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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. 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.

  14. 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.

  15. [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

  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. 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.

  2. 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.

  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. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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?

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  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. 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

  13. 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.

  14. 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.

  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. 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.

  4. 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

  5. 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

  6. 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

  7. 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.

  8. 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.

  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. 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.

  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. 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

  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. 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.

  4. 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

  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. 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.

  10. 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.

  11. 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

  12. 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

  13. 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

  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. 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.

  16. 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

  17. 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

  18. 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)

  19. 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

  20. 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.

  1. 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.

  2. 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.

  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. 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.

  5. 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...

  6. 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

  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. 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.

  11. 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.

  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. 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

  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. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. 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.

  6. 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

  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 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.

  15. 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

  16. 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.

  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. 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.

  2. 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.

  3. 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

  4. 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.

  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. 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

  13. 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

  14. 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

  15. 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.

  16. 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...

  17. 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.

  18. 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.

  19. 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

  20. 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

  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. 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.

  5. 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.

  6. 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.

  7. 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

  8. [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

  9. 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)

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. 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

  15. 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

  16. 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)

  17. 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.

  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. 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.

  7. 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.

  8. 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

  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 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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.

  16. 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.

  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. 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.

  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. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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

  11. 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.

  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. 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

  17. 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.

  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. 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

  3. 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

  4. 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.

  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. 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

  7. 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)..

  8. 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.

  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.

  11. Hydrogen rich gas generator

    NASA Technical Reports Server (NTRS)

    Houseman, J. (Inventor)

    1976-01-01

    A process and apparatus is described for producing a hydrogen rich gas by introducing a liquid hydrocarbon fuel in the form of a spray into a partial oxidation region and mixing with a mixture of steam and air that is preheated by indirect heat exchange with the formed hydrogen rich gas, igniting the hydrocarbon fuel spray mixed with the preheated mixture of steam and air within the partial oxidation region to form a hydrogen rich gas.

  12. Enhanced bioavailability of lycopene when consumed as cis-isomers from tangerine compared to red tomato juice, a randomized, cross-over clinical trial

    PubMed Central

    Cooperstone, Jessica L.; Ralston, Robin A.; Riedl, Ken M.; Haufe, Thomas C.; Schweiggert, Ralf M.; King, Samantha A.; Timmers, Cynthia D.; Francis, David M.; Lesinski, Gregory B.; Clinton, Steven K.; Schwartz, Steven J.

    2015-01-01

    Scope Tangerine tomatoes (Solanum lycopersicum) are rich in tetra-cis-lycopene resulting from natural variation in carotenoid isomerase. Our objective was to compare the bioavailability of lycopene from tangerine to red tomato juice, and elucidate physical deposition forms of these isomers in tomatoes by light and electron microscopy. Methods and results Following a randomized crossover design, subjects (n=11, 6M/5F) consumed two meals delivering 10 mg lycopene from tangerine (94% cis) or red tomato juice (10% cis). Blood was sampled over 12 hours and triglyceride-rich lipoprotein fractions of plasma (TRLs) were isolated and analyzed using HPLC-DAD-MS/MS. Lycopene was crystalline in red tomato chromoplasts and globular in tangerine tomatoes. With tangerine tomato juice we observed a marked 8.5-fold increase in lycopene bioavailability compared to red tomato juice (P<0.001). Fractional absorption was 47.70 ± 8.81% from tangerine and 4.98 ± 1.92% from red tomato juices. Large heterogeneity was observed among subjects. Conclusions Lycopene is markedly more bioavailable from tangerine than from red tomato juice, consistent with a predominance of cis-lycopene isomers and presence in chromoplasts in a lipid dissolved globular state. These results justify using tangerine tomatoes as a lycopene source in studies examining the potential health benefits of lycopene-rich foods. PMID:25620547

  13. Research: Rags to Rags? Riches to Riches?

    ERIC Educational Resources Information Center

    Bracey, Gerald W.

    2004-01-01

    Everyone has read about what might be called the "gold gap"--how the rich in this country are getting richer and controlling an ever-larger share of the nation's wealth. The Century Foundation has started publishing "Reality Check", a series of guides to campaign issues that sometimes finds gaps in these types of cherished delusions. The guides…

  14. GPUbased, Microsecond Latency, HectoChannel MIMO Feedback Control of Magnetically Confined Plasmas

    NASA Astrophysics Data System (ADS)

    Rath, Nikolaus

    Feedback control has become a crucial tool in the research on magnetic confinement of plasmas for achieving controlled nuclear fusion. This thesis presents a novel plasma feedback control system that, for the first time, employs a Graphics Processing Unit (GPU) for microsecond-latency, real-time control computations. This novel application area for GPU computing is opened up by a new system architecture that is optimized for low-latency computations on less than kilobyte sized data samples as they occur in typical plasma control algorithms. In contrast to traditional GPU computing approaches that target complex, high-throughput computations with massive amounts of data, the architecture presented in this thesis uses the GPU as the primary processing unit rather than as an auxiliary of the CPU, and data is transferred from A-D/D-A converters directly into GPU memory using peer-to-peer PCI Express transfers. The described design has been implemented in a new, GPU-based control system for the High-Beta Tokamak - Extended Pulse (HBT-EP) device. The system is built from commodity hardware and uses an NVIDIA GeForce GPU and D-TACQ A-D/D-A converters providing a total of 96 input and 64 output channels. The system is able to run with sampling periods down to 4 μs and latencies down to 8 μs. The GPU provides a total processing power of 1.5 x 1012 floating point operations per second. To illustrate the performance and versatility of both the general architecture and concrete implementation, a new control algorithm has been developed. The algorithm is designed for the control of multiple rotating magnetic perturbations in situations where the plasma equilibrium is not known exactly and features an adaptive system model: instead of requiring the rotation frequencies and growth rates embedded in the system model to be set a priori, the adaptive algorithm derives these parameters from the evolution of the perturbation amplitudes themselves. This results in non-linear control

  15. Processing Tangerine Tomatoes: Effects on Lycopene-Isomer Concentrations and Profile

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Because lycopene is a powerful biological antioxidant, its delivery to humans is of major concern. Cis-Lycopene isomers are more bioavailable than the all-trans isomer and thus more efficiently absorbed. Tangerine tomatoes, whose lycopene isomeric content is almost all tetra-cis, provide a useful ...

  16. PROCESSING TANGERINE TOMATOES: EFFECTS ON LYCOPENE-ISOMER CONCENTRATION AND PROFILE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Because lycopene is a powerful biological antioxidant, its delivery to humans is of major concern. cis-lycopene isomers are more bioavailable than the all-trans isomers and thus more efficiently absorbed. Tangerine tomatoes, whose lycopene isomeric content is almost all tetra-cis, provide a useful f...

  17. A Highly Sensitive Diketopyrrolopyrrole-Based Ambipolar Transistor for Selective Detection and Discrimination of Xylene Isomers.

    PubMed

    Wang, Bin; Huynh, Tan-Phat; Wu, Weiwei; Hayek, Naseem; Do, Thu Trang; Cancilla, John C; Torrecilla, Jose S; Nahid, Masrur Morshed; Colwell, John M; Gazit, Oz M; Puniredd, Sreenivasa Reddy; McNeill, Christopher R; Sonar, Prashant; Haick, Hossam

    2016-06-01

    An ambipolar poly(diketopyrrolopyrrole-terthiophene)-based field-effect transistor (FET) sensitively detects xylene isomers at low ppm levels with multiple sensing features. Combined with pattern-recognition algorithms, a sole ambipolar FET sensor, rather than arrays of sensors, can discriminate highly similar xylene structural isomers from one another. PMID:26996398

  18. Synthesis of a volatile compound of the (2 minus ) Ho-160 nuclear isomer

    SciTech Connect

    Hartmann, F.X.; Naumann, R.A. )

    1988-10-01

    The synthesis of volatile compounds of radioactive holmium atoms are described and the gamma-ray spectra following the decay of the longest-lived isomer (Ho-160) presented. This latter isomer has an ultra-low energy transition of potential interest in laser driven nuclear inter-level transfer studies.

  19. Comparison of some specific polychlorinated biphenyl isomers in human and monkey milk

    SciTech Connect

    Mes, J.; Marchand, L.

    1987-11-01

    The presence and levels of polychlorinated biphenyls (PCBs) in monkey milk have been reported earlier as part of studies which investigated the overall toxicity of PCBs in commercial Aroclors. Some of this information has served as a basis for an estimation of the potential health hazard of PCB contaminated breast milk to human infants. To further support such extrapolation from one primate situation to another, it would be desirable to know not only the levels of PCBs in the milk of these primates, but also the isomeric distribution in order to better evaluate the contribution of each isomer to the overall toxicity. A large concentration in breast milk of an isomer of relatively low toxicity may have the same effect on an infant as a smaller concentration of a highly toxic isomer. This paper compares the relative amounts of 29 selected PCB isomers in human milk and monkey milk samples. The selection of isomers was based on the most prevalent PCB isomers in human milk and represented approximately 80% of all reported isomers. In addition, Aroclor 1254, whose toxicity in monkeys has been investigated recently by several investigators, was analyzed for the same 29 selected PCB isomers.

  20. 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 trans isomers and 4% ar...

  1. TETRACHLORODIBENZODIOXIN ISOMER DIFFERENTIATION BY MICRO DIFFUSE REFLECTANCE FOURIER TRANSFORM INFRARED SPECTROMETRY AT THE LOW NANOGRAM LEVEL

    EPA Science Inventory

    Infrared diffuse reflectance spectra were recorded for the 22 tetrachlorodibenzodioxin isomers (TCDDs). By use of micro-DRIFT techniques and signal averaging, identifiable spectra for each of the isomers were achieved at low nanogram levels. Spectral features in the 1200/cm to 16...

  2. 40 CFR 180.436 - Cyfluthrin and the isomer beta-cyfluthrin; tolerances for residues.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... § 180.436, see the List of CFR Sections Affected, which appears in the Finding Aids section of the... 40 Protection of Environment 25 2012-07-01 2012-07-01 false Cyfluthrin and the isomer beta... FOOD Specific Tolerances § 180.436 Cyfluthrin and the isomer beta-cyfluthrin; tolerances for...

  3. 40 CFR 180.418 - Cypermethrin and an isomer zeta-cypermethrin; tolerances for residues.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 25 2013-07-01 2013-07-01 false Cypermethrin and an isomer zeta-cypermethrin; tolerances for residues. 180.418 Section 180.418 Protection of Environment ENVIRONMENTAL... FOOD Specific Tolerances § 180.418 Cypermethrin and an isomer zeta-cypermethrin; tolerances...

  4. 40 CFR 180.436 - Cyfluthrin and the isomer beta-cyfluthrin; tolerances for residues.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... § 180.436, see the List of CFR Sections Affected, which appears in the Finding Aids section of the... 40 Protection of Environment 24 2014-07-01 2014-07-01 false Cyfluthrin and the isomer beta... FOOD Specific Tolerances § 180.436 Cyfluthrin and the isomer beta-cyfluthrin; tolerances for...

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

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 24 2014-07-01 2014-07-01 false Cypermethrin and an isomer zeta-cypermethrin; tolerances for residues. 180.418 Section 180.418 Protection of Environment ENVIRONMENTAL... FOOD Specific Tolerances § 180.418 Cypermethrin and an isomer zeta-cypermethrin; tolerances...

  6. 40 CFR 180.436 - Cyfluthrin and the isomer beta-cyfluthrin; tolerances for residues.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... § 180.436, see the List of CFR Sections Affected, which appears in the Finding Aids section of the... 40 Protection of Environment 25 2013-07-01 2013-07-01 false Cyfluthrin and the isomer beta... FOOD Specific Tolerances § 180.436 Cyfluthrin and the isomer beta-cyfluthrin; tolerances for...

  7. 40 CFR 180.436 - Cyfluthrin and the isomer beta-cyfluthrin; tolerances for residues.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... § 180.436, see the List of CFR Sections Affected, which appears in the Finding Aids section of the... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Cyfluthrin and the isomer beta... FOOD Specific Tolerances § 180.436 Cyfluthrin and the isomer beta-cyfluthrin; tolerances for...

  8. 40 CFR 180.436 - Cyfluthrin and the isomer beta-cyfluthrin; tolerances for residues.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... § 180.436, see the List of CFR Sections Affected, which appears in the Finding Aids section of the... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Cyfluthrin and the isomer beta... FOOD Specific Tolerances § 180.436 Cyfluthrin and the isomer beta-cyfluthrin; tolerances for...

  9. Experimental Results from Oak Ridge Isomer Spectrometer and Separator (ORISS)

    NASA Astrophysics Data System (ADS)

    Piechaczek, A.; Batchelder, J. C.; Carter, H. K.; Goans, R. E.; Liu, S.; Shchepunov, V.; Zganjar, E. F.; Unirib Collaboration

    2013-10-01

    ORISS is a linear multi reflection time-of-flight mass analyzer developed by the University Radioactive Ion Beam Consortium. It will be used to separate any isobar and many isomers for decay spectroscopy experiments. The entire system's operation was demonstrated with a less than ideal multi-isotopic ion source and achieved a mass resolving power as high as 430,000. To better characterize the system we have installed a monoisotopic 133Cs ion source. The radiofrequency quadrupole ion cooler and buncher, which serves as the ion injector into ORISS, was tested in stand-alone mode and achieved a longitudinal emittance of 22 π eV × ns and transmission >40%. These very good results confirm our expectation that ORISS can achieve the design goals. Using the improved ion source, we expect, very soon, to demonstrate the complete system's design goals of 400,000 mass resolving power and 50% transmission.

  10. Lutein and Zeaxanthin Isomers in Eye Health and Disease.

    PubMed

    Mares, Julie

    2016-07-17

    Current evidence suggests lutein and its isomers play important roles in ocular development in utero and throughout the life span, in vision performance in young and later adulthood, and in lowering risk for the development of common age-related eye diseases in older age. These xanthophyll (oxygen-containing) carotenoids are found in a wide variety of vegetables and fruits, and they are present in especially high concentrations in leafy green vegetables. Additionally, egg yolks and human milk appear to be bioavailable sources. The prevalence of lutein, zeaxanthin, and meso-zeaxanthin in supplements is increasing. Setting optimal and safe ranges of intake requires additional research, particularly in pregnant and lactating women. Accumulating evidence about variable interindividual response to dietary intake of these carotenoids, based on genetic or metabolic influences, suggests that there may be subgroups that benefit from higher levels of intake and/or alternate strategies to improve lutein and zeaxanthin status. PMID:27431371

  11. Elongated shape isomers in the {sup 36}Ar nucleus

    SciTech Connect

    Cseh, Jozsef; Darai, Judit; Sciani, Wagner; Otani, Yul; Lepine-Szily, Alinka; Benjamim, Elisangela A.; Chamon, Luiz Carlos; Filho, Rubens Lichtenthaeler

    2009-09-15

    A recent analysis of the {sup 12}C+{sup 24}Mg scattering [W. Sciani et al., Phys. Rev. C 80, 034319 (2009)] suggests the existence of a hyperdeformed band in the {sup 36}Ar nucleus, completely in line with the predictions of {alpha}[W. D. M. Rae and A. C. Merchant, Phys. Lett. B279, 207 (1992)] and binary cluster calculations [J. Cseh et al., Phys. Rev. C 70, 034311 (2004)]. Here we review the structural understanding of the superdeformed and the hyperdeformed states of {sup 36}Ar 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.

  12. A new NMR approach for the assignment of symmetric isomers.

    PubMed

    Lunazzi, Lodovico; Mazzanti, Andrea

    2004-09-29

    Irradiation of the (13)C satellite (1% natural abundance) of the NMR (1)H signals yields NOE effects on the spatially close hydrogens of the same isotopomer but not on the hydrogens of the 99% isotopomer having only (12)C atoms. In a DPFGSE-NOE sequence, the latter signals are completely canceled, and it is possible, therefore, to detect NOE effects experienced by isochronous lines that would not be otherwise observable. This allows the structural assignments of symmetric isomers to be unambiguously obtained. Examples are reported for the cases of the cis and trans dimethylstilbene, cis and trans stilbeneoxide, 2,5- and 3,4-dimethylthiophene, 1,8- and 1,5-dimethylnaphthalene, syn and anti 1,2-bis(2-methyl-1-naphthyl)benzene, 1,3-cyclooctadiene, and cycloheptatriene. PMID:15382951

  13. Microsecond X-ray Absorption Spectroscopy Identification of Co(I) Intermediates in Cobaloxime-Catalyzed Hydrogen Evolution.

    PubMed

    Smolentsev, Grigory; Cecconi, Bianca; Guda, Alexander; Chavarot-Kerlidou, Murielle; van Bokhoven, Jeroen A; Nachtegaal, Maarten; Artero, Vincent

    2015-10-19

    Rational development of efficient photocatalytic systems for hydrogen production requires understanding the catalytic mechanism and detailed information about the structure of intermediates in the catalytic cycle. We demonstrate how time-resolved X-ray absorption spectroscopy in the microsecond time range can be used to identify such intermediates and to determine their local geometric structure. This method was used to obtain the solution structure of the Co(I) intermediate of cobaloxime, which is a non-noble metal catalyst for solar hydrogen production from water. Distances between cobalt and the nearest ligands including two solvent molecules and displacement of the cobalt atom out of plane formed by the planar ligands have been determined. Combining in situ X-ray absorption and UV/Vis data, we demonstrate how slight modification of the catalyst structure can lead to the formation of a catalytically inactive Co(I) state under similar conditions. Possible deactivation mechanisms are discussed. PMID:26388205

  14. Microsecond Molecular Dynamics Simulations of Influenza Neuraminidase Suggest a Mechanism for the Increased Virulence of Stalk-Deletion Mutants

    PubMed Central

    2016-01-01

    Deletions in the stalk of the influenza neuraminidase (NA) surface protein are associated with increased virulence, but the mechanisms responsible for this enhanced virulence are unclear. Here we use microsecond molecular dynamics simulations to explore the effect of stalk deletion on enzymatic activity, contrasting NA proteins from the A/swine/Shandong/N1/2009 strain both with and without a stalk deletion. By modeling and simulating neuraminidase apo glycoproteins embedded in complex-mixture lipid bilayers, we show that the geometry and dynamics of the neuraminidase enzymatic pocket may differ depending on stalk length, with possible repercussions on the binding of the endogenous sialylated-oligosaccharide receptors. We also use these simulations to predict previously unrecognized druggable “hotspots” on the neuraminidase surface that may prove useful for future efforts aimed at structure-based drug design. PMID:27141956

  15. The action of microsecond-pulsed plasma-activated media on the inactivation of human lung cancer cells

    NASA Astrophysics Data System (ADS)

    Kumar, Naresh; Park, Ji Hoon; Jeon, Su Nam; Park, Bong Sang; Choi, Eun Ha; Attri, Pankaj

    2016-03-01

    In the present work, we have generated reactive species (RS) through microsecond-pulsed plasma (MPP) in the cell culture media using a Marx generator with point-point electrodes of approximately 0.06 J discharge energy/pulse. RS generated in culture media through MPP have a selective action between growth of the H460 lung cancer cells and L132 normal lung cells. We observed that MPP-activated media (MPP-AM) induced apoptosis on H460 lung cancer cells through an oxidative DNA damage cascade. Additionally, we studied the apoptosis-related mRNA expression, DNA oxidation and polymerase-1 (PARP-1) cleaved analysis from treated cancer cells. The result proves that radicals generated through MPP play a pivotal role in the activation of media that induces the selective killing effect.

  16. μABC: a systematic microsecond molecular dynamics study of tetranucleotide sequence effects in B-DNA

    PubMed Central

    Pasi, Marco; Maddocks, John H.; Beveridge, David; Bishop, Thomas C.; Case, David A.; Cheatham, Thomas; Dans, Pablo D.; Jayaram, B.; Lankas, Filip; Laughton, Charles; Mitchell, Jonathan; Osman, Roman; Orozco, Modesto; Pérez, Alberto; Petkevičiūtė, Daiva; Spackova, Nada; Sponer, Jiri; Zakrzewska, Krystyna; Lavery, Richard

    2014-01-01

    We present the results of microsecond molecular dynamics simulations carried out by the ABC group of laboratories on a set of B-DNA oligomers containing the 136 distinct tetranucleotide base sequences. We demonstrate that the resulting trajectories have extensively sampled the conformational space accessible to B-DNA at room temperature. We confirm that base sequence effects depend strongly not only on the specific base pair step, but also on the specific base pairs that flank each step. Beyond sequence effects on average helical parameters and conformational fluctuations, we also identify tetranucleotide sequences that oscillate between several distinct conformational substates. By analyzing the conformation of the phosphodiester backbones, it is possible to understand for which sequences these substates will arise, and what impact they will have on specific helical parameters. PMID:25260586

  17. Microsecond Molecular Dynamics Simulations of Influenza Neuraminidase Suggest a Mechanism for the Increased Virulence of Stalk-Deletion Mutants.

    PubMed

    Durrant, Jacob D; Bush, Robin M; Amaro, Rommie E

    2016-08-25

    Deletions in the stalk of the influenza neuraminidase (NA) surface protein are associated with increased virulence, but the mechanisms responsible for this enhanced virulence are unclear. Here we use microsecond molecular dynamics simulations to explore the effect of stalk deletion on enzymatic activity, contrasting NA proteins from the A/swine/Shandong/N1/2009 strain both with and without a stalk deletion. By modeling and simulating neuraminidase apo glycoproteins embedded in complex-mixture lipid bilayers, we show that the geometry and dynamics of the neuraminidase enzymatic pocket may differ depending on stalk length, with possible repercussions on the binding of the endogenous sialylated-oligosaccharide receptors. We also use these simulations to predict previously unrecognized druggable "hotspots" on the neuraminidase surface that may prove useful for future efforts aimed at structure-based drug design. PMID:27141956

  18. Separation and conversion dynamics of nuclear-spin isomers of gaseous methanol

    PubMed Central

    Sun, Zhen-Dong; Ge, Meihua; Zheng, Yujun

    2015-01-01

    All symmetrical molecules with non-zero nuclear spin exist in nature as nuclear-spin isomers (NSIs). However, owing to the lack of experimental information, knowledge is rare about interconversions of NSIs of gaseous molecules with torsional symmetry. Here we report our separation and conversion observations on NSI-torsion-specific transition systems of gaseous methanol from a light-induced drift experiment involving partially spatial separation of the ortho and para isomers. We find that vibrationally excited molecules of the methanol spin isomer have a smaller collision cross-section than their ground-state counterparts. Interconversion of the enriched ortho isomer with the para isomer, which is generally considered improbable, has been quantitatively studied by sensitive detections of the spectral intensities. Rather counterintuitively, this reveals that the interconversion is inhibited with increasing pressure. Our results suggest that the spin conversion mechanism in methanol is via a quantum relaxation process with the quantum Zeno effect induced by molecular collisions. PMID:25880882

  19. Separation and conversion dynamics of nuclear-spin isomers of gaseous methanol

    NASA Astrophysics Data System (ADS)

    Sun, Zhen-Dong; Ge, Meihua; Zheng, Yujun

    2015-04-01

    All symmetrical molecules with non-zero nuclear spin exist in nature as nuclear-spin isomers (NSIs). However, owing to the lack of experimental information, knowledge is rare about interconversions of NSIs of gaseous molecules with torsional symmetry. Here we report our separation and conversion observations on NSI-torsion-specific transition systems of gaseous methanol from a light-induced drift experiment involving partially spatial separation of the ortho and para isomers. We find that vibrationally excited molecules of the methanol spin isomer have a smaller collision cross-section than their ground-state counterparts. Interconversion of the enriched ortho isomer with the para isomer, which is generally considered improbable, has been quantitatively studied by sensitive detections of the spectral intensities. Rather counterintuitively, this reveals that the interconversion is inhibited with increasing pressure. Our results suggest that the spin conversion mechanism in methanol is via a quantum relaxation process with the quantum Zeno effect induced by molecular collisions.

  20. Process for recovering 4,4 prime dihydroxydiphenyl sulfone from an isomer mixture

    SciTech Connect

    Zemlanicky, F.; Cooker, B.

    1991-03-19

    This patent describes a process for the recovery of 4,4{prime}-bisphenol sulfone from an isomer mixture comprising 4,4{prime}-bisphenol sulfone and 2,4{prime}-bisphenol sulfone. It comprises dissolving the isomer mixture in a basic aqueous solution comprising about one mole of base per mole of the mixture of 4,4{prime}-bisphenol sulfone and 2,4{prime}-bisphenol sulfone to form a basic isomer solution and adding acid to the isomer solution in an amount of from about 0.85 to 0.95 mole per mole of the 4,4{prime}-bisphenol sulfone wherein the acid is added in an amount sufficient to cause selective precipitation of crystals of 4,4{prime}-bisphenol sulfone yet in an amount less than sufficient to neutralize the isomer solution and removing the crystals of 4,4{prime}-bisphenol from the aqueous solution.

  1. Odd tensor electric transitions in high-spin Sn-isomers and generalized seniority

    NASA Astrophysics Data System (ADS)

    Maheshwari, Bhoomika; Jain, Ashok Kumar

    2016-02-01

    The similar behavior of the B (E 1) values of the recently observed 13- odd tensor E1 isomers and the B (E 2) values of the 10+ and 15- even tensor E2 isomers in the Sn-isotopes has been understood in terms of the generalized seniority for multi-j orbits by using the quasi-spin scheme. This simple approach proves to be quite successful in explaining the measured transition probabilities and the corresponding half-lives in the high-spin isomers of the semi-magic Sn-isotopes. Hence, we show for the first time the occurrence of seniority isomers in the 13- Sn-isomers, which decay by odd-tensor E1 transitions to the same seniority states.

  2. Thermodynamics and kinetics of guest-induced switching between "basket handle" porphyrin isomers.

    PubMed

    Deutman, Alexander B C; Woltinge, Tim; Smits, Jan M M; De Gelder, René; Elemans, Johannes A A W; Nolte, Roeland J M; Rowan, Alan E

    2014-01-01

    The synthesis and switching properties of two "basket handle" porphyrin isomers is described. The cis-oriented meso-phenyl groups of these porphyrins are linked at their ortho-positons via benzocrown-ether-based spacers, which as a result of slow atropisomerization are located either on the same side of the porphyrin plane (cis), or on opposite sides (trans). In solution, the cis-linked isomer slowly isomerizes in the direction of the thermodynamically more stable trans-isomer. In the presence of viologen (N,N'-dialkyl-4,4'-bipyridinium) derivatives, which have different affinities for the two isomers, the isomerization equilibrium could be significantly influenced. In addition, the presence of these guests was found to enhance the rate of the switching process, which was suggested to be caused by favorable interactions between the positively charged guest and the crown ethers of the receptor, stabilizing the transition state energies of the isomerization reaction between the two isomers. PMID:24762966

  3. Table of superdeformed nuclear bands and fission isomers

    SciTech Connect

    Firestone, R.B.; Singh, B.

    1994-06-01

    A minimum in the second potential well of deformed nuclei was predicted and the associated shell gaps are illustrated in the harmonic oscillator potential shell energy surface calculations shown in this report. A strong superdeformed minimum in {sup 152}Dy was predicted for {beta}{sub 2}-0.65. Subsequently, a discrete set of {gamma}-ray transitions in {sup 152}DY was observed and, assigned to the predicted superdeformed band. Extensive research at several laboratories has since focused on searching for other mass regions of large deformation. A new generation of {gamma}-ray detector arrays is already producing a wealth of information about the mechanisms for feeding and deexciting superdeformed bands. These bands have been found in three distinct regions near A=l30, 150, and 190. This research extends upon previous work in the actinide region near A=240 where fission isomers were identified and also associated with the second potential well. Quadrupole moment measurements for selected cases in each mass region are consistent with assigning the bands to excitations in the second local minimum. As part of our committment to maintain nuclear structure data as current as possible in the Evaluated Nuclear Structure Reference File (ENSDF) and the Table of Isotopes, we have updated the information on superdeformed nuclear bands. As of April 1994, we have complied data from 86 superdeformed bands and 46 fission isomers identified in 73 nuclides for this report. For each nuclide there is a complete level table listing both normal and superdeformed band assignments; level energy, spin, parity, half-life, magneto moments, decay branchings; and the energies, final levels, relative intensities, multipolarities, and mixing ratios for transitions deexciting each level. Mass excess, decay energies, and proton and neutron separation energies are also provided from the evaluation of Audi and Wapstra.

  4. Structures, bonding and energies of N 6 isomers

    NASA Astrophysics Data System (ADS)

    Glukhovtsev, Mikhail N.; von Ragué Schleyer, Paul

    1992-10-01

    The most stable N 6 isomer, a twisted open-chain C 2 structure, is 188.3 kcal/mol (MP4SDTQ/6-31G(d)//MP2(full)/6-31 G(d) + ZPE(MP2/6-31 G(d))) higher in energy than three N 2 molecules. In contrast to benzene, hexazine, N 6, prefers a non-planar twist-boat D 2 structure, but this is 26.0 kcal/mol less stable than the C 2 form. The D 6h altenative is a second-order saddle point at MP2 (full)/6-31G(d) 2.1 kcal/mol higher in energy at MP4SDTQ/6-311 (+s)G(d)//MP2(full)/6-311 (+s)G(2d) + ZPE (MP2/6-31G(d)). The homodesmotic and hyperhomodesmotic reaction energies indicate that the D 6h structure is destabilized (-17.6 and -10.4 kcal/mol, respectively), in contrast to the stabilization of benzene (23.9 and 20.3 kcal/mol, respectively, MP4SDTQ/6-31 G(d, p)//MP2(full)/6-31 G(d, p)). NBO analysis shows that none of the N atoms in the N 6 open-chain structures forms more than four covalent bonds. The other N 6 valence isomers, hexaaza-Dewar-benzene, hexaazabicyclopropenyl, and hexaazaprismane are higher in energy than hexazine (33.9, 29.6 and 115.8 kcal/mol, respectively) at MP4SDTQ(fc)/6-31 G(d)/MP2(full)/6-31 G(d) + ZPE(HF/6-31 G(d)).

  5. Organometal halide perovskite solar cell materials rationalized: ultrafast charge generation, high and microsecond-long balanced mobilities, and slow recombination.

    PubMed

    Ponseca, Carlito S; Savenije, Tom J; Abdellah, Mohamed; Zheng, Kaibo; Yartsev, Arkady; Pascher, Tobjörn; Harlang, Tobias; Chabera, Pavel; Pullerits, Tonu; Stepanov, Andrey; Wolf, Jean-Pierre; Sundström, Villy

    2014-04-01

    Organometal halide perovskite-based solar cells have recently been reported to be highly efficient, giving an overall power conversion efficiency of up to 15%. However, much of the fundamental photophysical properties underlying this performance has remained unknown. Here, we apply photoluminescence, transient absorption, time-resolved terahertz and microwave conductivity measurements to determine the time scales of generation and recombination of charge carriers as well as their transport properties in solution-processed CH3NH3PbI3 perovskite materials. We found that electron-hole pairs are generated almost instantaneously after photoexcitation and dissociate in 2 ps forming highly mobile charges (25 cm(2) V(-1) s(-1)) in the neat perovskite and in perovskite/alumina blends; almost balanced electron and hole mobilities remain very high up to the microsecond time scale. When the perovskite is introduced into a TiO2 mesoporous structure, electron injection from perovskite to the metal oxide is efficient in less than a picosecond, but the lower intrinsic electron mobility of TiO2 leads to unbalanced charge transport. Microwave conductivity measurements showed that the decay of mobile charges is very slow in CH3NH3PbI3, lasting up to tens of microseconds. These results unravel the remarkable intrinsic properties of CH3NH3PbI3 perovskite material if used as light absorber and charge transport layer. Moreover, finding a metal oxide with higher electron mobility may further increase the performance of this class of solar cells. PMID:24654882

  6. Coupling between Histone Conformations and DNA Geometry in Nucleosomes on a Microsecond Timescale: Atomistic Insights into Nucleosome Functions.

    PubMed

    Shaytan, Alexey K; Armeev, Grigoriy A; Goncearenco, Alexander; Zhurkin, Victor B; Landsman, David; Panchenko, Anna R

    2016-01-16

    An octamer of histone proteins wraps about 200bp of DNA into two superhelical turns to form nucleosomes found in chromatin. Although the static structure of the nucleosomal core particle has been solved, details of the dynamic interactions between histones and DNA remain elusive. We performed extensively long unconstrained, all-atom microsecond molecular dynamics simulations of nucleosomes including linker DNA segments and full-length histones in explicit solvent. For the first time, we were able to identify and characterize the rearrangements in nucleosomes on a microsecond timescale including the coupling between the conformation of the histone tails and the DNA geometry. We found that certain histone tail conformations promoted DNA bulging near its entry/exit sites, resulting in the formation of twist defects within the DNA. This led to a reorganization of histone-DNA interactions, suggestive of the formation of initial nucleosome sliding intermediates. We characterized the dynamics of the histone tails upon their condensation on the core and linker DNA and showed that tails may adopt conformationally constrained positions due to the insertion of "anchoring" lysines and arginines into the DNA minor grooves. Potentially, these phenomena affect the accessibility of post-translationally modified histone residues that serve as important sites for epigenetic marks (e.g., at H3K9, H3K27, H4K16), suggesting that interactions of the histone tails with the core and linker DNA modulate the processes of histone tail modifications and binding of the effector proteins. We discuss the implications of the observed results on the nucleosome function and compare our results to different experimental studies. PMID:26699921

  7. Tetrachlorodibenzo-p-dioxin isomer differentiation by capillary gas chromatography fourier transform-infrared spectroscopy

    SciTech Connect

    Grainger, J.; Gelbaum, L.T.

    1987-07-01

    Reference infrared vapor-phase spectra of the 22 tetrachlorodibenzodioxin (TCDD) isomers were recorded at low microgram concentrations. These reference spectra of synthetic mixture components separated chromatographically or by spectra subtraction exhibit distinct infrared spectra for each isomer. The infrared frequencies are delineated in correlation tables and are interpreted in terms of substitution patterns which determine the strength of the ether linkage. Absorbance values in the 1330-1280 cm (C-O-C asymmetric stretch) region correlate with specific substitution patterns and molecular geometry. Relative electron-with-drawing capacities for chlorinated aromatic rings in TCDD isomers were estimated on the basis of relative capacities determined for model compounds. Qualitative correlations were established between electron-with-drawing capacities and the effects of resonance and field interactions on the ether linkage absorption frequencies of individual TCDD isomers. Gas chromatography Fourier transform infrared (GC/FT-IR) isomer assignments are generally consistent with those obtained by proton Fourier transform nuclear magnetic resonance ( H FT/NMR) and flame ionization gas chromatography (GC/FID). A chromatographically independent method of assigning TCDD isomer structures on the basis of ether linkage asymmetric stretching frequencies was established by utilization of valence-bond approximations. GC/FT-IR assignments for several TCDD isomers differ from isomer assignments in previously publised results. A user-generated, vapor-phase reference library, containing individual TCDD spectra and spectra of isomer pairs that are incompletely resolved on chromatographic columns, correctly identified each isomer in variety of mixtures by means of a software algorithm.

