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Sample records for 57fe isomer shifts

  1. 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.

  2. Theoretical 57Fe Mössbauer spectroscopy: isomer shifts of [Fe]-hydrogenase intermediates.

    PubMed

    Hedegård, Erik Donovan; Knecht, Stefan; Ryde, Ulf; Kongsted, Jacob; Saue, Trond

    2014-03-14

    Mössbauer spectroscopy is an indispensable spectroscopic technique and analytical tool in iron coordination chemistry. The linear correlation between the electron density at the nucleus ("contact density") and experimental isomer shifts has been used to link calculated contact densities to experimental isomer shifts. Here we have investigated relativistic methods of systematically increasing sophistication, including the eXact 2-Component (X2C) Hamiltonian and a finite-nucleus model, for the calculation of isomer shifts of iron compounds. While being of similar accuracy as the full four-component treatment, X2C calculations are far more efficient. We find that effects of spin-orbit coupling can safely be neglected, leading to further speedup. Linear correlation plots using effective densities rather than contact densities versus experimental isomer shift lead to a correlation constant a = -0.294 a0(-3) mm s(-1) (PBE functional) which is close to an experimentally derived value. Isomer shifts of similar quality can thus be obtained both with and without fitting, which is not the case if one pursues a priori a non-relativistic model approach. As an application for a biologically relevant system, we have studied three recently proposed [Fe]-hydrogenase intermediates. The structures of these intermediates were extracted from QM/MM calculations using large QM regions surrounded by the full enzyme and a solvation shell of water molecules. We show that a comparison between calculated and experimentally observed isomer shifts can be used to discriminate between different intermediates, whereas calculated atomic charges do not necessarily correlate with Mössbauer isomer shifts. Detailed analysis reveals that the difference in isomer shifts between two intermediates is due to an overlap effect.

  3. Uncertainty budget for determinations of mean isomer shift from Mössbauer spectra

    NASA Astrophysics Data System (ADS)

    Fock, Jeppe; Bogart, Lara Katrina; Posth, Oliver; Hansen, Mikkel Fougt; Pankhurst, Quentin A.; Frandsen, Cathrine

    2016-12-01

    The magnetite/maghemite content within iron oxide nanoparticles can be determined using the mean isomer shift (overline {δ }). However, accurate characterisation of the composition is limited by the uncertainty associated with overline {δ }. We have identified four independent sources of uncertainty and developed a quantitative expression for the uncertainty budget. Sources of uncertainty are categorised as follows: that from the fitting of the Mössbauer spectrum ( σ fit), that of the calibration of the α-Fe reference spectrum ( σ cal), thermal corrections to the spectrum due to second order Doppler shift (SODS) ( σ Δ δ ) and other experimental errors ( σ err). Each contribution is discussed in detail using 57Fe Mössbauer spectra obtained from an iron oxide nanoparticle system at temperatures between 16 K and 295 K on different spectrometers in two different laboratories.

  4. 57Fe Mössbauer study of Lu2Fe3Si5 iron silicide superconductor

    DOE PAGES

    Ma, Xiaoming; Ran, Sheng; Pang, Hua; ...

    2015-03-28

    With the advent of Fe–As based superconductivity it has become important to study how superconductivity manifests itself in details of 57Fe Mössbauer spectroscopy of conventional, Fe-bearing superconductors. The iron-based superconductor Lu2Fe3Si5 has been studied by 57Fe Mössbauer spectroscopy over the temperature range from 4.4 K to room temperature with particular attention to the region close to the superconducting transition temperature (Tc=6.1 K). Consistent with the two crystallographic sites for Fe in this structure, the observed spectra appear to have a pattern consisting of two doublets over the whole temperature range. Furthermore, the value of Debye temperature was estimated from temperaturemore » dependence of the isomer shift and the total spectral area and compared with the specific heat capacity data. Neither abnormal behavior of the hyperfine parameters at or near Tc, nor phonon softening were observed.« less

  5. Electronic structure and isomer shifts of neptunium compounds

    NASA Astrophysics Data System (ADS)

    Svane, A.; Petit, L.; Temmerman, W. M.; Szotek, Z.

    2002-08-01

    The electronic structures of αNp metal and 28 Np compounds are calculated with the generalized gradient approximation to density-functional theory, implemented with the full-potential linear-muffin-tin-orbital method. The calculations are compared to experimental isomer shifts providing a calibration of the 237Np isomeric transition with a value of Δ=(-40.1+/-1.3)×10- 3 fm2 for the difference in nuclear radius between the excited isomeric level and the ground state. The isomer shift is primarily determined by the chemical environment. Decreasing the volume, either by external or chemical pressure, causes an f-->s+d charge transfer on Np, which leads to a higher electron contact density. The possible f-electron localization in Np compounds is discussed using self-interaction corrections, and it is concluded that f-electron localization has only a minor influence on the isomer shift.

  6. Systematic trends in the237neptunium Mössbauer isomer shift: Overlap of IV, V and VI neptunium oxidation states and correlation between isomer shift and crystal structure

    NASA Astrophysics Data System (ADS)

    Jové, J.; Cousson, A.; Abazli, H.; Tabuteau, A.; Thévenin, T.; Pagès, M.

    1988-01-01

    The influence of the neptunium ion environment on the237Np Mössbauer isomer shifts has been studied in various metal coordination complexes: fluorides, oxides, oxide fluorides and polycarboxylates. A linear dependence between the isomer shift and the mean neptunium-ligand distance in a series of hexavalent Np compounds has been evidenced and the feasibility of overlapped isomer shift areas, namely Np(IV), Np(V) and Np(VI) has been established.

  7. Study of 57 Fe Mössbauer effect in RFe2Zn20 ( R = Lu, Yb, Gd)

    DOE PAGES

    Bud’ko, Sergey L.; Kong, Tai; Ma, Xiaoming; ...

    2015-08-04

    In this document we report measurements of 57Fe Mössbauer spectra for RFe2Zn20 (R = Lu, Yb, Gd) from ~ 4.5 K to room temperature. The obtained isomer shift values are very similar for all three compounds, their temperature dependence was analyzed within the Debye model and resulted in an estimate of the Debye temperatures of 450-500 K. The values of quadrupole splitting at room temperature change with the cubic lattice constant a in a linear fashion. For GdFe2Zn20, ferromagnetic order is seen as an appearance of a sextet in the spectra. The 57Fe site hyperfine field for T → 0more » was evaluated to be ~ 2.4 T.« less

  8. Study of 57Fe Mössbauer effect in RFe2Zn20 ( R = Lu, Yb, Gd)

    DOE PAGES

    Bud’ko, Sergey L.; Kong, Tai; Ma, Xiaoming; ...

    2015-08-04

    In this document we report measurements of 57Fe Mössbauer spectra for RFe2Zn20 (R = Lu, Yb, Gd) from ~ 4.5 K to room temperature. The obtained isomer shift values are very similar for all three compounds, their temperature dependence was analyzed within the Debye model and resulted in an estimate of the Debye temperatures of 450-500 K. The values of quadrupole splitting at room temperature change with the cubic lattice constant a in a linear fashion. For GdFe2Zn20, ferromagnetic order is seen as an appearance of a sextet in the spectra. The 57Fe site hyperfine field for T → 0more » was evaluated to be ~ 2.4 T.« less

  9. /sup 57/Fe Mossbauer spectroscopy of U/sub 6/Fe

    SciTech Connect

    Lemon, G.; Boolchand, P.; Stevens, M.; DeLong, L.E.; Huber, J.G.; Marcuso, M.

    1986-04-01

    Samples of U/sub 6/Fe were prepared by arc melting U and enriched /sup 57/Fe. The samples display superconducting transitions which are sensitive to long-term exposure to air. Room temperature spectra of U/sub 6/Fe typically display a majority site A (quadrupole splitting ..delta.. = 0.749(3) mm/s, isomer shift delta = 0.482(6) mm/s relative to Cu) and a minority site B (..delta.. = 0.55(3) mm/s, sigma = 0.12(3) mm/s) with the site intensity ratio (I/sub B//I/sub A/) typically 0.05 to 0.10. The I/sub B//I/sub A/ intensity ratio increases upon air exposure of the samples. We have studied Moessbauer spectra as a function of temperature T in the range 15/sup 0/K less than or equal to T less than or equal to 310/sup 0/K paying particular attention to the T-variation of the isomer-shift and recoil-free-fraction of the majority site A. Results indicate a consistent softening of lattice vibrations of U/sub 6/Fe at T approx. = 170/sup 0/K.

  10. Mechanically-induced disorder in CaFe2As2: A 57Fe Mössbauer study

    DOE PAGES

    Ma, Xiaoming; Ran, Sheng; Canfield, Paul C.; ...

    2015-10-17

    57Fe Mössbauer spectroscopy was used to perform a microscopic study on the extremely pressure and strain sensitive compound, CaFe2As2, with different degrees of strain introduced by grinding and annealing. At the base temperature, in the antiferromagnetic/orthorhombic phase, compared to a sharp sextet Mössbauer spectrum of single crystal CaFe2As2, which is taken as an un-strained sample, an obviously broadened sextet and an extra doublet were observed for ground CaFe2As2 powders with different degrees of strain. The Mössbauer results suggest that the magnetic phase transition of CaFe2As2 can be inhomogeneously suppressed by the grinding induced strain to such an extent that themore » antiferromagnetic order in parts of the grains forming the powdered sample remain absent all the way down to 4.6 K. However, strain has almost no effect on the temperature dependent hyperfine magnetic field in the grains with magnetic order. Additional electronic and asymmetry information was obtained from the isomer shift and quadrupole splitting. Similar isomer shift values in the magnetic phase for samples with different degrees of strain, indicate that the stain does not bring any significant variation of the electronic density at 57Fe nucleus position. As a result, the absolute values of quadrupole shift in the magnetic phase decrease and approach zero with increasing degrees of strain, indicating that the strain reduces the average lattice asymmetry at Fe atom position.« less

  11. 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.

  12. Theoretical investigation of the 67Zn Mössbauer isomer shifts in the zinc chalcogenides

    NASA Astrophysics Data System (ADS)

    Svane, A.; Antoncik, E.

    1986-06-01

    The band structures of the zinc chalcogenides ZnO, ZnS, ZnSe, and ZnTe having the sphalerite crystal structure are calculated. The first-principles linear muffin-tin-orbital-atomic sphere approximation method is employed, in which all solid-state and scalar relativistic effects are taken into account, including the self-consistency of the crystal potential and the charge density. The corresponding electronic configurations are discussed, and the electron contact densities at the zinc nucleus are obtained and compared to experimental isomer-shift data with good agreement. The estimated static charge transfers of the zinc chalcogenides are demonstrated to correlate neatly with the isomer shift. For the first time an accurate value of the calibration constant for the 67Zn isomer transition is derived: ΔR/R=(7.0+/-1.0)×10-4.

  13. 237 Np Mössbauer isomer shifts in neptunium chalcogenides

    NASA Astrophysics Data System (ADS)

    Thévenin, T.; Jové, J.; Pagès, M.

    1984-10-01

    We report237Np Mössbauer spectrometry measurements on some Np polychalcogenides: NpS3, β-NpS2, Np3Se5, NpTe3, α-Np2S3 and γ-Np2Se3. The experiments have been performed at 4.2 K and 77 K. From the isomeric shift values, the oxidation state of the Np ion can easily be assigned in these kinds of compounds: Np(IV) in NpS3, β-NpS2 and Np(III) in NpTe3, α-Np2S3 and γ-Np2 Se3. A mixture of Np(III) and Np(IV) ions has been observed in Np3Se5. Comparisons of the IS values have pointed out the influence of the electronegativity of the chalcogen atom and of the bond length Np- X(X≡ S, Se, Te).

  14. Molecular orbital (MSXα) calculations of s-electron densities of tetrahedrally coordinated ferric iron: Comparison with experimental isomer shifts

    NASA Astrophysics Data System (ADS)

    Tang Kai, A.; Annersten, H.; Ericsson, T.

    1980-04-01

    The MSXα method has been used to calculate the s-electron densities at the nucleus for tetrahedrally coordinated ferric iron, (FeO4)5-, comparing the observed increase in isomer shift values with increasing Fe-O separation. The results give an isomer shift calibration constant of -0.3 (a.u. mm×s-1) assuming a constant ratio for the iron and oxygen sphere radii for the different polyhedra sizes. It is suggested that increasing bonding distances in tetrahedral coordination polyhedra are the dominant factors determining the value of the isomer shifts in Fe-Mg-silicates.

  15. 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.

  16. 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

    2016-05-06

    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.

  17. Quadrupole splitting and isomer shifts in Te oxides investigated using nuclear forward scattering

    NASA Astrophysics Data System (ADS)

    Klobes, Benedikt; Barrier, Nicolas; Vertruyen, Benedicte; Martin, Christine; Hermann, Raphaël P.

    2014-04-01

    Nuclear forward scattering by 125Te is a viable alternative to conventional 125Te Mössbauer spectroscopy avoiding all source related issues. Using reference compounds with known hyperfine parameters and Te oxides exhibiting stereochemically active lone pairs, we show that nuclear forward scattering by 125Te can be reliably used to extract quadrupole splitting energy and relative isomer shift. The rough correlation between Te-Ocoordination and quadrupole splitting energy as put forward by Takeda and Greenwood (J. Chem. Soc. Dalton, 2207, 1975), is corroborated by the presented results.

  18. Theoretical investigation of the isomer shifts of the 119Sn Mössbauer isotope

    NASA Astrophysics Data System (ADS)

    Svane, A.; Antoncik, E.

    1987-04-01

    We solve the electronic structure problem self-consistently for a series of crystalline solids, containing Sn as a component, with the use of the first-principles scalar-relativistic linear muffin-tin-orbital method in the local-density approximation. The crystals considered are the two allotropes α-Sn and β-Sn as well as the compounds SnO2, SnMg2, SnSb, and SnTe. The derived band structure is discussed and compared to previous calculations and experimental information. By extension of the radial integration of the Dirac equation to well within the nuclear regime, the valence-electron contribution to the charge density on the nuclear site is obtained. Excellent agreement is found when comparing with experimental isomer shifts. A value of ΔR/R=(1.34+/-0.07)×10-4 for the relative change of the radius of the 119Sn nucleus upon excitation is deduced. The observed trends in the isomer shifts are interpreted on the basis of the decomposition of the crystal wave function into angular momentum character.

  19. 57 Fe Mössbauer and magnetic studies of Nd3Fe24.5Cr4.5

    NASA Astrophysics Data System (ADS)

    Wang, J. L.; Md Din, M. F.; Campbell, S. J.; Kennedy, S. J.; Yang, F. M.; Wu, G. H.; Dou, S. X.

    2015-04-01

    The structural and magnetic properties of the rare earth transition metal compound Nd 3Fe 24.5Cr 4.5 have been investigated by variable temperature high resolution x-ray diffraction together with DC magnetization and 57Fe Mössbauer effect measurements. The magnetic ordering temperature has been found to be T C= 423(5) K with spin reorientation detected below room temperature around T sr= 158(5) K. Rietveld refinements indicate that Nd 3Fe 24.5Cr 4.5 crystallizes in the Nd 3(Fe,Ti) 29-type structure with the A2/m space group and a substantial magneto-volume effect is detected around T C. The Mössbauer spectra can be fitted well using five sub-spectra. The temperature dependence of the average hyperfine field has been analysed in terms of different power laws of the reduced temperature. The Debye temperature of Nd 3Fe 24.5Cr 4.5 has been determined as 𝜃 D= 400(± 30) K from a fit to the variable temperature isomer shift IS(T).

  20. Transition to collapsed tetragonal phase in CaFe2As2 single crystals as seen by 57Fe Mössbauer spectroscopy

    DOE PAGES

    Bud'ko, Sergey L.; Ma, Xiaoming; Tomić, Milan; ...

    2016-01-21

    Temperature dependent measurements of 57Fe Mössbauer spectra on CaFe2As2 single crystals in the tetragonal and collapsed tetragonal phases are reported. Clear features in the temperature dependencies of the isomer shift, relative spectra area, and quadrupole splitting are observed at the transition from the tetragonal to the collapsed tetragonal phase. From the temperature dependent isomer shift and spectral area data, an average stiffening of the phonon modes in the collapsed tetragonal phase is inferred. The quadrupole splitting increases by ~25% on cooling from room temperature to ~100 K in the tetragonal phase and is only weakly temperature dependent at low temperaturesmore » in the collapsed tetragonal phase, in agreement with the anisotropic thermal expansion in this material. In order to gain microscopic insight about these measurements, we perform ab initio density functional theory calculations of the electric field gradient and the electron density of CaFe2As2 in both phases. By comparing the experimental data with the calculations we are able to fully characterize the crystal structure of the samples in the collapsed-tetragonal phase through determination of the As z coordinate. Furthermore, based on the obtained temperature dependent structural data we are able to propose charge saturation of the Fe-As bond region as the mechanism behind the stabilization of the collapsed-tetragonal phase at ambient pressure.« less

  1. Transition to collapsed tetragonal phase in CaFe2As2 single crystals as seen by 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Bud'ko, Sergey L.; Ma, Xiaoming; Tomić, Milan; Ran, Sheng; Valentí, Roser; Canfield, Paul C.

    2016-01-01

    Temperature dependent measurements of 57Fe Mössbauer spectra on CaFe2As2 single crystals in the tetragonal and collapsed tetragonal phases are reported. Clear features in the temperature dependencies of the isomer shift, relative spectra area, and quadrupole splitting are observed at the transition from the tetragonal to the collapsed tetragonal phase. From the temperature dependent isomer shift and spectral area data, an average stiffening of the phonon modes in the collapsed tetragonal phase is inferred. The quadrupole splitting increases by ˜25 % on cooling from room temperature to ˜100 K in the tetragonal phase and is only weakly temperature dependent at low temperatures in the collapsed tetragonal phase, in agreement with the anisotropic thermal expansion in this material. In order to gain microscopic insight about these measurements, we perform ab initio density functional theory calculations of the electric field gradient and the electron density of CaFe2As2 in both phases. By comparing the experimental data with the calculations we are able to fully characterize the crystal structure of the samples in the collapsed-tetragonal phase through determination of the As z coordinate. Based on the obtained temperature dependent structural data we are able to propose charge saturation of the Fe-As bond region as the mechanism behind the stabilization of the collapsed-tetragonal phase at ambient pressure.

  2. Theoretical investigation of the isomer shift of InSb under pressure

    NASA Astrophysics Data System (ADS)

    Sharma, S.; Dewhurst, J. K.; Nordström, L.; Johansson, B.

    2002-04-01

    The nuclear calibration constant α for 121Sb is calculated from the correlation between the experimental isomer shift (IS) and theoretical contact charge densities. The contact charge densities are calculated using the full-potential linear augmented-plane-wave method, within both the local density and the generalized gradient approximations. The IS for Sb in various phases of InSb under pressure is then calculated. This study shows that before the transition of InSb to a metallic state, the Sb IS becomes more positive with increasing pressure. After each subsequent phase transformation the IS shows a large change in the negative direction. These results used in conjunction with Mössbauer experiments may be useful in identifying phases of InSb at high pressure.

  3. 57Fe Mössbauer study of the chainpur meteorite

    NASA Astrophysics Data System (ADS)

    Elewa, Nancy N.; Cobas, R.; Cadogan, J. M.

    2016-12-01

    The Chainpur meteorite is one of 23 ordinary chondrites classified as LL3-type (low-Fe & low-metal). It was observed as a shower of stones falling on May 9, 1907 in Uttar Pradesh, India. We report here the characterization of the Fe-bearing phases in this chondrite using 57Fe Mössbauer spectroscopy carried out at 298 K, 120 K, 50 K and 13 K. The paramagnetic doublets of olivine and pyroxene dominate the room temperature spectrum, accounting for around 70 % of the spectral area. Moreover, a doublet present with a spectral area of 5 % and assigned to a superparamagnetic Fe 3+ phase is a consequence of terrestrial weathering. On the basis of the measured 57Fe electric quadrupole splitting of the olivine component at room temperature we estimate the mean Fe:Mg ratio in this meteoritic olivine to be around 35:65 % although there is clearly a wide range of composition. The effects of magnetic ordering of the major components olivine and pyroxene are observed at 13 K.

  4. Designing and characterization of Fe(III) complexes of oxydiacetate containing α-diimine as auxiliary ligand: 57Fe-Mössbauer and cyclic voltammetric studies

    NASA Astrophysics Data System (ADS)

    Shahid, M.; Sharma, Prashant K.; Siddiqi, Zafar A.; Sama, Farasha; Ansari, Istikhar A.; Khalid, Mohd.

    2014-04-01

    The newly prepared complexes with stoichiometries [Fe(oda)(phen)Cl] (1), [Fe(oda)(4-picNO)(H2O)Cl)] (2) and [Fe2(oda)2(H2O)2Cl2] (3) [H2oda = oxydiacetic acid, phen = 1,10‧-phenantroline and 4-picNO = 4-picoline-N-oxide] were synthesized under varying experimental conditions. The complexes were characterized by spectral (IR, FAB-MS and Mössbauer), electrochemical and thermal studies. 57Fe-Mössbauer spectral data for complexes exhibit a quadrupole splitting confirming the presence of iron nuclei in asymmetric environment. The relevant parameters like isomer shift (δ), quadruple splitting (ΔEQ), line widths and peak height ratio (HWh/HWl) are consistent with high spin state of Fe(III) centre with the presence of Kramer’s double degeneracy in distorted octahedral environment. The electrochemical studies indicate existence of quasi-reversible redox couples (FeII/III) in solution.

  5. Magnetic properties of Al/57Fe/Cr multilayers

    NASA Astrophysics Data System (ADS)

    Jani, Snehal; Lakshmi, N.; Jain, Vishal; Reddy, V. R.; Gupta, Ajay; Venugopalan, K.

    2013-06-01

    Conversion Electron Mössbauer Spectroscopy (CEMS) and DC magnetization are used to compare magnetic properties of as-deposited multilayer (MLS) and Fe2CrAl thin film made from Al/57Fe/Cr MLS deposited by ion beam sputtering and then annealed in UHV. Interdiffusion of elements on annealing sample-1 at 500°C leads to formation of a single, disordered film of Fe2CrAl as evidenced by hyperfine field values obtained by CEMS in the film which compares well with that in bulk Fe2CrAl. CEMS also shows contributions from Fe, Fe/Cr and Fe/Al interfaces in the MLS. Saturation magnetization of as-deposited sample-1 is much less than pure Fe due to reduced Fe thickness because of interface formation and also reduction in Fe-Fe interaction due to intervening Al and Cr layers.

