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Sample records for rich microsecond isomers

  1. New Isomers in the Neutron-Rich Region Beyond 208Pb

    NASA Astrophysics Data System (ADS)

    Gottardo, A.; Valiente-Dobón, J. J.; Benzoni, G.; Gadea, A.; Lunardi, S.; Boutachkov, P.; Bruce, A. M.; Górska, M.; Grebosz, J.; Pietri, S.; Podolyák, Zs.; Pfützner, M.; Regan, P. H.; Weick, H.; Alcántara Núñez, J.; Algora, A.; Al-Dahan, N.; de Angelis, G.; Ayyad, Y.; Alkhomashi, N.; Allegro, P. R. P.; Bazzacco, D.; Benlliure, J.; Bowry, M.; Bracco, A.; Bunce, M.; Camera, F.; Casarejos, E.; Cortes, M. L.; Crespi, F. C. L.; Corsi, A.; Bacelar, A. M. Denis; Deo, A. Y.; Domingo-Pardo, C.; Doncel, M.; Dombradi, Zs.; Engert, T.; Eppinger, K.; Farrelly, G. F.; Farinon, F.; Farnea, E.; Geissel, H.; Gerl, J.; Goel, N.; Gregor, E.; Habermann, T.; Hoischen, R.; Janik, R.; John, P. R.; Klupp, S.; Kojouharov, I.; Kurz, N.; Lenzi, S. M.; Leoni, S.; Mandal, S.; Menegazzo, R.; Mengoni, D.; Million, B.; Modamio, V.; Morales, A. I.; Napoli, D. R.; Naqvi, F.; Nicolini, R.; Nociforo, C.; Prochazka, A.; Prokopowicz, W.; Recchia, F.; Ribas, R. V.; Reed, M. W.; Rudolph, D.; Sahin, E.; Schaffner, H.; Sharma, A.; Sitar, B.; Siwal, D.; Steiger, K.; Strmen, P.; Swan, T. P. D.; Szarka, I.; Ur, C. A.; Walker, P. M.; Wieland, O.; Wollersheim, H.-J.

    2014-03-01

    The region of neutron-rich nuclei beyond 208Pb has been very difficult to explore due to its high mass and exoticity. However, recent experimental improvements allowed one to perform a quite extended isomer decay spectroscopy of these nuclei.

  2. Observation of new K isomers among neutron-rich rare earth nuclei produced by in-flight fission of 345 MeV/nucleon 238U

    NASA Astrophysics Data System (ADS)

    Kameda, Daisuke; Kubo, Toshiyuki; BigRIPS new isotope Collaboration

    2014-09-01

    We have performed search for new K isomers for a wide range of neutron-rich rare earth nuclei using the BigRIPS separator at RIKEN RIBF. The rare earth nuclei were produced by in-flight fission of a 238U beam at 345 MeV/nucleon, and isomeric gamma rays were detected using four clover-type germanium detectors. As a result, we have observed a total of 25 new microsecond isomers: 158 m , 159 m , 160 mNd, 158 m , 159 m , 161 mPm, 160 m , 161 m , 162 mSm, 163 m , 164 mEu, 162 m , 164 m , 165 m , 166 mGd, 164 m , 165 m , 166 m , 167 m , 168 mTb, 167 m , 168 m , 169 m , 170 mDy, and 171mHo, and obtained a wealth of spectroscopic information on these nuclei. The nuclei in this region are predicted to be well deformed with a prolate shape, and Kisomers are expected to appear due to the K hindrance. In the present measurement, as anticipated, many of the observed new isomers have been interpreted as a K isomer, because we could identify some gamma rays which belong to the grand-state rotational band being fed by isomeric transitions. The systematics of known K isomers, such as those in neighboring higher- Zisotones, also help and support the interpretation of isomerism. Here we will report on the details of the experimental results and discuss the possible configurations of deformed orbits for the observed new K isomers.

  3. New μs isomers in the neutron-rich 210Hg nucleus

    NASA Astrophysics Data System (ADS)

    Gottardo, A.; Valiente-Dobón, J. J.; Benzoni, G.; Gadea, A.; Lunardi, S.; Boutachkov, P.; Bruce, A. M.; Górska, M.; Grebosz, J.; Pietri, S.; Podolyák, Zs.; Pfützner, M.; Regan, P. H.; Weick, H.; Alcántara Núñez, J.; Algora, A.; Al-Dahan, N.; de Angelis, G.; Ayyad, Y.; Alkhomashi, N.; Allegro, P. R. P.; Bazzacco, D.; Benlliure, J.; Bowry, M.; Bracco, A.; Bunce, M.; Camera, F.; Casarejos, E.; Cortes, M. L.; Crespi, F. C. L.; Corsi, A.; Denis Bacelar, A. M.; Deo, A. Y.; Domingo-Pardo, C.; Doncel, M.; Dombradi, Zs.; Engert, T.; Eppinger, K.; Farrelly, G. F.; Farinon, F.; Farnea, E.; Geissel, H.; Gerl, J.; Goel, N.; Gregor, E.; Habermann, T.; Hoischen, R.; Janik, R.; John, P. R.; Klupp, S.; Kojouharov, I.; Kurz, N.; Lenzi, S. M.; Leoni, S.; Mandal, S.; Menegazzo, R.; Mengoni, D.; Million, B.; Modamio, V.; Morales, A. I.; Napoli, D. R.; Naqvi, F.; Nicolini, R.; Nociforo, C.; Prochazka, A.; Prokopowicz, W.; Recchia, F.; Ribas, R. V.; Reed, M. W.; Rudolph, D.; Sahin, E.; Schaffner, H.; Sharma, A.; Sitar, B.; Siwal, D.; Steiger, K.; Strmen, P.; Swan, T. P. D.; Szarka, I.; Ur, C. A.; Walker, P. M.; Wieland, O.; Wollersheim, H.-J.

    2013-10-01

    Neutron-rich nuclei in the lead region, beyond N = 126, have been studied at the FRS-RISING setup at GSI, exploiting the fragmentation of a primary uranium beam. Two isomeric states have been identified in 210Hg: the 8+ isomer expected from the seniority scheme in the νg9/2 shell and a second one at low spin and low excitation energy. The decay strength of the 8+ isomer confirms the need of effective three-body forces in the case of neutron-rich lead isotopes. The other unexpected low-lying isomer has been tentatively assigned as a 3- state, although this is in contrast with theoretical expectations.

  4. Volatiles of Callicarpa macrophylla: a rich source of selinene isomers.

    PubMed

    Singh, Anil K; Chanotiya, Chandan S; Yadav, Anju; Kalra, Alok

    2010-02-01

    Variations in volatile composition of the leaf and fruit oils from Callicarpa macrophylla were compared, using GC-FID, Kovat's Index calculation, and GC/MS. The oils were rich in selinene derivatives. The fruit oil was comprised of 41.6% beta-selinene and 6% alpha-selinene. The leaves from both the harvests contained 29% and 20% beta-selinene and 1.7% alpha-selinene. In addition, dendrolasin, a potential perfumery natural furanoid sesquiterpenoid, was a characteristic of both leaf and fruit essential oils. PMID:20334142

  5. Isomers in Neutron-Rich A ?? 190 NNuclides from 208Pb Fragmentation

    SciTech Connect

    Caamano, M.; Walker, P. M.; Regan, P. H.; Pfutzner, M.; Podolyak, Zs.; Gerl, J.; Hellstrom, M.; Mayet, P.; Mineva, M. N.; Aprahamian, A.; Benlliure, J.; Bruce, A. M.; Butler, P. A.; Cortina Gil, D.; Cullen, D. M.; Doring, J.; Enqvist, T.; Fox, C.; Garces Narro, J.; Geissel, H.; Gelletly, W.; Giovinazzo, J.; Grawe, H.; Grzywacz, R.; Kleinbohl, A.; Korten, W.; Lewitowicz, M.; Lucas, R.; Mach, H.; O'Leary, C. D.; De Oliveira, F.; Pearson, C. J.; Rejmund, F.; Rejmund, M.; Sawicka, M.; Schaffner, H.; Schlegel, C.; Schmidt, K.; Schmidt, K.-H.; Stevenson, P. D.; Theisen, Ch.; Vives, F.; Warner, D. D.; Wheldon, C.; Wollersheim, H. J.; Wooding, S.; Xu, F.; Yordanov, O.

    2005-01-01

    Relativistic projectile fragmentation of {sup 208}Pb has been used to produce isomers in neutron-rich, A {approx} 190 nuclides. A forward-focusing spectrometer provided ion-by-ion mass and charge identification. The detection of gamma-rays emitted by stopped ions has led to the assignment of isomers in {sup 188}Ta, {sup 190}W, {sup 192}Re, {sup 193}Re, {sup 195}Os, {sup 197}Ir, {sup 198}Ir, {sup 200}Pt, {sup 201}Pt, {sup 202}Pt and {sup 203}Au, with half-lives ranging from approximately 10 ns to 1 ms. Tentative isomer information has been found also for {sup 174}Er, {sup 175}Er, {sup 185}Hf, {sup 191}Re, {sup 194}Re and {sup 199}Ir. In most cases, time-correlated, singles gamma-ray events provided the first spectroscopic data on excited states for each nuclide. In {sup 200}Pt and {sup 201}Pt, the assignments are supported by gamma-gamma coincidences. Isomeric ratios provide additional information, such as half-life and transition energy constraints in particular cases. The level structures of the platinum isotopes are discussed, and comparisons are made with isomer systematics.

  6. K-isomers in Hf nuclei at and beyond the neutron-rich edge of {beta}-stability.

    SciTech Connect

    Chowdhury, P.; Alarcao, R. D.; Seabury, E. H.; Walker, P. M.; Wheldon, C.; Ahmad. I.; Carpenter, M. P.; Hackman, G.; Janssens, R. V. F.; Khoo, T. L.; Nisius, D.; Reiter, P.

    1999-03-30

    New high-K isomers are populated in {sup 180,181,182}Hf nuclei via inelastic excitation and transfer reactions, using pulsed {sup 238}U beams on Hf targets. The new data explore K-hindrances for different multipolarities and the role of residual spin-spin interactions for multi-quasiparticle (qp) configurations at the neutron-rich edge of the {beta}-stability line. The mapping of 4-qp K-isomers in the A {approx} 180 region is extended into neutron-rich territory.

  7. E2 transition probabilities for decays of isomers observed in neutron-rich odd Sn isotopes

    DOE PAGESBeta

    Iskra, Ł. W.; Broda, R.; Janssens, R. V.F.; Wrzesiński, J.; Chiara, C. J.; Carpenter, M. P.; Fornal, B.; Hoteling, N.; Kondev, F. G.; Królas, W.; et al

    2015-01-01

    High-spin states were investigated with gamma coincidence techniques in neutron-rich Sn isotopes produced in fission processes following ⁴⁸Ca + ²⁰⁸Pb, ⁴⁸Ca + ²³⁸U, and ⁶⁴Ni + ²³⁸U reactions. By exploiting delayed and cross-coincidence techniques, level schemes have been delineated in odd ¹¹⁹⁻¹²⁵Sn isotopes. Particular attention was paid to the occurrence of 19/2⁺ and 23/2⁺ isomeric states for which the available information has now been significantly extended. Reduced transition probabilities, B(E2), extracted from the measured half-lives and the established details of the isomeric decays exhibit a striking regularity. This behavior was compared with the previously observed regularity of the B(E2) amplitudesmore » for the seniority ν = 2 and 3, 10⁺ and 27/2⁻ isomers in even- and odd-Sn isotopes, respectively.« less

  8. E2 transition probabilities for decays of isomers observed in neutron-rich odd Sn isotopes

    SciTech Connect

    Iskra, Ł. W.; Broda, R.; Janssens, R. V.F.; Wrzesiński, J.; Chiara, C. J.; Carpenter, M. P.; Fornal, B.; Hoteling, N.; Kondev, F. G.; Królas, W.; Lauritsen, T.; Pawłat, T.; Seweryniak, D.; Stefanescu, I.; Walters, W. B.; Zhu, S.

    2015-01-01

    High-spin states were investigated with gamma coincidence techniques in neutron-rich Sn isotopes produced in fission processes following ⁴⁸Ca + ²⁰⁸Pb, ⁴⁸Ca + ²³⁸U, and ⁶⁴Ni + ²³⁸U reactions. By exploiting delayed and cross-coincidence techniques, level schemes have been delineated in odd ¹¹⁹⁻¹²⁵Sn isotopes. Particular attention was paid to the occurrence of 19/2⁺ and 23/2⁺ isomeric states for which the available information has now been significantly extended. Reduced transition probabilities, B(E2), extracted from the measured half-lives and the established details of the isomeric decays exhibit a striking regularity. This behavior was compared with the previously observed regularity of the B(E2) amplitudes for the seniority ν = 2 and 3, 10⁺ and 27/2⁻ isomers in even- and odd-Sn isotopes, respectively.

  9. Discovery of Highly Excited Long-Lived Isomers in Neutron-Rich Hafnium and Tantalum Isotopes through Direct Mass Measurements

    SciTech Connect

    Reed, M. W.; Cullen, I. J.; Walker, P. M.; Deo, A. Y.; Kempley, R. S.; Swan, T. P. D.; Litvinov, Yu. A.; Winckler, N.; Blaum, K.; Bosch, F.; Dimopoulou, C.; Farinon, F.; Heil, M.; Knoebel, R.; Kozhuharov, C.; Kurcewicz, J.; Kuzminchuk, N.; Litvinov, S.; Nociforo, C.; Nolden, F.

    2010-10-22

    A study of cooled {sup 197}Au projectile-fragmentation products has been performed with a storage ring. This has enabled metastable nuclear excitations with energies up to 3 MeV, and half-lives extending to minutes or longer, to be identified in the neutron-rich nuclides {sup 183,184,186}Hf and {sup 186,187}Ta. The results support the prediction of a strongly favored isomer region near neutron number 116.

  10. Characterization of isomers in the neutron-rich odd-odd nucleus {sup 156}Pm

    SciTech Connect

    Sood, P. C.; Gowrishankar, R; Sai, K. Vijay; Sainath, M.

    2011-02-15

    Critical examination of the experimental data from {sup 156}Nd and {sup 156}Pm {beta} decays and the observed location of relevant neutron and proton orbitals in the neighboring odd-A isotones and isotopes, taken together with the low-lying two-quasiparticle (2qp) structures expected in {sup 156}Pm from the rotor-particle model, lead to the conclusion that a consistent description of all the available data is achieved with the I{sup {pi}}=4{sup +} spin-parity assignment to the 26.7s {sup 156}Pm ground state (g.s.) and assignment of I{sup {pi}}=1{sup +} to its 150.3-keV isomer with the 2qp configuration 4{sub g.s.}{sup +}{l_brace}p{sub o}:5/2[532{up_arrow}]{+-}n{sub o}:3/2[521{up_arrow}]{r_brace}1{sub 150}{sup +}. In the process, a two-neutron configuration is also suggested for the 1509-keV 4{sup +} level in the daughter nucleus {sup 156}Sm. The present analysis reiterates the important question of whether the {beta}-decay log ft value, by itself, can be employed to deduce the relative parity of the {beta}-connected states.

  11. Formation and infrared spectroscopic characterization of three oxygen-rich BiO4 isomers in solid argon.

    PubMed

    Wang, Caixia; Chen, Mohua; Li, Zhen Hua; Zhou, Mingfei

    2013-11-01

    The reactions of bismuth atoms and O2 have been investigated using matrix isolation infrared spectroscopy and density functional theory calculations. The ground state bismuth atoms react with dioxygen to form the BiOO and Bi(O2)2 complexes spontaneously on annealing. The BiOO molecule is characterized to be an end-on bonded superoxide complex, while the Bi(O2)2 molecule is characterized to be a superoxo bismuth peroxide complex, [Bi(3+)(O2(-))(O2(2-))]. Under UV-visible light irradiation, the Bi(O2)2 complex rearranges to the more stable OBiOOO isomer, an end-on bonded bismuth monoxide-ozonide complex. The end-on-bonded OBiOOO complex further rearranges to a more stable side-on bonded OBiO3 isomer upon sample annealing. In addition, the bent bismuth dioxide anion is also formed and assigned. PMID:24112025

  12. Decay of a {pi}h{sub 11/2} x {nu}h{sub 11/2} microsecond isomer in {sub 61}{sup 136}Pm{sub 75}

    SciTech Connect

    Rigby, S. V.; Cullen, D. M.; Mason, P. J. R.; Scholes, D. T.; Scholey, C.; Rahkila, P.; Eeckhaudt, S.; Grahn, T.; Greenlees, P.; Jones, P. M.; Julin, R.; Juutinen, S.; Kettunen, H.; Leino, M.; Leppaenen, A.-P.; Nieminen, P.; Nyman, M.; Pakarinen, J.; Uusitalo, J.

    2008-09-15

    An experiment has been performed to populate several extremely neutron-deficient nuclei around the mass-140 region of the nuclear chart, using a beam of {sup 54}Fe on a {sup 92}Mo target at an energy of 315 MeV. Analysis of these data using recoil-isomer tagging has established that the yrast {pi}h{sub 11/2} x {nu}h{sub 11/2},J{sup {pi}}=(8{sup +}), bandhead state in {sup 136}Pm is isomeric with a half-life of 1.5(1) {mu}s. This isomeric state decays via a 43-keV, probable-E1 transition to a J{sup {pi}}=(7{sup -}) state. Consideration of the theoretical Nilsson orbitals near the Fermi surface suggests that the J{sup {pi}}=(8{sup +}) state has a {nu}h{sub 11/2}[505](11/2){sup -} x {pi}h{sub 11/2}[532](5/2){sup -} configuration, which decays to the J{sup {pi}}=(7{sup -}) state with a {nu}h{sub 11/2}[505](11/2){sup -} x {pi}d{sub 5/2}[411](3/2){sup +} configuration. Differences in the shape-driving effects for these two configurations is reasoned to be responsible for the long half-life of the J{sup {pi}}=(8{sup +}) isomeric state. The non-observation of other {gamma} rays in prompt or delayed coincidence with the 43-keV transition suggests that this transition may feed another, longer lived isomeric state with a half-life of the order of milliseconds or greater. However, the present experiment was not sensitive to the decay of this new J{sup {pi}}=(7{sup -}) state by internal conversion or even {beta} decay.

  13. Three hen strains fed photoisomerized trans,trans CLA-rich soy oil exhibit different yolk accumulation rates and source-specific isomer deposition.

    PubMed

    Shinn, Sara E; Gilley, Alex D; Proctor, Andrew; Anthony, Nicholas B

    2015-04-01

    Most CLA chicken feeding trials used cis,trans (c,t) and trans,cis (t,c) CLA isomers to produce CLA-rich eggs, while reports of trans,trans (t,t) CLA enrichment in egg yolks are limited. The CLA yolk fatty acid profile changes and the 10-12 days of feeding needed for maximum CLA are well documented, but there is no information describing CLA accumulation during initial feed administration. In addition, no information on CLA accumulation rates in different hen strains is available. The aim of this study was to determine a mathematical model that described yolk CLA accumulation and depletion in three hen strains by using t,t CLA-rich soybean oil produced by photoisomerization. Diets of 30-week Leghorns, broilers, and jungle fowl were supplemented with 15% CLA-rich soy oil for 16 days, and eggs were collected for 32 days. Yolk fatty acid profiles were measured by GC-FID. CLA accumulation and depletion was modeled by both quadratic and piecewise regression analysis. A strong quadratic model was proposed, but it was not as effective as piecewise regression in describing CLA accumulation and depletion. Broiler hen eggs contained the greatest concentration of CLA at 3.2 mol/100 g egg yolk, then jungle fowl at 2.9 mol CLA, and Leghorns at 2.3 mol CLA. The t,t CLA isomer levels remained at 55% of total yolk CLA during CLA feeding. However, t-10,c-12 (t,c) CLA concentration increased slightly during CLA accumulation and was significantly greater than c-9,t-11 CLA. Jungle fowl had the smallest increase in yolk saturated fat with CLA yolk accumulation. PMID:25771890

  14. Microsecond switchable thermal antenna

    SciTech Connect

    Ben-Abdallah, Philippe Benisty, Henri; Besbes, Mondher

    2014-07-21

    We propose a thermal antenna that can be actively switched on and off at the microsecond scale by means of a phase transition of a metal-insulator material, the vanadium dioxide (VO{sub 2}). This thermal source is made of a periodically patterned tunable VO{sub 2} nanolayer, which support a surface phonon-polariton in the infrared range in their crystalline phase. Using electrodes properly registered with respect to the pattern, the VO{sub 2} phase transition can be locally triggered by ohmic heating so that the surface phonon-polariton can be diffracted by the induced grating, producing a highly directional thermal emission. Conversely, when heating less, the VO{sub 2} layers cool down below the transition temperature, the surface phonon-polariton cannot be diffracted anymore so that thermal emission is inhibited. This switchable antenna could find broad applications in the domain of active thermal coatings or in those of infrared spectroscopy and sensing.

  15. Interstellar isomers

    NASA Technical Reports Server (NTRS)

    Defrees, D.; Mclean, D.; Herbst, E.

    1986-01-01

    Both observational and theoretical studies of molecular clouds are hindered by many difficulties. One way to partially circumvent the difficulties of characterizing the chemistry within these objects is to study the relative abundances of isomers which are synthesized from a common set of precursors. Unfortunately, only one such system has been confirmed, the HCN/HNC pair of isomers. While the basic outlines of its chemistry have been known for some years, there are still many aspects of the chemistry which are unclear. Another potential pair of isomers is HCO+/HOC+; HCO+ is an abundant instellar molecule and a tentative identification of HOC+ has been made in Sgr B2. This identification is being challenged, however, based on theoretical and laboratory evidence that HOC+ reacts with H2. Another potential pair of interstellar isomers is methyl cyanide (CH3CN, acetonitrile) and methyl isocyanide (CH3NC). The cyanide is well known, however the isocyanide has yet to be observed despite theoretical predictions that appreciable quantities should be present.

  16. Decay studies of the neutron-rich isotopes sup 168 Dy and sup 168 Ho sup g and the identification of the new isomer sup 168 Ho sup m

    SciTech Connect

    Chasteler, R.M.; Nitschke, J.M.; Firestone, R.B.; Vierinen, K.S.; Wilmarth, P.A. )

    1990-11-01

    Multinucleon transfer reactions between {sup 170}Er ions and {sup nat}W targets with on-line mass separation were used to produce neutron-rich {ital A}=168 isotopes. {beta} and {gamma} spectroscopy was used to study the decay of these activities. A new isomer of holmium, {sup 168}Ho{sup {ital m}}, was identified to decay by an isomeric transition with a half-life of 132(4) s. A decay scheme for the most neutron-rich {ital A}=168 isotope, 8.8(3)-min {sup 168}Dy, was determined. Also, a new {ital Q}{sub {beta}}{sup {minus}} value of 2.93(3) MeV for the decay of 3.0-min {sup 168}Ho{sup {ital g}} has been obtained.

  17. g Factor of the 7- isomer in 126Sn and first observation of spin-alignment in relativistic fission

    NASA Astrophysics Data System (ADS)

    Ilie, G.; Neyens, G.; Simpson, G. S.; Jolie, J.; Blazhev, A.; Grawe, H.; Lozeva, R. L.; Vermeulen, N.; Atanasova, L.; Balabanski, D. L.; Becker, F.; Bednarczyk, P.; Brandau, C.; Caceres, L.; Chamoli, S. K.; Daugas, J. M.; Doornenbal, P.; Gerl, J.; Górska, M.; Grȩbosz, J.; Hass, M.; Ionescu-Bujor, M.; Jungclaus, A.; Kmiecik, M.; Kojouharov, I.; Kurz, N.; Maj, A.; Mallion, S.; Perru, O.; Pfützner, M.; Podolyák, Zs.; Prokopowicz, W.; De Rydt, M.; Saito, T. R.; Schaffner, H.; Turzó, K.; Walker, J.; Werner-Malento, E.; Wollersheim, H. J.

    2010-04-01

    We report on the g factor measurement of the isomeric 7 state (E=2219 keV, T1/2=5.9(8) μs) in the neutron-rich 126Sn nucleus. The nucleus was produced by the fission of a relativistic 238U beam and reaction products were selected by the FRS fragment separator at GSI. For the first time, spin-alignment was observed after relativistic fission. It was used to deduce the g factor of the 7 isomeric state, g(7)=-0.098(9), from the measured perturbed angular distribution of its γ decay using the RISING Cluster detectors. The observed value confirms the suggested ν(h11/2-1d3/2-1) dominant configuration, which has been proposed for the 7 isomers in neutron-rich Sn isotopes. The failure of the g factor additivity rule and the importance of core polarization evolution with increasing distance from the doubly-magic 132Sn is discussed. The first observation of 18(8)% of spin-alignment produced by the relativistic fission of a 238U beam paves the way to study moments of neutron-rich (sub-)microsecond isomers, which are difficult to align by other means.

  18. Long-lived K isomer and enhanced γ vibration in the neutron-rich nucleus 172Dy: Collectivity beyond double midshell

    NASA Astrophysics Data System (ADS)

    Watanabe, H.; Zhang, G. X.; Yoshida, K.; Walker, P. M.; Liu, J. J.; Wu, J.; Regan, P. H.; Söderström, P.-A.; Kanaoka, H.; Korkulu, Z.; Lee, P. S.; Nishimura, S.; 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.; Kondev, F. G.; Kubo, T.; Kubono, S.; Kurz, N.; Kuti, I.; Lalkovski, S.; Lane, G. J.; 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.

    2016-09-01

    The level structure of 172Dy has been investigated for the first time by means of decay spectroscopy following in-flight fission of a 238U beam. A long-lived isomeric state with T1/2 = 0.71 (5) s and Kπ =8- has been identified at 1278 keV, which decays to the ground-state and γ-vibrational bands through hindered electromagnetic transitions, as well as to the daughter nucleus 172Ho via allowed β decays. The robust nature of the Kπ =8- isomer and the ground-state rotational band reveals an axially-symmetric structure for this nucleus. Meanwhile, the γ-vibrational levels have been identified at unusually low excitation energy compared to the neighboring well-deformed nuclei, indicating the significance of the microscopic effect on the non-axial collectivity in this doubly mid-shell region. The underlying mechanism of enhanced γ vibration is discussed in comparison with the deformed Quasiparticle Random-Phase Approximation based on a Skyrme energy-density functional.

  19. Sub-microsecond-resolution probe microscopy

    SciTech Connect

    Ginger, David; Giridharagopal, Rajiv; Moore, David; Rayermann, Glennis; Reid, Obadiah

    2014-04-01

    Methods and apparatus are provided herein for time-resolved analysis of the effect of a perturbation (e.g., a light or voltage pulse) on a sample. By operating in the time domain, the provided method enables sub-microsecond time-resolved measurement of transient, or time-varying, forces acting on a cantilever.

  20. Power optimization in logic isomers

    NASA Technical Reports Server (NTRS)

    Panwar, Ramesh; Rennels, David; Alkalaj, Leon

    1993-01-01

    Logic isomers are labeled, 2-isomorphic graphs that implement the same logic function. Logic isomers may have significantly different power requirements even though they have the same number of transistors in the implementation. The power requirements of the isomers depend on the transition activity of the input signals. The power requirements of isomorphic graph isomers of n-input NAND and NOR gates are shown. Choosing the less power-consuming isomer instead of the others can yield significant power savings. Experimental results on a ripple-carry adder are presented to show that the implementation using the least power-consuming isomers requires approximately 10 percent less power than the implementation using the most power-consuming isomers. Simulations of other random logic designs also confirm that designs using less power-consuming isomers can reduce the logic power demand by approximately 10 percent as compared to designs using more power-consuming isomers.

  1. Atlas of Nuclear Isomers

    NASA Astrophysics Data System (ADS)

    Jain, Ashok Kumar; Maheshwari, Bhoomika; Garg, Swati; Patial, Monika; Singh, Balraj

    2015-09-01

    We present an atlas of nuclear isomers containing the experimental data for the isomers with a half-life ≥ 10 ns together with their various properties such as excitation-energy, half-life, decay mode(s), spin-parity, energies and multipolarities of emitted gamma transitions, etc. The ENSDF database complemented by the XUNDL database has been extensively used in extracting the relevant data. Recent literature from primary nuclear physics journals, and the NSR bibliographic database have been searched to ensure that the compiled data Table is as complete and current as possible. The data from NUBASE-12 have also been checked for completeness, but as far as possible original references have been cited. Many interesting systematic features of nuclear isomers emerge, some of them new; these are discussed and presented in various graphs and figures. The cutoff date for the extraction of data from the literature is August 15, 2015.

  2. Atlas of Nuclear Isomers

    SciTech Connect

    Jain, Ashok Kumar; Maheshwari, Bhoomika; Garg, Swati; Patial, Monika; Singh, Balraj

    2015-09-15

    We present an atlas of nuclear isomers containing the experimental data for the isomers with a half-life ≥ 10 ns together with their various properties such as excitation-energy, half-life, decay mode(s), spin-parity, energies and multipolarities of emitted gamma transitions, etc. The ENSDF database complemented by the XUNDL database has been extensively used in extracting the relevant data. Recent literature from primary nuclear physics journals, and the NSR bibliographic database have been searched to ensure that the compiled data Table is as complete and current as possible. The data from NUBASE-12 have also been checked for completeness, but as far as possible original references have been cited. Many interesting systematic features of nuclear isomers emerge, some of them new; these are discussed and presented in various graphs and figures. The cutoff date for the extraction of data from the literature is August 15, 2015.

  3. Efficient Illumination for Microsecond Tracking Microscopy

    PubMed Central

    Dulin, David; Barland, Stephane; Hachair, Xavier; Pedaci, Francesco

    2014-01-01

    The possibility to observe microsecond dynamics at the sub-micron scale, opened by recent technological advances in fast camera sensors, will affect many biophysical studies based on particle tracking in optical microscopy. A main limiting factor for further development of fast video microscopy remains the illumination of the sample, which must deliver sufficient light to the camera to allow microsecond exposure times. Here we systematically compare the main illumination systems employed in holographic tracking microscopy, and we show that a superluminescent diode and a modulated laser diode perform the best in terms of image quality and acquisition speed, respectively. In particular, we show that the simple and inexpensive laser illumination enables less than s camera exposure time at high magnification on a large field of view without coherence image artifacts, together with a good hologram quality that allows nm-tracking of microscopic beads to be performed. This comparison of sources can guide in choosing the most efficient illumination system with respect to the specific application. PMID:25251462

  4. Microsecond protein dynamics observed at the single-molecule level

    PubMed Central

    Otosu, Takuhiro; Ishii, Kunihiko; Tahara, Tahei

    2015-01-01

    How polypeptide chains acquire specific conformations to realize unique biological functions is a central problem of protein science. Single-molecule spectroscopy, combined with fluorescence resonance energy transfer, is utilized to study the conformational heterogeneity and the state-to-state transition dynamics of proteins on the submillisecond to second timescales. However, observation of the dynamics on the microsecond timescale is still very challenging. This timescale is important because the elementary processes of protein dynamics take place and direct comparison between experiment and simulation is possible. Here we report a new single-molecule technique to reveal the microsecond structural dynamics of proteins through correlation of the fluorescence lifetime. This method, two-dimensional fluorescence lifetime correlation spectroscopy, is applied to clarify the conformational dynamics of cytochrome c. Three conformational ensembles and the microsecond transitions in each ensemble are indicated from the correlation signal, demonstrating the importance of quantifying microsecond dynamics of proteins on the folding free energy landscape. PMID:26151767

  5. Fragmentation process induced by microsecond laser pulses during lithotripsy

    NASA Astrophysics Data System (ADS)

    Rink, K.; Delacrétaz, G.; Salathé, R. P.

    1992-07-01

    A fiber optic stress sensing technique is applied to evaluate the fragmentation mechanism for pulsed dye-laser lithotripsy. We demonstrate for the first time that the fragmentation process with microsecond laser pulses originates from the shock wave induced by the cavitation bubble collapse. This shock occurs some hundreds of microseconds after the laser pulse. The shock induced by the plasma expansion, which occurs during laser irradiation, has a minor effect.

  6. Microsecond delays on non-real time operating systems

    SciTech Connect

    Angstadt, R.; Estrada, J.; Diehl, H.T.; Flaugher, B.; Johnson, M.; /Fermilab

    2007-05-01

    We have developed microsecond timing and profiling software that runs on standard Windows and Linux based operating systems. This software is orders of magnitudes better than most of the standard native functions in wide use. Our software libraries calibrate RDTSC in microseconds or seconds to provide two different types of delays: a ''Guaranteed Minimum'' and a precision ''Long Delay'', which releases to the kernel. Both return profiling information of the actual delay.

  7. Microsecond Scale Vibrational Spectroscopic Imaging by Multiplex Stimulated Raman Scattering Microscopy

    PubMed Central

    Liao, Chien-Sheng; Slipchenko, Mikhail N.; Wang, Ping; Li, Junjie; Lee, Seung-Young; Oglesbee, Robert A.; Cheng, Ji-Xin

    2015-01-01

    Real-time vibrational spectroscopic imaging is desired for monitoring cellular states and cellular processes in a label-free manner. Raman spectroscopic imaging of highly dynamic systems is inhibited by relatively slow spectral acquisition on millisecond to second scale. Here, we report microsecond scale vibrational spectroscopic imaging by lock-in free parallel detection of spectrally dispersed stimulated Raman scattering signal. Using a homebuilt tuned amplifier array, our method enables Raman spectral acquisition, within the window defined by the broadband pulse, at the speed of 32 microseconds and with close to shot-noise limited detection sensitivity. Incorporated with multivariate curve resolution analysis, our platform allows compositional mapping of lipid droplets in single live cells, observation of intracellular retinoid metabolism, discrimination of fat droplets from protein-rich organelles in Caenorhabditis elegans, spectral detection of fast flowing tumor cells, and monitoring drug diffusion through skin tissue in vivo. The reported technique opens new opportunities for compositional analysis of cellular compartment in a microscope setting and high-throughput spectral profiling of single cells in a flow cytometer setting. PMID:26167336

  8. Using the USCCS for sub microsecond spacecraft clock calibration

    NASA Technical Reports Server (NTRS)

    Sank, Victor J.

    1993-01-01

    The Return Data Delay technique which requires knowledge of spacecraft range is commonly used for correlating a spacecraft clock against a ground time standard when millisecond accuracy is required. An analysis is presented that allows using the user spacecraft clock calibration system (USCCS) to correlate a spacecraft clock to better than one microsecond accuracy. The basic USCCS algorithm has been simplified and it is shown to result in about one microsecond accuracy without requiring orbital information. By considering the relative motion of the user satellite, the TDRS and the earth station about the center of the earth, a correction of almost two orders of magnitude can be made. Such accuracy is required for scientific investigations that require correlating coincident radiation or particle detection with a remote laboratory.

  9. Lasing efficiency of ethanol dye solutions under coherent microsecond pumping

    NASA Astrophysics Data System (ADS)

    Tarkovskiĭ, V. V.; Anufrik, S. S.

    2008-11-01

    It is established that the excitation wavelength plays an important role in the attainment of maximum efficiency and the time dependence of the pump and lasing pulses under coherent microsecond pumping of dye solutions because the losses due to the molecular absorption in the channel of excited triplet levels, thermooptical distortions, and products of photochemical transformations play a minor role in the total energy balance in comparison with the spectrally dependent loss in the channel of excited singlet levels.

  10. Developing Single-Molecule Technique with Microsecond Resolution

    NASA Astrophysics Data System (ADS)

    Akhterov, Maxim V.