  8. 40 CFR 180.438 - Lambda-cyhalothrin and an isomer gamma-cyhalothrin; tolerances for residues.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 24 2014-07-01 2014-07-01 false Lambda-cyhalothrin and an isomer gamma... FOOD Specific Tolerances § 180.438 Lambda-cyhalothrin and an isomer gamma-cyhalothrin; tolerances for... established for the combined residues of the pyrethroid [gamma-cyhalothrin (the isolated active isomer...

  9. 40 CFR 180.438 - Lambda-cyhalothrin and an isomer gamma-cyhalothrin; tolerances for residues.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Lambda-cyhalothrin and an isomer gamma... FOOD Specific Tolerances § 180.438 Lambda-cyhalothrin and an isomer gamma-cyhalothrin; tolerances for... established for the combined residues of the pyrethroid [gamma-cyhalothrin (the isolated active isomer...

  10. 40 CFR 180.438 - Lambda-cyhalothrin and an isomer gamma-cyhalothrin; tolerances for residues.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 25 2013-07-01 2013-07-01 false Lambda-cyhalothrin and an isomer gamma... FOOD Specific Tolerances § 180.438 Lambda-cyhalothrin and an isomer gamma-cyhalothrin; tolerances for... established for the combined residues of the pyrethroid [gamma-cyhalothrin (the isolated active isomer...

  11. 40 CFR 180.157 - Methyl 3-[(dimethoxyphos-phinyl) oxy]butenoate, alpha and beta isomers; tolerances for residues.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... isomers; tolerances for residues. 180.157 Section 180.157 Protection of Environment ENVIRONMENTAL... FOOD Specific Tolerances § 180.157 Methyl 3- butenoate, alpha and beta isomers; tolerances for residues... and beta isomers, in or on the following raw agricultural commodities: Commodity Parts per...

  12. 40 CFR 180.157 - Methyl 3-[(dimethoxyphos-phinyl) oxy]butenoate, alpha and beta isomers; tolerances for residues.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... isomers; tolerances for residues. 180.157 Section 180.157 Protection of Environment ENVIRONMENTAL... FOOD Specific Tolerances § 180.157 Methyl 3- butenoate, alpha and beta isomers; tolerances for residues... and beta isomers, in or on the following raw agricultural commodities: Commodity Parts per...

  13. 40 CFR 180.438 - Lambda-cyhalothrin and an isomer gamma-cyhalothrin; tolerances for residues.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Lambda-cyhalothrin and an isomer gamma... FOOD Specific Tolerances § 180.438 Lambda-cyhalothrin and an isomer gamma-cyhalothrin; tolerances for... established for the combined residues of the pyrethroid [gamma-cyhalothrin (the isolated active isomer...

  14. 40 CFR 180.438 - Lambda-cyhalothrin and an isomer gamma-cyhalothrin; tolerances for residues.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 25 2012-07-01 2012-07-01 false Lambda-cyhalothrin and an isomer gamma... FOOD Specific Tolerances § 180.438 Lambda-cyhalothrin and an isomer gamma-cyhalothrin; tolerances for... established for the combined residues of the pyrethroid [gamma-cyhalothrin (the isolated active isomer...

  15. Decay and Fission Hindrance of Two- and Four-Quasiparticle K Isomers in 254Rf

    NASA Astrophysics Data System (ADS)

    David, H. M.; Chen, J.; Seweryniak, D.; Kondev, F. G.; Gates, J. M.; Gregorich, K. E.; Ahmad, I.; Albers, M.; Alcorta, M.; Back, B. B.; Baartman, B.; Bertone, P. F.; Bernstein, L. A.; Campbell, C. M.; Carpenter, M. P.; Chiara, C. J.; Clark, R. M.; Cromaz, M.; Doherty, D. T.; Dracoulis, G. D.; Esker, N. E.; Fallon, P.; Gothe, O. R.; Greene, J. P.; Greenlees, P. T.; Hartley, D. J.; Hauschild, K.; Hoffman, C. R.; Hota, S. S.; Janssens, R. V. F.; Khoo, T. L.; Konki, J.; Kwarsick, J. T.; Lauritsen, T.; Macchiavelli, A. O.; Mudder, P. R.; Nair, C.; Qiu, Y.; Rissanen, J.; Rogers, A. M.; Ruotsalainen, P.; Savard, G.; Stolze, S.; Wiens, A.; Zhu, S.

    2015-09-01

    Two isomers decaying by electromagnetic transitions with half-lives of 4.7(1.1) and 247 (73 ) μ s have been discovered in the heavy 254Rf nucleus. The observation of the shorter-lived isomer was made possible by a novel application of a digital data acquisition system. The isomers were interpreted as the Kπ=8- , ν2(7 /2+[624 ],9 /2-[734 ]) two-quasineutron and the Kπ=1 6+, 8-ν2(7 /2+[624 ],9 /2-[734 ])⊗8-π2(7 /2-[514 ],9 /2+[624 ]) four-quasiparticle configurations, respectively. Surprisingly, the lifetime of the two-quasiparticle isomer is more than 4 orders of magnitude shorter than what has been observed for analogous isomers in the lighter N =150 isotones. The four-quasiparticle isomer is longer lived than the 254Rf ground state that decays exclusively by spontaneous fission with a half-life of 23.2 (1.1 ) μ s . The absence of sizable fission branches from either of the isomers implies unprecedented fission hindrance relative to the ground state.

  16. Structural-based differences in ecotoxicity of benzoquinoline isomers to the zebra mussel (Dreissena polymorpha)

    SciTech Connect

    Kraak, M.H.S.; Wijnands, P.; Govers, H.A.J.; Admiraal, W.; Voogt, P. de

    1997-10-01

    Effects of four benzoquinoline isomers on the filtration rate of the zebra mussel (Dreissena polymorpha) were analyzed, to study the effect of minor differences in chemical structure on adverse biological effects. Filtration rates were measured after 48 h of exposure to different concentrations of acridine, phenanthridine, benzo[f]quinoline, and benzo[h]quinoline in the water. The 50% effective concentration (EC50) values for filtration rate of the four isomers differed significantly. Effects increased in the order benzo[f], -[h], -[b], and -[c]quinoline, and the difference between the most toxic isomer and the least toxic isomer amounted to a factor of 30. Attempts were made to relate these differences in toxicity to the structure of the isomers. Size- or topology-related molecular descriptors provided insufficient resolution to distinguish between the benzoquinoline isomers, and none of the electronic descriptors separately provided a significant correlation with the observed effects. In an alternative approach, molecular shape, accessibility, and minimum agent-macromolecule distance were used to represent repulsive and attractive forces between the benzoquinoline isomers and biological membranes. This approach could tentatively explain the observed effects and is supported by a high correlation between the EC50 data and the reversed-phase C18-HPLC behavior of the benzoquinolines (k{sub 0}), which is likely to be governed by similar processes.

  17. Gas-phase Ion Isomer Analysis Reveals the Mechanism of Peptide Sequence Scrambling

    PubMed Central

    Jia, Chenxi; Wu, Zhe; Lietz, Christopher B.; Liang, Zhidan; Cui, Qiang; Li, Lingjun

    2014-01-01

    Peptide sequence scrambling during mass spectrometry-based gas-phase fragmentation analysis causes misidentification of peptides and proteins. Thus, there is a need to develop an efficient approach to probing the gas-phase fragment ion isomers related to sequence scrambling and the underlying fragmentation mechanism, which will facilitate the development of bioinformatics algorithm for proteomics research. Herein, we report on the first use of electron transfer dissociation (ETD)-produced diagnostic fragment ions to probe the components of gas-phase peptide fragment ion isomers. In combination with ion mobility spectrometry (IMS) and formaldehyde labeling, this novel strategy enables qualitative and quantitative analysis of b-type fragment ion isomers. ETD fragmentation produced diagnostic fragment ions indicative of the precursor ion isomer components, and subsequent IMS analysis of b ion isomers provided their quantitative and structural information. The isomer components of three representative b ions (b9, b10, and b33 from three different peptides) were accurately profiled by this method. IMS analysis of the b9 ion isomers exhibited dynamic conversion among these structures. Furthermore, molecular dynamics simulation predicted theoretical drift time values which were in good agreement with experimentally measured values. Our results strongly support the mechanism of peptide sequence scrambling via b ion cyclization, and provide the first experimental evidence to support that the conversion from molecular precursor ion to cyclic b ion (M→cb) pathway is less energetically (or kinetically) favored. PMID:24313304

  18. Search for a 2-quasiparticle high-K isomer in {sup 256}Rf

    SciTech Connect

    Robinson, A. P.; Jenkins, D. G.; Marley, P.; Khoo, T. L.; Seweryniak, D.; Ahmad, I.; Back, B. B.; Carpenter, M. P.; Davids, C. N.; Greene, J.; Janssens, R. V. F.; Kondev, F. G.; Lauritsen, T.; Lister, C. J.; McCutchan, E.; Peterson, D.; Stefanescu, I.; Zhu, S.; Asai, M.; Chowdhury, P.

    2011-06-15

    The energies of 2-quasiparticle (2-qp) states in heavy shell-stabilized nuclei provide information on the single-particle states that are responsible for the stability of superheavy nuclei. We have calculated the energies of 2-qp states in {sup 256}Rf, which suggest that a long-lived, low-energy 8{sup -} isomer should exist. A search was conducted for this isomer through a calorimetric conversion electron signal, sandwiched in time between implantation of a {sup 256}Rf nucleus and its fission decay, all within the same pixel of a double-sided Si strip detector. A 17(5)-{mu}s isomer was identified. However, its low population, {approx}5(2)% that of the ground state instead of the expected {approx}30%, suggests that it is more likely a 4-qp isomer. Possible reasons for the absence of an electromagnetic signature of a 2-qp isomer decay are discussed. These include the favored possibility that the isomer decays by fission, with a half-life indistinguishably close to that of the ground state. Another possibility, that there is no 2-qp isomer at all, would imply an abrupt termination of axially symmetric deformed shapes at Z=104, which describes nuclei with Z=92-103 very well.

  19. Search for a 2-quasiparticle high-K isomer in {sup 256}Rf.

    SciTech Connect

    Robinson, A. P.; Khoo, T. L.; Seweryniak, D.; Ahmad, I.; Asai, M.; Back, B. B.; Carpenter, M. P.; Davids, C. N.; Greene, J.; Janssens, R. V. F.; Kondev, F. G.; Lauritsen, T.; Lister, C. J.; McCutchan, E.; Peterson, D.; Zhu, S.

    2011-06-13

    The energies of 2-quasiparticle (2-qp) states in heavy shell-stabilized nuclei provide information on the single-particle states that are responsible for the stability of superheavy nuclei. We have calculated the energies of 2-qp states in {sup 256}Rf, which suggest that a long-lived, low-energy 8{sup -} isomer should exist. A search was conducted for this isomer through a calorimetric conversion electron signal, sandwiched in time between implantation of a {sup 256}Rf nucleus and its fission decay, all within the same pixel of a double-sided Si strip detector. A 17(5)-{micro}s isomer was identified. However, its low population, {approx}5(2)% that of the ground state instead of the expected {approx}30%, suggests that it is more likely a 4-qp isomer. Possible reasons for the absence of an electromagnetic signature of a 2-qp isomer decay are discussed. These include the favored possibility that the isomer decays by fission, with a half-life indistinguishably close to that of the ground state. Another possibility, that there is no 2-qp isomer at all, would imply an abrupt termination of axially symmetric deformed shapes at Z = 104, which describes nuclei with Z = 92-103 very well.

  20. Utilization of Lactate Isomers by Propionibacterium freudenreichii subsp. shermanii: Regulatory Role for Intracellular Pyruvate

    PubMed Central

    Crow, Vaughan L.

    1986-01-01

    Five strains of Propionibacterium freudenreichii subsp. shermanii utilized the l-(+) isomer of lactate at a faster rate than they did the d-(−) isomer when grown with a mixture of lactate isomers under a variety of conditions. ATCC 9614, grown anaerobically in defined medium containing 160 mM dl-lactate, utilized only 4 and 15% of the d-(−)-lactate by the time 50 and 90%, respectively, of the l-(+)-lactate was used. The intracellular pyruvate concentration was high (>100 mM) in the initial stages of lactate utilization, when either dl-lactate or the l-(+) isomer was the starting substrate. The concentration of this intermediate dropped during dl-lactate fermentation such that when only d-(−)-lactate remained, the concentration was <20 mM. When only the d-(−) isomer was initially present, a similar relatively low concentration of intracellular pyruvate was present, even at the start of lactate utilization. The NAD+-independent lactate dehydrogenase activities in extracts showed different kinetic properties with regard to pyruvate inhibition, depending upon the lactate isomer present. Pyruvate gave a competitive inhibitor pattern with l-(+)-lactate and a mixed-type inhibitor pattern with d-(−)-lactate. It is suggested that these properties of the lactate dehydrogenases and the intracellular pyruvate concentrations explain the preferential use of the l-(+) isomer. PMID:16347134

  1. Detailed Chemical Kinetic Reaction Mechanisms for Autoignition of Isomers of Heptane Under Rapid Compression

    SciTech Connect

    Westbrook, C K; Pitz, W J; Boercker, J E; Curran, H J; Griffiths, J F; Mohamed, C; Ribaucour, M

    2001-12-17

    Detailed chemical kinetic reaction mechanisms are developed for combustion of all nine isomers of heptane (C{sub 7}H{sub 16}), and these mechanisms are tested by simulating autoignition of each isomer under rapid compression machine conditions. The reaction mechanisms focus on the manner in which the molecular structure of each isomer determines the rates and product distributions of possible classes of reactions. The reaction pathways emphasize the importance of alkylperoxy radical isomerizations and addition reactions of molecular oxygen to alkyl and hydroperoxyalkyl radicals. A new reaction group has been added to past models, in which hydroperoxyalkyl radicals that originated with abstraction of an H atom from a tertiary site in the parent heptane molecule are assigned new reaction sequences involving additional internal H atom abstractions not previously allowed. This process accelerates autoignition in fuels with tertiary C-H bonds in the parent fuel. In addition, the rates of hydroperoxyalkylperoxy radical isomerization reactions have all been reduced so that they are now equal to rates of analogous alkylperoxy radical isomerizations, significantly improving agreement between computed and experimental ignition delay times in the rapid compression machine. Computed ignition delay times agree well with experimental results in the few cases where experiments have been carried out for specific heptane isomers, and predictive model calculations are reported for the remaining isomers. The computed results fall into three general groups; the first consists of the most reactive isomers, including n-heptane, 2-methyl hexane and 3-methyl hexane. The second group consists of the least reactive isomers, including 2,2-dimethyl pentane, 3,3-dimethyl pentane, 2,3-dimethyl pentane, 2,4-dimethyl pentane and 2,2,3-trimethyl butane. The remaining isomer, 3-ethyl pentane, was observed computationally to have an intermediate level of reactivity. These observations are generally

  2. Isomer Shift and Magnetic Moment of the Long-Lived 1 /2+ Isomer in 30,79Zn49: Signature of Shape Coexistence near 78Ni

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    Collinear laser spectroscopy is performed on the 30,79Zn49 isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred milliseconds half-life is confirmed, and the nuclear spins and moments of the ground and isomeric states in 79Zn as well as the isomer shift are measured. From the observed hyperfine structures, spins I =9 /2 and I =1 /2 are firmly assigned to the ground and isomeric states. The magnetic moment μ (79Zn)=-1.1866 (10 )μN , confirms the spin-parity 9 /2+ with a ν g9/2 -1 shell-model configuration, in excellent agreement with the prediction from large scale shell-model theories. The magnetic moment μ (Znm79)=-1.0180 (12 )μN supports a positive parity for the isomer, with a wave function dominated by a 2 h -1 p neutron excitation across the N =50 shell gap. The large isomer shift reveals an increase of the intruder isomer mean square charge radius with respect to that of the ground state, δ ⟨rc2⟩79 ,79 m=+0.204 (6 ) fm2 , providing first evidence of shape coexistence.

  3. Isomer Shift and Magnetic Moment of the Long-Lived 1/2^{+} Isomer in _{30}^{79}Zn_{49}: Signature of Shape Coexistence near ^{78}Ni.

    PubMed

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

    2016-05-01

    Collinear laser spectroscopy is performed on the _{30}^{79}Zn_{49} isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred milliseconds half-life is confirmed, and the nuclear spins and moments of the ground and isomeric states in ^{79}Zn as well as the isomer shift are measured. From the observed hyperfine structures, spins I=9/2 and I=1/2 are firmly assigned to the ground and isomeric states. The magnetic moment μ (^{79}Zn)=-1.1866(10)μ_{N}, confirms the spin-parity 9/2^{+} with a νg_{9/2}^{-1} shell-model configuration, in excellent agreement with the prediction from large scale shell-model theories. The magnetic moment μ (^{79m}Zn)=-1.0180(12)μ_{N} supports a positive parity for the isomer, with a wave function dominated by a 2h-1p neutron excitation across the N=50 shell gap. The large isomer shift reveals an increase of the intruder isomer mean square charge radius with respect to that of the ground state, δ⟨r_{c}^{2}⟩^{79,79m}=+0.204(6)  fm^{2}, providing first evidence of shape coexistence. PMID:27203317

  4. Interaction of Boron-Nitrogen Doped Benzene Isomers with Water.

    PubMed

    Yourdkhani, Sirous; Chojecki, Michał; Hapka, Michał; Korona, Tatiana

    2016-08-11

    The interaction of 1,2-dihydro-1,2-, 1,3-dihydro-1,3- and 1,4-dihydro-1,4-azaborine isomers with one and two water molecules has been studied using a variety of supermolecular (Møller-Plesset = MP, and coupled cluster = CC) as well as perturbational (symmetry-adapted perturbation theory = SAPT) electron-correlation methods in the complete basis-set limit. It has been found that the water molecule binds to azaborine isomers through O-H···π, π-H···O, and dihydrogen bonding linkages. The SAPT interaction energy decomposition shows that these complexes are mostly stabilized by dispersion followed closely by induction contributions. Pauli repulsion hinders water molecule to be polarized by azaborine in the O-H···π type of complexes. According to the interacting-quantum-atoms analysis, the structures with a primary binding of the O-H···π type benefit from an additional stabilization factor resulting from the interaction of the oxygen and the second hydrogen atom of water, i.e., the one which does not point toward the ring, while the interaction of hydrogens from water with azaborines plays a destabilizing role for the π-H···O type. The same method states that the intermolecular bindings between azaborines and the water molecule have a multicenter character with a small bond polarization, and they are classified as closed-shell (noncovalent) by quantum theory of atoms-in-molecules analysis at bond critical points. The complexes of azaborines with two water molecules tend to arrange in a circular fashion with a recognizable water dimer attached to the azaborine molecule. A comparison with the CCSD(T) benchmarks shows that the nonadditive contribution to the interaction energy of the trimers is negative and with a good accuracy can be accounted for by the MP2 method. A good agreement between Hartree-Fock (HF) and MP2 nonadditive energy, as well as the decomposition of HF nonadditive interaction energies divulge the importance of nonadditive induction

  5. Necessary conditions for the photogeneration of nitrosyl linkage isomers.

    PubMed

    Schaniel, Dominik; Woike, Theo

    2009-06-01

    We investigate the fundamental necessary conditions for optical generation of nitrosyl linkage isomers in ML(5)NO compounds (M = transition metal, L arbitrary ligand) on the examples of K(3)[Mn(CN)(5)NO].2H(2)O and Na(2)[Fe(CN)(5)NO].2H(2)O. We show that the NO linkage isomers of the side-on bonded type (SII, 90 degrees rotation of NO) and of the isonitrosyl type M-ON, where NO is O-bound to the metal M (SI, 180 degrees rotation of NO), can be generated if two conditions are fullfilled. First the optical excitation must lead to a change in the bond between the NO group and the central metal atom M, either by a metal-to-ligand charge transfer of type d -->pi*(NO) or by a d-->d(z(2)) transition, which changes the sigma bonding of the NO group to the metal, such that the vibrational deformation mode delta(M-N-O) can drive the system into the SII configuration. Second the excited state potential must posses a minimum close to the saddle point of the ground state surface between GS and SII, SI, or cross that surface, such that the relaxation from the excited state into the metastable minima can occur. The same is true for transfers between the two metastable states SII and SI. As a further constraint with respect to the amount of population, i.e. the number of complexes which can be transferred into SII or SI, the cross sections sigma(GS,SII,SI) of the states GS, SII, and SI must be considered. If sigma(GS) > sigma(SII) and sigma(SI) > sigma(SII) SII can be occupied while SI can be significantly occupied if sigma(GS) > sigma(SI) and sigma(SII) > sigma(SI). More simply speaking the depletion rate of the metastable state should be smaller than its population rate for a given wavelength. PMID:19458843

  6. Ab initio quantum chemical investigation of several isomers of anionic Si 6

    NASA Astrophysics Data System (ADS)

    Takahashi, Masae; Kawazoe, Yoshiyuki

    2006-02-01

    Eight isomers (planar hexagon, benzvalene, Dewar benzene, triangular prismane, bicyclopropenyl, octahedron, chair form, and twist boat form) of Si 6, Si62-, Si64-, and Si66-, have been searched for by the MP2 and B3LYP electronic structure calculations. Totally 14 isomers were found: two Si 6, six Si62-, five Si64-, and one Si66-. Two of them are different from the eight isomers: deformed triangle Si62-; pentagonal pyramidal Si64-. We discovered that the predicted stable shapes of Si62-, Si64-, and Si66- are octahedral, pentagonal pyramidal, and hexagonal, respectively, which agrees well with Wade rule.

  7. Theoretical studies of possible toroidal high-spin isomers in the light-mass region

    DOE PAGESBeta

    Staszczak, A.; Wong, Cheuk-Yin

    2016-05-11

    We review our theoretical knowledge of possible toroidal high-spin isomers in the light mass region in 28 A 52 obtained previously in cranked Skyrme-Hartree-Fock calculations. We report additional toroidal high-spin isomers in 56Ni with I=114 and 140, which follow the same (multi-particle) (multi-hole) systematics as other toroidal high-spin isomers. We examine the production of these exotic nuclei by fusion of various projectiles on 20Ne or 28Si as an active target in time-projection-chamber (TPC) experiments.

  8. Effects of high-order deformation on high-K isomers in superheavy nuclei

    SciTech Connect

    Liu, H. L.; Bertulani, C. A.; Xu, F. R.; Walker, P. M.

    2011-01-15

    Using, for the first time, configuration-constrained potential-energy-surface calculations with the inclusion of {beta}{sub 6} deformation, we find remarkable effects of the high-order deformation on the high-K isomers in {sup 254}No, the focus of recent spectroscopy experiments on superheavy nuclei. For shapes with multipolarity six, the isomers are more tightly bound and, microscopically, have enhanced deformed shell gaps at N=152 and Z=100. The inclusion of {beta}{sub 6} deformation significantly improves the description of the very heavy high-K isomers.

  9. Controlling the Excited-State Dynamics of Nuclear Spin Isomers Using the Dynamic Stark Effect.

    PubMed

    Waldl, Maria; Oppel, Markus; González, Leticia

    2016-07-14

    Stark control of chemical reactions uses intense laser pulses to distort the potential energy surfaces of a molecule, thus opening new chemical pathways. We use the concept of Stark shifts to convert a local minimum into a local maximum of the potential energy surface, triggering constructive and destructive wave-packet interferences, which then induce different dynamics on nuclear spin isomers in the electronically excited state of a quinodimethane derivative. Model quantum-dynamical simulations on reduced dimensionality using optimized ultrashort laser pulses demonstrate a difference of the excited-state dynamics of two sets of nuclear spin isomers, which ultimately can be used to discriminate between these isomers. PMID:26840424

  10. Theoretical studies of possible toroidal high-spin isomers in the light-mass region

    NASA Astrophysics Data System (ADS)

    Staszczak, Andrzej; Wong, Cheuk-Yin

    2016-05-01

    We review our theoretical knowledge of possible toroidal high-spin isomers in the light mass region in 28≤A≤52 obtained previously in cranked Skyrme-Hartree-Fock calculations. We report additional toroidal high-spin isomers in 56Ni with I=114ħ and 140ħ, which follow the same (multi-particle)-(multi-hole) systematics as other toroidal high-spin isomers. We examine the production of these exotic nuclei by fusion of various projectiles on 20Ne or 28Si as an active target in time-projection-chamber (TPC) experiments.

  11. Polymerization of the cis- and trans-isomers of bis(triethoxysilyl)-2-butene and comparison of their structural properties

    SciTech Connect

    Shaltout, R.M.; Loy, D.A.; Carpenter, J.P.; Dorhout, K.; Shea, K.J.

    1998-09-01

    The cis and trans isomers of bis-(triethoxysilyl)-2-butene were polymerized by the sol-gel method under various conditions. The trans isomer formed gels under all conditions. The cis isomer formed gels only under basic conditions. Under acidic conditions it formed soluble resins of molecular weight ranging from 88,000 to 180,000 Daltons. Solid state and solution {sup 29}Si NMR revealed that the trans isomer formed condensed gels, and that the resins formed by the cis isomer contained cyclic monomers and/or ordered oligomers.

  12. Ab initio SCF calculations on hydrogen bonded cresol isomers

    NASA Astrophysics Data System (ADS)

    Pohl, M.; Kleinermanns, K.

    1988-12-01

    Ab initio GAUSSIAN 80 calculations with two different basis sets (STO-3G and 4 31 G*) were performed on hydrogen bonded cresol isomers for comparison with experimental data from free jet fluorescence excitation spectroscopy. For m-cresol, the calculated barriers for hindered internal rotation of the OH-group and the CH3-group are in good agreement with experiment. The calculations show the trans-linear configuration of p-cresol· B-clusters ( B = H2O, CH3OH) to be more stable than the all-planar configuration. This agrees with CI calculations and microwave spectroscopic investigations of the water dimer. Calculations of both the intermolecular stretch and bend frequencies of p-cresol· B-clusters show little dependence on the all-planar or trans-linear configuration but a strong dependence on the choice of the basis set. With the minimal basis set STO-3G, the vibrational energies are generally too high. The agreement between the calculated vibrational frequencies from the 4 31 G* basis set and the experimental values is fair.

  13. Products from the Oxidation of Linear Isomers of Hexene

    PubMed Central

    Battin-Leclerc, Frédérique; Rodriguez, Anne; Husson, Benoit; Herbinet, Olivier; Glaude, Pierre-Alexandre; Wang, Zhandong; Cheng, Zhanjun; Qi, Fei

    2014-01-01

    The experimental study of the oxidation of the three linear isomers of hexene was performed in a quartz isothermal jet-stirred reactor (JSR) at temperatures ranging from 500 to 1100 K including the negative temperature coefficient (NTC) zone, at quasi-atmospheric pressure (1.07 bar), at a residence time of 2 s and with dilute stoichiometric mixtures. The fuel and reaction product mole fractions were measured using online gas chromatography. In the case of 1-hexene, the JSR has also been coupled through a molecular-beam sampling system to a reflectron time-of-flight mass spectrometer combined with tunable synchrotron vacuum ultraviolet photoionization. A difference of reactivity between the three fuels which varies with the temperature range has been observed and is discussed according to the changes in the possible reaction pathways when the double bond is displaced. An enhanced importance of the reactions via the Waddington mechanism and of those of allylic radicals with HO2 radicals can be noted for 2- and 3-hexenes compared to 1-hexene. PMID:24400665

  14. Precursor anion states in dissociative electron attachment to chlorophenol isomers

    NASA Astrophysics Data System (ADS)

    Kossoski, F.; Varella, M. T. do N.

    2016-07-01

    We report a theoretical study on low-energy (<10 eV) elastic electron scattering from chlorophenol isomers, namely, para-chlorophenol (pCP), meta-chlorophenol (mCP), and ortho-chlorophenol (oCP). The calculations were performed with the Schwinger multichannel method with pseudopotentials, and analysis of the computed integral cross sections and virtual orbitals revealed one σCCl ∗ , one σOH ∗ , and three π∗ shape resonances. We show that electron capture into the two lower lying π∗ orbitals initiates dissociative processes that lead to the elimination of the chloride ion, accounting for the two overlapping peaks where this fragment was observed. Despite the relatively small differences on the energetics of the π∗ resonances, a major isomeric effect was found on their corresponding autodetachment lifetimes, which accounts for the observed increasing cross sections in the progression pCP < mCP < oCP. In particular, dissociation from the π1 ∗ anion of pCP is largely suppressed because of the unfavorable mixing with the σCCl ∗ state. We found the intramolecular hydrogen bond present in oCP to have the opposite effects of stabilizing the σCCl ∗ resonance and destabilizing the σOH ∗ resonance. We also suggest that the hydrogen abstraction observed in chlorophenols and phenol actually takes place by a mechanism in which the incoming electron is directly attached to the dissociative σOH ∗ orbital.

  15. The CBM RICH detector

    NASA Astrophysics Data System (ADS)

    Adamczewski-Musch, J.; Akishin, P.; Becker, K.-H.; Belogurov, S.; Bendarouach, J.; Boldyreva, N.; Chernogorov, A.; Deveaux, C.; Dobyrn, V.; Dürr, M.; Eschke, J.; Förtsch, J.; Heep, J.; Höohne, C.; Kampert, K.-H.; Kochenda, L.; Kopfer, J.; Kravtsov, P.; Kres, I.; Lebedev, S.; Lebedeva, E.; Leonova, E.; Linev, S.; Mahmoud, T.; Michel, J.; Miftakhov, N.; Niebur, W.; Ovcharenko, E.; Pauly, C.; Pfeifer, D.; Querchfeld, S.; Rautenberg, J.; Reinecke, S.; Riabov, Y.; Roshchin, E.; Samsonov, V.; Tarasenkova, O.; Traxler, M.; Ugur, C.; Vznuzdaev, E.; Vznuzdaev, M.

    2016-05-01

    The CBM RICH detector will use CO2 as radiator gas, focussing glass mirrors with Al+MgF2 reflective and protective coating and Hamamatsu H12700 MAPMTs as photon detectors. The detector will serve for electron to pion separation up to momenta of 8 GeV/c and thus enable in CBM the measurement of electromagnetic radiation from the early and dense fireball in A+A collisions at SIS 100. In this article, the current status of the CBM RICH development will be presented including new measurements of the radiation hardness of the H12700 MAPMT and WLS coatings with p-terphenyl, the new concept for the readout electronics, and optimizations ongoing with respect to the mirror mount structure and overall geometry. Prior to the usage in CBM, part of the already ordered MAPMTs will be used to upgrade the HADES RICH detector for a new measurement campaign at SIS 18 from 2018-2020.

  16. Hydrogen rich gas generator

    NASA Technical Reports Server (NTRS)

    Houseman, J.; Rupe, J. H.; Kushida, R. O. (Inventor)

    1976-01-01

    A process and apparatus is described for producing a hydrogen rich gas by injecting air and hydrocarbon fuel at one end of a cylindrically shaped chamber to form a mixture and igniting the mixture to provide hot combustion gases by partial oxidation of the hydrocarbon fuel. The combustion gases move away from the ignition region to another region where water is injected to be turned into steam by the hot combustion gases. The steam which is formed mixes with the hot gases to yield a uniform hot gas whereby a steam reforming reaction with the hydrocarbon fuel takes place to produce a hydrogen rich gas.

  17. Identification of Geometrical Isomers of the Cobalt(III)-Iminodiacetate System.

    ERIC Educational Resources Information Center

    Lawrance, Geoffrey A.; Rix, Colin J.

    1979-01-01

    In this experiment, students prepare, isolate, and characterize two geometrical isomers of a metal coordination compound. This experiment provides a good introduction to the techniques of modern coordination chemistry. (BB)

  18. 40 CFR 180.1103 - Isomate-C; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... moth pheromone (Isomate-C) E,E-8,10-dodecenyl alcohol, dodecanol, tetradecanol is exempt from the requirements of a tolerance in or on all raw agricultural commodities when formulated in polyethylene...

  19. 40 CFR 180.1103 - Isomate-C; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... moth pheromone (Isomate-C) E,E-8,10-dodecenyl alcohol, dodecanol, tetradecanol is exempt from the requirements of a tolerance in or on all raw agricultural commodities when formulated in polyethylene...

  20. 40 CFR 180.1103 - Isomate-C; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... moth pheromone (Isomate-C) E,E-8,10-dodecenyl alcohol, dodecanol, tetradecanol is exempt from the requirements of a tolerance in or on all raw agricultural commodities when formulated in polyethylene...

  1. 40 CFR 180.1103 - Isomate-C; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... moth pheromone (Isomate-C) E,E-8,10-dodecenyl alcohol, dodecanol, tetradecanol is exempt from the requirements of a tolerance in or on all raw agricultural commodities when formulated in polyethylene...

  2. 40 CFR 180.1103 - Isomate-C; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... moth pheromone (Isomate-C) E,E-8,10-dodecenyl alcohol, dodecanol, tetradecanol is exempt from the requirements of a tolerance in or on all raw agricultural commodities when formulated in polyethylene...