  6. Iron-oxide aerogel and xerogel catalyst formulations: characterization by 57Fe Mössbauer and XAFS spectroscopies.

    PubMed

    Huggins, Frank E; Bali, Sumit; Huffman, Gerald P; Eyring, Edward M

    2010-06-01

    Iron in various iron-oxide aerogel and xerogel catalyst formulations (> or =85% Fe(2)O(3); < or =10% K, Co, Cu, or Pd) developed for possible use in Fischer-Tropsch synthesis (FTS) or the water-gas-shift (WGS) reaction has been examined by (57)Fe Mössbauer spectroscopy. The seventeen samples consisted of both as-prepared and calcined aerogels and xerogels and their products after use as catalysts for FTS or the WGS reaction. Complementary XAFS spectra were obtained on the occurrence of the secondary elements in some of the same materials. A broad, slightly asymmetric, two-peak Mössbauer spectrum was obtained from the different as-prepared and calcined catalyst formulations in the majority of cases. Such spectra could only be satisfactorily fit with three quadrupole doublet components, but no systematic trends in the isomer shift and quadrupole splitting parameters and area ratios of the individual components could be discerned that reflected variations in the composition or preparation of the aerogel or xerogel materials. However, significant reductions were noted in the Mössbauer effective thickness (recoilless absorption effect per unit mass of iron) parameter, chi(eff)/g, determined at room temperature, for aerogels and xerogels compared to bulk iron oxides, reflecting the openness and lack of rigidity of the aerogel and xerogel structures. Mössbauer measurements for two aerogels over the range from 15 to 292K confirmed the greatly diminished nature of this parameter at room temperature. Major increases in the effective thickness parameter were observed when the open structure of the aerogel or xerogel collapsed during calcination resulting in the formation of iron oxides (hematite, spinel ferrite). Similar structural changes were indicated by increases in this parameter after use of iron-oxide aerogels as catalysts for FTS or the WGS reaction, during which the iron-oxide aerogel was converted to a mixture of nonstoichiometric magnetite and the Hägg carbide

  7. Proton nuclear magnetic resonance identification and discrimination of side chain isomers of phytosterols using a lanthanide shift reagent.

    PubMed

    Iida, T; Tamura, T; Matsumoto, T

    1980-03-01

    Proton nuclear magnetic resonance (1H-NMR) spectra at 90 MHz were measured for a number of side chain isomers of phytosterols (sterols with a C8H17 side chain, and delta 24-, 24-methylene, delta 22-, 24-ethylidene, 24-methly, 24-ethyl, 24-methyl-delta 22-, 24-ethyl delta 22-, and 24-ethyl-delta 22,25(27)-sterols) with or without a lanthanide shift reagent, tris[1,1,1,2,2,3,3 - heptafluoro - 7,7 - dimethyloctane - 4,6 - dionato]ytterbium, Yb(fod)3, and the effect of Yb(fod)3 on the side chain methyl protons is discussed. The change of the chemical shifts induced Yb(fod)3 for the side chain methyls was expressed in terms of the induced shift ratios (ISR values), i.e., the ratios of the induced chemical shifts of the respective side chain methyls to that of the fastest moving side chain methyl. The ISR values were sentitive to minor structural and stereochemical differences, but almost independent of ring structures and of substrate concentrations, thus providing confirmatory evidence for the side chain structures. Also, the Yb(fod)3-induced spectral patterns observed in the high-field methyl region bore the fingerprints of the side chain structures. Several isomeric pairs of sterols, which differ only in the geometry of double bonds or the absolute configuration at C-24 in the side chain, i.e., cis- and trans-isomers of delta 22-and 24-ethylidene sterols, 24R/alpha- and 24S/beta-methyl sterols, 24R/alpha- and 24S/beta-ethyl sterols, and 24S/alpha- and 24R/beta-ethyl-delta 22-sterols, could be differentiated from each other under the influence of Yb(fod)3, even though they were measured at 90 MHz.

  8. Revisiting the Mössbauer Isomer Shifts of the FeMoco Cluster of Nitrogenase and the Cofactor Charge.

    PubMed

    Bjornsson, Ragnar; Neese, Frank; DeBeer, Serena

    2017-02-06

    Despite decades of research, the structure-activity relationship of nitrogenase is still not understood. Only recently was the full molecular structure of the FeMo cofactor (FeMoco) revealed, but the charge and metal oxidation states of FeMoco have been controversial. With the recent identification of the interstitial atom as a carbide and the more recent revised oxidation-state assignment of the molybdenum atom as Mo(III), here we revisit the Mössbauer properties of FeMoco. By a detailed error analysis of density functional theory-computed isomer shifts and computing isomer shifts relative to the P-cluster, we find that only the charge of [MoFe7S9C](1-) fits the experimental data. In view of the recent Mo(III) identification, the charge of [MoFe7S9C](1-) corresponds to a formal oxidation-state assignment of Mo(III)3Fe(II)4Fe(III), although due to spin delocalization, the physical oxidation state distribution might also be interpreted as Mo(III)1Fe(II)4Fe(2.5)2Fe(III), according to a localized orbital analysis of the MS = 3/2 broken symmetry solution. These results can be reconciled with the recent spatially resolved anomalous dispersion study by Einsle et al. that suggests the Mo(III)3Fe(II)4Fe(III) distribution, if some spin localization (either through interactions with the protein environment or through vibronic coupling) were to take place.

  9. Gebel Kamil Iron Meteorite: 57Fe Mössbauer Spectroscopy and Magnetic Properties Data

    NASA Astrophysics Data System (ADS)

    Dos Santos, E.; Munayco, P.; Gattacceca, J.; Rochette, P.; Scorzelli, R. B.; Folco, L.

    2014-09-01

    In this work, we present magnetic properties data along with mineralogical characterization by 57Fe Mössbauer spectroscopy for a shrapnel of Gebel Kamil meteorite, in order to evaluate the thermal/shock history revealed by these techniques.

  10. Mössbauer study 57Fe in ultrathin trilayer films with sharp and rough interfaces

    NASA Astrophysics Data System (ADS)

    Pogorily, A. N.; Bondarkova, G. V.; Razumov, O. N.; Shypil, E. V.

    2011-04-01

    Trilayer thin films Py/57Fe/Gd and Gd/57Fe/Py (Py: Fe20Ni80 permalloy) have been prepared by electron-beam evaporation and investigated using conversion-electron Mössbauer spectroscopy (CEMS), scanning tunneling microscopy (STM), polar magneto-optical Kerr effect (PMOKE), and ferromagnetic resonance (FMR). It was shown that the films deposited in the same vacuum and temperature runs but with the reverse order of the layers gave a different quality of interfaces: sharp (Py/57Fe/Gd) and rough (Gd/57Fe/Py). Different distribution of atoms in sharp and rough interfaces results in different magnetic properties: the Mössbauer spectra, FMR, and PMOKE data show the appearance of perpendicular magnetic anisotropy (PMA) and enhancement of magnetization in the samples with the rough Gd/Py interface.

  11. Water Solvent Effect on Theoretical Evaluation of (1)H NMR Chemical Shifts: o-Methyl-Inositol Isomer.

    PubMed

    Dos Santos, Hélio F; Chagas, Marcelo A; De Souza, Leonardo A; Rocha, Willian R; De Almeida, Mauro V; Anconi, Cleber P A; De Almeida, Wagner B

    2017-04-13

    In this paper, density functional theory calculations of nuclear magnetic resonance (NMR) chemical shifts for l-quebrachitol isomer, previously studied in our group, are reported with the aim of investigating in more detail the water solvent effect on the prediction of (1)H NMR spectra. In order to include explicit water molecules, 20 water-l-quebrachitol configurations obtained from Monte Carlo simulation were selected to perform geometry optimizations using the effective fragment potential method encompassing 60 water molecules around the solute. The solvated solute optimized geometries were then used in B3LYP/6-311+G(2d,p) NMR calculations with PCM-water. The inclusion of explicit solvent in the B3LYP NMR calculations resulted in large changes in the (1)H NMR profiles. We found a remarkable improvement in the agreement with experimental NMR profiles when the explicit hydrated l-quebrachitol structure is used in B3LYP (1)H NMR calculations, yielding a mean absolute error (MAE) of only 0.07 ppm, much lower than reported previously for the gas phase optimized structure (MAE = 0.11 ppm). In addition, a very improved match between theoretical and experimental (1)H NMR spectrum measured in D2O was achieved with the new hydrated optimized l-quebrachitol structure, showing that a fine-tuning of the theoretical NMR spectra can be accomplished once solvent effects are properly considered.

  12. Single-crystalline M-type Sr Hexaferrites studied by 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Nagasawa, Nobumoto; Ikeda, Shugo; Shimoda, Aiko; Waki, Takeshi; Tabata, Yoshikazu; Nakamura, Hiroyuki; Kobayashi, Hisao

    2016-12-01

    The 57Fe Mössbauer spectra of the single crystalline and the finely ground Sr1- x La x Fe12- y Co y O19 ( x = 0 : y = 0, x = 0.192 : y = 0.152 and x = 0.456 : y = 0.225) samples have been measured to investigate the La-Co substitution effects. All observed spectra at 150 K were well fitted using the five subspectra which correspond to the five crystallographical nonequivalent Fe sites in the M-type hexaferrite, indicating that the valence changes to Fe2+ ions in the Fe3+ ions were not observed in our Sr1- x La x Fe12- y Co y O19 samples. In SrFe12O19, the relative absorption intensities in the five subspectra show the large anisotropies in the recoilless fractions at the five Fe sites whereas these anisotropies were not observed in Sr0.544La0.456Fe11.775Co0.225O19. These results indicate the chemical compositional dependence on the anisotropies of the recoilless fractions at the five Fe sites. The substitution of a Co2+ ion for the Fe3+ ion changes the center shifts of the Fe3+ ions near the Co2+ ion by the perturbation of the Fe-O-Co hybridizations. Therefore, the Co2+ ions occupy the 4 f 1 and the 4 f 2 sites due to the chemical compositional dependences of the refined magnetic hyperfine field and center shifts of the Fe3+ ions.

  13. 237Np and 57Fe Mössbauer study of NpFeGa5

    NASA Astrophysics Data System (ADS)

    Homma, Y.; Nakada, M.; Nakamura, A.; Nasu, S.; Aoki, D.; Sakai, H.; Ikeda, S.; Yamamoto, E.; Haga, Y.; Ōnuki, Y.; Shiokawa, Y.

    2006-02-01

    57Fe and 237Np Mössbauer Ōmeasurements have been performed for NpFeGa5, which is one of the so-called neptunium 1-1-5 compounds. The 57Fe Mössbauer spectra below T N = 118 K show the magnetically ordered state. The magnitude of the hyperfine magnetic field at the 57Fe nucleus is determined to be 1.98 ± 0.05 T at 10 K. From the 237Np Mössbauer spectrum at 10 K, the hyperfine magnetic field at the 237Np nucleus is 203 T and the hyperfine coupling constant is determined to be 237 T/μB using the Np atomic magnetic moment of 0.86 μB determined by the neutron diffraction study.

  14. 237Np and 57Fe Mdssbauer study of NpFeGa5

    NASA Astrophysics Data System (ADS)

    Homma, Y.; Nakada, M.; Nakamura, A.; Nasu, S.; Aoki, D.; Sakai, H.; Ikeda, S.; Yamamoto, E.; Haga, Y.; Onuki, Y.; Shiokawa, Y.

    57Fe and 237Np Mössbauer Omeasurements have been performed for NpFeGa5, which is one of the so-called neptunium 1-1-5 compounds. The 57Fe Mössbauer spectra below T N=118 K show the magnetically ordered state. The magnitude of the hyperfine magnetic field at the 57Fe nucleus is determined to be 1.98 ± 0.05 T at 10K. From the 237Np Mössbauer spectrum at 10 K, the hyperfine magnetic field at the 237Np nucleus is 203 T and the hyperfine coupling constant is determined to be 237 T/μB using the Np atomic magnetic moment of 0.86 μB determined by the neutron diffraction study.

  15. The 57Fe hyperfine interactions in the iron-bearing phases in some LL ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Maksimova, A. A.; Grokhovsky, V. I.; Petrova, E. V.; Semionkin, V. A.

    2016-12-01

    The study of several LL ordinary chondrites such as NWA 6286 LL6, NWA 7857 LL6 and Chelyabinsk LL5 fragments with different lithology was carried out using scanning electron microscopy with energy dispersion spectroscopy, X-ray diffraction and 57Fe Mössbauer spectroscopy with a high velocity resolution at 295 K. Small variations in the 57Fe hyperfine parameters were revealed for the M1 and M2 sites in olivine, orthopyroxene and clinopyroxene as well as for α-Fe(Ni, Co), α 2-Fe(Ni, Co) and γ-Fe(Ni, Co) phases, and for troilite in different samples of studied LL ordinary chondrites.

  16. Demystifying fluorine chemical shifts: electronic structure calculations address origins of seemingly anomalous (19)F-NMR spectra of fluorohistidine isomers and analogues.

    PubMed

    Kasireddy, Chandana; Bann, James G; Mitchell-Koch, Katie R

    2015-11-11

    Fluorine NMR spectroscopy is a powerful tool for studying biomolecular structure, dynamics, and ligand binding, yet the origins of (19)F chemical shifts are not well understood. Herein, we use electronic structure calculations to describe the changes in (19)F chemical shifts of 2F- and 4F-histidine/(5-methyl)-imidazole upon acid titration. While the protonation of the 2F species results in a deshielded chemical shift, protonation of the 4F isomer results in an opposite, shielded chemical shift. The deshielding of 2F-histidine/(5-methyl)-imidazole upon protonation can be rationalized by concomitant decreases in charge density on fluorine and a reduced dipole moment. These correlations do not hold for 4F-histidine/(5-methyl)-imidazole, however. Molecular orbital calculations reveal that for the 4F species, there are no lone pair electrons on the fluorine until protonation. Analysis of a series of 4F-imidazole analogues, all with delocalized fluorine electron density, indicates that the deshielding of (19)F chemical shifts through substituent effects correlates with increased C-F bond polarity. In summary, the delocalization of fluorine electrons in the neutral 4F species, with gain of a lone pair upon protonation may help explain the difficulty in developing a predictive framework for fluorine chemical shifts. Ideas debated by chemists over 40 years ago, regarding fluorine's complex electronic effects, are shown to have relevance for understanding and predicting fluorine NMR spectra.

  17. Photoelectron spectroscopy of the [glycine.(H2O)1,2]- clusters: Sequential hydration shifts and observation of isomers

    NASA Astrophysics Data System (ADS)

    Diken, Eric G.; Headrick, Jeffrey M.; Johnson, Mark A.

    2005-06-01

    The electron binding energies of the small hydrated amino acid anions, [glycine•(H2O)1,2]-, are determined using photoelectron spectroscopy. The vertical electron detachment energies (VDEs) are found to increase by approximately 0.12 eV with each additional water molecule such that the higher electron binding isomer of the dihydrate is rather robust, with a VDE value of 0.33 eV. A weak binding isomer of the dihydrate is also recovered, however, with a VDE value (0.14 eV) lower than that of the monohydrate. Unlike the situation in the smaller (n⩽13) water cluster anions, the [Gly•(H2O)n⩾6]- clusters are observed to photodissociate via water monomer evaporation upon photoexcitation in the O-H stretching region. We discuss this observation in the context of the mechanism responsible for the previously observed [S. Xu, M. Nilles, and K. H. Bowen, Jr., J. Chem. Phys. 119, 10696 (2003)] sudden onset in the cluster formation at [Gly•(H2O)5]-.

  18. 57 Fe Mössbauer probe of spin crossover thin films on a bio-membrane

    NASA Astrophysics Data System (ADS)

    Naik, Anil D.; Garcia, Yann

    2012-03-01

    An illustrious complex [Fe(ptz)6](BF4)2 (ptz = 1-propyl-tetrazole) ( 1) which was produced in the form of submicron crystals and thin film on Allium cepa membrane was probed by 57Fe Mossbauer spectroscopy in order to follow its intrinsic spin crossover. In addition to a weak signal that corresponds to neat SCO compound significant amount of other iron compounds are found that could have morphed from 1 due to specific host-guest interaction on the lipid-bilayer of bio-membrane. Further complimentary information about biogenic role of membrane, was obtained from variable temperature Mossbauer spectroscopy on a ~5% enriched [57Fe(H2O)6](BF4)2 salt on this membrane.

  19. Microwave absorption and 57Fe Mössbauer properties of Ni-Ti doped barium hexaferrite

    NASA Astrophysics Data System (ADS)

    Harker, S. J.; Stewart, G. A.; Hutchison, W. D.; Amiet, A.; Tucker, D.

    2015-04-01

    The impact of doping the Fe component of barium hexaferrite with Ni0.5Ti0.5 is investigated using x-ray powder diffraction, 57Fe Mössbauer spectroscopy and microwave network analysis. The dopant ions exhibit a preference for the 2 b, 4 f 2 and 12 k-sites and the unit cell volume is observed to decrease. The ferromagnetic resonance frequency is reduced by about 11.5 GHz for each additional dopant ion per formula unit.

  20. A CEMS search for precipitate formation in 57Fe implanted ZnO

    NASA Astrophysics Data System (ADS)

    Bharuth-Ram, Krishanlal; Masenda, Hilary; Doyle, Terence B.; Geburt, Sebastian; Ronning, Carsten; Gunnlaugsson, Harald Palle

    2012-03-01

    Conversion electron Mössbauer Spectroscopy measurements have been made on ZnO single crystals implanted with 60 keV 57Fe to 4 and 8 at.% peak concentrations, and annealed up to 800°C. The spectra show quite strong changes with annealing, but no evidence of magnetic components, thus precluding the formation of large sized precipitates or secondary phases. Above an annealing temperature of 650°C, the dominant spectral component is a doublet with hyperfine parameters typical of Fe3 + , which is attributed to Fe3 + ions in nano-precipitates ˜5 nm in size.

  1. Mechanically - induced disorder in CaFe2As2: a 57Fe Mössbauer study

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoming; Ran, Sheng; Canfield, Paul C.; Bud'Ko, Sergey L.

    57 Fe Mössbauer spectroscopy was used to study an extremely pressure and strain sensitive compound, CaFe2As2, with different degrees of strain introduced by grinding and annealing. At the base temperature, in the antiferromagnetic/orthorhombic phase, compared to a sharp sextet Mössbauer spectrum of single crystal CaFe2As2, which is taken as an un-strained sample, an obviously broadened sextet and an extra doublet were observed for ground CaFe2As2 powders with different degrees of strain. The Mössbauer results suggest that the magnetic phase transition of CaFe2As2 can be inhomogeneously suppressed by the grinding induced strain to such an extent that the antiferromagnetic order in parts of the grains forming the powdered sample remain absent all the way down to 4.6 K. However, strain has almost no effect on the temperature dependent hyperfine magnetic field in the grains with magnetic order. The quadrupole shift in the magnetic phase approachs zero with increasing degrees of strain, indicating that the strain reduces the average lattice asymmetry at Fe atom position. Supported by US DOE under the Contract No. DE-AC02-07CH11358 and by the China Scholarship Council.

  2. First-principles investigation of 67Zn isomer shifts in ZnF2 and the chalcogenides ZnO, ZnS, ZnSe, and ZnTe

    NASA Astrophysics Data System (ADS)

    Mitchell, D. W.; Das, T. P.; Potzel, W.; Kalvius, G. M.; Karzel, H.; Schiessl, W.; Steiner, M.; Köfferlein, M.

    1993-12-01

    All-electron, self-consistent, Hartree-Fock cluster calculations have been carried out to derive electron densities at the zinc nucleus in the series of compounds ZnF2 (rutile-type structure), ZnO (rocksalt structure), ZnO (wurtzite structure), and the compounds ZnS, ZnSe, and ZnTe (all with the sphalerite structure). The derived density differences show a very good linear correlation with the experimental isomer shifts. The isomer shifts and results for the densities at the zinc nucleus have been combined to calculate a value for the change of the mean-square nuclear charge radius for the Mössbauer transition in 67Zn of Δ=+(13.9+/-1.4)×10-3 fm2. Our calculations clearly show the importance of the covalency of the Zn-ligand bond for the origin of the isomer shift and fully corroborate the experimental linear correlation between decreasing isomer shift values and increasing electronegativity of the ligands. The most important contribution to the electron-density differences at the zinc nucleus comes from the Zn(4s) electrons with a smaller but significant contribution from the Zn(3s) electrons appearing to arise primarily from the repulsive influence of the ligand-ion orbitals.

  3. Magnetic behaviour and DCEMS study of SnO2 films implanted with 57Fe

    NASA Astrophysics Data System (ADS)

    Nomura, K.; Iio, S.; Hirose, Y.; Reuther, H.; Nakanishi, A.

    2013-04-01

    Fe implanted SnO2 films (5 × 1016 and 1 × 1017 57Fe ions/cm2) characterized by conversion electron Mossbauer spectroscopy (CEMS) are reviewed. The substrate temperatures affect the growth of precipitated iron oxides. The Fe ion implanted film at room temperature (RT) shows no Kerr effect and no magnetic sextet in CEM spectra. The SnO2 film implanted with 57Fe at the substrate temperature of 300 °C show a small Kerr effect although the magnetic sextet is not observed, but post-annealing results in the disappearance of the Kerr effect. This magnetism is considered to be due to defect induced magnetism. Some samples were measured by CEMS at 15 K. SnO2 (0.1 at %Sb and 3 at %Sb) films, implanted at 500 °C and the post-annealed samples, show RT ferromagnetism due to formation of clusters of magnetite and maghemite, respectively. The layer by layer analysis of these films within 100 nm in thickness has been done by depth sensitive CEMS (DCEMS) using a He + 5 % CH4 gas counter. The structures and compositions of Fe implanted SnO2 films, and the effects due to post-annealing were investigated.

  4. Predominant and substoichiometric isomers of the plastid genome coexist within Juniperus plants and have shifted multiple times during cupressophyte evolution.

    PubMed

    Guo, Wenhu; Grewe, Felix; Cobo-Clark, Amie; Fan, Weishu; Duan, Zelin; Adams, Robert P; Schwarzbach, Andrea E; Mower, Jeffrey P

    2014-03-01

    Most land plant plastomes contain two copies of a large inverted repeat (IR) that promote high-frequency homologous recombination to generate isomeric genomic forms. Among conifer plastomes, this canonical IR is highly reduced in Pinaceae and completely lost from cupressophytes. However, both lineages have acquired short, novel IRs, some of which also exhibit recombinational activity to generate genomic structural diversity. This diversity has been shown to exist between, and occasionally within, cupressophyte species, but it is not known whether multiple genomic forms coexist within individual plants. To examine the recombinational potential of the novel cupressophyte IRs within individuals and between species, we sequenced the plastomes of four closely related species of Juniperus. The four plastomes have identical gene content and genome organization except for a large 36 kb inversion between approximately 250 bp IR containing trnQ-UUG. Southern blotting showed that different isomeric versions of the plastome predominate among individual junipers, whereas polymerase chain reaction and high-throughput read-pair mapping revealed the substoichiometric presence of the alternative isomeric form within each individual plant. Furthermore, our comparative genomic studies demonstrate that the predominant and substoichiometric arrangements of this IR have changed several times in other cupressophytes as well. These results provide compelling evidence for substoichiometric shifting of plastomic forms during cupressophyte evolution and suggest that substoichiometric shifting activity in plastid genomes may be adaptive.