    Molecular machines like proteins are responsible for many regulatory and catalytic functions. Specifically, molecular motions of proteins and their flexibility determine conformational states required for enzyme catalysis, signal transduction, and protein-protein interactions. However, the mechanisms for protein transitions between conformational states are often poorly understood, especially in the milli- to microsecond ranges where conventional optical techniques and computational modeling are most limited. This work describes development of an electronic single-molecule technique for monitoring microsecond motions of biological molecules. Dynamic changes of conductance through a transistor made of a single-walled carbon nanotube (SWNT-FET) report conformational changes of a protein molecule tethered to the SWNT sidewall. In principle, the high operating speed of SWNT-FETs could allow this technique to resolve molecular events with nanosecond resolution. This project focused on improving the technique to a 200 kHz effective bandwidth in order to resolve microsecond-scale dynamics. The improvement was achieved with a home-built electrochemical flow cell. By minimizing parasitic capacitance due to liquid coupling to electrodes and eliminating noise pickup, the flow cell enabled low-noise, high bandwidth measurement of molecular events as short as 2 mus. The apparatus was used to observe closing and opening motions of lysozyme. Preliminary results suggest that lysozyme has a distribution of possible velocities with the most probable speed approaching our experimental resolution of 2 mus.

  11. Nuclear isomers: stepping stones to the unknown

    SciTech Connect

    Walker, P. M.

    2006-03-13

    The utility of isomers for exploring the nuclear landscape is discussed, including their role in superheavy-element research, and the possibility of observing neutron radioactivity. Emphasis is given to K isomers in deformed nuclei. Transition rates are examined in the NpNn scheme for 2- and 3-quasiparticle K-isomer decays, and in connection with level densities for higher quasiparticle numbers.

  12. Microsecond yellow laser for subfoveal leaks in central serous chorioretinopathy

    PubMed Central

    Ambiya, Vikas; Goud, Abhilash; Mathai, Annie; Rani, Padmaja Kumari; Chhablani, Jay

    2016-01-01

    Purpose To evaluate the role of navigated yellow microsecond laser in treating subfoveal leaks in nonresolving central serous chorioretinopathy (CSC). Methods This prospective study included ten eyes of ten consecutive patients with nonresolving CSC with subfoveal leaks. All eyes were treated with 577 nm navigated yellow microsecond laser (5% duty cycle). Key inclusion criteria include a vision loss for a duration of minimum 3 months duration due to focal subfoveal leak on fluorescein angiography. Key exclusion criteria include prior treatment for CSC and any signs of chronic CSC. Comprehensive examination, in addition to low-contrast visual acuity assessment, microperimetry, autofluorescence, spectral domain optical coherence tomography, and fundus fluorescein angiography, was done at baseline, 1, 3, and 6 months after treatment. Rescue laser was performed as per predefined criteria at 3 months. Results The average best-corrected visual acuity improved from 73.3±16.1 letters to 75.8±14.0 (P=0.69) at 3 months and 76.9±13.0 (P=0.59) at 6 months, but was not statistically significant. Low-contrast visual acuity assessment (logMAR) improved from 0.41±0.32 to 0.35±0.42 (P=0.50) at 3 months and 0.28±0.33 (P=0.18) at 6 months. Average retinal sensitivity significantly improved from baseline 18.93±7.19 dB to 22.49±6.67 dB (P=0.01) at 3 months and 21.46±8.47 dB (P=0.04) at 6 months. Rescue laser was required only in one eye at 3 months; however, laser was required in three eyes at 6 months. Conclusion Microsecond laser is a safe and effective modality for treating cases of nonresolving CSC with subfoveal leaks. PMID:27570446

  13. [The sub-microsecond pulser applied for electroporation effect].

    PubMed

    Tan, Yafang; Yang, Hongchun; Wu, Jianxing; Yang, Xiaolin; Zhang, Yi; Zeng, Gang; Zhang, Xiaoyu

    2012-08-01

    A sub-microsecond pulse generation applied for electroporation effects of tumor cell is presented in this paper. The principle of the generator is that the expected pulse waveform is intercepted from the RC discharge curve by controlling the on-off states of two IGBT modules with a synchronous controller. Experimental tests indicate that the generator can produce adjustable pulse waveform parameters with 0.5-3.5kV amplitude, 300-800 ns pulse duration, 1-400Hz repetition frequency rate, and it is suitable for the study of the electroporation effect experiments. PMID:23016402

  14. Microsecond Microfluidic Mixing for Investigation of Protein Folding Kinetics

    SciTech Connect

    Hertzog, D E; Santiago, J G; Bakajin, O

    2003-06-25

    We have developed and characterized a mixer to study the reaction kinetics of protein folding on a microsecond timescale. The mixer uses hydrodynamic focusing of pressure-driven flow in a microfluidic channel to reduce diffusion times as first demonstrated by Knight et al.[1]. Features of the mixer include 1 {micro}s mixing times, sample consumptions of order 1 nl/s, loading sample volumes on the order of microliters, and the ability to manufacture in fused silica for compatibility with most spectroscopic methods.

  15. Microsecond Microfluidic Mixing for Investigation of Protein Folding Kinetics

    SciTech Connect

    Hertzog, D E; Santiago, J G; Bakajin, O

    2005-02-10

    We have developed and characterized a mixer to study the reaction kinetics of protein folding on a microsecond timescale. The mixer uses hydrodynamic focusing of pressure-driven flow in a microfluidic channel to reduce diffusion times as first demonstrated by Knight et al.[1]. Features of the mixer include 1 {micro}s mixing times, sample consumptions of order 1 nl/s, loading sample volumes on the order of microliters, and the ability to manufacture in fused silica for compatibility with most spectroscopic methods.

  16. Structure of three-quasiparticle isomers in {sup 169}Ho and {sup 171}Tm

    SciTech Connect

    Dracoulis, G. D.; Lane, G. J.; Hughes, R. O.; Kondev, F. G.; Chiara, C. J.; Watanabe, H.; Seweryniak, D.; Zhu, S.; Carpenter, M. P.; Janssens, R. V. F.; Lauritsen, T.; Lister, C. J.; McCutchan, E. A.; Stefanescu, I.; Chowdhury, P.

    2010-09-15

    A three-quasiparticle isomer with {tau}=170(8) {mu}s and K{sup {pi}=} (19/2{sup +}) has been identified in the neutron-rich isotope {sup 169}Ho. The isomer decays with K-forbidden transitions to members of a band associated with the 7/2{sup -}[523] proton configuration, whose structure is characterized through analysis of the in-band {gamma}-ray branching ratios. In the isotone {sup 171}Tm, the rotational band based on the known 19/2{sup +}, three-quasiparticle isomer has also been observed. Alternative one-proton two-neutron configurations for the isomer in {sup 169}Ho are discussed in terms of multiquasiparticle calculations and through a comparison with the structures observed in {sup 171}Tm.

  17. Structure of three-quasiparticle isomers in {sup 169}Ho and {sup 171}Tm.

    SciTech Connect

    Dracoulis, G. D.; Lane, G. J.; Hughes, R. O.; Kondev, F. G.; Watanabe, H.; Seweryniak, D.; Zhu, S.; Carpenter, M. P.; Chiara, C. J.; Janssens, R. V. F.; Lauritsen, T.; Lister, C. J.; McCutchan, E. A.; Stefanescu, I.; Chowdhury, P.

    2010-09-17

    A three-quasiparticle isomer with {tau}=170(8) {micro}s and K{sup {pi}} = (19/2{sup +}) has been identified in the neutron-rich isotope {sup 169}Ho. The isomer decays with K-forbidden transitions to members of a band associated with the 7/2-[523] proton configuration, whose structure is characterized through analysis of the in-band {gamma}-ray branching ratios. In the isotone {sup 171}Tm, the rotational band based on the known 19/2{sup +}, three-quasiparticle isomer has also been observed. Alternative one-proton two-neutron configurations for the isomer in {sup 169}Ho are discussed in terms of multiquasiparticle calculations and through a comparison with the structures observed in {sup 171}Tm.

  18. X-rays from a microsecond X-pinch

    SciTech Connect

    Appartaim, R. K.

    2013-08-28

    The characteristics of x-rays emitted by X-pinches driven by discharging a current of ∼320 kA with a quarter period of 1 μs in crossed 25 μm wires have been investigated. The x-ray emissions are studied using filtered silicon photodiodes, diamond radiation detectors, and pinhole cameras. The results show that predominantly x-rays from the microsecond X-pinch tend to be emitted in two distinct sets of bursts. The first is predominantly “soft,” i.e., with photon energy hν < 5 keV, followed by a second set of bursts beginning up to 100 ns following the initial bursts, and usually consisting of higher photon energies. Our results show, however, that the x-ray emissions do not contain a significant component with hν > 10 keV as might be expected from electron beam activity within the plasma or from the X-pinch diode. High-resolution images obtained with the observed x-rays suggest a well-defined small source of soft x-rays that demonstrates the potential of the microsecond X-pinch.

  19. Interconversion of diborane(4) isomers

    NASA Technical Reports Server (NTRS)

    Stanton, John F.; Gauss, Juergen; Bartlett, Rodney J.; Helgaker, Trygve; Jorgensen, Poul; Jensen, Hans J. A.; Taylor, Peter R.

    1992-01-01

    Highly correlated electronic structure computations using many-body perturbation theory and coupled-cluster gradient techniques are used to study the reaction pathway that links the two forms (C2u and D2d) of diborane(4). The results obtained indicate that a low-energy pathway exists for interconversion of the two low-lying isomers of diborane(4). The proposed mechanism consists of a single concerted but nonsynchronous rotation of the BH2 groups. The pathway first follows an idealized reaction coordinate which preserves C2 symmetry, but then bifurcates at a branch point, leading to two equivalent transition states which lack nontrivial elements of symmetry.

  20. High spin isomer beam line at RIKEN

    SciTech Connect

    Kishida, T.; Ideguchi, E.; Wu, H.Y.

    1996-12-31

    Nuclear high spin states have been the subject of extensive experimental and theoretical studies. For the production of high spin states, fusion reactions are usually used. The orbital angular momentum brought in the reaction is changed into the nuclear spin of the compound nucleus. However, the maximum induced angular momentum is limited in this mechanism by the maximum impact parameter of the fusion reaction and by the competition with fission reactions. It is, therefore, difficult to populate very high spin states, and as a result, large {gamma}-detector arrays have been developed in order to detect subtle signals from such very high spin states. The use of high spin isomers in the fusion reactions can break this limitation because the high spin isomers have their intrinsic angular momentum, which can bring the additional angular momentum without increasing the excitation energy. There are two methods to use the high spin isomers for secondary reactions: the use of the high spin isomers as a target and that as a beam. A high spin isomer target has already been developed and used for several experiments. But this method has an inevitable shortcoming that only {open_quotes}long-lived{close_quotes} isomers can be used for a target: {sup 178}Hf{sup m2} (16{sup +}) with a half-life of 31 years in the present case. By developing a high spin isomer beam, the authors can utilize various short-lived isomers with a short half-life around 1 {mu}s. The high spin isomer beam line of RIKEN Accelerator Facility is a unique apparatus in the world which provides a high spin isomer as a secondary beam. The combination of fusion-evaporation reaction and inverse kinematics are used to produce high spin isomer beams; in particular, the adoption of `inverse kinematics` is essential to use short-lived isomers as a beam.

  1. Microsecond-scale electric field pulses in cloud lightning discharges

    NASA Technical Reports Server (NTRS)

    Villanueva, Y.; Rakov, V. A.; Uman, M. A.; Brook, M.

    1994-01-01

    From wideband electric field records acquired using a 12-bit digitizing system with a 500-ns sampling interval, microsecond-scale pulses in different stages of cloud flashes in Florida and New Mexico are analyzed. Pulse occurrence statistics and waveshape characteristics are presented. The larger pulses tend to occur early in the flash, confirming the results of Bils et al. (1988) and in contrast with the three-stage representation of cloud-discharge electric fields suggested by Kitagawa and Brook (1960). Possible explanations for the discrepancy are discussed. The tendency for the larger pulses to occur early in the cloud flash suggests that they are related to the initial in-cloud channel formation processes and contradicts the common view found in the atmospheric radio-noise literature that the main sources of VLF/LF electromagnetic radiation in cloud flashes are the K processes which occur in the final, or J type, part of the cloud discharge.

  2. Faraday rotation imaging microscope with microsecond pulse magnet

    NASA Astrophysics Data System (ADS)

    Suwa, Masayori; Tsukahara, Satoshi; Watarai, Hitoshi

    2015-11-01

    We have fabricated a high-performance Faraday rotation (FR) imaging microscope that uses a microsecond pulse magnet comprising an insulated gated bipolar transistor and a 2 μF capacitor. Our microscope produced images with greater stability and sensitivity than those of previous microscopes that used millisecond pulse magnet; these improvements are likely due to high repetition rate and negligible Joule heating effects. The mechanical vibrations in the magnet coil caused by the pulsed current were significantly reduced. The present FR microscope constructed an averaged image from 1000 FR images within 10 min under 1.7 T. Applications of the FR microscope to discriminating three benzene derivatives in micro-capillaries and oscillation-free imaging of spherical polystyrene and polymethyl methacrylate microparticles demonstrated its high performance.

  3. E/Z Isomers and Isomerization

    NASA Astrophysics Data System (ADS)

    Liaaen-Jensen, Synnøve; Lutnœes, Bjart Frode

    The natural occurrence of several carotenoid cis isomers and their biological significance were not anticipated in 1962, when the classical monograph on cis-trans isomeric carotenoids [1] was published. More recent research has demonstrated that various cis isomers occur naturally in bacteria plants, algae and invertebrate animals, and are present in human blood and tissues. The participation of cis isomers in the biosynthethic route to coloured carotenoids is well established (Volume 3, Chapter 2). Important biological functions of (15Z)-carotenoids in photosynthesis have been revealed [2]. In relation to health aspects of carotenoids, the bioavailability of cis isomers may be higher than that of the all-trans isomer [3], and accumulated evidence suggests that cis/trans isomerization may occur in biological tissues, particularly of lycopene (31) in human serum [4] (Volume 5, Chapter 7).

  4. Introduction of a single isomer beta agonist.

    PubMed

    Rau, J L

    2000-08-01

    The release of levalbuterol offers the first approved single-isomer beta agonist for oral inhalation. Data from in vitro studies support the concept that S albuterol is not inactive and may have properties antagonistic to bronchodilation. There is some variability in the results of clinical studies with the separate isomers of albuterol, which suggests the need for further study. The introduction of levalbuterol into general clinical use in managing asthma and chronic obstructive disease should begin to offer additional information on the effects of a single isomer beta agonist in comparison to previous racemic mixtures. PMID:10963321

  5. Multi-quasiparticle isomers in the vicinity of {sup 132}Sn

    SciTech Connect

    Watanabe, Hiroshi

    2010-05-12

    Nuclear isomers with multi-quasiparticle configurations near closed shells serve as valuable experimental probes which reveal the nature of residual nucleon-nucleon interactions. We have populated stable and neutron-rich odd-A antimony (Z = 51) and iodine (Z = 53) isotopes using multi-nucleon transfer and fusion-fission reactions with {sup 136}Xe beams and also using incomplete-fusion reactions with {sup 7}Li beams. The decay properties of high-spin isomers have been investigated by means of time-correlated gamma-ray and electron spectroscopy and the measurement of gamma-ray angular correlations.

  6. Theoretical Insights from Facile Microsecond Simulation of the Glass Transition

    NASA Astrophysics Data System (ADS)

    Hung, Jui-Hsiang; Patra, Tarak; Simmons, David

    Despite more than half a century of research, the fundamental nature of the glass transition remains one of the major open questions in polymer science and condensed matter physics. Molecular dynamics simulations have provided key insights into this problem, but their ability to firmly establish the underlying nature of glass formation have been limited by the extreme computational difficulty of directly probing the deeply supercooled regime most relevant to this process. Here we describe a new protocol for simulation of the glass transition enabling facile access to in-equilibrium segmental relaxation times approaching and exceeding one microsecond - well into the deeply supercooled regime of most glass-forming liquids. Coupled with a well-validated strategy for extrapolation to experimental timescales, this approach provides vastly improved prediction of experimental glass transition temperatures. Here we combine data acquired through this protocol for the deeply supercooled regime of polymeric, inorganic, organic, and metallic glass formers to robustly test several theories of glass formation and identify microscopic phenomenological features shared across all classes of glass-forming liquid in the deeply supercooled regime. We acknowledge the W. M. Keck Foundation for financial support of this research.

  7. Microsecond-sustained lasing from colloidal quantum dot solids

    PubMed Central

    Adachi, Michael M.; Fan, Fengjia; Sellan, Daniel P.; Hoogland, Sjoerd; Voznyy, Oleksandr; Houtepen, Arjan J.; Parrish, Kevin D.; Kanjanaboos, Pongsakorn; Malen, Jonathan A.; Sargent, Edward H.

    2015-01-01

    Colloidal quantum dots have grown in interest as materials for light amplification and lasing in view of their bright photoluminescence, convenient solution processing and size-controlled spectral tunability. To date, lasing in colloidal quantum dot solids has been limited to the nanosecond temporal regime, curtailing their application in systems that require more sustained emission. Here we find that the chief cause of nanosecond-only operation has been thermal runaway: the combination of rapid heat injection from the pump source, poor heat removal and a highly temperature-dependent threshold. We show microsecond-sustained lasing, achieved by placing ultra-compact colloidal quantum dot films on a thermally conductive substrate, the combination of which minimizes heat accumulation. Specifically, we employ inorganic-halide-capped quantum dots that exhibit high modal gain (1,200 cm−1) and an ultralow amplified spontaneous emission threshold (average peak power of ∼50 kW cm−2) and rely on an optical structure that dissipates heat while offering minimal modal loss. PMID:26493282

  8. The microsecond old universe — Relics of QCD phase transition

    NASA Astrophysics Data System (ADS)

    Sinha, Bikash

    2014-07-01

    It is entirely plausible under reasonable conditions, that a first-order QCD phase transition occurred from quarks to hadrons when the universe was about a microsecond old. Relics, if there be any, after the quark-hadron phase transition are the most deciding signatures of the phase transition. It is shown in this paper that quark nuggets, the possible relics of first-order QCD phase transitions with baryon number larger than 1043 will survive the entire history of the universe up to now and can be considered as a candidate for the cold dark matter. The spin down core of the neutron star on the high density low temperature end of the QCD phase diagram initiates transition from hadrons to quarks. As the star spins down, the size of the core goes on increasing. Recently discovered massive Pulsar PSRJ 1614-2230 with a mass of 1.97 ± 0.04M⊙ most likely has a strongly interacting core. What possible observables can there be from these neutron stars?

  9. Understanding High Voltage Vacuum Insulators for Microsecond Pulses

    SciTech Connect

    J.B., J; D.A., G; T.L., H; E.J., L; R.D., S; L.K., T; G.E., V

    2007-08-15

    High voltage insulation is one of the main areas of pulsed power research and development since the surface of an insulator exposed to vacuum can fail electrically at an applied field more than an order or magnitude below the bulk dielectric strength of the insulator. This is troublesome for applications where high voltage conditioning of the insulator and electrodes is not practical and where relatively long pulses, on the order of several microseconds, are required. Here we give a summary of our approach to modeling and simulation efforts and experimental investigations for understanding flashover mechanism. The computational work is comprised of both filed and particle-in-cell modeling with state-of-the-art commercial codes. Experiments were performed in using an available 100-kV, 10-{micro}s pulse generator and vacuum chamber. The initial experiments were done with polyethylene insulator material in the shape of a truncated cone cut at +45{sup o} angle between flat electrodes with a gap of 1.0 cm. The insulator was sized so there were no flashovers or breakdowns under nominal operating conditions. Insulator flashover or gap closure was induced by introducing a plasma source, a tuft of velvet, in proximity to the insulator or electrode.

  10. Detonation initiation on the microsecond time scale: DDTs

    SciTech Connect

    Kassoy, Dr. David R; Kuehn, Jeffery A; Nabity, Mr. Matthew W.; Clarke, Dr. John F.

    2008-01-01

    Spatially resolved, thermal power deposition of limited duration into a finite volume of reactive gas is the initiator for a deflagration-to-detonation transition (DDT) on the microsecond time scale. The reactive Euler equations with one-step Arrhenius kinetics are used to derive novel formulas for velocity and temperature variation that describe the physical phenomena characteristic of DDTs. A transformation of the variables is shown to yield a canonical equation system, independent of the activation energy. Numerical solutions of the reactive Euler equations are used to describe the detailed sequence of reactive gasdynamic processes leading to an overdriven planar detonation far from the power deposition location. Results are presented for deposition into a region isolated from the planar boundary of the reactive gas as well as for that adjacent to the boundary. The role of compressions and shocks reflected from the boundary into the partially reacted hot gas is described. The quantitative dependences of DDT evolution on the magnitude of thermal power deposition and activation energy are identified.

  11. Detonation initiation on the microsecond time scale: DDTs

    SciTech Connect

    Kuehn, Jeffery A; Kassoy, Dr. David R; Nabity, Mr. Matthew W.; Clarke, Dr. John F.

    2006-01-01

    Spatially resolved, thermal power deposition of limited duration into a finite volume of reactive gas is the initiator for a deflagration-to-detonation transition (DDT) on the microsecond time scale. The reactive Euler equations with one-step Arrhenius kinetics are used to derive novel formulas for velocity and temperature variation that describe the physical phenomena characteristic of DDTs. A nonlinear transformation of the variables is shown to yield a canonical equation system, independent of the activation energy. Numerical solutions of the reactive Euler equations are used to describe the detailed sequence of reactive gas dynamic processes leading to an overdriven planar detonation far from the power deposition location. Results are presented for deposition into a region isolated from the planar boundary of the reactive gas as well as for that adjacent to the boundary. The role of compressions and shocks reflected from the boundary into the partially reacted hot gas is described. The quantitative dependences of DDT evolution on the magnitude of thermal power deposition and activation energy are identified.

  12. Precise inhibition is essential for microsecond interaural time difference coding

    NASA Astrophysics Data System (ADS)

    Brand, Antje; Behrend, Oliver; Marquardt, Torsten; McAlpine, David; Grothe, Benedikt

    2002-05-01

    Microsecond differences in the arrival time of a sound at the two ears (interaural time differences, ITDs) are the main cue for localizing low-frequency sounds in space. Traditionally, ITDs are thought to be encoded by an array of coincidence-detector neurons, receiving excitatory inputs from the two ears via axons of variable length (`delay lines'), to create a topographic map of azimuthal auditory space. Compelling evidence for the existence of such a map in the mammalian lTD detector, the medial superior olive (MSO), however, is lacking. Equally puzzling is the role of a-temporally very precise-glycine-mediated inhibitory input to MSO neurons. Using in vivo recordings from the MSO of the Mongolian gerbil, we found the responses of ITD-sensitive neurons to be inconsistent with the idea of a topographic map of auditory space. Moreover, local application of glycine and its antagonist strychnine by iontophoresis (through glass pipette electrodes, by means of an electric current) revealed that precisely timed glycine-controlled inhibition is a critical part of the mechanism by which the physiologically relevant range of ITDs is encoded in the MSO. A computer model, simulating the response of a coincidence-detector neuron with bilateral excitatory inputs and a temporally precise contralateral inhibitory input, supports this conclusion.

  13. Fireballs: Detonation Initiation on the Microsecond Time Scale

    NASA Astrophysics Data System (ADS)

    Kassoy, D. R.; Wojciechowski, K.

    2003-11-01

    A mathematical model is developed for detonation initiation following a time and spatially resolved burst of thermal power from an external source into a spherical target of reactive gas. The objective is to produce a detonation in or near the target with the least possible energy input. Source heating occurs on a sub-microsecond time scale, short compared to the acoustic time of the millimeter-sized target. This leads to a period of near inertial confinement, where the pressure rises with temperature, the density change is very small and local Mach number is extremely subsonic. As a result the thermal enegy change is maximized while the induced kinetic energy is minimized. The large temperature increase within the localized high pressure spot initiates a high activation energy, exothermic reaction which spreads hypersonically from the maximum temperature point. The chemical front is co-located with a large localized pressure gradient, responsible for rapid gas acceleration. A detonation appears at the edge of target, in the form of a strong shock with a coupled reaction zone. The evolutionary process differs fundamentally from that in a DDT and that in a traditional model of direct initiation.

  14. Microsecond-sustained lasing from colloidal quantum dot solids

    NASA Astrophysics Data System (ADS)

    Adachi, Michael M.; Fan, Fengjia; Sellan, Daniel P.; Hoogland, Sjoerd; Voznyy, Oleksandr; Houtepen, Arjan J.; Parrish, Kevin D.; Kanjanaboos, Pongsakorn; Malen, Jonathan A.; Sargent, Edward H.

    2015-10-01

    Colloidal quantum dots have grown in interest as materials for light amplification and lasing in view of their bright photoluminescence, convenient solution processing and size-controlled spectral tunability. To date, lasing in colloidal quantum dot solids has been limited to the nanosecond temporal regime, curtailing their application in systems that require more sustained emission. Here we find that the chief cause of nanosecond-only operation has been thermal runaway: the combination of rapid heat injection from the pump source, poor heat removal and a highly temperature-dependent threshold. We show microsecond-sustained lasing, achieved by placing ultra-compact colloidal quantum dot films on a thermally conductive substrate, the combination of which minimizes heat accumulation. Specifically, we employ inorganic-halide-capped quantum dots that exhibit high modal gain (1,200 cm-1) and an ultralow amplified spontaneous emission threshold (average peak power of ~50 kW cm-2) and rely on an optical structure that dissipates heat while offering minimal modal loss.

  15. Subthreshold kaons would reveal density isomers

    SciTech Connect

    Hartnack, C.; Aichelin, J.; Stoecker, H.; Greiner, W. Gesellschaft fuer Schwerionenforschung, D-64220 Darmstadt Institut fuer Theoretische Physik, Universitaet Frankfurt, D-60065 Frankfurt )

    1994-06-13

    If density isomers exist they can be detected by measuring the excitation function of subthreshold kaon production. When the system reaches the density where the density isomer has influence on the equation of state (which depends on the beam energy and on the optical potential), we observe a jump in the cross section of the kaons whereas other observables change little. Above threshold [bar [Lambda

  16. Energetic and Structural Study of Diphenylpyridine Isomers

    NASA Astrophysics Data System (ADS)

    Rocha, Marisa A. A.; Gomes, Lígia R.; Low, John N.; Santos, Luís M. N. B. F.

    2009-09-01

    The energetic and structural study of three diphenylpyridine isomers is presented in detail. The three isomers, 2,6-, 2,5-, and 3,5-diphenylpyridines, were synthesized via Suzuki-Miyaura methodology based on palladium catalysis, and the crystal structures of the isomers were obtained by X-ray diffraction. The relative energetic stabilities in the condensed and gaseous phases as well as volatilities and structures of the three studied isomers were evaluated, regarding the position of the phenyl groups relative to the nitrogen atom of the pyridine ring. The temperature, standard molar enthalpies, and entropies of fusion were measured and derived by differential scanning calorimetry. The vapor pressures of the considered isomers were determined by a static apparatus based on a MKS capacitance diaphragm manometer. The standard molar enthalpies, entropies, and Gibbs energies of sublimation, at T = 298.15 K, were derived, and the phase diagram near the triple point coordinates were determined for all isomers. The standard (p° = 0.1 MPa) molar enthalpies of combustion of all crystalline isomers were determined, at T = 298.15 K, by static bomb combustion calorimetry. The standard molar enthalpies of formation, in the crystalline and gaseous phases, at T = 298.15 K, were derived. The experimental results for the energetics in the gaseous phase of the three compounds were compared and assessed with the values obtained by ab initio calculations at different levels of theory (DFT and MP2) showing that, at this level of theory, the computational methods underestimate the energetic stability, in the gaseous phase, for these molecules. In order to understand the aromaticity in the central ring of each isomer, calculations of NICS (B3LYP/6-311G++(d,p) level of theory) values on the pyridine ring were also performed.

  17. 10 microsecond time resolution studies of Cygnus X-1

    SciTech Connect

    Wen, H.C.

    1997-06-01

    Time variability analyses have been applied to data composed of event times of X-rays emitted from the binary system Cygnus X-1 to search for unique black hole signatures. The X-ray data analyzed was collected at ten microsecond time resolution or better from two instruments, the High Energy Astrophysical Observatory (HEAO) A-1 detector and the Rossi X-ray Timing Explorer (XTE) Proportional Counter Array (PCA). HEAO A-1 and RXTE/PCA collected data from 1977--79 and from 1996 on with energy sensitivity from 1--25 keV and 2--60 keV, respectively. Variability characteristics predicted by various models of an accretion disk around a black hole have been searched for in the data. Drop-offs or quasi-periodic oscillations (QPOs) in the Fourier power spectra are expected from some of these models. The Fourier spectral technique was applied to the HEAO A-1 and RXTE/PCA data with careful consideration given for correcting the Poisson noise floor for instrumental effects. Evidence for a drop-off may be interpreted from the faster fall off in variability at frequencies greater than the observed breaks. Both breaks occur within the range of Keplerian frequencies associated with the inner edge radii of advection-dominated accretion disks predicted for Cyg X-1. The break between 10--20 Hz is also near the sharp rollover predicted by Nowak and Wagoner`s model of accretion disk turbulence. No QPOs were observed in the data for quality factors Q > 9 with a 95% confidence level upper limit for the fractional rms amplitude at 1.2% for a 16 M{sub {circle_dot}} black hole.

  18. Towards Microsecond Biological Molecular Dynamics Simulations on Hybrid Processors

    SciTech Connect

    Hampton, Scott S; Agarwal, Pratul K

    2010-01-01

    Biomolecular simulations continue to become an increasingly important component of molecular biochemistry and biophysics investigations. Performance improvements in the simulations based on molecular dynamics (MD) codes are widely desired. This is particularly driven by the rapid growth of biological data due to improvements in experimental techniques. Unfortunately, the factors, which allowed past performance improvements of MD simulations, particularly the increase in microprocessor clock frequencies, are no longer improving. Hence, novel software and hardware solutions are being explored for accelerating the performance of popular MD codes. In this paper, we describe our efforts to port and optimize LAMMPS, a popular MD framework, on hybrid processors: graphical processing units (GPUs) accelerated multi-core processors. Our implementation is based on porting the computationally expensive, non-bonded interaction terms on the GPUs, and overlapping the computation on the CPU and GPUs. This functionality is built on top of message passing interface (MPI) that allows multi-level parallelism to be extracted even at the workstation level with the multi-core CPUs as well as extend the implementation on GPU clusters. The results from a number of typically sized biomolecular systems are provided and analysis is performed on 3 generations of GPUs from NVIDIA. Our implementation allows up to 30-40 ns/day throughput on a single workstation as well as significant speedup over Cray XT5, a high-end supercomputing platform. Moreover, detailed analysis of the implementation indicates that further code optimization and improvements in GPUs will allow {approx}100 ns/day throughput on workstations and inexpensive GPU clusters, putting the widely-desired microsecond simulation time-scale within reach to a large user community.

  19. High-harmonic spectroscopy of molecular isomers

    SciTech Connect

    Wong, M. C. H.; Brichta, J.-P.; Bhardwaj, V. R.; Spanner, M.; Patchkovskii, S.

    2011-11-15

    We demonstrate that high-order-harmonic generation (HHG) spectroscopy can be used to probe stereoisomers of randomly oriented 1,2-dichloroethylene (C{sub 2}H{sub 2}Cl{sub 2}) and 2-butene (C{sub 4}H{sub 8}). The high-harmonic spectra of these isomers are distinguishable over a range of laser intensities and wavelengths. Time-dependent numerical calculations of angle-dependent ionization yields for 1,2-dichloroethylene suggest that the harmonic spectra of molecular isomers reflect differences in their strong-field ionization. The subcycle ionization yields for the cis isomer are an order of magnitude higher than those for the trans isomer. The sensitivity in discrimination of the harmonic spectra of cis- and trans- isomers is greater than 8 and 5 for 1,2-dichloroethylene and 2-butene, respectively. We show that HHG spectroscopy cannot differentiate the harmonic spectra of the two enantiomers of the chiral molecule propylene oxide (C{sub 3}H{sub 6}O).

  20. Understanding and Improving High Voltage Vacuum Insulators for Microsecond Pulses

    SciTech Connect

    Javedani, J B; Goerz, D A; Houck, T L; Lauer, E J; Speer, R D; Tully, L K; Vogtlin, G E; White, A D

    2007-03-05

    High voltage insulation is one of the main areas of pulsed power research and development, and dielectric breakdown is usually the limiting factor in attaining the highest possible performance in pulsed power devices. For many applications the delivery of pulsed power into a vacuum region is the most critical aspect of operation. The surface of an insulator exposed to vacuum can fail electrically at an applied field more than an order or magnitude below the bulk dielectric strength of the insulator. This mode of breakdown, called surface flashover, imposes serious limitations on the power flow into a vacuum region. This is especially troublesome for applications where high voltage conditioning of the insulator and electrodes is not practical and for applications where relatively long pulses, on the order of several microseconds, are required. The goal of this project is to establish a sound fundamental understanding of the mechanisms that lead to surface flashover, and then evaluate the most promising techniques to improve vacuum insulators and enable high voltage operation at stress levels near the intrinsic bulk breakdown limits of the material. The approach we proposed and followed was to develop this understanding through a combination of theoretical and computation methods coupled with experiments to validate and quantify expected behaviors. In this report we summarize our modeling and simulation efforts, theoretical studies, and experimental investigations. The computational work began by exploring the limits of commercially available codes and demonstrating methods to examine field enhancements and defect mechanisms at microscopic levels. Plasma simulations with particle codes used in conjunction with circuit models of the experimental apparatus enabled comparisons with experimental measurements. The large scale plasma (LSP) particle-in-cell (PIC) code was run on multiprocessor platforms and used to simulate expanding plasma conditions in vacuum gap regions

  1. Nuclear isomer suitable for gamma ray laser

    NASA Technical Reports Server (NTRS)

    Jha, S.

    1979-01-01

    The operation of gamma ray lasers (gasers) are studied. It is assumed that the nuclear isomers mentioned in previously published papers have inherent limitations. It is further assumed that the judicious use of Bormann effect or the application of the total external reflection of low energy gamma radiation at grazing angle of incidence may permit the use of a gaser crystal sufficiently long to achieve observable stimulated emission. It is suggested that a long lived 0(+) isomer decaying by low energy gamma ray emission to a short lived 2(+) excited nuclear state would be an attractive gaser candidate. It is also suggested that the nuclear isomer be incorporated in a matrix of refractory material having an electrostatic field gradient whose principal axis lies along the length of the medium. This results in the preferential transmission of electric quadrupole radiation along the length of the medium.

  2. K isomers as probes of nuclear structure

    SciTech Connect

    Tandel, S. K.

    2014-08-14

    K isomers are studied in Pu and Cm isotopes, and also in Hf and W nuclei. Many high-K states, several of which are isomeric, are identified. Lifetime measurements spanning the ns-s range have been performed, and decay paths of isomers established. Rotational bands built on high-K states are also identified in many cases. Isomer decays are considerably hindered in many instances, both in the A≈180 and 250 regions indicating that K is an approximately conserved quantum number. High-K states become the favored excitation mode at high spins in the A≈180 region. The energies of the 2-quasiparticle high-K states in Cm isotopes suggest the presence of a deformed subshell gap at N=152.

  3. The threshold photoelectron spectroscopy of the cis- and trans- 1-chloro 2-fluoro-ethene isomers: an experimental and quantum chemical study

    NASA Astrophysics Data System (ADS)

    Locht, R.; Dehareng, D.; Leyh, B.