  3. Removal of persistent organic pollutant hexachlorocyclohexane isomers by advanced oxidation process.

    PubMed

    2012-04-01

    Organochlorine insecticide Lindane (gamma-Hexachlorocyclohexane) and its isomers (alpha, beta, delta-HCH) are recalcitrant and toxic compounds. They were progressively banished in most of the countries, because of their persistence and toxicity. Due to their nonselective production process and widespread use, they are still occurring in the environment. These insecticides and isomers were detected in all media like soil, ground water, sediments, vegetables and even in human tissues. In this study, UV, H2O2, UV+H2O2, Fenton's reagent, UV+Fenton's reagent, Advanced Oxidation Process (AOP) have been applied for degradation of HCH isomers (a, beta, gamma and delta-HCH). The results revealed that the UV+H2O2 treatment was most effective, which could do 99% degradation of all isomers of HCH within 75 minutes. The results in detail are presented and discussed in this paper. PMID:24749381

  4. Simple Nuclear Structure in (111-129)Cd from Atomic Isomer Shifts.

    PubMed

    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

    2016-01-22

    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. PMID:26849588

  5. Effect of nitrate and phosphate on accumulation of β-carotene isomers in Dunaliella salina

    NASA Astrophysics Data System (ADS)

    Liu, Jian-Guo; Wu, Chao-Yuan; Chen, Nian-Hong; Wang, Yu-Jun; Yu, Li-Dong

    1996-06-01

    Dunaliella salina, a halotolerant unicellular green alga, can accumulate a large amount of β-carotene under certain environmental conditions. The isomers of β-carotene extracted from D. salina cultured in medium with different nitrate and phosphate concentrations were analysed by HPLC with Alox-T alumina column. At least six isomers were found in different proportions depending on the culture media's nitrate and/or phosphate concentrations. Nitrate and/or phosphate deficiency was conducive to the accumulation of total cis isomers but not of all trans isomer. It is suggested that 1 mmol/L KNO3 and 0.1 mmol/L KH2 PO4 are favourable for accumulation of total cis β-carotene.

  6. Differential Effect of Amphetamine Optical Isomers on Bender Gestalt Performance of the Minimally Brain Dysfunctioned

    ERIC Educational Resources Information Center

    Arnold, L. Eugene; And Others

    1978-01-01

    The differential effect of amphetamine optical isomers on Bender Gestalt performance was examined in 31 hyperkinetic minimally brain dysfunctioned children between the ages of 4 and 12 years, using a double-blind Latin-square crossover comparison. (Author)

  7. Structural isomers of C2N(+) - A selected-ion flow tube study

    NASA Technical Reports Server (NTRS)

    Knight, J. S.; Petrie, S. A. H.; Freeman, C. G.; Mcewan, M. J.; Mclean, A. D.

    1988-01-01

    Reactivities of the structural isomers CCN(+) and CNC(+) were examined in a selected-ion flow tube at 300 + or - 5 K. The less reactive CNC(+) isomer was identified as the product of the reactions of C(+) + HCN and C(+) + C2N2; in these reactions only CNC(+) can be produced because of energy constraints. Rate coefficients and branching ratios are reported for the reactions of each isomer with H2, CH4, NH3, H2O, C2H2, HCN, N2, O2, N2O, and CO2. Ab initio calculations are presented for CCN(+) and CNC(+); a saddle point for the reaction CCN(+) yielding CNC(+) is calculated to be 195 kJ/mol above CNC(+). The results provide evidence that the more reactive CCN(+) isomer is unlikely to be present in measurable densities in interstellar clouds.

  8. Separation of a Set of Peptide Sequence Isomers Using Differential Ion Mobility Spectrometry

    SciTech Connect

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

    2011-08-15

    Protein identification in bottom-up proteomics requires disentangling isomers of proteolytic peptides, a major class of which are sequence inversions. Separation of sequence isomers using ion mobility spectrometry (IMS) has been reported, but limited to pairs of species. Here we demonstrate baseline separation of all seven sequences for a tryptic peptide with eight residues using differential IMS or FAIMS. Evaluations of peak capacity of the method indicate that even larger libraries should generally be separated for heavier peptides with higher charge states.

  9. Effect of uniaxial tensile stress on the isomer shift of 57Fe in fcc stainless steels

    NASA Astrophysics Data System (ADS)

    Ratner, E.; Ron, M.

    1982-05-01

    The electron wave-function response to uniaxial tensile stress in fcc steels (SS310 and SS316) was investigated through the isomer shift of the Mössbauer effect. Stresses up to 12 kbar (the ultimate tensile stress is approximately 14 kbar) were applied at room temperature. The isomer shift changes linearly in these circumstances. It is concluded that, as in the case of hydrostatic pressure, the paramount factor here is the volume strain of the wave functions of 4S electrons.

  10. Superprolate shape of the spontaneous-fission isomer /sup 240/Am/sup m/

    SciTech Connect

    Pauling, L.

    1980-10-01

    A superprolate structure for nuclei with Aapprox.240 proposed in 1965 on the basis of the polyspheron theory leads to the value 0.66 for the deformation parameter ..beta... This value agrees well with a recently reported experimental value, 0.66 +- 0.04 for the spontaneous-fission isomer /sup 240/Am/sup m/, obtained by Bemis et al. from their measurement of the optical isomer shift. This agreement provides additional support for the proposed superprolate structure.

  11. Probing and evaluating anion-π interaction in meso-dinitrophenyl functionalized calix[4]pyrrole isomers.

    PubMed

    Kim, Ajeong; Ali, Rashid; Park, Seok Ho; Kim, Yong-Hoon; Park, Jung Su

    2016-09-25

    We investigate anion-π binding modes in a cis-isomer of 3,5-dinitrophenyl-substituted calix[4]pyrrole with various anions via X-ray crystallographic analyses and compare its binding affinities with those of the corresponding trans-isomer. Sandwich-type anion-π interactions prove to not only enhancing anion binding abilities but also altering the anion-binding selectivity of the calix[4]pyrrole framework. PMID:27549578

  12. FAST TRACK COMMUNICATION: Contrasting characteristics of sub-microsecond pulsed atmospheric air and atmospheric pressure helium-oxygen glow discharges

    NASA Astrophysics Data System (ADS)

    Walsh, J. L.; Liu, D. X.; Iza, F.; Rong, M. Z.; Kong, M. G.

    2010-01-01

    Glow discharges in air are often considered to be the ultimate low-temperature atmospheric pressure plasmas for numerous chamber-free applications. This is due to the ubiquitous presence of air and the perceived abundance of reactive oxygen and nitrogen species in air plasmas. In this paper, sub-microsecond pulsed atmospheric air plasmas are shown to produce a low concentration of excited oxygen atoms but an abundance of excited nitrogen species, UV photons and ozone molecules. This contrasts sharply with the efficient production of excited oxygen atoms in comparable helium-oxygen discharges. Relevant reaction chemistry analysed with a global model suggests that collisional excitation of O2 by helium metastables is significantly more efficient than electron dissociative excitation of O2, electron excitation of O and ion-ion recombination. These results suggest different practical uses of the two oxygen-containing atmospheric discharges, with air plasmas being well suited for nitrogen and UV based chemistry and He-O2 plasmas for excited atomic oxygen based chemistry.

  13. Recent Advances in Polarizable Force Fields for Macromolecules: Microsecond Simulations of Proteins Using the Classical Drude Oscillator Model

    PubMed Central

    2015-01-01

    In this Perspective, we summarize recent efforts to include the explicit treatment of induced electronic polarization in biomolecular force fields. Methods used to treat polarizability, including the induced dipole, fluctuating charge, and classical Drude oscillator models, are presented, including recent advances in force fields using those methods. This is followed by recent results obtained with the Drude model, including microsecond molecular dynamics (MD) simulations of multiple proteins in explicit solvent. Results show significant variability of backbone and side-chain dipole moments as a function of environment, including significant changes during individual simulations. Dipole moments of water in the vicinity of the proteins reveal small but systematic changes, with the direction of the changes dependent on the environment. Analyses of the full proteins show that the polarizable Drude model leads to larger values of the dielectric constant of the protein interior, especially in the case of hydrophobic regions. These results indicate that the inclusion of explicit electronic polarizability leads to significant differences in the physical forces affecting the structure and dynamics of proteins, which can be investigated in a computationally tractable fashion in the context of the Drude model. PMID:25247054

  14. Aryl-Decorated Ru(II) Polypyridyl-type Photosensitizer Approaching NIR Emission with Microsecond Excited State Lifetimes.

    PubMed

    Schlotthauer, Tina; Suchland, Benedikt; Görls, Helmar; Parada, Giovanny A; Hammarström, Leif; Schubert, Ulrich S; Jäger, Michael

    2016-06-01

    Bis-tridentate Ru(II) complexes based on the dqp scaffold (dqp is 2,6-di(quinolin-8-yl)pyridine) with multiple aryl substituents were explored to tailor the absorption and emission properties. A synthetic methodology was developed for the facile synthesis and purification of homo- and heteroleptic bis-tridentate Ru complexes. The effect of the aryl substituents in the para positions of the pyridine and quinoline subunits was detailed by X-ray crystallography, steady state and time-resolved spectroscopy, electrochemistry, and computational methods. The attachment of the aryl groups results in enhanced molar extinction coefficients with the largest effect in the pyridine position, whereas the quinoline substituent leads to red-shifted emission tailing into the NIR region (up to 800 nm). Notably, the excited state lifetimes remain in the microsecond time scale even in the presence of O2, whereas the emission quantum yields are slightly increased with respect to the parental complex [Ru(dqp)2](2+). The peripheral functional groups (Br, Me, OMe) have only a minor impact on the optical properties and are attractive to utilize such complexes as functional building blocks. PMID:27228222

  15. Microsecond atomic force sensing of protein conformational dynamics: Implications for the primary light-induced events in bacteriorhodopsin

    PubMed Central

    Rousso, Itay; Khachatryan, Edward; Gat, Yahaloma; Brodsky, Igor; Ottolenghi, Michael; Sheves, Mordechai; Lewis, Aaron

    1997-01-01

    In this paper a new atomic force sensing technique is presented for dynamically probing conformational changes in proteins. The method is applied to the light-induced changes in the membrane-bound proton pump bacteriorhodopsin (bR). The microsecond time-resolution of the method, as presently implemented, covers many of the intermediates of the bR photocycle which is well characterized by spectroscopical methods. In addition to the native pigment, we have studied bR proteins substituted with chemically modified retinal chromophores. These synthetic chromophores were designed to restrict their ability to isomerize, while maintaining the basic characteristic of a large light-induced charge redistribution in the vertically excited Franck–Condon state. An analysis of the atomic force sensing signals lead us to conclude that protein conformational changes in bR can be initiated as a result of a light-triggered redistribution of electronic charge in the retinal chromophore, even when isomerization cannot take place. Although the coupling mechanism of such changes to the light-induced proton pump is still not established, our data question the current working hypothesis which attributes all primary events in retinal proteins to an initial trans⇔cis isomerization. PMID:9223291

  16. Reorientation and Dimerization of the Membrane-Bound Antimicrobial Peptide PGLa from Microsecond All-Atom MD Simulations

    PubMed Central

    Ulmschneider, Jakob P.; Smith, Jeremy C.; Ulmschneider, Martin B.; Ulrich, Anne S.; Strandberg, Erik

    2012-01-01

    The membrane-active antimicrobial peptide PGLa from Xenopus laevis is known from solid-state 2H-, 15N-, and 19F-NMR spectroscopy to occupy two distinct α-helical surface adsorbed states in membranes: a surface-bound S-state with a tilt angle of ∼95° at low peptide/lipid molar ratio (P/L = 1:200), and an obliquely tilted T-state with a tilt angle of 127° at higher peptide concentration (P/L = 1:50). Using a rapid molecular-dynamics insertion protocol in combination with microsecond-scale simulation, we have characterized the structure of both states in detail. As expected, the amphiphilic peptide resides horizontally on the membrane surface in a monomeric form at a low P/L, whereas the T-state is seen in the simulations to be a symmetric antiparallel dimer, with close contacts between small glycine and alanine residues at the interface. The computed tilt angles and azimuthal rotations, as well as the quadrupolar splittings predicted from the simulations agree with the experimental NMR data. The simulations reveal many structural details previously inaccessible, such as the immersion depth of the peptide in the membrane and the packing of the dimerization interface. The study highlights the ability and limitations of current state-of-the-art multimicrosecond all-atom simulations of membrane-active peptides to complement experimental data from solid-state NMR. PMID:22947863

  17. Isomer Studies for Nuclei near the Proton Drip Line in the Mass 130-160 Region

    SciTech Connect

    Cullen, D. M.; Mason, P. J. R.; Khan, S.; Kishada, A. M.; Varley, B. J.; Rigby, S. V.; Scholey, C.; Greenlees, P.; Rahkila, P.; Jones, P. M.; Julin, R.; Juutinen, S.; Leino, M.; Leppaenen, A. P.; Nyman, M.; Uusitalo, J.; Grahn, T.; Nieminen, P.; Pakarinen, J.

    2007-11-30

    This report details the status of an experimental research programme which has studied isomeric states in the mass 130-160 region of the nuclear chart. Several new isomers have been established and characterised near the proton drip line using a recoil isomer tagging technique at the University of Jyvaeskylae, Finland. The latest experiments have been performed with a modified setup where the standard GREAT focal-plane double-sided silicon-strip detector was changed to a dual multi-wire proportional-counter arrangement. This new setup has improved capability for short-lived isomer studies where high focal-plane rates can be tolerated. The results of key recent experiments for nuclei situated above ({sup 153}Yb,{sup 152}Tm) and below ({sup 136}Pm,{sup 142}Tb) the N = 82 shell gap were presented along with an interpretation for the isomers. Finally, the future prospects of the technique, using an isomer-tagged differential-plunger setup, were discussed. This technique will be capable of establishing the deformation of the states above the isomers and will aid in the process of assigning underlying single-particle configurations to the isomeric states.

  18. From Rags to Riches

    ERIC Educational Resources Information Center

    Sweet, Colleen

    2008-01-01

    In this article, the author presents the "Rags to Riches" design project she introduced to her students. She assigned each of her students one item from an array to thrift store goods which included old scarves, sweaters, jackets, and even evening gowns. The design problem was to imagine what a clothing tag might look like if the assigned item…

  19. Thinking about "Rich" Tasks

    ERIC Educational Resources Information Center

    Box, Lorna; Watson, Anne

    2010-01-01

    This article presents an e-mail conversation between two teachers discussing how to have a "rich task" lesson in which they get to the heart of mathematical modeling and in which students are motivated into working on mathematics. One teacher emphasizes that the power of maths is in developing mathematical descriptions of situations by looking at…

  20. 241Am (n,gamma) isomer ratio measurement

    SciTech Connect

    Bond, Evelyn M; Vieira, David J; Moody, Walter A; Slemmons, Alice K

    2011-01-05

    The objective of this project is to improve the accuracy of the {sup 242}Cm/{sup 241}Am radiochemistry ratio. We have performed an activation experiment to measure the {sup 241}Am(n,{gamma}) cross section leading to either the ground state of {sup 242g}Am (t{sub 1/2} = 16 hr) which decays to {sup 242}Cm (t{sub 1/2} = 163 d) or the long-lived isomer {sup 242m}Am (t{sub 1/2} = 141 yr). This experiment will develop a new set of americium cross section evaluations that can be used with a measured {sup 242}Cm/{sup 241}Am radiochemical measurement for nuclear forensic purposes. This measurement is necessary to interpret the {sup 242}Cm/{sup 241}Am ratio because a good measurement of this neutron capture isomer ratio for {sup 241}Am does not exist. The targets were prepared in 2007 from {sup 241}Am purified from LANL stocks. Gold was added to the purified {sup 241}Am as an internal neutron fluence monitor. These targets were placed into a holder, packaged, and shipped to Forschungszentrum Karlsruhe, where they were irradiated at their Van de Graff facility in February 2008. One target was irradiated with {approx}25 keV quasimonoenergetic neutrons produced by the {sup 7}Li(p,n) reaction for 3 days and a second target was also irradiated for 3 days with {approx}500 keV neutrons. Because it will be necessary to separate the {sup 242}Cm from the {sup 241}Am in order to measure the amount of {sup 242}Cm by alpha spectrometry, research into methods for americium/curium separations were conducted concurrently. We found that anion exchange chromatography in methanol/nitric acid solutions produced good separations that could be completed in one day resulting in a sample with no residue. The samples were returned from Germany in July 2009 and were counted by gamma spectrometry. Chemical separations have commenced on the blank sample. Each sample will be spiked with {sup 244}Cm, dissolved and digested in nitric acid solutions. One third of each sample will be processed at a time

  1. Numerical investigation of temperature field Induced by dual wavelength lasers in sub-microsecond laser annealing technology for insulated gate bipolar transistor

    NASA Astrophysics Data System (ADS)

    Cui, GuoDong; Ma, Mingying; Wang, Fan; Sun, Gang; Lan, Yanping; Xu, Wen

    2015-07-01

    To enhance the performance of the Insulated Gate Bipolar Transistor (IGBT), sub-microsecond laser annealing (LA) is propitious to achieve maximal dopant activation with minimal diffusion. In this work, two different lasers are used as annealing resource: a continuous 808 nm laser with larger spot is applied to preheat the wafer and another sub-microsecond pulsed 527 nm laser is responsible to activate the dopant. To optimize the system's performance, a physical model is presented to predict the thermal effect of two laser fields interacting on wafer. Using the Finite-Element method (FEM), we numerically investigate the temperature field induced by lasers in detail. The process window corresponding to the lasers is also acquired which can satisfy the requirements of the IGBT's annealing.

  2. Vibronic Spectroscopy of a Structural Isomer of Quinoline: -

    NASA Astrophysics Data System (ADS)

    Mehta-Hurt, Deepali N.; Korn, Joseph A.; Zwier, Timothy S.

    2013-06-01

    This talk will present results of a gas phase, jet-cooled vibronic spectroscopy study of (Z)-phenylvinylnitrile ((Z)-C_6H_5-CH=CH-C=N, (Z)-PVN). With a substituent locked into a cis conformation with respect to the aromatic ring, (Z)-PVN is postulated to be a molecule with an ideal functionality to isomerize to quinoline upon photoexcitation. As such, (Z)-PVN is particularly relevant to Titan's nitrile-containing atmosphere, where much of the chemistry is photochemically driven. As a first step towards such photochemical studies, a fluorescence excitation spectrum of a mixture of (E)- and (Z)-PVN was collected spanning the range 33,300-35,580 cm^{-1} (300.0-281.0 nm). Previous investigations in the Zwier group pertaining to the vibronic spectroscopy of (E)-PVN allowed for the identification of peaks in the (E)- and (Z)-PVN composite spectrum that were solely due to (Z)-PVN, and the S_0-S_1 origin of (Z)-PVN was identified as a dominant band that occurs at 33,706 cm^{-1}. For additional confirmation, ultraviolet depletion spectroscopy (UVD) was used to obtain an isomer specific spectrum of (Z)-PVN as well as search for non-radiative transitions. Dispersed fluorescence spectra that characterize the vibronic activity have also been acquired. A comparison between the vibronic spectroscopy of (Z)-PVN with both (E)-PVN and (Z)-phenylvinylacetylene ((Z)-PVA), the hydrocarbon analog of (Z)-PVN, will be made in this talk.

  3. Formation of Meteoritic Amino Acids: Isovaline and its Isomers

    NASA Astrophysics Data System (ADS)

    Hudson, Reggie; Moore, Marla; Dworkin, Jason

    It has been known for several decades that amino acids, and other complex organics, are found in meteorites. In particular, Murchison (CM) samples contain over seventy amino acids, these being identified by high-level chromatographic methods. Among Murchison's amino acids, isovaline stands out as being both non-biological (non-protein) and having a relatively high abundance. While approximately equal amounts of D- and L- isovaline have been reported in Murchison and other CM meteorites, this molecule's structure appears to prohibit its racemization in aqueous solutions. We recently have investigated the low-temperature solid-phase chemistry of both isovaline and valine with an eye toward each molecule's formation, stability, and possible interconversions of their D and L enantiomers. Ion-irradiated isovalineand valine-containing ices were examined by IR spectroscopy and highly-sensitive liquid chromatography/time-of-flight mass spectral methods to assess both amino-acid destruction and racemization. Samples were studied in the presence and in the absence of water-ice, and the destruction of both isovaline and valine was measured as a function of radiation dose. In addition, we have synthesized isovaline, valine, and their amino acid isomers by solid-phase radiation-chemical pathways other than the oft-invoked Strecker process. This presentation will review and summarize some of our recent findings and place them in a context of related work. - Our work has been supported by a grant to the Goddard Center for Astrobiology through the NASA Astrobiology Institute. Experiments were performed in the Cosmic Ice Laboratory (RLH, MHM) and the Astrobiology Analytical Laboratory (JPD) at the NASA Goddard Space Flight Center.

  4. Comparative pharmacological activity of optical isomers of phenibut.

    PubMed

    Dambrova, Maija; Zvejniece, Liga; Liepinsh, Edgars; Cirule, Helena; Zharkova, Olga; Veinberg, Grigory; Kalvinsh, Ivars

    2008-03-31

    Phenibut (3-phenyl-4-aminobutyric acid) is a GABA (gamma-aminobutyric acid)-mimetic psychotropic drug which is clinically used in its racemic form. The aim of the present study was to compare the effects of racemic phenibut and its optical isomers in pharmacological tests and GABAB receptor binding studies. In pharmacological tests of locomotor activity, antidepressant and pain effects, S-phenibut was inactive in doses up to 500 mg/kg. In contrast, R-phenibut turned out to be two times more potent than racemic phenibut in most of the tests. In the forced swimming test, at a dose of 100 mg/kg only R-phenibut significantly decreased immobility time. Both R-phenibut and racemic phenibut showed analgesic activity in the tail-flick test with R-phenibut being slightly more active. An GABAB receptor-selective antagonist (3-aminopropyl)(diethoxymethyl)phosphinic acid (CGP35348) inhibited the antidepressant and antinociceptive effects of R-phenibut, as well as locomotor depressing activity of R-phenibut in open field test in vivo. The radioligand binding experiments using a selective GABAB receptor antagonist [3H]CGP54626 revealed that affinity constants for racemic phenibut, R-phenibut and reference GABA-mimetic baclofen were 177+/-2, 92+/-3, 6.0+/-1 microM, respectively. We conclude that the pharmacological activity of racemic phenibut relies on R-phenibut and this correlates to the binding affinity of enantiomers of phenibut to the GABAB receptor. PMID:18275958

  5. Precursor anion states in dissociative electron attachment to chlorophenol isomers.

    PubMed

    Kossoski, F; Varella, M T do N

    2016-07-28

    We report a theoretical study on low-energy (<10 eV) elastic electron scattering from chlorophenol isomers, namely, para-chlorophenol (pCP), meta-chlorophenol (mCP), and ortho-chlorophenol (oCP). The calculations were performed with the Schwinger multichannel method with pseudopotentials, and analysis of the computed integral cross sections and virtual orbitals revealed one σCCl (∗), one σOH (∗), and three π(∗) shape resonances. We show that electron capture into the two lower lying π(∗) orbitals initiates dissociative processes that lead to the elimination of the chloride ion, accounting for the two overlapping peaks where this fragment was observed. Despite the relatively small differences on the energetics of the π(∗) resonances, a major isomeric effect was found on their corresponding autodetachment lifetimes, which accounts for the observed increasing cross sections in the progression pCP < mCP < oCP. In particular, dissociation from the π1 (∗) anion of pCP is largely suppressed because of the unfavorable mixing with the σCCl (∗) state. We found the intramolecular hydrogen bond present in oCP to have the opposite effects of stabilizing the σCCl (∗) resonance and destabilizing the σOH (∗) resonance. We also suggest that the hydrogen abstraction observed in chlorophenols and phenol actually takes place by a mechanism in which the incoming electron is directly attached to the dissociative σOH (∗) orbital. PMID:27475364

  6. Experimental characterization of a micro-hole drilling process with short micro-second pulses by a CW single-mode fiber laser

    NASA Astrophysics Data System (ADS)

    Tu, Jay; Paleocrassas, Alexander G.; Reeves, Nicholas; Rajule, Nilesh

    2014-04-01

    Laser ablation with pulse durations in a few microseconds is a viable solution for micro-hole drilling applications which require large material removal rate (MRR) with moderate hole quality. However, the body of work regarding short microsecond laser drilling/ablation is small. The objective of this paper is to experimentally characterize this short micro-second laser micro-hole drilling technique using a 300 W, CW, single-mode fiber laser. This CW fiber laser is controlled to produce modulated pulses from 1 μs to 8 μs and these modulated laser pulses have a unique profile which contains an initial spike with a peak power of 1500 W for 1 μs, followed by the steady state power of 300 W. Because of its excellent beam quality, the laser beam produced by this fiber laser can be focused to a small spot size of 10 μm to achieve very high power density up to 1.9 GW/cm2. With one single laser pulse at approximately 1 μs, a blind hole of 167 μm in depth and 23 μm in opening diameter can be created in a stainless substrate. The experimental characterization of this micro-hole drilling process includes laser control, laser beam characterization, hole formation, photodiode measurements of the vapor intensity, high-speed photography of vapor/plasma formation, and spectroscopic measurements of plasma. The results show that, due to very high irradiance of the fiber laser beam, the absorbed energy not only is sufficient to melt and vaporize the material, but also is able to dissociate vapor into intense plasma at temperatures over 16,000 K. The hole drilling mechanism by this short microsecond laser ablation is due to a combination of adiabatic evaporation and ejection of fine droplets.

  7. Positron emission tomographic investigations of central muscarinic cholinergic receptors with three isomers of [76Br]BrQNP.

    PubMed

    Strijckmans, V; Bottlaender, M; Luo, H; Ottaviani, M; McPherson, D W; Loc'h, C; Fuseau, C; Knapp, F F; Mazière, B

    1997-05-01

    We studied the potential of three radiobrominated isomers of BrQNP, (Z(-,-)-[76Br]BrQNP, E(-,-)-[76Br]BrQNP and E(-,+)-[76Br]BrQNP), as suitable radioligands for imaging of central muscarinic cholinergic receptors in the human brain. These radioligands were stereospecifically prepared by electrophilic radiobromodestannylation of the respective tributylstannyl precursors using no-carrier-added [76Br]BrNH4 and peracetic acid. Preliminary pharmacological characterizations were determined by biodistribution, autoradiography, competition, displacement and metabolite studies in rats. The (-,-)-configuration presented important specific uptakes in brain muscarinic cholinergic receptor (mAChR)-rich structures and in heart, low metabolization rates and an apparent M2 selectivity. The (-,+)-configuration revealed more rapid clearance, lower uptake, a higher metabolization rate and an apparent M1 selectivity. Reversibility of the binding was confirmed for the three radiotracers. Positron emission tomography in the living baboon brain revealed high and rapid uptake in the brain and accumulation in the mAChR-rich structures studied. At 30 min p.i., the E(-,-)-radiotracer reached a plateau in cortex, pons and thalamus with concentrations of 29%, 24% and 19% ID/l, respectively. Z(-,-)-[76Br]BrQNP also accumulated in these structures, reaching a maximal uptake (27% ID/l) in the cortex 2 h p.i. At 5 min p.i. a plateau (17% ID/l) was only observed in the cortex for the E(-, +)-[76Br]BrQNP; by contrast, the other structures showed slow washout. After 3 weeks, the (-,-)-radiotracers were studied in the same baboon pretreated with dexetimide (1 mg/kg), a well-known muscarinic antagonist. In all the mAChR structures, the highly reduced uptake observed after this preloading step indicates that these radiotracers specifically bind to muscarinic receptors. Z(-, -)-[76Br]BrQNP, which is displaced in higher amounts from M2 mAChR-enriched structures, reveals an M2 affinity. The two isomers

  8. Analysis of eicosapentaenoic and docosahexaenoic acid geometrical isomers formed during fish oil deodorization.

    PubMed

    Fournier, Véronique; Juanéda, Pierre; Destaillats, Frédéric; Dionisi, Fabiola; Lambelet, Pierre; Sébédio, Jean-Louis; Berdeaux, Olivier

    2006-09-29

    Addition of long-chain polyunsaturated fatty acids (LC-PUFAs) from marine oil into food products implies preliminary refining procedures of the oil which thermal process affects the integrity of LC-PUFAs. Deodorization, the major step involving high temperatures, is a common process used for the refining of edible fats and oils. The present study evaluates the effect of deodorization temperature on the formation of LC-PUFA geometrical isomers. Chemically isomerized eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were used as reference samples. Fish oil samples have been deodorized at 180, 220 and 250 degrees C for 3 h and pure EPA and DHA fatty acid methyl esters (FAMEs) were chemically isomerized using p-toluenesulfinic acid as catalyst. FAMEs prepared from fish oil were fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC). Geometrical isomers produced by both processes were fractionated by silver-ion thin-layer chromatography (Ag-TLC) and silver-ion high-performance liquid chromatography (Ag-HPLC). The FAME fractions were subsequently analyzed by gas chromatography (GC) on a 100 m highly polar cyanopropylpolysiloxane coated capillary column, CP-Sil 88. Our results show that thermally induced geometrical isomerization appears to be a directed reaction and some ethylenic double bond positions on the hydrocarbon chain are more prone to stereomutation. Only minor changes were observed in the EPA and DHA trans isomers content and distribution after deodorization at 180 degrees C. The analyses of EPA and DHA isomer fractions revealed that it is possible to quantify EPA geometrical isomers by GC using the described conditions. However, we notice that a mono-trans isomer of DHA, formed during both chemical and thermal treatments, co-elute with all-cis DHA. This feature should be taken into consideration for the quantification of DHA geometrical isomers. PMID:16893549

  9. Osmoprotection by Pipecolic Acid in Sinorhizobium meliloti: Specific Effects of d and l Isomers

    PubMed Central

    Gouffi, Kamila; Bernard, Théophile; Blanco, Carlos

    2000-01-01

    dl-Pipecolic acid (dl-PIP) promotes growth restoration of Sinorhizobium meliloti cells facing inhibitory hyperosmolarity. Surprisingly, d and l isomers of this imino acid supplied separately were not effective. The uptake of l-PIP was significantly favored in the presence of the d isomer and by a hyperosmotic stress. Chromatographic analysis of the intracellular solutes showed that stressed cells did not accumulate radiolabeled l-PIP. Rather, it participates in the synthesis of the main endogenous osmolytes (glutamate and the dipeptide N-acetylglutaminylglutamine amide) during the lag phase, thus providing a means for the stressed cells to recover the osmotic balance. 13C nuclear magnetic resonance analysis was used to determine the fate of d-PIP taken into the cells. In the absence of l-PIP, the imported d isomer was readily degraded. Supplied together with its l isomer, d-PIP was accumulated temporarily and thus might contribute together with the endogenous osmolytes to enhance the internal osmotic strength. Furthermore, it started to disappear from the cytosol when the l isomer was no longer available in the culture medium (during the late exponential phase of growth). Together, these results show an uncommon mechanism of protection of osmotically stressed cells of S. meliloti. It was proved, for the first time, that the presence of the two isomers of the same molecule is necessary for it to manifest an osmoprotective activity. Indeed, d-PIP seems to play a major role in cellular osmoadaptation through both its own accumulation and improvement of the utilization of the l isomer as an immediate precursor of endogenous osmolytes. PMID:10831411

  10. A global search for the lowest energy isomer of C26

    NASA Astrophysics Data System (ADS)

    An, Jie; Gan, Li-Hua; Zhao, Jian-Qiang; Li, Rui

    2010-04-01

    The complete set of 2333 isomers of C26 fullerene composed of square, pentagonal, hexagonal, and heptagonal faces together with some noncage structures is investigated at the Hartree-Fock and density functional theory (DFT) levels. For the singlet states, a nonclassical isomer C26-10-01 with a square embedded is predicted by the DFT method as the lowest energy isomer, followed by the sole classical isomer C26-00-01. Further explorations reveal that the electronic ground state of C26-10-01 is triplet state in Cs symmetry, while that of C26-00-01 corresponds to its quintet in D3h symmetry. Both the total energies and nucleus independent chemical shift values at DFT level favor the classical isomer. It is found that both C26-00-01 and C26-10-01 possess high vertical electron affinity. The addition of electron(s) to C26-10-01 increases its aromatic character and encapsulation of Li atom into this cage is highly exothermic, indicating that it may be captured in the form of derivatives. To clarify the relative stabilities at elevated temperatures, the entropy contributions are taken into account based on the Gibbs free energy at the B3LYP/6-311+G∗ level. C26-10-01 behaves thermodynamically more stable than the classical isomer over a wide range of temperatures related to fullerene formation. The IR spectra of these two lowest energy isomers are simulated to facilitate their experimental identification.

  11. Accurate ab initio Quartic Force Fields of Cyclic and Bent HC2N Isomers

    NASA Technical Reports Server (NTRS)

    Inostroza, Natalia; Huang, Xinchuan; Lee, Timothy J.

    2012-01-01

    Highly correlated ab initio quartic force field (QFFs) are used to calculate the equilibrium structures and predict the spectroscopic parameters of three HC2N isomers. Specifically, the ground state quasilinear triplet and the lowest cyclic and bent singlet isomers are included in the present study. Extensive treatment of correlation effects were included using the singles and doubles coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations, denoted CCSD(T). Dunning s correlation-consistent basis sets cc-pVXZ, X=3,4,5, were used, and a three-point formula for extrapolation to the one-particle basis set limit was used. Core-correlation and scalar relativistic corrections were also included to yield highly accurate QFFs. The QFFs were used together with second-order perturbation theory (with proper treatment of Fermi resonances) and variational methods to solve the nuclear Schr dinger equation. The quasilinear nature of the triplet isomer is problematic, and it is concluded that a QFF is not adequate to describe properly all of the fundamental vibrational frequencies and spectroscopic constants (though some constants not dependent on the bending motion are well reproduced by perturbation theory). On the other hand, this procedure (a QFF together with either perturbation theory or variational methods) leads to highly accurate fundamental vibrational frequencies and spectroscopic constants for the cyclic and bent singlet isomers of HC2N. All three isomers possess significant dipole moments, 3.05D, 3.06D, and 1.71D, for the quasilinear triplet, the cyclic singlet, and the bent singlet isomers, respectively. It is concluded that the spectroscopic constants determined for the cyclic and bent singlet isomers are the most accurate available, and it is hoped that these will be useful in the interpretation of high-resolution astronomical observations or laboratory experiments.

