs. deactivation), different from the dominant findings of GLM-BA. This study used sICA to assess overlap of FNs extracted from four datasets, each related to a different cognitive task. FNs extracted from each dataset overlapped with each other extensively across most or all brain regions and showed task-related concurrent increases, decreases, or no changes in activity. These findings indicate that neural substrates showing task-related concurrent but different modulations in activity intermix with each other and distribute across most of the brain. Furthermore, spatial correlation analyses found that most FNs were highly consistent in spatial patterns across different datasets. This finding indicates that these FNs probably reflect large-scale patterns of task-related brain activity. We hypothesize that FN overlaps as revealed by sICA might relate to functional heterogeneity, balanced excitation and inhibition, and population sparseness of neuron activity, three fundamental properties of the brain. These possibilities deserve further investigation. PMID:25714362

  11. Calculation of the total electron excitation cross section in the Born approximation using Slater wave functions for the Li (2s yields 2p), Li (2s yields 3p), Na (3s yields 4p), Mg (3p yields 4s), Ca (4s yields 4p) and K (4s yields 4p) excitations. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Simsic, P. L.

    1974-01-01

    Excitation of neutral atoms by inelastic scattering of incident electrons in gaseous nebulae were investigated using Slater Wave functions to describe the initial and final states of the atom. Total cross sections using the Born Approximation are calculated for: Li(2s yields 2p), Na(3s yields 4p), k(4s yields 4p). The intensity of emitted radiation from gaseous nebulae is also calculated, and Maxwell distribution is employed to average the kinetic energy of electrons.

  12. The structure of the hydrated electron. Part 2. A mixed quantum/classical molecular dynamics embedded cluster density functional theory: single-excitation configuration interaction study.

    PubMed

    Shkrob, Ilya A; Glover, William J; Larsen, Ross E; Schwartz, Benjamin J

    2007-06-21

    Adiabatic mixed quantum/classical (MQC) molecular dynamics (MD) simulations were used to generate snapshots of the hydrated electron in liquid water at 300 K. Water cluster anions that include two complete solvation shells centered on the hydrated electron were extracted from the MQC MD simulations and embedded in a roughly 18 Ax18 Ax18 A matrix of fractional point charges designed to represent the rest of the solvent. Density functional theory (DFT) with the Becke-Lee-Yang-Parr functional and single-excitation configuration interaction (CIS) methods were then applied to these embedded clusters. The salient feature of these hybrid DFT(CIS)/MQC MD calculations is significant transfer (approximately 18%) of the excess electron's charge density into the 2p orbitals of oxygen atoms in OH groups forming the solvation cavity. We used the results of these calculations to examine the structure of the singly occupied and the lower unoccupied molecular orbitals, the density of states, the absorption spectra in the visible and ultraviolet, the hyperfine coupling (hfcc) tensors, and the infrared (IR) and Raman spectra of these embedded water cluster anions. The calculated hfcc tensors were used to compute electron paramagnetic resonance (EPR) and electron spin echo envelope modulation (ESEEM) spectra for the hydrated electron that compared favorably to the experimental spectra of trapped electrons in alkaline ice. The calculated vibrational spectra of the hydrated electron are consistent with the red-shifted bending and stretching frequencies observed in resonance Raman experiments. In addition to reproducing the visible/near IR absorption spectrum, the hybrid DFT model also accounts for the hydrated electron's 190-nm absorption band in the ultraviolet. Thus, our study suggests that to explain several important experimentally observed properties of the hydrated electron, many-electron effects must be accounted for: one-electron models that do not allow for mixing of the excess

  13. 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.

  14. Circadian regulation of human cortical excitability

    PubMed Central

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

    2016-01-01

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

  15. 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.

  16. 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.

  17. Molecular properties of excited electronic state: Formalism, implementation, and applications of analytical second energy derivatives within the framework of the time-dependent density functional theory/molecular mechanics

    NASA Astrophysics Data System (ADS)

    Zeng, Qiao; Liu, Jie; Liang, WanZhen

    2014-05-01

    This work extends our previous works [J. Liu and W. Z. Liang, J. Chem. Phys. 135, 014113 (2011); J. Liu and W. Z. Liang, J. Chem. Phys. 135, 184111 (2011)] on analytical excited-state energy Hessian within the framework of time-dependent density functional theory (TDDFT) to couple with molecular mechanics (MM). The formalism, implementation, and applications of analytical first and second energy derivatives of TDDFT/MM excited state with respect to the nuclear and electric perturbations are presented. Their performances are demonstrated by the calculations of adiabatic excitation energies, and excited-state geometries, harmonic vibrational frequencies, and infrared intensities for a number of benchmark systems. The consistent results with the full quantum mechanical method and other hybrid theoretical methods indicate the reliability of the current numerical implementation of developed algorithms. The computational accuracy and efficiency of the current analytical approach are also checked and the computational efficient strategies are suggested to speed up the calculations of complex systems with many MM degrees of freedom. Finally, we apply the current analytical approach in TDDFT/MM to a realistic system, a red fluorescent protein chromophore together with part of its nearby protein matrix. The calculated results indicate that the rearrangement of the hydrogen bond interactions between the chromophore and the protein matrix is responsible for the large Stokes shift.

  18. Molecular properties of excited electronic state: formalism, implementation, and applications of analytical second energy derivatives within the framework of the time-dependent density functional theory/molecular mechanics.

    PubMed

    Zeng, Qiao; Liu, Jie; Liang, WanZhen

    2014-05-14

    This work extends our previous works [J. Liu and W. Z. Liang, J. Chem. Phys. 135, 014113 (2011); J. Liu and W. Z. Liang, J. Chem. Phys. 135, 184111 (2011)] on analytical excited-state energy Hessian within the framework of time-dependent density functional theory (TDDFT) to couple with molecular mechanics (MM). The formalism, implementation, and applications of analytical first and second energy derivatives of TDDFT/MM excited state with respect to the nuclear and electric perturbations are presented. Their performances are demonstrated by the calculations of adiabatic excitation energies, and excited-state geometries, harmonic vibrational frequencies, and infrared intensities for a number of benchmark systems. The consistent results with the full quantum mechanical method and other hybrid theoretical methods indicate the reliability of the current numerical implementation of developed algorithms. The computational accuracy and efficiency of the current analytical approach are also checked and the computational efficient strategies are suggested to speed up the calculations of complex systems with many MM degrees of freedom. Finally, we apply the current analytical approach in TDDFT/MM to a realistic system, a red fluorescent protein chromophore together with part of its nearby protein matrix. The calculated results indicate that the rearrangement of the hydrogen bond interactions between the chromophore and the protein matrix is responsible for the large Stokes shift. PMID:24832314

  19. Direct non-Born-Oppenheimer variational calculations of all bound vibrational states corresponding to the first rotational excitation of D{sub 2} performed with explicitly correlated all-particle Gaussian functions

    SciTech Connect

    Sharkey, Keeper L.; Kirnosov, Nikita; Adamowicz, Ludwik

    2015-05-07

    Direct variational calculations where the Born-Oppenheimer approximation is not assumed are done for all rovibrational states of the D{sub 2} molecule corresponding to first excited rotational level (the N = 1 states). All-particle explicitly correlated Gaussian basis functions are used in the calculations. The exponential parameters of the Gaussians are optimized with the aid of analytically calculated energy gradient determined with respect to these parameters. The results allow to determine the ortho-para spin isomerization energies as a function of the vibrational quantum number.

  20. Application of unfolded principal component analysis-radial basis function neural network for determination of celecoxib in human serum by three-dimensional excitation-emission matrix fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Shahlaei, Mohsen; Bahrami, Gholamreza; Abdolmaleki, Sajjad; Sadrjavadi, Komail; Majnooni, Mohammad Bagher

    2015-03-01

    This study describes a simple and rapid approach of monitoring celecoxib (CLX). Unfolded principal component analysis-radial basis function neural network (UPCA-RBFNN) and excitation-emission spectra were combined to develop new model in the determination of CLX in human serum samples. Fluorescence landscapes with excitation wavelengths from 250 to 310 nm and emission wavelengths in the range 280-450 nm were obtained. The figures of merit for the developed model were evaluated. High performance liquid chromatography (HPLC) technique was also used as a standard method. Accuracy of the method was investigated by analysis of the serum samples spiked with various concentration of CLX and a recovery of 103.63% was obtained. The results indicated that the proposed method is an interesting alternative to the traditional techniques normally used for determining CLX such as HPLC.

  1. 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.

  2. Valence excitation energies of alkenes, carbonyl compounds, and azabenzenes by time-dependent density functional theory: Linear response of the ground state compared to collinear and noncollinear spin-flip TDDFT with the Tamm-Dancoff approximation

    NASA Astrophysics Data System (ADS)

    Isegawa, Miho; Truhlar, Donald G.

    2013-04-01

    Time-dependent density functional theory (TDDFT) holds great promise for studying photochemistry because of its affordable cost for large systems and for repeated calculations as required for direct dynamics. The chief obstacle is uncertain accuracy. There have been many validation studies, but there are also many formulations, and there have been few studies where several formulations were applied systematically to the same problems. Another issue, when TDDFT is applied with only a single exchange-correlation functional, is that errors in the functional may mask successes or failures of the formulation. Here, to try to sort out some of the issues, we apply eight formulations of adiabatic TDDFT to the first valence excitations of ten molecules with 18 density functionals of diverse types. The formulations examined are linear response from the ground state (LR-TDDFT), linear response from the ground state with the Tamm-Dancoff approximation (TDDFT-TDA), the original collinear spin-flip approximation with the Tamm-Dancoff (TD) approximation (SF1-TDDFT-TDA), the original noncollinear spin-flip approximation with the TDA approximation (SF1-NC-TDDFT-TDA), combined self-consistent-field (SCF) and collinear spin-flip calculations in the original spin-projected form (SF2-TDDFT-TDA) or non-spin-projected (NSF2-TDDFT-TDA), and combined SCF and noncollinear spin-flip calculations (SF2-NC-TDDFT-TDA and NSF2-NC-TDDFT-TDA). Comparing LR-TDDFT to TDDFT-TDA, we observed that the excitation energy is raised by the TDA; this brings the excitation energies underestimated by full linear response closer to experiment, but sometimes it makes the results worse. For ethylene and butadiene, the excitation energies are underestimated by LR-TDDFT, and the error becomes smaller making the TDA. Neither SF1-TDDFT-TDA nor SF2-TDDFT-TDA provides a lower mean unsigned error than LR-TDDFT or TDDFT-TDA. The comparison between collinear and noncollinear kernels shows that the noncollinear kernel

  3. Decreased face primary motor cortex (face-M1) excitability induced by noxious stimulation of the rat molar tooth pulp is dependent on the functional integrity of face-M1 astrocytes.

    PubMed

    Awamleh, L; Pun, H; Lee, J-C; Avivi-Arber, L

    2015-04-01

    Acute inflammatory dental pain is a prevalent condition often associated with limited jaw movements. Mustard oil (MO, a small-fiber excitant/inflammatory irritant) application to the rat molar tooth pulp induces increased excitability (i.e., central sensitization) of trigeminal medullary dorsal horn (MDH) nociceptive neurons that can be modulated by MDH application of the astrocytic inhibitor methionine sulfoximine (MSO). The objectives of the study were to determine whether MO application to the rat right maxillary first molar tooth pulp affects left face-M1 excitability manifested as altered intracortical microstimulation thresholds for evoking electromyographic activity in the right anterior digastric (RAD, jaw-opening muscle), and whether MSO application to face-M1 can modulate this MO effect. Under Ketamine general anesthesia, Sprague-Dawley male rats had a microelectrode positioned at a low-threshold (≤30 μA) face-M1 site. Then MO (n = 16) or control solution (n = 16) was applied to the previously exposed tooth pulp, and RAD threshold was monitored for 15 min. MSO (0.1 mM, n = 8) or saline (n = 8) was then applied to the face-M1, and RAD thresholds were monitored every 15 min for 120 min. ANOVA followed by post hoc Bonferroni was used to analyze data (p < 0.05). Within 15 min of MO (but not control) pulp application, RAD thresholds increased significantly (p < 0.001) as compared to baseline. One hour following MSO (but not saline) application to the face-M1, RAD thresholds decreased significantly (p = 0.005) toward baseline. These novel findings suggest that acute inflammatory dental pain is associated with decreased face-M1 excitability that may be dependent on the functional integrity of face-M1 astrocytes and related to mechanisms underlying limited jaw movements in acute orofacial pain conditions. PMID:25618005

  4. Does anodal transcranial direct current stimulation enhance excitability of the motor cortex and motor function in healthy individuals and subjects with stroke: a systematic review and meta-analysis.

    PubMed

    Bastani, A; Jaberzadeh, S

    2012-04-01

    The primary aim of this review is to evaluate the effects of anodal transcranial direct current stimulation (a-tDCS) on corticomotor excitability and motor function in healthy individuals and subjects with stroke. The secondary aim is to find a-tDCS optimal parameters for its maximal effects. Electronic databases were searched for studies into the effect of a-tDCS when compared to no stimulation. Studies which met the inclusion criteria were assessed and methodological quality was examined using PEDro and Downs and Black (D&B) assessment tools. Data from seven studies revealed increase in corticomotor excitability with a small but significant effect size (0.31 [0.14, 0.48], p=0.0003) in healthy subjects and data from two studies in subjects with stroke indicated significant results with moderate effect size (0.59 [0.24, 0.93], p=0.001) in favor of a-tDCS. Likewise, studies examining motor function demonstrated a small and non-significant effect (0.39 [-0.17, 0.94], p=0.17) in subjects with stroke and a large but non-significant effect (0.92 [-1.02, 2.87], p=0.35) in healthy subjects in favor of improvement in motor function. The results also indicate that efficacy of a-tDCS is dependent on current density and duration of application. A-tDCS increases corticomotor excitability in both healthy individuals and subjects with stroke. The results also show a trend in favor of motor function improvement following a-tDCS. A-tDCS is a non-invasive, cheap and easy-to-apply modality which could be used as a stand-alone technique or as an adds-on technique to enhance corticomotor excitability and the efficacy of motor training approaches. However, the small sample size of the included studies reduces the strength of the presented evidences and any conclusion in this regard should be considered cautiously.

  5. Nuclear model analysis of excitation functions of proton induced reactions on ⁸⁶Sr, ⁸⁸Sr and natZr: Evaluation of production routes of ⁸⁶Y.

    PubMed

    Zaneb, H; Hussain, M; Amjed, N; Qaim, S M

    2015-10-01

    The proton induced nuclear reactions on (86)Sr, (88)Sr and (nat)Zr were investigated for the production of (86)Y. The literature data were compared with the results of nuclear model calculations using the codes ALICE-IPPE, TALYS 1.6 and EMPIRE 3.2. The thick target yields of (86)Y were calculated from the recommended excitation functions. Analysis of radioyttrium impurities was also performed. A comparison of the various production routes showed that for medical applications of (86)Y, the reaction (86)Sr(p,n)(86)Y is the method of choice, which gives efficient yield with minimum impurities. PMID:26210800

  6. Does anodal transcranial direct current stimulation enhance excitability of the motor cortex and motor function in healthy individuals and subjects with stroke: a systematic review and meta-analysis.

    PubMed

    Bastani, A; Jaberzadeh, S

    2012-04-01

    The primary aim of this review is to evaluate the effects of anodal transcranial direct current stimulation (a-tDCS) on corticomotor excitability and motor function in healthy individuals and subjects with stroke. The secondary aim is to find a-tDCS optimal parameters for its maximal effects. Electronic databases were searched for studies into the effect of a-tDCS when compared to no stimulation. Studies which met the inclusion criteria were assessed and methodological quality was examined using PEDro and Downs and Black (D&B) assessment tools. Data from seven studies revealed increase in corticomotor excitability with a small but significant effect size (0.31 [0.14, 0.48], p=0.0003) in healthy subjects and data from two studies in subjects with stroke indicated significant results with moderate effect size (0.59 [0.24, 0.93], p=0.001) in favor of a-tDCS. Likewise, studies examining motor function demonstrated a small and non-significant effect (0.39 [-0.17, 0.94], p=0.17) in subjects with stroke and a large but non-significant effect (0.92 [-1.02, 2.87], p=0.35) in healthy subjects in favor of improvement in motor function. The results also indicate that efficacy of a-tDCS is dependent on current density and duration of application. A-tDCS increases corticomotor excitability in both healthy individuals and subjects with stroke. The results also show a trend in favor of motor function improvement following a-tDCS. A-tDCS is a non-invasive, cheap and easy-to-apply modality which could be used as a stand-alone technique or as an adds-on technique to enhance corticomotor excitability and the efficacy of motor training approaches. However, the small sample size of the included studies reduces the strength of the presented evidences and any conclusion in this regard should be considered cautiously. PMID:21978654

  7. Impedimetric Sensing Proprieties of ITO Electrodes Functionalized with PEDOT:PSS/Azo-Calix[4]Arene for the Detection of Al3+ Ions Under Light Excitation

    NASA Astrophysics Data System (ADS)

    Echabaane, M.; Rouis, A.; Mahjoub, M. A.; Bonnamour, I.; Ben Ouada, H.

    2016-08-01

    This study describes an investigation of the sensitivity of the azo-calix[4]arene/poly(3,4-ethylenedioxythiophene)/poly-(styrenesulfonate) (PEDOT:PSS) thin film deposited on the indium tin oxide (ITO) electrode surface toward aluminum ions (Al3+) under light excitation. Thin films were deposited by the spin-coating technique. Adhesion of these films to the ITO surface was highlighted by performing contact angle measurements. Then, interfaces of the azo-calix[4]arene/PEDOT:PSS thin film were characterized by impedance measurements using electrochemical impedance spectroscopy. Obtained impedance spectra were fitted using an equivalent circuit. Finally, evolutions of the different components of this circuit were studied. These evolutions show that the sensitivity of the azo-calix[4]arene/PEDOT:PSS/ITO electrode is remarkably improved under illumination.