  5. The 57Fe Synchrotron Mössbauer Source at the ESRF.

    PubMed

    Potapkin, Vasily; Chumakov, Aleksandr I; Smirnov, Gennadii V; Celse, Jean Philippe; Rüffer, Rudolf; McCammon, Catherine; Dubrovinsky, Leonid

    2012-07-01

    The design of a (57)Fe Synchrotron Mössbauer Source (SMS) for energy-domain Mössbauer spectroscopy using synchrotron radiation at the Nuclear Resonance beamline (ID18) at the European Synchrotron Radiation Facility is described. The SMS is based on a nuclear resonant monochromator employing pure nuclear reflections of an iron borate ((57)FeBO(3)) crystal. The source provides (57)Fe resonant radiation at 14.4 keV within a bandwidth of 15 neV which is tunable in energy over a range of about ±0.6 µeV. In contrast to radioactive sources, the beam of γ-radiation emitted by the SMS is almost fully resonant and fully polarized, has high brilliance and can be focused to a 10 µm × 5 µm spot size. Applications include, among others, the study of very small samples under extreme conditions, for example at ultrahigh pressure or combined high pressure and high temperature, and thin films under ultrahigh vacuum. The small cross section of the beam and its high intensity allow for rapid collection of Mössbauer data. For example, the measuring time of a spectrum for a sample in a diamond anvil cell at ∼100 GPa is around 10 min, whereas such an experiment with a radioactive point source would take more than one week and the data quality would be considerably less. The SMS is optimized for highest intensity and best energy resolution, which is achieved by collimation of the incident synchrotron radiation beam and thus illumination of the high-quality iron borate crystal within a narrow angular range around an optimal position of the rocking curve. The SMS is permanently located in an optics hutch and is operational immediately after moving it into the incident beam. The SMS is an in-line monochromator, i.e. the beam emitted by the SMS is directed almost exactly along the incident synchrotron radiation beam. Thus, the SMS can be easily utilized with all existing sample environments in the experimental hutches of the beamline. Owing to a very strong

  6. Interface and temperature dependent magnetic properties of 57Fe/Ti/Co multilayers

    NASA Astrophysics Data System (ADS)

    Jain, Vishal; Lakshmi, N.; Sudheesh, V. D.; Jain, Vivek Kumar; Reddy, V. R.; Venugopalan, K.; Gupta, Ajay

    2014-09-01

    The effect of thermal annealing on the interface of 57Fe/Ti/Co multilayer and associated changes in microstructure, hyperfine field and bulk magnetic properties such as saturation magnetization, coercivity and squareness has been studied by X-ray diffraction, X-ray reflectivity, conversion electron Mössbauer spectroscopy and vibrating sample magnetometry. With increase in annealing temperature, interdiffusion leads to an increase in the roughness, hyperfine fields and coercivity along with a decrease in saturation magnetization. Annealing at 823 K leads to the formation of a FeCo phase along with the precipitation of Ti. The electrical resistivity (ρ) of the as-deposited sample decreases on annealing and hence the thermal coefficient of resistance (TCR) goes from negative to positive on annealing the samples. All samples show Curie temperature in excess of 723 K.

  7. 57Fe Mössbauer spectroscopy used to develop understanding of a diamond preservation index model

    NASA Astrophysics Data System (ADS)

    Yambissa, M. T.; Forder, S. D.; Bingham, P. A.

    2016-12-01

    57Fe Mössbauer spectroscopy has provided precise and accurate iron redox ratios Fe2+/Fe3+ in ilmenite, FeTiO3, found within kimberlite samples from the Catoca and Camatxia kimberlite pipes from N.E. Angola. Ilmenite is one of the key indicator minerals for diamond survival and it is also one of the iron-bearing minerals with iron naturally occurring in one or both of the oxidation states Fe3+ and Fe2+. For this reason it is a good indicator for studying oxygen fugacities ( fO2) in mineral samples, which can then be related to iron redox ratios, Fe2+/Fe3+. In this paper we demonstrate that the oxidation state of the ilmenite mineral inclusion from sampled kimberlite rock is a key indicator of the oxidation state of the host kimberlite assemblage, which in turn determines the genesis of diamond, grade variation and diamond quality. Ilmenite samples from the two different diamondiferous kimberlite localities (Catoca and Camatxia) in the Lucapa graben, N.E. Angola, were studied using Mössbauer spectroscopy and X-Ray Diffractometry, in order to infer the oxidation state of their source regions in the mantle, oxygen partial pressure and diamond preservation conditions. The iron redox ratios, obtained using Mössbauer spectroscopy, show that the Catoca diamond kimberlite is more oxidised than kimberlite found in the Camatxia pipe, which is associated within the same geological tectonic structure. Here we demonstrate that57Fe Mössbauer spectroscopy can assist geologists and mining engineers to effectively evaluate and determine whether kimberlite deposits are economically feasible for diamond mining.

  8. Comment on "Calibration of (57)Fe Mössbauer constants by first principles" Phys. Chem. Chem. Phys., 2016, 18, 10201-10206.

    PubMed

    Grandjean, Fernande; Long, Gary J

    2016-09-21

    The proportionality constant, α, between the observed isomer shifts and the calculated electron probability density at the iron nucleus has been reevaluated in terms of the correct experimental isomer shifts relative to α-iron and their corresponding accuracy, which should be considered in the linear regression fit yielding α. The iron-57 excited state nuclear quadrupole moment, Q, is not a "relative" value and its widely accepted experimental value is 0.16(1) × 10(-28) m(2) as also confirmed by nuclear model calculations.

  9. Electronic Structures of the [Fe(N2)(SiP(iPr)3)](+1/0/-1) Electron Transfer Series: A Counterintuitive Correlation between Isomer Shifts and Oxidation States.

    PubMed

    Ye, Shengfa; Bill, Eckhard; Neese, Frank

    2016-04-04

    The electronic structure analysis of the low-spin iron(II/I/0) complexes [Fe(N2)(SiP(iPr)3)](+/0/-) (SiP(iPr)3 = [Si(o-C6H4P(i)Pr2)3](-)) recently published by J. Peters et al. (Nature Chem. 2010, 2, 558-565) reveals that the redox processes stringing this electron transfer series are best viewed as metal-centered reductions, i.e. Fe(II)N2(0) → Fe(I)N2(0) → Fe(0)N2(0). Superficially, the interpretation seems to be incompatible with the Mössbauer measurement, because the observed isomer shifts are more negative for the lower oxidation states, whereas typically iron-based reduction tends to increase the isomer shift. To rationalize the experimental findings, we analyzed the contributions from the 1s to 4s orbitals to the charge density at the Mössbauer nucleus and found that the positive correlation between the isomer shift and the oxidation state results from an unusual shrinking of the Fe-N2 bond upon reduction due to enhanced N2 to Fe π-backbonding. The other effects of reduction arising from shielding of the nuclear potential, decreasing covalency, and changes in the 4s population would induce the usual negative correlation. The structure distortion dictates the radial distribution of the 4s orbital and the charge density at the nucleus such that a virtually linear relationship between the isomer shift and the Fe-N2 distance could be identified for this series.

  10. 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.

  11. Cycloaddition Reaction of Vinylphenylfurans and Dimethyl Acetylenedicarboxylate to [8 + 2] Isomers via Tandem [4 + 2]/Diradical Alkene-Alkene Coupling/[1,3]-H Shift Reactions: Experimental Exploration and DFT Understanding of Reaction Mechanisms.

    PubMed

    Chen, Kai; Wu, Feng; Ye, Lijuan; Tian, Zi-You; Yu, Zhi-Xiang; Zhu, Shifa

    2016-09-16

    An experimental test of designed [8 + 2] reaction of vinylphenylfuran and dimethyl acetylenedicarboxylate (DMAD) has been carried out, showing that the reaction gave unexpected addition products under different conditions. When the reaction was conducted under thermal conditions in toluene, expoxyphenanthrene, which was named as a [8 + 2] isomer, was generated. The scope of this reaction has been investigated in the present study. In addition, experiments and DFT calculations have been conducted to investigate how the reaction between vinylphenylfuran and DMAD took place. Surprisingly, the reaction did not involve the expected [8 + 2] intermediate, o-quinodimethane. Instead, the reaction starts from intermolecular Diels-Alder reactions between DMAD and the furan moiety of vinylphenylfuran, followed by unexpected intramolecular alkene-alkene coupling. This step generates a diradical species, which then undergoes [1,3]-H shift to give the experimentally observed expoxyphenanthrene. DFT calculations revealed that, the [8 + 2] cycloadduct cannot be obtained because the [1,5]-H shift process from the [1,5]-vinyl shift intermediate is disfavored kinetically compared to the [1,3]-H shift to the [8 + 2] isomer.

  12. Mineralogy, 57Fe Mössbauer spectra and magnetization of chalcolithic pottery

    NASA Astrophysics Data System (ADS)

    Keller, R.; Masch, L.; Pohl, J.; Schmidbauer, E.

    2005-06-01

    Three chalcolithic pottery sherds, paint removed from the surface of each sherd, and an unheated red pigment (Tell-Halaf culture, Turkey) were analysed within the frame of archaeometric studies using mineralogical methods, 57Fe Mössbauer spectroscopy, magnetization and rotational hysteresis data. From mineralogical results, the individual minerals forming the cores of the sherds were determined. It was found that the sherds are lime-rich. High temperature X-ray analysis on comparable Ca-rich material showed that the established composition is consistent with a firing temperature of 750-950°C. Apart from the pigment, each Mössbauer spectrum of Fe-bearing components consists of dominating paramagnetic doublets, arising mostly from silicate phases, and of a six-line pattern with reduced intensity, due to ferri- and/or antiferromagnetic Fe-oxide phases. For three samples, an Fe3+ silicate component of the spectra is clearly dominating, which points to oxidizing conditions during firing. For the others Fe2+ and Fe3+ components occur in about equal intensities. For the pigment, the magnetic sextet is of similar intensity to the Fe3+ silicate component. From magnetic analysis of ferrimagnetic phases it follows that a low percentage of particles of solid solutions γ-Fe2O3 Fe3O4 exist, probably in part ≤0.1 μm in diameter. The ferrimagnetic particles of at least one paint are probably covered by a thin layer of hematite as found from rotational hysteresis data. An attempt is made to draw conclusions from the experimental results, regarding the firing conditions of the sherds and paints.

  13. Mössbauer spectroscopic study of 57Fe metabolic transformations in the rhizobacterium Azospirillum brasilense Sp245

    NASA Astrophysics Data System (ADS)

    Kamnev, Alexander A.; Tugarova, Anna V.; Kovács, Krisztina; Biró, Borbála; Homonnay, Zoltán; Kuzmann, Ernő

    2014-04-01

    Preliminary 57Fe transmission Mössbauer spectroscopic data were obtained for the first time for live cells of the plant-growth-promoting rhizobacterium Azospirillum brasilense (wild-type strain Sp245) grown aerobically with 57FeIII-nitrilotriacetate (NTA) complex as a sole source of iron. The results obtained have shown that live cells actively reduce part of the assimilated iron(III) to iron(II), the latter amounting up to 33 % of total cellular iron after 18 h of growth, and 48 % after additional 3 days of storage of the dense wet cell suspension in nutrient-free saline solution in air at room temperature (measured at 80 K). The cellular iron(II) was found to be represented by two quadrupole doublets of different high-spin forms, while the parameters of the cellular iron(III) were close to those typical for bacterioferritins.

  14. Nano-structure analysis of Fe implanted SnO2 films by 57Fe and 119Sn CEMS

    NASA Astrophysics Data System (ADS)

    Nomura, Kiyoshi; Reuther, Helfried

    2009-06-01

    SnO2 films were implanted with 57Fe at substrate temperatures of room temperature and 300°C. The chemical states of Fe and Sn were characterized by 57Fe CEMS and 119Sn CEMS, respectively. The implanted Fe species exist as Fe(II) and Fe(III) in SnO2 films, which also are reduced into Sn(II)on the implanted surface. The as prepared and post annealed at 500°C samples did not show Kerr effect, but the sample implanted with 1 × 1017 Fe ions/cm2 at 300°C showed Kerr effect although magnetic sextets were not clearly observed in the 57Fe CEM spectra. The Kerr effect disappeared after annealing. It suggests that the number of magnetic defects decreases by absorption of oxygen. Magnetic relaxation appeared in the case of low implantation of 5 × 1016 Fe ions/cm2, which is considered to be due to anti-ferromagnetism or paramagnetic relaxation.

  15. High-Pressure-Hydrogen-Induced Spin Reconfiguration in GdFe2 Observed by 57Fe-Polarized Synchrotron Radiation Mössbauer Spectroscopy with Nuclear Bragg Monochromator

    NASA Astrophysics Data System (ADS)

    Mitsui, Takaya; Imai, Yasuhiko; Hirao, Naohisa; Matsuoka, Takahiro; Nakamura, Yumiko; Sakaki, Kouji; Enoki, Hirotoshi; Ishimatsu, Naoki; Masuda, Ryo; Seto, Makoto

    2016-12-01

    57Fe-polarized synchrotron radiation Mössbauer spectroscopy (PSRMS) with an X-ray phase plate and a nuclear Bragg monochromator was used to study ferrimagnetic GdFe2 in high-pressure hydrogen. The pressure-dependent spectra clearly showed a two-step magnetic transition of GdFe2. 57Fe-PSRMS with circular polarization gave direct evidence that the Fe moment was directed parallel to the net magnetization of the GdFe2 hydride at 20 GPa. This spin configuration was opposite to that of the initial GdFe2, suggesting an extreme weakening of the antiferromagnetic interaction between Fe and Gd. 57Fe-PSRMS enables the characterization of the nonuniform properties of iron-based polycrystalline powder alloys. The excellent applicability of 57Fe-PSRMS covers a wide range of scientific fields.

  16. In-field {sup 57}Fe Mössbauer spectroscopy below spin-flop transition in powdered troilite (FeS) mineral

    SciTech Connect

    Cuda, Jan Tucek, Jiri; Filip, Jan; Malina, Ondrej; Krizek, Michal; Zboril, Radek

    2014-10-27

    Powdered troilite (FeS), extracted from the Cape York IIIA octahedrite meteorite, was investigated employing in-field {sup 57}Fe Mössbauer spectroscopy. The study identified a typical behavior of polycrystalline antiferromagnetic material under external magnetic fields. The in-field evolution of the {sup 57}Fe Mössbauer spectra showed that the spin-flop transition in the FeS system occurs at a field higher than 5 T.

  17. An 57Fe Mössbauer study of three Australian L5 ordinary-chondrite meteorites: dating Kinclaven-001

    NASA Astrophysics Data System (ADS)

    Cadogan, J. M.; Rebbouh, L.; Mills, J. V. J.; Bland, P. A.

    2013-12-01

    Three L5-type ordinary chondrite meteorites recovered from the Nullarbor Region of Western Australia were studied by 57Fe Mössbauer spectroscopy: Kinclaven-001, Camel Donga-007 and Gunnadorah-002. The relative amounts of the various Fe-bearing phases including the primary minerals (Olivine, Pyroxene, Troilite and Fe-Ni metal) and the ferric alteration products (Goethite, Maghemite/Magnetite) were obtained to determine the percentage of iron converted to Fe3 + by weathering processes. These data allow us to estimate the terrestrial age of Kinclaven-001 at 1,700 ± 1,300 yrs.

  18. 57Fe75Mo8Cu1B16 metallic glass studied by CEMS, CXMS and HEXRD

    NASA Astrophysics Data System (ADS)

    Cesnek, Martin; Miglierini, Marcel; Bednarčík, Jozef

    2016-10-01

    57Fe75Mo8Cu1B16 metallic glass prepared by single roller melt spinning was investigated by conversion electron Mössbauer spectroscopy, conversion X-ray Mössbauer spectroscopy and high-energy X-ray diffraction. All methods confirmed presence of amorphous structure without traces of a crystalline phase. Results obtained by Mössbauer spectrometry suggest predominant appearance of magnetic regions on side of the ribbon which was in contact with the quenching wheel. In situ High-energy X-ray diffraction experiment revealed transition from ferromagnetic to paramagnetic state and it was even possible to estimate the Curie temperature.

  19. The 57Fe hyperfine interactions in human liver ferritin and its iron-polymaltose analogues: the heterogeneous iron core model

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Alenkina, I. V.; Semionkin, V. A.

    2016-12-01

    Human liver ferritin and its iron-polymaltose pharmaceutical analogues Ferrum Lek, Maltofer® and Ferrifol® were studied using Mössbauer spectroscopy at 295 and 90 K. The Mössbauer spectra were fitted on the basis of a new model of heterogeneous iron core structure using five quadrupole doublets. These components were related to the corresponding more or less close-packed iron core layers/regions demonstrating some variations in the 57Fe hyperfine parameters for the studied samples.

  20. Large low-energy M1 strength for ^{56,57}Fe within the nuclear shell model.

    PubMed

    Brown, B Alex; Larsen, A C

    2014-12-19

    A strong enhancement at low γ-ray energies has recently been discovered in the γ-ray strength function of ^{56,57}Fe. In this work, we have for the first time obtained theoretical γ decay spectra for states up to ≈8  MeV in excitation for ^{56,57}Fe. We find large B(M1) values for low γ-ray energies that provide an explanation for the experimental observations. The role of mixed E2 transitions for the low-energy enhancement is addressed theoretically for the first time, and it is found that they contribute a rather small fraction. Our calculations clearly show that the high-ℓ(=f) diagonal terms are most important for the strong low-energy M1 transitions. As such types of 0ℏω transitions are expected for all nuclei, our results indicate that a low-energy M1 enhancement should be present throughout the nuclear chart. This could have far-reaching consequences for our understanding of the M1 strength function at high excitation energies, with profound implications for astrophysical reaction rates.

  1. Probe Mössbauer spectroscopy of mechanical alloying in binary Cr‐{sup 57}Fe(1 at%) system

    SciTech Connect

    Elsukov, Evgeny P. Kolodkin, Denis A. Ul'yanov, Alexander L. Porsev, Vitaly E.

    2014-10-27

    Solid state reactions during mechanical alloying (MA) in a binary mixture of powdered Cr and {sup 57}Fe in atomic ratio of 99:1 have been studied using {sup 57}Fe Mössbauer spectroscopy, X-ray diffraction and Auger spectrometry. The proposed model of MA includes formation of Cr(Fe){sub x}O{sub y} oxides at the contact places of Cr and Fe particles, formation of nanostructure with simultaneous dissolution of the oxides, penetration of Fe atoms along grain boundaries in close-to-boundary distorted zones of interfaces in a substitutional position, formation of the substitutional solid solution of Fe in Cr in the body of grains. It was shown that the increase in the BCC lattice parameter on increasing the milling time is due to the dissolution of oxides and formation of interstitial solid solution of O in Cr. There were established substantial differences in consumption of BCC Fe in a Mg → Al → Si → Cr sequence due to the major role of chemical interaction of Mg(Al,Si,Cr) with Fe.

  2. 57Fe Mössbauer spectroscopy, X-ray single-crystal diffractometry, and electronic structure calculations on natural alexandrite

    NASA Astrophysics Data System (ADS)

    Weber, Sven-Ulf; Grodzicki, Michael; Lottermoser, Werner; Redhammer, Günther J.; Tippelt, Gerold; Ponahlo, Johann; Amthauer, Georg

    2007-09-01

    Natural alexandrite Al2BeO4:Cr from Malyshevo near Terem Tschanka, Sverdlovsk, Ural, Russia, has been characterized by 57Fe Mössbauer spectroscopy, electron microprobe, X-ray single-crystal diffractometry and by electronic structure calculations in order to determine oxidation state and location of iron. The sample contains 0.3 wt% of total iron oxide. The 57Fe Mössbauer spectrum can be resolved into three doublets. Two of them with hyperfine parameters typical for octahedrally coordinated high-spin Fe3+ and Fe2+, respectively, are assigned to iron substituting for Al in the octahedral M2-site. The third doublet is attributed to Fe3+ in hematite. Electronic structure calculations in the local spin density approximation are in reasonable agreement with experimental data provided that expansion and/or distortion of the coordination octahedra are presumed upon iron substitution. The calculated hyperfine parameters of Fe3+ are almost identical for the M1 and M2 positions, but the calculated ligand-field splitting is by far too large for high-spin Fe3+ on M1.

  3. Low temperature Raman and high field 57Fe Mossbauer study of polycrystalline GaFeO3.

    PubMed

    Sharma, Kavita; Raghavendra Reddy, V; Kothari, Deepti; Gupta, Ajay; Banerjee, A; Sathe, V G

    2010-04-14

    The magnetic and phonon properties of polycrystalline magnetoelectric/multiferroic GaFeO(3) are studied. Using high field (57)Fe Mossbauer spectroscopy, occupation of Fe is observed at four cation sites. A Fe population of about 6% is observed at the tetrahedral Ga1 site, which explains the observed pinched-like M-H curve and initial sharp increase of the magnetization. The calculated net magnetization value from Mossbauer data suggests that the Fe moment at the Ga1 site is parallel to Fe1 and opposite to that of Fe2 and Ga2 sites, resulting in ferrimagnetism. From low temperature Raman data, anomalous temperature variation in frequency at T(C) is observed for the mode at ∼700 cm(-1).

  4. The quantitative determination of FeS2 phases in coal by means of 57Fe Mössbauer spectroscopy

    USGS Publications Warehouse

    Evans, B.J.; King, Hobart M.; Renton, John J.; Stiller, A.

    1990-01-01

    A knowledge of the concentration of pyrite and marcasite in coals can provide important insight into the genesis of coal deposits. Determinations of the relative amounts of pyrite and marcasite by traditional methods of coal analysis are, however, beset with many difficulties. Using 57Fe Mössbauer spectroscopy and a mild chemical treatment with hydrofluoric acid, a technique has been devised for the quantitative determination of the relative concentrations of pyrite and marcasite in samples of whole coals or their low-temperature ashes. The sample preparation procedure is comparable to less accurate methods. Good qualitative agreement has been obtained between ore microscopic and Mössbauer spectroscopic techniques for a series of extensively investigated whole coal samples.

  5. Thermal History of São João Nepomuceno (IVA) Iron Meteorite Inferred from Ganguly's Cooling Rate Model and 57Fe Mössbauer Spectroscopy Data

    NASA Astrophysics Data System (ADS)

    dos Santos, E.; Scorzelli, R. B.; Varela, M. E.

    2016-08-01

    The intracrystalline Fe-Mg distribution in orthopyroxenes, as measured by means of 57Fe Mössbauer spectroscopy and associated to Ganguly’s cooling rate numerical method, are used to infer the thermal history of São João Nepomuceno (IVA) meteorite.