  12. Conformational Changes and Slow Dynamics through Microsecond Polarized Atomistic Molecular Simulation of an Integral Kv1.2 Ion Channel

    PubMed Central

    Bjelkmar, Pär; Niemelä, Perttu S.; Vattulainen, Ilpo; Lindahl, Erik

    2009-01-01

    Structure and dynamics of voltage-gated ion channels, in particular the motion of the S4 helix, is a highly interesting and hotly debated topic in current membrane protein research. It has critical implications for insertion and stabilization of membrane proteins as well as for finding how transitions occur in membrane proteins—not to mention numerous applications in drug design. Here, we present a full 1 µs atomic-detail molecular dynamics simulation of an integral Kv1.2 ion channel, comprising 120,000 atoms. By applying 0.052 V/nm of hyperpolarization, we observe structural rearrangements, including up to 120° rotation of the S4 segment, changes in hydrogen-bonding patterns, but only low amounts of translation. A smaller rotation (∼35°) of the extracellular end of all S4 segments is present also in a reference 0.5 µs simulation without applied field, which indicates that the crystal structure might be slightly different from the natural state of the voltage sensor. The conformation change upon hyperpolarization is closely coupled to an increase in 310 helix contents in S4, starting from the intracellular side. This could support a model for transition from the crystal structure where the hyperpolarization destabilizes S4–lipid hydrogen bonds, which leads to the helix rotating to keep the arginine side chains away from the hydrophobic phase, and the driving force for final relaxation by downward translation is partly entropic, which would explain the slow process. The coordinates of the transmembrane part of the simulated channel actually stay closer to the recently determined higher-resolution Kv1.2 chimera channel than the starting structure for the entire second half of the simulation (0.5–1 µs). Together with lipids binding in matching positions and significant thinning of the membrane also observed in experiments, this provides additional support for the predictive power of microsecond-scale membrane protein simulations. PMID:19229308

  13. Temporal and spatial profiles of emission intensities in atmospheric pressure helium plasma jet driven by microsecond pulse: Experiment and simulation

    SciTech Connect

    Wang, Ruixue; Zhang, Cheng; Yan, Ping; Shao, Tao; Shen, Yuan; Zhu, Weidong; Babaeva, Natalia Yu.; Naidis, George V.

    2015-09-28

    A needle-circular electrode structure helium plasma jet driven by microsecond pulsed power is studied. Spatially resolved emission results show that the emission intensity of He(3{sup 3}S{sub 1}) line decreases monotonically along the axial direction, while those of N{sub 2}(C{sup 3}Π{sub u}), N{sub 2}{sup +}(B{sup 2}∑{sup +}{sub u}), and O(3p{sup 5}P) reach their maxima at 3 cm, 2.6 cm, and 1.4 cm, respectively. The plasma plume of the four species shows different characteristics: The N{sub 2} emission plume travels at a fast speed along the entire plasma jet; the N{sub 2}{sup +} emission plume is composed of a bright head and relatively weak tail and travels a shorter distance than the N{sub 2} emission plume; the He emission plume travels at a slower speed for only a very short distance; propagation of the O emission plume is not observed. Results of calculation of radiation fluxes emitted by positive streamers propagating along helium plasma jets are presented. It is shown, in agreement with the results of the present experiment and with other available experimental data, that the intensities of radiation of N{sub 2}(C{sup 3}Π{sub u}) molecules and He(3{sup 3}S{sub 1}) atoms vary with time (along the plasma jet) quite differently. The factors resulting in this difference are discussed.

  14. High longitudinal relaxivity of ultra-small gadolinium oxide prepared by microsecond laser ablation in diethylene glycol

    SciTech Connect

    Luo Ningqi; Xiao Jun; Hu Wenyong; Chen Dihu; Tian Xiumei; Yang Chuan; Li Li

    2013-04-28

    Ultra-small gadolinium oxide (Gd{sub 2}O{sub 3}) can be used as T{sub 1}-weighted Magnetic Resonance Imaging (MRI) contrast agent own to its high longitudinal relaxivity (r{sub 1}) and has attracted intensive attention in these years. In this paper, ultra-small Gd{sub 2}O{sub 3} nanoparticles of 3.8 nm in diameter have been successfully synthesized by a microsecond laser ablating a gadolinium (Gd) target in diethylene glycol (DEG). The growth inhibition effect induced by the large viscosity of DEG makes it possible to synthesize ultra-small Gd{sub 2}O{sub 3} by laser ablation in DEG. The r{sub 1} value and T{sub 1}-weighted MR images are measured by a 3.0 T MRI spectroscope. The results show these nanoparticles with a high r{sub 1} value of 9.76 s{sup -1} mM{sup -1} to be good MRI contrast agents. We propose an explanation for the high r{sub 1} value of ultra-small Gd{sub 2}O{sub 3} by considering the decreasing factor (surface to volume ratio of the nanoparticles, S/V) and the increasing factor (water hydration number of the Gd{sup 3+} on Gd{sub 2}O{sub 3} surface, q), which offer a new look into the relaxivity studies of MRI contrast agents. Our research provides a new approach to preparing ultra-small Gd{sub 2}O{sub 3} of high r{sub 1} value by laser ablation in DEG and develops the understanding of high relaxivity of ultra-small Gd{sub 2}O{sub 3} MRI contrast agents.

  15. Characterization of neutron emission from mega-ampere deuterium gas puff Z-pinch at microsecond implosion times

    NASA Astrophysics Data System (ADS)

    Klir, D.; Shishlov, A. V.; Kokshenev, V. A.; Kubes, P.; Labetsky, A. Yu; Rezac, K.; Cikhardt, J.; Fursov, F. I.; Kovalchuk, B. M.; Kravarik, J.; Kurmaev, N. E.; Ratakhin, N. A.; Sila, O.; Stodulka, J.

    2013-08-01

    Experiments with deuterium (D2) triple shell gas puffs were carried out on the GIT-12 generator at a 3 MA current level and microsecond implosion times. The outer, middle and inner nozzle diameters were 160 mm, 80 mm and 30 mm, respectively. The influence of the mass of deuterium shells on neutron emission times, neutron yields and neutron energy spectra was studied. The injected linear mass of deuterium varied between 50 and 255 µg cm-1. Gas puffs imploded onto the axis before the peak of generator current at 700-1100 ns. Most of the neutrons were emitted during the second neutron pulse after the development of instabilities. Despite higher currents, heavier gas puffs produced lower neutron yields. Optimal mass and a short time delay between the valve opening and the generator triggering were more important than the better coincidence of stagnation with peak current. The peak neutron yield from D(d, n)3He reactions reached 3 × 1011 at 2.8 MA current, 90 µg cm-1 injected linear mass and 37 mm anode-cathode gap. In the case of lower mass shots, a large number of 10 MeV neutrons were produced either by secondary DT reactions or by DD reactions of deuterons with energies above 7 MeV. The average neutron yield ratio Y>10 MeV/Y2.5 MeV reached (6 ± 3) × 10-4. Such a result can be explained by a power law distribution for deuterons as \\rmd N_d/\\rmd E_d\\propto E_d^{-3} . The optimization of a D2 gas puff Z-pinch and similarities to a plasma focus and its drive parameter are described.

  16. Validation of Force Fields of Rubber through Glass-Transition Temperature Calculation by Microsecond Atomic-Scale Molecular Dynamics Simulation.

    PubMed

    Sharma, Pragati; Roy, Sudip; Karimi-Varzaneh, Hossein Ali

    2016-02-25

    Microsecond atomic-scale molecular dynamics simulation has been employed to calculate the glass-transition temperature (Tg) of cis- and trans-1,4-polybutadiene (PB) and 1,4-polyisoprene (PI). Both all-atomistic and united-atom models have been simulated using force fields, already available in literature. The accuracy of these decade old force fields has been tested by comparing calculated glass-transition temperatures to the corresponding experimental values. Tg depicts the phase transition in elastomers and substantially affects various physical properties of polymers, and hence the reproducibility of Tg becomes very crucial from a thermodynamic point of view. Such validation using Tg also evaluates the ability of these force fields to be used for advanced materials like rubber nanocomposites, where Tg is greatly affected by the presence of fillers. We have calculated Tg for a total of eight systems, featuring all-atom and united-atom models of cis- and trans-PI and -PB, which are the major constituents of natural and synthetic rubber. Tuning and refinement of the force fields has also been done using quantum-chemical calculations to obtain desirable density and Tg. Thus, a set of properly validated force fields, capable of reproducing various macroscopic properties of rubber, has been provided. A novel polymer equilibration protocol, involving potential energy convergence as the equilibration criterion, has been proposed. We demonstrate that not only macroscopic polymer properties like density, thermal expansion coefficient, and Tg but also local structural characteristics like end-to-end distance (R) and radius of gyration (Rg) and mechanical properties like bulk modulus have also been equilibrated using our strategy. Complete decay of end-to-end vector autocorrelation function with time also supports proper equilibration using our strategy. PMID:26836395

  17. Impact of the electron environment on the lifetime of the {sup 229}Th{sup m} low-lying isomer

    SciTech Connect

    Karpeshin, F. F.; Trzhaskovskaya, M. B.

    2007-11-15

    The question of the lifetime of the {sup 229}Th{sup m} low-lying isomer is considered in light of current experimental research. A strong effect of the electron shell on lifetime is demonstrated, depending on the energy of the isomer. Calculations are performed within the framework of the multiconfiguration Dirac-Fock method. The calculated lifetime ranges from around 1 min down to 10{sup -5} s. Prospects for further experimental research of the isomer are discussed.

  18. Stability and isomerization reactions of phenyl cation C6H5+ isomers

    NASA Astrophysics Data System (ADS)

    Shi, Dandan; Yang, Xue; Zhang, Xiaomei; Shan, Shimin; Xu, Haifeng; Yan, Bing

    2016-03-01

    As a key polyatomic molecular cation that plays a pivotal role in growth of the polycyclic aromatic hydrocarbons, phenyl cation C6H5+ exhibits various isomers and isomerization reactions. Investigation on the structure and stability of the isomers as well as the isomerization is important for better understanding the chemical reactions involving C6H5+ cations. In this work, we have performed a theoretical study on the stability and isomerization reactions of C6H5+ isomers at density functional theory B3LYP/6-311G (d, p) level. We have obtained a total of 60 isomers of C6H5+ cations, most of which are reported for the first time. The geometries, vibrational frequencies, thermodynamic properties and stability of 28 out of 60 isomers have been summarized in detail. Different ring-to-ring and ring-to-chain isomerization pathways, which are connected via 28 transition states, have been investigated using the intrinsic reaction coordinate method. The results show that the isomerization reactions occur via hydrogen migration followed by bond-breaking and reconstruction.

  19. Experimental and theoretical cross sections for positron scattering from the pentane isomers

    NASA Astrophysics Data System (ADS)

    Chiari, L.; Zecca, A.; Blanco, F.; García, G.; Brunger, M. J.

    2016-02-01

    Isomerism is ubiquitous in chemistry, physics, and biology. In atomic and molecular physics, in particular, isomer effects are well known in electron-impact phenomena; however, very little is known for positron collisions. Here we report on a set of experimental and theoretical cross sections for low-energy positron scattering from the three structural isomers of pentane: normal-pentane, isopentane, and neopentane. Total cross sections for positron scattering from normal-pentane and isopentane were measured at the University of Trento at incident energies between 0.1 and 50 eV. Calculations of the total cross sections, integral cross sections for elastic scattering, positronium formation, and electronic excitations plus direct ionization, as well as elastic differential cross sections were computed for all three isomers between 1 and 1000 eV using the independent atom model with screening corrected additivity rule. No definitive evidence of a significant isomer effect in positron scattering from the pentane isomers appears to be present.

  20. Elucidation of Drug Metabolite Structural Isomers Using Molecular Modeling Coupled with Ion Mobility Mass Spectrometry.

    PubMed

    Reading, Eamonn; Munoz-Muriedas, Jordi; Roberts, Andrew D; Dear, Gordon J; Robinson, Carol V; Beaumont, Claire

    2016-02-16

    Ion mobility-mass spectrometry (IM-MS) in combination with molecular modeling offers the potential for small molecule structural isomer identification by measurement of their gas phase collision cross sections (CCSs). Successful application of this approach to drug metabolite identification would facilitate resource reduction, including animal usage, and may benefit other areas of pharmaceutical structural characterization including impurity profiling and degradation chemistry. However, the conformational behavior of drug molecules and their metabolites in the gas phase is poorly understood. Here the gas phase conformational space of drug and drug-like molecules has been investigated as well as the influence of protonation and adduct formation on the conformations of drug metabolite structural isomers. The use of CCSs, measured from IM-MS and molecular modeling information, for the structural identification of drug metabolites has also been critically assessed. Detection of structural isomers of drug metabolites using IM-MS is demonstrated and, in addition, a molecular modeling approach has been developed offering rapid conformational searching and energy assessment of candidate structures which agree with experimental CCSs. Here it is illustrated that isomers must possess markedly dissimilar CCS values for structural differentiation, the existence and extent of CCS differences being ionization state and molecule dependent. The results present that IM-MS and molecular modeling can inform on the identity of drug metabolites and highlight the limitations of this approach in differentiating structural isomers. PMID:26752623

  1. Theoretical investigation on isomer formation probability and free energy of small C clusters

    NASA Astrophysics Data System (ADS)

    Lin, Zheng-Zhe

    2015-06-01

    Molecular dynamics simulations and free energy calculations are employed to investigate the evolution, formation probability, detailed balance, and isomerization rate of small C cluster isomer at 2500 K. For C10, the isomer formation probability predicted by free energy is in good agreement with molecular dynamics simulation. However, for C20, C30, and C36, the formation probabilities predicted by free energy are not in agreement with molecular dynamics simulations. Although the cluster systems are in equilibrium, detailed balance is not reached. Such results may be attributed to high transformation barriers between cage, bowl, and sheet isomers. In summary, for mesoscopic nanosystems the free energy criterion, which commonly holds for macroscopic systems in dynamic equilibrium, may not provide a good prediction for isomer formation probability. New theoretical criterion should be further investigated for predicting the isomer formation probability of a mesoscopic nanosystem. Project supported by the National Natural Science Foundation of China (Grant No. 11304239) and the Fundamental Research Funds for the Central Universities.

  2. Trans isomers of EPA and DHA in omega-3 products on the European market.

    PubMed

    Sciotto, Caterina; Mjøs, Svein A

    2012-07-01

    The levels of trans isomers of eicosapentaenoic (EPA) acid and docosahexaenoic acid (DHA) in 77 omega-3 products on the European market have been studied. Fatty acids were analyzed as fatty acid methyl esters by gas chromatography with a flame ionization detector, using a cyanopropyl coated stationary phase. The amount of mono-trans EPA isomers relative to the corresponding all-cis isomer ranged from 0.19 to 4.5 %. The corresponding values for mono-trans DHA relative to the all-cis isomer ranged from 0.25 to 5.9 %. There was a strong correlation between the degree of isomerization of EPA and DHA, showing that DHA was 1.26 times more isomerized than EPA. Division of the samples into different product groups showed that samples with a low degree of isomerization were found in all groups, except one. This shows that a high degree of isomerization is avoidable, and also points to deodorization of the oils as the main source of trans isomers. PMID:22566205

  3. Search for the isomers of C2H3NO and C2H3NS in the Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Etim, Emmanuel; Chakrabarti, Sandip Kumar; Das, Ankan; Gorai, Prasanta; Arunan, Elangannan

    2016-07-01

    With about 40% of all the known interstellar and circumstellar molecules having their isomeric analogues as known astromolecules, isomerism remains one of the leading themes in interstellar chemistry. In this regard, the recent detection of methyl isocyanate (with a number of isomeric analogues) in the Sgr B2(N) giant molecular cloud opens a new window for the possible astronomical detection of other C_2H_3NO isomers. The present work looks at the possibility of detecting other isomers of methyl isocyanate by considering different factors such as thermodynamic stability of the different isomers with respect to the Energy, Stability and Abundance (ESA) relationship, effect of interstellar hydrogen bonding with respect to the formation these isomers on the surface of the interstellar dust grains, possible formation routes for these isomers, spectroscopic parameters for potential astromolecules among these isomers, chemical modeling among other studies. The same studies are repeated for the C_2H_3NS isomers which are the isoelectroninc analogues of the C_2H_3NO isomers taking into account the unique chemistry of S and O-containing interstellar molecular species. Among the C_2H_3NS isomers, methyl isothiocyanate remains the most potential candidate for astronomical observation.

  4. Linear and branched perfluorooctane sulfonate (PFOS) isomer patterns differ among several tissues and blood of polar bears.

    PubMed

    Greaves, Alana K; Letcher, Robert J

    2013-09-01

    Perfluorooctane sulfonate (PFOS) is a globally distributed persistent organic pollutant that has been found to bioaccumulate and biomagnify in aquatic food webs. Although principally in its linear isomeric configuration, 21-35% of the PFOS manufactured via electrochemical fluorination is produced as a branched structural isomer. PFOS isomer patterns were investigated in multiple tissues of polar bears (Ursus maritimus) from East Greenland. The liver (n = 9), blood (n = 19), brain (n = 16), muscle (n = 5), and adipose (n = 5) were analyzed for linear PFOS (n-PFOS), as well as multiple mono- and di-trifluoromethyl-substituted branched isomers. n-PFOS accounted for 93.0 ± 0.5% of Σ-PFOS isomer concentrations in the liver, whereas the proportion was significantly lower (p<0.05) in the blood (85.4 ± 0.5%). Branched isomers were quantifiable in the liver and blood, but not in the brain, muscle, or adipose. In both the liver and blood, 6-perfluoromethylheptane sulfonate (P6MHpS) was the dominant branched isomer (2.61 ± 0.10%, and 3.26 ± 0.13% of Σ-PFOS concentrations, respectively). No di-trifluoromethyl-substituted isomers were detectable in any of the tissues analyzed. These tissue-specific isomer patterns suggest isomer-specific pharmacokinetics, perhaps due to differences in protein affinities, and thus differences in protein interactions, as well transport, absorption, and/or metabolism in the body. PMID:23920361

  5. Energy landscapes in diexo and exo/endo isomers derived from Li 2B 12H 12

    NASA Astrophysics Data System (ADS)

    Oliva, Josep M.; Fernández-Barbero, Antonio; Serrano-Andrés, Luis; Canle-L., Moisés; Santaballa, J. Arturo; Fernández, M. Isabel

    2010-09-01

    In the pursuit of detecting the first endohedral polyhedral borane complex, we report a quantum-chemical computational study of energy landscapes for diexo isomers derived from Li 2B 12H 12 and the exo/endo isomer Li@{LiB 12H 12}. Geometries, electronic structure and energy barriers are computed for the interconversion between diexo isomers and the exo/ endo isomer, the latter leading to a thermal injection/ ejection mechanism of Li + from outside/ inside the complex [LiB 12H 12] -.

  6. [C72]—Fullerene: Enumeration of Substitution Isomers Based on the Vertex, Edge and Facial Differentiation

    NASA Astrophysics Data System (ADS)

    Smolyakov, V. M.; Sokolov, D. V.; Nilov, D. Yu.; Grebeshkov, V. V.; Bolshakov, V. V.

    2010-11-01

    The paper discusses substitution isomers [C72]—fullerene by vertices, edges and faces. The derivation of isomers is based on the Polya theorem [1]. Formulas of symmetry Z, generating functions for identification of the number of substitution isomers of [C72]—fullerene, distribution of isomers over families ρ(m) and depending on number m of places of substitution is established. Based on the models [2-5] an addictive assessment scheme of the properties of gaseous carbon clusters [C60]-[C100] is obtained, and calculations of gaseous carbon clusters ΔfH° 298к, S° 298к not studied experimentally yet, are carried out.

  7. In vitro interaction study of retinoic acid isomers with telmisartan and amlodipine by equilibrium dialysis method using UV spectroscopy

    NASA Astrophysics Data System (ADS)

    Varghese, Susheel John; Johny, Sojimol K.; Paul, David; Ravi, Thengungal Kochupappy

    2011-07-01

    The in vitro protein binding of retinoic acid isomers (isotretinoin and tretinoin) and the antihypertensive drugs (amlodipine and telmisartan) was studied by equilibrium dialysis method. In this study, free fraction of drugs and the % of binding of drugs in the mixture to bovine serum albumin (BSA) were calculated. The influence of retinoic acid isomers on the % of protein binding of telmisartan and amlodipine at physiological pH (7.4) and temperature (37 ± 0.5 °C) was also evaluated. The in vitro displacement interaction study of drugs telmisartan and amlodipine on retinoic acid isomers and also interaction of retinoic acid isomers on telmisartan and amlodipine were carried out.

  8. Sc2O@C(3v)(8)-C82: A Missing Isomer of Sc2O@C82.

    PubMed

    Tang, Qiangqiang; Abella, Laura; Hao, Yajuan; Li, Xiaohong; Wan, Yingbo; Rodríguez-Fortea, Antonio; Poblet, Josep M; Feng, Lai; Chen, Ning

    2016-02-15

    By introducing CO2 as the oxygen source during the arcing process, a new isomer of Sc2O@C82, Sc2O@C(3v)(8)-C82, previously investigated only by computational studies, was discovered and characterized by mass spectrometry, UV-vis-NIR absorption spectroscopy, cyclic voltammetry, (45)Sc NMR, density functional theory (DFT) calculations, and single-crystal X-ray diffraction. The crystallographic analysis unambiguously elucidated that the cage symmetry was assigned to C(3v)(8) and suggests that Sc2O cluster is disordered inside the cage. The comparative studies of crystallographic data further reveal that the Sc1-O-Sc2 angle is in the range of 131.0-148.9°, much larger than that of the Sc2S@C(3v)(8)-C82, demonstrating a significant flexibility of dimetallic clusters inside the cages. The electrochemical studies show that the electrochemical gap of Sc2O@C(3v)(8)-C82 is 1.71 eV, the largest among those of the oxide cluster fullerenes (OCFs) reported so far, well correlated with its rich abundance in the reaction mixture of OCF synthesis. Moreover, the comparative electrochemical studies suggest that both the dimetallic clusters and the cage structures have major influences on the electronic structures of the cluster fullerenes. Computational studies show that the cluster can rotate and change the Sc-O-Sc angle easily at rather low temperature. PMID:26840749

  9. Discovery and identification of a series of alkyl decalin isomers in petroleum geological samples.

    PubMed

    Wang, Huitong; Zhang, Shuichang; Weng, Na; Zhang, Bin; Zhu, Guangyou; Liu, Lingyan

    2015-07-01

    The comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC/TOFMS) has been used to characterize a crude oil and a source rock extract sample. During the process, a series of pairwise components between monocyclic alkanes and mono-aromatics have been discovered. After tentative assignments of decahydronaphthalene isomers, a series of alkyl decalin isomers have been synthesized and used for identification and validation of these petroleum compounds. From both the MS and chromatography information, these pairwise compounds were identified as 2-alkyl-decahydronaphthalenes and 1-alkyl-decahydronaphthalenes. The polarity of 1-alkyl-decahydronaphthalenes was stronger. Their long chain alkyl substituent groups may be due to bacterial transformation or different oil cracking events. This systematic profiling of alkyl-decahydronaphthalene isomers provides further understanding and recognition of these potential petroleum biomarkers. PMID:25945366

  10. Isomer specific kinetics of dopamine beta-hydroxylase and arylsulfatase towards catecholamine sulfates.

    PubMed

    Strobel, G; Werle, E; Weicker, H

    1990-01-01

    Both isomers of epinephrine sulfate were synthesized, unequivocally identified by 1H-NMR and highly purified from catecholamines (less than 90 ppm). Bacterial as well as pig liver arylsulfatase A and B demonstrated a higher substrate turnover of epinephrine-4-sulfate, norepinephrine-4-sulfate and dopamine-4-sulfate as compared to the 3-sulfate isomers. The arylsulfatase B however, is less important for the deconjugation of these sulfoconjugates than arylsulfatase A. Since arylsulfatase A occurs in most human tissues, it might be of physiological significance in the deconjugation of the catecholamine sulfate isomers. Furthermore the kinetic data at pH 7.4 and 6.9 suggest the increased cleavage of the sulfate group, e.g. during exercise-induced acidosis. In contrast to results reported in the literature, dopamine sulfates were no substrates of dopamine beta-hydroxylase. PMID:2317215

  11. Integrated cross sections for excitation of nuclear isomers by inelastic photon scattering at giant resonance

    NASA Astrophysics Data System (ADS)

    Sáfár, József; Lakosi, László

    2014-02-01

    In the view of the evidences arising from our experimental and theoretical studies, the long-standing picture of a two-humped excitation function for photoexcitation of isomers cannot be confirmed. Whereas the first maximum (at the photoneutron threshold) of the cross section of nuclear photon scattering can be attributed to inelastic (compound) scattering, the second large peak at about giant dipole resonance is mostly due to the elastic (direct) process. A second large peak or increase reported to appear in isomer production has been shown to be practically vanishing. On realizing such a situation, calculated estimates have been given for saturated integral cross section values for isomer activation, based on photoabsorption cross sections taken from the usual Lorentzian parametrization up to the photoneutron threshold. Results compare reasonably well to available experimental data acquired by gamma-ray spectrometry in a large set of stable nuclides having long-lived isomeric states.

  12. N22C2 versus N24: Role of molecular curvature in determining isomer stability

    PubMed Central

    Jasper, Shanese; Hammond, Asya; Thomas, Jessica; Kidd, Latoris

    2015-01-01

    Three-dimensional N22C2 cages are examined by theoretical calculations to determine relative stability among various isomers. Stability as a function of cage shape and stability as a function of carbon location are calculated and discussed. The results are compared to isomers of N24 to determine the effects of carbon substitution into the cage structure. Further, since the various cage shapes in this study vary by degree of curvature, model calculations are carried out to determine the energetic consequences of curving the local structure around nitrogen and carbon. The model calculations are compared to the actual results on the larger cages to determine how well curvature effects explain the relative stability of N22C2 isomer as compared to the corresponding N24. PMID:21923113

  13. Identification of L-Methionine-S-Sulfoximine as the Convulsant Isomer of Methionine Sulfoximine*

    PubMed Central

    Rowe, W. Bruce; Meister, Alton

    1970-01-01

    The convulsant agent methionine sulfoximine inhibits brain glutamine synthetase irreversibly and the inhibitor becomes bound to the active site of the enzyme as methionine sulfoximine phosphate. Only one of the four isomers of methionine sulfoximine, L-methionine-S-sulfoximine, inhibits glutamine synthetase. In the present work, D-methionine-SR-sulfoximine, and highly purified preparations of L-methionine-S-sulfoximine and L-methionine-R-sulfoximine were tested in mice for convulsant activity; only L-methionine-S-sulfoximine produced convulsions. The finding that only one of the four optical isomers of methionine sulfoximine induces convulsions, and that only this same isomer inhibits glutamine synthetase, lends support to the conclusion that these two effects of methionine sulfoximine are closely connected. PMID:4393740

  14. Reduction of MTT to Purple Formazan by Vitamin E Isomers in the Absence of Cells

    PubMed Central

    Lim, Su-Wen; Loh, Hwei-San; Ting, Kang-Nee; Bradshaw, Tracey Dawn; Allaudin, Zeenathul Nazariah

    2015-01-01

    The yellow tetrazolium salt 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) is widely used to determine cell viability in cell proliferation and cytotoxic assays. MTT is reduced by metabolically active cells to form an insoluble purple formazan product that is quantifiable by spectrophotometry. It is the most common and direct assay for cell viability. However, in this present study, we demonstrated that the vitamin E isomers α-β-γ-δ-tocotrienols and α-tocopherol were able to reduce MTT into a formazan product, despite the absence of living cells. For comparison, a second method for determining cell viability, which is the neutral red uptake assay, was used in parallel with the MTT assay. The results showed that neutral red did not interact with the vitamin E isomers. Our findings suggest that the MTT assay is not suitable for studying the proliferative effects of vitamin E isomers on cell growth. PMID:26868595

  15. Fast decay of a three-quasiparticle isomer in {sup 171}Tm

    SciTech Connect

    Walker, P. M.; Wood, R. J.; El-Masri, H. M.; Wheldon, C.; Dracoulis, G. D.; Kibedi, T.; Bark, R. A.; Davidson, P. M.; Lane, G. J.; Moon, C.; Bruce, A. M.; Orce, J. N.; Estevez, F. M. Prados; Byrne, A. P.; Wilson, A. N.

    2009-04-15

    Incomplete-fusion reactions have been used to study high-spin states in {sup 171}Tm. Gamma rays and conversion electrons were measured using pulsed-beam conditions for enhanced isomer sensitivity. A K{sup {pi}}=19/2{sup +}, three-quasiparticle isomer was identified, with a half-life of 1.7(2){mu}s. The faster than expected transition rates from the isomer can be understood as being due to a chance near-degeneracy, with mixing between the isomeric state and the I{sup {pi}}=19/2{sup +} member of the one-quasiparticle rotational band to which it decays. The implied mixing matrix element is 12(2) eV.

  16. Self-Assembly of Mesoscale Isomers: The Role of Pathways and Degrees of Freedom

    PubMed Central

    Pandey, Shivendra; Johnson, Daniel; Kaplan, Ryan; Klobusicky, Joseph; Menon, Govind; Gracias, David H.

    2014-01-01

    The spontaneous self-organization of conformational isomers from identical precursors is of fundamental importance in chemistry. Since the precursors are identical, it is the multi-unit interactions, characteristics of the intermediates, and assembly pathways that determine the final conformation. Here, we use geometric path sampling and a mesoscale experimental model to investigate the self-assembly of a model polyhedral system, an octahedron, that forms two isomers. We compute the set of all possible assembly pathways and analyze the degrees of freedom or rigidity of intermediates. Consequently, by manipulating the degrees of freedom of a precursor, we were able to experimentally enrich the formation of one isomer over the other. Our results suggest a new approach to direct pathways in both natural and synthetic self-assembly using simple geometric criteria. We also compare the process of folding and unfolding in this model with a geometric model for cyclohexane, a well-known molecule with chair and boat conformations. PMID:25299051

  17. In vivo formation of polyphosphoinositide isomers and association with progression of murine polycystic kidney disease.

    PubMed

    Aukema, H M; Chapkin, R S; Tomobe, K; Takahashi, H; Holub, B J

    1992-08-01

    Polyphosphoinositide isomers have been demonstrated to be important mediators of cell proliferation in vitro. The present study demonstrates, for the first time, the in vivo formation of the novel isomer, phosphatidylinositol(3)phosphate, in the kidney and liver of intact animals following intraperitoneal administration of [3H]myo-inositol. The formation of renal [3H]phosphatidylinositol(3)phosphate relative to total [3H]phosphatidylinositol-phosphate was positively correlated with cyst proliferation and renal enlargement in a murine model of polycystic kidney disease. Furthermore, despite no difference in the formation of renal [3H]phosphatidylinositol(4)phosphate, a markedly lower accumulation (by 48%) of [3H]phosphatidylinositol(4,5)bisphosphate was observed in the diseased animals as compared to controls. These results indicate that further studies on the in vivo formation of specific polyphosphoinositide isomers in disease states characterized by abnormal growth and oncogene expression are warranted. PMID:1327862

  18. Comparison of geometric, electronic, and vibrational properties for isomers of small fullerenes C20-C36.

    PubMed

    Małolepsza, Edyta; Witek, Henryk A; Irle, Stephan

    2007-07-26

    We employ the self-consistent-charge density-functional tight-binding (SCC-DFTB) method for computing geometric, electronic, and vibrational properties for various topological isomers of small fullerenes. We consider all 35 five- and six-member rings containing isomers of small fullerenes, C20, C24, C26, C28, C30, C32, C34, and C36, as first part of a larger effort to catalog CC distance distributions, valence CCC angle distributions, electronic densities of states (DOSs), vibrational densities of states (VDOSs), and infrared (IR) and Raman spectra for fullerenes C20-C180. Common features among the fullerenes are identified and properties characteristic for each specific fullerene isomer are discussed. PMID:17429953

  19. Two New Isomers of Palmityl-4-hydroxycinnamate from Flowers of Taraxacum Species.

    PubMed

    Dudáš, Matej; Vilková, Mária; Béres, Tibor; Repcák, Miroslav; Mártonfi, Pavol

    2016-06-01

    Two isomers, (Z)- and (E)-palmityl 4-hydroxycinnamate [hexadecyl(2Z)-3-(4-hydroxyphenyl)prop-2-enoate and hexadecyl(2E)-3-(4-hydroxyphenyl)prop-2-enoate] were isolated for the first time from ligulate flowers of Taraxacum linearisquameum Soest (sect. Taraxacum). The highest amount of these compounds was detected in pollen grains; 0.26 mg/100 mg DW of the (E)-isomer and 0.096 mg/100 mg DW of the (Z)-isomer. The structures of these compounds were elucidated by a combination of HPLC-ESI-Qtof-MS and 1D and 2D NMR spectroscopy. Their presence was confirmed in other species of Taraxacum, but they were not found in the male - sterile triploid agamospermous taxon T. parnassicum. PMID:27534130

  20. High-spin isomers in 212Rn in the region of triple neutron core-excitations

    NASA Astrophysics Data System (ADS)

    Dracoulis, G. D.; Lane, G. J.; Byrne, A. P.; Davidson, P. M.; Kibédi, T.; Nieminen, P.; Watanabe, H.; Wilson, A. N.

    2008-04-01

    The level scheme of 212Rn has been extended to spins of ∼ 38 ℏ and excitation energies of about 13 MeV using the 204Hg(13C, 5n)212Rn reaction and γ-ray spectroscopy. Time correlated techniques have been used to obtain sensitivity to weak transitions and channel selectivity. The excitation energy of the 22+ core-excited isomer has been established at 6174 keV. Two isomers with τ = 25 (2) ns and τ = 12 (2) ns are identified at 12211 and 12548 keV, respectively. These are the highest-spin nuclear isomers now known, and are attributed to configurations involving triple neutron core-excitations coupled to the aligned valence protons. Semi-empirical shell-model calculations can account for most states observed, but with significant energy discrepancies for some configurations.

  1. Computational design of multi-states monomolecular device using molecular hydrogen and C20 isomers

    NASA Astrophysics Data System (ADS)

    Ganji, M. Darvish

    2016-07-01

    We perform detailed calculations for the interaction of molecular hydrogen with C20isomers in the framework of density functional theory method. The adsorption of H2 outside the C20-e isomer with parallel orientation with respect to the plane of the hexagon is found to be the most stable adsorption configuration. Thus this might have potential for the hydrogen storing. We have also investigated the number and the position of adsorption sites in the pentagon for the parallel configurations of the H2/C20 systems. We find two stable configurations of the molecule for the C20-bowl isomer that have a small difference in energy. Thus, surprisingly, despite their apparent simplicity these H2/C20-bowl systems are shown to exhibit the flip-flop motion by a small current pulse. Hence, it might be a candidate for multi-states monomolecular device. Convenient experimental techniques such as field emission microscopy are proposed to test these predictions.