  8. Experimental study of excitation functions for the deuteron induced reactions 64Zn(d,2p)64Cu and 64Zn(d,alphan)61Cu using the stacked-foil technique.

    PubMed

    Daraban, L; Abbas, K; Simonelli, F; Adam-Rebeles, R; Gibson, N

    2008-02-01

    There is considerable, and growing, interest in the 64Cu radioisotope for application in Nuclear Medicine for PET imaging and targeted radiotherapy of tumours. We are investigating the cyclotron production of this isotope by way of deuteron bombardment of enriched 64Zn target material. In this study, experimental excitation functions for both the 64Zn(d,2p)64Cu and 64Zn(d,alphan)61Cu reactions up to 18.2 MeV deuteron energy have been measured using the stacked-foil technique. The deuteron energies in the various foils were calculated with the SRIM 2003 code and gamma-ray spectrometry was used to measure the activities of the various radioisotopes produced. Monitor foils were used to determine the deuteron beam current on the target stack. Theoretical excitation functions, calculated both with the Empire II code and with an updated version of the Alice code, were compared with the experimental results and a reasonable agreement was found. The experimental work was performed at the MC40 Cyclotron at the European Commission's Joint Research Centre at Ispra, Italy.

  9. Experimental studies of the 249Bk + 48Ca reaction including decay properties and excitation function for isotopes of element 117, and discovery of the new isotope 277Mt

    NASA Astrophysics Data System (ADS)

    Oganessian, Yu. Ts.; Abdullin, F. Sh.; Alexander, C.; Binder, J.; Boll, R. A.; Dmitriev, S. N.; Ezold, J.; Felker, K.; Gostic, J. M.; Grzywacz, R. K.; Hamilton, J. H.; Henderson, R. A.; Itkis, M. G.; Miernik, K.; Miller, D.; Moody, K. J.; Polyakov, A. N.; Ramayya, A. V.; Roberto, J. B.; Ryabinin, M. A.; Rykaczewski, K. P.; Sagaidak, R. N.; Shaughnessy, D. A.; Shirokovsky, I. V.; Shumeiko, M. V.; Stoyer, M. A.; Stoyer, N. J.; Subbotin, V. G.; Sukhov, A. M.; Tsyganov, Yu. S.; Utyonkov, V. K.; Voinov, A. A.; Vostokin, G. K.

    2013-05-01

    Studies of superheavy nuclei produced in the 249Bk + 48Ca reaction were performed using the Dubna Gas Filled Recoil Separator. The cross section for the production of 293117 and 294117 isotopes was measured at five excitation energies of the 297117 compound nucleus ranging from 30 to 48 MeV and yielding maximum values of 1.1-0.6+1.2 pb for the 3n and 2.4-1.4+3.3 pb for the 4n reaction channels. Alpha emission from 281Rg competing with spontaneous fission (α/SF decay probability 1:9) was observed for the first time leading to the identification of the new isotope 277Mt (TSF≈5 ms). The measured decay properties are in good agreement with those expected based on the properties of neighboring even-Z and odd-Z nuclei. The α energies and half-lives of odd-Z isotopes observed in the 293117 and 294117 decay chains together with results obtained for lower-Z superheavy nuclei demonstrate enhanced stability with increasing neutron number toward the predicted new magic number N=184.

  10. 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

  11. Operant conditioning to increase ankle control or decrease reflex excitability improves reflex modulation and walking function in chronic spinal cord injury.

    PubMed

    Manella, Kathleen J; Roach, Kathryn E; Field-Fote, Edelle C

    2013-06-01

    Ankle clonus is common after spinal cord injury (SCI) and is attributed to loss of supraspinally mediated inhibition of soleus stretch reflexes and maladaptive reorganization of spinal reflex pathways. The maladaptive reorganization underlying ankle clonus is associated with other abnormalities, such as coactivation and reciprocal facilitation of tibialis anterior (TA) and soleus (SOL), which contribute to impaired walking ability in individuals with motor-incomplete SCI. Operant conditioning can increase muscle activation and decrease stretch reflexes in individuals with SCI. We compared two operant conditioning-based interventions in individuals with ankle clonus and impaired walking ability due to SCI. Training included either voluntary TA activation (TA↑) to enhance supraspinal drive or SOL H-reflex suppression (SOL↓) to modulate reflex pathways at the spinal cord level. We measured clonus duration, plantar flexor reflex threshold angle, timed toe tapping, dorsiflexion (DF) active range of motion, lower extremity motor scores (LEMS), walking foot clearance, speed and distance, SOL H-reflex amplitude modulation as an index of reciprocal inhibition, presynaptic inhibition, low-frequency depression, and SOL-to-TA clonus coactivation ratio. TA↑ decreased plantar flexor reflex threshold angle (-4.33°) and DF active range-of-motion angle (-4.32°) and increased LEMS of DF (+0.8 points), total LEMS of the training leg (+2.2 points), and nontraining leg (+0.8 points), and increased walking foot clearance (+ 4.8 mm) and distance (+12.09 m). SOL↓ decreased SOL-to-TA coactivation ratio (-0.21), increased nontraining leg LEMS (+1.8 points), walking speed (+0.02 m/s), and distance (+6.25 m). In sum, we found increased voluntary control associated with TA↑ outcomes and decreased reflex excitability associated with SOL↓ outcomes.

  12. 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

  13. 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.

  14. 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.

  15. Nonorthogonal orbital based N-body reduced density matrices and their applications to valence bond theory. I. Hamiltonian matrix elements between internally contracted excited valence bond wave functions.

    PubMed

    Chen, Zhenhua; Chen, Xun; Wu, Wei

    2013-04-28

    In this series, the n-body reduced density matrix (n-RDM) approach for nonorthogonal orbitals and their applications to ab initio valence bond (VB) methods are presented. As the first paper of this series, Hamiltonian matrix elements between internally contracted VB wave functions are explicitly provided by means of nonorthogonal orbital based RDM approach. To this end, a more generalized Wick's theorem, called enhanced Wick's theorem, is presented both in arithmetical and in graphical forms, by which the deduction of expressions for the matrix elements between internally contracted VB wave functions is dramatically simplified, and the matrix elements are finally expressed in terms of tensor contractions of electronic integrals and n-RDMs of the reference VB self-consistent field wave function. A string-based algorithm is developed for the purpose of evaluating n-RDMs in an efficient way. Using the techniques presented in this paper, one is able to develop new methods and efficient algorithms for nonorthogonal orbital based many-electron theory much easier than by use of the first quantized formulism.

  16. Nonorthogonal orbital based N-body reduced density matrices and their applications to valence bond theory. I. Hamiltonian matrix elements between internally contracted excited valence bond wave functions

    NASA Astrophysics Data System (ADS)

    Chen, Zhenhua; Chen, Xun; Wu, Wei

    2013-04-01

    In this series, the n-body reduced density matrix (n-RDM) approach for nonorthogonal orbitals and their applications to ab initio valence bond (VB) methods are presented. As the first paper of this series, Hamiltonian matrix elements between internally contracted VB wave functions are explicitly provided by means of nonorthogonal orbital based RDM approach. To this end, a more generalized Wick's theorem, called enhanced Wick's theorem, is presented both in arithmetical and in graphical forms, by which the deduction of expressions for the matrix elements between internally contracted VB wave functions is dramatically simplified, and the matrix elements are finally expressed in terms of tensor contractions of electronic integrals and n-RDMs of the reference VB self-consistent field wave function. A string-based algorithm is developed for the purpose of evaluating n-RDMs in an efficient way. Using the techniques presented in this paper, one is able to develop new methods and efficient algorithms for nonorthogonal orbital based many-electron theory much easier than by use of the first quantized formulism.

  17. Nonorthogonal orbital based N-body reduced density matrices and their applications to valence bond theory. I. Hamiltonian matrix elements between internally contracted excited valence bond wave functions.

    PubMed

    Chen, Zhenhua; Chen, Xun; Wu, Wei

    2013-04-28

    In this series, the n-body reduced density matrix (n-RDM) approach for nonorthogonal orbitals and their applications to ab initio valence bond (VB) methods are presented. As the first paper of this series, Hamiltonian matrix elements between internally contracted VB wave functions are explicitly provided by means of nonorthogonal orbital based RDM approach. To this end, a more generalized Wick's theorem, called enhanced Wick's theorem, is presented both in arithmetical and in graphical forms, by which the deduction of expressions for the matrix elements between internally contracted VB wave functions is dramatically simplified, and the matrix elements are finally expressed in terms of tensor contractions of electronic integrals and n-RDMs of the reference VB self-consistent field wave function. A string-based algorithm is developed for the purpose of evaluating n-RDMs in an efficient way. Using the techniques presented in this paper, one is able to develop new methods and efficient algorithms for nonorthogonal orbital based many-electron theory much easier than by use of the first quantized formulism. PMID:23635123

  18. 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

  19. 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

  20. Comparing modern measurements of the {sup 11}B(d,n{gamma}{sub 15.1}){sup 12}C excitation function with previous values

    SciTech Connect

    Cooper, Kevin W.; Massey, Thomas N.; Ingram, David C.

    2013-04-19

    A possible means of active interrogation of special nuclear materials is detection of signature emissions following induced photofission. This method requires a probe gamma-ray beam to induce the photofission. The {sup 11}B(d,n{gamma}{sub 15.1}){sup 12}C reaction is a candidate for the source of this probe beam. The reaction is prolific and the produced 15.1 MeV gamma-ray is close to a photofission cross-section peak for {sup 235,238}U and {sup 238,239}Pu. In order to model an active interrogation system using the {sup 11}B(d,n{gamma}{sub 15.1}){sup 12}C reaction as a source probe an accurate value for its differential crosssection must be included in data libraries. Measurements of the differential cross-section for the {sup 11}B(d,n{gamma}{sub 15.1}){sup 12}C reaction have been carried out with a BGO detector and found to differ from previous measurements reported by Kavanagh (1958) and Kuan (1964). The discrepancy in the measurements may be explained by examining the detector response function used by Kavanagh and presumably Kuan to that modeled with MCNP5. A comparison of the MCNP5 and Kavanagh detector response functions normalized to the 15.1 MeV gamma-ray peak pulse height shows a factor of approximately 1.7 difference in integrated counts. Applying this correction to the differential cross-section previously reported by Kuan brings the values into agreement, within uncertainties, to the more recent measurements. The evaluation of the detector response function for the 15.1 MeV gamma-ray signal in the NaI detector reported by Kavanagh to that modeled by MCNP5 is shown. This result is applied to the comparison of recent measurements on the {sup 11}B(d,n{gamma}{sub 15.1}){sup 12}C reaction differential cross-section to those previously reported.

  1. 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.

  2. Hydrogen Bonds in Excited State Proton Transfer

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Magnetostrictive resonance excitation

    DOEpatents

    Schwarz, Ricardo B.; Kuokkala, Veli-Tapani

    1992-01-01

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

  9. 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.

  10. Phospholipase A2 – nexus of aging, oxidative stress, neuronal excitability, and functional decline of the aging nervous system? Insights from a snail model system of neuronal aging and age-associated memory impairment

    PubMed Central

    Hermann, Petra M.; Watson, Shawn N.; Wildering, Willem C.

    2014-01-01

    The aging brain undergoes a range of changes varying from subtle structural and physiological changes causing only minor functional decline under healthy normal aging conditions, to severe cognitive or neurological impairment associated with extensive loss of neurons and circuits due to age-associated neurodegenerative disease conditions. Understanding how biological aging processes affect the brain and how they contribute to the onset and progress of age-associated neurodegenerative diseases is a core research goal in contemporary neuroscience. This review focuses on the idea that changes in intrinsic neuronal electrical excitability associated with (per)oxidation of membrane lipids and activation of phospholipase A2 (PLA2) enzymes are an important mechanism of learning and memory failure under normal aging conditions. Specifically, in the context of this special issue on the biology of cognitive aging we portray the opportunities offered by the identifiable neurons and behaviorally characterized neural circuits of the freshwater snail Lymnaea stagnalis in neuronal aging research and recapitulate recent insights indicating a key role of lipid peroxidation-induced PLA2 as instruments of aging, oxidative stress and inflammation in age-associated neuronal and memory impairment in this model system. The findings are discussed in view of accumulating evidence suggesting involvement of analogous mechanisms in the etiology of age-associated dysfunction and disease of the human and mammalian brain. PMID:25538730

  11. Spin-flip, tensor equation-of-motion configuration interaction with a density-functional correction: A spin-complete method for exploring excited-state potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Xing; Herbert, John M.

    2015-12-01

    We revisit the formalism of the spin-adapted, spin-flip (SA-SF) configuration-interaction singles (CIS) method based on a tensor equation-of-motion formalism that affords proper spin eigenstates without sacrificing single-reference simplicity. Matrix elements for SA-SF-CIS are then modified in a manner similar to collinear spin-flip time-dependent density functional theory (SF-TDDFT), to include a DFT exchange-correlation correction. The performance of this method, which we call SA-SF-DFT, is evaluated numerically and we find that it systematically improves the energies of electronic states that exhibit significant spin contamination within the conventional SF-TDDFT approach. The new method cures the state assignment problem that plagues geometry optimizations and ab initio molecular dynamics simulations using traditional SF-TDDFT, without sacrificing computational efficiency, and furthermore provides correct topology at conical intersections, including those that involve the ground state, unlike conventional TDDFT. As such, SA-SF-DFT appears to be a promising method for generating excited-state potential energy surfaces at DFT cost.

  12. Spin-flip, tensor equation-of-motion configuration interaction with a density-functional correction: A spin-complete method for exploring excited-state potential energy surfaces

    SciTech Connect

    Zhang, Xing; Herbert, John M.

    2015-12-21

    We revisit the formalism of the spin-adapted, spin-flip (SA-SF) configuration-interaction singles (CIS) method based on a tensor equation-of-motion formalism that affords proper spin eigenstates without sacrificing single-reference simplicity. Matrix elements for SA-SF-CIS are then modified in a manner similar to collinear spin-flip time-dependent density functional theory (SF-TDDFT), to include a DFT exchange-correlation correction. The performance of this method, which we call SA-SF-DFT, is evaluated numerically and we find that it systematically improves the energies of electronic states that exhibit significant spin contamination within the conventional SF-TDDFT approach. The new method cures the state assignment problem that plagues geometry optimizations and ab initio molecular dynamics simulations using traditional SF-TDDFT, without sacrificing computational efficiency, and furthermore provides correct topology at conical intersections, including those that involve the ground state, unlike conventional TDDFT. As such, SA-SF-DFT appears to be a promising method for generating excited-state potential energy surfaces at DFT cost.

  13. 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 .

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Theoretical Studies of Chemical Reactions following Electronic Excitation

    NASA Technical Reports Server (NTRS)

    Chaban, Galina M.

    2003-01-01

    The use of multi-configurational wave functions is demonstrated for several processes: tautomerization reactions in the ground and excited states of the DNA base adenine, dissociation of glycine molecule after electronic excitation, and decomposition/deformation of novel rare gas molecules HRgF. These processes involve bond brealung/formation and require multi-configurational approaches that include dynamic correlation.

  2. 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.

  3. Charge-Transfer Versus Charge-Transfer-Like Excitations Revisited

    SciTech Connect

    Moore, Barry; Sun, Haitao; Govind, Niranjan; Kowalski, Karol; Autschbach, Jochen

    2015-07-14

    Criteria to assess charge-transfer (CT) and `CT-like' character of electronic excitations are examined. Time-dependent density functional theory (TDDFT) with non-hybrid, hybrid, and tuned long-range corrected (LC) functionals is compared with with coupled-cluster (CC) benchmarks. The test set includes an organic CT complex, two `push-pull' donor-acceptor chromophores, a cyanine dye, and several polycyclic aromatic hydrocarbons. Proper CT is easily identified. Excitations with significant density changes upon excitation within regions of close spatial proximity can also be diagnosed. For such excitations, the use of LC functionals in TDDFT sometimes leads to dramatic improvements of the singlet energies, similar to proper CT, which has led to the concept of `CT-like' excitations. However, `CT-like' excitations are not like charge transfer, and the improvements are not obtained for the right reasons. The triplet excitation energies are underestimated for all systems, often severely. For the `CT-like' candidates, when going from a non-hybrid to an LC functional the error in the singlet-triplet (S/T) separation changes from negative to positive, providing error compensation. For the cyanine, the S/T separation is too large with all functionals, leading to the best error compensation for non-hybrid functionals.

  4. 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

  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. The temperature dependence of electrical excitability in fish hearts.

    PubMed

    Vornanen, Matti

    2016-07-01

    Environmental temperature has pervasive effects on the rate of life processes in ectothermic animals. Animal performance is affected by temperature, but there are finite thermal limits for vital body functions, including contraction of the heart. This Review discusses the electrical excitation that initiates and controls the rate and rhythm of fish cardiac contraction and is therefore a central factor in the temperature-dependent modulation of fish cardiac function. The control of cardiac electrical excitability should be sensitive enough to respond to temperature changes but simultaneously robust enough to protect against cardiac arrhythmia; therefore, the thermal resilience and plasticity of electrical excitation are physiological qualities that may affect the ability of fishes to adjust to climate change. Acute changes in temperature alter the frequency of the heartbeat and the duration of atrial and ventricular action potentials (APs). Prolonged exposure to new thermal conditions induces compensatory changes in ion channel expression and function, which usually partially alleviate the direct effects of temperature on cardiac APs and heart rate. The most heat-sensitive molecular components contributing to the electrical excitation of the fish heart seem to be Na(+) channels, which may set the upper thermal limit for the cardiac excitability by compromising the initiation of the cardiac AP at high temperatures. In cardiac and other excitable cells, the different temperature dependencies of the outward K(+) current and inward Na(+) current may compromise electrical excitability at temperature extremes, a hypothesis termed the temperature-dependent depression of electrical excitation. PMID:27385752

  7. The Novel KV7.2/KV7.3 Channel Opener ICA-069673 Reveals Subtype-Specific Functional Roles in Guinea Pig Detrusor Smooth Muscle Excitability and Contractility.

