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Sample records for isomerization transition state

  1. Thermal isomerization of azobenzenes: on the performance of Eyring transition state theory

    Science.gov (United States)

    Rietze, Clemens; Titov, Evgenii; Lindner, Steven; Saalfrank, Peter

    2017-08-01

    The thermal Z\\to E (back-)isomerization of azobenzenes is a prototypical reaction occurring in molecular switches. It has been studied for decades, yet its kinetics is not fully understood. In this paper, quantum chemical calculations are performed to model the kinetics of an experimental benchmark system, where a modified azobenzene (AzoBiPyB) is embedded in a metal-organic framework (MOF). The molecule can be switched thermally from cis to trans, under solvent-free conditions. We critically test the validity of Eyring transition state theory for this reaction. As previously found for other azobenzenes (albeit in solution), good agreement between theory and experiment emerges for activation energies and activation free energies, already at a comparatively simple level of theory, B3LYP/6-31G* including dispersion corrections. However, theoretical Arrhenius prefactors and activation entropies are in qualitiative disagreement with experiment. Several factors are discussed that may have an influence on activation entropies, among them dynamical and geometric constraints (imposed by the MOF). For a simpler model—Z\\to E isomerization in azobenzene—a systematic test of quantum chemical methods from both density functional theory and wavefunction theory is carried out in the context of Eyring theory. Also, the effect of anharmonicities on activation entropies is discussed for this model system. Our work highlights capabilities and shortcomings of Eyring transition state theory and quantum chemical methods, when applied for the Z\\to E (back-)isomerization of azobenzenes under solvent-free conditions.

  2. Ensemble of Transition State Structures for the Cis-Trans Isomerization of N-Methylacetamide

    Energy Technology Data Exchange (ETDEWEB)

    Mantz, Yves A. [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Branduardi, Davide [Italian Inst. of Technology, Genoa (Italy); Bussi, Giovanni [Univ. of Modena and Reggio Emilia and INFM-CNR (Italy); Parrinello, Michele [ETH Zurich, Lugano (Switzerland). Dept. of Chemistry and Applied Biosciences

    2009-09-17

    The cis-trans isomerization of N-methylacetamide (NMA), a model peptidic fragment, is studied theoretically in vacuo and in explicit water solvent at 300 K using the metadynamics technique. The computed cis-trans free energy difference is very similar for NMA(g) and NMA(aq), in agreement with experimental measurements of population ratios and theoretical studies at 0 K. By exploiting the flexibility in the definition of a pair of recently introduced collective variables (Branduardi, D.; Gervasio, F. L.; Parrinello, M. J. Chem. Phys. 2007, 126, 054103), an ensemble of transition state structures is generated at finite temperature for both NMA(g) and NMA(aq), as verified by computing committor distribution functions. Ensemble members of NMA(g) are shown to have correlated values of the backbone dihedral angle and a second dihedral angle involving the amide hydrogen atom. The dynamical character of these structures is preserved in the presence of solvent, whose influence on the committor functions can be modeled using effective friction/noise terms.

  3. Isomeric states in 253No and 253Fm

    International Nuclear Information System (INIS)

    Antalic, S.; Kalaninova, Z.; Saro, S.; Venhart, M.; Hessberger, F.P.; Ackermann, D.; Heinz, S.; Kindler, B.; Khuyagbaatar, J.; Kojouharov, I.; Kuusiniemi, P.; Lommel, B.; Mann, R.; Sulignano, B.; Hofmann, S.; Leino, M.; Nishio, K.; Streicher, B.

    2011-01-01

    Nuclear structure and decay of isomeric states in 253 No were investigated. The isotope was produced by the reaction 48 Ca + 207 Pb. The excitation energy of the known single-particle isomeric state (5/2 + [622]) was measured by delayed coincidences between γ-rays and implanted evaporation residues and was placed into the level scheme. In addition, decay of a high-lying multi-quasiparticle isomer in 253 No was studied using e - -γ coincidence measurements. A rotational band populated by its de-excitation was identified in 253 No. A new isomeric state in 253 Fm was observed and a partial-level scheme for this isotope is suggested. In addition γ transitions from excited levels are reported for 253 Md. (orig.)

  4. Study of the isomeric states of 66As

    International Nuclear Information System (INIS)

    Czajkowski, S.; Blank, B.; Andriamonje, S.; Attallah, F.; Boue, F.; Davi, F.; Del Moral, R.; Fleury, A.; Musquere, A.; Pravikoff, M.S.; Dufour, J-P; Grzywacz, R.; Janas, Z.; Karny, M.; Pfuetzner, M.; Donzaud, C.; Grewe, A.; Heinz, A.; Junghans, A.; Lewitowicz, M.; Sauvestre, J-E.

    1997-01-01

    The most neutron-deficient isotopes in the N = Z region are an important source of information on the neutron-proton interaction far off stability. The isotopes in this region are characterized by an extreme sensitivity of the deformation to the isospin variations. Here the structure of deformed shells are favoring the high spin states the lifetime of which being sufficient long to be observed after flight time of the order of the microsecond. The study of the decay of this isomeric states permits to approach the structure of the first excited levels of this isotopes. Recent experiments at GANIL with the SISSI - LISE 3 spectrometer were performed to study the neutron deficient nucleus 66 As. This nucleus was produced in the fragmentation of 70 MeV/u 78 Kr primary beam in a nickel target. Two new isomeric states have been observed. From the observed γ transitions a decay scheme is proposed

  5. Determination of the production rate of low intensity isomeric transitions

    International Nuclear Information System (INIS)

    Lakosi, L.; Veres, A.; Tam, N.C.; Pavlicsek, I.

    1992-01-01

    Flat 2π and cylindrical 4π multiwire proportional counters were built for counting for low energy internal conversion electrons from the nuclear isomers 83m Kr, 103m Rh and 189m Os, induced by irradiation with high intensity 60 Co and 4 MeV bremsstrahlung sources. The β-decay of 176m Lu was recorded by a plastic scintillator. In this way higher sensitivities were attained than by detecting γ-rays or characteristic X-rays associated with the isomeric transitions, and the excitation of 189m Os by low energy 137 Cs and 300 kV X-ray sources also became detectable. Comparatively large isomeric activities produced by linac irradiation were standardizing by a Ge spectrometer for calibrating proportional and scintillation counting. (orig.)

  6. High spin states and isomeric decays in doubly-odd 208Fr

    International Nuclear Information System (INIS)

    Kanjilal, D.; Bhattacharya, S.; Goswami, A.; Kshetri, R.; Raut, R.; Saha, S.; Bhowmik, R.K.; Gehlot, J.; Muralithar, S.; Singh, R.P.; Jnaneswari, G.; Mukherjee, G.; Mukherjee, B.

    2010-01-01

    Neutron deficient isotopes of francium (Z=87, N∼121-123) as excited nuclei were produced in the fusion-evaporation reaction: 197 Au( 16 O, xn) 213-x Fr at 100 MeV. The γ rays from the residues were observed through the high sensitivity Germanium Clover detector array INGA. The decay of the high spin states and the isomeric states of the doubly-odd 208 Fr nuclei, identified from the known sequence of ground state transitions, were observed. The half-lives of the E γ =194(2) keV isomeric transition, known from earlier observations, was measured to be T 1/2 =233(18) ns. A second isomeric transition at E γ =383(2) keV and T 1/2 =33(7) ns was also found. The measured half-lives were compared with the corresponding single particle estimates, based on the level scheme obtained from the experiment.

  7. Internal conversion of the (13/2+→5/2-) isomeric transition in 199Hg

    International Nuclear Information System (INIS)

    Radha Krishna, K.; Chandrasekhar Rao, M.V.S.; Sree Krishna Murty, G.; Venkateswara Rao, N.; Bhuloka Reddy, S.; Satyanarayana, G.; Sastry, D.L.; Iyer, M.R.; Sahasrabhude, S.G.

    1990-01-01

    The total conversion coefficient of the M4 transition (374 KeV) in the decay of the 13/2 + isomeric state to 5/2 - state in 199 Hg measured using the relative gamma intensity method α T is determined to be 6.34 ± 0.29 in agreement with the theory due to Rosel et al. (author). 1 tab., 3 figs., 11 refs

  8. Absolute E3 and M2 transition probabilities for the electromagnetic decay of the I{sup {pi}}=K{sup {pi}}=8{sup -} isomeric state in {sup 132}Ce

    Energy Technology Data Exchange (ETDEWEB)

    Perkowski, J.; Andrzejewski, J.; Krol, A. [University of Lodz, Faculty of Physics and Applied Informatics, Lodz (Poland); Srebrny, J.; Kownacki, J.; Zielinska, M. [University of Warsaw, Heavy Ion Laboratory, Warsaw (Poland); Bruce, A.M. [University of Brighton, School of Environment and Technology, Brighton (United Kingdom); Droste, C.; Grodner, E.; Morek, T. [University of Warsaw, Nuclear Physics Division, IEP, Warsaw (Poland); Kisielinski, M. [University of Warsaw, Heavy Ion Laboratory, Warsaw (Poland); The Andrzej Soltan Institute for Nuclear Studies, Warsaw (Poland); Korman, A. [The Andrzej Soltan Institute for Nuclear Studies, Warsaw (Poland); Kowalczyk, M.; Mierzejewski, J. [University of Warsaw, Heavy Ion Laboratory, Warsaw (Poland); University of Warsaw, Nuclear Physics Division, IEP, Warsaw (Poland); Marganiec, J. [University of Lodz, Faculty of Physics and Applied Informatics, Lodz (Poland); Gesellschaft fuer Schwerionenforschung (GSI), Reactions and Nuclear Astrophysics Division, Darmstadt (Germany); Sobczak, K. [University of Lodz, Faculty of Physics and Applied Informatics, Lodz (Poland); Institute of Physics Polish Academy of Sciences, Warsaw (Poland); Trzaska, W.H. [University of Jyvaeskylae, Department of Physics, Survontie 9, P.O. Box 35, Jyvaeskylae (Finland); Helsinki Institute of Physics, Survontie 9, P.O. Box 35, Helsinki (Finland)

    2009-12-15

    The decay of the I{sup {pi}}=K{sup {pi}}=8{sup -} isomeric state at 2340keV in {sup 132}Ce has been investigated in the {sup 120}Sn({sup 16}O,4n){sup 132}Ce reaction. The measurements were carried out in e-{gamma} and {gamma}-{gamma} coincidence modes using an electron spectrometer coupled to the OSIRIS II gamma-ray array at the Heavy Ion Laboratory of the University of Warsaw. Experimentally obtained internal conversion coefficients for the 8{sup -}{yields}6{sup +} and 8{sup -}{yields}5{sup +} transitions allowed the multipolarities, mixing ratios, reduced transition probabilities and hindrance factors to be determined. (orig.)

  9. Synthesis of heterocycles through transition-metal-catalyzed isomerization reactions

    DEFF Research Database (Denmark)

    Ishøy, Mette; Nielsen, Thomas Eiland

    2014-01-01

    of structurally complex and diverse heterocycles. In this Concept article, we attempt to cover this area of research through a selection of recent versatile examples. A sea of opportunities! Transition-metal-catalyzed isomerization of N- and O-allylic compounds provides a mild, selective and synthetically...... versatile method to form iminium and oxocarbenium ions. Given the number of reactions involving these highly electrophilic intermediates, this concept provides a sea of opportunities for heterocycle synthesis, (see scheme; Nu=nucleophile). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim....

  10. A system to measure isomeric state half-lives in the 10 ns to 10 μs range

    Energy Technology Data Exchange (ETDEWEB)

    Toufen, D. L., E-mail: dennis@if.usp.br [Institute of Physics, University of São Paulo, C.P. 66318, 05315-970 São Paulo, São Paulo (Brazil); Federal Institute of Education, Science and Technology of São Paulo - IFSP, 07115-000 Guarulhos, São Paulo (Brazil); Allegro, P. R. P.; Medina, N. H.; Oliveira, J. R. B.; Cybulska, E. W.; Seale, W. A.; Ribas, R. V. [Institute of Physics, University of São Paulo, C.P. 66318, 05315-970 São Paulo, São Paulo (Brazil); Linares, R. [Fluminense Federal University, 24220-900 Niterói, Rio de Janeiro (Brazil); Silveira, M. A. G. [Universitary Center of FEI, 09850-901 São Bernardo do Campo, São Paulo (Brazil)

    2014-07-15

    The Isomeric State Measurement System (SISMEI) was developed to search for isomeric nuclear states produced by fusion-evaporation reactions. The SISMEI consists of 10 plastic phoswich telescopes, two lead shields, one NaI(Tl) scintillation detector, two Compton suppressed HPGe γ-ray detectors, and a cone with a recoil product catcher. The new system was tested at the 8 UD Pelletron tandem accelerator of the University of São Paulo with the measurement of two known isomeric states: {sup 54}Fe, 10{sup +} state (E = 6527.1 (11) keV, T{sub 1/2} = 364(7) ns) and the 5/2{sup +} state of {sup 19}F (E = 197.143 (4) keV, T{sub 1/2} = 89.3 (10) ns). The results indicate that the system is capable of identifying delayed transitions, of measuring isomeric state lifetimes, and of identifying the feeding transitions of the isomeric state through the delayed γ-γ coincidence method. The measured half-life for the 10{sup +} state was T{sub 1/2} = 365(14) ns and for the 5/2{sup +} state, 100(36) ns.

  11. A system to measure isomeric state half-lives in the 10 ns to 10 μs range

    Science.gov (United States)

    Toufen, D. L.; Allegro, P. R. P.; Medina, N. H.; Oliveira, J. R. B.; Cybulska, E. W.; Seale, W. A.; Linares, R.; Silveira, M. A. G.; Ribas, R. V.

    2014-07-01

    The Isomeric State Measurement System (SISMEI) was developed to search for isomeric nuclear states produced by fusion-evaporation reactions. The SISMEI consists of 10 plastic phoswich telescopes, two lead shields, one NaI(Tl) scintillation detector, two Compton suppressed HPGe γ-ray detectors, and a cone with a recoil product catcher. The new system was tested at the 8 UD Pelletron tandem accelerator of the University of São Paulo with the measurement of two known isomeric states: 54Fe, 10+ state (E = 6527.1 (11) keV, T1/2 = 364(7) ns) and the 5/2+ state of 19F (E = 197.143 (4) keV, T1/2 = 89.3 (10) ns). The results indicate that the system is capable of identifying delayed transitions, of measuring isomeric state lifetimes, and of identifying the feeding transitions of the isomeric state through the delayed γ-γ coincidence method. The measured half-life for the 10+ state was T1/2 = 365(14) ns and for the 5/2+ state, 100(36) ns.

  12. Observation of excited states and isomeric decays in doubly-odd 208Fr

    International Nuclear Information System (INIS)

    Kanjilal, D.; Bhattacharya, S.; Goswami, A.; Kshetri, R.; Raut, R.; Saha, S.; Bhowmik, R.K.; Gehlot, J.; Jnaneswari, G.; Muralithar, S.; Singh, R.P.; Mukherjee, B.; Mukherjee, G.

    2009-01-01

    The nuclei near the doubly magic 208 Pb are predicted to exhibit various interesting structural phenomena, one of which is a wealth of isomerism. However, a detailed study of high spin states of 211, 212, 213 Fr has already been done. Structure of such trans-Lead nuclei can be interpreted in terms of the shell model states, and the high spin states of these nuclei are interpreted. One of the major interests in the spectroscopic investigation of these nuclei is the role played by the i 13/2 state in creating isomeric levels which decay through transitions of higher muiltipolarity, or are hindered by the close proximity of the levels below. A systematic study of these nuclei will possibly reveal many other interesting structural features

  13. High spin states and isomeric decays in doubly-odd {sup 208}Fr

    Energy Technology Data Exchange (ETDEWEB)

    Kanjilal, D.; Bhattacharya, S.; Goswami, A.; Kshetri, R.; Raut, R. [Nuclear and Atomic Physics Division, Saha Institute of Nuclear Physics, Kolkata 700064 (India); Saha, S., E-mail: satyajit.saha@saha.ac.i [Nuclear and Atomic Physics Division, Saha Institute of Nuclear Physics, Kolkata 700064 (India); Bhowmik, R.K.; Gehlot, J.; Muralithar, S.; Singh, R.P. [Inter University Accelerator Centre, New Delhi 110067 (India); Jnaneswari, G. [Department of Physics, Andhra University, Vishakhapatnam 530003 (India); Mukherjee, G. [Variable Energy Cyclotron Centre, Kolkata 700064 (India); Mukherjee, B. [Department of Physics, Visva Bharati, Santiniketan 731235 (India)

    2010-10-15

    Neutron deficient isotopes of francium (Z=87, N{approx}121-123) as excited nuclei were produced in the fusion-evaporation reaction: {sup 197}Au({sup 16}O, xn) {sup 213-x}Fr at 100 MeV. The {gamma} rays from the residues were observed through the high sensitivity Germanium Clover detector array INGA. The decay of the high spin states and the isomeric states of the doubly-odd {sup 208}Fr nuclei, identified from the known sequence of ground state transitions, were observed. The half-lives of the E{sub {gamma}=}194(2) keV isomeric transition, known from earlier observations, was measured to be T{sub 1/2}=233(18) ns. A second isomeric transition at E{sub {gamma}=}383(2) keV and T{sub 1/2}=33(7) ns was also found. The measured half-lives were compared with the corresponding single particle estimates, based on the level scheme obtained from the experiment.

  14. The study of a new short-life isomeric state in 38K

    International Nuclear Information System (INIS)

    Iordachescu, A.

    1976-01-01

    The 38 K nucleus having a protone and neutron hole coupled with a 40 Ca inert core has a structure analysed easily by the shell model. A new short life, high spin and highly excited isomeric state of the 38 K nucleus has been studied in detail using this model. Theoretical aspects connected with static and dynamic electromagnetic moments of the nucleus state, with the magnetic moment of the nucleus and the selection rules according to the isotopic spin are presented in the case of gamma transitions. Experimentallz/ presented in the case of gamma transitions. Experimentally, it has been used a combination between a natural pulsation of the cyclotron beam and an external pulsation by electrostatic deflexion, thus obtaining a pulsation beam of 12-26 MeV alpha particles. As targets, a series of chemical chlorine combinations have been utilized, the isomeric state being obtained by the reaction 35 Cl(α,n) 38 K, having the isomeric level (1fsub(7/2))sub(7+)sup(2). (author)

  15. Abnormal radioactive decays out of long-lived super- and hyper-deformed isomeric states

    International Nuclear Information System (INIS)

    Marinov, A.; Gelberg, S.; Kolb, D.

    2000-01-01

    Complete text of publication follows. Recently (1-3) long-lived isomeric states have been found in the super- and hyper-deformed wells of the potential. These isomers manifested themselves by abnormal particle decays. An isomeric state in the superdeformed well of the potential in the parent nucleus can decay by very enhanced α-particle groups to superdeformed states in the daughter (1) or by very retarded α-particles (3) and also by protons (2) to normal states in the daughters. Similarly an isomeric state in the hyper-deformed well may decay by very retarded α-particle groups to superdeformed states (3), or by very enhanced α-groups to hyper-deformed states in the daughter nucleus (4). All these very unusual decay modes have been observed experimentally (1-4). For instance, a very high energy α-group of 8.6 MeV with 40d ≤ t 1/2 ≤ 2y (retardation factor of ∼10 13 ) has been observed in 195 Hg and interpreted as a III min → II min α-transition (3). Likewise, relatively low-energy and very enhanced α-particle groups (enhancement factors of 10 5 to 10 7 ) have been seen in several actinide sources and interpreted as due to II min → II min and III min → III min transitions (4). These unusual decay modes introduce new considerations in the study of heavy and superheavy elements. For instance, if low-energy α-particle groups around 4.4 - 4.6 MeV have been seen in nature (5), they may be interpreted as due to very enhanced III min → III min transitions in the superheavy element region around Z = 108 (eka-Os) with t 1/2 ∼10 8 y rather than ∼10 15 y as expected for normal α-transitions of such energies in this region, or due to very retarded III min → II min or II min → I min decays in nuclei around Os itself. In both cases, if such activities have been seen in nature, they indicate that the existence of the II min and III min isomeric states may be important in the nucleosynthesis process. It should be mentioned that long-lived high

  16. First observation of high spin states and isomeric decay in 210Fr

    International Nuclear Information System (INIS)

    Kanjilal, D.; Saha, S.; Bhattacharya, S.; Goswami, A.; Kshetri, R.; Raut, R.; Muralithar, S.; Singh, R. P.; Mukherjee, G.; Mukherjee, B.

    2011-01-01

    The first observation of the prompt and the delayed γ transitions involving the high spin states in 210 Fr is reported. The decay of the high spin states and the isomeric levels of 210 Fr, identified for the first time from the known sequence of low-lying transitions found earlier in the α decay of 214 Ac, were studied. High spin states of the doubly-odd 210 Fr, which were produced by the fusion evaporation reaction 197 Au ( 16 O, xn) 213-x Fr, were populated and the subsequent emitted γ rays were detected through the high-sensitivity germanium clover detector array INGA. The level scheme up to yrast levels of 5.3 MeV excitation energy and ∼20(ℎ/2π) angular momentum could be established for the first time through γγ, γγΔT coincidence, and DCO ratio measurements. A new low-lying isomeric transition at E γ = 203(2) keV was observed. The half-life was measured to be T 1/2 = 41(2) ns. The measured half-life was compared with the corresponding single-particle estimate, based on the level scheme obtained from the experiment.

  17. Dipole-resonance assisted isomerization in the electronic ground state using few-cycle infrared pulses.

    Science.gov (United States)

    Skocek, Oliver; Uiberacker, Christoph; Jakubetz, Werner

    2011-06-30

    A computational investigation of HCN → HNC isomerization in the electronic ground state by one- and few-cycle infrared pulses is presented. Starting from a vibrationally pre-excited reagent state, isomerization yields of more than 50% are obtained using single one- to five-cycle pulses. The principal mechanism includes two steps of population transfer by dipole-resonance (DR), and hence, the success of the method is closely linked to the polarity of the system and, in particular, the stepwise change of the dipole moment from reactant to transition state and on to products. The yield drops massively if the diagonal dipole matrix elements are artificially set to zero. In detail, the mechanism includes DR-induced preparation of a delocalized vibrational wavepacket, which traverses the barrier region and is finally trapped in the product well by DR-dominated de-excitation. The excitation and de-excitation steps are triggered by pulse lobes of opposite field direction. As the number of optical cycles is increased, the leading field lobes prepare a vibrational superposition state by off-resonant ladder climbing, which is then subjected to the three steps of the principal isomerization mechanism. DR excitation is more efficient from a preformed vibrational wavepacket than from a molecular eigenstate. The entire process can be loosely described as Tannor-Kosloff-Rice type transfer mechanism on a single potential surface effected by a single pulse, individual field lobes assuming the roles of pump- and dump-pulses. Pre-excitation to a transient wavepacket can be enhanced by applying a separate, comparatively weak few-cycle prepulse, in which the prepulse prepares a vibrational wavepacket. The two-pulse setup corresponds to a double Tannor-Kosloff-Rice control scheme on a single potential surface.

  18. Molecular and excited state properties of isomeric scarlet disperse dyes

    Science.gov (United States)

    Lim, Jihye; Szymczyk, Malgorzata; Mehraban, Nahid; Ding, Yi; Parrillo-Chapman, Lisa; El-Shafei, Ahmed; Freeman, Harold S.

    2018-06-01

    This work was part of an investigation aimed at characterizing the molecular and excited state properties of currently available disperse dyes developed to provide stability to extensive sunlight exposures when adsorbed on poly(ethylene terephthalate) (PET) fibers. Having completed the characterization of yellow, magenta, and cyan disperse dyes for PET-based fabrics used outdoors, our attention turned to the colors designed to enhance the color gamut of a standard 4-member (cyan/yellow/magenta/black) color set. The present study pertained specifically to the characterization of commercially available scarlet dyes. In this regard, HPLC analysis showed that a scarlet product used for PET coloration was mainly a 70/30 mixture of dyes, and the use of HRMS and single crystal X-ray diffraction analyses indicated that these two dyes were azo compounds derived from isomeric pyridine-based couplers which differed in the location of the primary amino (sbnd NH2) and anilino (sbnd NHPh) groups attached to the pyridine ring. One dye structure has the sbnd NHPh group para to the azo group (Sc2), while the other has that group in the ortho position (Sc3). The presence of either ortho substituent provides photostabilization through intramolecular H-bonding with the azo moiety. Further, results from molecular modeling studies showed that the lower excited state oxidation potential of Sc3 relative to that of Sc2 allows Sc3 to function as an energy quencher for the excited state of Sc2 - through thermodynamically favorable electron transfer.

  19. New isomeric states in 152,154,156Nd produced by spontaneous fission of 252Cf

    International Nuclear Information System (INIS)

    Gautherin, C.; Houry, M.; Korten, W.; Le Coz, Y.; Lucas, R.; Phan, X.H.; Theisen, C.; Belier, G.; Girod, M.; Meot, V.; Peru, S.; Astier, A.; Ducroux, L.; Meyer, M.; Redon, N.

    1998-01-01

    Isomeric states have been observed in fission-fragments produced by spontaneous fission of 252 Cf. These states are found in neutron rich nuclei of different structure and deformations. About 50 isomeric nuclei have been observed using coincidences between γ-rays identified in EUROGAM II and fission fragments detected in photovoltaic cells (SAPhIR). Lifetimes in the range from 20 ns to 2μs have been measured. Presented calculations based on HFB+D1S force on new measured isomeric states in the 152,154,156 Nd show evidence for K-isomers. (orig.)

  20. High-spin μs isomeric states in 96 Ag

    International Nuclear Information System (INIS)

    Becerril, A. D.; Lorusso, G.; Amthor, A. M.; Brown, B. A.; Estrade, A.; Guess, C. J.; Hitt, G. W.; Meharchand, R.; Schatz, H.; Smith, K.; Zegers, R. G. T.; Baumann, T.; Bazin, D.; Ginter, T.; Hausmann, M.; Minamisono, K.; Portillo, M.; Stolz, A.; Berryman, J. S.; Crawford, H. L.

    2011-01-01

    The isomeric and β decays of the N=Z+2 nucleus 96 Ag were investigated at the National Superconducting Cyclotron Laboratory. A cascade of γ-ray transitions originating from the deexcitation of a microsecond isomer was observed for the first time and was found in coincidence with two previously known transitions with energies of 470 and 667 keV. The isomeric half-life was determined as 1.45(7) μs, more precise than previously reported. The existence of a second, longer-lived microsecond isomer, associated with a 743-keV γ transition, is also proposed here. Shell model results within the (p 3/2 p 1/2 f 5/2 g 9/2 ) model space, using the jj44b interaction, reproduced level energies and isomeric decay half-lives reasonably well.

  1. High spin states in 63Cu. 17/2+ isomeric yrast state

    International Nuclear Information System (INIS)

    Tsan Ung Chan; Bruandet, J.F.; Dauchy, A.; Giorni, A.; Glasser, F.; Morand, C.; Chambon, B.; Drain, D.

    1979-01-01

    The 63 Cu nucleus has been studied via the reaction 61 Ni(α, pnγ), using different in beam γ spectroscopy techniques. An isomeric high-spin Yrast state 17/2 + (tau = 6.1 +- 0.6ns) is located at 4498 keV. The gsub(9/2) shell must be involved to explain positive high-spin states established in this work [fr

  2. First observation of isomeric state in {sup 97}Rb

    Energy Technology Data Exchange (ETDEWEB)

    Rudigier, Matthias; Blazhev, Andrey; Regis, Jean-Marc; Warr, Nigel; Jolie, Jan; Fransen, Christoph; Hackstein, Matthias; Pfeiffer, Michael; Rother, Wolfram; Thomas, Tim [IKP, Univ. Koeln (Germany); Simpson, Gary; Ramdhane, Mourad [LPSC, Grenoble (France); Koester, Ulli; Materna, Thomas; Urban, Waldemar [ILL, Grenoble (France); Daugas, Jean-Michel [CEA, DAM, DIF, Arpajon (France)

    2012-07-01

    Data on a new microsecond isomer in {sup 97}Rb are presented. The measurement was conducted at the LOHENGRIN mass separator at the ILL, Grenoble. We were able to deduce the level energy and lifetime of the state. The multipolarity of the transition to the ground state was determined using conversion electron spectroscopy. This information enabled us to assign a spin and parity to the state, based on quasi-particle-rotor model calculations. The nucleus {sup 97}Rb has neutron number 60, and is thus situated in the shape-phase transition line of the mass 100 nuclei. It is discussed how the new state fits into the region and the Rb-isotopic chain. Furthermore some new results on the decay of the 9/2{sup +} microsecond isomer of {sup 97}Sr are presented and discussed.

  3. Isomeric States in the Second and Third Well of the Potential and Long-Lived Superheavy Element

    International Nuclear Information System (INIS)

    Marinov, A.; Gelberg, S.; Kolb, D.

    1999-01-01

    Recently, in a study of the 16 O + 197 Au and 28 Si + 181 Ta reactions near and below the Coulomb barrier, long-lived high spin isomeric states have been found by us in the second and third well of the potential-energy surfaces. Such isomeric states have very unusual physical properties. In addition to their very long lifetimes, much longer than of their corresponding ground states, they have very unusual decay properties. They may decay by 5 to 7 orders of magnitude enhanced alpha particles, in transitions from the second or third well of the potential in the parent nuclei to the respective well in the daughters, or by very retarded alpha particles, in transitions from the second well in the parent nucleus to normal states in the daughter, or from the third well in the parent to the second well in the daughter. They also may decay by long-lived proton activities, in transitions from the second well in the parent nucleus to the normal states in the daughter. Experimental evidences for all these new phenomena will be presented in the conference. The existence of long-lived isomeric states in the second and third well of the potential is very important when the production of superheavy elements is considered. Because of the very much reduced extra-push energy needed for their production, they may be produced much easier than the normal states, in reactions between very heavy nuclei. In particular, the discovery of the long-lived superheavy element with Z = 112 can consistently be understood

  4. Using {sup 233}U-doped crystals to access the few-eV isomeric transition in {sup 229}Th

    Energy Technology Data Exchange (ETDEWEB)

    Stellmer, Simon; Schreitl, Matthias; Kazakov, Georgy A.; Sterba, Johannes H.; Schumm, Thorsten [Vienna Center for Quantum Science and Technology (VCQ) and Atominstitut, TU Wien, Vienna (Austria)

    2016-07-01

    The isotope {sup 229}Th possesses an exceptionally low-lying isomeric state at an energy of only a few eV. While direct laser excitation of the isomer is a tantalizing future prospect, the stage is not yet set for nuclear laser spectroscopy: too little is known about the energy, lifetime, and internal conversion pathways of the isomer. Alternative routes to populate the isomer are needed for further investigations. We use the alpha decay {sup 233}U →{sup 229g,m}Th to populate the isomer with a probability of 2%. The {sup 233}U is embedded into VUV-transparent crystals, as the isomer transition is expected around 160 nm. The wavelength of the gamma ray, emitted upon de-excitation of the isomer into the ground state, is measured with a spectrometer. Calculations show that the isomer emission is not obscured by radioluminescence of the crystal. We report on the current status of the experiment.

  5. Identification of levels above 6{sup -} isomeric state in {sup 66}Cu

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Purnima; Palit, R.; Biswas, S.; Saha, S. [Tata Institute of Fundamental Research, Department of Nuclear and Atomic Physics, Mumbai (India); Choudhury, D. [Horia Hulubei National Institute for Physics and Nuclear Engineering, ELI-NP, Magurele (Romania); Srivastava, P.C. [Indian Institute of Technology Roorkee, Department of Physics, Roorkee (India); Sethi, J. [Tata Institute of Fundamental Research, Department of Nuclear and Atomic Physics, Mumbai (India); University of Maryland, Department of Chemistry and Biochemistry, College Park, MD (United States)

    2017-04-15

    Excited states in odd-odd {sup 66}Cu were investigated in a reaction between a 136 MeV {sup 30}Si beam and a {sup 65}Cu target with the Indian National Gamma Array. Six new transitions have been identified including four transitions feeding the 600 ns 6{sup -} isomeric state from an investigation of prompt-prompt and prompt-delayed coincidence events. The results of the present work have extended the level structure of this nucleus up to I{sup π} = (9{sup -}). In addition, new information on the set of πp{sub 3/2}νg{sub 9/2} multiplets in this nucleus have been added. Shell model calculations were performed within the fpg{sub 9/2} and f{sub 5/2}pg{sub 9/2} model spaces. The results of shell model calculations using the fpg{sub 9/2} model space have been observed to be in better agreement with experimental excitation energies up to the highest spin observed. The results of the present work highlight the necessity of f{sub 7/2} proton holes to describe the positive as well as negative parity states in {sup 66}Cu. (orig.)

  6. Remind of the classification of some known isomeric transitions; Rappel de la classification des transitions isomeriques connues

    Energy Technology Data Exchange (ETDEWEB)

    Ballini, R; Levi, C; Papineau, L [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1953-07-01

    Relations of Berthelot (model of the liquid drop) and of Weisskopf (odd core to 'single' proton), between l'energie of a transition and her 'partial period' of emission of a {alpha} photon, are represented by easily usable diagrams. These relations are compared to the empiric relations for a certain number of groups of transitions. With regard to the M4 transitions, a rectification is given to the mode of treatment of the experimental results who had been proposed by Goldhaber and SUNYAR (1951). A test of systematic has been done, concerning the energy of isomeric transitions (grouping around some energies, variation of the nature, and of the energy of the transitions with Z, N and A). (author) [French] Les relations de Berthelot (modele de la goutte liquide) et de Weisskopf (noyau impair a proton ''celibataire''), entre l'energie d'une transition et la ''periode partielle'' d'emission d'un photon {alpha}, sont representees par des graphiques facilement utilisables. Ces relations sont comparees aux relations empiriques pour un certain nombre de groupes de transitions. En ce qui concerne les transitions M4, une rectification est donnee au mode de traitement des resultats experimentaux qui avait ete propose par GOLDHABER et SUNYAR (1951). Un essai de systematique a ete effectue, concernant l'energie des transitions isomeriques (groupement autour de certaines energies, variation de la nature et de l'energie des transitions avec Z, N et A). (auteur)

  7. Results of a Direct Search Using Synchrotron Radiation for the Low-Energy (229)Th Nuclear Isomeric Transition.

    Science.gov (United States)

    Jeet, Justin; Schneider, Christian; Sullivan, Scott T; Rellergert, Wade G; Mirzadeh, Saed; Cassanho, A; Jenssen, H P; Tkalya, Eugene V; Hudson, Eric R

    2015-06-26

    We report the results of a direct search for the (229)Th (I(π)=3/2(+)←5/2(+)) nuclear isomeric transition, performed by exposing (229)Th-doped LiSrAlF(6) crystals to tunable vacuum-ultraviolet synchrotron radiation and observing any resulting fluorescence. We also use existing nuclear physics data to establish a range of possible transition strengths for the isomeric transition. We find no evidence for the thorium nuclear transition between 7.3 eV and 8.8 eV with transition lifetime (1-2) s≲τ≲(2000-5600)  s. This measurement excludes roughly half of the favored transition search area and can be used to direct future searches.

  8. Excitation of isomeric states 1h11/2 in (γ, n) reactions

    International Nuclear Information System (INIS)

    Tonchev, A.P.; Gangrskij, Yu.P.; Belov, A.G.

    1995-01-01

    The cross sections of (γ, n) reactions were measured for ground and isomeric states 1h 11/2 in 16 isotopes of Pd, Cd, Sn, Te, Ba, Ce, Nd and Sm. The energy of γ-rays was placed in the region of Giant Dipole Resonance. An activation method of measurements has been used. IR dependence of neutron and proton number in nucleus was detected and of excitation energy of residual nucleus as well. Different factors influencing the values of the isomeric ratios are discussed. 20 refs., 5 figs., 2 tabs

  9. Concurrent Mass Measurement and Laser Spectroscopy for Unambiguous Isomeric State Assignment

    Science.gov (United States)

    Lascar, Daniel; Babcock, Carla; Henderson, Jack; Pearson, Matt

    2017-09-01

    Recent work by the TITAN group at TRIUMF on isomeric state mass measurements of odd-A, neutron-rich cadmium nuclei has shown a disconnect between experiment and theory in 127 g , mCd. The spin and parity assignments of the ground and isomeric states are assigned as 3/2+ and 11/2-, respectively, primarily via systematic arguments. Conversely, state of the art shell model and ab initio calculations show a reversal of the states, predicting a ground state of 11/2- and a 3/2+ isomer. Penning Trap Mass Spectrometry (PTMS) can measure the energy separation between the ground state and the isomer without ambiguity but cannot, on its own, comment on the spin and parity. Collinear Laser Spectroscopy (CLS) experiments have been performed on 127Cd and have elegantly demonstrated the existence of both 3/2+ and 11/2- states. What CLS cannot do, on its own, is assign an ordering to those states. If, however, a PTMS and CLS experiment could be performed concurrently using identical beams from the same facility then there exists sufficient information shared between both experiments that a definitive assignment can be made. We present a concept for a new slate of measurements using existing experimental facilities simultaneously, with shared resources, to definitively assign spin and parity for ground and isomeric states in short-lived nuclei.

  10. New isomeric states in {sup 152,154,156}Nd produced by spontaneous fission of {sup 252}Cf

    Energy Technology Data Exchange (ETDEWEB)

    Gautherin, C.; Houry, M.; Korten, W.; Le Coz, Y.; Lucas, R.; Phan, X.H.; Theisen, C. [Commissariat l`Energie Atomique de Saclay, Gif sur Yvette (France). DSM/DAPINA/SPhN; Badimon, C.; Barreau, G.; Doan, T.P.; Pedemay, G. [Centre d`Etudes Nucleaires de Bordeaux-Gradignan, Domaine du Haut Vigneau, F-33175 Gradignan (France); Belier, G.; Girod, M.; Meot, V.; Peru, S. [Commissariat a l`Energie Atomique de Bruyeres-le-Chatel, DAM/SPN, BP12, F-91680 Bruyeres-le-Chatel (France); Astier, A.; Ducroux, L.; Meyer, M.; Redon, N. [Institut de Physique Nucleaire de Lyon, F-69622 Villeurbanne Cedex (France)

    1998-04-01

    Isomeric states have been observed in fission-fragments produced by spontaneous fission of {sup 252}Cf. These states are found in neutron rich nuclei of different structure and deformations. About 50 isomeric nuclei have been observed using coincidences between {gamma}-rays identified in EUROGAM II and fission fragments detected in photovoltaic cells (SAPhIR). Lifetimes in the range from 20 ns to 2{mu}s have been measured. Presented calculations based on HFB+D1S force on new measured isomeric states in the {sup 152,154,156}Nd show evidence for K-isomers. (orig.) With 8 figs., 27 refs.

  11. Multi-quasiparticle high-K isomeric states in deformed nuclei

    Directory of Open Access Journals (Sweden)

    Xu F. R.

    2016-01-01

    Full Text Available In the past years, we have made many theoretical investigations on multi-quasiparticle high-K isomeric states. A deformation-pairing-configuration self-consistent calculation has been developed by calculating a configuration-constrained multi-quasiparticle potential energy surface (PES. The specific single-particle orbits that define the high-K configuration are identified and tracked (adiabatically blocked by calculating the average Nilsson numbers. The deformed Woods-Saxon potential was taken to give single-particle orbits. The configuration-constrained PES takes into account the shape polarization effect. Such calculations give good results on excitation energies, deformations and other structure information about multi-quasiparticle high-K isomeric states. Many different mass regions have been investigated.

  12. High rate gamma spectroscopy system for activation analysis of short-lived isomeric transitions

    Energy Technology Data Exchange (ETDEWEB)

    Westphall, G P [Atominstitut der Oesterreichischen Hochschulen, Vienna

    1976-07-15

    A high rate spectroscopy system specially suited for measurement of short-lived isomeric transitions is described, which, as part of a fast activation analysis facility at the TRIGA Mark II reactor, provides for automatic recording and immediate evaluation of gamma spectra taken from nuclides activated at stationary or pulsed reactor power. The system consists of a commercial de-coupled Ge(Li)-detector of 70 cm/sup 3/ modified for recycling operation for input rates in excess of 500000 c/s /sup 60/Co, a time variant trapezoidal shaping section and a fast constant dead-time ADC coupled to a programmed multichannel analyzer. Novel circuits for efficient pile-up rejection and time variant base line restoration extend the concept of gated integration up to count rates of more than 200000 c/s /sup 60/Co. Time-sequenced recording of spectra is performed by a minicomputer operated as a front-end processor of a larger laboratory computer, where final data processing takes place. New concepts for very simple and cost-effective implementation of multichannel analyzers by means of general purpose small computers are described.

  13. A high rate gamma spectroscopy system for activation analysis of short lived isomeric transitions

    Energy Technology Data Exchange (ETDEWEB)

    Westphal, G P [Atominstitut, Vienna (Austria)

    1976-07-01

    A high rate spectroscopy system specially suited for measurement of short-lived isomeric transitions is described, which, as part of a fast activation analysis facility at the TRIGA Mark II reactor, provides for automatic recording and immediate evaluation of gamma spectra taken from nuclides activated at stationary or pulsed reactor power. The system consists of a commercial DC-coupled Ge(Li)-detector of 70 cm{sup 3} modified for recycling operation for input rates in excess of 500,000 c/s Co-60, a time variant trapezoidal shaping section and a fast constant dead-time ADC coupled to a programmed multi-channel analyzer. Novel circuits for efficient pile-up rejection and time variant base line restoration extend the concept of gated integration up to count rates of more than 300,000 c/s Co-60. Time-sequenced recording of spectra is performed by a mini computer operated as a front-end processor of a larger laboratory computer, where final data processing takes place. New concepts for very simple and cost-effective implementation of multi-channel analyzers by means of general purpose small computers are described. (author)

  14. Gamma radiation and temperature influence on the chemical effect produced by isomeric transition in the telluric acid

    International Nuclear Information System (INIS)

    Muriel G, M.

    1976-01-01

    When the gamma radiation due to the isomeric transition is internally converted an autoionization is produced. For atoms with a high atomic number this autoionization can be a large one and produce a fragmentation in a molecule. In the specific case of the solid state these fragments remain trapped in different places of the crystalline system. This can be considered as chemical change in the original molecule. These damages produced by the nuclear transformation can be measured by different methods: heating, gamma rays, pressure, etc. In this work the results of an experimental measurement of the behavior of the crystalline telluric acid molecule fragments under gamma radiation (0 to 20 Mrads) with controlled temperature of 2 0 C (-196 0 C to 50 0 C) it is presented. It was observed that the values of the mentioned behavior vary rapidly at first for relatively low doses and that for larger doses these values remained constant. Besides with a lower temperature these variation are progressively lower. (author)

  15. g-factor of the 7- isomeric state in 128Ba

    International Nuclear Information System (INIS)

    Kaur, J.; Bansal, N.; Bhati, A.K.; Sharma, V.R.; Kumar, H.; Kumar, R.; Bhowmik, R.K.; Kumar, V.

    2014-01-01

    The time differential perturbed angular distribution technique (TDPAD) has been used to measure the g-factor of the 2396 keV, 7 - isomeric state in 128 Ba. The measured value of g(7 - ) is 1.21 ± 0.01. This value is about 80% higher than the value for the expected configuration of the state and also different in sign. This clearly shows that the configuration of the state does not correspond to the pure two quasineutron configuration that was assigned to it through previous results of in-beam γ-ray spectroscopy

  16. Cis-to- Trans Isomerization of Azobenzene Derivatives Studied with Transition Path Sampling and Quantum Mechanical/Molecular Mechanical Molecular Dynamics.

    Science.gov (United States)

    Muždalo, Anja; Saalfrank, Peter; Vreede, Jocelyne; Santer, Mark

    2018-04-10

    Azobenzene-based molecular photoswitches are becoming increasingly important for the development of photoresponsive, functional soft-matter material systems. Upon illumination with light, fast interconversion between a more stable trans and a metastable cis configuration can be established resulting in pronounced changes in conformation, dipole moment or hydrophobicity. A rational design of functional photosensitive molecules with embedded azo moieties requires a thorough understanding of isomerization mechanisms and rates, especially the thermally activated relaxation. For small azo derivatives considered in the gas phase or simple solvents, Eyring's classical transition state theory (TST) approach yields useful predictions for trends in activation energies or corresponding half-life times of the cis isomer. However, TST or improved theories cannot easily be applied when the azo moiety is part of a larger molecular complex or embedded into a heterogeneous environment, where a multitude of possible reaction pathways may exist. In these cases, only the sampling of an ensemble of dynamic reactive trajectories (transition path sampling, TPS) with explicit models of the environment may reveal the nature of the processes involved. In the present work we show how a TPS approach can conveniently be implemented for the phenomenon of relaxation-isomerization of azobenzenes starting with the simple examples of pure azobenzene and a push-pull derivative immersed in a polar (DMSO) and apolar (toluene) solvent. The latter are represented explicitly at a molecular mechanical (MM) and the azo moiety at a quantum mechanical (QM) level. We demonstrate for the push-pull azobenzene that path sampling in combination with the chosen QM/MM scheme produces the expected change in isomerization pathway from inversion to rotation in going from a low to a high permittivity (explicit) solvent model. We discuss the potential of the simulation procedure presented for comparative calculation of

  17. Magnetic dipole moments of High-K isomeric states in Hf isotopes

    CERN Multimedia

    Walters, W; Nishimura, K; Bingham, C R

    2007-01-01

    It is proposed to make precision measurements of the magnetic moments of 5 multi-quasi-particle K-isomers in Hf nuclei by the Nuclear Magnetic Resonance of Oriented Nuclei (NMR/ON) technique using the NICOLE on-line nuclear orientation facility and exploiting the unique HfF$_{3}$ beams recently available at ISOLDE. Results will be used to extract single-particle and collective g-factors of the isomeric states and their excitations and to shed new light on their structure.

  18. Variational Transition State Theory

    Energy Technology Data Exchange (ETDEWEB)

    Truhlar, Donald G. [Univ. of Minnesota, Minneapolis, MN (United States)

    2016-09-29

    This is the final report on a project involving the development and applications of variational transition state theory. This project involved the development of variational transition state theory for gas-phase reactions, including optimized multidimensional tunneling contributions and the application of this theory to gas-phase reactions with a special emphasis on developing reaction rate theory in directions that are important for applications to combustion. The development of variational transition state theory with optimized multidimensional tunneling as a useful computational tool for combustion kinetics involved eight objectives.

  19. A VUV detection system for the direct photonic identification of the first excited isomeric state of "2"2"9Th

    International Nuclear Information System (INIS)

    Seiferle, B.; Von der Wense, L.; Thirolf, P.G.; Laatiaoui, M.

    2016-01-01

    With an expected energy of 7.6(5) eV, "2"2"9Th possesses the lowest excited nuclear state in the landscape of all presently known nuclei. The energy corresponds to a wavelength of about 160 nm and would conceptually allow for an optical laser excitation of a nuclear transition. We report on a VUV optical detection system that was designed for the direct detection of the isomeric ground-state transition of "2"2"9Th. "2"2"9"("m") Th ions originating from a "2"3"3U α-recoil source are collected on a micro electrode that is placed in the focus of an annular parabolic mirror. The latter is used to parallelize the UV fluorescence that may emerge from the isomeric ground-state transition of "2"2"9Th. The parallelized light is then focused by a second annular parabolic mirror onto a CsI-coated position-sensitive MCP detector behind the mirror exit. To achieve a high signal-to-background ratio, a small spot size on the MCP detector needs to be achieved. Besides extensive ray-tracing simulations of the optical setup, we present a procedure for its alignment, as well as test measurements using a D_2 lamp, where a focal-spot size of ∼100 μm has been achieved. Assuming a purely photonic decay, a signal-to-background ratio of ∼7000:1 could be achieved. (authors)

  20. Communication: Electronic flux induced by crossing the transition state

    Science.gov (United States)

    Jia, Dongming; Manz, Jörn; Yang, Yonggang

    2018-01-01

    We present a new effect of chemical reactions, e.g., isomerizations, that occurs when the reactants pass along the transition state, on the way to products. It is based on the well-known fact that at the transition state, the electronic structure of one isomer changes to the other. We discover that this switch of electronic structure causes a strong electronic flux that is well distinguishable from the usual flux of electrons that travel with the nuclei. As a simple but clear example, the effect is demonstrated here for bond length isomerization of Na2 (21Σu+), with adiabatic crossing the barrier between the inner and outer wells of the double minimum potential that support different "Rydberg" and "ionic" type electronic structures, respectively.

  1. Measurements of 14-MeV neutron cross-sections for the production of isomeric states in hafnium isotopes

    International Nuclear Information System (INIS)

    Patrick, B.H.; Sowerby, M.G.; Wilkins, C.G.; Russen, L.C.

    1990-01-01

    The cross sections for the production of isomeric states in the reactions 179 Hf(n,2n) 178m2 Hf, 180 Hf(n,2n) 179m2 Hf, 179 Hf(n,n') 179m2 Hf with 14 MeV neutrons have been measured and compared with the theoretical ones. 4 refs, 3 figs, 4 tabs

  2. Counting efficiencies by liquid scintillation counting. Single isomeric transitions; Eficiencia de recuento por centelleo liquido. Transiciones isomericas simples

    Energy Technology Data Exchange (ETDEWEB)

    Grau Carles, A.; Grau Malonda, A.

    1995-07-01

    In this work we present liquid scintillation counting efficiency tables for several radionuclides with single isomeric transitions, in which electron conversion and gamma emission processes are competitive. We study the radionuclides: 58mCo, 77mSe, 79mBr, 87mSr, S9mY, 93mNb, 103mRh, 107mAg, 109mAg, 113mIn, 131mXe, I33mXe, 135raBa, 137mBa, 167raEr, for two different scintillators, Ultima-Gold and Insta-Gel. We consider volumes of 10 and 15 mL for Ultima Gold, and 15 mL for Insta-Gel. (Author) 18 refs.

  3. The decay of 399 KeV isomeric state in 197Pt

    International Nuclear Information System (INIS)

    Soares, J.C.; Melo, A.A.; Gil, F.B.; Dias, H.

    1981-02-01

    The nuclear levels in 197 Pt have been studied from decay of 95.4 min 197 (sup m)Pt. The isomeric state was produced by (n,#betta#) reaction on the enriched 196 Pt. The #betta#-ray spectra have been observed with a hyperpure Ge detector and a large volume Ge(Li) detector. The half lives of the 399 KeV and the 53 KeV states were determined with improved precision. The results are: T1/2 (399 KeV) = 95.41 +- 0.18 min and T1/2(53 KeV) = 16.58 +- 0.17 ns. The g-factor of the 53 Kev 5/2 - state has been measured by the gamma-gamma time differential perturbed angular correlation (TDPAC) method in an external magnetic field of 25,1 kG using the 346 - 53 KeV gamma cascade. The value of g-factor was obtained to be + 0.335 +- 0.010. This result is compared with the known g-factors of the similar states in 195 Pt, and in 197 Hg and 199 Hg and also with the theoretical calculations based on the quasiparticle-phonon coupling scheme. Possibility of using the 346 - 53 KeV gamma cascade in 197 Pt in the future TDPAC studies is discussed. (Author) [pt

  4. Thermal solid-state Z/E isomerization of 2-alkylidene-4-oxothiazolidines: effects of non-covalent interactions

    Directory of Open Access Journals (Sweden)

    ZDRAVKO DŽAMBASKI

    2011-03-01

    Full Text Available Configurational isomerization of stereo-defined 5-substituted and unsubstituted 2-alkylidene-4-oxothiazolidines (1 in the solid state, giving the Z/E mixtures in various ratios, was investigated by 1H-NMR spectroscopy, X-ray powder crystallography and differential scanning calorimetry (DSC. The Z/E composition can be rationalized in terms of non-covalent interactions, involving intermolecular and intramolecular hydrogen bonding and directional non-bonded 1,5-type S×××O interactions. X-Ray powder crystallography, using selected crystalline (Z-4-oxothiazolidine substrates, revealed transformation to the amorphous state during the irreversible Z®E process. A correlation between previous results on the Z/E isomerization in solution and now in the solid state was established.

  5. Advances in gamma ray resonant scattering and absorption long-lived isomeric nuclear states

    CERN Document Server

    Davydov, Andrey V

    2015-01-01

    This book presents the basics and advanced topics of research of gamma ray physics. It describes measuring of  Fermi surfaces with gamma resonance spectroscopy and the theory of angular distributions of resonantly scattered gamma rays. The dependence of excited-nuclei average lifetime on the shape of the exciting-radiation spectrum and electron binding energies in the spectra of scattered gamma rays is described. Resonant excitation by gamma rays of nuclear isomeric states with long lifetime leads to the emission and absorption lines. In the book, a new gamma spectroscopic method, gravitational gamma spectrometry, is developed. It has a resolution hundred million times higher than the usual Mössbauer spectrometer. Another important topic of this book is resonant scattering of annihilation quanta by nuclei with excited states in connection with positron annihilation. The application of the methods described is to explain the phenomenon of Coulomb fragmentation of gamma-source molecules and resonant scatt...

  6. The introduction of hydrogen bond and hydrophobicity effects into the rotational isomeric states model for conformational analysis of unfolded peptides

    Science.gov (United States)

    Engin, Ozge; Sayar, Mehmet; Erman, Burak

    2009-03-01

    Relative contributions of local and non-local interactions to the unfolded conformations of peptides are examined by using the rotational isomeric states model which is a Markov model based on pairwise interactions of torsion angles. The isomeric states of a residue are well described by the Ramachandran map of backbone torsion angles. The statistical weight matrices for the states are determined by molecular dynamics simulations applied to monopeptides and dipeptides. Conformational properties of tripeptides formed from combinations of alanine, valine, tyrosine and tryptophan are investigated based on the Markov model. Comparison with molecular dynamics simulation results on these tripeptides identifies the sequence-distant long-range interactions that are missing in the Markov model. These are essentially the hydrogen bond and hydrophobic interactions that are obtained between the first and the third residue of a tripeptide. A systematic correction is proposed for incorporating these long-range interactions into the rotational isomeric states model. Preliminary results suggest that the Markov assumption can be improved significantly by renormalizing the statistical weight matrices to include the effects of the long-range correlations.

  7. The introduction of hydrogen bond and hydrophobicity effects into the rotational isomeric states model for conformational analysis of unfolded peptides

    International Nuclear Information System (INIS)

    Engin, Ozge; Sayar, Mehmet; Erman, Burak

    2009-01-01

    Relative contributions of local and non-local interactions to the unfolded conformations of peptides are examined by using the rotational isomeric states model which is a Markov model based on pairwise interactions of torsion angles. The isomeric states of a residue are well described by the Ramachandran map of backbone torsion angles. The statistical weight matrices for the states are determined by molecular dynamics simulations applied to monopeptides and dipeptides. Conformational properties of tripeptides formed from combinations of alanine, valine, tyrosine and tryptophan are investigated based on the Markov model. Comparison with molecular dynamics simulation results on these tripeptides identifies the sequence-distant long-range interactions that are missing in the Markov model. These are essentially the hydrogen bond and hydrophobic interactions that are obtained between the first and the third residue of a tripeptide. A systematic correction is proposed for incorporating these long-range interactions into the rotational isomeric states model. Preliminary results suggest that the Markov assumption can be improved significantly by renormalizing the statistical weight matrices to include the effects of the long-range correlations

  8. Investigating the large deformation of the 5 /2+ isomeric state in 73Zn: An indicator for triaxiality

    Science.gov (United States)

    Yang, X. F.; Tsunoda, Y.; Babcock, C.; Billowes, J.; Bissell, M. L.; Blaum, K.; Cheal, B.; Flanagan, K. T.; Garcia Ruiz, R. F.; Gins, W.; Gorges, C.; Grob, L. K.; Heylen, H.; Kaufmann, S.; Kowalska, M.; Krämer, J.; Malbrunot-Ettenauer, S.; Neugart, R.; Neyens, G.; Nörtershäuser, W.; Otsuka, T.; Papuga, J.; Sánchez, R.; Wraith, C.; Xie, L.; Yordanov, D. T.

    2018-04-01

    Recently reported nuclear spins and moments of neutron-rich Zn isotopes measured at ISOLDE-CERN [C. Wraith et al., Phys. Lett. B 771, 385 (2017), 10.1016/j.physletb.2017.05.085] show an uncommon behavior of the isomeric state in 73Zn. Additional details relating to the measurement and analysis of the Znm73 hyperfine structure are addressed here to further support its spin-parity assignment 5 /2+ and to estimate its half-life. A systematic investigation of this 5 /2+ isomer indicates that significant collectivity appears due to proton/neutron E 2 excitations across the proton Z = 28 and neutron N = 50 shell gaps. This is confirmed by the good agreement of the observed quadrupole moments with large scale Monte Carlo shell model calculations. In addition, potential energy surface calculations in combination with T plots reveal a triaxial shape for this isomeric state.

  9. Xylene isomerization

    KAUST Repository

    Bilaus, Rakan Sulaiman; Pinnau, Ingo

    2016-01-01

    at isomenzation conditions and producing an isomerized product comprising a higher proportion of p-xylene than in the feed mixture, wherein the catalyst comprises an acidic sulfonated catalytic membrane. Xylene isomenzation can also be coupled with a p

  10. Probing the Single-Particle Character of Rotational States in F 19 Using a Short-Lived Isomeric Beam

    Science.gov (United States)

    Santiago-Gonzalez, D.; Auranen, K.; Avila, M. L.; Ayangeakaa, A. D.; Back, B. B.; Bottoni, S.; Carpenter, M. P.; Chen, J.; Deibel, C. M.; Hood, A. A.; Hoffman, C. R.; Janssens, R. V. F.; Jiang, C. L.; Kay, B. P.; Kuvin, S. A.; Lauer, A.; Schiffer, J. P.; Sethi, J.; Talwar, R.; Wiedenhöver, I.; Winkelbauer, J.; Zhu, S.

    2018-03-01

    A beam containing a substantial component of both the Jπ=5+ , T1 /2=162 ns isomeric state of F 18 and its 1+, 109.77-min ground state is utilized to study members of the ground-state rotational band in F 19 through the neutron transfer reaction (d ,p ) in inverse kinematics. The resulting spectroscopic strengths confirm the single-particle nature of the 13 /2+ band-terminating state. The agreement between shell-model calculations using an interaction constructed within the s d shell, and our experimental results reinforces the idea of a single-particle-collective duality in the descriptions of the structure of atomic nuclei.

  11. Variational transition state theory

    International Nuclear Information System (INIS)

    Truhlar, D.G.

    1986-01-01

    This project is concerned with the development and applications of generalized transition state theory and multidimensional tunneling approximations to chemical reaction rates. They have developed and implemented several practical versions of variational transition state theory (VTST), namely canonical variational theory (CVT), improved canonical variational theory (ICVT), and microcanonical variational theory (μVT). They have also developed and implemented several accurate multidimensional semiclassical tunneling approximations, the most accurate of which are the small-curvature semiclassical adiabatic (SCSA), large-curvature version-3 (LC3), and least-action (LA) approximations. They have applied the methods to thermal rate constants, using transmission coefficients based on ground-state tunneling, and they have also presented and applied adiabatic and diabatic extensions to calculated rate constants for vibrationally excited reactants. Their general goal is to develop accurate methods for calculating chemical reaction rate constants that remain practical even for reasonably complicated molecules. The approximations mentioned above yield rate constants for systems whose potential energy surface is known or assumed. Thus a second, equally important aspect of their work is the determination or modeling, semi-empirically and/or from electronic structure calculations, of potential energy surfaces

  12. Changes in Atmospheric Butanes and Pentanes and Their Isomeric Ratios in the Continental United States

    Science.gov (United States)

    Rossabi, Sam; Helmig, Detlev

    2018-04-01

    Nonmethane hydrocarbons have been used as tracers in research on emissions and atmospheric oxidation chemistry. This research investigates source region mixing ratio trends of the nonmethane hydrocarbons i-butane, n-butane, i-pentane, and n-pentane, and the (i/n) isomeric ratios of these compounds between 2001 and 2015. Data collected at Photochemical Assessment Monitoring Stations, mandated by the U.S. Environmental Protection Agency in ozone nonattainment areas, and data collected at Global Greenhouse Gas Reference Network sites within the National Oceanic and Atmospheric Administration network, and analyzed at the Institute of Arctic and Alpine Research at the University of Colorado-Boulder, were examined. Among all considered species, linear regression analyses on concentration time series had negative slopes at 81% of sites, indicating predominantly declining butane and pentane atmospheric concentrations. Mostly negative slopes (78% of sites) were found for the (i/n) butane and pentane isomeric ratios, including all six and seven statistically significant (i/n) butane and pentane trends, respectively. Over the 15 year investigation period and averaged over all sites, total relative changes were 30 and 45% for the (i/n) ratios of butanes and pentanes, respectively, with a relative increase in the prominence of the n-isomers. Most likely causes include changing isomeric ratios in gasoline sector emissions, and increasing influence of oil and natural gas industry emissions. Changes in concentrations and isomeric ratios depend on proximity of contributing emission sources to measurement sites.

  13. Part A. Neutron activation analysis of selenium and vanadium in biological matrices. Part B. Isomeric transition activation in aqueous solutions of alkyl bromides

    International Nuclear Information System (INIS)

    Ebrahim, A.

    1988-01-01

    Several procedures were evaluated for determination of selenium in biological fluids and vanadium in biological tissues by neutron activation analysis (NAA) employing 77m Se and 52 V isotopes, respectively. Procedures for determination of total selenium, trimethylselenonium (TMSe) ion and selenite (SeO 3 2- ) ion in urine and serum and for total selenoamino acids in urine were developed by utilizing anion exchange chromatography and molecular NAA. A pre-column derivatization of selenoamino acids with o-phthalaldehyde was necessary for their determination. Also an analytical approach was developed for determination of trace vanadium in liver samples from normal and diabetic rats as well as human and cow. Reactions of bromine-80 activated by radiative neutron capture and bromine-82 activated by isomeric transition were investigated in aqueous solutions of bromomethane and 1-bromobutane. Bromine-80 organic yields decreased with decreasing solute concentrations. The tendency for aggregation of the solute molecules diminished as the solute concentration approached zero where the probable state of the solute approached a monomolecular dispersion. Unlike reactions of 80 Br born by 79 Br(n,γ) 80 Br reaction, the total organic product yields resulting from the 82m Br(I.T.) 82 Br process showed no solute concentration dependence

  14. Iodine-Catalyzed Isomerization of Dimethyl Muconate

    Energy Technology Data Exchange (ETDEWEB)

    Settle, Amy E [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Berstis, Laura R [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Zhang, Shuting [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rorrer, Nicholas [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Hu, Haiming [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Richards, Ryan [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Beckham, Gregg T [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Crowley, Michael F [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Vardon, Derek R [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2018-04-12

    cis,cis-Muconic acid is a platform biobased chemical that can be upgraded to drop-in commodity and novel monomers. Among the possible drop-in products, dimethyl terephthalate can be synthesized via esterification, isomerization, Diels-Alder cycloaddition, and dehydrogenation. The isomerization of cis,cis-dimethyl muconate (ccDMM) to the trans,trans-form (ttDMM) can be catalyzed by iodine; however, studies have yet to address (i) the mechanism and reaction barriers unique to DMM, and (ii) the influence of solvent, potential for catalyst recycle, and recovery of high-purity ttDMM. To address this gap, we apply a joint computational and experimental approach to investigate iodine-catalyzed isomerization of DMM. Density functional theory calculations identified unique regiochemical considerations due to the large number of halogen-diene coordination schemes. Both transition state theory and experiments estimate significant barrier reductions with photodissociated iodine. Solvent selection was critical for rapid kinetics, likely due to solvent complexation with iodine. Under select conditions, ttDMM yields of 95% were achieved in <1 h with methanol, followed by high purity recovery (>98%) with crystallization. Lastly, post-reaction iodine can be recovered and recycled with minimal loss of activity. Overall, these findings provide new insight into the mechanism and conditions necessary for DMM isomerization with iodine to advance the state-of-the-art for biobased chemicals.

  15. The role of dissociation channels of excited electronic states in quantum optimal control of ozone isomerization: A three-state dynamical model

    Energy Technology Data Exchange (ETDEWEB)

    Kurosaki, Yuzuru, E-mail: kurosaki.yuzuru@jaea.go.jp [Quantum Beam Science Directorate, Tokai Research and Development Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Ho, Tak-San, E-mail: tsho@Princeton.EDU [Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States); Rabitz, Herschel, E-mail: hrabitz@Princeton.EDU [Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States)

    2016-05-01

    The prospect of performing the open → cyclic ozone isomerization has attracted much research attention. Here we explore this consideration theoretically by performing quantum optimal control calculations to demonstrate the important role that excited-state dissociation channels could play in the isomerization transformation. In the calculations we use a three-state, one-dimensional dynamical model constructed from the lowest five {sup 1}A′ potential energy curves obtained with high-level ab initio calculations. Besides the laser field-dipole couplings between all three states, this model also includes the diabatic coupling between the two excited states at an avoided crossing leading to competing dissociation channels that can further hinder the isomerization process. The present three-state optimal control simulations examine two possible control pathways previously considered in a two-state model, and reveal that only one of the pathways is viable, achieving a robust ∼95% yield to the cyclic target in the three-state model. This work represents a step towards an ultimate model for the open → cyclic ozone transformation capable of giving adequate guidance about the necessary experimental control field resources as well as an estimate of the ro-vibronic spectral character of cyclic ozone as a basis for an appropriate probe of its formation.

  16. Radioactive nuclide production and isomeric state branching ratios in P + W reactions to 200 mev

    International Nuclear Information System (INIS)

    Young, P.G.; Chadwick, M.B.

    1995-01-01

    Calculations of nuclide yields from spallation reactions usually assume that the products are formed in their ground states. We are performing calculations of product yields from proton reactions on tungsten isotopes that explicitly account for formation of the residual nuclei in excited states. The Hauser-Feshbach statistical/preequilibrium code GNASH, with full accounting for angular momentum conservation and electromagnetic transitions, is utilized in the calculations. We present preliminary results for isomer branching ratios for proton reactions to 200 MeV for several products including the 31-y, 16+ state in l78 Hf and the 25-d, 25/2- state in 179 Hf. Knowledge of such branching ratios, might be important for concepts such as accelerator production of tritium that utilize intermediate-energy proton reactions on tungsten

  17. Variational transition-state theory

    International Nuclear Information System (INIS)

    Truhlar, D.G.; Garrett, B.C.