  2. Differential Potency of 2,6-Dimethylcyclohexanol Isomers for Positive Modulation of GABAA Receptor Currents.

    PubMed

    Chowdhury, Luvana; Croft, Celine J; Goel, Shikha; Zaman, Naina; Tai, Angela C-S; Walch, Erin M; Smith, Kelly; Page, Alexandra; Shea, Kevin M; Hall, C Dennis; Jishkariani, D; Pillai, Girinath G; Hall, Adam C

    2016-06-01

    GABAA receptors meet all of the pharmacological requirements necessary to be considered important targets for the action of general anesthetic agents in the mammalian brain. In the following patch-clamp study, the relative modulatory effects of 2,6-dimethylcyclohexanol diastereomers were investigated on human GABAA (α1β3γ2s) receptor currents stably expressed in human embryonic kidney cells. Cis,cis-, trans,trans-, and cis,trans-isomers were isolated from commercially available 2,6-dimethylcyclohexanol and were tested for positive modulation of submaximal GABA responses. For example, the addition of 30 μM cis,cis-isomer resulted in an approximately 2- to 3-fold enhancement of the EC20 GABA current. Coapplications of 30 μM 2,6-dimethylcyclohexanol isomers produced a range of positive enhancements of control GABA responses with a rank order for positive modulation: cis,cis > trans,trans ≥ mixture of isomers > > cis,trans-isomer. In molecular modeling studies, the three cyclohexanol isomers bound with the highest binding energies to a pocket within transmembrane helices M1 and M2 of the β3 subunit through hydrogen-bonding interactions with a glutamine at the 224 position and a tyrosine at the 220 position. The energies for binding to and hydrogen-bond lengths within this pocket corresponded with the relative potencies of the agents for positive modulation of GABAA receptor currents (cis,cis > trans,trans > cis,trans-2,6-dimethylcyclohexanol). In conclusion, the stereochemical configuration within the dimethylcyclohexanols is an important molecular feature in conferring positive modulation of GABAA receptor activity and for binding to the receptor, a consideration that needs to be taken into account when designing novel anesthetics with enhanced therapeutic indices. PMID:27029583

  3. Preparative isolation and structural characterization of sucrose ester isomers from oriental tobacco.

    PubMed

    Jia, Chunxiao; Wang, Yingying; Zhu, Yonghua; Xu, Chunping; Mao, Duobin

    2013-05-01

    To date, the structures of the sucrose tetraester (STE) isomers, a main kind of sucrose esters (SEs) in Solanum, have not been conclusively assigned. In this study, three groups of STE isomers with the molecular weight 650, 664 and 678 (designated as STE I, STE II and STE III, respectively) have been isolated and purified from the oriental tobacco-Komotini Basma using a semi-preparative RP-HPLC method. The full characterization of the isomers in the three groups of STE were investigated for the first time by MS (HRMS, MS(2)) and NMR ((1)H, (13)C, HSQC) spectroscopy combined with alkaline hydrolysis and STE derivation experiments. The STE III (a single compound) was confirmed as a known sucrose tetraester. Furthermore, the STE II was found to contain three isomers and the structures were first unambiguously established as 6-O-acetyl (2,3 or 2,4 or 3,4)-di-O-3-methylvaleryl-(4 or 3 or 2)-O-2-methylbutyryl-α-d-glucopyranosyl-β-d-fructofuranoside. Finally, the STE I was discovered to contain seven isomers and the structures were elucidated as 6-O-acetyl (2 or 3 or 4)-O-3-methylvaleryl-(3,4 or 2,4 or 2,3)-di-O-2-methylbutyryl-α-d-glucopyranosyl-β-d-fructofuranoside, 6-O-acetyl (2 or 3 or 4)-O-3-methylvaleryl-(3,4 or 2,4 or 2,3)-di-O-isovaleryl-α-d-glucopyranosyl-β-d-fructofuranoside and 6-O-acetyl (2,3 or 2,4 or 3,4)-di-O-3-methylvaleryl-(4 or 3 or 2)-O-isobutyryl-α-d-glucopyranosyl-β-d-fructofuranoside (one of the 3 isomers). PMID:23542308

  4. Comparison of suppression of mutagenicity of benzo(a)pyrene among methylsulfonyl polychlorinated biphenyl isomers

    SciTech Connect

    Kiyohara, Chikako; Hirohata, Tomio; Omura, Minoru; Masuda, Yoshito

    1992-06-01

    Methylsulfonyl (MSF) derivatives of polychlorinated biphenyls (PCBs) were first identified in fat from seals in the Baltic. Since then, a number of these substances have been demonstrated in animals. They were also isolated from the excreta of mice and rats treated with tri-, tetra-, penta- or hexachlorobiphenyls. Studies on the metabolic fates of several structurally defined chlorobiphenyls in mice showed that, in addition to the hydroxy species that were considered to be major metabolites of PCBs, sulfur-containing compounds were formed by the mercapturic acid pathway from PCB arene oxide. The accumulations of some MSF-PCB isomers have been evidenced not only in the mice experimentally ingested with certain PCBs but also in a human being accidentally exposed to PCBs. Even health people were found to have MSF-PCB isomers at concentrations as high as those of PCBs. It is noteworthy that some MSF-PCB isomers have been demonstrated to be toxic for rats and mice. Moreover, our preliminary study indicated that some MSF-PCB isomers have an inhibitory potency against the aryl hydrocarbon hydroxylase (AHH) activity, a well-known drug-metabolizing enzyme, in cultured human lymphoblastoid cells. These effects of MSF-PCB isomers seemed comparable to those of the well known 7,8-benzoflavone (7,8-BF), which inhibits chemical carcinogenesis. In the present study, we studied the effect of 11 MSF-PCB isomers and 7,8-BF on the mutagenicity of benzo(a)pyrene (BP) using Salmonella strains TA98 and TA100 in the Ames assay. In addition, the relationship between the results of Ames assay and the AHH assay was investigated. 17 refs., 3 tabs.

  5. Prompt and delayed spectroscopy of {sup 142}Tb using recoil-isomer tagging

    SciTech Connect

    Mason, P. J. R.; Cullen, D. M.; Kishada, A. M.; Rigby, S. V.; Varley, B. J.; Scholey, C.; Eeckhaudt, S.; Grahn, T.; Greenlees, P. T.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Leppaenen, A.-P.; Maentyniemi, K.; Nieminen, P.; Nyman, M.; Pakarinen, J.

    2009-02-15

    Recoil-isomer tagging has been used to characterize the states built upon an I{sup {pi}}=8{sup +} isomer in {sup 142}Tb. High-spin states of the neutron-deficient nucleus {sup 142}Tb were populated using an {sup 54}Fe beam, accelerated onto a {sup 92}Mo target of thickness {approx}500 {mu}g/cm{sup 2} at energies of 245, 252, and 265 MeV using the K130 cyclotron at the University of Jyvaeskylae, Finland. Use of the JUROGAM target-position Ge-detector array coupled with the GREAT focal-plane spectrometer at the RITU gas-filled recoil separator has significantly increased the efficiency of the isomer-tagging technique. The rotational band built upon the I{sup {pi}}=8{sup +} isomeric state was established with isomer-tagged {gamma}-{gamma} coincidence data and angular distributions were measured for some of the more intensely populated states. Two previously unobserved bands that bypass the isomer were also established. The new data have been interpreted within the framework of the cranked-shell model. The data show good agreement with the calculated triaxial nuclear shape with {gamma}=-30 deg. for the {sup 142m2}Tb isomeric state. The B(M1)/B(E2) branching ratios, nuclear alignment, signature splitting, and reduced transition probability, B(E1), of the isomeric state have been systematically compared with those of the neighboring nuclei. These comparisons give further evidence for the {pi}h{sub 11/2} x {nu}h{sub 11/2} configuration of the isomer.

  6. New isomers and medium-spin structure of the {sup 95}Y nucleus

    SciTech Connect

    Urban, W.; Sieja, K.; Simpson, G. S.; Rzaca-Urban, T.; Zlomaniec, A.; Lukasiewicz, M.; Smith, A. G.; Durell, J. L.; Smith, J. F.; Varley, B. J.; Nowacki, F.; Ahmad, I.

    2009-04-15

    Excited states in {sup 95}Y, populated following the spontaneous fission of {sup 248}Cm and {sup 252}Cf and following fission of {sup 235}U induced by thermal neutrons, were studied by means of {gamma} spectroscopy using the EUROGAM2 and GAMMASPHERE multidetector Ge arrays and the LOHENGRIN fission-fragment separator, respectively. We have found a new (17/2{sup -}) isomer in {sup 95}Y at 3142.2 keV with a half-life of T{sub 1/2}=14.9(5) ns. Another isomer was identified in {sup 95}Y at 5022.1 keV and it was assigned a spin-parity (27/2{sup -}). For this isomer a half-life of T{sub 1/2}=65(4) ns was determined and four decay branches were found, including an E3 decay. A new E3 decay branch was also found for the known, 1087.5-keV isomer in {sup 95}Y, for which we measured a half-life of 51.2(9) {mu}s. The B(E3) and B(E1) transition rates, of 2.0 and 3.8x10{sup -7} W.u., respectively, observed in {sup 95}Y are significantly lower than in the neighboring {sup 96}Zr core, suggesting that octupole correlations in this region are mainly due to the coupling of proton {delta}j=3 orbitals. Shell-model calculations indicate that the (27/2{sup -}) isomer in {sup 95}Y corresponds to the {pi}g{sub 9/2}{nu}(g{sub 7/2}h{sub 11/2}) maximally aligned configuration and that all three isomers in {sup 95}Y decay, primarily, by M2 transitions between proton g{sub 9/2} and f{sub 5/2} orbitals.

  7. Pulpal Effects of Enamel Ablation With a Microsecond Pulsed λ=9.3-μm CO2 Laser

    PubMed Central

    Staninec, Michal; Darling, Cynthia L.; Goodis, Harold E.; Pierre, Daniel; Cox, Darren P.; Fan, Kenneth; Larson, Michael; Parisi, Renaldo; Hsu, Dennis; Manesh, Saman K.; Ho, Chi; Hosseini, Mehran; Fried, Daniel

    2011-01-01

    Background and Objectives In vitro studies have shown that CO2 lasers operating at the highly absorbed 9.3 and 9.6-μm wavelengths with a pulse duration in the range of 10–20-microsecond are well suited for the efficient ablation of enamel and dentin with minimal peripheral thermal damage. Even though these CO2 lasers are highly promising, they have yet to receive FDA approval. Clinical studies are necessary to determine if excessive heat deposition in the tooth may have any detrimental pulpal effects, particularly at higher ablative fluencies. The purpose of this study was to evaluate the pulpal safety of laser irradiation of tooth occlusal surfaces under the conditions required for small conservative preparations confined to enamel. Study Design/Materials and Methods Test subjects requiring removal of third molar teeth were recruited and teeth scheduled for extraction were irradiated using a pulsed CO2 laser at a wavelength of 9.3 μm operating at 25 or 50 Hz using a incident fluence of 20 J/cm2 for a total of 3,000 laser pulses (36 J) for both rates with water cooling. Two control groups were used, one with no treatment and one with a small cut made with a conventional high-speed hand-piece. No anesthetic was used for any of the procedures and tooth vitality was evaluated prior to treatment by heat, cold and electrical testing. Short term effects were observed on teeth extracted within 72 hours after treatment and long term effects were observed on teeth extracted 90 days after treatment. The pulps of the teeth were fixed with formalin immediately after extraction and subjected to histological examination. Additionally, micro-thermocouple measurements were used to estimate the potential temperature rise in the pulp chamber of extracted teeth employing the same irradiation conditions used in vivo. Results Pulpal thermocouple measurements showed the internal temperature rise in the tooth was within safe limits, 3.3±4°C without water cooling versus 1.7±6

  8. Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli

    PubMed Central

    Siletsky, Sergey A.; Zaspa, Andrey A.; Poole, Robert K.; Borisov, Vitaliy B.

    2014-01-01

    Cytochrome bd is a tri-heme (b558, b595, d) respiratory oxygen reductase that is found in many bacteria including pathogenic species. It couples the electron transfer from quinol to O2 with generation of an electrochemical proton gradient. We examined photolysis and subsequent recombination of CO with isolated cytochrome bd from Escherichia coli in one-electron reduced (MV) and fully reduced (R) states by microsecond time-resolved absorption spectroscopy at 532-nm excitation. Both Soret and visible band regions were examined. CO photodissociation from MV enzyme possibly causes fast (τ<1.5 µs) electron transfer from heme d to heme b595 in a small fraction of the protein, not reported earlier. Then the electron migrates to heme b558 (τ∼16 µs). It returns from the b-hemes to heme d with τ∼180 µs. Unlike cytochrome bd in the R state, in MV enzyme the apparent contribution of absorbance changes associated with CO dissociation from heme d is small, if any. Photodissociation of CO from heme d in MV enzyme is suggested to be accompanied by the binding of an internal ligand (L) at the opposite side of the heme. CO recombines with heme d (τ∼16 µs) yielding a transient hexacoordinate state (CO-Fe2+-L). Then the ligand slowly (τ∼30 ms) dissociates from heme d. Recombination of CO with a reduced heme b in a fraction of the MV sample may also contribute to the 30-ms phase. In R enzyme, CO recombines to heme d (τ∼20 µs), some heme b558 (τ∼0.2–3 ms), and finally migrates from heme d to heme b595 (τ∼24 ms) in ∼5% of the enzyme population. Data are consistent with the recent nanosecond study of Rappaport et al. conducted on the membranes at 640-nm excitation but limited to the Soret band. The additional phases were revealed due to differences in excitation and other experimental conditions. PMID:24755641

  9. Nucleation and stabilization of carbon-rich structures in interstellar media

    SciTech Connect

    Patra, N.; Král, P.; Sadeghpour, H. R. E-mail: pkral@uic.edu

    2014-04-10

    We study the conditions under which carbon clusters of different sizes form and stabilize. We describe the approach to equilibrium by simulating tenuous carbon gas dynamics to long times. First, we use reactive molecular dynamics simulations to describe the nucleation of long chains, large clusters, and complex cage structures in carbon- and hydrogen-rich interstellar gas phases. We study how temperature, particle density, the presence of hydrogen, and carbon inflow affect the nucleation of molecular moieties with different characteristics, in accordance with astrophysical conditions. We extend the simulations to densities that are orders of magnitude lower than current laboratory densities, to temperatures that are relevant to circumstellar environments of planetary nebulae, and microsecond formation times. We correlate cluster size distributions from the simulations with thermodynamic equilibrium at low temperatures and gas densities, where entropy plays a significant role.

  10. Tryptophan-ethylester, the false (unveiled) melatonin isomer in red wine.

    PubMed

    Iriti, Marcello; Vigentini, Ileana

    2015-01-01

    Among the food plants, the presence of melatonin in grapes (Vitis vinifera L.) deserves particular attention because of the production of wine, an alcoholic beverage of economic relevance and with putative healthy effects. Furthermore, melatonin isomers have been detected in wine too. Recently, one of these isomers has been identified as tryptophan-ethylester, a compound with the same molecular weight of melatonin. In this Commentary, we briefly comment the source(s) of tryptophan-ethylester in wine and the putative nutritional role(s). PMID:25922582

  11. Solvent effects on reactivity properties of dicarba-closo-dodecarboranes isomers

    NASA Astrophysics Data System (ADS)

    Junqueira, G. M. A.; Rocha, L. C.; Cotta, V. T.; César, E. T.

    2012-06-01

    In this Letter, a discussion on global reactivity indexes - electronic chemical potential (μ), chemical hardness (η) and electrophilicity (ω) - for dicarba-closo-dodecarboranes isomers, in gas phase and aqueous solution is reported. A sequential Monte Carlo/quantum mechanics methodology (S-MC/QM) was used in simulations. The results obtained showed the solvent must be considered on reactivity properties of the studied compounds. Generally, the solvated isomers become softer (η decreases) and the μ increases comparing to gas phase values, indicating the charge transfer from solvent to the solute.

  12. Conversion-electron experiment to characterize the decay of the /sup 237/Np shape isomer

    SciTech Connect

    Henry, E.A.; Becker, J.A.; Bauer, R.W.; Gardner, D.G.; Decman, D.J.; Meyer, R.A.; Roy, N.; Sale, K.E.

    1987-12-08

    Conversion electrons from the decay of low-lying levels of /sup 237/Np have been measured to detect the population of these levels by gamma-ray decay of the /sup 237/Np shape isomer. Analysis of the 208-keV transition L conversion-electron peak gives an upper limit of about 17 ..mu..b for the population of the 3/2/sup -/ 267-keV level in /sup 237/Np from the shape isomer decay. Model calculations are compared with the measured limit. Improvements are suggested for this experiment. 9 refs., 4 figs.

  13. Laboratory data base for isomer-specific determination of polychlorinated biphenyls

    SciTech Connect

    Schwartz, T.R.; Campbell, R.D.; Stalling, D.L.; Little, R.L.; Petty, J.D.; Hogan, J.W.; Kaiser, E.M.

    1984-07-01

    A computer-assisted technique for quantitative determination of polychlorinated biphenyl isomers is described. PCB isomers were identified by use of a retention index system with n-alkyl trichloroacetates as retention index marker compounds. A laboratory data base system was developed to aid in editing and quantitation of data generated from capillary gas chromatographic data. Data base management was provided by computer programs written in DSM-11 (Digital Standard MUMPS) for the PDP-11 family of computers. 13 references, 4 figures, 2 tables.

  14. Isomers of the DNA bases and their possible role in base pair mismatch

    NASA Astrophysics Data System (ADS)

    Michaelian, Karo; Romero, Aldo

    2004-03-01

    We have found stable isomers of the two DNA purines, adenine and guanine, in global searches using a force field potential and ab initio local relaxations. The stability characteristics were investigated by searching for the lowest energy connecting saddles, and by using Car-Parrinello molecular dynamics. Expected equilibrium concentrations and possible non-equilibrium production mechanisms are discussed. It is suggested that these isomers may play a role in base-pair miss-match leading to point mutation of the gnome, and in a number of other important biological processes based on the purine structures.

  15. High spin states above the 28{sup {minus}} isomer in {sup 152}Ho

    SciTech Connect

    Rizzutto, M.A.; Ribas, R.V.; Cybulska, E.W.; Oliveira, J.R.; Zahn, G.S.; Medina, N.H.; Bazzacco, D.; Medina, N.H.; Brandolini, F.; Burch, R.; Lunardi, S.; Pavan, P.; Alvarez, C.R.; Spolaore, P.

    1997-03-01

    The structure of the high spin states above the 28{sup {minus}} isomer in the odd-odd {sup 152}Ho nucleus was investigated using the GASP {gamma}-ray spectrometer coupled to the recoil mass spectrometer CAMEL. The {sup 152}Ho nucleus was populated through the {sup 120}Sn({sup 37}Cl,5n) fusion reaction at a beam energy of 187 MeV. A complex level scheme above that isomer was established up to an excitation energy of 13 MeV and I{approx} 40{h_bar}. No rotational bands were observed. {copyright} {ital 1997} {ital The American Physical Society}

  16. Pressure dependence of the isomer shifts in Gd2Fe17: An ab initio calculation

    NASA Astrophysics Data System (ADS)

    Komelj, M.; Grotheer, O.; Fähnle, M.

    1999-05-01

    The geometrical and chemical effects of interstitial doping on the average isomer shifts in the systems Gd2Fe17C3 and Gd2Fe17N3 are studied within the framework of the local density approximation using the linear-muffin-tin-orbital method in the atomic-sphere approximation. The sensitivity of the results on the details of the calculation is discussed. It is shown that it is not possible to extract reliable information on the geometrical effect of volume expansion upon interstitial doping of such system on the average isomer shifts by experiments on non-doped samples under compression.

  17. Laminar burning velocities and flame instabilities of butanol isomers-air mixtures

    SciTech Connect

    Gu, Xiaolei; Huang, Zuohua; Wu, Si; Li, Qianqian

    2010-12-15

    Laminar burning velocities and flame instabilities of the butanol-air premixed flames and its isomers are investigated using the spherically expanding flame with central ignition at initial temperature of 428 K and initial pressures of 0.10 MPa, 0.25 MPa, 0.50 MPa and 0.75 MPa. Laminar burning velocities and sensitivity factor of n-butanol-air mixtures are computed using a newly developed kinetic mechanism. Unstretched laminar burning velocity, adiabatic temperature, Lewis number, Markstein length, critical flame radius and Peclet number are obtained over a wide range of equivalence ratios. Effect of molecular structure on laminar burning velocity of the isomers of butanol is analyzed from the aspect of C-H bond dissociation energy. Study indicates that although adiabatic flame temperatures of the isomers of butanol are the same, laminar burning velocities give an obvious difference among the isomers of butanol. This indicates that molecular structure has a large influence on laminar burning velocities of the isomers of butanol. Branching (-CH3) will decrease laminar burning velocity. Hydroxyl functional group (-OH) attaching to the terminal carbon atoms gives higher laminar burning velocity compared to that attaching to the inner carbon atoms. Calculated dissociation bond energies show that terminal C-H bonds have larger bond energies than that of inner C-H bonds. n-Butanol, no branching and with hydroxyl functional group (-OH) attaching to the terminal carbon atom, gives the largest laminar burning velocity. tert-Butanol, with highly branching and hydroxyl functional group (-OH) attaching to the inner carbon atom, gives the lowest laminar burning velocity. Laminar burning velocities of iso-butanol and sec-butanol are between those of n-butanol and tert-butanol. The instant of transition to cellularity is experimentally determined for the isomers of butanol and subsequently interpreted on the basis of hydrodynamic and diffusion-thermal instabilities. Little effect

  18. Isomer ratio measurements as a probe of the dynamics of breakup and incomplete fusion

    SciTech Connect

    Gasques, L. R.; Dasgupta, M.; Hinde, D. J.; Peatey, T.; Diaz-Torres, A.; Newton, J. O.

    2006-12-15

    The incomplete fusion mechanism following breakup of {sup 6,7}Li and {sup 9}Be projectiles incident on targets of {sup 209}Bi and {sup 208}Pb is investigated through isomer ratio measurements for the {sup 212}At and {sup 211}Po products. The phenomenological analysis presented in this paper indicates that incomplete fusion brings relatively more angular momentum into the system than equivalent reactions with a direct beam of the fused fragment. This is attributed to the trajectories of breakup fragments. Calculations with a 3D classical trajectory model support this. Isomer ratio measurements for incomplete fusion reactions can provide a test of new theoretical models of breakup and fusion.

  19. Tryptophan-Ethylester, the False (Unveiled) Melatonin Isomer in Red Wine

    PubMed Central

    Iriti, Marcello; Vigentini, Ileana

    2015-01-01

    Among the food plants, the presence of melatonin in grapes (Vitis vinifera L.) deserves particular attention because of the production of wine, an alcoholic beverage of economic relevance and with putative healthy effects. Furthermore, melatonin isomers have been detected in wine too. Recently, one of these isomers has been identified as tryptophan-ethylester, a compound with the same molecular weight of melatonin. In this Commentary, we briefly comment the source(s) of tryptophan-ethylester in wine and the putative nutritional role(s). PMID:25922582

  20. New decay scheme of the 85Sb 51 136 6- isomer

    NASA Astrophysics Data System (ADS)

    Lozeva, R.; Odahara, A.; Moon, C.-B.; Nishimura, S.; Doornenbal, P.; Naïdja, H.; Nowacki, F.; Söderström, P.-A.; Sumikama, T.; Lorusso, G.; Wu, J.; Xu, Z. Y.; Baba, H.; Browne, F.; Daido, R.; Daugas, J.-M.; Didierjean, F.; Fang, Y.; Isobe, T.; Kojouharov, I.; Kurz, N.; Patel, Z.; Rice, S.; Sakurai, H.; Schaffner, H.; Sinclair, L.; Watanabe, H.; Yagi, A.; Yokoyama, R.; Kubo, T.; Inabe, N.; Suzuki, H.; Fukuda, N.; Kameda, D.; Takeda, H.; Ahn, D. S.; Murai, D.; Bello Garrote, F. L.; Ideguchi, E.; Ishigaki, T.; Jung, H. S.; Komatsubara, T.; Kwon, Y. K.; Morimoto, S.; Niikura, M.; Nishibata, H.; Nishizuka, I.; Shimoda, T.; Tshoo, K.

    2015-08-01

    We report new data on the 136Sb6- yrast isomer with T1 /2=489 (40 ) μ s and π g7/2 1×ν f7/2 3 configuration, populated in the projectile fission of 238U on a 9Be target. The analysis confirms the lifetime, providing a good accuracy measurement. In addition, the decay of the isomer to the ground state is newly suggested. Our result for the isomeric decay scheme is in a good agreement with shell-model calculations.

  1. A microsecond time resolved x-ray absorption near edge structure synchrotron study of phase transitions in Fe undergoing ramp heating at high pressure

    SciTech Connect

    Marini, C.; Mathon, O.; Pascarelli, S.; Occelli, F.; Torchio, R.; Recoules, V.; Loubeyre, P.

    2014-03-07

    We report a microsecond time-resolved x-ray absorption near edge structure study using synchrotron radiation to dynamically detect structural phase transitions in Fe undergoing rapid heating along a quasi-isochoric path. Within a few ms, we observed two structural phase transitions, which transform the ambient bcc phase of Fe into the fcc phase, and then into the liquid phase. This example illustrates the opportunities offered by energy dispersive x-ray absorption spectroscopy in the study of matter under extreme dynamic conditions. Advanced simulations are compared to these data.

  2. The Oxygen-Rich Beryllium Oxides BeO4 and BeO6.

    PubMed

    Zhang, Qingnan; Jerabek, Paul; Chen, Mohua; Zhou, Mingfei; Frenking, Gernot

    2016-08-26

    Two novel isomers of BeO4 with the structures OBeOOO and OBe(O3 ) in the electronic triplet state have been prepared as well as the known disuperoxide complex Be(O2 )2 in solid noble-gas matrices. We also report the synthesis of the oxygen-rich bis(ozonide) complex Be(O3 )2 in the triplet state which has a D2d equilibrium geometry. The molecular structures were identified by infrared absorption spectroscopy with isotopic substitutions as well as quantum chemical calculations. PMID:27494950

  3. Metabolism of a- and y-hexabromocyclododecane and enantioselective fractions of a-, ß-, y-isomers in mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Commercial HBCD is a mixture of three major isomers, a, ß, and ', with the '-diastereoisomer predominating (>70%). Thus, the prevalence of the a-isomer as an environmental contaminant must be explained by either different pharmacokinetics, or by isomerization of the '-diastereoisomer. a- and '-[14...

  4. Anomalous Reactivity and Selectivity in the Intermolecular Diels-Alder Reactions of Multisubstituted Acyclic Dienes with Geometrical Isomers of Enals.

    PubMed

    Zhou, Jia-Hui; Cai, Sai-Hu; Xu, Yun-He; Loh, Teck-Peng

    2016-05-20

    A Lewis-acid catalyzed intermolecular Diels-Alder reaction between multisubstituted acyclic dienes and the E and Z isomers of α,β-enals was studied. It was found that the diene reacted selectively with the Z-isomer of the α,β-enal. PMID:27132468

  5. Analysis of 2,4,6-nonatrienal geometrical isomers from male flea beetles, Epitrix hirtipennis and E. fuscula

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Geometrical isomers of 2,4,6-nonatrienal have been reported from a variety of food- and insect-related sources. It was discovered recently that the eggplant flea beetle, Epitrix fuscula, uses the (2E,4E,6Z) and (2E,4E,6E) isomers as components of its male-produced aggregation pheromone. Here, we l...

  6. An efficient approach for theoretical study on the low-energy isomers of large fullerenes C90-C140

    NASA Astrophysics Data System (ADS)

    Cai, Wensheng; Xu, Lei; Shao, Nan; Shao, Xueguang; Guo, Qingxiang

    2005-05-01

    An approach that consists of a molecular mechanics method based on the second generation reactive empirical bond order (REBO) potential and the more accurate semiempirical method PM3 (Parametric Method No. 3) was proposed to predict the energetically favored isomers of the fullerenes from C90 to C140 at the semiempirical level. All the 578 701 isolated-pentagon-rule isomers of fullerenes from C90 to C140 were enumerated from topological structures and systematically searched using an energy minimization method to select the best 100 low-energy isomers based on the REBO potential for each fullerene. Then these candidate isomers were further optimized by PM3 and ranked again to determine the top low-energy isomers. This approach was applied to calculate the energetically favored isomers of C90-C140. The results of C90-C120 are in good agreement with the published results by quantum-chemical methods. Furthermore, the top five low-energy isomers of C90-C120, as well as C122-C140 which have scarcely been systematically studied before, are also predicted with the approach. The analysis of the structures showed that the hexagon-neighbor rule is an important factor to the stability of C90-C140. The time cost for the systematical search based on the REBO potential was also discussed. It indicates that the approach proposed is efficient for predicting the energetically favored isomers of large fullerenes at the semiempirical level.

  7. 40 CFR 180.449 - Avermectin B1 and its delta-8,9-isomer; tolerances for residues.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... § 180.449, see the List of CFR Sections Affected, which appears in the Finding Aids section of the... 40 Protection of Environment 25 2012-07-01 2012-07-01 false Avermectin B1 and its delta-8,9-isomer... Tolerances § 180.449 Avermectin B1 and its delta-8,9-isomer; tolerances for residues. (a) General....

  8. 40 CFR 180.449 - Avermectin B1 and its delta-8,9-isomer; tolerances for residues.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... § 180.449, see the List of CFR Sections Affected, which appears in the Finding Aids section of the... 40 Protection of Environment 25 2013-07-01 2013-07-01 false Avermectin B1 and its delta-8,9-isomer... Tolerances § 180.449 Avermectin B1 and its delta-8,9-isomer; tolerances for residues. (a) General....

  9. 40 CFR 180.449 - Avermectin B1 and its delta-8,9-isomer; tolerances for residues.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Federal Register citations affecting § 180.449, see the List of CFR Sections Affected, which appears in... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Avermectin B1 and its delta-8,9-isomer... Tolerances § 180.449 Avermectin B1 and its delta-8,9-isomer; tolerances for residues. (a) General....

  10. 40 CFR 180.449 - Avermectin B1 and its delta-8,9-isomer; tolerances for residues.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... § 180.449, see the List of CFR Sections Affected, which appears in the Finding Aids section of the... 40 Protection of Environment 24 2014-07-01 2014-07-01 false Avermectin B1 and its delta-8,9-isomer... Tolerances § 180.449 Avermectin B1 and its delta-8,9-isomer; tolerances for residues. (a) General....

  11. 40 CFR 180.449 - Avermectin B1 and its delta-8,9-isomer; tolerances for residues.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Federal Register citations affecting § 180.449, see the List of CFR Sections Affected, which appears in... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Avermectin B1 and its delta-8,9-isomer... Tolerances § 180.449 Avermectin B1 and its delta-8,9-isomer; tolerances for residues. (a) General....

  12. Enumeration of chiral and positional isomers of substituted fullerene cages (C[sub 20]-C[sub 70])

    SciTech Connect

    Balasubramanian, K. )

    1993-07-08

    Enumeration of chiral isomers of substituted fullerene cages (C[sub 20]-C[sub 70]) is considered using the generalized character cycle index (GCCI) of the alternating representation of the point group of the parent cage. It is shown that there are no chiral isomers for the monsubstituted C[sub 20], C[sub 24], C[sub 28], C[sub 30], C[sub 36], and C[sub 60] fullerene cages but there are chiral isomers for other monosubstituted cages. All cages considered here possess chiral isomers for disubstituted cages. It is shown that the number of positional isomers can be obtained using the GCCI of the totally symmetric representation. We also enumerate the [sup 13]C NMR signals of all fullerene cages C[sub 20]-C[sub 70]. 30 refs., 4 figs., 6 tabs.

  13. FT-Raman spectroscopy of structural isomers of Pt(II) complex PtCl2(PEt3)2

    NASA Astrophysics Data System (ADS)

    Bhatt, Himal; Deo, M. N.; Vishwakarma, S. R.; Bajaj, Naini; Sharma, Surinder M.

    2015-06-01

    We report here the detailed spectroscopic aspects of the structural isomers of Pt(II) complex PtCl2(P(C2H5)3)2 using FT-Raman spectroscopy. A comparison of the structural contraction instigated by lowering the temperature up to liquid nitrogen temperature in the cis and trans isomers has been presented. The lattice region lying in the far infrared region upto 50cm-1 has been analyzed in detail to probe the structural modifications. It was found that the ambient temperature lower symmetry structure of the cis isomer is preserved at low temperatures. The trans isomer, stabilizing in a high symmetry structure at room temperature, transforms to a low symmetry structure on lowering the temperature, which can be attributed to a loss of inversion symmetry of the trans isomer.

  14. CuCl2 for the isolation of a broad array of endohedral fullerenes containing metallic, metallic carbide, metallic nitride, and metallic oxide clusters, and separation of their structural isomers.

    PubMed

    Stevenson, Steven; Rottinger, Khristina A

    2013-08-19

    A typical arc-synthesis generates many types of fullerenes and endohedrals. Resulting soot extracts contain a complex mixture of >50 types of fullerenes, metallofullerenes, and their structural isomers. Prior to application development, novel separation methods are required to fractionate this rich array of metallic, metallic carbide, metallic nitride, and metallic oxide endohedrals, all of which can be present in a single, soot extract. Herein, we report the discovery of CuCl2 as a Lewis acid that will selectively precipitate only the more reactive members of each of these endohedral families. The more reactive Sc4O2@Ih-C80, Sc3C2@Ih-C80, and Sc3N@D3h-C78 endohedrals are quickly removed from extracts to greatly decrease the number of endohedrals present in a sample. Experiments indicate that enrichment factors of several orders of magnitude can be achieved within minutes of reaction time. CuCl2 also has sufficient selectivity to resolve and separate structural isomers, as demonstrated with Er2@C82 (isomer I, Cs(6)-C82 versus isomer III). The selective complexation of CuCl2 with fullerenes can be correlated to their first oxidation potential. We estimate a significantly lower threshold of precipitation for CuCl2 (<0.19 V) compared to stronger Lewis acids. Fullerenes and metallofullerenes having first oxidation potentials above 0.19 V tend to remain unreacted in solution. In contrast, species with first oxidation potentials below 0.19 V (vs Fc/Fc(+)) precipitate via complexation, and are easily decomplexed. CuCl2 is compared to Lewis acids having higher precipitation thresholds (e.g., FeCl3) in our goal to predict a priori which endohedrals would remain in solution versus which endohedral species would complex and precipitate. The ability to predict endohedral precipitation a priori is beneficial to the design of purification strategies for metallofullerenes. PMID:23952569

  15. 40 CFR 180.1073 - Isomate-M; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Isomate-M; exemption from the requirement of a tolerance. 180.1073 Section 180.1073 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1073...