    PubMed

    Provence, Aaron; Malysz, John; Petkov, Georgi V

    2015-09-01

    The physiologic roles of voltage-gated KV7 channel subtypes (KV7.1-KV7.5) in detrusor smooth muscle (DSM) are poorly understood. Here, we sought to elucidate the functional roles of KV7.2/KV7.3 channels in guinea pig DSM excitability and contractility using the novel KV7.2/KV7.3 channel activator ICA-069673 [N-(2-chloro-5-pyrimidinyl)-3,4-difluorobenzamide]. We employed a multilevel experimental approach using Western blot analysis, immunocytochemistry, isometric DSM tension recordings, fluorescence Ca(2+) imaging, and perforated whole-cell patch-clamp electrophysiology. Western blot experiments revealed the protein expression of KV7.2 and KV7.3 channel subunits in DSM tissue. In isolated DSM cells, immunocytochemistry with confocal microscopy further confirmed protein expression for KV7.2 and KV7.3 channel subunits, where they localize within the vicinity of the cell membrane. ICA-069673 inhibited spontaneous phasic, pharmacologically induced, and nerve-evoked contractions in DSM isolated strips in a concentration-dependent manner. The inhibitory effects of ICA-069673 on DSM spontaneous phasic and tonic contractions were abolished in the presence of the KV7 channel inhibitor XE991 [10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone dihydrochloride]. Under conditions of elevated extracellular K(+) (60 mM), the effects of ICA-069673 on DSM tonic contractions were significantly attenuated. ICA-069673 decreased the global intracellular Ca(2+) concentration in DSM cells, an effect blocked by the L-type Ca(2+) channel inhibitor nifedipine. ICA-069673 hyperpolarized the membrane potential and inhibited spontaneous action potentials of isolated DSM cells, effects that were blocked in the presence of XE991. In conclusion, using the novel KV7.2/KV7.3 channel activator ICA-069673, this study provides strong evidence for a critical role for the KV7.2- and KV7.3-containing channels in DSM function at both cellular and tissue levels.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. Excited-State Dynamics of Overlapped Optically-Allowed 1Bu+ and Optically-Forbidden 1Bu− or 3Ag− Vibronic Levels of Carotenoids: Possible Roles in the Light-Harvesting Function

    PubMed Central

    Koyama, Yasushi; Kakitani, Yoshinori; Miki, Takeshi; Christiana, Rebecca; Nagae, Hiroyoshi

    2010-01-01

    The unique excited-state properties of the overlapped (diabatic) optically-allowed 1Bu+ and the optically-forbidden 1Bu− or 3Ag− vibronic levels close to conical intersection (‘the diabatic pair’) are summarized: Pump-probe spectroscopy after selective excitation with ∼100 fs pulses of all-trans carotenoids (Cars) in nonpolar solvent identified a symmetry selection rule in the diabatic electronic mixing and diabatic internal conversion, i.e., ‘1Bu+-to-1Bu− is allowed but 1Bu+-to-3Ag− is forbidden’. On the other hand, pump-probe spectroscopy after coherent excitation with ∼30 fs of all-trans Cars in THF generated stimulated emission with quantum beat, consisting of the long-lived coherent diabatic cross term and a pair of short-lived incoherent terms. PMID:20480049

  14. 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.

  15. 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.

  16. Calculating singlet excited states: Comparison with fast time-resolved infrared spectroscopy of coumarins

    NASA Astrophysics Data System (ADS)

    Hanson-Heine, Magnus W. D.; Wriglesworth, Alisdair; Uroos, Maliha; Calladine, James A.; Murphy, Thomas S.; Hamilton, Michelle; Clark, Ian P.; Towrie, Michael; Dowden, James; Besley, Nicholas A.; George, Michael W.

    2015-04-01

    In contrast to the ground state, the calculation of the infrared (IR) spectroscopy of molecular singlet excited states represents a substantial challenge. Here, we use the structural IR fingerprint of the singlet excited states of a range of coumarin dyes to assess the accuracy of density functional theory based methods for the calculation of excited state IR spectroscopy. It is shown that excited state Kohn-Sham density functional theory provides a high level of accuracy and represents an alternative approach to time-dependent density functional theory for simulating the IR spectroscopy of singlet excited states.

  17. Calculating singlet excited states: Comparison with fast time-resolved infrared spectroscopy of coumarins.

    PubMed

    Hanson-Heine, Magnus W D; Wriglesworth, Alisdair; Uroos, Maliha; Calladine, James A; Murphy, Thomas S; Hamilton, Michelle; Clark, Ian P; Towrie, Michael; Dowden, James; Besley, Nicholas A; George, Michael W

    2015-04-21

    In contrast to the ground state, the calculation of the infrared (IR) spectroscopy of molecular singlet excited states represents a substantial challenge. Here, we use the structural IR fingerprint of the singlet excited states of a range of coumarin dyes to assess the accuracy of density functional theory based methods for the calculation of excited state IR spectroscopy. It is shown that excited state Kohn-Sham density functional theory provides a high level of accuracy and represents an alternative approach to time-dependent density functional theory for simulating the IR spectroscopy of singlet excited states.

  18. 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.

  19. 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.

  20. Calculation for the excitation functions of the {sup 93}Nb(p,n){sup 93}Mo{sup m}, {sup 93}Nb(p,{alpha}n){sup 89}Zr, and {sup 93}Nb(p,np+pn){sup 92}Nb{sup m} reactions

    SciTech Connect

    Gul, K.

    2009-04-15

    Statistical model calculation has been carried out for the excitation functions of the {sup 93}Nb(p,n){sup 93}Mo{sup m}, {sup 93}Nb(p,{alpha}n){sup 89}Zr, and {sup 93}Nb(p,np+pn){sup 92}Nb{sup m} reactions up to a 20-MeV proton energy range using global reaction parameters. The results are compared and discussed with reported measurements. The calculation for the excitation function of the {sup 93}Nb(p,n){sup 93}Mo{sup m} reaction can only match the measured magnitudes of cross sections if we postulate the existence of two energy levels with spin-parity values of 19/2{sup +} and 17/2{sup -} lying immediately above the 2.425 MeV (21/2{sup +}) isomeric state. The existence of the hypothetical levels has been discussed in the light of reported shell-model calculations.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Nitric oxide and the autonomic regulation of cardiac excitability. The G.L. Brown Prize Lecture.

    PubMed

    Paterson, D

    2001-01-01

    Cardiac sympathetic imbalance and arrhythmia; Nitric oxide-cGMP pathway and the cholinergic modulation of cardiac excitability; Nitric oxide-cGMP pathway and the sympathetic modulation of cardiac excitability; Functional significance of nitric oxide in the autonomic regulation of cardiac excitability; Summary; References. Experimental Physiology (2001) 86.1, 1-12.

  7. Nitric oxide and the autonomic regulation of cardiac excitability. The G.L. Brown Prize Lecture.

    PubMed

    Paterson, D

    2001-01-01

    Cardiac sympathetic imbalance and arrhythmia; Nitric oxide-cGMP pathway and the cholinergic modulation of cardiac excitability; Nitric oxide-cGMP pathway and the sympathetic modulation of cardiac excitability; Functional significance of nitric oxide in the autonomic regulation of cardiac excitability; Summary; References. Experimental Physiology (2001) 86.1, 1-12. PMID:11429613

  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. 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. 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.

  12. Amino Acid Mean Excitation Energies and Directional Dependencies from Core and Bond Calculations

    SciTech Connect

    Sabin, John R.; Oddershede, Jens; Sauer, Stephan P. A.

    2008-12-08

    We determine the mean excitation energies of several amino acids using a Bragg Rule developed for molecular fragments or functional groups. As the composition of the amino acids is very similar, we find that the amino acids have similar mean excitation energies (approximately 70 eV). Differences arise from variation of the side chains (-R); addition of-CH2-groups decreases the mean excitation energy. We also speculate concerning the directional dependence of the amino acid mean excitation energies.

  13. 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.

  14. 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.

  15. A note on calm excited states of inflation

    SciTech Connect

    Ashoorioon, Amjad; Shiu, Gary E-mail: shiu@physics.wisc.edu

    2011-03-01

    We identify a two-parameter family of excited states within slow-roll inflation for which either the corrections to the two-point function or the characteristic signatures of excited states in the three-point function — i.e. the enhancement for the flattened momenta configurations– are absent. These excited states may nonetheless violate the adiabaticity condition maximally. We dub these initial states of inflation calm excited states. We show that these two sets do not intersect, i.e., those that leave the power-spectrum invariant can be distinguished from their bispectra, and vice versa. The same set of calm excited states that leave the two-point function invariant for slow-roll inflation, do the same task for DBI inflation. However, at the level of three-point function, the calm excited states whose flattened configuration signature is absent for slow-roll inflation, will lead to an enhancement for DBI inflation generally, although the signature is smaller than what suggested by earlier analysis. This example also illustrates that imposing the Wronskian condition is important for obtaining a correct estimate of the non-Gaussian signatures.

  16. 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.

  17. 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

  18. Rotational excitation of physisorbed molecules by resonant electron scattering

    NASA Astrophysics Data System (ADS)

    Teillet-Billy, D.; Gauyacq, J. P.

    2002-04-01

    The resonant rotational excitation of physisorbed H 2 molecules by low energy electron impact is studied using the rotational sudden approximation. The rotational excitation efficiency is analysed as a function of the constraint imposed on the molecular rotation by the adsorption. This allows the description of the variation of the energy loss spectrum corresponding to rovibrational excitation as a function of the constraint on molecular rotation. This model study is then used to discuss the recent results by Svensson et al. [Phys. Rev. Lett. 83 (1999) 124] on the rovibrational excitation of H 2 molecules adsorbed at steps on Cu(5 1 0), in terms of quasi-2D rotor and of constrained 3D rotors.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. Excited nucleon spectrum with two flavors of dynamical fermions

    SciTech Connect

    M. Bulava, John; Edward, Robert; Engelson, Eric; Joo, Balint; Lichtl, Adam; Lin, Huey-Wen; Mathur, Nilmani; Morningstar, Colin; Richards, David; Wallace, Stephen

    2009-01-01

    We compute the spectrum of excited nucleons using the anisotropic Wilson lattice with two flavors of dynamical fermions. Using optimized sets of operators which transform irreducibly under the octahedral group, matrices of correlation functions are computed. We apply the variational method to these matrices to extract excited energy eigenstates. We obtain several states for each irrep and identify the continuum spin for the lowest-lying states, including a $J^P={5/2}^-$ state.

  4. 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.

  5. A benchmark study of electronic excitation energies, transition moments, and excited-state energy gradients on the nicotine molecule

    SciTech Connect

    Egidi, Franco Segado, Mireia; Barone, Vincenzo; Koch, Henrik; Cappelli, Chiara

    2014-12-14

    In this work, we report a comparative study of computed excitation energies, oscillator strengths, and excited-state energy gradients of (S)-nicotine, chosen as a test case, using multireference methods, coupled cluster singles and doubles, and methods based on time-dependent density functional theory. This system was chosen because its apparent simplicity hides a complex electronic structure, as several different types of valence excitations are possible, including n-π{sup *}, π-π{sup *}, and charge-transfer states, and in order to simulate its spectrum it is necessary to describe all of them consistently well by the chosen method.

  6. A benchmark study of electronic excitation energies, transition moments, and excited-state energy gradients on the nicotine molecule

    NASA Astrophysics Data System (ADS)

    Egidi, Franco; Segado, Mireia; Koch, Henrik; Cappelli, Chiara; Barone, Vincenzo

    2014-12-01

    In this work, we report a comparative study of computed excitation energies, oscillator strengths, and excited-state energy gradients of (S)-nicotine, chosen as a test case, using multireference methods, coupled cluster singles and doubles, and methods based on time-dependent density functional theory. This system was chosen because its apparent simplicity hides a complex electronic structure, as several different types of valence excitations are possible, including n-π*, π-π*, and charge-transfer states, and in order to simulate its spectrum it is necessary to describe all of them consistently well by the chosen method.

  7. Analysis of the geodetic residuals as differences between geodetic and sum of the atmospheric and ocean excitation of polar motion

    NASA Astrophysics Data System (ADS)

    Kolaczek, B.; Pasnicka, M.; Nastula, J.

    2012-12-01

    Up to now studies of geophysical excitation of polar motion containing AAM (Atmospheric Angular Momentum), OAM (Oceanic Angular Momentum) and HAM (Hydrological Angular Momentum) excitation functions of polar motion have not achieved the total agreement between geophysical and determined geodetic excitation (GAM, Geodetic AngularMomentum) functions of polar motion...

  8. The triplet excited state of Bodipy: formation, modulation and application.

    PubMed

    Zhao, Jianzhang; Xu, Kejing; Yang, Wenbo; Wang, Zhijia; Zhong, Fangfang

    2015-12-21

    Boron dipyrromethene (Bodipy) is one of the most extensively investigated organic chromophores. Most of the investigations are focused on the singlet excited state of Bodipy, such as fluorescence. In stark contrast, the study of the triplet excited state of Bodipy is limited, but it is an emerging area, since the triplet state of Bodipy is tremendously important for several areas, such as the fundamental photochemistry study, photodynamic therapy (PDT), photocatalysis and triplet-triplet annihilation (TTA) upconversion. The recent developments in the study of the production, modulation and application of the triplet excited state of Bodipy are discussed in this review article. The formation of the triplet state of Bodipy upon photoexcitation, via the well known approach such as the heavy atom effect (including I, Br, Ru, Ir, etc.), and the new methods, such as using a spin converter (e.g. C60), charge recombination, exciton coupling and the doubly substituted excited state, are summarized. All the Bodipy-based triplet photosensitizers show strong absorption of visible or near IR light and the long-lived triplet excited state, which are important for the application of the triplet excited state in PDT or photocatalysis. Moreover, the methods for switching (or modulation) of the triplet excited state of Bodipy were discussed, such as those based on the photo-induced electron transfer (PET), by controlling the competing Förster-resonance-energy-transfer (FRET), or the intermolecular charge transfer (ICT). Controlling the triplet excited state will give functional molecules such as activatable PDT reagents or molecular devices. It is worth noting that switching of the singlet excited state and the triplet state of Bodipy may follow different principles. Application of the triplet excited state of Bodipy in PDT, hydrogen (H2) production, photoredox catalytic organic reactions and TTA upconversion were discussed. The challenges and the opportunities in these areas were

  9. 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.

  10. Electron impact excitation of highly charged sodium-like ions

    NASA Technical Reports Server (NTRS)

    Blaha, M.; Davis, J.

    1978-01-01

    Optical transition probabilities and electron collision strengths for Ca X, Fe XVI, Zn XX, Kr XXVI and Mo XXXII are calculated for transitions between n equal to 3 and n equal to 4 levels. The calculations neglect relativistic effects on the radial functions. A semi-empirical approach provides wave functions of the excited states; a distorted wave function without exchange is employed to obtain the excitation cross sections. The density dependence of the relative intensities of certain emission lines in the sodium isoelectronic sequence is also discussed.

  11. 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

  12. 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.

  13. Excitation of earth's polar motion by atmospheric angular momentum variations, 1980-1990

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin F.

    1993-01-01

    We compute the polar-motion excitation function due to the atmospheric angular momentum (AAM) for both IB (inverted-barometer) and non-IB cases, as well as the excitation function from geodetically observed Earth orientation data for the period 1980-1990. The two are then compared in studying the AAM contribution to the polar motion excitation. The polar drifts with periods longer than about two years have similar characteristics, but the comparison is inconclusive because of data uncertainties. For the seasonal wobble excitation, the agreement is poor except for the prograde annual wobble, indicating the influence of other geophysical excitations than AAM. For the Chandler wobble excitation, a correlation coefficient of 0.53 for non-IB and 0.58 for IB are found for 1986-1990. Together with a coherence spectral analysis, they clearly demonstrate a strong contribution of AAM to the Chandler wobble excitation.

  14. 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.

  15. 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

  16. 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.

  17. Shell-model description of E1 excitation

    NASA Astrophysics Data System (ADS)

    Shimizu, Noritaka; Utsuno, Yutaka; Togashi, Tomoaki; Otsuka, Takaharu; Honma, Michio

    2014-09-01

    We discuss a microscopic description of E1 excitations based on shell-model calculations. We performed large-scale shell-model calculations for Ca isotopes with Lanczos-strength-function method and sd - pf - sdg model space allowing up to 3 ℏω excitation and obtained their photoabsorption cross sections. It gives a very good description of giant dipole and low-lying pygmy resonances rather independently of smoothing parameter. We also present the feasiblity of the Monte Carlo shell model (MCSM) to study the E1 excitation in order to to treat larger model space. By using the MCSM we discuss some results about light nuclei. We discuss a microscopic description of E1 excitations based on shell-model calculations. We performed large-scale shell-model calculations for Ca isotopes with Lanczos-strength-function method and sd - pf - sdg model space allowing up to 3 ℏω excitation and obtained their photoabsorption cross sections. It gives a very good description of giant dipole and low-lying pygmy resonances rather independently of smoothing parameter. We also present the feasiblity of the Monte Carlo shell model (MCSM) to study the E1 excitation in order to to treat larger model space. By using the MCSM we discuss some results about light nuclei. This study is supported by HPCI strategic program field 5 and KAKENHI Grand 25870168.