    1980-01-01

    A general introduction to and some results from studies of a procedure called variational transition-state theory are presented. A fundamental assumption of this theory is that the net rate of forward reaction at equilibrium equals the equilibrium flux in the product direction through the transition state where the transition state is a surface in phase space dividing reactants from products. Classical generalized-transition-state-theory calculations for nine collinear systems are compared to classical trajectory calculations. This new technique should provide useful insight into the successes and failures of the conventional theory and useful quantitative estimates of possible errors on the predictions of conventional transition-state theory. This should also contribute to a more accurate theory now available for the practical calculations of chemical reaction rates and thermochemical and structural interpretations of rate processes

  18. Half-lives of ground and isomeric states in {sup 97}Cd and the astrophysical origin of {sup 96}Ru

    Energy Technology Data Exchange (ETDEWEB)

    Lorusso, G., E-mail: lorusso@ribf.riken.j [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Becerril, A.; Amthor, A. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Baumann, T.; Bazin, D. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Berryman, J.S. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Brown, B.A. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Cyburt, R.H. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Crawford, H.L. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States)

    2011-05-09

    First experimental evidence for a high-spin isomer (25/2{sup +}) in {sup 97}Cd, a waiting point in the astrophysical rapid proton capture process, is presented. The data were obtained in {beta}-decay studies at NSCL using the new RF Fragment Separator system and detecting {beta}-delayed protons and {beta}-delayed {gamma} rays. Decays from ground and isomeric states were disentangled, and proton emission branches were determined for the first time. We find half-lives of 1.10(8) s and 3.8(2) s, and {beta}-delayed proton emission branches of 12(2)% and 25(4)% were deduced for the ground and isomeric states, respectively. With these results, the nuclear data needed to determine an rp-process contribution to the unknown origin of solar {sup 96}Ru are in place. When the new data are included in astrophysical rp-process calculations, one finds that an rp-process origin of {sup 96}Ru is unlikely.

  19. Quantum optimal control pathways of ozone isomerization dynamics subject to competing dissociation: A two-state one-dimensional model

    International Nuclear Information System (INIS)

    Kurosaki, Yuzuru; Ho, Tak-San; Rabitz, Herschel

    2014-01-01

    We construct a two-state one-dimensional reaction-path model for ozone open → cyclic isomerization dynamics. The model is based on the intrinsic reaction coordinate connecting the cyclic and open isomers with the O 2 + O asymptote on the ground-state 1 A ′ potential energy surface obtained with the high-level ab initio method. Using this two-state model time-dependent wave packet optimal control simulations are carried out. Two possible pathways are identified along with their respective band-limited optimal control fields; for pathway 1 the wave packet initially associated with the open isomer is first pumped into a shallow well on the excited electronic state potential curve and then driven back to the ground electronic state to form the cyclic isomer, whereas for pathway 2 the corresponding wave packet is excited directly to the primary well of the excited state potential curve. The simulations reveal that the optimal field for pathway 1 produces a final yield of nearly 100% with substantially smaller intensity than that obtained in a previous study [Y. Kurosaki, M. Artamonov, T.-S. Ho, and H. Rabitz, J. Chem. Phys. 131, 044306 (2009)] using a single-state one-dimensional model. Pathway 2, due to its strong coupling to the dissociation channel, is less effective than pathway 1. The simulations also show that nonlinear field effects due to molecular polarizability and hyperpolarizability are small for pathway 1 but could become significant for pathway 2 because much higher field intensity is involved in the latter. The results suggest that a practical control may be feasible with the aid of a few lowly excited electronic states for ozone isomerization

  20. Isomeric Targets and Beams

    International Nuclear Information System (INIS)

    Oganesyan, Yu.Ts.; Karamyan, S.A.

    1994-01-01

    One of the main topics of modern nuclear physics is the investigation of exotic nuclei including hyper-nuclei, trans fermium elements, proton and neutron rich isotopes near drip lines as well as high-spin excited states and states with anomalous deformation. The isomerism of nuclei is closely related with such phenomena as the alignment of single-particle orbitals, the coexistence of various deformations and the manifestation of intruder-levels from neighbouring shells. The investigation of electromagnetic and nuclear interactions of isomers could give important information on their shell structure and its role in the mechanism of nuclear reactions. For such experiments one can either make isomeric targets (sufficiently long-lived) or use the methods of acceleration of isomeric nuclei. Recently, an exotic 16 + four-quasiparticle isomer of 178 Hf m 2 was produced in a micro weight quantity and the first nuclear reactions on it were successfully observed. The talk describes these experiments as well as new ideas for the continuation of the studies and some advantageous ways for the isomeric beams production by the method of direct acceleration or by the secondary beam method. 35 refs., 15 figs., 8 tabs

  1. Xylene isomerization

    KAUST Repository

    Bilaus, Rakan Sulaiman

    2016-06-23

    A process for producing xylenes, in particular para-xylene that is less energy intensive than conventional processes is provided. In an embodiment the process comprises contacting a feed mixture in an isomenzation zone with a catalyst at isomenzation conditions and producing an isomerized product comprising a higher proportion of p-xylene than in the feed mixture, wherein the catalyst comprises an acidic sulfonated catalytic membrane. Xylene isomenzation can also be coupled with a p-xylene extraction process, where the raffinate (p-xylene deprived stream) from the extraction process is fed to an isomenzation reactor to produce p-xylene. In an embodiment, the process can comprise: a) providing a feed stream comprising a mixture of xylene isomers including p-xylene; b) extracting p-xylene from the feed stream using a separator to separate the feed stream into a p-xylene rich stream and a p-xylene deprived stream; and c) delivering the p-xylene deprived stream to an isomenzation unit, the isomenzation unit including an acidic sulfonated catalytic membrane, and using the isomenzation unit to produce an isomerized product comprising a higher proportion of p-xylene than in the p-xylene deprived stream delivered to the isomenzation unit. In any one or more aspects, the isomenzation unit can be operated at a temperature in the range of less than 350°, for example about 20°C to about 200°C.

  2. Isomeric and high-spin states of 94Tc and the search for yrast isomers near N~50

    Science.gov (United States)

    Lee, I. Y.; Johnson, N. R.; McGowan, F. K.; Young, G. R.; Guidry, M. W.; Yates, S. W.

    1981-07-01

    A search for isomers in the N~50 region has produced no evidence of high-spin yrast isomerism. A new 4.5-ns low-multiplicity isomer has been identified and assigned to 94Tc, while the yrast sequence of 94Tc has been established to more than 5 MeV in excitation energy. [NUCLEAR REACTIONS 76Ge, 78Se(20Ne,xnypγ), E=80.9 MeV, 89Y, 93Nb(10B,xnypγ), E=52.0,58.4,62.8 MeV; measured Eγ, Iγ, γ-γ prompt and delayed coin, γ-X coin; deduced levels, t12 of 94Tc isomer, yrast states.

  3. Experimental grounds for nuclear shape isomerism

    International Nuclear Information System (INIS)

    Makarenko, V.E.

    1995-11-01

    Experimental data on fission isomeric states of actinide nuclei - half lives, energies, quantum numbers, decay branches and spectroscopic properties - are discussed. Quite a few results find their explanation in the framework of nuclear shape isomerism hypothesis being the in-thing for about thirty years. Others seem to be the hints to the quasiparticle nature of fission isomers. The problem could be solved by direct measurement of nuclear spin for isomeric states. (author). 44 refs, 1 tab

  4. State diagrams of tokamaks and state transitions

    International Nuclear Information System (INIS)

    Minardi, E.

    1992-01-01

    In a simple one-fluid cylindrical model of transport and of dissipative effects, the family of the magnetic states of the Tokamak which correspond to a vanishing entropy production in the confinement region is characterized by a define relation or ''state equation'' involving the relevant parameters of the discharge. An investigation is made as to how the entropy production changes when the current density profile is rearranged by a perturbation which conserves the poloidal magnetic flux. It is shown that for a sufficiently short time interval, that is to say t 2 E τ s where τ E is the energy confinement time and τ s is the resistive time, neighbouring bifurcating equilibria exist which can be reached with a flux-conserving transition and with increase of the magnetic entropy. The family of these new states can also be characterized by a state equation involving the relevant discharge parameters. When the state equations of the two families are simultaneously satisfied by the same set of parameter values, a flux-conserving, entropy-increasing transition may take place between states of the two families. The modifications of the current density and of the temperature profiles involved in the transition and the conditions that the discharge parameters should satisfy in order that the transition could occur are investigated. (author)

  5. Prompt and delayed spectroscopy of At203 : Observation of a shears band and a 29/2+ isomeric state

    Energy Technology Data Exchange (ETDEWEB)

    Auranen, K.; Uusitalo, J.; Juutinen, S.; Badran, H.; Defranchi Bisso, F.; Cox, D.; Grahn, T.; Greenlees, P. T.; Herzáň, A.; Jakobsson, U.; Julin, R.; Konki, J.; Leino, M.; Lightfoot, A.; Mallaburn, M. J.; Neuvonen, O.; Pakarinen, J.; Papadakis, P.; Partanen, J.; Rahkila, P.; Sandzelius, M.; Sarén, J.; Scholey, C.; Sorri, J.; Stolze, S.; Wang, Y. K.

    2018-02-01

    Using fusion-evaporation reactions, a gas-filled recoil separator, recoil-gating technique and recoil-isomer decay tagging technique we have extended the level scheme of At-203 (N = 118) significantly. We have observed an isomeric [tau = 14.1(3) mu s] state with a spin and parity of 29/2(+). The isomeric state is suggested to originate from the pi(h(9/2)) circle times |Po-202; 11(-)> coupling, and it is depopulated through 286 keV E2 and 366 keV E3 transitions. In addition, we have observed a cascade of magnetic-dipole transitions which is suggested to be generated by the shears mechanism.

  6. Study of the stability of the ground states and K-isomeric states of 250Fm and 254102 against spontaneous fission

    International Nuclear Information System (INIS)

    Lazarev, Yu.A.; Lobanov, Yu.V.; Sagajdak, R.N.; Utenkov, V.K.; Kharitonov, Yu.P.; Shirokovskij, I.V.; Tret'yakova, S.P.; Oganessyan, Yu.Ts.

    1988-01-01

    By employing the 249 Cf( 4 He, 3n) and 208 Pb( 48 Ca,2n) reactions, experiments to study the stability against spontaneous fission of the nuclides 250 Fm and 254 102 as well as of the two-quasi-particle (2 q-p) K isomers 250 Fm (T 1/2 =1,8±0,1 s) and 254 102 (T 1/2 =0,28±0,04 s) have been performed. The groundstate spontaneous fission of the two nuclides has been discovered and the corresponding branching ratios b sf and partial half-lives T sf , respectively, have been determined to be: (6,9±1,0)x10 -5 , 0,83±0,15 yr for 250 Fm; (1,7±0,5)x10 -3 , (3,2±0,9)x10 4 s for 254 102. As a by-product of these studies, new data about cross sections of the 206,208 Pb( 48 Ca,xn) reactions have been obtained. Experiments designed to search for the spontaneous fission of the 2 q-p K-isometric states in 250 Fm and 254 102 have not revealed the effect in question. The lower limits of the ratios of the partial spontaneous fission half-lives for the 2 q-p K-isomeric states to those for the respective ground states, T * sf /T sf , have been established to be≥10 -1 for 250m Fm/ 250 Fm and ≥5x10 -3 for 254m 102/ 254 102. This means that the stability of the 2 q-p K-isomeric states in 250 Fm and 254 102 against spontaneous fission is practically not inferior to that of the ground states of these nuclei. In accord with the experimental findings, the theoretical estimates of T * sf /T sf made in the present paper show that, due to the influence of the specialization and blocking effects on the potential energy and the effective mass associated with fission, spontaneous fission from 2 q-p K-isomeric states cannot be facilitated but, on the contrary, should be essentially hindered compared with ground-state spontaneous fission

  7. Deconstructing field-induced ketene isomerization through Lagrangian descriptors.

    Science.gov (United States)

    Craven, Galen T; Hernandez, Rigoberto

    2016-02-07

    The time-dependent geometrical separatrices governing state transitions in field-induced ketene isomerization are constructed using the method of Lagrangian descriptors. We obtain the stable and unstable manifolds of time-varying transition states as dynamic phase space objects governing configurational changes when the ketene molecule is subjected to an oscillating electric field. The dynamics of the isomerization reaction are modeled through classical trajectory studies on the Gezelter-Miller potential energy surface and an approximate dipole moment model which is coupled to a time-dependent electric field. We obtain a representation of the reaction geometry, over varying field strengths and oscillation frequencies, by partitioning an initial phase space into basins labeled according to which product state is reached at a given time. The borders between these basins are in agreement with those obtained using Lagrangian descriptors, even in regimes exhibiting chaotic dynamics. Major outcomes of this work are: validation and extension of a transition state theory framework built from Lagrangian descriptors, elaboration of the applicability for this theory to periodically- and aperiodically-driven molecular systems, and prediction of regimes in which isomerization of ketene and its derivatives may be controlled using an external field.

  8. Consequences of acid strength for isomerization and elimination catalysis on solid acids.

    Science.gov (United States)

    Macht, Josef; Carr, Robert T; Iglesia, Enrique

    2009-05-13

    We address here the manner in which acid catalysis senses the strength of solid acids. Acid strengths for Keggin polyoxometalate (POM) clusters and zeolites, chosen because of their accurately known structures, are described rigorously by their deprotonation energies (DPE). Mechanistic interpretations of the measured dynamics of alkane isomerization and alkanol dehydration are used to obtain rate and equilibrium constants and energies for intermediates and transition states and to relate them to acid strength. n-Hexane isomerization rates were limited by isomerization of alkoxide intermediates on bifunctional metal-acid mixtures designed to maintain alkane-alkene equilibrium. Isomerization rate constants were normalized by the number of accessible protons, measured by titration with 2,6-di-tert-butylpyridine during catalysis. Equilibrium constants for alkoxides formed by protonation of n-hexene increased slightly with deprotonation energies (DPE), while isomerization rate constants decreased and activation barriers increased with increasing DPE, as also shown for alkanol dehydration reactions. These trends are consistent with thermochemical analyses of the transition states involved in isomerization and elimination steps. For all reactions, barriers increased by less than the concomitant increase in DPE upon changes in composition, because electrostatic stabilization of ion-pairs at the relevant transition states becomes more effective for weaker acids, as a result of their higher charge density at the anionic conjugate base. Alkoxide isomerization barriers were more sensitive to DPE than for elimination from H-bonded alkanols, the step that limits 2-butanol and 1-butanol dehydration rates; the latter two reactions showed similar DPE sensitivities, despite significant differences in their rates and activation barriers, indicating that slower reactions are not necessarily more sensitive to acid strength, but instead reflect the involvement of more unstable organic

  9. Possible evidence for shape isomeric γ-decay in μ- atoms of 238U

    International Nuclear Information System (INIS)

    Fromm, W.D.; Ortlepp, H.-G.; Polikanov, S.M.; Schmidt, U.; Zorin, G.N.; Arlt, R.; Musiol, G.

    1977-01-01

    A search for the γ-decay of the shape isomer in muonic 238 U excited by radiationless transitions has been performed. Seven delayed transitions in the energy region of 700 to 3200 keV have been observed with a large Ge(Li) detector. Two transitions with Esub(γ)=2215 and 3131 keV have been attributed to the decay of the shape isomeric state into levels in the first well. The isomeric shift of the second minimum Esub(II) approximately 600 keV in the presence of the muon and the decrease of the lifetime of the shape isomer to tau=12+-2 ns give arguments in favour of the connection of shape isomerism with large quadrupole deformations. (Auth.)

  10. Experiments with neutron-rich isomeric beams

    International Nuclear Information System (INIS)

    Rykaczewski, K.; Lewitowicz, M.; Pfuetzner, M.

    1998-01-01

    A review of experimental results obtained on microsecond-isomeric states in neutron-rich nuclei produced in fragmentation reactions and studied with SISSI-Alpha-LISE3 spectrometer system at GANIL Caen is given. The perspectives of experiments based on secondary reactions with isomeric beams are presented

  11. Internal conversion coefficients of M4 isomeric transitions in /sup 125/ /sup 127/ /sup 129/Te decay

    Energy Technology Data Exchange (ETDEWEB)

    Soni, S K; Kumar, A; Gupta, S L; Pancholi, S C [Delhi Univ. (India). Dept. of Physics and Astrophysics

    1977-01-01

    The internal conversion coefficients have been measured using a high resolution low energy Ge(Li) detector for the following M4 transitions: /sup 125/Te: 109.27 keV transition ..cap alpha..sub(T) = 357 +- 11; RG method, /sup 127/Te: 88,26 keV transition ..cap alpha..sub(K) = 484 +- 23; XPG method, /sup 129/Te: 105.50 keV transition ..cap alpha..sub(K) = 213 +- 10; XPG method. It is observed that these values are lower by 2.5-3.6% as compared with Hager and Seltzer's calculations. A comparison between experimental and theoretical ..cap alpha..sub(K) and ..cap alpha..sub(T) values for eleven M4 transitions shows that the experimental values are systematically lower.

  12. Effect of Isomerization on Excited-State Dynamics of Carotenoid Fucoxanthin

    Czech Academy of Sciences Publication Activity Database

    Kuznetsova, V.; Chábera, P.; Litvín, Radek; Polívka, Tomáš; Fuciman, M.

    2017-01-01

    Roč. 121, č. 17 (2017), s. 4438-4447 ISSN 1520-6106 Institutional support: RVO:60077344 Keywords : charge-transfer state * light-harvesting complex * pump-probe spectroscopy * ultrafast dynamics Subject RIV: BO - Biophysics OBOR OECD: Biophysics Impact factor: 3.177, year: 2016

  13. Transition state structures in solution

    International Nuclear Information System (INIS)

    Bertran, J.; Lluch, J. M.; Gonzalez-Lafont, A.; Dillet, V.; Perez, V.

    1995-01-01

    In the present paper the location of transition state structures for reactions in solution has been studied. Continuum model calculations have been carried out on the Friedel-Crafts alkylation reaction and a proton transfer through a water molecule between two oxygen atoms in formic acid. In this model the separation between the chemical system and the solvent has been introduced. On the other hand, the discrete Monte Carlo methodology has also been used to simulate the solvent effect on dissociative electron transfer processes. In this model, the hypothesis of separability is not assumed. Finally, the validity of both approaches is discussed

  14. g-factor of the 9/2+ isomeric state in 65Ni from transfer reaction

    International Nuclear Information System (INIS)

    Georgiev, G.; Matea, I.; Balabanski, D.L.; Daugas, J.M.; Meot, V.; Morel, P.; Oliveira Santos, F. de; Lewitowicz, M.; Franchoo, S.; Ibrahim, F.; Le Blanc, F.; Sorlin, O.; Stanoiu, M.; Verney, D.; Lo Bianco, G.; Saltarelli, A.; Lukyanov, S.; Penionzhkevich, Yu.E.; Neyens, G.; Vermeulen, N.; Yordanov, D.; Tarisien, M.

    2006-01-01

    We report a measurement of the g-factor of the I π =9/2 + , t 1/2 =22 ns isomer in 65 Ni. The state of interest was populated and spin-oriented using a single-neutron transfer on an enriched 64 Ni target. The value, which was obtained, g(9/2 + , 65m Ni)=-0.296(3) is well in agreement with the g-factors of the other 9/2 + states in the region and with large-basis shell model calculations. The known g-factor of the 9/2 + isomer in 63 Ni was used in order to verify the strength of the hyperfine field of Ni(Ni) at room temperature. (orig.)

  15. Observation of a γ-decaying millisecond isomeric state in 128Cd80

    Directory of Open Access Journals (Sweden)

    A. Jungclaus

    2017-09-01

    Full Text Available A new high-spin isomer in the neutron-rich nucleus 128Cd was populated in the projectile fission of a 238U beam at the Radioactive Isotope Beam Factory at RIKEN. A half-life of T1/2=6.3(8 ms was measured for the new state which was tentatively assigned a spin/parity of (15−. The experimental results are compared to shell model calculations performed using state-of-the-art realistic effective interactions and to the neighbouring nucleus 129Cd. In the present experiment no evidence was found for the decay of a 18+ E6 spin-trap isomer, based on the complete alignment of the two-neutron and two-proton holes in the 0h11/2 and the 0g9/2 orbit, respectively, which is predicted to exist by the shell model.

  16. Neutron knockout from 68,70Ni ground and isomeric states.

    Science.gov (United States)

    Recchia, F.; Weisshaar, D.; Gade, A.; Tostevin, J. A.; Janssens, R. V. F.; Albers, M.; Bader, V. M.; Baugher, T.; Bazin, D.; Berryman, J. S.; Brown, B. A.; Campbell, C. M.; Carpenter, M. P.; Chen, J.; Chiara, C. J.; Crawford, H. L.; Hoffman, C. R.; Kondev, F. G.; Korichi, A.; Langer, C.; Lauritsen, T.; Liddick, S. N.; Lunderberg, E.; Noji, S.; Prokop, C.; Stroberg, S. R.; Suchyta, S.; Wimmer, K.; Zhu, S.

    2018-02-01

    Neutron-rich isotopes are an important source of new information on nuclear physics. Specifically, the spin-isospin components in the nucleon-nucleon (NN) interaction, e.g., the proton-neutron tensor force, are expected to modify shell structure in exotic nuclei. These potential changes in the intrinsic shell structure are of fundamental interest. The study of the excitation energy of states corresponding to specific configurations in even-even isotopes, together with the single-particle character of the first excited states of odd-A, neutron-rich Ni isotopes, probes the evolution of the neutron orbitals around the Fermi surface as a function of the neutron number a step forward in the understanding of the region and the nature of the NN interaction at large N/Z ratios. In an experiment carried out at the National Superconducting Cyclotron Laboratory [1], new spectroscopic information was obtained for 68Ni and the distribution of single-particle strengths in 67,69Ni was characterized by means of single-neutron knockout from 68,70Ni secondary beams. The spectroscopic strengths, deduced from the measured partial cross sections to the individual states tagged by their de-exciting gamma rays, is used to identify and quantify configurations that involve neutron excitations across the N = 40 harmonic oscillator shell closure. The de-excitation γ rays were measured with the GRETINA tracking array [2]. The results challenge the validity of the most current shell-model Hamiltonians and effective interactions, highlighting shortcomings that cannot yet be explained. These results suggest that our understanding of the low-energy states in such nuclei is not complete and requires further investigation.

  17. Microwave assisted synthesis and solid-state characterization of lithocholyl amides of isomeric aminopyridines

    Czech Academy of Sciences Publication Activity Database

    Ahonen, K. V.; Lahtinen, M. K.; Valkonen, A. M.; Dračínský, Martin; Kolehmainen, E. T.

    2011-01-01

    Roč. 76, č. 3 (2011), s. 261-268 ISSN 0039-128X R&D Projects: GA AV ČR KJB400550903 Grant - others:AV ČR(CZ) M200380901; Academy of Finland(FI) 7127006; Academy of Finland(FI) 212588 Institutional research plan: CEZ:AV0Z40550506 Keywords : solid-state NMR * x-ray diffraction * litocholic acid Subject RIV: CC - Organic Chemistry Impact factor: 2.829, year: 2011

  18. Observation of a γ -decaying millisecond isomeric state in 128 Cd 80

    Energy Technology Data Exchange (ETDEWEB)

    Jungclaus, A.; Grawe, H.; Nishimura, S.; Doornenbal, P.; Lorusso, G.; Simpson, G. S.; Söderström, P. -A.; Sumikama, T.; Taprogge, J.; Xu, Z. Y.; Baba, H.; Browne, F.; Fukuda, N.; Gernhäuser, R.; Gey, G.; Inabe, N.; Isobe, T.; Jung, H. S.; Kameda, D.; Kim, G. D.; Kim, Y. -K.; Kojouharov, I.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Li, Z.; Sakurai, H.; Schaffner, H.; Shimizu, Y.; Steiger, K.; Suzuki, H.; Takeda, H.; Vajta, Zs.; Watanabe, H.; Wu, J.; Yagi, A.; Yoshinaga, K.; Benzoni, G.; Bönig, S.; Chae, K. Y.; Coraggio, L.; Daugas, J. -M.; Drouet, F.; Gadea, A.; Gargano, A.; Ilieva, S.; Itaco, N.; Kondev, F. G.; Kröll, T.; Lane, G. J.; Montaner-Pizá, A.; Moschner, K.; Mücher, D.; Naqvi, F.; Niikura, M.; Nishibata, H.; Odahara, A.; Orlandi, R.; Patel, Z.; Podolyák, Zs.; Wendt, A.

    2017-09-01

    A new high-spin isomer in the neutron-rich nucleus 128Cd was populated in the projectile fission of a 238U beam at the Radioactive Isotope Beam Factory at RIKEN. A half-life of T1/2 = 6.3(8) ms was measured for the new state which was tentatively assigned a spin/parity of (15-). The experimental results are compared to shell model calculations performed using state-of-the-art realistic effective interactions and to the neighbouring nucleus 129Cd. In the present experiment no evidence was found for the decay of a 18+ E6 spin-trap isomer, based on the complete alignment of the two-neutron and two-proton holes in the 0h11/2 and the 0g9/2 orbit, respectively, which is predicted to exist by the shell model.

  19. Isomeric and high-spin states of 94Tc and the search for yrast isomers near Napprox.50

    International Nuclear Information System (INIS)

    Lee, I.Y.; Johnson, N.R.; McGowan, F.K.; Young, G.R.; Guidry, M.W.; Yates, S.W.

    1981-01-01

    A search for isomers in the Napprox.50 region has produced no evidence of high-spin yrast isomerism. A new 4.5-ns low-multiplicity isomer has been identified and assigned to 94 Tc, while the yrast sequence of 94 Tc has been established to more than 5 MeV in excitation energy

  20. State Transitions in Semiarid Landscapes

    Science.gov (United States)

    Phillips, J. D.

    2012-04-01

    The U.S. Department of Agriculture has developed a large number of state-and-transition models (STM) to predict and interpret changes in vegetation communities in drylands of the southwestern U.S. These are represented as box-and-arrow models indicating potential changes in response to various combinations of management practices and environmental forcings. Analysis of the 320 STMs developed for areas within the state of Texas reveals two important aspects of environmental change in semiarid environments. First, the STMs are highly local—they are specific to very particular combinations of landform, soil, and climate. This is consistent with the perfect landscape concept in geomorphology, which emphasizes the irreducible importance of geographically and historically contingent local factors in addition to universal laws or principles in determining the state or condition of landscapes. Second, analysis of the STMs using algebraic graph theory shows that a majority of them have structures that tend to amplify effects of change and disturbances. In many cases the STMs represent a form of self-organization characterized by the potential of divergent behavior rather than convergence toward a dominant pattern or outcome. These results indicate that geomorphic, hydrologic, and ecological responses to climate and land use change are likely to be highly variable and idiosyncratic, both within and between semiarid landscapes of Texas.

  1. Theoretical and experimental study of the relaxation of excited states of the DCM laser dye. Intra-molecular electron transfer and photo-isomerization. Solvent effects

    International Nuclear Information System (INIS)

    Marguet, Sylvie

    1992-01-01

    This research thesis reports the study of a styrenic laser dye, the 4-(dicyanomethylene)-2-methyl-6-[p-(dimethylamino) styryl]-4H-pyrane or DCM for the characterization of the first electronic states and of the influence of the solvent on efficiencies of different relaxation processes of the first excited state S1 of the DCM. Due to the presence of a combination of a donor group and acceptor group, this compound has interesting properties of intra-molecular charge transfer and of photo-isomerization which highly depend on solvent polarity. Two approaches have been adopted to study these complementary processes: an experimental approach (determination of rate constants of the different deactivation ways of the S1 state by measuring fluorescence quantum efficiencies, photo-isomerization quantum efficiencies, and fluorescence lifetimes of DCM in about twenty solvent of increasing polarity), and a computational approach (a CS-INDO-MRI type quantum chemistry calculation to obtain potential energy curves, charge distributions, and dipolar moments of DCM first electronic states) [fr

  2. Modulating the Physical and Electronic Properties over Positional Isomerism: The Dispirofluorene-Dihydroindacenodithiophene (DSF-IDT) Family.

    Science.gov (United States)

    Peltier, Jean-David; Heinrich, Benoît; Donnio, Bertrand; Jeannin, Olivier; Rault-Berthelot, Joëlle; Poriel, Cyril

    2017-12-06

    We report the first studies on the intrinsic properties of a meta-substituted dihydroindacenodithienyl fragment and more generally the strong impact of positional isomerism on dihydroindacenodithiophene derivatives. The influence of the para and meta linkages has notably been highlighted not only for the electronic properties in solution (electrochemical properties, anodic polymerization, HOMO/LUMO energy levels, optical transitions, fluorescence spectra) but also on the physical properties in the solid state (molecular organization, crystallinity, and phase transitions). The positional isomerism hence appears to be a very efficient tool to drastically tune the properties of dihydroindacenodithiophene derivatives. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Geometrical Optimization Approach to Isomerization: Models and Limitations.

    Science.gov (United States)

    Chang, Bo Y; Shin, Seokmin; Engel, Volker; Sola, Ignacio R

    2017-11-02

    We study laser-driven isomerization reactions through an excited electronic state using the recently developed Geometrical Optimization procedure. Our goal is to analyze whether an initial wave packet in the ground state, with optimized amplitudes and phases, can be used to enhance the yield of the reaction at faster rates, driven by a single picosecond pulse or a pair of femtosecond pulses resonant with the electronic transition. We show that the symmetry of the system imposes limitations in the optimization procedure, such that the method rediscovers the pump-dump mechanism.

  4. Variations of structures and solid-state conductivity of isomeric silver(I) coordination polymers having linear and V-shaped thiophene-centered ditriazole ligands

    International Nuclear Information System (INIS)

    Hu, Bin; Geng, Jiao; Zhang, Lie; Huang, Wei

    2014-01-01

    A pair of new linear and V-shaped acceptor–donor–acceptor (A−D−A) thiophene-centered ditriazole structural isomers, i.e., 2,5-di(1H-1,2,4-triazol-1-yl)thiophene (L 1 ) and 3,4-di(1H-1,2,4-triazol-1-yl)thiophene (L 2 ), has been synthesized and characterized. They are used as μ 2 -bridging ligands to prepare a pair of silver(I) coordination polymers formulated as [Ag(L 1 )(NO 3 )] n (1) and [Ag(L 2 )(NO 3 )] n (2), which are also structural isomers at the supramolecular level. X-ray single-crystal diffraction analyses for 1 and 2 reveal that they exhibit the same one-dimensional (1D) coordination polymers but different structural architectures because of the distinguishable shape and configuration of isomeric ligands (L 1 and L 2 ) and the alterations of the coordination numbers. More interestingly, compared with the free ligands, 1D silver(I) polymeric isomers 1 and 2 show significant enhancement of solid-state conductivity to different extents (1.42×10 4 and 2.17×10 3 times), where 6.96 times' enhancement of solid-state conductivity from 1 to 2 has been observed. The formation of Ag–N coordinative bonds and the configurational discrepancy of L 1 and L 2 are believed to play important roles in facilitating the electron transport between molecules, which can also be supported by Density Function Theory calculations of their band gaps. - Graphical abstract: A pair of linear and V-shaped isomeric thiophene-centered ditriazole ligands (L 1 ) and L 2 are used to prepare a pair of silver(I) polymeric isomers (1 and 2), where significant enhancement of solid-state conductivity to different extents are observed originating from the distinguishable shape and configuration of isomeric ligands. - Highlights: • A pair of linear and V-shaped thiophene-centered ditriazole structural isomers is prepared. • They are used as µ 2 -bridging ligands to prepare a pair of silver(I) polymeric isomers. • Significant enhancement of solid-state conductivity is observed

  5. Bifurcations of transition states: Morse bifurcations

    International Nuclear Information System (INIS)

    MacKay, R S; Strub, D C

    2014-01-01

    A transition state for a Hamiltonian system is a closed, invariant, oriented, codimension-2 submanifold of an energy level that can be spanned by two compact codimension-1 surfaces of unidirectional flux whose union, called a dividing surface, locally separates the energy level into two components and has no local recrossings. For this to happen robustly to all smooth perturbations, the transition state must be normally hyperbolic. The dividing surface then has locally minimal geometric flux through it, giving an upper bound on the rate of transport in either direction. Transition states diffeomorphic to S 2m−3 are known to exist for energies just above any index-1 critical point of a Hamiltonian of m degrees of freedom, with dividing surfaces S 2m−2 . The question addressed here is what qualitative changes in the transition state, and consequently the dividing surface, may occur as the energy or other parameters are varied? We find that there is a class of systems for which the transition state becomes singular and then regains normal hyperbolicity with a change in diffeomorphism class. These are Morse bifurcations. Various examples are considered. Firstly, some simple examples in which transition states connect or disconnect, and the dividing surface may become a torus or other. Then, we show how sequences of Morse bifurcations producing various interesting forms of transition state and dividing surface are present in reacting systems, by considering a hypothetical class of bimolecular reactions in gas phase. (paper)

  6. Transition-metal-free synthesis of imidazo[2,1-b]thiazoles and thiazolo[3,2-a]benzimidazoles via an S-propargylation/5-exo-dig cyclization/isomerization sequence using propargyl tosylates as substrates.

    Science.gov (United States)

    Omar, Mohamed A; Frey, Wolfgang; Conrad, Jürgen; Beifuss, Uwe

    2014-11-07

    A transition-metal-free route for the synthesis of several N-fused heterocycles, including thiazolo[3,2-a]benzimidazoles and imidazo[2,1-b]thiazoles, is reported. The reaction between propargyl tosylates and 2-mercaptobenzimidazoles under basic conditions results in 3-substituted thiazolo[3,2-a]benzimidazoles, in yields up to 92% in a single synthesis step. With 2-mercaptoimidazoles as the substrate, the corresponding imidazo[2,1-b]thiazoles were exclusively obtained. The transformation is considered to proceed as an intermolecular S-propargylation that is followed by 5-exo-dig ring closure and double-bond isomerization.

  7. Transitions between compound states of spherical nuclei

    International Nuclear Information System (INIS)

    Kadmenskii, S.G.; Markushev, V.P.; Furman, V.I.

    1980-01-01

    Wigner's statistical matrices are used to study the average reduced g widths and their dispersion for g transitions from a compound state c to another state f, with a lower excitation energy but of arbitrary complexity, for spherical nuclei. It is found that the Porter--Thomas distribution holds for the g widths for all cases of practical interest. In g transitions between compound states c and c' with E/sub g/< or =2 MeV, the most important transitions are M1 transitions involving the major many-quasiparticle components of state c and E1 transitions involving the minor components of state c. It is shown that the strength functions predicted by the various theories for M1 and E1 transitions between compound states with E/sub g/< or =2 MeV are similar. Preference is assigned to the M1-transition version because of experimental results on (n,ga) reactions with thermal and resonance neutrons

  8. CP/MAS 13C NMR characterization of the isomeric states and intermolecular packing in tris(8-hydroxyquinoline) aluminum(III) (Alq3).

    Science.gov (United States)

    Kaji, Hironori; Kusaka, Yasunari; Onoyama, Goro; Horii, Fumitaka

    2006-04-05

    The isomeric states and intermolecular packing of tris(8-hydroxyquinoline) aluminum(III) (Alq(3)) in the alpha-, gamma-, and delta-crystalline forms and in the amorphous state, which are important for understanding the light-emitting and electron-transport properties, have been analyzed by CP/MAS (13)C NMR. This simple NMR experiment shows that the isomeric state of alpha- and amorphous Alq(3) is meridional, whereas that of gamma- and delta-Alq(3) is facial. In the amorphous Alq(3), the inclusion of facial isomers has been under debate. Our experiments show that meridional isomers are dominant in the amorphous Alq(3), although the existence of facial isomers cannot be completely denied. The local structure of amorphous Alq(3) is similar to that of alpha-Alq(3) and is significantly different from those of gamma- and delta-Alq(3). Among these Alq(3) samples, the effect of intermolecular interaction is not found only for gamma-Alq(3). This finding can explain the good solvent solubility of gamma-Alq(3), compared with the other crystalline forms. It is also shown that the structures are locally disordered not only for amorphous Alq(3) but also for alpha-Alq(3), although clear X-ray diffraction peaks are observed for alpha-Alq(3). In contrast, the local structures of gamma- and delta-Alq(3) are well defined. A clear relation is found between the spectral patterns of CP/MAS (13)C NMR and the fluorescence wavelengths; the samples, which consist of facial isomers, show blue-shifted fluorescence compared with those of meridionals.

  9. Optimal trajectories of brain state transitions.

    Science.gov (United States)

    Gu, Shi; Betzel, Richard F; Mattar, Marcelo G; Cieslak, Matthew; Delio, Philip R; Grafton, Scott T; Pasqualetti, Fabio; Bassett, Danielle S

    2017-03-01

    The complexity of neural dynamics stems in part from the complexity of the underlying anatomy. Yet how white matter structure constrains how the brain transitions from one cognitive state to another remains unknown. Here we address this question by drawing on recent advances in network control theory to model the underlying mechanisms of brain state transitions as elicited by the collective control of region sets. We find that previously identified attention and executive control systems are poised to affect a broad array of state transitions that cannot easily be classified by traditional engineering-based notions of control. This theoretical versatility comes with a vulnerability to injury. In patients with mild traumatic brain injury, we observe a loss of specificity in putative control processes, suggesting greater susceptibility to neurophysiological noise. These results offer fundamental insights into the mechanisms driving brain state transitions in healthy cognition and their alteration following injury. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  10. Isomers chart; Table des isomeres

    Energy Technology Data Exchange (ETDEWEB)

    Dupont-Gautier, P; Chantelot, S; Moisson, N [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-07-01

    The nuclear isomers are nuclides offering the same mass number and the same atomic number, but different energy levels. In the following chart the zero energy ground states are omitted and the metastable isomers, i.e. of non-zero energy, known and of measurable lifetime, are listed. The lower limit of this lifetime was set here to 0.1 x 10{sup -6} s. The various isomers were classified in increasing lifetimes. (authors) [French] Les isomeres nucleaires sont des nucleides presentant le meme nombre de masse et le meme numero atomique, mais des niveaux energetiques differents. Dans la table suivante, on a neglige les etats fondamentaux d'energie nulle et on a recense les isomeres metastables, c'est-a-dire d'energie non nulle, connus et de periode mesurable. La limite inferieure de cette periode a ete fixee ici a 0,1 x 10{sup -6} s. Les differents isomeres ont ete classes par periodes croissantes. (auteurs)

  11. Isomers chart; Table des isomeres

    Energy Technology Data Exchange (ETDEWEB)

    Dupont-Gautier, P.; Chantelot, S.; Moisson, N. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-07-01

    The nuclear isomers are nuclides offering the same mass number and the same atomic number, but different energy levels. In the following chart the zero energy ground states are omitted and the metastable isomers, i.e. of non-zero energy, known and of measurable lifetime, are listed. The lower limit of this lifetime was set here to 0.1 x 10{sup -6} s. The various isomers were classified in increasing lifetimes. (authors) [French] Les isomeres nucleaires sont des nucleides presentant le meme nombre de masse et le meme numero atomique, mais des niveaux energetiques differents. Dans la table suivante, on a neglige les etats fondamentaux d'energie nulle et on a recense les isomeres metastables, c'est-a-dire d'energie non nulle, connus et de periode mesurable. La limite inferieure de cette periode a ete fixee ici a 0,1 x 10{sup -6} s. Les differents isomeres ont ete classes par periodes croissantes. (auteurs)

  12. Identification of ensuremath J^{π = 19/2^+} and ensuremath 23/2^+ isomeric states in 127Sb

    Science.gov (United States)

    Watanabe, H.; Lane, G. J.; Dracoulis, G. D.; Byrne, A. P.; Nieminen, P.; Kondev, F. G.; Ogawa, K.; Carpenter, M. P.; Janssens, R. V. F.; Lauritsen, T.; Seweryniak, D.; Zhu, S.; Chowdhury, P.

    2009-11-01

    The nucleus ensuremath ^{127Sb} , which is on the neutron-rich periphery of the ensuremath β -stability region, has been populated in complex nuclear reactions involving deep-inelastic and fusion-fission processes with ensuremath {^{136}Xe} beams incident on thick targets. The previously known isomer at 2325 keV in ensuremath {^{127}Sb} has been assigned spin and parity ensuremath 23/2^+ , based on the measured ensuremath γ - ensuremath γ angular correlations and total internal conversion coefficients. The half-life has been determined to be 234(12) ns, somewhat longer than the value reported previously. The 2194 keV state has been assigned ensuremath J^{π} = 19/2^+ and identified as an isomer with ensuremath T_{1/2} = 14(1) ns , decaying by two ensuremath E2 branches. The observed level energies and transition strengths are compared with the predictions of a shell model calculation. Two ensuremath 15/2^+ states have been identified close in energy, and their properties are discussed in terms of mixing between vibrational and three-quasiparticle configurations.

  13. Splitting sensitivity of the ground and 7.6 eV isomeric states of 229Th

    International Nuclear Information System (INIS)

    Hayes, A. C.; Friar, J. L.; Moeller, P.

    2008-01-01

    The lowest-known excited state in nuclei is the 7.6 eV isomer of 229 Th. This energy is within the range of laser-based investigations that could allow accurate measurements of possible temporal variation of this energy splitting. This in turn could probe temporal variation of the fine-structure constant or other parameters in the nuclear Hamiltonian. We investigate the sensitivity of this transition energy to these quantities. We find that the two states are predicted to have identical deformations and thus the same Coulomb energies within the accuracy of the model (viz., within roughly 30 keV). We therefore find no enhanced sensitivity to variation of the fine-structure constant. In the case of the strong interaction the energy splitting is found to have a complicated dependence on several parameters of the interaction, which makes an accurate prediction of sensitivity to temporal changes of fundamental constants problematical. Neither the strong- nor Coulomb-interaction contributions to the energy splitting of this doublet can be constrained within an accuracy better than a few tens of keV, so that only upper limits can be set on the possible sensitivity to temporal variations of the fundamental constants

  14. Dependency in State Transitions of Wind Turbines

    DEFF Research Database (Denmark)

    Herp, Jürgen; Ramezani, Mohammad Hossein; S. Nadimi, Esmaeil

    2017-01-01

    © 2017 IEEE. Turbine states and predicting the transition into failure states ahead of time is important in operation and maintenance of wind turbines. This study presents a method to monitor state transitions of a wind turbine based on the online inference on residuals. In a Bayesian framework...... be abstracted from generated data. Two models are presented: 1) assuming independence and 2) assuming dependence between states. In order to select the right models, machine learning is utilized to update hyperparameters on the conditional probabilities. Comparing fixed to learned hyperparameters points out...... the impact machine learning concepts have on the predictive performance of the presented models. In conclusion, a study on model residuals is performed to highlight the contribution to wind turbine monitoring. The presented algorithm can consistently detect the state transition under various configurations...

  15. Reduced dimension rovibrational variational calculations of the S{sub 1} state of C{sub 2}H{sub 2}. II. The S{sub 1} rovibrational manifold and the effects of isomerization

    Energy Technology Data Exchange (ETDEWEB)

    Changala, P. Bryan, E-mail: bryan.changala@colorado.edu; Baraban, Joshua H.; Field, Robert W. [Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Stanton, John F. [Department of Chemistry and Biochemistry, Institute for Theoretical Chemistry, The University of Texas at Austin, Austin, Texas 78712 (United States); Merer, Anthony J. [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan and Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1 (Canada)

    2014-01-14

    Reduced dimension variational calculations have been performed for the rovibrational level structure of the S{sub 1} state of acetylene. The state exhibits an unusually complicated level structure, for various reasons. First, the potential energy surface has two accessible conformers, trans and cis. The cis conformer lies about 2700 cm{sup −1} above the trans, and the barrier to cis-trans isomerization lies about 5000 cm{sup −1} above the trans minimum. The trans vibrations ν{sub 4} (torsion) and ν{sub 6} (asym. bend) interact very strongly by Darling-Dennison and Coriolis resonances, such that their combination levels and overtones form polyads with unexpected structures. Both conformers exhibit very large x{sub 36} cross-anharmonicity since the pathway to isomerization is a combination of ν{sub 6} and ν{sub 3} (sym. bend). Near the isomerization barrier, the vibrational levels show an even-odd K-staggering of their rotational levels as a result of quantum mechanical tunneling through the barrier. The present calculations address all of these complications, and reproduce the observed K-structures of the bending and C–C stretching levels with good qualitative accuracy. It is expected that they will assist with the assignment of the irregular patterns near the isomerization barrier.

  16. Excitation of the isomeric states 1h sub 1 sub 1 sub / sub 2 in the nuclear reactions with gamma-quanta, neutrons and at beta decay

    CERN Document Server

    Belov, A G; Melnikova, L M; Ponomarev, V Yu; Tsoneva, N; Stoyanov, C; Balabanov, N P; Tonchev, A P

    2001-01-01

    The isomeric ratios (IR) were measured in the isotones with N = 81 ( sup 1 sup 3 sup 5 Xe, sup 1 sup 3 sup 7 Ba, sup 1 sup 3 sup 9 Ce, sup 1 sup 4 sup 1 Nd, and sup 1 sup 4 sup 3 Sm). Isomers with J suppi 11/2 sup - were excited in the reactions (n, gamma), (gamma, n), and beta sup + decay of sup 1 sup 3 sup 9 Pr and sup 1 sup 4 sup 1 Pm. The activation methods of gamma-spectrum measurement of reaction products was used. The marked difference of IR was observed in the isotones with the different atomic numbers Z but in the same reactions. The calculations of IR using low-level spectrum of final nuclei and probability of radiation transitions on the base of the quasiparticle phonon model were performed. The satisfactory agreement of the measured and calculated IR was obtained for all studied isotopes. The dependence of IR on Z is explained by the different energy of reaction and different probability levels population of the activation

  17. A structural phase transition coupled to the Fe{sup 3+} spin-state crossover in anhydrous RbMn[Fe(CN){sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Rykov, A. I., E-mail: rykov3@yahoo.com; Wang, J., E-mail: wangjh@dicp.ac.cn; Zhang, T. [Chinese Academy of Sciences, Moessbauer Effect Data Center, Dalian Institute of Chemical Physics (China); Nomura, K. [University of Tokyo, Graduate School of Engineering (Japan)

    2013-04-15

    Linkage isomerism is the coexistence of iso-compositional molecules or solids differing by connectivity of the metal to a ligand. In a crystalline solid state, the rotation is possible for asymmetric ligands, e.g., for cyanide ligand. Here we report on our observation of a phase transition in anhydrous RbMn[Fe(CN){sub 6}] (nearly stoichiometric) and on the effect of linkage isomerism ensuing our interpretation of the results of Moessbauer study in which we observe the iron spin state crossover among two phases involved into this transition. The anhydrous RbMn[Fe(CN){sub 6}] can be prepared via prolonged thermal treatment (1 week at at 80 Degree-Sign C) of the as-synthesized hydrated RbMn[Fe(CN){sub 6}]{center_dot}H{sub 2}O. The latter compound famous for its charge-transfer phase transition is a precursor in our case. As the temperature is raising above 80 Degree-Sign C (remaining below 100 Degree-Sign C) we observe RbMn[Fe(CN){sub 6}] that inherited its F-43 m symmetry from RbMn[Fe(CN){sub 6}]{center_dot}H{sub 2}O transforming to a phase of the Fm-3 m symmetry. In the latter, more than half of Fe{sup 3 + } ions are in high-spin state. We suggest a plausible way to explain the spin-crossover that is to allow the linkage isomerism by rotation of the cyanide ligands.

  18. Low-lying isomeric levels in Cu75

    Science.gov (United States)

    Daugas, J. M.; Faul, T.; Grawe, H.; Pfützner, M.; Grzywacz, R.; Lewitowicz, M.; Achouri, N. L.; Angélique, J. C.; Baiborodin, D.; Bentida, R.; Béraud, R.; Borcea, C.; Bingham, C. R.; Catford, W. N.; Emsallem, A.; de France, G.; Grzywacz, K. L.; Lemmon, R. C.; Lopez Jimenez, M. J.; de Oliveira Santos, F.; Regan, P. H.; Rykaczewski, K.; Sauvestre, J. E.; Sawicka, M.; Stanoiu, M.; Sieja, K.; Nowacki, F.

    2010-03-01

    Isomeric low-lying states were identified and investigated in the Cu75 nucleus. Two states at 61.8(5)- and 128.3(7)-keV excitation energies with half-lives of 370(40)- and 170(15)-ns were assigned as Cu75m1 and Cu75m2, respectively. The measured half-lives combined with the recent spin assignment of the ground state allow one to deduce tentatively spin and parity of the two isomers and the dominant multipolarities of the isomeric transitions with respect to the systematics of the Cu isotopes. Shell-model calculations using an up-to-date effective interaction reproduce the evolution of the 1/2-, 3/2-, and 5/2- states for the neutron-rich odd-mass Cu isotopes when filling the νg9/2. The results indicate a significant change in the nuclear structure in this region, where a single-particle 5/2- state coexists with more and more collective 3/2- and 1/2- levels at low excitation energies.

  19. Visualizing cell state transition using Raman spectroscopy.

    Directory of Open Access Journals (Sweden)

    Taro Ichimura

    Full Text Available System level understanding of the cell requires detailed description of the cell state, which is often characterized by the expression levels of proteins. However, understanding the cell state requires comprehensive information of the cell, which is usually obtained from a large number of cells and their disruption. In this study, we used Raman spectroscopy, which can report changes in the cell state without introducing any label, as a non-invasive method with single cell capability. Significant differences in Raman spectra were observed at the levels of both the cytosol and nucleus in different cell-lines from mouse, indicating that Raman spectra reflect differences in the cell state. Difference in cell state was observed before and after the induction of differentiation in neuroblastoma and adipocytes, showing that Raman spectra can detect subtle changes in the cell state. Cell state transitions during embryonic stem cell (ESC differentiation were visualized when Raman spectroscopy was coupled with principal component analysis (PCA, which showed gradual transition in the cell states during differentiation. Detailed analysis showed that the diversity between cells are large in undifferentiated ESC and in mesenchymal stem cells compared with terminally differentiated cells, implying that the cell state in stem cells stochastically fluctuates during the self-renewal process. The present study strongly indicates that Raman spectral morphology, in combination with PCA, can be used to establish cells' fingerprints, which can be useful for distinguishing and identifying different cellular states.

  20. Transition state theory for enzyme kinetics

    Science.gov (United States)

    Truhlar, Donald G.

    2015-01-01

    This article is an essay that discusses the concepts underlying the application of modern transition state theory to reactions in enzymes. Issues covered include the potential of mean force, the quantization of vibrations, the free energy of activation, and transmission coefficients to account for nonequilibrium effect, recrossing, and tunneling. PMID:26008760

  1. Stability and isomerization reactions of phenyl cation C{sub 6}H{sub 5}{sup +} isomers

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Dandan [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy (Jilin University), Changchun 130012 (China); Yang, Xue [College of Science, Jilin Institute of Chemical Technology, Jilin 132022 (China); Zhang, Xiaomei; Shan, Shimin [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy (Jilin University), Changchun 130012 (China); Xu, Haifeng, E-mail: xuhf@jlu.edu.cn [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy (Jilin University), Changchun 130012 (China); Yan, Bing, E-mail: yanbing@jlu.edu.cn [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy (Jilin University), Changchun 130012 (China)

    2016-03-01

    Highlights: • A total of 60 isomers of C{sub 6}H{sub 5}{sup +} cations were obtained at density functional theory. • The stability and isomerization reactions of C{sub 6}H{sub 5}{sup +} isomers were performed. • The structures, frequencies, thermodynamic properties of isomers were summarized. • Ring to ring or chain isomerization pathways were investigated using IRC method. • Result shows reactions contain hydrogen transfer, bond broken and reconstruction. - Abstract: As a key polyatomic molecular cation that plays a pivotal role in growth of the polycyclic aromatic hydrocarbons, phenyl cation C{sub 6}H{sub 5}{sup +} exhibits various isomers and isomerization reactions. Investigation on the structure and stability of the isomers as well as the isomerization is important for better understanding the chemical reactions involving C{sub 6}H{sub 5}{sup +} cations. In this work, we have performed a theoretical study on the stability and isomerization reactions of C{sub 6}H{sub 5}{sup +} isomers at density functional theory B3LYP/6-311G (d, p) level. We have obtained a total of 60 isomers of C{sub 6}H{sub 5}{sup +} cations, most of which are reported for the first time. The geometries, vibrational frequencies, thermodynamic properties and stability of 28 out of 60 isomers have been summarized in detail. Different ring-to-ring and ring-to-chain isomerization pathways, which are connected via 28 transition states, have been investigated using the intrinsic reaction coordinate method. The results show that the isomerization reactions occur via hydrogen migration followed by bond-breaking and reconstruction.

  2. Spontaneous Isomerization of Peptide Cation Radicals Following Electron Transfer Dissociation Revealed by UV-Vis Photodissociation Action Spectroscopy.

    Science.gov (United States)

    Imaoka, Naruaki; Houferak, Camille; Murphy, Megan P; Nguyen, Huong T H; Dang, Andy; Tureček, František

    2018-01-16

    Peptide cation radicals of the z-type were produced by electron transfer dissociation (ETD) of peptide dications and studied by UV-Vis photodissociation (UVPD) action spectroscopy. Cation radicals containing the Asp (D), Asn (N), Glu (E), and Gln (Q) residues were found to spontaneously isomerize by hydrogen atom migrations upon ETD. Canonical N-terminal [z 4 + H] +● fragment ion-radicals of the R-C ● H-CONH- type, initially formed by N-C α bond cleavage, were found to be minor components of the stable ion fraction. Vibronically broadened UV-Vis absorption spectra were calculated by time-dependent density functional theory for several [ ● DAAR + H] + isomers and used to assign structures to the action spectra. The potential energy surface of [ ● DAAR + H] + isomers was mapped by ab initio and density functional theory calculations that revealed multiple isomerization pathways by hydrogen atom migrations. The transition-state energies for the isomerizations were found to be lower than the dissociation thresholds, accounting for the isomerization in non-dissociating ions. The facile isomerization in [ ● XAAR + H] + ions (X = D, N, E, and Q) was attributed to low-energy intermediates having the radical defect in the side chain that can promote hydrogen migration along backbone C α positions. A similar side-chain mediated mechanism is suggested for the facile intermolecular hydrogen migration between the c- and [z + H] ● -ETD fragments containing Asp, Asn, Glu, and Gln residues. Graphical Abstract ᅟ.

  3. Spontaneous Isomerization of Peptide Cation Radicals Following Electron Transfer Dissociation Revealed by UV-Vis Photodissociation Action Spectroscopy

    Science.gov (United States)

    Imaoka, Naruaki; Houferak, Camille; Murphy, Megan P.; Nguyen, Huong T. H.; Dang, Andy; Tureček, František

    2018-01-01

    Peptide cation radicals of the z-type were produced by electron transfer dissociation (ETD) of peptide dications and studied by UV-Vis photodissociation (UVPD) action spectroscopy. Cation radicals containing the Asp (D), Asn (N), Glu (E), and Gln (Q) residues were found to spontaneously isomerize by hydrogen atom migrations upon ETD. Canonical N-terminal [z4 + H]+● fragment ion-radicals of the R-C●H-CONH- type, initially formed by N-Cα bond cleavage, were found to be minor components of the stable ion fraction. Vibronically broadened UV-Vis absorption spectra were calculated by time-dependent density functional theory for several [●DAAR + H]+ isomers and used to assign structures to the action spectra. The potential energy surface of [●DAAR + H]+ isomers was mapped by ab initio and density functional theory calculations that revealed multiple isomerization pathways by hydrogen atom migrations. The transition-state energies for the isomerizations were found to be lower than the dissociation thresholds, accounting for the isomerization in non-dissociating ions. The facile isomerization in [●XAAR + H]+ ions (X = D, N, E, and Q) was attributed to low-energy intermediates having the radical defect in the side chain that can promote hydrogen migration along backbone Cα positions. A similar side-chain mediated mechanism is suggested for the facile intermolecular hydrogen migration between the c- and [z + H]●-ETD fragments containing Asp, Asn, Glu, and Gln residues. [Figure not available: see fulltext.

  4. A Model of Mental State Transition Network

    Science.gov (United States)

    Xiang, Hua; Jiang, Peilin; Xiao, Shuang; Ren, Fuji; Kuroiwa, Shingo

    Emotion is one of the most essential and basic attributes of human intelligence. Current AI (Artificial Intelligence) research is concentrating on physical components of emotion, rarely is it carried out from the view of psychology directly(1). Study on the model of artificial psychology is the first step in the development of human-computer interaction. As affective computing remains unpredictable, creating a reasonable mental model becomes the primary task for building a hybrid system. A pragmatic mental model is also the fundament of some key topics such as recognition and synthesis of emotions. In this paper a Mental State Transition Network Model(2) is proposed to detect human emotions. By a series of psychological experiments, we present a new way to predict coming human's emotions depending on the various current emotional states under various stimuli. Besides, people in different genders and characters are taken into consideration in our investigation. According to the psychological experiments data derived from 200 questionnaires, a Mental State Transition Network Model for describing the transitions in distribution among the emotions and relationships between internal mental situations and external are concluded. Further more the coefficients of the mental transition network model were achieved. Comparing seven relative evaluating experiments, an average precision rate of 0.843 is achieved using a set of samples for the proposed model.

  5. Strongly Enhanced Low Energy Alpha-Particle Decay in Heavy Actinide Nuclei and Long-Lived Superdeformed and Hyperdeformed Isomeric States

    CERN Document Server

    Marinov, Amnon; Kolb, D.; Weil, J.L.

    2001-01-01

    Relatively low energy and very enhanced alpha-particle groups have been observed in various actinide fractions produced via secondary reactions in a CERN W target which had been irradiated with 24-GeV protons. In particular, 5.14, 5.27 and 5.53 MeV alpha-particle groups with corresponding half-lives of 3.8(+ -)1.0 y, 625(+ -)84 d and 26(+ -)7 d, have been seen in Bk, Es and Lr-No sources, respectively. The measured energies are a few MeV lower than the known g.s. to g.s. alpha-decays in the corresponding neutron-deficient actinide nuclei. The half-lives are 4 to 7 orders of magnitude shorter than expected from the systematics of alpha-particle decay in this region of nuclei. The deduced evaporation residue cross sections are in the mb region, about 4 orders of magnitude higher than expected. A consistent interpretation of the data is given in terms of production of long-lived isomeric states in the second and third wells of the potential-energy surfaces of the parent nuclei, which decay to the corresponding w...

  6. Cross sections measurement of isomeric states formation in nuclear reactions induced by neutrons of 14 Mev and comparison with statistical theories

    International Nuclear Information System (INIS)

    El Bardouni, T.

    1989-01-01

    Excitation functions of some (n,2n), (n,p) and (n,alpha) reactions on isotopes taken in different mass regions have been measured around 14 Mev. We give more interest to reactions leading to residual nucleus in isomeric states. Quasi-monoenergetic neutrons are produced via the T(d,n)alpha reaction and activation technique is combined to high resolution gamma-ray spectrometry. In the measurement of samples activities, we have scanned carefully the different origins of uncertainties and taken into account all necessary corrections. We have also carried out a detailed study about the nuclear reactions theory (compound nucleus and Geometry Dependent Hybrid Models) in order to compare our measurements results and theoretical calculations. The EMPIRE code (based on compound nucleus and Geometry Dependent Hybrid Models), that we have adapted on IBM Personal Computer, allows us to reproduce with great satisfaction the measured excitation functions without adjusting the models parameters. So we can rely on the EMPIRE code, as it is done in its work, in the prediction of some nuclear reactions excitation functions that cannot be determined by means of activation technique and gamma-ray spectrometry. 88 refs., 43 figs., 16 tabs., 1 chart. (author)

  7. Thermal Neutron Capture and Thermal Neutron Burn-up of K isomeric state of 177mLu: a way to the Neutron Super-Elastic Scattering cross section

    International Nuclear Information System (INIS)

    Roig, O.; Belier, G.; Meot, V.; Daugas, J.-M.; Romain, P.; Aupiais, J.; Jutier, Ch.; Le Petit, G.; Letourneau, A.; Marie, F.; Veyssiere, Ch.

    2006-01-01

    Thermal neutron radiative capture and burn-up measurements of the K isomeric state in 177Lu form part of an original method to indirectly obtain the neutron super-elastic scattering cross section at thermal energy. Neutron super-elastic scattering, also called neutron inelastic acceleration, occurs during the neutron collisions with an excited nuclear level. In this reaction, the nucleus could partly transfer its excitation energy to the scattered neutron

  8. Quantum Phase Transitions in Matrix Product States

    International Nuclear Information System (INIS)

    Jing-Min, Zhu

    2008-01-01

    We present a new general and much simpler scheme to construct various quantum phase transitions (QPTs) in spin chain systems with matrix product ground states. By use of the scheme we take into account one kind of matrix product state (MPS) QPT and provide a concrete model. We also study the properties of the concrete example and show that a kind of QPT appears, accompanied by the appearance of the discontinuity of the parity absent block physical observable, diverging correlation length only for the parity absent block operator, and other properties which are that the fixed point of the transition point is an isolated intermediate-coupling fixed point of renormalization flow and the entanglement entropy of a half-infinite chain is discontinuous

  9. Quantum phase transitions in matrix product states

    International Nuclear Information System (INIS)

    Zhu Jingmin

    2008-01-01

    We present a new general and much simpler scheme to construct various quantum phase transitions (QPTs) in spin chain systems with matrix product ground states. By use of the scheme we take into account one kind of matrix product state (MPS) QPT and provide a concrete model. We also study the properties of the concrete example and show that a kind of QPT appears, accompanied by the appearance of the discontinuity of the parity absent block physical observable, diverging correlation length only for the parity absent block operator, and other properties which are that the fixed point of the transition point is an isolated intermediate-coupling fixed point of renormalization flow and the entanglement entropy of a half-infinite chain is discontinuous. (authors)

  10. Collective coordinates and an accompanying metric force in structural isomerization dynamics of molecules

    International Nuclear Information System (INIS)

    Yanao, Tomohiro; Takatsuka, Kazuo

    2003-01-01

    Structural isomerization dynamics of three- and four-atom clusters of vanishing total angular momentum is studied in terms of internal coordinates of n-body systems on the basis of a gauge theory. The so-called principal-axis hyperspherical coordinates are employed effectively as collective variables for the study of isomerization reactions. It turns out that the non-Euclidean metric on the internal space gives rise to a force, which works in response to internal motions called the democratic (kinematic) rotations in the internal space. This metric force generally tends to induce an asymmetry in mass balance of a system, and is coupled with the usual potential force to give rise to trapped motions in the vicinity of the transition states of the cluster. This observation provides a different perspective for the so-called recrossing problem in chemical reaction dynamics

  11. Computational Studies of Bridging Structures and Isomerism in Substituted Disilynes.

    Science.gov (United States)

    Serafin, Lukasz M; Law, Mark M; van Mourik, Tanja

    2013-06-11

    The substituted disilyne molecules, Si2Li2 and Si2HX, where X = Li, F, and Cl, have been investigated using the high-level CCSD(T) and CCSD(T)-F12 ab initio methods. The calculations have found or confirmed the existence of several isomeric forms and transition states for each molecule. Optimized geometries, relative energies, and harmonic vibration frequencies are reported. Bridging structures exist in all cases. Comparisons are made with existing literature results for the related Si2H2, C2X2, and C2HX isomerizing systems. Additionally, CCSD(T) and CCSD(T)-F12 calculations were performed for Si2H2, for which experimental spectroscopic data are available. Results calculated with CCSD(T)-F12 and the cc-pVTZ-F12 basis set are of comparable quality as those computed with CCSD(T) and the much larger cc-pV(6+d)Z basis set, at much less computational cost. We recommend the CCSD(T)-F12/cc-pVTZ-F12 level of theory as a very attractive alternative to conventional CCSD(T).

  12. Molecular Switch for Sub-Diffraction Laser Lithography by Photoenol Intermediate-State Cis-Trans Isomerization.

    Science.gov (United States)

    Mueller, Patrick; Zieger, Markus M; Richter, Benjamin; Quick, Alexander S; Fischer, Joachim; Mueller, Jonathan B; Zhou, Lu; Nienhaus, Gerd Ulrich; Bastmeyer, Martin; Barner-Kowollik, Christopher; Wegener, Martin

    2017-06-27

    Recent developments in stimulated-emission depletion (STED) microscopy have led to a step change in the achievable resolution and allowed breaking the diffraction limit by large factors. The core principle is based on a reversible molecular switch, allowing for light-triggered activation and deactivation in combination with a laser focus that incorporates a point or line of zero intensity. In the past years, the concept has been transferred from microscopy to maskless laser lithography, namely direct laser writing (DLW), in order to overcome the diffraction limit for optical lithography. Herein, we propose and experimentally introduce a system that realizes such a molecular switch for lithography. Specifically, the population of intermediate-state photoenol isomers of α-methyl benzaldehydes generated by two-photon absorption at 700 nm fundamental wavelength can be reversibly depleted by simultaneous irradiation at 440 nm, suppressing the subsequent Diels-Alder cycloaddition reaction which constitutes the chemical core of the writing process. We demonstrate the potential of the proposed mechanism for STED-inspired DLW by covalently functionalizing the surface of glass substrates via the photoenol-driven STED-inspired process exploiting reversible photoenol activation with a polymerization initiator. Subsequently, macromolecules are grown from the functionalized areas and the spatially coded glass slides are characterized by atomic-force microscopy. Our approach allows lines with a full-width-at-half-maximum of down to 60 nm and line gratings with a lateral resolution of 100 nm to be written, both surpassing the diffraction limit.

  13. K isomerism and collectivity in neutron-rich rare-earth isotopes

    Science.gov (United States)

    Patel, Zena

    Neutron-rich rare-earth isotopes were produced by in-flight fission of 238U ions at the Radioactive Isotope Beam Factory (RIBF), RIKEN, Japan. In-flight fission of a heavy, high-intensity beam of 238U ions on a light target provides the cleanest secondary beams of neutron-rich nuclei in the rare-earth region of isotopes. In-flight fission is advantageous over other methods of nuclear production, as it allows for a secondary beam to be extracted, from which the beam species can be separated and identified. The excited states of nuclei are studied by delayed isomeric or beta-delayed gamma-ray spectroscopy. New K isomers were found in Sm (Z=62), Eu (Z=63), and Gd (Z=64) isotopes. The key results are discussed here. Excited states in the N=102 isotones 166Gd and 164Sm have been observed following isomeric decay for the first time. The K-isomeric states in 166Gd and 164Sm are due to 2-quasiparticle configurations. Based on the decay patterns and potential energy surface calculations, including beta6 deformation, both isomers are assigned a (6-) spin-parity. The half-lives of the isomeric states have been measured to be 950(60)ns and 600(140)ns for 166Gd and 164Sm respectively. Collective observables are discussed in light of the systematics of the region, giving insight into nuclear shape evolution. The decrease in the ground state band energies of 166Gd and 164Sm (N=102) compared to 164Gd and 162Sm (N=100) respectively, presents evidence for the predicted deformed shell closure at N=100. A 4-quasiparticle isomeric state has been discovered in 160Sm: the lightest deformed nucleus with a 4-quasiparticle isomer to date. The isomeric state is assigned an (11+) spin-parity with a measured half-life of 1.8(4)us. The (11+) isomeric state decays into a rotational band structure, based on a (6-) v5/2-[523] ⊗ v7/2+[633] bandhead, determined from the extracted gK-gR values. Potential energy surface and blocked BCS calculations were performed in the deformed midshell region

  14. Determination of the quadrupole moment of the fission-isomeric state in 238U by a modified charge-plunger method

    International Nuclear Information System (INIS)

    Pedersen, J.; Goerlach, U.; Habs, D.; Just, M.; Metag, V.; Mosler, E.; Schukraft, J.; Singer, P.; Specht, H.J.; Ulfert, G.