  6. Single-Crystal 57Fe Q-Band ENDOR Study of the 4 Iron-4 Sulfur Cluster in its Reduced [4Fe-4S] 1+ State

    NASA Astrophysics Data System (ADS)

    Moriaud, Fabrice; Gambarelli, Serge; Lamotte, Bernard; Mouesca, Jean-Marie

    2001-12-01

    57Fe Q-band ENDOR has been used to study the [4Fe-4S]1+ state created by γ irradiation of single crystals of the synthetic model compound [N(C2H5)4]2[Fe4S4(SCH2C6H5)4] enriched in 57Fe. This compound is an excellent biomimetic model of the active sites of many 4 iron-4 sulfur proteins, enabling detailed and systematic studies of its oxidized [4Fe-4S]3+ and reduced [4Fe-4S]1+ paramagnetic states. Taking advantage of the fact that Q-band ENDOR, in contrast with X-Band ENDOR, allows for a very good separation of the 57Fe transitions from those of the protons, the complete hyperfine tensors of the four iron atoms for the [4Fe-4S]1+ species has been measured with precision. For each iron atom, the electron orbital and electron spin isotropic contributions have been determined separately. Moreover, it is remarkable that two 57Fe hyperfine tensors attributed to the ferrous pair of iron atoms are very different. In effect, one tensor presents a much larger anisotropic part and a much smaller isotropic part than those of the other. This difference has been interpreted in terms of a differential electron orbital hyperfine interaction among the two ferrous ions.

  7. Progressive Oxidation of Pyrite in Five Bituminous Coal Samples: An As XANES and 57Fe Mossbauer Spectroscopic Study

    SciTech Connect

    Kolker,A.; Huggins, F.

    2007-01-01

    Naturally occurring pyrite commonly contains minor substituted metals and metalloids (As, Se, Hg, Cu, Ni, etc.) that can be released to the environment as a result of its weathering. Arsenic, often the most abundant minor constituent in pyrite, is a sensitive monitor of progressive pyrite oxidation in coal. To test the effect of pyrite composition and environmental parameters on the rate and extent of pyrite oxidation in coal, splits of five bituminous coal samples having differing amounts of pyrite and extents of As substitution in the pyrite, were exposed to a range of simulated weathering conditions over a period of 17 months. Samples investigated include a Springfield coal from Indiana (whole coal pyritic S = 2.13 wt.%; As in pyrite = detection limit (d.l.) to 0.06 wt.%), two Pittsburgh coal samples from West Virginia (pyritic S = 1.32-1.58 wt.%; As in pyrite = d.l. to 0.34 wt.%), and two samples from the Warrior Basin, Alabama (pyritic S = 0.26-0.27 wt.%; As in pyrite = d.l. to 2.72 wt.%). Samples were collected from active mine faces, and expected differences in the concentration of As in pyrite were confirmed by electron microprobe analysis. Experimental weathering conditions in test chambers were maintained as follows: (1) dry Ar atmosphere; (2) dry O{sub 2} atmosphere; (3) room atmosphere (relative humidity {approx}20-60%); and (4) room atmosphere with samples wetted periodically with double-distilled water. Sample splits were removed after one month, nine months, and 17 months to monitor the extent of As and Fe oxidation using As X-ray absorption near-edge structure (XANES) spectroscopy and {sup 57}Fe Mossbauer spectroscopy, respectively. Arsenic XANES spectroscopy shows progressive oxidation of pyritic As to arsenate, with wetted samples showing the most rapid oxidation. {sup 57}Fe Mossbauer spectroscopy also shows a much greater proportion of Fe{sup 3+} forms (jarosite, Fe{sup 3+} sulfate, FeOOH) for samples stored under wet conditions, but much less

  8. Progressive oxidation of pyrite in five bituminous coal samples: An As XANES and 57Fe Mössbauer spectroscopic study

    USGS Publications Warehouse

    Kolker, Allan; Huggins, Frank E.

    2007-01-01

    Naturally occurring pyrite commonly contains minor substituted metals and metalloids (As, Se, Hg, Cu, Ni, etc.) that can be released to the environment as a result of its weathering. Arsenic, often the most abundant minor constituent in pyrite, is a sensitive monitor of progressive pyrite oxidation in coal. To test the effect of pyrite composition and environmental parameters on the rate and extent of pyrite oxidation in coal, splits of five bituminous coal samples having differing amounts of pyrite and extents of As substitution in the pyrite, were exposed to a range of simulated weathering conditions over a period of 17 months. Samples investigated include a Springfield coal from Indiana (whole coal pyritic S = 2.13 wt.%; As in pyrite = detection limit (d.l.) to 0.06 wt.%), two Pittsburgh coal samples from West Virginia (pyritic S = 1.32–1.58 wt.%; As in pyrite = d.l. to 0.34 wt.%), and two samples from the Warrior Basin, Alabama (pyritic S = 0.26–0.27 wt.%; As in pyrite = d.l. to 2.72 wt.%). Samples were collected from active mine faces, and expected differences in the concentration of As in pyrite were confirmed by electron microprobe analysis. Experimental weathering conditions in test chambers were maintained as follows: (1) dry Ar atmosphere; (2) dry O2 atmosphere; (3) room atmosphere (relative humidity ∼20–60%); and (4) room atmosphere with samples wetted periodically with double-distilled water. Sample splits were removed after one month, nine months, and 17 months to monitor the extent of As and Fe oxidation using As X-ray absorption near-edge structure (XANES) spectroscopy and 57Fe Mössbauer spectroscopy, respectively. Arsenic XANES spectroscopy shows progressive oxidation of pyritic As to arsenate, with wetted samples showing the most rapid oxidation. 57Fe Mössbauer spectroscopy also shows a much greater proportion of Fe3+ forms (jarosite, Fe3+ sulfate, FeOOH) for samples stored under wet conditions, but much less

  9. Sensitivity of 57Fe emission Mössbauer spectroscopy to Ar and C induced defects in ZnO

    NASA Astrophysics Data System (ADS)

    Bharuth-Ram, K.; Mølholt, T. E.; Langouche, G.; Geburt, S.; Ronning, C.; Doyle, T. B.; Gunnlaugsson, H. P.; Johnston, K.; Mantovan, R.; Masenda, H.; Naidoo, D.; Ncube, M.; Gislason, H.; Ólafsson, S.; Weyer, G.

    2016-12-01

    Emission Mössbauer Spectroscopy (eMS) measurements, following low fluence (<1012 cm-2) implantation of 57Mn (t 1/2 = 1.5 min.) into ZnO single crystals pre-implanted with Ar and C ions, has been utilized to test the sensitivity of the 57Fe eMS technique to the different types of defects generated by the different ion species. The dominant feature of the Mössbauer spectrum of the Ar implanted ZnO sample was a magnetic hyperfine field distribution component, attributed to paramagnetic Fe3+, while that of the C implanted sample was a doublet attributed to substitutional Fe2+ forming a complex with the C dopant ions in the 2- state at O vacancies. Magnetization measurements on the two samples, on the other hand, yield practically identical m(H) curves. The distinctly different eMS spectra of the two samples display the sensitivity of the probe nucleus to the defects produced by the different ion species.

  10. A study of thermodynamic properties of dilute Fe-Ru alloys by 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Idczak, R.; Konieczny, R.; Chojcan, J.

    2016-12-01

    The room temperature Mössbauer spectra of 57Fe were measured for Fe1- x Ru x solid solutions with x in the range 0.01 ≤ x ≤ 0.08. The obtained data were analysed in terms of short-range order parameter (SRO) and the binding energy E b between two ruthenium atoms in the studied materials using the extended Hrynkiewicz-Królas idea. The extrapolated value of E b for x = 0 was used to compute the enthalpy of solution H FeRu of Ru in Fe matrix. The result was compared with corresponding values given in the literature which were derived from experimental calorimetric data as well as with the value resulting from the cellular atomic model of alloys by Miedema. It was found that all the H FeRu values are negative or Ru atoms interact repulsively. At the same time, the Mössbauer data were used to determine values of the short-range order parameter α 1. For the as-obtained samples in which atoms are frozen-in high temperature state, close to the melting point, the negative α 1 values were found. The findings indicates ordering tendencies in such specimens. On the other hand, in the case of the annealed samples where the observed distributions of atoms should be frozen-in state corresponding to the temperature 700 K, the Fe1- x Ru x alloys with x ≥ 0.05 exhibit clustering tendencies (a predominance of Fe-Fe and Ru-Ru bonds), which manifest themselves by positive values of the calculated SRO parameter. The clustering process leads to a local increase in ruthenium concentration and nucleation of a new ruthenium-rich phase with the hcp structure.

  11. The role of alpha-iron and cementite phases in the growing mechanism of carbon nanotubes: a 57Fe Mössbauer spectroscopy study.

    PubMed

    Pérez-Cabero, M; Taboada, J B; Guerrero-Ruiz, A; Overweg, A R; Rodríguez-Ramos, I

    2006-03-14

    57Fe Mössbauer spectroscopy was used to study the reduction behavior at temperatures as high as 1073 K of an iron/silica catalyst, and also the carbonaceous materials isolated after acetylene decomposition over this catalyst at several temperatures (873-1073 K). The products were previously characterized by transmission electron microscopy and it was clearly proven that the concentration of carbon nanotubes increased when reaction reached highest temperatures. This was related with an increment in cementite concentration (generated from initial alpha-iron and the progressive reduction of the remnant Fe+2 caused by acetylene decomposition) as detected by 57Fe Mössbauer. These results undoubtedly revealed the role of alpha-iron as active center for acetylene decomposition and cementite as main carbide intermediate species in the catalytic growth of CNTs.

  12. Effect of 57Fe-goethite Amendment on Microbial Community Composition and Dynamics During the Transition from Iron to Sulfate Reduction

    NASA Astrophysics Data System (ADS)

    Moon, H.; McGuiness, L.; Kukkadapu, R. K.; Peacock, A.; Komlos, J.; Kerkhof, L.; Long, P. E.; Jaffe, P. R.

    2009-12-01

    Due to an increasing interest in microbial biostimulation for the purpose of U(VI) bioreduction, which proceeds via iron reduction, there is a growing need for a better understanding of the associated biogeochemical dynamics. This includes Fe(III) availability as well as the microbial community changes, including the activity of iron-reducers during the biostimulation period even after the onset of sulfate reduction. An up-flow column experiment was conducted with Old Rifle site sediments, where half of the columns had sediment that was augmented with 57Fe-goethite to track minute goethite changes after the onset of sulfate reduction, and to study the effects of increased Fe(III) levels on the overall biostimulation dynamics. The addition of the 57Fe-goethite did not delay the onset of sulfate reduction, but slightly suppressed the overall rate of sulfate reduction and hence acetate utilization. Mossbauer analyses confirmed that there was bioavailable iron present after the onset of sulfate reduction and that iron was still being reduced during sulfate reduction. Addition of the 57Fe-goethite to the sediment had a noticeable effect on the overall composition of the microbial population. 16S rRNA analyses of biostimulatd sediment using TRFLP showed that Geobacter sp. were still active and replicating after sulfate reduction had occurred for over 30 days. DNA fingerprints of the sediment-attached microbial communities were dominated by 5 TRFs, that comprised 25-57 % of the total profile. Augmentation of sediments with the 57Fe-goethite resulted in somewhat higher numbers of Geobacter-like species throughout the experiment, and during sulfate reduction slightly lower numbers of sulfate reducers. These columns also had a slightly improved U(VI) removal efficiency, which might be attributed to the higher Geobacter-like numbers.

  13. '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.

  14. 57Fe Mössbauer spectroscopy on disordered crystalline media with Ca-gallogermanate type structure. I. In the paramagnetic range

    NASA Astrophysics Data System (ADS)

    Barb, D.; Constantinescu, S.; Tarina, D.

    1995-12-01

    Polycrystalline strontium iron germanates of the type Sr3- y Ln y Fe2+ y Ge4- y O14(Ln=La, Nd; y=0, 1) were investigated by57Fe Mössbauer spectroscopy in the temperature range 4.2 300 K. The crystal chemistry and the distribution of Fe3+ ions in the structure, as well as the crystallographic inequivalence of the oxygen polyhedra occupied by iron, were studied over the whole paramagnetic temperature region. A correlation of the experimental data with a local environment computation is given.

  15. 57Fe- and 119Sn-Moessbauer Studies of Tin Doped Chromium Iron Oxides of Composition {alpha}-Cr2-xFexO3

    SciTech Connect

    Helgason, Oern; Berry, Frank J.; Ren Xiaolin; Moyo, Thomas

    2005-04-26

    Tin-doped iron chromium oxides of composition {alpha}-Cr2-xFexO3 prepared by the calcination of precipitates adopt the corundum-related structure. 57Fe Moessbauer spectroscopy shows the materials to be composed of small superparamagnetic particles and no evidence for a Morin transition was observed above 80K. The supertransferred hyperfine magnetic field at the tin site is shown by 119Sn Moessbauer spectroscopy to be less than that experienced in tin-doped {alpha}-Fe2O3.

  16. Different 57Fe microenvironments in the nanosized iron cores in human liver ferritin and its pharmaceutical analogues on the basis of temperature dependent Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Alenkina, I. V.; Klencsár, Z.; Kuzmann, E.; Semionkin, V. A.

    2017-02-01

    Mössbauer spectra of human liver ferritin and its pharmaceutical analogues Ferrum Lek and Maltofer® measured at various temperatures within the range of 295-83 K were fitted using five quadrupole doublets related to different 57Fe microenvironments in various layers/regions of the ferrihydrite and akaganéite iron cores. The observed anomalous temperature dependences of some Mössbauer parameters were considered as a result of low temperature structural rearrangements in different layers/regions in the iron core.

  17. 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.

  18. 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.

  19. Monte Carlo simulation of dose distribution in water around 57Fe3O4 magnetite nanoparticle in the nuclear gamma resonance condition

    NASA Astrophysics Data System (ADS)

    Gabbasov, R.; Polikarpov, M.; Safronov, V.; Sozontov, E.; Yurenya, A.; Panchenko, V.

    2016-12-01

    In this work was proposed a new radiotherapy enhancement method consisting of the administration of magnetic nanoparticles into the cells with further irradiation with a gamma-ray beam. As a result, adjusting the energy distribution of a gamma-ray beam and 57Fe abundance it is possible to achieve an extremely intensive electron emission because of a nuclear resonance. The produced conversion and Auger electrons can be used as an effective tool for DNA lesions production. We developed a Monte Carlo model for an electron and gamma emission by 57Fe nucleus using the Geant4 program package. The parameters of a resonant absorption were taken from Mössbauer spectra of magnetite nanoparticles synthesized for the administration into live cells. The space distribution of the radiation dose showed an increase in the dose of 2-2.5 times in the case of the natural abundance and more than 50 times in the case of the 66 % enrichment of the nanoparticles.

  20. Nuclear shape isomers

    NASA Astrophysics Data System (ADS)

    Möller, P.; Sierk, A. J.; Bengtsson, R.; Sagawa, H.; Ichikawa, T.

    2012-03-01

    We calculate potential-energy surfaces as functions of spheroidal (ɛ2), hexadecapole (ɛ4), and axial-asymmetry (γ) shape coordinates for 7206 nuclei from A=31 to A=290. We tabulate the deformations and energies of all minima deeper than 0.2 MeV and of the saddles between all pairs of minima. The tabulation is terminated at N=160. Our study is based on the FRLDM macroscopic-microscopic model defined in ATOMIC DATA AND NUCLEAR DATA TABLES [P. Möller, J.R. Nix, W.D. Myers, W.J. Swiatecki, At. Data Nucl. Data Tables 59 (1995) 185]. We also present potential-energy contour plots versus ɛ2 and γ for 1224 even-even nuclei in the region studied. We can identify nuclei for which a necessary condition for shape isomers occurs, namely multiple minima in the calculated potential-energy surface. We find that the vast majority of nuclear shape isomers occur in the A=80 region, the A=100 region, and in a more extended region centered around 208Pb. A calculated region of shape isomers that has so far not been extensively explored is the region of neutron-deficient actinides "north-east" of 208Pb.

  1. Exogenous iron redistribution between brain and spleen after the administration of the 57Fe3O4 ferrofluid into the ventricle of the brain

    NASA Astrophysics Data System (ADS)

    Gabbasov, Raul; Polikarpov, Dmitry; Cherepanov, Valery; Chuev, Michael; Mischenko, Ilya; Loginiva, Nadezhda; Loseva, Elena; Nikitin, Maxim; Panchenko, Vladislav

    2017-04-01

    Iron clearance pathways after the injection of 57Fe3O4-based dextran-stabilized ferrofluid into the brain ventricles were studied by Mössbauer spectroscopy and histologically. The nanoparticles appeared in spleen tissues within 3 h after transcranial injection. We separated and independently estimated concentrations of iron encapsulated in nanoparticles and iron encapsulated in proteins in the all rat organs. It was found that the dextran coated initial nanoparticles of the ferrofluid disintegrated in the brain into separate superparamagnetic nanoparticles within a week after the injection.The nanoparticles completely exited from the brain in a few weeks. The exogenous iron appeared in the spleen in 3 h after the injection and remained in the spleen for more than month. The appearance of additional component in Mössbauer spectra of spleen samples revealed a fundamental difference in the mechanisms of processing of iron nanoparticles in this organ, which was also confirmed by histological examination.

  2. Nuclear resonant scattering measurements on {sup 57}Fe by multichannel scaling with a 64-pixel silicon avalanche photodiode linear-array detector

    SciTech Connect

    Kishimoto, S. Haruki, R.; Mitsui, T.; Yoda, Y.; Taniguchi, T.; Shimazaki, S.; Ikeno, M.; Saito, M.; Tanaka, M.

    2014-11-15

    We developed a silicon avalanche photodiode (Si-APD) linear-array detector for use in nuclear resonant scattering experiments using synchrotron X-rays. The Si-APD linear array consists of 64 pixels (pixel size: 100 × 200 μm{sup 2}) with a pixel pitch of 150 μm and depletion depth of 10 μm. An ultrafast frontend circuit allows the X-ray detector to obtain a high output rate of >10{sup 7} cps per pixel. High-performance integrated circuits achieve multichannel scaling over 1024 continuous time bins with a 1 ns resolution for each pixel without dead time. The multichannel scaling method enabled us to record a time spectrum of the 14.4 keV nuclear radiation at each pixel with a time resolution of 1.4 ns (FWHM). This method was successfully applied to nuclear forward scattering and nuclear small-angle scattering on {sup 57}Fe.

  3. Mössbauer and X-ray study of biodegradation of 57Fe3 O 4 magnetic nanoparticles in rat brain

    NASA Astrophysics Data System (ADS)

    Gabbasov, R. R.; Cherepanov, V. M.; Chuev, M. A.; Lomov, A. A.; Mischenko, I. N.; Nikitin, M. P.; Polikarpov, M. A.; Panchenko, V. Y.

    2016-12-01

    Biodegradation of a 57Fe3 O 4 - based dextran - stabilized ferrofluid in the ventricular cavities of the rat brain was studied by X-ray diffraction and Mössbauer spectroscopy. A two-step process of biodegradation, consisting of fast disintegration of the initial composite magnetic beads into separate superparamagnetic nanoparticles and subsequent slow dissolution of the nanoparticles has been found. Joint fitting of the couples of Mössbauer spectra measured at different temperatures in the formalism of multi-level relaxation model with one set of fitting parameters, allowed us to measure concentration of exogenous iron in the rat brain as a function of time after the injection of nanoparticles.

  4. Search for 14.4 keV solar axions emitted in the M1-transition of {sup 57}Fe nuclei with CAST

    SciTech Connect

    Andriamonje, S.; Aune, S.; Dafni, T.; Ferrer-Ribas, E.; Autiero, D.; Barth, K.; Davenport, M.; Lella, L. Di; Belov, A.; Beltrán, B.; Carmona, J.M.; Cebrián, S.; Bräuninger, H.; Englhauser, J.; Friedrich, P.; Collar, J.I.; Eleftheriadis, C.; Fanourakis, G.; Fischer, H.; Franz, J.; Collaboration: CAST collaboration; and others

    2009-12-01

    We have searched for 14.4 keV solar axions or more general axion-like particles (ALPs), that may be emitted in the M1 nuclear transition of {sup 57}Fe, by using the axion-to-photon conversion in the CERN Axion Solar Telescope (CAST) with evacuated magnet bores (Phase I). From the absence of excess of the monoenergetic X-rays when the magnet was pointing to the Sun, we set model-independent constraints on the coupling constants of pseudoscalar particles that couple to two photons and to a nucleon g{sub aγ}|−1.19g{sub aN}{sup 0}+g{sub aN}{sup 3}| < 1.36 × 10{sup −16} GeV{sup −1} for m{sub a} < 0.03 eV at the 95% confidence level.

  5. Thermal decomposition and reconstruction of CaFe-layered double hydroxide studied by X-ray diffractometry and 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Bugris, Valéria; Ádok-Sipiczki, Mónika; Anitics, Tamás; Kuzmann, Ernő; Homonnay, Zoltán; Kukovecz, Ákos; Kónya, Zoltán; Sipos, Pál; Pálinkó, István

    2015-06-01

    In spite of numerous investigations on the various processes of the thermal decomposition and rehydration of layered double hydroxides (LDHs) by a variety sophisticated experimental means, many details are still unexplored and some contradictions are still unresolved. In this work, our efforts were focussed on clarifying the composition, structure and properties of thermally decomposed metaphases originating from CaFe-LDH, heat treated in the 373-973 K temperature range. The structure reconstruction ability of mixed metal oxide phases obtained after heat treatments was also investigated, mainly concentrating on the changes in the microenvironment of Fe(III), in the presence of controlled amount of water vapour (i.e., at different relative humidities). All samples were characterised by X-ray diffractometry, and the iron-containing phases were studied by 57Fe Mössbauer spectroscopy.

  6. Structure and oscillational motion of /sup 57/Fe atoms in interstitial sites in Al as determined from interference of Moessbauer. gamma. radiation

    SciTech Connect

    Pauling, L.

    1981-12-01

    The first excited site of the /sup 57/Fe atom entrapped in an interstitial site in aluminum, as reported by W. Petry, G. Vogl, and W. Mansel (Phys. Rev. Lett. 45, 1862 (1980)) from a Moessbauer spectroscopic study of a single crystal, is analyzed by consideration of the value of the Hooke's law constant of the Fe-Al bonds obtained from the values for elemental Fe and Al. The eight wavefunctions for the eightfold nearly degenerate excited state are described as 2s1p1d1f hybrids of three-dimensional harmonic oscillator wavefunctions relative to the center of the undistorted Al/sub 6/ octahedron or as localized 1s functions relative to the center of the distorted octahedron. These considerations provide a qualitative understanding of the observations on this system.