  18. 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

  19. 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

  20. Indirect excitation of ultrafast demagnetization

    DOE PAGES

    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

  1. 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.

  2. 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.

  3. Up-converted fluorescence from photosynthetic light-harvesting complexes linearly dependent on excitation intensity.

    PubMed

    Leiger, Kristjan; Freiberg, Arvi

    2016-01-01

    Weak up-converted fluorescence related to bacteriochlorophyll a was recorded from various detergent-isolated and membrane-embedded light-harvesting pigment-protein complexes as well as from the functional membranes of photosynthetic purple bacteria under continuous-wave infrared laser excitation at 1064 nm, far outside the optically allowed singlet absorption bands of the chromophore. The fluorescence increases linearly with the excitation power, distinguishing it from the previously observed two-photon excited fluorescence upon femtosecond pulse excitation. Possible mechanisms of this excitation are discussed.

  4. Excitation of singlet levels of a singly charged scandium ion in e-Sc collisions

    NASA Astrophysics Data System (ADS)

    Smirnov, Yu. M.

    2011-09-01

    The excitation of singlet levels of the singly charged scandium ion is experimentally studied in collisions of slow electrons with scandium atoms. At the exciting electron energy of 30 eV, 59 excitation cross sections are measured. In the electron energy range of 0-200 eV, seven optical excitation functions are recorded. On the basis of these data the total excitation cross sections are calculated for 11 even and 9 odd levels of Sc II, as well as the contribution of cascade population to 8 even and 7 odd levels.

  5. TlII excitation cross-sections in collisions of slow electrons with thallium atoms

    NASA Astrophysics Data System (ADS)

    Smirnov, Yu M.

    2016-09-01

    Excitation of a singly-charged thallium ion in electron collisions with thallium atoms has been studied experimentally. Seventy excitation cross sections have been measured at an exciting electron energy of 30 eV. Ten optical excitation functions (OEFs) have been recorded in the incident electron energy range of 0-200 eV. For seven TlII spectral series, the dependence of excitation cross-sections on the principal quantum numbers of upper levels has been studied. A comparison of findings with data from preceding publications is presented.

  6. The heating of interstellar clouds by vibrationally excited molecular hydrogen

    NASA Technical Reports Server (NTRS)

    Stecher, T. P.; Williams, D. A.

    1972-01-01

    The possibility that vibrationally excited H2 may be collisionally de-excited, so providing a heating mechanism for interstellar clouds which operates by coupling the stellar radiation to the gas, is discussed. The majority of excitations in the Lyman and Werner bands of H2 return the molecules to the ground electronic state in a vibrationally excited level, the most favored level being 7. The heating rate obtained in this way is compared with other mechanisms which have been postulated, and the results of calculations of temperature as a function of depth into clouds of different densities are presented. It appears that this mechanism is a significant one, which should be taken into account in detailed models of dense clouds.

  7. Photoionization of ground and excited states of Ti I

    NASA Astrophysics Data System (ADS)

    Nahar, Sultana N.

    2015-07-01

    Detailed photoionization of ground and many excited states with autoionizing resonances of neutral Ti are presented. Ti I with 22 electrons forms a large number of bound states, the present work finds a total of 908 bound states with n ⩽ 10 and l ⩽ 8 . Photoionization cross sections (σPI) for all these bound states have been obtained. Calculations were carried out in the close-coupling R-matrix method using a wave function expansion that included 36 states of core ion Ti II. It is found that the resonances enhance the low energy region of photoionization of the ground and low lying excited states. The resonant features will increase the opacity, as expected of astrophysical observation, and hence play important role in determination of abundances in the elements in the astronomical objects. The excited states also show prominent structures of Seaton or photo-excitation-of-core resonances.

  8. Excitation of weakly bound molecules to trilobitelike Rydberg states.

    PubMed

    Bellos, M A; Carollo, R; Banerjee, J; Eyler, E E; Gould, P L; Stwalley, W C

    2013-08-01

    We observe "trilobitelike" states of ultracold (85)Rb(2) molecules, in which a ground-state atom is bound by the electronic wave function of its Rydberg-atom partner. We populate these states through the ultraviolet excitation of weakly bound molecules, and access a regime of trilobitelike states at low principal quantum numbers and with vibrational turning points around 35 Bohr radii. This demonstrates that, unlike previous studies that used free-to-bound transitions, trilobitelike states can also be excited through bound-to-bound transitions. This approach provides high excitation probabilities without requiring high-density samples, and affords the ability to control the excitation radius by selection of the initial-state vibrational level.

  9. Photothermally excited force modulation microscopy for broadband nanomechanical property measurements

    SciTech Connect

    Wagner, Ryan Killgore, Jason P.

    2015-11-16

    We demonstrate photothermally excited force modulation microscopy (PTE FMM) for mechanical property characterization across a broad frequency range with an atomic force microscope (AFM). Photothermal excitation allows for an AFM cantilever driving force that varies smoothly as a function of drive frequency, thus avoiding the problem of spurious resonant vibrations that hinder piezoelectric excitation schemes. A complication of PTE FMM is that the sub-resonance cantilever vibration shape is fundamentally different compared to piezoelectric excitation. By directly measuring the vibrational shape of the cantilever, we show that PTE FMM is an accurate nanomechanical characterization method. PTE FMM is a pathway towards the characterization of frequency sensitive specimens such as polymers and biomaterials with frequency range limited only by the resonance frequency of the cantilever and the low frequency limit of the AFM.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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...

  16. 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...

  17. 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...

  18. 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

  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. Regional Multi-Fluid-Based Geophysical Excitation of Polar Motion

    NASA Technical Reports Server (NTRS)

    Nastula, Jolanta; Salstein, David A.; Gross, Richard

    2011-01-01

    By analyzing geophysical fluids geographic distribution, we can isolate the regional provenance for some of the important signals in polar motion. An understanding of such will enable us to determine whether certain climate signals can have an impact on polar motion. Here we have compared regional patterns of three surficial fluids: the atmosphere, ocean and land-based hydrosphere. The oceanic excitation function of polar motion was estimated with the ECCO/JPL data - assimilating model, and the atmospheric excitation function was determined from NCEP/NCAR reanalyses. The excitation function due to land hydrology was estimated from the Gravity Recovery and Climate Experiment (GRACE) data by an indirect approach that determines water thickness. Our attention focuses on the regional distribution of atmospheric and oceanic excitation of the annual and Chandler wobbles during 1993-2010, and on hydrologic excitation of these wobbles during 2002.9-2011.5. It is found that the regions of maximum fractional covariance (those exceeding a value of 3 .10 -3) for the annual band are over south Asia, southeast Asia and south central Indian ocean, for hydrology, atmosphere and ocean respectively; and for the Chandler period, areas over North America, Asia, and South America; and scattered across the southern oceans for the atmosphere and oceans respectively

  7. 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.

  8. 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.

  9. Excited-State Deactivation of Branched Phthalocyanine Compounds.

    PubMed

    Zhu, Huaning; Li, Yang; Chen, Jun; Zhou, Meng; Niu, Yingli; Zhang, Xinxing; Guo, Qianjin; Wang, Shuangqing; Yang, Guoqiang; Xia, Andong

    2015-12-21

    The excited-state relaxation dynamics and chromophore interactions in two phthalocyanine compounds (bis- and trisphthalocyanines) are studied by using steady-state and femtosecond transient absorption spectral measurements, where the excited-state energy-transfer mechanism is explored. By exciting phthalocyanine compounds to their second electronically excited states and probing the subsequent relaxation dynamics, a multitude of deactivation pathways are identified. The transient absorption spectra show the relaxation pathway from the exciton state to excimer state and then back to the ground state in bisphthalocyanine (bis-Pc). In trisphthalocyanine (tris-Pc), the monomeric and dimeric subunits are excited and the excitation energy transfers from the monomeric vibrationally hot S1 state to the exciton state of a pre-associated dimer, with subsequent relaxation to the ground state through the excimer state. The theoretical calculations and steady-state spectra also show a face-to-face conformation in bis-Pc, whereas in tris-Pc, two of the three phthalocyanine branches form a pre-associated face-to-face dimeric conformation with the third one acting as a monomeric unit; this is consistent with the results of the transient absorption experiments from the perspective of molecular structure. The detailed structure-property relationships in phthalocyanine compounds is useful for exploring the function of molecular aggregates in energy migration of natural photosynthesis systems.

  10. Change in types of neuronal excitability via bifurcation control.

    PubMed

    Xie, Yong; Aihara, Kazuyuki; Kang, Yan Mei

    2008-02-01

    This paper proposes an approach to changing the types of neuronal excitability via bifurcation control. A washout filter-aided dynamic feedback controller is introduced to bifurcation dynamics of a two-dimensional Hindmarsh-Rose type model neuron, which shows a saddle-node on invariant circle (SNIC) bifurcation from quiescence to periodic spiking and then exhibits type-I excitability. At first, a Hopf bifurcation is created at a desired parameter value before the SNIC bifurcation occurs, and then the criticality of the created Hopf bifurcation is regulated by choosing appropriate values of the controller parameters. In this manner, the model neuron starts to show type-II excitability. Therefore the type of neuronal excitability is transformed from type-I excitability to type-II excitability for the model neuron via the washout filter-aided dynamic feedback controller. In such a controller, the linear control gain is determined by the two basic critical conditions for the Hopf bifurcation, i.e., the eigenvalue assignment and the transversality condition. We apply the center manifold and normal form theory to deduce a closed-form analytic expression for the bifurcation stability coefficient, which is a function with respect to the nonlinear control gain. A suitable nonlinear control gain is chosen to make the bifurcation stability coefficient negative, and thus the criticality of the created Hopf bifurcation can be changed from subcritical to supercritical. In addition, the amplitude of the corresponding periodic solution can be also regulated by the nonlinear control gain.

  11. Is event-related desynchronization a biomarker representing corticospinal excitability?

    PubMed

    Takemi, Mitsuaki; Masakado, Yoshihisa; Liu, Meigen; Ushiba, Junichi

    2013-01-01

    Brain computer interfaces (BCIs) using event-related desynchronization (ERD) of the electroencephalogram (EEG), which is believed to represent increased activation of the sensorimotor cortex, have attracted attention as tools for rehabilitation of upper limb motor functions in hemiplegic stroke patients. However, it remains unclear whether the corticospinal excitability is actually correlated with ERD. The purpose of this study was to assess the association between the ERD magnitude and the excitability of primary motor cortex (M1) and spinal motoneurons. M1 excitability was tested by motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) using transcranial magnetic stimulation, and spinal motoneuronal excitability was tested by F-waves using peripheral nerve stimulation. Results showed that large ERD during motor imagery was associated with significantly increased F-wave persistence and reduced SICI, but no significant changes in ICF and the response average of F-wave amplitudes. Our findings suggest that ERD magnitude during motor imagery represents the instantaneous excitability of both M1 and spinal motoneurons. This study provides electrophysiological evidence that ERD-based BCI with motor imagery task increases corticospinal excitability as changes accompanying actual movements.

  12. Dissociative excitation and fragmentation of S8 by electron impact.

    PubMed

    Brotton, S J; McConkey, J W

    2011-05-28

    The vacuum-ultraviolet emission spectrum from 136 nm to 168 nm following the dissociative excitation of a predominantly S(8) target by electron impact at 100 eV incident energy was measured. The relative cross sections for the dominant multiplets at 138.9, 142.9, 147.9, and 166.7 nm are presented. Excitation functions are shown for electron-impact energies from below threshold to 360 eV for the two most prominent emissions at 142.5 nm and 147.4 nm. Five thresholds are clearly apparent in both excitation functions. For the four highest energy channels, the energy separation between the adjacent thresholds is approximately constant and the cross sections reduce regularly as the threshold energies increase. We suggest possible fragmentation pathways of the dissociating S(8) molecule that reproduce the energies of our observed thresholds.

  13. Excitation energies along a range-separated adiabatic connection

    SciTech Connect

    Rebolini, Elisa Toulouse, Julien Savin, Andreas; Teale, Andrew M.; Helgaker, Trygve

    2014-07-28

    We present a study of the variation of total energies and excitation energies along a range-separated adiabatic connection. This connection links the non-interacting Kohn–Sham electronic system to the physical interacting system by progressively switching on the electron–electron interactions whilst simultaneously adjusting a one-electron effective potential so as to keep the ground-state density constant. The interactions are introduced in a range-dependent manner, first introducing predominantly long-range, and then all-range, interactions as the physical system is approached, as opposed to the conventional adiabatic connection where the interactions are introduced by globally scaling the standard Coulomb interaction. Reference data are reported for the He and Be atoms and the H{sub 2} molecule, obtained by calculating the short-range effective potential at the full configuration-interaction level using Lieb's Legendre-transform approach. As the strength of the electron–electron interactions increases, the excitation energies, calculated for the partially interacting systems along the adiabatic connection, offer increasingly accurate approximations to the exact excitation energies. Importantly, the excitation energies calculated at an intermediate point of the adiabatic connection are much better approximations to the exact excitation energies than are the corresponding Kohn–Sham excitation energies. This is particularly evident in situations involving strong static correlation effects and states with multiple excitation character, such as the dissociating H{sub 2} molecule. These results highlight the utility of long-range interacting reference systems as a starting point for the calculation of excitation energies and are of interest for developing and analyzing practical approximate range-separated density-functional methodologies.

  14. Characterizing RNA Excited States Using NMR Relaxation Dispersion.

    PubMed

    Xue, Yi; Kellogg, Dawn; Kimsey, Isaac J; Sathyamoorthy, Bharathwaj; Stein, Zachary W; McBrairty, Mitchell; Al-Hashimi, Hashim M

    2015-01-01

    Changes in RNA secondary structure play fundamental roles in the cellular functions of a growing number of noncoding RNAs. This chapter describes NMR-based approaches for characterizing microsecond-to-millisecond changes in RNA secondary structure that are directed toward short-lived and low-populated species often referred to as "excited states." Compared to larger scale changes in RNA secondary structure, transitions toward excited states do not require assistance from chaperones, are often orders of magnitude faster, and are localized to a small number of nearby base pairs in and around noncanonical motifs. Here, we describe a procedure for characterizing RNA excited states using off-resonance R1ρ NMR relaxation dispersion utilizing low-to-high spin-lock fields (25-3000 Hz). R1ρ NMR relaxation dispersion experiments are used to measure carbon and nitrogen chemical shifts in base and sugar moieties of the excited state. The chemical shift data are then interpreted with the aid of secondary structure prediction to infer potential excited states that feature alternative secondary structures. Candidate structures are then tested by using mutations, single-atom substitutions, or by changing physiochemical conditions, such as pH and temperature, to either stabilize or destabilize the candidate excited state. The resulting chemical shifts of the mutants or under different physiochemical conditions are then compared to those of the ground and excited states. Application is illustrated with a focus on the transactivation response element from the human immune deficiency virus type 1, which exists in dynamic equilibrium with at least two distinct excited states. PMID:26068737

  15. Characterizing RNA Excited States using NMR Relaxation Dispersion

    PubMed Central

    Xue, Yi; Kellogg, Dawn; Kimsey, Isaac J; Sathyamoorthy, Bharathwaj; Stein, Zachary W; McBrairty, Mitchell; Al-Hashimi, Hashim M.

    2016-01-01

    Changes in RNA secondary structure play fundamental roles in the cellular functions of a growing number of non-coding RNAs. This chapter describes NMR-based approaches for characterizing microsecond-to-millisecond changes in RNA secondary structure that are directed toward short-lived and low-populated species often referred to as “excited states”. Compared to larger-scale changes in RNA secondary structure, transitions towards excited states do not require assistance from chaperones, are often orders of magnitude faster, and are localized to a small number of nearby base pairs in and around non-canonical motifs. Here we describe a procedure for characterizing RNA excited states using off-resonance R1ρ NMR relaxation dispersion utilizing low-to-high spin-lock fields (25–3000 Hz). R1ρ NMR relaxation dispersion experiments are used to measure carbon and nitrogen chemical shifts in base and sugar moieties of the excited state. The chemical shift data is then interpreted with the aid of secondary structure prediction to infer potential excited states that feature alternative secondary structures. Candidate structures are then tested by using mutations, single-atom substitutions, or by changing physiochemical conditions, such as pH and temperature, to either stabilize or destabilize the candidate excited state. The resulting chemical shifts of the mutants or under different physiochemical conditions are then compared to those of the ground and excited state. Application is illustrated with a focus on the transactivation response element (TAR) from the human immune deficiency virus type 1 (HIV-1), which exists in dynamic equilibrium with at least two distinct excited states. PMID:26068737

  16. Characterizing RNA Excited States Using NMR Relaxation Dispersion.

    PubMed

    Xue, Yi; Kellogg, Dawn; Kimsey, Isaac J; Sathyamoorthy, Bharathwaj; Stein, Zachary W; McBrairty, Mitchell; Al-Hashimi, Hashim M

    2015-01-01

    Changes in RNA secondary structure play fundamental roles in the cellular functions of a growing number of noncoding RNAs. This chapter describes NMR-based approaches for characterizing microsecond-to-millisecond changes in RNA secondary structure that are directed toward short-lived and low-populated species often referred to as "excited states." Compared to larger scale changes in RNA secondary structure, transitions toward excited states do not require assistance from chaperones, are often orders of magnitude faster, and are localized to a small number of nearby base pairs in and around noncanonical motifs. Here, we describe a procedure for characterizing RNA excited states using off-resonance R1ρ NMR relaxation dispersion utilizing low-to-high spin-lock fields (25-3000 Hz). R1ρ NMR relaxation dispersion experiments are used to measure carbon and nitrogen chemical shifts in base and sugar moieties of the excited state. The chemical shift data are then interpreted with the aid of secondary structure prediction to infer potential excited states that feature alternative secondary structures. Candidate structures are then tested by using mutations, single-atom substitutions, or by changing physiochemical conditions, such as pH and temperature, to either stabilize or destabilize the candidate excited state. The resulting chemical shifts of the mutants or under different physiochemical conditions are then compared to those of the ground and excited states. Application is illustrated with a focus on the transactivation response element from the human immune deficiency virus type 1, which exists in dynamic equilibrium with at least two distinct excited states.