    1978-01-01

    A modified version of the charge plunger method has been developed which, by utilizing electrostatic fields, renders possible the separation of low- and high-charge recoil ions over short flight distances. With this technique the quadrupole moment of the 200 ns fission isomer in 238 U has been determined to be (29 +- 3) b. The corresponding deformation of c/a = (1.8 +- 0.1) provides another quantitative proof for shape isomerism in the actinide region. (orig.) [de

  15. Vibrational nonadiabaticity and tunneling effects in transition state theory

    International Nuclear Information System (INIS)

    Marcus, R.A.

    1979-01-01

    The usual quantum mechanical derivation of transition state theory is a statistical one (a quasi-equilibrium is assumed) or dynamical. The typical dynamical one defines a set of internal states and assumes vibrational adiabaticity. Effects of nonadiabaticity before and after the transition state are included in the present derivation, assuming a classical treatment of the reaction coordinate. The relation to a dynamical derivation of classical mechanical transition state theory is described, and tunneling effects are considered

  16. Evaluation of isomeric excitation functions in neutron induced reactions

    International Nuclear Information System (INIS)

    Grudzevich, O.; Ignatyuk, A.; Zolotarev, K.

    1992-01-01

    The possibilities of isomer levels experimental excitation functions description with theoretical models are discussed. It is shown that the experimental data in many cases can be described by theoretical models quite well without parameter fitting. However, large discrepancies are observed for some reactions. In our opinion, these discrepancies are due to uncertainties of discrete level schemes, schemes of gamma-transitions between levels and spin dependence of level density. Small values of isomeric ratios (< 0.1) have been described with the largest errors. The simple formulae for energy dependence of isomeric ratio for (n,g) reaction has been proposed. (author). 53 refs, 10 figs, 8 tabs

  17. Ground-state and isomeric-state cross sections for the {sup 138}Ce(n,2n){sup 137}Ce reaction from its threshold to 20 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Junhua [Hexi Univ., Zhangye (China). Inst. of Theoretical Physics; Hexi Univ., Zhangye (China). School of Physics and Electromechanical Engineering; An, Li; Jiang, Li [Chinese Academy of Engineering Physics, Mianyang (China). Inst. of Nuclear Physics and Chemistry

    2015-07-01

    The cross sections of the {sup 138}Ce(n,2n){sup 137}Ce reactions and their isomeric cross section ratios σ{sub m}/σ{sub g} were measured at three neutron energies between 13.5 and 14.8 MeV using the activation technique. CeO{sub 2} samples and Nb monitor foils were activated together to determine the reaction cross section and the incident neutron flux. The monoenergetic neutron beams were formed via the {sup 3}H(d,n){sup 4}He reaction. The activities induced in the reaction products were measured using high-resolution γ-ray spectroscopy. The pure cross section of the ground-state was derived from the absolute cross section of the metastable state and the residual nuclear decay analysis. The cross sections were also estimated using the nuclear model code, TALYS-1.6 with different level density options at neutron energies varying from the reaction threshold to 20 MeV. Results are discussed and compared with the corresponding literature data.

  18. Theoretical study of isomerization and decomposition of propenal

    International Nuclear Information System (INIS)

    Chin, Chih-Hao; Lee, Shih-Huang

    2011-01-01

    We investigated the dynamics of isomerization and multi-channel dissociation of propenal (CH 2 CHCHO), methyl ketene (CH 3 CHCO), hydroxyl propadiene (CH 2 CH 2 CHOH), and hydroxyl cyclopropene (cyclic-C 3 H 3 -OH) in the ground potential-energy surface using quantum-chemical calculations. Optimized structures and vibrational frequencies of molecular species were computed with method B3LYP/6-311G(d,p). Total energies of molecules at optimized structures were computed at the CCSD(T)/6-311+G(3df,2p) level of theory. We established the potential-energy surface for decomposition to CH 2 CHCO + H, CH 2 CH + HCO, CH 2 CH 2 /CH 3 CH + CO, CHCH/CH 2 C + H 2 CO, CHCCHO/CH 2 CCO + H 2 , CHCH + CO + H 2 , CH 3 + HCCO, CH 2 CCH + OH, and CH 2 CC/cyclic-C 3 H 2 + H 2 O. Microcanonical rate coefficients of various reactions of trans-propenal with internal energies 148 and 182 kcal mol -1 were calculated using Rice-Ramsperger-Kassel-Marcus and Variational transition state theories. Product branching ratios were derivable using numerical integration of kinetic master equations and the steady-state approximation. The concerted three-body dissociation of trans-propenal to fragments C 2 H 2 + CO + H 2 is the prevailing channel in present calculations. In contrast, C 3 H 3 O + H, C 2 H 3 + HCO and C 2 H 4 + CO were identified as major channels in the photolysis of trans-propenal. The discrepancy between calculations and experiments in product branching ratios indicates that the three major photodissociation channels occur mainly on an excited potential-energy surface whereas the other channels occur mainly on the ground potential-energy surface. This work provides profound insight in the mechanisms of isomerization and multichannel dissociation of the system C 3 H 4 O.

  19. M1 transitions between superdeformed states in 195Tl

    International Nuclear Information System (INIS)

    Zheng Xing; Xingqu Chen; Xiaochun Wang

    1996-01-01

    Using a triaxial-particle-rotor model, the quadrupole and dipole transition energies, kinematic and dynamic moments of inertia, electromagnetic transition probabilities and the relative intensity of the E2 γ-transitions are calculated for superdeformed bands in 195 Tl. A strong perturbation effect of rotation on transition energies and M1 and E2 transitions of superdeformed states is investigated. The total M1 transitions, enhanced by internal conversion, are expected to compete strongly with the E2 γ-ray at low spins in the superdeformed 195 Tl nucleus. (author)

  20. Fluctuating States: What is the Probability of a Thermodynamical Transition?

    Directory of Open Access Journals (Sweden)

    Álvaro M. Alhambra

    2016-10-01

    Full Text Available If the second law of thermodynamics forbids a transition from one state to another, then it is still possible to make the transition happen by using a sufficient amount of work. But if we do not have access to this amount of work, can the transition happen probabilistically? In the thermodynamic limit, this probability tends to zero, but here we find that for finite-sized and quantum systems it can be finite. We compute the maximum probability of a transition or a thermodynamical fluctuation from any initial state to any final state and show that this maximum can be achieved for any final state that is block diagonal in the energy eigenbasis. We also find upper and lower bounds on this transition probability, in terms of the work of transition. As a by-product, we introduce a finite set of thermodynamical monotones related to the thermomajorization criteria which governs state transitions and compute the work of transition in terms of them. The trade-off between the probability of a transition and any partial work added to aid in that transition is also considered. Our results have applications in entanglement theory, and we find the amount of entanglement required (or gained when transforming one pure entangled state into any other.

  1. Isomerization Intermediates In Solution Phase Photochemistry Of Stilbenes

    Science.gov (United States)

    Doany, F. E.; Hochstrasser, R. M.; Greene, B. I.

    1985-04-01

    Picosecond and subpicosecond spectroscopic studies have revealed evidence for an isomerization intermediate between cis and trans in the photoinduced isomerism of both stilbene and biindanyledene ("stiff" stilbene). In stiff stilbene, a transient absorption at 351 nm displays time evolution and viscosity dependence consistent with absorption by a twisted intermediate ("phantom" state) with a lOps lifetime. An analagous bottleneck state with a life-time of 4ps is also consistent with the ground state recovery dynamics of t-stilbene following excitation of c-stilbene when monitored with 0.1ps resolution.

  2. A Quantum Version of Wigner's Transition State Theory

    NARCIS (Netherlands)

    Schubert, R.; Waalkens, H.; Wiggins, S.

    A quantum version of a recent realization of Wigner's transition state theory in phase space is presented. The theory developed builds on a quantum normal form which locally decouples the quantum dynamics near the transition state to any desired order in (h) over bar. This leads to an explicit

  3. A Quantum Version of Wigner’s Transition State Theory

    NARCIS (Netherlands)

    Schubert, R.; Waalkens, H.; Wiggins, S.

    2009-01-01

    A quantum version of a recent realization of Wigner’s transition state theory in phase space is presented. The theory developed builds on a quantum normal form which locally decouples the quantum dynamics near the transition state to any desired order in ħ. This leads to an explicit algorithm to

  4. Periodic-orbit formula for quantum reactions through transition states

    NARCIS (Netherlands)

    Schubert, Roman; Waalkens, Holger; Goussev, Arseni; Wiggins, Stephen

    2010-01-01

    Transition state theory forms the basis of computing reaction rates in chemical and other systems. Recently, it has been shown how transition state theory can rigorously be realized in phase space by using an explicit algorithm. The quantization has been demonstrated to lead to an efficient

  5. The Variable Transition State in Polar Additions to Pi Bonds

    Science.gov (United States)

    Weiss, Hilton M.

    2010-01-01

    A vast majority of polar additions of Bronsted acids to alkynes involve a termolecular transition state. With strong acids, considerable positive charge is developed on carbon and Markovnikov addition predominates. In less acidic solutions, however, the reaction is much slower and the transition state more closely resembles the olefinic product.…

  6. Retrieving molecular structural information and tracking HNC/HCN isomerization process with high harmonic generation by ultrashort laser pulses

    International Nuclear Information System (INIS)

    Nguyen Ngoc Ty; Le Van Hoang; Vu Ngoc Tuoc; Le Anh Thu

    2010-01-01

    We investigate the possibility of applying the iterative method, suggested in our previous work, for HCN molecule and its HNC isomer. We found that the high-order harmonic generation (HHG) spectra are quite insensitive to the change of H-C (or H-N) bond length so that only the inter-nuclear C-N distance can be retrieved from the high-order harmonic spectra using ultrashort intense lasers. Furthermore, by analyzing the HHG spectra emitted by HCN during the chemical reaction path of isomerization we identify the intensity peaks nearby the stable, metastable and transition states. this finding can be useful for tracking the HNC/HNC isomerization process. (author)

  7. DFT study on the isomerization and tautomerism in vitamins B3 (niacin), B5 (pantothenic acid) and B7 (biotin)

    Science.gov (United States)

    Valadbeigi, Younes; Farrokhpour, Hossein; Tabrizchi, Mahmoud

    2014-05-01

    Isomerization and tautomerism of the three water soluble vitamins including B3, B5 and B7 were studied applying density functional theory using B3LYP method in gas and aqueous phases. Activation energies (Ea), Gibbs free energies of activation (ΔG#), and imaginary frequencies of the transition state structures were calculated for all the isomerization and tautomerism reactions. Activation energies of the neutral → zwitterion (amine-enamine) tautomerism in vitamin B3 were 310-360 kJ/mol where these values for the keto-enol tautomerism were 100-130 kJ/mol. It was found that water molecule catalyzes the tautomerism and decreases the activation energies about 90-160 kJ/mol.

  8. An isomeric reaction benchmark set to test if the performance of state-of-the-art density functionals can be regarded as independent of the external potential.

    Science.gov (United States)

    Schwabe, Tobias

    2014-07-28

    Some representative density functionals are assessed for isomerization reactions in which heteroatoms are systematically substituted with heavier members of the same element group. By this, it is investigated if the functional performance depends on the elements involved, i.e. on the external potential imposed by the atomic nuclei. Special emphasis is placed on reliable theoretical reference data and the attempt to minimize basis set effects. Both issues are challenging for molecules including heavy elements. The data suggest that no general bias can be identified for the functionals under investigation except for one case - M11-L. Nevertheless, large deviations from the reference data can be found for all functional approximations in some cases. The average error range for the nine functionals in this test is 17.6 kcal mol(-1). These outliers depreciate the general reliability of density functional approximations.

  9. Role of Chemical Reactivity and Transition State Modeling for Virtual Screening.

    Science.gov (United States)

    Karthikeyan, Muthukumarasamy; Vyas, Renu; Tambe, Sanjeev S; Radhamohan, Deepthi; Kulkarni, Bhaskar D

    2015-01-01

    Every drug discovery research program involves synthesis of a novel and potential drug molecule utilizing atom efficient, economical and environment friendly synthetic strategies. The current work focuses on the role of the reactivity based fingerprints of compounds as filters for virtual screening using a tool ChemScore. A reactant-like (RLS) and a product- like (PLS) score can be predicted for a given compound using the binary fingerprints derived from the numerous known organic reactions which capture the molecule-molecule interactions in the form of addition, substitution, rearrangement, elimination and isomerization reactions. The reaction fingerprints were applied to large databases in biology and chemistry, namely ChEMBL, KEGG, HMDB, DSSTox, and the Drug Bank database. A large network of 1113 synthetic reactions was constructed to visualize and ascertain the reactant product mappings in the chemical reaction space. The cumulative reaction fingerprints were computed for 4000 molecules belonging to 29 therapeutic classes of compounds, and these were found capable of discriminating between the cognition disorder related and anti-allergy compounds with reasonable accuracy of 75% and AUC 0.8. In this study, the transition state based fingerprints were also developed and used effectively for virtual screening in drug related databases. The methodology presented here provides an efficient handle for the rapid scoring of molecular libraries for virtual screening.

  10. Localized-to-extended-states transition below the Fermi level

    Science.gov (United States)

    Tito, M. A.; Pusep, Yu. A.

    2018-05-01

    Time-resolved photoluminescence is employed to examine a transition from localized to extended electron states below the Fermi level in multiple narrow quantum well GaAs/AlGaAs heterostructures, where disorder was generated by interface roughness. Such a transition resembles the metal-insulator transition profoundly investigated by electric transport measurements. An important distinction distinguishes the localized-to-extended-states transition studied here: it takes place below the Fermi level in an electron system with a constant concentration, which implies unchanging Coulomb correlations. Moreover, for such a localized-to-extended-states transition the temperature is shown to be irrelevant. In the insulating regime the magnetic field was found to cause an additional momentum relaxation which considerably enhanced the recombination rate. Thus, we propose a method to explore the evolution of the localized electron states in a system with a fixed disorder and Coulomb interaction.

  11. Magnetic Ground State Properties of Transition Metals

    DEFF Research Database (Denmark)

    Andersen, O. K.; Madsen, J.; Poulsen, U. K.

    1977-01-01

    We review a simple one-electron theory of the magnetic and cohesive properties of ferro- and nearly ferromagnetic transition metals at 0 K. The theory is based on the density functional formalism, it makes use of the local spin density and atomic sphere approximations and it may, with further app...

  12. Contribution to the experimental survey of the nuclear isomerism. Application of the deferred coincidences method to research and to the survey of metastable states of short period; Contribution a l'etude experimentale de l'isomerie nucleaire. Application de la methode des coincidences differees a la recherche et a l'etude d'etats metastables de periode courte

    Energy Technology Data Exchange (ETDEWEB)

    Ballini, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1953-06-15

    Various methods of the physics brought many informations on the nuclear elements which one can arrange some ponderable quantities, what is the case of the steady elements and some, unsteady elements, as most of natural radioelements. On the other hand, elements of shorter life duration, and notably those that are carried to an excited state, are more badly known, and one can get information to their consideration that by the mediator of the properties of the transitions that they undergo, when they give birth has best-known nuclear cash: among these transitions represent the isomeric transitions. The goal of this work is the survey of the isomeric transitions from metastable states of short period, included in the domain of the microsecond to some milliseconds. The method of the deferred coincidences has been put to the point and applied in this goal while using the advantages of the selectors to several channels, under two main aspects where the device to several channels was either a selector of time, either a selector of amplitudes. This method served to study the working of Geiger-Muller counter and to measure with precision the period of {sup 181}Ta{sup *} in of the varied experimental conditions. The adopted value is 17,2 {+-}0,2 {mu}s. This work also found an immediate practical application to the setting in evidence of very weak quantities of hafnium in zirconium, of which it constitutes a tenacious and difficult impurity to analyze by the ordinary ways. (M.B.) [French] Les diverses methodes de la physique ont apporte de nombreux renseignements sur les especes nucleaires dont on peut disposer en quantites ponderables, ce qui est le cas des especes stables et de certaines especes instables, comme la plupart des radioelements naturels. Par contre, les noyaux de duree de vie plus courte, et notamment ceux qui sont portes a un etat excite, sont plus mal connus, et on ne peut obtenir de renseignements a leur egard que par l'intermediaire des proprietes des

  13. High-Pressure Limit Rate Rules for α-H Isomerization of Hydroperoxyalkylperoxy Radicals

    KAUST Repository

    Mohamed, Samah Y

    2018-03-09

    Hydroperoxyalkylperoxy (OOQOOH) radical isomerization is an important low-temperature chain branching reaction within the mechanism of hydrocarbon oxidation. This isomerization may proceed via the migration of the α-hydrogen to the hydroperoxide group. In this work, a combination of high level composite methods - CBS-QB3, G3 and G4 - is used to determine the high-pressure-limit rate parameters for the title reaction. Rate rules for H-migration reactions proceeding through 5-, 6-, 7- and 8-membered ring transitions states are determined. Migrations from primary, secondary and tertiary carbon sites to the peroxy group are considered. Chirality is also investigated by considering two diastereomers for reactants and transition states with two chiral centers. This is important since chirality may influence the energy barrier of the reaction as well as the rotational energy barriers of hindered rotors in chemical species and transition states. The effect of chirality and hydrogen bonding interactions in the investigated energies and rate constants is studied. The results show that while the energy difference between two diastereomers ranges from 0.1 - 3.2 kcal, chirality hardly affects the kinetics, except at low temperatures (atmospheric conditions) or when two chiral centers are present in the reactant. Regarding the effects of the peroxy group position and the H-migration ring size, it is found that in most cases, the 1,5 and 1,6 H-migration reactions have similar rates at low temperatures (below ~830K) since the 1,6 H-migration proceeds via a cyclohexane-like transition state similar to that of the 1,5 H-migration.

  14. Observation of Hyperfine Transitions in Trapped Ground-State Antihydrogen

    CERN Document Server

    Olin, Arthur

    2015-01-01

    This paper discusses the first observation of stimulated magnetic resonance transitions between the hyperfine levels of trapped ground state atomic antihydrogen, confirming its presence in the ALPHA apparatus. Our observations show that these transitions are consistent with the values in hydrogen to within 4~parts~in~$10^3$. Simulations of the trapped antiatoms in a microwave field are consistent with our measurements.

  15. Observation of hyperfine transitions in trapped ground-state antihydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Collaboration: A. Olin for the ALPHA Collaboration

    2015-08-15

    This paper discusses the first observation of stimulated magnetic resonance transitions between the hyperfine levels of trapped ground state atomic antihydrogen, confirming its presence in the ALPHA apparatus. Our observations show that these transitions are consistent with the values in hydrogen to within 4 parts in 10{sup 3}. Simulations of the trapped antiatoms in a microwave field are consistent with our measurements.

  16. Toward spectroscopically accurate global ab initio potential energy surface for the acetylene-vinylidene isomerization

    Science.gov (United States)

    Han, Huixian; Li, Anyang; Guo, Hua

    2014-12-01

    A new full-dimensional global potential energy surface (PES) for the acetylene-vinylidene isomerization on the ground (S0) electronic state has been constructed by fitting ˜37 000 high-level ab initio points using the permutation invariant polynomial-neural network method with a root mean square error of 9.54 cm-1. The geometries and harmonic vibrational frequencies of acetylene, vinylidene, and all other stationary points (two distinct transition states and one secondary minimum in between) have been determined on this PES. Furthermore, acetylene vibrational energy levels have been calculated using the Lanczos algorithm with an exact (J = 0) Hamiltonian. The vibrational energies up to 12 700 cm-1 above the zero-point energy are in excellent agreement with the experimentally derived effective Hamiltonians, suggesting that the PES is approaching spectroscopic accuracy. In addition, analyses of the wavefunctions confirm the experimentally observed emergence of the local bending and counter-rotational modes in the highly excited bending vibrational states. The reproduction of the experimentally derived effective Hamiltonians for highly excited bending states signals the coming of age for the ab initio based PES, which can now be trusted for studying the isomerization reaction.

  17. Toward spectroscopically accurate global ab initio potential energy surface for the acetylene-vinylidene isomerization

    International Nuclear Information System (INIS)

    Han, Huixian; Li, Anyang; Guo, Hua

    2014-01-01

    A new full-dimensional global potential energy surface (PES) for the acetylene-vinylidene isomerization on the ground (S 0 ) electronic state has been constructed by fitting ∼37 000 high-level ab initio points using the permutation invariant polynomial-neural network method with a root mean square error of 9.54 cm −1 . The geometries and harmonic vibrational frequencies of acetylene, vinylidene, and all other stationary points (two distinct transition states and one secondary minimum in between) have been determined on this PES. Furthermore, acetylene vibrational energy levels have been calculated using the Lanczos algorithm with an exact (J = 0) Hamiltonian. The vibrational energies up to 12 700 cm −1 above the zero-point energy are in excellent agreement with the experimentally derived effective Hamiltonians, suggesting that the PES is approaching spectroscopic accuracy. In addition, analyses of the wavefunctions confirm the experimentally observed emergence of the local bending and counter-rotational modes in the highly excited bending vibrational states. The reproduction of the experimentally derived effective Hamiltonians for highly excited bending states signals the coming of age for the ab initio based PES, which can now be trusted for studying the isomerization reaction

  18. Quantifying the limits of transition state theory in enzymatic catalysis.

    Science.gov (United States)

    Zinovjev, Kirill; Tuñón, Iñaki

    2017-11-21

    While being one of the most popular reaction rate theories, the applicability of transition state theory to the study of enzymatic reactions has been often challenged. The complex dynamic nature of the protein environment raised the question about the validity of the nonrecrossing hypothesis, a cornerstone in this theory. We present a computational strategy to quantify the error associated to transition state theory from the number of recrossings observed at the equicommittor, which is the best possible dividing surface. Application of a direct multidimensional transition state optimization to the hydride transfer step in human dihydrofolate reductase shows that both the participation of the protein degrees of freedom in the reaction coordinate and the error associated to the nonrecrossing hypothesis are small. Thus, the use of transition state theory, even with simplified reaction coordinates, provides a good theoretical framework for the study of enzymatic catalysis. Copyright © 2017 the Author(s). Published by PNAS.

  19. Quantum catalysis : the modelling of catalytic transition states

    NARCIS (Netherlands)

    Hall, M.B.; Margl, P.; Naray-Szabo, G.; Schramm, Vern; Truhlar, D.G.; Santen, van R.A.; Warshel, A.; Whitten, J.L.; Truhlar, D.G.; Morokuma, K.

    1999-01-01

    A review with 101 refs.; we present an introduction to the computational modeling of transition states for catalytic reactions. We consider both homogeneous catalysis and heterogeneous catalysis, including organometallic catalysts, enzymes, zeolites and metal oxides, and metal surfaces. We summarize

  20. Gamma transitions between compound states in spherical nuclei

    International Nuclear Information System (INIS)

    Kadmenskij, S.G.; Markushev, V.P.; Furman, V.I.

    1980-01-01

    Average values of the reduced γ widths and their dispersions are investigated, basing on the Wigner statistical matrix method, for γ transitions from a compound state c into a less-energy excited state f of an arbitrary complexity in spherical nuclei. It is shown that in all the cases of practical interest the Porter-Thomas distribution is valid for the γ widths. It is found that in the γ transitions between compound states c and c' with Esub(γ) <= 2 MeV the dominating role is played by the M1 transitions due to the main multiquasiparticle states of c, and by the E1 transitions, due to small components of the state c. In framework of the existent theoretical schemes it is shown that the strength functions of the M1 and E1 transitions between the compound states with Esub(γ) <2 MeV are close. It is deduced thet the variant of the M1 transitions is preferable in view of the experimental results on the (n, γα) reactions induced by thermal and resonance neutrons

  1. Schiff base switch II precedes the retinal thermal isomerization in the photocycle of bacteriorhodopsin.

    Directory of Open Access Journals (Sweden)

    Ting Wang

    Full Text Available In bacteriorhodopsin, the order of molecular events that control the cytoplasmic or extracellular accessibility of the Schiff bases (SB are not well understood. We use molecular dynamics simulations to study a process involved in the second accessibility switch of SB that occurs after its reprotonation in the N intermediate of the photocycle. We find that once protonated, the SB C15 = NZ bond switches from a cytoplasmic facing (13-cis, 15-anti configuration to an extracellular facing (13-cis, 15-syn configuration on the pico to nanosecond timescale. Significantly, rotation about the retinal's C13 = C14 double bond is not observed. The dynamics of the isomeric state transitions of the protonated SB are strongly influenced by the surrounding charges and dielectric effects of other buried ions, particularly D96 and D212. Our simulations indicate that the thermal isomerization of retinal from 13-cis back to all-trans likely occurs independently from and after the SB C15 = NZ rotation in the N-to-O transition.

  2. Evaluation of excitation functions for isomeric levels in neutron reactions

    International Nuclear Information System (INIS)

    Grudzevich, O.T.; Zelenetskij, A.V.; Zolotarev, K.I.; Kornilov, N.V.; Pashchenko, A.B.

    1993-07-01

    The authors consider the use of theoretical models to describe experimental excitation functions for isomeric levels in neutron reactions and to predict the cross-sections when no experimental data are available. It is shown that, in many cases, experimental data can be described quite satisfactorily by calculations without adjustment of parameters. For threshold reactions at a neutron energy of ∼ 14 MeV the agreement between calculated and experimental isomeric ratios is ∼ 20%, and is determined mainly by errors in the experimental ratios. However, for some reactions there are considerable differences between experimental and calculated data, which are due, in the authors' opinion, to uncertainties in the schemes of the low-lying levels and of gamma transitions between levels and to the spin dependence of level density. The small isomeric ratio values R<0.1 are described with the lowest accuracy. A formula is suggested for the energy dependence of the isomeric ratio in the (n,γ) reaction. (author)

  3. Densification and state transition across the Missouri Ozarks landscape

    Science.gov (United States)

    Brice B. Hanberry; John M. Kabrick; Hong S. He

    2014-01-01

    World-wide, some biomes are densifying, or increasing in dense woody vegetation, and shifting to alternative stable states. We quantified densification and state transition between forests ecosystems in historical (ca. 1815-1850) and current (2004-2008) surveys of the Missouri Ozark Highlands, a 5-million ha landscape in southern Missouri, USA. To estimate density of...

  4. GENESIS - The GENEric SImulation System for Modelling State Transitions.

    Science.gov (United States)

    Gillman, Matthew S

    2017-09-20

    This software implements a discrete time Markov chain model, used to model transitions between states when the transition probabilities are known a priori . It is highly configurable; the user supplies two text files, a "state transition table" and a "config file", to the Perl script genesis.pl. Given the content of these files, the script generates a set of C++ classes based on the State design pattern, and a main program, which can then be compiled and run. The C++ code generated is based on the specification in the text files. Both multiple branching and bi-directional transitions are allowed. The software has been used to model the natural histories of colorectal cancer in Mexico. Although written primarily to model such disease processes, it can be used in any process which depends on discrete states with known transition probabilities between those states. One suitable area may be in environmental modelling. A test suite is supplied with the distribution. Due to its high degree of configurability and flexibility, this software has good re-use potential. It is stored on the Figshare repository.

  5. State-to-State Mode Specificity: Energy Sequestration and Flow Gated by Transition State.

    Science.gov (United States)

    Zhao, Bin; Sun, Zhigang; Guo, Hua

    2015-12-23

    Energy flow and sequestration at the state-to-state level are investigated for a prototypical four-atom reaction, H2 + OH → H + H2O, using a transition-state wave packet (TSWP) method. The product state distribution is found to depend strongly on the reactant vibrational excitation, indicating mode specificity at the state-to-state level. From a local-mode perspective, it is shown that the vibrational excitation of the H2O product derives from two different sources, one attributable to the energy flow along the reaction coordinate into the newly formed OH bond and the other due to the sequestration of the vibrational energy in the OH spectator moiety during the reaction. The analysis provided a unified interpretation of some seemingly contradicting experimental observations. It is further shown that the transfer of vibrational energy from the OH reactant to H2O product is gated by the transition state, accomplished coherently by multiple TSWPs with the corresponding OH vibrational excitation.

  6. Quantum optimal control of ozone isomerization

    International Nuclear Information System (INIS)

    Artamonov, Maxim; Ho, Tak-San; Rabitz, Herschel

    2004-01-01

    We present a feasibility study of ozone isomerization based on a recent ab initio potential energy surface and a model Hamiltonian constructed by holding the bond lengths constant and using the valence angle as the isomerization coordinate. Optimal control theory is used to find an electric field that drives isomerization with a yield of 95% to the symmetric metastable triangular form of ozone. A frequency filter is applied as an additional spectral constraint limiting the field bandwidth. A post-facto analysis is performed showing a degree of inherent robustness of the isomerization yield to field noise

  7. A comprehensive mechanistic picture of the isomerizing alkoxycarbonylation of plant oils

    KAUST Repository

    Roesle, Philipp

    2014-12-03

    Theoretical studies on the overall catalytic cycle of isomerizing alkoxycarbonylation reveal the steric congestion around the diphosphine coordinated Pd-center as decisive for selectivity and productivity. The energy profile of isomerization is flat with diphosphines of variable steric bulk, but the preference for the formation of the linear Pd-alkyl species is more pronounced with sterically demanding diphosphines. CO insertion is feasible and reversible for all Pd-alkyl species studied and only little affected by the diphosphine. The overall rate-limiting step associated with the highest energetic barrier is methanolysis of the Pd-acyl species. Considering methanolysis of the linear Pd-acyl species, whose energetic barrier is lowest within all the Pd-acyl species studied, the barrier is calculated to be lower for more congesting diphosphines. Calculations indicate that energy differences of methanolysis of the linear versus branched Pd-acyls are more pronounced for more bulky diphosphines, due to involvement of different numbers of methanol molecules in the transition state. Experimental studies under pressure reactor conditions showed a faster conversion of shorter chain olefin substrates, but virtually no effect of the double bond position within the substrate. Compared to higher olefins, ethylene carbonylation under identical conditions is much faster, likely due not just to the occurrence of reactive linear acyls exclusively but also to an intrinsically favorable insertion reactivity of the olefin. The alcoholysis reaction is slowed down for higher alcohols, evidenced by pressure reactor and NMR studies. Multiple unsaturated fatty acids were observed to form a terminal Pd-allyl species upon reaction with the catalytically active Pd-hydride species. This process and further carbonylation are slow compared to isomerizing methoxycarbonylation of monounsaturated fatty acids, but selective.

  8. A comprehensive mechanistic picture of the isomerizing alkoxycarbonylation of plant oils.

    Science.gov (United States)

    Roesle, Philipp; Caporaso, Lucia; Schnitte, Manuel; Goldbach, Verena; Cavallo, Luigi; Mecking, Stefan

    2014-12-03

    Theoretical studies on the overall catalytic cycle of isomerizing alkoxycarbonylation reveal the steric congestion around the diphosphine coordinated Pd-center as decisive for selectivity and productivity. The energy profile of isomerization is flat with diphosphines of variable steric bulk, but the preference for the formation of the linear Pd-alkyl species is more pronounced with sterically demanding diphosphines. CO insertion is feasible and reversible for all Pd-alkyl species studied and only little affected by the diphosphine. The overall rate-limiting step associated with the highest energetic barrier is methanolysis of the Pd-acyl species. Considering methanolysis of the linear Pd-acyl species, whose energetic barrier is lowest within all the Pd-acyl species studied, the barrier is calculated to be lower for more congesting diphosphines. Calculations indicate that energy differences of methanolysis of the linear versus branched Pd-acyls are more pronounced for more bulky diphosphines, due to involvement of different numbers of methanol molecules in the transition state. Experimental studies under pressure reactor conditions showed a faster conversion of shorter chain olefin substrates, but virtually no effect of the double bond position within the substrate. Compared to higher olefins, ethylene carbonylation under identical conditions is much faster, likely due not just to the occurrence of reactive linear acyls exclusively but also to an intrinsically favorable insertion reactivity of the olefin. The alcoholysis reaction is slowed down for higher alcohols, evidenced by pressure reactor and NMR studies. Multiple unsaturated fatty acids were observed to form a terminal Pd-allyl species upon reaction with the catalytically active Pd-hydride species. This process and further carbonylation are slow compared to isomerizing methoxycarbonylation of monounsaturated fatty acids, but selective.

  9. Configurational isomerism in polyoxovanadates

    Energy Technology Data Exchange (ETDEWEB)

    Mahnke, Lisa K.; Naether, Christian; Bensch, Wolfgang [Institut fuer Anorganische Chemie, Christian-Albrechts-Universitaet, Kiel (Germany); Kondinski, Aleksandar; Van Leusen, Jan; Monakhov, Kirill Yu.; Koegerler, Paul [Institut fuer Anorganische Chemie, RWTH Aachen University (Germany); Warzok, Ulrike; Schalley, Christoph A. [Institut fuer Chemie und Biochemie, Freie Universitaet Berlin (Germany)

    2018-03-05

    A water-soluble derivative of the polyoxovanadate {V_1_5E_6O_4_2} (E=semimetal) archetype enables the study of cluster shell rearrangements driven by supramolecular interactions. A reaction unique to E=Sb, induced exclusively by ligand metathesis in peripheral [Ni(ethylenediamine){sub 3}]{sup 2+} counterions, results in the formation of the metastable α{sub 1}* configurational isomer of the {V_1_4Sb_8O_4_2} cluster type. Contrary to all other polyoxovanadate shell architectures, this isomer comprises an inward-oriented vanadyl group and is ca. 50 and 12 kJ mol{sup -1} higher in energy than the previously isolated α and β isomers, respectively. We discuss this unexpected reaction in light of supramolecular Sb-O..V and Sb-O..Sb contacts manifested in {V_1_4Sb_8O_4_2}{sub 2} dimers detected in the solid state. ESI MS experiments confirm the stability of these dimers also in solution and in the gas phase. DFT calculations indicate that other, as of yet elusive isomers of {V_1_4Sb_8}, might be accessible as well. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. State transitions, hysteresis, and control parameters on DIII-D

    International Nuclear Information System (INIS)

    Thomas, D.M.; Groebner, R.J.; Carlstrom, T.N.; Osborne, T.H.; Petrie, T.W.

    1998-07-01

    The theory of turbulence decorrelation by ExB velocity shear is the leading candidate to explain the changes in turbulence and transport that are seen at the plasma edge at the L to H transition. Based on this, a key question is: What are the conditions or control parameters needed to begin the formation of the E r shear layer and thus trigger the L to H transition? On the DIII-D tokamak, the authors are attacking this question both through direct tests of the various theories and by trying to gain insight into the fundamental physics by investigating the control parameters which have a major effect on the power threshold. In this paper the authors describe results of studies on oscillating discharges where the plasma transitions continuously between L and H states. By following the dynamics of the plasma state through the forward and back transitions, they can represent the evolution of various control parameter candidates as a trajectory in various parametric spaces. The shape of these control curves can illustrate the specific nonlinearities governing the L-H transition problem, and under the proper conditions may be interpreted in the context of various phase-transition based models. In particular, the hysteresis exhibited in the various curves may help to clarify causality (what are the critical parameters) and may serve as tests of the models, given sufficient experimental accuracy. At present they are looking at T e , E r and ballooning/diamagnetic parameters as possible control parameter candidates

  11. Direct observation of an isomeric state in {sup 98}Rb and nuclear properties of exotic rubidium isotopes measured by laser spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Procter, T.J.; Garnsworthy, A.B.; Levy, C.D.P.; Pearson, M.R. [TRIUMF, Vancouver, British Columbia (Canada); Behr, J.A.; Dilling, J. [TRIUMF, Vancouver, British Columbia (Canada); University of British Columbia, Department of Physics, Vancouver, British Columbia (Canada); Billowes, J. [The University of Manchester, School of Physics and Astronomy, Manchester (United Kingdom); Buchinger, F.; Crawford, J.E.; Leary, A.; Shelbaya, O.; Al Tamimi, W. [McGill University, Physics Department, Montreal, Quebec (Canada); Cheal, B. [University of Liverpool, Department of Physics, Liverpool (United Kingdom); Mane, E. [TRIUMF, Vancouver, British Columbia (Canada); Ministry of External Relations, Rio Bianco Institute, Brasilia (Brazil); Stolz, M. [Technische Universitaet Berlin, Berlin (Germany); Voss, A. [TRIUMF, Vancouver, British Columbia (Canada); University of Jyvaeskylae, Department of Physics, Jyvaeskylae (Finland)

    2015-02-01

    Fast-beam collinear laser spectroscopy experiments on rubidium have been performed at the ISAC radioactive ion beam facility at TRIUMF. Most recently, the neutron-rich {sup 98}Rb isotope has been studied for the investigation of shape coexistence. Two long-lived nuclear states in {sup 98}Rb have been clearly observed for the first time: a low-spin state, assigned a spin of I = 0, and a high-spin state. The high-spin state is tentatively assigned a spin of I = 3 based on this analysis in combination with gamma decay results. The measured nuclear properties of the two states are presented, alongside unpublished values of the neutron-deficient isotopes investigated previously. The mean-square charge radii of both states in {sup 98}Rb are observed to continue along the isodeformation line present after the N = 60 onset of deformation. (orig.)

  12. Promotion of selective pathways in isomerizing functionalization of plant oils by rigid framework substituents

    KAUST Repository

    Christl, Josefine T.

    2014-10-14

    The 1,2-(CH2P(1-adamantyl)2)2C6H4 (dadpx) coordinated palladium complex [(dadpx)Pd(OTf)2] (1) is a catalyst precursor for the isomerizing methoxycarbonylation of the internal double bond of methyl oleate, with an unprecedented selectivity (96%) for the linear diester 1,19-dimethyl nonadecanedioate. Rapid formation of the catalytically active solvent-coordinated hydride species [(dadpx)PdH(MeOH)]+ (3-MeOH) is evidenced by NMR spectroscopy, and further isolation and X-ray crystal structure analysis of [(dadpx)PdH(PPh3)]+ (3-PPh3). DFT calculations of key steps of the catalytic cycle unravel methanolysis as the decisive step for enhanced selectivity and the influence of the rigid adamantyl framework on this step by destabilization of transition states of unselective pathways.

  13. E3-transitions in sup(105, 107, 109, 111)Ag

    International Nuclear Information System (INIS)

    Shevelev, G.A.; Troitskaya, A.G.; Kartashov, V.M.

    1978-01-01

    Electron radiation of the isomeric transitions of the sup(105-111)Ag odd nuclei was studied using an iron magnetic πsup(√2) beta spectrometer. For most isomeric transitions, relative intensities of the K, L, M, and N lines have been measured; for sup(105-111)Ag and 111 Cd they were measured for the first time. Energy of gamma transitions, relative intensities of internal conversion electrons (ICE) compared with the theoretical ICE values for the E3 transitions are presented. The observations for all the shells are in a fairly gool agreement with the calculations. Systematics of low-lying excited states of the silver nuclei involved is proposed. It has been established that spins and parities of the first excited states of the sup(105-111)Ag odd nuclei are 7/2 + . Multipolarities of isomeric transitions from these staes are pure E3. Spin and parity 9/2 + of the second excited states may be uniquely determined unly for 109 Ag from direct measurements of the ICE transition at 45.8 keV

  14. Boundary layer turbulence in transitional and developed states

    Science.gov (United States)

    Park, George Ilhwan; Wallace, James M.; Wu, Xiaohua; Moin, Parviz

    2012-03-01

    Using the recent direct numerical simulations by Wu and Moin ["Transitional and turbulent boundary layer with heat transfer," Phys. Fluids 22, 85 (2010)] of a flat-plate boundary layer with a passively heated wall, statistical properties of the turbulence in transition at Reθ ≈ 300, from individual turbulent spots, and at Reθ ≈ 500, where the spots merge (distributions of the mean velocity, Reynolds stresses, kinetic energy production, and dissipation rates, enstrophy and its components) have been compared to these statistical properties for the developed boundary layer turbulence at Reθ = 1840. When the distributions in the transitional regions are conditionally averaged so as to exclude locations and times when the flow is not turbulent, they closely resemble the distributions in the developed turbulent state at the higher Reynolds number, especially in the buffer layer. Skin friction coefficients, determined in this conditional manner at the two Reynolds numbers in the transitional flow are, of course, much larger than when their values are obtained by including both turbulent and non-turbulent information there, and the conditional averaged values are consistent with the 1/7th power law approximation. An octant analysis based on the combinations of signs of the velocity and temperature fluctuations, u, v, and θ shows that the momentum and heat fluxes are predominantly of the mean gradient type in both the transitional and developed regions. The fluxes appear to be closely associated with vortices that transport momentum and heat toward and away from the wall in both regions of the flow. The results suggest that there may be little fundamental difference between the nonlinear processes involved in the formation of turbulent spots that appear in transition and those that sustain the turbulence when it is developed. They also support the view that the transport processes and the vortical structures that drive them in developed and transitional boundary

  15. Federal and state benefits for transition age youth.

    Science.gov (United States)

    Altman, Stephanie; O'Connor, Sarah; Anapolsky, Ellyce; Sexton, Laura

    2014-01-01

    While all children face challenges as they become adults, children with chronic medical conditions or disabilities face unique barriers in their transition to adulthood. Children, especially those who are low income and have special needs, are eligible for a range of supports including income supports, health care coverage, vocational and educational supports. These supports are critical to sound health because they ensure access to necessary medical services, while also offsetting the social determinants that negatively affect health. Unfortunately, as children transition into adulthood, eligibility for these benefits can change abruptly or even end entirely. If medical providers have a better understanding of five transition key dates, they can positively impact their patients' health by ensuring continuous coverage through the transition to adulthood. The key dates are as follows: (1) transition services for students with an Individualized Education Program (IEP) must begin by age 16 (in some states such as Illinois, these services must be in place by age 14 1/2); (2) at age 18, eligibility for income supports may change; (3) at age 19, eligibility for Medicaid may change; (4) at graduation, eligibility for educational supports will end unless steps are taken to extend those benefits until age 22; and (5) when individuals prepare to enter the workforce, they will become eligible for vocational rehabilitation services. With an understanding of these key transition dates and how to partner with social services and advocacy organizations on behalf of their patients, medical providers can help to ensure that transition-age patients retain the holistic social services and supports they need to protect their health.

  16. Excitation of 107m,109m Ag isomeric states in the fast neutron inelastic scattering at the Ibr-2 reactor of JINR

    International Nuclear Information System (INIS)

    Alpatov, V.G.; Davydov, A.V.; Isaev, Yu.N.

    1997-01-01

    The excitation cross sections of long-living isomers of 107m,109m Ag nuclei were measured for the fast neutron inelastic scattering reactions at the Ibr-2 reactor of JINR (Dubna) by means of a comparison with the yield of the 103m Rh isomer. The excitation cross sections of the latter are known for analogous reactions in the wide energy range. The measured cross sections are the following: σ( 107m Ag) 204 ± 18 mb, σ( 109m Ag) = 262 ± 26 mb. These values are essentially lower than the excitation cross section of the 103m Rh isomer. The analysis of the data on level structures and transitions between these levels for rhodium and silver nuclei together with the data on γ-spectra created in the reactions (n, n ' γ) shows that the essential difference between excitation cross sections of Rh and Ag isomers can be explained by different populations of corresponding levels

  17. Along the N=126 closed shell: study of $^{205}$Au through its $\\pi h_{11/2}^{-1}$ isomeric decay

    CERN Multimedia

    2002-01-01

    Excited states have been identified in only three of the N=126 closed shell nuclei 'below' $^{208}$Pb, $^{207}$Tl, $^{206}$Hg and very recently $^{204}$Pt. We aim to extend our knowledge of the neutron-rich N=126 nuclei by observing the internal decay of the $\\pi h^{-1}_{11/2}$ excited state in $^{205}$Au, which is expected to be isomeric. In addition, the decay of the analogous states in the N=122 and N=124 $^{201,203}$Au will be studied. The lifetimes of the expected isomeric states are crucial for the success of the experiment, and they are estimated to be in the range of 0.3-20 s. These are long enough to enable the extraction from the source, but shorter than the $\\beta$-decay half-lives. Proton single-particle energies and transition rates will be extracted, providing information about the robustness of the N=126 shell-closure. Three days of beam-time is requested.

  18. Antiferrodistortive phase transitions and ground state of PZT ceramics

    International Nuclear Information System (INIS)

    Pandey, Dhananjai

    2013-01-01

    The ground state of the technologically important Pb(Zr x Ti (1-x) )O 3 , commonly known as PZT, ceramics is currently under intense debate. The phase diagram of this material shows a morphotropic phase boundary (MPB) for x∼0.52 at 300K, across which a composition induced structural phase transition occurs leading to maximization of the piezoelectric properties. In search for the true ground state of the PZT in the MPB region, Beatrix Noheda and coworkers first discovered a phase transition from tetragonal (space group P4mm) to an M A type monoclinic phase (space group Cm) at low temperatures for x=0.52. Soon afterwards, we discovered yet another low temperature phase transition for the same composition in which the M A type (Cm) monoclinic phase transforms to another monoclinic phase with Cc space group. We have shown that the Cm to Cc phase transition is an antiferrodistortive (AFD) transition involving tilting of oxygen octahedra leading to unit cell doubling and causing appearance of superlattice reflections which are observable in the electron and neutron diffraction patterns only and not in the XRD patterns, as a result of which Noheda and coworkers missed the Cc phase in their synchrotron XRD studies at low temperatures. Our findings were confirmed by leading groups using neutron, TEM, Raman and high pressure diffraction studies. The first principles calculations also confirmed that the true ground state of PZT in the MPB region has Cc space group. However, in the last couple of years, the Cc space group of the ground state has become controversial with an alternative proposal of R3c as the space group of the ground state phase which is proposed to coexist with the metastable Cm phase. In order to resolve this controversy, we recently revisited the issue using pure PZT and 6% Sr 2+ substituted PZT, the latter samples show larger tilt angle on account of the reduction in the average cationic radius at the Pb 2+ site. Using high wavelength neutrons and high

  19. Optimal control of transitions between nonequilibrium steady states.

    Directory of Open Access Journals (Sweden)

    Patrick R Zulkowski

    Full Text Available Biological systems fundamentally exist out of equilibrium in order to preserve organized structures and processes. Many changing cellular conditions can be represented as transitions between nonequilibrium steady states, and organisms have an interest in optimizing such transitions. Using the Hatano-Sasa Y-value, we extend a recently developed geometrical framework for determining optimal protocols so that it can be applied to systems driven from nonequilibrium steady states. We calculate and numerically verify optimal protocols for a colloidal particle dragged through solution by a translating optical trap with two controllable parameters. We offer experimental predictions, specifically that optimal protocols are significantly less costly than naive ones. Optimal protocols similar to these may ultimately point to design principles for biological energy transduction systems and guide the design of artificial molecular machines.

  20. Charge states of ions, and mechanisms of charge ordering transitions

    Science.gov (United States)

    Pickett, Warren E.; Quan, Yundi; Pardo, Victor

    2014-07-01

    To gain insight into the mechanism of charge ordering transitions, which conventionally are pictured as a disproportionation of an ion M as 2Mn+→M(n+1)+ + M(n-1)+, we (1) review and reconsider the charge state (or oxidation number) picture itself, (2) introduce new results for the putative charge ordering compound AgNiO2 and the dual charge state insulator AgO, and (3) analyze the cationic occupations of the actual (not formal) charge, and work to reconcile the conundrums that arise. We establish that several of the clearest cases of charge ordering transitions involve no disproportion (no charge transfer between the cations, and hence no charge ordering), and that the experimental data used to support charge ordering can be accounted for within density functional-based calculations that contain no charge transfer between cations. We propose that the charge state picture retains meaning and importance, at least in many cases, if one focuses on Wannier functions rather than atomic orbitals. The challenge of modeling charge ordering transitions with model Hamiltonians isdiscussed.

  1. Excitation of 107m,109mAg isomeric states in the inelastic scattering of fast neutrons from the IBR-2 reactor of JINR

    International Nuclear Information System (INIS)

    Alpatov, V. G.; Borzakov, S. B.; Davydov, A. V.; Isaev, Yu. N.; Kartashov, G. R.; Korotkov, M. M.; Nazarov, V. M.; Pavlov, S. S.; Peresedov, V. F.; Rad'ko, V. E.; Samoylov, V. M.; Chinaeva, V. P.

    1997-01-01

    The cross sections for the excitation of long-lived isomers of 107,109 Ag nuclei are measured in the inelastic scattering of fast neutrons from the IBR-2 reactor of JINR (Dubna). The measurements are performed by means of comparison with the yield of the 103m Rh isomer, for which the excitation cross sections are known over a wide energy range for similar reactions induced by monochromatic neutrons. The measured cross sections proved to be σ( 107m Ag)=204±18 mb and σ( 109m Ag)=262±26 mb. These values are significantly smaller than the cross section for the excitation of the 103m Rh isomer. An analysis employing information about the arrangement of energy levels in Rh and Ag and about transitions between these levels, as well as data on the spectra of γ rays emitted in (n,n'γ) reactions, reveals that the distinction between the cross sections for the excitation of Rh and Ag isomers can be explained by the difference in the population of corresponding levels of Rh and Ag nuclei

  2. Isomeric rations study for the α + 70 Ge

    International Nuclear Information System (INIS)

    Hora Villano, M.H. da.

    1984-12-01

    Isomeric ratios for 73 Se F,I produced in the reaction α + 70 Ge with incidence laboratory energy ranging from 8 to 28 MeV, have been measured using off-line γ-ray spectroscopy. Relative formation cross-section for isomeric and ground states were obtained with NAT Ge targets. Compound nucleus statistical analyses were performed using computer codes Alice and Julian. Unlike to Alice code, the Julian code predictions agreed quite well with the experimental results. This agreement may be explained by the inclusion of the γ competition in the deexcitation channels of the compound nucleus and by the correct level density calculation of the emission probabilities in the Julian code. Finally angular momentum populations for isomers formations in the reaction 70 Ge(α, n) 73 have been determined. (author)

  3. Transitional millisecond pulsars in the low-level accretion state

    Science.gov (United States)

    Jaodard, Amruta D.; Hessels, Jason W. T.; Archibald, Anne; Bogdanov, Slavko; Deller, Adam; Hernandez Santisteban, Juan; Patruno, Alessandro; D'Angelo, Caroline; Bassa, Cees; Amruta Jaodand

    2018-01-01

    In the canonical pulsar recycling scenario, a slowly spinning neutron star can be rejuvenated to rapid spin rates by the transfer of angular momentum and mass from a binary companion star. Over the last decade, the discovery of three transitional millisecond pulsars (tMSPs) has allowed us to study recycling in detail. These systems transition between accretion-powered (X-ray) and rotation-powered (radio) pulsar states within just a few days, raising questions such as: what triggers the state transition, when does the recycling process truly end, and what will the radio pulsar’s final spin rate be? Systematic multi-wavelength campaigns over the last decade have provided critical insights: multi-year-long, low-level accretion states showing coherent X-ray pulsations; extremely stable, bi-modal X-ray light curves; outflows probed by radio continuum emission; a surprising gamma-ray brightening during accretion, etc. In my thesis I am trying to bring these clues together to understand the low-level accretion process that recycles a pulsar. For example, recently we timed PSR J1023+0038 in the accretion state and found it to be spinning down ~26% faster compared to the non-accreting radio pulsar state. We are currently conducting simultaneous multi-wavelength campaigns (XMM, HST, Kepler and VLA) to understand the global variability of the accretion flow, as well as high-energy Fermi-LAT observations to probe the gamma-ray emission mechanism. I will highlight these recent developments, while also presenting a broad overview of tMSPs as exciting new laboratories to test low-level accretion onto magnetized neutron stars.

  4. A United States regulator's perspective on the ongoing chlorofluorocarbon transition.

    Science.gov (United States)

    Meyer, R J

    1999-12-01

    The Food and Drug Administration (FDA) put in place a general ban on the use of chlorofluorocarbons for the products it regulates (medical devices, drugs, and foods) in 1978, exempting those products where chlorofluorocarbon use was determined to be essential for the public health. In the intervening years, as the international commitment to a full transition away from all chlorofluorocarbon use took shape under the Montreal Protocol, the FDA has worked with industry to facilitate the development and testing of alternative technologies and products for inhalation drug products. As these alternative products begin to move from testing through the approval process and into marketing, the FDA is working collaboratively with the Environmental Protection Agency, other governmental agencies, and nongovernmental stakeholders to develop a transition policy for the United States. The transition policy for metered dose inhalers must be one that achieves the dual aims of first protecting the patients who rely on these vital medical products, while also achieving the public health need of protecting the ozone layer. As a part of developing such a transition strategy, the FDA published an advance notice of proposed rulemaking (ANPRM) in March 1997. The ANPRM proposed mechanisms by which the FDA could determine when chlorofluorocarbon use in a drug product could no longer be considered essential. The ANPRM resulted in a large amount of valuable public debate and input. The FDA is now working to incorporate the knowledge gained from these public comments as it continues the rule-making process.

  5. Photoionization and trans-to-cis isomerization of β-cyclodextrin-encapsulated azobenzene induced by two-color two-laser-pulse excitation.

    Science.gov (United States)

    Takeshita, Tatsuya; Hara, Michihiro

    2018-03-15

    Azobenzene (1) and the complex resulting from the incorporation of 1 with cyclodextrin (1/CD) are attractive for light-driven applications such as micromachining and chemical biology tools. The highly sensitive photoresponse of 1 is crucial for light-driven applications containing both 1 and 1/CD to reach their full potential. In this study, we investigated the photoionization and trans-to-cis isomerization of 1/CD induced by one- and two-color two-laser pulse excitation. Photoionization of 1/CD, which was induced by stepwise two-photon absorption, was observed using laser pulse excitation at 266nm. Additionally, simultaneous irradiation with 266 and 532nm laser pulses increased the trans-to-cis isomerization yield (Υ t→c ) by 27%. It was concluded that the increase in Υ t→c was caused by the occurrence of trans-to-cis isomerization in the higher-energy singlet state (S n ), which was reached by S 1 →S n transition induced by laser pulse excitation at 532nm. The results of this study are potentially applicable in light-driven applications such as micromachining and chemical biology tools. Copyright © 2018 Elsevier B.V. All rights reserved.

  6. Isotropic-nematic transition in shear flow: State selection, coexistence, phase transitions, and critical behavior

    Science.gov (United States)

    Olmsted, Peter D.; Goldbart, Paul M.

    1992-10-01

    Macroscopic fluid motion can have dramatic consequences near the isotropic-nematic transition in fluids of nematogens. We explore some of these consequences using both deterministic and stochastic descriptions involving coupled hydrodynamic equations of motion for the nematic order parameter and fluid velocity fields. By analyzing the deterministic equations of motion we identify the locally stable states of homogeneous nematic order and strain rate, thus determining the homogeneous nonequilibrium steady states which the fluid may adopt. By examining inhomogeneous steady states we construct the analog of a first-order phase boundary, i.e., a line in the nonequilibrium phase diagram spanned by temperature and applied stress, at which nonequilibrium states may coexist, and which terminates in a nonequilibrium analog of a critical point. From an analysis of the nematic order-parameter discontinuity across the coexistence line, along with properties of the interface between homogeneous states, we extract the analog of classical equilibrium critical behavior near the nonequilibrium critical point. We develop a theory of fluctuations about biaxial nonequilibrium steady states by augmenting the deterministic description with noise terms, to simulate the effect of thermal fluctuations. We use this description to discuss the scattering of polarized light by order-parameter fluctuations near the nonequilibrium critical point and also in weak shear flow near the equilibrium phase transition. We find that fluids of nematogens near an appropriate temperature and strain rate exhibit the analog of critical opalescence, the intensity of which is sensitive to the polarizations of the incident and scattered light, and to the precise form of the critical mode.

  7. Transitional states of central serotonin receptors in Parkinson's disease

    International Nuclear Information System (INIS)

    Kienzl, E.; Riederer, P.; Jellinger, K.; Wesemann, W.; Marburg Univ.

    1981-01-01

    Crude membrane preparations from the frontal cortex of controls and pakinsonian patients were used to demonstrate affinity changes of the specific 3 H-5-hydroxytryptamine (5-HT) binding sites. Two such sites were noteable in controls, a finding consistent with earlier observations. In Parkinson's disease, both high- and low-affinity sites are significantly decreased. Additional experiments either with prolonged incubation times or pre-incubation with N-ethylmaleimide change the two affinities to a single high-affinity or low-affinity constant. The concept of transitional states of 5-HT receptors is discussed and seems to have important implications in the treatment of parkinsonism. (author)

  8. Transitional states of central serotonin receptors in Parkinson's disease

    Energy Technology Data Exchange (ETDEWEB)

    Kienzl, E; Riederer, P; Jellinger, K; Wesemann, W [Krankenhaus der Stadt Wien-Lainz (Austria). Ludwig Boltzmann Inst. fuer Neurobiologie; Marburg Univ. (Germany, F.R.). Inst. fuer Physiologie II, Abt. fuer Neurochemie)

    1981-01-01

    Crude membrane preparations from the frontal cortex of controls and pakinsonian patients were used to demonstrate affinity changes of the specific /sup 3/H-5-hydroxytryptamine (5-HT) binding sites. Two such sites were noteable in controls, a finding consistent with earlier observations. In Parkinson's disease, both high- and low-affinity sites are significantly decreased. Additional experiments either with prolonged incubation times or pre-incubation with N-ethylmaleimide change the two affinities to a single high-affinity or low-affinity constant. The concept of transitional states of 5-HT receptors is discussed and seems to have important implications in the treatment of parkinsonism.

  9. Communication: An accurate calculation of the S1 C2H2 cis-trans isomerization barrier height

    International Nuclear Information System (INIS)

    Baraban, Joshua H.; Matthews, Devin A.; Stanton, John F.

    2016-01-01

    A high level ab initio calculation of the cis-trans isomerization barrier height in the first excited singlet electronic state of acetylene is found to agree very well with a recent experimental determination.

  10. Pion condensation and density isomerism in nuclear matter

    International Nuclear Information System (INIS)

    Hecking, P.; Weise, W.

    1979-01-01

    The possible existence of density isomers in nuclear matter, induced by pion condensation, is discussed; the nuclear equation of state is treated within the framework of the sigma model. Repulsive short-range baryon-baryon correlations, the admixture of Δ (1232) isobars and finite-range pion-baryon vertex form factors are taken into account. The strong dependence of density isomerism on the high density extrapolation of the equation of state for normal nuclear matter is also investigated. We find that, once finite range pion-baryon vertices are introduced, the appearance of density isomers becomes unlikely

  11. Isomeric island in the vicinity of 66Fe

    International Nuclear Information System (INIS)

    Daugas, J. M.; Belier, G.; Girod, M.; Goutte, H.; Meot, V.; Perru, O.; Roig, O.; Sauvestre, J. E.; Sawicka, M.; Pfuetzner, M.; Zylicz, J.; Matea, I.; Giovinazzo, J.; Grawe, H.; Becker, F.; Mayet, P.; Grzywacz, R.; Achouri, N. L.; Angelique, J. C.; Baiborodin, D.

    2006-01-01

    An island of isomers have recently been observed on both sides of the N=40 shell below the Ni isotopes. Isomeric states in the 65Fe and 67Fe allow the knowledge of the single particle structure around the νg9/2 shell. Moreover, the excitation energy of the first 2+ and 4+ states in the 68Fe have been established by β-γ correlation. The evolution of the structure of the Fe isotopes going far away from the valley of stability is, for the first time, given for N>40

  12. Special features of isomeric ratios in nuclear reactions induced by various projectile particles

    Energy Technology Data Exchange (ETDEWEB)

    Danagulyan, A. S.; Hovhannisyan, G. H., E-mail: hov-gohar@ysu.am; Bakhshiyan, T. M.; Martirosyan, G. V. [Yerevan State University (Armenia)

    2016-05-15

    Calculations for (p, n) and (α, p3n) reactions were performed with the aid of the TALYS-1.4 code. Reactions in which the mass numbers of target and product nuclei were identical were examined in the range of A = 44–124. Excitation functions were obtained for product nuclei in ground and isomeric states, and isomeric ratios were calculated. The calculated data reflect well the dependence of the isomeric ratios on the projectile type. A comparison of the calculated and experimental data reveals, that, for some nuclei in a high-spin state, the calculated data fall greatly short of their experimental counterparts. These discrepancies may be due to the presence of high-spin yrast states and rotational bands in these nuclei. Calculations involving various level-density models included in the TALYS-1.4 code with allowance for the enhancement of collective effects do not remove the discrepancies in the majority of cases.

  13. Neutron transition densities for the 2+-8+ multiplet of states in 90Zr

    International Nuclear Information System (INIS)

    Onegin, M.S.; Plavko, A.V.

    2004-01-01

    Neutron transition densities for the 2 + -8 + levels in 90 Zr were extracted in the process of analyzing (p,p ' ) scattering at 400 MeV. They were compared with the calculated neutron transition densities and with the experimental proton transition densities. Radial distributions of the experimental neutron and proton transition densities for each state were found to be different. (orig.)

  14. Transit Car Performance Comparison, State-of-the-Art Car vs. PATCO Transit Car, NYCTA R-46, MBTA Silverbirds

    Science.gov (United States)

    1978-02-01

    The first phase of this contract authorized the design, development, and demonstration of two State-Of-The-Art Cars (SOAC). This document reports on the gathering of comparative test data on existing in-service transit cars. The three transit cars se...

  15. A new fundamental type of conformational isomerism

    Science.gov (United States)

    Canfield, Peter J.; Blake, Iain M.; Cai, Zheng-Li; Luck, Ian J.; Krausz, Elmars; Kobayashi, Rika; Reimers, Jeffrey R.; Crossley, Maxwell J.

    2018-06-01

    Isomerism is a fundamental chemical concept, reflecting the fact that the arrangement of atoms in a molecular entity has a profound influence on its chemical and physical properties. Here we describe a previously unclassified fundamental form of conformational isomerism through four resolved stereoisomers of a transoid (BF)O(BF)-quinoxalinoporphyrin. These comprise two pairs of enantiomers that manifest structural relationships not describable within existing IUPAC nomenclature and terminology. They undergo thermal diastereomeric interconversion over a barrier of 104 ± 2 kJ mol-1, which we term `akamptisomerization'. Feasible interconversion processes between conceivable synthesis products and reaction intermediates were mapped out by density functional theory calculations, identifying bond-angle inversion (BAI) at a singly bonded atom as the reaction mechanism. We also introduce the necessary BAI stereodescriptors parvo and amplo. Based on an extended polytope formalism of molecular structure and stereoisomerization, BAI-driven akamptisomerization is shown to be the final fundamental type of conformational isomerization.

  16. An Investigation of the Enolization and Isomeric Products Distribution in the Water Promoted Aldol Reaction of Tropinone and Granatanone

    Directory of Open Access Journals (Sweden)

    Ryszard Lazny

    2016-01-01

    Full Text Available The exo,anti/exo,syn-diastereoselectivity of water promoted direct aldol reactions of tropinone and granatanone (pseudopelletierine is strongly dependent on the amount of water added and aromatic aldehyde used. DFT methods were applied to calculate the free energies of tropinone and granatanone enols, transition states, and isomeric aldol products. A theoretical model was verified by comparison of results from several DFT methods and functionals with experiments. The 6-31g(d/CPCM method proved most suited to the problem, although all methods tested predicted similar trends. Explicit inclusion of a water molecule bonded to the amino ketones resulted in increased stability of the enol forms. The dependence of the anti/syn-diastereoselectivity on the amount of water used may be rationalized on the basis of change in the polarity of the reaction medium. The predicted stabilities of competing products agreed with experimental results supporting the notion of thermodynamic control. The isomeric products distributions for the aldol reaction of several aromatic aldehydes in solventless (neat conditions were accurately calculated from free energies of the aldol addition step in the gas phase using B3LYP/6-31g(d method and in aqueous conditions using the CPCM-B3LYP/6-31g(d model. Our methodology can be useful for predicting the outcome of this type of aldol reactions.

  17. A MECHANISM FOR HYSTERESIS IN BLACK HOLE BINARY STATE TRANSITIONS

    International Nuclear Information System (INIS)

    Begelman, Mitchell C.; Armitage, Philip J.

    2014-01-01

    We suggest that the hysteretic cycle of black hole state transitions arises from two established properties of accretion disks: the increase in turbulent stress in disks threaded by a net magnetic field and the ability of thick (but not thin) disks to advect such a field radially. During quiescence, magnetic field loops are generated by the magnetorotational instability at the interface between the inner hot flow and outer thin disk. Vertical flux is advected into and accumulates stochastically within the inner flow, where it stimulates the turbulence so that α ∼ 1. The transition to a geometrically thin inner disk occurs when L ∼ α 2 L Edd ∼ L Edd , and the first ''thin'' disk to form is itself moderately thick, strongly magnetized, and able to advect field inward. These properties favor episodic jet production. As the accretion rate declines magnetic flux escapes, α decreases to α ∼ 0.01-0.1, and a hot inner flow is not re-established until L << L Edd . We discuss possible observational consequences of our scenario

  18. Easy Synthesis of Two Positional Isomeric Tetrazole Libraries

    NARCIS (Netherlands)

    Wang, Yuanze; Patil, Pravin; Dömling, Alexander

    2016-01-01

    A fast and efficient synthesis of libraries of positional isomeric 1H-tetrazoles and 5H-tetrazoles, for the purpose of testing binding hypothesis of isomeric tetrazoles in fragment-based drug discovery, is described.

  19. Bound states of quarks and gluons and hadronic transitions

    International Nuclear Information System (INIS)

    Castro, Antonio Soares de.