  16. Clusterization in the shape isomers of the {sup 56}Ni nucleus

    SciTech Connect

    Darai, J.; Cseh, J.; Antonenko, N. V.; Jolos, R. V.; Royer, G.; Algora, A.; Hess, P. O.; Scheid, W.

    2011-08-15

    The interrelation of the quadrupole deformation and clusterization is investigated in the example of the {sup 56}Ni nucleus. The shape isomers, including superdeformed and hyperdeformed states, are obtained as stability regions of the quasidynamical U(3) symmetry based on a Nilsson calculation. Their possible binary clusterizations are investigated by considering both the consequences of the Pauli exclusion principle and the energetic preference.

  17. Prospects for measuring the 229Th isomer energy using a metallic magnetic microcalorimeter☆

    PubMed Central

    Kazakov, G.A.; Schauer, V.; Schwestka, J.; Stellmer, S.P.; Sterba, J.H.; Fleischmann, A.; Gastaldo, L.; Pabinger, A.; Enss, C.; Schumm, T.

    2014-01-01

    The Thorium-229 isotope features a nuclear isomer state with an extremely low energy. The currently most accepted energy value, 7.8±0.5 eV, was obtained from an indirect measurement using a NASA x-ray microcalorimeter with an instrumental resolution 26 eV. We study, how state-of-the-art magnetic metallic microcalorimeters with an energy resolution down to a few eV can be used to measure the isomer energy. In particular, resolving the 29.18 keV doublet in the γ-spectrum following the α-decay of Uranium-233, corresponding to the decay into the ground and isomer state, allows to measure the isomer transition energy without additional theoretical input parameters, and increase the energy accuracy. We study the possibility of resolving the 29.18 keV line as a doublet and the dependence of the attainable precision of the energy measurement on the signal and background count rates and the instrumental resolution. PMID:25844000

  18. Structural analysis of novel kestose isomers isolated from sugar beet molasses.

    PubMed

    Shiomi, Norio; Abe, Tatsuya; Kikuchi, Hiroto; Aritsuka, Tsutomu; Takata, Yusuke; Fukushi, Eri; Fukushi, Yukiharu; Kawabata, Jun; Ueno, Keiji; Onodera, Shuichi

    2016-04-01

    Eight kestose isomers were isolated from sugar beet molasses by carbon-Celite column chromatography and HPLC. GC-FID and GC-MS analyses of methyl derivatives, MALD-TOF-MS measurements and NMR spectra were used to confirm the structural characteristics of the isomers. The (1)H and (13)C NMR signals of each isomer saccharide were assigned using COSY, E-HSQC, HSQC-TOCSY, HMBC and H2BC techniques. These kestose isomers were identified as α-D-fructofuranosyl-(2- > 2)-α-D-glucopyranosyl-(1 < ->2)-β-D-fructofuranoside, α-D-fructofuranosyl-(2- > 3)-β-D-fructofuranosyl-(2 < ->1)-α-D-glucopyranoside, α-D-fructofuranosyl-(2- > 4)-β-D-fructofuranosyl-(2 < ->1)-α-D-glucopyranoside, β-D-fructofuranosyl-(2- > 4)-β-D-fructofuranosyl-(2 < ->1)-α-D-glucopyranoside, β-D-fructofuranosyl-(2- > 3)-α-D-glucopyranosyl-(1 < ->2)-β-D-fructofuranoside, α-D-fructofuranosyl-(2- > 1)-β-D-fructofuranosyl-(2 < ->1)-α-D-glucopyranoside, α-D-fructofuranosyl-(2- > 6)-α-D-glucopyranosyl-(1 < ->2)-β-D-fructofuranoside, and α-D-fructofuranosyl-(2- > 6)-β-D-fructofuranosyl-(2 < ->1)-α-D-glucopyranoside. The former five compounds are novel saccharides. PMID:26918514

  19. Toward the laboratory identification of [O,N,S,S] isomers: Implications for biological NO chemistry

    NASA Astrophysics Data System (ADS)

    Ayari, Tarek; Jaidane, Nejm-Eddine; Al Mogren, Muneerah Mogren; Francisco, Joseph S.; Hochlaf, Majdi

    2016-06-01

    Benchmark ab initio calculations are performed to investigate the stable isomers of [O,N,S,S]. These computations are carried out using coupled cluster (RCCSD(T)) and explicitly correlated coupled cluster methods (RCCSD(T)-F12). In addition to the already known cis isomer of SSNO, nine other stable forms are predicted. The most stable isomer is cis-OSNS. Nine structures are chain bent-bent with relatively large dipole moments which make them detectable, as cis-SSNO, by infrared, far-infrared, and microwave spectroscopies. We found also a C2v isomer (NS2O). Since these species are strongly suggested to play an important role as intermediates during the bioactive reaction products of the NO/H2S interaction, the rotational and vibrational spectroscopic parameters are presented to help aid the in vivo identification and assignment of these spectra. Results from this work show that [O,N,S,S] may play key roles during nitric oxide transport and deliver in biological media, as well as, provide an explanation for the weak characteristic of disulfide bridges within proteins.

  20. Infrared spectroscopy of the acetyl cation and its protonated ketene isomer

    NASA Astrophysics Data System (ADS)

    Mosley, J. D.; Young, J. W.; Duncan, M. A.

    2014-07-01

    [C2,H3,O]+ ions are generated with a pulsed discharge in a supersonic expansion containing methyl acetate or acetone. These ions are mass selected and their infrared spectra are recorded via laser photodissociation and the method of argon tagging. Computational chemistry is employed to investigate structural isomers and their spectra. The acetyl cation (CH3CO+) is the global minimum and protonated ketene (CH2COH+) is the next lowest energy isomer (+176.2 kJ/mol). When methyl acetate is employed as the precursor, the infrared spectrum reveals that only the acetyl cation is formed. Partially resolved rotational structure reveals rotation about the C3 axis. When acetone is used as the precursor, acetyl is still the most abundant cation, but there is also a minor component of protonated ketene. Computations reveal a significant barrier to interconversion between the two isomers (+221 kJ/mol), indicating that protonated ketene must be obtained via kinetic trapping. Both isomers may be present in interstellar environments, and their implications for astrochemistry are discussed.

  1. Long-read pyrosequencing using pure 2'-deoxyadenosine-5'-O'-(1-thiotriphosphate) Sp-isomer.

    PubMed

    Gharizadeh, Baback; Nordström, Tommy; Ahmadian, Afshin; Ronaghi, Mostafa; Nyrén, Pål

    2002-02-01

    Pyrosequencing, a nonelectrophoretic DNA sequencing method that uses a luciferase-based enzymatic system to monitor DNA synthesis in real time, has so far been limited to sequencing of short stretches of DNA. To increase the signal-to-noise ratio in pyrosequencing the natural dATP was replaced by dATPalphaS (M. Ronaghi et al., 1996, Anal. Biochem. 242, 84-89). The applied dATPalphaS was a mixture of two isomers (Sp and Rp). We show here that by the introduction of pure 2'-deoxyadenosine-5'-O'-(1-thiotriphosphate) Sp-isomer in pyrosequencing substantial longer reads could be obtained. The pure Sp-isomer allowed lower nucleotide concentration to be used and improved the possibility to read through poly(T) regions. In general, a doubling of the read length could be obtained by the use of pure Sp-isomer. Pyrosequencing data for 50 to 100 bases could be generated on different types of template. The longer read will enable numerous new applications, such as identification and typing of medically important microorganisms as well as resequencing of DNA fragments for mutation screening and clone checking. PMID:11811970

  2. Characterization of canthaxanthin isomers isolated from a new soil Dietzia sp. and their antioxidant activities.

    PubMed

    Venugopalan, Vijaylatha; Tripathi, Subhash K; Nahar, Pradip; Saradhi, P Pardha; Das, Rakha H; Gautam, Hemant K

    2013-02-01

    Canthaxanthin (cx) is a potent antioxidant that is chemically synthesized at the industrial scale and has imperative applications in the cosmetic and feed industries. An orange pigmented mesophilic bacterium, designated as K44, was isolated from soil samples of Kargil, India. Biochemical tests, 16S rRNA gene sequencing, and FAME analysis of the bacterium indicated it to belong in the genus Dietzia and is distinct from human isolates. The strain showed 98% 16S rRNA gene sequence homology with Dietzia maris DSM 43102. High-performance liquid chromatography profile of the pigments isolated from K44 showed two major peaks absorbing at 465.3 and 475 nm. The liquid chromatography-mass spectrometry (LC-MS) analysis of both these peaks revealed their m/z to be 564. The molecular weights, LC-MS/MS fragmentation patterns, and lambdamax of these fractions corresponded to all-trans- (475 nm) and 9-cis-(465.3 nm) cx isomers. The antioxidant activities of cis- and trans-cx isomers isolated from this bacterium were found to differ, where the cis-isomer showed higher free radical, superoxide radical, and reactive oxygen species scavenging activities than the alltrans- isomer, suggesting that 9-cis-cx is more effective as an antioxidant than the all-trans-cx. PMID:23412067

  3. Kinetics of the alkaline dehydrochlorination of the alpha-isomer of hexachlorocyclohexane upon micellar catalysis

    SciTech Connect

    Sirovskii, F.S.; Berlin, E.R.; Molodchikov, S.I.; Skibinskaya, M.B.; Stepanova, N.N.; Treger, Yu.A.

    1986-11-01

    A study was carried out on the kinetics of the alkaline dehydrochlorination of the ..cap alpha..-isomer of hexachlorocyclohexane in the pH range from 7 to 10 upon catalysis by benzyldimethylalkylammonium chloride (BDMAC) micelles. The activation parameters and kinetic equation were found.

  4. Photocontrolled nitric oxide release from two nitrosylruthenium isomer complexes and their potential biomedical applications

    NASA Astrophysics Data System (ADS)

    Liu, Jiao; Duan, Qingqing; Wang, Jianru; Song, Zhen; Qiao, Xiaoyan; Wang, Hongfei

    2015-01-01

    Nitric oxide (NO) has key regulatory roles in various biological and medical processes. The control of its local concentration, which is crucial for obtaining the desired effect, can be achieved with exogenous NO donors. Release of NO from metal-nitrosyl complexes upon exposure to light is a strategy that could allow for the site-specific delivery of the reactive species NO to physiological targets. The photodissociation of NO from two nitrosylruthenium(II) isomer complexes {cis- and trans-[Ru(OAc)2NO]} was demonstrated by matrix-assisted laser desorption ionization time-of-flight mass spectrometry spectra, and electron paramagnetic resonance spectra further prove the photoinduced NO release by spin trapping of NO free radicals upon photoirradiation. Real-time NO release was quantitatively measured by electrochemistry with an NO-specific electrode. The quantitative control of NO release from [Ru(OAc)2NO] in aqueous solutions was done by photoirradiation at different wavelengths. Both isomers show photoinduced damage on plasmid DNA, but the trans isomer has higher cytotoxicity and photocytotoxicity activity against the HeLa tumor cell line than that of the cis isomer. Nitrosylruthenium(II) complex, with 8-quinolinol derivatives as ligands, has a great potential as a photoactivated NO donor reagent for biomedical applications.

  5. Analysis and Characterization of Trans Isomers by Silver-Ion HPLC

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Produced by the partial hydrogenation of vegetable oils and present in animal fats and selected seed oils, trans fatty acids [both configurational (cis vs trans) and positional (double bond location may vary from the delta-4 to the delta-16 position on the fatty acid carbon chain) isomers continue t...

  6. Positional isomers of cyanostilbene: two-component molecular assembly and multiple-stimuli responsive luminescence

    NASA Astrophysics Data System (ADS)

    Fan, Guoling; Yan, Dongpeng

    2014-05-01

    An understanding of the aggregates and properties of positional isomers can not only uncover how a slight difference in molecular structure alter crystal packing and bulk solid-state properties, but also plays an important role in developing new types of molecule-based functional materials. Herein, we report a study of the molecular packing and static/dynamic luminescence properties of three cyanostilbene (CS)-based isomers (CS1, CS2, CS3) within their single- and two-component molecular solids. Changing the positions of the cyano substitutents in the CS isomers has a marked influence on their packing modes and luminescent properties. Moreover, two-component CS-based materials have been constructed, which exhibit tunable conformations and packing fashions, as well as fluorescence properties, which differ from the pristine CS solids. The CS-based two-component molecular materials show solvent-responsive luminescence due to the dynamic disassembly of the samples. Moreover, it was found that the system based on CS2 and octafluoronaphthalene shows reversible photochromic fluorescence upon alternating light illumination and grinding. Such co-assembly procedures provide a facile way to fabricate patterned luminescent film materials. Therefore, this work not only affords new insight into the relationship between isomers and luminescence from molecular and supramolecular perspectives, but provides an effective strategy to develop multiple-stimuli-responsive luminescent materials.

  7. 40 CFR 180.1073 - Isomate-M; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Isomate-M; exemption from the requirement of a tolerance. 180.1073 Section 180.1073 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1073...

  8. The sim operon facilitates the transport and metabolism of sucrose isomers in Lactobacillus casei ATCC 334.

    PubMed

    Thompson, John; Jakubovics, Nicholas; Abraham, Bindu; Hess, Sonja; Pikis, Andreas

    2008-05-01

    Inspection of the genome sequence of Lactobacillus casei ATCC 334 revealed two operons that might dissimilate the five isomers of sucrose. To test this hypothesis, cells of L. casei ATCC 334 were grown in a defined medium supplemented with various sugars, including each of the five isomeric disaccharides. Extracts prepared from cells grown on the sucrose isomers contained high levels of two polypeptides with M(r)s of approximately 50,000 and approximately 17,500. Neither protein was present in cells grown on glucose, maltose or sucrose. Proteomic, enzymatic, and Western blot analyses identified the approximately 50-kDa protein as an NAD(+)- and metal ion-dependent phospho-alpha-glucosidase. The oligomeric enzyme was purified, and a catalytic mechanism is proposed. The smaller polypeptide represented an EIIA component of the phosphoenolpyruvate-dependent sugar phosphotransferase system. Phospho-alpha-glucosidase and EIIA are encoded by genes at the LSEI_0369 (simA) and LSEI_0374 (simF) loci, respectively, in a block of seven genes comprising the sucrose isomer metabolism (sim) operon. Northern blot analyses provided evidence that three mRNA transcripts were up-regulated during logarithmic growth of L. casei ATCC 334 on sucrose isomers. Internal simA and simF gene probes hybridized to approximately 1.5- and approximately 1.3-kb transcripts, respectively. A 6.8-kb mRNA transcript was detected by both probes, which was indicative of cotranscription of the entire sim operon. PMID:18310337

  9. Observation of a new high-spin isomer in {sup 94}Pd

    SciTech Connect

    Brock, T. S.; Nara Singh, B. S.; Wadsworth, R.; Boutachkov, P.; Gorska, M.; Grawe, H.; Pietri, S.; Domingo-Pardo, C.; Caceres, L.; Engert, T.; Farinon, F.; Gerl, J.; Goel, N.; Kojuharov, I.; Kurz, N.; Nociforo, C.; Prochazka, A.; Schaffner, H.; Weick, H.; Braun, N.

    2010-12-15

    A second {gamma}-decaying high-spin isomeric state, with a half-life of 197(22)ns, has been identified in the N=Z+2 nuclide {sup 94}Pd as part of a stopped-beam Rare Isotope Spectroscopic INvestigation at GSI (RISING) experiment. Weisskopf estimates were used to establish a tentative spin/parity of 19{sup -}, corresponding to the maximum possible spin of a negative parity state in the restricted (p{sub 1/2}, g{sub 9/2}) model space of empirical shell model calculations. The reproduction of the E3 decay properties of the isomer required an extension of the model space to include the f{sub 5/2} and p{sub 3/2} orbitals using the CD-Bonn potential. This is the first time that such an extension has been required for a high-spin isomer in the vicinity of {sup 100}Sn and reveals the importance of such orbits for understanding the decay properties of high-spin isomers in this region. However, despite the need for the extended model space for the E3 decay, the dominant configuration for the 19{sup -} state remains ({pi}p{sub 1/2}{sup -1}g{sub 9/2}{sup -3}){sub 11} x ({nu}g{sub 9/2}{sup -2}){sub 8}. The half-life of the known, 14{sup +}, isomer was remeasured and yielded a value of 499(13) ns.

  10. Toward the laboratory identification of [O,N,S,S] isomers: Implications for biological NO chemistry.

    PubMed

    Ayari, Tarek; Jaidane, Nejm-Eddine; Al Mogren, Muneerah Mogren; Francisco, Joseph S; Hochlaf, Majdi

    2016-06-21

    Benchmark ab initio calculations are performed to investigate the stable isomers of [O,N,S,S]. These computations are carried out using coupled cluster (RCCSD(T)) and explicitly correlated coupled cluster methods (RCCSD(T)-F12). In addition to the already known cis isomer of SSNO, nine other stable forms are predicted. The most stable isomer is cis-OSNS. Nine structures are chain bent-bent with relatively large dipole moments which make them detectable, as cis-SSNO, by infrared, far-infrared, and microwave spectroscopies. We found also a C2v isomer (NS2O). Since these species are strongly suggested to play an important role as intermediates during the bioactive reaction products of the NO/H2S interaction, the rotational and vibrational spectroscopic parameters are presented to help aid the in vivo identification and assignment of these spectra. Results from this work show that [O,N,S,S] may play key roles during nitric oxide transport and deliver in biological media, as well as, provide an explanation for the weak characteristic of disulfide bridges within proteins. PMID:27334171

  11. USE OF THE 'ORTHO EFFECT' FOR CHLORINATED BIPHENYL AND BROMINATED BIPHENYL ISOMER IDENTIFICATION

    EPA Science Inventory

    The ortho effect observed for chlorinated biphenyls (PCBs) and brominated biphenyls (PBBs) having 2,2; 2,2', 6 or 2,2', 6,6' halogens, can be combined with GC retention index for isomer specific identifications by gas chromatography/mass spectrometry (GC/MS). This technique relia...

  12. Production ratio of meta-stable isomer in {sup 180}Ta by neutrino-induced reactions

    SciTech Connect

    Hayakawa, Takehito; Kajino, Toshitaka; Chiba, Satoshi; Mathews, Grant

    2010-05-12

    The nucleosynthesis of {sup 180}Ta has remained an unsolved problem and as its origin many nucleosynthesis mechanisms have been proposed. This isotope has the unique feature that the naturally occurring abundance of {sup 180}Ta is actually a meta-stable isomer (half-life of >=10{sup 15} yr), while the ground state is a 1{sup +} unstable state which beta-decays with a half-life of only 8.15 hr. We have made a new time-dependent calculation of {sup 180}Ta meta-stable isomer residual ratio after supernova neutrino-induced reactions. This isomer residual ratio is crucial for understanding the production and survival of this naturally occurring rare isotope. We have constructed a new model under temperature evolution after type II supernova explosion. We include the explicit linking between the isomer and all known excited states and found that the residual ratio is insensitive to astrophysical parameters such as neutrino energy spectrum, explosion energy, decay time constant. We find that the explicit time evolution of the synthesis of {sup 180}Ta avoids the overproduction relative to {sup 138}La for a neutrino process neutrino temperature of 4 MeV.

  13. Isolation and crystallographic identification of four isomers of Sm@C90.

    PubMed

    Yang, Hua; Jin, Hongxiao; Zhen, Hongyu; Wang, Zhimin; Liu, Ziyang; Beavers, Christine M; Mercado, Brandon Q; Olmstead, Marilyn M; Balch, Alan L

    2011-04-27

    Four isomers with the composition SmC(90) were obtained from carbon soot produced by electric arc vaporization of carbon rods doped with Sm(2)O(3). These were labeled Sm@C(90)(I), Sm@C(90)(II), Sm@C(90)(III), and Sm@C(90)(IV) in order of their elution times during chromatography on a Buckyprep column with toluene as the eluent. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni(octaethylporphyrin) reveals the identities of the individual isomers as follows: I, Sm@C(2)(40)-C(90); II, Sm@C(2)(42)-C(90); III, Sm@C(2v)(46)-C(90) and IV, Sm@C(2)(45)-C(90). This is the most extensive series of isomers of any endohedral fullerene to have their individual structures determined by single-crystal X-ray diffraction. The cage structures of these four isomers can be related pairwise to one another in a formal sense through sequential Stone-Wales transformations. PMID:21452811

  14. Photocontrolled nitric oxide release from two nitrosylruthenium isomer complexes and their potential biomedical applications.

    PubMed

    Liu, Jiao; Duan, Qingqing; Wang, Jianru; Song, Zhen; Qiao, Xiaoyan; Wang, Hongfei

    2015-01-01

    Nitric oxide (NO) has key regulatory roles in various biological and medical processes. The control of its local concentration, which is crucial for obtaining the desired effect, can be achieved with exogenous NO donors. Release of NO from metal-nitrosyl complexes upon exposure to light is a strategy that could allow for the site-specific delivery of the reactive species NO to physiological targets. The photodissociation of NO from two nitrosylruthenium(II) isomer complexes {cis- and trans-[Ru(OAc)(2mqn)(2)NO]} was demonstrated by matrix-assisted laser desorption ionization time-of-flight mass spectrometry spectra, and electron paramagnetic resonance spectra further prove the photoinduced NO release by spin trapping of NO free radicals upon photoirradiation. Real-time NO release was quantitatively measured by electrochemistry with an NO-specific electrode. The quantitative control of NO release from [Ru(OAc)(2mqn)(2)NO] in aqueous solutions was done by photoirradiation at different wavelengths. Both isomers show photoinduced damage on plasmid DNA, but the trans isomer has higher cytotoxicity and photocytotoxicity activity against the HeLa tumor cell line than that of the cis isomer. Nitrosylruthenium(II) complex, with 8-quinolinol derivatives as ligands, has a great potential as a photoactivated NO donor reagent for biomedical applications. PMID:25621873

  15. Photocrystallography reveals new metastable nitrosyl linkage isomers in the solid state.

    PubMed

    Raithby, Paul R

    2015-01-01

    Using the combined techniques of photocrystallography and infrared spectroscopy is a very powerful method for generating and establishing the structures of metastable linkage isomers in the solid state as exemplified by the work of Casaretto et al. [IUCrJ (2015), 2, 35-44] on [RuCl(NO)2(PPh3)2]BF4. PMID:25610621

  16. Formation of isomers of anionic hemiesters of sugars and carbonic acid in aqueous medium.

    PubMed

    Dos Santos, Vagner B; Vidal, Denis T R; Francisco, Kelliton J M; Ducati, Lucas C; do Lago, Claudimir L

    2016-06-16

    Hemiesters of carbonic acid can be freely formed in aqueous media containing HCO3(-)/CO2 and mono- or poly-hydroxy compounds. Herein, (13)C NMR spectroscopy was used to identify isomers formed in aqueous solutions of glycerol (a prototype compound) and seven carbohydrates, as well as to estimate the equilibrium constant of formation (Keq). Although both isomers are formed, glycerol 1-carbonate corresponds to 90% of the product. While fructose and ribose form an indistinct mixture of isomers, the anomers of d-glucopyranose 6-carbonate correspond to 74% of the eight isomers of glucose carbonate that were detected. The values of Keq for the disaccharides sucrose (4.3) and maltose (4.2) are about twice the values for the monosaccharides glucose (2.0) and fructose (2.3). Ribose (Keq = 0.89)-the only sugar without a significant concentration of a species containing a -CH2OH group in an aqueous solution-resulted in the smallest Keq. On the basis of the Keq value and the concentrations of HCO3(-) and glucose in blood, one can anticipate a concentration of 2-4 µmol L(-1) for glucose 6-carbonate, which corresponds to ca. of 10% of its phosphate counterpart (glucose 6-phosphate). PMID:27111726

  17. C18-unsaturated branched-chain fatty acid isomers: characterization and physical properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Iso-oleic acid is a mixture of C18-unsaturated branched-chain fatty acid isomers with a methyl group on various positions of the alkyl chain, which is the product of the skeletal isomerization reaction of oleic acid and is the intermediate used to make isostearic acid (C18-saturated branched-chain f...

  18. Improved synthesis and characterization of saturated branched-chain fatty acid isomers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The development of viable technologies for producing green products from renewable fats and oils is highly desirable since such materials can serve as replacements for non-renewable and poorly biodegradable petroleum-based products. Mixtures of saturated branched-chain fatty acid isomers (sbc-FAs),...

  19. Differential effects of conjugated linoleic acid isomers on the biophysical and biochemical properties of model membranes

    PubMed Central

    Subbaiah, Papasani V.; Sircar, Debajit; Aizezi, Buzulagu; Mintzer, Evan

    2010-01-01

    Conjugated linoleic acids (CLA) are known to exert several isomer-specific biological effects, but their mechanisms of action are unclear. In order to determine whether the physicochemical effects of CLA on membranes play a role in their isomer-specific effects, we synthesized phosphatidylcholines (PCs) with 16:0 at sn-1 position and one of four CLA isomers (trans10 cis12 (A), trans9 trans11 (B), cis9 trans11 (C), and cis9 cis11 (D)) at sn-2, and determined their biophysical properties in monolayers and bilayers. The surface areas of the PCs with the two natural CLA (A and C) were similar at all pressures, but they differed significantly in presence of cholesterol, with PC-A condensing more than PC-C. Liposomes of PC-A similarly showed increased binding of cholesterol compared to PC-C liposomes. PC-A liposomes were less permeable to carboxyfluorescein compared to PC-C liposomes. The PC with two trans double bonds (B) showed the highest affinity to cholesterol and lowest permeability. The two natural CLA PCs (A and C) stimulated lecithin-cholesterol acyltransferase activity by 2-fold, whereas the unnatural CLA PCs (B and D) were inhibitory. These results suggest that the differences in the biophysical properties of CLA isomers A and C may partly contribute to the known differences in their biological effects. PMID:20004173

  20. 57Fe quadrupole splitting and isomer shift in various oxyhemoglobins: study using Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Berkovsky, A. L.; Kumar, A.; Kundu, S.; Vinogradov, A. V.; Konstantinova, T. S.; Semionkin, V. A.

    2010-04-01

    A comparative study of normal human, rabbit and pig oxyhemoglobins and oxyhemoglobin from patients with chronic myeloleukemia and multiple myeloma using Mössbauer spectroscopy with a high velocity resolution demonstrated small variations of the 57Fe quadrupole splitting and isomer shift. These variations may be a result of small structural differences in the heme iron stereochemistry of various hemoglobins.

  1. Excitation of the {sup 229m}Th nuclear isomer via resonance conversion in ionized atoms

    SciTech Connect

    Karpeshin, F. F.; Trzhaskovskaya, M. B.

    2015-09-15

    Pressing problems concerning the optical pumping of the 7.6-eV {sup 229m}Th nuclear isomer, which is a candidate for a new nuclear optical reference point for frequencies, are examined. Physics behind the mechanism of the two-photon optical pumping of the isomer is considered. It is shown that, irrespective of the pumping scheme, a dominant contribution comes, in accord with what was proven earlier for the 3.5-eV isomer, from the resonance 8s–7s transition. Details of an optimum experimental scheme are discussed. It is shown that, after isomer excitation, the atom involved remains with a high probability in an excited state at an energy of about 0.5 eV rather than in the ground state, the required energy of the two photons being equal to the energy of the nuclear level plus the energy of the lowest 7s state of the atom. The estimated pumping time is about 1.5 s in the case where the field strength of each laser is 1 V/cm.

  2. Using One's Hands for Naming Optical Isomers and Other Stereochemical Positions.

    ERIC Educational Resources Information Center

    Mezl, Vasek A.

    1996-01-01

    Presents a method that allows students to use their hands to obtain the stereochemistry of chiral centers without redrawing the structure. Discusses the use of the model in: determining the configurations of amino acids, determining if sugars are D or L isomers, the sequence rule procedure, prochirality, naming the sides of trigonal carbons, and…

  3. Structural Isomer Identification via NMR: A Nuclear Magnetic Resonance Experiment for Organic, Analytical, or Physical Chemistry.

    ERIC Educational Resources Information Center

    Szafran, Zvi

    1985-01-01

    Background information, procedures used, and typical results obtained are provided for an experiment that examines the ability of nuclear magnetic resonance (NMR) to distinguish between structural isomers via resonance multiplicities and chemical shifts. Reasons for incorporating the experiment into organic, analytical, or physical chemistry…

  4. Isomer residual ratio of odd-odd isotope {sup 180}Ta in supernova nucleosynthsis

    SciTech Connect

    Hayakawa, Takehito; Kajino, Toshitaka; Chiba, Satoshi; Mathews, Grant

    2010-06-01

    The nucleosynthesis of {sup 180}Ta has remained an unsolved problem and as its origin many nucleosynthesis mechanisms have been proposed. This isotope has the unique feature that the naturally occurring abundance of {sup 180}Ta is actually a meta-stable isomer (half-life of >=10{sup 15} yr), while the ground state is a 1{sup +} unstable state which beta-decays with a half-life of only 8.15 hr. We have made a new time-dependent calculation of {sup 180}Ta meta-stable isomer residual ratio after supernova neutrino-induced reactions. This residual isomer ratio is crucial for understanding the production and survival of this naturally occurring rare isotope. We have constructed a new model under temperature evolution after type II supernova explosion. We include the explicit linking between the isomer and all known excited states and found that the residual ratio is insensitive to astrophysical parameters such as neutrino energy spectrum, explosion energy, decay time constant. We find that the explicit time evolution of the synthesis of {sup 180}Ta avoids the overproduction relative to {sup 138}La for a neutrino process neutrino temperature of 4 MeV.

  5. Infrared spectroscopy of the acetyl cation and its protonated ketene isomer

    SciTech Connect

    Mosley, J. D.; Young, J. W.; Duncan, M. A.

    2014-07-14

    [C{sub 2},H{sub 3},O]{sup +} ions are generated with a pulsed discharge in a supersonic expansion containing methyl acetate or acetone. These ions are mass selected and their infrared spectra are recorded via laser photodissociation and the method of argon tagging. Computational chemistry is employed to investigate structural isomers and their spectra. The acetyl cation (CH{sub 3}CO{sup +}) is the global minimum and protonated ketene (CH{sub 2}COH{sup +}) is the next lowest energy isomer (+176.2 kJ/mol). When methyl acetate is employed as the precursor, the infrared spectrum reveals that only the acetyl cation is formed. Partially resolved rotational structure reveals rotation about the C{sub 3} axis. When acetone is used as the precursor, acetyl is still the most abundant cation, but there is also a minor component of protonated ketene. Computations reveal a significant barrier to interconversion between the two isomers (+221 kJ/mol), indicating that protonated ketene must be obtained via kinetic trapping. Both isomers may be present in interstellar environments, and their implications for astrochemistry are discussed.

  6. Infrared Spectra of (CO2)2-OCS Complex: Infrared Observation of Two Distinct Barrel-Shaped Isomers

    NASA Astrophysics Data System (ADS)

    Norooz Oliaee, J.; Dehghany, M.; Mivehvar, F.; Moazzen-Ahmadi, N.; McKellar, A. R. W.

    2010-06-01

    Spectra of (CO2)2-OCS complex in the region of the OCS ν 1 fundamental (˜ 2062 cm-1) are observed using a tunable diode laser to probe a pulsed supersonic slit jet expansion. A previous microwave study of the complex by Peebles and Kuczkowskia gave a distorted triangular cylinder. The geometerical disposition of the three dimer faces of this trimer are quite similar to the slipped CO2 dimer, the lowest energy form of OCS-CO2 (isomer a), also observed and analyzed in the microwave region, and the higher energy form of OCS-CO2 (isomer b), first observed by our group in the infrared region. Here we report the observation and analysis of two infrared bands, corresponding to two distinct isomers of the (CO2)2-OCS complex. A band around 2058.8 cm-1 was assigned to isomer I, which is the same as that studied previously by microwave spectroscopy. A second band around 2051.7 cm-1 was assigned to a higher energy isomer of the complex, isomer II, has not been observed previously, but expected on the basis of ab initio calculations. Approximate structural parameters for this new isomer were obtained by means of isotopic substitution. In contrast to isomer I, the geometerical disposition of the faces containing OCS and CO2 in isomer II are similar to isomer b of the OCS-CO2 complex. S. A. Peebles and R. L. Kuczkowski, J. Chem. Phys. 109, 5277 (1998). S. E. Novick, R. D. Suenram, and F. J. Lovas, J. Chem. Phys. 88, 687 (1988). M. Dehghany, J. Nooroz Oliaee, M. Afshari, N. Moazzen-Ahmadi, and A. R. W. McKellar, J. Chem. Phys. 130, 224310 (2009). H. Valdés and J. A. Sordo, Int. J. Comput. Chem. 23, 444 (2002).

  7. Evaluation of Enhanced Comprehensive 2-D Gas Chromatography-Time-Of-Flight Mass Spectrometry for the Separation of Recalcitrant Polychlorinated Biphenyl Isomers

    EPA Science Inventory

    The separation of some recalcitrant polychlorinated biphenyl (PCB) isomers in extracts from environmental compartments has been a daunting task for environmental chemists. Summed quantitation values for coeluting PCB isomers are often reported. This composite data obscures the ac...

  8. Structures of Two Isomers of Nitrous Oxide Tetramer from Their Infrared Spectra

    NASA Astrophysics Data System (ADS)

    Oliaee, J. Norooz; Mivehvar, F.; Dehghany, M.; Moazzen-Ahmadi, N.; McKellar, A. R. W.