    2014-09-01

    The threshold photoelectron spectra (TPES) of the two vicinal isomers of the 1,2-C2H2FCl molecule have been investigated in the 9-24 eV energy range using synchrotron radiation. Eight (for the cis-isomer) or nine (for the trans-isomer) bands have been observed and the corresponding ionization energies have been determined. The spectroscopic assignments are based on high level quantum chemical ab initio calculations for both isomers. Most of the observed spectral features could be interpreted. For both species the first three TPES bands exhibit a rich vibrational structure. Vibrational energies were determined and assignments were also supported by quantum chemical calculations of vibrational wavenumbers for these three ionic states of both isomers.

  4. An Assessment of Nuclear Isomers as an Energy Storage Medium

    SciTech Connect

    Hartouni, Edward P.

    2009-03-16

    Nuclear Isomers have been suggested as a potential high energy density medium that might be used to store energy. This talk assesses the state of the science supporting key elements of using nuclear isomers in energy storage applications. The focus is on the nuclear isomer {sup 178m2}Hf which has been most widely suggested for energy storage applications. However, the science issues apply to all nuclear isomer. The assessment addresses the production of the nuclear isomer, and inducing the release of the isomer. Also discussed are novel speculations on photon and/or neutron chain reactions, both as a 'pure' material as well as mixed with other materials.

  5. An Assessment of Nuclear Isomers as an Energy Storage Medium

    SciTech Connect

    Hartouni, E P

    2008-12-08

    Nuclear Isomers have been suggested as a potential high energy density medium that might be used to store energy. This talk assesses the state of the science supporting key elements of using nuclear isomers in energy storage applications. The focus is on the nuclear isomer {sup 178m2}Hf which has been most widely suggested for energy storage applications. However, the science issues apply to all nuclear isomer. The assessment addresses the production of the nuclear isomer, and inducing the release of the isomer. Also discussed are novel speculations on photon and/or neutron chain reactions, both as a 'pure' material as well as mixed with other materials.

  6. New Millisecond Isomer Lifetime Measurements at LANSCE

    SciTech Connect

    Devlin, M. Nelson, R.O.; Fotiades, N.; O'Donnell, J.M.

    2014-06-15

    New half-life measurements have been made of the millisecond isomers {sup 71m}Ge, {sup 114m2}I, {sup 208m}Bi, {sup 88m1}Y, {sup 88m2}Y, and {sup 75m}As populated in neutron-induced reactions. These measurements were made using the unique time structure of the LANSCE/WNR neutron source, by observing the γ-ray decays of the isomers during the time between the LANSCE proton macropulses. Two different LANSCE proton beam time structures were used. The GEANIE array of HPGe detectors was used to detect the γ-ray decays.

  7. 'Melatonin isomer' in wine is not an isomer of the melatonin but tryptophan-ethylester.

    PubMed

    Gardana, Claudio; Iriti, Marcello; Stuknytė, Milda; De Noni, Ivano; Simonetti, Paolo

    2014-11-01

    Melatonin is a neurohormone, chronobiotic, and antioxidant compound found in wine and deriving directly from grapes and/or synthesized by yeast during alcoholic fermentation. In addition, a melatonin isomer has been detected in different foods, wine among them. The special interest for melatonin isomer related to the fact that it was found in greater quantities than melatonin and probably shares some of its biological properties. Despite this, its chemical structure has not yet been defined; although some researchers hypothesize, it could be melatonin with the ethylacetamide group shifted into position N1. Thus, the aim of our study was to identify the structures of the melatonin isomer. For this purpose, melatonin and melatonin isomer in Syrah wine were separated chromatographically by a sub-2 μm particle column and detected by tandem mass spectrometry. The sample was then purified and concentrated by solid-phase extraction, hydrolyzed with alkali or esterase, and substrates and products quantified by UPLC-MS/MS. Moreover, melatonin, melatonin isomer, and their product ions were evaluated by high-resolution mass spectrometry. The amount of melatonin isomer and melatonin in the wine was 84 ± 4 and 3 ± 0 ng/mL, respectively. In the solutions, containing diluted alkali or esterase, melatonin isomer was hydrolyzed in about 8 min. Correspondingly, tryptophan was detected, and its amount increased and reached the maximum concentration in about 8 min. Melatonin concentration was not affected by diluted alkali or esterase. The fragmentation pattern of melatonin isomer was different from that of melatonin but comparable to that of tryptophan-ethylester. Finally, the so-called melatonin isomer identity was verified by cochromatography with authentic standard of tryptophan-ethylester. PMID:25251161

  8. Introduction of Branching Degrees of Octane Isomers.

    PubMed

    Perdih, Anton

    2016-01-01

    The concept of branching degrees is introduced. In the case of octane isomers it is derived from the values of a set of their physicochemical properties, calculating for each isomer the average of the normalized values and these averages are defined as branching degrees of octane isomers. The sequence of these branching degrees of octane isomers does not differ much from the »regular« one defined earlier. 2,2-Dimethylhexane appears to be less branched than 3,4-dimethylhexane and 3-ethyl, 2-methylpentane, whereas 2,3,4-trimethylpentane appears to be less branched than 3-ethyl, 3-methylpentane. While the increasing number of branches gives rise to increasing branching degrees, the peripheral position of branches and the separation between branches decreases the value of the branching degree. The central position of branches increases it. A bigger branch increases it more than a smaller one. The quantification of these structural features and their correlations with few indices is given as well. PMID:27333567

  9. Excitation of nuclear isomers by X rays from laser plasma

    SciTech Connect

    Andreev, Aleksandr A; Karpeshin, F; Trzhaskovskaya, M B; Platonov, Konstantin Yu; Rozhdestvenskii, Yu V

    2010-06-23

    The possibility of obtaining isomer nuclei is studied by the example of the molybdenum isomer {sup 93}Mo upon irradiation of a niobium {sup 93}Nb target by {approx}50-J, 100-fs laser pulses. It is shown that the modern laser technique allows production of isomer nuclei by accelerated protons and radiative de-excitation of isomer nuclear states by thermal or line X-rays from laser plasma. (interaction of laser radiation with matter. laser plasma)

  10. Decay properties of high-spin isomers and other structures in {sup 121}Sb and {sup 123}Sb

    SciTech Connect

    Watanabe, H.; Lane, G. J.; Dracoulis, G. D.; Kibedi, T.; Nieminen, P.; Hughes, R. O.; Byrne, A. P.; Kondev, F. G.; Carpenter, M. P.; Janssens, R. V. F.; Lauritsen, T.; Seweryniak, D.; Zhu, S.; Chowdhury, P.; Moon, C.-B.

    2009-02-15

    High-spin states populated in the decay of microsecond isomers in the transitional nuclei {sup 121}Sb and {sup 123}Sb have been investigated in detail in several experiments using {gamma}-ray and electron spectroscopy. The nuclei were formed using multinucleon transfer and fusion-fission reactions with {sup 136}Xe beams and also using the {sup 120}Sn({sup 7}Li,{alpha}2n){sup 121}Sb and {sup 122}Sn({sup 7}Li,{alpha}2n){sup 123}Sb incomplete-fusion reactions. Isomeric half-lives ranging from several nanoseconds to a few hundred microseconds were determined by means of conventional decay curve analyses, whereas very short-lived isomers (T{sub 1/2}{approx}1 ns) were identified using the generalized centroid-shift method. A number of new transitions were observed, including a branch through spherical states from the 19/2{sup +} member of the 9/2{sup +} deformed band in {sup 121}Sb, in competition with the main decay path through the rotational band. This is attributed to mixing between the 19/2{sup +} band member and a 19/2{sup +} spherical state. Both levels are predicted to coincide approximately in energy in {sup 121}Sb. The fact that a 25/2{sup +} isomer occurs for A=121 and the lighter isotopes, while a 23/2{sup +} isomer is observed for A=123-131 is explained through a multistate mixing calculation, taking into account the gradual shift of the 2d{sub 5/2} and 1g{sub 7/2} proton orbitals and the change in proton-neutron effective interactions from an attractive particle-particle type in the lower part of the shell to a repulsive particle-hole type with increasing the neutron number toward the N=82 shell closure. The observed enhancement of the B(E2;19/2{sup -}{yields}15/2{sup -}) values in {sup 121}Sb and {sup 123}Sb over the B(E2;7{sup -}{yields}5{sup -}) values in the corresponding Sn cores is discussed in terms of configuration mixing between spherical and deformed states.

  11. Plasma Emission Spectra of Opuntia Nopalea Obtained with Microsecond Laser Pulses

    SciTech Connect

    Ponce, L.; Flores, T.; Arronte, A.; Flores, A.

    2008-04-15

    Laser-induced Plasma Spectroscopy was performed during the spines ablation of Opuntia by using Nd:YAG microsecond laser pulses. The results show strong absorption in Glochids that causes the intense electronic noise on the spectra. This process is consider suitable for practical elimination of spines in alimentary products like opuntia.

  12. Parallel line raster eliminates ambiguities in reading timing of pulses less than 500 microseconds apart

    NASA Technical Reports Server (NTRS)

    Horne, A. P.

    1966-01-01

    Parallel horizontal line raster is used for precision timing of events occurring less than 500 microseconds apart for observation of hypervelocity phenomena. The raster uses a staircase vertical deflection and eliminates ambiguities in reading timing of pulses close to the end of each line.

  13. Microsecond-long lasing delays in thin P-clad InGaAs QW lasers

    SciTech Connect

    Wu, C.H.; Miester, C.F; Zory, P.S.; Emanuel, M.A.

    1996-06-01

    Microsecond-long lasing delays have been observed in wide-stripe, thin p-clad, InGaAs single quantum well (QW) lasers with ``thick`` p{sup +} cap layers. Computer modeling indicates that localized refractive index changes in the cap layer due to ohmic heating from the con- tact resistance may be the root cause.

  14. Ten-Microsecond Molecular Dynamics Simulation of a Fast-Folding WW Domain

    PubMed Central

    Freddolino, Peter L.; Liu, Feng; Gruebele, Martin; Schulten, Klaus

    2008-01-01

    All-atom molecular dynamics (MD) simulations of protein folding allow analysis of the folding process at an unprecedented level of detail. Unfortunately, such simulations have not yet reached their full potential both due to difficulties in sufficiently sampling the microsecond timescales needed for folding, and because the force field used may yield neither the correct dynamical sequence of events nor the folded structure. The ongoing study of protein folding through computational methods thus requires both improvements in the performance of molecular dynamics programs to make longer timescales accessible, and testing of force fields in the context of folding simulations. We report a ten-microsecond simulation of an incipient downhill-folding WW domain mutant along with measurement of a molecular time and activated folding time of 1.5 microseconds and 13.3 microseconds, respectively. The protein simulated in explicit solvent exhibits several metastable states with incorrect topology and does not assume the native state during the present simulations. PMID:18339748

  15. Isomer Shifts in Solid State Chemistry

    NASA Astrophysics Data System (ADS)

    Wagner, F. E.; Stievano, L.

    The isomer shift of the Mössbauer resonance is a rather unique quantity that cannot be obtained by any of the other techniques used for measuring hyperfine interactions in solids, such as NMR or perturbed angular correlations (TDPAC). It shifts the resonance pattern as a whole without affecting the magnetic dipole and electric quadrupole hyperfine splittings. Methods that measure only these hyperfine splittings are insensitive to the isomer shift. The magnitude of the observed shift is proportional to the product of a nuclear parameter, the change Δ⟨r 2⟩ of the nuclear radius that goes along with the Mössbauer transition, and to an electronic property of the material, the electron density ρ(0) at the Mössbauer nucleus or, more precisely, to the difference Δρ(0) of the electron densities at the Mössbauer nuclei in the materials of which the source and the absorber are made. The electron density at the nucleus is due to s-electrons and, to a lesser extent and mainly in heavy nuclei, to relativistic p1 / 2-electrons. All the other electrons have a vanishing density inside the nucleus and do not contribute. Thus, to a very good accuracy, the Mössbauer isomer shift enables one to obtain information on the s-electron density at the Mössbauer nuclei in solids.

  16. Biodegradation of cresol isomers in anoxic aquifers.

    PubMed Central

    Smolenski, W J; Suflita, J M

    1987-01-01

    The biodegradation of o-, m-, and p-cresol was examined in material obtained from a shallow anaerobic alluvial sand aquifer. The cresol isomers were preferentially metabolized, with p-cresol being the most easily degraded. m-Cresol was more persistent than the para-isomer, and o-cresol persisted for over 90 days. Biodegradation of cresol isomers was favored under sulfate-reducing conditions (SRC) compared with that under methanogenic conditions (MC). Slurries that were acclimated to p-cresol metabolism transformed this substrate at 18 and 330 nmol/h per g (dry weight) for MC and SRC, respectively. Inhibition of electron flow to sulfate reduction with 2.0 mM molybdate reduced p-cresol metabolism in incubations containing sulfate. When methanogenesis was blocked with 5 mM bromoethanesulfonic acid in incubations lacking sulfate, p-cresol catabolism was retarded. Under SRC 3.4 mol of sulfate was consumed per mol of p-cresol metabolized. The addition of sulfate to methanogenic incubations stimulated p-cresol degradation. Simultaneous adaptation studies in combination with spectrophotometric and chromatographic analysis of metabolites indicated that p-cresol was oxidized under SRC to p-hydroxybenzoate via the corresponding alcohol and aldehyde. This series of reactions was inhibited under sulfate-limited or aerobic conditions. Therefore, the primary catabolic event for p-cresol decomposition under SRC appears to involve the hydroxylation of the aryl methyl group. PMID:3579279

  17. Cyanomethanimine Isomers in Cold Interstellar Clouds: Insights from Electronic Structure and Kinetic Calculations

    NASA Astrophysics Data System (ADS)

    Vazart, Fanny; Latouche, Camille; Skouteris, Dimitrios; Balucani, Nadia; Barone, Vincenzo

    2015-09-01

    New insights into the formation of interstellar cyanomethanimine, a species of great relevance in prebiotic chemistry, are provided by electronic structure and kinetic calculations for the reaction CN + CH2 = NH. This reaction is a facile formation route of Z,E-C-cyanomethanimine, even under the extreme conditions of density and temperature typical of cold interstellar clouds. E-C-cyanomethanimine has been recently identified in Sgr B2(N) in the Green Bank Telescope (GBT) PRIMOS survey by P. Zaleski et al. and no efficient formation routes have been envisaged so far. The rate coefficient expression for the reaction channel leading to the observed isomer E-C-cyanomethanimine is 3.15 × 10-10 × (T/300)0.152 × e(-0.0948/T). According to the present study, the more stable Z-C-cyanomethanimine isomer is formed with a slightly larger yield (4.59 × 10-10 × (T/300)0.153 × e(-0.0871/T). As the detection of E-isomer is favored due to its larger dipole moment, the missing detection of the Z-isomer can be due to the sensitivity limit of the GBT PRIMOS survey and the detection of the Z-isomer should be attempted with more sensitive instrumentation. The CN + CH2 = NH reaction can also play a role in the chemistry of the upper atmosphere of Titan where the cyanomethanimine products can contribute to the buildup of the observed nitrogen-rich organic aerosols that cover the moon.

  18. In vitro micellarization and intestinal cell uptake of cis isomers of lycopene exceed those of all-trans lycopene.

    PubMed

    Failla, Mark L; Chitchumroonchokchai, Chureeporn; Ishida, Betty K

    2008-03-01

    The ratio of cis and all-trans lycopene (LYC) in human and animal tissues exceeds that in foods. The basis for this difference remains unknown, although differences in their stability, transport, and metabolism have been suggested. Here, we systematically compared the digestive stability, efficiency of micellarization, and uptake and intracellular stability of cis and all-trans isomers of LYC and carotenes using the coupled in vitro digestion and Caco-2 human intestinal cell model. Aril and oil from the carotenoid-rich gac fruit (Momordica cochinchinensis Spreng) were cooked with rice to provide a natural source of LYC and carotenes. The ratio of cis:trans isomers of LYC and beta-carotene was similar before and after simulated gastric and small intestinal digestion with recovery of total carotenoids in the digesta exceeding 70%. Micellarization of cis isomers of LYC during digestion of meals with both gac aril and oil was significantly greater than that of the all-trans isomer but less than for the carotenes. Uptake of cis isomers of LYC by Caco-2 cells was similar to that of carotenes and significantly greater than all-trans LYC. Micellarized carotenoids were relatively stable in micelles incubated in the cell culture environment and after accumulation in Caco-2 cells. These data suggest that the greater bioaccessibility of cis compared with all-trans isomers of LYC contributes to the enrichment of the cis isomers in tissues and that gac fruit is an excellent source of bioaccessible LYC and provitamin A carotenoids. PMID:18287353

  19. Two-quasiparticle structures and isomers in {sup 168}Er, {sup 170}Er, and {sup 172}Er.

    SciTech Connect

    Dracoulis, G. D.; Lane, G. J.; Kondev, F. G.; Watanabe, H.; Seweryniak, D.; Zhu, S.; Carpenter, M. P.; Chiara, C. J.; Janssens, R. V. F.; Lauritsen, T.; Lister, C. J.; McCutchan, E. A.; Stefanescu, I.; Australian National Univ.; RIKEN; Univ. of Maryland

    2010-05-01

    The stable and neutron-rich isotopes 168Er, 170Er, and 172Er have been studied with Gammasphere using inelastic excitation with energetic 136Xe beams. The previously assigned structures based on the proposed K?=4- isomeric intrinsic states in both 168Er and 170Er have been re-evaluated and an equivalent band identified in 172Er. In 170Er, the identification of a K?=6- band with transitions close in energy to those of the 4- band leads to a modified interpretation, since the overlap would have compromised previous analyses. The gK-gR values for the 4- bands deduced from the in-band ?-ray intensities for the sequence of isotopes suggest a predominantly two-neutron configuration in 168Er, an equally mixed two-neutron, two-proton configuration in 170Er, and a two-proton configuration in 172Er. A comprehensive decay scheme for the previously proposed 6+ isomer in 172Er has also been established, as well as band structures built on this isomer that closely resemble the 6+ and 7- two-neutron structures known in the isotone 174Yb. The implied K hindrances are discussed. The main decay path of the 6+ isomer occurs through the newly identified 4- isomer. The measured lifetimes of the 4- and 6+ isomers in 172Er are 57(3) and 822(90) ns, respectively. Multiquasiparticle calculations support the suggested configuration changes across the isotopic chain.

  20. The interstellar chemistry of H2C3O isomers

    NASA Astrophysics Data System (ADS)

    Loison, Jean-Christophe; Agúndez, Marcelino; Marcelino, Núria; Wakelam, Valentine; Hickson, Kevin M.; Cernicharo, José; Gerin, Maryvonne; Roueff, Evelyne; Guélin, Michel

    2016-03-01

    We present the detection of two H2C3O isomers, propynal and cyclopropenone, toward various starless cores and molecular clouds, together with upper limits for the third isomer propadienone. We review the processes controlling the abundances of H2C3O isomers in interstellar media showing that the reactions involved are gas-phase ones. We show that the abundances of these species are controlled by kinetic rather than thermodynamic effects.

  1. The interstellar chemistry of H2C3O isomers

    PubMed Central

    Loison, Jean-Christophe; Agúndez, Marcelino; Marcelino, Núria; Wakelam, Valentine; Hickson, Kevin M.; Cernicharo, José; Gerin, Maryvonne; Roueff, Evelyne; Guélin, Michel

    2016-01-01

    We present the detection of two H2C3O isomers, propynal and cyclopropenone, toward various starless cores and molecular clouds, together with upper limits for the third isomer propadienone. We review the processes controlling the abundances of H2C3O isomers in interstellar media showing that the reactions involved are gas-phase ones. We show that the abundances of these species are controlled by kinetic rather than thermodynamic effects. PMID:27013768

  2. Separation of steroid isomers by ion mobility mass spectrometry.

    PubMed

    Ahonen, Linda; Fasciotti, Maíra; Gennäs, Gustav Boije Af; Kotiaho, Tapio; Daroda, Romeu J; Eberlin, Marcos; Kostiainen, Risto

    2013-10-01

    Ion mobility mass spectrometry performed in a compact traveling wave cell (TWIM-MS) is shown to provide a reliable, fast and repeatable method to separate derivatized steroid isomers. Three steroid isomer pairs were analyzed in their native form and as their p-toluenesulfonyl isocyanate derivatives. The native steroids were separated from each other, but no separation could be attained for the isomers. The derivatized steroid isomers were, however, properly separated by TWIM-MS with peak-to-peak resolutions close to or as high as baseline resolution (Rp-p=0.77-1.08). PMID:23992881

  3. Analyzing ion distributions around DNA: sequence-dependence of potassium ion distributions from microsecond molecular dynamics

    PubMed Central

    Pasi, Marco; Maddocks, John H.; Lavery, Richard

    2015-01-01

    Microsecond molecular dynamics simulations of B-DNA oligomers carried out in an aqueous environment with a physiological salt concentration enable us to perform a detailed analysis of how potassium ions interact with the double helix. The oligomers studied contain all 136 distinct tetranucleotides and we are thus able to make a comprehensive analysis of base sequence effects. Using a recently developed curvilinear helicoidal coordinate method we are able to analyze the details of ion populations and densities within the major and minor grooves and in the space surrounding DNA. The results show higher ion populations than have typically been observed in earlier studies and sequence effects that go beyond the nature of individual base pairs or base pair steps. We also show that, in some special cases, ion distributions converge very slowly and, on a microsecond timescale, do not reflect the symmetry of the corresponding base sequence. PMID:25662221

  4. Pushing single molecule techniques to microsecond resolution proves that T4 Lysozyme is a Brownian ratchet

    NASA Astrophysics Data System (ADS)

    Akhterov, Maxim V.; Choi, Yongki; Olsen, Tivoli J.; Sims, Patrick C.; Iftikhar, Mariam; Gul, O. Tolga; Corso, Brad L.; Weiss, Gregory A.; Collins, Philip G.

    2015-03-01

    Single-molecule techniques can monitor conformational dynamics of proteins, but such methods usually lack the resolution to directly observe conformational pathways or intermediate conformational states. We have recently described a single-molecule electronic technique that breaks this barrier. Using a 1 MHz-bandwidth carbon nanotube transistor, the transition pathways between open and closed conformations of T4 lysozyme have been recorded with a microsecond resolution. We directly resolve a smooth, continuous transition with an average duration of 37 microseconds. Unexpectedly, the mechanical closing and re-opening of the enzyme have identical distributions of transition durations, and the motion is independent of the enzyme catalyzing the substrate. These results illustrate the principle of microscopic reversibility applied to a Brownian ratchet, with lysozyme tracing a single pathway for closing and the reverse pathway for enzyme opening, regardless of its instantaneous catalytic productivity.

  5. Laser-driven microsecond temperature cycles analyzed by fluorescence polarization microscopy.

    PubMed

    Zondervan, Rob; Kulzer, Florian; van der Meer, Harmen; Disselhorst, Jos A J M; Orrit, Michel

    2006-04-15

    We demonstrate a novel technique to achieve fast thermal cycles of a small sample (a few femtoliters). Modulating a continuous near-infrared laser focused on a metal film, we can drive the local temperature from 130 to 300 K and back, within a few microseconds. By fluorescence microscopy of dyes in a thin glycerol film, we record images of the hot spot, calibrate its temperature, and follow its variations in real time. The temperature dependence of fluorescence anisotropy, due to photophysics and rotational diffusion, gives a steady-state temperature calibration between 200 and 350 K. From 200 to 220 K, we monitor temperature more accurately by fluorescence autocorrelation, a probe for rotational diffusion. Time-resolved measurements of fluorescence anisotropy give heating and cooling times of a few microseconds, short enough to supercool pure water. We designed our method to repeatedly cycle a single (bio)molecule between ambient and cryostat temperatures with microsecond time resolution. Successive measurements of a structurally relevant variable will decompose a dynamical process into structural snapshots. Such temperature-cycle experiments, which combine a high time resolution with long observation times, can thus be expected to yield new insights into complex processes such as protein folding. PMID:16443653

  6. Use of microsecond current prepulse for dramatic improvements of wire array Z-pinch implosion

    NASA Astrophysics Data System (ADS)

    Calamy, H.; Lassalle, F.; Loyen, A.; Zucchini, F.; Chittenden, J. P.; Hamann, F.; Maury, P.; Georges, A.; Bedoch, J. P.; Morell, A.

    2008-01-01

    The Sphinx machine [F. Lassalle et al., "Status on the SPHINX machine based on the 1microsecond LTD technology"] based on microsecond linear transformer driver (LTD) technology is used to implode an aluminium wire array with an outer diameter up to 140mm and maximum current from 3.5to5MA. 700to800ns implosion Z-pinch experiments are performed on this driver essentially with aluminium. Best results obtained before the improvement described in this paper were 1-3TW radial total power, 100-300kJ total yield, and 20-30kJ energy above 1keV. An auxiliary generator was added to the Sphinx machine in order to allow a multi microsecond current to be injected through the wire array load before the start of the main current. Amplitude and duration of this current prepulse are adjustable, with maxima ˜10kA and 50μs. This prepulse dramatically changes the ablation phase leading to an improvement of the axial homogeneity of both the implosion and the final radiating column. Total power was multiplied by a factor of 6, total yield by a factor of 2.5 with a reproducible behavior. This paper presents experimental results, magnetohydrodynamic simulations, and analysis of the effect of such a long current prepulse.

  7. Use of microsecond current prepulse for dramatic improvements of wire array Z-pinch implosion

    SciTech Connect

    Calamy, H.; Lassalle, F.; Loyen, A.; Zucchini, F.; Chittenden, J. P.; Hamann, F.; Maury, P.; Georges, A.; Bedoch, J. P.; Morell, A.

    2008-01-15

    The Sphinx machine [F. Lassalle et al., 'Status on the SPHINX machine based on the 1microsecond LTD technology'] based on microsecond linear transformer driver (LTD) technology is used to implode an aluminium wire array with an outer diameter up to 140 mm and maximum current from 3.5 to 5 MA. 700 to 800 ns implosion Z-pinch experiments are performed on this driver essentially with aluminium. Best results obtained before the improvement described in this paper were 1-3 TW radial total power, 100-300 kJ total yield, and 20-30 kJ energy above 1 keV. An auxiliary generator was added to the Sphinx machine in order to allow a multi microsecond current to be injected through the wire array load before the start of the main current. Amplitude and duration of this current prepulse are adjustable, with maxima {approx}10 kA and 50 {mu}s. This prepulse dramatically changes the ablation phase leading to an improvement of the axial homogeneity of both the implosion and the final radiating column. Total power was multiplied by a factor of 6, total yield by a factor of 2.5 with a reproducible behavior. This paper presents experimental results, magnetohydrodynamic simulations, and analysis of the effect of such a long current prepulse.

  8. Pulsed Electron Beam Water Radiolysis for Sub-Microsecond Hydroxyl Radical Protein Footprinting

    PubMed Central

    Watson, Caroline; Janik, Ireneusz; Zhuang, Tiandi; Charvátová, Olga; Woods, Robert J.; Sharp, Joshua S.

    2009-01-01

    Hydroxyl radical footprinting is a valuable technique for studying protein structure, but care must be taken to ensure that the protein does not unfold during the labeling process due to oxidative damage. Footprinting methods based on sub-microsecond laser photolysis of peroxide that complete the labeling process faster than the protein can unfold have been recently described; however, the mere presence of large amounts of hydrogen peroxide can also cause uncontrolled oxidation and minor conformational changes. We have developed a novel method for sub-microsecond hydroxyl radical protein footprinting using a pulsed electron beam from a 2 MeV Van de Graaff electron accelerator to generate a high concentration of hydroxyl radicals by radiolysis of water. The amount of oxidation can be controlled by buffer composition, pulsewidth, dose, and dissolved nitrous oxide gas in the sample. Our results with ubiquitin and β-lactoglobulin A demonstrate that one sub-microsecond electron beam pulse produces extensive protein surface modifications. Highly reactive residues that are buried within the protein structure are not oxidized, indicating that the protein retains its folded structure during the labeling process. Time-resolved spectroscopy indicates that the major part of protein oxidation is complete in a timescale shorter than that of large scale protein motions. PMID:19265387

  9. Physical chemistry and membrane properties of two phosphatidylinositol bisphosphate isomers.

    PubMed

    Slochower, David R; Wang, Yu-Hsiu; Radhakrishnan, Ravi; Janmey, Paul A

    2015-05-21

    The most highly charged phospholipids, polyphosphoinositides, are often involved in signaling pathways that originate at cell-cell and cell-matrix contacts, and different isomers of polyphosphoinositides have distinct biological functions that cannot be explained by separate highly specific protein ligand binding sites [Lemmon, Nat. Rev. Mol. Cell Biol., 2008, 9, 99-111]. PtdIns(3,5)P2 is a low abundance phosphoinositide localized to cytoplasmic-facing membrane surfaces, with relatively few known ligands, yet PtdIns(3,5)P2 plays a key role in controlling membrane trafficking events and cellular stress responses that cannot be duplicated by other phosphoinositides [Dove et al., Nature, 1997, 390, 187-192; Michell, FEBS J., 2013, 280, 6281-6294]. Here we show that PtdIns(3,5)P2 is structurally distinct from PtdIns(4,5)P2 and other more common phospholipids, with unique physical chemistry. Using multiscale molecular dynamics techniques on the quantum level, single molecule, and in bilayer settings, we found that the negative charge of PtdIns(3,5)P2 is spread over a larger area, compared to PtdIns(4,5)P2, leading to a decreased ability to bind divalent ions. Additionally, our results match well with experimental data characterizing the cluster forming potential of these isomers in the presence of Ca(2+) [Wang et al., J. Am. Chem. Soc., 2012, 134, 3387-3395; van den Bogaart et al., Nature, 2011, 479, 552-555]. Our results demonstrate that the different cellular roles of PtdIns(4,5)P2 and PtdIns(3,5)P2in vivo are not simply determined by their localization by enzymes that produce or degrade them, but also by their molecular size, ability to chelate ions, and the partial dehydration of those ions, which might affect the ability of PtdIns(3,5)P2 and PtdIns(4,5)P2 to form phosphoinositide-rich clusters in vitro and in vivo. PMID:25901568

  10. 27 CFR 21.120 - Nitropropane, mixed isomers of.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Nitropropane, mixed isomers of. 21.120 Section 21.120 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE... Denaturants § 21.120 Nitropropane, mixed isomers of. (a) Nitropropane content. A minimum of 94 percent...

  11. Stereospecific Synthesis of the Geometrical Isomers of a Natural Product

    ERIC Educational Resources Information Center

    Grove, T.; DiLella, D.; Volker, E.

    2006-01-01

    Stereospecific synthesis of a geometrical isomer is not a common topic for the introductory organic chemistry laboratory. We have developed and tested an experiment for the synthesis of (Z) and (E) isomers that has been performed successfully by undergraduate students. The experiment is presented to the students as a puzzle in which they must…

  12. 27 CFR 21.120 - Nitropropane, mixed isomers of.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Nitropropane, mixed isomers of. 21.120 Section 21.120 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE... Denaturants § 21.120 Nitropropane, mixed isomers of. (a) Nitropropane content. A minimum of 94 percent...

  13. 27 CFR 21.120 - Nitropropane, mixed isomers of.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Nitropropane, mixed isomers of. 21.120 Section 21.120 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE... Denaturants § 21.120 Nitropropane, mixed isomers of. (a) Nitropropane content. A minimum of 94 percent...

  14. 27 CFR 21.120 - Nitropropane, mixed isomers of.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Nitropropane, mixed isomers of. 21.120 Section 21.120 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE... Denaturants § 21.120 Nitropropane, mixed isomers of. (a) Nitropropane content. A minimum of 94 percent...

  15. 27 CFR 21.120 - Nitropropane, mixed isomers of.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Nitropropane, mixed isomers of. 21.120 Section 21.120 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE... Denaturants § 21.120 Nitropropane, mixed isomers of. (a) Nitropropane content. A minimum of 94 percent...

  16. Pseudo-discontinuities in the isomer shift near magnetic transitions

    NASA Astrophysics Data System (ADS)

    Kolk, B.; Hall, D. B.; Zheng, Y.; Lumetta, J. T.

    1983-12-01

    It is shown that a relatively small non-linear behavior of the velocity drive system used in Mössbauer effect studies yields pseudo-discontinuities in the isomer shift near the critical temperature T c of a magnetic-paramagnetic transition. The anomaly of the57Fe isomer shift in iron is attributed to this effect.

  17. Laboratory detection of the elusive HSCO+ isomer.

    PubMed

    McCarthy, M C; Thaddeus, P

    2007-12-14

    The rotational spectrum of protonated carbonyl sulfide, HSCO(+), has now been detected in the centimeter-wave band in a molecular beam by Fourier transform microwave spectroscopy. Rotational and centrifugal distortion constants have been determined from transitions in the K(a)=0 ladder of the normal isotopic species, and DSCO(+) and H(34)SCO(+). HSCO(+) is systematically more abundant by a factor of three than HOCS(+), the isomer obtained by attaching the H(+) to the other end of the molecule, which ab initio calculations long predicted to be higher in energy by 4-5 kcalmol. Because HSCO(+) is comparable in polarity to HOCS(+) and is apparently more stable and because OCS is widely distributed in astronomical sources, HSCO(+) is a good candidate for detection with radio telescopes. PMID:18081381

  18. Remotely Controlled Isomer Selective Molecular Switching.

    PubMed

    Schendel, Verena; Borca, Bogdana; Pentegov, Ivan; Michnowicz, Tomasz; Kraft, Ulrike; Klauk, Hagen; Wahl, Peter; Schlickum, Uta; Kern, Klaus

    2016-01-13

    Nonlocal addressing-the "remote control"-of molecular switches promises more efficient processing for information technology, where fast speed of switching is essential. The surface state of the (111) facets of noble metals, a confined two-dimensional electron gas, provides a medium that enables transport of signals over large distances and hence can be used to address an entire ensemble of molecules simultaneously with a single stimulus. In this study we employ this characteristic to trigger a conformational switch in anthradithiophene (ADT) molecules by injection of hot carriers from a scanning tunneling microscope (STM) tip into the surface state of Cu(111). The carriers propagate laterally and trigger the switch in molecules at distances as far as 100 nm from the tip location. The switching process is shown to be long-ranged, fully reversible, and isomer selective, discriminating between cis and trans diastereomers, enabling maximum control. PMID:26619213

  19. Isomer ratio calculations using modeled discrete levels

    SciTech Connect

    Gardner, M.A.; Gardner, D.G.; Hoff, R.W.

    1984-10-16

    Isomer ratio calculations were made for the reactions: /sup 175/Lu(n,..gamma..)/sup 176m,g/Lu, /sup 175/Lu(n,2n)/sup 174m,g/Lu, /sup 237/Np(n,2n)/sup 236m,g/Np, /sup 241/Am(n,..gamma..)/sup 242m,g/Am, and /sup 243/Am(n,..gamma..)/sup 244m,g/Am using modeled level structures in the deformed, odd-odd product nuclei. The hundreds of discrete levels and their gamma-ray branching ratios provided by the modeling are necessary to achieve agreement with experiment. Many rotational bands must be included in order to obtain a sufficiently representative selection of K quantum numbers. The levels of each band must be extended to appropriately high values of angular momentum.

  20. Complete Hexose Isomer Identification with Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Nagy, Gabe; Pohl, Nicola L. B.

    2015-04-01

    The first analytical method is presented for the identification and absolute configuration determination of all 24 aldohexose and 2-ketohexose isomers, including the D and L enantiomers for allose, altrose, galactose, glucose, gulose, idose, mannose, talose, fructose, psicose, sorbose, and tagatose. Two unique fixed ligand kinetic method combinations were discovered to create significant enough energetic differences to achieve chiral discrimination among all 24 hexoses. Each of these 24 hexoses yields unique ratios of a specific pair of fragment ions that allows for simultaneous determination of identification and absolute configuration. This mass spectrometric-based methodology can be readily employed for accurate identification of any isolated monosaccharide from an unknown biological source. This work provides a key step towards the goal of complete de novo carbohydrate analysis.