  17. 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.

  18. Visible-wavelength two-photon excitation microscopy for fluorescent protein imaging

    NASA Astrophysics Data System (ADS)

    Yamanaka, Masahito; Saito, Kenta; Smith, Nicholas I.; Arai, Yoshiyuki; Uegaki, Kumiko; Yonemaru, Yasuo; Mochizuki, Kentaro; Kawata, Satoshi; Nagai, Takeharu; Fujita, Katsumasa

    2015-10-01

    The simultaneous observation of multiple fluorescent proteins (FPs) by optical microscopy is revealing mechanisms by which proteins and organelles control a variety of cellular functions. Here we show the use of visible-light based two-photon excitation for simultaneously imaging multiple FPs. We demonstrated that multiple fluorescent targets can be concurrently excited by the absorption of two photons from the visible wavelength range and can be applied in multicolor fluorescence imaging. The technique also allows simultaneous single-photon excitation to offer simultaneous excitation of FPs across the entire range of visible wavelengths from a single excitation source. The calculation of point spread functions shows that the visible-wavelength two-photon excitation provides the fundamental improvement of spatial resolution compared to conventional confocal microscopy.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Self-excited multifractal dynamics

    NASA Astrophysics Data System (ADS)

    Filimonov, V.; Sornette, D.

    2011-05-01

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

  7. Atomic electron excitation probabilities during orbital electron capture by the nucleus

    NASA Technical Reports Server (NTRS)

    Crasemann, B.; Chen, M. H.; Briand, J. P.; Chevallier, P.; Chetioui, A.; Tavernier, M.

    1979-01-01

    Approximate probabilities of electron excitation (shakeup/shakeoff) from various atomic states during nuclear ns electron capture have been calculated in the sudden approximation, using Hartree-Fock wave functions. Total excitation probabilities are much lower than during inner-shell ionization by photons or electrons, and ns states are more likely to be excited than np states. This latter result is borne out by K-alpha X-ray satellite spectra.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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)

  13. 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

  14. Prolactin receptor in regulation of neuronal excitability and channels.

    PubMed

    Patil, Mayur J; Henry, Michael A; Akopian, Armen N

    2014-01-01

    Prolactin (PRL) activates PRL receptor isoforms to exert regulation of specific neuronal circuitries, and to control numerous physiological and clinically-relevant functions including; maternal behavior, energy balance and food intake, stress and trauma responses, anxiety, neurogenesis, migraine and pain. PRL controls these critical functions by regulating receptor potential thresholds, neuronal excitability and/or neurotransmission efficiency. PRL also influences neuronal functions via activation of certain neurons, resulting in Ca(2+) influx and/or electrical firing with subsequent release of neurotransmitters. Although PRL was identified almost a century ago, very little specific information is known about how PRL regulates neuronal functions. Nevertheless, important initial steps have recently been made including the identification of PRL-induced transient signaling pathways in neurons and the modulation of neuronal transient receptor potential (TRP) and Ca(2+) -dependent K(+) channels by PRL. In this review, we summarize current knowledge and recent progress in understanding the regulation of neuronal excitability and channels by PRL.

  15. Comparison of regional hydrological excitation of polar motion derived from hydrological models and the GRACE gravity field data

    NASA Astrophysics Data System (ADS)

    Nastula, J.; Kolaczek, B.; Salstein, D. A.

    2009-09-01

    Global geophysical excitation functions of polar motion do not explain fully the observed polar motion as determined by geodetic techniques. The impact of continental hydrologic signals, from land water, snow, and ice, on polar motion excitation HAM (Hydrological Angular Momentum), is still inadequately estimated and not known so well as atmospheric and oceanic ones. Recently the GRACE (Gravity Recovery and Climate Experiment) satellite mission monitoring Earth's time variable gravity field has allowed us to determine global mass term of the polar motion excitation functions, which inherently includes the atmospheric, oceanic and hydrological portions. We use these terms to make comparisons with the mass term of the geodetic and geophysical excitation functions of polar motion on seasonal scales. Global GRACE excitation function of polar motion and hydrological excitation function of polar motion have been determined and were studied earlier

  16. 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)

  17. 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)

  18. Two-photon excitation laser scanning microscopy: applications in neuroscience

    NASA Astrophysics Data System (ADS)

    Denk, Winfried

    1996-05-01

    High resolution fluorescence imaging in intact tissues faces special challenges posed by scattering of excitation and fluorescence light and the need to avoid photodynamic damage. Significant improvements over conventional widefield and confocal imaging are provided when two-photon excitation is used. Applications to the functional imaging of the calcium dynamics in synaptic spines, small invertebrate neurites, and auditory hair cells are shown. Two-photon absorption induced photolysis can also be used for scanning photochemical microscopy and for high resolution measurements of diffusional coupling between cellular compartments.

  19. Biocompound detection through fluorescence excitation-emission matrix analysis

    NASA Astrophysics Data System (ADS)

    Twede, David R.; Sanders, Lee C.; Wagner, Michael L.

    2004-01-01

    The excitation-emission matrix (EEM) is the luminescence spectral emission intensity of fluorescent compounds as a function of the excitation wavelength. EEMs offer the promise of an additional degree of information for enhanced compound detection and identification. Veridian has collected pure-component EEMs of amino acids (Trp, Phe, Tyr), Bacillus globigii (bg), Bacillus thuringiensis (bt,), and selected backgrounds. Also collected were EEMs of mixtures of amino acids and of bg in solution with a few backgrounds. The EEMs of pure components and mixtures were analyzed for phenomenology and for potential methods of unmixing and identifying the constituents of EEMs having mixed components of a similar nature.

  20. Biocompound detection through fluorescence excitation-emission matrix analysis

    NASA Astrophysics Data System (ADS)

    Twede, David R.; Sanders, Lee C.; Wagner, Michael L.

    2003-12-01

    The excitation-emission matrix (EEM) is the luminescence spectral emission intensity of fluorescent compounds as a function of the excitation wavelength. EEMs offer the promise of an additional degree of information for enhanced compound detection and identification. Veridian has collected pure-component EEMs of amino acids (Trp, Phe, Tyr), Bacillus globigii (bg), Bacillus thuringiensis (bt,), and selected backgrounds. Also collected were EEMs of mixtures of amino acids and of bg in solution with a few backgrounds. The EEMs of pure components and mixtures were analyzed for phenomenology and for potential methods of unmixing and identifying the constituents of EEMs having mixed components of a similar nature.

  1. Robust population inversion by polarization selective pulsed excitation.

    PubMed

    Mantei, D; Förstner, J; Gordon, S; Leier, Y A; Rai, A K; Reuter, D; Wieck, A D; Zrenner, A

    2015-05-22

    The coherent state preparation and control of single quantum systems is an important prerequisite for the implementation of functional quantum devices. Prominent examples for such systems are semiconductor quantum dots, which exhibit a fine structure split single exciton state and a V-type three level structure, given by a common ground state and two distinguishable and separately excitable transitions. In this work we introduce a novel concept for the preparation of a robust inversion by the sequential excitation in a V-type system via distinguishable paths.

  2. Cavity modes and their excitations in elliptical plasmonic patch nanoantennas.

    PubMed

    Chakrabarty, Ayan; Wang, Feng; Minkowski, Fred; Sun, Kai; Wei, Qi-Huo

    2012-05-21

    We present experimental and theoretical studies of two dimensional periodic arrays of elliptical plasmonic patch nanoantennas. Experimental and simulation results demonstrate that the azimuthal symmetry breaking of the metal patches leads to the occurrence of even and odd resonant cavity modes and the excitation geometries dependent on their modal symmetries. We show that the cavity modes can be described by the product of radial and angular Mathieu functions with excellent agreements with both simulations and experiments. The effects of the patch periodicity on the excitation of the surface plasmon and its coupling with the cavity modes are also discussed. PMID:22714147

  3. Excited State Electronic Properties of Sodium Iodide and Cesium Iodide

    SciTech Connect

    Campbell, Luke W.; Gao, Fei

    2013-05-01

    We compute from first principles the dielectric function, loss function, lifetime and scattering rate of quasiparticles due to electronic losses, and secondary particle spectrum due to plasmon decay in two scintillating alkali halides, sodium iodide and cesium iodide. Particular emphasis is placed on quasiparticles within several multiples of the band gap from the band edges. A theory for the decay spectra of plasmons and other electronic excitations in crystals is presented. Applications to Monte Carlo radiation transport codes are discussed.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Photoionization of furan from the ground and excited electronic states

    NASA Astrophysics Data System (ADS)

    Ponzi, Aurora; Sapunar, Marin; Angeli, Celestino; Cimiraglia, Renzo; Došlić, Nada; Decleva, Piero

    2016-02-01

    Here we present a comparative computational study of the photoionization of furan from the ground and the two lowest-lying excited electronic states. The study aims to assess the quality of the computational methods currently employed for treating bound and continuum states in photoionization. For the ionization from the ground electronic state, we show that the Dyson orbital approach combined with an accurate solution of the continuum one particle wave functions in a multicenter B-spline basis, at the density functional theory (DFT) level, provides cross sections and asymmetry parameters in excellent agreement with experimental data. On the contrary, when the Dyson orbitals approach is combined with the Coulomb and orthogonalized Coulomb treatments of the continuum, the results are qualitatively different. In excited electronic states, three electronic structure methods, TDDFT, ADC(2), and CASSCF, have been used for the computation of the Dyson orbitals, while the continuum was treated at the B-spline/DFT level. We show that photoionization observables are sensitive probes of the nature of the excited states as well as of the quality of excited state wave functions. This paves the way for applications in more complex situations such as time resolved photoionization spectroscopy.

  9. Photoionization of furan from the ground and excited electronic states.

    PubMed

    Ponzi, Aurora; Sapunar, Marin; Angeli, Celestino; Cimiraglia, Renzo; Došlić, Nađa; Decleva, Piero

    2016-02-28

    Here we present a comparative computational study of the photoionization of furan from the ground and the two lowest-lying excited electronic states. The study aims to assess the quality of the computational methods currently employed for treating bound and continuum states in photoionization. For the ionization from the ground electronic state, we show that the Dyson orbital approach combined with an accurate solution of the continuum one particle wave functions in a multicenter B-spline basis, at the density functional theory (DFT) level, provides cross sections and asymmetry parameters in excellent agreement with experimental data. On the contrary, when the Dyson orbitals approach is combined with the Coulomb and orthogonalized Coulomb treatments of the continuum, the results are qualitatively different. In excited electronic states, three electronic structure methods, TDDFT, ADC(2), and CASSCF, have been used for the computation of the Dyson orbitals, while the continuum was treated at the B-spline/DFT level. We show that photoionization observables are sensitive probes of the nature of the excited states as well as of the quality of excited state wave functions. This paves the way for applications in more complex situations such as time resolved photoionization spectroscopy. PMID:26931702

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. [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

  17. 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.

  18. [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.

  19. 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.

  20. Modeling K,ATP-Dependent Excitability in Pancreatic Islets

    PubMed Central

    Silva, Jonathan R.; Cooper, Paige; Nichols, Colin G.

    2014-01-01

    In pancreatic β-cells, K,ATP channels respond to changes in glucose to regulate cell excitability and insulin release. Confirming a high sensitivity of electrical activity to K,ATP activity, mutations that cause gain of K,ATP function cause neonatal diabetes. Our aim was to quantitatively assess the contribution of K,ATP current to the regulation of glucose-dependent bursting by reproducing experimentally observed changes in excitability when K,ATP conductance is altered by genetic manipulation. A recent detailed computational model of single cell pancreatic β-cell excitability reproduces the β-cell response to varying glucose concentrations. However, initial simulations showed that the model underrepresents the significance of K,ATP activity and was unable to reproduce K,ATP conductance-dependent changes in excitability. By altering the ATP and glucose dependence of the L-type Ca2+ channel and the Na-K ATPase to better fit experiment, appropriate dependence of excitability on K,ATP conductance was reproduced. Because experiments were conducted in islets, which contain cell-to-cell variability, we extended the model from a single cell to a three-dimensional model (10×10×10 cell) islet with 1000 cells. For each cell, the conductance of the major currents was allowed to vary as was the gap junction conductance between cells. This showed that single cell glucose-dependent behavior was then highly variable, but was uniform in coupled islets. The study highlights the importance of parameterization of detailed models of β-cell excitability and suggests future experiments that will lead to improved characterization of β-cell excitability and the control of insulin secretion. PMID:25418087

  1. Excited States of the divacancy in SiC

    NASA Astrophysics Data System (ADS)

    Bockstedte, Michel; Garratt, Thomas; Ivady, Viktor; Gali, Adam

    2014-03-01

    The divacancy in SiC - a technologically mature material that fulfills the necessary requirements for hosting defect based quantum computing - is a good candidate for implementing a solid state quantum bit. Its ground state is isovalent to the NV center in diamond as demonstrated by density functional theory (DFT). Furthermore, coherent manipulation of divacancy spins in SiC has been demonstrated. The similarities to NV might indicate that the same inter system crossing (ICS) from the high to the low spin state is responsible for its spin-dependent fluorescent signal. By DFT and a DFT-based multi-reference hamiltonian we analyze the excited state spectrum of the defects. In contrast to the current picture of the spin dynamics of the NV center, we predict that a static Jahn-Teller effect in the first excited triplet states governs an ICS both with the excited and ground state of the divacancy.

  2. Anti-Stokes Fluorescent Probe with Incoherent Excitation

    PubMed Central

    Li, Yang; Zhou, Shifeng; Dong, Guoping; Peng, Mingying; Wondraczek, Lothar; Qiu, Jianrong

    2014-01-01

    Although inorganic anti-Stokes fluorescent probes have long been developed, the operational mode of today's most advanced examples still involves the harsh requirement of coherent laser excitation, which often yields unexpected light disturbance or even photon-induced deterioration during optical imaging. Here, we demonstrate an efficient anti-Stokes fluorescent probe with incoherent excitation. We show that the probe can be operated under light-emitting diode excitation and provides tunable anti-Stokes energy shift and decay kinetics, which allow for rapid and deep tissue imaging over a very large area with negligible photodestruction. Charging of the probe can be achieved by either X-rays or ultraviolet-visible light irradiation, which enables multiplexed detection and function integration with standard X-ray medical imaging devices. PMID:24518662

  3. Theoretical Studies on the Reaction Pathways of Electronically Excited Daaf

    NASA Astrophysics Data System (ADS)

    Quenneville, J.; Moore, D. S.

    2009-12-01

    The use of temporally and spectrally shaped ultrafast laser pulses to initiate, as well as detect, high explosives is being explored at Los Alamos. High level ab initio calculations, presented here, are employed to help guide and interpret the experiments. The ground and first excited electronic states of 3, 3'-diamino-4, 4'-azoxyfurazan (DAAF) are investigated using complete active space self-consistent field (CASSCF) and time-dependent density functional theory (TD-DFT). The geometrical and energetic character of the excited state minima, conical intersections and reaction pathways of DAAF are described. Two radiative and two non-radiative excited state population quenching mechanisms are outlined, and possible pathways for photochemical and spectroscopic control are discussed.

  4. Electron impact excitation of argon in the extreme vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Mentall, J. E.; Morgan, H. D.

    1976-01-01

    Polarization-free excitation cross sections in the extreme vacuum ultraviolet have been measured for electron impact on Ar. Observed spectral features were those lines of Ar I and Ar II which lie between 700 and 1100 A. Excitation functions were measured for the Ar I resonance line at 1048 A and the Ar II resonance line at 920 A. Peak cross sections for these two lines were found to be (39.4 plus or minus 7.9) x 10 to the -18th and (6.9 plus or minus 1.4) x 10 to the -18th, respectively. At low energies, excitation of the Ar II resonance line is dominated by an electron exchange transition.

  5. Magnetic excitations in single crystal PrNiSn

    NASA Astrophysics Data System (ADS)

    Beirne, E. D.; McEwen, K. A.; Habicht, K.; Fort, D.

    Inelastic neutron scattering results from a single crystal of the rare earth intermetallic PrNiSn are presented. Crystalline electric field excitations are found at 0.5, 2.4 and around 3.5 meV. The lower modes show little dispersion over q, but the 3.5 meV splits into two excitations, most clearly seen along the c* direction. Fitting the modes with gaussian functions allows us to show the pronounced dispersion to be of the form E(q)=E0+J1cos(qπ) for the upper mode, and E(q)=E0+J1cos(qπ)+J2cos(2qπ) for the lower mode. This suggests a longer range interaction for the lower mode. The lowest excitation at 0.5 meV confirms predictions made from previous measurements on polycrystalline samples that indicate a low lying CEF level.