  7. Study of the fission isomer 240mAm (S. F. ) using laser-induced nuclear polarization. [Cross section of 238U(7Li,5n) at 48 MeV

    SciTech Connect

    Beene, J. R.; Bemis, Jr., C. E.; Young, J. P.; Kramer, S. D.

    1980-01-01

    The optical isomer shift was measured for the spontaneously fissioning isomer /sup 240m/Am. This shift is approximately 27 times greater than the /sup 241/Am-/sup 243/Am isotope shift, and confirms the conventional identification of fission isomers with large deformation. The measured isomer shift is consistent with a nuclear quadrupole moment of 30.4 b, in agreement with theoretical expectations. 2 figures. (RWR)

  8. The 57Fe hyperfine interactions in iron storage proteins in liver and spleen tissues from normal human and two patients with mantle cell lymphoma and acute myeloid leukemia: a Mössbauer effect study

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Alenkina, I. V.; Vinogradov, A. V.; Konstantinova, T. S.; Semionkin, V. A.

    2015-04-01

    Study of human spleen and liver tissues from healthy persons and two patients with mantle cell lymphoma and acute myeloid leukemia was carried out using Mössbauer spectroscopy with a high velocity resolution. Small variations in the 57Fe hyperfine parameters for normal and patient's tissues were detected and related to small variations in the 57Fe local microenvironment in ferrihydrite cores. The differences in the relative parts of more crystalline and more amorphous core regions were also supposed for iron storage proteins in normal and patients' spleen and liver tissues.

  9. Structure comparison between Th2Zn17-type and TbCu7-type Sm Fe intermetallic compounds and their nitrides by means of 57Fe-Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Sakai, Yoichi; Omatsuzawa, Ryo; Sakazaki, Iwao; Suzuki, Sayaka; Hashino, Hayato; Saito, Takanobu; Iriyama, Takahiko

    2005-11-01

    Samarium iron intermetallic compounds were prepared by a melt spinning method with low and high wheel speeds, which resulted in a Th2Zn17-type and a TbCu7-type structure, respectively. Structure comparison between these types was investigated for Sm Fe intermetallic compounds and their nitrides by 57Fe-Mössbauer spectroscopy.

  10. High field magnetic transitions in the mixed holmium-yttrium iron garnet Ho(0.43)Y(2.57)Fe(5)O(12).

    PubMed

    Bouguerra, A; Khène, S; de Brion, S; Chouteau, G; Fillion, G

    2005-01-12

    High static magnetic field magnetization measurements have been performed up to 23 T on Ho(0.43)Y(2.57)Fe(5)O(12) single crystals at helium temperature (T = 4.2 K) with fields applied along the three main cubic axes: [Formula: see text], [Formula: see text] and [Formula: see text]. The change from the spontaneous ferrimagnetic structure in zero magnetic field to the fully ferromagnetic one in high field takes place through several intermediate phases separated by transitions with step-like magnetization behaviour, but without any observed hysteresis. Using the effective spin Hamiltonian approximation, we show that the general features of these transitions can be accounted for by a large magnetocristalline anisotropy of the Ho(3+) moments of the uniaxial type along the local z axis of each rare-earth site. The model is in better agreement with the experiments than its Ising limit, widely used before, but is still unsuccessful in predicting the 'umbrella' magnetic structures found by previous neutron and NMR experiments.

  11. Time differential 57Fe Mössbauer spectrometer with unique 4π YAP:Ce 122.06 keV gamma-photon detector

    NASA Astrophysics Data System (ADS)

    Novak, Petr; Pechousek, Jiri; Prochazka, Vit; Navarik, Jakub; Kouril, Lukas; Kohout, Pavel; Vrba, Vlastimil; Machala, Libor

    2016-10-01

    This paper presents a conceptually new design of the 57Fe Time Differential Mössbauer Spectrometer (TDMS) with the gamma-photon detector optimized for registration of a radiation emitted in a maximum solid angle. A high detection efficiency of 80% in 4π region was achieved for 122.06 keV photons emitted from 57Co source. Detector parameters have been optimized for the use in the Time Differential Mössbauer Spectroscopy where the high time resolution in range of 176-200 ns is highly required. Technical concept of the TDMS is based on the virtual instrumentation technique and uses fast digital oscilloscope. Performance and detector utilization have been clarified by decreasing the Mössbauer spectral line-width of K2MgFe(CN)6 reference sample from 0.33 mm/s (integral mode) to 0.23 mm/s (time differential mode). This report also describes characterization and utilization of the detector together with additional electronic blocks and two-channel fast data-acquisition system construction.

  12. Sensitivity of the CUORE detector to 14.4 keV solar axions emitted by the M1 nuclear transition of {sup 57}Fe

    SciTech Connect

    Li, Dawei; Creswick, Richard J.; III, Frank T. Avignone; Wang, Yuanxu E-mail: creswick.rj@sc.edu E-mail: wangyx@henu.edu.cn

    2016-02-01

    In this paper we present a calculation of the sensitivity of the CUORE detector to the monoenergetic 14.4 keV solar axions emitted by the M1 nuclear transition of {sup 57}Fe in the Sun and detected by inverse coherent Bragg-Primakoff conversion in single-crystal TeO{sub 2} bolometers. The expected counting rate is calculated using density functional theory for the electron charge density of TeO{sub 2} and realistic background and energy resolution of CUORE. Monte Carlo simulations for 5y × 741 kg=3705 kg y of exposure are analyzed using time correlation of individual events with the theoretical time-dependent counting rate. We find an expected model-independent limit on the product of the axion-photon coupling and the axion-nucleon coupling g{sub aγγ}g{sub aN}{sup eff} < 1.105 × 10{sup −16} /GeV for axion masses less than 500 eV with 95% confidence level.

  13. Magnetic hysteresis properties and 57Fe Mössbauer spectroscopy of iron and stony-iron meteorites: Implications for mineralogy and thermal history

    NASA Astrophysics Data System (ADS)

    Dos Santos, E.; Gattacceca, J.; Rochette, P.; Scorzelli, R. B.; Fillion, G.

    2015-05-01

    Since the solid matter in our solar system began to assemble 4.57 billion years ago, meteorites have recorded a large range of processes, including metamorphism, melting, irradiation and hypervelocity impacts. These processes as well as solar system magnetic fields can be accessed through the investigation of magnetic properties of meteorites. In this work, we present magnetic hysteresis properties, isothermal remanent magnetization acquisition curves and 57Fe Mössbauer spectra for nineteen iron and eleven stony-iron meteorites. These data will be the background for a discussion about the thermal and shock history of these meteorites. Although Mössbauer spectroscopy and hysteresis measurements are not able to provide cooling rates like the conventional metallographic method does, we show that the combination of the ordering degree of taenite phase measured by Mössbauer spectroscopy and hysteresis properties are useful for constraining the thermal and shock history of meteorites. In particular, strong shock and the associated thermal event that result in disordering of tetrataenite can be easily identified.

  14. Interplay between magnetism and superconductivity in EuFe2-xCoxAs2 studied by 57Fe and 151Eu Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Błachowski, A.; Ruebenbauer, K.; Żukrowski, J.; Bukowski, Z.; Rogacki, K.; Moll, P. J. W.; Karpinski, J.

    2011-11-01

    The compound EuFe2-xCoxAs2 was investigated by means of 57Fe and 151Eu Mössbauer spectroscopy versus temperature (4.2-300 K) for x = 0 (parent), x = 0.34-0.39 (superconductor), and x = 0.58 (overdoped). It was found that the spin density wave (SDW) is suppressed by Co substitution; however, it survives in the region of superconductivity, but iron spectra exhibit some nonmagnetic components in the superconducting region. Europium orders magnetically, regardless of the cobalt concentration, with the spin reorientation from the a-axis in the parent compound toward the c-axis with increasing replacement of iron by cobalt. The reorientation takes place close to the a-c plane. Some trivalent europium appears in EuFe2-xCoxAs2 versus substitution due to the chemical pressure induced by Co atoms, and it experiences some transferred hyperfine field from Eu2+. Iron experiences some transferred field due to the europium ordering for substituted samples in the SDW and nonmagnetic state both, while the transferred field is undetectable in the parent compound. Superconductivity coexists with the 4f-europium magnetic order within the same volume. It seems that superconductivity has some filamentary character in EuFe2-xCoxAs2, and it is confined to the nonmagnetic component seen by the iron Mössbauer spectroscopy.

  15. Constraints on the oxidation state of the mantle: An electrochemical and sup 57 Fe Moessbauer study of mantle-derived ilmenites

    SciTech Connect

    Virgo, D.; Luth, R.W. ); Moats, M.A.; Ulmer, G.C. )

    1988-07-01

    Ilmenite samples from four kimberlite localities were studied using electrochemical, Moessbauer spectroscopic, and microprobe analytical techniques in order to infer the oxidation state of their source regions in the mantle. The values of Fe{sup 3+}/{Sigma}Fe calculated from analyses, using three different electron microanalytical instruments assuming ilmenite stoichiometry, are consistently higher than those derived from the Moessbauer data, by as much as 100%. Furthermore, the range in Fe{sup 3+}/{Sigma}Fe calculated using the analyses from different instruments and/or different correction schemes is nearly as large. Thus Fe{sup 3+}/{Sigma}Fe calculated from microprobe analyses should be taken with caution, even if the precision appears high. {sup 57}Fe Moessbauer spectroscopy on the electrochemical experiment run products demonstrates that Fe{sup 3+}/{Sigma}Fe is significantly lower than it is for the natural C-bearing ilmenites. In contrast, the ilmenite that lacked C did not change Fe{sup 3+}/{Sigma}Fe during the electrochemical experiment. Examination of the reduced samples with SEM established that the natural, single-phase ilmenites exsolved during the electrochemical experiment to form ilmenite{sub ss} + spinel{sub ss}. The initial, reduced trends in the electrochemical experiments for the C-bearing ilmenites are attributed to disequilibrium interactions between the decomposing sample and the evolved gas in the electrochemical cell and do not represent the quenched mantle memory nor the intrinsic f{sub O{sub 2}} of the sample prior to reduction. Furthermore, the oxidized f{sub O{sub 2}} trend is interpreted, for the carbon-bearing samples, are representing the f{sub O{sub 2}} of the ilmenite{sub ss} + spinel{sub ss} assemblage and not the intrinsic f{sub o{sub 2}} of the mantle-derived ilemnite{sub ss}.

  16. Magnetic and 57Fe Mössbauer study of the single molecule magnet behavior of a Dy3Fe7 coordination cluster.

    PubMed

    Abbas, Ghulam; Lan, Yanhua; Mereacre, Valeriu; Wernsdorfer, Wolfgang; Clérac, Rodolphe; Buth, Gernot; Sougrati, Moulay T; Grandjean, Fernande; Long, Gary J; Anson, Christopher E; Powell, Annie K

    2009-10-05

    The reaction between N-methydiethanolamine (mdeaH(2)), benzoic acid, FeCl(3), and DyCl(3) yields a decanuclear coordination cluster, [Dy(3)Fe(7)(mu(4)-O)(2)(mu(3)-OH)(2)(mdea)(7)(mu-benzoate)(4)(N(3))(6)] x 2 H(2)O x 7 CH(3)OH (1) whose single crystal structure exhibits three and seven crystallographically distinct Dy(III) and Fe(III) ions; six of the Fe(III) ions are pseudo-octahedrally coordinated, whereas the seventh has a trigonal-bipyramidal coordination geometry. Both direct current (dc) and alternating current (ac) magnetic susceptibility studies indicate that, upon cooling, intracluster antiferromagnetic interactions are dominant in 1, yielding a ferrimagnetic spin arrangement. The out-of-phase (chi'') ac susceptibility reveals that 1 undergoes a slow relaxation of its magnetization mainly resulting from the anisotropy of the Dy(III) ions. This slow relaxation has been confirmed both by magnetization measurements on an oriented single crystal of 1 and by the observation of hysteresis loops below 1.9 K. The macroscopic magnetic studies yield an effective energy barrier, U(eff), of 33.4 K for this relaxation, a barrier that is the highest yet reported for a lanthanide(III)-Fe(III) single molecule magnet. The (57)Fe Mössbauer spectra of 1 obtained between 3 and 35 K are consistent with the presence of Fe(III) intracluster antiferromagnetic coupling with slow magnetic relaxation relative to the Larmor precession time, thus confirming, on a microscopic scale, the presence of a barrier to the magnetic relaxation below 35 K. Between 55 and 295 K the Mössbauer spectra reveal paramagnetic behavior with six partially resolved quadrupole doublets, one for the trigonal-bipyramidal Fe(III) site and five for the six pseudo-octahedral Fe(III) sites.

  17. Redox condition of the late Neoproterozoic pelagic deep ocean: 57Fe Mössbauer analyses of pelagic mudstones in the Ediacaran accretionary complex, Wales, UK

    NASA Astrophysics Data System (ADS)

    Sato, Tomohiko; Sawaki, Yusuke; Asanuma, Hisashi; Fujisaki, Wataru; Okada, Yoshihiro; Maruyama, Shigenori; Isozaki, Yukio; Shozugawa, Katsumi; Matsuo, Motoyuki; Windley, Brian F.

    2015-11-01

    We report geological and geochemical analysis of Neoproterozoic pelagic deep-sea mudstones in an accretionary complex in Lleyn, Wales, UK. Ocean plate stratigraphy at Porth Felen, NW Lleyn, consists of mid-ocean ridge basalt (> 4 m), bedded dolostone (2 m), black mudstone (5 m), hemipelagic siliceous mudstone (1 m,) and turbiditic sandstone (15 m), in ascending order. The absence of terrigenous clastics confirms that the black and siliceous mudstone was deposited in a pelagic deep-sea. Based on the youngest U-Pb age (564 Ma) of detrital zircons separated from overlying sandstone, the deep-sea black mudstone was deposited in the late Ediacaran. The 5 m-thick black mudstone contains the following distinctive lithologies: (i) black mudstone with thin pyritic layers (0.8 m), (ii) alternation of black mudstone and gray/dark gray siliceous mudstone (2.4 m), (iii) thinly-laminated dark gray shale (1 m), and (iv) black mudstone with thin pyritic layers (1 m). 57Fe Mössbauer spectroscopy confirms that these black mudstones contain pyrite without hematite. In contrast, red bedded claystones (no younger than 542 Ma) in the neighboring Braich section contain hematite as their main iron mineral. These deep-sea mudstones in the Lleyn Peninsula record a change of redox condition on the pelagic deep-sea floor during the Ediacaran. The black mudstone at Porth Felen shows that deep-sea anoxia existed in the late Ediacaran. The eventual change from a reducing to an oxidizing deep-sea environment likely occurred in the late Ediacaran (ca. 564-542 Ma).

  18. Observation of Enhancement of the Morin Transition Temperature in Iridium-Doped α-Fe2O3 Thin Film by 57Fe-Grazing Incidence Synchrotron Radiation Mössbauer Spectroscopy

    NASA Astrophysics Data System (ADS)

    Mitsui, Takaya; Mibu, Ko; Seto, Makoto; Kurokuzu, Masayuki; Pati, Satya Prakash; Nozaki, Tomohiro; Sahashi, Masashi

    2016-06-01

    The Morin transition of a (0001)-oriented iridium-doped α-Fe2O3 thin film deposited on an Al2O3(0001) substrate was studied by 57Fe-grazing incidence synchrotron radiation Mössbauer spectroscopy (GISRMS). Temperature-dependent spectra proved that the iridium doping markedly enhanced the Morin temperature of the α-Fe2O3 thin film; the iron spin directions were perpendicular to the film plane at temperatures below 100 °C, while they were in-plane at temperatures above 150 °C. The antiferromagnetic ordering was maintained far above 400 °C. The results demonstrated the availabilities of 57Fe-GISRMS, which enables a very quick evaluation of the magnetism in antiferromagnetic ultrathin films at high temperatures.

  19. Noncollinear Fe spin structure in (Sm-Co)/Fe exchange-spring bilayers: Layer-resolved 57Fe Mössbauer spectroscopy and electronic structure calculations

    NASA Astrophysics Data System (ADS)

    Uzdin, V. M.; Vega, A.; Khrenov, A.; Keune, W.; Kuncser, V. E.; Jiang, J. S.; Bader, S. D.

    2012-01-01

    Magnetization reversal in nanoscale (Sm-Co)/Fe (hard/soft) bilayer exchange-spring magnets with in-plane uniaxial magnetic anisotropy was investigated by magnetometry, conversion-electron Mössbauer spectroscopy (CEMS) and atomistic Fe spin-structure calculations. Magnetization loops along the easy direction exhibit signatures typical of exchange-spring magnets. In-field CEMS at inclined γ-ray incidence onto thin (2 nm) 57Fe probe layers embedded at various depths in the 20-nm-thick natural (soft) Fe layer provides depth-dependent information (via the line-intensity ratio R23 as a function of the applied field H) about the in-plane rotation of Fe spins. A minimum in the R23-vs-H dependence at (Hmin, Rmin) determines the field where Fe magnetic moments roughly adopt an average perpendicular orientation during their reversal from positive to negative easy-axis orientation. A monotonic decrease of Hmin with distance from the hard/soft interface is observed. Rotation of Fe spins takes place even in the interface region in applied fields far below the field of irreversible switching, Hirr, of the hard phase. Formation of an Fe-Co alloy is detected in the interface region. For comparison, the noncollinear Fe spin structure during reversal and the resulting R23 ratio were obtained by electronic-structure calculations based on a quantum-mechanical Hamiltonian for itinerant electrons. The coupling at the hard/soft interface is described by the uniaxial exchange-anisotropy field, hint, as a parameter. Our calculated R23 ratios as a function of the (reduced) applied field h exhibit similar features as observed in the experiment, in particular a minimum at (hmin, Rmin). Rmin is found to increase with hint, thus providing a measure of the interface coupling. Evidence is provided for the existence of fluctuations of the interface coupling. The calculations also show that the Fe spin spiral formed during reversal is highly inhomogeneous. In general, our simulation of the Fe spin

  20. Noncollinear Fe spin structure in (Sm-Co)/Fe exchange-spring bilayers: layer-resolved {sup 57}Fe Mssbauer spectroscopy and electronic structure calculations.

    SciTech Connect

    Uzdin, V. M.; Vega, A.; Khrenov, A.; Keune, W.; Kuncser, V. E.; Jiang, J. S.; Bader, S. D.

    2012-01-01

    Magnetization reversal in nanoscale (Sm-Co)/Fe (hard/soft) bilayer exchange-spring magnets with in-plane uniaxial magnetic anisotropy was investigated by magnetometry, conversion-electron Moessbauer spectroscopy (CEMS) and atomistic Fe spin-structure calculations. Magnetization loops along the easy direction exhibit signatures typical of exchange-spring magnets. In-field CEMS at inclined {gamma}-ray incidence onto thin (2 nm) {sup 57}Fe probe layers embedded at various depths in the 20-nm-thick natural (soft) Fe layer provides depth-dependent information (via the line-intensity ratio R{sub 23} as a function of the applied field H) about the in-plane rotation of Fe spins. A minimum in the R{sub 23}-vs-H dependence at (H{sub min}, R{sub min}) determines the field where Fe magnetic moments roughly adopt an average perpendicular orientation during their reversal from positive to negative easy-axis orientation. A monotonic decrease of H{sub min} with distance from the hard/soft interface is observed. Rotation of Fe spins takes place even in the interface region in applied fields far below the field of irreversible switching, H{sub irr}, of the hard phase. Formation of an Fe-Co alloy is detected in the interface region. For comparison, the noncollinear Fe spin structure during reversal and the resulting R{sub 23} ratio were obtained by electronic-structure calculations based on a quantum-mechanical Hamiltonian for itinerant electrons. The coupling at the hard/soft interface is described by the uniaxial exchange-anisotropy field, hint, as a parameter. Our calculated R{sub 23} ratios as a function of the (reduced) applied field h exhibit similar features as observed in the experiment, in particular a minimum at (h{sub min}, R{sub min}). R{sub min} is found to increase with hint, thus providing a measure of the interface coupling. Evidence is provided for the existence of fluctuations of the interface coupling. The calculations also show that the Fe spin spiral formed

  1. Scrutinizing Al-like 10+51V, 11+53Cr, 12+55Mn, 13+57Fe, 14+59Co, 15+61Ni, and 16+63Cu 1ions for atomic clocks with uncertainties below the 10-19 level

    NASA Astrophysics Data System (ADS)

    Yu, Yan-mei; Sahoo, B. K.

    2016-12-01

    We investigate the transition between the fine structure levels of the ground state, 3 p 2P1 /2→3 p 2P3 /2 , of the highly charged Al-like 10+51V, 11+53Cr, 12+55Mn, 13+57Fe, 14+59Co, 15+61Ni, and 16+63Cu ions for frequency standards. To comprehend them as prospective atomic clocks, we determine their transition wavelengths, quality factors, and various plausible systematics during the measurements. Since most of these ions have nuclear spin I =3 /2 , uncertainties due to dominant quadrupole shifts can be evaded in the F =0 hyperfine level of the 3 p 2P3 /2 state. Other dominant systematics such as quadratic Stark and black-body radiation shifts have been evaluated precisely demonstrating the feasibility of achieving high accuracy, below 10-19 fractional uncertainty, atomic clocks using the above transitions. Moreover, relativistic sensitivity coefficients are determined to find out the aptness of these proposed clocks to investigate possible temporal variation of the fine structure constant. To carry out these analysis, a relativistic coupled-cluster method considering Dirac-Coulomb-Breit Hamiltonian along with lower-order quantum electrodynamics interactions is employed and many spectroscopic properties are evaluated. These properties are also of immense interest for astrophysical studies.

  2. Ab initio study of cyanoguanidine isomers

    NASA Astrophysics Data System (ADS)

    Arbuznikov, A. V.; Sheludyakova, L. A.; Burgina, E. B.

    1995-06-01

    An ab initio quantum chemical study of the geometric structure and stability of cyanoguanidine isomers was carried out at the Hartree-Fock and Møller-Plesset levels of theory. Two stable separable isomers ('cyanioime' and 'cyanoamine') are found. This gives evidence in favour of the vibrational spectroscopy data showing the existence of both isomers.

  3. Ab initio study of cyanoguanidine isomers

    NASA Astrophysics Data System (ADS)

    Arbuznikov, A. V.; Sheludyakova, L. A.; Burgina, E. B.

    1995-06-01

    An ab initio quantum chemical study of the geometric structure and stability of cyanoguanidine isomers was carried out at the Hartree-Fock and Møller-Plesset levels of theory. Two stable separable isomers (‘cyanioime' and ‘cyanoamine') are found. This gives evidence in favour of the vibrational spectroscopy data showing the existence of both isomers.

  4. 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.

  5. Laser-optical studies of the spontaneous-fission isomer /sup 240m/Am

    SciTech Connect

    Beene, J.R.; Bemis, C.E. Jr.; Kramer, S.D.; Young, J.P.