  1. Nuclear structure and depletion of nuclear isomers using electron linacs

    SciTech Connect

    Carroll, J. J.; Litz, M. S.; Henriquez, S. L.; Burns, D. A.; Netherton, K. A.; Pereira, N. R.; Karamian, S. A.

    2013-04-19

    Long-lived nuclear excited states (isomers) have proven important to understanding nuclear structure. With some isomers having half-lives of decades or longer, and intrinsic energy densities reaching 10{sup 12} J/kg, they have also been suggested for a wide range of applications. The ability to effectively transfer a population of nuclei from an isomer to shorter-lived levels will determine the feasibility of any applications. Here is described a first demonstration of the induced depletion of a population of the 438 year isomer of {sup 108}Ag to its 2.38 min ground state, using 6 MeV bremsstrahlung from a modified medical electron linac. The experiment suggests refinements to be implemented in the future and how a similar approach might be applied to study induced depletion of the 1200 year isomer of {sup 166}Ho.

  2. Microsecond electrophoresis

    PubMed Central

    Plenert, Matthew L.; Shear, Jason B.

    2003-01-01

    Although analysis strategies exist for probing a diverse array of molecular properties, most of these approaches are not amenable to the study of reaction intermediates and other transient species. Separations in particular can provide detailed information on attributes not readily measured by spectroscopy but typically are performed over time scales much longer than the life span of highly unstable compounds. Here we report the development of an electrophoretic strategy that dramatically extends the practical speed limit for fractionations and demonstrate its utility in examining transient hydroxyindole photoproducts. Fluorescent reaction intermediates are optically generated in femtoliter volumes within a flowing reagent stream and are differentially transported at velocities as large as 1.3 m⋅s−1, thereby minimizing band variance and allowing multicomponent reaction mixtures to be resolved over separation paths as short as 9 μm. Analyte migration times and band variances do not deviate significantly from basic theory for separations performed with fields that exceed 0.1 MV⋅cm−1, indicating that effects from Joule heating are minor. We demonstrate the feasibility of achieving baseline resolution of a binary mixture in <10 μs, nearly 100-fold faster than previously possible. Application of this approach to the study of a range of short-lived molecules should be feasible. PMID:12629208

  3. Comparison of the repeated dose toxicity of isomers of dinitrotoluene.

    PubMed

    Lent, Emily May; Crouse, Lee C B; Quinn, Michael J; Wallace, Shannon M

    2012-03-01

    Dinitrotoluene (DNT) is a nitroaromatic explosive used in propellant mixtures and in the production of plastics. Isomers of DNT were administered daily via oral gavage to male Sprague-Dawley rats for 14 days to determine the subacute toxicity of individual isomers of DNT. The 3,5-DNT isomer was the most toxic isomer, inducing weight loss and mortality within 3 days. Cyanosis and anemia were observed for all isomers. Exposure to 2,4-, 2,6-, and 3,5-DNT resulted in decreased testes mass and degenerative histopathological changes. Increased splenic mass was observed for 2,4-, 2,6-, and 2,5-DNT. Extramedullary hematopoiesis of the spleen was noted for all isomers, while lymphoid hyperplasia of the spleen was noted for all isomers except 2,5-DNT. Increased liver mass was observed for 2,3-DNT and 3,4-DNT. Hepatocellular lesions were observed for 2,6-DNT and 2,4-DNT. Neurotoxic effects were noted for 3,4-DNT, 2,4-DNT, and 3,5-DNT. PMID:22422434

  4. Adsorption of hexane isomers on ion-exchanged mordenite

    SciTech Connect

    Huddersman, K.

    1996-10-01

    To remove lead from petrol and thereby promote a cleaner environment, other means must be found to keep the octane number or anti-knock qualities of the petrol high. It is found that this can be accomplished by increasing the proportion of highly branched chain hydrocarbon isomers in the fuel. This in turn promotes processes for the separation of the hydrocarbon isomers and in the case of hexane, it is an easy matter to separate out n-hexane from the more substituted isomers but it is difficult to separate out the mono- from the di-branched isomers. This work addresses itself to such challenging separations using modified zeolites as the separating agent, and by studying the heats of sorption of these isomers on zeolites using gas chromatographic techniques to find a trend in the potential abilities of these modified zeolites to effect a good separation. In this work mordenite zeolite was modified by a range of double cation exchanges and the resulting modified zeolites were investigated for their ability to sorb the hexane isomers 3-methylpentane and 2,3-dimethylbutane. These two isomers are closely related in size as they both have the same kinetic diameter of 0.56 nm. In this work only heats of sorption have been investigated and measurement of the diffusion coefficients, which also affect the ability of the modified zeolites to act as good separating agents, is currently under investigation.

  5. Magnetoacoustic imaging of magnetic iron oxide nanoparticles embedded in biological tissues with microsecond magnetic stimulation

    NASA Astrophysics Data System (ADS)

    Hu, Gang; He, Bin

    2012-01-01

    We present an experimental study on magnetoacoustic imaging of superparamagnetic iron oxide (SPIO) nanoparticles embedded in biological tissues. In experiments, a large-current-carrying coil is used to deliver microsecond pulsed magnetic stimulation to samples. The ultrasound signals induced by magnetic forces on SPIO nanoparticles are measured by a rotating transducer. The distribution of nanoparticles is reconstructed by a back-projection imaging algorithm. The results demonstrated the feasibility to obtain cross-sectional image of magnetic nanoparticle targets with faithful dimensional and positional information, which suggests a promising tool for tomographic reconstruction of magnetic nanoparticle-labeled diseased tissues (e.g., cancerous tumor) in molecular or clinic imaging.

  6. Cooling rate and stress relaxation in silica melts and glasses via microsecond molecular dyanmics

    SciTech Connect

    Lane, J. Matthew D.

    2015-07-22

    We have conducted extremely long molecular dynamics simulations of glasses to microsecond times, which close the gap between experimental and atomistic simulation time scales by two to three orders of magnitude. The static, thermal, and structural properties of silica glass are reported for glass cooling rates down to 5×109 K/s and viscoelastic response in silica melts and glasses are studied over nine decades of time. We finally present results from relaxation of hydrostatic compressive stress in silica and show that time-temperature superposition holds in these systems for temperatures from 3500 to 1000 K.

  7. Cooling rate and stress relaxation in silica melts and glasses via microsecond molecular dyanmics

    DOE PAGESBeta

    Lane, J. Matthew D.

    2015-07-22

    We have conducted extremely long molecular dynamics simulations of glasses to microsecond times, which close the gap between experimental and atomistic simulation time scales by two to three orders of magnitude. The static, thermal, and structural properties of silica glass are reported for glass cooling rates down to 5×109 K/s and viscoelastic response in silica melts and glasses are studied over nine decades of time. We finally present results from relaxation of hydrostatic compressive stress in silica and show that time-temperature superposition holds in these systems for temperatures from 3500 to 1000 K.

  8. Temperature-Jump Fluorescence Provides Evidence for Fully Reversible Microsecond Dynamics in a Thermophilic Alcohol Dehydrogenase

    PubMed Central

    2015-01-01

    Protein dynamics on the microsecond (μs) time scale were investigated by temperature-jump fluorescence spectroscopy as a function of temperature in two variants of a thermophilic alcohol dehydrogenase: W87F and W87F:H43A. Both mutants exhibit a fast, temperature-independent μs decrease in fluorescence followed by a slower full recovery of the initial fluorescence. The results, which rule out an ionizing histidine as the origin of the fluorescence quenching, are discussed in the context of a Trp49-containing dimer interface that acts as a conduit for thermally activated structural change within the protein interior. PMID:26223665

  9. Microsecond linear optical response in the unusual nematic phase of achiral bimesogens

    NASA Astrophysics Data System (ADS)

    Panov, V. P.; Balachandran, R.; Nagaraj, M.; Vij, J. K.; Tamba, M. G.; Kohlmeier, A.; Mehl, G. H.

    2011-12-01

    Some hydrocarbon linked mesogenic dimers are known to exhibit an additional nematic phase (Nx) below a conventional uniaxial nematic (Nu) phase. Although composed of non-chiral molecules, the Nx phase is found to exhibit linear (polar) switching under applied electric field. This switching has remarkably low response time of the order of a few microseconds. Two chiral domains with opposite handedness and consequently opposite responses are found in planar cells. Uniformly lying helix, electroclinic, and flexoelectric effects are given as possible causes for this intriguing phenomenon.

  10. Experimental Study of Implosion Dynamics of Multi-Shell Z-Pinches at Microsecond Implosion Times

    NASA Astrophysics Data System (ADS)

    Shishlov, Alexander V.; Chaikovsky, Stanislav A.; Fedunin, Anatoly V.; Fursov, Fedor I.; Kokshenev, Vladimir A.; Kurmaev, Nikolai E.; Labetsky, Aleksey Yu.; Oreshkin, Vladimir I.; Rousskikh, Alexander G.; Zhidkova, Natalia A.

    2006-01-01

    A set of experiments has been conducted on the GIT-12 generator (4.7 MA, 1.7 μs) operating at microsecond mode. The experiments were carried out with multi-shell gas puffs. Dynamics of current-carrying plasma was registered by a set of B-dots monitors placed at different radii inside a multi-shell gas puff. The experimental data obtained with the help of B-dots monitors are compared with 0D snow-plow simulations of implosion dynamics and discussed taking into consideration the data from other Z-pinch diagnostics.

  11. Separation and identification of indene–C70 bisadduct isomers

    PubMed Central

    Zhang, Bolong; Subbiah, Jegadesan; Jones, David J

    2016-01-01

    Summary Following an initial work on the isolation of a single geometric isomer from an indene–C70 bisadduct (IC70BA) mixture, we report the full fractionation and identification of the bisadduct species in the material. Eleven fractions of IC70BA isomers were separated by high-performance liquid chromatography. A number of fractions contained relatively pure isomer species and their configuration were deduced using a variety of analytical techniques including 1H and 13C NMR and UV–vis spectroscopy. The electrochemical properties and the organic solar cell device performance were investigated for fractions where a reasonable quantity of sample could be isolated. PMID:27340480

  12. High-spin torus isomers and their precession motions

    NASA Astrophysics Data System (ADS)

    Ichikawa, T.; Matsuyanagi, K.; Maruhn, J. A.; Itagaki, N.

    2014-09-01

    Background: In our previous study, we found that an exotic isomer with a torus shape may exist in the high-spin, highly excited states of Ca40. The z component of the total angular momentum, Jz=60ℏ, of this torus isomer is constructed by totally aligning 12 single-particle angular momenta in the direction of the symmetry axis of the density distribution. The torus isomer executes precession motion with the rigid-body moments of inertia about an axis perpendicular to the symmetry axis. The investigation, however, has been focused only on Ca40. Purpose: We systematically investigate the existence of exotic torus isomers and their precession motions for a series of N =Z even-even nuclei from Si28 to Ni56. We analyze the microscopic shell structure of the torus isomer and discuss why the torus shape is generated beyond the limit of large oblate deformation. Method: We use the cranked three-dimensional Hartree-Fock method with various Skyrme interactions in a systematic search for high-spin torus isomers. We use the three-dimensional time-dependent Hartree-Fock method for describing the precession motion of the torus isomer. Results: We obtain high-spin torus isomers in Ar36,Ca40,Ti44,Cr48, and Fe52. The emergence of the torus isomers is associated with the alignments of single-particle angular momenta, which is the same mechanism as found in Ca40. It is found that all the obtained torus isomers execute the precession motion at least two rotational periods. The moment of inertia about a perpendicular axis, which characterizes the precession motion, is found to be close to the classical rigid-body value. Conclusions: The high-spin torus isomer of Ca40 is not an exceptional case. Similar torus isomers exist widely in nuclei from Ar36 to Fe52 and they execute the precession motion. The torus shape is generated beyond the limit of large oblate deformation by eliminating the 0s components from all the deformed single-particle wave functions to maximize their mutual

  13. Raman spectroscopic analysis of isomers of biliverdin dimethyl ester.

    PubMed

    Matysik, J; Hildebrandt, P; Smit, K; Mark, F; Gärtner, W; Braslavsky, S E; Schaffner, K; Schrader, B

    1997-06-01

    The constitutional isomers of biliverdin dimethyl ester, IX alpha and XIII alpha, were studied by resonance Raman spectroscopy. The far-reaching spectral similarities suggest that despite the different substitution patterns, the compositions of the normal modes are closely related. This conclusion does not hold only for the parent state (ZZZ, sss configuration) but also for the configurational isomers which were obtained upon double-bond photoisomerization. Based on a comparison of the resonance Raman spectra, a EZZ configuration is proposed for one of the two photoisomers of biliverdin dimethyl ester IX alpha, while a ZZE, ssa configuration has been assigned previously to the second isomer. PMID:9226559

  14. Detection of Actinides via Nuclear Isomer De-Excitation

    SciTech Connect

    Francy, Christopher J.

    2009-07-01

    This dissertation discusses a data collection experiment within the Actinide Isomer Identification project (AID). The AID project is the investigation of an active interrogation technique that utilizes nuclear isomer production, with the goal of assisting in the interdiction of illicit nuclear materials. In an attempt to find and characterize isomers belonging to 235U and its fission fragments, a 232Th target was bombarded with a monoenergetic 6Li ion beam, operating at 45 MeV.

  15. Diastereomeric Ellagitannin Isomers from Penthorum chinense.

    PubMed

    Era, Manami; Matsuo, Yosuke; Shii, Takuya; Saito, Yoshinori; Tanaka, Takashi; Jiang, Zhi-Hong

    2015-08-28

    From the dried stem of Penthorum chinense (Penthoraceae), 1-O-galloyl-4,6-(R)-hexahydroxydiphenoyl (HHDP)-β-D-glucose and 2',4',6'-trihydroxyacetophenone 4'-O-[4,6-(R)-HHDP]-β-D-glucoside were isolated together with their (S)-HHDP isomers. Ellagitannins with a 4,6-(S)-HHDP-glucose moiety are widely distributed in the plant kingdom; however, 4,6-(R)-HHDP glucoses are extremely rare. Lowest-energy conformers of 1-O-galloyl-(S)- and (R)-HHDP-glucopyranoses were derived by density functional theory calculations, and the calculated (1)H and (13)C NMR chemical shifts and the (1)H-(1)H coupling constants were in agreement with the experimental values. The results revealed a conformational difference of the diastereomeric macrocyclic ester rings. In addition, a new compound, 1',3',5'-trihydroxybenzene 1'-O-[4,6-(S)-HHDP]-β-D-glucoside, was also isolated. PMID:26218585

  16. Isomer spectroscopy of {sup 127}Cd

    SciTech Connect

    Naqvi, F.; Gorska, M.; Grawe, H.; Beck, T.; Doornenbal, P.; Geissel, H.; Gerl, J.; Kojouharov, I.; Kurz, N.; Montes, F.; Prokopowicz, W.; Schaffner, H.; Tashenov, S.; Wollersheim, H. J.; Caceres, L.; Jungclaus, A.; Pfuetzner, M.; Werner-Malento, E.; Nowacki, F.; Sieja, K.

    2010-09-15

    The spin and configurational structure of excited states of {sup 127}Cd, the two-proton and three-neutron hole neighbor of {sup 132}Sn, has been studied. An isomeric state with a half-life of 17.5(3) {mu}s was populated in the fragmentation of a {sup 136}Xe beam on a {sup 9}Be target at a beam energy of 750 MeV/u. Time distributions of the delayed {gamma} transitions and {gamma}{gamma} coincidence relations were exploited to construct a decay scheme. The observed yrast (19/2){sup +} isomer is proposed to have dominant configurations of {nu}(h{sub 11/2}{sup -3}){pi}(g{sub 9/2}{sup -1},p{sub 1/2}{sup -1}), {nu}(h{sub 11/2}{sup -2}d{sub 3/2}{sup -1}){pi}(g{sub 9/2}{sup -2}), and {nu}(h{sub 11/2}{sup -2},s{sub 1/2}{sup -1}){pi}(g{sub 9/2}{sup -2}) and to decay by two competing stretched M2 and E3 transitions. Experimental results are compared with the isotone {sup 129}Sn. The new information provides input for the proton-neutron interaction and the evolution of neutron hole energies in nuclei around the doubly magic {sup 132}Sn core.

  17. Development of a microsecond X-ray protein footprinting facility at the Advanced Light Source

    PubMed Central

    Gupta, Sayan; Celestre, Richard; Petzold, Christopher J.; Chance, Mark R.; Ralston, Corie

    2014-01-01

    X-ray footprinting (XF) is an important structural biology tool used to determine macromolecular conformations and dynamics of both nucleic acids and proteins in solution on a wide range of timescales. With the impending shut-down of the National Synchrotron Light Source, it is ever more important that this tool continues to be developed at other synchrotron facilities to accommodate XF users. Toward this end, a collaborative XF program has been initiated at the Advanced Light Source using the white-light bending-magnet beamlines 5.3.1 and 3.2.1. Accessibility of the microsecond time regime for protein footprinting is demonstrated at beamline 5.3.1 using the high flux density provided by a focusing mirror in combination with a micro-capillary flow cell. It is further reported that, by saturating samples with nitrous oxide, the radiolytic labeling efficiency is increased and the imprints of bound versus bulk water can be distinguished. These results both demonstrate the suitability of the Advanced Light Source as a second home for the XF experiment, and pave the way for obtaining high-quality structural data on complex protein samples and dynamics information on the microsecond timescale. PMID:24971962

  18. Tuning Neuronal Hardware with Microsecond Precision: Sound Localization in the Barn Owl

    NASA Astrophysics Data System (ADS)

    van Hemmen, J. Leo

    1998-03-01

    In auditory and electrosensory neuronal systems, there seems to exist an unresolved paradox: They encode behaviorally relevant signals in the range of a few microseconds with neurons that are at least one order of magnitude slower. The barn owl's auditory system is a prominent example that may serve to provide a solution(W. Gerstner, R. Kempter, J.L. van Hemmen, and H. Wagner, Nature 383) (1996) 76--78 to the above paradox. First, neuronal output is much more accurate than the input, phprovided the presynaptic spikes arrive coherently on the average -- as they do in the adult animal. Second, this coherence in signal arrival times can be attained through unsupervised Hebbian learning (`tuning') during ontogenetic development. The learning rule governing the strength of a synapse is based on the precise timing of input as compared to output spikes. Third, the learning rule also selects the correct delays from two independent groups of input, for example, from the left and right ear and, thus, can explain the tuning to interaural time differences in the microsecond range that underlies sound localization. The relation to stochastic resonance is indicated.

  19. Dynamics of Lipids, Cholesterol, and Transmembrane α-Helices from Microsecond Molecular Dynamics Simulations

    PubMed Central

    2015-01-01

    Extensive all-atom molecular dynamics (∼24 μs total) allowed exploration of configurational space and calculation of lateral diffusion coefficients of the components of a protein-embedded, cholesterol-containing model bilayer. The three model membranes are composed of an ∼50/50 (by mole) dipalmitoylphosphatidylcholine (DPPC)/cholesterol bilayer and contained an α-helical transmembrane protein (HIV-1 gp41 TM). Despite the high concentration of cholesterol, normal Brownian motion was observed and the calculated diffusion coefficients (on the order of 10–9 cm2/s) are consistent with experiments. Diffusion is sensitive to a variety of parameters, and a temperature difference of ∼4 K from thermostat artifacts resulted in 2–10-fold differences in diffusion coefficients and significant differences in lipid order, membrane thickness, and unit cell area. Also, the specific peptide sequence likely underlies the consistently observed faster diffusion in one leaflet. Although the simulations here present molecular dynamics (MD) an order of magnitude longer than those from previous studies, the three systems did not approach ergodicity. The distributions of cholesterol and DPPC around the peptides changed on the microsecond time scale, but not significantly enough to thoroughly explore configurational space. These simulations support conclusions of other recent microsecond MD in that even longer time scales are needed for equilibration of model membranes and simulations of more realistic cellular or viral bilayers. PMID:25380392

  20. Aging Characteristics on Epoxy Resin Surface Under Repetitive Microsecond Pulses in Air at Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Xie, Qing; Liu, Xiong; Zhang, Cheng; Wang, Ruixue; Rao, Zhangquan; Shao, Tao

    2016-03-01

    Research on aging characteristics of epoxy resin (EP) under repetitive microsecond pulses is important for the design of insulating materials in high power apparatus. It is because that very fast transient overvoltage always occurs in a power system, which causes flashover and is one of the main factors causing aging effects of EP materials. Therefore, it is essential to obtain a better understanding of the aging effect on an EP surface resulting from flashover. In this work, aging effects on an EP surface were investigated by surface flashover discharge under repetitive microsecond pulses in atmospheric pressure. The investigations of parameters such as the surface micro-morphology and chemical composition of the insulation material under different degrees of aging were conducted with the aid of measurement methods such as atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Results showed that with the accumulation of aging energy on the material surface, the particles formed on the material surface increased both in number and size, leading to the growth of surface roughness and a reduction in the water contact angle; the surface also became more absorbent. Furthermore, in the aging process, the molecular chains of EP on the surface were broken, resulting in oxidation and carbonisation. supported by the Natural Science Foundation of Hebei Province (No. E2015502081), National Natural Science Foundation of China (Nos. 51222701, 51307060), and the National Basic Research Program of China (No. 2014CB239505-3)

  1. Microsecond Time Resolution Optical Photometry using a H.E.S.S. Cherenkov Telescope

    SciTech Connect

    Deil, Christoph; Domainko, Wilfried; Hermann, German

    2008-02-22

    We have constructed an optical photometer with microsecond time resolution, which is currently being operated on one of the H.E.S.S. telescopes. H.E.S.S. is an array of four Cherenkov telescopes, each with a 107 m{sup 2} mirror, located in the Khomas highland in Namibia. In its normal mode of operation H.E.S.S. observes Cherenkov light from air showers generated by very high energy gamma-rays in the upper atmosphere. Our detector consists of seven photomultipliers, one in the center to record the lightcurve from the target and six concentric photomultipliers as a veto system to reject disturbing signals e.g. from meteorites or lightning at the horizon. The data acquisition system has been designed to continuously record the signals with zero deadtime. The Crab pulsar has been observed to verify the performance of the instrument and the GPS timing system. Compact galactic targets were observed to search for flares on timescales of a few microseconds to {approx}100 ms. The design and sensitivity of the instrument as well as the data analysis method are presented.

  2. Microsecond acquisition of heterogeneous structure in the folding of a TIM barrel protein

    SciTech Connect

    Wu, Ying; Kondrashkina, Elena; Kayatekin, Can; Matthews, C. Robert; Bilsel, Osman

    2008-09-29

    The earliest kinetic folding events for ({beta}{alpha}){sub 8} barrels reflect the appearance of off-pathway intermediates. Continuous-flow microchannel mixing methods interfaced to small-angle x-ray scattering (SAXS), circular dichroism (CD), time-resolved Foerster resonant energy transfer (trFRET), and time-resolved fluorescence anisotropy (trFLAN) have been used to directly monitor global and specific dimensional properties of the partially folded state in the microsecond time range for a representative ({beta}{alpha}){sub 8} barrel protein. Within 150 {micro}s, the {alpha}-subunit of Trp synthase ({alpha}TS) experiences a global collapse and the partial formation of secondary structure. The time resolution of the folding reaction was enhanced with trFRET and trFLAN to show that, within 30 {micro}s, a distinct and autonomous partially collapsed structure has already formed in the N-terminal and central regions but not in the C-terminal region. A distance distribution analysis of the trFRET data confirmed the presence of a heterogeneous ensemble that persists for several hundreds of microseconds. Ready access to locally folded, stable substructures may be a hallmark of repeat-module proteins and the source of early kinetic traps in these very common motifs. Their folding free-energy landscapes should be elaborated to capture this source of frustration.

  3. Simple Nuclear Structure in Cd-129111 from Atomic Isomer Shifts

    NASA Astrophysics Data System (ADS)

    Yordanov, D. T.; Balabanski, D. L.; Bissell, M. L.; Blaum, K.; Budinčević, I.; Cheal, B.; Flanagan, K.; Frömmgen, N.; Georgiev, G.; Geppert, Ch.; Hammen, M.; Kowalska, M.; Kreim, K.; Krieger, A.; Meng, J.; Neugart, R.; Neyens, G.; Nörtershäuser, W.; Rajabali, M. M.; Papuga, J.; Schmidt, S.; Zhao, P. W.

    2016-01-01

    Isomer shifts have been determined in 111-129>Cd by high-resolution laser spectroscopy at CERN-ISOLDE. The corresponding mean square charge-radii changes, from the 1 /2+ and the 3 /2+ ground states to the 11 /2- isomers, have been found to follow a distinct parabolic dependence as a function of the atomic mass number. Since the isomers have been previously associated with simplicity due to the linear mass dependence of their quadrupole moments, the regularity of the isomer shifts suggests a higher order of symmetry affecting the ground states in addition. A comprehensive description assuming nuclear deformation is found to accurately reproduce the radii differences in conjunction with the known quadrupole moments. This intuitive interpretation is supported by covariant density functional theory.

  4. ORAL TOXICOLOGY STUDIES WITH XYLENE ISOMERS AND MIXED XYLENES

    EPA Science Inventory

    Xylene isomers and mixed xylenes were administered to male and female Sprague-Dawley rats to evaluate their effects on standard toxicological parameters rnhich included body and organ weights, hematology, serum chemistries, urinalysis and histopathological examination. n the init...

  5. Molecular structure of uranium carbides: isomers of UC3.

    PubMed

    Zalazar, M Fernanda; Rayón, Víctor M; Largo, Antonio

    2013-03-21

    In this article, the most relevant isomers of uranium tricarbide are studied through quantum chemical methods. It is found that the most stable isomer has a fan geometry in which the uranium atom is bonded to a quasilinear C3 unit. Both, a rhombic and a ring CU(C2) structures are found about 104-125 kJ/mol higher in energy. Other possible isomers including linear geometries are located even higher. For each structure, we provide predictions for those molecular properties (vibrational frequencies, IR intensities, dipole moments) that could eventually help in their experimental detection. We also discuss the possible routes for the formation of the different UC3 isomers as well as the bonding situation by means of a topological analysis of the electron density. PMID:23534639

  6. Molecular structure of uranium carbides: Isomers of UC3

    NASA Astrophysics Data System (ADS)

    Zalazar, M. Fernanda; Rayón, Víctor M.; Largo, Antonio

    2013-03-01

    In this article, the most relevant isomers of uranium tricarbide are studied through quantum chemical methods. It is found that the most stable isomer has a fan geometry in which the uranium atom is bonded to a quasilinear C3 unit. Both, a rhombic and a ring CU(C2) structures are found about 104-125 kJ/mol higher in energy. Other possible isomers including linear geometries are located even higher. For each structure, we provide predictions for those molecular properties (vibrational frequencies, IR intensities, dipole moments) that could eventually help in their experimental detection. We also discuss the possible routes for the formation of the different UC3 isomers as well as the bonding situation by means of a topological analysis of the electron density.

  7. Enhanced Raman spectroscopic study of rotational isomers on metal surfaces

    NASA Technical Reports Server (NTRS)

    Loo, B. H.; Lee, Y. G.; Frazier, D. O.

    1986-01-01

    Surfaced-enhanced Raman spectroscopy has been used to study rotational isomers of succinonitrile and N-methyl-thioacetamide on Cu and Ag surfaces. Both the gauche and trans conformers of succinonitrile are found to chemisorb on the metal surface. The doubly degenerate nu(C-triple bond-N) in the free molecules is removed when succinonitrile adsorbs on copper, which indicates that the two (C-triple bond-N) groups are no longer chemically equivalent. Both conformers are found to coordinate to the copper surface through the pi system of one of the two (C-triple bond-N) groups. In the case of N-methyl-thioacetamide, the population of the cis isomer is greatly increased on Cu and Ag surfaces. This is probably due to surface-induced cis-trans isomerization, in which the predominant trans isomer is converted to the cis isomer.

  8. Synthesis of dibenzylamino-1-methylcyclohexanol and dibenzylamino-1-trifluoromethylcyclohexanol isomers.

    PubMed

    Jones, D Heulyn; Bresciani, Stefano; Tellam, James P; Wojno, Justyna; Cooper, Anthony W J; Kennedy, Alan R; Tomkinson, Nicholas C O

    2016-01-01

    The isomers of dibenzylamino-1-methylcyclohexan-1-ol and dibenzylamino-1-trifluoromethylcyclohexan-1-ol have been prepared. The stereochemistry of these compounds was unequivocally assigned through a combination of NMR spectroscopy and single crystal X-ray analysis. The cis-isomer of 3-N,N-dibenzylamino-1-trifluoromethylcyclohexanol and its derivatives display an unusual conformational behaviour in both solution-phase and the solid-state, where the amino group usually adopts an axial conformation. PMID:26468867

  9. Differential Degradation of Nonylphenol Isomers by Sphingomonas xenophaga Bayram

    PubMed Central

    Gabriel, Frédéric L. P.; Giger, Walter; Guenther, Klaus; Kohler, Hans-Peter E.

    2005-01-01

    Sphingomonas xenophaga Bayram, isolated from the activated sludge of a municipal wastewater treatment plant, was able to utilize 4-(1-ethyl-1,4-dimethylpentyl)phenol, one of the main isomers of technical nonylphenol mixtures, as a sole carbon and energy source. The isolate degraded 1 mg of 4-(1-ethyl-1,4-dimethylpentyl)phenol/ml in minimal medium within 1 week. Growth experiments with five nonylphenol isomers showed that the three isomers with quaternary benzylic carbon atoms [(1,1,2,4-tetramethylpentyl)phenol, 4-(1-ethyl-1,4-dimethylpentyl)phenol, and 4-(1,1-dimethylheptyl)phenol] served as growth substrates, whereas the isomers containing one or two hydrogen atoms in the benzylic position [4-(1-methyloctyl)phenol and 4-n-nonylphenol] did not. However, when the isomers were incubated as a mixture, all were degraded to a certain degree. Differential degradation was clearly evident, as isomers with more highly branched alkyl side chains were degraded much faster than the others. Furthermore, the C9 alcohols 2,3,5-trimethylhexan-2-ol, 3,6-dimethylheptan-3-ol, and 2-methyloctan-2-ol, derived from the three nonylphenol isomers with quaternary benzylic carbon atoms, were detected in the culture fluid by gas chromatography-mass spectrometry, but no analogous metabolites could be found originating from 4-(1-methyloctyl)phenol and 4-n-nonylphenol. We propose that 4-(1-methyloctyl)phenol and 4-n-nonylphenol were cometabolically transformed in the growth experiments with the mixture but that, unlike the other isomers, they did not participate in the reactions leading to the detachment of the alkyl moiety. This hypothesis was corroborated by the observed accumulation in the culture fluid of an as yet unidentified metabolite derived from 4-(1-methyloctyl)phenol. PMID:15746308

  10. Conversion electron spectroscopy at the FMA focal plane: Decay studies of proton-rich N {approximately} 82 nuclei

    SciTech Connect

    Nisius, D.; Janssens, R.V.F.; Ahmad, I.

    1995-08-01

    The FMA has proven to be an ideal instrument for the detailed study of the decay of microsecond isomers behind the focal plane following mass selection. In reactions leading to the population of nuclei with isomeric lifetimes longer than their flight time through the device, decay gamma rays and conversion electrons can be detected in an environment free from the backgrounds of prompt radiation and delta electrons. This was a very successful technique to study proton (h{sub 11/2}){sup n} seniority isomers in nuclei with Z > 64 and N {approximately} 82. Since isomeric decay gamma rays are emitted isotropically, conversion electrons are essential for the assignment of multipolarities in these nuclei. Furthermore, the low-energy transitions that depopulate isomeric states are typically highly converted and can escape gamma-ray detection, but they can be identified by their conversion electrons.

  11. Existence of Exotic Torus Isomer States and Their Precession Motions

    NASA Astrophysics Data System (ADS)

    Ichikawa, Takatoshi; Matsuyanagi, Kenichi; Maruhn, Joachim A.; Itagaki, Naoyuki

    We systematically investigate the existence of exotic high-spin torus isomers and their precession motions for a series of N = Z even-even nuclei from 28Si to 56Ni. For this purpose, we use the cranked three-dimensional Hatree-Fock (HF) method in a systematic search for high-spin torus isomers and the three-dimensional time-dependent Hatree-Fock (TDHF) method for describing the precession motion of the torus isomer. We obtain high-spin torus isomers in 36Ar, 40Ca, 44Ti, 48Cr, and 52Fe. The emergence of the torus isomers is associated with the alignments of single-particle angular momenta, which is the same mechanism as found in 40Ca. We find that all the obtained torus isomers execute the precession motion at least two rotational periods. The moment of inertia about a perpendicular axis, which characterizes the precession motion, is found to be close to the classical rigid-body value.

  12. The combustion kinetics of octane isomers

    SciTech Connect

    Burcat, A.; Pitz, W.J.; Westbrook, C.K.

    1990-03-29

    Shock tube experiments provide conditions for testing kinetic models that are unique, since this is the only common environment in which initiation reactions, primarily the unimolecular decompositions of the fuel, play an important role. At least two factors are known to be very important, the fuel molecule size and its precise structure. Iso-octane has an octane number of 100, which reflects the relative difficulty with which iso-octanes/air mixtures ignite. Conversely, C{sub 8}H{sub 18}, the straight chain n-octane, ignites very easily, with an octane number of approximately zero. The present work addresses the importance of fuel structure for large hydrocarbon fuels, by comparing the ignition of isomers of octane under shock tube conditions. Ignition delay times were performed with n-octane, a linear chain molecular with only primary and secondary C-H bonds, 2-3-4-trimethyl-pentane has a highly branched molecule and contains only primary and tertiary C-H bonds, and iso-octane a molecule which includes a mixture of primary, secondary, and tertiary C-H bonds. Also 1-octene, a simple straight chain alkene was included. The experiments were run in a single pulse stainless steel shock tube. 475 shocks were performed. They were spread as follows: (1) 164 experiments with 1-octene (C{sub 8}H{sub 16}). (2) 137 experiments with 2,2,4 tri-methyl pentane. (3) 30 experiments with 2,3,4 tri-methyl pentane. (4) 144 experiments with n-octane. 3 refs.