  6. Asymmetric excitation of surface plasmons by dark mode coupling

    PubMed Central

    Zhang, Xueqian; Xu, Quan; Li, Quan; Xu, Yuehong; Gu, Jianqiang; Tian, Zhen; Ouyang, Chunmei; Liu, Yongmin; Zhang, Shuang; Zhang, Xixiang; Han, Jiaguang; Zhang, Weili

    2016-01-01

    Control over surface plasmons (SPs) is essential in a variety of cutting-edge applications, such as highly integrated photonic signal processing systems, deep-subwavelength lasing, high-resolution imaging, and ultrasensitive biomedical detection. Recently, asymmetric excitation of SPs has attracted enormous interest. In free space, the analog of electromagnetically induced transparency (EIT) in metamaterials has been widely investigated to uniquely manipulate the electromagnetic waves. In the near field, we show that the dark mode coupling mechanism of the classical EIT effect enables an exotic and straightforward excitation of SPs in a metasurface system. This leads to not only resonant excitation of asymmetric SPs but also controllable exotic SP focusing by the use of the Huygens-Fresnel principle. Our experimental findings manifest the potential of developing plasmonic metadevices with unique functionalities. PMID:26989777

  7. Asymmetric excitation of surface plasmons by dark mode coupling.

    PubMed

    Zhang, Xueqian; Xu, Quan; Li, Quan; Xu, Yuehong; Gu, Jianqiang; Tian, Zhen; Ouyang, Chunmei; Liu, Yongmin; Zhang, Shuang; Zhang, Xixiang; Han, Jiaguang; Zhang, Weili

    2016-02-01

    Control over surface plasmons (SPs) is essential in a variety of cutting-edge applications, such as highly integrated photonic signal processing systems, deep-subwavelength lasing, high-resolution imaging, and ultrasensitive biomedical detection. Recently, asymmetric excitation of SPs has attracted enormous interest. In free space, the analog of electromagnetically induced transparency (EIT) in metamaterials has been widely investigated to uniquely manipulate the electromagnetic waves. In the near field, we show that the dark mode coupling mechanism of the classical EIT effect enables an exotic and straightforward excitation of SPs in a metasurface system. This leads to not only resonant excitation of asymmetric SPs but also controllable exotic SP focusing by the use of the Huygens-Fresnel principle. Our experimental findings manifest the potential of developing plasmonic metadevices with unique functionalities. PMID:26989777

  8. Localized excitations in hydrogen-bonded molecular crystals

    NASA Astrophysics Data System (ADS)

    Alexander, D. M.; Krumhansl, J. A.

    1986-05-01

    Localized excitations analogous to the small Holstein polaron, to localized modes in alkali halides, and to localized excitonic states, are postulated for a set of internal vibrational modes in crystalline acetanilide. The theoretical framework in which one can describe the characteristics of the ir and Raman spectroscopy peaks associated with these localized states is adequately provided by the Davydov model (formally equivalent to the Holstein polaron model). The possible low-lying excitations arising from this model are determined using a variational approach. Hence, the contribution to the spectral function due to each type of excitation can be calculated. The internal modes of chief concern here are the amide-I (CO stretch) and the N-H stretch modes for which we demonstrate consistency of the theoretical model with the available ir data. Past theoretical approaches will be discussed and reasons why one should prefer one description over another will be examined.

  9. DFT calculations of molecular excited states using an orbital-dependent nonadiabatic exchange kernel

    SciTech Connect

    Ipatov, A. N.

    2010-02-15

    A density functional method for computing molecular excitation spectra is presented that uses a frequency-dependent kernel and takes into account the nonlocality of exchange interaction. Owing to its high numerical stability and the use of a nonadiabatic (frequency-dependent) exchange kernel, the proposed approach provides a qualitatively correct description of the asymptotic behavior of charge-transfer excitation energies.

  10. 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.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Fuelling, Stephan R. K.

    1991-02-01

    sections for both excitation and ionization-excitation of He following bombardment by fast H_sp{n}{+} (n = 1,2,3) particles (v = 1.5 to 8 v_0) have been measured. Cross sections for populating different He(1snp) and He^+(np) (n = 2 to 5) states are determined as a function of the projectile velocity, mass, atomic and molecular structure, and the number of interacting electrons. It is found that excitation and ionization-excitation cross sections obtained are largest for H_sp{3}{+} molecular ions and smallest for protons, approximately in accord with a simple scaling relation.

  13. On enhancement of vibration-based energy harvesting by a random parametric excitation

    NASA Astrophysics Data System (ADS)

    Bobryk, Roman V.; Yurchenko, Daniil

    2016-03-01

    An electromechanical linear oscillator with a random ambient excitation and telegraphic noise parametric excitation is considered as an energy harvester model. It is shown that a parametric colored excitation can have a dramatic effect on the enhancement of the energy harvesting. A close relation with mean-square stability of the oscillator is established. Four sources of the ambient excitation are considered: the white noise, the Ornstein-Uhlenbeck noise, the harmonic noise and the periodic function. Analytical expressions for stationary electrical net mean power are presented for all the considered cases, confirming the proposed approach.

  14. Nuclear Excitation by a Strong Short Laser Pulse

    SciTech Connect

    Weidenmueller, Hans A.

    2011-05-06

    We derive the conditions on laser energy and photon number under which a short strong laser pulse excites a collective nuclear mode. We use the Giant Dipole Resonance as a representative example, and a random-matrix description of the fine-structure states and perturbation theory as tools. We identify the relevant observable as the nuclear time-decay function. That function is the Fourier transform of the autocorrelation function of the associated scattering matrix and contains information not otherwise available. We evaluate that function in specific cases and show that it may deviate significantly from an exponential.

  15. Comparison of the geophysical excitations of polar motion from the period: 1980.0-2009.0

    NASA Astrophysics Data System (ADS)

    Nastula, Jolanta; Paśnicka, Małgorzata; Kołaczek, Barbara

    2011-06-01

    In this study we compared contributions to polar motion excitation determined separately from each of three kinds of geophysical data: atmospheric pressure, equivalent water height estimated from hydrological models, and harmonic coefficients of the Earth gravity field obtained from Gravity Recovery and Climate Experiment (GRACE). Hydrological excitation function (Hydrological Angular Momentum — HAM) has been estimated from models of global hydrology, based on the observed distribution of surfacewater, snow, ice, and soil moisture. In our considerationwe used several global models of land hydrosphere and models ofAtmospheric Angular Momentum (AAM) and Oceanic Angular Momentum (OAM). All of themwere compared with observed Geodetic Angular Momentum (GAM). The spectra of the following excitation functions of polar motion: GAM, AAM+OAM, AAM+OAM+HAM, GAM-AAM-OAM residual geodetic excitation function, and HAM were computed too. The time variable spectra of geodetic, gravimetric, and the sum of atmospheric, oceanic, and hydrological excitation functions are also presented. Phasor diagrams of the seasonal components of polar motion excitation functions of all HAM excitation functions as well as of two GRACE solutions: Center for Space Research (CSR), Centre National d'Etudes Spatiales/Groupe de Recherche en Geodesie Spatiale (CNES/GRGS) were determined and discussed.

  16. Direct observation of photoinduced bent nitrosyl excited-state complexes

    SciTech Connect

    Sawyer, Karma R.; Steele, Ryan P.; Glascoe, Elizabeth A.; Cahoon, James F.; Schlegel, Jacob P.; Head-Gordon, Martin; Harris, Charles B.

    2008-06-28

    Ground state structures with side-on nitrosyl ({eta}{sup 2}-NO) and isonitrosyl (ON) ligands have been observed in a variety of transition-metal complexes. In contrast, excited state structures with bent-NO ligands have been proposed for years but never directly observed. Here we use picosecond time-resolved infrared spectroscopy and density functional theory (DFT) modeling to study the photochemistry of Co(CO){sub 3}(NO), a model transition-metal-NO compound. Surprisingly, we have observed no evidence for ON and {eta}{sup 2}-NO structural isomers, but have observed two bent-NO complexes. DFT modeling of the ground and excited state potentials indicates that the bent-NO complexes correspond to triplet excited states. Photolysis of Co(CO){sub 3}(NO) with a 400-nm pump pulse leads to population of a manifold of excited states which decay to form an excited state triplet bent-NO complex within 1 ps. This structure relaxes to the ground triplet state in ca. 350 ps to form a second bent-NO structure.

  17. 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}.

  18. 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.

  19. 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

  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.

  1. Hydrological excitation of polar motion by different variables of the GLDAS models

    NASA Astrophysics Data System (ADS)

    Wińska, Małgorzata; Nastula, Jolanta

    Continental hydrological loading, by land water, snow, and ice, is an element that is strongly needed for a full understanding of the excitation of polar motion. In this study we compute different estimations of hydrological excitation functions of polar motion (Hydrological Angular Momentum - HAM) using various variables from the Global Land Data Assimilation System (GLDAS) models of land hydrosphere. The main aim of this study is to show the influence of different variables for example: total evapotranspiration, runoff, snowmelt, soil moisture to polar motion excitations in annual and short term scale. In our consideration we employ several realizations of the GLDAS model as: GLDAS Common Land Model (CLM), GLDAS Mosaic Model, GLDAS National Centers for Environmental Prediction/Oregon State University/Air Force/Hydrologic Research Lab Model (Noah), GLDAS Variable Infiltration Capacity (VIC) Model. Hydrological excitation functions of polar motion, both global and regional, are determined by using selected variables of these GLDAS realizations. First we compare a timing, spectra and phase diagrams of different regional and global HAMs with each other. Next, we estimate, the hydrological signal in geodetically observed polar motion excitation by subtracting the atmospheric -- AAM (pressure + wind) and oceanic -- OAM (bottom pressure + currents) contributions. Finally, the hydrological excitations are compared to these hydrological signal in observed polar motion excitation series. The results help us understand which variables of considered hydrological models are the most important for the polar motion excitation and how well we can close polar motion excitation budget in the seasonal and inter-annual spectral ranges.

  2. Field-dependent molecular ionization and excitation energies: Implications for electrically insulating liquids

    NASA Astrophysics Data System (ADS)

    Davari, N.; Åstrand, P.-O.; Unge, M.; Lundgaard, L. E.; Linhjell, D.

    2014-03-01

    The molecular ionization potential has a relatively strong electric-field dependence as compared to the excitation energies which has implications for electrical insulation since the excited states work as an energy sink emitting light in the UV/VIS region. At some threshold field, all the excited states of the molecule have vanished and the molecule is a two-state system with the ground state and the ionized state, which has been hypothesized as a possible origin of different streamer propagation modes. Constrained density-functional theory is used to calculate the field-dependent ionization potential of different types of molecules relevant for electrically insulating liquids. The low singlet-singlet excitation energies of each molecule have also been calculated using time-dependent density functional theory. It is shown that low-energy singlet-singlet excitation of the type n → π* (lone pair to unoccupied π* orbital) has the ability to survive at higher fields. This type of excitation can for example be found in esters, diketones and many color dyes. For alkanes (as for example n-tridecane and cyclohexane) on the other hand, all the excited states, in particular the σ → σ* excitations vanish in electric fields higher than 10 MV/cm. Further implications for the design of electrically insulating dielectric liquids based on the molecular ionization potential and excitation energies are discussed.

  3. Causal evolutions of bulk local excitations from CFT

    NASA Astrophysics Data System (ADS)

    Goto, Kanato; Miyaji, Masamichi; Takayanagi, Tadashi

    2016-09-01

    Bulk localized excited states in an AdS spacetime can be constructed from Ishibashi states with respect to the global conformal symmetry in the dual CFT. We study boundary two point functions of primary operators in the presence of bulk localized excitations in two dimensional CFTs. From two point functions in holographic CFTs, we observe causal propagations of radiations when the mass of dual bulk scalar field is close to the BF bound. This behavior for holographic CFTs is consistent with the locality and causality in classical gravity duals. We also show that this cannot be seen in free fermion CFTs. Moreover, we find that the short distance behavior of two point functions is universal and obeys the relation which generalizes the first law of entanglement entropy.

  4. Resonance Raman spectra of organic molecules absorbed on inorganic semiconducting surfaces: Contribution from both localized intramolecular excitation and intermolecular charge transfer excitation

    SciTech Connect

    Ye, ChuanXiang; Zhao, Yi E-mail: liangwz@xmu.edu.cn; Liang, WanZhen E-mail: liangwz@xmu.edu.cn

    2015-10-21

    The time-dependent correlation function approach for the calculations of absorption and resonance Raman spectra (RRS) of organic molecules absorbed on semiconductor surfaces [Y. Zhao and W. Z. Liang, J. Chem. Phys. 135, 044108 (2011)] is extended to include the contribution of the intermolecular charge transfer (CT) excitation from the absorbers to the semiconducting nanoparticles. The results demonstrate that the bidirectionally interfacial CT significantly modifies the spectral line shapes. Although the intermolecular CT excitation makes the absorption spectra red shift slightly, it essentially changes the relative intensities of mode-specific RRS and causes the oscillation behavior of surface enhanced Raman spectra with respect to interfacial electronic couplings. Furthermore, the constructive and destructive interferences of RRS from the localized molecular excitation and CT excitation are observed with respect to the electronic coupling and the bottom position of conductor band. The interferences are determined by both excitation pathways and bidirectionally interfacial CT.

  5. Excited flavin and pterin coenzyme molecules in evolution.

    PubMed

    Kritsky, M S; Telegina, T A; Vechtomova, Y L; Kolesnikov, M P; Lyudnikova, T A; Golub, O A

    2010-10-01

    Excited flavin and pterin molecules are active in intermolecular energy transfer and in photocatalysis of redox reactions resulting in conservation of free energy. Flavin-containing pigments produced in models of the prebiotic environment are capable of converting photon energy into the energy of phosphoanhydride bonds of ATP. However, during evolution photochemical reactions involving excited FMN or FAD molecules failed to become participants of bioenergy transfer systems, but they appear in enzymes responsible for repair of UV-damaged DNA (DNA photolyases) and also in receptors of blue and UV-A light regulating vital functions of organisms. The families of these photoproteins (DNA-photolyases and cryptochromes, LOV-domain- and BLUF-domain-containing proteins) are different in the structure and in mechanisms of the photoprocesses. The excited flavin molecules are involved in photochemical processes in reaction centers of these photoproteins. In DNA photolyases and cryptochromes the excitation energy on the reaction center flavin is supplied from an antenna molecule that is bound with the same polypeptide. The role of antenna is played by MTHF or by 8-HDF in some DNA photolyases, i.e. also by molecules with known coenzyme functions in biocatalysis. Differences in the structure of chromophore-binding domains suggest an independent origin of the photoprotein families. The analysis of structure and properties of coenzyme molecules reveals some specific features that were significant in evolution for their being selected as chromophores in these proteins.

  6. Description of electronic excited states using electron correlation operator.

    PubMed

    Nichols, Bryan; Rassolov, Vitaly A

    2013-09-14

    The electron correlation energy in a chemical system is defined as a difference between the energy of an exact energy for a given Hamiltonian, and a mean-field, or single determinant, approximation to it. A promising way to model electron correlation is through the expectation value of a linear two-electron operator for the Kohn-Sham single determinant wavefunction. For practical reasons, it is desirable for such an operator to be universal, i.e., independent of the positions and types of nuclei in a molecule. The correlation operator models the effect of electron correlation on the interaction energy in a electron pair. We choose an operator expanded in a small number of Gaussians as a model for electron correlation, and test it by computing atomic and molecular adiabatic excited states. The computations are performed within the Δ Self-Consistent Field (ΔSCF) formalism, and are compared to the time-dependent density functional theory model with popular density functionals. The simplest form of the correlation operator contains only one parameter derived from the helium atom ground state correlation energy. The correlation operator approach significantly outperforms other methods in computation of atomic excitation energies. The accuracy of molecular excitation energies computed with the correlation operator is limited by the shortcomings of the ΔSCF methodology in describing excited states.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Characteristics of Symmetric and Asymmetric Fission Modes as a Function of the Compound Nucleus Excitation in the Proton-Induced Fission of 233Pa, 239Np and 243Am

    SciTech Connect

    Beresova, M.; Kliman, J.; Krupa, L.; Bogatchev, A. A.; Itkis, I. M.; Itkis, M. G.; Kniajeva, G. N.; Kondratiev, N. A.; Kozulin, E. M.; Pokrovsky, I. V.; Dorvaux, O.; Khlebnikov, S.; Lyapin, V.; Rubchenia, W.; Stuttge, L.; Trzaska, W.; Vakhtin, D.

    2007-05-22

    Average preequilibrium average statistical prescission and postscission neutron multiplicities as well as average {gamma}-ray multiplicity , average energy emitted by {gamma}-rays and average energy per one gamma quantum <{epsilon}{gamma}> as a function of mass and total kinetic energy (TKE) of fission fragments were measured in the proton-induced reactions p+232Th{yields}233Pa, p+238U{yields}239Np and p+242Pu{yields}243Am (at proton energy Ep=13, 20, 40 and 55 MeV). The fragment mass and energy distributions (MEDs) have been analyzed in terms of the multimodal fission. The decomposition of the experimental MEDs onto the MEDs of the distinct modes has been fulfilled in the framework of a method that is free from any parameterization of the distinct fission mode mass distribution shapes. The main characteristics for symmetric and asymmetric modes have been studied in their dependence on the compound nucleus composition and proton energy. The manifestation of multimodal fission in average {gamma}-ray multiplicities of fission fragments was also studied in this work.

  12. Influence of Electron Molecule Resonant Vibrational Collisions over the Symmetric Mode and Direct Excitation-Dissociation Cross Sections of CO2 on the Electron Energy Distribution Function and Dissociation Mechanisms in Cold Pure CO2 Plasmas.