    1982-01-01

    Improved optical pumping experiments on the /sup 240m/Am fission isomer have been performed using the Laser Induced Nuclear Polarization (LINUP) technique. Results of these experiments are discussed in terms of the constraints they place on the spectroscopic properties of /sup 240m/Am. In addition, a quantitative analysis of the isomer shift in terms of nuclear shape is undertaken making use of recent muonic x-ray data on /sup 241/Am and /sup 243/Am.

  6. 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.

  7. LAS bioconcentration is isomer specific

    SciTech Connect

    Tolls, J.; Haller, M.; Graaf, I. de; Thijssen, M.H.C.; Sijm, D.T.H.M.

    1995-12-31

    The authors measured parent compound specific bioconcentration data for linear alkylbenzene sulfonates in Pimephales promelas. They did so by using cold, custom synthesized sulfophenyl alkanes. They observed that, within homologous series of isomers, the uptake rate constants (k{sub 1}) and the bioconcentration factor (BCF) increase with increasing number of carbon atoms in the alkyl chain (n{sub C-atoms}). In contrast, the elimination rate constant k{sub 2} appears to be independent of the alkyl chain length. Regressions of log BCF vs n{sub C-atoms} yielded different slopes for the homologous groups of the 5- and the 2-sulfophenyl alkane isomers. Regression of all log BCF-data vs log 1/CMC yielded a good description of the data. However, when regressing the data for both homologous series separately again very different slopes are obtained. The results therefore indicate that hydrophobicity-bioconcentration relationships may be different for different homologous groups of sulfophenyl alkanes.

  8. Isotope shifts and hyperfine structure of the Fe I 372-nm resonance line

    SciTech Connect

    Krins, S.; Huet, N.; Bastin, T.; Oppel, S.; Zanthier, J. von

    2009-12-15

    We report measurements of the isotope shifts of the 3d{sup 6}4s{sup 2} a {sup 5}D{sub 4}-3d{sup 6}4s4p z {sup 5}F{sub 5}{sup o} Fe I resonance line at 372 nm between all four stable isotopes {sup 54}Fe, {sup 56}Fe, {sup 57}Fe, and {sup 58}Fe, as well as the complete hyperfine structure of that line for {sup 57}Fe, the only stable isotope having a nonzero nuclear spin. The field and specific mass shift coefficients of the transition have been derived from the data, as well as the experimental value for the hyperfine structure magnetic dipole coupling constant A of the excited state of the transition in {sup 57}Fe: A(3d{sup 6}4s4p z {sup 5}F{sub 5}{sup o})=81.69(86) MHz. The measurements were carried out by means of high-resolution Doppler-free laser saturated absorption spectroscopy in a Fe-Ar hollow cathode discharge cell using both natural and enriched iron samples. The measured isotope shifts and hyperfine constants are reported with uncertainties at the percent level.

  9. Fe-doped ZnO nanoparticles: the oxidation number and local charge on iron, studied by 57Fe Mößbauer spectroscopy and DFT calculations.

    PubMed

    Xiao, Jianping; Kuc, Agnieszka; Pokhrel, Suman; Mädler, Lutz; Pöttgen, Rainer; Winter, Florian; Frauenheim, Thomas; Heine, Thomas

    2013-03-04

    Iron bru: Fe-doped ZnO may contain Fe(2+) and Fe(3+) species. Whilst Mößbauer spectroscopy can distinguish these sites in pure oxides FeO and Fe(2)O(3), it gives very similar shifts for Fe-doped phases. This result is rationalized by electron redistribution from the dopant site to the crystal matrix. Mößbauer shifts correlate with the local charge on the Fe sites and different dopant sites can be identified by the Mößbauer quadrupole splitting (see figure).

  10. 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.

  11. 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.

  12. Mössbauer study of exogenous iron redistribution between the brain and the liver after administration of 57Fe3O4 ferrofluid in the ventricle of the rat brain

    NASA Astrophysics Data System (ADS)

    Polikarpov, Dmitry; Gabbasov, Raul; Cherepanov, Valery; Loginova, Natalia; Loseva, Elena; Nikitin, Maxim; Yurenia, Anton; Panchenko, Vladislav

    2015-04-01

    Iron clearance pathways after the injection of 57Fe3O4-based ferrofluid into the brain ventricles were studied histologically and by Mössbauer spectroscopy. It was found that the dextran coated initial nanobeads of the ferrofluid disintegrated in the brain into separate superparamagnetic nanoparticles within a week after the injection. The exogenous iron completely exited all ventricular cavities of the brain within a week after the injection but remained in the white matter for months. Kupffer cells with the exogenous iron appeared in the rat liver 2 hours after the injection. Their concentration reached its maximum on the third day and dropped to zero within a week. The exogenous iron appeared in the spleen a week after the injection and remained in the spleen for months.

  13. Fe-implanted 6H-SiC: Direct evidence of Fe{sub 3}Si nanoparticles observed by atom probe tomography and {sup 57}Fe Mössbauer spectroscopy

    SciTech Connect

    Diallo, M. L.; Fnidiki, A. Lardé, R.; Cuvilly, F.; Blum, I.; Lechevallier, L.; Debelle, A.; Thomé, L.; Viret, M.; Marteau, M.; Eyidi, D.; Declémy, A.

    2015-05-14

    In order to understand ferromagnetic ordering in SiC-based diluted magnetic semiconductors, Fe-implanted 6H-SiC subsequently annealed was studied by Atom Probe Tomography, {sup 57}Fe Mössbauer spectroscopy and SQUID magnetometry. Thanks to its 3D imaging capabilities at the atomic scale, Atom Probe Tomography appears as the most suitable technique to investigate the Fe distribution in the 6H-SiC host semiconductor and to evidence secondary phases. This study definitely evidences the formation of Fe{sub 3}Si nano-sized clusters after annealing. These clusters are unambiguously responsible for the main part of the magnetic properties observed in the annealed samples.

  14. Effects of Al substitution and thermal annealing on magnetoelectric Ba0.5Sr1.5Zn2Fe12O22 investigated by the enhancement factor of 57Fe nuclear magnetic resonance.

    PubMed

    Kwon, Sangil; Kang, Byeongki; Kim, Changsoo; Jo, Euna; Lee, Soonchil; Chai, Yi Sheng; Chun, Sae Hwan; Kim, Kee Hoon

    2014-04-09

    The magnetoelectric properties of hexaferrite Ba0.5Sr1.5Zn2Fe12O22 are significantly improved by Al substitution and thermal annealing. Measuring the enhancement factor of 57Fe NMR, we found direct microscopic evidence that the magnetic moments of the L and S blocks are rotated by a magnetic field in such a way as to increase the net magnetic moment of a magnetic unit, even after the field is removed. Al substitution makes magnetoelectric property arise easily by suppressing the easy-plane anisotropy. The effect of thermal annealing is to stabilize the multiferroic state by reducing the number of pinning sites and the electron spin fluctuation. The transverse conic structure gradually changes to the alternating longitudinal conic structure where spins fluctuate more severely.

  15. Structure, phase transitions, 55Mn NMR, 57Fe Mössbauer studies and magnetoresistive properties of La0.6Sr0.3Mn1.1-xFexO3

    NASA Astrophysics Data System (ADS)

    Pashchenko, A. V.; Pashchenko, V. P.; Revenko, Yu. F.; Prokopenko, V. K.; Shemyakov, A. A.; Levchenko, G. G.; Pismenova, N. E.; Kitaev, V. V.; Gufan, Yu. M.; Sil'cheva, A. G.; Dyakonov, V. P.

    2014-11-01

    The influence of substitution of Fe ions for manganese on the structure, phase transitions, magnetoresistance, 55Mn NMR and 57Fe Mössbauer spectra in the ceramic La0.6Sr0.3Mn1.1-xFexO3 (x=0-0.15) samples has been studied by X-ray diffraction, electron microscopy, magnetic, 55Mn NMR and 57Fe Mössbauer methods. The real rhombohedral perovskite structure (R3barc) is established to contain the different valence manganese ions (Mn3+ and Mn4+), anion and cation vacancies as well as nanostructural clusters with Mn2+ located in the A-sites. Temperature dependences of the a lattice parameter, a(T), demonstrate the anomalies near the Curie temperature, Tc. Wide asymmetric 55Mn NMR spectra confirm the high frequency electron double exchange between Mn3+ and Mn4+ ions and irregularity of their surrounding by other ions and defects. According to the Mössbauer spectroscopy data, Fe3+ ions (~80%) substitute for Mn3+ and partially Mn4+ in the B-positions. The rest of Fe3+ (Fe2+) ions and clusters with Mn2+ are located in the A-positions. The temperatures of metal-semiconductor and ferromagnet-paramagnet phase transitions are reduced with increasing x, and the magnetic irregularity increases due to the weakening high-frequency Mn3+↔Mn4+ double exchange by Fe3+ ions. The amount of ferromagnetic phase is also reduced. The anomalous hysteresis is interpreted as a result of anisotropy of exchange interaction between the ferromagnetic matrix and antiferromagnetic cluster containing MnA2+ ions. The phase diagram demonstrates the strong correlated interrelation among magnetic, transport and magnetoresistance properties.

  16. 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).

  17. X-ray powder diffraction and 57Fe Mössbauer spectroscopy of synthetic trioctahedral micas {K}[Me3]

    NASA Astrophysics Data System (ADS)

    Redhammer, G. J.; Amthauer, G.; Lottermoser, W.; Bernroider, M.; Tippelt, G.; Roth, G.

    2005-11-01

    Trioctahedral 1 M micas have been synthesized along (pseudo)binary joins using hydrothermal techniques and controlled oxygen fugacities. Octahedrally coordinated iron in annite {K}[Fe3]57Fe Mössbauer spectroscopy. With increasing substitution of iron by smaller divalent cations the quadrupole splitting distribution (QSD) evolves from a broad bimodal distribution in annite to a smaller unimodal distribution in Mg2+ and Ni2+-rich samples so that for high substitution rates more regular local environments are dominating. These results, however, can not be interpreted in terms of an octahedral cation ordering scheme. For none of the micas investigated reliable Fe2+ M2/M1 area ratios can be extracted. fMoreover, the complete QSD is shifted towards higher quadrupole splitting values. Similar observations were obtained for substituting Fe2+ by Mg2+ and Ni2+ in tetra-ferri-annite free of octahedral coordinated trivalent cations. Unlike in the Al3+ bearing micas a third QSD component is missing which supports the claim that the appearance of this third QSD component is closely related to the presence of trivalent cations (Al3+, Fe3+) in octahedra coordination.

  18. 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…

  19. Collective Lamb shift in single-photon superradiance.

    PubMed

    Röhlsberger, Ralf; Schlage, Kai; Sahoo, Balaram; Couet, Sebastien; Rüffer, Rudolf

    2010-06-04

    Superradiance, the cooperative spontaneous emission of photons from an ensemble of identical atoms, provides valuable insights into the many-body physics of photons and atoms. We show that an ensemble of resonant atoms embedded in the center of a planar cavity can be collectively excited by synchrotron radiation into a purely superradiant state. The collective coupling of the atoms via the radiation field leads to a substantial radiative shift of the transition energy, the collective Lamb shift. We simultaneously measured the temporal evolution of the superradiant decay and the collective Lamb shift of resonant 57Fe nuclei excited with 14.4-kilo-electron volt synchrotron radiation. Our experimental technique provides a simple method for spectroscopic analysis of the superradiant emission.

  20. Spectral identification of fullerene C82 isomers

    NASA Astrophysics Data System (ADS)

    Gao, Bin; Liu, Lei; Wang, ChunRu; Wu, ZiYu; Luo, Yi

    2007-10-01

    Ultraviolet photoelectron spectra (UPS) of C82 isomers have been calculated using hybrid density functional theory in combination with the Gelius model [Proceedings of the International Conference on Electron spectroscopy, edited by D. A. Shirley (North-Holland, Amsterdam, 1972), p. 311; J. Electron Spectrosc. Relat. Phenom. 5, 985 (1974)]. The calculated UPS spectra are found to be isomer dependent and in good agreement with the experimental counterparts. Near-edge x-ray absorption fine structure (NEXAFS), x-ray photoelectron spectroscopy (XPS), x-ray emission spectroscopy, and the resonant inelastic x-ray scattering (RIXS) spectra of three important isomers [3(C2), 6(Cs), and 9(C2v)] have also been simulated. Strong isomer dependence has also been found for NEXAFS, XPS, and RIXS spectra.

  1. 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.

  2. {sup 57}Fe Moessbauer and x-ray magnetic circular dichroism study of magnetic compensation of the rare-earth sublattice in Nd{sub 2-x}Ho{sub x}Fe{sub 14}B compounds

    SciTech Connect

    Chaboy, J.; Piquer, C.; Plugaru, N.; Bartolome, F.; Laguna-Marco, M. A.

    2007-10-01

    We present here a study of the magnetic properties of the Nd{sub 2-x}Ho{sub x}Fe{sub 14}B series. The macroscopic properties of these compounds evolve continuously from those of Nd{sub 2}Fe{sub 14}B to those of Ho{sub 2}Fe{sub 14}B as Ho gradually replaces Nd. The system shows a compensation of the rare-earth sublattice magnetization for a critical concentration, x{sub c}=0.55, that is reflected into the anomalous behavior of both macroscopic and microscopic magnetic probes. The combined analysis of magnetization, {sup 57}Fe Moessbauer spectroscopy and Fe K-edge x-ray magnetic circular dichroism (XMCD) measurements suggests that the origin of the anomalous magnetic behavior found at x{sub c}=0.55 is mainly due to the Ho sublattice. Moreover, the analysis of the Fe K-edge XMCD signals reveal the presence of a rare-earth contribution, reflecting the coupling of the rare-earth and Fe magnetic moments, which can lead to the possibility of disentangling the magnetic behavior of both Fe and R atoms using a single absorption edge.

  3. Internal electron conversion of the isomeric {sup 57}Fe nucleus state with an energy of 14.4 keV excited by the radiation of the plasma of a high-power femtosecond laser pulse

    SciTech Connect

    Golovin, G V; Savel'ev-Trofimov, Andrei B; Uryupina, D S; Volkov, Roman V

    2011-03-31

    We recorded the spectrum of delayed secondary electrons ejected from the target, which was coated with a layer of iron enriched with the {sup 57}Fe isotope to 98%, under its irradiation by fluxes of broadband X-ray radiation and fast electrons from the plasma produced by a femtosecond laser pulse at an intensity of 10{sup 17} W cm{sup -2}. Maxima were identified at energies of 5.6, 7.2, and 13.6 keV in the spectrum obtained for a delay of 90 - 120 ns. The two last-listed maxima owe their origin to the internal electron conversion of the isomeric level with an energy of 14.4 keV and a lifetime of 98 ns to the K and L shells of atomic iron, respectively; the first-named level arises from a cascade K - L{sub 2}L{sub 3} Auger process. Photoexcitaion by the X-ray plasma radiation is shown to be the principal channel of the isomeric level excitation. (interaction of laser radiation with matter)

  4. In-situ 57Fe Mössbauer characterization of iron oxides in pigments of a rupestrian painting from the Serra da Capivara National Park, in Brazil, with the backscattering Mössbauer spectrometer MIMOS II

    NASA Astrophysics Data System (ADS)

    Soares Meneses Lage, Maria Conceiç ao; Duarte Cavalcante, Luis Carlos; Klingelhöfer, Göstar; Fabris, José Domingos

    2016-12-01

    It is reported the use of the miniaturized portable 57Fe Mössbauer backscattering spectrometer MIMOS II to perform in situ measurements in the archaeological site known as Toca do Boqueirão do Sítio da Pedra Furada (BPF), in Serra da Capivara National Park, in order to specifically examine shades of dark red pigments and compare their differences relatively to the light red part of the same painting. The hyperfine Mössbauer parameters reveal that the dark red area of the rupestrian painting is composed of three populations of hematite and of a small proportion of maghemite, whereas the light red are of the same painting contain hematite mixed with a small proportion of maghemite and a (super)paramagnetic Fe 3+. The Fe content in the dark red area from the rupestrian painting is of approximately twice the amount in the light red of the same prehistoric graphism. The corresponding analysis of red ochre sample collected in the excavation of these archaeological site exhibited two populations of hematite and also a small proportion of maghemite.

  5. 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).

  6. Cis and Trans Isomers of Cycloalkenes

    NASA Astrophysics Data System (ADS)

    Barrows, Susan E.; Eberlein, Thomas H.

    2005-09-01

    As a rule, a trans disubstituted alkene is more stable than the corresponding cis isomer. For cycloalkenes of fewer than eleven members, cis isomers are more stable than their trans counterparts. Although this exception to the normal rule is occasionally noted in beginning organic chemistry textbooks, it is often done without a careful analysis of the reasons behind it. The purpose of this article is to provide that analysis. In order for a cycloalkene to accommodate a trans double bond one or more of the following nonideal geometries must occur: a twisted π bond; pyramidal sp 2 -carbon atoms; nonideal sp 3 bond angles; or longer than normal C C single and double bonds. This article provides a list of experimentally determined relative energies of the cis and trans isomers within the series cycloheptene cycloundecene, along with computationally derived energies at several levels of theory. It also examines the geometric distortions through which cycloalkenes relieve the strain introduced by a trans double bond.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Correlations between mass activity and physicochemical properties of Fe/N/C catalysts for the ORR in PEM fuel cell via 57Fe Mössbauer spectroscopy and other techniques.

    PubMed

    Kramm, Ulrike I; Lefèvre, Michel; Larouche, Nicholas; Schmeisser, Dieter; Dodelet, Jean-Pol

    2014-01-22

    The aim of this work is to clarify the origin of the enhanced PEM-FC performance of catalysts prepared by the procedures described in Science 2009, 324, 71 and Nat. Commun. 2011, 2, 416. Catalysts were characterized after a first heat treatment in argon at 1050 °C (Ar) and a second heat treatment in ammonia at 950 °C (Ar + NH3). For the NC catalysts a variation of the nitrogen precursor was also implemented. (57)Fe Mössbauer spectroscopy, X-ray photoelectron spectroscopy, neutron activation analysis, and N2 sorption measurements were used to characterize all catalysts. The results were correlated to the mass activity of these catalysts measured at 0.8 V in H2/O2 PEM-FC. It was found that all catalysts contain the same FeN4-like species already found in INRS Standard (Phys. Chem. Chem. Phys. 2012, 14, 11673). Among all FeN4-like species, only D1 sites, assigned to FeN4/C, and D3, assigned to N-FeN2+2 /C sites, were active for the oxygen reduction reaction (ORR). The difference between INRS Standard and the new catalysts is simply that there are many more D1 and D3 sites available in the new catalysts. All (Ar + NH3)-type catalysts have a much larger porosity than Ar-type catalysts, while the maximum number of their active sites is only slightly larger after a second heat treatment in NH3. The large difference in activity between the Ar-type catalysts and the Ar + NH3 ones stems from the availability of the sites to perform ORR, as many sites of the Ar-type catalysts are secluded in the material, while they are available at the surface of the Ar + NH3-type catalysts.

  12. Organometallic chemistry: Heavyweight isomer brings stability

    NASA Astrophysics Data System (ADS)

    Scheschkewitz, David

    2016-11-01

    Due to its high reactivity, vinylidene -- the sole 'electron-precise' isomer of acetylene -- is only known to exist in the gas phase. Now, a stable base-free digermanium version of a vinylidene has been isolated by the clever use of suitable substituents.

  13. 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.

  14. Separation and identification of Taxifolin 3-O-glucoside isomers from Chamaecyparis obtusa (Cupressaceae).

    PubMed

    Sakushima, Akiyo; Ohno, Kosei; Coskun, Makusut; Seki, Koh-Ichi; Ohkura, Kazue

    2002-12-01

    Taxifolin 3-O-glucoside isomers, [(2R, 3R)-, (2R, 3S)-, (2S, 3R)- and (2S, 3S)-] were isolated from leaves of Chamaecyparis obtuse (Cupressaceae). Their structures were elucidated on the basis of UV, MS, CD, 1H- and 13C-NMR spectral data, including 2D shift correlation. It was found that the compounds could be distinguished by the use of 1H- and 13C-NMR spectral data.

  15. 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)

  16. Identification of structurally closely related monosaccharide and disaccharide isomers by PMP labeling in conjunction with IM-MS/MS

    PubMed Central

    Yang, Hongmei; Shi, Lei; Zhuang, Xiaoyu; Su, Rui; Wan, Debin; Song, Fengrui; Li, Jinying; Liu, Shuying

    2016-01-01

    It remains particularly difficult for gaining unambiguous information on anomer, linkage, and position isomers of oligosaccharides using conventional mass spectrometry (MS) methods. In our laboratory, an ion mobility (IM) shift strategy was employed to improve confidence in the identification of structurally closely related disaccharide and monosaccharide isomers using IMMS. Higher separation between structural isomers was achieved using 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatization in comparison with phenylhydrazine (PHN) derivatization. Furthermore, the combination of pre-IM fragmentation of PMP derivatives provided sufficient resolution to separate the isomers not resolved in the IMMS. To chart the structural variation observed in IMMS, the collision cross sections (CCSs) for the corresponding ions were measured. We analyzed nine disaccharide and three monosaccharide isomers that differ in composition, linkages, or configuration. Our data show that coexisting carbohydrate isomers can be identified by the PMP labeling technique in conjunction with ion-mobility separation and tandem mass spectrometry. The practical application of this rapid and effective method that requires only small amounts of sample is demonstrated by the successful analysis of water-soluble ginseng extract. This demonstrated the potential of this method to measure a variety of heterogeneous sample mixtures, which may have an important impact on the field of glycomics. PMID:27306514

  17. Pairing correlations in high-spin isomers

    SciTech Connect

    Odahara, A.; Gono, Y.; Fukuchi, T.; Wakabayashi, Y.; Sagawa, H.; Satula, W.; Nazarewicz, W.

    2005-12-15

    High-spin isomers with J{sup {pi}}=49/2{sup +} and 27{sup +} have been systematically observed in a number of N=83 isotones with 60{<=}Z{<=}67 at excitation energies {approx}9 MeV. Based on experimental excitation energies, an odd-even binding energy staggering has been extracted for the first time for these multi-quasiparticle states. Surprisingly, the magnitude of the odd-even effect in high-spin isomers turned out to be very close to that in ground states, thus challenging conventional wisdom that pairing correlations are reduced in highly excited states. Theoretical analysis based on mean-field theory explains the observed proton number dependence of the odd-even effect as a manifestation of strong pairing correlations in the highly excited states. Mean-field effects and the proton-neutron residual interaction on the odd-even staggering are also examined.