  13. Anaerobic biodegradability of phthalic acid isomers and related compounds.

    PubMed

    Kleerebezem, R; Pol, L W; Lettinga, G

    1999-02-01

    All three phthalic acid isomers (ortho, meta and para benzene dicarboxylic acid) are produced in massive amounts, and used in the chemical industry as plasticizers or for the production of polyester. Wastestreams generated during the production of phthalate isomers generally contain high concentrations of aromatic acids. To study the potential biodegradability of these primarily anthropogenic compounds in anaerobic bioreactors, biodegradability studies were performed. Compounds tested were benzoate, ortho-phthalate, isophthalate, terephthalate, dimethyl phthalate, dimethyl terephthalate, para-toluate and para-xylene. Seed materials tested were two types of granular sludge and digested sewage sludge. It was found that all phthalate isomers and their corresponding dimethyl-esters, could be completely mineralized by all seed materials studied. Lag phases required for 50% degradation of these compounds, ranged from 17 to 156 days. The observed degradation curves could be explained by growth of an initially small amount of organisms in the inoculum with the specific ability to degrade one phthalate isomer. The observed order in the length of the lag phases for the phthalate isomers is: phthalate < terephthalate < isophthalate. This order appears to be related to the environmental abundancy of the different phthalate isomers. The initial step in the degradation pathway of both dimethyl phthalate esters was hydrolysis of the ester sidechain, resulting in the formation of the corresponding mono-methyl-phthalate isomer and phthalate isomer. The rate limiting step in mineralization of both dimethyl phthalate and dimethyl terephthalate was found to be fermentation of the phthalate isomer. Para-toluate was degraded only by digested sewage sludge after a lag phase of 425 days. The observed degradation rates of this compound were very low. No mineralization of para-xylene was observed. In general, the differences in the lag phases between different seed materials were relatively

  14. Characterization of the Azirinyl Cation and Its Isomers.

    PubMed

    Kokkila Schumacher, Sara I L; Bera, Partha P; Lee, Timothy J

    2016-03-01

    The azirinyl cation (C2H2N(+)) and its geometrical isomers could be present in the interstellar medium. The C2H2N(+) isomers are, however, difficult to identify in interstellar chemistry because of the lack of high-resolution spectroscopic data from laboratory experiments. Ab initio quantum chemical methods were used to characterize the structures, relative energies, and spectroscopic and physical properties of the low energy isomers of the azirinyl cation. We have employed second-order Møller-Plesset perturbation theory (MP2), second-order Z-averaged perturbation theory (ZAPT2), and coupled cluster theory with singles and doubles with perturbative triples CCSD(T) methods along with large correlation consistent basis sets such as cc-pVTZ, cc-pCVTZ, cc-pVQZ, cc-pCVQZ, and cc-pV5Z. Harmonic vibrational frequencies, dipole moments, rotational constants, and proton affinities for the lowest energy isomers were calculated using the CCSD(T) method. Azirinyl cation, a cyclic isomer, is lowest in energy at all levels of theory employed. Azirinyl cation is followed by the cyanomethyl cation (H2CCN)(+), isocyanomethyl cation (H2CNC)(+), and a quasilinear HCCNH(+) cation, which are 13.8, 17.3, and 21.5 kcal mol(-1) above the cyclic isomer, respectively, at the CCSD(T)/cc-pV5Z level of theory. The lowest three isomers all have C2v symmetry and (1)A1 ground electronic states. The quasilinear HCCNH(+) cation has a Cs symmetry planar structure, and a (3)A″ electronic ground state, unlike what some previous work suggested. PMID:26840658

  15. Computations of 36 tautomer/isomer equilibria of different lactams.

    PubMed

    Galstyan, Gegham; Knapp, Ernst-Walter

    2012-06-28

    Gas-phase energies of 36 tautomer/isomer pairs of 18 six-membered N-heterocyclic compounds were computed quantum chemically. Among the considered B3LYP, BH&HLYP, BH&HLYP(G), and PW6B95 DFT functionals, the latter two provide accurate tautomer/isomer pair energies with root-mean-square deviations (rmsd) relative to experiments of 0.2 and 0.3 kcal/mol, respectively. Since only few (namely five) experimental data are available, 15 tautomer/isomer pair energies were computed with the very precise QCISD(T)(quadruple-ζ) method serving as reference. Relative to this reference the PW6B95 DFT functional is slightly superior to the BH&HLYP(G) functional, yielding an rmsd of 0.7 and 0.8 kcal/mol, respectively. In contrast to BH&HLYP(G), the PW6B95 DFT functional yields also accurate tautomer/isomer pair energies if zwitterionic structures are involved. The tautomer/isomer pair states possess different amounts of aromaticity. This is characterized by nucleus-independent chemical shift (NICS) values. The tautomer/isomer pair reference energies, from which the energies computed with PW6B95 are subtracted, correlate linearly with the corresponding differences in the NICS values. This correlation is used to construct a correction term for the pair energies computed with PW6B95, yielding tautomer/isomer pair energies with rmsd of 0.3 kcal/mol with respect to the more CPU time demanding QCISD(T)(quadruple-ζ) method. PMID:22646903

  16. Progress toward a microsecond duration, repetitive, intense-ion beam for active spectroscopic measurements on ITER

    SciTech Connect

    Davis, H.A.; Bartsch, R.R.; Barnes, C.W.

    1996-06-01

    The authors describe the design of an intense, pulsed, repetitive, neutral beam based on magnetically insulated diode technology for injection into ITER for spectroscopic measurements of thermalizing alpha particle and thermal helium density profiles, ion temperature, plasma rotation, and low Z impurity concentrations in the confinement region. The beam is being developed to enhance low signal-to-noise ratios expected with conventional steady-state ion beams because of severe beam attenuation and intense bremstrahlung emission. A 5 GW (e.g., 100 keV, 50 kA) one-microsecond-duration beam would increase the signal by 10{sup 3} compared to a conventional 5 MW beam with signal-to-noise ratios comparable to those from a chopped conventional beam in one second.

  17. Stimulation of secretion from bovine adrenal chromaffin cells by microsecond bursts of therapeutic levels of ultrasound.

    PubMed Central

    Robinson, I M; Kinnick, R R; Greenleaf, J F; Fernandez, J M

    1996-01-01

    1. In this study the secretory response of individual bovine adrenal chromaffin cells was monitored using amperometric carbon-fibre microelectrodes. Cells were stimulated to secrete by exposure to 20-100 microseconds long tonebursts of ultrasound (2-4 x 10(5) Pa; peak pressure at 1 MHz). 2. Three types of secretory responses were observed: an almost instantaneous response, a delayed release of catecholamines, or a series of 'burst-like' secretory bouts. 3. Fura-2 measurements of intracellular Ca2+ concentrations showed that the release of catecholamines was accompanied by an increase in the intracellular Ca2+ concentration. In the absence of extracellular Ca2+, secretory responses were not evoked showing that Ca2+ entry was necessary to elicit catecholamine release. Images Figure 1 PMID:8730600

  18. Study of Vacuum Insulator Flashover for Pulse Lengths of Multi-Microseconds

    SciTech Connect

    Houck, T; Goerz, D; Javedani, J; Lauer, E; Tully, L; Vogtlin, G

    2006-07-31

    We are studying the flashover of vacuum insulators for applications where high voltage conditioning of the insulator and electrodes is not practical and for pulse lengths on the order of several microseconds. The study is centered about experiments performed with a 100-kV, 10-ms pulsed power system and supported by a combination of theoretical and computational modeling. The base line geometry is a cylindrically symmetric, +45{sup o} insulator between flat electrodes. In the experiments, flashovers or breakdowns are localized by operating at field stresses slightly below the level needed for explosive emissions with the base line geometry. The electrodes and/or insulator are then seeded with an emission source, e.g. a tuft of velvet, or a known mechanical defect. Various standard techniques are employed to suppress cathode-originating flashovers/breakdowns. We present the results of our experiments and discuss the capabilities of modeling insulator flashover.

  19. Insights from Micro-second Atomistic Simulations of Melittin in Thin Lipid Bilayers.

    PubMed

    Upadhyay, Sanjay K; Wang, Yukun; Zhao, Tangzhen; Ulmschneider, Jakob P

    2015-06-01

    The membrane disruption and pore-forming mechanism of melittin has been widely explored by experiments and computational studies. However, the precise mechanism is still enigmatic, and further study is required to turn antimicrobial peptides into future promising drugs against microbes. In this study, unbiased microsecond (µs) time scale (total 17 µs) atomistic molecular dynamics simulation were performed on multiple melittin systems in 1,2-dimyristoyl-sn-glycero-3-phosphocholine membrane to capture the various events during the membrane disorder produced by melittin. We observed bent U-shaped conformations of melittin, penetrated deeply into the membrane in all simulations, and a special double U-shaped structure. However, no peptide transmembrane insertion, nor pore formation was seen, indicating that these processes occur on much longer timescales, and suggesting that many prior computational studies of melittin were not sufficiently unbiased. PMID:25963936

  20. Analysis of the operating regimes of microsecond-conduction-time plasma opening switches

    NASA Astrophysics Data System (ADS)

    Cassany, B.; Grua, P.

    1995-07-01

    A theoretical model for the microsecond-conduction-time plasma opening switch (POS) based on magnetohydrodynamics is presented. The operating processes are associated with the magnetic field transport in the switch. The concept of the freezing-in of magnetic field in fluids is used to analyse the dynamics of this field in the plasma. One-dimensional and two-dimensional numerical simulations lead to the identification of two operating regimes, related to the Hall and the snowplow effects. The transition between these two regimes is determined by the plasma density. Scaling relations are developed from this model. In particular the electrical charge Q, conducted by the POS during the conduction time, provides a useful tool for comparisons between theory and experiments; it is shown to be the essential parameter for the switch design.

  1. Simulating the Thermal Response of High Explosives on Time Scales of Days to Microseconds

    SciTech Connect

    Yoh, J J; McClelland, M A

    2003-07-16

    We present an overview of computational techniques for simulating the thermal cookoff of high explosives using a multi-physics hydrodynamics code, ALE3D. Recent improvements to the code have aided our computational capability in modeling the response of energetic materials systems exposed to extreme thermal environments, such as fires. We consider an idealized model process for a confined explosive involving the transition from slow heating to rapid deflagration in which the time scale changes from days to hundreds of microseconds. The heating stage involves thermal expansion and decomposition according to an Arrhenius kinetics model while a pressure-dependent burn model is employed during the explosive phase. We describe and demonstrate the numerical strategies employed to make the transition from slow to fast dynamics.

  2. From microseconds to seconds and minutes—time computation in insect hearing

    PubMed Central

    Hartbauer, Manfred; Römer, Heiner

    2014-01-01

    The computation of time in the auditory system of insects is of relevance at rather different time scales, covering a large range from microseconds to several minutes. At the one end of this range, only a few microseconds of interaural time differences are available for directional hearing, due to the small distance between the ears, usually considered too small to be processed reliably by simple nervous systems. Synapses of interneurons in the afferent auditory pathway are, however, very sensitive to a time difference of only 1–2 ms provided by the latency shift of afferent activity with changing sound direction. At a much larger time scale of several tens of milliseconds to seconds, time processing is important in the context species recognition, but also for those insects where males produce acoustic signals within choruses, and the temporal relationship between song elements strongly deviates from a random distribution. In these situations, some species exhibit a more or less strict phase relationship of song elements, based on phase response properties of their song oscillator. Here we review evidence on how this may influence mate choice decisions. In the same dimension of some tens of milliseconds we find species of katydids with a duetting communication scheme, where one sex only performs phonotaxis to the other sex if the acoustic response falls within a very short time window after its own call. Such time windows show some features unique to insects, and although its neuronal implementation is unknown so far, the similarity with time processing for target range detection in bat echolocation will be discussed. Finally, the time scale being processed must be extended into the range of many minutes, since some acoustic insects produce singing bouts lasting quite long, and female preferences may be based on total signaling time. PMID:24782783

  3. From microseconds to seconds and minutes-time computation in insect hearing.

    PubMed

    Hartbauer, Manfred; Römer, Heiner

    2014-01-01

    The computation of time in the auditory system of insects is of relevance at rather different time scales, covering a large range from microseconds to several minutes. At the one end of this range, only a few microseconds of interaural time differences are available for directional hearing, due to the small distance between the ears, usually considered too small to be processed reliably by simple nervous systems. Synapses of interneurons in the afferent auditory pathway are, however, very sensitive to a time difference of only 1-2 ms provided by the latency shift of afferent activity with changing sound direction. At a much larger time scale of several tens of milliseconds to seconds, time processing is important in the context species recognition, but also for those insects where males produce acoustic signals within choruses, and the temporal relationship between song elements strongly deviates from a random distribution. In these situations, some species exhibit a more or less strict phase relationship of song elements, based on phase response properties of their song oscillator. Here we review evidence on how this may influence mate choice decisions. In the same dimension of some tens of milliseconds we find species of katydids with a duetting communication scheme, where one sex only performs phonotaxis to the other sex if the acoustic response falls within a very short time window after its own call. Such time windows show some features unique to insects, and although its neuronal implementation is unknown so far, the similarity with time processing for target range detection in bat echolocation will be discussed. Finally, the time scale being processed must be extended into the range of many minutes, since some acoustic insects produce singing bouts lasting quite long, and female preferences may be based on total signaling time. PMID:24782783

  4. Histotripsy Produced by Hundred-Microsecond-Long Focused Ultrasonic Pulses: A Preliminary Study.

    PubMed

    Guan, Yubo; Lu, Mingzhu; Li, Yujiao; Liu, Fenfen; Gao, Ya; Dong, Tengju; Wan, Mingxi

    2016-09-01

    A new strategy is proposed in this study to rapidly generate mechanical homogenized lesions using hundred-microsecond-long pulses. The pulsing scheme was divided into two stages: generating sufficient bubble seed nuclei via acceleration by boiling bubbles and efficiently forming a mechanically homogenized and regularly shaped lesion with a homogenate inside via inertial cavitation. The duty cycle was set at 4.9%/3.9% in stage 1 and 1%/0.88% in stage 2 by changing the pulse duration (PD) and off-time independently. The pulse sequence was 500-μs/400-μs PD with a 100-Hz pulse repetition frequency (PRF) in stage 1, followed by 500-μs/400-μs PD with a 100-Hz PRF and 200-μs PD with a 200-Hz PRF in stage 2. Experiments were conducted on polyacrylamide phantoms with bovine serum albumin and on ex vivo porcine kidney tissues using a single-element 1.06-MHz transducer at an 8-MPa peak negative pressure with shock waves. The lesion evolution and dynamic elastic modulus variation in the phantoms and the histology in the tissue samples were investigated. The results indicate that the two-stage treatment using hundred-microsecond-long pulses can efficiently produce mechanically homogenized lesions with smooth borders, long tear shapes and the total homogenate inside. The time to generate a single mechanically homogenized lesion is shortened from >50 s to 17.1 s. PMID:27318864

  5. Astropulse: A Search for Microsecond Transient Radio Signals Using Distributed Computing. I. Methodology

    NASA Astrophysics Data System (ADS)

    Von Korff, J.; Demorest, P.; Heien, E.; Korpela, E.; Werthimer, D.; Cobb, J.; Lebofsky, M.; Anderson, D.; Bankay, B.; Siemion, A.

    2013-04-01

    We are performing a transient, microsecond timescale radio sky survey, called "Astropulse," using the Arecibo telescope. Astropulse searches for brief (0.4 μs to 204.8 μs ), wideband (relative to its 2.5 MHz bandwidth) radio pulses centered at 1420 MHz. Astropulse is a commensal (piggyback) survey, and scans the sky between declinations of -1.°33 and 38.°03. We obtained 1540 hr of data in each of seven beams of the ALFA receiver, with two polarizations per beam. The data are one-bit complex sampled at the Nyquist limit of 0.4 μs per sample. Examination of timescales on the order of microseconds is possible because we used coherent dedispersion, a technique that has frequently been used for targeted observations, but has never been associated with a radio sky survey. The more usual technique, incoherent dedispersion, cannot resolve signals below a minimum timescale which depends on the signal's dispersion measure (DM) and frequency. However, coherent dedispersion requires more intensive computation than incoherent dedispersion. The required processing power was provided by BOINC, the Berkeley Open Infrastructure for Network Computing. BOINC is a distributed computing system, allowing us to utilize hundreds of thousands of volunteers' computers to perform the necessary calculations for coherent dedispersion. Astrophysical events that might produce brief radio pulses include giant pulses from pulsars, rotating radio transients, exploding primordial black holes, or new sources yet to be imagined. Radio frequency interference and noise contaminate the data; these are mitigated by a number of techniques including multi-polarization correlation, DM repetition detection, and frequency profiling.

  6. ASTROPULSE: A SEARCH FOR MICROSECOND TRANSIENT RADIO SIGNALS USING DISTRIBUTED COMPUTING. I. METHODOLOGY

    SciTech Connect

    Von Korff, J.; Heien, E.; Korpela, E.; Werthimer, D.; Cobb, J.; Lebofsky, M.; Anderson, D.; Bankay, B.; Siemion, A.; Demorest, P.

    2013-04-10

    We are performing a transient, microsecond timescale radio sky survey, called 'Astropulse', using the Arecibo telescope. Astropulse searches for brief (0.4 {mu}s to 204.8 {mu}s ), wideband (relative to its 2.5 MHz bandwidth) radio pulses centered at 1420 MHz. Astropulse is a commensal (piggyback) survey, and scans the sky between declinations of -1. Degree-Sign 33 and 38. Degree-Sign 03. We obtained 1540 hr of data in each of seven beams of the ALFA receiver, with two polarizations per beam. The data are one-bit complex sampled at the Nyquist limit of 0.4 {mu}s per sample. Examination of timescales on the order of microseconds is possible because we used coherent dedispersion, a technique that has frequently been used for targeted observations, but has never been associated with a radio sky survey. The more usual technique, incoherent dedispersion, cannot resolve signals below a minimum timescale which depends on the signal's dispersion measure (DM) and frequency. However, coherent dedispersion requires more intensive computation than incoherent dedispersion. The required processing power was provided by BOINC, the Berkeley Open Infrastructure for Network Computing. BOINC is a distributed computing system, allowing us to utilize hundreds of thousands of volunteers' computers to perform the necessary calculations for coherent dedispersion. Astrophysical events that might produce brief radio pulses include giant pulses from pulsars, rotating radio transients, exploding primordial black holes, or new sources yet to be imagined. Radio frequency interference and noise contaminate the data; these are mitigated by a number of techniques including multi-polarization correlation, DM repetition detection, and frequency profiling.

  7. Lipase-catalyzed fractionation of conjugated linoleic acid isomers.

    PubMed

    Haas, M J; Kramer, J K; McNeill, G; Scott, K; Foglia, T A; Sehat, N; Fritsche, J; Mossoba, M M; Yurawecz, M P

    1999-09-01

    The abilities of lipases produced by the fungus Geotrichum candidum to selectively fractionate mixtures of conjugated linoleic acid (CLA) isomers during esterification of mixed CLA free fatty acids and during hydrolysis of mixed CLA methyl esters were examined. The enzymes were highly selective for cis-9,trans-11-18:2. A commercial CLA methyl ester preparation, containing at least 12 species representing four positional CLA isomers, was incubated in aqueous solution with either a commercial G. candidum lipase preparation (Amano GC-4) or lipase produced from a cloned high-selectivity G. candidum lipase B gene. In both instances selective hydrolysis of the cis-9,trans-11-18:2 methyl ester occurred, with negligible hydrolysis of other CLA isomers. The content of cis-9, trans-11-18:2 in the resulting free fatty acid fraction was between 94 (lipase B reaction) and 77% (GC-4 reaction). The commercial CLA mixture contained only trace amounts of trans-9,cis-11-18:2, and there was no evidence that this isomer was hydrolyzed by the enzyme. Analogous results were obtained with these enzymes in the esterification in organic solvent of a commercial preparation of CLA free fatty acids containing at least 12 CLA isomers. In this case, G. candidum lipase B generated a methyl ester fraction that contained >98% cis-9,trans-11-18:2. Geotrichum candidum lipases B and GC-4 also demonstrated high selectivity in the esterification of CLA with ethanol, generating ethyl ester fractions containing 96 and 80%, respectively, of the cis-9,trans-11 isomer. In a second set of experiments, CLA synthesized from pure linoleic acid, composed essentially of two isomers, cis-9,trans-11 and trans-10,cis-12, was utilized. This was subjected to esterification with octanol in an aqueous reaction system using Amano GC-4 lipase as catalyst. The resulting ester fraction contained up to 97% of the cis-9,trans-11 isomer. After adjustment of the reaction conditions, a concentration of 85% trans-10,cis-12

  8. A new high-spin isomer in 195Bi

    NASA Astrophysics Data System (ADS)

    Roy, T.; Mukherjee, G.; Madhavan, N.; Rana, T. K.; Bhattacharya, Soumik; Asgar, Md. A.; Bala, I.; Basu, K.; Bhattacharjee, S. S.; Bhattacharya, C.; Bhattacharya, S.; Bhattacharyya, S.; Gehlot, J.; Ghugre, S. S.; Gurjar, R. K.; Jhingan, A.; Kumar, R.; Muralithar, S.; Nath, S.; Pai, H.; Palit, R.; Raut, R.; Singh, R. P.; Sinha, A. K.; Varughese, T.

    2015-11-01

    A new high-spin isomer has been identified in 195Bi at the focal plane of the HYbrid Recoil mass Analyser (HYRA) used in the gas-filled mode. The fusion evaporation reactions 169Tm (30Si, x n) 193, 195Bi were used with the beam energies on targets of 168 and 146MeV for 6n and 4n channels, respectively. The evaporation residues, separated from the fission fragments, and their decays were detected at the focal plane of HYRA using MWPC, Si-Pad and clover HPGe detectors. The half-life of the new isomer in 195Bi has been measured to be 1.6(1)μs. The configuration of the new isomer has been proposed and compared with the other isomers in this region. The Total Routhian Surface (TRS) calculations for the three-quasiparticle configurations corresponding to the new isomer suggest an oblate deformation for this isomeric state. The same calculations for different configurations in 195Bi and for the even-even 194Pb core indicate that the proton i 13/2 orbital has a large shape driving effect towards oblate shape in these nuclei.

  9. Two-quasiparticle isomer, E1 hindrances and residual interactions in {sup 172}Tm

    SciTech Connect

    Hughes, R. O.; Lane, G. J.; Dracoulis, G. D.; Kibedi, T.; Nieminen, P.; Watanabe, H.

    2008-04-15

    The structure of the neutron-rich nucleus {sup 172}Tm has been studied using incomplete fusion of {sup 7}Li on an {sup 170}Er target at 30 MeV. A 190-{mu}s isomer at an excitation energy of 476 keV was identified using chopped beams and {gamma}-ray spectroscopy. The isomer decays with very inhibited E1 transitions to the rotational bands based on the parallel and antiparallel couplings of the {nu}5/2{sup -}[512] x {pi}1/2{sup +}[411] configuration, the latter (K{sup {pi}}=2{sup -}) being the ground state. The isomeric state has been assigned J{sup {pi}}=6{sup +}, arising from the energetically favored (parallel) coupling of the {nu}5/2{sup -}[512] x {pi}7/2{sup -}[523] configuration. The proton-neutron residual interaction was deduced for the configuration of the isomeric state and is found to agree with previous empirical studies.

  10. Separation of Peptide Isomers with Variant Modified Sites by High-Resolution Differential Ion Mobility Spectrometry

    SciTech Connect

    Shvartsburg, Alexandre A.; Creese, Andrew; Smith, Richard D.; Cooper, Helen J.

    2010-10-01

    Many proteins and proteolytic peptides incorporate the same post-translational modification (PTM) at different sites, creating multiple localization variants with different functions or activities that may coexist in cells. Current analytical methods based on liquid chromatography (LC) followed by tandem mass spectrometry (MS/MS) are challenged by such isomers that often co-elute in LC and/or produce non-unique fragments. Application of ion mobility spectrometry (IMS) has previously been explored, but success was limited by insufficient resolution. We show that the recently developed high-resolution differential ion mobility spectrometry (FAIMS) using helium-rich gases can readily separate phosphopeptides with variant modified sites. Specifically, use of He/N2 mixtures containing up to 74% He has allowed separating to >95% three monophosphorylated peptides of identical sequence. Similar separation was achieved at 50% He, using an elevated electric field. Bisphosphorylated isomers that differ in only one modification site were separated to the same extent. We anticipate the FAIMS capabilities for such separations to extend to other PTMs.

  11. Separation of Peptide Isomers with Variant Modified Sites by High-Resolution Differential Ion Mobility Spectrometry

    PubMed Central

    Shvartsburg, Alexandre A.; Creese, Andrew J.; Smith, Richard D.; Cooper, Helen J.

    2010-01-01

    Many proteins and proteolytic peptides incorporate the same post-translational modification (PTM) at different sites, creating multiple localization variants with different functions or activities that may coexist in cells. Current analytical methods based on liquid chromatography (LC) followed by tandem mass spectrometry (MS/MS) are challenged by such isomers that often co-elute in LC and/or produce non-unique fragment ions. The application of ion mobility spectrometry (IMS) was explored, but success has been limited by insufficient resolution. We show that high-resolution differential ion mobility spectrometry (FAIMS) employing helium-rich gases can readily separate phosphopeptides with variant modification sites. Use of He/N2 mixtures containing up to 74% He has allowed separating to >95% three monophosphorylated peptides of identical sequence. Similar separation was achieved at 50% He, using an elevated electric field. Bisphosphorylated isomers that differ in only one modification site were separated to the same extent. We anticipate FAIMS capabilities for such separations to extend to other PTMs. PMID:20843012

  12. Near-IR absorbance changes and electrogenic reactions in the microsecond-to-second time domain in Photosystem I.

    PubMed Central

    Vassiliev, I R; Jung, Y S; Mamedov, M D; Semenov AYu; Golbeck, J H

    1997-01-01

    The back-reaction kinetics in Photosystem I (PS I) were studied on the microsecond-to-s time scale in cyanobacterial preparations, which differed in the number of iron-sulfur clusters to assess the contributions of particular components to the reduction of P700+. In membrane fragments and in trimeric P700-FA/FB complexes, the major contribution to the absorbance change at 820 nm (delta A820) was the back-reaction of FA- and/or FB- with lifetimes of approximately 10 and 80 ms (approximately 10% and 40% relative amplitude). The decay of photoinduced electric potential (delta psi) across a membrane with directionally incorporated P700-FA/FB complexes had similar kinetics. HgCl2-treated PS I complexes, which contain FA but no FB, retain both of these kinetic components, indicating that neither can be assigned uniquely to a specific acceptor. These results suggest that FA- reduces P700+ directly and argue for a rapid electron equilibration between FA and FB, which would eliminate their kinetic distinction in a back-reaction. In PsaC-depleted P700-Fx cores, as well as in P700-FA/FB complexes with chemically reduced FA and FB, the major contribution to the delta A820 and the delta psi decay is a biphasic back-reaction of F-X (approximately 400 microseconds and 1.5 ms) with some contribution from A-1 (approximately 10 microseconds and 100 microseconds), the latter of which is variable depending on experimental conditions. The delta A820 decay in a P700-A1 core devoid of all iron-sulfur clusters comprises two phases with lifetimes of 10 microseconds and 130 microseconds (2.7:1 ratio). The biexponential back-reaction kinetics found for each of the electron acceptors may be related to existence of different conformational states of the PS I complex. In all preparations studied, excitation at 532 nm with flash energies exceeding 10 mJ gives rise to formation of antenna 3Chl, which also contributes to delta A820 decay on the tens-of-microsecond time scale. A distinction between

  13. Preferential polymerization and adsorption of L-optical isomers of amino acids relative to D-optical isomers on kaolinite templates.

    NASA Technical Reports Server (NTRS)

    Jackson, T. A.

    1971-01-01

    Experiments on the polymerization of the L- and D-optical isomers of aspartic acid and serine using kaolinite as a catalyst showed that the L-optical isomers were polymerized at a much higher rate than the D-optical isomers; racemic (DL-) mixtures were polymerized at an intermediate rate. The peptides formed from the L-monomers were preferentially adsorbed by the clay. In the absence of kaolinite, no significant or consistent difference in the behavior of the L- and D-optical isomers was observed. In experiments on the adsorption of L- and D-phenylalanine by kaolinite, the L-optical isomer was preferentially adsorbed.

  14. Separation of glyceride positional isomers by silver ion chromatography.

    PubMed

    Févrie, P; Bine, A; Dufossé, L; Grée, R; Yvergnaux, F

    2001-07-20

    Separation of triglyceride and diglyceride positional isomers by silver ion high-performance liquid chromatography coupled with an evaporative light-scattering detector is described. The triglyceride isomers had a fatty acid composition of CLC and CCL, where C and L were caprylic acid and linoleic acid, respectively. Diglyceride isomers, 1,2(2,3)-diglyceride and 1,3-diglyceride, which contained caprylic acid were separated too. A solvent system based on n-hexane, 2-propanol, ethyl acetate, and acetonitrile with a flow-rate of 0.8 ml/min was developed. Calibration curves of CLC and CCL were achieved with triolein as internal standard. Using this method, the incorporation of linoleic acid onto specific a position of glycerol backbone can be monitored. PMID:11510559

  15. Identification of the isomers using principal component analysis (PCA) method

    NASA Astrophysics Data System (ADS)

    Kepceoǧlu, Abdullah; Gündoǧdu, Yasemin; Ledingham, Kenneth William David; Kilic, Hamdi Sukur

    2016-03-01

    In this work, we have carried out a detailed statistical analysis for experimental data of mass spectra from xylene isomers. Principle Component Analysis (PCA) was used to identify the isomers which cannot be distinguished using conventional statistical methods for interpretation of their mass spectra. Experiments have been carried out using a linear TOF-MS coupled to a femtosecond laser system as an energy source for the ionisation processes. We have performed experiments and collected data which has been analysed and interpreted using PCA as a multivariate analysis of these spectra. This demonstrates the strength of the method to get an insight for distinguishing the isomers which cannot be identified using conventional mass analysis obtained through dissociative ionisation processes on these molecules. The PCA results dependending on the laser pulse energy and the background pressure in the spectrometers have been presented in this work.

  16. Separation of branched hexane isomers using zeolite molecular sieves

    SciTech Connect

    Huddersman, K.; Klimczyk, M.

    1996-02-01

    A range of small, medium and large pore zeolite, and their modified forms are studied for their ability to separate di- from monobranched isomers of hexane. The separation studies are carried out using high-temperature (250--350 C) gas chromatography. Beta(H,Ba) is found to be the most effective separator of 2,3-dimethylbutane and 3-methyl-pentane and is therefore studied for its sorption capacities toward the two hexane isomers. This work is directed to the improvement of the quality of petrol by separating hydrocarbon mixtures using zeolites. Since maximum hydrocarbon branching is desirable in petrol (hydrocarbons with a branching structure burn more efficiently and thus have a higher octane rating), catalytic isomerization is used to isomerize straight-chain hydrocarbons to their mono- or dibranched isomers.

  17. Metastable isomers - A new class of interstellar molecules

    NASA Technical Reports Server (NTRS)

    Green, S.; Herbst, E.

    1979-01-01

    The abundances of a variety of metastable isomers of small organic molecules, analogous to HNC/HCN, in dense interstellar clouds are considered. These metastable species, some of which are thought to exist as intermediates in laboratory organic chemical reactions, are of considerable interest to chemists. Current ideas of gas-phase, ion-molecule chemistry are utilized to demonstrate that such metastable species should often be present in dense clouds in sufficient abundance to be observed. Unfortunately, the spectral constants of metastable isomers have rarely been determined in the laboratory, and quantum chemical calculations of a varying degree of accuracy must be utilized; results are included of some new quantum chemical calculations. The interstellar chemistry and expected microwave spectra of a representative sample of possibly important interstellar metastable isomers are discussed.

  18. FY2010 Annual Report for the Actinide Isomer Detection Project

    SciTech Connect

    Warren, Glen A.; Francy, Christopher J.; Ressler, Jennifer J.; Erikson, Luke E.; Miller, Erin A.; Hatarik, R.

    2011-01-01

    This project seeks to identify a new signature for actinide element detection in active interrogation. This technique works by exciting and identifying long-lived nuclear excited states (isomers) in the actinide isotopes and/or primary fission products. Observation of isomers in the fission products will provide a signature for fissile material. For the actinide isomers, the decay time and energy of the isomeric state is unique to a particular isotope, providing an unambiguous signature for Special Nuclear Materials (SNM). Future work will include a follow-up measurement scheduled for December 2010 at LBNL. Lessons learned from the July 2010 measurements will be incorporated into these new measurements. Analysis of both the July and December experiments will be completed in a few months. A research paper to be submitted to a peer-reviewed journal will be drafted if the conclusions from the measurements warrant publication.

  19. Spectroscopy of {sup 144}Ho using recoil-isomer tagging

    SciTech Connect

    Mason, P. J. R; Cullen, D. M.; Scholey, C.; Greenlees, P. T.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Nyman, M.; Peura, P.; Puurunen, A.; Rahkila, P.; Ruotsalainen, P.; Sorri, J.; Saren, J.; Uusitalo, J.; Xu, F. R.

    2010-02-15

    Excited states in the proton-unbound odd-odd nucleus {sup 144}Ho have been populated using the {sup 92}Mo({sup 54}Fe,pn){sup 144}Ho reaction and studied using the recoil-isomer-tagging technique. The alignment properties and signature splitting of the rotational band above the I{sup p}i=(8{sup +}){sup 144m}Ho isomer have been analyzed and the isomer confirmed to have a pih{sub 11/2} x nuh{sub 11/2} two-quasiparticle configuration. The configuration-constrained blocking method has been used to calculate the shapes of the ground and isomeric states, which are both predicted to have triaxial nuclear shapes with |gamma|approx =24 deg.

  20. Anaerobic degradation of phthalate isomers by methanogenic consortia

    SciTech Connect

    Kleerebezem, R.; Pol, L.W.H.; Lettinga, G.

    1999-03-01

    Three methanogenic enrichment cultures, grown on ortho-phthalate, iso-phthalate, or terephthalate were obtained from digested sewage sludge or methanogenic granular sludge. Cultures grown on one of the phthalate isomers were not capable of degrading the other phthalate isomers. All three cultures had the ability to degrade benzoate. Maximum specific growth rates ({mu}{sub S}{sup max}) and biomass yields (Y{sub X{sub tot}S}) of the mixed cultures were determined by using both the phthalate isomers and benzoate as substrates. Comparable values for these parameters were found for all three cultures. Values for {mu}{sub X}{sup max} and Y{sub X{sub tot}S} were higher for growth on benzoate compared to the phthalate isomers. Based on measured and estimated values for the microbial yield of the methanogens in the mixed culture, specific yields for the phthalate and benzoate fermenting organisms were calculated. A kinetic model, involving three microbial species, was developed to predict intermediate acetate and hydrogen accumulation and the final production of methane. Values for the ratio of the concentrations of methanogenic organisms, versus the phthalate isomer and benzoate fermenting organisms, and apparent half-saturation constants (K{sub S}) for the methanogens were calculated. By using this combination of measured and estimated parameter values, a reasonable description of intermediate accumulation and methane formation was obtained, with the initial concentration of phthalate fermenting organisms being the only variable. The energetic efficiency for growth of the fermenting organisms on the phthalate isomers was calculated to be significantly smaller than for growth on benzoate.

  1. Synthesis and characterization of tetrakis-silylated C60 isomers.

    PubMed

    Maeda, Yutaka; Rahman, G M Aminur; Wakahara, Takatsugu; Kako, Masahiro; Okamura, Mutsuo; Sato, Soichi; Akasaka, Takeshi; Kobayashi, Kaoru; Nagase, Shigeru

    2003-08-22

    A photochemical reaction of C(60) with disilane in a 2:3 ratio affords the isomer mixture of the tetrakis-adduct of C(60)((t)BuPh(2)Si)(4) as the major product. The use of a three-stage HPLC separation system isolated three of their isomers. Their structural assignments were based on FAB mass, UV-vis, NMR, and cyclic voltammetry (CV) measurements. The CV analysis showed that the terakis-adduct has lower oxidation and higher reduction potentials than the bis-adduct C(60)((t)BuPh(2)Si)(2) and the parent C(60). PMID:12919050

  2. Computation of Mössbauer isomer shifts from first principles

    NASA Astrophysics Data System (ADS)

    Zwanziger, J. W.

    2009-05-01

    Computation of the observables of a Mössbauer spectrum, primarily the isomer shift, from a first-principles approach is described. The framework used is density functional theory using the projector augmented wave formalism (DFT PAW), which enables efficient computation even of many-electron solids such as SnCl2. The proper PAW version of the isomer shift is derived and shown to be correct through comparison of computed shifts and experiment in a variety of compounds based on tin, germanium and zinc. The effects of pressure are considered as well as motional effects including the Lamb-Mössbauer factor and the second-order Doppler shift.

  3. New high spin isomers obtained in thermal fission

    SciTech Connect

    Fogelberg, B.; Mach, H.; Gausemel, H.; Omtvedt, J. P.; Mezilev, K. A.