    2010-06-01

    Weakly bound complexes provide a convenient starting point for a detailed understanding of different pathways that can be taken between the gas and condensed phases of matter. In this regard, it is of considerable interest to determine the number of isomers for a cluster size and if and how geometrical choices made in the early stages of condensation influence the growth of larger clusters. Although it is expected that the number of isomers grows rapidly with cluster size, in many cases only a single isomer is observed experimentally. High resolution spectroscopy has provided information on structural and vibrational dynamics of a large number of binary and ternary complexes formed from related linear triatomic molecules such as CO2, N2O, OCS and CS2. But, there are much fewer detailed experimental studies which provide structures for the important cluster sizes in the range of % 4˜ 10 monomers. Here we report the structural determination of two isomers of nitrous oxide tetramer from their infrared spectra in the ν 1 fundamental region (% ˜ 2230 cm-1). Two bands are observed and analyzed, corresponding to two distinct isomers of the complex. A perpendicular band centered at % 2232.209 cm-1 has been assigned to an isomer with S4 symmetry (a subgroup of D2d group). This is a rare symmetry group, but provides all the necessary ingredients. It allows for a tilt of the monomers from the symmetry axis of the complex as well as a twist. The experimentally determined structure has the monomers more or less perpendicular to the symmetry axis. A second band centered at 2237.424 cm-1 was assigned to a structure close to a perfect barrel-shaped tetramer with D2d symmetry. This is a prolate symmetric top which gives parallel bands for the pure isotopomers and a c-type band for the mixed isotopomer containing three 15N2 O monomers. This isomer is the same species as that observed by R.E. Miller and L. Pederson. I R. E. Miller and L. Pederson, Chem. Phys. Lett. 275, 307 (1997).

  9. Platelet-Rich Plasma

    PubMed Central

    Cole, Brian J.; Seroyer, Shane T.; Filardo, Giuseppe; Bajaj, Sarvottam; Fortier, Lisa A.

    2010-01-01

    Context: Platelet-rich plasma (PRP) may affect soft tissue healing via growth factors released after platelet degranulation. Because of this potential benefit, clinicians have begun to inject PRP for the treatment of tendon, ligament, muscle, and cartilage injuries and early osteoarthritis. Evidence Acquisition: A PubMed search was performed for studies relating to PRP, growth factors, and soft tissue injuries from 1990 to 2010. Relevant references from these studies were also retrieved. Results: Soft tissue injury is a major source of disability that may often be complicated by prolonged and incomplete recovery. Numerous growth factors may potentiate the healing and regeneration of tendons and ligaments. The potential benefits of biologically enhanced healing processes have led to a recent interest in the use of PRP in orthopaedic sports medicine. There has been widespread anecdotal use of PRP for muscle strains, tendinopathy, and ligament injuries and as a surgical adjuvant to rotator cuff repair, anterior cruciate ligament reconstruction, and meniscal or labral repairs. Although the fascination with this emerging technology has led to a dramatic increase in its use, scientific data supporting this use are still in their infancy. Conclusions: The literature is replete with studies on the basic science of growth factors and their relation to the maintenance, proliferation, and regeneration of various tissues and tissue-derived cells. Despite the promising results of several animal studies, well-controlled human studies are lacking. PMID:23015939

  10. Tuneable microsecond-pulsed glow discharge design for the simultaneous acquisition of elemental and molecular chemical information using a time-of-flight mass spectrometer.

    PubMed

    Solà-Vázquez, Auristela; Martín, Antonio; Costa-Fernández, José M; Pereiro, Rosario; Sanz-Medel, Alfredo

    2009-04-01

    A microsecond-pulsed direct current glow discharge (GD) was interfaced and synchronized to a time-of-flight mass spectrometer MS(TOF) for time-gated generation and detection of elemental, structural, and molecular ions. In this way, sequential collection of the mass spectra at different temporal regimes occurring during the GD pulse cycle is allowed. The capabilities of this setup were explored using bromochloromethane as model analyte. A simple GD chamber, developed in our laboratory and characterized by a low plasma volume minimizing dilution of the sample but showing great robustness to the entrance of organic compounds in the microsecond-pulsed plasma, has been used. An exhaustive analytical characterization of the GD-MS(TOF) prototype has been performed. Calibration curves for bromochloromethane observed at the different time regimes of the GD pulse cycle (that is, for elemental, fragment, and molecular ions from the analyte) showed very good linearity for the measurement of the different involved ions, with precisions in the range of 7-13% (relative standard deviation). Actual detection limits obtained for bromochloromethane were in the range of 1-3 microg/L for elements monitoring in the GD pulse "prepeak", in the range of 11-13 microg/L when monitoring analyte fragments in the plateau, and about 238 microg/L when measuring the molecular peak in the afterpeak regime. PMID:19256521

  11. Differential developmental toxicity of naphthoic acid isomers in medaka (Oryzias latipes) embryos.

    PubMed

    Carney, Michael W; Erwin, Kyle; Hardman, Ron; Yuen, Bonny; Volz, David C; Hinton, David E; Kullman, Seth W

    2008-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are widespread persistent pollutants that readily undergo biotic and abiotic conversion to numerous transformation products in rivers, lakes and estuarine sediments. Here we characterize the developmental toxicity of four PAH transformation products each structural isomers of hydroxynaphthoic acid: 1H2NA, 2H1NA, 2H3NA, and 6H2NA. Medaka fish (Oryzias latipes) embryos and eleutheroembryos were used to determine toxicity. A 96-well micro-plate format was used to establish a robust, statistically significant platform for assessment of early life stages. Individual naphthoic acid isomers demonstrated a rank order of toxicity with 1H2NA>2H1NA>2H3NA>6H2NA being more toxic. Abnormalities of circulatory system were most pronounced including pericardial edema and tube heart. To determine if HNA isomers were AhR ligands, spatial-temporal expression and activity of CYP1A was measured via in vivo EROD assessments. qPCR measurement of CYP1A induction proved different between isomers dosed at respective concentrations affecting 50% of exposed individuals (EC50s). In vitro, all ANH isomers transactivated mouse AhR using a medaka CYP1A promoter specific reporter assay. Circulatory abnormalities followed P450 induction and response was consistent with PAH toxicity. A 96-well micro-plates proved suitable as exposure chambers and provided statistically sound evaluations as well as efficient toxicity screens. Our results demonstrate the use of medaka embryos for toxicity analysis thereby achieving REACH objectives for the reduction of adult animal testing in toxicity evaluations. PMID:18433798

  12. Portable, Battery Operated Capillary Electrophoresis with Optical Isomer Resolution Integrated with Ionization Source for Mass Spectrometry.

    PubMed

    Moini, Mehdi; Rollman, Christopher M

    2016-03-01

    We introduce a battery operated capillary electrophoresis electrospray ionization (CE/ESI) source for mass spectrometry with optical isomer separation capability. The source fits in front of low or high resolution mass spectrometers similar to a nanospray source with about the same weight and size. The source has two high voltage power supplies (±25 kV HVPS) capable of operating in forward or reverse polarity modes and powered by a 12 V rechargeable lithium ion battery with operation time of ~10 h. In ultrafast CE mode, in which short narrow capillaries (≤15 μm i.d., 15-25 cm long) and field gradients ≥1000 V/cm are used, peak widths at the base are <1 s wide. Under these conditions, the source provides high resolution separation, including optical isomer resolution in ~1 min. Using a low resolution mass spectrometer (LTQ Velos) with a scan time of 0.07 s/scan, baseline separation of amino acids and their optical isomers were achieved in ~1 min. Moreover, bovine serum albumin (BSA) was analyzed in ~1 min with 56% coverage using the data-dependent MS/MS. Using a high resolution mass spectrometer (Thermo Orbitrap Elite) with 15,000 resolution, the fastest scan time achieved was 0.15 s, which was adequate for CE-MS analysis when optical isomer separation is not required or when the optical isomers were well separated. Figures of merit including a detection limit of 2 fmol and linear dynamic range of two orders of magnitude were achieved for amino acids. PMID:26644308

  13. Probing ground and low-lying excited states for HIO2 isomers

    NASA Astrophysics Data System (ADS)

    de Souza, Gabriel L. C.; Brown, Alex

    2014-12-01

    We present a computational study on HIO2 molecules. Ground state properties such as equilibrium structures, relative energetics, vibrational frequencies, and infrared intensities were obtained for all the isomers at the coupled-cluster with single and double excitations as well as perturbative inclusion of triples (CCSD(T)) level of theory with the aug-cc-pVTZ-PP basis set and ECP-28-PP effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. The HOIO structure is confirmed as the lowest energy isomer. The relative energies are shown to be HOIO < HOOI < HI(O)O. The HO(O)I isomer is only stable at the density functional theory (DFT) level of theory. The transition states determined show interconversion of the isomers is possible. In order to facilitate future experimental identification, vibrational frequencies are also determined for all corresponding deuterated species. Vertical excitation energies for the three lowest-lying singlet and triplet excited states were determined using the configuration interaction singles, time-dependent density functional theory (TD-DFT)/B3LYP, TD-DFT/G96PW91, and equation of motion-CCSD approaches with the LANL2DZ basis set plus effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. It is shown that HOIO and HOOI isomers have excited states accessible at solar wavelengths (<4.0 eV) but these states have very small oscillator strengths (<2 × 10-3).

  14. Probing ground and low-lying excited states for HIO2 isomers.

    PubMed

    de Souza, Gabriel L C; Brown, Alex

    2014-12-21

    We present a computational study on HIO2 molecules. Ground state properties such as equilibrium structures, relative energetics, vibrational frequencies, and infrared intensities were obtained for all the isomers at the coupled-cluster with single and double excitations as well as perturbative inclusion of triples (CCSD(T)) level of theory with the aug-cc-pVTZ-PP basis set and ECP-28-PP effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. The HOIO structure is confirmed as the lowest energy isomer. The relative energies are shown to be HOIO < HOOI < HI(O)O. The HO(O)I isomer is only stable at the density functional theory (DFT) level of theory. The transition states determined show interconversion of the isomers is possible. In order to facilitate future experimental identification, vibrational frequencies are also determined for all corresponding deuterated species. Vertical excitation energies for the three lowest-lying singlet and triplet excited states were determined using the configuration interaction singles, time-dependent density functional theory (TD-DFT)/B3LYP, TD-DFT/G96PW91, and equation of motion-CCSD approaches with the LANL2DZ basis set plus effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. It is shown that HOIO and HOOI isomers have excited states accessible at solar wavelengths (<4.0 eV) but these states have very small oscillator strengths (<2 × 10(-3)). PMID:25527931

  15. Vitamin E and cancer: An insight into the anticancer activities of vitamin E isomers and analogs.

    PubMed

    Constantinou, Constantina; Papas, Andreas; Constantinou, Andreas I

    2008-08-15

    Current observations in the literature suggest that vitamin E may be a suitable candidate for the adjuvant treatment of cancer. Even though historically most research focused on alpha-tocopherol, more recent evidence suggests that the other isomers of vitamin E (beta-, gamma- and delta-tocopherols and alpha-, beta-, gamma- and delta-tocotrienols) differ in their proapoptotic potencies. The main focus of this communication is the current understanding of the molecular mechanisms regulated by vitamin E isomers and their analogs during the induction of apoptosis. This review highlights that the mitochondria are the major target for the induction of apoptosis by vitamin E isomers and analogs and that the various signaling pathways regulated by these agents are likely to contribute towards maximizing the intrinsic pathway of apoptosis triggered initially by the mitochondria. Overall, the presentation of recent studies from the literature in this communication allows the drawing of the following important conclusions: (i) no direct link exists between the antioxidant activity of each isomer/derivative and proapoptotic potency, (ii) tocotrienols are more effective proapoptotic agents than tocopherols, (iii) synthetic modifications of the naturally occurring compounds may improve their apoptotic potency and (iv) vitamin E isomers and derivatives regulate caspase-independent pathways of apoptosis. The latter combined with the evidence presented in this review regarding the additive or synergistic anticarcinogenic effects obtained when vitamin E analogs are used in combination with other cancer chemotherapeutic agents, supports further research to design the most promising vitamin E derivatives and clinically test them in adjuvant chemotherapeutic treatments. PMID:18512238

  16. Conformational preferences and synthesis of isomers Z and E of oxazole-dehydrophenylalanine.

    PubMed

    Staś, Monika; Bujak, Maciej; Broda, Małgorzata A; Siodłak, Dawid

    2016-05-01

    Dehydrophenylalanine, ΔPhe, is the most commonly studied α,β-dehydroamino acid. In nature, further modifications of the α,β-dehydroamino acids were found, for example, replacement of the C-terminal amide group by oxazole ring. The conformational properties of oxazole-dehydrophenylalanine residue (ΔPhe-Ozl), both isomers Z and E, were investigated. To determine all possible conformations, theoretical calculations were performed using Ac-(Z/E)-ΔPhe-Ozl(4-Me) model compounds at M06-2X/6-31++G(d,p) level of theory. Ac-(Z/E)-ΔPhe-Ozl-4-COOEt compounds were synthesized and the conformational preferences of each isomer, Z and E, were investigated using FTIR and NMR-NOE in solutions of increasing polarity (CHCl3 , DMSO-d6). The solid-state low-temperature structures of Ac-(Z)-ΔPhe-Ozl-4-COOEt and its intermediate analog Ac-(Z)-ΔPhe-Ozn(4-OH)-4-COOEt were also determined. In a weakly polar environment, the ΔPhe-Ozl residue has a tendency to adopt the conformation β2 with the calculated φ and ψ angles of -127° and 0° for the isomer Z and -170° and 26° for the isomer E. The increase of environment polarity favors the helical conformation α and the beta-turn like conformation β, but the conformation β2 seems to be still accessible. The (E)-ΔPhe-Ozl residue can be obtained from the isomer Z in photoisomerization reaction. However, hydroxyl-oxazoline-dehydrophenylalanine ΔPhe-Ozn(4-OH) decomposes in such conditions. Alternatively, (E)-ΔPhe-NH2 can be applied as a substrate in the Hantzsch reaction. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 283-294, 2016. PMID:27061820

  17. Surface behavior of amphiphiles in aqueous solution: a comparison between different pentanol isomers.

    PubMed

    Walz, M-M; Caleman, C; Werner, J; Ekholm, V; Lundberg, D; Prisle, N L; Öhrwall, G; Björneholm, O

    2015-06-01

    Position isomerism is ubiquitous in atmospheric oxidation reactions. Therefore, we have compared surface-active oxygenated amphiphilic isomers (1- and 3-pentanol) at the aqueous surface with surface- and chemically sensitive X-ray photoelectron spectroscopy (XPS), which reveals information about the surface structure on a molecular level. The experimental data are complemented with molecular dynamics (MD) simulations. A concentration-dependent orientation and solvation of the amphiphiles at the aqueous surface is observed. At bulk concentrations as low as around 100 mM, a monolayer starts to form for both isomers, with the hydroxyl groups pointing towards the bulk water and the alkyl chains pointing towards the vacuum. The monolayer (ML) packing density of 3-pentanol is approx. 70% of the one observed for 1-pentanol, with a molar surface concentration that is approx. 90 times higher than the bulk concentration for both molecules. The molecular area at ML coverage (≈100 mM) was calculated to be around 32 ± 2 Å(2) per molecule for 1-pentanol and around 46 ± 2 Å(2) per molecule for 3-pentanol, which results in a higher surface concentration (molecules per cm(2)) for the linear isomer. In general we conclude therefore that isomers - with comparable surface activities - that have smaller molecular areas will be more abundant at the interface in comparison to isomers with larger molecular areas, which might be of crucial importance for the understanding of key properties of aerosols, such as evaporation and uptake capabilities as well as their reactivity. PMID:25953683

  18. Portable, Battery Operated Capillary Electrophoresis with Optical Isomer Resolution Integrated with Ionization Source for Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Moini, Mehdi; Rollman, Christopher M.

    2016-03-01

    We introduce a battery operated capillary electrophoresis electrospray ionization (CE/ESI) source for mass spectrometry with optical isomer separation capability. The source fits in front of low or high resolution mass spectrometers similar to a nanospray source with about the same weight and size. The source has two high voltage power supplies (±25 kV HVPS) capable of operating in forward or reverse polarity modes and powered by a 12 V rechargeable lithium ion battery with operation time of ~10 h. In ultrafast CE mode, in which short narrow capillaries (≤15 μm i.d., 15-25 cm long) and field gradients ≥1000 V/cm are used, peak widths at the base are <1 s wide. Under these conditions, the source provides high resolution separation, including optical isomer resolution in ~1 min. Using a low resolution mass spectrometer (LTQ Velos) with a scan time of 0.07 s/scan, baseline separation of amino acids and their optical isomers were achieved in ~1 min. Moreover, bovine serum albumin (BSA) was analyzed in ~1 min with 56% coverage using the data-dependent MS/MS. Using a high resolution mass spectrometer (Thermo Orbitrap Elite) with 15,000 resolution, the fastest scan time achieved was 0.15 s, which was adequate for CE-MS analysis when optical isomer separation is not required or when the optical isomers were well separated. Figures of merit including a detection limit of 2 fmol and linear dynamic range of two orders of magnitude were achieved for amino acids.

  19. Probing ground and low-lying excited states for HIO{sub 2} isomers

    SciTech Connect

    Souza, Gabriel L. C. de; Brown, Alex

    2014-12-21

    We present a computational study on HIO{sub 2} molecules. Ground state properties such as equilibrium structures, relative energetics, vibrational frequencies, and infrared intensities were obtained for all the isomers at the coupled-cluster with single and double excitations as well as perturbative inclusion of triples (CCSD(T)) level of theory with the aug-cc-pVTZ-PP basis set and ECP-28-PP effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. The HOIO structure is confirmed as the lowest energy isomer. The relative energies are shown to be HOIO < HOOI < HI(O)O. The HO(O)I isomer is only stable at the density functional theory (DFT) level of theory. The transition states determined show interconversion of the isomers is possible. In order to facilitate future experimental identification, vibrational frequencies are also determined for all corresponding deuterated species. Vertical excitation energies for the three lowest-lying singlet and triplet excited states were determined using the configuration interaction singles, time-dependent density functional theory (TD-DFT)/B3LYP, TD-DFT/G96PW91, and equation of motion-CCSD approaches with the LANL2DZ basis set plus effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. It is shown that HOIO and HOOI isomers have excited states accessible at solar wavelengths (<4.0 eV) but these states have very small oscillator strengths (<2 × 10{sup −3})

  20. Differential accumulation and elimination behavior of perfluoroalkyl Acid isomers in occupational workers in a manufactory in China.

    PubMed

    Gao, Yan; Fu, Jianjie; Cao, Huiming; Wang, Yawei; Zhang, Aiqian; Liang, Yong; Wang, Thanh; Zhao, Chunyan; Jiang, Guibin

    2015-06-01

    In this study, serum and urine samples were collected from 36 occupational workers in a fluorochemical manufacturing plant in China from 2008 to 2012 to evaluate the body burden and possible elimination of linear and branched perfluoroalkyl acids (PFAAs). Indoor dust, total suspended particles (TSP), diet, and drinking water samples were also collected to trace the occupational exposure pathway to PFAA isomers. The geometric mean concentrations of perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA), and perfluorohexanesulfonate (PFHxS) isomers in the serum were 1386, 371, and 863 ng mL(-1), respectively. The linear isomer of PFOS, PFOA, and PFHxS was the most predominant PFAA in the serum, with mean proportions of 63.3, 91.1, and 92.7% respectively, which were higher than the proportions in urine. The most important exposure routes to PFAA isomers in the occupational workers were considered to be the intake of indoor dust and TSP. A renal clearance estimation indicated that branched PFAA isomers had a higher renal clearance rate than did the corresponding linear isomers. Molecular docking modeling implied that linear PFOS (n-PFOS) had a stronger interaction with human serum albumin (HSA) than branched isomers did, which could decrease the proportion of n-PFOS in the blood of humans via the transport of HSA. PMID:25927957

  1. Biochemical Characterization of Inducible 'Reductase' Component of Benzoate Dioxygenase and Phthalate Isomer Dioxygenases from Pseudomonas aeruginosa strain PP4.

    PubMed

    Karandikar, Rohini; Badri, Abinaya; Phale, Prashant S

    2015-09-01

    The first step involved in the degradation of phthalate isomers (phthalate, isophthalate and terephthalate) is the double hydroxylation by respective aromatic-ring hydroxylating dioxygenases. These are two component enzymes consisting of 'oxygenase' and 'reductase' components. Soil isolate Pseudomonas aeruginosa strain PP4 degrades phthalate isomers via protocatechuate and benzoate via catechol 'ortho' ring cleavage pathway. Metabolic studies suggest that strain PP4 has carbon source-specific inducible phthalate isomer dioxygenase and benzoate dioxygenase. Thus, it was of interest to study the properties of reductase components of these enzymes. Reductase activity from phthalate isomer-grown cells was 3-5-folds higher than benzoate grown cells. In-gel activity staining profile showed a reductase activity band of R f 0.56 for phthalate isomer-grown cells as compared to R f 0.73 from benzoate-grown cells. Partially purified reductase components from phthalate isomer grown cells showed K m in the range of 30-40 μM and V max = 34-48 μmol min(-1) mg(-1). However, reductase from benzoate grown cells showed K m = 49 μM and V max = 10 μmol min(-1) mg(-1). Strikingly similar molecular and kinetic properties of reductase component from phthalate isomer-grown cells suggest that probably the same reductase component is employed in three phthalate isomer dioxygenases. However, reductase component is different, with respect to kinetic properties and zymogram analysis, from benzoate-grown cells when compared to that from phthalate isomer grown cells of PP4. PMID:26201480

  2. Positional Isomers of Aspirin Are Equally Potent in Inhibiting Colon Cancer Cell Growth: Differences in Mode of Cyclooxygenase Inhibition

    PubMed Central

    Kodela, Ravinder; Chattopadhyay, Mitali; Goswami, Satindra; Gan, Zong Yuan; Rao, Praveen P. N.; Nia, Kamran V.; Velázquez-Martínez, Carlos A.

    2013-01-01

    We compared the differential effects of positional isomers of acetylsalicylic acid (o-ASA, m-ASA, and p-ASA) on cyclooxygenase (COX) inhibition, gastric prostaglandin E2 (PGE2), malondialdehyde, tumor necrosis factor-alpha (TNF-α) levels, superoxide dismutase (SOD) activity, human adenocarcinoma colon cancer cell growth inhibition, cell proliferation, apoptosis, and cell-cycle progression. We also evaluated the gastric toxicity exerted by ASA isomers. All ASA isomers inhibit COX enzymes, but only the o-ASA exerted an irreversible inhibitory profile. We did not observe a significant difference between ASA isomers in their ability to decrease the in vivo synthesis of PGE2 and SOD activity. Furthermore, all isomers increased the levels of gastric and TNF-α when administered orally at equimolar doses. We observed a dose-dependent cell growth inhibitory effect; the order of potency was p-ASA > m-ASA ≈ o-ASA. There was a dose-dependent decrease in cell proliferation and an increase in apoptosis, with a concomitant Go/G1 arrest. The ulcerogenic profile of the three ASA isomers showed a significant difference between o-ASA (aspirin) and its two positional isomers when administered orally at equimolar doses (1 mmol/kg); the ulcer index (UI) for o-ASA indicated extensive mucosal injury (UI = 38), whereas m-ASA and p-ASA produced a significantly decreased toxic response (UI = 12 and 8, respectively) under the same experimental conditions. These results suggest that the three positional isomers of ASA exert practically the same biologic profile in vitro and in vivo but showed different safety profiles. The mechanism of gastric ulcer formation exerted by aspirin and its two isomers warrants a more detailed and thorough investigation. PMID:23349335

  3. Assessment of the in vivo genotoxicity of isomers of dinitrotoluene using the alkaline Comet and peripheral blood micronucleus assays.

    PubMed

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

    2012-02-18

    Dinitrotoluene (DNT) is a nitroaromatic explosive that exists as six isomers; two major isomers (2,4- and 2,6-DNT) and four minor isomers (2,3-, 2,5-, 3,4-, and 3,5-DNT). DNT has been found in soil, surface water, and groundwater near ammunition production plants. The major isomers of DNT are classified as "likely to cause cancer in humans."In vitro studies have provided conflicting data regarding the genotoxicity of the minor isomers. Studies indicate that metabolism in the gut and liver are necessary to convert DNT to genotoxic compounds. As such, in the present study the genotoxicity of isomers of DNT was assessed using two in vivo genotoxicity assays. The Comet assay was used to detect DNA damage in liver cells from male Sprague-Dawley rats following oral exposure (14-day) to individual isomers of DNT. The micronucleus assay was conducted using flow cytometric analysis to detect chromosomal damage in peripheral blood. Treatment with 2,3-, 3,4-, 2,4-, 2,5- and 3,5-DNT did not induce DNA damage in liver cells or increase the frequency of micronucleated reticulocytes (MN-RET) in peripheral blood at the doses tested. Treatment with 2,6-DNT induced DNA damage in liver tissue at all doses tested, but did not increase the frequency of micronucleated reticulocytes (MN-RET) in peripheral blood. Thus, 2,4-DNT and the minor isomers were not genotoxic under these test conditions, while 2,6-DNT was genotoxic in the target tissue, the liver. These results support previous research which indicated that the hepatocarcinogenicity of technical grade DNT (TG-DNT) could be attributed to the 2,6-DNT isomer. PMID:22155124

  4. Are isomers of the vinyl cyanide ion missing links for interstellar pyrimidine formation?

    NASA Astrophysics Data System (ADS)

    Bera, Partha P.; Lee, Timothy J.; Schaefer, Henry F.

    2009-08-01

    In the interstellar medium (ISM) there are many regions where the formation of molecules is kinetically driven rather than thermochemically, which can lead to the formation of many isomers even though some may be fairly higher in energy relative to the molecular global minimum. Recent laboratory experiments where noble gas cations are reacted with pyrimidine favored the formation of C3H3N+, but the molecular structure(s) of this fragment was not determined. Microscopic reversibility means that pyrimidine could form under interstellar conditions should the required C3H3N+ reactant be detected in the ISM. Hence C3H3N+ could be a strong candidate for involvement in the formation of heterocyclic biomolecules such as pyrimidine in the ISM. In this study, we have investigated the low energy isomers of the acrylonitrile ion (C3H3N+) using density functional theory as well as high levels of ab initio theory, namely, the singles and doubles coupled-cluster theory that includes a perturbational correction for connected triple excitations, denoted as CCSD(T). An automated stochastic search procedure, Kick, has been employed to find isomers on the ground state doublet potential energy surface. Several new structures, along with all the previously reported minima, have been found. The global minimum H2CCCNH+ is energetically much lower than either H2CC(H)CN+, the acrylonitrile ion, or HCC(H)NCH+, the most likely intermediate of the reaction between HCCH+ and HCN. These isomers are connected to the global minimum via several transition states and intermediates. The results indicate that not only the global minimum but also several higher energy isomers of the C3H3N+ ion could be important in interstellar pyrimidine formation. The isomeric molecules have the necessary CCNC backbone needed for the reaction with HCN to form the cyclic pyrimidine framework. The structural and rotational parameters of all the isomers studied in this work have been predicted at the CCSD(T) level of

  5. High-K isomers in {sup 176}W and mechanisms of K-violation

    SciTech Connect

    Crowell, B.; Janssens, R.V.F.; Blumenthal, D.J.

    1995-08-01

    K-isomers are states in deformed nuclei whose {gamma}-decay is hindered by selection rules involving K, the projection of the angular momentum along the axis of symmetry of the nucleus. Previous work with the Argonne Notre Dame BGO Array delineated the existence of two K-isomers in {sup 176}W, one of which had a very unusual pattern of decay. A short description of this work was published as a letter, and a more complete account is being readied for submission. These results provided evidence that quantum-mechanical fluctuations in the nuclear shape may be responsible for some of the observed K-violating transitions. In addition, hints were present in the data of the existence of another K-isomer with an even higher in. An experiment was performed in September 1994 to observe this isomer, using the reaction {sup 50}Ti({sup 130}Te,4n), and a technique in which recoiling {sup 176}W nuclei were created 17-cm upstream of the center of the array and caught on a Pb catcher foil at the center. Intense ({approximately} 3 pnA) beams of {sup 130}Te were supplied by the ECR source using a new sputtering technique. The recoil-shadow geometry was highly successful at removing the background from non-isomeric decays, allowing the weakly populated K-isomers to be detected cleanly. In addition, the availability of pulsed beams from ATLAS and the timing data from the BGO array provided a second technique for isolating the decays of interest, by selecting events in which a given number of BGO detectors fired between beam pulses. This method was used in the previous experiment, and was also applied in this experiment as a second level of selection. As a result, gamma-ray transitions were detected in the present experiment with intensities as small as {approximately} 0.02 % of the {sup 176}W reaction channel. The existence of the new isomer was confirmed, and a partial level-scheme was constructed.

  6. Differential adsorption of complex organic molecules isomers at interstellar ice surfaces

    NASA Astrophysics Data System (ADS)

    Lattelais, M.; Bertin, M.; Mokrane, H.; Romanzin, C.; Michaut, X.; Jeseck, P.; Fillion, J.-H.; Chaabouni, H.; Congiu, E.; Dulieu, F.; Baouche, S.; Lemaire, J.-L.; Pauzat, , F.; Pilmé, J.; Minot, C.; Ellinger, Y.

    2011-08-01

    Context. Over 20 of the ~150 different species detected in the interstellar and circumstellar media have also been identified in icy environments. For most of the species observed so far in the interstellar medium (ISM), the most abundant isomer of a given generic chemical formula is the most stable one (minimum energy principle - MEP) with few exceptions such as, for example, CH3COOH/HCOOCH3 and CH3CH2OH/CH3OCH3, whose formation is thought to occur on the icy mantles of interstellar grains. Aims: We investigate whether differences found in the compositions of molecular ices and the surrounding gas phase could originate from differences between the adsorption of one isomer from that of another at the ice surface. Methods: We performed a coherent and concerted theoretical/experimental study of the adsorption energies of the four molecules mentioned above, i.e. acetic acid (AA)/methyl formate (MF) and ethanol (EtOH)/dimethyl ether (DME) on the surface of water ice at low temperature. The question was first addressed theoretically at LCT using solid state periodic density functional theory (DFT) to represent the organized solid support. The experimental determination of the ice/molecule interaction energies was then carried out independently by two teams at LPMAA and LERMA/LAMAp using temperature programmed desorption (TPD) under an ultra-high vacuum (UHV) between 70 and 160 K. Results: For each pair of isomers, theory and experiments both agree that the most stable isomer (AA or EtOH) interacts more efficiently with the water ice than the higher energy isomer (MF or DME). This differential adsorption can be clearly seen in the different desorption temperatures of the isomers. It is not related to their intrinsic stability but instead to both AA and EtOH producing more and stronger hydrogen bonds with the ice surface. Conclusions: We show that hydrogen bonding may play an important role in the release of organic species from grains and propose that, depending on the

  7. Are isomers of the vinyl cyanide ion missing links for interstellar pyrimidine formation?

    SciTech Connect

    Bera, Partha P.; Lee, Timothy J.; Schaefer, Henry F. III

    2009-08-21

    In the interstellar medium (ISM) there are many regions where the formation of molecules is kinetically driven rather than thermochemically, which can lead to the formation of many isomers even though some may be fairly higher in energy relative to the molecular global minimum. Recent laboratory experiments where noble gas cations are reacted with pyrimidine favored the formation of C{sub 3}H{sub 3}N{sup +}, but the molecular structure(s) of this fragment was not determined. Microscopic reversibility means that pyrimidine could form under interstellar conditions should the required C{sub 3}H{sub 3}N{sup +} reactant be detected in the ISM. Hence C{sub 3}H{sub 3}N{sup +} could be a strong candidate for involvement in the formation of heterocyclic biomolecules such as pyrimidine in the ISM. In this study, we have investigated the low energy isomers of the acrylonitrile ion (C{sub 3}H{sub 3}N{sup +}) using density functional theory as well as high levels of ab initio theory, namely, the singles and doubles coupled-cluster theory that includes a perturbational correction for connected triple excitations, denoted as CCSD(T). An automated stochastic search procedure, Kick, has been employed to find isomers on the ground state doublet potential energy surface. Several new structures, along with all the previously reported minima, have been found. The global minimum H{sub 2}CCCNH{sup +} is energetically much lower than either H{sub 2}CC(H)CN{sup +}, the acrylonitrile ion, or HCC(H)NCH{sup +}, the most likely intermediate of the reaction between HCCH{sup +} and HCN. These isomers are connected to the global minimum via several transition states and intermediates. The results indicate that not only the global minimum but also several higher energy isomers of the C{sub 3}H{sub 3}N{sup +} ion could be important in interstellar pyrimidine formation. The isomeric molecules have the necessary CCNC backbone needed for the reaction with HCN to form the cyclic pyrimidine framework

  8. Effectiveness of α-, γ- and δ-Tocopherol in a CLA-Rich Oil

    PubMed Central

    Márquez-Ruiz, Gloria; García-Martínez, María del Carmen; Holgado, Francisca; Velasco, Joaquín

    2014-01-01

    Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of octadecadienoic acid with conjugated double bounds. Positive health properties have been attributed to some isomers, such as anticarcinogenic activity, antiartherosclerotic effects and reduction of body fat gain. Hence, oils rich in CLA such as Tonalin® oil (TO), normally obtained through alkaline isomerization of safflower oil (SO), an oil rich in linoleic acid (LA), are currently used in functional foods. However, special care must be taken to protect them from oxidation to ensure the quality of the supplemented foods. The objective of this work was to evaluate the oxidation and effectiveness of different tocopherol homologues (α-, γ- and δ-), alone or in combination with synergists (ascorbyl palmitate and lecithin), in TO compared to SO at different conditions, ambient temperature (25 °C) and accelerated conditions in Rancimat (100 °C). The oils, the oils devoid of their antioxidants and the latter containing the antioxidants added were assayed. Results showed great differences between SO and TO in terms of formation of hydroperoxides and polymers and also in the effectiveness of tocopherols to delay oxidation. TO showed higher levels of polymerization and, in general, the effectiveness of tocopherol homologues, alone or in combination with synergists, was also lower in the TO. PMID:26784671

  9. Effectiveness of α-, γ- and δ-Tocopherol in a CLA-Rich Oil.

    PubMed

    Márquez-Ruiz, Gloria; García-Martínez, María Del Carmen; Holgado, Francisca; Velasco, Joaquín

    2014-01-01

    Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of octadecadienoic acid with conjugated double bounds. Positive health properties have been attributed to some isomers, such as anticarcinogenic activity, antiartherosclerotic effects and reduction of body fat gain. Hence, oils rich in CLA such as Tonalin(®) oil (TO), normally obtained through alkaline isomerization of safflower oil (SO), an oil rich in linoleic acid (LA), are currently used in functional foods. However, special care must be taken to protect them from oxidation to ensure the quality of the supplemented foods. The objective of this work was to evaluate the oxidation and effectiveness of different tocopherol homologues (α-, γ- and δ-), alone or in combination with synergists (ascorbyl palmitate and lecithin), in TO compared to SO at different conditions, ambient temperature (25 °C) and accelerated conditions in Rancimat (100 °C). The oils, the oils devoid of their antioxidants and the latter containing the antioxidants added were assayed. Results showed great differences between SO and TO in terms of formation of hydroperoxides and polymers and also in the effectiveness of tocopherols to delay oxidation. TO showed higher levels of polymerization and, in general, the effectiveness of tocopherol homologues, alone or in combination with synergists, was also lower in the TO. PMID:26784671

  10. Comparison of isomers of ketamine on catalepsy in the rat and electrical activity of the brain and behavior in the cat.