  18. Modelling Study of Interstellar Ethanimine Isomers

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    Ethanimine (CH3CHNH) , including both the E- and Z- isomers, were detected towards the star-forming region Sgr B2(N) using the GBT PRIMOS data (Loomis et al 2013), and were recently imaged by the ACTA (Corby et al. 2015). These aldimines can serve as precursors of biological molecules such as amino acids thus are considered prebiotic molecules in interstellar medium. In this study, we present chemical simulations of ethanimine with various physical conditions. From models for Sgr B2(N) and environs, calculated ethanimine abundances show reasonable agreement with observed values, while the translucent cloud models yield much lower abundances. These results agree with locations suggested by observations that ethanimine isomers were detected in the foreground of the shells of the hot core.

  19. Measurements of Short-Lived Fission Isomers

    NASA Astrophysics Data System (ADS)

    Finch, Sean; Bhike, Megha; Howell, Calvin; Krishichayan, Fnu; Tornow, Werner

    2016-09-01

    Fission yields of the short lived isomers 134mTe (T1 / 2 = 162 ns) and 136mXe (T1 / 2 = 2 . 95 μs) were measured for 235U and 238U. The isomers were detected by the γ rays associated with the decay of the isomeric states using high-purity germanium detectors. Fission was induced using both monoenergetic γ rays and neutrons. At TUNL's High-Intensity Gamma-ray Source (HI γS), γ rays of 9 and 11 MeV were produced . Monoenergetic 8 MeV neutrons were produced at TUNL's tandem accelerator laboratory. Both beams were pulsed to allow for precise time-gated spectroscopy of both prompt and delayed γ rays following fission. This technique offers a non-destructive probe of special nuclear materials that is sensitive to the isotopic identity of the fissile material.

  20. Porphycenes and Related Isomers: Synthetic Aspects.

    PubMed

    Anguera, Gonzalo; Sánchez-García, David

    2017-02-22

    Porphyrins, called the pigments of life, have been studied for decades. However, the first constitutional isomer of porphyrin, porphycene, was not synthesized until 1986. This milestone marked the beginning of a new era in the field of porphyrinoids and presented opportunities for the creation of an abundance of new pigments. The unique structural and electronic features of these compounds give rise to interesting physical and optical properties with applications in biomedicine and materials science. This review focuses on the synthetic methodologies available for the preparation of porphycenes (functionalized porphycenes, extended porphycenes, benzoporphycenes, naphthoporphycenes, and heteroanalogues) and the other known isomers, namely, corrphycene, hemiporphycene, and isoporphycene. Although the classical synthetic approaches are discussed, particular emphasis is placed on improvements to the known methodologies and recent advances in the field.

  1. K Isomer in {sup 252}No

    SciTech Connect

    Sulignano, B.; Theisen, Ch.; Drouart, A.; Goergen, A.; Korten, W.; Obertelli, A.; Ackermann, D.; Hessberger, F. P.; Hofmann, S.; Antalic, S.; Venhart, M.; Dorvaux, O.; Piot, J.; Greenlees, P. T.; Jakobsson, U.; Jones, P.; Julin, R.; Juutinen, S.

    2010-04-30

    In this paper we discuss the discovery of an isomeric state in {sup 252}No and a recent experiment studying the rotational band built upon this isomeric state. Results from the later experiment help to assign the structure of the isomer on the basis of purely experimental data, and to disentangle between different theoretical interpretations. Comparison with similar states in {sup 250}Fm and {sup 254}No provides important information and helps the development of self -consistent theories.

  2. 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

  3. Conjugated linoleic acid isomers: differences in metabolism and biological effects.

    PubMed

    Churruca, Itziar; Fernández-Quintela, Alfredo; Portillo, Maria Puy

    2009-01-01

    The term conjugated linoleic acid (CLA) refers to a mixture of linoleic acid positional and geometric isomers, characterized by having conjugated double bonds, not separated by a methylene group as in linoleic acid. CLA isomers appear as a minor component of the lipid fraction, found mainly in meat and dairy products from cows and sheep. The most abundant isomer is cis-9,trans-11, which represents up to 80% of total CLA in food. These isomers are metabolized in the body through different metabolic pathways, but important differences, that can have physiological consequences, are observed between the two main isomers. The trans-10,cis-12 isomer is more efficiently oxidized than the cis-9,trans-11 isomer, due to the position of its double bounds. Interest in CLA arose in its anticarcinogenic action but there is an increasing amount of specific scientific literature concerning the biological effects and properties of CLA. Numerous biological effects of CLA are due to the separate action of the most studied isomers, cis-9,trans-11 and trans-10,cis-12. It is also likely that some effects are induced and/or enhanced by these isomers acting synergistically. Although the cis-9,trans-11 isomer is mainly responsible for the anticarcinogenic effect, the trans-10,cis-12 isomer reduces body fat and it is referred as the most effective isomer affecting blood lipids. As far as insulin function is concerned, both isomers seem to be responsible for insulin resistance in humans. Finally, with regard to the immune system it is not clear whether individual isomers of CLA could act similarly or differently.

  4. Energy calibration issues in nuclear resonant vibrational spectroscopy: observing small spectral shifts and making fast calibrations.

    PubMed

    Wang, Hongxin; Yoda, Yoshitaka; Dong, Weibing; Huang, Songping D

    2013-09-01

    The conventional energy calibration for nuclear resonant vibrational spectroscopy (NRVS) is usually long. Meanwhile, taking NRVS samples out of the cryostat increases the chance of sample damage, which makes it impossible to carry out an energy calibration during one NRVS measurement. In this study, by manipulating the 14.4 keV beam through the main measurement chamber without moving out the NRVS sample, two alternative calibration procedures have been proposed and established: (i) an in situ calibration procedure, which measures the main NRVS sample at stage A and the calibration sample at stage B simultaneously, and calibrates the energies for observing extremely small spectral shifts; for example, the 0.3 meV energy shift between the 100%-(57)Fe-enriched [Fe4S4Cl4](=) and 10%-(57)Fe and 90%-(54)Fe labeled [Fe4S4Cl4](=) has been well resolved; (ii) a quick-switching energy calibration procedure, which reduces each calibration time from 3-4 h to about 30 min. Although the quick-switching calibration is not in situ, it is suitable for normal NRVS measurements.

  5. Retinal isomer ratio in dark-adapted purple membrane and bacteriorhodopsin monomers.

    PubMed

    Scherrer, P; Mathew, M K; Sperling, W; Stoeckenius, W

    1989-01-24

    On the basis of data obtained by spectroscopic analysis and chromatography of retinal extracts, a consensus has been adopted that dark-adapted purple membrane (pm) contains 13-cis- and all-trans-retinal in equal amounts, whereas the light-adapted membrane contains all-trans-retinal only. We have developed an improved extraction technique which extracts up to 70% of the retinal in pm within 4 min. In the extracts from dark-adapted pm at room temperature, we consistently find 66-67% 13-cis-retinal and 33-34% all-trans-retinal, and more than 98.5% all-trans isomer in light-adapted samples. The spectrum obtained by reconstitution of bacterioopsin with 13-cis-retinal at 2 degrees C (to minimize isomerization) shows an absorbance maximum at 554 nm and agrees well with the spectrum for the 13-cis component calculated from the dark-adapted and light-adapted bR spectra with our extraction data. The ratio of 13-cis:all-trans isomer in dark-adapted pm is 2:1 and nearly constant between 0 and 38 degrees C but begins to decrease distinctly above 40 degrees C, and more rapidly near 70 degrees C, reaching 0.75 at 90 degrees C. The van't Hoff plot of the isomer ratio shows a nonlinear temperature dependence above 40 degrees C, indicating a more complex system than a simple thermal 13-cis/all-trans isomer equilibrium. We attribute the broadening, absorbance decrease, and blut shift of the visible absorption band with increasing temperature to the appearance of at least one and possibly two or three new chromophores which contain, mainly or exclusively, the all-trans isomer.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Shifting Attention

    ERIC Educational Resources Information Center

    Ingram, Jenni

    2014-01-01

    This article examines the shifts in attention and focus as one teacher introduces and explains an image that represents the processes involved in a numeric problem that his students have been working on. This paper takes a micro-analytic approach to examine how the focus of attention shifts through what the teacher and students do and say in the…

  7. Foundations of Isomer Physics for Energy Applications

    DTIC Science & Technology

    2008-10-16

    expected to impact the values of detector efficiencies determined from the counts within full-energy peaks. If the goal of the miniball system was to be...This occurs because F(t) is a very steep function . The shortest half-life is expected for decay that reaches the 6* level of the daughter, giving...10-16-2008 2. REPORT TYPE Final Technical Report 3. DATES COVERED (From - To) 9/15/2005 - 5-31-2006 4. TITLE AND SUBTITLE Foundations of Isomer

  8. The interstellar chemistry of H2C3O isomers.

    PubMed

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

    2016-03-11

    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.

  9. 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

  10. Unprecedented χ isomers of single-side triol-functionalized Anderson polyoxometalates and their proton-controlled isomer transformation.

    PubMed

    Zhang, Jiangwei; Liu, Zhenhua; Huang, Yichao; zhang, Jin; Hao, Jian; Wei, Yongge

    2015-06-04

    The μ2-O atom in Anderson polyoxometalates was regioselectively activated by the introduction of protons, which, upon functionalization with triol ligands, could afford a series of unique χ isomers of the organically-derived Anderson cluster {[RCC(CH2O)3]MMo6O18(OH)3}(3-). Herein proton-controlled isomer transformation between the δ and χ isomer was observed by using the fingerprint region in the IR spectra and (13)C NMR spectra.

  11. The truth about the lower plasma concentration of the (-)-isomer after racemic doxazosin administration in rats: Stereoselective inhibition of the (-)-isomer by the (+)-isomer at CYP3A.

    PubMed

    Kong, Dezhi; Li, Qing; Zhang, Panpan; Zhang, Wei; Zhen, Yaqin; Ren, Leiming

    2015-09-18

    Doxazosin (DOX), a long-lasting α1-adrenoceptor antagonist, is used clinically as a racemate that consists of two optical isomers. In humans and rats, following oral administration of racemic DOX [(±)-DOX], the plasma concentration of the (-)-isomer is lower than that of the (+)-isomer, but the mechanism for this interaction is not known. In this study, a chiral HPLC with fluorescence detection was used to measure the drug concentrations for analysis of the stereoselective metabolism of DOX in in vivo and in vitro experiments. We found that the plasma levels of the (-)-isomer were significantly lower than those of the (+)-enantiomer following i.v. administration of (±)-DOX to the rats and that the depletion rate constant (kdep) of (-)-DOX (0.0107±0.0007L/min) was significantly larger than that of (+)-DOX (kdep 0.0088±0.0005L/min) (p<0.05) when (±)-DOX was incubated with rat liver microsomes (RLMs). However, (-)-DOX was not depleted faster than (+)-DOX following their separate incubation with RLMs. The metabolism of (-)- or (+)-isomer in RLMs was catalysed by CYP3A because the depletion of the compounds was inhibited by ketoconazole (a potent CYP3A-selective inhibitor) similarly. More importantly, the kdep of (+)-DOX in the 1.0/2.0 and 0.5/2.5 (+)-DOX/(-)-DOX mixtures was significantly lower than that of (-)-DOX in the 1.0/2.0 and 0.5/2.5 (-)-DOX/(+)-DOX mixtures (p<0.05). In conclusion, although (-)-DOX is not depleted faster than (+)-DOX when only a single isomer of DOX is incubated with rat liver microsomes, it is depleted much faster than (+)-DOX when a mixture of the two isomers was used, suggesting a prominent and stereoselective inhibition of the (-)-isomer over the (+)-isomer at the CYP3A enzyme.

  12. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, M. B.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Laurie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Lui, J.; Macias, B.; Arbeille, P.; Danielson, R.; Chang, D.; Gunga, H.; Johnston, S.; Westby, C.; Ribeiro, L.; Ploutz-Snyder, R.; Smith, S.

    2015-01-01

    INTRODUCTION: Mechanisms responsible for the ocular structural and functional changes that characterize the visual impairment and intracranial pressure (ICP) syndrome (VIIP) are unclear, but hypothesized to be secondary to the cephalad fluid shift experienced in spaceflight. This study will relate the fluid distribution and compartmentalization associated with long-duration spaceflight with VIIP symptoms. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as the VIIP-related effects of those shifts, can be predicted preflight with acute hemodynamic manipulations, and also if lower body negative pressure (LBNP) can reverse the VIIP effects. METHODS: Physiologic variables will be examined pre-, in- and post-flight in 10 International Space Station crewmembers including: fluid compartmentalization (D2O and NaBr dilution); interstitial tissue thickness (ultrasound); vascular dimensions and dynamics (ultrasound and MRI (including cerebrospinal fluid pulsatility)); ocular measures (optical coherence tomography, intraocular pressure, ultrasound); and ICP measures (tympanic membrane displacement, otoacoustic emissions). Pre- and post-flight measures will be assessed while upright, supine and during 15 deg head-down tilt (HDT). In-flight measures will occur early and late during 6 or 12 month missions. LBNP will be evaluated as a countermeasure during HDT and during spaceflight. RESULTS: The first two crewmembers are in the preflight testing phase. Preliminary results characterize the acute fluid shifts experienced from upright, to supine and HDT postures (increased stroke volume, jugular dimensions and measures of ICP) which are reversed with 25 millimeters Hg LBNP. DISCUSSION: Initial results indicate that acute cephalad fluid shifts may be related to VIIP symptoms, but also may be reversible by LBNP. The effect of a chronic fluid shift has yet to be evaluated. Learning Objectives: Current spaceflight VIIP research is described

  13. 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...

  14. 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…

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. Isomer Spectroscopy of the Heaviest Elements

    NASA Astrophysics Data System (ADS)

    Clark, Roderick

    2009-05-01

    A new generation of experiments on the structure and properties of the heaviest elements is being performed in laboratories around the world. These studies are addressing fundamental questions such as the maximum mass and charge that a nucleus can attain. Long-lived high-K isomers are found in the region of prolate-deformed trans-fermium nuclei and by studying their decay one can learn about the single-particle structure, pairing correlations, and excitation modes of the heaviest nuclei. Recent decay spectroscopy experiments using the Berkeley Gas-Filled Separator (BGS) at the 88-Inch Cyclotron of the Lawrence Berkeley National Laboratory have yielded a wealth of detailed new information on many nuclei in the trans-fermium region. I will discuss these new results and their implications.

  20. Complete Hexose Isomer Identification with Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Nagy, Gabe; Pohl, Nicola L. B.

    2015-04-01

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

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

    SciTech Connect

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

    2013-04-19

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

  2. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, M.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Lauriie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Ribeiro, L.; Lui, J.; Macias, B.; Arbeille, P.; Danielson, R.; Chang, D.; Johnston, S.; Ploutz-Snyder, R.; Smith, S.

    2016-01-01

    NASA is focusing on long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low-Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but more than 50% of ISS astronauts experienced more profound, chronic changes with objective structural and functional findings such as papilledema and choroidal folds. Globe flattening, optic nerve sheath dilation, and optic nerve tortuosity also are apparent. This pattern is referred to as the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with the spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight, and to correlate these findings with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as the VIIP-related effects of those shifts, is predicted by the crewmember's preflight conditions and responses to acute hemodynamic manipulations (such as head-down tilt). Lastly, we will evaluate the patterns of fluid distribution in ISS astronauts during acute reversal of fluid shifts through application of lower body negative pressure (LBNP) interventions to characterize and explain general and individual responses. METHODS: We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the Figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, calcaneus tissue thickness (by

  3. Failures of fractional crystallization: ordered co-crystals of isomers and near isomers.

    PubMed

    Kelley, Steven P; Fábián, László; Brock, Carolyn Pratt

    2011-02-01

    A list of 270 structures of ordered co-crystals of isomers, near isomers and molecules that are almost the same has been compiled. Searches for structures containing isomers could be automated by the use of IUPAC International Chemical Identifier (InChI™) strings but searches for co-crystals of very similar molecules were more labor intensive. Compounds in which the heteromolecular A···B interactions are clearly better than the average of the homomolecular A···A and B···B interactions were excluded. The two largest structural classes found include co-crystals of configurational diastereomers and of quasienantiomers (or quasiracemates). These two groups overlap. There are 114 co-crystals of diastereomers and the same number of quasiracemates, with 71 structures being counted in both groups; together the groups account for 157 structures or 58% of the total. The large number of quasiracemates is strong evidence for inversion symmetry being very favorable for crystal packing. Co-crystallization of two diastereomers is especially likely if a 1,1 switch of a methyl group and an H atom, or of an inversion of a [2.2.1] or [2.2.2] cage, in one of the diastereomers would make the two molecules enantiomers.

  4. Isomers and Enhanced Stability of Superheavy Elements

    NASA Astrophysics Data System (ADS)

    Kondev, Filip; Anl, Lbnl, Anu, Csnsm, Llnl, Usna, U. Of Edinburgh, U. Of Jyväskylä, U. Of Massachusetts, Lowell Collaboration

    2014-09-01

    There has been continuing activity addressing the complex question of whether excited isomeric states would lead to enhanced stability of superheavy nuclei, given changes in the fission barriers, α-decay probabilities and the effects of nuclear structure (such as K-hindrance). Recently, we have carried out new studies of the 254Rf isotope using the 50Ti + 206Pb reaction at Argonne National Laboratory and Lawrence Berkeley National Laboratory. A digital data acquisition system was deployed in both experiments, which allowed the identification of implant and decay events that were separated by time as short as hundreds of nanoseconds. Two isomeric states were discovered in 254Rf with half-lives of ~4 μs and ~300 μs, the latter being an order of magnitude longer lived than the ground state. In addition, K-isomers in 244Cm and 246Cm were also studied following β- decays of 244Am (Kπ = 6+) and 246Am (Kπ = 7-) mass-separated sources, respectively. The emphasis was on elucidating details of the level schemes, which allowed reliable values for the strength of the K-forbidden transitions to be determined and compared with systematics in other regions of the nuclear chart. There has been continuing activity addressing the complex question of whether excited isomeric states would lead to enhanced stability of superheavy nuclei, given changes in the fission barriers, α-decay probabilities and the effects of nuclear structure (such as K-hindrance). Recently, we have carried out new studies of the 254Rf isotope using the 50Ti + 206Pb reaction at Argonne National Laboratory and Lawrence Berkeley National Laboratory. A digital data acquisition system was deployed in both experiments, which allowed the identification of implant and decay events that were separated by time as short as hundreds of nanoseconds. Two isomeric states were discovered in 254Rf with half-lives of ~4 μs and ~300 μs, the latter being an order of magnitude longer lived than the ground state. In

  5. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, Michael; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Sargsyan, A.; Martin, D.; Lui, J.; Macias, B.; Arbeille, P.; Platts, S.

    2014-01-01

    NASA is focusing on long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but more than 30% of ISS astronauts experience more profound, chronic changes with objective structural and functional findings such as papilledema and choroidal folds. Globe flattening, optic nerve sheath dilation, and optic nerve tortuosity also are apparent. This pattern is referred to as the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with the space flight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration space flight, and to correlate these findings with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during space flight, as well as the VIIP-related effects of those shifts, is predicted by the crewmember's pre-flight condition and responses to acute hemodynamic manipulations (such as head-down tilt). Lastly, we will evaluate the patterns of fluid distribution in ISS astronauts during acute reversal of fluid shifts through application of lower body negative pressure (LBNP) interventions to characterize and explain general and individual responses. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the Figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, calcaneus tissue thickness (by ultrasound

  6. 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.

  7. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, M. B.; Hargens, A. R.; Dulchavsky, S. A.; Arbeille, P.; Danielson, R. W.; Ebert, D. J.; Garcia, K. M.; Johnston, S. L.; Laurie, S. S.; Lee, S. M. C.; Liu, J.; Macias, B.; Martin, D. S.; Minkoff, L.; Ploutz-Snyder, R.; Ribeiro, L. C.; Sargsyan, A.; Smith, S. M.

    2017-01-01

    Introduction. NASA's Human Research Program is focused on addressing health risks associated with long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but now more than 50 percent of ISS astronauts have experienced more profound, chronic changes with objective structural findings such as optic disc edema, globe flattening and choroidal folds. These structural and functional changes are referred to as the visual impairment and intracranial pressure (VIIP) syndrome. Development of VIIP symptoms may be related to elevated intracranial pressure (ICP) secondary to spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight and to determine if a relation exists with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as any VIIP-related effects of those shifts, are predicted by the crewmember's pre-flight status and responses to acute hemodynamic manipulations, specifically posture changes and lower body negative pressure. Methods. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, and calcaneus tissue thickness (by ultrasound); (3) vascular dimensions by ultrasound (jugular veins, cerebral and carotid arteries, vertebral arteries and veins, portal vein); (4) vascular dynamics by MRI (head/neck blood flow, cerebrospinal fluid

  8. Electropolymerization mechanisms of hydroxyphenylacetic acid isomers

    NASA Astrophysics Data System (ADS)

    Rodrigues, Luciano P.; Ferreira, Deusmaque C.; Sonoda, Milton Taidi; Madurro, Ana Graci B.; Abrahão, Odonírio; Madurro, João M.

    2014-08-01

    Three different films of conducting polymers with free carboxylic functional groups were obtained from 2,3 and 4-hydroxyphenylacetic acid isomers (HPA) and the respective electropolymerization mechanisms were elucidated by DFT calculations. The different properties observed at these new material characterizations, obtained by means of cyclic voltammetry on graphite, are in agreement with theoretical interpretation presented for each reaction mechanisms, which involves the different radical cation coupling and formation of aromatic polyethers with free carboxyl groups, characterized by FTIR spectrometry and electrochemical tests. The computational chemistry analysis of the radical cations spin densities and partial atomic charges variation during the monomer oxidations, indicates the most probably reactive sites for their coupling, allowing the proposition of HPA electropolymerization mechanisms. The poly(2-HPA) had the largest yield in the electropolymerization reaction and the lowest electron transfer. The poly(4-HPA) displayed the lowest yield and the largest electron transfer coefficient, with poly(3-HPA) presenting intermediate values between the former two. Therefore, poly(3-HPA) is a very promising polymer for the platform development for electronic systems, which require materials with good electronic conductivity allied to intrinsic flexibility of polymeric materials.

  9. 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.

  10. The proportion of lycopene isomers in human plasma is modulated by lycopene isomer profile in the meal but not by lycopene preparation.