    1998-10-26

    The product nuclei following fission often are initially highly excited and have high angular momenta. As a consequence, there is a substantial probability for the population of isomeric yrast traps in the vicinity of closed shells. The excitation energies and decay properties of such isomers give important formation regarding the shell structure and interaction energies. Recent experiments at the OSIRIS mass separator have revealed a number of isomers in the {sup 132}Sn region having angular momenta exceeding 10 units. A brief presentation is given of some experimental results and their interpretation.

  4. Isomer Triggering via Nuclear Excitation by Electron Capture

    SciTech Connect

    Palffy, Adriana; Evers, Joerg; Keitel, Christoph H.

    2007-10-26

    Triggering of long-lived nuclear isomeric states via coupling to the atomic shells in the process of nuclear excitation by electron capture (NEEC) is studied. NEEC occurring in highly charged ions can excite the isomeric state to a triggering level that subsequently decays to the ground state. We present total cross sections for NEEC isomer triggering considering experimentally confirmed low-lying triggering levels and reaction rates based on realistic experimental parameters in ion storage rings. A comparison with other isomer triggering mechanisms shows that, among these, NEEC is the most efficient.

  5. Differentiation of optical isomers through enhanced weak-field interactions

    NASA Technical Reports Server (NTRS)

    Aronowitz, S.

    1980-01-01

    The influence of weak field interaction terms due to the cooperative effects which arise from a macroscopic assemblage of interacting sites is studied. Differential adsorption of optical isomers onto an achiral surface is predicted to occur if the surface was continuous and sufficiently large. However, the quantity of discontinuous crystal surfaces did not enhance the percentage of differentiation and thus the procedure of using large quantities of small particles was not a viable technique for obtaining a detectable differentiation of optical isomers on an achiral surface.

  6. An Unusual Conformational Isomer of Verrucosidin Backbone from a Hydrothermal Vent Fungus, Penicillium sp. Y-50-10

    PubMed Central

    Pan, Chengqian; Shi, Yutong; Auckloo, Bibi Nazia; Chen, Xuegang; Chen, Chen-Tung Arthur; Tao, Xinyi; Wu, Bin

    2016-01-01

    A new verrucosidin derivative, methyl isoverrucosidinol (1), was isolated from the marine fungus Penicillium sp. Y-50-10, dwelling in sulfur rich sediment in the Kueishantao hydrothermal vents off Taiwan. The structure was established by spectroscopic means including HRMS and 2D-NMR spectroscopic analysis. The absolute configuration was defined mainly by comparison of quantum chemical TDDFT calculated and experimental ECD spectra. Among hitherto known compounds with a verrucosidine backbone isolated from natural resource, compound 1 represents the first example of a new conformational isomer of its skeleton, exhibiting antibiotic activity against Bacillus subtilis with MIC value 32 μg/mL. PMID:27548192

  7. An Unusual Conformational Isomer of Verrucosidin Backbone from a Hydrothermal Vent Fungus, Penicillium sp. Y-50-10.

    PubMed

    Pan, Chengqian; Shi, Yutong; Auckloo, Bibi Nazia; Chen, Xuegang; Chen, Chen-Tung Arthur; Tao, Xinyi; Wu, Bin

    2016-01-01

    A new verrucosidin derivative, methyl isoverrucosidinol (1), was isolated from the marine fungus Penicillium sp. Y-50-10, dwelling in sulfur rich sediment in the Kueishantao hydrothermal vents off Taiwan. The structure was established by spectroscopic means including HRMS and 2D-NMR spectroscopic analysis. The absolute configuration was defined mainly by comparison of quantum chemical TDDFT calculated and experimental ECD spectra. Among hitherto known compounds with a verrucosidine backbone isolated from natural resource, compound 1 represents the first example of a new conformational isomer of its skeleton, exhibiting antibiotic activity against Bacillus subtilis with MIC value 32 μg/mL. PMID:27548192

  8. Photoelectron Spectroscopy and Ab Initio Calculations of CS3(-) Isomers: Carbon Trisulfide and Carbon Disulfide S-Sulfide Anions.

    PubMed

    Nakanishi, Ryuzo; Kato, Shugo; Matsuyama, Yasushi; Nagata, Takashi

    2016-09-01

    Carbon sulfides are known as a class of binary compounds that can exist in various isomeric and/or polymeric forms. As for a sulfur-rich compound with the composition formula CS3, two possible constitutional isomers have been proposed experimentally or theoretically for the neutral species and its corresponding radical cation and anion. Although the previous studies claim that one isomer has a carbon trisulfide (CS3) C-centered configuration and the other has a carbon disulfide S-sulfide (SCSS) chain configuration, they have not yet been fully identified by a spectroscopic method. In this study, we have prepared the anions of those isomers in the gas phase by employing two types of reactions: dissociative electron attachment to 1,3-dithiole-2-thione for CS3(-) formation and the S(-) + CS2 ion-molecule reaction for SCSS(-). Photoelectron spectroscopic measurements reveal that the reactions result in the production of two anionic species that can be well distinguished by their vertical detachment energy. With the aid of ab initio calculations, they are identified distinctively as the anions of carbon trisulfide and carbon disulfide S-sulfide. PMID:27533492

  9. Solid-state NMR approaches to internal dynamics of proteins: from picoseconds to microseconds and seconds.

    PubMed

    Krushelnitsky, Alexey; Reichert, Detlef; Saalwächter, Kay

    2013-09-17

    Solid-state nuclear magnetic resonance (NMR) spectroscopy has matured to the point that it is possible to determine the structure of proteins in immobilized states, such as within microcrystals or embedded in membranes. Currently, researchers continue to develop and apply NMR techniques that can deliver site-resolved dynamic information toward the goal of understanding protein function at the atomic scale. As a widely-used, natural approach, researchers have mostly measured longitudinal (T1) relaxation times, which, like in solution-state NMR, are sensitive to picosecond and nanosecond motions, and motionally averaged dipolar couplings, which provide an integral amplitude of all motions with a correlation time of up to a few microseconds. While overall Brownian tumbling in solution mostly precludes access to slower internal dynamics, dedicated solid-state NMR approaches are now emerging as powerful new options. In this Account, we give an overview of the classes of solid-state NMR experiments that have expanded the accessible range correlation times from microseconds to many milliseconds. The measurement of relaxation times in the rotating frame, T1ρ, now allows researchers to access the microsecond range. Using our recent theoretical work, researchers can now quantitatively analyze this data to distinguish relaxation due to chemical-shift anisotropy (CSA) from that due to dipole-dipole couplings. Off-resonance irradiation allows researchers to extend the frequency range of such experiments. We have built multidimensional analogues of T2-type or line shape experiments using variants of the dipolar-chemical shift correlation (DIPSHIFT) experiment that are particularly suited to extract intermediate time scale motions in the millisecond range. In addition, we have continuously improved variants of exchange experiments, mostly relying on the recoupling of anisotropic interactions to address ultraslow motions in the ms to s ranges. The NH dipolar coupling offers a

  10. DNA-decorated carbon nanotube-based FETs as ultrasensitive chemical sensors: Discrimination of homologues, structural isomers, and optical isomers

    NASA Astrophysics Data System (ADS)

    Khamis, S. M.; Jones, R. A.; Johnson, A. T. C.; Preti, G.; Kwak, J.; Gelperin, A.

    2012-06-01

    We have explored the abilities of all-electronic DNA-carbon nanotube (DNA-NT) vapor sensors to discriminate very similar classes of molecules. We screened hundreds of DNA-NT devices against a panel of compounds chosen because of their similarities. We demonstrated that DNA-NT vapor sensors readily discriminate between series of chemical homologues that differ by single methyl groups. DNA-NT devices also discriminate among structural isomers and optical isomers, a trait common in biological olfactory systems, but only recently demonstrated for electronic FET based chemical sensors.

  11. A Comparative Study on the Effects of Millisecond- and Microsecond-Pulsed Electric Field Treatments on the Permeabilization and Extraction of Pigments from Chlorella vulgaris.

    PubMed

    Luengo, Elisa; Martínez, Juan Manuel; Coustets, Mathilde; Álvarez, Ignacio; Teissié, Justin; Rols, Marie-Pierre; Raso, Javier

    2015-10-01

    The interdependencies of the two main processing parameters affecting "electroporation" (electric field strength and pulse duration) while using pulse duration in the range of milliseconds and microseconds on the permeabilization, inactivation, and extraction of pigments from Chlorella vulgaris was compared. While irreversible "electroporation" was observed above 4 kV/cm in the millisecond range, electric field strengths of ≥10 kV/cm were required in the microseconds range. However, to cause the electroporation of most of the 90 % of the population of C. vulgaris in the millisecond (5 kV/cm, 20 pulses) or microsecond (15 kV/cm, 25 pulses) range, the specific energy that was delivered was lower for microsecond treatments (16.87 kJ/L) than in millisecond treatments (150 kJ/L). In terms of the specific energy required to cause microalgae inactivation, treatments in the microsecond range also resulted in greater energy efficiency. The comparison of extraction yields in the range of milliseconds (5 kV, 20 ms) and microseconds (20, 25 pulses) under the conditions in which the maximum extraction was observed revealed that the improvement in the carotenoid extraction was similar and chlorophyll a and b extraction was slightly higher for treatments in the microsecond range. The specific energy that was required for the treatment in the millisecond range (150 kJ/L) was much higher than those required in the microsecond range (30 kJ/L). The comparison of the efficacy of both types of pulses on the extraction enhancement just after the treatment and after a post-pulse incubation period seemed to indicate that PEF in the millisecond range created irreversible alterations while, in the microsecond range, the defects were a dynamic structure along the post-pulse time that caused a subsequent increment in the extraction yield. PMID:25819916

  12. Isomer-Specific Distribution of Perfluoroalkyl Substances in Blood.

    PubMed

    Jin, Hangbiao; Zhang, Yifeng; Jiang, Weiwei; Zhu, Lingyan; Martin, Jonathan W

    2016-07-19

    Perfluoroalkyl substances (PFASs) such as perfluorohexanesulfonate (PFHxS), perfluorooctanoate (PFOA), perfluorooctanesulfonate (PFOS) and PFOS-precursors are routinely measured in human plasma and serum, but their relative abundance in the blood cell fraction has not been carefully examined, particularly at the isomer-specific level. Human plasma and whole blood were collected and partitioning behaviors of PFASs and their isomers between plasma and blood cells were investigated. In human samples, mass fraction in plasma (Fp) for PFASs increased among perfluoroalkyl carboxylates as the carbon chain length increased from C6 (mean 0.24) to C11 (0.87), indicating preference for the plasma fraction with increasing chain length. However, among perfluoroalkyl sulfonates, PFHxS (mean 0.87) had a slightly higher Fp than PFOS (0.85). In vitro assays with spiked Sprague-Dawley rat blood were also conducted, and the results showed that PFOS-precursors had lower Fp values than perfluoroalkyl acids, with perfluoroctanesulfonamide having the lowest Fp (mean 0.24). Consistently, linear isomers of PFOS and PFOS-precursors had lower mean Fp than their corresponding total branched isomers. Multiplying by a factor of 2 is not a reasonable method to convert from whole blood to plasma PFAS concentrations, and current ratios could be used as more accurate conversion factors. PMID:27295125

  13. Short-lived isomers in 192Po and 194Po

    NASA Astrophysics Data System (ADS)

    Andel, B.; Andreyev, A. N.; Antalic, S.; Heßberger, F. P.; Ackermann, D.; Hofmann, S.; Huyse, M.; Kalaninová, Z.; Kindler, B.; Kojouharov, I.; Kuusiniemi, P.; Lommel, B.; Nishio, K.; Page, R. D.; Sulignano, B.; Van Duppen, P.

    2016-06-01

    Isomeric states in 194Po and 192Po were studied at the velocity filter SHIP. The isotopes were produced in the fusion-evaporation reactions 141Pr(56Fe, p 2 n )194Po and 144Sm(51V, p 2 n )192Po . Several new γ -ray transitions were attributed to the isomers and γ -γ coincidences for both isomers were studied for the first time. The 459-keV transition earlier, tentatively proposed as de-exciting the isomeric level in 194Po, was replaced by a new 248-keV transition, and the spin of this isomer was reassigned from (11-) to (10-). The de-excitation of the (11-) isomeric level in 192Po by the 154-keV transition was confirmed and a parallel de-excitation by a 733-keV (E 3 ) transition to (8+) level of the ground-state band was suggested. Moreover, side feeding to the (4+) level of the ground-state band was proposed. The paper also discusses strengths of transitions de-exciting 11- isomers in neighboring Po and Pb isotopes.

  14. Conjugated Linoleic Acids and Inflammation: Isomer and Tissue Specific Responses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Conjugated linoleic acids (CLAs) are a series of geometric and positional isomers of linoleic acid that have been studied for their effects against diabetes, cancer, and atherosclerosis, all conditions with an inflammatory component. Despite the continued interest in CLA, there are many controversi...

  15. Enantioselective separation of defined endocrine-disrupting nonylphenol isomers.

    PubMed

    Acir, Ismail-Hakki; Wüst, Matthias; Guenther, Klaus

    2016-08-01

    Nonylphenol is in the focus of worldwide endocrine-disrupter research and accounted for as a priority hazardous substance of the Water Framework Directive of the European Union. Technical nonylphenol consists of a very complex mixture of isomers and enantiomers. As estrogenic effect and degradation behavior in environmental processes of single nonylphenols are heavily dependent on the structure of the nonyl side chain, it is absolutely necessary to consider the nonylphenol problem from an isomer and enantiomer-specific viewpoint. In this study, an enantiomer-specific separation of eight defined synthesized nonylphenol isomers by five different special chiral cyclodextrin columns was performed underivatized and after methylation, silylation, and acylation. This work demonstrates that three columns out of the investigated five show an excellent separation behavior for the studied different nonylphenol isomers and can be used for the enantiomer-specific determination of nonylphenols in food, other biological matrices, and environmental samples in the future. Graphical abstract Enantiomeric pair of 4-NP170 (4-[1-ethyl-1,3,3-trimethylbutyl]phenol). PMID:27236316

  16. Flexible metal–organic supramolecular isomers for gas separation

    SciTech Connect

    Motkuri, Radha K.; Tian, Jian; Thallapally, Praveen K.; Fernandez, Carlos A.; Dalgarno, Scott J.; Warren, John E.; McGrail, B. Peter; Atwood, Jerry L.

    2010-01-01

    Here in we report three porous metal-organic supramolecular isomers (PtS, Diamondoid and Lonsdaleite networks) generated from a single building block (tetrakis[4-(carboxyphenyl)oxamethyl]methane, 1), with the differences in solid-state packing, amount of gas uptake and selectivity towards other gases and so on

  17. Identification of position isomers by energy-resolved mass spectrometry.

    PubMed

    Menachery, Sunil Paul M; Laprévote, Olivier; Nguyen, Thao P; Aravind, Usha K; Gopinathan, Pramod; Aravindakumar, Charuvila T

    2015-07-01

    This study reports an energy-resolved mass spectrometric (ERMS) strategy for the characterization of position isomers derived from the reaction of hydroxyl radicals ((●)OH) with diphenhydramine (DPH) that are usually hard to differentiate by other methods. The isomer analogues formed by (●)OH attack on the side chain of DPH are identified with the help of a specific fragment ion peak (m/z 88) in the collision-induced dissociation (CID) spectrum of the protonated molecule. In the negative ion mode, the breakdown curves of the deprotonated molecules show an order of stability (supported by density functional theory (DFT) calculations) ortho > meta > para of the positional isomers formed by the hydroxylation of the aromatic ring. The gas phase stability of the deprotonated molecules [M - H](-) towards the benzylic cleavage depends mainly on the formation of intramolecular hydrogen bonds and of the mesomeric effect of the phenol hydroxyl. The [M - H](-) molecules of ortho and meta isomers result a peak at m/z 183 with notably different intensities because of the presence/absence of an intramolecular hydrogen bonding between the OH group and C9 protons. The ERMS approach discussed in this report might be an effective replacement for the conventional methods that requires very costly and time-consuming separation/purification methods along with the use of multi-spectroscopic methods. PMID:26349650

  18. Identification of a shape isomer in 235U.

    PubMed

    Oberstedt, A; Oberstedt, S; Gawrys, M; Kornilov, N

    2007-07-27

    The shape isomer in 235U has been searched for in a neutron-induced fission experiment on 234U, which was performed at the isomer spectrometer NEPTUNE of the EC-JRC IRMM. A neutron source, with a tunable pulse frequency in the Hz to kHz range and its individually adjustable neutron pulse width in connection with an appropriate detector system turned out to be the ideal instrument to perform an isomer search, when decay half-lives above 100 micros are expected. From the delayed fission events observed for two different NEPTUNE settings and at mean incident neutron energies En=0.95 and 1.27 MeV the isomeric fission half-life could be determined to be T1/2=(3.6+/-1.8) ms. The corresponding cross section was determined to sigmaif=(10+/-8) microb. With these results an experimental confirmation for the existence of a superdeformed shape isomer in odd-uranium isotopes is given for the first time. PMID:17678355

  19. Electronic Structure Mediated Vibrational Coherence in Methyl Acetophenone Isomers

    NASA Astrophysics Data System (ADS)

    Konar, Arkaprabha; Shu, Yinan; Lozovoy, Vadim; Levine, Benjamin; Dantus, Marcos

    2014-05-01

    The role of ground and excited state electronic structures in influencing the vibrational coherences in gas phase polyatomic molecules has been a hot topic for quite some time. Here we explore the time resolved dynamics of acetophenone and its methyl substituted isomer when excited by intense 800nm femtosecond pump and probe pulses. The parent ion yield show 500 fs modulations that die down within 3ps. Similar modulations having the same timescales in the parent ion yield are also observed for the p-methyl isomer. The o-methyl isomer however shows longer 1ps modulations. Interestingly enough no oscillations are observed for the meta isomer. Quantum chemical calculations at the CASSCF/6-311G level of theory predicts that upon excitation the neutral ground state is planar and the energy spacing between the levels is very small. Preliminary calculations also predict torsional motion coupled to electronic modulations on the D0 state and further calculations are being performed to ascertain the involvement of the D1 and D2 states. This could help us better understand the electronic effect of substitution on a benzene ring.

  20. Electronic Structure Mediated Vibrational Coherence in Methyl Acetophenone Isomers

    NASA Astrophysics Data System (ADS)

    Konar, Arkaprabha; Shu, Yinan; Levine, Benjamin; Lozovoy, Vadim; Dantus, Marcos

    2014-03-01

    The role of ground and excited state electronic structures in influencing the vibrational coherences in gas phase polyatomic molecules has been a hot topic for quite some time. Here we explore the time resolved dynamics of acetophenone and its methyl substituted isomer when excited by intense 800nm femtosecond pump and probe pulses. The parent ion yield show 500 fs modulations that die down within 3ps. Similar modulations having the same timescales in the parent ion yield are also observed for the p-methyl isomer. The o-methyl isomer however shows longer 1ps modulations. Interestingly enough no oscillations are observed for the meta isomer. Quantum chemical calculations at the CASSCF/6-311G level of theory predicts that upon excitation the neutral ground state is planar and the energy spacing between the levels is very small. Preliminary calculations also predict torsional motion coupled to electronic modulations on the D0 state and further calculations are being performed to ascertain the involvement of the D1 and D2 states. This could help us better understand the electronic effect of substitution on a benzene ring.

  1. Fuel properties of heptadecene isomers prepared via tandem isomerization-decarboxylation of oleic acid

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heptadecene isomers were prepared via tandem isomerization-decarboxylation of oleic acid using catalytic triruthenium dodecacarbonyl [Ru3(CO)12]. Chromatographic and spectroscopic characterization of the isolated heptadecene mixture indicated that it consisted of 96% internal isomers and 4% aromatic...

  2. Computational Docking of the Isomers of Nonylphenol to the Ligand Binding Domain of the Estrogen Receptor

    EPA Science Inventory

    Nonylphenols are environmentally persistent endocrine disrupting chemicals. They exist in the environment as complex mixtures containing many nonylphenol isomers. Environmental mixtures of nonylphenols, along with a few single isomers have been tested for their capacity to inte...

  3. FY2011 Annual Report for the Actinide Isomer Detection Project

    SciTech Connect

    Warren, Glen A.; Francy, Christopher J.; Ressler, Jennifer J.; Erikson, Luke E.; Tatishvili, Gocha; Hatarik, R.

    2011-10-01

    This project seeks to identify a new signature for actinide element detection in active interrogation. This technique works by exciting and identifying long-lived nuclear excited states (isomers) in the actinide isotopes and/or primary fission products. Observation of isomers in the fission products will provide a signature for fissile material. For the actinide isomers, the decay time and energy of the isomeric state is unique to a particular isotope, providing an unambiguous signature for SNM. This project entails isomer identification and characterization and neutron population studies. This document summarizes activities from its third year - completion of the isomer identification characterization experiments and initialization of the neutron population experiments. The population and decay of the isomeric state in 235U remain elusive, although a number of candidate gamma rays have been identified. In the course of the experiments, a number of fission fragment isomers were populated and measured [Ressler 2010]. The decays from these isomers may also provide a suitable signature for the presence of fissile material. Several measurements were conducted throughout this project. This report focuses on the results of an experiment conducted collaboratively by PNNL, LLNL and LBNL in December 2010 at LBNL. The measurement involved measuring the gamma-rays emitted from an HEU target when bombarded with 11 MeV neutrons. This report discussed the analysis and resulting conclusions from those measurements. There was one strong candidate, at 1204 keV, of an isomeric signature of 235U. The half-life of the state is estimated to be 9.3 {mu}s. The measured time dependence fits the decay time structure very well. Other possible explanations for the 1204-keV state were investigated, but they could not explain the gamma ray. Unfortunately, the relatively limited statistics of the measurement limit, and the lack of understanding of some of the systematic of the experiment, limit

  4. Ultrafast x-ray photoelectron spectroscopy in the microsecond time domain

    NASA Astrophysics Data System (ADS)

    Höfert, O.; Gleichweit, C.; Steinrück, H.-P.; Papp, C.

    2013-09-01

    We introduce a new approach for ultrafast in situ high-resolution X-ray photoelectron spectroscopy (XPS) to study surface processes and reaction kinetics on the microsecond timescale. The main idea is to follow the intensity at a fixed binding energy using a commercial 7 channeltron electron analyzer with a modified signal processing setup. This concept allows for flexible switching between measuring conventional XP spectra and ultrafast XPS. The experimental modifications are described in detail. As an example, we present measurements for the adsorption and desorption of CO on Pt(111), performed at the synchrotron radiation facility BESSY II, with a time resolution of 500 μs. Due to the ultrafast measurements, we are able to follow adsorption and desorption in situ at pressures of 2 × 10-6 mbar and temperatures up to 500 K. The data are consistently analyzed using a simple model in line with data obtained with conventional fast XPS at temperatures below 460 K. Technically, our new approach allows measurement on even shorter timescales, down to 20 μs.

  5. Microsecond gain-switched master oscillator power amplifier (1958 nm) with high pulse energy

    SciTech Connect

    Ke Yin; Weiqiang Yang; Bin Zhang; Ying Li; Jing Hou

    2014-02-28

    An all-fibre master oscillator power amplifier (MOPA) emitting high-energy pulses at 1958 nm is presented. The seed laser is a microsecond gain-switched thulium-doped fibre laser (TDFL) pumped with a commercial 1550-nm pulsed fibre laser. The TDFL operates at a repetition rate f in the range of 10 to 100 kHz. The two-stage thulium-doped fibre amplifier is built to scale the energy of the pulses generated by the seed laser. The maximum output pulse energy higher than 0.5 mJ at 10 kHz is achieved which is comparable with the theoretical maximum extractable pulse energy. The slope efficiency of the second stage amplifier with respect to the pump power is 30.4% at f = 10 kHz. The wavelength of the output pulse laser is centred near 1958 nm at a spectral width of 0.25 nm after amplification. Neither nonlinear effects nor significant amplified spontaneous emission (ASE) is observed in the amplification experiments. (lasers)

  6. Studies of the dynamics of a 1-microsecond X-pinch

    NASA Astrophysics Data System (ADS)

    Appartaim, Richard; Green, Danielle

    2015-11-01

    The 1- μs X-pinch (0.3 kA/ns) has been shown to produce intense soft x-rays with a spatially reproducible source location and fine size (i .e . < 10 μm) . For certain applications these x-rays are comparable in their utility to those produced on pulsed-power devices but have the advantage of a much lower component of hard x-rays. Many of the critical plasma dynamics are also similar to those observed in the fast rise-time (1 kA/ns) experiments. However, the longer rise time of the microsecond discharge can lead to important differences in wire ablation rates and transition to coronal plasma, plasma current distribution and plasma dynamics. We present recent results of these plasma dynamics using optical techniques such as shadowgraphy, schlieren and framing photography, as well as x-ray observation techniques including filtered PCD and Si diode measurements, pinhole photography and x-ray spectroscopy. We demonstrate potential applications including the relevance of the observed plasma jets to astrophysical jets. Supported by DOE Grant DE-FG02-0547253ER.

  7. Three-dimensional multispectral hand-held optoacoustic imaging with microsecond-level delayed laser pulses

    NASA Astrophysics Data System (ADS)

    Deán-Ben, X. L.; Bay, Erwin; Razansky, Daniel

    2015-03-01

    Three-dimensional hand-held optoacoustic imaging comes with important advantages that prompt the clinical translation of this modality, with applications envisioned in cardiovascular and peripheral vascular disease, disorders of the lymphatic system, breast cancer, arthritis or inflammation. Of particular importance is the multispectral acquisition of data by exciting the tissue at several wavelengths, which enables functional imaging applications. However, multispectral imaging of entire three-dimensional regions is significantly challenged by motion artefacts in concurrent acquisitions at different wavelengths. A method based on acquisition of volumetric datasets having a microsecond-level delay between pulses at different wavelengths is described in this work. This method can avoid image artefacts imposed by a scanning velocity greater than 2 m/s, thus, does not only facilitate imaging influenced by respiratory, cardiac or other intrinsic fast movements in living tissues, but can achieve artifact-free imaging in the presence of more significant motion, e.g., abrupt displacements during handheld-mode operation in a clinical environment.

  8. Microsecond regime optical cross connect: 32 port to 32 port scalable device

    NASA Astrophysics Data System (ADS)

    Lynn, Brittany; Miles, Alexander; Blanche, Pierre-Alexandre; Wissinger, John; Carothers, Daniel; Norwood, Robert A.; Peyghambarian, N.

    2014-03-01

    Presented here is a 32 × 32 optical switch for telecommunications applications capable of reconfiguring at speeds of up to 12 microseconds. The free space switching mechanism in this interconnect is a digital micromirror device (DMD) consisting of a 2D array of 10.8μm mirrors optimized for implementation at 1.55μm. Hinged along one axis, each micromirror is capable of accessing one of two positions in binary fashion. In general reflection based applications this corresponds to the ability to manifest only two display states with each mirror, but by employing this binary state system to display a set of binary amplitude holograms, we are able to access hundreds of distinct locations in space. We previously demonstrated a 7 × 7 switch employing this technology, providing a proof of concept device validating our initial design principles but exhibiting high insertion and wavelength dependent losses. The current system employs 1920 × 1080 DMD, allowing us to increase the number of accessible ports to 32 × 32. Adjustments in imaging, coupling component design and wavelength control were also made in order to improve the overall loss of the switch. This optical switch performs in a bit-rate and protocol independent manner, enabling its use across various network fabrics and data rates. Additionally, by employing a diffractive switching mechanism, we are able to implement a variety of ancillary features such as dynamic beam pick-off for monitoring purposes, beam division for multicasting applications and in situ attenuation control.

  9. Ultrafast x-ray photoelectron spectroscopy in the microsecond time domain

    SciTech Connect

    Höfert, O.; Gleichweit, C.; Steinrück, H.-P.; Papp, C.

    2013-09-15

    We introduce a new approach for ultrafast in situ high-resolution X-ray photoelectron spectroscopy (XPS) to study surface processes and reaction kinetics on the microsecond timescale. The main idea is to follow the intensity at a fixed binding energy using a commercial 7 channeltron electron analyzer with a modified signal processing setup. This concept allows for flexible switching between measuring conventional XP spectra and ultrafast XPS. The experimental modifications are described in detail. As an example, we present measurements for the adsorption and desorption of CO on Pt(111), performed at the synchrotron radiation facility BESSY II, with a time resolution of 500 μs. Due to the ultrafast measurements, we are able to follow adsorption and desorption in situ at pressures of 2 × 10{sup −6} mbar and temperatures up to 500 K. The data are consistently analyzed using a simple model in line with data obtained with conventional fast XPS at temperatures below 460 K. Technically, our new approach allows measurement on even shorter timescales, down to 20 μs.

  10. Mechanisms of allosteric gene regulation by NMR quantification of microsecond-millisecond protein dynamics.

    PubMed

    Kleckner, Ian R; Gollnick, Paul; Foster, Mark P

    2012-01-13

    The trp RNA-binding attenuation protein (TRAP) is a paradigmatic allosteric protein that regulates the tryptophan biosynthetic genes associated with the trp operon in bacilli. The ring-shaped 11-mer TRAP is activated for recognition of a specific trp-mRNA target by binding up to 11 tryptophan molecules. To characterize the mechanisms of tryptophan-induced TRAP activation, we have performed methyl relaxation dispersion (MRD) nuclear magnetic resonance (NMR) experiments that probe the time-dependent structure of TRAP in the microsecond-to-millisecond "chemical exchange" time window. We find significant side chain flexibility localized to the RNA and tryptophan binding sites of the apo protein and that these dynamics are dramatically reduced upon ligand binding. Analysis of the MRD NMR data provides insights into the structural nature of transiently populated conformations sampled in solution by apo TRAP. The MRD data are inconsistent with global two-state exchange, indicating that conformational sampling in apo TRAP is asynchronous. These findings imply a temporally heterogeneous population of structures that are incompatible with RNA binding and substantiate the study of TRAP as a paradigm for probing and understanding essential dynamics in allosteric, regulatory proteins. PMID:22115774

  11. [Microsecond Pulsed Hollow Cathode Lamp as Enhanced Excitation Source of Hydride Generation Atomic Fluorescence Spectrometry].

    PubMed

    Zhang, Shuo

    2015-09-01

    The spectral, electrical and atomic fluorescence characteristics of As, Se, Sb and Pb hollow cathode lamps (HCLs) powered by a laboratory-built high current microsecond pulse (HCMP) power supply were studied, and the feasibility of using HCMP-HCLs as the excitation source of hydride generation atomic fluorescence spectrometry (HG-AFS) was evaluated. Under the HCMP power supply mode, the As, Se, Sb, Pb HCLs can maintain stable glow discharge at frequency of 100~1000 Hz, pulse width of 4.0~20 μs and pulse current up to 4.0 A. Relationship between the intensity of characteristic emission lines and HCMP power supply parameters, such as pulse current, power supply voltage, pulse width and frequency, was studied in detail. Compared with the conventional pulsed (CP) HCLs used in commercial AFS instruments, HCMP-HCLs have a narrower pulse width and much stronger pulse current. Under the optimized HCMP power supply parameters, the intensity of atomic emission lines of As, Se, Sb HCLs had sharp enhancement and that indicated their capacity of being a novel HG-AFS excitation source. However, the attenuation of atomic lines and enhancement of ionic lines negated such feasibility of HCMP-Pb HCL. Then the HG-AFS analytical capability of using the HCMP-As/Se/Sb HCLs excitation source was established and results showed that the HCMP-HCL is a promising excitation source for HG-AFS. PMID:26669140

  12. Evaluating Letter Recognition, Flicker Fusion, and the Talbot-Plateau Law using Microsecond-Duration Flashes

    PubMed Central

    Greene, Ernest

    2015-01-01

    Four experiments examined the ability of respondents to identify letters that were displayed on an LED array with flashes lasting little more than a microsecond. The first experiment displayed each letter with a single, simultaneous flash of all the dots forming the letter and established the relation of flash intensity to the probability of letter identification. The second experiment displayed the letters with multiple flashes at different frequencies to determine the probability that the sequence of flashes would be perceived as fused. The third experiment displayed the letters at a frequency that was above the flicker-fusion frequency, varying flash intensity to establish the amount needed to elicit a given probability of letter identification. The fourth experiment displayed each letter twice, once at a frequency where no flicker was perceived and also with steady light emission. The intensity of each flash was fixed and the steady intensity was varied; respondents were asked to judge whether the fused-flicker display and the steady display appeared to be the same brightness. Steady intensity was about double the average flash intensity where the two conditions were perceived as being equal in brightness. This is at odds with Talbot-Plateau law, which predicts that these two values should be equal. The law was formulated relative to a flash lasting half of each period, so it is surprising that it comes this close to being correct where the flash occupies only a millionth of the total period. PMID:25875652

  13. Investigating the allosteric reverse signalling of PARP inhibitors with microsecond molecular dynamic simulations and fluorescence anisotropy.

    PubMed

    Marchand, Jean-Rémy; Carotti, Andrea; Passeri, Daniela; Filipponi, Paolo; Liscio, Paride; Camaioni, Emidio; Pellicciari, Roberto; Gioiello, Antimo; Macchiarulo, Antonio

    2014-10-01

    The inhibition of the poly(ADP-ribose) polymerase (PARP) family members is a strategy pursued for the development of novel therapeutic agents in a range of diseases, including stroke, cardiac ischemia, cancer, inflammation and diabetes. Even though some PARP-1 inhibitors have advanced to clinical setting for cancer therapy, a great deal of attention is being devoted to understand the polypharmacology of current PARP inhibitors. Besides blocking the catalytic activity, recent works have shown that some PARP inhibitors exhibit a poisoning activity, by trapping the enzyme at damaged sites of DNA and forming cytotoxic complexes. In this study we have used microsecond molecular dynamics to study the allosteric reverse signalling that is at the basis of such an effect. We show that Olaparib, but not Veliparib and HYDAMTIQ, is able to induce a specific conformational drift of the WGR domain of PARP-1, which stabilizes PARP-1/DNA complex through the locking of several salt bridge interactions. Fluorescence anisotropy assays support such a mechanism, providing the first experimental evidence that HYDAMTIQ, a potent PARP inhibitor with neuroprotective properties, is less potent than Olaparib to trap PARP-1/DNA complex. PMID:25062913

  14. Microsecond protein dynamics measured by 13Calpha rotating-frame spin relaxation.

    PubMed

    Lundström, Patrik; Akke, Mikael

    2005-09-01

    NMR spin relaxation in the rotating frame (R1rho) is a unique method for atomic-resolution characterization of conformational (chemical) exchange processes occurring on the microsecond timescale. We present a rotating-frame 13C(alpha) relaxation dispersion experiment for measuring conformational dynamics in uniformly 13C-labeled proteins. The experiment was validated by using the E140Q mutant of the C-terminal fragment of calmodulin, which exhibits significant conformational exchange between two major conformations, as gauged from previous 15N and 1H relaxation studies. Consistent with previous work, the present 13C(alpha) R1rho experiment detects conformational-exchange dynamics throughout the protein. The average correlation time of =25+/-8 micros is in excellent agreement with those determined previously from 1H and 15N R1rho relaxation data: =19+/-7 and 21+/-3 micros, respectively. The extracted chemical-shift differences between the exchanging states reveal significant fluctuations in dihedral angles within single regions of Ramachandran phi-psi space, that were not identified from the 1H and 15N relaxation data. The present results underscore the advantage of using several types of nuclei to probe exchange dynamics in biomolecules. PMID:16028301

  15. Microsecond folding and domain motions of a spider silk protein structural switch.

    PubMed

    Ries, Julia; Schwarze, Simone; Johnson, Christopher M; Neuweiler, Hannes

    2014-12-10

    Web spiders rapidly assemble protein monomers, so-called spidroins, into extraordinarily tough silk fibers. The process involves the pH-triggered self-association of the spidroin N-terminal domain (NTD), which contains a structural switch connecting spidroins to supermolecules. Single-molecule spectroscopy can detect conformational heterogeneity that is hidden to conventional methods, but motions of the NTD are beyond the resolution limit. Here, we engineered probes for 1 nm conformational changes based on the phenomenon of fluorescence quenching by photoinduced electron transfer into the isolated NTD of a spidroin from the nursery web spider Euprosthenops australis. Correlation analysis of single-molecule fluorescence fluctuations uncovered site-dependent nanosecond-to-microsecond movement of secondary and tertiary structure. Kinetic amplitudes were most pronounced for helices that are part of the association interface and where structural studies show large displacements between monomeric and dimeric conformations. A single tryptophan at the center of the five-helix bundle toggled conformations in ∼100 μs and in a pH-dependent manner. Equilibrium denaturation and temperature-jump relaxation experiments revealed cooperative and ultrafast folding in only 60 μs. We deduced a free-energy surface that exhibits native-state ruggedness with apparently similar barrier heights to folding and native motions. Observed equilibrium dynamics within the domain suggest a conformational selection mechanism in the rapid association of spidroins through their NTDs during silk synthesis by web spiders. PMID:25382060

  16. Production of long-lived hafnium isomers in reactor irradiations

    NASA Astrophysics Data System (ADS)

    Karamian, S. A.; Carroll, J. J.; Adam, J.; Kulagin, E. N.; Shabalin, E. P.