    PubMed

    Benthuysen, J L; Hance, A J; Quam, D D; Winters, W D

    1989-10-01

    The present study compared the relative potency and efficacy of the two isomers of ketamine on the duration of catalepsy (loss of righting reflex) in female rats and on the behavior and electroencephalogram of cats. In the rat, at small doses, the S(+) isomer was more potent than the R(-) isomer or racemic ketamine, while at larger doses, the S(+) isomer and the racemate were equipotent and the R(-) isomer was significantly less potent. Tolerance developed rapidly to the effects of either isomer and both were equally cross-tolerant to racemic ketamine. Sub-effective doses of morphine significantly increased the potency of S(+), R(-) and racemic ketamine on the duration of catalepsy. Sub-effective doses of either isomer augmented the duration of catalepsy, induced by small doses of morphine, but reduced that of large doses. In cats, there was a parallel time course and progression of behavioral and electroencephalographic states in response to equal total doses of either racemic ketamine, an artificial 50:50 mixture of S(+) and R(-) isomers, or the S(+) isomer alone; approximately equivalent effects required twice the dose of the R(-) isomer. It is concluded that there is a common site of action for the two isomers, but there is also a stereospecific difference in potency, as regards the induction of catalepsy in the rat and behavioral and electroencephalographic effects in the cat. Stereospecificity was not apparent in the development of tolerance, cross-tolerance or the augmentation of the response to morphine. PMID:2812279

  11. Interactions between major chlorogenic acid isomers and chemical changes in coffee brew that affect antioxidant activities.

    PubMed

    Liang, Ningjian; Xue, Wei; Kennepohl, Pierre; Kitts, David D

    2016-12-15

    Coffee bean source and roasting conditions significantly (p<0.05) affected the content of chlorogenic acid (CGA) isomers, several indices of browning and subsequent antioxidant values. Principal component analysis was used to interpret the correlations between physiochemical and antioxidant parameters of coffee. CGA isomer content was positively correlated (p<0.001) to capacity of coffee to reduce nitric oxide and scavenge Frémy's salt. Indices of browning in roasted coffee were positively correlated (p<0.001) to ABTS and TEMPO radical scavenging capacity, respectively. Only the CGA content of coffee corresponded to intracellular antioxidant capacity measured in Caco-2 intestinal cells. This study concluded that the intracellular antioxidant capacity that best describes potential health benefits of coffee positively corresponds best with CGA content. PMID:27451179

  12. Real-time fingerprinting of structural isomers using laser induced breakdown spectroscopy.

    PubMed

    Myakalwar, Ashwin Kumar; Anubham, Siva Kumar; Paidi, Santosh Kumar; Barman, Ishan; Gundawar, Manoj Kumar

    2016-05-10

    Laser induced breakdown spectroscopy (LIBS) has surfaced as an attractive alternative to mass spectrometry and wet chemistry methods for chemical identification, driven by its real-time, label-free nature. Rapid analysis needs, especially in high-energy materials and pharmaceutical compounds, have further fueled an increasing number of refinements in LIBS. Yet, isomers are seldom identifiable by LIBS as they generate nearly identical spectra. Here we employ a suite of chemometric approaches to exploit the subtle, but reproducible, differences in LIBS spectra acquired from structural isomers, a set of pyrazoles, to develop a sensitive and reliable segmentation method. We also investigate the possible mechanistic principles (causation) behind such spectral variations and confirm their statistically significant nature that empowers the excellent classification performance. PMID:27090343

  13. Isomer production in intermediate-energy deuteron-induced reactions on a gold target

    NASA Astrophysics Data System (ADS)

    Balabekyan, A. R.; Karapetyan, G. S.; Demekhina, N. A.; Drnoyan, D. R.; Zhemenik, V. I.; Adam, J.; Zavorka, L.; Solnyshkin, A. A.; Tsoupko-Sitnikov, V. M.; Guimarães, V.; Deppman, A.

    2016-05-01

    Residual nuclei formed at ground and isomeric states from the interaction of 4.4 GeV deuteron with a gold target have been measured and investigated by the induced-activity method. Eight isomeric and ground-state pairs of target residues in the mass range of 44 isomer ratios were obtained from the cross-section production. From the isomer ratio data of the formed 196Au and 197Hg nuclei, the average intrinsic angular momentum of the composite system was estimated by means of a simple statistical model based on the formalism developed by Huizenga and Vandenbosch.

  14. Mass spectrometry and decay spectroscopy of isomers across the Z=82 shell closure

    NASA Astrophysics Data System (ADS)

    Stanja, J.; Borgmann, Ch.; Agramunt, J.; Algora, A.; Beck, D.; Blaum, K.; Böhm, Ch.; Breitenfeldt, M.; Cocolios, T. E.; Fraile, L. M.; Herfurth, F.; Herlert, A.; Kowalska, M.; Kreim, S.; Lunney, D.; Manea, V.; Minaya Ramirez, E.; Naimi, S.; Neidherr, D.; Rosenbusch, M.; Schweikhard, L.; Simpson, G.; Wienholtz, F.; Wolf, R. N.; Zuber, K.

    2013-11-01

    Recent results from a measurement campaign studying the isomerism in neutron-deficient Tl isotopes are presented. The measurements make use of a nuclear spectroscopy setup coupled to the high-resolution Penning-trap mass spectrometer ISOLTRAP at CERN's radioactive ion-beam facility ISOLDE. The mass values of 190,194Tl are improved and a mass-spin-state assignment is carried out. An additional mass measurement of the grandparent nuclide 198At allows the deduction of the spin-state ordering in 190Tl. As a result, the excitation energies of the isomers in both Tl isotopes are determined for the first time to Eex(194Tl)=260(15) keV and Eex(190Tl)=89(12) keV. Furthermore, this allows anchoring of the ground-state and isomer masses of 194Bi, 202Fr, and 206Ac, which are linked by two independent α-decay chains.

  15. Response of great horned owls given the optical isomers of ketamine.

    PubMed

    Redig, P T; Larson, A A; Duke, G E

    1984-01-01

    The relative anesthetic effects of the 2 purified isomers and the racemic mixture of ketamine were compared in 6 great horned owls (Bubo virginianus), a species in which racemic ketamine is poorly tolerated. Other investigators have reported that the L(-) form is only a 3rd as potent as the D(+) form with respect to analgesic action in mammals. Accordingly, the racemic and the - forms were given at 2 X and 3 X, respectively, the dose of the + form in an attempt to achieve a potentially equivalent state of anesthesia. At these dose levels, there was no difference observed in the average duration of anesthesia with the 3 ketamine preparations. The - isomer yielded a poorer anesthetic response characterized by inadequate muscle relaxation, cardiac arrhythmias, and marked excitatory behavior during recovery. With the dosages used, the + form and the racemate were comparable in degree of muscle relaxation produced. The + form yielded smoother inductions and less cardiac arrhythmia than did the racemate. PMID:6703445

  16. Preferential Isomer Formation Observed in H3+ + CO by Crossed Beam Imaging

    PubMed Central

    2016-01-01

    The proton transfer reaction H3+ + CO is one of the cornerstone chemical processes in the interstellar medium. Here, the dynamics of this reaction have been investigated using crossed beam velocity map imaging. Formyl product cations are found to be predominantly scattered into the forward direction irrespective of the collision energy. In this process, a high amount of energy is transferred to internal product excitation. By fitting a sum of two distribution functions to the measured internal energy distributions, the product isomer ratio is extracted. A small HOC+ fraction is obtained at a collision energy of 1.8 eV, characterized by an upper limit of 24% with a confidence level of 84%. At lower collision energies, the data indicate purely HCO+ formation. Such low values are unexpected given the previously predicted efficient formation of both HCO+ and HOC+ isomers for thermal conditions. This is discussed in light of the direct reaction dynamics that are observed. PMID:27352138

  17. Experimental and computational investigation of the thermochemistry of the six isomers of dichloroaniline.

    PubMed

    Ribeiro da Silva, Manuel A V; Amaral, Luísa M P F; Gomes, José R B

    2006-07-27

    The standard (p(o) = 0.1 MPa) molar enthalpies of formation of 2,3-, 2,4-, 2,5-, 2,6-, 3,4- and 3,5-dichloroanilines were derived from the standard molar energies of combustion, in oxygen, to yield CO(2)(g), N(2)(g) and HCl.600H(2)O(l), at T = 298.15 K, measured by rotating bomb combustion calorimetry. The Calvet high-temperature vacuum sublimation technique was used to measure the enthalpies of sublimation of the six isomers. These two thermodynamic parameters yielded the standard molar enthalpies of formation of the six isomers of dichloroaniline, in the gaseous phase, at T = 298.15 K. The gas-phase enthalpies of formation were also estimated by G3MP2B3 calculations, which were further extended to the computation of gas-phase acidities, proton affinities, and ionization enthalpies. PMID:16854047

  18. Polymerization of the E and Z Isomers of Bis-(Triethoxysilyl)-2-Butene

    SciTech Connect

    Carpenter, J.P. Dorhout, K.; Loy, D.A.; Shaltout, R.M.; Shea, K.J.

    1999-05-11

    We have synthesized the Z and E isomers of 1,4-bis(triethoxysilyl)-2- butene and polymerized them under acid and base catalyzed sol-gel conditions. As expected the E system formed crosslinked, insoluble gels. The Z isomer, by nature of its geometry, formed high molecular weight, soluble polymeric products under acidic conditions. We were able to prepare and isolate both the cyclic disilsesquioxane monomer, and its dimer. Comparison of their spectral characterization with that of the soluble polymers suggests that the cyclics are present within the polymers. lle synthesis of a dimer likely present at some early stage of the polymerization suggests that we may be able to control the reaction and form rigid polymers with controllable tacticity. In addition, most of the gels were found to be non-porous indicating that the gels were, in fact, more compliant than ethenylene-bridged polysilsesquioxanes leading to collapse of pores during drying.

  19. Site-Specific Mapping of Sialic Acid Linkage Isomers by Ion Mobility Spectrometry.

    PubMed

    Guttman, Miklos; Lee, Kelly K

    2016-05-17

    Detailed structural elucidation of protein glycosylation is a tedious process often involving several techniques. Glycomics and glycoproteomics approaches with mass spectrometry offer a rapid platform for glycan profiling but are limited by the inability to resolve isobaric species such as linkage and positional isomers. Recently, ion mobility spectrometry (IMS) has been shown to effectively resolve isobaric oligosaccharides, but the utility of IMS to obtain glycan structural information on a site-specific level with proteomic analyses has yet to be investigated. Here, we report that the addition of IMS to conventional glycoproteomics platforms adds additional information regarding glycan structure and is particularly useful for differentiation of sialic acid linkage isomers on both N- and O-linked glycopeptides. With further development IMS may hold the potential for rapid and complete structural elucidation of glycan chains at a site-specific level. PMID:27089023

  20. Cage connectivity and frontier π orbitals govern the relative stability of charged fullerene isomers

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Díaz-Tendero, Sergio; Alcamí, Manuel; Martín, Fernando

    2015-11-01

    Fullerene anions and cations have unique structural, electronic, magnetic and chemical properties that make them substantially different from neutral fullerenes. Although much theoretical effort has been devoted to characterizing and predicting their properties, this has been limited to a fraction of isomeric forms, mostly for fullerene anions, and has practically ignored fullerene cations. Here we show that the concepts of cage connectivity and frontier π orbitals allow one to understand the relative stability of charged fullerene isomers without performing elaborate quantum chemistry calculations. The latter is not a trivial matter, as the number of possible isomers for a medium-sized fullerene is many more than 100,000. The model correctly predicts the structures observed experimentally and explains why the isolated pentagon rule is often violated for fullerene anions, but the opposite is found for fullerene cations. These predictions are relevant in fields as diverse as astrophysics, electrochemistry and supramolecular chemistry.

  1. Cage connectivity and frontier π orbitals govern the relative stability of charged fullerene isomers.

    PubMed

    Wang, Yang; Díaz-Tendero, Sergio; Alcamí, Manuel; Martín, Fernando

    2015-11-01

    Fullerene anions and cations have unique structural, electronic, magnetic and chemical properties that make them substantially different from neutral fullerenes. Although much theoretical effort has been devoted to characterizing and predicting their properties, this has been limited to a fraction of isomeric forms, mostly for fullerene anions, and has practically ignored fullerene cations. Here we show that the concepts of cage connectivity and frontier π orbitals allow one to understand the relative stability of charged fullerene isomers without performing elaborate quantum chemistry calculations. The latter is not a trivial matter, as the number of possible isomers for a medium-sized fullerene is many more than 100,000. The model correctly predicts the structures observed experimentally and explains why the isolated pentagon rule is often violated for fullerene anions, but the opposite is found for fullerene cations. These predictions are relevant in fields as diverse as astrophysics, electrochemistry and supramolecular chemistry. PMID:26492014

  2. Aminophenol isomers unraveled by conformer-specific far-IR action spectroscopy.

    PubMed

    Yatsyna, Vasyl; Bakker, Daniël J; Feifel, Raimund; Rijs, Anouk M; Zhaunerchyk, Vitali

    2016-02-17

    Spectroscopic studies of molecular structure can strongly benefit from extending the conventional mid-IR range to the far-IR and THz regions, as low-frequency molecular vibrations provide unique fingerprints and high sensitivity to intra- and intermolecular interactions. In this work, the gas-phase conformer specific far-IR spectra of aminophenol isomers, recorded in the spectral range of 220-800 cm(-1) at the free-electron laser laboratory FELIX in Nijmegen (the Netherlands), are reported. Many distinct far-IR vibrational signatures which are specific for the molecular structure of the different aminophenol isomers are revealed and assigned. The observed far-IR transitions of the NH2 wagging (inversion) motion have been treated with a double-minimum harmonic well potential model that has enabled us to obtain the inversion barrier values. Moreover, we discuss the limitations and capability of conventional DFT frequency calculations to describe the far-IR vibrational modes. PMID:26854118

  3. Deformation increase of high-spin core-excited isomers in the astatine nuclei

    SciTech Connect

    Scheveneels, G.; Hardeman, F.; Neyens, G.; Coussement, R. )

    1991-06-01

    Quadrupole moments of six high-spin isomers in the At isotopes have been measured with the level-mixing-spectroscopy method: {sup 208}At(16{sup {minus}}), {sup 209}At(29/2{sup +}), {sup 210}At(19{sup +},15{sup {minus}}), {sup 211}At(39/2{sup {minus}},29/2{sup +}). The results show that level mixing spectroscopy is a promising technique to determine quadrupole moments of isomers that are difficult to measure by other in-beam hyperfine interaction methods. A large increase of the quadrupole moment is observed if neutrons are excited across or removed from the {ital N}=126 shell closure. This behavior is explained in terms of an enhanced core softness for fewer core neutrons; the aligned valence particles, moving in equatorial orbits, then easily polarize the core towards oblate deformation.

  4. Identification of an {alpha}-decaying (9{sup -}) isomer in {sup 216}Fr

    SciTech Connect

    Kurcewicz, J.; Karny, M.; Korgul, A.; Kurcewicz, W.; Kurpeta, J.; Lewandowski, S.; Majorkiewicz, P.; Plochocki, A.; Wojtasiewicz, A.; Czarnacki, W.; Kasztelan, M.; Kisielinski, M.; Penttilae, H.; Roussiere, B.; Steczkiewicz, O.

    2007-11-15

    The {alpha} decay of the trans-lead isotopes {sup 212}At, {sup 216}Fr, and {sup 220}Ac was investigated by using mass-separated sources and analog as well as digital signal processing. By measuring {alpha}-{alpha} time correlations evidence was obtained for the occurrence of an {alpha}-decaying (9{sup -}) isomer in {sup 216}Fr. The {alpha}-decay energy and half-life amount to 9000(5) keV and 850(30) ns, respectively. The excitation energy of the isomer is compared with shell-model predictions for the high-spin members of the {pi}(h{sub 9/2}){nu}(g{sub 9/2}) multiplet, and the relevance of the new data concerning the search for reflection asymmetry is presented.

  5. High-K isomers in transactinide nuclei close to N = 162

    SciTech Connect

    Prassa, V. Nikšić, T.; Vretenar, D.; Lu, Bing-Nan; Ackermann, D.

    2015-10-15

    Transactinide nuclei around neutron number N = 162 display axially deformed equilibrium shapes, as shown in our previous analysis [1] of constrained mean-field energy surfaces and collective excitation spectra. In the present study we are particularly interested in the occurrence of high-K isomers in the axially deformed isotopes of Rf (Z = 104), Sg (Z = 106), Hs (Z = 108), and Ds (Z = 110), with neutron number N = 160 − 166 and the effect of the N=162 closure on the structure and distribution of two-quasiparticle (2qp) states. The evolution of high-K isomers is analysed in a self-consistent axially-symmetric relativistic Hartree-Bogoliubov calculation using the blocking approximation with time-reversal symmetry breaking.

  6. Enhancement in fecal excretion of dioxin isomer in mice by several dietary fibers.

    PubMed

    Aozasa, O; Ohta, S; Nakao, T; Miyata, H; Nomura, T

    2001-10-01

    The effect of increased nutrients (protein, lipid, vitamins and minerals) on dioxin-induced toxic manifestations such as immune suppression, hepatic hypertrophy, splenic atrophy and enzyme induction was investigated in mice after oral administration of 1,2,3,4,7,8-HxCDD (HxCDD) as one of a representative compound of dioxin isomers. Consequently, it appeared that increased minerals and vitamins in the diet prevented immune suppression by HxCDD. In addition, to clarify the additive effect of nutrients and the ability to hasten the excretion of dioxins by dietary fiber, the adsorbing of dioxins by 16 dietary fibers was investigated by in vitro experiment. Among 16 dietary fibers, locust bean gum, pectin, alginic acid, guar gum, chitin and cellulose were effective in binding dioxin isomers. These dietary fibers also enhanced the fecal excretion of HxCDD in mice. PMID:11572611

  7. Thermochemical stabilities and vibrational spectra of isomers of the chlorine oxide dimer

    NASA Technical Reports Server (NTRS)

    Mcgrath, M. P.; Clemitshaw, K. C.; Rowland, F. S.; Hehre, W. J.

    1988-01-01

    Molecular orbital calculations were performed to determine the relative thermochemical stabilities and IR vibrational spectra of isomers of the ClO dimer. Two straight-chain isomers (ClOOCl and ClOClO) and one branched species (ClClO2) were identified as energy minima on the Cl2O2 potential surface. It is shown that ClOOCl and ClClO2 are comparable in terms of stability, while ClOClO is about 11 kcal/mol higher in energy. The IR spectra obtained by Molina and Molina (1987) as a result of the reaction of chlorine atoms with ClO precursors are consistent with the production of the two most stable forms of Cl2O2.

  8. Exclusive accumulation of Z-isomers of monolignols and their glucosides in bark of Fagus grandifolia

    NASA Technical Reports Server (NTRS)

    Lewis, N. G.; Inciong, E. J.; Ohashi, H.; Towers, G. H.; Yamamoto, E.

    1988-01-01

    In addition to Z-coniferyl and Z-sinapyl alcohols, bark extracts of Fagus grandifolia also contain significant amounts of the glucosides, Z-coniferin, Z-isoconiferin (previously called faguside) and Z-syringin. The corresponding E-isomers of these glucosides do not accumulate to a detectable level. The accumulation of the Z-isomers suggests that either they are not lignin precursors or that they are reservoirs of monolignols for subsequent lignin biosynthesis; it is not possible to distinguish between these alternatives. The co-occurrence of Z-coniferin and Z-isoconiferin demonstrate that glucosylation of monolignols can occur at either the phenolic or the allylic hydroxyl groups.

  9. Large-scale shell model study of the newly found isomer in 136La

    NASA Astrophysics Data System (ADS)

    Teruya, E.; Yoshinaga, N.; Higashiyama, K.; Nishibata, H.; Odahara, A.; Shimoda, T.

    2016-07-01

    The doubly-odd nucleus 136La is theoretically studied in terms of a large-scale shell model. The energy spectrum and transition rates are calculated and compared with the most updated experimental data. The isomerism is investigated for the first 14+ state, which was found to be an isomer in the previous study [Phys. Rev. C 91, 054305 (2015), 10.1103/PhysRevC.91.054305]. It is found that the 14+ state becomes an isomer due to a band crossing of two bands with completely different configurations. The yrast band with the (ν h11/2 -1⊗π h11 /2 ) configuration is investigated, revealing a staggering nature in M 1 transition rates.

  10. Separation of the isomers of benzene poly(carboxylic acid)s by quaternary ammonium salt via formation of deep eutectic solvents.

    PubMed

    Hou, Yucui; Li, Jian; Ren, Shuhang; Niu, Muge; Wu, Weize

    2014-11-26

    Because of similar properties and very low volatility, isomers of benzene poly(carboxylic acid)s (BPCAs) are very difficult to separate. In this work, we found that isomers of BPCAs could be separated efficiently by quaternary ammonium salts (QASs) via formation of deep eutectic solvents (DESs). Three kinds of QASs were used to separate the isomers of BPCAs, including the isomers of benzene tricarboxylic acids (trimellitic acid, trimesic acid, and hemimellitic acid) and the isomers of benzene dicarboxylic acids (phthalic acid and isophthalic acid). Among the QASs, tetraethylammonium chloride was found to have the best performance, which could completely separate BPCA isomers in methyl ethyl ketone solutions. It was found that the hydrogen bond forming between QAS and BPCA results in the selective separation of BPCA isomers. QAS in DES was regenerated effectively by the antisolvent method, and the regenerated QAS was reused four times with the same high efficiency. PMID:25351281

  11. Discrimination of nuclear spin isomers exploiting the excited state dynamics of a quinodimethane derivative

    SciTech Connect

    Obaid, Rana; Kinzel, Daniel; Oppel, Markus González, Leticia

    2014-10-28

    Despite the concept of nuclear spin isomers (NSIs) exists since the early days of quantum mechanics, only few approaches have been suggested to separate different NSIs. Here, a method is proposed to discriminate different NSIs of a quinodimethane derivative using its electronic excited state dynamics. After electronic excitation by a laser field with femtosecond time duration, a difference in the behavior of several quantum mechanical operators can be observed. A pump-probe experimental approach for separating these different NSIs is then proposed.

  12. High-spin isomers in some of the heaviest nuclei: Spectra, decays, and population

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Scheid, W.

    2010-02-15

    The isotopic dependence of two-quasiparticle isomeric states in Fm and No is treated for future experiments. The population of the isomeric states in evaporation residues is considered. In several even isotopes of Rf, Sg, Hs, and Ds, the K isomers and their decay modes are predicted. An alpha-decay chain through the isomeric states of superheavy nuclei is demonstrated for the first time and proposed for the experimental verification.

  13. Retinal isomer composition in some bacteriorhodopsin mutants under light and dark adaptation conditions

    SciTech Connect

    Song, L.; Yang, D.; El-Sayed, M.A.; Lanyi, J.K.

    1995-06-15

    The isomeric composition of retinal was measured in a number of bacteriorhodopsin (bR) mutants (D85N, D212N, R82A, Y185F, and D115N) under various conditions, using a rapid retinal extraction technique followed by HPLC analysis. Besides the 13-cis and the all-trans retinal isomers observed in wild type (wt) bR under physiological conditions, the 11-cis and 9-cis retinal isomers were observed in variable but minor amounts in the bR mutants. In addition, the values of the equilibrium constant at two temperatures and the enthalpy change for the all-trans to 13-cis isomerization process in the dark-adapted state of D212N, D85N, deionized blue bR, and wt bR were determined. We find that perturbation of the retinal cavity (pocket) by residue replacement changes the relative thermal stability of the different retinal isomers, allowing for thermal-and/or photoisomerization of the retinal chromophore along C{sub 9}-C{sub 10} and C{sub 11}-C{sub 12} bonds to moderately compete with the isomerization around the C{sub 13}-C{sub 14} bond. The bR mutants expressed in Halobacterium salinarium studied in the present work showed normal 13-cis to all-trans light adaptation, in contrast with abnormal all-trans to 13-cis light adaptation observed for D212E, D212A, and D212N expressed in Escherichia coli, suggesting an influence of the purple membrane lattice and/or the lipids on the stability of the different retinal isomers within the protein. 38 refs., 2 tabs.

  14. Investigation of HNCO Isomer Formation in Ice Mantles by UV and Thermal Processing: An Experimental Approach

    NASA Astrophysics Data System (ADS)

    Jiménez-Escobar, A.; Giuliano, B. M.; Muñoz Caro, G. M.; Cernicharo, J.; Marcelino, N.

    2014-06-01

    Current gas-phase models do not account for the abundances of HNCO isomers detected in various environments, suggesting their formation in icy grain mantles. We attempted to study a formation channel of HNCO and its possible isomers by vacuum-UV photoprocessing of interstellar ice analogs containing H2O, NH3, CO, HCN, CH3OH, CH4, and N2 followed by warm-up under astrophysically relevant conditions. Only the H2O:NH3:CO and H2O:HCN ice mixtures led to the production of HNCO species. The possible isomerization of HNCO to its higher energy tautomers following irradiation or due to ice warm-up has been scrutinized. The photochemistry and thermal chemistry of H2O:NH3:CO and H2O:HCN ices were simulated using the Interstellar Astrochemistry Chamber, a state-of-the-art ultra-high-vacuum setup. The ice was monitored in situ by Fourier transform mid-infrared spectroscopy in transmittance. A quadrupole mass spectrometer detected the desorption of the molecules in the gas phase. UV photoprocessing of H2O:NH3:CO and H2O:HCN ices lead to the formation of OCN- as a main product in the solid state and a minor amount of HNCO. The second isomer HOCN has been tentatively identified. Despite its low efficiency, the formation of HNCO and the HOCN isomers by UV photoprocessing of realistic simulated ice mantles might explain the observed abundances of these species in photodissociation regions, hot cores, and dark clouds.

  15. Low and High Temperature Combustion Chemistry of Butanol Isomers in Premixed Flames and Autoignition Systems

    SciTech Connect

    Sarathy, S M; Pitz, W J; Westbrook, C K; Mehl, M; Yasunaga, K; Curran, H J; Tsujimura, T; Osswald, P; Kohse-Hoinghaus, K

    2010-12-12

    Butanol is a fuel that has been proposed as a bio-derived alternative to conventional petroleum derived fuels. The structural isomer in traditional 'bio-butanol' fuel is n-butanol, but newer conversion technologies produce iso-butanol as a fuel. In order to better understand the combustion chemistry of bio-butanol, this study presents a comprehensive chemical kinetic model for all the four isomers of butanol (e.g., 1-, 2-, iso- and tert-butanol). The proposed model includes detailed high temperature and low temperature reaction pathways. In this study, the primary experimental validation target for the model is premixed flat low-pressure flame species profiles obtained using molecular beam mass spectrometry (MBMS). The model is also validated against previously published data for premixed flame velocity and n-butanol rapid compression machine and shock tube ignition delay. The agreement with these data sets is reasonably good. The dominant reaction pathways at the various pressures and temperatures studied are elucidated. At low temperature conditions, we found that the reaction of alphahydroxybutyl with O{sub 2} was important in controlling the reactivity of the system, and for correctly predicting C{sub 4} aldehyde profiles in low pressure premixed flames. Enol-keto isomerization reactions assisted by HO{sub 2} were also found to be important in converting enols to aldehydes and ketones in the low pressure premixed flames. In the paper, we describe how the structural features of the four different butanol isomers lead to differences in the combustion properties of each isomer.

  16. Regiospecific formation of cobamide isomers is directed by CobT.

    PubMed

    Crofts, Terence S; Hazra, Amrita B; Tran, Jennifer L A; Sokolovskaya, Olga M; Osadchiy, Vadim; Ad, Omer; Pelton, Jeffrey; Bauer, Stefan; Taga, Michiko E

    2014-12-16

    Cobamides, which include vitamin B₁₂ (cobalamin), are a class of modified tetrapyrroles synthesized exclusively by prokaryotes that function as cofactors for diverse biological processes. Cobamides contain a centrally bound cobalt ion that coordinates to upper and lower axial ligands. The lower ligand is covalently linked to a phosphoribosyl moiety through an alpha-glycosidic bond formed by the CobT enzyme. CobT can catalyze the phosphoribosylation of a variety of substrates. We investigated the ability of CobT to act on either of two nitrogen atoms within a single, asymmetric benzimidazole substrate to form two isomeric riboside phosphate products. Reactions containing asymmetric benzimidazoles as substrates for homologues of CobT from different bacteria resulted in the production of distinct ratios of two isomeric products, with some CobT homologues favoring the production of a single isomer and others forming a mixture of products. These preferences were reflected in the production of cobamide isomers with lower ligands attached in different orientations, some of which are novel cobamides that have not been characterized previously. Two isomers of methoxybenzimidazolylcobamide were found to be unequal in their ability to support ethanolamine ammonia-lyase dependent growth in Salmonella enterica, suggesting that CobT's regiospecificity could be biologically important. We also observed differences in pKa, which can influence the reactivity of the cofactor and could contribute to these distinct biological activities. Relaxed regiospecificity was achieved by introducing a single point mutation in an active site residue of CobT. These new cobamide isomers could be used to probe the mechanisms of cobamide-dependent enzymes. PMID:25412146

  17. Synthesis of defined endocrine-disrupting nonylphenol isomers for biological and environmental studies.

    PubMed

    Boehme, Roswitha M; Andries, Thomas; Dötz, Karl Heinz; Thiele, Bjoern; Guenther, Klaus

    2010-08-01

    Nonylphenols are very important environmentally relevant substances in the focus of the world-wide endocrine disrupter research for over 25 years. Thus, they are among the 10 priority hazardous substances of the new European Union Water Framework Directive. They consist of a very complex mixture of isomers representing therefore a multi-component problem like dioxins or PCBs. As estrogenic effect and degradation behavior in the environment of individual 4-nonylphenols are heavily dependent on the structure and bulkiness of the side chain, it is absolutely necessary to consider the nonylphenol problem from an isomer-specific viewpoint. Therefore a range of 28 differently branched nonylphenol isomers were synthesized for biological and environmental studies. Nonylphenols with a quaternary alpha-carbon, like 4-(1,1,3,4-tetramethylpentyl)phenol (4-NP(95)) and 4-(1-ethyl-1,3,3-trimethylbutyl)phenol (4-NP(170)), were obtained by Friedel-Crafts alkylation of anisole with tertiary nonyl bromides and demethylation with BI(3). Nonylphenols with a tertiary alpha-carbon, such as 4-(1,2-dimethylheptyl)phenol (4-NP(10)) and 4-(1,2,4-trimethylhexyl)phenol (4-NP(41)), were accessible via coupling of p-methoxyphenylmagnesium bromide with ketones. Nonylphenols bearing a quaternary beta-carbon, like 4-(2,2-dimethylheptyl)phenol (4-NP(15)) and 4-(1,2,2-trimethylhexyl)phenol (4-NP(39)), were synthesized starting from 4'-methoxyisobutyrophenone. The compounds were characterized by GC-MS and NMR-spectroscopy. The individual isomers were designated according to the Juelich Nomenclature. PMID:20452641

  18. Investigation of HNCO isomer formation in ice mantles by UV and thermal processing: An experimental approach

    SciTech Connect

    Jiménez-Escobar, A.; Giuliano, B. M.; Caro, G. M. Muñoz; Cernicharo, J.; Marcelino, N.

    2014-06-10

    Current gas-phase models do not account for the abundances of HNCO isomers detected in various environments, suggesting their formation in icy grain mantles. We attempted to study a formation channel of HNCO and its possible isomers by vacuum-UV photoprocessing of interstellar ice analogs containing H{sub 2}O, NH{sub 3}, CO, HCN, CH{sub 3}OH, CH{sub 4}, and N{sub 2} followed by warm-up under astrophysically relevant conditions. Only the H{sub 2}O:NH{sub 3}:CO and H{sub 2}O:HCN ice mixtures led to the production of HNCO species. The possible isomerization of HNCO to its higher energy tautomers following irradiation or due to ice warm-up has been scrutinized. The photochemistry and thermal chemistry of H{sub 2}O:NH{sub 3}:CO and H{sub 2}O:HCN ices were simulated using the Interstellar Astrochemistry Chamber, a state-of-the-art ultra-high-vacuum setup. The ice was monitored in situ by Fourier transform mid-infrared spectroscopy in transmittance. A quadrupole mass spectrometer detected the desorption of the molecules in the gas phase. UV photoprocessing of H{sub 2}O:NH{sub 3}:CO and H{sub 2}O:HCN ices lead to the formation of OCN{sup –} as a main product in the solid state and a minor amount of HNCO. The second isomer HOCN has been tentatively identified. Despite its low efficiency, the formation of HNCO and the HOCN isomers by UV photoprocessing of realistic simulated ice mantles might explain the observed abundances of these species in photodissociation regions, hot cores, and dark clouds.

  19. A highly aluminum-doped β-isomer Keggin-type tungstoaluminate.

    PubMed

    Han, Zhangang; Zhang, Huixia; Yan, Jinshuang; Zhai, Xueliang

    2016-09-28

    A trialuminum-substituted β-isomer Keggin-type tungstoaluminate was synthesized and characterized, in which the pure metal-oxygen cluster [AlW8.5Al0.5{Al(OH2)}3(OH)3O34](6.5-) consists of three kinds of aluminum sites: the central Al(1), the doped Al(5), and the substituted Al(2) and Al(3) centers. PMID:27549221

  20. PARTICLE-HOLE NATURE OF THE LIGHT HIGH-SPIN TOROIDAL ISOMERS

    SciTech Connect

    Staszczak, A.; Wong, Cheuk-Yin

    2015-01-01

    Nuclei under non-collective rotation with a large angular momentum above some threshold can assume a toroidal shape. In our previous work, we showed by using cranked Skyrme Hartree Fock approach that even even, N = Z, high-K, toroidal isomeric states may have general occurrences for light nuclei with 28 < A < 52. We present here some additional results and systematics on the particle-hole nature of these high-spin toroidal isomers.