    1990-05-01

    A potential which incorporates the concepts of confinement and asymptotic freedom, previously utilized in the description of the spectroscopy of mesons and baryons, is extended to the gluon sector. The mass spectroscopy of glueballs and hybrids is analyzed considering only pairwise potentials and massive constituent gluons. The mass spectrum of the color octet two-gluon system is adopted as a suitable description of the intermediate states of hadronic transitions, within the framework of the multipole expansion for quantum chromodynamics. The spin-dependent effects in the gluonium spectrum, associated with the Coulombian potential, are calculated through the inverted first Born approximation for the gluon-gluon scattering. (author). 102 refs, 1 fig, 13 tabs

  20. A Stochastic Description of Transition Between Granular Flow States

    International Nuclear Information System (INIS)

    Huang Decai; Sun Gang; Lu Kunquan

    2007-01-01

    Two-dimensional granular flow in a channel with small exit is studied by molecular dynamics simulations. We firstly define a key area near the exit, which is considered to be the choke area of the system. Then we observe the time variation of the local packing fraction and flow rate in this area for several fixed inflow rate, and find that these quantities change abruptly when the transition from dilute flow state to dense flow state happens. A relationship between the local flow rate and the local packing fraction in the key area is also given. The relationship is a continuous function under the fixed particle number condition, and has the characteristic that the flow rate has a maximum at a moderate packing fraction and the packing fraction is terminated at a high value with negative slope. By use of the relationship, the properties of the flow states under the fixed inflow rate condition are discussed in detail, and the discontinuities and the complex time variation behavior observed in the preexisting works are naturally explained by a stochastic process.

  1. Multi-state succession in wetlands: a novel use of state and transition models

    Science.gov (United States)

    Zweig, Christa L.; Kitchens, Wiley M.

    2009-01-01

    The complexity of ecosystems and mechanisms of succession are often simplified by linear and mathematical models used to understand and predict system behavior. Such models often do not incorporate multivariate, nonlinear feedbacks in pattern and process that include multiple scales of organization inherent within real-world systems. Wetlands are ecosystems with unique, nonlinear patterns of succession due to the regular, but often inconstant, presence of water on the landscape. We develop a general, nonspatial state and transition (S and T) succession conceptual model for wetlands and apply the general framework by creating annotated succession/management models and hypotheses for use in impact analysis on a portion of an imperiled wetland. The S and T models for our study area, Water Conservation Area 3A South (WCA3), Florida, USA, included hydrologic and peat depth values from multivariate analyses and classification and regression trees. We used the freeware Vegetation Dynamics Development Tool as an exploratory application to evaluate our S and T models with different management actions (equal chance [a control condition], deeper conditions, dry conditions, and increased hydrologic range) for three communities: slough, sawgrass (Cladium jamaicense), and wet prairie. Deeper conditions and increased hydrologic range behaved similarly, with the transition of community states to deeper states, particularly for sawgrass and slough. Hydrology is the primary mechanism for multi-state transitions within our study period, and we show both an immediate and lagged effect on vegetation, depending on community state. We consider these S and T succession models as a fraction of the framework for the Everglades. They are hypotheses for use in adaptive management, represent the community response to hydrology, and illustrate which aspects of hydrologic variability are important to community structure. We intend for these models to act as a foundation for further restoration

  2. The Astrophysical Weeds: Rotational Transitions in Excited Vibrational States

    Science.gov (United States)

    Alonso, José L.; Kolesniková, Lucie; Alonso, Elena R.; Mata, Santiago

    2017-06-01

    The number of unidentified lines in the millimeter and submillimeter wave surveys of the interstellar medium has grown rapidly. The major contributions are due to rotational transitions in excited vibrational states of a relatively few molecules that are called the astrophysical weeds. necessary data to deal with spectral lines from astrophysical weeds species can be obtained from detailed laboratory rotational measurements in the microwave and millimeter wave region. A general procedure is being used at Valladolid combining different time and/or frequency domain spectroscopic tools of varying importance for providing the precise set of spectroscopic constants that could be used to search for this species in the ISM. This is illustrated in the present contribution through its application to several significant examples. Fortman, S. M., Medvedev, I. R., Neese, C.F., & De Lucia, F.C. 2010, ApJ,725, 1682 Rotational Spectra in 29 Vibrationally Excited States of Interstellar Aminoacetonitrile, L. Kolesniková, E. R. Alonso, S. Mata, and J. L. Alonso, The Astrophysical Journal Supplement Series 2017, (in press).

  3. The phase transition to an inhomogeneous condensate state

    International Nuclear Information System (INIS)

    Voskresensky, D.N.

    1984-01-01

    The Lagrangian (free energy) of the model with a complex scalar order parameter in which the phase transition to an inhomogeneous condensate state exists is constructed in the coordinate representation. In the case of condensation of charged particles (for example paired electrons) interaction with the electromagnetic field is included. The excitation spectrum in the presence of the condensate is found. The oscillations are strongly anisotropic. It is shown that superfluidity is absent for an uncharged system but that the charged one has the property of superconductivity. The important role of thermal fluctuations is demonstrated. They drastically change the behaviour of the condensate system. The condensation in a finite system is considered. A study is carried out for the behaviour of an inhomogeneous condensate in magnetic field. It is shown that the inhomogeneous condensate is a type II superconductor with Ginzburg-Landau parameter kappa >> 1, but that the structure of the mixed state of the system is unusual - consisting of plane layers of the normal phase, when Hsub(c1)< H< H'sub(c2). The distribution of condensate in the strong magnetic field H'sub(c2)< H< Hsub(c2) is also studied. (Auth.)

  4. Montecarlo calculation of the isomeric cross sections ratio for the reaction 237Np(n,2n)236Np

    International Nuclear Information System (INIS)

    Cleri, F.

    1988-01-01

    A Montecarlo calculation of the isomeric cross section ratio for the (n,2n) reaction on 237 Np has been carried out based on the Hauser-Feshbach formulation. A standard energy-dependent optical model potential was used, with zero deformation parameters and no spin-orbit coupling. Investigation was made about the role of the energy cut-off value, of the higher multipole (E2) transition, of the gamma-ray versus second neutron emission, of the value of the spin cutt-off parameter. The results give the correct qualitative energy dependence of the branching ratio, with the assumption that the 1 - level is the ground state. The spin cut-off value obtained indicates a less pronounced deviation of the nuclear moment of inertia from the rigid-body value, with respect to older evaluations for high-mass nuclei. (author)

  5. Probing the Single-Particle Character of Rotational States in F19 Using a Short-Lived Isomeric Beam

    Energy Technology Data Exchange (ETDEWEB)

    Santiago-Gonzalez, D.; Auranen, K.; Avila, M. L.; Ayangeakaa, A. D.; Back, B. B.; Bottoni, S.; Carpenter, M. P.; Chen, J.; Deibel, C. M.; Hood, A. A.; Hoffman, C. R.; Janssens, R. V. F.; Jiang, C. L.; Kay, B. P.; Kuvin, S. A.; Lauer, A.; Schiffer, J. P.; Sethi, J.; Talwar, R.; Wiedenhöver, I.; Winkelbauer, J.; Zhu, S.

    2018-03-01

    A beam containing a substantial component of both the J(pi) = 5(+), T-1/2 = 162 ns isomeric state of F-18 and its 1(+), 109.77-min ground state is utilized to study members of the ground-state rotational band in F-19 through the neutron transfer reaction (d,p) in inverse kinematics. The resulting spectroscopic strengths confirm the single-particle nature of the 13/2(+) band-terminating state. The agreement between shell-model calculations using an interaction constructed within the sd shell, and our experimental results reinforces the idea of a single-particle-collective duality in the descriptions of the structure of atomic nuclei.

  6. Formation, isomerization, and derivatization of keggin tungstoaluminates.

    Science.gov (United States)

    Jennifer J. Cowan; Alan J. Bailey; Robert A. Heintz; Bao T. Do; Kenneth I. Hardcastle; Craig L. Hill; Ira A. Weinstock

    2001-01-01

    Trends in the stability of ¥á and ©¬-Keggin heteropolytungstates of the second-row main-group heteroatoms Al(III), Si(IV), and P(V) are elaborated by data that establish the roles of kinetic and thermodynamic control in the formation and isomerization of Keggin tungstoaluminates. Slow, room-temperature co-...

  7. Isomeric periodic mesoporous organosilicas with controllable properties

    NARCIS (Netherlands)

    Vercaemst, C.; Ide, I.; Friedrich, H.; de Jong, K.P.; Verpoort, F.; van der Voort, P.

    2009-01-01

    The synthesis procedure for isomeric periodic mesoporous organosilicas with E-configured ethenylene bridges was investigated using the homemade pure E-isomer of 1,2-bis(triethoxysilyl)ethene. The pH, aging temperature and the presence of cosolvents played a key role in obtaining well-ordered

  8. Trimethylphosphide isomerization in lanthanum ions presence

    International Nuclear Information System (INIS)

    Zacharias, M.A.; Massabni, A.M.G.

    1984-01-01

    The integration between the trimethilphosphide and the lanthanum ions carry to the formation of solid complexes in a relation of 6:1 where the ligand is the phosphonate what is resultant of the isomerization of trimetylphosphite. By the RMN -1 H and infra-red spectra the products were characterized. (L.M.J.) [pt

  9. Crystal structure of isomeric boron difluoride acetylnaphtholates

    International Nuclear Information System (INIS)

    Bukvetskij, B.V.; Fedorenko, E.V.; Mirochnik, A.G.; Karasev, V.E.

    2006-01-01

    Crystal structures of luminescent isomeric acetylnaphtholates of boron difluoride are investigated. Full X-ray structural analysis is done at 293 K. Coordinated of atoms, bond angles, bond lengths, interatomic distances are determined. Results of comparative evaluations of the isomers are represented [ru

  10. Cryo-EM structure of isomeric molluscan hemocyanin triggered by viral infection.

    Directory of Open Access Journals (Sweden)

    Hongtao Zhu

    Full Text Available Hemocyanins (Hcs of arthropods and mollusks function not only as oxygen transporters, but also as phenoloxidases (POs. In invertebrates, PO is an important component in the innate immune cascade, where it functions as the initiator of melanin synthesis, a pigment involved in encapsulating and killing of pathogenic microbes. Although structures of Hc from several species of invertebrates have been reported, the structural basis for how PO activity is triggered by structural changes of Hc in vivo remains poorly understood. Here, we report a 6.8 Å cryo-electron microscopy (cryo-EM structure of the isomeric form of hemocyanin, which was isolated from Abalone Shriveling syndrome-associated Virus (AbSV infected abalone (Halitotis diversicolor, and build a pseudoatomic model of isomeric H. diversicolor hemocyanin 1 (HdH1. Our results show that, compared with native form of HdH1, the architecture of isomeric HdH1 turns into a more relaxed form. The interactions between certain functional units (FUs present in the native form of Hc either decreased or were totally abolished in the isomeric form of Hc. As a result of that, native state Hc switches to its isomeric form, enabling it to play its role in innate immune responses against invading pathogens.

  11. Discovering Unique, Low-Energy Transition States Using Evolutionary Molecular Memetic Computing

    DEFF Research Database (Denmark)

    Ellabaan, Mostafa M Hashim; Ong, Y.S.; Handoko, S.D.

    2013-01-01

    In the last few decades, identification of transition states has experienced significant growth in research interests from various scientific communities. As per the transition states theory, reaction paths and landscape analysis as well as many thermodynamic properties of biochemical systems can...... be accurately identified through the transition states. Transition states describe the paths of molecular systems in transiting across stable states. In this article, we present the discovery of unique, low-energy transition states and showcase the efficacy of their identification using the memetic computing...... paradigm under a Molecular Memetic Computing (MMC) framework. In essence, the MMC is equipped with the tree-based representation of non-cyclic molecules and the covalent-bond-driven evolutionary operators, in addition to the typical backbone of memetic algorithms. Herein, we employ genetic algorithm...

  12. Revisiting the polytopal rearrangements in penta-coordinate d7-metallocomplexes: modified Berry pseudorotation, octahedral switch, and butterfly isomerization.

    Science.gov (United States)

    Asatryan, Rubik; Ruckenstein, Eli; Hachmann, Johannes

    2017-08-01

    This paper provides a first-principles theoretical investigation of the polytopal rearrangements and fluxional behavior of five-coordinate d 7 -transition metal complexes. Our work is primarily based on a potential energy surface analysis of the iron tetracarbonyl hydride radical HFe˙(CO) 4 . We demonstrate the existence of distorted coordination geometries in this prototypical system and, for the first time, introduce three general rearrangement mechanisms, which account for the non-ideal coordination. The first of these mechanisms constitutes a modified version of the Berry pseudorotation via a square-based pyramidal C 4v transition state that connects two chemically identical edge-bridged tetrahedral stereoisomers of C 2v symmetry. It differs from the classical Berry mechanism, which involves two regular D 3h equilibrium structures and a C 4v transition state. The second mechanism is related to the famous "tetrahedral jump" hypothesis, postulated by Muetterties for a number of d 6 HML 4 and H 2 ML 4 complexes. Here, our study suggests two fluxional rearrangement pathways via distinct types of C 2v transition states. Both pathways of this mechanism can be described as a single-ligand migration to a vacant position of an "octahedron", thus interchanging (switching) the apical and basal ligands of the initial quasi-square pyramidal isomer, which is considered as an idealized octahedron with a vacancy. Accordingly, we call this mechanism "octahedral switch". The third mechanism follows a butterfly-type isomerization featuring a key-angle deformation, and we thus call it "butterfly isomerization". It connects the quasi-square pyramidal and edge-bridged tetrahedral isomers of HFe˙(CO) 4 through a distorted edge-bridged tetrahedral transition state of C s symmetry. Our paper discusses the overall features of the isomers and rearrangement mechanisms as well as their implications. We rationalize the existence of each stationary point through an electronic structure

  13. Cat's claw oxindole alkaloid isomerization induced by common extraction methods

    Directory of Open Access Journals (Sweden)

    Samuel Kaiser

    2013-01-01

    Full Text Available Cat's claw oxindole alkaloids are prone to isomerization in aqueous solution. However, studies on their behavior in extraction processes are scarce. This paper addressed the issue by considering five commonly used extraction processes. Unlike dynamic maceration (DM and ultrasound-assisted extraction, substantial isomerization was induced by static maceration, turbo-extraction and reflux extraction. After heating under reflux in DM, the kinetic order of isomerization was established and equations were fitted successfully using a four-parameter Weibull model (R² > 0.999. Different isomerization rates and equilibrium constants were verified, revealing a possible matrix effect on alkaloid isomerization.

  14. Detecting critical state before phase transition of complex biological systems by hidden Markov model.

    Science.gov (United States)

    Chen, Pei; Liu, Rui; Li, Yongjun; Chen, Luonan

    2016-07-15

    Identifying the critical state or pre-transition state just before the occurrence of a phase transition is a challenging task, because the state of the system may show little apparent change before this critical transition during the gradual parameter variations. Such dynamics of phase transition is generally composed of three stages, i.e. before-transition state, pre-transition state and after-transition state, which can be considered as three different Markov processes. By exploring the rich dynamical information provided by high-throughput data, we present a novel computational method, i.e. hidden Markov model (HMM) based approach, to detect the switching point of the two Markov processes from the before-transition state (a stationary Markov process) to the pre-transition state (a time-varying Markov process), thereby identifying the pre-transition state or early-warning signals of the phase transition. To validate the effectiveness, we apply this method to detect the signals of the imminent phase transitions of complex systems based on the simulated datasets, and further identify the pre-transition states as well as their critical modules for three real datasets, i.e. the acute lung injury triggered by phosgene inhalation, MCF-7 human breast cancer caused by heregulin and HCV-induced dysplasia and hepatocellular carcinoma. Both functional and pathway enrichment analyses validate the computational results. The source code and some supporting files are available at https://github.com/rabbitpei/HMM_based-method lnchen@sibs.ac.cn or liyj@scut.edu.cn Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  15. Is isomerism a risk factor for intestinal volvulus?

    Science.gov (United States)

    Landisch, Rachel M; Loomba, Rohit S; Salazar, Jose H; Buelow, Matthew W; Frommelt, Michele; Anderson, Robert H; Wagner, Amy J

    2018-03-06

    Isomerism, or heterotaxy syndrome, affects many organ systems anatomically and functionally. Intestinal malrotation is common in patients with isomerism. Despite a low reported risk of volvulus, some physicians perform routine screening and prophylactic Ladd procedures on asymptomatic patients with isomerism who are found to have intestinal malrotation. The primary aim of this study was to determine if isomerism is an independent risk factor for volvulus. Kid's Inpatient Database data from 1997 to 2012 was utilized for this study. Characteristics of admissions with and without isomerism were compared with a particular focus on intestinal malrotation, volvulus, and Ladd procedure. A logistic regression was conducted to determine independent risk factors for volvulus with respect to isomerism. 15,962,403 inpatient admissions were included in the analysis, of which 7970 (0.05%) patients had isomerism, and 6 patients (0.1%) developed volvulus. Isomerism was associated with a 52-fold increase in the odds of intestinal malrotation by univariate analysis. Of 251 with isomerism and intestinal malrotation, only 2.4% experienced volvulus. Logistic regression demonstrated that isomerism was not an independent risk factor for volvulus. Isomerism is associated with an increased risk of intestinal malrotation but is not an independent risk factor for volvulus. Prognosis study. Level III. Copyright © 2018 Elsevier Inc. All rights reserved.

  16. Modelling transition states of a small once-through boiler

    Energy Technology Data Exchange (ETDEWEB)

    Talonpoika, T [Lappeenranta Univ. of Technology (Finland). Dept. of Energy Technology

    1998-12-31

    This article presents a model for the unsteady dynamic behaviour of a once-through counter flow boiler that uses an organic working fluid. The boiler is a compact waste-heat boiler without a furnace and it has a preheater, a vaporiser and a superheater. The relative lengths of the boiler parts vary with the operating conditions since they are all parts of a single tube. The boiler model is presented using a selected example case that uses toluene as the process fluid and flue gas from natural gas combustion as the heat source. The dynamic behaviour of the boiler means transition from the steady initial state towards another steady state that corresponds to the changed process conditions. The solution method chosen is to find such a pressure of the process fluid that the mass of the process fluid in the boiler equals the mass calculated using the mass flows into and out of the boiler during a time step, using the finite difference method. A special method of fast calculation of the thermal properties is used, because most of the calculation time is spent in calculating the fluid properties. The boiler is divided into elements. The values of the thermodynamic properties and mass flows are calculated in the nodes that connect the elements. Dynamic behaviour is limited to the process fluid and tube wall, and the heat source is regarded as to be steady. The elements that connect the preheater to the vaporiser and the vaporiser to the superheater are treated in a special way that takes into account a flexible change from one part to the other. The initial state of the boiler is received from a steady process model that is not a part of the boiler model. The known boundary values that may vary during the dynamic calculation were the inlet temperature and mass flow rates of both the heat source fluid and the process fluid. The dynamic boiler model is analysed for linear and step charges of the entering fluid temperatures and flow rates. The heat source side tests show that

  17. Modelling transition states of a small once-through boiler

    Energy Technology Data Exchange (ETDEWEB)

    Talonpoika, T. [Lappeenranta Univ. of Technology (Finland). Dept. of Energy Technology

    1997-12-31

    This article presents a model for the unsteady dynamic behaviour of a once-through counter flow boiler that uses an organic working fluid. The boiler is a compact waste-heat boiler without a furnace and it has a preheater, a vaporiser and a superheater. The relative lengths of the boiler parts vary with the operating conditions since they are all parts of a single tube. The boiler model is presented using a selected example case that uses toluene as the process fluid and flue gas from natural gas combustion as the heat source. The dynamic behaviour of the boiler means transition from the steady initial state towards another steady state that corresponds to the changed process conditions. The solution method chosen is to find such a pressure of the process fluid that the mass of the process fluid in the boiler equals the mass calculated using the mass flows into and out of the boiler during a time step, using the finite difference method. A special method of fast calculation of the thermal properties is used, because most of the calculation time is spent in calculating the fluid properties. The boiler is divided into elements. The values of the thermodynamic properties and mass flows are calculated in the nodes that connect the elements. Dynamic behaviour is limited to the process fluid and tube wall, and the heat source is regarded as to be steady. The elements that connect the preheater to the vaporiser and the vaporiser to the superheater are treated in a special way that takes into account a flexible change from one part to the other. The initial state of the boiler is received from a steady process model that is not a part of the boiler model. The known boundary values that may vary during the dynamic calculation were the inlet temperature and mass flow rates of both the heat source fluid and the process fluid. The dynamic boiler model is analysed for linear and step charges of the entering fluid temperatures and flow rates. The heat source side tests show that

  18. Three equations of state and their application to transition metals

    Energy Technology Data Exchange (ETDEWEB)

    Tian Ronggang; Sun Jiuxun; Yang Wei; Yu Fei, E-mail: sjx@uestc.edu.c [Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2010-10-15

    A modified generalized Morse (mGMSE) equation of state (EOS) is proposed that can incorporate the cohesive energy data correctly. It is compared with a four-parameter modified Rose (MR) EOS, which is proposed by following Rose's approach, and the Murnaghan (MNH) EOS. The MR, mGMSE and MNH EOSs are applied to five transition metals and then compared to the available experimental compression data. The results obtained show that for all pressure ranges, the mGMSE EOS fits experimental data most accurately. From a comparison of the variation in pressure and energy versus the compression ratio between MR and mGMSE EOSs, it is clear that the pressure and energy of the MR EOS oscillate both in the neighborhood of (V/V{sub 0}) {approx} 0.005 and in the range (V/V{sub 0})> 1. Generally speaking, the mGMSE EOS has many evident advantages over the other two EOSs, while the practical applications of the MR EOS are seriously limited because of physically incorrect oscillations.

  19. Three equations of state and their application to transition metals

    International Nuclear Information System (INIS)

    Tian Ronggang; Sun Jiuxun; Yang Wei; Yu Fei

    2010-01-01

    A modified generalized Morse (mGMSE) equation of state (EOS) is proposed that can incorporate the cohesive energy data correctly. It is compared with a four-parameter modified Rose (MR) EOS, which is proposed by following Rose's approach, and the Murnaghan (MNH) EOS. The MR, mGMSE and MNH EOSs are applied to five transition metals and then compared to the available experimental compression data. The results obtained show that for all pressure ranges, the mGMSE EOS fits experimental data most accurately. From a comparison of the variation in pressure and energy versus the compression ratio between MR and mGMSE EOSs, it is clear that the pressure and energy of the MR EOS oscillate both in the neighborhood of (V/V 0 ) ∼ 0.005 and in the range (V/V 0 )> 1. Generally speaking, the mGMSE EOS has many evident advantages over the other two EOSs, while the practical applications of the MR EOS are seriously limited because of physically incorrect oscillations.

  20. Three equations of state and their application to transition metals

    Science.gov (United States)

    Ronggang, Tian; Jiuxun, Sun; Wei, Yang; Fei, Yu

    2010-10-01

    A modified generalized Morse (mGMSE) equation of state (EOS) is proposed that can incorporate the cohesive energy data correctly. It is compared with a four-parameter modified Rose (MR) EOS, which is proposed by following Rose's approach, and the Murnaghan (MNH) EOS. The MR, mGMSE and MNH EOSs are applied to five transition metals and then compared to the available experimental compression data. The results obtained show that for all pressure ranges, the mGMSE EOS fits experimental data most accurately. From a comparison of the variation in pressure and energy versus the compression ratio between MR and mGMSE EOSs, it is clear that the pressure and energy of the MR EOS oscillate both in the neighborhood of (V/V0 ) ≈ 0.005 and in the range (V/V0 )> 1. Generally speaking, the mGMSE EOS has many evident advantages over the other two EOSs, while the practical applications of the MR EOS are seriously limited because of physically incorrect oscillations.

  1. Transition-state theory predicts clogging at the microscale

    Science.gov (United States)

    Laar, T. Van De; Klooster, S. Ten; Schroën, K.; Sprakel, J.

    2016-06-01

    Clogging is one of the main failure mechanisms encountered in industrial processes such as membrane filtration. Our understanding of the factors that govern the build-up of fouling layers and the emergence of clogs is largely incomplete, so that prevention of clogging remains an immense and costly challenge. In this paper we use a microfluidic model combined with quantitative real-time imaging to explore the influence of pore geometry and particle interactions on suspension clogging in constrictions, two crucial factors which remain relatively unexplored. We find a distinct dependence of the clogging rate on the entrance angle to a membrane pore which we explain quantitatively by deriving a model, based on transition-state theory, which describes the effect of viscous forces on the rate with which particles accumulate at the channel walls. With the same model we can also predict the effect of the particle interaction potential on the clogging rate. In both cases we find excellent agreement between our experimental data and theory. A better understanding of these clogging mechanisms and the influence of design parameters could form a stepping stone to delay or prevent clogging by rational membrane design.

  2. State-Transition Structures in Physics and in Computation

    Science.gov (United States)

    Petri, C. A.

    1982-12-01

    In order to establish close connections between physical and computational processes, it is assumed that the concepts of “state” and of “transition” are acceptable both to physicists and to computer scientists, at least in an informal way. The aim of this paper is to propose formal definitions of state and transition elements on the basis of very low level physical concepts in such a way that (1) all physically possible computations can be described as embedded in physical processes; (2) the computational aspects of physical processes can be described on a well-defined level of abstraction; (3) the gulf between the continuous models of physics and the discrete models of computer science can be bridged by simple mathematical constructs which may be given a physical interpretation; (4) a combinatorial, nonstatistical definition of “information” can be given on low levels of abstraction which may serve as a basis to derive higher-level concepts of information, e.g., by a statistical or probabilistic approach. Conceivable practical consequences are discussed.

  3. Youth and administrator perspectives on transition in Kentucky's state agency schools.

    Science.gov (United States)

    Marshall, Amy; Powell, Norman; Pierce, Doris; Nolan, Ronnie; Fehringer, Elaine

    2012-01-01

    Students, a large percentage with disabilities, are at high risk for poor post-secondary outcomes in state agency education programs. This mixed-methods study describes the understandings of student transitions in state agency education programs from the perspectives of youth and administrators. Results indicated that: transition is more narrowly defined within alternative education programs; key strengths of transition practice are present in nontraditional schools; and the coordination barriers within this fluid inter-agency transition system are most apparent in students' frequent inter-setting transitions between nontraditional and home schools.

  4. Characterizing gamma fields using isomeric activation ratios

    Science.gov (United States)

    Venkataraman, Ramkumar; Fleming, Ronald F.

    1994-12-01

    Isomeric activities were induced in indium by gamma irradiation in three different gamma fields, through the reactions 115In(γ, γ') 115mIn and 113In(γ, γ') 113mIn. The irradiation fields were (i) the 15 kCi 60Co source available in the University, (ii) the spent fuel gamma irradiator in the pool of the University's Ford Nuclear Reactor (FNR) and (iii) south face of the core of the FNR during routine shut downs. Isomeric activation ratios can serve to characterize gamma fields, provided the response functions of the two (γ, γ') reactions sample different energy regimes of the gamma spectrum present in the irradiation fields. The response of an isomeric activation detector, in turn, depends on the number of activation energy levels of the nuclide and the probabilities with which the activation levels de-populate to the isomeric level. The reaction rate ratio RIn115m/ RIn113m was measured in the three gamma fields. The measured ratios were (i) 1.210 ± 0.011 in the 60Co source, (ii) 1.314 ± 0.060 in the spent fuel gamma irradiator and (iii) 1.298 ± 0.039 in a location alongside the FNR core during routine shut downs. The measured reaction rate ratios are not only close to each other, but close to unity as well. This indicates that the excitation functions for the reactions 115In(γ, γ') 115mIn and 113In(γ, γ') 113mIn have similar shapes and that for the nuclides 115In and 113In, the number of activation energy levels and the probabilities with which they populate the isomeric levels are very similar to each other. Thus, the ratio RIn115m/ RIn113m will not yield any information regarding the shape of gamma spectrum in the field of measurement. However by choosing (γ, γ') reactions with different shapes for the excitation functions one can measure a set of isomeric activation ratios that characterize a given gamma field.

  5. Discontinuous jamming transitions in soft materials: coexistence of flowing and jammed states

    International Nuclear Information System (INIS)

    Dennin, Michael

    2008-01-01

    Many systems in nature exhibit transitions between fluid-like states and solid-like states, or 'jamming transitions'. There is a strong theoretical foundation for understanding equilibrium phase transitions that involve solidification, or jamming. Other jamming transitions, such as the glass transition, are less well understood. The jamming phase diagram has been proposed to unify the description of equilibrium phase transitions, the glass transitions, and other nonequilibrium jamming transitions. As with equilibrium phase transitions, which can either be first order (discontinuous in a relevant order parameter) or second order (continuous), one would expect that generalized jamming transitions can be continuous or discontinuous. In studies of flow in complex fluids, there is a wide range of evidence for discontinuous transitions, mostly in the context of shear localization, or shear banding. In this paper, I review the experimental evidence for discontinuous transitions. I focus on systems in which there is a discontinuity in the rate of strain between two, coexisting states: one in which the material is flowing and the other in which it is solid-like. (topical review)

  6. Model of Ca(2+) Concentration Controlled by Sarcoplasmic Reticulum of Skeletal Muscle, Using the State Transition

    National Research Council Canada - National Science Library

    Yokota, M

    2001-01-01

    ...). This report proposed a model that represents Ca(2+) in a muscle cell controlled by the SR using a state transition probability model in which one state means that protein in the SR is binding ligands, and the other...

  7. Transitions in the computational power of thermal states for measurement-based quantum computation

    International Nuclear Information System (INIS)

    Barrett, Sean D.; Bartlett, Stephen D.; Jennings, David; Doherty, Andrew C.; Rudolph, Terry

    2009-01-01

    We show that the usefulness of the thermal state of a specific spin-lattice model for measurement-based quantum computing exhibits a transition between two distinct 'phases' - one in which every state is a universal resource for quantum computation, and another in which any local measurement sequence can be simulated efficiently on a classical computer. Remarkably, this transition in computational power does not coincide with any phase transition, classical, or quantum in the underlying spin-lattice model.

  8. Status of Credentialing Structures Related to Secondary Transition: A State-Level Policy Analysis

    Science.gov (United States)

    Simonsen, Monica L.; Novak, Jeanne A.; Mazzotti, Valerie L.

    2018-01-01

    To understand the current status of transition-related credentialing systems in driving personnel preparation, it is necessary to identify which state education and rehabilitation services agencies are currently providing certification and licensure in the area of secondary transition. The purpose of this study was to examine the current state of…

  9. 31 CFR 560.406 - Transshipment or transit through United States prohibited.

    Science.gov (United States)

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Transshipment or transit through United States prohibited. 560.406 Section 560.406 Money and Finance: Treasury Regulations Relating to... TRANSACTIONS REGULATIONS Interpretations § 560.406 Transshipment or transit through United States prohibited...

  10. Digital soil mapping as a tool for quantifying state-and-transition models

    Science.gov (United States)

    Ecological sites and associated state-and-transition models (STMs) are rapidly becoming important land management tools in rangeland systems in the US and around the world. Descriptions of states and transitions are largely developed from expert knowledge and generally accepted species and community...

  11. Predicting landscape vegetation dynamics using state-and-transition simulation models

    Science.gov (United States)

    Colin J. Daniel; Leonardo. Frid

    2012-01-01

    This paper outlines how state-and-transition simulation models (STSMs) can be used to project changes in vegetation over time across a landscape. STSMs are stochastic, empirical simulation models that use an adapted Markov chain approach to predict how vegetation will transition between states over time, typically in response to interactions between succession,...

  12. Grassland to shrubland state transitions enhance carbon sequestration in the northern Chihuahuan Desert

    Science.gov (United States)

    M. D. Petrie; S. L. Collins; A. M. Swann; P. L. Ford; M. E. Litvak

    2015-01-01

    The replacement of native C4-dominated grassland by C3-dominated shrubland is considered an ecological state transition where different ecological communities can exist under similar environmental conditions. These state transitions are occurring globally, and may be exacerbated by climate change. One consequence of the global increase in woody vegetation may be...

  13. Destabilization in the isomeric nitrobenzonitriles: an experimental thermochemical study

    International Nuclear Information System (INIS)

    Roux, Maria Victoria; Jimenez, Pilar; Davalos, Juan Z.; Temprado, Manuel; Liebman, Joel F.

    2003-01-01

    The enthalpies of combustion and of sublimation, respectively, of the three isomeric nitrobenzonitriles have been measured: o-, {(-3456.3±2.9), (88.1±1.4)} kJ·mol -1 ; m-, {(-3442.8±3.3), (92.8±0.3)} kJ·mol -1 ; p-, {(-3448.2±3.6), (91.1±1.3)} kJ·mol -1 . In turn, from these values, the standard molar enthalpies of formation for the condensed and gaseous state, respectively, have been derived: o-, {(130.1±3.1), (218.2±3.4)} kJ·mol -1 ; m-, {(116.5±3.5), (209.3±3.5)} kJ·mol -1 ; p-, {(122.0±3.8), (213.1±4.0)} kJ·mol -1 . Destabilization energies associated with the presence of the two electron-withdrawing groups have been determined, for o-, m-, and p-nitrobenzonitrile, {(17.6±4.1), (8.7±4.2), and (12.5±4.6)} kJ·mol -1 , respectively, and are consistent with those obtained for the corresponding sets of isomeric methyl benzenedicarboxylates, dicyanobenzenes, dinitrobenzenes, and (neutral and ionized) nitrobenzoic acids

  14. Isomerization of C[sub 4] alkenes

    Science.gov (United States)

    Smith, L.A. Jr.

    1984-11-13

    A method is described for isomerizing isobutene or n-butene to produce a mixture of isobutene and normal butene, and polymerizing at least a portion thereof to produce isobutene/n-butene co-dimer, which comprises feeding at least 80 weight % of either the isobutene or n-butene to a catalytic distillation reactor containing a fixed bed acidic cation exchange resin catalyst packing which provides both the catalyst sites and distillation sites for the reaction products, isomerizing a portion of the isobutene or n-butene to produce a mixture of isobutene and n-butene and reacting at least a portion of the isobutene and n-butene to form co-dimer of isobutene and n-butene, whereby an overhead fraction containing any unreacted isobutene and n-butene and a bottoms fraction containing co-dimer is produced. The result of the reaction is substantially the same regardless whether the feed is isobutene or n-butene. Other aspects of the invention, include combinations of procedures to produce high purity isobutene and n-butene. Either isobutene or n-butene product (depending on the desired product) can be recycled as feed, thus substantially carrying out the isomerization to extinction and total conversion to the desired product. 1 fig.

  15. Atomic final-state effects in nuclear transitions

    International Nuclear Information System (INIS)

    Griffiths, A.; Vogel, P.

    1991-01-01

    The interaction of a nuclear gamma radiation with the atomic electron cloud gives rise to a phase shift in the nuclear electromagnetic transition amplitude. The resulting interference parameters ξ(πL) are of significance to the analysis of time-reversal experiments. We calculate these parameters for E1, E2, E3, M1, and M2 gamma transitions in a number of nuclei. We also discuss the implication of these results for simultaneous parity- and time-reversal-violating experiments

  16. Energy Demand Modeling Methodology of Key State Transitions of Turning Processes

    Directory of Open Access Journals (Sweden)

    Shun Jia

    2017-04-01

    Full Text Available Energy demand modeling of machining processes is the foundation of energy optimization. Energy demand of machining state transition is integral to the energy requirements of the machining process. However, research focus on energy modeling of state transition is scarce. To fill this gap, an energy demand modeling methodology of key state transitions of the turning process is proposed. The establishment of an energy demand model of state transition could improve the accuracy of the energy model of the machining process, which also provides an accurate model and reliable data for energy optimization of the machining process. Finally, case studies were conducted on a CK6153i CNC lathe, the results demonstrating that predictive accuracy with the proposed method is generally above 90% for the state transition cases.

  17. Pediatricians Transitioning Practices, Youth With Special Health Care Needs in New York State.

    Science.gov (United States)

    Davidson, Lynn F; Chhabra, Rosy; Cohen, Hillel W; Lechuga, Claudia; Diaz, Patricia; Racine, Andrew

    2015-10-01

    To assess current practices of New York State pediatricians as they transition youth with special health care needs to adult-oriented medical care. A survey of New York State pediatricians included 6 critical steps from 2002 consensus statement, 11 essential steps adapted from recent literature, and questions targeting age of starting transition and availability of transition policy. Of 181 respondents, only 11% have a transition policy. Most assist patients in transition process; identify an adult provider (92%); and create portable medical summary (57%). Only 3% start planning process at recommended age. No respondents are compliant with all 6 critical steps; subspecialists were more likely to report compliance to more than 4 steps. Participating pediatricians are making gains, yet effort is needed, to incorporate the essential steps into practice for transitioning youth with special health care needs. Recognition of barriers, use of electronic tools, and clarifying subspecialist's approach, may improve compliance with transition recommendations. © The Author(s) 2015.

  18. Cation transport in isomeric pentanes

    International Nuclear Information System (INIS)

    Gyoergy, Istvan; Gee, Norman; Freeman, G.R.

    1985-01-01

    The cation mobility μsub(+) is measured in n-pentane, isopentane, neo-pentane, and mixtures of n- and neo-pentane over conditions from the normal liquid, through the critical fluid, to the low density gas. Most of the liquid data correlate with the reduced temperature T/Tsub(c). The T/Tsub(c) reflects free volume and viscosity changes. Comparison is made to neutral molecule diffusion. The transition from viscosity control of mobility in the liquid to density control in the dilute gas occurs over the reduced viscosity region 3 > eta/etasub(c) > 0.6, which corresponds to the reduced density region 1.9 > eta/etasub(c) > 0.5. In the saturated gas etaμsub(+) is similar in all pentanes, but iso- approximately> n- > neo-pentane. At constant density dμsub(+)/dT >= 0 for gases. The average gas nμsub(+) is similar in all pentanes, but iso- approximately> n- > neo-pentane. At constant density dμsub(+)/dT >= 0 for gases. The average momentum transfer cross sections in the n-/neo-pentane mixtures are similar to those in neo-pentane at low T but similar to those in n-pentane at high T. The present findings are combined with previous electron mobility data in addressing the effect of hydrocarbon molecular (external) shape on the electric breakdown strength of gases

  19. β-γ and isomeric decay spectroscopy of 168Dy

    Directory of Open Access Journals (Sweden)

    Zhang G.X.

    2018-01-01

    Full Text Available This contribution will report on the experimental work on the level structure of 168Dy. The experimental data have been taken as part of the EURICA decay spectroscopy campaign at RIBF, RIKEN in November 2014. In the experiment, a 238U primary beam is accelerated up to 345 MeV/u with an average intensity of 12 pnA. The nuclei of interest are produced by in-flight fission of 238U impinging on Be target with a thickness of 5 mm. The excited states of 168Dy have been populated through the decay from a newly identified isomeric state and via the β decay from 168Tb. In this contribution, scientific motivations, experimental procedure and some preliminary results for this study are presented.

  20. β-γ and isomeric decay spectroscopy of 168Dy

    Science.gov (United States)

    Zhang, G. X.; Watanabe, H.; Kondev, F. G.; Lane, G. J.; Regan, P. H.; Söderström, P.-A.; Walker, P. M.; Kanaoka, H.; Korkulu, Z.; Lee, P. S.; Liu, J. J.; Nishimura, S.; Wu, J.; Yagi, A.; Ahn, D. S.; Alharbi, T.; Baba, H.; Browne, F.; Bruce, A. M.; Carroll, R. J.; Chae, K. Y.; Dombradi, Zs.; Doornenbal, P.; Estrade, A.; Fukuda, N.; Griffin, C.; Ideguchi, E.; Inabe, N.; Isobe, T.; Kanaya, S.; Kojouharov, I.; Kubo, T.; Kubono, S.; Kurz, N.; Kuti, I.; Lalkovski, S.; Lee, C. S.; Lee, E. J.; Lorusso, G.; Lotay, G.; Moon, C.-B.; Nishizuka, I.; Nita, C. R.; Odahara, A.; Patel, Z.; Phong, V. H.; Podolyák, Zs.; Roberts, O. J.; Sakurai, H.; Schaffner, H.; Shand, C. M.; Shimizu, Y.; Sumikama, T.; Suzuki, H.; Takeda, H.; Terashima, S.; Vajta, Zs.; Valiente-Dóbon, J. J.; Xu, Z. Y.

    2018-05-01

    This contribution will report on the experimental work on the level structure of 168Dy. The experimental data have been taken as part of the EURICA decay spectroscopy campaign at RIBF, RIKEN in November 2014. In the experiment, a 238U primary beam is accelerated up to 345 MeV/u with an average intensity of 12 pnA. The nuclei of interest are produced by in-flight fission of 238U impinging on Be target with a thickness of 5 mm. The excited states of 168Dy have been populated through the decay from a newly identified isomeric state and via the β decay from 168Tb. In this contribution, scientific motivations, experimental procedure and some preliminary results for this study are presented.

  1. Lithuanian health care in transitional state: ethical problems

    Directory of Open Access Journals (Sweden)

    Žekas Romualdas

    2005-11-01

    Full Text Available Abstract Background Throughout the economic and political reforms in post-communist countries, significant changes have also occurred in public morality. One of the tasks of the Lithuanian health policy is to create mechanisms for strengthening the significance of ethical considerations in the decision-making processes concerning health care of individuals and groups of individuals, as well as considering the positions of physicians and the health care system itself in a general way. Thus, health care ethics could be analyzed at two levels: the micro level (the ethics of doctor-patient relationships and the macro level (the ethics of health policy-making, which can be realized by applying the principles of equal access, reasonable quality, affordable care and shared responsibilities. To date, the first level remains dominant, but the need arises for our attention to refocus now from the micro level to the patterns of managing and delivering care, managing the health care resources, and conducting business practices. Discussion In attempting to increase the efficiency of health services in Lithuania, a common strategy has been in place for the last fifteen years. Decentralization and privatization have been implemented as part of its policy to achieve greater efficiency. Although decentralization in theory is supposed to improve efficiency, in practice the reform of decentralization has still to be completely implemented in Lithuania. Debates on health policy in Lithuania also include the issue of private versus public health care. Although the approach of private health care is changing in a positive way, it is obvious that reduced access to health services is the most vulnerable aspect. In the Lithuanian Health Program adopted in July 1998, the target of equity was stressed, stating that by 2010, differences in health and health care between various socio-economic groups should be reduced by 25%. Summary The restructuring of health care system

  2. Lithuanian health care in transitional state: ethical problems.

    Science.gov (United States)

    Jakusovaite, Irayda; Darulis, Zilvinas; Zekas, Romualdas

    2005-11-09

    Throughout the economic and political reforms in post-communist countries, significant changes have also occurred in public morality. One of the tasks of the Lithuanian health policy is to create mechanisms for strengthening the significance of ethical considerations in the decision-making processes concerning health care of individuals and groups of individuals, as well as considering the positions of physicians and the health care system itself in a general way. Thus, health care ethics could be analyzed at two levels: the micro level (the ethics of doctor-patient relationships) and the macro level (the ethics of health policy-making, which can be realized by applying the principles of equal access, reasonable quality, affordable care and shared responsibilities). To date, the first level remains dominant, but the need arises for our attention to refocus now from the micro level to the patterns of managing and delivering care, managing the health care resources, and conducting business practices. In attempting to increase the efficiency of health services in Lithuania, a common strategy has been in place for the last fifteen years. Decentralization and privatization have been implemented as part of its policy to achieve greater efficiency. Although decentralization in theory is supposed to improve efficiency, in practice the reform of decentralization has still to be completely implemented in Lithuania. Debates on health policy in Lithuania also include the issue of private versus public health care. Although the approach of private health care is changing in a positive way, it is obvious that reduced access to health services is the most vulnerable aspect. In the Lithuanian Health Program adopted in July 1998, the target of equity was stressed, stating that by 2010, differences in health and health care between various socio-economic groups should be reduced by 25%. The restructuring of health care system in Lithuania should be based on a balance between

  3. Photochromic ruthenium sulfoxide complexes: evidence for isomerization through a conical intersection.

    Science.gov (United States)

    McClure, Beth Anne; Mockus, Nicholas V; Butcher, Dennis P; Lutterman, Daniel A; Turro, Claudia; Petersen, Jeffrey L; Rack, Jeffrey J

    2009-09-07

    The complexes [Ru(bpy)(2)(OS)](PF(6)) and [Ru(bpy)(2)(OSO)](PF(6)), where bpy is 2,2'-bipyridine, OS is 2-methylthiobenzoate, and OSO is 2-methylsulfinylbenzoate, have been studied. The electrochemical and photochemical reactivity of [Ru(bpy)(2)(OSO)](+) is consistent with an isomerization of the bound sulfoxide from S-bonded (S-) to O-bonded (O-) following irradiation or electrochemical oxidation. Charge transfer excitation of [Ru(bpy)(2)(OSO)](+) in MeOH results in the appearance of two new metal-to-ligand charge transfer (MLCT) maxima at 355 and 496 nm, while the peak at 396 nm diminishes in intensity. The isomerization is reversible at room temperature in alcohol or propylene carbonate solution. In the absence of light, solutions of O-[Ru(bpy)(2)(OSO)](+) revert to S-[Ru(bpy)(2)(OSO)](+). Kinetic analysis reveals a biexponential decay with rate constants of 5.66(3) x 10(-4) s(-1) and 3.1(1) x 10(-5) s(-1). Cyclic voltammograms of S-[Ru(bpy)(2)(OSO)](+) are consistent with electron-transfer-triggered isomerization of the sulfoxide. Analysis of these voltammograms reveal E(S)(o)' = 0.86 V and E(O)(o)' = 0.49 V versus Ag/Ag(+) for the S- and O-bonded Ru(3+/2+) couples, respectively, in propylene carbonate. We found k(S-->O) = 0.090(15) s(-1) in propylene carbonate and k(S-->O) = 0.11(3) s(-1) in acetonitrile on Ru(III), which is considerably slower than has been reported for other sulfoxide isomerizations on ruthenium polypyridyl complexes following oxidation. The photoisomerization quantum yield (Phi(S-->O) = 0.45, methanol) is quite large, indicating a rapid excited state isomerization rate constant. The kinetic trace at 500 nm is monoexponential with tau = 150 ps, which is assigned to the excited S-->O isomerization rate. There is no spectroscopic or kinetic evidence for an O-bonded (3)MLCT excited state in the spectral evolution of S-[Ru(bpy)(2)(OSO)](+) to O-[Ru(bpy)(2)(OSO)](+). Thus, isomerization occurs nonadiabatically from an S-bonded (or eta(2

  4. Hybrid phase transition into an absorbing state: Percolation and avalanches

    Science.gov (United States)

    Lee, Deokjae; Choi, S.; Stippinger, M.; Kertész, J.; Kahng, B.

    2016-04-01

    Interdependent networks are more fragile under random attacks than simplex networks, because interlayer dependencies lead to cascading failures and finally to a sudden collapse. This is a hybrid phase transition (HPT), meaning that at the transition point the order parameter has a jump but there are also critical phenomena related to it. Here we study these phenomena on the Erdős-Rényi and the two-dimensional interdependent networks and show that the hybrid percolation transition exhibits two kinds of critical behaviors: divergence of the fluctuations of the order parameter and power-law size distribution of finite avalanches at a transition point. At the transition point global or "infinite" avalanches occur, while the finite ones have a power law size distribution; thus the avalanche statistics also has the nature of a HPT. The exponent βm of the order parameter is 1 /2 under general conditions, while the value of the exponent γm characterizing the fluctuations of the order parameter depends on the system. The critical behavior of the finite avalanches can be described by another set of exponents, βa and γa. These two critical behaviors are coupled by a scaling law: 1 -βm=γa .

  5. Complex transitions between spike, burst or chaos synchronization states in coupled neurons with coexisting bursting patterns

    International Nuclear Information System (INIS)

    Gu Hua-Guang; Chen Sheng-Gen; Li Yu-Ye

    2015-01-01

    We investigated the synchronization dynamics of a coupled neuronal system composed of two identical Chay model neurons. The Chay model showed coexisting period-1 and period-2 bursting patterns as a parameter and initial values are varied. We simulated multiple periodic and chaotic bursting patterns with non-(NS), burst phase (BS), spike phase (SS), complete (CS), and lag synchronization states. When the coexisting behavior is near period-2 bursting, the transitions of synchronization states of the coupled system follows very complex transitions that begins with transitions between BS and SS, moves to transitions between CS and SS, and to CS. Most initial values lead to the CS state of period-2 bursting while only a few lead to the CS state of period-1 bursting. When the coexisting behavior is near period-1 bursting, the transitions begin with NS, move to transitions between SS and BS, to transitions between SS and CS, and then to CS. Most initial values lead to the CS state of period-1 bursting but a few lead to the CS state of period-2 bursting. The BS was identified as chaos synchronization. The patterns for NS and transitions between BS and SS are insensitive to initial values. The patterns for transitions between CS and SS and the CS state are sensitive to them. The number of spikes per burst of non-CS bursting increases with increasing coupling strength. These results not only reveal the initial value- and parameter-dependent synchronization transitions of coupled systems with coexisting behaviors, but also facilitate interpretation of various bursting patterns and synchronization transitions generated in the nervous system with weak coupling strength. (paper)

  6. Thermal E/ Z Isomerization in First Generation Molecular Motors.

    Science.gov (United States)

    Kuwahara, Shunsuke; Suzuki, Yuri; Sugita, Naoya; Ikeda, Mari; Nagatsugi, Fumi; Harada, Nobuyuki; Habata, Yoichi

    2018-04-20

    Determination of a thermal E/ Z isomerization barrier of first generation molecular motors is reported. Stable ( E)-1a directly converts to stable ( Z)-1c without photochemical E/ Z isomerization. The activation Gibbs energy of the isomerization was determined to be 123 kJ mol -1 by circular dichroism spectral changes. Density functional theory calculations show that ( Z)-1c is ∼11.4 kJ mol -1 more stable than ( E)-1a.

  7. Modeling Enzymatic Transition States by Force Field Methods

    DEFF Research Database (Denmark)

    Hansen, Mikkel Bo; Jensen, Hans Jørgen Aagaard; Jensen, Frank

    2009-01-01

    The SEAM method, which models a transition structure as a minimum on the seam of two diabatic surfaces represented by force field functions, has been used to generate 20 transition structures for the decarboxylation of orotidine by the orotidine-5'-monophosphate decarboxylase enzyme. The dependence...... of the TS geometry on the flexibility of the system has been probed by fixing layers of atoms around the active site and using increasingly larger nonbonded cutoffs. The variability over the 20 structures is found to decrease as the system is made more flexible. Relative energies have been calculated...... by various electronic structure methods, where part of the enzyme is represented by a force field description and the effects of the solvent are represented by a continuum model. The relative energies vary by several hundreds of kJ/mol between the transition structures, and tests showed that a large part...

  8. Isomerization and dissociation in competition: the two-component dissociation rates of methyl acetate ions

    Science.gov (United States)

    Mazyar, Oleg A.; Mayer, Paul M.; Baer, Tomas

    1997-11-01

    Threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy has been used to investigate the unimolecular chemistry of metastable methyl acetate ions, CH3COOCH3.+. The rate of molecular ion fragmentation with the loss of CH3O. and CH2OH radicals as a function of ion internal energy was obtained from the coincidence data and used in conjunction with Rice-Ramsperger-Kassel-Markus and ab initio molecular orbital calculations to model the dissociation/isomerization mechanism of the methyl acetate ion (A). The data were found to be consistent with the mechanism involving a hydrogen-bridged complex CH3CO[middle dot][middle dot][middle dot]H[middle dot][middle dot][middle dot]OCH2.+(E) as the direct precursor of the observed fragments CH3CO+ and CH2OH.. The two-component decay rates were modeled with a three-well-two-product potential energy surface including the distonic ion CH3C(OH)OCH2.+(B) and enol isomer CH2C(OH)OCH3.+(C), which are formed from the methyl acetate ion by two consecutive [1,4]-hydrogen shifts. The 0 K heats of formation of isomers B and C as well as transition states TSAB, TSBC, and TSBE (relative to isomer A) were calculated from Rice-Ramsperger-Kassel-Markus (RRKM) theory.

  9. Observation of an isomeric level in 239U by means of the 238U(n,γ)239U reaction

    International Nuclear Information System (INIS)

    Thomas, B.W.; Murray, J.; Rae, E.R.

    1970-01-01

    Low-energy-capture gamma-ray spectra ( 238 U up to a neutron energy of 350 eV. The data were obtained using a 25-cm 3 Ge(Li) detector at the Harwell 45 MeV Electron Linac. Capture events were recorded as functions of gamma-ray energy and neutron time-of-flight, and by suitable analysis of the data time-of-flight spectra have been obtained for individual gamma-rays. The strongest low-energy gamma-ray, at 134 keV, depopulates a level in 239 U at the same energy by an E2-transition to the ground state. The time-of-flight spectrum for this transition indicates that the 134-keV level is isomeric with a half-life of approximately 1 microsecond. This is evident from the long tails on the low-energy side of each resonance, which are not present for other regions of the gamma-ray spectrum. The possibility of using low-energy gamma-rays as a measure of the total capture cross-section is investigated by comparing the time-of-flight spectrum for the 134-keV transition with that for a Moxon-Rae detector under the same experimental conditions. (author)

  10. Parameter optimization for transitions between memory states in small arrays of Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Rezac, Jacob D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computer Science and Mathematics Division; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computing and Computational Sciences Directorate; Univ. of Delaware, Newark, DE (United States). Dept. of Mathematical Sciences; Imam, Neena [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computing and Computational Sciences Directorate; Braiman, Yehuda [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computer Science and Mathematics Division; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computing and Computational Sciences Directorate; ; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Mechanical, Aerospace, and Biomedical Engineering

    2017-01-11

    Coupled arrays of Josephson junctions possess multiple stable zero voltage states. Such states can store information and consequently can be utilized for cryogenic memory applications. Basic memory operations can be implemented by sending a pulse to one of the junctions and studying transitions between the states. In order to be suitable for memory operations, such transitions between the states have to be fast and energy efficient. Here in this article we employed simulated annealing, a stochastic optimization algorithm, to study parameter optimization of array parameters which minimizes times and energies of transitions between specifically chosen states that can be utilized for memory operations (Read, Write, and Reset). Simulation results show that such transitions occur with access times on the order of 10–100 ps and access energies on the order of 10-19–5×10-18 J. Numerical simulations are validated with approximate analytical results.

  11. Transition probabilities of health states for workers in Malaysia using a Markov chain model

    Science.gov (United States)

    Samsuddin, Shamshimah; Ismail, Noriszura

    2017-04-01

    The aim of our study is to estimate the transition probabilities of health states for workers in Malaysia who contribute to the Employment Injury Scheme under the Social Security Organization Malaysia using the Markov chain model. Our study uses four states of health (active, temporary disability, permanent disability and death) based on the data collected from the longitudinal studies of workers in Malaysia for 5 years. The transition probabilities vary by health state, age and gender. The results show that men employees are more likely to have higher transition probabilities to any health state compared to women employees. The transition probabilities can be used to predict the future health of workers in terms of a function of current age, gender and health state.

  12. Chaotic Dynamics Mediates Brain State Transitions, Driven by Changes in Extracellular Ion Concentrations

    DEFF Research Database (Denmark)

    Rasmussen, Rune; H. Jensen, Mogens; L. Heltberg, Mathias

    2017-01-01

    Previous studies have suggested that changes in extracellular ion concentrations initiate the transition from an activity state that characterizes sleep in cortical neurons to states that characterize wakeful- ness. However, because neuronal activity and extra- cellular ion concentrations...... are interdependent, isolating their unique roles during sleep-wake transitions is not possible in vivo. Here, we extend the Averaged-Neuron model and demonstrate that, although changes in extracellular ion concentrations occur concurrently, decreasing the conductance of calcium-dependent potassium channels initiates...... the transition from sleep to wakefulness. We find that sleep is governed by stable, self-sustained oscillations in neuronal firing patterns, whereas the quiet awake state and active awake state are both governed by irregular oscillations and chaotic dynamics; transitions between these separable awake states...

  13. UP-DOWN cortical dynamics reflect state transitions in a bistable network.

    Science.gov (United States)

    Jercog, Daniel; Roxin, Alex; Barthó, Peter; Luczak, Artur; Compte, Albert; de la Rocha, Jaime

    2017-08-04

    In the idling brain, neuronal circuits transition between periods of sustained firing (UP state) and quiescence (DOWN state), a pattern the mechanisms of which remain unclear. Here we analyzed spontaneous cortical population activity from anesthetized rats and found that UP and DOWN durations were highly variable and that population rates showed no significant decay during UP periods. We built a network rate model with excitatory (E) and inhibitory (I) populations exhibiting a novel bistable regime between a quiescent and an inhibition-stabilized state of arbitrarily low rate. Fluctuations triggered state transitions, while adaptation in E cells paradoxically caused a marginal decay of E-rate but a marked decay of I-rate in UP periods, a prediction that we validated experimentally. A spiking network implementation further predicted that DOWN-to-UP transitions must be caused by synchronous high-amplitude events. Our findings provide evidence of bistable cortical networks that exhibit non-rhythmic state transitions when the brain rests.

  14. Identifying transition rates of ionic channels via observations at a single state

    CERN Document Server

    Deng Ying Chun; Qian Min Ping; Feng Jian Feng

    2003-01-01

    We consider how to determine all transition rates of an ion channel when it can be described by a birth-death chain or a Markov chain on a star-graph with continuous time. It is found that all transition rates are uniquely determined by the distribution of its lifetime and death-time histograms at a single state. An algorithm to calculate the transition rates exactly, based on the statistics of the lifetime and death-time of the Markov chain at the state, is provided. Examples to illustrate how an ion channel activity is fully determined by the observation of a single state of the ion channel are included.

  15. Identifying transition rates of ionic channels via observations at a single state

    International Nuclear Information System (INIS)

    Deng Yingchun; Peng Shenglun; Qian Minping; Feng Jianfeng

    2003-01-01

    We consider how to determine all transition rates of an ion channel when it can be described by a birth-death chain or a Markov chain on a star-graph with continuous time. It is found that all transition rates are uniquely determined by the distribution of its lifetime and death-time histograms at a single state. An algorithm to calculate the transition rates exactly, based on the statistics of the lifetime and death-time of the Markov chain at the state, is provided. Examples to illustrate how an ion channel activity is fully determined by the observation of a single state of the ion channel are included

  16. Identifying transition rates of ionic channels via observations at a single state

    Energy Technology Data Exchange (ETDEWEB)

    Deng Yingchun [School of Mathematics, Peking University, Beijing (China); Peng Shenglun [School of Mathematics, Peking University, Beijing (China); Qian Minping [School of Mathematics, Peking University, Beijing (China); Feng Jianfeng [COGS, Sussex University, Brighton (United Kingdom)

    2003-02-07

    We consider how to determine all transition rates of an ion channel when it can be described by a birth-death chain or a Markov chain on a star-graph with continuous time. It is found that all transition rates are uniquely determined by the distribution of its lifetime and death-time histograms at a single state. An algorithm to calculate the transition rates exactly, based on the statistics of the lifetime and death-time of the Markov chain at the state, is provided. Examples to illustrate how an ion channel activity is fully determined by the observation of a single state of the ion channel are included.

  17. Coherent state approach for the Φ6-lattice model and phase transitions

    International Nuclear Information System (INIS)

    Aguero-Granados, M.A.; Makhan'kov, V.G.

    1991-01-01

    Phase transitions in the lattice version of the Φ 6 -field theory are studied. The generalized coherent states approach to is used. In such a way the roles of kinks and bubbles in phase transitions have been reexamined. It is shown via a numerical analysis that first and second order phase transitions appear due to the behaviour of kinks and bubbles excitations. 12 refs.; 10 figs

  18. High-spin states and coexisting states in the Pt-Au transition region

    International Nuclear Information System (INIS)

    Riedinger, L.L.; Carpenter, M.P.; Courtney, L.H.; Janzen, V.P.; Schmitz, W.

    1986-01-01

    High-spin states in the N = 104 to 108 region have been studied by in-beam spectroscopy techniques in a number of Ir, Pt, and Au nuclei. These measurements have been performed at tandem Van de Graaff facilities at the Oak Ridge National Laboratory and at McMaster University. Through comparison of band crossings in a variety of odd-A and even-A nuclei, we are able to assign the first neutron and first proton alignment processes, which are nearly degenerate for 184 Pt. These measurements yield the trend of these crossing frequencies with N and Z in this region. Knowledge of this trend is important, since these crossing frequencies can give an estimate of how the shape parameters vary across this transitional region. 22 refs., 7 figs., 1 tab

  19. An isomerization-induced cage-breaking process in a molecular glass former below Tg

    International Nuclear Information System (INIS)

    Teboul, V.; Saiddine, M.; Accary, J.-B.; Nunzi, J.-M.

    2011-01-01

    A recent experimental [P. Karageorgiev, D. Neher, B. Schulz, B. Stiller, U. Pietsch, M. Giersig, L. Brehmer, Nature Mater. 4, 699 (2005)] study has found liquidlike diffusion below the glass-transition temperature in azobenzene-containing materials under irradiation. This result suggests that the isomerization-induced massive mass transport that leads to surface relief gratings formation in these materials, is induced by this huge increase of the matrix diffusion coefficient around the probe. In order to investigate the microscopic origin of the increase of the diffusion, we use molecular dynamics simulations of the photoisomerization of probe dispersed red 1 molecules dispersed inside a glassy molecular matrix. Results show that the increased diffusion is due to an isomerization-induced cage-breaking process. A process that explains the induced cooperative motions recently observed in these photoactive materials.

  20. Liquid state properties of certain noble and transition metals

    International Nuclear Information System (INIS)

    Bhuiyan, G.M.; Rahman, A.; Khaleque, M.A.; Rashid, R.I.M.A.; Mujibur Rahman, S.M.

    1998-07-01

    Certain structural, thermodynamic and atomic transport properties of a number of liquid noble and transition metals are reported. The underlying theory combines together a simple form of the N-body potential and the thermodynamically self-consistent variational modified hypernetted chain (VMHNC) theory of liquid. The static structure factors calculated by using the VMHNC resemble the hard sphere (HS) values. Consequently the HS model is used to calculate the thermodynamic properties viz. specific heat, entropy, isothermal compressibility and atomic transport properties. (author)

  1. Change of State of a Dynamical Unit in the Transition of Coherence

    International Nuclear Information System (INIS)

    Yang Yan-Jin; Du Ru-Hai; Wang Sheng-Jun; Jin Tao; Qu Shi-Xian

    2015-01-01

    The change of state of one map in the network of nonlocal coupled logistic maps at the transition of coherence is studied. With the increase of coupling strength, the network dynamics transits from the incoherent state into the coherent state. In the process, the iteration of the map first changes from chaos to period state, then from periodic to chaotic state again. For the periodic doubling bifurcations, similar to an isolated map, the largest Lyapunov exponent tends to zero from a negative value. However, the states of coupled maps exhibit complex behavior rather than converge to a few fixed values. The behavior brings a new chimera state of coupled logistic maps. The bifurcation diagram is identical to the phase order of maps iterations. For the bifurcation between 1-band and multi-band chaos, the symmetry of chaotic bands emerges and the transition of the order of iteration direction occurs

  2. Study on State Transition Method Applied to Motion Planning for a Humanoid Robot

    Directory of Open Access Journals (Sweden)

    Xuyang Wang

    2008-11-01

    Full Text Available This paper presents an approach of motion planning for a humanoid robot using a state transition method. In this method, motion planning is simplified by introducing a state-space to describe the whole motion series. And each state in the state-space corresponds to a contact state specified during the motion. The continuous motion is represented by a sequence of discrete states. The concept of the transition between two neighboring states, that is the state transition, can be realized by using some traditional path planning methods. Considering the dynamical stability of the robot, a state transition method based on search strategy is proposed. Different sets of trajectories are generated by using a variable 5th-order polynomial interpolation method. After quantifying the stabilities of these trajectories, the trajectories with the largest stability margin are selected as the final state transition trajectories. Rising motion process is exemplified to validate the method and the simulation results show the proposed method to be feasible and effective.

  3. Steps for Implementing a State-Level Professional Development Plan for Secondary Transition

    Science.gov (United States)

    Mazzotti, Valerie L.; Rowe, Dawn A.; Simonsen, Monica; Boaz, Bonnie; VanAvery, Cynthia

    2018-01-01

    To scale up and sustain the use of evidence-based practices, it is imperative that state education agencies systematically implement professional development that represents best practice. By delivering quality professional development to local districts, it is more likely that transition personnel will implement transition programs and practices…

  4. Observation of electric quadrupole transitions to Rydberg nd states of ultracold rubidium atoms

    NARCIS (Netherlands)

    Tong, D.; Farooqi, S.M.; Kempen, van E.G.M.; Pavlovic, Z.; Stanojevic, J.; Coté, R.; Eyler, E.E.; Gould, P.L.

    2009-01-01

    We report the observation of dipole-forbidden, but quadrupole-allowed, one-photon transitions to high-Rydberg states in Rb. Using pulsed uv excitation of ultracold atoms in a magneto-optical trap, we excite 5s¿nd transitions over a range of principal quantum numbers n=27–59. Compared to

  5. Equation of state description of the dark energy transition between quintessence and phantom regimes

    International Nuclear Information System (INIS)

    Stefancic, Hrvoje

    2006-01-01

    The dark energy crossing of the cosmological constant boundary (the transition between the quintessence and phantom regimes) is described in terms of the implicitly defined dark energy equation of state. The generalizations of the models explicitly constructed to exhibit the crossing provide the insight into the cancellation mechanism which makes the transition possible

  6. Absolute E0 and E2 transition rates and collective states in 116Sn

    International Nuclear Information System (INIS)

    Kantele, J.; Julin, R.; Luontama, M.; Passoja, A.; Poikolainen, T.; Baecklin, A.; Jonsson, N.-G.

    1978-08-01

    Absolute E0 and E2 transition rates in 116 Sn have been measured using several newly developed techniques. Many E2 transitions are observed to have a collective character with B(E2) values of up to 60 W.u. The presence of deformed excited states in 116 Sn is discussed in view of the results obtained. (author)

  7. Estimation and asymptotic theory for transition probabilities in Markov Renewal Multi–state models

    NARCIS (Netherlands)

    Spitoni, C.; Verduijn, M.; Putter, H.

    2012-01-01

    In this paper we discuss estimation of transition probabilities for semi–Markov multi–state models. Non–parametric and semi–parametric estimators of the transition probabilities for a large class of models (forward going models) are proposed. Large sample theory is derived using the functional

  8. Formation of a Ξ-hypernucleus and transitions to double-Λ states

    International Nuclear Information System (INIS)

    Ikeda, Kiyomi; Takahashi, Miho; Fukuda, Tomokazu; Motoba, Toshio; Yamamoto, Yasuo.