    2006-06-01

    Experiments on production of long-lived Hf178m isomer in reactor irradiations are described. Properties of this nuclide are promising for its potential application as a relatively safe power source characterized by high density of accumulated energy. Metal natHf samples were activated in the Dubna IBR-2 reactor at positions corresponding to different neutron fluxes. Samples were bare or shielded by Cd and B 4C layers. The gamma activity of the samples was analyzed with Ge gamma spectrometers during a two-year period following their irradiation. In the presence of dominant activation products 175Hf and 181Hf, the high-spin isomers Hf178m and Hf179m were also detected despite relatively low levels. The isomer-to-ground state ratios and cross-sections were determined from the measured yields. For Hf178m, the cross-section for burnup (destruction) by neutron capture after its production was also estimated, clarifying the results from earlier experiments. In the context of suggestions for use of Hf178m for applications, the results confirm that large-scale production of this isomer by reactor irradiations is not feasible. In contrast, the efficiency of production of Hf179m is much higher and an amount of about 10 16 atoms may be produced in standard reactor irradiations. For Hf178m, more productive methods are known, in particular fast neutron irradiations at E n ≥ 14 MeV and spallation reactions at intermediate energies. Neutron cross-sections for isomers may also be significant in astrophysics.

  17. Isomer-specific combustion chemistry in allene and propyne flames

    SciTech Connect

    Hansen, Nils; Miller, James A.; Westmoreland, Phillip R.; Kasper, Tina; Kohse-Hoeinghaus, Katharina; Wang, Juan; Cool, Terrill A.

    2009-11-15

    A combined experimental and modeling study is performed to clarify the isomer-specific combustion chemistry in flames fueled by the C{sub 3}H{sub 4} isomers allene and propyne. To this end, mole fraction profiles of several flame species in stoichiometric allene (propyne)/O{sub 2}/Ar flames are analyzed by means of a chemical kinetic model. The premixed flames are stabilized on a flat-flame burner under a reduced pressure of 25 Torr (=33.3 mbar). Quantitative species profiles are determined by flame-sampling molecular-beam mass spectrometry, and the isomer-specific flame compositions are unraveled by employing photoionization with tunable vacuum-ultraviolet synchrotron radiation. The temperature profiles are measured by OH laser-induced fluorescence. Experimental and modeled mole fraction profiles of selected flame species are discussed with respect to the isomer-specific combustion chemistry in both flames. The emphasis is put on main reaction pathways of fuel consumption, of allene and propyne isomerization, and of isomer-specific formation of C{sub 6} aromatic species. The present model includes the latest theoretical rate coefficients for reactions on a C{sub 3}H{sub 5} potential [J.A. Miller, J.P. Senosiain, S.J. Klippenstein, Y. Georgievskii, J. Phys. Chem. A 112 (2008) 9429-9438] and for the propargyl recombination reactions [Y. Georgievskii, S.J. Klippenstein, J.A. Miller, Phys. Chem. Chem. Phys. 9 (2007) 4259-4268]. Larger peak mole fractions of propargyl, allyl, and benzene are observed in the allene flame than in the propyne flame. In these flames virtually all of the benzene is formed by the propargyl recombination reaction. (author)

  18. Cyclodextrin and its complexation for resolution of isomers using diffusion ordered spectroscopy

    NASA Astrophysics Data System (ADS)

    Chaudhari, Sachin R.; Srinivasa; Suryaprakash, N.

    2013-02-01

    Diffusion ordered spectroscopy (DOSY) generally fails to separate the peaks pertaining to isomeric species possessing identical molecular weights and similar hydrodynamic radii. The present study demonstrates the resolution of isomers using α/β-cyclodextrin as a co-solute by Matrix Assisted Diffusion Ordered Spectroscopy. The resolution of isomers has been achieved by measuring the significant differences in the diffusion rates between the positional isomers of aminobenzoic acids, benzenedicarboxylic acids and between the cis, trans isomers, fumaric acid and maleic acid.

  19. Effects of diffusion on energy transfer in solution using a microsecond decay time rhenium metal ligand complex as the donor

    NASA Astrophysics Data System (ADS)

    Kuśba, Józef; Piszczek, Grzegorz; Gryczynski, Ignacy; Johnson, Michael L.; Lakowicz, Joseph R.

    2000-03-01

    We used resonance energy transfer and frequency-domain fluorometry to measure slow donor to acceptor diffusion in viscous media. The frequency-domain RET data were analyzed using a new numerical algorithm for predicting the donor intensity decay in the presence of diffusion occurring within the donor decay time. By the use of a rhenium metal-ligand complex as a microsecond decay time donor we were able to measure mutual donor-to-acceptor diffusion coefficients as low as 2×10 -8 cm 2/s. The availability of microsecond decay time luminophores and appropriate theory suggests the use of diffusion-enhanced energy transfer for measurement of diffusive processes and structural dynamics in biological systems.

  20. Isomer-specific biodegradation of nonylphenol in an activated sludge bioreactor and structure-biodegradability relationship.

    PubMed

    Lu, Zhijiang; Reif, Rubén; Gan, Jay

    2015-01-01

    Nonylphenol (NP), one of the priority hazardous substances, is in fact a mixture of numerous isomers. It is inconclusive whether or not biodegradation during wastewater treatment process is isomer-specific, leading to the environmental release of NP in different isomer profiles. In this study, we evaluated the isomer selectivity of 19 NP isomers in a laboratory-scale continuous flow conventional activated sludge bioreactor under various operational conditions. The removal efficiency of NP isomers ranged from 90 to 99%, depending on the operational conditions and isomer structures. Isomer selective biodegradation resulted in the increase of composition of recalcitrant isomers, such as, NP₁₉₃a/b, NP₁₁₀a and NP₁₉₄ in the effluent. Moreover, biodegradability was related to the bulkiness of α-substituents and followed α-dimethyl > α-ethyl-α-methyl > α-methyl-α-n-propyl > α-iso-propyl-α-methyl. Steric effect index, a quantitative descriptor of steric hindrance, was linearly correlated with residues of NP isomers in the effluent (R² = 0.76). Decrease of temperature to 10 °C decreased the overall biodegradability and also enhanced the relative enrichment of recalcitrant isomers. These findings suggest that isomer compositions of NP entering the environment may be different from those in technical mixtures and that isomeric selectivity should be taken into account to better understand the occurrence, fate, and ecological risks of NP. PMID:25462736

  1. 40 CFR 180.418 - Cypermethrin and an isomer zeta-cypermethrin; tolerances for residues.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Cypermethrin and an isomer zeta... FOOD Specific Tolerances § 180.418 Cypermethrin and an isomer zeta-cypermethrin; tolerances for... (±))(cis-trans 3-(2,2-dichloroethenyl)-2,2 dimethylcyclopropanecarboxylate and its inactive R-isomers in...

  2. 40 CFR 180.418 - Cypermethrin and an isomer zeta-cypermethrin; tolerances for residues.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 25 2012-07-01 2012-07-01 false Cypermethrin and an isomer zeta... FOOD Specific Tolerances § 180.418 Cypermethrin and an isomer zeta-cypermethrin; tolerances for... (±))(cis-trans 3-(2,2-dichloroethenyl)-2,2 dimethylcyclopropanecarboxylate and its inactive R-isomers in...

  3. 40 CFR 721.10564 - Mixed amino diaryl sulfone isomers (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Mixed amino diaryl sulfone isomers... Specific Chemical Substances § 721.10564 Mixed amino diaryl sulfone isomers (generic). (a) Chemical... as mixed amino diaryl sulfone isomers (PMN P-08-39) is subject to reporting under this section...

  4. 40 CFR 721.10564 - Mixed amino diaryl sulfone isomers (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Mixed amino diaryl sulfone isomers... Specific Chemical Substances § 721.10564 Mixed amino diaryl sulfone isomers (generic). (a) Chemical... as mixed amino diaryl sulfone isomers (PMN P-08-39) is subject to reporting under this section...

  5. 40 CFR 180.418 - Cypermethrin and an isomer zeta-cypermethrin; tolerances for residues.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Cypermethrin and an isomer zeta... FOOD Specific Tolerances § 180.418 Cypermethrin and an isomer zeta-cypermethrin; tolerances for... (±))(cis-trans 3-(2,2-dichloroethenyl)-2,2 dimethylcyclopropanecarboxylate and its inactive R-isomers in...

  6. Analysis of the pH-dependent thermodynamic stability, local motions, and microsecond folding kinetics of carbonmonoxycytochrome c.

    PubMed

    Kumar, Rajesh

    2016-09-15

    This paper analyzes the effect of pH on thermodynamic stability, low-frequency local motions and microsecond folding kinetics of carbonmonoxycytochrome c (Cyt-CO) all across the alkaline pH-unfolding transition of protein. Thermodynamic analysis of urea-induced unfolding transitions of Cyt-CO measured between pH 6 and pH 11.9 reveals that Cyt-CO is maximally stable at pH∼9.5. Dilution of unfolded Cyt-CO into refolding medium forms a native-like compact state (NCO-state), where Fe(2+)-CO interaction persists. Kinetic and thermodynamic parameters measured for slow thermally-driven CO dissociation (NCO→N+CO) and association (N+CO→NCO) reactions between pH 6.5 and pH 13 reveal that the thermal-motions of M80-containing Ω-loop are decreased in subdenaturing limit of alkaline pH. Laser photolysis of Fe(2+)-CO bond in NCO-state triggers the microsecond folding (NCO→N). The microsecond kinetics measured all across the alkaline pH-unfolding transition of Cyt-CO produce rate rollover in the refolding limb of chevron plot, which suggests a glass transition of NCO en route to N. Between pH 7 and pH 11.9, the natural logarithm of the microsecond folding rate varies by < 1.5 units while the natural logarithm of apparent equilibrium constant varies by 11.8 units. This finding indicates that the pH-dependent ionic-interactions greatly affect the global stability of protein but have very small effect on folding kinetics. PMID:27424489

  7. Wire Array Z-pinches on Sphinx Machine: Experimental Results and Relevant Points of Microsecond Implosion Physics

    NASA Astrophysics Data System (ADS)

    Calamy, H.; Hamann, F.; Lassalle, F.; Bayol, F.; Mangeant, C.; Morell, A.; Huet, D.; Bedoch, J. P.; Chittenden, J. P.; Lebedev, S. V.; Jennings, C. A.; Bland, S. N.

    2006-01-01

    Centre d'Etudes de Gramat (France) has developed an efficient long implosion time (800 ns) Aluminum plasma radiation source (PRS). Based on the LTD technology, the SPHINX facility is developed as a 1-3MJ, 1μs rise time, 4-10 MA current driver. In this paper, it was used in 1MJ, 4MA configuration to drive Aluminum nested wire arrays Z-pinches with K-shell yield up to 20 kJ and a FWHM of the x-ray pulse of about 50 ns. We present latest SPHINX experiments and some of the main physic issues of the microsecond regime. Experimental setup and results are described with the aim of giving trends that have been obtained. The main features of microsecond implosion of wire arrays can be analyzed thanks to same methods and theories as used for faster Z-pinches. The effect of load polarity was examined. The stability of the implosion , one of the critical point of microsecond wire arrays due to the load dimensions imposed by the time scale, is tackled. A simple scaling from 100 ns Z-pinch results to 800 ns ones gives good results and the use of nested arrays improves dramatically the implosion quality and the Kshell yield of the load. However, additional effects such as the impact of the return current can geometry on the implosion have to be taken into account on our loads. Axial inhomogeneity of the implosion the origin of which is not yet well understood occurs in some shots and impacts the radiation output. The shape of the radiative pulse is discussed and compared with the homogeneity of the implosion. Numerical 2D R-Z and R-θ simulations are used to highlight some experimental results and understand the plasma conditions during these microsecond wire arrays implosions.

  8. Wire Array Z-pinches on Sphinx Machine: Experimental Results and Relevant Points of Microsecond Implosion Physics

    SciTech Connect

    Calamy, H.; Hamann, F.; Lassalle, F.; Bayol, F.; Mangeant, C.; Morell, A.; Huet, D.; Bedoch, J.P.; Chittenden, J.P.; Lebedev, S.V.; Jennings, C.A.; Bland, S.N.

    2006-01-05

    Centre d'Etudes de Gramat (France) has developed an efficient long implosion time (800 ns) Aluminum plasma radiation source (PRS). Based on the LTD technology, the SPHINX facility is developed as a 1-3MJ, 1{mu}s rise time, 4-10 MA current driver. In this paper, it was used in 1MJ, 4MA configuration to drive Aluminum nested wire arrays Z-pinches with K-shell yield up to 20 kJ and a FWHM of the x-ray pulse of about 50 ns. We present latest SPHINX experiments and some of the main physic issues of the microsecond regime. Experimental setup and results are described with the aim of giving trends that have been obtained. The main features of microsecond implosion of wire arrays can be analyzed thanks to same methods and theories as used for faster Z-pinches. The effect of load polarity was examined. The stability of the implosion , one of the critical point of microsecond wire arrays due to the load dimensions imposed by the time scale, is tackled. A simple scaling from 100 ns Z-pinch results to 800 ns ones gives good results and the use of nested arrays improves dramatically the implosion quality and the Kshell yield of the load. However, additional effects such as the impact of the return current can geometry on the implosion have to be taken into account on our loads. Axial inhomogeneity of the implosion the origin of which is not yet well understood occurs in some shots and impacts the radiation output. The shape of the radiative pulse is discussed and compared with the homogeneity of the implosion. Numerical 2D R-Z and R-{theta} simulations are used to highlight some experimental results and understand the plasma conditions during these microsecond wire arrays implosions.

  9. A comparison between characteristics of atmospheric-pressure plasma jets sustained by nanosecond- and microsecond-pulse generators in helium

    SciTech Connect

    Zhang, Cheng; Shao, Tao Wang, Ruixue; Yan, Ping; Zhou, Zhongsheng; Zhou, Yixiao

    2014-10-15

    Power source is an important parameter that can affect the characteristics of atmospheric-pressure plasma jets (APPJs), because it can play a key role on the discharge characteristics and ionization process of APPJs. In this paper, the characteristics of helium APPJs sustained by both nanosecond-pulse and microsecond-pulse generators are compared from the aspects of plume length, discharge current, consumption power, energy, and optical emission spectrum. Experimental results showed that the pulsed APPJ was initiated near the high-voltage electrode with a small curvature radius, and then the stable helium APPJ could be observed when the applied voltage increased. Moreover, the discharge current of the nanosecond-pulse APPJ was larger than that of the microsecond-pulse APPJ. Furthermore, although the nanosecond-pulse generator consumed less energy than the microsecond-pulse generator, longer plume length, larger instantaneous power per pulse and stronger spectral line intensity could be obtained in the nanosecond-pulse excitation case. In addition, some discussion indicated that the rise time of the applied voltage could play a prominent role on the generation of APPJs.

  10. Microsecond pulsed hydrogen/deuterium exchange of electrosprayed ubiquitin ions stored in a linear ion trap.

    PubMed

    Rajabi, Khadijeh

    2015-02-01

    A pulse of D2O vapour on the order of microseconds is allowed to react with the +6 to +9 charge states of ubiquitin confined in a linear ion trap (LIT). Two envelopes of peaks are detected for the ions of ubiquitin, corresponding to the ions that exchange more quickly and more slowly. The deuterium uptake of the protonated sites on ubiquitin ions accounts for the ion population with the fast exchange. The hydrogen/deuterium exchange (HDX) kinetics of ubiquitin ions trapped in the LIT for 200 ms showed comparable structural transitions to those trapped for 300 ms. When ions are trapped for longer, i.e. up to 2000 ms, mainly the slow exchanging ion population is detected. In all experiments the +7 ions exchange the most, suggesting a short distance between the surface protonated sites and nearby charged sites, and concomitantly high accessibility of surface protonated sites towards D2O. The +6 ions are more compact than the +7 ions but have one fewer protonated site, therefore fewer surface availabilities for D2O attack. The data suggest that the +6 ions keep most of their solution-phase contacts intact while the hydrophobic core is slightly interrupted in the +7 ions, possibly due to the exposure of charged His68 that is normally buried in the hydrophobic pocket. The +8 and +9 ions have more protonated sites but are less compact than the +7 ions because of Coulombic repulsion, resulting in a larger distance between the protonated sites and the basic sites. The data indicate that the HDX mechanism of ions with the slower exchange corresponding to the second envelope of peaks is primarily governed via a relay mechanism. The results suggest that the pulsed HDX MS method is sampling a population of ubiquitin ions with a similar backbone fold to the solution. PMID:25553956

  11. Microsecond barrier-limited chain collapse observed by time-resolved FRET and SAXS

    PubMed Central

    Kathuria, Sagar V.; Kayatekin, Can; Barrea, Raul; Kondrashkina, Elena; Graceffa, Rita; Guo, Liang; Nobrega, R. Paul; Chakravarthy, Srinivas; Matthews, C. Robert; Irving, Thomas C.; Bilsel, Osman

    2014-01-01

    It is generally held that random coil polypeptide chains undergo a barrier-less continuous collapse when the solvent conditions are changed to favor the fully-folded native conformation. We test this hypothesis by probing intramolecular distance distributions during folding in one of the paradigms of folding reactions, that of cytochrome c. The Trp59 to heme distance was probed by time-resolved Förster resonance energy transfer (trFRET) in the microsecond time range of refolding. Contrary to expectation, a state with a Trp59-heme distance close to that of the GdnHCl denatured state is present after ~27 µs of folding. A concomitant decrease in the population of this state and an increase in the population of a compact high-FRET state (efficiency > 90%) show that the collapse is barrier-limited. Small-angle x-ray scattering measurements over a similar time range show that the radius of gyration under native favoring conditions is comparable to that of the GdnHCl denatured unfolded state. An independent comprehensive global thermodynamic analysis reveals that marginally stable partially folded structures are also present in the nominally unfolded GdnHCl denatured state. These observations suggest that specifically collapsed intermediate structures with low stability in rapid equilibrium with the unfolded state may contribute to the apparent chain contraction observed in previous fluorescence studies using steady state detection. In the absence of significant dynamic averaging of marginally stable partially folded states and with use of probes sensitive to distance distributions, barrier-limited chain contraction is observed upon transfer of the GdnHCl denatured state ensemble to native like conditions. PMID:24607691

  12. Methods for the Detection and Characterization of Silica Colloids by Microsecond spICP-MS.

    PubMed

    Montaño, Manuel D; Majestic, Brian J; Jämting, Åsa K; Westerhoff, Paul; Ranville, James F

    2016-05-01

    The rapid development of nanotechnology has led to concerns over their environmental risk. Current analytical techniques are underdeveloped and lack the sensitivity and specificity to characterize these materials in complex environmental and biological matrices. To this end, single particle ICP-MS (spICP-MS) has been developed in the past decade, with the capability to detect and characterize nanomaterials at environmentally relevant concentrations in complex environmental and biological matrices. However, some nanomaterials are composed of elements inherently difficult to quantify by quadrupole ICP-MS due to abundant molecular interferences, such as dinitrogen ions interfering with the detection of silicon. Three approaches aimed at reducing the contribution of these background molecular interferences in the analysis of (28)Si are explored in an attempt to detect and characterize silica colloids. Helium collision cell gases and reactive ammonia gas are investigated for their conventional use in reducing the signal generated from the dinitrogen interference and background silicon ions leaching from glass components of the instrumentation. A new approach brought on by the advent of microsecond dwell times in single particle ICP-MS allows for the detection and characterization of silica colloids without the need for these cell gases, as at shorter dwell times the proportion of signal attributed to a nanoparticle event is greater relative to the constant dinitrogen signal. It is demonstrated that the accurate detection and characterization of these materials will be reliant on achieving a balance between reducing the contribution of the background interference, while still registering the maximum amount of signal generated by the particle event. PMID:27055808

  13. Microsecond Molecular Dynamics Simulations of Intrinsically Disordered Proteins Involved in the Oxidative Stress Response

    PubMed Central

    Cino, Elio A.; Wong-ekkabut, Jirasak; Karttunen, Mikko; Choy, Wing-Yiu

    2011-01-01

    Intrinsically disordered proteins (IDPs) are abundant in cells and have central roles in protein-protein interaction networks. Interactions between the IDP Prothymosin alpha (ProTα) and the Neh2 domain of Nuclear factor erythroid 2-related factor 2 (Nrf2), with a common binding partner, Kelch-like ECH-associated protein 1(Keap1), are essential for regulating cellular response to oxidative stress. Misregulation of this pathway can lead to neurodegenerative diseases, premature aging and cancer. In order to understand the mechanisms these two disordered proteins employ to bind to Keap1, we performed extensive 0.5–1.0 microsecond atomistic molecular dynamics (MD) simulations and isothermal titration calorimetry experiments to investigate the structure/dynamics of free-state ProTα and Neh2 and their thermodynamics of bindings. The results show that in their free states, both ProTα and Neh2 have propensities to form bound-state-like β-turn structures but to different extents. We also found that, for both proteins, residues outside the Keap1-binding motifs may play important roles in stabilizing the bound-state-like structures. Based on our findings, we propose that the binding of disordered ProTα and Neh2 to Keap1 occurs synergistically via preformed structural elements (PSEs) and coupled folding and binding, with a heavy bias towards PSEs, particularly for Neh2. Our results provide insights into the molecular mechanisms Neh2 and ProTα bind to Keap1, information that is useful for developing therapeutics to enhance the oxidative stress response. PMID:22125611

  14. In-vitro bipolar nano- and microsecond electro-pulse bursts for irreversible electroporation therapies.

    PubMed

    Sano, Michael B; Arena, Christopher B; DeWitt, Matthew R; Saur, Dieter; Davalos, Rafael V

    2014-12-01

    Under the influence of external electric fields, cells experience a rapid potential buildup across the cell membrane. Above a critical threshold of electric field strength, permanent cell damage can occur, resulting in cell death. Typical investigations of electroporation effects focus on two distinct regimes. The first uses sub-microsecond duration, high field strength pulses while the second uses longer (50 μs+) duration, but lower field strength pulses. Here we investigate the effects of pulses between these two extremes. The charging behavior of the cell membrane and nuclear envelope is evaluated numerically in response to bipolar pulses between 250 ns and 50 μs. Typical irreversible electroporation protocols expose cells to 90 monopolar pulses, each 100 μs in duration with a 1 second inter-pulse delay. Here, we replace each monopolar waveform with a burst of alternating polarity pulses, while keeping the total energized time (100 μs), burst number (80), and inter-burst delay (1s) the same. We show that these bursts result in instantaneous and delayed cell death mechanisms and that there exists an inverse relationship between pulse-width and toxicity despite the delivery of equal quantities of energy. At 1500 V/cm only treatments with bursts containing 50 μs pulses (2×) resulted in viability below 10%. At 4000 V/cm, bursts with 1 μs (100×), 2 μs (50×), 5 μs (20×), 10 μs (10×), and 50 μs (2×) duration pulses reduced viability below 10% while bursts with 500 ns (200×) and 250 ns (400×) pulses resulted in viabilities of 31% and 92%, respectively. PMID:25131187

  15. DNA interaction with cis- and trans- isomers of photosensitive surfactant

    NASA Astrophysics Data System (ADS)

    Unksov, I. N.; Kasyanenko, N. A.

    2014-12-01

    Interaction between DNA and photosensitive cationic surfactant in a solution is studied. Studies were conducted to examine the impact of the surfactant in its cis- conformation on the size of DNA molecule and also to investigate the phase behavior of the system depending on DNA and surfactant concentration. We conclude that trans- isomer of surfactant requires its smaller concentration to reach the DNA compaction compared with cis- isomer received by UV radiation of solutions. Studies of DNA-surfactant systems were performed by means of spectrophotometry and viscometry. Variation of surfactant concentration enables us to determine the precipitation zone on phase diagram. From the viscosity study it can be indicated that precipitation zone is narrower for UV-radiated surfactant and it shifts to higher surfactant concentration. Also we examine the reversibility of DNA compaction in systems with the surfactant in its trans- form.

  16. Spectroscopic Studies of the Several Isomers of UO3

    SciTech Connect

    Sweet, Lucas E.; Reilly, Dallas D.; Abrecht, David G.; Buck, Edgar C.; Meier, David E.; Su, Yin-Fong; Brauer, Carolyn S.; Schwantes, Jon M.; Tonkyn, Russell G.; Szecsody, James E.; Blake, Thomas A.; Johnson, Timothy J.

    2013-09-26

    Uranium trioxide is known to adopt seven different structural forms. While these structural forms have been well characterized using x-ray or neutron diffraction techniques, little work has been done to characterize their spectroscopic properties, particularly of the pure phases. Since the structural isomers of UO3 all have similar thermodynamic stabilities and most tend to hydrolyze under open atmospheric conditions, mixtures of UO3 phases and the hydrolysis products are common. Much effort went into isolating pure phases of UO3. Utilizing x-ray diffraction as a sample identification check, UV/Vis/NIR spectroscopic signatures of α-UO3, β-UO3, γ-UO3 and UO2(OH)2 products were obtained. The spectra of the pure phases can now be used to characterize typical samples of UO3, which are often mixtures of isomers.

  17. Density Functional Exploration of C4H3N Isomers.

    PubMed

    Custer, Thomas; Szczepaniak, Urszula; Gronowski, Marcin; Fabisiewicz, Emilia; Couturier-Tamburelli, Isabelle; Kołos, Robert

    2016-07-28

    Molecules having C4H3N stoichiometry are of astrophysical interest. Two of these, methylcyanoacetylene (CH3C3N) and its structural isomer allenyl cyanide (H2CCCHN), have been observed in interstellar space, while several more have been examined in laboratories. Here we describe, for a broad range of C4H3N isomers, density functional calculations (B3LYP/aug-cc-pVTZ) of molecular parameters including the energetics, geometries, rotational constants, electric dipole moments, polarizabilities, vibrational IR frequencies, IR absorption intensities, and Raman activities. Singlet-triplet splittings as well as singlet vertical electronic excitation energies are given for selected species. The identification of less stable C4H3N molecules, generated in ongoing spectroscopic experiments, relies heavily on these quantum chemical predictions. PMID:27341606

  18. The structural and dynamical variables of pentane isomers

    NASA Astrophysics Data System (ADS)

    Patel, Tarika K.; Vaghela, M. V.; Gajjar, P. N.

    2016-05-01

    We derived structural and dynamical properties of pentane isomers: normal pentane, iso-pentane and neo pentane for liquid and gaseous state. We use molecular dynamics simulation to calculate the dynamical properties of pentane isomers for number of particles 729 using the intermolecular potential and force due to Lenard Jones potential. The computations also include mean square displacement and self diffusion co-efficient using Einstein relation. In structural properties, structure factor and phonon frequency are obtaining from P Y Method and Hubbard and Beeby Approach respectively. The Intermolecular potential and self diffusion co-efficient depend on the branching in the structure. The pair correlation function and phonon dispersion curves revels the complex structure of neo-pentane with respect to iso-pentane and n-pentane.

  19. Characterization of geometric isomers of Norbornene end-capped imides

    NASA Technical Reports Server (NTRS)

    Young, P. R.; Chang, A. C.

    1983-01-01

    Three geometric isomers from the thermal isomerization of methylene-4,4' bis(endo-N-phenylbicyclo/2.2.1/hept-2-ene-5,6-di carboximide) (I) were chromatographically separated and isolated in order to investigate the thermal cure of norbornene end-capped imide oligomers, which display considerable promise for use in various aerospace adhesive and composite applications. Endo-endo (I), endo-exo (II), and exo-exo (III) configurations were assigned to each compound based on the results of NMR spectroscopy. Several chromatographic, spectroscopic, and thermal techniques were then used to characterize these three isomers which serve as model compounds for norbornene end-capped polyimides. It was found that each compound thermally isomerized to an equilibrium mixture of all three compounds prior to cure. It is proposed that these compounds react by different mechanisms in air and nitrogen.

  20. Condensations of single DNA molecules induced by heptaplatin and its chiral isomer

    SciTech Connect

    Zhang, Hong-Yan; Liu, Yu-Ru; Li, Wei; Li, Hui; Dou, Shuo-Xing; Xie, Ping; Wang, Wei-Chi; Wang, Peng-Ye

    2014-08-15

    Heptaplatin is a third-generation platinum antitumor drug. It has a chiral isomer. We studied the interactions between the two isomers and DNA by using magnetic tweezers and atomic force microscopy (AFM) to investigate the effect of chiralities of the isomers on the interactions. We found that the extension curves and average condensation rates of DNA molecules incubated with heptaplatin were nearly the same as those incubated with its chiral isomer. In addition, the structures of DNA molecules incubated with heptaplatin were also similar to those incubated with its chiral isomer. These results indicate the difference in chirality of the two isomers does not induce different interactions of the isomers with DNA. Our study may facilitate the understanding of interactions of platinum complexes with DNA and the design of new antitumor platinum complexes.

  1. HPLC separation and FT-IR isomer differentiation of the 1,2,4,7/1,2,4,8-tetrachlorodibenzodioxin isomer pair: A theoretical/empirical approach to dibenzodioxin isomer assignmentt

    SciTech Connect

    Grainger, J.; Barnhart, E.; Patterson D.G. Jr.; Presser, D.

    1988-02-01

    The 1,2,4,7-and 1,2,4,8-tetrachlorodibenzodioxin (TCDD) isomers were separated by reversed-phase high-performance liquid chromatography (HPLC) with the use of a pyrene column. Fourier transform infrared (FT-IR) matrix isolation and vapor-phase spectra of the individual isomers were recorded. The spectra of the HPLC-seprated isomers correlate well with spectral subtraction results and were found to be distinct in three spectral regions: one of which allows for isomer structural assignment. Ambiguities and differences in published TCDD isomer FT-IR assignments are discussed in terms of a qualitative valence-bond approach and empirically derived estimates of ether linkage asymmetric stretching frequencies.

  2. Virtual libraries of tetrapyrrole macrocycles. Combinatorics, isomers, product distributions, and data mining.

    PubMed

    Taniguchi, Masahiko; Du, Hai; Lindsey, Jonathan S

    2011-09-26

    A software program (PorphyrinViLiGe) has been developed to enumerate the type and relative amounts of substituted tetrapyrrole macrocycles in a virtual library formed by one of four different classes of reactions. The classes include (1) 4-fold reaction of n disubstituted heterocycles (e.g., pyrroles or diiminoisoindolines) to form β-substituted porphyrins, β-substituted tetraazaporphyrins, or α- or β-substituted phthalocyanines; (2) combination of m aminoketones and n diones to form m × n pyrroles, which upon 4-fold reaction give β-substituted porphyrins; (3) derivatization of an 8-point tetrapyrrole scaffold with n reagents, and (4) 4-fold reaction of n aldehydes and pyrrole to form meso-substituted porphyrins. The program accommodates variable ratios of reactants, reversible or irreversible reaction (reaction classes 1 and 2), and degenerate modes of formation. Pólya's theorem (for enumeration of cyclic entities) has also been implemented and provides validation for reaction classes 3 and 4. The output includes the number and identity of distinct reaction-accessible substituent combinations, the number and identity of isomers thereof, and the theoretical mass spectrum. Provisions for data mining enable assessment of the number of products having a chosen pattern of substituents. Examples include derivatization of an octa-substituted phthalocyanine with eight reagents to afford a library of 2,099,728 members (yet only 6435 distinct substituent combinations) and reversible reaction of six distinct disubstituted pyrroles to afford 2649 members (yet only 126 distinct substituent combinations). In general, libraries of substituted tetrapyrrole macrocycles occupy a synthetically accessible region of chemical space that is rich in isomers (>99% or 95% for the two examples, respectively). PMID:21866949

  3. Flame Propagation of Butanol Isomers/Air Mixtures

    SciTech Connect

    Veloo, Peter S.; Egolfopoulos, Fokion N.

    2011-01-01

    An experimental and computational study was conducted on the propagation of flames of saturated butanol isomers. The experiments were performed in the counterflow configuration under atmospheric pressure, unburned mixture temperature of 343 K, and for a wide range of equivalence ratios. The experiments were simulated using a recent kinetic model for the four isomers of butanol. Results indicate that n-butanol/air flames propagate somewhat faster than both sec-butanol/air and iso-butanol/air flames, and that tert-butanol/air flames propagate notably slower compared to the other three isomers. Reaction path analysis of tert-butanol/air flames revealed that iso-butene is a major intermediate, which subsequently reacts to form the resonantly stable iso-butenyl radical retarding thus the overall reactivity of tert-butanol/air flames relatively to the other three isomers. Through sensitivity analysis, it was determined that the mass burning rates of sec-butanol/air and iso-butanol/air flames are sensitive largely to hydrogen, carbon monoxide, and C{sub 1}–C{sub 2} hydrocarbon kinetics and not to fuel-specific reactions similarly to n-butanol/air flames. However, for tert-butanol/air flames notable sensitivity to fuel-specific reactions exists. While the numerical results predicted closely the experimental data for n-butanol/air and sec-butanol/air flames, they overpredicted and underpredicted the laminar flame speeds for iso-butanol/air and tert-butanol/air flames respectively. It was demonstrated further that the underprediction of the laminar flame speeds of tert-butanol/air flames by the model was most likely due to deficiencies of the C{sub 4}-alkene kinetics.

  4. Nuclear States with Abnormally Large Radii (size Isomers)

    NASA Astrophysics Data System (ADS)

    Ogloblin, A. A.; Demyanova, A. S.; Danilov, A. N.; Belyaeva, T. L.; Goncharov, S. A.

    2015-06-01

    Application of the methods of measuring the radii of the short-lived excited states (Modified diffraction model MDM, Inelastic nuclear rainbow scattering method INRS, Asymptotic normalization coefficients method ANC) to the analysis of some nuclear reactions provide evidence of existing in 9Be, 11B, 12C, 13C the excited states whose radii exceed those of the corresponding ground states by ~ 30%. Two types of structure of these "size isomers" were identified: neutron halo an α-clusters.

  5. [Determination of dimethylbenzoic acid isomers in urine by gas chromatography].