    PubMed

    Pietanza, L D; Colonna, G; Laporta, V; Celiberto, R; D'Ammando, G; Laricchiuta, A; Capitelli, M

    2016-05-01

    A new set of electron-vibrational (e-V) processes linking the first 10 vibrational levels of the symmetric mode of CO2 is derived by using a decoupled vibrational model and inserted in the Boltzmann equation for the electron energy distribution function (eedf). The new eedf and dissociation rates are in satisfactory agreement with the corresponding ones obtained by using the e-V cross sections reported in the database of Hake and Phelps (H-P). Large differences are, on the contrary, found when the experimental dissociation cross sections of Cosby and Helm are inserted in the Boltzman equation. Comparison of the corresponding rates with those obtained by using the low-energy threshold energy, reported in the H-P database, shows differences up to orders of magnitude, which decrease with the increasing of the reduced electric field. In all cases, we show the importance of superelastic vibrational collisions in affecting eedf and dissociation rates either in the direct electron impact mechanism or in the pure vibrational mechanism. PMID:27064438

  13. Transmission of excitations in a spin-1 Bose-Einstein condensate through a barrier

    SciTech Connect

    Watabe, Shohei; Kato, Yusuke

    2011-05-15

    We investigate tunneling of excitations across a potential barrier separating two spin-1 Bose-Einstein condensates. Using mean-field theory at absolute zero temperature, we determine the transmission coefficients of excitations in the saturated magnetization state and unsaturated magnetization states. All excitations, except the quadrupolar spin mode in the saturated magnetization state, show the anomalous tunneling phenomenon characterized as perfect tunneling in the low-momentum limit through a potential barrier. The quadrupolar spin mode in the saturated magnetization state, whose spectrum is massive, shows total reflection. We discuss properties common between excitations showing the anomalous tunneling phenomenon. Excitations showing perfect tunneling have a gapless spectrum in the absence of the magnetic field, and their wave functions in the low-energy limit are the same as the condensate wave function.

  14. Fractionally Charged Zero-Energy Single-Particle Excitations in a Driven Fermi Sea

    NASA Astrophysics Data System (ADS)

    Moskalets, Michael

    2016-07-01

    A voltage pulse of a Lorentzian shape carrying half of the flux quantum excites out of a zero-temperature Fermi sea an electron in a mixed state, which looks like a quasiparticle with an effectively fractional charge e /2 . A prominent feature of such an excitation is a narrow peak in the energy distribution function lying exactly at the Fermi energy μ . Another spectacular feature is that the distribution function has symmetric tails around μ , which results in a zero-energy excitation. This sounds improbable since at zero temperature all available states below μ are fully occupied. The resolution lies in the fact that such a voltage pulse also excites electron-hole pairs, which free some space below μ and thus allow a zero-energy quasiparticle to exist. I discuss also how to address separately electron-hole pairs and a fractionally charged zero-energy excitation in an experiment.

  15. Excitation energies and Stokes shifts from a restricted open-shell Kohn-Sham approach

    NASA Astrophysics Data System (ADS)

    Kowalczyk, Tim; Tsuchimochi, Takashi; Chen, Po-Ta; Top, Laken; Van Voorhis, Troy

    2013-04-01

    Restricted open-shell Kohn-Sham (ROKS) theory provides a powerful computational tool for calculating singlet excited state energies and dynamics. However, the possibility of multiple solutions to the ROKS equations — with the associated difficulty of automatically selecting the physically meaningful solution — limits its usefulness for intensive applications such as long-time Born-Oppenheimer molecular dynamics. We present an implementation of ROKS for excited states which prescribes the physically correct solution from an overlap criterion and guarantees that this solution is stationary, allowing for straightforward evaluation of nuclear gradients. The method is used to benchmark ROKS for vertical excitation energies of small and large organic dyes and for the calculation of Stokes shifts. With common density functional approximations, ROKS vertical excitation energies, and Stokes shifts show similar accuracy to those from time-dependent density functional theory and Δ-self-consistent-field approaches. Advantages of the ROKS approach for excited state structure and molecular dynamics are discussed.

  16. Identification of spatially correlated excitations on a bending plate using the Virtual Fields Method

    NASA Astrophysics Data System (ADS)

    Berry, Alain; Robin, Olivier

    2016-08-01

    This paper aims at identifying the autospectral density and spatial correlation functions of random excitations acting on the surface of a thin plate, from its measured vibration response. The general framework is the Virtual Fields Method (VFM), which was previously applied by the authors to the identification of deterministic excitations on plates. In the present paper, the VFM framework is extended to the case of spatially correlated excitations. It is shown that extraction of the loading power spectral density requires measuring power spectral density functions of transverse displacements and bending curvatures, which can be typically derived from contactless Laser Doppler Vibrometry measurements. The paper details the implementation of the VFM for random excitations, presents numerical simulations and experimental results for diffuse acoustic field excitation of a plate.

  17. Electronic excitations and correlation effects in metals

    SciTech Connect

    Eguiluz, A.G.; Schoene, W.D. |

    1997-07-01

    Theoretical descriptions of the spectrum of electronic excitations in real metals have not yet reached a fully predictive, first-principles stage. In this paper the authors begin by presenting brief highlights of recent progress made in the evaluation of dynamical electronic response in metals. A comparison between calculated and measured spectra--they use the loss spectra of Al and Cs as test cases--leads them to the conclusion that, even in weakly-correlated metals, correlation effects beyond mean-field theory play an important role. Furthermore, the effects of the underlying band structure turn out to be significant. Calculations which incorporate the effects of both dynamical correlations and band structure from first principles are not yet available. As a first step towards such goal, they outline a numerical algorithm for the self-consistent solution of the Dyson equation for the one-particle Green`s function. The self-energy is evaluated within the shielded-interaction approximation of Baym and Kadanoff. Their method, which is fully conserving, is a finite-temperature scheme which determines the Green`s function and the self-energy at the Matsubara frequencies on the imaginary axis. The analytical continuation to real frequencies is performed via Pade` approximant. They present results for the homogeneous electron gas which exemplify the importance of many-body self-consistency.

  18. Inflammation increases the excitability of masseter muscle afferents.

    PubMed

    Harriott, A M; Dessem, D; Gold, M S

    2006-08-11

    Temporomandibular disorder is a major health problem associated with chronic orofacial pain in the masticatory muscles and/or temporomandibular joint. Evidence suggests that changes in primary afferents innervating the muscles of mastication may contribute to temporomandibular disorder. However, there has been little systematic study of the mechanisms controlling the excitability of these muscle afferents, nor their response to inflammation. In the present study, we tested the hypotheses that inflammation increases the excitability of sensory neurons innervating the masseter muscle of the rat and that the ionic mechanisms underlying these changes are unique to these neurons. We examined inflammation-induced changes in the excitability of trigeminal ganglia muscle neurons following intramuscular injections of complete Freund's adjuvant. Three days after complete Freund's adjuvant injection acutely dissociated, retrogradely labeled trigeminal ganglia neurons were studied using whole cell patch clamp techniques. Complete Freund's adjuvant-induced inflammation was associated with an increase in neuronal excitability marked by a significant decrease in rheobase and increase in the slope of the stimulus response function assessed with depolarizing current injection. The increase in excitability was associated with significant decreases in the rate of action potential fall and the duration of the action potential afterhyperpolarization. These changes in excitability and action potential waveform were associated with significant shifts in the voltage-dependence of activation and steady-state availability of voltage-gated K(+) current as well as significant decreases in the density of voltage-gated K(+) current subject to steady-state inactivation. These data suggest that K(+) channel subtypes may provide novel targets for the treatment of pain arising from inflamed muscle. These results also support the hypothesis that the underlying mechanisms of pain arising from

  19. Modular Hamiltonian for Excited States in Conformal Field Theory

    NASA Astrophysics Data System (ADS)

    Lashkari, Nima

    2016-07-01

    We present a novel replica trick that computes the relative entropy of two arbitrary states in conformal field theory. Our replica trick is based on the analytic continuation of partition functions that break the Zn replica symmetry. It provides a method for computing arbitrary matrix elements of the modular Hamiltonian corresponding to excited states in terms of correlation functions. We show that the quantum Fisher information in vacuum can be expressed in terms of two-point functions on the replica geometry. We perform sample calculations in two-dimensional conformal field theories.

  20. Modular Hamiltonian for Excited States in Conformal Field Theory.

    PubMed

    Lashkari, Nima

    2016-07-22

    We present a novel replica trick that computes the relative entropy of two arbitrary states in conformal field theory. Our replica trick is based on the analytic continuation of partition functions that break the Z_{n} replica symmetry. It provides a method for computing arbitrary matrix elements of the modular Hamiltonian corresponding to excited states in terms of correlation functions. We show that the quantum Fisher information in vacuum can be expressed in terms of two-point functions on the replica geometry. We perform sample calculations in two-dimensional conformal field theories. PMID:27494465

  1. Modular Hamiltonian for Excited States in Conformal Field Theory.

    PubMed

    Lashkari, Nima

    2016-07-22

    We present a novel replica trick that computes the relative entropy of two arbitrary states in conformal field theory. Our replica trick is based on the analytic continuation of partition functions that break the Z_{n} replica symmetry. It provides a method for computing arbitrary matrix elements of the modular Hamiltonian corresponding to excited states in terms of correlation functions. We show that the quantum Fisher information in vacuum can be expressed in terms of two-point functions on the replica geometry. We perform sample calculations in two-dimensional conformal field theories.

  2. 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.

  3. 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.

  4. Stepwise two-photon excited fluorescence from higher excited states of chlorophylls in photosynthetic antenna complexes.

    PubMed

    Leupold, Dieter; Teuchner, Klaus; Ehlert, Jürgen; Irrgang, Klaus-Dieter; Renger, Gernot; Lokstein, Heiko

    2006-09-01

    Stepwise two-photon excited fluorescence (TPEF) spectra of the photosynthetic antenna complexes PCP, CP47, CP29, and light-harvesting complex II (LHC II) were measured. TPEF emitted from higher excited states of chlorophyll (Chl) a and b was elicited via consecutive absorption of two photons in the Chl a/b Qy range induced by tunable 100-fs laser pulses. Global analyses of the TPEF line shapes with a model function for monomeric Chl a in a proteinaceous environment allow distinction between contributions from monomeric Chls a and b, strongly excitonically coupled Chls a, and Chl a/b heterodimers/-oligomers. The analyses indicate that the longest wavelength-absorbing Chl species in the Qy region of LHC II is a Chl a homodimer with additional contributions from adjacent Chl b. Likewise, in CP47 a spectral form at approximately 680 nm (that is, however, not the red-most species) is also due to strongly coupled Chls a. In contrast to LHC II, the red-most Chl subband of CP29 is due to a monomeric Chl a. The two Chls b in CP29 exhibit marked differences: a Chl b absorbing at approximately 650 nm is not excitonically coupled to other Chls. Based on this finding, the refractive index of its microenvironment can be determined to be 1.48. The second Chl b in CP29 (absorbing at approximately 640 nm) is strongly coupled to Chl a. Implications of the findings with respect to excitation energy transfer pathways and rates are discussed. Moreover, the results will be related to most recent structural analyses.

  5. System and method for characterizing voiced excitations of speech and acoustic signals, removing acoustic noise from speech, and synthesizing speech

    DOEpatents

    Burnett, Greg C.; Holzrichter, John F.; Ng, Lawrence C.

    2002-01-01

    Low power EM waves are used to detect motions of vocal tract tissues of the human speech system before, during, and after voiced speech. A voiced excitation function is derived. The excitation function provides speech production information to enhance speech characterization and to enable noise removal from human speech.

  6. 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.

  7. 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

  8. 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.

  9. Multiphoton excitation fluorescence microscopy and spectroscopy of in vivo human skin.

    PubMed Central

    Masters, B R; So, P T; Gratton, E

    1997-01-01

    Multiphoton excitation microscopy at 730 nm and 960 nm was used to image in vivo human skin autofluorescence from the surface to a depth of approximately 200 microm. The emission spectra and fluorescence lifetime images were obtained at selected locations near the surface (0-50 microm) and at deeper depths (100-150 microm) for both excitation wavelengths. Cell borders and cell nuclei were the prominent structures observed. The spectroscopic data suggest that reduced pyridine nucleotides, NAD(P)H, are the primary source of the skin autofluorescence at 730 nm excitation. With 960 nm excitation, a two-photon fluorescence emission at 520 nm indicates the presence of a variable, position-dependent intensity component of flavoprotein. A second fluorescence emission component, which starts at 425 nm, is observed with 960-nm excitation. Such fluorescence emission at wavelengths less than half the excitation wavelength suggests an excitation process involving three or more photons. This conjecture is further confirmed by the observation of the super-quadratic dependence of the fluorescence intensity on the excitation power. Further work is required to spectroscopically identify these emitting species. This study demonstrates the use of multiphoton excitation microscopy for functional imaging of the metabolic states of in vivo human skin cells. Images FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 PMID:9168018

  10. Electron impact excitation of helium in Debye plasma

    SciTech Connect

    Diallo, S.; Gomis, L.; Faye, I. G.; Tall, M. S.; Diédhiou, I.; Diatta, C. S.; Zammit, M.

    2015-03-15

    The probability, differential, and integral scattering cross sections of the 1{sup 1}S→2{sup 1}S and 1{sup 1}S→2{sup 1}P transitions of helium have been calculated in the first Born approximation. The projectile-target interactions depending on the temperature and the density of plasma are described by the Debye-Hückel model. Wave functions of the target before and after collision were modeled by non orthogonal Hartree-Fock orbitals. The wave functions parameters are calculated with the Ritz variational method. We improve our unscreened first Born approximation integral cross sections by using the BE-scaled (B stands for binding energy and E excitation energy) method. The second Born approximation has also been used to calculate the excitation cross sections in Debye plasma. Our calculations are compared to other theoretical and experimental results where applicable.

  11. Luminescence efficiency of silica during ion beam excitation

    NASA Astrophysics Data System (ADS)

    Abu-Hassan, L. H.; Townsend, P. D.

    1988-05-01

    During ion beam implantation of silica light is produced by electronic excitation of the glass network. In order to vary the mechanisms of excitation and decay data were taken with a wide range of ions and ion energies (e.g. H +, H +2, He +, Ne +, N +, N +2 and A + from 5 keV to 2.8 MeV). The results suggest that the light is generated with different luminescence efficiency in regions of electronic damage, collision damage and, in the case of nitrogen, of impurities. Additionally, exciton or electron diffusion from the implanted region generates luminescence several microns beneath the implant. The relative efficiencies in these processes are discussed. One consequence of these differences is that in measurements of the luminescence efficiency as a function of energy one observes an apparent peak in efficiency if the sequence commences at high energy. The "peak" is a function of the initial energy.

  12. Seasonal induction of GABAergic excitation in the central mammalian clock

    PubMed Central

    Farajnia, Sahar; van Westering, Tirsa L. E.; Meijer, Johanna H.; Michel, Stephan

    2014-01-01

    The balance between excitation and inhibition is essential for the proper function of neuronal networks in the brain. The inhibitory neurotransmitter γ-aminobutyric acid (GABA) contributes to the network dynamics within the suprachiasmatic nucleus (SCN), which is involved in seasonal encoding. We investigated GABAergic activity and observed mainly inhibitory action in SCN neurons of mice exposed to a short-day photoperiod. Remarkably, the GABAergic activity in a long-day photoperiod shifts from inhibition toward excitation. The mechanistic basis for this appears to be a change in the equilibrium potential of GABA-evoked current. These results emphasize that environmental conditions can have substantial effects on the function of a key neurotransmitter in the central nervous system. PMID:24979761

  13. First Principles Charge Transfer Excitations in Curved Aromatic Materials

    NASA Astrophysics Data System (ADS)

    Zoppi, Laura; Martin Samos, Layla; Baldridge, Kim K.

    Understanding excitation properties and charge transport phenomena of curved π-conjugated materials is critical for a rational utilization of buckybowls as electrically active materials in solid-state devices. In this respect, the class of materials based on the smallest bowl-shaped fullerene fragment, corannulene, C20H10, offers a unique possibility for building up scaffolds with a tunable spectrum of structural and electronic properties. Here, GW-BSE based approaches are applied to investigation and prediction of charge transfer excitations of C20H10 materials systems at functional interfaces, with a special emphasis on design aspects of materials relevant in the experimental domain. Theoretical predictions together with experimental findings illustrate the possibility of integrating corannulene electronic functions in molecular devices

  14. Dark excited States of carotenoid regulated by bacteriochlorophyll in photosynthetic light harvesting.

    PubMed

    Nakamura, Ryosuke; Nakagawa, Katsunori; Nango, Mamoru; Hashimoto, Hideki; Yoshizawa, Masayuki

    2011-03-31

    In photosynthesis, carotenoids play important roles in light harvesting (LH) and photoprotective functions, which have been described mainly in terms of two singlet excited states of carotenoids: S(1) and S(2). In addition to the "dark" S(1) state, another dark state, S*, was recently identified and its involvement in photosynthetic functions was determined. However, there is no consistent picture concerning its nature or the mechanism of its formation. One particularly anomalous behavior obtained from femtosecond transient absorption (TA) spectroscopy is that the S*/S(1) population ratio depends on the excitation intensity. Here, we focus on the effect of nearby bacteriochlorophyll (BChl) on the relaxation dynamics of carotenoid in the LH complex. We performed femtosecond TA spectroscopy combined with pre-excitation of BChl in the reconstituted LH1 complex from Rhodospirillum rubrum S1. We observed that the energy flow from S(1), including its vibrationally excited hot states, to S* occurs only when nearby BChl is excited into Q(y), resulting in an increase in S*/S(1). We also examined the excitation-intensity dependence of S*/S(1) by conventional TA spectroscopy. A comparison between the pre-excitation effect and excitation-intensity dependence shows a strong correlation of S*/S(1) with the number of BChls excited into Q(y). In addition, we observed an increase in triplet formation as the S* population increased, indicating that S* is an electronic excited state that is the precursor to triplet formation. Our findings provide an explanation for observed spectroscopic features, including the excitation-intensity dependences debated so far, and offer new insights into energy deactivation mechanisms inherent in the LH antenna.

  15. 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

  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.