    1993-06-01

    A scenario is given for the formation of Ξ - states and the transitions to states with double-Λ in anticipation of observations, especially in the KEK-E224 experiment. First, the production cross sections of Ξ - hypernuclear states by (K - , K + ) reactions are calculated within the framework of the distorted-wave impulse approximation. Next, the transition rates from Ξ - hypernuclear states to possible double-Λ states are obtained, which are closely related to single- and double-Λ emissions after the Ξ - p→ΛΛ conversion in nuclei. (author)

  9. Probing the transition state for nucleic acid hybridization using phi-value analysis.

    Science.gov (United States)

    Kim, Jandi; Shin, Jong-Shik

    2010-04-27

    Genetic regulation by noncoding RNA elements such as microRNA and small interfering RNA (siRNA) involves hybridization of a short single-stranded RNA with a complementary segment in a target mRNA. The physical basis of the hybridization process between the structured nucleic acids is not well understood primarily because of the lack of information about the transition-state structure. Here we use transition-state theory, inspired by phi-value analysis in protein folding studies, to provide quantitative analysis of the relationship between changes in the secondary structure stability and the activation free energy. Time course monitoring of the hybridization reaction was performed under pseudo-steady-state conditions using a single fluorophore. The phi-value analysis indicates that the native secondary structure remains intact in the transition state. The nativelike transition state was confirmed via examination of the salt dependence of the hybridization kinetics, indicating that the number of sodium ions associated with the transition state was not substantially affected by changes in the native secondary structure. These results propose that hybridization between structured nucleic acids undergoes a transition state leading to formation of a nucleation complex and then is followed by sequential displacement of preexisting base pairings involving successive small energy barriers. The proposed mechanism might provide new insight into physical processes during small RNA-mediated gene silencing, which is essential to selection of a target mRNA segment for siRNA design.

  10. Finite-time quantum-to-classical transition for a Schroedinger-cat state

    International Nuclear Information System (INIS)

    Paavola, Janika; Hall, Michael J. W.; Paris, Matteo G. A.; Maniscalco, Sabrina

    2011-01-01

    The transition from quantum to classical, in the case of a quantum harmonic oscillator, is typically identified with the transition from a quantum superposition of macroscopically distinguishable states, such as the Schroedinger-cat state, into the corresponding statistical mixture. This transition is commonly characterized by the asymptotic loss of the interference term in the Wigner representation of the cat state. In this paper we show that the quantum-to-classical transition has different dynamical features depending on the measure for nonclassicality used. Measures based on an operatorial definition have well-defined physical meaning and allow a deeper understanding of the quantum-to-classical transition. Our analysis shows that, for most nonclassicality measures, the Schroedinger-cat state becomes classical after a finite time. Moreover, our results challenge the prevailing idea that more macroscopic states are more susceptible to decoherence in the sense that the transition from quantum to classical occurs faster. Since nonclassicality is a prerequisite for entanglement generation our results also bridge the gap between decoherence, which is lost only asymptotically, and entanglement, which may show a ''sudden death''. In fact, whereas the loss of coherences still remains asymptotic, we emphasize that the transition from quantum to classical can indeed occur at a finite time.

  11. State and Federal project development procedures for bus rapid transit : managing differences and reducing implementation delays

    Science.gov (United States)

    2011-08-01

    This report documents an investigation into the transportation project development process in the : context of the implementation of bus rapid transit systems on the State Highway System as well as such : systems being part of the Federal New Starts ...

  12. Enhancing pairwise state-transition weights: A new weighting scheme in simulated tempering that can minimize transition time between a pair of conformational states

    Science.gov (United States)

    Qiao, Qin; Zhang, Hou-Dao; Huang, Xuhui

    2016-04-01

    Simulated tempering (ST) is a widely used enhancing sampling method for Molecular Dynamics simulations. As one expanded ensemble method, ST is a combination of canonical ensembles at different temperatures and the acceptance probability of cross-temperature transitions is determined by both the temperature difference and the weights of each temperature. One popular way to obtain the weights is to adopt the free energy of each canonical ensemble, which achieves uniform sampling among temperature space. However, this uniform distribution in temperature space may not be optimal since high temperatures do not always speed up the conformational transitions of interest, as anti-Arrhenius kinetics are prevalent in protein and RNA folding. Here, we propose a new method: Enhancing Pairwise State-transition Weights (EPSW), to obtain the optimal weights by minimizing the round-trip time for transitions among different metastable states at the temperature of interest in ST. The novelty of the EPSW algorithm lies in explicitly considering the kinetics of conformation transitions when optimizing the weights of different temperatures. We further demonstrate the power of EPSW in three different systems: a simple two-temperature model, a two-dimensional model for protein folding with anti-Arrhenius kinetics, and the alanine dipeptide. The results from these three systems showed that the new algorithm can substantially accelerate the transitions between conformational states of interest in the ST expanded ensemble and further facilitate the convergence of thermodynamics compared to the widely used free energy weights. We anticipate that this algorithm is particularly useful for studying functional conformational changes of biological systems where the initial and final states are often known from structural biology experiments.

  13. Enhancing pairwise state-transition weights: A new weighting scheme in simulated tempering that can minimize transition time between a pair of conformational states

    International Nuclear Information System (INIS)

    Qiao, Qin; Zhang, Hou-Dao; Huang, Xuhui

    2016-01-01

    Simulated tempering (ST) is a widely used enhancing sampling method for Molecular Dynamics simulations. As one expanded ensemble method, ST is a combination of canonical ensembles at different temperatures and the acceptance probability of cross-temperature transitions is determined by both the temperature difference and the weights of each temperature. One popular way to obtain the weights is to adopt the free energy of each canonical ensemble, which achieves uniform sampling among temperature space. However, this uniform distribution in temperature space may not be optimal since high temperatures do not always speed up the conformational transitions of interest, as anti-Arrhenius kinetics are prevalent in protein and RNA folding. Here, we propose a new method: Enhancing Pairwise State-transition Weights (EPSW), to obtain the optimal weights by minimizing the round-trip time for transitions among different metastable states at the temperature of interest in ST. The novelty of the EPSW algorithm lies in explicitly considering the kinetics of conformation transitions when optimizing the weights of different temperatures. We further demonstrate the power of EPSW in three different systems: a simple two-temperature model, a two-dimensional model for protein folding with anti-Arrhenius kinetics, and the alanine dipeptide. The results from these three systems showed that the new algorithm can substantially accelerate the transitions between conformational states of interest in the ST expanded ensemble and further facilitate the convergence of thermodynamics compared to the widely used free energy weights. We anticipate that this algorithm is particularly useful for studying functional conformational changes of biological systems where the initial and final states are often known from structural biology experiments.

  14. Enhancing pairwise state-transition weights: A new weighting scheme in simulated tempering that can minimize transition time between a pair of conformational states

    Energy Technology Data Exchange (ETDEWEB)

    Qiao, Qin, E-mail: qqiao@ust.hk; Zhang, Hou-Dao [Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Huang, Xuhui, E-mail: xuhuihuang@ust.hk [Department of Chemistry, Division of Biomedical Engineering, Center of Systems Biology and Human Health, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); The HKUST Shenzhen Research Institute, Shenzhen (China)

    2016-04-21

    Simulated tempering (ST) is a widely used enhancing sampling method for Molecular Dynamics simulations. As one expanded ensemble method, ST is a combination of canonical ensembles at different temperatures and the acceptance probability of cross-temperature transitions is determined by both the temperature difference and the weights of each temperature. One popular way to obtain the weights is to adopt the free energy of each canonical ensemble, which achieves uniform sampling among temperature space. However, this uniform distribution in temperature space may not be optimal since high temperatures do not always speed up the conformational transitions of interest, as anti-Arrhenius kinetics are prevalent in protein and RNA folding. Here, we propose a new method: Enhancing Pairwise State-transition Weights (EPSW), to obtain the optimal weights by minimizing the round-trip time for transitions among different metastable states at the temperature of interest in ST. The novelty of the EPSW algorithm lies in explicitly considering the kinetics of conformation transitions when optimizing the weights of different temperatures. We further demonstrate the power of EPSW in three different systems: a simple two-temperature model, a two-dimensional model for protein folding with anti-Arrhenius kinetics, and the alanine dipeptide. The results from these three systems showed that the new algorithm can substantially accelerate the transitions between conformational states of interest in the ST expanded ensemble and further facilitate the convergence of thermodynamics compared to the widely used free energy weights. We anticipate that this algorithm is particularly useful for studying functional conformational changes of biological systems where the initial and final states are often known from structural biology experiments.

  15. Designing bifunctional alkene isomerization catalysts using predictive modelling

    NARCIS (Netherlands)

    Landman, I.R.; Paulson, E.R.; Rheingold, A.L.; Grotjahn, D.B.; Rothenberg, G.

    2017-01-01

    Controlling the isomerization of alkenes is important for the manufacturing of fuel additives, fine-chemicals and pharmaceuticals. But even if isomerization seems to be a simple unimolecular process, the factors that govern catalyst performance are far from clear. Here we present a set of models

  16. Modeling of charge-transfer transitions and excited states in d6 transition metal complexes by DFT techniques

    Czech Academy of Sciences Publication Activity Database

    Vlček, Antonín; Záliš, Stanislav

    2007-01-01

    Roč. 251, 3-4 (2007), s. 258-287 ISSN 0010-8545 R&D Projects: GA MŠk 1P05OC068; GA MŠk OC 139 Institutional research plan: CEZ:AV0Z40400503 Keywords : charge-transfer transition * DFT technique * excited states * spectroscopy Subject RIV: CG - Electrochemistry Impact factor: 8.568, year: 2007

  17. 40 CFR 70.4 - State program submittals and transition.

    Science.gov (United States)

    2010-07-01

    ... description in narrative form of the scope, structure, coverage, and processes of the State program. (ii) A description of the organization and structure of the agency or agencies that will have responsibility for... strategies). (5) A complete description of the State's compliance tracking and enforcement program or...

  18. Walking associated with public transit: moving toward increased physical activity in the United States.

    Science.gov (United States)

    Freeland, Amy L; Banerjee, Shailendra N; Dannenberg, Andrew L; Wendel, Arthur M

    2013-03-01

    We assessed changes in transit-associated walking in the United States from 2001 to 2009 and documented their importance to public health. We examined transit walk times using the National Household Travel Survey, a telephone survey administered by the US Department of Transportation to examine travel behavior in the United States. People are more likely to transit walk if they are from lower income households, are non-White, and live in large urban areas with access to rail systems. Transit walkers in large urban areas with a rail system were 72% more likely to transit walk 30 minutes or more per day than were those without a rail system. From 2001 to 2009, the estimated number of transit walkers rose from 7.5 million to 9.6 million (a 28% increase); those whose transit-associated walking time was 30 minutes or more increased from approximately 2.6 million to 3.4 million (a 31% increase). Transit walking contributes to meeting physical activity recommendations. Study results may contribute to transportation-related health impact assessment studies evaluating the impact of proposed transit systems on physical activity, potentially influencing transportation planning decisions.

  19. MARKETING PLANNING: STATE OF THE ARTIN A TRANSITIONAL ECONOMY

    Directory of Open Access Journals (Sweden)

    Tamara Jovanov Marjanova

    2014-07-01

    Full Text Available This paper is provoked by the distorted marketing practices of companies that operate in a transitional economy, specifically Republic of Macedonia.The analysis has two main purposes: 1. to identify the weaknesses in the marketing planning process, 2. to prove the connection of continuous formal marketing planning with business performance, i.e.profitability and market share. Datawasobtainedfromprimary and secondaryresearch. Primary research was conducted in the food, i.e. confectionery industry, with two techniques – survey and interview with the managers of 38% of the registered companies in the industry. Secondary research was based onbooks, journals, web-cites.The analysiswasexecutedwith IBM SPSS 19. Conclusionsare provided through descriptive and deductive statistical analysis. The findings show that the companies have multiple weaknesses in the marketing planning process (continuous formal marketing planning occurs rarely, there is lack of knowledge regarding the systematic planning process and a tendency of misuse of analytical tools. Additionally, a connection and dependence of business performance on continuous formal marketing planning was found. Limitations arise from the sample size and the (one chosen industry sector. However, there are evident practical and social implicationswhich can contribute to better competitiveness:possibilities for correction of current practices and development of a systematic marketing planning process. This research is of a great value on a national level because it is one of few that analyzes this subject through primary data. Also, the results can be consulted by researchers and practitioners from other transitional economies.

  20. Glass Transitions in a Monatomic Liquid with Two Glassy States

    Science.gov (United States)

    Gordon, Andrew; Giovambattista, Nicolas

    2014-04-01

    We perform out-of-equilibrium molecular dynamics simulations of a monatomic liquid that exhibits liquid and glass polymorphism, with two distinct glasses, low- (LDA) and high-density (HDA) amorphous solids. By performing isobaric heating simulations of LDA and HDA at different pressures, we determine (a) the glass transition temperature of LDA and HDA, TgLDA(P) and TgHDA(P), as well as (b) the corresponding glass-glass transformation temperatures, TLDA-HDA(P) and THDA-LDA(P). It is found that TgLDA(P) is anomalous; i.e., it decreases with increasing pressure, while TgHDA(P) increases with increasing pressure. Interestingly, the TgLDA(P) and TLDA-HDA(P) loci, as well as the TgHDA(P) and THDA-LDA(P) loci, constitute smooth single lines in the P -T plane, suggesting that heating-induced glass-glass and glass transitions are related. We discuss the present results in the context of water experiments and simulations.

  1. New transition in the vortex liquid state of YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Kwok, Wai-Kwong; Karapetrov, Goran; Welp, Ulrich; Rydh, Andreas; Crabtree, George W.; Paulius, Lisa; Figueras, Jordi; Puig, Teresa; Obradors, X.

    2006-01-01

    We have carried out angular dependent magneto-transport measurements on optimally doped, untwinned YBa 2 Cu 3 O 7-δ crystals irradiated with high energy heavy ions to determine the onset of vortex line tension in the vortex liquid state. The dose matching field was controlled and kept at a low level to partially preserve the first order vortex lattice melting transition. A Bose glass transition is observed below the lower critical point which then transforms into a first order phase transition near 4 T. We find that the locus of points which indicates the onset of vortex line tension overlaps with the Bose glass transition line at low fields and then deviates at higher fields, indicating a new transition line in the vortex liquid state. This new line in the vortex liquid phase is dose independent and extends beyond the upper critical point

  2. Topological quantum phase transitions and edge states in spin-orbital coupled Fermi gases.

    Science.gov (United States)

    Zhou, Tao; Gao, Yi; Wang, Z D

    2014-06-11

    We study superconducting states in the presence of spin-orbital coupling and Zeeman field. It is found that a phase transition from a Fulde-Ferrell-Larkin-Ovchinnikov state to the topological superconducting state occurs upon increasing the spin-orbital coupling. The nature of this topological phase transition and its critical property are investigated numerically. Physical properties of the topological superconducting phase are also explored. Moreover, the local density of states is calculated, through which the topological feature may be tested experimentally.

  3. Rapid Communication: seniority changing transitions in yrast states ...

    Indian Academy of Sciences (India)

    Bhoomika Maheshwari

    2017-10-26

    Oct 26, 2017 ... Rapid Communication: v = 2 seniority changing ... has been extensively used to understand various system- .... states. This understanding supports the previous inter- ..... Financial support from the Ministry of Human Resource.

  4. Superconducting states and depinning transitions of Josephson ladders

    International Nuclear Information System (INIS)

    Barahona, M.; Strogatz, S.H.; Orlando, T.P.

    1998-01-01

    We present analytical and numerical studies of pinned superconducting states of open-ended Josephson ladder arrays, neglecting inductances but taking edge effects into account. Treating the edge effects perturbatively, we find analytical approximations for three of these superconducting states emdash the no-vortex, fully frustrated, and single-vortex states emdash as functions of the dc bias current I and the frustration f. Bifurcation theory is used to derive formulas for the depinning currents and critical frustrations at which the superconducting states disappear or lose dynamical stability as I and f are varied. These results are combined to yield a zero-temperature stability diagram of the system with respect to I and f. To highlight the effects of the edges, we compare this dynamical stability diagram to the thermodynamic phase diagram for the infinite system where edges have been neglected. We briefly indicate how to extend our methods to include self-inductances. copyright 1998 The American Physical Society

  5. The United States and China in Power Transition

    Science.gov (United States)

    2011-12-01

    requirement for a state is survival. In an international system where states operate under anarchy (without a higher authority above them) and each...See Bon- nie S. Glaser and Evan S. Medeiros, “The Changing Ecology of Foreign Policy-making in China: the Ascension and Demise of the Theory of...enticement of foreign investment,163 increased efforts on ecologi - cal protection (such as reforestation164), promotion of education,165 and

  6. Shape transition of state density for bosonic systems

    Indian Academy of Sciences (India)

    ... while the shape of the state density for EGOE(2) with m ≫ 2, is close to Gaussian. The change in shape of the state density, from semicircle to Gaussian for EGOE(k), as m increases from k to m ≫ k for fermions, has been explained mathematically by Mon and French [4] and also by Benet. Pramana – J. Phys., Vol. 81, No.

  7. Evidence from n=2 fine structure transitions for the production of fast excited state positronium

    International Nuclear Information System (INIS)

    Ley, R.; Niebling, K.D.; Schwarz, R.; Werth, G.

    1990-01-01

    Fine structure transitions in the first excited state of positronium (Ps) have been measured using 'Backscatter Ps' production on a Mo surface by observation of a change in the emitted Lyman-α intensity under resonant microwave irradiation. Production, fine structure transitions and Lyman-α decay of the Ps atoms took place inside a waveguide designed to transmit the microwave frequencies of 8.6, 13.0 and 18.5 GHz for the transitions from the 2 3 S 1 state to the 2 3 P J , J=2, 1, 0, states, respectively. In the presence of a magnetic field, all transitions observed show a shift to higher frequencies, compared with earlier calculations and measurements in zero magnetic field. The deviations exceed the expected Zeeman shift significantly but may be explained by assuming a motional Stark effect for Ps with kinetic energies of several eV. (author)

  8. Employment outcomes of transition-aged adults with autism spectrum disorders: a state of the States report.

    Science.gov (United States)

    Burgess, Sloane; Cimera, Robert E

    2014-01-01

    The primary purpose of this study was to evaluate the employment outcomes of transition-aged adults with autism spectrum disorders (ASD) served by vocational rehabilitation services (VR) over the last 10 years by state. A secondary purpose was to compare employment outcomes of individuals with ASD to those of the overall transition-aged population served by VR for the same time period. Although there was variability both within and among states, the results of this study indicate that, over time, the number of young adults with ASD seeking VR services has increased; however, employment outcomes including the percent of adults with ASD achieving employment, the number of hours worked, and wages earned have not improved for this group. The cost to provide VR services to transition-aged adults with ASD was relatively stable over time. Transition-aged adults with ASD were more likely to become successfully employed as a result of receiving VR services than the overall population of transition-aged adults served by VR. However, the employed transition-aged adults consistently worked fewer hours and earned lower wages than those in the overall population. Factors that may influence variability within and among states, and between groups, and implications for research and practice are discussed.

  9. Quantum phase transitions between a class of symmetry protected topological states

    Energy Technology Data Exchange (ETDEWEB)

    Tsui, Lokman; Jiang, Hong-Chen; Lu, Yuan-Ming; Lee, Dung-Hai

    2015-07-01

    The subject of this paper is the phase transition between symmetry protected topological states (SPTs). We consider spatial dimension d and symmetry group G so that the cohomology group, Hd+1(G,U(1)), contains at least one Z2n or Z factor. We show that the phase transition between the trivial SPT and the root states that generate the Z2n or Z groups can be induced on the boundary of a (d+1)-dimensional View the MathML source-symmetric SPT by a View the MathML source symmetry breaking field. Moreover we show these boundary phase transitions can be “transplanted” to d dimensions and realized in lattice models as a function of a tuning parameter. The price one pays is for the critical value of the tuning parameter there is an extra non-local (duality-like) symmetry. In the case where the phase transition is continuous, our theory predicts the presence of unusual (sometimes fractionalized) excitations corresponding to delocalized boundary excitations of the non-trivial SPT on one side of the transition. This theory also predicts other phase transition scenarios including first order transition and transition via an intermediate symmetry breaking phase.

  10. TRANSIT

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. TRANSIT. SYSTEM: DETERMINE 2D-POSITION GLOBALLY BUT INTERMITTENT (POST-FACTO). IMPROVED ACCURACY. PRINCIPLE: POLAR SATELLITES WITH INNOVATIONS OF: GRAVITY-GRADIENT ATTITUDE CONTROL; DRAG COMPENSATION. WORKS ...

  11. Travel Patterns And Characteristics Of Transit Users In New York State

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Ho-Ling [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wilson, Daniel W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Reuscher, Tim [Macrosys, Arlington, VA (United States); Chin, Shih-Miao [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Taylor, Rob D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-12-01

    This research is a detailed examination of the travel behaviors and patterns of transit users within New York State (NYS), primarily based on travel data provided by the National Household Travel Survey (NHTS) in 2009 and the associated Add-on sample households purchased by the New York State Department of Transportation (NYSDOT). Other data sources analyzed in this study include: NYS General Transit Feed Specification (GTFS) to assist in analyzing spatial relationships for access to transit and the creation of Transit Shed geographic areas of 1, 2.5, and 5 miles from transit stop locations, LandScan population database to understand transit coverage, and Census Bureau s American Community Survey (ACS) data to examine general transit patterns and trends in NYS over time. The majority of analyses performed in this research aimed at identifying transit trip locations, understanding differences in transit usage by traveler demographics, as well as producing trip/mode-specific summary statistics including travel distance, trip duration, time of trip, and travel purpose of transit trips made by NYS residents, while also analyzing regional differences and unique travel characteristics and patterns. The analysis was divided into two aggregated geographic regions: New York Metropolitan Transportation Council (NYMTC) and NYS minus NYMTC (Rest of NYS). The inclusion of NYMTC in all analysis would likely produce misleading conclusions for other regions in NYS. TRANSIT COVERAGE The NYS transit network has significant coverage in terms of transit stop locations across the state s population. Out of the 19.3 million NYS population in 2011, about 15.3 million (or 79%) resided within the 1-mile transit shed. This NYS population transit coverage increased to 16.9 million (or 88%) when a 2.5-mile transit shed was considered; and raised to 17.7 million (or 92%) when the 5-mile transit shed was applied. KEY FINDINGS Based on 2009 NHTS data, about 40% of NYMTC households used transit

  12. Isomeric Detergent Comparison for Membrane Protein Stability

    DEFF Research Database (Denmark)

    Cho, Kyung Ho; Hariharan, Parameswaran; Mortensen, Jonas S.

    2016-01-01

    and utility, particularly for eukaryotic membrane proteins and membrane protein complexes. Thus, a number of new agents have been devised; some have made significant contributions to membrane protein structural studies. However, few detergent design principles are available. In this study, we prepared meta...... and ortho isomers of the previously reported para-substituted xylene-linked maltoside amphiphiles (XMAs), along with alkyl chain-length variation. The isomeric XMAs were assessed with three membrane proteins, and the meta isomer with a C12 alkyl chain was most effective at maintaining solubility....../stability of the membrane proteins. We propose that interplay between the hydrophile–lipophile balance (HLB) and alkyl chain length is of central importance for high detergent efficacy. In addition, differences in inter-alkyl-chain distance between the isomers influence the ability of the detergents to stabilise membrane...

  13. Aql X-1 transition towards the soft (banana) state accompanied by radio/NIR detection

    Science.gov (United States)

    Sivakoff, G. R.; Miller-Jones, J.; Fox, O.; Linares, M.; Altamirano, D.; Russell, D.

    2009-11-01

    The currently active neutron star transient and atoll source Aql X-1 (Linares et al., ATEL #2288) has begun the transition from the hard (extreme island) state to the soft (banana) state (Rodriguez et al. ATEL #2299). This transition likely began around 2009 Nov 15 (MJD = 55150). The latest RXTE PCA observation (2009 Nov 17, MJD=55152.17+/-0.02, 2-60 keV fractional rms variability amplitude of ~11% for 0.1-10 Hz) indicates that the source is in the intermediate (island) state.

  14. Cygnus X-3 transition from the ultrasoft to the hard state

    DEFF Research Database (Denmark)

    Beckmann, V.; Soldi, S.; Belanger, G.

    2007-01-01

    Aims. The nature of Cygnus X-3 is still not understood well. This binary system might host a black hole or a neutron star. Recent observations by INTEGRAL have shown that Cygnus X- 3 was again in an extremely ultrasoft state. Here we present our analysis of the transition from the ultrasoft state...

  15. E2 transition probabilities between Nilsson states in odd-A nuclei

    International Nuclear Information System (INIS)

    Krpic, D.K.; Savic, I.M.; Anicin, I.V.

    1976-01-01

    Presented here are the matrices needed for the calculation of E2 transition probabilities between all pairs of Nilsson states with ΔN = 0 and ΔK = 0, 1, 2. The needed coefficients of states are tabulated by Nilsson and by Davidson

  16. Glauber amplitudes for transitions from low lying states in hydrogen atom by charged particle impact

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, S; Srivastava, M K [Roorkee Univ. (India). Dept. of Physics

    1977-07-01

    The Glauber amplitudes for the general transition nlm ..-->.. n'1'm' in charged particle - hydrogen atom collisions have been obtained in the form of a one-dimensional integral. The final expression involves only a few hypergeometric functions if n is not too large and is particularly suited to study excitation to highly excited states from a low lying state.

  17. From War to Politics : Non-State Armed Groups in Transition, 2009 ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    An earlier project (103613) resulted in the creation of a research network on the experience of non-state armed groups (NSAGs) who have made the transition from armed resistance during protracted violent conflicts to political engagement in peace negotiations and post-war state building. This project will continue the ...

  18. Theoretical expression of the internal conversion coefficient of a M1 transition between two atomic states

    International Nuclear Information System (INIS)

    Attallah, F.; Chemin, J.F.; Scheurer, J.N.; Karpeshin, F.; Harston, M.

    1997-01-01

    We have established a general relation for the expression of the internal conversion of an M 1 transition a 1s electronic state to an empty ns electronic bound state. Under the hypothesis that the density of the electron level ρ n satisfies the condition ρ n Γ >> 1 (where Γ is the total width of the excited atomic state) a calculation in the first order gives a relation for the internal conversion coefficient.This relation shows that the internal conversion coefficient takes a resonant character when the nuclear energy transition is smaller than the binding energy of the 1s electron. An application of this relation to an M 1 transition in the case of the ion 125 T e with a charge state Q = 45 and an 1s electron binding energy E B 45 = 35.581 KeV gives the value for the internal conversion coefficient R = 5.7

  19. An infrared study of the nitro—nitrito linkage isomerization in solid nitro- and nitritopentamminecobalt(III) chloride

    Science.gov (United States)

    Heyns, A. M.; de Waal, D.

    1989-01-01

    The photochemical isomerization reaction of [Co(NH 3) 5NO 2]Cl 2 to [Co(NH 3) 5ONO]Cl 2 has been studied in the solid state by means of i.r. spectroscopy. The reaction is first order with k = 2.53±0.05 × 10 -4s -1 and is much faster ( t1/2=49min) than the well-known spontaneous nitrito → nitro isomerization ( t1/2 = 6 days). The i.r. bands of both the NH 3 and ONO - -groups in the range 4000-50 cm -1 indicate minor differences between the structures of freshly and photochemically prepared [Co(NH 3) 5ONO]Cl 2. The far i.r. spectra indicate the disorder existing in the intermediate products during the isomerization processes.

  20. Isomeric shift compensation when using resonance detectors in Moessbauer spectroscopy

    International Nuclear Information System (INIS)

    Irkaev, S.M.; Semenkin, V.A.; Sokolov, M.M.

    1981-01-01

    Method for compensation of isomeric shift of lines observed during operation of resonance detectors being part of spectrometers of nuclear gamma resonance is suggested. A flowsheet of device permitting to realize the method described is given. The method is based on using the Doppler effect. A source of resonance radiation is moved at a constant velocity, which is choosen so as to compensate energy shift of lines of the source and convertors of the resonance detector. The absorber under investigation is put in motion with a constant acceleration. The resonance detector signals are amplified selected according to amplitude by a discriminator and come to the input of multichannel analyzer operating in the regime of subsequent scaling. Analysis of experimental spectra obtained at velocities of source movement from 0 to +3 mm/s shows that value of resonance absorption effect drops as increasing energy shift in the source-converter system. It is concluded that application of the method described will permit to considerably extend the field of application of resonance detectors in the Moessbauer spectroscopy and investigate in practice all the isotopes having converted transitions [ru

  1. Graphene oxide catalyzed cis-trans isomerization of azobenzene

    Directory of Open Access Journals (Sweden)

    Dongha Shin

    2014-09-01

    Full Text Available We report the fast cis-trans isomerization of an amine-substituted azobenzene catalyzed by graphene oxide (GO, where the amine functionality facilitates the charge transfer from azobenzene to graphene oxide in contrast to non-substituted azobenzene. This catalytic effect was not observed in stilbene analogues, which strongly supports the existence of different isomerization pathways between azobenzene and stilbene. The graphene oxide catalyzed isomerization is expected to be useful as a new photoisomerization based sensing platform complementary to GO-based fluorescence quenching methods.

  2. State transitions in the 2001/2002 outburst of XTE J1650-500

    International Nuclear Information System (INIS)

    Rossi, S.; Homan, J.; Miller, J.M.; Belloni, T.

    2004-01-01

    We present a study of the X-ray transient and black hole candidate XTE J1650-500 during its 2001/2002 outburst. The source made two state transitions between the hard and soft states, at luminosity levels that differ by a factor of ∼5-10. The first transition, between hard and soft, lasted for ∼30 days and showed two parts; one part in which the spectral properties evolve smoothly away from the hard state and another that we identify as the 'steep power law state'. The two parts showed different behavior of the Fe K emission line and QPO frequencies. The second transition, from soft to hard, lasted only ∼15 days and showed no evidence of the presence of the 'steep power law state'. Comparing observations from the early rise and the decay of the outburst, we conclude that the source can be in the hard state in a range of more than 10 4 in luminosity. We briefly discuss the state transitions in the framework of a two-flow model

  3. Insights in the Rhodium-Catalyzed Tandem Isomerization-Hydroformylation of 10-Undecenitrile: Evidence for a Fast Isomerization Regime

    Directory of Open Access Journals (Sweden)

    Lucas Le Goanvic

    2018-04-01

    Full Text Available The tandem isomerization-hydroformylation of 10-undecenitrile (1 into the corresponding linear aldehyde (2 with a Rh-biphephos system was studied and the formation of internal olefin isomers (1-int-x was monitored over time. The existence of an “isomerization phenomenon” was evidenced, where fast isomerization of 1 into up to 70% of 1-int-x followed by fast back-isomerization of 1-int-x into 1 and, in turn, into 2 occurs. This fast dynamic isomerization regime is favored at high syngas pressure (40 bar and low biphephos-to-Rh ratio (5–10, and it is best observed at relatively high catalyst loadings ([1]0/[Rh] ≤ 3000. The latter regime is indeed evanescent, and gives place to a second stage in which isomerization of internal olefins (and eventual conversion into 2 proceeds much more slowly. The results are tentatively rationalized by the formation of an unstable species that promotes dynamic isomerization and which slowly vanishes or collapses into a Rh-biphephos species which is the one responsible for hydroformylation.

  4. g-factor of the 7/2+ isomeric bandhead in 175 W

    International Nuclear Information System (INIS)

    Ionescu-Bujor, M.; Iordachescu, A.; Marginean, N.; Brandolini, F.; Pavan, P.; Lenzi, S.M.; De Poli, M.; Gadea, A.; Martinez, T.; Medina, N.H.; Ribas, R.V.; Podolyak, Zs.

    2000-01-01

    Considerable effort is presently devoted to the investigation of the high-K isomers of multi-quasiparticle intrinsic structure systematically found in the deformed nuclei with Z=72-76 of the A ≅ 180 mass region. The configuration assignments for these isomers are based on measured static moments, as well as, on experimental branching ratios in the associated bands, from which (g K - g R )/Q 0 are derived. In the multi-quasiparticle state g-factor calculations, values taken from neighbouring odd-mass nuclei are generally used for the proton and neutron deformed single-particle g-factors. A good knowledge of these quantities is required for reliable high-K state g-factor evaluations. In the present work we report on the g-factor measurement for the low-lying J π = 7/2 + isomer bandhead in 175 W described by the neutron 7/2 + [633] Nilsson orbital. The isomeric state was populated in the 164 Dy( 16 O,5n) 175 W reaction using the 83 MeV pulsed 16 O beam (pulse width 1.5 ns, repetition period 800 ns) delivered by the LNL XTU-Tandem. The target consisted of 0.5 mg/cm 2 metallic 164 Dy on thick Pb backing which stopped the recoiling 175 W nuclei and the 16 O beam. The target was placed in an external magnetic field of 27.2(6) kG whose direction was periodically reversed. The 7/2 + isomeric state with T 1/2 = 216(6) ns and E x =234.9 keV de-excites by a dipole transition of 130.9 keV to the 5/2 - level. The angular distribution of the 130.9 keV gamma-ray has been observed time-differentially by using two planar Ge detectors placed at ± 135 angle with respect to the beam direction. The background corrected time spectra I(t,θ) obtained for the magnetic field direction up and down were used to form the experimental modulation ratio R exp (t)=[I↑(t,θ) - I ↓ (t,θ)]/[I↑(t,θ) + I ↓ (t,θ)]. The modulation pattern revealed Larmor oscillations with an amplitude strongly attenuated in time. The observed damping of the anisotropy has been attributed to quadrupole

  5. Structural transition, subgap states, and carrier transport in anion-engineered zinc oxynitride nanocrystalline films

    International Nuclear Information System (INIS)

    Xian, Fenglin; Ye, Jiandong; Gu, Shulin; Tan, Hark Hoe; Jagadish, Chennupati

    2016-01-01

    In this work, anion alloying is engineered in ZnON nanocrystalline films, and the resultant evolution of the structural transition, subgap states, and carrier transport is investigated. A broad distribution of sub-gap states above the valence band maximum is introduced by nitrogen due to the hybridization of N 2p and O 2p orbitals. The phase transition from partially amorphous states to full crystallinity occurs above a characteristic growth temperature of 100 °C, and the localized states are suppressed greatly due to the reduction of nitrogen composition. The electronic properties are dominated by grain boundary scattering and electron transport across boundary barriers through thermal activation at band edge states at high temperatures. The conductivity below 130 K exhibits a weak temperature dependence, which is a signature of variable-range hopping conduction between localized states introduced by nitrogen incorporation.

  6. Walk, Bicycle, and Transit Trips of Transit-Dependent and Choice Riders in the 2009 United States National Household Travel Survey.

    Science.gov (United States)

    Lachapelle, Ugo

    2015-08-01

    Previous research has shown that public transit use may be associated with active transportation. Access to a car may influence active transportation of transit riders. Using the 2009 United States National Household Travel Survey (NHTS), transit users ≥ 16 years old (n = 25,550) were categorized according to driver status and number of cars and drivers in the household. This typology ranged from choice transit riders (ie, "fully motorized drivers") to transit-dependent riders (ie, "unmotorized nondriver"). Transit trips, walking trips, and bicycling trips of transit users are estimated in negative binomial models against the car availability typology. Sixteen percent of participants took transit in the past month; most (86%) lived in car-owning households. As income increased, car availability also increased. Transit user groups with lower car availability were generally more likely than fully motorized drivers to take more public transit, walking, and bicycle trips. Transit riders have varying levels of vehicle access; their use of combinations of alternative modes of transportation fluctuates accordingly. Transit-dependent individuals without cars or sharing cars used active transportation more frequently than car owners. Policies to reduce vehicle ownership in households may enable increases in the use of alternative modes of transportation for transit users, even when cars are still owned.

  7. State safety oversight program : audit of the tri-state oversight committee and the Washington metropolitan area transit authority, final audit report, March 4, 2010.

    Science.gov (United States)

    2010-03-04

    The Federal Transit Administration (FTA) conducted an on-site audit of the safety program implemented by the Washington Metropolitan Area Transit Authority (WMATA) and overseen by the Tri-State Oversight Committee (TOC) between December 14 and 17, 20...

  8. Behavior of the excited deformed band and search for shape isomerism in 184Hg

    International Nuclear Information System (INIS)

    Cole, J.D.; Hamilton, J.H.; Ramayya, A.V.; Nettles, W.G.; Kawakami, H.; Spejewski, E.H.; Ijaz, M.A.; Toth, K.S.; Robinson, E.L.; Sastry, K.S.R.; Lin, J.; Avignone, F.T.; Brantley, W.H.; Rao, P.V.G.

    1976-01-01

    The new isotope 184 Tl has been identified with T 1 / 2 =11 +- 1 sec and the levels in 184 Hg investigated from its decay. The 0 + band head of a deformed band was found to drop to 375 keV in agreement with theoretical predictions. The mean life of the 375-keV 0 + level was measured to be 0.9 +- 0.3 nsec which is a factor of 10 faster than theoretically predicted for a shape-isomeric E2 transition

  9. Phase Transitions in Definite Total Spin States of Two-Component Fermi Gases.

    Science.gov (United States)

    Yurovsky, Vladimir A

    2017-05-19

    Second-order phase transitions have no latent heat and are characterized by a change in symmetry. In addition to the conventional symmetric and antisymmetric states under permutations of bosons and fermions, mathematical group-representation theory allows for non-Abelian permutation symmetry. Such symmetry can be hidden in states with defined total spins of spinor gases, which can be formed in optical cavities. The present work shows that the symmetry reveals itself in spin-independent or coordinate-independent properties of these gases, namely as non-Abelian entropy in thermodynamic properties. In weakly interacting Fermi gases, two phases appear associated with fermionic and non-Abelian symmetry under permutations of particle states, respectively. The second-order transitions between the phases are characterized by discontinuities in specific heat. Unlike other phase transitions, the present ones are not caused by interactions and can appear even in ideal gases. Similar effects in Bose gases and strong interactions are discussed.

  10. Visualization of the Differential Transition State Stabilization within the Active Site Environment

    Directory of Open Access Journals (Sweden)

    Jerzy Leszczynski

    2004-05-01

    Full Text Available Abstract: Increasing interest in the enzymatic reaction mechanisms and in the nature of catalytic effects in enzymes causes the need of appropriate visualization methods. A new interactive method to investigate catalytic effects using differential transition state stabilization approach (DTSS [1, 2] is presented. The catalytic properties of the active site of cytidine deaminase (E.C. 3.5.4.5 is visualized in the form of differential electrostatic properties. The visualization was implemented using scripting interface of VMD [3]. Cumulative Atomic Multipole Moments (CAMM [4,5,6] were utilized for efficient yet accurate evaluation of the electrostatic properties. The implementation is efficient enough for interactive presentation of catalytic effects in the active site of the enzyme due to transition state or substrate movement. This system of visualization of DTTS approach can be potentially used to validate hypotheses regarding the catalytic mechanism or to study binding properties of transition state analogues.

  11. Photoisomerization Mechanism of Ruthenium Sulfoxide Complexes: Role of the Metal-Centered Excited State in the Bond Rupture and Bond Construction Processes.

    Science.gov (United States)

    Li, Huifang; Zhang, Lisheng; Zheng, Lvyin; Li, Xun; Fan, Xiaolin; Zhao, Yi

    2016-09-26

    Phototriggered intramolecular isomerization in a series of ruthenium sulfoxide complexes, [Ru(L)(tpy)(DMSO)](n+) (where tpy=2,2':6',2''-terpyridine; DMSO=dimethyl sulfoxide; L=2,2'-bipyridine (bpy), n=2; N,N,N',N'-tetramethylethylenediamine (tmen) n=2; picolinate (pic), n=1; acetylacetonate (acac), n=1; oxalate (ox), n=0; malonate (mal), n=0), was investigated theoretically. It is observed that the metal-centered ligand field ((3) MC) state plays an important role in the excited state S→O isomerization of the coordinated DMSO ligand. If the population of (3) MCS state is thermally accessible and no (3) MCO can be populated from this state, photoisomerization will be turned off because the (3) MCS excited state is expected to lead to fast radiationless decay back to the original (1) GSS ground state or photodecomposition along the Ru(2+) -S stretching coordinate. On the contrary, if the population of (3) MCS (or (3) MCO ) state is inaccessible, photoinduced S→O isomerization can proceed adiabatically on the potential energy surface of the metal-to-ligand charge transfer excited states ((3) MLCTS →(3) MLCTO ). It is hoped that these results can provide valuable information for the excited state isomerization in photochromic d(6) transition-metal complexes, which is both experimentally and intellectually challenging as a field of study. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Yields and isomeric ratio of xenon and krypton isotopes from thermal neutron fission of 235U

    International Nuclear Information System (INIS)

    Hsu, S.S.; Lin, J.T.; Yang, C.M.; Yu, Y.W.

    1981-01-01

    The experimental cumulative yields of 85 Kr/sup m/, 87 Kr, 88 Kr, 133 Xe/sup g/, 135 Xe/sup m/, and 135 Xe/sup g/ and the independent isomeric yield of 133 Xe/sup m/ in the thermal neutron fission of 235 U have been measured by the gas chromatographic method. The independent yields of 133 Xe/sup g/, 135 Xe/sup m/, and 135 Xe/sup g/ were deduced with the aid of 133 I and 135 I data. The isomeric yield ratios of 133 Xe and 135 Xe have been computed and compared with theoretical values since they have the same high spin state J = 11/2 - and low spin ground state J = 3/2 + . The influence of the shell effect on the fission isomeric yield ratio is discussed. From the measured independent yield of Xe isotopes plus the reported data, the Xe-isotopic distribution curve has been constructed. The curve is compared with the isotopic distribution curves of Xe isotopes formed in 11.5 GeV proton interactions with 238 U and Cs isotopes formed in 24 GeV proton interactions with 238 U. Upon fitting the yield curves we find that only those products with N/Z> or =1.48 fit a curve typical of a binary fission process

  13. The first observation of EO transitions from negative parity states in even-even nucleus 160Dy

    International Nuclear Information System (INIS)

    Grigoriev, E.P.

    1988-01-01

    In even-even deformed nuclei up to now EO-transitions were found only between the states of the same spin belonging to Κ π = O + rotational bands. There is no forbidenness for EO-transitions between states belonging to bands with any other quantum number Κ provided both initial and final states have the same J π Κ values. EO-transitions may depopulate odd-parity states. In odd nuclei β-vibrational states are identified by transition with EO-components. Here transitions also proceed between states with the same J π K numbers. Even-even nuclide 160 Dy is the first nucleus where the EO-transitions between odd-parity states have been found

  14. Synthesis and Characterisation of Eight Isomeric Bis(2-pyridyloxynaphthalenes

    Directory of Open Access Journals (Sweden)

    Peter J. Steel

    2006-09-01

    Full Text Available Eight isomeric bis(2-pyridyloxynaphthalenes have been prepared from reactions of 2-bromopyridine with the appropriate dihydroxynaphthalene and the products fully characterised by 1- and 2-D NMR spectroscopy.

  15. {sup 13}C-NMR studies on disulfide bond isomerization in bovine pancreatic trypsin inhibitor (BPTI)

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Mitsuhiro [Kumamoto University, Department of Structural BioImaging, Faculty of Life Sciences (Japan); Miyanoiri, Yohei [Nagoya University, Structural Biology Research Center, Graduate School of Science (Japan); Terauchi, Tsutomu [Tokyo Metropolitan University, Graduate School of Science and Engineering (Japan); Kainosho, Masatsune, E-mail: kainosho@tmu.ac.jp [Nagoya University, Structural Biology Research Center, Graduate School of Science (Japan)

    2016-09-15

    Conformational isomerization of disulfide bonds is associated with the dynamics and thus the functional aspects of proteins. However, our understanding of the isomerization is limited by experimental difficulties in probing it. We explored the disulfide conformational isomerization of the Cys14–Cys38 disulfide bond in bovine pancreatic trypsin inhibitor (BPTI), by performing an NMR line-shape analysis of its Cys carbon peaks. In this approach, 1D {sup 13}C spectra were recorded at small temperature intervals for BPTI samples selectively labeled with site-specifically {sup 13}C-enriched Cys, and the recorded peaks were displayed in the order of the temperature after the spectral scales were normalized to a carbon peak. Over the profile of the line-shape, exchange broadening that altered with temperature was manifested for the carbon peaks of Cys14 and Cys38. The Cys14–Cys38 disulfide bond reportedly exists in equilibrium between a high-populated (M) and two low-populated states (m{sub c14} and m{sub c38}). Consistent with the three-site exchange model, biphasic exchange broadening arising from the two processes was observed for the peak of the Cys14 α-carbon. As the exchange broadening is maximized when the exchange rate equals the chemical shift difference in Hz between equilibrating sites, semi-quantitative information that was useful for establishing conditions for {sup 13}C relaxation dispersion experiments was obtained through the carbon line-shape profile. With respect to the m{sub c38} isomerization, the {sup 1}H-{sup 13}C signals at the β-position of the minor state were resolved from the major peaks and detected by exchange experiments at a low temperature.

  16. Transitions between states of labor-force participation among older Israelis

    OpenAIRE

    Achdut, Leah; Tur-Sinai, Aviad; Troitsky, Rita

    2014-01-01

    The study examines the labor-force behavior of Israelis at older ages, focusing on the determinants of the transitions between states of labor-force participation between 2005 and 2010. The study uses panel data from the first two waves of the SHARE-Israel longitudinal survey. A multinomial logit model is used to examine the impact of sociodemographic characteristics, health state, and economic resources on labor-force transitions of people aged 50–67. The results emphasize the role of age an...

  17. Optical nonlinearities of excitonic states in atomically thin 2D transition metal dichalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Soh, Daniel Beom Soo [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Proliferation Signatures Discovery and Exploitation Department

    2017-08-01

    We calculated the optical nonlinearities of the atomically thin monolayer transition metal dichalcogenide material (particularly MoS2), particularly for those linear and nonlinear transition processes that utilize the bound exciton states. We adopted the bound and the unbound exciton states as the basis for the Hilbert space, and derived all the dynamical density matrices that provides the induced current density, from which the nonlinear susceptibilities can be drawn order-by-order via perturbative calculations. We provide the nonlinear susceptibilities for the linear, the second-harmonic, the third-harmonic, and the kerr-type two-photon processes.

  18. Kinetic Analysis for Macrocyclizations Involving Anionic Template at the Transition State

    Directory of Open Access Journals (Sweden)

    Vicente Martí-Centelles

    2012-01-01

    competitive oligomerization/polymerization processes yielding undesired oligomeric/polymeric byproducts. The effect of anions has also been included in the kinetic models, as they can act as catalytic templates in the transition state reducing and stabilizing the transition state. The corresponding differential equation systems for each kinetic model can be solved numerically. Through a comprehensive analysis of these results, it is possible to obtain a better understanding of the different parameters that are involved in the macrocyclization reaction mechanism and to develop strategies for the optimization of the desired processes.

  19. A Semi-Continuous State-Transition Probability HMM-Based Voice Activity Detector

    Directory of Open Access Journals (Sweden)

    H. Othman

    2007-02-01

    Full Text Available We introduce an efficient hidden Markov model-based voice activity detection (VAD algorithm with time-variant state-transition probabilities in the underlying Markov chain. The transition probabilities vary in an exponential charge/discharge scheme and are softly merged with state conditional likelihood into a final VAD decision. Working in the domain of ITU-T G.729 parameters, with no additional cost for feature extraction, the proposed algorithm significantly outperforms G.729 Annex B VAD while providing a balanced tradeoff between clipping and false detection errors. The performance compares very favorably with the adaptive multirate VAD, option 2 (AMR2.

  20. Lifetime measurements and dipole transition rates for superdeformed states in {sup 190}Hg.

    Energy Technology Data Exchange (ETDEWEB)

    Amro, H.

    1999-03-24

    The Doppler-shift attenuation method was used to measure life-times of superdeformed (SD) states for both the yrast and the first excited superdeformed band of {sup 190}Hg. Intrinsic quadruple moments Q{sub 0} were extracted. For the first time, the dipole transition rates have been extracted for the inter-band transitions which connect the excited SD band to the yrast states in the second minimum. The results support the interpretation of the excited SD band as a rotational band built on an octupole vibration.

  1. Lifetime measurements and dipole transition rates for superdeformed states in 190Hg

    International Nuclear Information System (INIS)

    Amro, H.

    1999-01-01

    The Doppler-shift attenuation method was used to measure life-times of superdeformed (SD) states for both the yrast and the first excited superdeformed band of 190 Hg. Intrinsic quadruple moments Q 0 were extracted. For the first time, the dipole transition rates have been extracted for the inter-band transitions which connect the excited SD band to the yrast states in the second minimum. The results support the interpretation of the excited SD band as a rotational band built on an octupole vibration

  2. A Semi-Continuous State-Transition Probability HMM-Based Voice Activity Detector

    Directory of Open Access Journals (Sweden)

    Othman H

    2007-01-01

    Full Text Available We introduce an efficient hidden Markov model-based voice activity detection (VAD algorithm with time-variant state-transition probabilities in the underlying Markov chain. The transition probabilities vary in an exponential charge/discharge scheme and are softly merged with state conditional likelihood into a final VAD decision. Working in the domain of ITU-T G.729 parameters, with no additional cost for feature extraction, the proposed algorithm significantly outperforms G.729 Annex B VAD while providing a balanced tradeoff between clipping and false detection errors. The performance compares very favorably with the adaptive multirate VAD, option 2 (AMR2.

  3. Isomerizations of the Nitromethane Radical Cation in the Gas Phase

    DEFF Research Database (Denmark)

    Egsgaard, Helge; Carlsen, Lars; Elbel, Susanne

    1986-01-01

    The concurrent isomerizations of the nitromethane radical cation to its aci-nitromethane and methylnitrite isomers, respectively, has been established based on metastable ion studies and collision activation mass spectrometry. The energy diagram for the ionized nitromethane/aci-nitromethane tauto......The concurrent isomerizations of the nitromethane radical cation to its aci-nitromethane and methylnitrite isomers, respectively, has been established based on metastable ion studies and collision activation mass spectrometry. The energy diagram for the ionized nitromethane...

  4. State-Transition-Aware Spilling Heuristic for MLC STT-RAM-Based Registers

    Directory of Open Access Journals (Sweden)

    Yuanhui Ni

    2017-01-01

    Full Text Available Multilevel Cell Spin-Transfer Torque Random Access Memory (MLC STT-RAM is a promising nonvolatile memory technology to build registers for its natural immunity to electromagnetic radiation in rad-hard space environment. Unlike traditional SRAM-based registers, MLC STT-RAM exhibits unbalanced write state transitions due to the fact that the magnetization directions of hard and soft domains cannot be flipped independently. This feature leads to nonuniform costs of write states in terms of latency and energy. However, current SRAM-targeting register allocations do not have a clear understanding of the impact of the different write state-transition costs. As a result, those approaches heuristically select variables to be spilled without considering the spilling priority imposed by MLC STT-RAM. Aiming to address this limitation, this paper proposes a state-transition-aware spilling cost minimization (SSCM policy, to save power when MLC STT-RAM is employed in register design. Specifically, the spilling cost model is first constructed according to the linear combination of different state-transition frequencies. Directed by the proposed cost model, the compiler picks up spilling candidates to achieve lower power and higher performance. Experimental results show that the proposed SSCM technique can save energy by 19.4% and improve the lifetime by 23.2% of MLC STT-RAM-based register design.

  5. Columbus State University Global Observation and Outreach for the 2012 Transit of Venus

    Science.gov (United States)

    Perry, Matthew; McCarty, C.; Bartow, M.; Hood, J. C.; Lodder, K.; Johnson, M.; Cruzen, S. T.; Williams, R. N.

    2013-01-01

    Faculty, staff and students from Columbus State University’s (CSU’s) Coca-Cola Space Science Center presented a webcast of the 2012 Transit of Venus from three continents to a global audience of 1.4 million unique viewers. Team members imaged the transit with telescopes using white-light, hydrogen-alpha, and calcium filters, from Alice Springs, Australia; the Gobi Desert, Mongolia; Bryce Canyon, UT; and Columbus, GA. Images were webcast live during the transit in partnership with NASA’s Sun-Earth Day program, and Science Center staff members were featured on NASA TV. Local members of the public were brought in for a series of outreach initiatives, in both Georgia and Australia, before and during the transit. The data recorded from the various locations have been archived for use in demonstrating principles such as the historical measurement of the astronomical unit.

  6. Study of shape transition in the neutron-rich Os isotopes

    Directory of Open Access Journals (Sweden)

    John P.R.

    2014-03-01

    Full Text Available The neutron-rich isotopes of tungsten, osmium and platinum have different shapes in their ground states and present also shape transitions phenomena. Spectroscopic information for these nuclei is scarce and often limited to the gamma rays from the decay of isomeric states. For the neutron-rich even-even osmium isotopes 194Os and 198Os, a shape transition between a slightly prolate deformed to an oblate deformed ground state was deduced from the observed level schemes. For the even-even nucleus lying in between, 196Os, no gamma ray transition is known. In order to elucidate the shape transition and to test the nuclear models describing it, this region was investigated through gamma-ray spectroscopy using the AGATA demonstrator and the large acceptance heavy-ion spectrometer PRISMA at LNL, Italy. A two-nucleon transfer from a 198Pt target to a stable 82Se beam was utilized to populate medium-high spin states of 196Os. The analysis method and preliminary results, including the first life-time measurement of isomeric states with AGATA, are presented.

  7. Specification, construction, and exact reduction of state transition system models of biochemical processes.

    Science.gov (United States)

    Bugenhagen, Scott M; Beard, Daniel A

    2012-10-21

    Biochemical reaction systems may be viewed as discrete event processes characterized by a number of states and state transitions. These systems may be modeled as state transition systems with transitions representing individual reaction events. Since they often involve a large number of interactions, it can be difficult to construct such a model for a system, and since the resulting state-level model can involve a huge number of states, model analysis can be difficult or impossible. Here, we describe methods for the high-level specification of a system using hypergraphs, for the automated generation of a state-level model from a high-level model, and for the exact reduction of a state-level model using information from the high-level model. Exact reduction is achieved through the automated application to the high-level model of the symmetry reduction technique and reduction by decomposition by independent subsystems, allowing potentially significant reductions without the need to generate a full model. The application of the method to biochemical reaction systems is illustrated by models describing a hypothetical ion-channel at several levels of complexity. The method allows for the reduction of the otherwise intractable example models to a manageable size.

  8. Romania - New E.U. Member State, A New Phase of Its Transition

    Directory of Open Access Journals (Sweden)

    Marius PROFIROIU

    2011-06-01

    Full Text Available Ever since Romania started its transition in the 1990s, it consistently scored poorly in various comparative performance assessments aimed at rating developing countries. In this paper we analyze whether Romania has managed to overcome the transition period or not, by pointing out both the drawbacks as well as the progress that has been made over the transition period, but most of all since our accession to the European Union in 2007. We discuss the concept of good governance for a new EU member state, by focusing on the state of public governance in Romania, but also addressing the other two important actors in the society, the private sector and the civil society.

  9. Transition state theory approach to polymer escape from a one dimensional potential well.

    Science.gov (United States)

    Mökkönen, Harri; Ikonen, Timo; Ala-Nissila, Tapio; Jónsson, Hannes

    2015-06-14

    The rate of escape of an ideal bead-spring polymer in a symmetric double-well potential is calculated using transition state theory (TST) and the results compared with direct dynamical simulations. The minimum energy path of the transitions becomes flat and the dynamics diffusive for long polymers making the Kramers-Langer estimate poor. However, TST with dynamical corrections based on short time trajectories started at the transition state gives rate constant estimates that agree within a factor of two with the molecular dynamics simulations over a wide range of bead coupling constants and polymer lengths. The computational effort required by the TST approach does not depend on the escape rate and is much smaller than that required by molecular dynamics simulations.

  10. Experiences of Nigerian Internationally Educated Nurses Transitioning to United States Health Care Settings.

    Science.gov (United States)

    Iheduru-Anderson, Kechinyere C; Wahi, Monika M

    2018-04-01

    Successful transition to practice of internationally educated nurses (IENs) can critically affect quality of care. The aim of this study was to characterize the facilitators and barriers to transition of Nigerian IENs (NIENs) to the United States health care setting. Using a descriptive phenomenology approach, 6 NIENs were interviewed about their transitional experiences in the United States. Thematic methods were used for data analysis. The three major themes identified from the participants' stories were "fear/anger and disappointment" (FAD), "road/journey to success/overcoming challenges" (RJO), and "moving forward" (MF). The FAD theme predominated, including experiences of racism, bullying, and inequality. The RJO theme included resilience, and the MF theme encompassed personal growth. NIENs face personal and organizational barriers to adaptation, especially fear, anger and disappointment. Future research should seek to develop a model for optimal adaptation that focuses on improving both personal and organizational facilitators and decreasing barriers.

  11. Study of the photochemical isomerization of ergosterol

    International Nuclear Information System (INIS)

    Mermet-Bouvier, Rene

    1972-01-01

    The photochemical reaction scheme of Ergosterol-Vitamin D 2 was studied. The schemes proposed in published literature are described together with earlier methods used for the analysis and determination. The method used is then discussed. In the first part, the factors concerning the changes occurring in molecular systems exposed to radiation, and the formalism used, are examined. Investigations of linear molecular systems and their applications to the reaction scheme of Ergosterol-Vitamin D 2 are discussed. The properties which enable the last three reaction schemes proposed in the literature to be distinguished are described. In the second part, the experimental analytical methods and the determinations made of the different isomers formed are presented. Chromatographic techniques (thin films, columns, gaseous phase) suitable for separating the various isomeric species are used. The existence of 8 isomers was established as well as a transformation occurring in one of them. The ultraviolet and infrared spectra were obtained. A reaction scheme is proposed (in which all the quantum yield values are given) from comparisons between the calculated and experimental values of the eigenvalue of the absolute minimum value λ m and the eigenvector corresponding to V m . (author) [fr

  12. State-and-transition simulation models: a framework for forecasting landscape change

    Science.gov (United States)

    Daniel, Colin; Frid, Leonardo; Sleeter, Benjamin M.; Fortin, Marie-Josée

    2016-01-01

    SummaryA wide range of spatially explicit simulation models have been developed to forecast landscape dynamics, including models for projecting changes in both vegetation and land use. While these models have generally been developed as separate applications, each with a separate purpose and audience, they share many common features.We present a general framework, called a state-and-transition simulation model (STSM), which captures a number of these common features, accompanied by a software product, called ST-Sim, to build and run such models. The STSM method divides a landscape into a set of discrete spatial units and simulates the discrete state of each cell forward as a discrete-time-inhomogeneous stochastic process. The method differs from a spatially interacting Markov chain in several important ways, including the ability to add discrete counters such as age and time-since-transition as state variables, to specify one-step transition rates as either probabilities or target areas, and to represent multiple types of transitions between pairs of states.We demonstrate the STSM method using a model of land-use/land-cover (LULC) change for the state of Hawai'i, USA. Processes represented in this example include expansion/contraction of agricultural lands, urbanization, wildfire, shrub encroachment into grassland and harvest of tree plantations; the model also projects shifts in moisture zones due to climate change. Key model output includes projections of the future spatial and temporal distribution of LULC classes and moisture zones across the landscape over the next 50 years.State-and-transition simulation models can be applied to a wide range of landscapes, including questions of both land-use change and vegetation dynamics. Because the method is inherently stochastic, it is well suited for characterizing uncertainty in model projections. When combined with the ST-Sim software, STSMs offer a simple yet powerful means for developing a wide range of models of

  13. Structure of states and reduced probabilities of electromagnetic transitions in 169Yb

    International Nuclear Information System (INIS)

    Bonch-Osmolovskaya, N.A.; Morozov, V.A.; Khudajberdyev, Eh.N.

    1988-01-01

    The effect of accounting the Pauli principle on the structure and energy of nonrotational states of 169 Yb deformed nucleus as well as on reduced probabilities of E2-transitions B(E2) is studied within the framework of the quasiparticle-phonon model (QPM). The amplitudes of states mixing due to Coriolis interaction and reduced probabilities of gamma transition within the framework of nonadiabatic rotation model are also calculated. The results are compared with calculations made within QPM with account of Coriolis interaction but excluding the Pauli principle in the wave state function. It is shown that to describe correctly both the level structure and reduced probabilities B(E2) it is necessary to include all types of interaction : quasiparticle interaction with phonons with account of the Pauli principle in the wave state functions and Coriolis interactions. Now no uniform theoretical approach exists

  14. Critical behaviour of continuous phase transitions with infinitely many absorbing states

    International Nuclear Information System (INIS)

    Hua Dayin; Wang Lieyan; Chen Ting

    2006-01-01

    A lattice gas model is proposed for the A 2 + 2B 2 → 2B 2 A reaction system with particle diffusion. In the model, A 2 dissociates in the random dimer-filling mechanism and B 2 dissociation is in the end-on dimer-filling mechanism. A reactive window appears and the system exhibits a continuous phase transition from a reactive state to a covered state with infinitely many absorbing states. When the diffusion of particle A and AB is included, there are still infinitely many absorbing states for the continuous phase transition, but it is found that the critical behaviour changes from the directed percolation (DP) class to the pair contact process with diffusion (PCPD) class

  15. M1 transitions between low-lying states in the sdg-IBM-2

    Science.gov (United States)

    Casperson, Robert; Werner, Volker

    2006-10-01

    The interplay between collective and single-particle degrees of freedom for nuclei in the A=90 region have recently been under investigation. In Molybdenum and Ruthenium nuclei, collective symmetric and mixed-symmetric structures have been identified, while in Zirconium, underlying shell-structure plays an enhanced role. Collective symmetric structures appear when protons and neutrons are in phase, whereas mixed-symmetric structures occur when they are not. The one-phonon 2^+ mixed-symmetric state was identified from strong M1 transitions to the 2^+1 state. Similar transitions were observed between higher-spin states, and are predicted by the shell model. These phenomena will be investigated within the sdg Interacting Boson Model 2 in order to obtain a better understanding about the structure of the states involved, and results from first model calculations will be presented. Work supported by US DOE under grant number DE-FG02-91ER-40609.

  16. Discussion of isomeric ratios in (p, n) and (d, 2n) reaction

    Energy Technology Data Exchange (ETDEWEB)

    Bakhshiyan, T. M., E-mail: tiruhi44@mail.ru [Yerevan State University (Armenia)

    2016-01-15

    Isomeric ratios (IR) in the (p, n) and (d, 2n) reactions are considered. The dependence of IR values on the projectile type and energy, the target- and product-nucleus spin, the spin difference between the isomeric and ground states of products, and the product mass number is discussed. The isomeric ratios for 46 product nuclei (from {sup 44m,g}Sc to {sup 127m,g}Xe) obtained in reactions where target and product nuclei have identical mass numbers were calculated at energies from the reaction threshold to 50 MeV (with a step of ΔE = 1 MeV). The calculations in question were performed with the aid of the TALYS 1.4 code package. The calculated IR values were compared with their experimental counterparts available from the literature (EXFOR database). In the majority of cases, the calculated IR values agree well with the experimental data in question. It is noteworthy that the IR values obtained in (d, 2n) reactions are substantially greater than those in (p, n) reactions.

  17. Comparison of 3D Classical Trajectory and Transition-State Theory Reaction Cross Sections

    Science.gov (United States)

    Koeppl, G. W.; Karplus, Martin

    1970-10-01

    Although there is excellent agreement for a system such as H+H{sub 2} --> H{sub 2}+H, in which both the potential and the particle masses are symmetric, significant deviations occur for more asymmetric reactions. A detailed analysis show that the calculated differences are from the violation of two assumptions of transition-state theory.

  18. Transition State Gauche Effects Control the Torquoselectivities of the Electrocyclizations of Chiral 1-Azatrienes.

    Science.gov (United States)

    Patel, Ashay; Vella, Joseph R; Ma, Zhi-Xiong; Hsung, R P; Houk, K N

    2015-12-04

    Hsung et al. have reported a series of torquoselective electrocyclizations of chiral 1-azahexa-1E,3Z,5E-trienes that yield functionalized dihydropyridines. To understand the origins of the torquoselectivities of these azaelectrocyclizations, we modeled these electrocyclic ring closures using the M06-2X density functional. A new stereochemical model that rationalizes the observed 1,2 stereoinduction emerges from these computations. This model is an improvement and generalization of the "inside-alkoxy" model used to rationalize stereoselectivities of the 1,3-dipolar cycloaddition of chiral allyl ethers and emphasizes a stabilizing hyperconjugative effect, which we have termed a transition state gauche effect. This stereoelectronic effect controls the conformational preferences at the electrocyclization transition states, and only in one of the allowed disrotatory electrocyclization transition states is the ideal stereoelectronic arrangement achieved without the introduction of a steric clash. Computational experiments confirm the role of this effect as a stereodeterminant since substrates with electropositive groups and electronegative groups have different conformational preferences at the transition state and undergo ring closure with divergent stereochemical outcomes. This predicted reversal of stereoselectivity for the ring closures of several silyl substituted azatrienes have been demonstrated experimentally.

  19. Efficient Computation of Transition State Resonances and Reaction Rates from a Quantum Normal Form

    NARCIS (Netherlands)

    Schubert, Roman; Waalkens, Holger; Wiggins, Stephen

    2006-01-01

    A quantum version of a recent formulation of transition state theory in phase space is presented. The theory developed provides an algorithm to compute quantum reaction rates and the associated Gamov-Siegert resonances with very high accuracy. The algorithm is especially efficient for

  20. Educational Transitions in the United States: Reflections on the American Dream

    Science.gov (United States)

    Crawford, Paul T.

    2012-01-01

    Education involves socialization so that individuals become productive members of society. At present, in the United States, educational transitions are primarily viewed in terms of their location in an outcomes-oriented process and framed as helping people achieve the American Dream, but in terms of the status quo national economic interest. But…

  1. Wigner's dynamical transition state theory in phase space : classical and quantum

    NARCIS (Netherlands)

    Waalkens, Holger; Schubert, Roman; Wiggins, Stephen

    We develop Wigner's approach to a dynamical transition state theory in phase space in both the classical and quantum mechanical settings. The key to our development is the construction of a normal form for describing the dynamics in the neighbourhood of a specific type of saddle point that governs

  2. Approaches to incorporating climate change effects in state and transition simulation models of vegetation

    Science.gov (United States)

    Becky K. Kerns; Miles A. Hemstrom; David Conklin; Gabriel I. Yospin; Bart Johnson; Dominique Bachelet; Scott Bridgham

    2012-01-01

    Understanding landscape vegetation dynamics often involves the use of scientifically-based modeling tools that are capable of testing alternative management scenarios given complex ecological, management, and social conditions. State-and-transition simulation model (STSM) frameworks and software such as PATH and VDDT are commonly used tools that simulate how landscapes...