    PubMed

    Kostrzewski, P; Wiaderna-Brycht, A; Czerski, B

    1994-01-01

    Trimethylobenzene (TMB) is a main ingredient of many organic solvents used in industry. In Farbasol (Polish trade name of the solvent) TMB occurs as a mixture of three isomers: pseudocumene (1, 2, 4-TMB) 30%; mesitylene (1, 3, 5-TMB) 15%; hemimellitene (1,2,3-TMB) 5%. As it is known in human organism, TMB is metabolized mainly to dimethylbenzoic (DMBA) and dimethylhippuric (DMHA) acids, and some authors suggest, that the acids excreted in urine can be biological indicators of exposure to TMB. This study was aimed at developing the method of determination of DMBA isomers in urine. Biological material was hydrolyzed with sodium hydroxide and next extracted with diethyl ether. DMBA concentration in urine was determined by gas chromatography using a variant of quantitative analysis with internal standard (5-methyl-2-isopropylphenol, thymol). Analytical parameters of the developed method of determination of DMBA isomers in urine such as linearity, precision, reproducibility, stability (192 days, when urine samples stored at-18 degrees C), detectability limit (400 micrograms/dm3) have been fully compatible with the requirements of biological monitoring. In order to confirm the presence of DMBA isomers in urine, four volunteers were exposed (8 hours) to Farbasol in toxicological chamber. The TMB concentration in the air, determined by means of gas chromatograph (HP 5890), amounted to 100 mg/m3 (MAC value in Poland). In urine samples collected 2,3-; 2,4-; 2,5-; 2,6-; 3,4-; 3,5-dimethylbenzoic acids were identified by means of GC/MSD.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8170375

  6. Spectroscopic and computational study of a new isomer of salinomycin

    NASA Astrophysics Data System (ADS)

    Pankiewicz, Radosław

    2013-09-01

    A new derivative of polyether ionophore salinomycin was obtained as a result of a rearrangement catalysed by sulphuric acid in two-phase medium of water/methylene chloride solution. The new isomer was fully characterized by multinuclear 2D NMR, NOESY and MALDI-TOF. The properties of the new compound were additionally study by semiempirical (PM5) and DFT (B3LYP) methods. A potential mechanism of the rearrangement was also proposed.

  7. Distinct carbon isotope fractionation during anaerobic degradation of dichlorobenzene isomers.

    PubMed

    Liang, Xiaoming; Mundle, Scott O C; Nelson, Jennifer L; Passeport, Elodie; Chan, Calvin C H; Lacrampe-Couloume, Georges; Zinder, Stephen H; Sherwood Lollar, Barbara

    2014-05-01

    Chlorinated benzenes are ubiquitous organic contaminants found in groundwater and soils. Compound specific isotope analysis (CSIA) has been increasingly used to assess natural attenuation of chlorinated contaminants, in which anaerobic reductive dechlorination plays an essential role. In this work, carbon isotope fractionation of the three dichlorobenzene (DCB) isomers was investigated during anaerobic reductive dehalogenation in methanogenic laboratory microcosms. Large isotope fractionation of 1,3-DCB and 1,4-DCB was observed while only a small isotope effect occurred for 1,2-DCB. Bulk enrichment factors (εbulk) were determined from a Rayleigh model: -0.8 ± 0.1 ‰ for 1,2-DCB, -5.4 ± 0.4 ‰ for 1,3-DCB, and -6.3 ± 0.2 ‰ for 1,4-DCB. εbulk values were converted to apparent kinetic isotope effects for carbon (AKIE) in order to characterize the carbon isotope effect at the reactive positions for the DCB isomers. AKIE values are 1.005 ± 0.001, 1.034 ± 0.003, and 1.039 ± 0.001 for 1,2-DCB, 1,3-DCB, and 1,4-DCB, respectively. The large difference in AKIE values between 1,2-DCB and 1,3-DCB (or 1,4-DCB) suggests distinct reaction pathways may be involved for different DCB isomers during microbial reductive dechlorination by the methanogenic cultures. PMID:24758692

  8. Six-quasiparticle isomer in {sup 140}Nd

    SciTech Connect

    Petrache, C. M.; Fantuzi, M.; Mengoni, D.; Petrache, D.; Bark, R. A.; Murray, S. T. H.; Lawrie, E. A.; Lawrie, J. J.; Mullins, S. M.; Lang, S.; Maliage, S. M.; Ramashidzha, T. M.; Ntshangase, S. S.; Ragnarsson, I.

    2006-09-15

    A search for isomeric states was performed in the nucleus {sub 60}{sup 140}Nd{sub 80} using in-beam {gamma}-ray spectroscopy and the {sup 126}Te({sup 18}O,4n) reaction. Prompt and delayed {gamma}-ray coincidences were measured with the AFRODITE spectrometer using the pulsed beam delivered by the Separated Sector Cyclotron of iThemba LABS. One new isomer was identified, with spin-parity I{sup {pi}}=20{sup +} and lifetime T{sub 1/2}{>=}400 ns, at an excitation energy E{sub x}=7430 keV. The lifetime of the 10{sup +} isomer at E{sub x}=3619 keV was determined to be 32.9(1.8) ns, confirming the previously reported value. The configuration of the I{sup {pi}}=20{sup +} isomer is assigned based on configuration-dependent cranked Nilsson-Strutinsky (CNS) calculations as a state {pi}(d{sub 5/2}g{sub 7/2}){sub 10{sup +}}{sup -4}x{nu}(h{sub 11/2}{sup -2}){sub 10{sup +}}, with the spin vectors of the six holes in the {sub 64}{sup 146}Gd{sub 82} core fully aligned.

  9. Determination of the ^229Th isomer half-life

    NASA Astrophysics Data System (ADS)

    Burke, Jason; Beck, Bret; Becker, John; Haydell, Michael; Norman, Rick; Scielzo, Nicholas; Sheets, Steven; Swanberg, Erik

    2009-10-01

    Recently there has been renewed interest in studying the nuclear properties of the ^229Th isomer. ^229Th has the lowest known isomer at 7.6 eV [1]. Direct laser manipulation of the ground and first excited states could lead to the realization of the world's first nuclear clock. To understand the linewidth of the isomeric state we are conducting experiments to directly observe the half-life of the isomer decay. We use a novel ``hot-atom'' technique in which we catch the recoiling ^229Th nuclei following the alpha decay of ^233U -> ^229Th + α. On average 2% of the ^229Th populate the isomeric 3/2+ state compared to the 5/2+ ground state. Recoils are collected on various catcher plate materials, rotated in vacuum in front of an einzel lense and multi-channel plate detector. The internal conversion electrons are counted as a function of time to determine the half-life. Varying the catcher plate material we can investigate the effect that the materials have on the half-life. Determination of the half-life we will provide valuable guidance to Th trapping research [2]. 1) Beck et al., PRL 98, 142501 (2007) 2) Campbell et al., PRL 102, 233004 (2009) This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  10. Inner-shell and double ionization potentials of aminophenol isomers.

    SciTech Connect

    Kryzhevoi, N. V.; Santra, R.; Cederbaum, L. S.

    2011-01-01

    A comprehensive study of single and double core ionization potentials of the aminophenol molecule is reported. The role of relaxation, correlation, relativistic, and basis set effects in these potentials is clarified. Special attention is paid to the isomer dependence of the single and double core ionization potentials. Some of them are also compared with the respective values of the phenol and aniline molecules. It is shown that the core level single ionization potentials of the para-, meta-, and ortho-aminophenol molecules differ only slightly from each other, rendering these structural isomers challenging to distinguish for conventional x-ray photoelectron spectroscopy. In contrast, the energy needed to remove two core electrons from different atoms depends noticeably on the mutual arrangement and even on the relative orientations of the hydroxyl and amine groups. Together with the electrostatic repulsion between the two core holes, relaxation effects accompanying double core ionization play a crucial role here. The pronounced sensitivity of the double ionization potentials, therefore, enables a spectroscopic characterization of the electronic structure of aminophenol isomers by means of x-ray two-photon photoelectron spectroscopy.

  11. Oxidative Transformation of Aminodinitrotoluene Isomers by Multicomponent Dioxygenases

    PubMed Central

    Johnson, Glenn R.; Smets, Barth F.; Spain, Jim C.

    2001-01-01

    The electron-withdrawing nitro substituents of 2,4,6-trinitrotoluene (TNT) make the aromatic ring highly resistant to oxidative transformation. The typical biological transformation of TNT involves reduction of one or more of the nitro groups of the ring to produce the corresponding amine. Reduction of a single nitro substituent of TNT to an amino substituent increases the electron density of the aromatic nucleus considerably. The comparatively electron-dense nuclei of the aminodinitrotoluene (ADNT) isomers would be expected to be more susceptible to oxygenase attack than TNT. The hypothesis was tested by evaluating three nitroarene dioxygenases for the ability to hydroxylate the ADNT isomers. The predominant reaction was dioxygenation of the ring to yield nitrite and the corresponding aminomethylnitrocatechol. A secondary reaction was benzylic monooxygenation to form aminodinitrobenzyl alcohol. The substrate preferences and catalytic specificities of the three enzymes differed considerably. The discovery that the ADNT isomers are substrates for the nitroarene dioxygenases reveals the potential for extensive bacterial transformation of TNT under aerobic conditions. PMID:11722893

  12. Isomer Energy Differences for the C4H3 and C4H5 Isomers UsingDiffusion Monte Carlo

    SciTech Connect

    Domin, D.; Lester Jr., W.A.; Whitesides, R.; Frenklach, M.

    2007-12-01

    A new diffusion Monte Carlo study is performed on the isomers of C{sub 4}H{sub 3} and C{sub 4}H{sub 5} emulating the methodology of a previous study [Int. J. Chem. Kinetics 33, 808 (2001)]. Using the same trial wave function form of the previous study, substantially different isomerization energies were found owing to the use of larger walker populations in the present work. The energy differences between the E and I isomers of C{sub 4}H{sub 3} were found to be 10.5 {+-} 0.5 kcal/mol and for C{sub 4}H{sub 5}, 9.7 {+-} 0.6 kcal/mol. These results are in reasonable accord with recent MRCI and CCSD(T) findings.

  13. Distribution of perfluorooctane sulfonate isomers and predicted risk of thyroid hormonal perturbation in drinking water.

    PubMed

    Yu, Nanyang; Wang, Xiaoxiang; Zhang, Beibei; Yang, Jingping; Li, Meiying; Li, Jun; Shi, Wei; Wei, Si; Yu, Hongxia

    2015-06-01

    We documented the distribution of seven perfluorooctane sulfonate (PFOS) isomers in drinking water in Jiangsu Province, China. Compared to the 30% proportion of branched PFOS in technical PFOS, the levels of branched PFOS in drinking water increased to 31.8%-44.6% of total PFOS. Because of previous risk assessment without considering the PFOS isomer profile and the toxicity of individual PFOS isomers, here we performed a new health risk assessment of PFOS for thyroid hormonal perturbation in drinking water with the contribution from individual PFOS isomers. The risk quotients (RQs) of individual PFOS isomers indicated that linear PFOS contributed most to the risk among all the target PFOS isomers (83.0%-90.2% of the total PFOS RQ), and that risk from 6m-PFOS (5.2%-11.9% of the total PFOS RQ) was higher than that from other branched PFOS isomers. We found that the risks associated with PFOS in drinking water would be overestimated by 10.0%-91.7% if contributions from individual PFOS isomers were not considered. The results revealed that the PFOS isomer profile and the toxicity of individual PFOS isomers were important factors in health risk assessment of PFOS and should be considered in the future risk assessments. PMID:25813491

  14. Evaluation of number concentration quantification by single-particle inductively coupled plasma mass spectrometry: microsecond vs. millisecond dwell times.

    PubMed

    Abad-Álvaro, Isabel; Peña-Vázquez, Elena; Bolea, Eduardo; Bermejo-Barrera, Pilar; Castillo, Juan R; Laborda, Francisco

    2016-07-01

    The quality of the quantitative information in single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) depends directly on the number concentration of the nanoparticles in the sample analyzed, which is proportional to the flux of nanoparticles through the plasma. Particle number concentrations must be selected in accordance with the data acquisition frequency, to control the precision from counting statistics and the bias, which is produced by the occurrence of multiple-particle events recorded as single-particle events. With quadrupole mass spectrometers, the frequency of data acquisition is directly controlled by the dwell time. The effect of dwell times from milli- to microseconds (10 ms, 5 ms, 100 μs, and 50 μs) on the quality of the quantitative data has been studied. Working with dwell times in the millisecond range, precision figures about 5 % were achieved, whereas using microsecond dwell times, the suitable fluxes of nanoparticles are higher and precision was reduced down to 1 %; this was independent of the dwell time selected. Moreover, due to the lower occurrence of multiple-nanoparticle events, linear ranges are wider when dwell times equal to or shorter than 100 μs are used. A calculation tool is provided to determine the optimal concentration for any instrument or experimental conditions selected. On the other hand, the use of dwell times in the microsecond range reduces significantly the contribution of the background and/or the presence of dissolved species, in comparison with the use of millisecond dwell times. Although the use of dwell times equal to or shorter than 100 μs offers improved performance working in single-particle mode, the use of conventional dwell times (3-10 ms) should not be discarded, once their limitations are known. PMID:27086011

  15. Structure, dynamics, and energetics of lysobisphosphatidic acid (LBPA) isomers.

    PubMed

    Goursot, A; Mineva, T; Bissig, C; Gruenberg, J; Salahub, D R

    2010-12-01

    Lysobisphosphatidic acid (LBPA), or bis(monoacylglycerol)phosphate, is a very interesting lipid, that is mainly found in late endosomes. It has several intriguing characteristics, which differ from those of other animal glycerophospholipids, that may be related to its specific functions, particularly in the metabolism of cholesterol. Its phosphodiester group is bonded at the sn-1 (sn-1') positions of the glycerols rather than at sn-3 (sn-3'); the position of the two fatty acid chains is still under debate but, increasingly, arguments favor the sn-2, sn-2' position in the native molecule, whereas isolation procedures or acidic conditions lead to the thermodynamically more stable sn-3, sn-3' structure. Because of these peculiar features, it can be expected that LBPA shape and interactions with membrane lipids and proteins are related to its structure at the molecular level. We applied quantum mechanical methods to study the structures and stabilities of the 2,2' and 3,3' LBPA isomers, using a step-by-step procedure from glycerol to precursors (in vitro syntheses) and to the final isoforms. The structures of the two positional LBPA isomers are substantially different, showing that the binding positions of the fatty acid chains on the glycerol backbone determine the shape of the LBPA molecule and thus, possibly, its functions. The 3,3' LBPA structures obtained are more stable with respect to the 2,2' form, as expected from experiment. If one argues that the in vivo synthesis starts from the present glycerol conformers and considering the most stable bis(glycero)phosphate structures, the 2,2' isoform should be the most probable isomer. PMID:21053942

  16. Differential adsorption of CHON isomers at interstellar grain surfaces

    NASA Astrophysics Data System (ADS)

    Lattelais, M.; Pauzat, F.; Ellinger, Y.; Ceccarelli, C.

    2015-06-01

    Context. The CHON generic chemical formula covers different isomers such as isocyanic acid (HNCO), cyanic acid (HOCN), fulminic acid (HCNO), and isofulminic acid (HONC); the first three have been identified in a large variety of environments in the interstellar medium (ISM). Several phenomena could be at the origin of the observed abundances, such as different pathways of formation and destruction involving gas phase reactions with different possible activation barriers and/or surface processes depending on the local temperature and the nature of the support. Aims: The scope of this article is to shed some light on the interaction of the CHON isomers with interstellar grains as a function of the nature of the surface and to determine the corresponding adsorption energies in order to find whether this phenomenon could play a role in the abundances observed in the ISM. Methods: The question was addressed by means of numerical simulations using first principle periodic density functional theory (DFT) to represent the grain support as a solid of infinite dimension. Results: Regardless of the nature of the model surface (water ice, graphene, silica), two different classes of isomers were identified: weakly bound (HNCO and HCNO) and strongly bound (HOCN and HONC), with the adsorption energies of the latter group being about twice those of the former. The range of the adsorption energies is (from highest to lowest) HOCN > HONC > HNCO > HCNO. They are totally disconnected from the relative stabilities, which range from HNCO > HOCN > HCNO > HONC. Conclusions: The possibility of hydrogen bonding is the discriminating factor in the trapping of CHON species on grain surfaces. Whatever the environment, differential adsorption is effective and its contribution to the molecular abundances should not be ignored. The theoretical adsorption energies provided here could be profitably used for a more realistic modeling of molecule-surfaces interactions.

  17. Ototoxicity of the three xylene isomers in the rat.

    PubMed

    Maguin, Katy; Lataye, Robert; Campo, Pierre; Cossec, Benoît; Burgart, Manuella; Waniusiow, Delphine

    2006-01-01

    Numerous experiments have shown that the aromatic solvents can affect the auditory system in the rat, the cochlea being targeted first. Solvents differ in cochleotoxic potency: for example, styrene is more ototoxic than toluene or xylenes. The goal of this study was to determine the relative ototoxicity of the three isomers of xylene (o-, m- or p-xylene). Moreover, by dosing with the two urinary metabolites of xylene, methylhippuric (MHAs) and mercapturic acids (MBAs), this study points toward a causal relationship between the cochleotoxic effects and potential reactive intermediates arising from the biotransformation of the parent molecules. Separate groups of rats were exposed by inhalation to one isomer following this schedule: 1800 ppm, 6 h/d, 5 d/wk for 3 wk. Auditory thresholds were determined with brainstem-auditory evoked potentials. Morphological analysis of the organ of Corti was performed by counting both sensory and spiral ganglion cells. Among the three isomers, only p-xylene was cochleotoxic. A 39-dB permanent threshold shift was obtained over the tested frequencies range from 8 to 20 kHz. Whereas outer hair cells were largely injured, no significant morphological change was observed within spiral ganglia. The concentrations of urinary p-, o- or m-MHA were greater (p-MHA: 33.2 g/g; o-MHA: 7.8 g/g; m-MHA: 20.4 g/g) than those obtained for MBAs (p-MBA: 0.04 g/g; o-MBA: 6.2 g/g; m-MBA: 0.03 g/g). Besides, there is a large difference between o-MBA (6.2 g/g) and p-MBA (0.04 g/g). As a result, since the cysteine conjugates are not determinant in the ototoxic process of xylenes, the location of the methyl groups around the benzene nucleus could play a key role. PMID:17045780

  18. Elongated shape isomers in the Ar36 nucleus

    NASA Astrophysics Data System (ADS)

    Cseh, József; Darai, Judit; Sciani, Wagner; Otani, Yul; Lépine-Szily, Alinka; Benjamim, Elisangela A.; Chamon, Luiz Carlos; Filho, Rubens Lichtenthäler

    2009-09-01

    A recent analysis of the C12+Mg24 scattering [W. Sciani , Phys. Rev. C 80, 034319 (2009)] suggests the existence of a hyperdeformed band in the Ar36 nucleus, completely in line with the predictions of α [W. D. M. Rae and A. C. Merchant, Phys. Lett. B279, 207 (1992)] and binary cluster calculations [J. Cseh , Phys. Rev. C 70, 034311 (2004)]. Here we review the structural understanding of the superdeformed and the hyperdeformed states of Ar36 and present new results on the shape isomers as well. Special attention is paid to the clusterization of these states, which indicates the appropriate reaction channels for their formation.

  19. Interstellar Isomers: The Importance of Bonding Energy Differences

    NASA Technical Reports Server (NTRS)

    Remijan, Anthony J.; Hollis, J. M.; Lovas, F. J.; Plusquellic, D. F.; Jewell, P. R.

    2005-01-01

    We present strong detections of methyl cyanide (CH3CN), vinyl cyanide (CH2CHCN), ethyl cyanide (CH3CH2CN) and cyanodiacetylene (HC4CN) molecules with the Green Bank Telescope (GBT) toward the Sgr B2(N) molecular cloud. Attempts to detect the corresponding isocyanide isomers were only successful in the case of methyl isocyanide (CH3NC) for its J(sub K) = 1(sub 0) - 0(sub 0) transition, which is the first interstellar report of this line. To determine the spatial distribution of CH3NC, we used archival Berkeley-Illinois-Maryland Association (BIMA) array data for the J(sub K) = 1(sub 0) - 0(sub 0) transitions but no emission was detected. From ab initio calculations, the bonding energy difference between the cyanide and isocyanide molecules is greater than 8500 per centimeter (greater than 12,000 K). Thus, cyanides are the more stable isomers and would likely be formed more preferentially over their isocyanide counterparts. That we detect CH3NC emission with a single antenna (Gaussian beamsize(omega(sub B))=1723 arcsec(sup 2)) but not with an interferometer (omega(sub b)=192 arcsec(sup 2)), strongly suggests that CH3NC has a widespread spatial distribution toward the Sgr B2(N) region. Other investigators have shown that CH3CN is present both in the LMH hot core of Sgr B2(N) and in the surrounding medium, while we have shown that CH3NC appears to be deficient in the LMH hot core. Thus, largescale, non-thermal processes in the surrounding medium may account for the conversion of CH3CN to CH3NC while the LMH hot core, which is dominated by thermal processes, does not produce a significant amount of CH3NC. Ice analog experiments by other investigators have shown that radiation bombardment of CH3CN can produce CH3NC, thus supporting our observations. We conclude that isomers separated by such large bonding energy differences are distributed in different interstellar environments, making the evaluation of column density ratios between such isomers irrelevant unless it can

  20. Astropulse: A search for microsecond transient radio signals using distributed computing

    NASA Astrophysics Data System (ADS)

    von Korff, Joshua Solomon

    I performed a transient, microsecond timescale radio sky survey, called "Astropulse," using the Arecibo telescope in Puerto Rico. Astropulse searches for brief (0.4 mus to 204.8 mus), wideband (relative to its 2.5 MHz bandwidth) radio pulses centered at 1,420 MHz, a range that includes the hyperfine hydrogen line. Astropulse is a commensal survey, obtaining its data by sharing telescope time with other surveys, such as PALFA. I scanned the sky visible to Arecibo, between declinations of --1.33 and 38.03 degrees, with varying dwell times depending on the requirements of our partner surveys. I analyzed 1,540 hours of data in each of 7 beams of the ALFA receiver, with 2 polarizations per beam, for a total of 21,600 hours of data. The data were 1-bit complex sampled at the Nyquist limit of 0.4 mus per sample. Examination of timescales less than 12.8 mus would have been impossible if not for my use of coherent dedispersion, a technique that has frequently been used for targeted observations, but has never before been associated with a radio sky survey. I performed nonlinear coherent dedispersion, reversing the broadening effects on signals caused by their passage through the interstellar medium (ISM). Coherent dedispersion requires intensive computations, and needs far more processing power than the more usual incoherent dedispersion. This processing power was provided by BOINC, the Berkeley Open Infrastructure for Network Computing. BOINC is a distributed computing system, which allowed me to utilize hundreds of thousands of volunteers' computers to perform the necessary calculations for coherent dedispersion. Each volunteer's computer requires about a week to process a single 8 MB "workunit," corresponding to 13 s of data from a single beam and polarization. In all, Astropulse analyzed over 48 TB of data. I did not aim to detect any particular astrophysical source, intending rather to perform a survey of the transient radio sky. Astrophysical events that might produce

  1. Breaking the millisecond barrier on SpiNNaker: implementing asynchronous event-based plastic models with microsecond resolution.

    PubMed

    Lagorce, Xavier; Stromatias, Evangelos; Galluppi, Francesco; Plana, Luis A; Liu, Shih-Chii; Furber, Steve B; Benosman, Ryad B

    2015-01-01

    Spike-based neuromorphic sensors such as retinas and cochleas, change the way in which the world is sampled. Instead of producing data sampled at a constant rate, these sensors output spikes that are asynchronous and event driven. The event-based nature of neuromorphic sensors implies a complete paradigm shift in current perception algorithms toward those that emphasize the importance of precise timing. The spikes produced by these sensors usually have a time resolution in the order of microseconds. This high temporal resolution is a crucial factor in learning tasks. It is also widely used in the field of biological neural networks. Sound localization for instance relies on detecting time lags between the two ears which, in the barn owl, reaches a temporal resolution of 5 μs. Current available neuromorphic computation platforms such as SpiNNaker often limit their users to a time resolution in the order of milliseconds that is not compatible with the asynchronous outputs of neuromorphic sensors. To overcome these limitations and allow for the exploration of new types of neuromorphic computing architectures, we introduce a novel software framework on the SpiNNaker platform. This framework allows for simulations of spiking networks and plasticity mechanisms using a completely asynchronous and event-based scheme running with a microsecond time resolution. Results on two example networks using this new implementation are presented. PMID:26106288

  2. On-the-fly decoding luminescence lifetimes in the microsecond region for lanthanide-encoded suspension arrays

    PubMed Central

    Lu, Yiqing; Lu, Jie; Zhao, Jiangbo; Cusido, Janet; Raymo, Françisco M; Yuan, Jingli; Yang, Sean; Leif, Robert C.; Huo, Yujing; Piper, James A.; Paul Robinson, J; Goldys, Ewa M.; Jin, Dayong

    2014-01-01

    Significant multiplexing capacity of optical time-domain coding has been recently demonstrated by tuning luminescence lifetimes of the upconversion nanoparticles called ‘τ-Dots’. It provides a large dynamic range of lifetimes from microseconds to milliseconds, which allows creating large libraries of nanotags/microcarriers. However, a robust approach is required to rapidly and accurately measure the luminescence lifetimes from the relatively slow-decaying signals. Here we show a fast algorithm suitable for the microsecond region with precision closely approaching the theoretical limit and compatible with the rapid scanning cytometry technique. We exploit this approach to further extend optical time-domain multiplexing to the downconversion luminescence, using luminescence microspheres wherein lifetimes are tuned through luminescence resonance energy transfer. We demonstrate real-time discrimination of these microspheres in the rapid scanning cytometry, and apply them to the multiplexed probing of pathogen DNA strands. Our results indicate that tunable luminescence lifetimes have considerable potential in high-throughput analytical sciences. PMID:24796249

  3. Search of the energetic gamma-ray experiment telescope (EGRET) data for high-energy gamma-ray microsecond bursts

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Bertsch, D. L.; Dingus, B. L.; Esposito, J. A.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Lin, Y. C.; Mattox, J. R.

    1994-01-01

    Hawking (1974) and Page & Hawking (1976) investigated theoretically the possibility of detecting high-energy gamma rays produced by the quantum-mechanical decay of a small black hole created in the early universe. They concluded that, at the very end of the life of the small black hole, it would radiate a burst of gamma rays peaked near 250 MeV with a total energy of about 10(exp 34) ergs in the order of a microsecond or less. The characteristics of a black hole are determined by laws of physics beyond the range of current particle accelerators; hence, the search for these short bursts of high-energy gamma rays provides at least the possibility of being the first test of this region of physics. The Compton Observatory Energetic Gamma-Ray Experiment Telescope (EGRET) has the capability of detecting directly the gamma rays from such bursts at a much fainter level than SAS 2, and a search of the EGRET data has led to an upper limit of 5 x 10(exp -2) black hole decays per cu pc per yr, placing constraints on this and other theories predicting microsecond high-energy gamma-ray bursts.

  4. Breaking the millisecond barrier on SpiNNaker: implementing asynchronous event-based plastic models with microsecond resolution

    PubMed Central

    Lagorce, Xavier; Stromatias, Evangelos; Galluppi, Francesco; Plana, Luis A.; Liu, Shih-Chii; Furber, Steve B.; Benosman, Ryad B.

    2015-01-01

    Spike-based neuromorphic sensors such as retinas and cochleas, change the way in which the world is sampled. Instead of producing data sampled at a constant rate, these sensors output spikes that are asynchronous and event driven. The event-based nature of neuromorphic sensors implies a complete paradigm shift in current perception algorithms toward those that emphasize the importance of precise timing. The spikes produced by these sensors usually have a time resolution in the order of microseconds. This high temporal resolution is a crucial factor in learning tasks. It is also widely used in the field of biological neural networks. Sound localization for instance relies on detecting time lags between the two ears which, in the barn owl, reaches a temporal resolution of 5 μs. Current available neuromorphic computation platforms such as SpiNNaker often limit their users to a time resolution in the order of milliseconds that is not compatible with the asynchronous outputs of neuromorphic sensors. To overcome these limitations and allow for the exploration of new types of neuromorphic computing architectures, we introduce a novel software framework on the SpiNNaker platform. This framework allows for simulations of spiking networks and plasticity mechanisms using a completely asynchronous and event-based scheme running with a microsecond time resolution. Results on two example networks using this new implementation are presented. PMID:26106288

  5. Pentachlorodibenzo-p-dioxin isomer differentiation by capillary gas chromatography Fourier transform infrared spectroscopy

    SciTech Connect

    Grainger, J.; Reddy, V.V.; Patterson D.G. Jr.

    1988-07-01

    Reference infrared vapor-phase spectra of the 14 pentachlorodibenzo-p-dioxin (PnCDD) isomers were recorded at low microgram concentrations. A unique infrared spectrum corresponding to each chromatographically separated or spectrally subtracted mixture component was observed. The structures for individual isomers in each isomer pair were assigned by qualitative valence-bond evaluations and empirically derived quantitative estimations of ether linkage asymmetric stretching frequencies (..nu../sub =/). Correlations between calculated ether linkage (C-O-C) bond angles and ..nu../sub COC(asym)/ indicate the existence of buttressed 1,6 and 1,9 nonbonded interactions not observed in tetrachlorodibenzo-p-dioxin (TCDD) isomers.

  6. Gamma-ray spectroscopy of the ^238U shape isomer.

    NASA Astrophysics Data System (ADS)

    Hauschild, K.; Bauer, R. W.; Becker, J. A.; Bernstein, L. A.; Britt, H. C.; Younes, W.; Fotiades, N.

    1997-04-01

    The γ--rays de--exciting the fission isomers ^236U and ^238U are very different despite similar excitation energies, lifetimes and low--lying yrast structures. The predominant γ--ray decay branch for ^236U^m is a 1.783 MeV E1 transition (J. Schirmer, et al., Phys. Rev. Lett. 63), 2196 (1989); and Refs. therein., while ^238U^m is depopulated by a 2.513 MeV E2 γ-ray (J. Kantele, et al., Phys. Rev. C 29), 1693 (1984); and Refs. therein.. Approximately 65% of the γ--branch de-exciting ^238U^m remains to be identified. To determine the multipolarity of the remaining γ-branch out of ^238U^m we used the Gammasphere array at LBNL and the ^238U(d,pn) reaction at Ed = 20 MeV. A search for excited states in the 2^nd well has also been conducted. Preliminary results will be presented, and the γ--decay of the shape isomers discussed in context with the recent A ~190 SD decay--out results (T. L. Khoo, et al., Phys. Rev. Lett. 76), 1583 (1996); A. Lopez-Martens, et al., Phys. Lett. B380, 18 (1996); K. Hauschild, et al., submitted to Phys. Rev. C (1996)..

  7. Isom's thickness noise for axial and centrifugal subsonic fans

    NASA Astrophysics Data System (ADS)

    Khelladi, S.; Kouidri, S.; Rey, R.

    2008-06-01

    The thickness noise predicted by the Ffowcs Williams and Hawkings (FW&H) equation depends on the normal velocity vn which is very sensitive to the meshing size. Isom showed that in a far field a monopolar source is equivalent to a dipolar source induced by a uniform distribution of the load on the entire moving surface. Consequently, the calculation of the thickness noise becomes completely independent of the normal velocity vn. Its expression, as suggested by Farassat, is for any moving surface. The main objective of this work is to determine a specific expression of Isom's thickness noise in time and frequency domains for axial and centrifugal subsonic fans. The proposed form of the thickness noise enables to highlight the effect of each geometrical parameter of the fan on the overall thickness noise, on the one hand, and presents a fast computational mean and low memory storage capability since the acoustic pressure in the frequency domain is calculated for only one blade, on the other.

  8. The prenucleosome, a stable conformational isomer of the nucleosome

    PubMed Central

    Fei, Jia; Torigoe, Sharon E.; Brown, Christopher R.; Khuong, Mai T.; Kassavetis, George A.; Boeger, Hinrich; Kadonaga, James T.

    2015-01-01

    Chromatin comprises nucleosomes as well as nonnucleosomal histone–DNA particles. Prenucleosomes are rapidly formed histone–DNA particles that can be converted into canonical nucleosomes by a motor protein such as ACF. Here we show that the prenucleosome is a stable conformational isomer of the nucleosome. It consists of a histone octamer associated with ∼80 base pair (bp) of DNA, which is located at a position that corresponds to the central 80 bp of a nucleosome core particle. Monomeric prenucleosomes with free flanking DNA do not spontaneously fold into nucleosomes but can be converted into canonical nucleosomes by an ATP-driven motor protein such as ACF or Chd1. In addition, histone H3K56, which is located at the DNA entry and exit points of a canonical nucleosome, is specifically acetylated by p300 in prenucleosomes relative to nucleosomes. Prenucleosomes assembled in vitro exhibit properties that are strikingly similar to those of nonnucleosomal histone–DNA particles in the upstream region of active promoters in vivo. These findings suggest that the prenucleosome, the only known stable conformational isomer of the nucleosome, is related to nonnucleosomal histone–DNA species in the cell. PMID:26680301

  9. Chemical Simulations of Prebiotic Molecules: Interstellar Ethanimine Isomers

    NASA Astrophysics Data System (ADS)

    Quan, Donghui; Herbst, Eric; Corby, Joanna F.; Durr, Allison; Hassel, George

    2016-06-01

    The E- and Z-isomers of ethanimine (CH3CHNH) were recently detected toward the star-forming region Sagittarius (Sgr) B2(N) using the Green Bank Telescope PRIMOS cm-wave spectral data, and imaged by the Australia Telescope Compact Array. Ethanimine is not reported in the hot cores of Sgr B2, but only in gas that absorbs at +64 and +82 km s‑1 in the foreground of continuum emission generated by H ii regions. The ethanimine isomers can serve as precursors of the amino acid alanine and may play important roles in forming biological molecules in the interstellar medium. Here we present a study of the chemistry of ethanimine using a gas-grain simulation based on rate equations, with both isothermal and warm-up conditions. In addition, the density, kinetic temperature, and cosmic ray ionization rate have been varied. For a variety of physical conditions in the warm-up models for Sgr B2(N) and environs, the simulations show reasonable agreement with observationally obtained abundances. Isothermal models of translucent clouds along the same line of sight yield much lower abundances, so that ethanimine would be much more difficult to detect in these sources despite the fact that other complex molecules have been detected there.

  10. A [10]Annulene isomer may be aromatic, after all

    SciTech Connect

    Sulzbach, H.M.; Schleyer, P.R. von Univ. Erlangen-Nuernberg ); Jiao, H. ); Xie, Y.; Schaefer, H.F. III )

    1995-02-01

    Despite its adherence to Huckel's rule, $LB 10$RB annulene is thought to prefer nonaromatic, nonplanar structures. This seemingly reasonable conclusion is based on experimental studies carried out a quarter century ago, but the detailed nature of the [10]annulene isomers has not been fully elucidated. A new, nearly planar aromatic monotrans [10]annulene configuration has now been characterized at the second-order perturbation (MP2) and density functional (B3LYP) levels of theory. The structure, with a symmetry plane that bisects the molecule, is not a stationary point at uncorrelated levels, but it is the most stable [10]annulene isomer at MP2(fc)/DZd and at higher levels. The inner hydrogen is only bent out of the approximate carbon plane by about 20[degree]. The estimated aromatic stabilization energy (17.7 kcal/mol, after correction for strain), the diamagnetic susceptibility exaltation ([Lambda] = -66.9 ppm cgs, [Lambda][sub Naphtalene] = -28.2), and the upfield NMR chemical shift of the inner hydrogen ([delta] = -6.1 ppm) confirm the aromaticity of this new C[sub s] [10]annulene conformation. 23 refs., 3 figs., 5 tabs.