  17. 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

  18. Electronic excited states and relaxation dynamics in polymer heterojunction systems

    NASA Astrophysics Data System (ADS)

    Ramon, John Glenn Santos

    The potential for using conducting polymers as the active material in optoelectronic devices has come to fruition in the past few years. Understanding the fundamental photophysics behind their operations points to the significant role played by the polymer interface in their performance. Current device architectures involve the use of bulk heterojunctions which intimately blend the donor and acceptor polymers to significantly increase not only their interfacial surface area but also the probability of exciton formation within the vicinity of the interface. In this dissertation, we detail the role played by the interface on the behavior and performance of bulk heterojunction systems. First, we explore the relation between the exciton binding energy to the band offset in determining device characteristics. As a general rule, when the exciton binding energy is greater than the band offset, the exciton remains the lowest energy excited state leading to efficient light-emitting properties. On the other hand, if the offset is greater than the binding energy, charge separation becomes favorable leading to better photovoltaic behavior. Here, we use a Wannier function, configuration interaction based approach to examine the essential excited states and predict the vibronic absorption and emission spectra of the PPV/BBL, TFB/F8BT and PFB/F8BT heterojunctions. Our results underscore the role of vibrational relaxation in the formation of charge-transfer states following photoexcitation. In addition, we look at the relaxation dynamics that occur upon photoexcitation. For this, we adopt the Marcus-Hush semiclassical method to account for lattice reorganization in the calculation of the interconversion rates in TFB/F8BT and PFB/F8BT. We find that, while a tightly bound charge-transfer state (exciplex) remains the lowest excited state, a regeneration pathway to the optically active lowest excitonic state in TFB/F8BT is possible via thermal repopulation from the exciplex. Finally

  19. Viewing Instructions Accompanying Action Observation Modulate Corticospinal Excitability

    PubMed Central

    Wright, David J.; McCormick, Sheree A.; Williams, Jacqueline; Holmes, Paul S.

    2016-01-01

    Action observation interventions may have the potential to contribute to improved motor function in motor (re)learning settings by promoting functional activity and plasticity in the motor regions of the brain. Optimal methods for delivering such interventions, however, have yet to be established. This experiment investigated the effect on corticospinal excitability of manipulating the viewing instructions provided to participants (N = 21) prior to action observation. Specifically, motor evoked potential responses measured from the right hand muscles following single-pulse transcranial magnetic stimulation (TMS) to the left motor cortex were compared when participants were instructed to observe finger-thumb opposition movement sequences: (i) passively; (ii) with the intent to imitate the observed movement; or (iii) whilst simultaneously and actively imagining that they were performing the movement as they observed it. All three action observation viewing instructions facilitated corticospinal excitability to a greater extent than did observation of a static hand. In addition, the extent to which corticospinal excitability was facilitated was greater during combined observation and imagery, compared to passive observation. These findings have important implications for the design of action observation interventions in motor (re)learning settings, where instructions that encourage observers to simultaneously imagine themselves performing the observed movement may offer the current optimal method for improving motor function through action observation. PMID:26869901

  20. New two-photon excitation chromophores for cellular imaging

    NASA Astrophysics Data System (ADS)

    D'Alfonso, Laura; Chirico, Giuseppe; Collini, Maddalena; Baldini, Giancarlo; Diaspro, Alberto; Ramoino, Paola; Abbotto, Alessandro; Beverina, Luca; Pagani, Giorgio A.

    2003-10-01

    The one photon and two photon excitation spectral properties (absorption, emission spectra, singlet lifetime) of a very efficient two photon absorber, dimethyl-pepep, have been measured in solution. The one photon excitation peak lye near 525 nm and the emission falls at 600 nm, where autofluorescence of cells is weak. The value of the singlet-triplet conversion rate, obtained by two-photon excitation fluorescence correlation spectroscopy, has a quadratic dependence on the excitation power and is comparable to that shown by the dye rhodamine. Preliminary results on stained cells from yeast Saccaromices cerevisiae and Paramecium primaurelia show that the dye preferentially stains DNA in the cell. A direct comparison with a DNA stainer, Dapi, is also performed. Some measurements of the dye functionalized to react with lysine and n-terminal residues of protein are presented. Moreover, this dye can be employed in order to follow in detail some cellular processes such as nuclei division. In vitro fluorescence titration of dimethyl-pepep with calf thymus DNA allowed to estimate the values of the dye-DNA association constant versus ionic strength, and an affinity close to that of ethidium bromide is found.

  1. Structures and Low-Energy Excitations of Amorphous Gas Hydrates

    NASA Astrophysics Data System (ADS)

    Kikuchi, Tatsuya; Inamura, Yasuhiro; Onoda-Yamamuro, Noriko; Yamamuro, Osamu

    2012-09-01

    We have prepared amorphous clathrate hydrates of Ar, CD4, Xe, and SF6 by depositing mixed vapors of water and guest molecules on a substrate at ca. 10 K. The structure and vibrational density of states were investigated by neutron diffraction and inelastic scattering techniques, respectively. The radial distribution functions of the amorphous hydrates are larger than that of pure amorphous ice in the region around 4 Å (the center-edge distance of the 12-hedral cage), indicating that a local cagelike structure is maintained even in the amorphous solids. The incorporation of the guest molecules decreases the intensity of the phonon excitation below 7 meV, which is known as a low-energy excitation characteristic of amorphous ice. This may be due to the effect that the disorder, defects and distortion producing the low-energy excitation are reduced by a hydrophobic hydration between the guest and water molecules and the resultant hydrogen-bond formation. A similar effect was also observed in the libration mode of water molecules at about 60 meV. The present work has revealed the relation among the local cage formation, hydrogen bonds, and low energy excitations in amorphous hydrates that is the simplest hydrophobic hydration system (H2O--gas mixture).

  2. Communication: excitation band modulation with high-order photonic band gap in PMMA:Eu(TTA)3(TPPO)2 opals.

    PubMed

    Xu, Wen; Bai, Xue; Zhu, Yongsheng; Liu, Tong; Xu, Sai; Dong, Biao; Song, Hongwei

    2013-05-14

    Changes in the excitation spectra of luminescent species inserted in photorefractive crystals as a function of changes in the high-order photonic band gap (PBG) have not been previously observed. In this communication, we present our results monitoring the excitation band of Eu(TTA)3(TPPO)2 inserted in the PMMA opal photonic crystals as a function of the changes in the high-order PBG of the crystals. We find shifts in the complex excitation band and changes in the integrated emission intensity that correlates with shifts in the high-order PBG through coupling to the excitation transition. PMID:23676019

  3. Communication: Excitation band modulation with high-order photonic band gap in PMMA:Eu(TTA)3(TPPO)2 opals

    NASA Astrophysics Data System (ADS)

    Xu, Wen; Bai, Xue; Zhu, Yongsheng; Liu, Tong; Xu, Sai; Dong, Biao; Song, Hongwei

    2013-05-01

    Changes in the excitation spectra of luminescent species inserted in photorefractive crystals as a function of changes in the high-order photonic band gap (PBG) have not been previously observed. In this communication, we present our results monitoring the excitation band of Eu(TTA)3(TPPO)2 inserted in the PMMA opal photonic crystals as a function of the changes in the high-order PBG of the crystals. We find shifts in the complex excitation band and changes in the integrated emission intensity that correlates with shifts in the high-order PBG through coupling to the excitation transition.

  4. Communication: excitation band modulation with high-order photonic band gap in PMMA:Eu(TTA)3(TPPO)2 opals.

    PubMed

    Xu, Wen; Bai, Xue; Zhu, Yongsheng; Liu, Tong; Xu, Sai; Dong, Biao; Song, Hongwei

    2013-05-14

    Changes in the excitation spectra of luminescent species inserted in photorefractive crystals as a function of changes in the high-order photonic band gap (PBG) have not been previously observed. In this communication, we present our results monitoring the excitation band of Eu(TTA)3(TPPO)2 inserted in the PMMA opal photonic crystals as a function of the changes in the high-order PBG of the crystals. We find shifts in the complex excitation band and changes in the integrated emission intensity that correlates with shifts in the high-order PBG through coupling to the excitation transition.

  5. Vertical and adiabatic excitations in anthracene from quantum Monte Carlo: Constrained energy minimization for structural and electronic excited-state properties in the JAGP ansatz

    NASA Astrophysics Data System (ADS)

    Dupuy, Nicolas; Bouaouli, Samira; Mauri, Francesco; Sorella, Sandro; Casula, Michele

    2015-06-01

    We study the ionization energy, electron affinity, and the π → π∗ (1La) excitation energy of the anthracene molecule, by means of variational quantum Monte Carlo (QMC) methods based on a Jastrow correlated antisymmetrized geminal power (JAGP) wave function, developed on molecular orbitals (MOs). The MO-based JAGP ansatz allows one to rigorously treat electron transitions, such as the HOMO → LUMO one, which underlies the 1La excited state. We present a QMC optimization scheme able to preserve the rank of the antisymmetrized geminal power matrix, thanks to a constrained minimization with projectors built upon symmetry selected MOs. We show that this approach leads to stable energy minimization and geometry relaxation of both ground and excited states, performed consistently within the correlated QMC framework. Geometry optimization of excited states is needed to make a reliable and direct comparison with experimental adiabatic excitation energies. This is particularly important in π-conjugated and polycyclic aromatic hydrocarbons, where there is a strong interplay between low-lying energy excitations and structural modifications, playing a functional role in many photochemical processes. Anthracene is an ideal benchmark to test these effects. Its geometry relaxation energies upon electron excitation are of up to 0.3 eV in the neutral 1La excited state, while they are of the order of 0.1 eV in electron addition and removal processes. Significant modifications of the ground state bond length alternation are revealed in the QMC excited state geometry optimizations. Our QMC study yields benchmark results for both geometries and energies, with values below chemical accuracy if compared to experiments, once zero point energy effects are taken into account.

  6. Vertical and adiabatic excitations in anthracene from quantum Monte Carlo: Constrained energy minimization for structural and electronic excited-state properties in the JAGP ansatz

    SciTech Connect

    Dupuy, Nicolas; Bouaouli, Samira; Mauri, Francesco Casula, Michele; Sorella, Sandro

    2015-06-07

    We study the ionization energy, electron affinity, and the π → π{sup ∗} ({sup 1}L{sub a}) excitation energy of the anthracene molecule, by means of variational quantum Monte Carlo (QMC) methods based on a Jastrow correlated antisymmetrized geminal power (JAGP) wave function, developed on molecular orbitals (MOs). The MO-based JAGP ansatz allows one to rigorously treat electron transitions, such as the HOMO → LUMO one, which underlies the {sup 1}L{sub a} excited state. We present a QMC optimization scheme able to preserve the rank of the antisymmetrized geminal power matrix, thanks to a constrained minimization with projectors built upon symmetry selected MOs. We show that this approach leads to stable energy minimization and geometry relaxation of both ground and excited states, performed consistently within the correlated QMC framework. Geometry optimization of excited states is needed to make a reliable and direct comparison with experimental adiabatic excitation energies. This is particularly important in π-conjugated and polycyclic aromatic hydrocarbons, where there is a strong interplay between low-lying energy excitations and structural modifications, playing a functional role in many photochemical processes. Anthracene is an ideal benchmark to test these effects. Its geometry relaxation energies upon electron excitation are of up to 0.3 eV in the neutral {sup 1}L{sub a} excited state, while they are of the order of 0.1 eV in electron addition and removal processes. Significant modifications of the ground state bond length alternation are revealed in the QMC excited state geometry optimizations. Our QMC study yields benchmark results for both geometries and energies, with values below chemical accuracy if compared to experiments, once zero point energy effects are taken into account.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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…

  12. 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.

  13. 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.

  14. Excitation-scanning hyperspectral imaging microscope

    PubMed Central

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

    2014-01-01

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

  15. First-order derivative couplings between excited states from adiabatic TDDFT response theory

    SciTech Connect

    Ou, Qi; Subotnik, Joseph E.; Bellchambers, Gregory D.; Furche, Filipp

    2015-02-14

    We present a complete derivation of derivative couplings between excited states in the framework of adiabatic time-dependent density functional response theory. Explicit working equations are given and the resulting derivative couplings are compared with derivative couplings from a pseudo-wavefunction ansatz. For degenerate excited states, i.e., close to a conical intersection (CI), the two approaches are identical apart from an antisymmetric overlap term. However, if the difference between two excitation energies equals another excitation energy, the couplings from response theory exhibit an unphysical divergence. This spurious behavior is a result of the adiabatic or static kernel approximation of time-dependent density functional theory leading to an incorrect analytical structure of the quadratic response function. Numerical examples for couplings close to a CI and for well-separated electronic states are given.

  16. Double, Rydberg and Charge Transfer Excitations from Pairing Matrix Fluctuation and Particle-Particle Random Phase Approximation

    NASA Astrophysics Data System (ADS)

    Yang, Yang; van Aggelen, Helen; Yang, Weitao

    2014-03-01

    Double, Rydberg and charge transfer (CT) excitations have been great challenges for time-dependent density functional theory (TDDFT). Starting from an (N +/- 2) -electron single-determinant reference, we investigate excitations for the N-electron system through the pairing matrix fluctuation, which contains information on two-electron addition/removal processes. We adopt the particle-particle random phase approximation (pp-RPA) and the particle-particle Tamm-Dancoff approximation (pp-TDA) to approximate the pairing matrix fluctuation and then determine excitation energies by the differences of two-electron addition/removal energies. This approach captures all types of interesting excitations: single and double excitations are described accurately, Rydberg excitations are in good agreement with experimental data and CT excitations display correct 1/R dependence. Furthermore, the pp-RPA and the pp-TDA have a computational cost similar to TDDFT and consequently are promising for practical calculations.

  17. Double, Rydberg and charge transfer excitations from pairing matrix fluctuation and particle-particle random phase approximation

    SciTech Connect

    Yang, Yang; Aggelen, Helen van; Yang, Weitao

    2013-12-14

    Double, Rydberg, and charge transfer (CT) excitations have been great challenges for time-dependent density functional theory (TDDFT). Starting from an (N ± 2)-electron single-determinant reference, we investigate excitations for the N-electron system through the pairing matrix fluctuation, which contains information on two-electron addition/removal processes. We adopt the particle-particle random phase approximation (pp-RPA) and the particle-particle Tamm-Dancoff approximation (pp-TDA) to approximate the pairing matrix fluctuation and then determine excitation energies by the differences of two-electron addition/removal energies. This approach captures all types of interesting excitations: single and double excitations are described accurately, Rydberg excitations are in good agreement with experimental data and CT excitations display correct 1/R dependence. Furthermore, the pp-RPA and the pp-TDA have a computational cost similar to TDDFT and consequently are promising for practical calculations.

  18. Double, Rydberg and charge transfer excitations from pairing matrix fluctuation and particle-particle random phase approximation

    NASA Astrophysics Data System (ADS)

    Yang, Yang; van Aggelen, Helen; Yang, Weitao

    2013-12-01

    Double, Rydberg, and charge transfer (CT) excitations have been great challenges for time-dependent density functional theory (TDDFT). Starting from an (N ± 2)-electron single-determinant reference, we investigate excitations for the N-electron system through the pairing matrix fluctuation, which contains information on two-electron addition/removal processes. We adopt the particle-particle random phase approximation (pp-RPA) and the particle-particle Tamm-Dancoff approximation (pp-TDA) to approximate the pairing matrix fluctuation and then determine excitation energies by the differences of two-electron addition/removal energies. This approach captures all types of interesting excitations: single and double excitations are described accurately, Rydberg excitations are in good agreement with experimental data and CT excitations display correct 1/R dependence. Furthermore, the pp-RPA and the pp-TDA have a computational cost similar to TDDFT and consequently are promising for practical calculations.

  19. Double, Rydberg and charge transfer excitations from pairing matrix fluctuation and particle-particle random phase approximation.

    PubMed

    Yang, Yang; van Aggelen, Helen; Yang, Weitao

    2013-12-14

    Double, Rydberg, and charge transfer (CT) excitations have been great challenges for time-dependent density functional theory (TDDFT). Starting from an (N ± 2)-electron single-determinant reference, we investigate excitations for the N-electron system through the pairing matrix fluctuation, which contains information on two-electron addition/removal processes. We adopt the particle-particle random phase approximation (pp-RPA) and the particle-particle Tamm-Dancoff approximation (pp-TDA) to approximate the pairing matrix fluctuation and then determine excitation energies by the differences of two-electron addition/removal energies. This approach captures all types of interesting excitations: single and double excitations are described accurately, Rydberg excitations are in good agreement with experimental data and CT excitations display correct 1/R dependence. Furthermore, the pp-RPA and the pp-TDA have a computational cost similar to TDDFT and consequently are promising for practical calculations.

  20. RIC-3 phosphorylation enables dual regulation of excitation and inhibition of Caenorhabditis elegans muscle.

    PubMed

    Safdie, Gracia; Liewald, Jana F; Kagan, Sarah; Battat, Emil; Gottschalk, Alexander; Treinin, Millet

    2016-10-01

    Brain function depends on a delicate balance between excitation and inhibition. Similarly, Caenorhabditis elegans motor system function depends on a precise balance between excitation and inhibition, as C. elegans muscles receive both inhibitory, GABAergic and excitatory, cholinergic inputs from motor neurons. Here we show that phosphorylation of the ER-resident chaperone of nicotinic acetylcholine receptors, RIC-3, leads to increased muscle excitability. RIC-3 phosphorylation at Ser-164 depends on opposing functions of the phosphatase calcineurin (TAX-6), and of the casein kinase II homologue KIN-10. Effects of calcineurin down-regulation and of phosphorylated RIC-3 on muscle excitability are mediated by GABAA receptor inhibition. Thus RIC-3 phosphorylation enables effects of this chaperone on GABAA receptors in addition to nAChRs. This dual effect provides coordinated regulation of excitation and inhibition and enables fine-tuning of the excitation-inhibition balance. Moreover, regulation of inhibitory GABAA signaling by calcineurin, a calcium- and calmodulin-dependent phosphatase, enables homeostatic balancing of excitation and inhibition.