  3. State-and-transition model archetypes: a global taxonomy of rangeland change

    Science.gov (United States)

    State and transition models (STMs) synthesize science-based and local knowledge to formally represent the dynamics of rangeland and other ecosystems. Mental models or concepts of ecosystem dynamics implicitly underlie all management decisions in rangelands and thus how people influence rangeland sus...

  4. Forecasting timber, biomass, and tree carbon pools with the output of state and transition models

    Science.gov (United States)

    Xiaoping Zhou; Miles A. Hemstrom

    2012-01-01

    The Integrated Landscape Assessment Project (ILAP) uses spatial vegetation data and state and transition models (STM) to forecast future vegetation conditions and the interacting effects of natural disturbances and management activities. Results from ILAP will help land managers, planners, and policymakers evaluate management strategies that reduce fire risk, improve...

  5. The Multi-state Latent Factor Intensity Model for Credit Rating Transitions

    NARCIS (Netherlands)

    Koopman, S.J.; Lucas, A.; Monteiro, A.

    2008-01-01

    A new empirical reduced-form model for credit rating transitions is introduced. It is a parametric intensity-based duration model with multiple states and driven by exogenous covariates and latent dynamic factors. The model has a generalized semi-Markov structure designed to accommodate many of the

  6. Theory of pure rotational transitions in doubly degenerate torsional states of ethane

    Science.gov (United States)

    Rosenberg, A.; Susskind, J.

    1979-01-01

    It is shown that pure rotational transitions in doubly degenerate torsional states of C2H6 (with selection rules Delta K = 0, plus or minus 1) are made allowed by Coriolis interaction between torsion and dipole-allowed vibrations. Expressions are presented for integrated intensities from which strengths of lines in the millimeter region can be calculated.

  7. The transition between undiluted and oligomer-diluted states of nearly monodisperse polystyrenes in extensional flow

    DEFF Research Database (Denmark)

    Huang, Qian; Rasmussen, Henrik K.

    2017-01-01

    , proposed by Rasmussen and Huang (Rheol Acta 53(3):199–208 (2014a)), predicts the extensional viscosity well for the dilutions with lower concentrations. However, for the 70 and 90% 545 kg/mole samples which represent the transition between the diluted and undiluted states, the model predictions are less...

  8. Molecular dynamics simulations from putative transition states of alpha-spectrin SH3 domain

    NARCIS (Netherlands)

    Periole, Xavier; Vendruscolo, Michele; Mark, Alan E.

    2007-01-01

    A series of molecular dynamics simulations in explicit solvent were started from nine structural models of the transition state of the SH3 domain of alpha-spectrin, which were generated by Lindorff Larsen et al. (Nat Struct Mol Biol 2004;11:443-449) using molecular dynamics simulations in which

  9. Molecular isomerization induced by ultrashort infrared pulses. II. Pump-dump isomerization using pairs of time-delayed half-cycle pulses.

    Science.gov (United States)

    Uiberacker, Christoph; Jakubetz, Werner

    2004-06-22

    We investigate population transfer across the barrier in a double-well potential, induced by a pair of time-delayed single-lobe half-cycle pulses. We apply this setup both to a one-dimensional (1D) quartic model potential and to a three-dimensional potential representing HCN-->HNC isomerization. Overall the results for the two systems are similar, although in the 3D system some additional features appear not seen in the 1D case. The generic mechanism of population transfer is the preparation by the pump pulse of a wave packet involving delocalized states above the barrier, followed by the essentially 1D motion of the delocalized part of wave packet across the barrier, and the eventual de-excitation by the dump pulse to localized states in the other well. The correct timing is given by the well-to-well passage time of the wave packet and its recurrence properties, and by the signs of the field lobes which determine the direction and acceleration or deceleration of the wave packet motion. In the 3D system an additional pump-pump-dump mechanism linked to wave packet motion in the reagent well can mediate isomerization. Since the transfer time and the pulse durations are of the same order of magnitude, there is also a marked dependence of the dynamics and the transfer yield on the pulse duration. Our analysis also sheds light on the pronounced carrier envelope phase dependence previously observed for isomerization and molecular dissociation with one-cycle and sub-one-cycle pulses. (c) 2004 American Institute of Physics.

  10. Transition by breaking of analyticity in the ground state of Josephson junction arrays as a static signature of the vortex jamming transition

    KAUST Repository

    Nogawa, Tomoaki; Yoshino, Hajime; Kim, Bongsoo

    2012-01-01

    -dimensional periodicity whose reciprocal lattice vector depends on λ and is incommensurate with the substrate lattice. Approaching the isotropic point λ=1, the so-called hull function of the ground state exhibits analyticity breaking similar to the Aubry transition

  11. The coherent state variational algorithm and the QCD deconfinement phase transition

    International Nuclear Information System (INIS)

    Somsky, W.R.

    1989-01-01

    This thesis describes the coherent state variational algorithm, its implementation in a recently completed set of computer programs, and its application to the study of the QCD deconfinement phase transition. The coherent state variational algorithm is a computational method for studying the large-N limit of non-abelian gauge theories by direct exploitation of the classical nature of this limit. Unlike Monte Carlo methods, this technique is applicable to both euclidean and hamiltonian formulations of lattice gauge theories and is deterministic, rather than statistical, in nature. The first part of this thesis presents the theoretical basis of the coherent state algorithm and describes the application of the algorithm, to non-abelian lattice gauge theories. The second part describes the symbolic methods involved in the computer implementation of the coherent state algorithm and gives an overview of the programs which form the full coherent state implementation. The final part of this thesis discusses the application of the coherent state algorithm to the study of the QCD deconfinement phase transition at large N. The results obtained are indicative of a second-order transition for lattices of temporal extent N ν = 1 and N τ = 2 in both three and four space-time dimensions

  12. Grassland to shrubland state transitions enhance carbon sequestration in the northern Chihuahuan Desert.

    Science.gov (United States)

    Petrie, M D; Collins, S L; Swann, A M; Ford, P L; Litvak, M E

    2015-03-01

    The replacement of native C4 -dominated grassland by C3 -dominated shrubland is considered an ecological state transition where different ecological communities can exist under similar environmental conditions. These state transitions are occurring globally, and may be exacerbated by climate change. One consequence of the global increase in woody vegetation may be enhanced ecosystem carbon sequestration, although the responses of arid and semiarid ecosystems may be highly variable. During a drier than average period from 2007 to 2011 in the northern Chihuahuan Desert, we found established shrubland to sequester 49 g C m(-2) yr(-1) on average, while nearby native C4 grassland was a net source of 31 g C m(-2) yr(-1) over this same period. Differences in C exchange between these ecosystems were pronounced--grassland had similar productivity compared to shrubland but experienced higher C efflux via ecosystem respiration, while shrubland was a consistent C sink because of a longer growing season and lower ecosystem respiration. At daily timescales, rates of carbon exchange were more sensitive to soil moisture variation in grassland than shrubland, such that grassland had a net uptake of C when wet but lost C when dry. Thus, even under unfavorable, drier than average climate conditions, the state transition from grassland to shrubland resulted in a substantial increase in terrestrial C sequestration. These results illustrate the inherent tradeoffs in quantifying ecosystem services that result from ecological state transitions, such as shrub encroachment. In this case, the deleterious changes to ecosystem services often linked to grassland to shrubland state transitions may at least be partially offset by increased ecosystem carbon sequestration. © 2014 John Wiley & Sons Ltd.

  13. Heterogeneous distribution of water in the mantle transition zone beneath United States inferred from seismic observations

    Science.gov (United States)

    Wang, Y.; Pavlis, G. L.; Li, M.

    2017-12-01

    The amount of water in the Earth's deep mantle is critical for the evolution of the solid Earth and the atmosphere. Mineral physics studies have revealed that Wadsleyite and Ringwoodite in the mantle transition zone could store several times the volume of water in the ocean. However, the water content and its distribution in the transition zone remain enigmatic due to lack of direct observations. Here we use seismic data from the full deployment of the Earthscope Transportable Array to produce 3D image of P to S scattering of the mantle transition zone beneath the United States. We compute the image volume from 141,080 pairs of high quality receiver functions defined by the Earthscope Automated Receiver Survey, reprocessed by the generalized iterative deconvolution method and imaged by the plane wave migration method. We find that the transition zone is filled with previously unrecognized small-scale heterogeneities that produce pervasive, negative polarity P to S conversions. Seismic synthetic modeling using a point source simulation method suggests two possible structures for these objects: 1) a set of randomly distributed blobs of slight difference in size, and 2) near vertical diapir structures from small scale convections. Combining with geodynamic simulations, we interpret the observation as compositional heterogeneity from small-scale, low-velocity bodies that are water enriched. Our results indicate there is a heterogeneous distribution of water through the entire mantle transition zone beneath the contiguous United States.

  14. Phase transitions of sodium niobate powder and ceramics, prepared by solid state synthesis

    Science.gov (United States)

    Koruza, J.; Tellier, J.; Malič, B.; Bobnar, V.; Kosec, M.

    2010-12-01

    Phase transitions of sodium niobate, prepared by the solid state synthesis method, were examined using dielectric measurements, differential scanning calorimetry, and high temperature x-ray diffraction, in order to contribute to the clarification of its structural behavior below 400 °C. Four phase transitions were detected in the ceramic sample using dielectric measurements and differential scanning calorimetry and the obtained temperatures were in a good agreement with previous reports for the transitions of the P polymorph. The anomaly observed by dielectric measurements in the vicinity of 150 °C was frequency dependent and could be related to the dynamics of the ferroelectric nanoregions. The phase transitions of the as-synthesized NaNbO3 powder were investigated using differential scanning calorimetry and high temperature x-ray diffraction. The results show the existence of the Q polymorph at room temperature, not previously reported for the powder, which undergoes a transition to the R polymorph upon heating through a temperature region between 265 and 326.5 °C. This transition is mainly related to the displacement of Na into a more symmetric position and a minor change in the tilting system. The structures at room temperature, 250, 300, and 420 °C were refined by the Rietveld method and the evolution of the tilting system of the octahedral network and cationic displacement are reported.

  15. Phase transitions of sodium niobate powder and ceramics, prepared by solid state synthesis

    International Nuclear Information System (INIS)

    Koruza, J.; Tellier, J.; Malic, B.; Bobnar, V.; Kosec, M.

    2010-01-01

    Phase transitions of sodium niobate, prepared by the solid state synthesis method, were examined using dielectric measurements, differential scanning calorimetry, and high temperature x-ray diffraction, in order to contribute to the clarification of its structural behavior below 400 deg. C. Four phase transitions were detected in the ceramic sample using dielectric measurements and differential scanning calorimetry and the obtained temperatures were in a good agreement with previous reports for the transitions of the P polymorph. The anomaly observed by dielectric measurements in the vicinity of 150 deg. C was frequency dependent and could be related to the dynamics of the ferroelectric nanoregions. The phase transitions of the as-synthesized NaNbO 3 powder were investigated using differential scanning calorimetry and high temperature x-ray diffraction. The results show the existence of the Q polymorph at room temperature, not previously reported for the powder, which undergoes a transition to the R polymorph upon heating through a temperature region between 265 and 326.5 deg. C. This transition is mainly related to the displacement of Na into a more symmetric position and a minor change in the tilting system. The structures at room temperature, 250, 300, and 420 deg. C were refined by the Rietveld method and the evolution of the tilting system of the octahedral network and cationic displacement are reported.

  16. Capturing the state transitions of seizure-like events using Hidden Markov models.

    Science.gov (United States)

    Guirgis, Mirna; Serletis, Demitre; Carlen, Peter L; Bardakjian, Berj L

    2011-01-01

    The purpose of this study was to investigate the number of states present in the progression of a seizure-like event (SLE). Of particular interest is to determine if there are more than two clearly defined states, as this would suggest that there is a distinct state preceding an SLE. Whole-intact hippocampus from C57/BL mice was used to model epileptiform activity induced by the perfusion of a low Mg(2+)/high K(+) solution while extracellular field potentials were recorded from CA3 pyramidal neurons. Hidden Markov models (HMM) were used to model the state transitions of the recorded SLEs by incorporating various features of the Hilbert transform into the training algorithm; specifically, 2- and 3-state HMMs were explored. Although the 2-state model was able to distinguish between SLE and nonSLE behavior, it provided no improvements compared to visual inspection alone. However, the 3-state model was able to capture two distinct nonSLE states that visual inspection failed to discriminate. Moreover, by developing an HMM based system a priori knowledge of the state transitions was not required making this an ideal platform for seizure prediction algorithms.

  17. EVIDENCE OF LIGHT-BENDING EFFECTS AND ITS IMPLICATION FOR SPECTRAL STATE TRANSITIONS

    International Nuclear Information System (INIS)

    Reis, R. C.; Miller, J. M.; Reynolds, M. T.; Fabian, A. C.; Walton, D. J.; Steiner, J. F.; Cackett, E.

    2013-01-01

    It has long been speculated that the nature of the hard X-ray corona may be an important second driver of black hole state transitions, in addition to the mass accretion rate through the disk. However, a clear physical picture of coronal changes has not yet emerged. We present results from a systematic analysis of Rossi X-Ray Timing Explorer observations of the stellar-mass black hole binary XTE J1650-500. All spectra with significant hard X-ray detections were fit using a self-consistent, relativistically blurred disk reflection model suited to high ionization regimes. Importantly, we find evidence that both the spectral and timing properties of black hole states may be partially driven by the height of the X-ray corona above the disk, and related changes in how gravitational light bending affects the corona-disk interaction. Specifically, the evolution of the power-law, thermal disk, and relativistically convolved reflection components in our spectral analysis indicates that: (1) the disk inner radius remains constant at r in =1.65 ± 0.08 GM/c 2 (consistent with values found for the ISCO of XTE J1650-500 in other works) throughout the transition from the brighter phases of the low-hard state to the intermediate states (both the hard-intermediate and soft-intermediate), through to the soft state and back; (2) the ratio between the observed reflected X-ray flux and power-law continuum (the 'reflection fraction', R) increases sharply at the transition between the hard-intermediate and soft-intermediate states ('ballistic' jets are sometimes launched at this transition); (3) both the frequency and coherence of the high-frequency quasi-periodic oscillations observed in XTE J1650-500 increase with R. We discuss our results in terms of black hole states and the nature of black hole accretion flows across the mass scale.

  18. Density of phonon-fracton states of disordered solids in the vicinity of percolation phase transitions

    International Nuclear Information System (INIS)

    Korzhenevskii, A.L.; Luzhkov, A.A.

    1991-01-01

    The development of a theory of phase transitions in disordered materials is still one of the central problems in solid-state physics. The model of a percolation phase transition plays the same role among the models put forward to account for phase transitions in disordered media as does the Ising model for second-order phase transitions in ideal crystals. In addition to the clear picture of the processes occurring in the course of a percolation phase transition, a scaling theory has been developed and various techniques have been used to calculate the critical exponents describing the thermodynamics of a medium in the vicinity of the percolation threshold. The authors adopt a field-theoretic approach in a study of acoustic properties of disordered solids undergoing percolation phase transitions characterized by h ∼ 1. Among these transitions they concentrate on the case with the simplest type of striction interaction when the solution of a stochastic vector differential equation of motion describing the behavior of an elastic medium in the critical region can be reduced to a scalar equation. The results of their calculations by the field renormalization group method confirmed the existence of the scaling relationships between the critical exponents and also the conclusion on the nature of short- and long-wavelength vibrations near the percolation threshold, which follow from phenomenological considerations of the scaling theory. The values of the upper critical dimensionality and of the critical exponents of the problem are shown to differ from the values applicable to percolation phase transitions characterized by h much-lt 1

  19. Immigration transition and depressive symptoms: four major ethnic groups of midlife women in the United States.

    Science.gov (United States)

    Im, Eun-Ok; Chang, Sun Ju; Chee, Wonshik; Chee, Eunice; Mao, Jun James

    2015-01-01

    The purpose of this study was to explore the relationships between immigration transition and depressive symptoms among 1,054 midlife women in the United States. This was a secondary analysis of the data from two national Internet survey studies. Questions on background characteristics and immigration transition and the Depression Index for Midlife Women were used to collect the data. The data were analyzed using inferential statistics including multiple regressions. Immigrants reported lower numbers of symptoms and less severe symptoms than nonimmigrants (p immigration status were significant predictors of depressive symptoms (R(2) =.01, p <.05).

  20. Theory of collisional excitation transition between Rydberg states of atoms. Non-inertial mechanism

    International Nuclear Information System (INIS)

    Kaulakys, B.P.

    1982-01-01

    The transitions between highly states of an atom due to the collision of its core with another atom are considered. The cross sections of the change of highly excited electron angular momentum, in the case of the transitions when the main quantum number is constant, are expressed in terms of transport cross sections of the perturbing atom scattering on the ion of Rydberg atom. It is shown that the cross sections of the momentum mixing at thermal rapidities are lower than the cross sections of the atom-ion elastic scattering

  1. Chaotic state to self-organized critical state transition of serrated flow dynamics during brittle-to-ductile transition in metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C.; Wang, W. H.; Bai, H. Y., E-mail: hybai@aphy.iphy.ac.cn [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Sun, B. A. [Centre for Advanced Structural Materials, Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon Tong, Kowloon (Hong Kong)

    2016-02-07

    We study serrated flow dynamics during brittle-to-ductile transition induced by tuning the sample aspect ratio in a Zr-based metallic glass. The statistical analysis reveals that the serrated flow dynamics transforms from a chaotic state characterized by Gaussian-distribution serrations corresponding to stick-slip motion of randomly generated and uncorrelated single shear band and brittle behavior, into a self-organized critical state featured by intermittent scale-free distribution of shear avalanches corresponding to a collective motion of multiple shear bands and ductile behavior. The correlation found between serrated flow dynamics and plastic deformation might shed light on the plastic deformation dynamic and mechanism in metallic glasses.

  2. Classical to quantum mechanical tunneling mechanism crossover in thermal transitions between magnetic states.

    Science.gov (United States)

    Vlasov, Sergei; Bessarab, Pavel F; Uzdin, Valery M; Jónsson, Hannes

    2016-12-22

    Transitions between states of a magnetic system can occur by jumps over an energy barrier or by quantum mechanical tunneling through the energy barrier. The rate of such transitions is an important consideration when the stability of magnetic states is assessed for example for nanoscale candidates for data storage devices. The shift in transition mechanism from jumps to tunneling as the temperature is lowered is analyzed and a general expression derived for the crossover temperature. The jump rate is evaluated using a harmonic approximation to transition state theory. First, the minimum energy path for the transition is found with the geodesic nudged elastic band method. The activation energy for the jumps is obtained from the maximum along the path, a saddle point on the energy surface, and the eigenvalues of the Hessian matrix at that point as well as at the initial state minimum used to estimate the entropic pre-exponential factor. The crossover temperature for quantum mechanical tunneling is evaluated from the second derivatives of the energy with respect to orientation of the spin vector at the saddle point. The resulting expression is applied to test problems where analytical results have previously been derived, namely uniaxial and biaxial spin systems with two-fold anisotropy. The effect of adding four-fold anisotropy on the crossover temperature is demonstrated. Calculations of the jump rate and crossover temperature for tunneling are also made for a molecular magnet containing an Mn 4 group. The results are in excellent agreement with previously reported experimental measurements on this system.

  3. On matrix stabilisation of d- and f-transition metal ions in unstable oxidation states

    Energy Technology Data Exchange (ETDEWEB)

    Kiselev, Yurii M [Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

    2009-01-31

    The state-of-the-art in matrix stabilisation of d- and f-transition metal ions in unstable oxidation states is analysed. Main aspects of this problem concerning the genealogy of appropriate matrix systems are classified. Relevant examples are given and the data that contradict the scheme proposed are discussed. The thermodynamics of the matrix stabilisation effect is considered using the concept of isomorphic miscibility. The influence of defects and non-equilibrium on the matrix stabilisation effect is discussed. The problem of identification of the oxidation states in matrix systems is examined and various types of matrix systems are considered.

  4. Structure of transition nuclei states in fermion dynamic-symmetry model

    International Nuclear Information System (INIS)

    Baktybaev, K.; Kojlyk, N.O.; Romankulov, K.

    2007-01-01

    In the paper collective structures of osmium heavy isotopes nucleons are studied. Results of diagonalization of SO(6) symmetric Hamiltonian of fermion-dynamical symmetry-model are comparing with results of other phenomenological methods such as Bohr-Mottelson model and interacting bosons model. For heavy osmium isotopes not only collective excitations spectral bands but also for probability of E2-electromagnet transition are which are compared with existing experimental data. It is revealed, that complexity of state structure for examined nuclei is related with competition and interweaving of rotation and vibration states and also more complicated states of γ instable nature

  5. On matrix stabilisation of d- and f-transition metal ions in unstable oxidation states

    International Nuclear Information System (INIS)

    Kiselev, Yurii M

    2009-01-01

    The state-of-the-art in matrix stabilisation of d- and f-transition metal ions in unstable oxidation states is analysed. Main aspects of this problem concerning the genealogy of appropriate matrix systems are classified. Relevant examples are given and the data that contradict the scheme proposed are discussed. The thermodynamics of the matrix stabilisation effect is considered using the concept of isomorphic miscibility. The influence of defects and non-equilibrium on the matrix stabilisation effect is discussed. The problem of identification of the oxidation states in matrix systems is examined and various types of matrix systems are considered.

  6. Macroscopic Quantum States and Quantum Phase Transition in the Dicke Model

    International Nuclear Information System (INIS)

    Lian Jin-Ling; Zhang Yuan-Wei; Liang Jiu-Qing

    2012-01-01

    The energy spectrum of Dicke Hamiltonians with and without the rotating wave approximation for an arbitrary atom number is obtained analytically by means of the variational method, in which the effective pseudo-spin Hamiltonian resulting from the expectation value in the boson-field coherent state is diagonalized by the spin-coherent-state transformation. In addition to the ground-state energy, an excited macroscopic quantum-state is found corresponding to the south- and north-pole gauges of the spin-coherent states, respectively. Our results of ground-state energies in exact agreement with various approaches show that these models exhibit a zero-temperature quantum phase transition of the second order for any number of atoms, which was commonly considered as a phenomenon of the thermodynamic limit with the atom number tending to infinity. The critical behavior of the geometric phase is analyzed. (general)

  7. Improving gasoline quality produced from MIDOR light naphtha isomerization unit

    Directory of Open Access Journals (Sweden)

    M.F. Mohamed

    2017-03-01

    Full Text Available Isomerization process became one of the best gasoline production sources, as it gives a high octane product while saving environment from pollution impacts. This paper presents a practical study that aims to improve the gasoline quality and economic income of an existing light naphtha isomerization unit used for octane improvement. The study included selecting the optimum combination of isomerization unit equipment that gives better product specifications for a specified feed. Eight scenarios were studied and simulated to predict the product specs. The original studied unit is MIDOR light naphtha isomerization unit at Alexandria-Egypt that recycles the unconverted hexane (C6. The other studied scenarios were adding fractionators for separating feed iso-pentanes, and recycling unconverted pentanes, hexanes and/or combinations of these fractionators. The results show a change in octane number of gasoline product for a specific feed. Once through process with no extra fractionators has lower octane number of 81 while that with de-iso-pentanizer–de-pentanizer and de-hexanizer produces gasoline with 92.3 octane number. Detailed economic study was done to calculate the return on investment “ROI” for each process option based on equipment, utilities, feed and product prices. Once through simple isomerization unit had the lowest ROI of 14.3% per year while the combination of De-iso-pentanizer with the De-hexanizer had the best ROI of 26.6% per year.

  8. A universal indicator of critical state transitions in noisy complex networked systems.

    Science.gov (United States)

    Liang, Junhao; Hu, Yanqing; Chen, Guanrong; Zhou, Tianshou

    2017-02-23

    Critical transition, a phenomenon that a system shifts suddenly from one state to another, occurs in many real-world complex networks. We propose an analytical framework for exactly predicting the critical transition in a complex networked system subjected to noise effects. Our prediction is based on the characteristic return time of a simple one-dimensional system derived from the original higher-dimensional system. This characteristic time, which can be easily calculated using network data, allows us to systematically separate the respective roles of dynamics, noise and topology of the underlying networked system. We find that the noise can either prevent or enhance critical transitions, playing a key role in compensating the network structural defect which suffers from either internal failures or environmental changes, or both. Our analysis of realistic or artificial examples reveals that the characteristic return time is an effective indicator for forecasting the sudden deterioration of complex networks.

  9. Generic finite size scaling for discontinuous nonequilibrium phase transitions into absorbing states

    Science.gov (United States)

    de Oliveira, M. M.; da Luz, M. G. E.; Fiore, C. E.

    2015-12-01

    Based on quasistationary distribution ideas, a general finite size scaling theory is proposed for discontinuous nonequilibrium phase transitions into absorbing states. Analogously to the equilibrium case, we show that quantities such as response functions, cumulants, and equal area probability distributions all scale with the volume, thus allowing proper estimates for the thermodynamic limit. To illustrate these results, five very distinct lattice models displaying nonequilibrium transitions—to single and infinitely many absorbing states—are investigated. The innate difficulties in analyzing absorbing phase transitions are circumvented through quasistationary simulation methods. Our findings (allied to numerical studies in the literature) strongly point to a unifying discontinuous phase transition scaling behavior for equilibrium and this important class of nonequilibrium systems.

  10. Generating feasible transition paths for testing from an extended finite state machine (EFSM) with the counter problem

    OpenAIRE

    Kalaji, AS; Hierons, RM; Swift, S

    2009-01-01

    The extended finite state machine (EFSM) is a powerful approach for modeling state-based systems. However, testing from EFSMs is complicated by the existence of infeasible paths. One important problem is the existence of a transition with a guard that references a counter variable whose value depends on previous transitions. The presence of such transitions in paths often leads to infeasible paths. This paper proposes a novel approach to bypass the counter problem. The proposed approach is ev...

  11. State transition storyboards: A tool for designing the Goldstone solar system radar data acquisition system user interface software

    Science.gov (United States)

    Howard, S. D.

    1987-01-01

    Effective user interface design in software systems is a complex task that takes place without adequate modeling tools. By combining state transition diagrams and the storyboard technique of filmmakers, State Transition Storyboards were developed to provide a detailed modeling technique for the Goldstone Solar System Radar Data Acquisition System human-machine interface. Illustrations are included with a description of the modeling technique.

  12. Integrating continuous stocks and flows into state-and-transition simulation models of landscape change

    Science.gov (United States)

    Daniel, Colin J.; Sleeter, Benjamin M.; Frid, Leonardo; Fortin, Marie-Josée

    2018-01-01

    State-and-transition simulation models (STSMs) provide a general framework for forecasting landscape dynamics, including projections of both vegetation and land-use/land-cover (LULC) change. The STSM method divides a landscape into spatially-referenced cells and then simulates the state of each cell forward in time, as a discrete-time stochastic process using a Monte Carlo approach, in response to any number of possible transitions. A current limitation of the STSM method, however, is that all of the state variables must be discrete.Here we present a new approach for extending a STSM, in order to account for continuous state variables, called a state-and-transition simulation model with stocks and flows (STSM-SF). The STSM-SF method allows for any number of continuous stocks to be defined for every spatial cell in the STSM, along with a suite of continuous flows specifying the rates at which stock levels change over time. The change in the level of each stock is then simulated forward in time, for each spatial cell, as a discrete-time stochastic process. The method differs from the traditional systems dynamics approach to stock-flow modelling in that the stocks and flows can be spatially-explicit, and the flows can be expressed as a function of the STSM states and transitions.We demonstrate the STSM-SF method by integrating a spatially-explicit carbon (C) budget model with a STSM of LULC change for the state of Hawai'i, USA. In this example, continuous stocks are pools of terrestrial C, while the flows are the possible fluxes of C between these pools. Importantly, several of these C fluxes are triggered by corresponding LULC transitions in the STSM. Model outputs include changes in the spatial and temporal distribution of C pools and fluxes across the landscape in response to projected future changes in LULC over the next 50 years.The new STSM-SF method allows both discrete and continuous state variables to be integrated into a STSM, including interactions between

  13. Nuclear matter at high density: Phase transitions, multiquark states, and supernova outbursts

    International Nuclear Information System (INIS)

    Krivoruchenko, M. I.; Nadyozhin, D. K.; Rasinkova, T. L.; Simonov, Yu. A.; Trusov, M. A.; Yudin, A. V.

    2011-01-01

    Phase transition from hadronic matter to quark-gluon matter is discussed for various regimes of temperature and baryon number density. For small and medium densities, the phase transition is accurately described in the framework of the Field Correlation Method, whereas at high density predictions are less certain and leave room for the phenomenological models. We study formation of multiquark states (MQS) at zero temperature and high density. Relevant MQS components of the nuclear matter can be described using a previously developed formalism of the quark compound bags (QCB). Partialwave analysis of nucleon-nucleon scattering indicates the existence of 6QS which manifest themselves as poles of P matrix. In the framework of the QCB model, we formulate a self-consistent system of coupled equations for the nucleon and 6QS propagators in nuclear matter and the G matrix. The approach provides a link between high-density nuclear matter with the MQS components and the cumulative effect observed in reactions on the nuclei, which requires the admixture of MQS in the wave functions of nuclei kinematically. 6QS determines the natural scale of the density for a possible phase transition into theMQS phase of nuclear matter. Such a phase transition can lead to dynamic instability of newly born protoneutron stars and dramatically affect the dynamics of supernovae. Numerical simulations show that the phase transition may be a good remedy for the triggering supernova explosions in the spherically symmetric supernovamodels. A specific signature of the phase transition is an additional neutrino peak in the neutrino light curve. For a Galactic core-collapse supernova, such a peak could be resolved by the present neutrino detectors. The possibility of extracting the parameters of the phase of transition from observation of the neutrino signal is discussed also.

  14. Nuclear matter at high density: Phase transitions, multiquark states, and supernova outbursts

    Energy Technology Data Exchange (ETDEWEB)

    Krivoruchenko, M. I.; Nadyozhin, D. K.; Rasinkova, T. L.; Simonov, Yu. A.; Trusov, M. A., E-mail: trusov@itep.ru; Yudin, A. V. [Institute for Theoretical and Experimental Physics (Russian Federation)

    2011-03-15

    Phase transition from hadronic matter to quark-gluon matter is discussed for various regimes of temperature and baryon number density. For small and medium densities, the phase transition is accurately described in the framework of the Field Correlation Method, whereas at high density predictions are less certain and leave room for the phenomenological models. We study formation of multiquark states (MQS) at zero temperature and high density. Relevant MQS components of the nuclear matter can be described using a previously developed formalism of the quark compound bags (QCB). Partialwave analysis of nucleon-nucleon scattering indicates the existence of 6QS which manifest themselves as poles of P matrix. In the framework of the QCB model, we formulate a self-consistent system of coupled equations for the nucleon and 6QS propagators in nuclear matter and the G matrix. The approach provides a link between high-density nuclear matter with the MQS components and the cumulative effect observed in reactions on the nuclei, which requires the admixture of MQS in the wave functions of nuclei kinematically. 6QS determines the natural scale of the density for a possible phase transition into theMQS phase of nuclear matter. Such a phase transition can lead to dynamic instability of newly born protoneutron stars and dramatically affect the dynamics of supernovae. Numerical simulations show that the phase transition may be a good remedy for the triggering supernova explosions in the spherically symmetric supernovamodels. A specific signature of the phase transition is an additional neutrino peak in the neutrino light curve. For a Galactic core-collapse supernova, such a peak could be resolved by the present neutrino detectors. The possibility of extracting the parameters of the phase of transition from observation of the neutrino signal is discussed also.

  15. Accurate potential energy curves, spectroscopic parameters, transition dipole moments, and transition probabilities of 21 low-lying states of the CO+ cation

    Science.gov (United States)

    Xing, Wei; Shi, Deheng; Zhang, Jicai; Sun, Jinfeng; Zhu, Zunlue

    2018-05-01

    This paper calculates the potential energy curves of 21 Λ-S and 42 Ω states, which arise from the first two dissociation asymptotes of the CO+ cation. The calculations are conducted using the complete active space self-consistent field method, which is followed by the valence internally contracted multireference configuration interaction approach with the Davidson correction. To improve the reliability and accuracy of the potential energy curves, core-valence correlation and scalar relativistic corrections, as well as the extrapolation of potential energies to the complete basis set limit are taken into account. The spectroscopic parameters and vibrational levels are determined. The spin-orbit coupling effect on the spectroscopic parameters and vibrational levels is evaluated. To better study the transition probabilities, the transition dipole moments are computed. The Franck-Condon factors and Einstein coefficients of some emissions are calculated. The radiative lifetimes are determined for a number of vibrational levels of several states. The transitions between different Λ-S states are evaluated. Spectroscopic routines for observing these states are proposed. The spectroscopic parameters, vibrational levels, transition dipole moments, and transition probabilities reported in this paper can be considered to be very reliable and can be used as guidelines for detecting these states in an appropriate spectroscopy experiment, especially for the states that were very difficult to observe or were not detected in previous experiments.

  16. Isomerization and fluorescence depolarization of merocyanine 540 ...

    Indian Academy of Sciences (India)

    , ... polymers resemble globular proteins and can encapsulate hydrophobic solutes. ... PAA opens up due to electrostatic repulsion, the fluorescent probe becomes exposed to ... conformational transition of such polymers have been studied by ...

  17. The transition between energy efficient and energy inefficient states in Cameroon

    International Nuclear Information System (INIS)

    Adom, Philip Kofi

    2016-01-01

    I use a two-state (energy efficient/inefficient) Markov-switching dynamic model to study energy efficiency in Cameroon in a novel manner, employing yearly data covering 1971 to 2012. I find that the duration of an energy inefficient state is about twice as long as an energy efficient state, mainly due to fuel subsidies, low income, high corruption, regulatory inefficiencies, poorly developed infrastructure and undeveloped markets. To escape from an energy inefficient state a broad policy overhaul is needed. Trade liberalization and related growth policies together with the removal of fuel subsidies are useful, but insufficient policy measures; the results suggest that they should be combined with structural policies, aiming at institutional structure and investment in infrastructure. - Highlights: • I investigate the transition between energy efficient/inefficient states. • On the average, energy inefficient state persists more than energy efficient state. • The duration of energy inefficient state is about twice as long as energy efficient state. • Price, income and trade openness have distinct energy saving effect irrespective of state. • A broad policy overhaul is needed to escape the energy inefficient state.

  18. What factors are associated with state performance on provision of transition services to CSHCN?

    Science.gov (United States)

    Kane, Debra J; Kasehagen, Laurin; Punyko, Judy; Carle, Adam C; Penziner, Andy; Thorson, Sarah

    2009-12-01

    To examine whether individual, condition-related, and system-related characteristics are associated with state performance (high, medium, low) on the provision of transition services to children with special health care needs (CSHCN). We conducted descriptive, bivariate, and multivariable analyses of 16876 children aged 12 to 17 years by using data from the 2005-2006 National Survey of Children With Special Health Care Needs. Polytomous logistic regression was used to compare the characteristics of CSHCN residing within high-, medium-, and low-performance states, with low-performance states serving as the reference group. Compared with non-Hispanic white CSHCN, Hispanic (adjusted odds ratio [aOR]: 0.25 [95% confidence interval (CI): 0.17-0.37]) and non-Hispanic black (aOR: 0.44 [95% CI: 0.30-0.62]) CSHCN were less likely to reside in a high-performance than in a low-performance state. Compared with CSHCN who had a medical home or adequate insurance coverage, CSHCN who did not have a medical home or adequate insurance coverage were less likely to reside in a high-performance than in a low-performance state (aOR: 0.73 [95% CI: 0.57-0.95]; aOR: 0.73 [95% CI: 0.58-0.93], respectively). Key factors found to be important in a state's performance on provision of transition services to CSHCN were race/ethnicity and having a medical home and adequate insurance coverage. Efforts to support the Maternal and Child Health Bureau's integration of system-level factors in quality-improvement activities, particularly establishing a medical home and attaining and maintaining adequate insurance, are likely to help states improve their performance on provision of transition services.

  19. Study of radicals, clusters and transition state species by anion photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, Don Wesley [Univ. of California, Berkeley, CA (United States)

    1994-08-01

    Free radicals, elemental and van der Waals clusters and transition state species for bimolecular chemical reactions are investigated using anion photoelectron spectroscopy. Several low-lying electronic states of ozone have been identified via photoelectron spectroscopy of O3-. A characterization of these states is important to models for atmospheric ozone reaction kinetics. The fluoroformyloxyl radical, FCO2, has been investigated, providing vibrational frequencies and energies for two electronic states. The technique has also been employed to make the first direct observation and characterization of the NNO2 molecule. Several electronic states are observed for this species which is believed to play a role as a reactive intermediate in the N + NO2 reaction. The experimental results for all three of these radicals are supplemented by ab initio investigations of their molecular properties. The clusters investigations include studies of elemental carbon clusters (C2- - C11-), and van der Waals clusters (X-(CO2)n, X = I, Br, Cl; n {le} 13 and I- (N2O)n=1--11). Primarily linear clusters are observed for the smaller carbon clusters, while the spectra of the larger clusters contain contribution from cyclic anion photodetachment. Very interesting ion-solvent interactions are observed in the X-(CO2)n clusters. The transition state regions for several bimolecular chemical reactions have also been investigated by photodetachment of a negative ion precursor possessing a geometry similar to that of the transition state species. These spectra show features which are assigned to motions of the unstable neutral complex existing between reactants and products.

  20. Study of radicals, clusters and transition state species by anion photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Arnold, D.W.

    1994-08-01

    Free radicals, elemental and van der Waals clusters and transition state species for bimolecular chemical reactions are investigated using anion photoelectron spectroscopy. Several low-lying electronic states of ozone have been identified via photoelectron spectroscopy of O 3 - . A characterization of these states is important to models for atmospheric ozone reaction kinetics. The fluoroformyloxyl radical, FCO 2 , has been investigated, providing vibrational frequencies and energies for two electronic states. The technique has also been employed to make the first direct observation and characterization of the NNO 2 molecule. Several electronic states are observed for this species which is believed to play a role as a reactive intermediate in the N + NO 2 reaction. The experimental results for all three of these radicals are supplemented by ab initio investigations of their molecular properties. The clusters investigations include studies of elemental carbon clusters (C 2 - - C 11 - ), and van der Waals clusters (X - (CO 2 ) n , X = I, Br, Cl; n ≤ 13 and I - (N 2 O) n=1--11 ). Primarily linear clusters are observed for the smaller carbon clusters, while the spectra of the larger clusters contain contribution from cyclic anion photodetachment. Very interesting ion-solvent interactions are observed in the X - (CO 2 )n clusters. The transition state regions for several bimolecular chemical reactions have also been investigated by photodetachment of a negative ion precursor possessing a geometry similar to that of the transition state species. These spectra show features which are assigned to motions of the unstable neutral complex existing between reactants and products

  1. Radiochemical study of isomerization of free butyl cations

    International Nuclear Information System (INIS)

    Sinotova, E.N.; Nefedov, V.D.; Skorokhodov, S.S.; Arkhipov, Yu.M.

    1987-01-01

    Ion-molecular reactions of free butyl cations, generated by nuclear chemical method, with carbon monoxide containing small quantities of ethanol vapors are studied. Carbon monoxide was used to fix instable butyl cations in the form of corresponding acyl ions. Ester of α-methyl-butyric acid appears to be the only product of free butyl cation interaction with carbon monoxide in the presence of ethanol vapors. That means, that up to the moment of butyl cation reaction with carbon monoxide, the primary butyl cations are almost completely isomerized into secondary in agreement with results of previous investigations. This allows one to study free butyl cation isomerization process according to ion-molecular reaction product isomeric composition

  2. Pressure controlled transition into a self-induced topological superconducting surface state

    KAUST Repository

    Zhu, Zhiyong; Cheng, Yingchun; Schwingenschlö gl, Udo

    2014-01-01

    Ab-initio calculations show a pressure induced trivial-nontrivial-trivial topological phase transition in the normal state of 1T-TiSe2. The pressure range in which the nontrivial phase emerges overlaps with that of the superconducting ground state. Thus, topological superconductivity can be induced in protected surface states by the proximity effect of superconducting bulk states. This kind of self-induced topological surface superconductivity is promising for a realization of Majorana fermions due to the absence of lattice and chemical potential mismatches. For appropriate electron doping, the formation of the topological superconducting surface state in 1T-TiSe 2 becomes accessible to experiments as it can be controlled by pressure.

  3. Pressure controlled transition into a self-induced topological superconducting surface state

    KAUST Repository

    Zhu, Zhiyong

    2014-02-07

    Ab-initio calculations show a pressure induced trivial-nontrivial-trivial topological phase transition in the normal state of 1T-TiSe2. The pressure range in which the nontrivial phase emerges overlaps with that of the superconducting ground state. Thus, topological superconductivity can be induced in protected surface states by the proximity effect of superconducting bulk states. This kind of self-induced topological surface superconductivity is promising for a realization of Majorana fermions due to the absence of lattice and chemical potential mismatches. For appropriate electron doping, the formation of the topological superconducting surface state in 1T-TiSe 2 becomes accessible to experiments as it can be controlled by pressure.

  4. Single-step linking transition from superdeformed to spherical states in {sup 143}Eu

    Energy Technology Data Exchange (ETDEWEB)

    Atac, A.; Axelsson, A.; Persson, J. [Uppsala Univ. (Sweden)] [and others

    1996-12-31

    A discrete {gamma}-ray transition which connects the second lowest SD state with a normally deformed one in {sup 143}Eu has been discovered. It has an energy of 3360.6 keV and carries 3.2 % of the full intensity of the SD band. It feeds into a nearly spherical state which is above the I = 35/2{sup +}, E=4947 keV level. The exact placement of the single-step link could, however, not be established due to the especially complicated level scheme in the region of interest. The angular correlation study favours a stretched dipole character for the 3360.6 keV transition. The single-step link agrees well with the previously determined two-step links, both with respect to energy and spin.

  5. An expression of excess work during the transition between nonequilibrium steady states

    International Nuclear Information System (INIS)

    Yuge, Tatsuro

    2014-01-01

    Excess work is a nondiverging part of the work during the transition between nonequilibrium steady states (NESSs). It is a central quantity in steady-state thermodynamics (SST), which is a candidate for nonequilibrium thermodynamics theory. We derive an expression of excess work during quasistatic transitions between NESSs by using the macroscopic linear response relation of the NESS. This expression is a line integral of a vector potential in the space of control parameters. We show a relationship between the vector potential and the response function of the NESS, and thus obtain a relationship between the SST and a macroscopic quantity. We also connect the macroscopic formulation to microscopic physics through a microscopic expression of the nonequilibrium response function, which gives a result that is consistent with previous studies. (paper)

  6. Heat capacity for systems with excited-state quantum phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Cejnar, Pavel; Stránský, Pavel, E-mail: stransky@ipnp.troja.mff.cuni.cz

    2017-03-18

    Heat capacities of model systems with finite numbers of effective degrees of freedom are evaluated using canonical and microcanonical thermodynamics. Discrepancies between both approaches, which are observed even in the infinite-size limit, are particularly large in systems that exhibit an excited-state quantum phase transition. The corresponding irregularity of the spectrum generates a singularity in the microcanonical heat capacity and affects smoothly the canonical heat capacity. - Highlights: • Thermodynamics of systems with excited-state quantum phase transitions • ESQPT-generated singularities of the microcanonical heat capacity • Non-monotonous dependences of the canonical heat capacity • Discord between canonical and microcanonical pictures in the infinite-size limit.

  7. On the valence state of Yb and Ce in transition metal intermetallic compounds

    International Nuclear Information System (INIS)

    Boer, F.R. de; Dijkman, W.H.; Mattens, W.C.M.

    1979-01-01

    In the pure state Yb is a divalent metal, similar to Ca; in alloys it can become trivalent like the majority of the rare earth metals. Using a value of 38 kJ (mol Yb) -1 for the energy difference between divalent and trivalent Yb metal and using model calculations for the heat of formation of intermetallic compounds, the authors are able to account for the existing information on the valence state of Yb in transition metal compounds. A similar analysis of compounds of Ce with transition metals shows that a model in which the 4f electron is treated as a core electron, i.e. being absent in the tetravalent modification of Ce and present as a fully localized electron in trivalent Ce, does not apply. (Auth.)

  8. Cyclic electron flow is redox-controlled but independent of state transition.

    Science.gov (United States)

    Takahashi, Hiroko; Clowez, Sophie; Wollman, Francis-André; Vallon, Olivier; Rappaport, Fabrice

    2013-01-01

    Photosynthesis is the biological process that feeds the biosphere with reduced carbon. The assimilation of CO2 requires the fine tuning of two co-existing functional modes: linear electron flow, which provides NADPH and ATP, and cyclic electron flow, which only sustains ATP synthesis. Although the importance of this fine tuning is appreciated, its mechanism remains equivocal. Here we show that cyclic electron flow as well as formation of supercomplexes, thought to contribute to the enhancement of cyclic electron flow, are promoted in reducing conditions with no correlation with the reorganization of the thylakoid membranes associated with the migration of antenna proteins towards Photosystems I or II, a process known as state transition. We show that cyclic electron flow is tuned by the redox power and this provides a mechanistic model applying to the entire green lineage including the vast majority of the cases in which state transition only involves a moderate fraction of the antenna.

  9. Chapter 5: Application of state-and-transition models to evaluate wildlife habitat

    Science.gov (United States)

    Anita T. Morzillo; Pamela Comeleo; Blair Csuti; Stephanie Lee

    2014-01-01

    Wildlife habitat analysis often is a central focus of natural resources management and policy. State-and-transition models (STMs) allow for simulation of landscape level ecological processes, and for managers to test “what if” scenarios of how those processes may affect wildlife habitat. This chapter describes the methods used to link STM output to wildlife habitat to...

  10. Regimes of radiative and nonradiative transitions in transport through an electronic system in a photon cavity reaching a steady state

    Science.gov (United States)

    Gudmundsson, Vidar; Jonsson, Thorsteinn H.; Bernodusson, Maria Laura; Abdullah, Nzar Rauf; Sitek, Anna; Goan, Hsi-Sheng; Tang, Chi-Shung; Manolescu, Andrei

    2017-01-01

    We analyze how a multilevel many-electron system in a photon cavity approaches the steady state when coupled to external leads. When a plunger gate is used to lower cavity photon dressed one- and two-electron states below the bias window defined by the external leads, we can identify one regime with nonradiative transitions dominating the electron transport, and another regime with radiative transitions. Both transitions trap the electrons in the states below the bias bringing the system into a steady state. The order of the two regimes and their relative strength depends on the location of the bias window in the energy spectrum of the system and the initial conditions.

  11. cis–trans Isomerization of silybins A and B

    Directory of Open Access Journals (Sweden)

    Michaela Novotná

    2014-05-01

    Full Text Available Methods were developed and optimized for the preparation of the 2,3-cis- and the 10,11-cis-isomers of silybin by the Lewis acid catalyzed (BF3∙OEt2 isomerization of silybins A (1a and B (1b (trans-isomers. The absolute configuration of all optically pure compounds was determined by using NMR and comparing their electronic circular dichroism data with model compounds of known absolute configurations. Mechanisms for cis–trans-isomerization of silybin are proposed and supported by quantum mechanical calculations.

  12. Photoemission from solids: the transition from solid-state to atomic physics

    International Nuclear Information System (INIS)

    Shirley, D.A.

    1980-08-01

    As the photon energy is increased, photoemission from solids undergoes a slow transition from solid-state to atomic behavior. However, throughout the energy range hν = 10 to 1000 eV or higher both types of phenomena are present. Thus angle-resolved photoemission can only be understood quantitatively if each experimenter recognizes the presence of band-structure, photoelectron diffraction, and photoelectron asymmetry effects. The quest for this understanding will build some interesting bridges between solid-state and atomic physics and should also yield important new insights about the phenomena associated with photoemission

  13. State-and-transition prototype model of riparian vegetation downstream of Glen Canyon Dam, Arizona

    Science.gov (United States)

    Ralston, Barbara E.; Starfield, Anthony M.; Black, Ronald S.; Van Lonkhuyzen, Robert A.

    2014-01-01

    Facing an altered riparian plant community dominated by nonnative species, resource managers are increasingly interested in understanding how to manage and promote healthy riparian habitats in which native species dominate. For regulated rivers, managing flows is one tool resource managers consider to achieve these goals. Among many factors that can influence riparian community composition, hydrology is a primary forcing variable. Frame-based models, used successfully in grassland systems, provide an opportunity for stakeholders concerned with riparian systems to evaluate potential riparian vegetation responses to alternative flows. Frame-based, state-and-transition models of riparian vegetation for reattachment bars, separation bars, and the channel margin found on the Colorado River downstream of Glen Canyon Dam were constructed using information from the literature. Frame-based models can be simple spreadsheet models (created in Microsoft® Excel) or developed further with programming languages (for example, C-sharp). The models described here include seven community states and five dam operations that cause transitions between states. Each model divides operations into growing (April–September) and non-growing seasons (October–March) and incorporates upper and lower bar models, using stage elevation as a division. The inputs (operations) can be used by stakeholders to evaluate flows that may promote dynamic riparian vegetation states, or identify those flow options that may promote less desirable states (for example, Tamarisk [Tamarix sp.] temporarily flooded shrubland). This prototype model, although simple, can still elicit discussion about operational options and vegetation response.

  14. Magnetic states, correlation effects and metal-insulator transition in FCC lattice

    Science.gov (United States)

    Timirgazin, M. A.; Igoshev, P. A.; Arzhnikov, A. K.; Irkhin, V. Yu

    2016-12-01

    The ground-state magnetic phase diagram (including collinear and spiral states) of the single-band Hubbard model for the face-centered cubic lattice and related metal-insulator transition (MIT) are investigated within the slave-boson approach by Kotliar and Ruckenstein. The correlation-induced electron spectrum narrowing and a comparison with a generalized Hartree-Fock approximation allow one to estimate the strength of correlation effects. This, as well as the MIT scenario, depends dramatically on the ratio of the next-nearest and nearest electron hopping integrals {{t}\\prime}/t . In contrast with metallic state, possessing substantial band narrowing, insulator one is only weakly correlated. The magnetic (Slater) scenario of MIT is found to be superior over the Mott one. Unlike simple and body-centered cubic lattices, MIT is the first order transition (discontinuous) for most {{t}\\prime}/t . The insulator state is type-II or type-III antiferromagnet, and the metallic state is spin-spiral, collinear antiferromagnet or paramagnet depending on {{t}\\prime}/t . The picture of magnetic ordering is compared with that in the standard localized-electron (Heisenberg) model.

  15. β decay and isomeric properties of neutron-rich Ca and Sc isotopes

    International Nuclear Information System (INIS)

    Crawford, H. L.; Mantica, P. F.; Berryman, J. S.; Stoker, J. B.; Janssens, R. V. F.; Carpenter, M. P.; Kay, B. P.; Lauritsen, T.; Zhu, S.; Broda, R.; Cieplicka, N.; Fornal, B.; Grinyer, G. F.; Minamisono, K.; Hoteling, N.; Stefanescu, I.; Walters, W. B.

    2010-01-01

    The isomeric and β-decay properties of neutron-rich 53-57 Sc and 53,54 Ca nuclei near neutron number N=32 are reported, and the low-energy level schemes of 53,54,56 Sc and 53-57 Ti are presented. The low-energy level structures of the 21 Sc isotopes are discussed in terms of the coupling of the valence 1f 7/2 proton to states in the corresponding 20 Ca cores. Implications with respect to the robustness of the N=32 subshell closure are discussed, as well as the repercussions for a possible N=34 subshell closure.

  16. Isomeric N-Annulated Perylene Diimide Dimers for Organic Solar Cells.

    Science.gov (United States)

    Ma, Zetong; Fu, Huiting; Meng, Dong; Jiang, Wei; Sun, Yanming; Wang, Zhaohui

    2018-04-16

    Two isomeric N-annulated perylene diimide dimers, namely, p-BDNP and m-BDNP were designed and synthesized via geometric tuning. The distinct molecular geometry and packing arrangements of isomers with almost identical optical and electrochemical properties rendered us an in-depth understanding of the molecular structure-aggregation state-photovoltaic performance relationship. Blended with the commercially available donor PCE-10, p-BDNP and m-BDNP showed distinct differences in photovoltaic performance with power conversion efficiencies (PCEs) of 5.01 % and 4.15 %, respectively. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Transient transition from free carrier metallic state to exciton insulating state in GaAs by ultrafast photoexcitation

    Science.gov (United States)

    Nie, X. C.; Song, Hai-Ying; Zhang, Xiu; Gu, Peng; Liu, Shi-Bing; Li, Fan; Meng, Jian-Qiao; Duan, Yu-Xia; Liu, H. Y.

    2018-03-01

    We present systematic studies of the transient dynamics of GaAs by ultrafast time-resolved reflectivity. In photoexcited non-equilibrium states, we found a sign reverse in reflectivity change ΔR/R, from positive around room temperature to negative at cryogenic temperatures. The former corresponds to a free carrier metallic state, while the latter is attributed to an exciton insulating state, in which the transient electronic properties is mostly dominated by excitons, resulting in a transient metal–insulator transition (MIT). Two transition temperatures (T 1 and T 2) are well identified by analyzing the intensity change of the transient reflectivity. We found that photoexcited MIT starts emerging at T 1 as high as ∼ 230 K, in terms of a dip feature at 0.4 ps, and becomes stabilized below T 2 that is up to ∼ 180 K, associated with a negative constant after 40 ps. Our results address a phase diagram that provides a framework for the inducing of MIT through temperature and photoexcitation, and may shed light on the understanding of light-semiconductor interaction and exciton physics.

  18. First identification of the 02+ state in 30Mg via its E0 transition

    International Nuclear Information System (INIS)

    Schwerdtfeger, Wolfgang Norbert Erik

    2008-01-01

    The known 1789 keV level in 30 Mg turned out to be a candidate for the 0 2 + state due to its long lifetime of 3.9(4) ns and the absence of a γ transition to the ground state. This triggered our search on the 0 2 + →0 1 + E0 transition in 30 Mg following the β decay of 30 Na: β decay electrons were detected in a scintillation detector, while conversion electrons were focused onto a cooled Si(Li) detector using a Mini-Orange and detected with high resolution, which simultaneously suppresses the high background of β decay electrons. Due to the large Q value of the β decay of 30 Na (17.3 MeV) the suppression of the coincident background induced by high-energy γ rays and subsequently Compton-scattered electrons turned out to be the key challenge for the success of this experiment. In order to optimise the background suppression and thus the sensitivity to weak E0 transitions, offline test measurements using an 90 Y and a 152 Eu source were performed together with GEANT4 simulations. Resulting from these test measurements a highly sensitive experimental setup was designed and built, consequently minimising the amount of high-Z material in the target chamber, reducing X-ray production. As a by-product from test measurements the database value of the half-life of the 0 2 + state in 90 Zr could be corrected by more than 30 % to be t 1/2 =41(1) ns. Finally, in a β decay experiment at the ISOLDE facility at CERN the 0 2 + →0 1 + E0 transition in 30 Mg could be identified at the expected transition energy of 1788 keV proving for the first time shape coexistence at the borderline of the 'Island of Inversion'. This identification allows to determine the electric monopole strength as ρ 2 (E0)=26.2(7.5) x 10 -3 , indicating a rather weak mixing between the states in two potential minima in a simplified two-level mixing model. This result allows to extract the mixing amplitude between the two 0 + states as a=0.179(83). This experimental finding represents the first

  19. State governance evolution in resource-rich transition economies: An application to Russia and Kazakhstan

    Energy Technology Data Exchange (ETDEWEB)

    Kalyuzhnova, Yelena; Nygaard, Christian [The Centre for Euro-Asian Studies, The University of Reading, Whiteknights, PO Box, Reading RG6 6AA (United Kingdom)

    2008-06-15

    Following a decade of transition in the Former Soviet Union (FSU), governance of the oil and gas sectors has evolved to economic nationalism. In the newly independent states this has manifested itself through greater (direct) state ownership or participation in oil and gas production, at the expense of both domestic (in the case of Russia) and international oil companies, as well as legislative developments that increase the flow of oil and gas value to the state. Here we analyse some of the dynamics giving rise to economic nationalism within a model of a state capacity and the ability to implement policy and extract value. Our analysis is based on the institutional and economic functioning of the oil and gas sector. We analyse a vector of institutions and examine Production Sharing Agreements and National Oil Companies. (author)

  20. Dynamics of SARS-coronavirus HR2 domain in the prefusion and transition states

    Science.gov (United States)

    McReynolds, Susanna; Jiang, Shaokai; Rong, Lijun; Caffrey, Michael

    2009-12-01

    The envelope glycoproteins S1 and S2 of severe acute respiratory syndrome coronavirus (SARS-CoV) mediate viral entry by conformational change from a prefusion state to a postfusion state that enables fusion of the viral and target membranes. In this work we present the characterization of the dynamic properties of the SARS-CoV S2-HR2 domain (residues 1141-1193 of S) in the prefusion and newly discovered transition states by NMR 15N relaxation studies. The dynamic properties of the different states, which are stabilized under different experimental conditions, extend the current model of viral membrane fusion and give insight into the design of structure-based antagonists of SARS-CoV in particular, as well as other enveloped viruses such as HIV.

  1. Unambiguously identifying spin states of transition-metal ions in the Earth (Invited)

    Science.gov (United States)

    Hsu, H.

    2010-12-01

    The spin state of a transition-metal ion in crystalline solids, defined by the number of unpaired electrons in the ion’s incomplete 3d shell, may vary with many factors, such as temperature, pressure, strain, and the local atomic configuration, to name a few. Such a phenomenon, known as spin-state crossover, plays a crucial role in spintronic materials. Recently, the pressure-induced spin-state crossover in iron-bearing minerals has been recognized to affect the minerals’ structural and elastic properties. However, the detailed mechanism of such crossover in iron-bearing magnesium silicate perovskite, the most abundant mineral in the Earth, remains unclear. A significant part of this confusion arises from the difficulty in reliably extracting the spin state from experiments. For the same reason, the thermally-induced spin-state crossover in lanthanum cobaltite (LaCoO3) has been controversial for more than four decades. In this talk, I will discuss how first-principle calculations can help clarifying these long-standing controversies. In addition to the total energy, equation of state, and elastic properties of each spin state, first-principle calculations also predict the electric field gradient (EFG) at the nucleus of each transition-metal ion. Our calculations showed that the nuclear EFG, a quantity that can be measured via Mössbauer or nuclear magnetic resonance (NMR) spectroscopy, depends primarily on the spin state, irrespective of the concentration or configuration of transition-metal ions. Such robustness makes EFG a unique fingerprint to identify the spin state. The combination of first-principle calculations and Mössbauer/NMR spectroscopy can therefore be a reliable and efficient approach in tackling spin-state crossover problems in the Earth. This work was primarily supported by the MRSEC Program of NSF under Awards Number DMR-0212302 and DMR-0819885, and partially supported by NSF under ATM-0428774 (V-Lab), EAR-1019853, and EAR-0810272. The

  2. Triggering of 178Hfm2 by photoinduced electron transition

    Directory of Open Access Journals (Sweden)

    A. Ya. Dzyublik

    2013-03-01

    Full Text Available We considered the NEET (nuclear excitation by electron transition as a possible triggering mechanism of the isomer 178Hfm2 during ionization of the L3 atomic shell by x-rays. This isomer is assumed to be excited into an intermediate state by E1 electronic transition between M5 and L3 shells. Simple nonrelativistic formulas are derived for the NEET probability. The estimations show the probability to be less than the experimental data of [1] by one order of magnitude. The intermediate level is found to decay bypassing the isomeric level 16+, if the nucleus attributes a triaxial shape in the state and, besides, there exists a level 13- shifted with respect to 15- by 400 keV. We have shown also that the NEET cross section as a function of the energy of x-ray photons , has to accept constant value above the L photoionization threshold in contrast to narrow peak observed by [1].

  3. Spectroscopic parameters, vibrational levels, transition dipole moments and transition probabilities of the 9 low-lying states of the NCl+ cation

    Science.gov (United States)

    Yin, Yuan; Shi, Deheng; Sun, Jinfeng; Zhu, Zunlue

    2018-03-01

    This work calculates the potential energy curves of 9 Λ-S and 28 Ω states of the NCl+ cation. The technique employed is the complete active space self-consistent field method, which is followed by the internally contracted multireference configuration interaction approach with the Davidson correction. The Λ-S states are X2Π, 12Σ+, 14Π, 14Σ+, 14Σ-, 24Π, 14Δ, 16Σ+, and 16Π, which are yielded from the first two dissociation channels of NCl+ cation. The Ω states are generated from these Λ-S states. The 14Π, 14Δ, 16Σ+, and 16Π states are inverted with the spin-orbit coupling effect included. The 14Σ+, 16Σ+, and 16Π states are very weakly bound, whose well depths are only several-hundred cm- 1. One avoided crossing of PECs occurs between the 12Σ+ and 22Σ+ states. To improve the quality of potential energy curves, core-valence correlation and scalar relativistic corrections are included. The potential energies are extrapolated to the complete basis set limit. The spectroscopic parameters and vibrational levels are calculated. The transition dipole moments are computed. The Franck-Condon factors, Einstein coefficients, and radiative lifetimes of many transitions are determined. The spectroscopic approaches are proposed for observing these states according to the transition probabilities. The spin-orbit coupling effect on the spectroscopic and vibrational properties is evaluated. The spectroscopic parameters, vibrational levels, transition dipole moments, as well as transition probabilities reported in this paper could be considered to be very reliable.

  4. Capturing the photo-signaling state of a photoreceptor in a steady-state fashion by binding a transition metal complex.

    Science.gov (United States)

    Yu, Pengyun; Song, Lei; Qin, Jun; Wang, Jianping

    2017-11-01

    Binding a small molecule to proteins causes conformational changes, but often to a limited extent. Here, we demonstrate that the interaction of a CO-releasing molecule (CORM3) with a photoreceptor photoactive yellow protein (PYP) drives large structural changes in the latter. The interaction of CORM3 and a mutant of PYP, Met100Ala, not only trigger the isomerization of its chromophore, p-coumaric acid, from its anionic trans configuration to a protonated cis configuration, but also increases the content of β-sheet at the cost of α-helix and random coil in the secondary structure of the protein. The CORM3 derived Met100Ala is found to highly resemble the signaling state, which is one of the key photo-intermediates of this photoactive protein, in both protein local conformation and chromophore configuration. The organometallic reagents hold promise as protein engineering tools. This work highlights a novel approach to structurally accessing short lived intermediates of proteins in a steady-state fashion. © 2017 The Protein Society.

  5. Using a State-and-Transition Approach to Manage Endangered Eucalyptus albens (White Box) Woodlands

    Science.gov (United States)

    Spooner, Peter G.; Allcock, Kimberly G.

    2006-11-01

    Eucalyptus albens (White Box) woodlands are among the most poorly conserved and threatened communities in Australia. Remnants are under further threat from stock grazing, deteriorating soil conditions, weed invasion, and salinity. There is an urgent need to restore degraded White Box and other woodland ecosystems to improve landscape function. However, there is still a poor understanding of the ecology of degraded woodland ecosystems in fragmented agricultural landscapes, and consequently a lack of precise scientific guidelines to manage these ecosystems in a conservation context. State and Transition Models (STMs) have received a great deal of attention, mainly in rangeland applications, as a suitable framework for understanding the ecology of complex ecosystems and to guide management. We have developed a STM for endangered White Box woodlands and discuss the merits of using this approach for land managers of other endangered ecosystems. An STM approach provides a greater understanding of the range of states, transitions, and thresholds possible in an ecosystem, and provides a summary of processes driving the system. Importantly, our proposed STM could be used to clarify the level of “intactness” of degraded White Box woodland sites, and provide the impetus to manage different states in complementary ways, rather than attempting to restore ecosystems to one pristine stable state. We suggest that this approach has considerable potential to integrate researcher and land manager knowledge, focus future experimental studies, and ultimately serve as a decision support tool in setting realistic and achievable conservation and restoration goals.

  6. Activation cross section and isomeric cross section ratios for the (n ,2 n ) reaction on 153Eu

    Science.gov (United States)

    Luo, Junhua; Jiang, Li; Li, Suyuan

    2017-10-01

    The 153Eu(n ,2 n ) m1,m2,g152Eu cross section was measured by means of the activation technique at three neutron energies in the range 13-15 MeV. The quasimonoenergetic neutron beam was formed via the 3H(d ,n ) 4He reaction, in the Pd-300 Neutron Generator at the Chinese Academy of Engineering Physics (CAEP). The activities induced in the reaction products were measured using high-resolution γ-ray spectroscopy. The cross section of the population of the second high-spin (8-) isomeric state was measured along with the reaction cross section populating both the ground (3-) and the first isomeric state (0-). Cross sections were also evaluated theoretically using the numerical code TALYS-1.8, with different level density options at neutron energies varying from the reaction threshold to 20 MeV. Results are discussed and compared with the corresponding literature.

  7. cis-trans Isomerization of silybins A and B

    Czech Academy of Sciences Publication Activity Database

    Novotná, Michaela; Gažák, Radek; Biedermann, David; Di Meo, F.; Marhol, Petr; Kuzma, Marek; Bednárová, Lucie; Fuksová, Kateřina; Trouillas, P.; Křen, Vladimír

    -, č. 10 (2014), s. 1047-1063 ISSN 1860-5397 R&D Projects: GA ČR GAP207/10/0288; GA MŠk LH13097; GA MŠk(CZ) LD13041 Institutional support: RVO:61388971 ; RVO:61388963 Keywords : isomerization * silibinin * silybin Subject RIV: CC - Organic Chemistry Impact factor: 2.762, year: 2014

  8. Isomerization of β-carotene by titanium tetrachloride catalyst

    Indian Academy of Sciences (India)

    TECS

    2007-05-04

    May 4, 2007 ... antioxidant because of the presence of a long chain of conjugated carbon-carbon double bonds. ... such as extraction, chromatography etc. It has been reported that the chlorinated solvents can promote isomerization of trans conjugated polyenes such as β-carotene during extraction.5. Also, the isomeriza-.

  9. Isomerization of 2-phospha-4-silabicyclo[1.10]butane

    NARCIS (Netherlands)

    Slootweg, J.C.; Ehlers, A.W.; Lammertsma, K.

    2004-01-01

    In analogy with the valence isomerism of the hydrocarbons bicyclobutane, 1,3-butadiene and cyclobutene, the rearrangements for 2-phospha-4-sila- bicyclo[1.1.0]butane were studied at the B3LYP/6-311+G** level of theory. The monocyclic 1,2-dihydro-1,2-phosphasilete is shown to be the thermodynamically

  10. Second-chance forward isomerization dynamics of the red/green cyanobacteriochrome NpR6012g4 from Nostoc punctiforme.

    Science.gov (United States)

    Kim, Peter W; Freer, Lucy H; Rockwell, Nathan C; Martin, Shelley S; Lagarias, J Clark; Larsen, Delmar S

    2012-01-11

    The primary ultrafast Z-to-E isomerization photodynamics of the phytochrome-related cyanobacteriochrome NpR6012g4 from Nostoc punctiforme was studied by transient absorption pump-dump-probe spectroscopy. A 2 ps dump pulse resonant with the stimulated emission band depleted 21% of the excited-state population, while the initial photoproduct Lumi-R was depleted by only 11%. We observed a red-shifted ground-state intermediate (GSI) that we assign to a metastable state that failed to isomerize fully. Multicomponent global analysis implicates the generation of additional Lumi-R from the GSI via crossing over the ground-state thermal barrier for full isomerization, explaining the discrepancy between excited-state and Lumi-R depletion by the dump pulse. This second-chance ground-state dynamics provides a plausible explanation for the unusually high quantum yield of 40% for the primary isomerization step in the forward reaction of NpR6012g4. © 2011 American Chemical Society

  11. High-spin states in the transitional odd-odd nuclei 150Eu and 152Tb

    International Nuclear Information System (INIS)

    Barneoud, D.; Foin, C.; Pinston, J.A.; Monnand, E.

    1983-06-01

    The ( 7 Li, 5n) and ( 11 B, 5n) reactions have been used to study the high-spin states in the two odd-odd nuclei 150 Eu and 152 Tb. Three decoupled bands have been evidenced in each nucleus belonging to the same configurations [f 7/2]sub(n) [h 11/2]sub(p), [h 9/2]sub(n) [h 11/2 ]sub(p) and [i 13/2]sub(n) [h 11/2]sub(p). The latter one is well developped and improves our knowledge of this system between the spherical and deformed region. The analysis of the collective moment of inertia and transition ratios strongly suggests an increase of the deformation when the rotational frequency increases in these two transitional nuclei 150 Eu and 152 Tb

  12. Quantum phase transitions in matrix product states of one-dimensional spin-1 chains

    International Nuclear Information System (INIS)

    Zhu Jingmin

    2014-01-01

    We present a new model of quantum phase transitions in matrix product systems of one-dimensional spin-1 chains and study the phases coexistence phenomenon. We find that in the thermodynamic limit the proposed system has three different quantum phases and by adjusting the control parameters we are able to realize any phase, any two phases equal coexistence and the three phases equal coexistence. At every critical point the physical quantities including the entanglement are not discontinuous and the matrix product system has long-range correlation and N-spin maximal entanglement. We believe that our work is helpful for having a comprehensive understanding of quantum phase transitions in matrix product states of one-dimensional spin chains and of certain directive significance to the preparation and control of one-dimensional spin lattice models with stable coherence and N-spin maximal entanglement. (author)

  13. Transition from diamagnetic to ferromagnetic state in laser ablated nitrogen doped ZnO thin films

    Directory of Open Access Journals (Sweden)

    Kajal Jindal

    2015-02-01

    Full Text Available Transition from room temperature diamagnetic to ferromagnetic state in N doped ZnO (ZnO:N films grown by pulsed laser deposition with tunable energy density has been identified. ZnO:N films deposited with moderate laser energy density of 2.5 J/cm2 are single phase and nearly defect free having N dopant substitution at O sites in ZnO lattice, exhibiting intrinsic ferromagnetism. When energy density reduces (<2.5 J/cm2, defects in ZnO:N film degrades ferromagnetism and exhibit diamagnetic phase when grown at energy density of 1.0 J/cm2. Growth kinetics, which in turn depends on laser energy density is playing important role in making transition from ferromagnetic to diamagnetic in ZnO:N films.

  14. Role of entropy and structural parameters in the spin-state transition of LaCoO3

    Science.gov (United States)

    Chakrabarti, Bismayan; Birol, Turan; Haule, Kristjan

    2017-11-01

    The spin-state transition in LaCoO3 has eluded description for decades despite concerted theoretical and experimental effort. In this study, we approach this problem using fully charge self-consistent density functional theory + embedded dynamical mean field theory (DFT+DMFT). We show from first principles that LaCoO3 cannot be described by a single, pure spin state at any temperature. Instead, we observe a gradual change in the population of higher-spin multiplets with increasing temperature, with the high-spin multiplets being excited at the onset of the spin-state transition followed by the intermediate-spin multiplets being excited at the metal-insulator-transition temperature. We explicitly elucidate the critical role of lattice expansion and oxygen octahedral rotations in the spin-state transition. We also reproduce, from first principles, that the spin-state transition and the metal-insulator transition in LaCoO3 occur at different temperature scales. In addition, our results shed light on the importance of electronic entropy in driving the spin-state transition, which has so far been ignored in all first-principles studies of this material.

  15. Symptoms experienced during menopausal transition: Korean women in South Korea and the United States.

    Science.gov (United States)

    Im, Eun-Ok

    2003-10-01

    This article reports on cultural influences on symptoms experienced during menopausal transition of Korean women in South Korea and Korean immigrant women in the United States. Data from independent studies of two groups of Korean women were triangulated and analyzed using descriptive and inferential statistics. The analysis indicated that Korean women in South Korea tended to report more symptoms than Korean immigrant women in the United States. Types and severity of prevalent symptoms were also found to be different between the two groups. The findings suggest that recent introduction of menopausal industries in South Korea and contextual influences on Korean women's work and immigration in the United States would be the reason for differences. Based on the findings, implications for future research are proposed.

  16. Enhanced Prognostic Model for Lithium Ion Batteries Based on Particle Filter State Transition Model Modification

    Directory of Open Access Journals (Sweden)

    Buddhi Arachchige

    2017-11-01

    Full Text Available This paper focuses on predicting the End of Life and End of Discharge of Lithium ion batteries using a battery capacity fade model and a battery discharge model. The proposed framework will be able to estimate the Remaining Useful Life (RUL and the Remaining charge through capacity fade and discharge models. A particle filter is implemented that estimates the battery’s State of Charge (SOC and State of Life (SOL by utilizing the battery’s physical data such as voltage, temperature, and current measurements. The accuracy of the prognostic framework has been improved by enhancing the particle filter state transition model to incorporate different environmental and loading conditions without retuning the model parameters. The effect of capacity fade in the reduction of the EOD (End of Discharge time with cycling has also been included, integrating both EOL (End of Life and EOD prediction models in order to get more accuracy in the estimations.

  17. SDF1-CXCR4 Signaling Contributes to the Transition from Acute to Chronic Pain State.

    Science.gov (United States)

    Yang, Fei; Sun, Wei; Luo, Wen-Jun; Yang, Yan; Yang, Fan; Wang, Xiao-Liang; Chen, Jun

    2017-05-01

    Emerging evidence has demonstrated the involvement of stromal cell-derived factor 1 (SDF1, also known as CXCL12)-CXCR4 signaling in a variety of pain state. However, the underlying mechanisms of SDF1-CXCR4 signaling leading to the maintenance of chronic pain states are poorly understood. In the present study, we sought to explore the role of SDF1-CXCR4 signaling in the forming of neuroplasticity by applying a model of the transition from acute to chronic pain state, named as hyperalgesic priming. Utilizing intraplantar bee venom (BV) injection, we successfully established hyperalgesic priming state and found that peripheral treating with AMD3100, a CXCR4 antagonist, or knocking down CXCR4 by intraganglionar CXCR4 small interfering RNA (siRNA) injection could prevent BV-induced primary mechanical hyperalgesia and hyperalgesic priming. Moreover, we showed that single intraplantar active SDF1 protein injection is sufficient to induce acute mechanical hyperalgesia and hyperalgesic priming through CXC4. Intraplantar coinjection of ERK inhibitor, U0126, and PI3K inhibitor, LY294002, as well as two protein translation inhibitors, temsirolimus and cordycepin, prevented the development of SDF1-induced acute mechanical hyperalgesia and hyperalgesic priming. Finally, on the models of complete Freund's adjuvant (CFA)-induced chronic inflammatory pain and spared nerve injury (SNI)-induced chronic neuropathic pain, we observed that knock-down of CXCR4 could both prevent the development and reverse the maintenance of chronic pain state. In conclusion, our present data suggested that through regulating ERK and PI3K-AKT pathways-mediated protein translation SDF1-CXCR4 signaling mediates the transition from acute pain to chronic pain state and finally contributes to the development and maintenance of chronic pain.

  18. Powder keg divisions in the critical state regime: transition from continuous to explosive percolation

    Science.gov (United States)

    Zhou, Zongzheng; Tordesillas, Antoinette

    2017-06-01

    The underlying microstructure and dynamics of a dense granular material as it evolves towards the "critical state", a limit state in which the system deforms with an essentially constant volume and stress ratio, remains widely debated in the micromechanics of granular media community. Strain localization, a common mechanism in the large strain regime, further complicates the characterization of this limit state. Here we revisit the evolution to this limit state within the framework of modern percolation theory. Attention is paid to motion transfer: in this context, percolation translates to the emergence of a large-scale connectivity in graphs that embody information on individual grain displacements. We construct each graph G(r) by connecting nodes, representing the grains, within a distance r in the displacement-state-space. As r increases, we observe a percolation transition on G(r). The size of the jump discontinuity increases in the lead up to failure, indicating that the nature of percolation transition changes from continuous to explosive. We attribute this to the emergence of collective motion, which manifests in increasingly isolated communities in G(r). At the limit state, where the jump discontinuity is highest and invariant across the different unjamming cycles (drops in stress ratio), G(r) encapsulates multiple kinematically distinct communities that are mediated by nodes corresponding to those grains in the shear band. This finding casts light on the dual and opposing roles of the shear band: a mechanism that creates powder keg divisions in the sample, while simultaneously acting as a mechanical link that transfers motion through such subdivisions moving in relative rigid-body motion.

  19. Edge states in the climate system: exploring global instabilities and critical transitions

    Science.gov (United States)

    Lucarini, Valerio; Bódai, Tamás

    2017-07-01

    Multistability is a ubiquitous feature in systems of geophysical relevance and provides key challenges for our ability to predict a system’s response to perturbations. Near critical transitions small causes can lead to large effects and—for all practical purposes—irreversible changes in the properties of the system. As is well known, the Earth climate is multistable: present astronomical and astrophysical conditions support two stable regimes, the warm climate we live in, and a snowball climate characterized by global glaciation. We first provide an overview of methods and ideas relevant for studying the climate response to forcings and focus on the properties of critical transitions in the context of both stochastic and deterministic dynamics, and assess strengths and weaknesses of simplified approaches to the problem. Following an idea developed by Eckhardt and collaborators for the investigation of multistable turbulent fluid dynamical systems, we study the global instability giving rise to the snowball/warm multistability in the climate system by identifying the climatic edge state, a saddle embedded in the boundary between the two basins of attraction of the stable climates. The edge state attracts initial conditions belonging to such a boundary and, while being defined by the deterministic dynamics, is the gate facilitating noise-induced transitions between competing attractors. We use a simplified yet Earth-like intermediate complexity climate model constructed by coupling a primitive equations model of the atmosphere with a simple diffusive ocean. We refer to the climatic edge states as Melancholia states and provide an extensive analysis of their features. We study their dynamics, their symmetry properties, and we follow a complex set of bifurcations. We find situations where the Melancholia state has chaotic dynamics. In these cases, we have that the basin boundary between the two basins of attraction is a strange geometric set with a nearly zero

  20. First spatial separation of a heavy ion isomeric beam with a multiple-reflection time-of-flight mass spectrometer

    Science.gov (United States)

    Dickel, T.; Plaß, W. R.; Ayet San Andres, S.; Ebert, J.; Geissel, H.; Haettner, E.; Hornung, C.; Miskun, I.; Pietri, S.; Purushothaman, S.; Reiter, M. P.; Rink, A.-K.; Scheidenberger, C.; Weick, H.; Dendooven, P.; Diwisch, M.; Greiner, F.; Heiße, F.; Knöbel, R.; Lippert, W.; Moore, I. D.; Pohjalainen, I.; Prochazka, A.; Ranjan, M.; Takechi, M.; Winfield, J. S.; Xu, X.

    2015-05-01

    211Po ions in the ground and isomeric states were produced via 238U projectile fragmentation at 1000 MeV/u. The 211Po ions were spatially separated in flight from the primary beam and other reaction products by the fragment separator FRS. The ions were energy-bunched, slowed-down and thermalized in a gas-filled cryogenic stopping cell (CSC). They were then extracted from the CSC and injected into a high-resolution multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). The excitation energy of the isomer and, for the first time, the isomeric-to-ground state ratio were determined from the measured mass spectrum. In the subsequent experimental step, the isomers were spatially separated from the ions in the ground state by an ion deflector and finally collected with a silicon detector for decay spectroscopy. This pioneering experimental result opens up unique perspectives for isomer-resolved studies. With this versatile experimental method new isomers with half-lives longer than a few milliseconds can be discovered and their decay properties can be measured with highest sensitivity and selectivity. These experiments can be extended to studies with isomeric beams in nuclear reactions.

  1. Quantitative chemical state XPS analysis of first row transition metals, oxides and hydroxides

    Energy Technology Data Exchange (ETDEWEB)

    Biesinger, M C; Payne, B P; McIntryre, N S [Department of Chemistry, University of Western Ontario, London, Ontario, N6A 5B7 (Canada); Hart, B R; Lau, L Wm [Surface Science Western, Room G1, Western Science Centre, University of Western Ontario, London, Ontario, N6A 5B7 (Canada); Grosvenor, A P [Department of Chemistry, Gunning/Lemieux Chemistry Centre, University of Alberta, Edmonton, Alberta, T6G 2G2 (Canada); Smart, R StC [ACeSSS, Applied Centre for Structural and Synchrotron Studies, University of South Australia, Mawson Lakes, SA 5095 (Australia)], E-mail: biesingr@uwo.ca

    2008-03-15

    Practical quantitative chemical state X-ray photoelectron spectroscopy (XPS) analysis of first row transition metals, oxides and hydroxides is challenging due to the complexity of their M 2p spectra. Complex multiplet splitting, shake-up and plasmon loss structure can play a role in the interpretation of the chemical states present. This paper will show practical curve fitting procedures for the quantitative measurement of different chemical states for metal oxides and hydroxides from a survey of transition metals. It will also discuss some of the limitations and pitfalls present as well as give practical examples of their successful use. These curve-fitting procedures are based on 1) standard spectra from quality reference samples, 2) a survey of appropriate literature databases and/or a compilation of literature references, 3) fitting of multiplet split spectra based on spectra of numerous reference materials and theoretical modelling, 4) spectral subtractions routines, again using reference spectra, and 5) specific literature references where fitting procedures are available.

  2. Analysis of the chloroplast protein kinase Stt7 during state transitions.

    Directory of Open Access Journals (Sweden)

    Sylvain Lemeille

    2009-03-01

    Full Text Available State transitions allow for the balancing of the light excitation energy between photosystem I and photosystem II and for optimal photosynthetic activity when photosynthetic organisms are subjected to changing light conditions. This process is regulated by the redox state of the plastoquinone pool through the Stt7/STN7 protein kinase required for phosphorylation of the light-harvesting complex LHCII and for the reversible displacement of the mobile LHCII between the photosystems. We show that Stt7 is associated with photosynthetic complexes including LHCII, photosystem I, and the cytochrome b6f complex. Our data reveal that Stt7 acts in catalytic amounts. We also provide evidence that Stt7 contains a transmembrane region that separates its catalytic kinase domain on the stromal side from its N-terminal end in the thylakoid lumen with two conserved Cys that are critical for its activity and state transitions. On the basis of these data, we propose that the activity of Stt7 is regulated through its transmembrane domain and that a disulfide bond between the two lumen Cys is essential for its activity. The high-light-induced reduction of this bond may occur through a transthylakoid thiol-reducing pathway driven by the ferredoxin-thioredoxin system which is also required for cytochrome b6f assembly and heme biogenesis.

  3. Quantitative chemical state XPS analysis of first row transition metals, oxides and hydroxides

    International Nuclear Information System (INIS)

    Biesinger, M C; Payne, B P; McIntryre, N S; Hart, B R; Lau, L Wm; Grosvenor, A P; Smart, R StC

    2008-01-01

    Practical quantitative chemical state X-ray photoelectron spectroscopy (XPS) analysis of first row transition metals, oxides and hydroxides is challenging due to the complexity of their M 2p spectra. Complex multiplet splitting, shake-up and plasmon loss structure can play a role in the interpretation of the chemical states present. This paper will show practical curve fitting procedures for the quantitative measurement of different chemical states for metal oxides and hydroxides from a survey of transition metals. It will also discuss some of the limitations and pitfalls present as well as give practical examples of their successful use. These curve-fitting procedures are based on 1) standard spectra from quality reference samples, 2) a survey of appropriate literature databases and/or a compilation of literature references, 3) fitting of multiplet split spectra based on spectra of numerous reference materials and theoretical modelling, 4) spectral subtractions routines, again using reference spectra, and 5) specific literature references where fitting procedures are available

  4. Variational transition-state theory. Progress report, February 1981-January 1983

    International Nuclear Information System (INIS)

    Truhlar, D.G.

    1983-01-01

    During the past two years we have extended the variational transition-state theory in several ways. Especially notable is that we have developed several new methods for calculating tunneling probabilities, including two general techniques applicable to systems with small and large reaction-path curvature. We have tested these methods successfully against accurate quantal calculations, and we have applied them to real systems in three dimensions. We have also developed general algorithms for variational transition state theory calculations on polyatomic systems and we have applied these to the combustion reaction OH + H 2 → H 2 O + H. We have developed and successfully applied a statistical-diabatic theory for state-selected rates. We made a totally ab initio prediction of an absolute chemical reaction rate, for the reaction Mu + H 2 → MuH + H, using an accurate potential energy surface and ethods that we had demonstrated to be reliable by tests against accurate quantal collinear results. This prediction has now been confirmed by unpublished experiments; I believe that this is the first reliable ab initio prediction of a chemical rection rate prior to its measurement. In the rest of this technical progress report we give further details of these and other studies we have carried out in the last two years under this contract

  5. Dynamics of Number of Packets in Transit in Free Flow State of Data Network

    International Nuclear Information System (INIS)

    Shengkun Xie; Lawniczak, A.T.

    2011-01-01

    We study how the dynamics of Number of Packets in Transit (NPT) is affected by the coupling of a routing type with a volume of incoming packet traffic in a data network model of packet switching type. The NPT is a network performance indicator of an aggregate type that measures in '' real time '', how many packets are in the network on their routes to their destinations. We conduct our investigation using a time-discrete simulation model that is an abstraction of the Network Layer of the ISO OSI Seven Layer Reference Model. This model focuses on packets and their routing. We consider a static routing and two different types of dynamic routings coupled with different volumes of incoming packet traffic in the network free flow state. Our study shows that the order of the values of the NPT mean value time series depends on the coupling of a routing type with a volume of incoming packet traffic and changes when the volume of incoming packet traffic increases and is closed to the critical source load values, i.e. when it is closed to the phase transition points from the network free flow state to its congested states. (authors)

  6. Four Generations of Transition State Analogues for Human Purine Nucleoside Phosphorylase

    Energy Technology Data Exchange (ETDEWEB)

    Ho, M.; Shi, W; Rinaldo-Mathis, A; Tyler, P; Evans, G; Almo, S; Schramm, V

    2010-01-01

    Inhibition of human purine nucleoside phosphorylase (PNP) stops growth of activated T-cells and the formation of 6-oxypurine bases, making it a target for leukemia, autoimmune disorders, and gout. Four generations of ribocation transition-state mimics bound to PNP are structurally characterized. Immucillin-H (K*{sub i} = 58 pM, first-generation) contains an iminoribitol cation with four asymmetric carbons. DADMe-Immucillin-H (K*{sub i} = 9 pM, second-generation), uses a methylene-bridged dihydroxypyrrolidine cation with two asymmetric centers. DATMe-Immucillin-H (K*{sub i} = 9 pM, third-generation) contains an open-chain amino alcohol cation with two asymmetric carbons. SerMe-ImmH (K*{sub i} = 5 pM, fourth-generation) uses achiral dihydroxyaminoalcohol seramide as the ribocation mimic. Crystal structures of PNPs establish features of tight binding to be; (1) ion-pair formation between bound phosphate (or its mimic) and inhibitor cation, (2) leaving-group interactions to N1, O6, and N7 of 9-deazahypoxanthine, (3) interaction between phosphate and inhibitor hydroxyl groups, and (4) His257 interacting with the 5{prime}-hydroxyl group. The first generation analogue is an imperfect fit to the catalytic site with a long ion pair distance between the iminoribitol and bound phosphate and weaker interactions to the leaving group. Increasing the ribocation to leaving-group distance in the second- to fourth-generation analogues provides powerful binding interactions and a facile synthetic route to powerful inhibitors. Despite chemical diversity in the four generations of transition-state analogues, the catalytic site geometry is almost the same for all analogues. Multiple solutions in transition-state analogue design are available to convert the energy of catalytic rate enhancement to binding energy in human PNP.

  7. The influence of constitutional isomerism and change on molecular recognition processes.

    Science.gov (United States)

    Williams, Avril R; Northrop, Brian H; Houk, Kendall N; Stoddart, J Fraser; Williams, David J

    2004-10-25

    Three constitutionally isomeric bis(naphthylmethyl)ammonium ions, in which the two naphthyl groups are substituted 1) both at their 1-positions, 2) one at its 1-position and the other at its 2-position, and 3) both at their 2-positions, have been investigated separately in solution for their propensities to undergo spontaneous self-assembly with three different [24]crown-8 derivatives, namely, pyrido[24]crown-8 (P24C8), dipyrido[24]crown-8 (DP24C8) and dibenzo[24]crown-8 (DB24C8), in turn to form [2]pseudorotaxanes. The strengths of the 1:1 complexes depend on the composition of the secondary dialkylammonium ions and on the nature of the crown ether hosts; generally, as far as the guest cation is concerned, the 1/1- and 2/2-isomers form stronger complexes, as indicated by stability constant measurements, than the 1/2-isomer and, as far as the crown ethers are concerned, the more flexible P24C8 is a much more efficient host than either DP24C8 or DB24C8. The rates of formation of the [2]pseudorotaxanes are fast (i.e., taking no more than a few minutes) in solution with the exception of one case, that is, in which the crown ether host is DB24C8 and the guest cation is the 1/1-isomer, when it can take upwards of one month for the complexation-decomplexation equilibrium to be established at room temperature. In all cases, the equilibrium between complexed and uncomplexed species is slow on the NMR timescale, allowing the determination of stability constants to be made readily using the single-point method. X-ray crystallography and molecular modeling have been used to gain insight into ground and transition state interactions, respectively, in some of the [2]pseudorotaxanes. The relative stabilities of the three [2]pseudorotaxanes formed by each guest cation in the presence of the three crown ether hosts were also evaluated in solution by competition experiments that were monitored by (1)H NMR spectroscopy. By and large the results of the competition experiments could

  8. Study of the strength distribution of primary γ-transitions in the decay from superdeformed states in 194Hg

    International Nuclear Information System (INIS)

    Lopez-Martens, A.P.; Doessing, T.; Khoo, T.L.; Korichi, A.; Hannachi, F.; Calderin, I.J.; Lauritsen, T.; Ahmad, I.; Carpenter, M.P.; Fischer, S.M.; Hackman, G.; Janssens, R.V.F.; Nisius, D.; Reiter, P.; Amro, H.; Moore, E.F.

    1999-01-01

    The strength distribution of the primary γ rays in the decay from superdeformed (SD) states is investigated by applying the maximum likelihood method. For the 194 Hg nucleus, 41 primary transitions are identified above 2600 keV. It is concluded that they represent the strongest 10% of the transitions selected stochastically from a Porter-Thomas distribution. This would support the scenario of a statistical decay of SD states via coupling to a compound state at normal deformation. However, the occurrence of several very strong 'one-step linking' transitions is found to have a very small probability. Based on the absence of strong primary transitions from SD states in adjacent nuclei, the situation in 194 Hg is viewed as a very lucky incidence

  9. Are boat transition states likely to occur in Cope rearrangements? A DFT study of the biogenesis of germacranes

    Directory of Open Access Journals (Sweden)

    José Enrique Barquera-Lozada

    2017-09-01

    Full Text Available It has been proposed that elemanes are biogenetically formed from germacranes by Cope sigmatropic rearrangements. Normally, this reaction proceeds through a transition state with a chair conformation. However, the transformation of schkuhriolide (germacrane into elemanschkuhriolide (elemane may occur through a boat transition state due to the final configuration of the elemanschkuhriolide, but this transition state is questionable due to its high energy. The possible mechanisms of this transformation were studied in the density functional theory frame. The mechanistic differences between the transformation of (Z,E-germacranes and (E,E-germacranes were also studied. We found that (Z,E-germacranolides are significantly more stable than (E,E-germacranolides and elemanolides. In the specific case of schkuhriolide, even when the boat transition state is not energetically favored, a previous hemiacetalization lowers enough the energetic barrier to allow the formation of a very stable elemanolide that is even more stable than its (Z,E-germacrane.

  10. Experimental and theoretical examples of the value and limitations of transition state theory

    International Nuclear Information System (INIS)

    Golden, D.M.

    1979-01-01

    Value and limitations of transition-state theory (TST) are reviewed. TST analyses of the temperature dependence of the ''direct'' reactions CH 3 + CH 3 CHO → CH 4 + CH 3 CO (1) and O + CH 4 → OH + CH 3 (2) are presented in detail, and other examples of TST usefulness are recalled. Limitations are discussed for bimolecular processes in terms of ''complex'' vs ''direct'' mechanisms. The reaction OH + CO → CO 2 + H is discussed in this context. Limitations for unimolecular processes seem to arise only for simple bond fission processes, and recent advances are noted. 2 figures, 5 tables

  11. Spin-State Transition in La1-xSrxCoO3 Single Crystals

    Science.gov (United States)

    Bhardwaj, S.; Prabhakaran, D.; Awasthi, A. M.

    2011-07-01

    We present a study of the thermal conductivity (κ), specific heat (Cp) and Raman spectra of La1-xSrxCoO3 (x = 0,0.1) single crystals. Both the specimens have low thermal conductivity and board Raman peaks, arising from strong scattering of phonons by lattice disorder, produced by (and doping-enhanced) spin-states admixture of the Co3+ ions. The thermal conductivity anomalously deviates from ˜1/T behaviour at high (room) temperatures, expected of an insulator. High-temperature specific heat reveals large decrease in the metal-insulator (M-I) transition temperature with Sr-doping.

  12. Transition probabilities of 36Cl and 36Ar excited states in heavy ion reactions

    International Nuclear Information System (INIS)

    Costa, G.J.; Alexander, T.K.; Forster, J.S.; McDonald, A.B.; Towner, I.S.

    The reactions 2 H( 35 Cl,pγ) and 2 H( 35 Cl,nγ) have been used to determine by the recoil-distance method, the lifetimes of levels in 36 Cl and 36 Ar respectively. Large discrepancies exist in the literature for some lifetimes of 36 Cl levels. Transition rates found for decay of the negative parity states in 36 Ar (4178 (3 - ), 4974 (2 - ) and 5171 (5 - ) keV), are compared whith the Maripuu-Hokken model and RPA and TDA predictions [fr

  13. Density induced phase transitions in the Schwinger model. A study with matrix product states

    Energy Technology Data Exchange (ETDEWEB)

    Banuls, Mari Carmen; Cirac, J. Ignacio; Kuehn, Stefan [Max-Planck-Institut fuer Quantenoptik (MPQ), Garching (Germany); Cichy, Krzysztof [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik; Adam Mickiewicz Univ., Poznan (Poland). Faculty of Physics; Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

    2017-02-15

    We numerically study the zero temperature phase structure of the multiflavor Schwinger model at nonzero chemical potential. Using matrix product states, we reproduce analytical results for the phase structure for two flavors in the massless case and extend the computation to the massive case, where no analytical predictions are available. Our calculations allow us to locate phase transitions in the mass-chemical potential plane with great precision and provide a concrete example of tensor networks overcoming the sign problem in a lattice gauge theory calculation.

  14. Stress-induced state transitions in flexible liquid-crystal devices

    International Nuclear Information System (INIS)

    Ho, I-Lin; Chang, Yia-Chung

    2012-01-01

    This work studies the stress-strain dynamics for the transient optoelectronic characteristics of flexible liquid-crystal (LC) devices. Due to the fast response of LC directors, the configuration of the LC is assumed to be in quasi-equilibrium during the process of elastic deformations of the flexible structures. The LC medium hence can be treated effectively as a thin-film layer and can approximately follow the strain-stress mechanism in the solids. Relevant theoretical algorithms are studied in this work, and numerical results present the stress-induced state transitions in the π cell.

  15. The transition between monostable and bistable states induced by time delay in intracellular calcium oscillation

    International Nuclear Information System (INIS)

    Duan, Wei-Long

    2013-01-01

    The revised role of the time delay of active processes with colored noises of transmission of intracellular Ca 2+ in intracellular calcium oscillation (ICO) is investigated by means of a first-order algorithm based on stochastic simulation. The simulation results indicate that time delay induces a double critical phenomenon and a transition between the monostable and bistable states of the ICO system. In addition, as the time delay increases, for a cytosolic Ca 2+ concentration with weak colored noises there appears a calcium burst, and the Ca 2+ concentration of the calcium store shows nonmonotonic variation. (paper)

  16. Experimental and theoretical examples of the value and limitations of transition state theory

    Science.gov (United States)

    Golden, D. M.

    1979-01-01

    Value and limitations of transition-state theory (TST) are reviewed. TST analyses of the temperature dependence of the 'direct' reactions CH3 + CH3CHO yields CH4 + CH3CO(1) and O + CH4 yields OH + CH3(2) are presented in detail, and other examples of TST usefulness are recalled. Limitations are discussed for bimolecular processes in terms of 'complex' vs. 'direct' mechanisms. The reaction OH + CO yields CO2 + H is discussed in this context. Limitations for unimolecular processes seem to arise only for simple bond fission processes, and recent advances are noted.

  17. Variational transition state theory for multidimensional activated rate processes in the presence of anisotropic friction

    Science.gov (United States)

    Berezhkovskii, Alexander M.; Frishman, Anatoli M.; Pollak, Eli

    1994-09-01

    Variational transition state theory (VTST) is applied to the study of the activated escape of a particle trapped in a multidimensional potential well and coupled to a heat bath. Special attention is given to the dependence of the rate constant on the friction coefficients in the case of anisotropic friction. It is demonstrated explicitly that both the traditional as well as the nontraditional scenarios for the particle escape are recovered uniformly within the framework of VTST. Effects such as saddle point avoidance and friction dependence of the activation energy are derived from VTST using optimized planar dividing surfaces.

  18. Specific features of cavitation phenomena during transition of nitrogen tetroxide and nitrine into metastable state

    International Nuclear Information System (INIS)

    Ermashkevich, V.N.

    1981-01-01

    Some cases of nitrogen tetroxide and nitrine (the nitrogen tetroxide and nitrogen oxide mixture) transition into the metastable state are considered. The influence of some technological processes and NPP control operations on spontaneous superheated liquid boiling in the pipelines and at pump inlet as well as that of the produced gas-liquid mixture on the pump cavitational stoppage are pointed out. It is shown that in the case of eliminating the spontaneous liquid boiling cause, the pump restores its parameters to their original quantities [ru

  19. Surface hopping, transition state theory and decoherence. I. Scattering theory and time-reversibility.

    Science.gov (United States)

    Jain, Amber; Herman, Michael F; Ouyang, Wenjun; Subotnik, Joseph E

    2015-10-07

    We provide an in-depth investigation of transmission coefficients as computed using the augmented-fewest switches surface hopping algorithm in the low energy regime. Empirically, microscopic reversibility is shown to hold approximately. Furthermore, we show that, in some circumstances, including decoherence on top of surface hopping calculations can help recover (as opposed to destroy) oscillations in the transmission coefficient as a function of energy; these oscillations can be studied analytically with semiclassical scattering theory. Finally, in the spirit of transition state theory, we also show that transmission coefficients can be calculated rather accurately starting from the curve crossing point and running trajectories forwards and backwards.

  20. The Welfare to Work Transition in the United States: Implications for Work-Related Learning

    Science.gov (United States)

    Fisher, James C.; Martin, Larry G.

    2000-11-01

    This paper summarizes the legislation upon which the current welfare-to-work transition in the United States is based and describes characteristics of the former welfare population from which various tiers of employment options have emerged: unsubsidized-employed workers, subsidized-employed workers, subsidized-unemployed recipients, and unsubsidized-unemployed individuals. It also discusses current program emphases, and presents a format for directions for future program development which includes academic programs, situated cognition programs, integrated literacy/occupational skills programs, and integrated literacy/soft skills training.

  1. Core-state models for fuel management of equilibrium and transition cycles in pressurized water reactors

    International Nuclear Information System (INIS)

    Aragones, J.M.; Martinez-Val, J.M.; Corella, M.R.

    1977-01-01

    Fuel management requires that mass, energy, and reactivity balance be satisfied in each reload cycle. Procedures for selection of alternatives, core-state models, and fuel cost calculations have been developed for both equilibrium and transition cycles. Effective cycle lengths and fuel cycle variables--namely, reload batch size, schedule of incore residence for the fuel, feed enrichments, energy sharing cycle by cycle, and discharge burnup and isotopics--are the variables being considered for fuel management planning with a given energy generation plan, fuel design, recycling strategy, and financial assumptions

  2. Response to work transitions by United States Army personnel: effects of self-esteem, self-efficacy, and career resilience.

    Science.gov (United States)

    Gowan, M A; Craft, S L; Zimmermann, R A

    2000-06-01

    This paper examined association of self-esteem, self-efficacy, and career resilience with the responses of 171 United States Army personnel making the transition to civilian jobs. Specifically, the study addresses whether personality traits are related to the appraisal of the transition from Army to civilian life and to how individuals plan to manage the transition to yield employment success. Self-esteem, self-efficacy, and career resilience were the personality variables examined. Only self-esteem and career resilience were related to harm appraisals of the transition. None of the personality variables were related to use of coping strategies. Limitations of the study and suggestions for research are provided.

  3. MRCI study on the spectroscopic parameters, transition dipole moments and transition probabilities of 16 low-lying states of the BeB radical

    Science.gov (United States)

    Zhou, Dan; Shi, Deheng; Sun, Jinfeng; Zhu, Zunlue

    2018-03-01

    In this work, we calculate the potential energy curves of 16 Λ-S and 36 Ω states of beryllium boride (BeB) radical using the complete active space self-consistent field method, followed by the valence internally contracted multireference configuration interaction approach with Davidson correction. The 16 Λ-S states are the X2Π, A2Σ+, B2Π, C2Δ, D2Ʃ-, E2Σ+, G2Π, I2Σ+, a4Σ-, b4Π, c4Σ-, d4Δ, e4Σ+, g4Π, h4Π, and 24Σ+, which are obtained from the first three dissociation channels of the BeB radical. The Ω states are obtained from the Λ-S states. Of the Λ-S states, the G2Π, I2Σ+, and h4Π states exhibit double well curves. The G2Π, b4Π, and g4Π states are inverted with the spin-orbit coupling effect included. The d4Δ, e4Σ+, and g4Π states as well as the second well of the h4Π state are very weakly bound. Avoided crossings exist between the G2Π and H2Π states, the A2Σ+ and E2Σ+ states, the c4Σ- and f4Σ- states, the g4Π and h4Π states, the I2Σ+ and 42Σ+ states, as well as the 24Σ+ and 34Σ+ states. To improve the quality of the potential energy curves, core-valence correlation and scalar relativistic corrections, as well as the extrapolation of the potential energies to the complete basis set limit, are included. The transition dipole moments are computed. Spectroscopic parameters and vibrational levels are determined along with Franck-Condon factors, Einstein coefficients, and radiative lifetimes of many electronic transitions. The transition probabilities are evaluated. The spin-orbit coupling effect on the spectroscopic parameters and vibrational levels is discussed. The spectroscopic parameters, vibrational levels, and transition probabilities reported in this paper can be considered very reliable and can be employed to predict these states in an appropriate spectroscopy experiment.

  4. Coupled superconducting qudit-resonator system: Energy spectrum, state population, and state transition under microwave drive

    Science.gov (United States)

    Liu, W. Y.; Xu, H. K.; Su, F. F.; Li, Z. Y.; Tian, Ye; Han, Siyuan; Zhao, S. P.

    2018-03-01

    Superconducting quantum multilevel systems coupled to resonators have recently been considered in some applications such as microwave lasing and high-fidelity quantum logical gates. In this work, using an rf-SQUID type phase qudit coupled to a microwave coplanar waveguide resonator, we study both theoretically and experimentally the energy spectrum of the system when the qudit level spacings are varied around the resonator frequency by changing the magnetic flux applied to the qudit loop. We show that the experimental result can be well described by a theoretical model that extends from the usual two-level Jaynes-Cummings system to the present four-level system. It is also shown that due to the small anharmonicity of the phase device a simplified model capturing the leading state interactions fits the experimental spectra very well. Furthermore we use the Lindblad master equation containing various relaxation and dephasing processes to calculate the level populations in the simpler qutrit-resonator system, which allows a clear understanding of the dynamics of the system under the microwave drive. Our results help to better understand and perform the experiments of coupled multilevel and resonator systems and can be applied in the case of transmon or Xmon qudits having similar anharmonicity to the present phase device.

  5. Powder keg divisions in the critical state regime: transition from continuous to explosive percolation

    Directory of Open Access Journals (Sweden)

    Zhou Zongzheng

    2017-01-01

    Full Text Available The underlying microstructure and dynamics of a dense granular material as it evolves towards the “critical state”, a limit state in which the system deforms with an essentially constant volume and stress ratio, remains widely debated in the micromechanics of granular media community. Strain localization, a common mechanism in the large strain regime, further complicates the characterization of this limit state. Here we revisit the evolution to this limit state within the framework of modern percolation theory. Attention is paid to motion transfer: in this context, percolation translates to the emergence of a large-scale connectivity in graphs that embody information on individual grain displacements. We construct each graph G(r by connecting nodes, representing the grains, within a distance r in the displacement-state-space. As r increases, we observe a percolation transition on G(r. The size of the jump discontinuity increases in the lead up to failure, indicating that the nature of percolation transition changes from continuous to explosive. We attribute this to the emergence of collective motion, which manifests in increasingly isolated communities in G(r. At the limit state, where the jump discontinuity is highest and invariant across the different unjamming cycles (drops in stress ratio, G(r encapsulates multiple kinematically distinct communities that are mediated by nodes corresponding to those grains in the shear band. This finding casts light on the dual and opposing roles of the shear band: a mechanism that creates powder keg divisions in the sample, while simultaneously acting as a mechanical link that transfers motion through such subdivisions moving in relative rigid-body motion.

  6. A hyperactive transcriptional state marks genome reactivation at the mitosis–G1 transition

    Science.gov (United States)

    Hsiung, Chris C.-S.; Bartman, Caroline R.; Huang, Peng; Ginart, Paul; Stonestrom, Aaron J.; Keller, Cheryl A.; Face, Carolyne; Jahn, Kristen S.; Evans, Perry; Sankaranarayanan, Laavanya; Giardine, Belinda; Hardison, Ross C.; Raj, Arjun; Blobel, Gerd A.

    2016-01-01

    During mitosis, RNA polymerase II (Pol II) and many transcription factors dissociate from chromatin, and transcription ceases globally. Transcription is known to restart in bulk by telophase, but whether de novo transcription at the mitosis–G1 transition is in any way distinct from later in interphase remains unknown. We tracked Pol II occupancy genome-wide in mammalian cells progressing from mitosis through late G1. Unexpectedly, during the earliest rounds of transcription at the mitosis–G1 transition, ∼50% of active genes and distal enhancers exhibit a spike in transcription, exceeding levels observed later in G1 phase. Enhancer–promoter chromatin contacts are depleted during mitosis and restored rapidly upon G1 entry but do not spike. Of the chromatin-associated features examined, histone H3 Lys27 acetylation levels at individual loci in mitosis best predict the mitosis–G1 transcriptional spike. Single-molecule RNA imaging supports that the mitosis–G1 transcriptional spike can constitute the maximum transcriptional activity per DNA copy throughout the cell division cycle. The transcriptional spike occurs heterogeneously and propagates to cell-to-cell differences in mature mRNA expression. Our results raise the possibility that passage through the mitosis–G1 transition might predispose cells to diverge in gene expression states. PMID:27340175

  7. A hyperactive transcriptional state marks genome reactivation at the mitosis-G1 transition.

    Science.gov (United States)

    Hsiung, Chris C-S; Bartman, Caroline R; Huang, Peng; Ginart, Paul; Stonestrom, Aaron J; Keller, Cheryl A; Face, Carolyne; Jahn, Kristen S; Evans, Perry; Sankaranarayanan, Laavanya; Giardine, Belinda; Hardison, Ross C; Raj, Arjun; Blobel, Gerd A

    2016-06-15

    During mitosis, RNA polymerase II (Pol II) and many transcription factors dissociate from chromatin, and transcription ceases globally. Transcription is known to restart in bulk by telophase, but whether de novo transcription at the mitosis-G1 transition is in any way distinct from later in interphase remains unknown. We tracked Pol II occupancy genome-wide in mammalian cells progressing from mitosis through late G1. Unexpectedly, during the earliest rounds of transcription at the mitosis-G1 transition, ∼50% of active genes and distal enhancers exhibit a spike in transcription, exceeding levels observed later in G1 phase. Enhancer-promoter chromatin contacts are depleted during mitosis and restored rapidly upon G1 entry but do not spike. Of the chromatin-associated features examined, histone H3 Lys27 acetylation levels at individual loci in mitosis best predict the mitosis-G1 transcriptional spike. Single-molecule RNA imaging supports that the mitosis-G1 transcriptional spike can constitute the maximum transcriptional activity per DNA copy throughout the cell division cycle. The transcriptional spike occurs heterogeneously and propagates to cell-to-cell differences in mature mRNA expression. Our results raise the possibility that passage through the mitosis-G1 transition might predispose cells to diverge in gene expression states. © 2016 Hsiung et al.; Published by Cold Spring Harbor Laboratory Press.

  8. Cell-State Transitions Regulated by SLUG Are Critical for Tissue Regeneration and Tumor Initiation

    Directory of Open Access Journals (Sweden)

    Sarah Phillips

    2014-05-01

    Full Text Available Perturbations in stem cell activity and differentiation can lead to developmental defects and cancer. We use an approach involving a quantitative model of cell-state transitions in vitro to gain insights into how SLUG/SNAI2, a key developmental transcription factor, modulates mammary epithelial stem cell activity and differentiation in vivo. In the absence of SLUG, stem cells fail to transition into basal progenitor cells, while existing basal progenitor cells undergo luminal differentiation; together, these changes result in abnormal mammary architecture and defects in tissue function. Furthermore, we show that in the absence of SLUG, mammary stem cell activity necessary for tissue regeneration and cancer initiation is lost. Mechanistically, SLUG regulates differentiation and cellular plasticity by recruiting the chromatin modifier lysine-specific demethylase 1 (LSD1 to promoters of lineage-specific genes to repress transcription. Together, these results demonstrate that SLUG plays a dual role in repressing luminal epithelial differentiation while unlocking stem cell transitions necessary for tumorigenesis.

  9. The nuclear industry's transition to risk-informed regulation and operation in the United States

    International Nuclear Information System (INIS)

    Kadak, Andrew C.; Matsuo, Toshihiro

    2007-01-01

    This paper summarizes a study of the transition of the United States nuclear industry from a prescriptive regulatory structure to a more risk informed approach to operations and regulations. The transition occurred over a 20 yr period in which gradual changes were made in the fundamental regulations and to the approach to nuclear safety and operations. While the number of actual regulatory changes were few, they are continuing. The utilities that embraced risk informed operations made dramatic changes in the way they approached operations and outage management. Those utilities that used risk in operations showed dramatic improvement in safety based on Institute of Nuclear Power Operations (INPO) performance indicators. It was also shown that the use of risk did not negatively affect safety performance of the plants compared to standard prescriptive approaches. This was despite having greater flexibility in compliance to regulatory standards and the use of the newly instituted risk-informed reactor oversight process. Key factors affecting the successful transition to a more risk-informed approach to regulations and operations are: strong top management support and leadership both at the regulator and the utility; education and training in risk principles and probabilistic risk Assessment tools for engineers, operators and maintenance staff; a slow and steady introduction of risk initiatives in areas that can show value to both the regulator and the industry; a transparent regulatory foundation built around a safety goal policy and the development of a strong safety culture at the utility to allow for more independence in safety compliance and risk management. The experience of the United States shows positive results in both safety and economics. The INPO and NRC metrics presented show that the use of risk information in operations and regulation is marginally better with no degradation in safety when plants that have embraced risk-informed approaches are compared

  10. Spectroscopy of 215Ra: the shell model and enhanced E3 transitions

    International Nuclear Information System (INIS)

    Stuchbery, A.E.; Dracoulis, G.D.; Kibedi, T.; Fabricius, B.; Lane, G.J.; Poletti, A.R.; Baxter, A.M.

    1998-01-01

    Excited states in the N=127 nucleus 215 Ra have been studied using γ-ray and electron spectroscopy following reactions of 13 C on 206 Pb targets. Levels were identified up to spins of ∝61/2 ℎ and excitation energies of ∝6 MeV. Enhanced octupole transitions are a feature of the level scheme. Lifetimes and magnetic moments were measured for several isomeric levels. The level scheme, transition rates and magnetic moments are compared with empirical shell model calculations and multiparticle octupole-coupled shell model calculations. In general, the experimental data are well described, but in comparison with its success in describing enhanced E3 transitions between related states in the radon isotopes, some limitations of the multiparticle octupole-coupling approach are revealed in 215 Ra. (orig.)

  11. Thermally and vibrationally induced conformational isomerizations, infrared spectra, and photochemistry of gallic acid in low-temperature matrices

    Science.gov (United States)

    Justino, Licínia L. G.; Reva, Igor; Fausto, Rui

    2016-07-01

    Near-infrared (near-IR) narrowband selective vibrational excitation and annealing of gallic acid (3,4,5-trihydroxybenzoic acid) isolated in cryogenic matrices were used to induce interconversions between its most stable conformers. The isomerizations were probed by infrared spectroscopy. An extensive set of quantum chemical calculations, carried out at the DFT(B3LYP)/6-311++G(d,p) level of approximation, was used to undertake a detailed analysis of the ground state potential energy surface of the molecule. This investigation of the molecule conformational space allowed extracting mechanistic insights into the observed annealing- or near-IR-induced isomerization processes. The infrared spectra of the two most stable conformers of gallic acid in N2, Xe, and Ar matrices were fully assigned. Finally, the UV-induced photochemistry of the matrix isolated compound was investigated.

  12. Thermally and vibrationally induced conformational isomerizations, infrared spectra, and photochemistry of gallic acid in low-temperature matrices

    International Nuclear Information System (INIS)

    Justino, Licínia L. G.; Reva, Igor; Fausto, Rui

    2016-01-01

    Near-infrared (near-IR) narrowband selective vibrational excitation and annealing of gallic acid (3,4,5-trihydroxybenzoic acid) isolated in cryogenic matrices were used to induce interconversions between its most stable conformers. The isomerizations were probed by infrared spectroscopy. An extensive set of quantum chemical calculations, carried out at the DFT(B3LYP)/6-311++G(d,p) level of approximation, was used to undertake a detailed analysis of the ground state potential energy surface of the molecule. This investigation of the molecule conformational space allowed extracting mechanistic insights into the observed annealing- or near-IR-induced isomerization processes. The infrared spectra of the two most stable conformers of gallic acid in N 2 , Xe, and Ar matrices were fully assigned. Finally, the UV-induced photochemistry of the matrix isolated compound was investigated.

  13. Thermally and vibrationally induced conformational isomerizations, infrared spectra, and photochemistry of gallic acid in low-temperature matrices

    Energy Technology Data Exchange (ETDEWEB)

    Justino, Licínia L. G., E-mail: liciniaj@ci.uc.pt; Reva, Igor; Fausto, Rui [CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra (Portugal)

    2016-07-07

    Near-infrared (near-IR) narrowband selective vibrational excitation and annealing of gallic acid (3,4,5-trihydroxybenzoic acid) isolated in cryogenic matrices were used to induce interconversions between its most stable conformers. The isomerizations were probed by infrared spectroscopy. An extensive set of quantum chemical calculations, carried out at the DFT(B3LYP)/6-311++G(d,p) level of approximation, was used to undertake a detailed analysis of the ground state potential energy surface of the molecule. This investigation of the molecule conformational space allowed extracting mechanistic insights into the observed annealing- or near-IR-induced isomerization processes. The infrared spectra of the two most stable conformers of gallic acid in N{sub 2}, Xe, and Ar matrices were fully assigned. Finally, the UV-induced photochemistry of the matrix isolated compound was investigated.

  14. Left cardiac isomerism in the Sonic hedgehog null mouse.

    Science.gov (United States)

    Hildreth, Victoria; Webb, Sandra; Chaudhry, Bill; Peat, Jonathan D; Phillips, Helen M; Brown, Nigel; Anderson, Robert H; Henderson, Deborah J

    2009-06-01

    Sonic hedgehog (Shh) is a secreted morphogen necessary for the production of sidedness in the developing embryo. In this study, we describe the morphology of the atrial chambers and atrioventricular junctions of the Shh null mouse heart. We demonstrate that the essential phenotypic feature is isomerism of the left atrial appendages, in combination with an atrioventricular septal defect and a common atrioventricular junction. These malformations are known to be frequent in humans with left isomerism. To confirm the presence of left isomerism, we show that Pitx2c, a recognized determinant of morphological leftness, is expressed in the Shh null mutants on both the right and left sides of the inflow region, and on both sides of the solitary arterial trunk exiting from the heart. It has been established that derivatives of the second heart field expressing Isl1 are asymmetrically distributed in the developing normal heart. We now show that this population is reduced in the hearts from the Shh null mutants, likely contributing to the defects. To distinguish the consequences of reduced contributions from the second heart field from those of left-right patterning disturbance, we disrupted the movement of second heart field cells into the heart by expressing dominant-negative Rho kinase in the population of cells expressing Isl1. This resulted in absence of the vestibular spine, and presence of atrioventricular septal defects closely resembling those seen in the hearts from the Shh null mutants. The primary atrial septum, however, was well formed, and there was no evidence of isomerism of the atrial appendages, suggesting that these features do not relate to disruption of the contributions made by the second heart field. We demonstrate, therefore, that the Shh null mouse is a model of isomerism of the left atrial appendages, and show that the recognized associated malformations found at the venous pole of the heart in the setting of left isomerism are likely to arise from

  15. An equation-of-state-meter of quantum chromodynamics transition from deep learning.

    Science.gov (United States)

    Pang, Long-Gang; Zhou, Kai; Su, Nan; Petersen, Hannah; Stöcker, Horst; Wang, Xin-Nian

    2018-01-15

    A primordial state of matter consisting of free quarks and gluons that existed in the early universe a few microseconds after the Big Bang is also expected to form in high-energy heavy-ion collisions. Determining the equation of state (EoS) of such a primordial matter is the ultimate goal of high-energy heavy-ion experiments. Here we use supervised learning with a deep convolutional neural network to identify the EoS employed in the relativistic hydrodynamic simulations of heavy ion collisions. High-level correlations of particle spectra in transverse momentum and azimuthal angle learned by the network act as an effective EoS-meter in deciphering the nature of the phase transition in quantum chromodynamics. Such EoS-meter is model-independent and insensitive to other simulation inputs including the initial conditions for hydrodynamic simulations.

  16. State estimation for Markov-type genetic regulatory networks with delays and uncertain mode transition rates

    International Nuclear Information System (INIS)

    Liang Jinling; Lam, James; Wang Zidong

    2009-01-01

    This Letter is concerned with the robust state estimation problem for uncertain time-delay Markovian jumping genetic regulatory networks (GRNs) with SUM logic, where the uncertainties enter into both the network parameters and the mode transition rate. The nonlinear functions describing the feedback regulation are assumed to satisfy the sector-like conditions. The main purpose of the problem addressed is to design a linear estimator to approximate the true concentrations of the mRNA and protein through available measurement outputs. By resorting to the Lyapunov functional method and some stochastic analysis tools, it is shown that if a set of linear matrix inequalities (LMIs) is feasible, the desired state estimator, that can ensure the estimation error dynamics to be globally robustly asymptotically stable in the mean square, exists. The obtained LMI conditions are dependent on both the lower and the upper bounds of the delays. An illustrative example is presented to demonstrate the feasibility of the proposed estimation schemes.

  17. Probing the transition state region in catalytic CO oxidation on Ru

    Energy Technology Data Exchange (ETDEWEB)

    Ostrom, H. [Stockholm Univ. (Sweden); Oberg, H. [Stockholm Univ. (Sweden); Xin, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); LaRue, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States); Beye, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Dell' Angela, M. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); Gladh, J. [Stockholm Univ. (Sweden); Ng, M. L. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Sellberg, J. A. [Stockholm Univ. (Sweden); SLAC National Accelerator Lab., Menlo Park, CA (United States); Kaya, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Mercurio, G. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); Nordlund, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hantschmann, M. [Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Hieke, F. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); Kuhn, D. [Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Schlotter, W. F. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Dakovski, G. L. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Turner, J. J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Minitti, M. P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Mitra, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Moeller, S. P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Fohlisch, A. [Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Univ. Potsdam, Potsdam (Germany); Wolf, M. [Fritz-Haber Institute of the Max-Planck-Society, Berlin (Germany); Wurth, W. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); DESY Photon Science, Hamburg (Germany); Persson, M. [The Univ. of Liverpool, Liverpool (United Kingdom); Norskov, J. K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States); Abild-Pedersen, F. [Stanford Univ., Stanford, CA (United States); Ogasawara, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Pettersson, L. G. M. [Stockholm Univ. (Sweden); Nilsson, A. [Stockholm Univ. (Sweden); SLAC National Accelerator Lab., Menlo Park, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-02-12

    Femtosecond x-ray laser pulses are used to probe the CO oxidation reaction on ruthenium (Ru) initiated by an optical laser pulse. On a time scale of a few hundred femtoseconds, the optical laser pulse excites motions of CO and O on the surface, allowing the reactants to collide, and, with a transient close to a picosecond (ps), new electronic states appear in the O K-edge x-ray absorption spectrum. Density functional theory calculations indicate that these result from changes in the adsorption site and bond formation between CO and O with a distribution of OC–O bond lengths close to the transition state (TS). After 1 ps, 10% of the CO populate the TS region, which is consistent with predictions based on a quantum oscillator model.

  18. Reassessment of fission fragment angular distributions from continuum states in the context of transition-state theory

    International Nuclear Information System (INIS)

    Vaz, L.C.; Alexander, J.M.

    1983-01-01

    Fission angular distributions have been studied for years and have been treated as classic examples of transition-state theory. Early work involving composite nuclei of relatively low excitation energy Esup(*) ( 2 0 (K 2 0 = Psub(eff)T/(h/2π) 2 ) are presented along with comparissons of Psub(eff) to moments of inertia for saddle-point nuclei from the rotating liquid drop model. This model gives an excellent guide for the intermediate spin zone (30 < or approx. I < or approx. 65), while strong shell and/or pairing effects are evident for excitations less than < or approx. 35 MeV. Observations of strong anisotropies for very high-spin systems signal the demise of certain approximations commonly made in the theory, and suggestions are made toward this end. (orig.)

  19. Post-transition state dynamics and product energy partitioning following thermal excitation of the F⋯HCH2CN transition state: Disagreement with experiment

    Science.gov (United States)

    Pratihar, Subha; Ma, Xinyou; Xie, Jing; Scott, Rebecca; Gao, Eric; Ruscic, Branko; Aquino, Adelia J. A.; Setser, Donald W.; Hase, William L.

    2017-10-01

    Born-Oppenheimer direct dynamics simulations were performed to study atomistic details of the F + CH3CN → HF + CH2CN H-atom abstraction reaction. The simulation trajectories were calculated with a combined M06-2X/MP2 algorithm utilizing the 6-311++G** basis set. The experiments were performed at 300 K, and assuming the accuracy of transition state theory (TST), the trajectories were initiated at the F⋯HCH2CN abstraction TS with a 300 K Boltzmann distribution of energy and directed towards products. Recrossing of the TS was negligible, confirming the accuracy of TST. HF formation was rapid, occurring within 0.014 ps of the trajectory initiation. The intrinsic reaction coordinate (IRC) for reaction involves rotation of HF about CH2CN and then trapping in the CH2CN⋯HF post-reaction potential energy well of ˜10 kcal/mol with respect to the HF + CH2CN products. In contrast to this IRC, five different trajectory types were observed: the majority proceeded by direct H-atom transfer and only 11% approximately following the IRC. The HF vibrational and rotational quantum numbers, n and J, were calculated when HF was initially formed and they increase as potential energy is released in forming the HF + CH2CN products. The population of the HF product vibrational states is only in qualitative agreement with experiment, with the simulations showing depressed and enhanced populations of the n = 1 and 2 states as compared to experiment. Simulations with an anharmonic zero-point energy constraint gave product distributions for relative translation, HF rotation, HF vibration, CH2CN rotation, and CH2CN vibration as 5%, 11%, 60%, 7%, and 16%, respectively. In contrast, the experimental energy partitioning percentages to HF rotation and vibration are 6% and 41%. Comparisons are made between the current simulation and those for other F + H-atom abstraction reactions. The simulation product energy partitioning and HF vibrational population for F + CH3CN → HF + CH2CN

  20. Post-transition state dynamics and product energy partitioning following thermal excitation of the F⋯HCH2CN transition state: Disagreement with experiment.

    Science.gov (United States)

    Pratihar, Subha; Ma, Xinyou; Xie, Jing; Scott, Rebecca; Gao, Eric; Ruscic, Branko; Aquino, Adelia J A; Setser, Donald W; Hase, William L

    2017-10-14

    Born-Oppenheimer direct dynamics simulations were performed to study atomistic details of the F + CH 3 CN → HF + CH 2 CN H-atom abstraction reaction. The simulation trajectories were calculated with a combined M06-2X/MP2 algorithm utilizing the 6-311++G** basis set. The experiments were performed at 300 K, and assuming the accuracy of transition state theory (TST), the trajectories were initiated at the F⋯HCH 2 CN abstraction TS with a 300 K Boltzmann distribution of energy and directed towards products. Recrossing of the TS was negligible, confirming the accuracy of TST. HF formation was rapid, occurring within 0.014 ps of the trajectory initiation. The intrinsic reaction coordinate (IRC) for reaction involves rotation of HF about CH 2 CN and then trapping in the CH 2 CN⋯HF post-reaction potential energy well of ∼10 kcal/mol with respect to the HF + CH 2 CN products. In contrast to this IRC, five different trajectory types were observed: the majority proceeded by direct H-atom transfer and only 11% approximately following the IRC. The HF vibrational and rotational quantum numbers, n and J, were calculated when HF was initially formed and they increase as potential energy is released in forming the HF + CH 2 CN products. The population of the HF product vibrational states is only in qualitative agreement with experiment, with the simulations showing depressed and enhanced populations of the n = 1 and 2 states as compared to experiment. Simulations with an anharmonic zero-point energy constraint gave product distributions for relative translation, HF rotation, HF vibration, CH 2 CN rotation, and CH 2 CN vibration as 5%, 11%, 60%, 7%, and 16%, respectively. In contrast, the experimental energy partitioning percentages to HF rotation and vibration are 6% and 41%. Comparisons are made between the current simulation and those for other F + H-atom abstraction reactions. The simulation product energy partitioning and HF vibrational population for F + CH 3 CN

  1. Light-induced linkage isomerization of photochromic [Ru(bpy){sub 2}(R-OSO)]{sup +} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Springfeld, Kristin; Dieckmann, Volker; Eicke, Sebastian; Imlau, Mirco [Department of Physics, University of Osnabrueck (Germany); Rack, Jeffrey J. [Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio (United States)

    2010-07-01

    Ruthenium sulfoxides exhibit light-induced linkage isomerization of the SO-bond with remarkable photosensitivity S=(0.25{+-}0.03) Ws cm{sup -1} and extended lifetimes of the related metastable states in the order of 10{sup 4} s. The isomerization is accompanied with tremendous changes of the optical extinction up to 9350 cm{sup -1} mol{sup -1} thus enabling the study of linkage isomerization by means of time-resolved optical spectroscopy. Here, the influence of ligand substitution is studied via inspection of the photosensitivity and the generation and relaxation dynamics of the photochromic response as a function of temperature (pump at {lambda}=405 nm, probe at {lambda}=532 nm). The spectra of the modified compounds, where ligands R=Bn, BnCl, and BnMe were attached to OSO, were compared with the reference system [Ru(bpy){sub 2}(OSO)]{sup +}. It turns out, that the new ligands affect the absorption features and the photosensitivity of the system only slightly. In contrast, a strong influence of the thermal relaxation of the metastable states is uncovered. Remarkably, the influence on the frequency factors is much more pronounced than on the activation energies achieved by Arrhenius' law.

  2. The thermal Z-isomerization-induced change in solubility and physical properties of (all-E)-lycopene.

    Science.gov (United States)

    Murakami, Kazuya; Honda, Masaki; Takemura, Ryota; Fukaya, Tetsuya; Kubota, Mitsuhiro; Wahyudiono; Kanda, Hideki; Goto, Motonobu

    2017-09-16

    The effect of Z-isomerization of (all-E)-lycopene on its solubility in organic solvents and physical properties was investigated. Lycopene samples containing different Z-isomer contents (23.8%, 46.9%, and 75.6% of total lycopene) were prepared from high-purity (all-E)-lycopene by thermal Z-isomerization in dichloromethane (CH 2 Cl 2 ). As the Z-isomer content increased, the relative solubility of lycopene significantly improved. Although (all-E)-lycopene barely dissolved in ethanol (0.6 mg/L), the solubilities of lycopene containing 23.8%, 46.9%, and 75.6% Z-isomers were 484.5, 914.7, and 2401.7 mg/L, respectively. Furthermore, differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses clearly indicated that (all-E)-lycopene was present in the crystal state, while Z-isomers of lycopene were present in amorphous states. A number of studies have suggested that Z-isomers of lycopene are better absorbed in the human body than the all-E-isomer. This may be due to the change in solubility and physical properties of lycopene by the Z-isomerization. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. The peptide-receptive transition state of MHC-1 molecules: Insight from structure and molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Robinson H.; Mage, M.; Dolan, M.; Wang, R.; Boyd, L.; Revilleza, M.; Natarajan, K.; Myers, N.; Hansen, T.; Margulies, D.

    2012-05-01

    MHC class I (MHC-I) proteins of the adaptive immune system require antigenic peptides for maintenance of mature conformation and immune function via specific recognition by MHC-I-restricted CD8(+) T lymphocytes. New MHC-I molecules in the endoplasmic reticulum are held by chaperones in a peptide-receptive (PR) transition state pending release by tightly binding peptides. In this study, we show, by crystallographic, docking, and molecular dynamics methods, dramatic movement of a hinged unit containing a conserved 3(10) helix that flips from an exposed 'open' position in the PR transition state to a 'closed' position with buried hydrophobic side chains in the peptide-loaded mature molecule. Crystallography of hinged unit residues 46-53 of murine H-2L(d) MHC-I H chain, complexed with mAb 64-3-7, demonstrates solvent exposure of these residues in the PR conformation. Docking and molecular dynamics predict how this segment moves to help form the A and B pockets crucial for the tight peptide binding needed for stability of the mature peptide-loaded conformation, chaperone dissociation, and Ag presentation.

  4. A critical assessment of theoretical methods for finding reaction pathways and transition states of surface processes

    International Nuclear Information System (INIS)

    Klimes, JirI; Michaelides, Angelos; Bowler, David R

    2010-01-01

    The performance of a variety of techniques for locating transition states on potential energy surfaces is evaluated within the density functional theory framework. Diffusion of a water molecule across NaCl(001) and HCl bond breaking on the same surface are treated as general test cases; the former is an example of a low barrier diffusion process and the latter an example of a relatively high barrier covalent bond rupture event. The methods considered include the nudged elastic band (NEB), Dewar, Healy and Stewart (DHS), dimer, constrained optimization (CO), activation-relaxation technique (ART) and one-side growing string (OGS) as well as novel combinations of the DHS with growing string (DHS + GS) and DHS plus climbing image (CI-DHS). A key conclusion to come from this study is that the NEB method is relatively fast, especially when just a single (climbing) image is used. Indeed, using more images represents an unnecessary computational burden for our set of processes. The dimer method exhibits variable performance; being poor for the water diffusion processes, which have small activation energies, but much more efficient for the HCl bond breaking process which has a higher barrier. When only a poor initial guess of the transition state geometry is available, the CI-DHS scheme is one of the most efficient techniques considered. And as a means to quickly establish an approximate minimum energy pathway the DHS + GS scheme offers some potential.

  5. Transitions between states of labor-force participation among older Israelis.

    Science.gov (United States)

    Achdut, Leah; Tur-Sinai, Aviad; Troitsky, Rita

    2015-03-01

    The study examines the labor-force behavior of Israelis at older ages, focusing on the determinants of the transitions between states of labor-force participation between 2005 and 2010. The study uses panel data from the first two waves of the SHARE-Israel longitudinal survey. A multinomial logit model is used to examine the impact of sociodemographic characteristics, health state, and economic resources on labor-force transitions of people aged 50-67. The results emphasize the role of age and poor health in "pushing" older people out of the labor force or "keeping" them there. Spouse's participation is found to encourage individuals to leave the labor force or to refrain from joining it. However, living with a participating spouse is negatively associated with staying out of the labor force, consistent with the dominance of the complementarity of leisure effect found in the literature. Wealth as an economic resource available to individuals for retirement is also found to encourage individuals to leave the labor force or to refrain from joining it.

  6. Efficient Sampling of the Structure of Crypto Generators' State Transition Graphs

    Science.gov (United States)

    Keller, Jörg

    Cryptographic generators, e.g. stream cipher generators like the A5/1 used in GSM networks or pseudo-random number generators, are widely used in cryptographic network protocols. Basically, they are finite state machines with deterministic transition functions. Their state transition graphs typically cannot be analyzed analytically, nor can they be explored completely because of their size which typically is at least n = 264. Yet, their structure, i.e. number and sizes of weakly connected components, is of interest because a structure deviating significantly from expected values for random graphs may form a distinguishing attack that indicates a weakness or backdoor. By sampling, one randomly chooses k nodes, derives their distribution onto connected components by graph exploration, and extrapolates these results to the complete graph. In known algorithms, the computational cost to determine the component for one randomly chosen node is up to O(√n), which severely restricts the sample size k. We present an algorithm where the computational cost to find the connected component for one randomly chosen node is O(1), so that a much larger sample size k can be analyzed in a given time. We report on the performance of a prototype implementation, and about preliminary analysis for several generators.

  7. In-Situ Phase Transition Control in the Supercooled State for Robust Active Glass Fiber.

    Science.gov (United States)

    Lv, Shichao; Cao, Maoqing; Li, Chaoyu; Li, Jiang; Qiu, Jianrong; Zhou, Shifeng

    2017-06-21

    The construction of a dopant-activated photonic composite is of great technological importance for various applications, including smart lighting, optical amplification, laser, and optical detection. The bonding arrangement around the introduced dopants largely determines the properties, yet it remains a daunting challenge to manipulate the local state of the matrix (i.e., phase) inside the transparent composite in a controllable manner. Here we demonstrate that the relaxation of the supercooled state enables in-situ phase transition control in glass. Benefiting from the unique local atom arrangement manner, the strategy offers the possibility for simultaneously tuning the chemical environment of the incorporated dopant and engineering the dopant-host interaction. This allows us to effectively activate the dopant with high efficiency (calculated as ∼100%) and profoundly enhance the dopant-host energy-exchange interaction. Our results highlight that the in-situ phase transition control in glass may provide new opportunities for fabrication of unusual photonic materials with intense broadband emission at ∼1100 nm and development of the robust optical detection unit with high compactness and broadband photon-harvesting capability (from X-ray to ultraviolet light).

  8. Secondary deuterium isotope effects and transition state structure in the aromatic claisen rearrangement

    International Nuclear Information System (INIS)

    McMichael, K.D.; Korver, G.L.

    1979-01-01

    Kinetic experiments were carried out simultaneously on separate methyl salicylate solutions of allyl phenyl ether and its deuterated phenyl analogues at 170 to 195 0 C. Gas chromatographic analysis for allyl phenyl ether using an internal standard (anisole) and mechanical integration produced concentration/time data which were fitted to the exponential form of the first-order rate equation by a standard and nonlinear least-square program. At least 15 points were obtained for each run, covering 10 to 85% reaction. The derived isotope effects show no temperature dependence. Averages for 6 runs with each compound are k/sub H//k/sub α-D 2 / = 1.18 and K/sub H//k/sub γ-D 2 / = 0.95. An equilibrium α effect of 1.30 and a γ effect of 0.87 may be calculated for both deuterium atoms at 185 0 C. These results show that the C--H vibration frequencies are approximately (1.18 - 1)/(1.27 - 1) or 57 to 77% of the way from those of allyl phenyl ether to those of the cyclohexadiene intermediate. The C--H frequencies of the γ carbon in the transition state are about (0.95 - 1)/(0.88 - 1) or 22 to 62% of the way to those of the intermediate. The structure of the transition state, as far as these bonding frequencies are concerned, is consistent with the Claisen rearrangement

  9. High Pressure ZZ-Exchange NMR Reveals Key Features of Protein Folding Transition States.

    Science.gov (United States)

    Zhang, Yi; Kitazawa, Soichiro; Peran, Ivan; Stenzoski, Natalie; McCallum, Scott A; Raleigh, Daniel P; Royer, Catherine A

    2016-11-23

    Understanding protein folding mechanisms and their sequence dependence requires the determination of residue-specific apparent kinetic rate constants for the folding and unfolding reactions. Conventional two-dimensional NMR, such as HSQC experiments, can provide residue-specific information for proteins. However, folding is generally too fast for such experiments. ZZ-exchange NMR spectroscopy allows determination of folding and unfolding rates on much faster time scales, yet even this regime is not fast enough for many protein folding reactions. The application of high hydrostatic pressure slows folding by orders of magnitude due to positive activation volumes for the folding reaction. We combined high pressure perturbation with ZZ-exchange spectroscopy on two autonomously folding protein domains derived from the ribosomal protein, L9. We obtained residue-specific apparent rates at 2500 bar for the N-terminal domain of L9 (NTL9), and rates at atmospheric pressure for a mutant of the C-terminal domain (CTL9) from pressure dependent ZZ-exchange measurements. Our results revealed that NTL9 folding is almost perfectly two-state, while small deviations from two-state behavior were observed for CTL9. Both domains exhibited large positive activation volumes for folding. The volumetric properties of these domains reveal that their transition states contain most of the internal solvent excluded voids that are found in the hydrophobic cores of the respective native states. These results demonstrate that by coupling it with high pressure, ZZ-exchange can be extended to investigate a large number of protein conformational transitions.

  10. Reversibility of magnetic field driven transition from electronic phase separation state to single-phase state in manganites: A microscopic view

    Science.gov (United States)

    Liu, Hao; Lin, Lingfang; Yu, Yang; Lin, Hanxuan; Zhu, Yinyan; Miao, Tian; Bai, Yu; Shi, Qian; Cai, Peng; Kou, Yunfang; Lan, Fanli; Wang, Wenbin; Zhou, Xiaodong; Dong, Shuai; Yin, Lifeng; Shen, Jian

    2017-11-01

    Electronic phase separation (EPS) is a common phenomenon in strongly correlated oxides. For colossal magnetoresistive (CMR) manganites, the EPS is so pronounced that not only does it govern the CMR behavior, but also raises a question whether EPS exists as a ground state for systems or a metastable state. While it has been well known that a magnetic field can drive the transition of the EPS state into a single-phase state in manganites, the reversibility of this transition is not well studied. In this work we use magnetic force microscopy (MFM) to directly visualize the reversibility of the field driven transition between the EPS state and the single-phase state at different temperatures. The MFM images correspond well with the global magnetic and transport property measurements, uncovering the underlying mechanism of the field driven transition between the EPS state and the single-phase state. We argue that EPS state is a consequence of system quenching whose response to an external magnetic field is governed by a local energy landscape.

  11. Inhibition and Structure of Trichomonas vaginalis Purine Nucleoside Phosphorylase with Picomolar Transition State Analogues

    Energy Technology Data Exchange (ETDEWEB)

    Rinaldo-Matthis,A.; Wing, C.; Ghanem, M.; Deng, H.; Wu, P.; Gupta, A.; Tyler, P.; Evans, G.; Furneaux, R.; et al.

    2007-01-01

    Trichomonas vaginalis is a parasitic protozoan purine auxotroph possessing a unique purine salvage pathway consisting of a bacterial type purine nucleoside phosphorylase (PNP) and a purine nucleoside kinase. Thus, T. vaginalis PNP (TvPNP) functions in the reverse direction relative to the PNPs in other organisms. Immucillin-A (ImmA) and DADMe-Immucillin-A (DADMe-ImmA) are transition stte mimics of adenosine with geometric and electrostatic features that resemble early and late transition states of adenosine at the transition state stabilized by TvPNP. ImmA demonstrates slow-onset tight-binding inhibition with TvPNP, to give an equilibrium dissociation constant of 87 pM, an inhibitor release half-time of 17.2 min, and a K{sub m}/K{sub d} ratio of 70,100. DADMe-ImmA resembles a late ribooxacarbenium ion transition state for TvPNP to give a dissociation constant of 30 pM, an inhibitor release half-time of 64 min, and a K{sub m}/K{sub d} ratio of 203,300. The tight binding of DADMe-ImmA supports a late S{sub N}1 transition state. Despite their tight binding to TvPNP, ImmA and DADMe-ImmA are weak inhibitors of human and P. falciparum PNPs. The crystal structures of the TvPNP-ImmA{center_dot}PO{sub 4} and TvPNP{center_dot}DADMe-ImmA{center_dot}PO{sub 4} ternary complexes differ from previous structures with substrate anologues. The tight binding with DADMe-ImmA is in part due to a 2.7 {angstrom} ionic interaction between a PO{sub 4} oxygen and the N1 cation of the hydroxypyrrolidine and is weaker in the TvPNP{center_dot}ImmA{center_dot}PO{sub 4} structure at 3.5 {angstrom}. However, the TvPNP{center_dot}ImmA{center_dot}PO{sub 4} structure includes hydrogen bonds between the 2'-hydroxyl and the protein that are not present in TvPNP{center_dot}DADMe-ImmA{center_dot}PO{sub 4}. These structures explain why DADMe-ImmA binds tighter than ImmA. Immucillin-H is a 12 nM inhibitor of TvPNP but a 56 pM inhibitor of human PNP. And this difference is explained by isotope

  12. High energy (MeV) ion-irradiated π-conjugated polyaniline: Transition from insulating state to carbonized conducting state

    International Nuclear Information System (INIS)

    Park, S.K.; Lee, S.Y.; Lee, C.S.; Kim, H.M.; Joo, J.; Beag, Y.W.; Koh, S.K.

    2004-01-01

    High energy (MeV) C 2+ , F 2+ , and Cl 2+ ions were irradiated onto π-conjugated polyaniline emeraldine base (PAN-EB) samples. The energy of an ion beam was controlled to a range of 3-4.5 MeV, with the ion dosage varying from 1x10 12 to 1x10 16 ions/cm 2 . The highest dc conductivity (σ dc ) at room temperature was measured to be ∼60 S/cm for 4.5 MeV Cl 2+ ion-irradiated PAN-EB samples with a dose of 1x10 16 ions/cm 2 . We observed the transition of high energy ion-irradiated PAN-EB samples from insulating state to conducting state as a function of ion dosage based on σ dc and its temperature dependence. The characteristic peaks of the Raman spectrum of the PAN-EB samples were reduced, while the D-peak (disordered peak) and the G peak (graphitic peak) appeared as the ion dose increased. From the analysis of the D and G peaks of the Raman spectra of the systems compared to multiwalled carbon nanotubes, ion-irradiated graphites, and annealed carbon films, the number of the clusters of hexagon rings with conducting sp 2 -bonded carbons increased with ion dosage. We also observed the increase in the size of the nanocrystalline graphitic domain of the systems with increasing ion dosage. The intensity of normalized electron paramagnelic resonance signal also increased in correlation with ion dose. The results of this study demonstrate that π-conjugated pristine PAN-EB systems changed from insulating state to carbonized conducting state through high energy ion irradiation with high ion dosage

  13. 1,2-Fluorine Radical Rearrangements: Isomerization Events in Perfluorinated Radicals.

    Science.gov (United States)

    Van Hoomissen, Daniel J; Vyas, Shubham

    2017-11-16

    Devising effective degradation technologies for perfluoroalkyl substances (PFASs) is an active area of research, where the molecular mechanisms involving both oxidative and reductive pathways are still elusive. One commonly neglected pathway in PFAS degradation is fluorine atom migration in perfluoroalkyl radicals, which was largely assumed to be implausible because of the high C-F bond strength. Using density functional theory calculations, it was demonstrated that 1,2-F atom migrations are thermodynamically favored when the fluorine atom migrated from a less branched carbon center to a more branched carbon center. Activation barriers for these rearrangements were within 19-29 kcal/mol, which are possible to easily overcome at elevated temperatures or in photochemically activated species in the gas or aqueous phase. It was also found that the activation barriers for the 1,2-F atom migration are lowered as much as by 10 kcal/mol when common oxidative degradation products such as HF assisted the rearrangements or if the resulting radical center was stabilized by vicinal π-bonds. Natural bond orbital analyses showed that fluorine moves as a radical in a noncharge-separated state. These findings add an important reaction to the existing knowledge of mechanisms for PFAS degradation and highlights the fact that 1,2-F atom shifts may be a small channel for isomerization of these compounds, but upon availability of mineralization products, this isomerization process could become more prominent.

  14. Meissner effects, vortex core states, and the vortex glass phase transition

    International Nuclear Information System (INIS)

    Huang, Ming.

    1991-01-01

    This thesis covers three topics involving Meissner effects and the resulting defect structures. The first is a study of Meissner effects in superconductivity and in systems with broken translational symmetry. The Meissner effect in the superconductors is a rigidity against external magnetic field caused by the breaking of the gauge symmetry. Other condensed matter systems also exhibit rigidities like this: The breaking of the translational symmetry in a cubic-liquid-crystal causes the system to expel twist deformations and the breaking of the translational symmetry in a nematic liquid crystal gives it a tendency to expel twist and bend deformations. In this thesis, the author studies these generalized Meissner effects in detail. The second is a study of the quasiparticle states bound to the vortex defect in superconductors. Scanning-tunneling-microscope measurements by Harald Hess et al. of the local density of states in a vortex core show a pronounced peak at small bias. These measurements contradict with previous theoretical calculations. Here, he solves the Bogoliubov equations to obtain the local density of states in the core and satisfactorily explain the experimental observations. He also predicted additional structure in the local density of states which were later observed in experiments. The third is a study of vortex dynamics in the presence of disorder. A mean field theory is developed for the recently proposed normal to superconducting vortex glass transition. Using techniques developed to study the critical dynamics of spin glasses, he calculates the mean field vortex glass phase boundary and the critical exponents

  15. Cosmological implications of the transition from the false vacuum to the true vacuum state

    Energy Technology Data Exchange (ETDEWEB)

    Stachowski, Aleksander [Jagiellonian University, Astronomical Observatory, Krakow (Poland); Szydlowski, Marek [Jagiellonian University, Astronomical Observatory, Krakow (Poland); Jagiellonian University, Mark Kac Complex Systems Research Centre, Krakow (Poland); Urbanowski, Krzysztof [University of Zielona Gora, Institute of Physics, Zielona Gora (Poland)

    2017-06-15

    We study cosmology with running dark energy. The energy density of dark energy is obtained from the quantum process of transition from the false vacuum state to the true vacuum state. We use the Breit-Wigner energy distribution function to model the quantum unstable systems and obtain the energy density of the dark energy parametrization ρ{sub de}(t). We also use Krauss and Dent's idea linking properties of the quantum mechanical decay of unstable states with the properties of the observed Universe. In the cosmological model with this parametrization there is an energy transfer between dark matter and dark energy. The intensity of this process, measured by a parameter α, distinguishes two scenarios. As the Universe starts from the false vacuum state, for the small value of α (0 < α < 0.4) it goes through an intermediate oscillatory (quantum) regime of the density of dark energy, while for α > 0.4 the density of the dark energy jumps down. In both cases the present value of the density of dark energy is reached. From a statistical analysis we find this model to be in good agreement with the astronomical data and practically indistinguishable from the ΛCDM model. (orig.)

  16. GRHL3 binding and enhancers rearrange as epidermal keratinocytes transition between functional states.

    Directory of Open Access Journals (Sweden)

    Rachel Herndon Klein

    2017-04-01

    Full Text Available Transcription factor binding, chromatin modifications and large scale chromatin re-organization underlie progressive, irreversible cell lineage commitments and differentiation. We know little, however, about chromatin changes as cells enter transient, reversible states such as migration. Here we demonstrate that when human progenitor keratinocytes either differentiate or migrate they form complements of typical enhancers and super-enhancers that are unique for each state. Unique super-enhancers for each cellular state link to gene expression that confers functions associated with the respective cell state. These super-enhancers are also enriched for skin disease sequence variants. GRHL3, a transcription factor that promotes both differentiation and migration, binds preferentially to super-enhancers in differentiating keratinocytes, while during migration, it binds preferentially to promoters along with REST, repressing the expression of migration inhibitors. Key epidermal differentiation transcription factor genes, including GRHL3, are located within super-enhancers, and many of these transcription factors in turn bind to and regulate super-enhancers. Furthermore, GRHL3 represses the formation of a number of progenitor and non-keratinocyte super-enhancers in differentiating keratinocytes. Hence, chromatin relocates GRHL3 binding and enhancers to regulate both the irreversible commitment of progenitor keratinocytes to differentiation and their reversible transition to migration.

  17. Cosmological implications of the transition from the false vacuum to the true vacuum state

    International Nuclear Information System (INIS)

    Stachowski, Aleksander; Szydlowski, Marek; Urbanowski, Krzysztof

    2017-01-01

    We study cosmology with running dark energy. The energy density of dark energy is obtained from the quantum process of transition from the false vacuum state to the true vacuum state. We use the Breit-Wigner energy distribution function to model the quantum unstable systems and obtain the energy density of the dark energy parametrization ρ_d_e(t). We also use Krauss and Dent's idea linking properties of the quantum mechanical decay of unstable states with the properties of the observed Universe. In the cosmological model with this parametrization there is an energy transfer between dark matter and dark energy. The intensity of this process, measured by a parameter α, distinguishes two scenarios. As the Universe starts from the false vacuum state, for the small value of α (0 0.4 the density of the dark energy jumps down. In both cases the present value of the density of dark energy is reached. From a statistical analysis we find this model to be in good agreement with the astronomical data and practically indistinguishable from the ΛCDM model. (orig.)

  18. Surface study of mixtures containing cyclic ethers and isomeric chlorobutanes

    International Nuclear Information System (INIS)

    Royo, F.M.; Villares, A.; Martin, S.; Giner, B.; Lafuente, C.

    2007-01-01

    Experimental surface tensions and the corresponding surface tensions deviations for the mixtures containing 1,3-dioxolane or 1,4-dioxane and 1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane or 2-chloro-2-methylpropane, measured with a drop volume tensiometer, are reported at the temperatures of 298.15 K and 313.15 K. The excess surface concentrations of isomeric chlorobutanes are also evaluated using a monolayer model

  19. Effects of a Transition to a Hydrogen Economy on Employment in the United States

    International Nuclear Information System (INIS)

    Tolley, George S.; Jones, Donald W.; Mintz, Marianne M.; Smith, Barton A.; Carlson, Eric; Unnasch, Stefan; Lawrence, Michael; Chmelynski, Harry

    2008-01-01

    The U.S. Department of Energy report, Effects of a Transition to a Hydrogen Economy on Employment in the United States Report to Congress, estimates the effects on employment of a U.S. economy transformation to hydrogen between 2020 and 2050. The report includes study results on employment impacts from hydrogen market expansion in the transportation, stationary, and portable power sectors and highlights possible skill and education needs. This study is in response to Section 1820 of the Energy Policy Act of 2005 (Public Law 109-58) (EPACT). Section 1820, 'Overall Employment in a Hydrogen Economy', requires the Secretary of Energy to carry out a study of the effects of a transition to a hydrogen economy on several employment (types) in the United States. As required by Section 1820, the present report considers: (1) Replacement effects of new goods and services; (2) International competition; (3) Workforce training requirements; (4) Multiple possible fuel cycles, including usage of raw materials; (5) Rates of market penetration of technologies; (6) Regional variations based on geography; and (7) Specific recommendations of the study Both the Administration's National Energy Policy and the Department's Strategic Plan call for reducing U.S. reliance on imported oil and reducing greenhouse gas emissions. The National Energy Policy also acknowledges the need to increase energy supplies and use more energy-efficient technologies and practices. President Bush proposed in his January 2003 State of the Union Address to advance research on hydrogen so that it has the potential to play a major role in America's future energy system. Consistent with these aims, EPACT 2005 authorizes a research, development, and demonstration program for hydrogen and fuel cell technology. Projected results for the national employment impacts, projections of the job creation and job replacement underlying the total employment changes, training implications, regional employment impacts and the

  20. Effects of a Transition to a Hydrogen Economy on Employment in the United States

    Energy Technology Data Exchange (ETDEWEB)

    Tolley, George S.; Jones, Donald W. Mintz, Marianne M.; Smith, Barton A.; Carlson, Eric; Unnasch, Stefan; Lawrence, Michael; Chmelynski, Harry

    2008-07-01

    The U.S. Department of Energy report, Effects of a Transition to a Hydrogen Economy on Employment in the United States Report to Congress, estimates the effects on employment of a U.S. economy transformation to hydrogen between 2020 and 2050. The report includes study results on employment impacts from hydrogen market expansion in the transportation, stationary, and portable power sectors and highlights possible skill and education needs. This study is in response to Section 1820 of the Energy Policy Act of 2005 (Public Law 109-58) (EPACT). Section 1820, “Overall Employment in a Hydrogen Economy,” requires the Secretary of Energy to carry out a study of the effects of a transition to a hydrogen economy on several employment [types] in the United States. As required by Section 1820, the present report considers: • Replacement effects of new goods and services • International competition • Workforce training requirements • Multiple possible fuel cycles, including usage of raw materials • Rates of market penetration of technologies • Regional variations based on geography • Specific recommendations of the study Both the Administration’s National Energy Policy and the Department’s Strategic Plan call for reducing U.S. reliance on imported oil and reducing greenhouse gas emissions. The National Energy Policy also acknowledges the need to increase energy supplies and use more energy-efficient technologies and practices. President Bush proposed in his January 2003 State of the Union Address to advance research on hydrogen so that it has the potential to play a major role in America’s future energy system. Consistent with these aims, EPACT 2005 authorizes a research, development, and demonstration program for hydrogen and fuel cell technology. Projected results for the national employment impacts, projections of the job creation and job replacement underlying the total employment changes, training implications, regional employment impacts and the

  1. M1 and E2 transitions in the ground-state configuration of atomic ...

    Indian Academy of Sciences (India)

    have calculated the forbidden transition (M1 and E2) parameters such as transition energies, log- arithmic weighted ... Keywords. Forbidden transitions; transition energies; logarithmic weighted oscillator strengths; .... optimizing the energy function based on the non-relativistic Hamiltonian of an atom,. HNR = N. ∑ j=1. (12∇ ...

  2. Molecular water oxidation mechanisms followed by transition metals: state of the art.

    Science.gov (United States)

    Sala, Xavier; Maji, Somnath; Bofill, Roger; García-Antón, Jordi; Escriche, Lluís; Llobet, Antoni

    2014-02-18

    One clean alternative to fossil fuels would be to split water using sunlight. However, to achieve this goal, researchers still need to fully understand and control several key chemical reactions. One of them is the catalytic oxidation of water to molecular oxygen, which also occurs at the oxygen evolving center of photosystem II in green plants and algae. Despite its importance for biology and renewable energy, the mechanism of this reaction is not fully understood. Transition metal water oxidation catalysts in homogeneous media offer a superb platform for researchers to investigate and extract the crucial information to describe the different steps involved in this complex reaction accurately. The mechanistic information extracted at a molecular level allows researchers to understand both the factors that govern this reaction and the ones that derail the system to cause decomposition. As a result, rugged and efficient water oxidation catalysts with potential technological applications can be developed. In this Account, we discuss the current mechanistic understanding of the water oxidation reaction catalyzed by transition metals in the homogeneous phase, based on work developed in our laboratories and complemented by research from other groups. Rather than reviewing all of the catalysts described to date, we focus systematically on the several key elements and their rationale from molecules studied in homogeneous media. We organize these catalysts based on how the crucial oxygen-oxygen bond step takes place, whether via a water nucleophilic attack or via the interaction of two M-O units, rather than based on the nuclearity of the water oxidation catalysts. Furthermore we have used DFT methodology to characterize key intermediates and transition states. The combination of both theory and experiments has allowed us to get a complete view of the water oxidation cycle for the different catalysts studied. Finally, we also describe the various deactivation pathways for

  3. State and transition models: Theory, applications, and challenges. In: Briske, D.D. Rangeland Systems: Processes, Management and Challenges

    Science.gov (United States)

    State and transition models (STMs) are used for communicating about ecosystem change in rangelands and other ecosystems, especially the implications for management. The fundamental premise that rangelands can exhibit multiple states is now widely accepted. The current application of STMs for managem...

  4. The shape of the melting curve and phase transitions in the liquid state

    International Nuclear Information System (INIS)

    Yahel, Eyal

    2014-01-01

    The phase diagram of elemental liquids has been found to be surprisingly rich, including variations in the melting curve and transitions in the liquid phase. The effect of these transitions on the shape of the melting curve is reviewed and analyzed. First-order phase transitions intersecting the melting curve imply piecewise continuous melting curves, with solid-solid transitions generating upward kinks or minima and liquid-liquid transitions generating downward kinks or maxima

  5. Nuclear isomerism in fission fragments produced by the spontaneous fission of {sup 252}Cf; Isomerisme nucleaire dans les fragments de fission produits dans la fission spontanee du {sup 252}Cf

    Energy Technology Data Exchange (ETDEWEB)

    Gautherin, C

    1997-09-01

    This thesis is devoted to the study of the nuclear structure of neutron-rich nuclei, via the search of isomeric nuclear states. Neutron-rich nuclei were produced in the spontaneous fission of {sup 252}Cf. The experimental study of isomeric states in these nuclei was performed with the {gamma}-array EUROGAM II, coupled to an additional and original fission fragment detector composed by photovoltaic cells, SAPhIR. The photovoltaic cells are well adapted to detect low energy heavy ions and have good energy and time resolutions to obtain a good fission fragment detection. This experiment led to the discovery of new isomeric states in {sup 135}Xe, {sup 104}Mo, {sup 146,147,148}Ce and {sup 152,154,156}Nd, with lifetimes between 60 ns and 2 {mu}s. Level schemes of these nuclei have been completed. An interpretation of the isomeric states in the nuclei {sup 154,156}Nd and {sup 156,158}Sm was performed by Hartree-Fock-Bogolyubov calculations using the DIS Gogny force with two quasi-particles excitations. The confrontation with the experimental results led to an interpretation of these isomeric states as K-isomers. (author)

  6. Prioritizing bird conservation actions in the Prairie Hardwood transition of the Midwestern United States

    Science.gov (United States)

    Thogmartin, Wayne E.; Crimmins, Shawn M.; Pearce, Jennie

    2014-01-01

    Large-scale planning for the conservation of species is often hindered by a poor understanding of factors limiting populations. In regions with declining wildlife populations, it is critical that objective metrics of conservation success are developed to ensure that conservation actions achieve desired results. Using spatially explicit estimates of bird abundance, we evaluated several management alternatives for conserving bird populations in the Prairie Hardwood Transition of the United States. We designed landscapes conserving species at 50% of their current predicted abundance as well as landscapes attempting to achieve species population targets (which often required the doubling of current abundance). Conserving species at reduced (half of current) abundance led to few conservation conflicts. However, because of extensive modification of the landscape to suit human use, strategies for achieving regional population targets for forest bird species would be difficult under even ideal circumstances, and even more so if maintenance of grassland bird populations is also desired. Our results indicated that large-scale restoration of agricultural lands to native grassland and forest habitats may be the most productive conservation action for increasing bird population sizes but the level of landscape transition required to approach target bird population sizes may be societally unacceptable.

  7. Surface-Induced Frustration in Solid State Polymorphic Transition of Native Cellulose Nanocrystals.

    Science.gov (United States)

    Salminen, Reeta; Baccile, Niki; Reza, Mehedi; Kontturi, Eero

    2017-06-12

    The presence of an interface generally influences crystallization of polymers from melt or from solution. Here, by contrast, we explore the effect of surface immobilization in a direct solid state polymorphic transition on individual cellulose nanocrystals (CNCs), extracted from a plant-based origin. The conversion from native cellulose I to cellulose III crystal occurred via a host-guest inclusion of ethylene diamine inside the crystal. A 60% reduction in CNC width (height) in atomic force microscopy images suggested that when immobilized on a flat modified silica surface, the stresses caused by the inclusion or the subsequent regeneration resulted in exfoliation, hypothetically, between the van der Waals bonded sheets within the crystal. Virtually no changes in dimensions were visible when the polymorphic transition was performed to nonimmobilized CNCs in bulk dispersion. With reservations and by acknowledging the obvious dissimilarities, the exfoliation of cellulose crystal sheets can be viewed as analogous to exfoliation of 2D structures like graphene from a van der Waals stacked solid. Here, the detachment is triggered by an inclusion of a guest molecule inside a host cellulose crystal and the stresses caused by the firm attachment of the CNC on a solid substrate, leading to detachment of molecular sheets or stacks of sheets.

  8. Post-transition state dynamics and product energy partitioning following thermal excitation of the F∙∙∙HCH2 CN transition state: Disagreement with experiment

    Energy Technology Data Exchange (ETDEWEB)

    Pratihar, Subha [Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, USA; Ma, Xinyou [Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, USA; Xie, Jing [Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA; Scott, Rebecca [Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, USA; Gao, Eric [Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, USA; Ruscic, Branko [Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA and Computation Institute, University of Chicago, Chicago, Illinois 60637, USA; Aquino, Adelia J. A. [Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, USA; School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, People’s Republic of China; Institute for Soil Research University of Natural Resources and Life Sciences Vienna, Peter-Jordan-Strasse 82, A-1190 Vienna, Austria; Setser, Donald W. [Institute for Soil Research University of Natural Resources and Life Sciences Vienna, Peter-Jordan-Strasse 82, A-1190 Vienna, Austria; Hase, William L. [Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, USA

    2017-10-14

    Born-Oppenheimer direct dynamics simulations were performed to study atomistic details of the F + CH3CN → HF + CH2CN H-atom abstraction reaction. The simulation trajectories were calculated with a combined M06-2X/MP2 algorithm utilizing the 6-311++G** basis set. In accord with experiment and assuming the accuracy of transition state theory (TST), the trajectories were initiated at the F-HCH2CN abstraction TS with a 300 K Boltzmann distribution of energy and directed towards products. Recrossing of the TS was negligible, confirming the accuracy of TST for the simulation. HF formation was rapid, occurring within 0.014 ps of the trajectory initiation. The intrinsic reaction coordinate (IRC) for reaction involves rotation of HF about CH2CN and then trapping in the CH2CN-HF post-reaction potential energy well of ~10 kcal/mol with respect to the HF + CH2CN products. In contrast to this IRC, five different trajectory types were observed, with the majority involving direct dissociation and only 11% approximately following the IRC. The HF vibrational and rotational quantum numbers, n and J, were calculated when HF was initially formed and they increase as potential energy is released in forming the HF + CH2CN products. The population of the HF product vibrational states is only in qualitative agreement with experiment, with the simulations showing depressed and enhanced populations of the n = 1 and 2 states as compared to experiment. From the simulations and with an anharmonic zero-point energy constraint, the percentage partitioning of the product energy to relative translation, HF rotation, HF vibration, CH2CN rotation and CH2CN vibration is 5, 11, 60, 7, and 16%, respectively. In contrast the experimental energy partitioning percentages to HF rotation and vibration are 6 and 41%. Comparisons are made between the current simulation and those for other F + H

  9. Transition by breaking of analyticity in the ground state of Josephson junction arrays as a static signature of the vortex jamming transition

    KAUST Repository

    Nogawa, Tomoaki

    2012-05-22

    We investigate the ground state of the irrationally frustrated Josephson junction array with a controlling anisotropy parameter λ that is the ratio of the longitudinal Josephson coupling to the transverse one. We find that the ground state has one-dimensional periodicity whose reciprocal lattice vector depends on λ and is incommensurate with the substrate lattice. Approaching the isotropic point λ=1, the so-called hull function of the ground state exhibits analyticity breaking similar to the Aubry transition in the Frenkel-Kontorova model. We find a scaling law for the harmonic spectrum of the hull functions, which suggests the existence of a characteristic length scale diverging at the isotropic point. This critical behavior is directly connected to the jamming transition previously observed in the current-voltage characteristics by a numerical simulation. On top of the ground state there is a gapless continuous band of metastable states, which exhibit the same critical behavior as the ground state. © 2012 American Physical Society.

  10. Insights from the structure of a smallpox virus topoisomerase-DNA transition state mimic

    Science.gov (United States)

    Perry, Kay; Hwang, Young; Bushman, Frederic D.; Van Duyne, Gregory D.

    2010-01-01

    Summary Poxviruses encode their own type IB topoisomerases (TopIBs) which release superhelical tension generated by replication and transcription of their genomes. To investigate the reaction catalyzed viral TopIBs, we have determined the structure of a variola virus topoisomerase-DNA complex trapped as a vanadate transition state mimic. The structure reveals how the viral TopIB enzymes are likely to position the DNA duplex for ligation following relaxation of supercoils and identifies the sources of friction observed in single molecule experiments that argue against free rotation. The structure also identifies a conformational change in the leaving group sugar that must occur prior to cleavage and reveals a mechanism for promoting ligation following relaxation of supercoils that involves a novel Asp-minor groove interaction. Overall, the new structural data support a common catalytic mechanism for the TopIB superfamily but indicate distinct methods for controlling duplex rotation in the small vs. large enzyme subfamilies. PMID:20152159

  11. Phase Transition in the Density of States of Quantum Spin Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Erdős, László, E-mail: lerdos@ist.ac.at [IST Austria (Austria); Schröder, Dominik, E-mail: schroeder.dominik@gmail.com [Ludwig-Maximilians-Universität München (Germany)

    2014-12-15

    We prove that the empirical density of states of quantum spin glasses on arbitrary graphs converges to a normal distribution as long as the maximal degree is negligible compared with the total number of edges. This extends the recent results of Keating et al. (2014) that were proved for graphs with bounded chromatic number and with symmetric coupling distribution. Furthermore, we generalise the result to arbitrary hypergraphs. We test the optimality of our condition on the maximal degree for p-uniform hypergraphs that correspond to p-spin glass Hamiltonians acting on n distinguishable spin- 1/2 particles. At the critical threshold p = n{sup 1/2} we find a sharp classical-quantum phase transition between the normal distribution and the Wigner semicircle law. The former is characteristic to classical systems with commuting variables, while the latter is a signature of noncommutative random matrix theory.

  12. Radiation and penetration matrix elements for magnetic quadrupole transitions between Nilsson states in odd nuclei

    International Nuclear Information System (INIS)

    Feresin, A.P.; Guseva, I.S.

    1984-01-01

    Single-particle matrix elements for magnetic quadrupole gamma radiation in odd deformed nuclei, calculated with the aid of Nilsson-potential wave functions, are presented. Also given are the internal conversion penetration matrix elements, calculated in the same manner. The penetration matrix elements are needed to estimate the nuclear penetration parameter, which determines the deviation of experimental internal conversion coefficients from their standard values given in tables. Matrix elements are given for transitions between all pairs of Nilsson single-particle states with ΔN = 1 and ΔK = 0, 1, and 2 for the nuclear shells with 4< or =N< or =7 and for the two deformation values epsilon = 0.2 and 0.3

  13. Laboratory Observation of a Plasma-Flow-State Transition from Diverging to Stretching a Magnetic Nozzle.

    Science.gov (United States)

    Takahashi, Kazunori; Ando, Akira

    2017-06-02

    An axial magnetic field induced by a plasma flow in a divergent magnetic nozzle is measured when injecting the plasma flow from a radio frequency (rf) plasma source located upstream of the nozzle. The source is operated with a pulsed rf power of 5 kW, and the high density plasma flow is sustained only for the initial ∼100  μsec of the discharge. The measurement shows a decrease in the axial magnetic field near the source exit, whereas an increase in the field is detected at the downstream side of the magnetic nozzle. These results demonstrate a spatial transition of the plasma-flow state from diverging to stretching the magnetic nozzle, where the importance of both the Alfvén and ion Mach numbers is shown.

  14. Ground state oxygen holes and the metal-insulator transition in rare earth nickelates

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, Thorsten; Bisogni, Valentina; Huang, Yaobo; Strocov, Vladimir [Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Catalano, Sara; Gibert, Marta; Scherwitzl, Raoul; Zubko, Pavlo; Triscone, Jean-Marc [Departement de Physique de la Matiere Condensee, University of Geneva (Switzerland); Green, Robert J.; Balandeh, Shadi; Sawatzky, George [Department of Physics and Astronomy, University of British Columbia, Vancouver (Canada)

    2015-07-01

    Perovskite rare-earth (Re) nickelates ReNiO{sub 3} continue to attract a lot of interest owing to their intriguing properties like a sharp metal to insulator transition (MIT), unusual magnetic order and expected superconductivity in specifically tuned super-lattices. Full understanding of these materials, however, is hampered by the difficulties in describing their electronic ground state (GS). From X-ray absorption (XAS) at the Ni 2p{sub 3/2} edge of thin films of NdNiO{sub 3} and corresponding RIXS maps vs. incident and transferred photon energies we reveal that the electronic GS configuration of NdNiO{sub 3} is composed of delocalized and localized components. Our study conveys that a Ni 3d{sup 8}-like configuration with holes at oxygen takes on the leading role in the GS and the MIT of ReNiO{sub 3} as proposed by recent model theories.

  15. Surface hopping, transition state theory, and decoherence. II. Thermal rate constants and detailed balance

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Amber; Subotnik, Joseph E., E-mail: subotnik@sas.upenn.edu [Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104 (United States)

    2015-10-07

    We investigate a simple approach to compute a non-adiabatic thermal rate constant using the fewest switches surface hopping (FSSH) dynamics. We study the effects of both decoherence (using our augmented-FSSH (A-FSSH) algorithm) and forbidden hops over a large range of parameters, including high and low friction regimes, and weak and strong electronic coupling regimes. Furthermore, when possible, we benchmark our results against exact hierarchy equations of motion results, where we usually find a maximum error of roughly a factor of two (at reasonably large temperatures). In agreement with Hammes-Schiffer and Tully, we find that a merger of transition state theory and surface hopping can be both accurate and efficient when performed correctly. We further show that detailed balance is followed approximately by A-FSSH dynamics.

  16. A state-and-transition simulation modeling approach for estimating the historical range of variability

    Directory of Open Access Journals (Sweden)

    Kori Blankenship

    2015-04-01

    Full Text Available Reference ecological conditions offer important context for land managers as they assess the condition of their landscapes and provide benchmarks for desired future conditions. State-and-transition simulation models (STSMs are commonly used to estimate reference conditions that can be used to evaluate current ecosystem conditions and to guide land management decisions and activities. The LANDFIRE program created more than 1,000 STSMs and used them to assess departure from a mean reference value for ecosystems in the United States. While the mean provides a useful benchmark, land managers and researchers are often interested in the range of variability around the mean. This range, frequently referred to as the historical range of variability (HRV, offers model users improved understanding of ecosystem function, more information with which to evaluate ecosystem change and potentially greater flexibility in management options. We developed a method for using LANDFIRE STSMs to estimate the HRV around the mean reference condition for each model state in ecosystems by varying the fire probabilities. The approach is flexible and can be adapted for use in a variety of ecosystems. HRV analysis can be combined with other information to help guide complex land management decisions.

  17. Prediction of monomer reactivity in radical copolymerizations from transition state quantum chemical descriptors

    Directory of Open Access Journals (Sweden)

    Zhengde Tan

    2013-01-01

    Full Text Available In comparison with the Q-e scheme, the Revised Patterns Scheme: the U, V Version (the U-V scheme has greatly improved both its accessibility and its accuracy in interpreting and predicting the reactivity of a monomer in free-radical copolymerizations. Quantitative structure-activity relationship (QSAR models were developed to predict the reactivity parameters u and v of the U-V scheme, by applying genetic algorithm (GA and support vector machine (SVM techniques. Quantum chemical descriptors used for QSAR models were calculated from transition state species with structures C¹H3 - C²HR³• or •C¹H2 - C²H2R³ (formed from vinyl monomers C¹H²=C²HR³ + H•, using density functional theory (DFT, at the UB3LYP level of theory with 6-31G(d basis set. The optimum support vector regression (SVR model of the reactivity parameter u based on Gaussian radial basis function (RBF kernel (C = 10, ε = 10- 5 and γ = 1.0 produced root-mean-square (rms errors for the training, validation and prediction sets being 0.220, 0.326 and 0.345, respectively. The optimal SVR model for v with the RBF kernel (C = 20, ε = 10- 4 and γ = 1.2 produced rms errors for the training set of 0.123, the validation set of 0.206 and the prediction set of 0.238. The feasibility of applying the transition state quantum chemical descriptors to develop SVM models for reactivity parameters u and v in the U-V scheme has been demonstrated.

  18. Linking state-and-transition simulation and timber supply models for forest biomass production scenarios

    Directory of Open Access Journals (Sweden)

    Jennifer K. Costanza

    2015-03-01

    Full Text Available We linked state-and-transition simulation models (STSMs with an economics-based timber supply model to examine landscape dynamics in North Carolina through 2050 for three scenarios of forest biomass production. Forest biomass could be an important source of renewable energy in the future, but there is currently much uncertainty about how biomass production would impact landscapes. In the southeastern US, if forests become important sources of biomass for bioenergy, we expect increased land-use change and forest management. STSMs are ideal for simulating these landscape changes, but the amounts of change will depend on drivers such as timber prices and demand for forest land, which are best captured with forest economic models. We first developed state-and-transition model pathways in the ST-Sim software platform for 49 vegetation and land-use types that incorporated each expected type of landscape change. Next, for the three biomass production scenarios, the SubRegional Timber Supply Model (SRTS was used to determine the annual areas of thinning and harvest in five broad forest types, as well as annual areas converted among those forest types, agricultural, and urban lands. The SRTS output was used to define area targets for STSMs in ST-Sim under two scenarios of biomass production and one baseline, business-as-usual scenario. We show that ST-Sim output matched SRTS targets in most cases. Landscape dynamics results indicate that, compared with the baseline scenario, forest biomass production leads to more forest and, specifically, more intensively managed forest on the landscape by 2050. Thus, the STSMs, informed by forest economics models, provide important information about potential landscape effects of bioenergy production.

  19. Using state-and-transition modeling to account for imperfect detection in invasive species management

    Science.gov (United States)

    Frid, Leonardo; Holcombe, Tracy; Morisette, Jeffrey T.; Olsson, Aaryn D.; Brigham, Lindy; Bean, Travis M.; Betancourt, Julio L.; Bryan, Katherine

    2013-01-01

    Buffelgrass, a highly competitive and flammable African bunchgrass, is spreading rapidly across both urban and natural areas in the Sonoran Desert of southern and central Arizona. Damages include increased fire risk, losses in biodiversity, and diminished revenues and quality of life. Feasibility of sustained and successful mitigation will depend heavily on rates of spread, treatment capacity, and cost–benefit analysis. We created a decision support model for the wildland–urban interface north of Tucson, AZ, using a spatial state-and-transition simulation modeling framework, the Tool for Exploratory Landscape Scenario Analyses. We addressed the issues of undetected invasions, identifying potentially suitable habitat and calibrating spread rates, while answering questions about how to allocate resources among inventory, treatment, and maintenance. Inputs to the model include a state-and-transition simulation model to describe the succession and control of buffelgrass, a habitat suitability model, management planning zones, spread vectors, estimated dispersal kernels for buffelgrass, and maps of current distribution. Our spatial simulations showed that without treatment, buffelgrass infestations that started with as little as 80 ha (198 ac) could grow to more than 6,000 ha by the year 2060. In contrast, applying unlimited management resources could limit 2060 infestation levels to approximately 50 ha. The application of sufficient resources toward inventory is important because undetected patches of buffelgrass will tend to grow exponentially. In our simulations, areas affected by buffelgrass may increase substantially over the next 50 yr, but a large, upfront investment in buffelgrass control could reduce the infested area and overall management costs.

  20. Linking state-and-transition simulation and timber supply models for forest biomass production scenarios

    Science.gov (United States)

    Costanza, Jennifer; Abt, Robert C.; McKerrow, Alexa; Collazo, Jaime

    2015-01-01

    We linked state-and-transition simulation models (STSMs) with an economics-based timber supply model to examine landscape dynamics in North Carolina through 2050 for three scenarios of forest biomass production. Forest biomass could be an important source of renewable energy in the future, but there is currently much uncertainty about how biomass production would impact landscapes. In the southeastern US, if forests become important sources of biomass for bioenergy, we expect increased land-use change and forest management. STSMs are ideal for simulating these landscape changes, but the amounts of change will depend on drivers such as timber prices and demand for forest land, which are best captured with forest economic models. We first developed state-and-transition model pathways in the ST-Sim software platform for 49 vegetation and land-use types that incorporated each expected type of landscape change. Next, for the three biomass production scenarios, the SubRegional Timber Supply Model (SRTS) was used to determine the annual areas of thinning and harvest in five broad forest types, as well as annual areas converted among those forest types, agricultural, and urban lands. The SRTS output was used to define area targets for STSMs in ST-Sim under two scenarios of biomass production and one baseline, business-as-usual scenario. We show that ST-Sim output matched SRTS targets in most cases. Landscape dynamics results indicate that, compared with the baseline scenario, forest biomass production leads to more forest and, specifically, more intensively managed forest on the landscape by 2050. Thus, the STSMs, informed by forest economics models, provide important information about potential landscape effects of bioenergy production.

  1. Preferential treatment in transition economy the case of state-owned enterprises in the textile and garment industry in Vietnam

    OpenAIRE

    Knutsen, Hege Merete; Nguyen, Cuong Manh

    2004-01-01

    The article examines the role and contribution of preferential treatment of state enterprises to growth in the textile and garment industry. State enterprises are still the largest single sector in the textile and garment industry in Vietnam, but are losing market shares to private Vietnamese enterprises and foreign-owned enterprises despite the benefits that they enjoy. However, in the present context of economic transition and keen competition in the global market, well-managed state enterp...

  2. Comparative Analysis of Light-Harvesting Antennae and State Transition in chlorina and cpSRP Mutants1[OPEN

    Science.gov (United States)

    Wang, Peng

    2016-01-01

    State transitions in photosynthesis provide for the dynamic allocation of a mobile fraction of light-harvesting complex II (LHCII) to photosystem II (PSII) in state I and to photosystem I (PSI) in state II. In the state I-to-state II transition, LHCII is phosphorylated by STN7 and associates with PSI to favor absorption cross-section of PSI. Here, we used Arabidopsis (Arabidopsis thaliana) mutants with defects in chlorophyll (Chl) b biosynthesis or in the chloroplast signal recognition particle (cpSRP) machinery to study the flexible formation of PS-LHC supercomplexes. Intriguingly, we found that impaired Chl b biosynthesis in chlorina1-2 (ch1-2) led to preferentially stabilized LHCI rather than LHCII, while the contents of both LHCI and LHCII were equally depressed in the cpSRP43-deficient mutant (chaos). In view of recent findings on the modified state transitions in LHCI-deficient mutants (Benson et al., 2015), the ch1-2 and chaos mutants were used to assess the influence of varying LHCI/LHCII antenna size on state transitions. Under state II conditions, LHCII-PSI supercomplexes were not formed in both ch1-2 and chaos plants. LHCII phosphorylation was drastically reduced in ch1-2, and the inactivation of STN7 correlates with the lack of state transitions. In contrast, phosphorylated LHCII in chaos was observed to be exclusively associated with PSII complexes, indicating a lack of mobile LHCII in chaos. Thus, the comparative analysis of ch1-2 and chaos mutants provides new evidence for the flexible organization of LHCs and enhances our understanding of the reversible allocation of LHCII to the two photosystems. PMID:27663408

  3. Comparative Analysis of Light-Harvesting Antennae and State Transition in chlorina and cpSRP Mutants.

    Science.gov (United States)

    Wang, Peng; Grimm, Bernhard

    2016-11-01

    State transitions in photosynthesis provide for the dynamic allocation of a mobile fraction of light-harvesting complex II (LHCII) to photosystem II (PSII) in state I and to photosystem I (PSI) in state II. In the state I-to-state II transition, LHCII is phosphorylated by STN7 and associates with PSI to favor absorption cross-section of PSI. Here, we used Arabidopsis (Arabidopsis thaliana) mutants with defects in chlorophyll (Chl) b biosynthesis or in the chloroplast signal recognition particle (cpSRP) machinery to study the flexible formation of PS-LHC supercomplexes. Intriguingly, we found that impaired Chl b biosynthesis in chlorina1-2 (ch1-2) led to preferentially stabilized LHCI rather than LHCII, while the contents of both LHCI and LHCII were equally depressed in the cpSRP43-deficient mutant (chaos). In view of recent findings on the modified state transitions in LHCI-deficient mutants (Benson et al., 2015), the ch1-2 and chaos mutants were used to assess the influence of varying LHCI/LHCII antenna size on state transitions. Under state II conditions, LHCII-PSI supercomplexes were not formed in both ch1-2 and chaos plants. LHCII phosphorylation was drastically reduced in ch1-2, and the inactivation of STN7 correlates with the lack of state transitions. In contrast, phosphorylated LHCII in chaos was observed to be exclusively associated with PSII complexes, indicating a lack of mobile LHCII in chaos Thus, the comparative analysis of ch1-2 and chaos mutants provides new evidence for the flexible organization of LHCs and enhances our understanding of the reversible allocation of LHCII to the two photosystems. © 2016 American Society of Plant Biologists. All Rights Reserved.

  4. Generalized transition state theory. Quantum effects for collinear reactions of hydrogen molecules and isotopically substituted hydrogen molecules

    International Nuclear Information System (INIS)

    Garrett, B.C.; Truhlar, D.G.

    1979-01-01

    Canonical variational transition state theory, microcanonical variational transition state theory, and Miller's unified statistical theory were used in an attempt to correct two major deficiencies of the conventional transition state theory. These are: (1) the necessity of extra assumptions to include quantum mechanical tunneling effects and (2) the fundamental assumption that trajectories crossing a dividing surface in phase space proceed directly to products. The accuracy of these approximate methods were tested by performing calculations for several collinear reactions of hydrogen, deuterium, chlorine, or iodine, with five isotopes of hydrogen molecules and comparison of these results with those from accurate quantitative calculations of the reaction probabilities as functions of energy and of the thermal rate constants as functions of temperature. 49 references, 28 figures, 17 tables

  5. Structured pathway across the transition state for peptide folding revealed by molecular dynamics simulations.

    Directory of Open Access Journals (Sweden)

    Lipi Thukral

    2011-09-01

    Full Text Available Small globular proteins and peptides commonly exhibit two-state folding kinetics in which the rate limiting step of folding is the surmounting of a single free energy barrier at the transition state (TS separating the folded and the unfolded states. An intriguing question is whether the polypeptide chain reaches, and leaves, the TS by completely random fluctuations, or whether there is a directed, stepwise process. Here, the folding TS of a 15-residue β-hairpin peptide, Peptide 1, is characterized using independent 2.5 μs-long unbiased atomistic molecular dynamics (MD simulations (a total of 15 μs. The trajectories were started from fully unfolded structures. Multiple (spontaneous folding events to the NMR-derived conformation are observed, allowing both structural and dynamical characterization of the folding TS. A common loop-like topology is observed in all the TS structures with native end-to-end and turn contacts, while the central segments of the strands are not in contact. Non-native sidechain contacts are present in the TS between the only tryptophan (W11 and the turn region (P7-G9. Prior to the TS the turn is found to be already locked by the W11 sidechain, while the ends are apart. Once the ends have also come into contact, the TS is reached. Finally, along the reactive folding paths the cooperative loss of the W11 non-native contacts and the formation of the central inter-strand native contacts lead to the peptide rapidly proceeding from the TS to the native state. The present results indicate a directed stepwise process to folding the peptide.

  6. Transit Marketing : Review of the State-of-the-Art and a Handbook of Current Practice

    Science.gov (United States)

    1985-04-01

    Over the past decade, marketing has been given increased emphasis as a way to improve both transit rideship and productivity. While there is near universal agreement among transit managers that some level of marketing is necessary, there is far from ...

  7. A harmonic transition state theory model for defect initiation in crystals

    International Nuclear Information System (INIS)

    Delph, T J; Cao, P; Park, H S; Zimmerman, J A

    2013-01-01

    We outline here a model for the initiation of defects in crystals based upon harmonic transition state theory (hTST). This model combines a previously developed model for zero-temperature defect initiation with a multi-dimensional hTST model that is capable of accurately predicting the effects of temperature and loading rate upon defect initiation. The model has several features that set it apart from previous efforts along these lines, most notably a straightforward method of determining the energy barrier between adjacent equilibrium states that does not depend upon a priori information concerning the nature of the defect. We apply the model to two examples, triaxial stretching of a perfect fcc crystal and nanoindentation of a gold substrate. Very good agreement is found between the predictions of the model and independent molecular dynamics (MD) simulations. Among other things, the model predicts a strong dependence of the defect initiation behavior upon the loading parameter. A very attractive feature of this model is that it is valid for arbitrarily slow loading rates, in particular loading rates achievable in the laboratory, and suffers from none of the limitations in this regard inherent in MD simulations. (paper)

  8. Orbit covariance propagation via quadratic-order state transition matrix in curvilinear coordinates

    Science.gov (United States)

    Hernando-Ayuso, Javier; Bombardelli, Claudio

    2017-09-01

    In this paper, an analytical second-order state transition matrix (STM) for relative motion in curvilinear coordinates is presented and applied to the problem of orbit uncertainty propagation in nearly circular orbits (eccentricity smaller than 0.1). The matrix is obtained by linearization around a second-order analytical approximation of the relative motion recently proposed by one of the authors and can be seen as a second-order extension of the curvilinear Clohessy-Wiltshire (C-W) solution. The accuracy of the uncertainty propagation is assessed by comparison with numerical results based on Monte Carlo propagation of a high-fidelity model including geopotential and third-body perturbations. Results show that the proposed STM can greatly improve the accuracy of the predicted relative state: the average error is found to be at least one order of magnitude smaller compared to the curvilinear C-W solution. In addition, the effect of environmental perturbations on the uncertainty propagation is shown to be negligible up to several revolutions in the geostationary region and for a few revolutions in low Earth orbit in the worst case.

  9. Hydrostatic pressure effects on the state density and optical transitions in quantum dots

    International Nuclear Information System (INIS)

    Galindez-Ramirez, G; Perez-Merchancano, S T; Paredes Gutierrez, H; Gonzalez, J D

    2010-01-01

    Using the effective mass approximation and variational method we have computed the effects of hydrostatic pressure on the absorption and photoluminescence spectra in spherical quantum dot GaAs-(Ga, Al) As, considering a finite confinement potential of this particular work we show the optical transitions in quantum of various sizes in the presence of hydrogenic impurities and hydrostatic pressure effects. Our first result describes the spectrum of optical absorption of 500 A QD for different values of hydrostatic pressure P = 0, 20 and 40 Kbar. The absorption peaks are sensitive to the displacement of the impurity center to the edge of the quantum dot and even more when the hydrostatic pressure changes in both cases showing that to the extent that these two effects are stronger quantum dots respond more efficiently. Also this result can be seen in the study of the photoluminescence spectrum as in the case of acceptor impurities consider them more efficiently capture carriers or electrons that pass from the conduction band to the valence band. Density states with randomly distributed impurity show that the additional peaks in the curves of the density of impurity states appear due to the presence of the additional hydrostatic pressure effects.

  10. Bus Rapid Transit and Socioeconomic Condition of Bus Commuters in Lagos State

    Directory of Open Access Journals (Sweden)

    Owolabi L. Kuye

    2017-10-01

    Full Text Available Road transport is one of the most common means of transportation across the world. Bus transportation in Nigeria had witnessed many problems for the past decades considering the growing population with the attendant loss of lives and properties in most cities like Lagos in Nigeria. This paper focuses on the adequacy of services provided by Bus Rapid Transit (BRT in Lagos State with respect to the extent to which it influences the socioeconomic conditions of bus commuters. It examines the effect of services rendered by BRT on cost reduction potential, income and safety. Multistage sampling technique was used to select 20 samples each from all respondents in all local government area in Lagos State to reach a total of three hundred and thirty (330 samples. The data collection instrument was the questionnaire which was validated. Data collected were analysed with the use of descriptive statistics such as means, percentages and standard deviation and inferential statistics such as regression and analysis of variance techniques. Findings showed that BRT services has reduced the cost of bus commuters and also increased safety and security thereby increasing the socioeconomic condition of Lagosians. The study recommends improvements in BRT services through the deployment of technology as it had been used in developed countries.

  11. Energy use, efficiency gains and emission abatement in transitional industrialised economies. Poland and the Baltic states

    Energy Technology Data Exchange (ETDEWEB)

    Salay, Juergen

    1999-05-01

    This thesis is a study of how energy use and air pollution in Poland, Estonia, Latvia and Lithuania have been affected by the economic transition after 1989. It consists of six articles, which examine three different aspects of these changes. The first group of articles analyses the structure of energy use in the Baltic states (Article 1) and Poland (Articles 2 and 3) at the outset of transition. The results show that these countries had a primary energy consumption per GDP which was two to three times higher than in developed market economics because of a more energy intensive structure of the economy and higher specific energy intensities in many sectors of the economy. They also had significantly higher levels of air pollution per primary energy consumption and GDP because of a heavy reliance on fossil fuels, an energy intensive economy and an ineffective control of emissions. The deep fall in energy consumption during the first phase of transition was due to a sharp drop in industrial output and higher fuel prices. In the Baltic states, part of the fall in energy consumption was the result of shortfalls in the supply of oil and gas from Russia. The second group of articles (Articles 4 and 5) examines changes in electricity production, fuel consumption, generation efficiency and sulphur dioxide (SO{sub 2}) emissions in the Polish power industry between 1988 and 1997. The results show that SO{sub 2} emissions dropped by 45 per cent between 1988 and 1997. The drop in emissions was partly the result of a fall in economic activity and electricity production in the early 1990s. Other reasons were more important. One reason was the restructuring of the power industry, during which hard budget constraints were introduced and the price of coal was raised. Another reason for the fall in emissions was the reorganisation and stricter enforcement of environmental protection. Together, these reforms created strong incentives for power plants to switch to high-quality coal

  12. Formation of a Zn3067 isomer state by bombardment with neutrons

    International Nuclear Information System (INIS)

    Montes Ponce de Leon, J.; Sanchez del Rio, C.

    1956-01-01

    In this paper the identification of the isomeric state of Zn 6 7 by a new method is described Isotopes Zn 6 6 y Zn 6 7 being both stable, the capture of slow neutrons by Zn 6 6 leads sometimes to the formation of the isomeric state of Zn 6 7 ; the state is identified by its half-life measured by means of delayed coincidences between the capture and the isomeric gamma rays. (Author)

  13. Communication: State-to-state dynamics of the Cl + H2O → HCl + OH reaction: Energy flow into reaction coordinate and transition-state control of product energy disposal

    International Nuclear Information System (INIS)

    Zhao, Bin; Guo, Hua; Sun, Zhigang

    2015-01-01

    Quantum state-to-state dynamics of a prototypical four-atom reaction, namely, Cl + H 2 O → HCl + OH, is investigated for the first time in full dimensionality using a transition-state wave packet method. The state-to-state reactivity and its dependence on the reactant internal excitations are analyzed and found to share many similarities both energetically and dynamically with the H + H 2 O → H 2 + OH reaction. The strong enhancement of reactivity by the H 2 O stretching vibrational excitations in both reactions is attributed to the favorable energy flow into the reaction coordinate near the transition state. On the other hand, the insensitivity of the product state distributions with regard to reactant internal excitation stems apparently from the transition-state control of product energy disposal

  14. Communication: State-to-state dynamics of the Cl + H2O → HCl + OH reaction: Energy flow into reaction coordinate and transition-state control of product energy disposal.

    Science.gov (United States)

    Zhao, Bin; Sun, Zhigang; Guo, Hua

    2015-06-28

    Quantum state-to-state dynamics of a prototypical four-atom reaction, namely, Cl + H2O → HCl + OH, is investigated for the first time in full dimensionality using a transition-state wave packet method. The state-to-state reactivity and its dependence on the reactant internal excitations are analyzed and found to share many similarities both energetically and dynamically with the H + H2O → H2 + OH reaction. The strong enhancement of reactivity by the H2O stretching vibrational excitations in both reactions is attributed to the favorable energy flow into the reaction coordinate near the transition state. On the other hand, the insensitivity of the product state distributions with regard to reactant internal excitation stems apparently from the transition-state control of product energy disposal.

  15. Tracer kinetic investigations on isomerization and synthesis of /sup 8/C-aromates. II. Isomerization of ethylbenzene by means of heterogeneous catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Dermietzel, J; Roesseler, M; Jockisch, W; Wienhold, C [Akademie der Wissenschaften der DDR, Leipzig. Zentralinstitut fuer Isotopen- und Strahlenforschung; Franke, H; Klempin, J; Barz, H J [VEB Petrolchemisches Kombinat Schwedt (German Democratic Republic)

    1978-01-01

    The mechanism of ethylbenzene isomerization on Pt/Al/sub 2/O/sub 3/ catalysts by means of /sup 14/C labelled compounds has been investigated, measuring the isotope distribution between ring and alkyl carbon atoms. The results suggest that ethylbenzene isomerizes via structure rearrangement involving ring carbon atoms. A similar mechanism takes place in xylene isomerization under increased hydrogen partial pressure, while under normal pressure 1,2-methyl group shifting is dominating. All three xylenes are formed from ethylbenzene by parallel reactions.

  16. Racial and ethnic differences in the transition to a teenage birth in the United States.

    Science.gov (United States)

    Manlove, Jennifer; Steward-Streng, Nicole; Peterson, Kristen; Scott, Mindy; Wildsmith, Elizabeth

    2013-06-01

    Rates of teenage childbearing are high in the United States, and they differ substantially by race and ethnicity and nativity status. Data from the National Longitudinal Survey of Youth 1997 cohort were used to link characteristics of white, black, U.S.-born Hispanic and foreign-born Hispanic adolescents to teenage childbearing. Following a sample of 3,294 females aged 12-16 through age 19, discrete-time logistic regression analyses were used to examine which domains of teenagers' lives were associated with the transition to a teenage birth for each racial and ethnic group, and whether these associations help explain racial and ethnic and nativity differences in this transition. In a baseline multivariate analysis controlling for age, compared with whites, foreign-born Hispanics had more than three times the odds of a teenage birth (odds ratio, 3.5), while blacks and native-born Hispanics had about twice the odds (2.1 and 1.9, respectively). Additional controls (for family environments; individual, peer and dating characteristics; characteristics of first sexual relationships; and subsequent sexual experience) reduced the difference between blacks and whites, and between foreign-born Hispanics and whites, and eliminated the difference between U.S.-born Hispanics and whites. Further, if racial or ethnic minority adolescents had the same distribution as did white teenagers across all characteristics, the predicted probability of a teenage birth would be reduced by 40% for blacks and 35% for U.S.-born Hispanics. Differences in the context of adolescence may account for a substantial portion of racial, ethnic and nativity differences in teenage childbearing. Copyright © 2013 by the Guttmacher Institute.

  17. Linking ecosystem services with state-and-transition models to evaluate rangeland management decisions

    Science.gov (United States)

    Lohani, S.; Heilman, P.; deSteiguer, J. E.; Guertin, D. P.; Wissler, C.; McClaran, M. P.

    2014-12-01

    Quantifying ecosystem services is a crucial topic for land management decision making. However, market prices are usually not able to capture all the ecosystem services and disservices. Ecosystem services from rangelands, that cover 70% of the world's land area, are even less well-understood since knowledge of rangelands is limited. This study generated a management framework for rangelands that uses remote sensing to generate state and transition models (STMs) for a large area and a linear programming (LP) model that uses ecosystem services to evaluate natural and/or management induced transitions as described in the STM. The LP optimization model determines the best management plan for a plot of semi-arid land in the Empire Ranch in southeastern Arizona. The model allocated land among management activities (do nothing, grazing, fire, and brush removal) to optimize net benefits and determined the impact of monetizing environmental services and disservices on net benefits, acreage allocation and production output. The ecosystem services under study were forage production (AUM/ac/yr), sediment (lbs/ac/yr), water runoff (inches/yr), soil loss (lbs/ac/yr) and recreation (thousands of number of visitors/ac/yr). The optimization model was run for three different scenarios - private rancher, public rancher including environmental services and excluding disservices, and public rancher including both services and disservices. The net benefit was the highest for the public rancher excluding the disservices. A result from the study is a constrained optimization model that incorporates ecosystem services to analyze investments on conservation and management activities. Rangeland managers can use this model to understand and explain, not prescribe, the tradeoffs of management investments.

  18. Combined Function of Brønsted and Lewis Acidity in the Zeolite-Catalyzed Isomerization of Glucose to Fructose in Alcohols

    DEFF Research Database (Denmark)

    Shunmugavel, Saravanamurugan; Riisager, Anders; Taarning, Esben

    2016-01-01

    Glucose conversion via fructose to useful chemicals and fuels has attracted considerable attention. Isomerization of glucose to fructose can proceed along several different reaction pathways involving different sugar intermediates and isomeric forms. Presently, the roles of the substrate isomeric...

  19. Isomerization of Internal Alkynes to Iridium(III Allene Complexes via C–H Bond Activation: Expanded Substrate Scope, and Progress towards a Catalytic Methodology

    Directory of Open Access Journals (Sweden)

    Neha Phadke

    2015-11-01

    Full Text Available The synthesis of a series of allene complexes (POCOPIr(η2-RC=.=CR’ 1b–4b (POCOP = 2,6-bis(di-tert-butylphosphonitobenzene via isomerization of internal alkynes is reported. We have demonstrated that the application of this methodology is viable for the isomerization of a wide variety of alkyne substrates. Deuterium labeling experiments support our proposed mechanism. The structures of the allene complexes 1b–4b were determined using spectroscopic data analysis. Additionally, the solid-state molecular structure of complex 2b was determined using single crystal X-ray diffraction studies and it confirmed the assignment of an iridium-bound allene isomerization product. The rates of isomerization were measured using NMR techniques over a range of temperatures to allow determination of thermodynamic parameters. Finally, we report a preliminary step towards developing a catalytic methodology; the allene may be liberated from the metal center by exposure of the complex to an atmosphere of carbon monoxide.

  20. Thermal decay of rhodopsin: role of hydrogen bonds in thermal isomerization of 11-cis retinal in the binding site and hydrolysis of protonated Schiff base.

    Science.gov (United States)

    Liu, Jian; Liu, Monica Yun; Nguyen, Jennifer B; Bhagat, Aditi; Mooney, Victoria; Yan, Elsa C Y

    2009-07-01

    Although thermal stability of the G protein-coupled receptor rhodopsin is directly related to its extremely low dark noise level and has recently generated considerable interest, the chemistry behind the thermal decay process of rhodopsin has remained unclear. Using UV-vis spectroscopy and HPLC analysis, we have demonstrated that the thermal decay of rhodopsin involves both hydrolysis of the protonated Schiff base and thermal isomerization of 11-cis to all-trans retinal. Examining the unfolding of rhodopsin by circular dichroism spectroscopy and measuring the rate of thermal isomerization of 11-cis retinal in solution, we conclude that the observed thermal isomerization of 11-cis to all-trans retinal happens when 11-cis retinal is in the binding pocket of rhodopsin. Furthermore, we demonstrate that solvent deuterium isotope effects are involved in the thermal decay process by decreasing the rates of thermal isomerization and hydrolysis, suggesting that the rate-determining step of these processes involves breaking hydrogen bonds. These results provide insight into understanding the critical role of an extensive hydrogen-bonding network on stabilizing the inactive state of rhodopsin and contribute to our current understanding of the low dark noise level of rhodopsin, which enables this specialized protein to function as an extremely sensitive biological light detector. Because similar hydrogen-bonding networks have also been suggested by structural analysis of two other GPCRs, beta1 and beta2 adrenergic receptors, our results could reveal a general role of hydrogen bonds in facilitating GPCR function.