    PubMed

    Richelle, Myriam; Lambelet, Pierre; Rytz, Andreas; Tavazzi, Isabelle; Mermoud, Anne-France; Juhel, Christine; Borel, Patrick; Bortlik, Karlheinz

    2012-05-01

    Dietary lycopene consists mostly of the (all-E) isomer. Upon absorption, (all-E) lycopene undergoes isomerisation into various (Z)-isomers. Because these isomers offer potentially better health benefits than the (all-E) isomer, the aim of the present study was to investigate if the profile of lycopene isomers in intestinal lipoproteins is affected by the profile of lycopene isomers in the meal and by the tomato preparation. Six postprandial, crossover tests were performed in healthy men. Three meals provided about 70 % of the lycopene as (Z)-isomers, either mainly as 5-(Z) or 13-(Z), or as a mixture of 9-(Z) and 13-(Z) lycopene, while three tomato preparations provided lycopene mainly as the (all-E) isomer. Consumption of the 5-(Z) lycopene-rich meal led to a high (60 %) proportion of this isomer in TAG-rich lipoproteins (TRL), indicating a good absorption and/or a low intestinal conversion of this isomer. By contrast, consumption of meals rich in 9-(Z) and 13-(Z) lycopene isomers resulted in a low level of these isomers but high amounts of the 5-(Z) and (all-E) isomers in TRL. This indicates that the 9-(Z) and 13-(Z) isomers were less absorbed or were converted into 5-(Z) and (all-E) isomers. Dietary (Z)-lycopene isomers were, therefore, differently isomerised and released in TRL during their intestinal absorption in men. Consuming the three meals rich in (all-E) lycopene resulted in similar proportions of lycopene isomers in TRL: 60 % (all-E), 20 % 5-(Z), 9 % 13-(Z), 2 % 9-(Z) and 9 % unidentified (Z)-isomers. These results show that the tomato preparation has no impact on the lycopene isomerisation occurring during absorption in humans.

  11. 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.

  12. Carotenoids and their isomers: color pigments in fruits and vegetables.

    PubMed

    Khoo, Hock-Eng; Prasad, K Nagendra; Kong, Kin-Weng; Jiang, Yueming; Ismail, Amin

    2011-02-18

    Fruits and vegetables are colorful pigment-containing food sources. Owing to their nutritional benefits and phytochemicals, they are considered as 'functional food ingredients'. Carotenoids are some of the most vital colored phytochemicals, occurring as all-trans and cis-isomers, and accounting for the brilliant colors of a variety of fruits and vegetables. Carotenoids extensively studied in this regard include β-carotene, lycopene, lutein and zeaxanthin. Coloration of fruits and vegetables depends on their growth maturity, concentration of carotenoid isomers, and food processing methods. This article focuses more on several carotenoids and their isomers present in different fruits and vegetables along with their concentrations. Carotenoids and their geometric isomers also play an important role in protecting cells from oxidation and cellular damages.

  13. Tocopherol isomers in intravenous lipid emulsions and resultant plasma concentrations.

    PubMed

    Gutcher, G R; Lax, A A; Farrell, P M

    1984-01-01

    Conflicting reports exist regarding the relative tocopherol isomer content of Intralipid ranging from 99% as alpha-tocopherol to as much as 90% as gamma-tocopherol. Our direct assay of Intralipid as well as plasma levels measured in premature infants receiving Intralipid confirm the existence of a low alpha, high gamma-tocopherol content and imply the need for alpha-tocopherol supplementation in patients receiving Intralipid, particularly the relatively tocopherol-deficient premature infant. Furthermore, the observation of abnormal erythrocyte hemolysis test values despite "normal" total tocopherol plasma concentrations may be explained by high plasma levels of non-alpha, biologically less active isomers. The quantitation of tocopherol isomers helps explain this discrepancy and suggests the need for future studies of vitamin E status to employ measurements of tocopherol isomers in reporting results.

  14. 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.

  15. 57Fe NMR study of the magnetoelectric hexaferrite Ba0.5Sr1.5Zn2Fe12O22 and Ba0.5Sr1.5Zn2(Fe0.92Al0.08)12O22

    NASA Astrophysics Data System (ADS)

    Kwon, Sangil; Yoon, Dong Young; Lee, Soonchil; Chai, Yi Sheng; Chun, Sae Hwan; Kim, Kee Hoon

    2013-08-01

    Magnetoelectric hexaferrite Ba0.5Sr1.5Zn2Fe12O22 (BSZFO) and Ba0.5Sr1.5Zn2(Fe0.92Al0.08)12O22 (BSZFAO) were investigated by 57Fe nuclear magnetic resonance (NMR). The spin-canting angles of all NMR peaks were measured to assign each peak to corresponding Fe3+ sites. It was revealed that the spin-canting angle of Fe3+ ions at off-centered octahedra is fixed and Al3+ ions substitute for Fe3+ ions at those sites. The temperature dependence of the NMR frequency indicates that the low-temperature excitation is spin wave in ferromagnetic phase.

  16. Differential degradation of nonylphenol isomers by Sphingomonas xenophaga Bayram.

    PubMed

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

    2005-03-01

    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.

  17. 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

  18. DFT/TDDFT investigation on the chemical reactivities, aromatic properties, and UV-Vis absorption spectra of 1-butoxy-4-methoxybenzenepillar[5]arene constitutional isomers.

    PubMed

    Zhang, Jian; Ren, Shuqing

    2016-09-01

    We investigate the chemical reactivities, aromatic properties, and UV-Vis absorption spectra of four constitutional isomers of 1-butoxy-4-methoxybenzenepillar[5]arene with the DFT and TDDFT methods. These characteristics in the gas and solvent phases are discussed on the basis of electronic energy, the highest occupied molecular orbital energy, electrophilicity, global hardness, chemical potential, and nucleus-independent chemical shift. The out-of-plane component of the NICS values reveals that there is a great contrast between aromatic rings of the isomer and benzene. The most intense wavelengths of BMpillar[5]arenes are all made up of delocalized-delocalized π → π* transition.

  19. Anaerobic Degradation of Phthalate Isomers by Methanogenic Consortia

    PubMed Central

    Kleerebezem, Robbert; Pol, Look W. Hulshoff; Lettinga, Gatze

    1999-01-01

    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 (μSmax) and biomass yields (YXtotS) 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 μSmax and YXtotS 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 (KS) 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. PMID:10049876

  20. Site-specific protein glycosylation analysis with glycan isomer differentiation.

    PubMed

    Hua, Serenus; Nwosu, Charles C; Strum, John S; Seipert, Richard R; An, Hyun Joo; Zivkovic, Angela M; German, J Bruce; Lebrilla, Carlito B

    2012-05-01

    Glycosylation is one of the most common yet diverse post-translational modifications. Information on glycan heterogeneity and glycosite occupancy is increasingly recognized as crucial to understanding glycoprotein structure and function. Yet, no approach currently exists with which to holistically consider both the proteomic and glycomic aspects of a system. Here, we developed a novel method of comprehensive glycosite profiling using nanoflow liquid chromatography/mass spectrometry (nano-LC/MS) that shows glycan isomer-specific differentiation on specific sites. Glycoproteins were digested by controlled non-specific proteolysis in order to produce informative glycopeptides. High-resolution, isomer-sensitive chromatographic separation of the glycopeptides was achieved using microfluidic chip-based capillaries packed with graphitized carbon. Integrated LC/MS/MS not only confirmed glycopeptide composition but also differentiated glycan and peptide isomers and yielded structural information on both the glycan and peptide moieties. Our analysis identified at least 13 distinct glycans (including isomers) corresponding to five compositions at the single N-glycosylation site on bovine ribonuclease B, 59 distinct glycans at five N-glycosylation sites on bovine lactoferrin, 13 distinct glycans at one N-glycosylation site on four subclasses of human immunoglobulin G, and 20 distinct glycans at five O-glycosylation sites on bovine κ-casein. Porous graphitized carbon provided effective separation of glycopeptide isomers. The integration of nano-LC with MS and MS/MS of non-specifically cleaved glycopeptides allows quantitative, isomer-sensitive, and site-specific glycoprotein analysis.

  1. Infrared spectroscopy of the bent isomer of N 2O-HF

    NASA Astrophysics Data System (ADS)

    Dayton, D. C.; Miller, R. E.

    1988-02-01

    We report the infrared spectrum of the bent isomer of N 2O-HF in which the HF subnit is hydrogen bonded to the oxygen. This isomer was previously observed using microwave spectroscopy, while recent infrared measurements by Lovejoy and Nesbitt have shown that a linear (or slightly bent) ONNHF isomer also exists. We find that the linear ONNHF isomer is present under identical beam conditions to those used to record the spectrum of the bent isomer.

  2. Monopole-driven shell evolution below the doubly magic nucleus 132Sn explored with the long-lived isomer in 126Pd.

    PubMed

    Watanabe, H; Lorusso, G; Nishimura, S; Otsuka, T; Ogawa, K; Xu, Z Y; Sumikama, T; Söderström, P-A; Doornenbal, P; Li, Z; Browne, F; Gey, G; Jung, H S; Taprogge, J; Vajta, Zs; Wu, J; Yagi, A; Baba, H; Benzoni, G; Chae, K Y; Crespi, F C L; Fukuda, N; Gernhäuser, R; Inabe, N; Isobe, T; Jungclaus, A; Kameda, D; Kim, G D; Kim, Y K; Kojouharov, I; Kondev, F G; Kubo, T; Kurz, N; Kwon, Y K; Lane, G J; Moon, C-B; Montaner-Pizá, A; Moschner, K; Naqvi, F; Niikura, M; Nishibata, H; Nishimura, D; Odahara, A; Orlandi, R; Patel, Z; Podolyák, Zs; Sakurai, H; Schaffner, H; Simpson, G S; Steiger, K; Suzuki, H; Takeda, H; Wendt, A; Yoshinaga, K

    2014-07-25

    A new isomer with a half-life of 23.0(8) ms has been identified at 2406 keV in (126)Pd and is proposed to have a spin and parity of 10(+) with a maximally aligned configuration comprising two neutron holes in the 1h(11/2) orbit. In addition to an internal-decay branch through a hindered electric octupole transition, β decay from the long-lived isomer was observed to populate excited states at high spins in (126)Ag. The smaller energy difference between the 10(+) and 7(-) isomers in (126)Pd than in the heavier N=80 isotones can be interpreted as being ascribed to the monopole shift of the 1h(11/2) neutron orbit. The effects of the monopole interaction on the evolution of single-neutron energies below (132)Sn are discussed in terms of the central and tensor forces.

  3. Monopole-Driven Shell Evolution below the Doubly Magic Nucleus Sn132 Explored with the Long-Lived Isomer in Pd126

    NASA Astrophysics Data System (ADS)

    Watanabe, H.; Lorusso, G.; Nishimura, S.; Otsuka, T.; Ogawa, K.; Xu, Z. Y.; Sumikama, T.; Söderström, P.-A.; Doornenbal, P.; Li, Z.; Browne, F.; Gey, G.; Jung, H. S.; Taprogge, J.; Vajta, Zs.; Wu, J.; Yagi, A.; Baba, H.; Benzoni, G.; Chae, K. Y.; Crespi, F. C. L.; Fukuda, N.; Gernhäuser, R.; Inabe, N.; Isobe, T.; Jungclaus, A.; Kameda, D.; Kim, G. D.; Kim, Y. K.; Kojouharov, I.; Kondev, F. G.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Lane, G. J.; Moon, C.-B.; Montaner-Pizá, A.; Moschner, K.; Naqvi, F.; Niikura, M.; Nishibata, H.; Nishimura, D.; Odahara, A.; Orlandi, R.; Patel, Z.; Podolyák, Zs.; Sakurai, H.; Schaffner, H.; Simpson, G. S.; Steiger, K.; Suzuki, H.; Takeda, H.; Wendt, A.; Yoshinaga, K.

    2014-07-01

    A new isomer with a half-life of 23.0(8) ms has been identified at 2406 keV in Pd126 and is proposed to have a spin and parity of 10+ with a maximally aligned configuration comprising two neutron holes in the 1h11/2 orbit. In addition to an internal-decay branch through a hindered electric octupole transition, β decay from the long-lived isomer was observed to populate excited states at high spins in Ag126. The smaller energy difference between the 10+ and 7- isomers in Pd126 than in the heavier N =80 isotones can be interpreted as being ascribed to the monopole shift of the 1h11/2 neutron orbit. The effects of the monopole interaction on the evolution of single-neutron energies below Sn132 are discussed in terms of the central and tensor forces.

  4. Shifting sugars and shifting paradigms.

    PubMed

    Siegal, Mark L

    2015-02-01

    No organism lives in a constant environment. Based on classical studies in molecular biology, many have viewed microbes as following strict rules for shifting their metabolic activities when prevailing conditions change. For example, students learn that the bacterium Escherichia coli makes proteins for digesting lactose only when lactose is available and glucose, a better sugar, is not. However, recent studies, including three PLOS Biology papers examining sugar utilization in the budding yeast Saccharomyces cerevisiae, show that considerable heterogeneity in response to complex environments exists within and between populations. These results join similar recent results in other organisms that suggest that microbial populations anticipate predictable environmental changes and hedge their bets against unpredictable ones. The classical view therefore represents but one special case in a range of evolutionary adaptations to environmental changes that all organisms face.

  5. Composition Shift as a Function of Thickness in Fe3-δO4(001) Epitaxial Films

    NASA Astrophysics Data System (ADS)

    Minagawa, Makoto; Yanagihara, Hideto; Uwabo, Kazuyuki; Kita, Eiji; Mibu, Ko

    2010-08-01

    We report on a thickness-dependent composition shift and a valency change in B-site Fe in Fe3-δO4(001) epitaxial films prepared by ozone-assisted molecular beam epitaxy. Conversion electron Mössbauer spectroscopy (CEMS) measurements for locally inserted 57Fe-enriched probe layers showed that a pure γ-Fe2O3 film can be obtained only if the film is sufficiently thin, and that the composition shift occurs when the thickness increases. The resistivity of Fe3-δO4 films having different thicknesses exhibited a significant decrease with an increase in the thickness, consistent with the CEMS experiment. These results indicate that γ-Fe2O3 films do not preferably grow homoepitaxially and that careful control of the growth is necessary to apply γ-Fe2O3 films to spintronics devices.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Sequence Analysis of Trimer Isomers Formed by Montmorillonite Catalysis in the Reaction of Binary Monomer Mixtures

    NASA Astrophysics Data System (ADS)

    Ertem, Gözen; Hazen, Robert M.; Dworkin, Jason P.

    2007-10-01

    Oligonucleotides are structurally similar to short RNA strands. Therefore, their formation via non-enzymatic reactions is highly relevant to Gilbert's RNA world scenario (1986) and the origin of life. In laboratory synthesis of oligonucleotides from monomers, it is necessary to remove the water molecules from the reaction medium to shift the equilibrium in favor of oligonucleotide formation, which would have been impossible for reactions that took place in dilute solutions on the early Earth. Model studies designed to address this problem demonstrate that montmorillonite, a phyllosilicate common on Earth and identified on Mars, efficiently catalyzes phosphodiester-bond formation between activated mononucleotides in dilute solutions and produces RNA-like oligomers. The purpose of this study was to examine the sequences and regiospecificity of trimer isomers formed in the reaction of 5'-phosphorimidazolides of adenosine and uridine. Results demonstrated that regiospecificity and sequence specificity observed in the dimer fractions are conserved in their elongation products. With regard to regiospecificity, 61% of the linkages were found to be RNA-like 3',5'-phosphodiester bonds. With regard to sequence specificity, we found that 88% of the linear trimers were hetero-isomers with 61% A-monomer and 39% U-monomer incorporation. These results lend support to Bernal's hypothesis that minerals may have played a significant role in the chemical processes that led to the origin of life by catalyzing the formation of phosphodiester bonds in RNA-like oligomers.

  11. Differences in CLA isomer distribution of cow's milk lipids.

    PubMed

    Kraft, Jana; Collomb, Marius; Möckel, Peter; Sieber, Robert; Jahreis, Gerhard

    2003-06-01

    The uniqueness of ruminant milk lipids is based on their high concentration of CLA. Maximal CLA concentrations in milk lipids require optimal conditions of ruminal fermentation and substrate availability, conditions like those present in pasture-fed cows. Our previous work showed that farm management (indoor feeding vs. pasture feeding) markedly influenced the CLA concentration. In this study, the objective was to evaluate the influence of the farm management system as dependent on different locations. Milk samples from different locations (Thuringia and the Alps, representing diverse altitudes) were collected during the summer months and analyzed for FA profile and CLA isomer distribution. The proportion of PUFA and total CLA in milk fat was significantly lower in milk from indoor cows compared with the pasture cows in the Alps. The trans-11 18:1 in milk fat of Alpine cows was elevated, in contrast to lower values for trans-10 18:1. Milk from cows grazing pasture in the Alps was higher in EPA and lower in arachidonic acid than milk from indoor-fed cows. The proportion of cis,trans/trans,cis isomers of CLA was 10 times higher from the indoor cows than from the Alpine cows. In addition to the major isomer cis-9,trans-11, this difference also occurred for the trans-11,cis-13 isomer, which represented more than a fourth of the total CLA present in milk fat. This is the first report showing a special isomer distribution in the milk fat of cows living under very natural conditions. We hypothesize that the CLA isomer trans-11,cis-13 is formed in large quantity as a result of grazing mountain pasture, which is rich in alpha-linolenic acid.

  12. Energy spectrum and optical transitions in C80 fullerene isomers

    NASA Astrophysics Data System (ADS)

    Lobanov, B. V.; Murzashev, A. I.

    2013-04-01

    The energy spectra of all isomers of the C80 fullerene have been calculated in terms of the Schubin-Wonsowskii-Hubbard model. On this basis, their optical absorption spectra have also been calculated. The optical absorption spectra calculated for the endohedral Ca@C80, Ba@C80, and Sr@C80 fullerenes with the I h symmetry agree well with the experimental data. This circumstance allows us to conclude that the optical absorption spectra of other isomers (for which experimental data are unavailable) obtained in this work can be used for their identification.

  13. 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.

  14. HiFSA Fingerprinting Applied to Isomers with Near-Identical NMR Spectra: The Silybin/Isosilybin Case

    PubMed Central

    Napolitano, José G.; Lankin, David C.; Graf, Tyler N.; Friesen, J. Brent; Chen, Shao-Nong; McAlpine, James B.; Oberlies, Nicholas H.; Pauli, Guido F.

    2013-01-01

    This study demonstrates how regio- and diastereo-isomers with near-identical NMR spectra can be distinguished and unambiguously assigned using quantum mechanical driven, 1H iterative Full Spin Analysis (HiFSA). The method is illustrated with four natural products, the flavonolignans silybin A, silybin B, isosilybin A, and isosilybin B, which exhibit extremely similar coupling patterns and chemical shift differences well below the commonly reported level of accuracy of 0.01 ppm. The HiFSA approach generated highly reproducible 1H NMR fingerprints that enable distinction of all four isomers at 1H frequencies from 300 to 900 MHz. Furthermore, it is demonstrated that the underlying numeric 1H NMR profiles, combined with iterative computational analysis, allow parallel quantification of all four isomers, even in difficult to characterize reference materials and mixtures. The results shed new light on the historical challenges to the qualitative and quantitative analysis of these therapeutically relevant flavonolignans and open new opportunities to explore hidden diversity in the chemical space of organic molecules. PMID:23461697

  15. Positional isomers of bispyridine benzene derivatives induce efficacy changes on mGlu5 negative allosteric modulation.

    PubMed

    Gómez-Santacana, Xavier; Dalton, James A R; Rovira, Xavier; Pin, Jean Philippe; Goudet, Cyril; Gorostiza, Pau; Giraldo, Jesús; Llebaria, Amadeu

    2017-02-15

    Modulation of metabotropic glutamate receptor 5 (mGlu5) with partial allosteric antagonists has received increased interest due to their favourable in vivo activity profiles compared to the unfavourable side-effects of full inverse agonists. Here we report on a series of bispyridine benzene derivatives with a functional molecular switch affecting antagonistic efficacy, shifting from inverse agonism to partial antagonism with only a single change in the substitution pattern of the benzene ring. These efficacy changes are explained through computational docking, revealing two different receptor conformations of different energetic stability and different positional isomer binding preferences.

  16. Biotransformations of 2-hydroxy-2-(ethoxyphenylphosphinyl)acetic acid and the determination of the absolute configuration of all isomers.

    PubMed

    Majewska, Paulina

    2015-08-01

    2-Hydroxy-2-(ethoxyphenylphosphinyl)acetic acid, a new type of organophosphorus compound possessing two stereogenic centers, was investigated. Racemic 2-butyryloxy-2-(ethoxyphenylphosphinyl)acetic acid was synthesized and hydrolyzed using four bacterial species as biocatalysts. In all cases the reaction was more or less stereoselective and isomers bearing a phosphorus atom with an (SP)-configuration were hydrolyzed preferentially. The observed (1)H and (31)P NMR chemical shifts of Mosher esters of 2-hydroxy-2-(ethoxyphenylphosphinyl)acetic acid were correlated with the configurations of both stereogenic centers of all four stereoisomers.

  17. Characterization and determination of piperine and piperine isomers in eggs.

    PubMed

    Ternes, Waldemar; Krause, Edburga L

    2002-09-01

    A new analytical method for the determination of piperine and its isomers in egg yolk and albumen is described here. All four isomers were separated by HPLC and detected using UV, DAD and electrochemical detection. The absolute detection limit (UV detection, S/ N=3) of a standard solution of piperine was 370 pg piperine. The correlation coefficients for the linear calibration graphs (concentration range: c=100 ng-10 micro g piperine isomer/mL) are generally better than 0.996. The piperine isomers were characterized and identified by spectroscopy (MS, (1)H-NMR, FT-IR). The method was successfully applied to the determination of piperine deposits in eggs (egg yolk and albumen) after feeding hens with piperine-spiked feed. The detection limit for piperine (24.8(+/-0.2) ng/g egg yolk and 37.9(+/-4.9) ng/g albumen) and the recoveries (70.3(+/-7.7)% (egg yolk) and 75.7(+/-1.9)% (albumen)) of piperine were determined.

  18. Fermentation of five sucrose isomers by human dental plaque bacteria.

    PubMed

    Matsuyama, J; Sato, T; Hoshino, E; Noda, T; Takahashi, N

    2003-01-01

    Sucrose has five structural isomers: palatinose, trehalulose, turanose, maltulose and leucrose. Although these isomers have been reported to be noncariogenic disaccharides, which cannot be utilized by mutans streptococci, there is no information about their fermentability by other bacteria in dental plaque. The purpose of the present study was to examine whether these isomers were fermented by predominant bacteria in human dental plaque. Clinical bacterial isolates obtained from dental plaque from 3 children aged 22 months to 50 months (146 strains) were inoculated into 3 ml of peptone-yeast extract (PY medium) containing glucose for 1 day, then an aliquot of 20 microl of culture medium was inoculated into 1 ml of PY medium containing 1% (w/v) of the respective test carbohydrates. After incubation for 1 day, the pH values and the optical density at 660 nm of the cultures were measured. Fermentation ability was measured by pH or=0.5. Of the clinical isolates, 33% fermented palatinose, and 69% of these were Actinomyces species. All of the palatinose-fermenting bacterial strains fermented trehalulose, 25% fermented turanose, 70% fermented maltulose and 23% fermented leucrose. We therefore conclude that, in human dental plaque, there are significant numbers of bacteria that are able to ferment sucrose isomers.

  19. The molecular properties of nitrobenzanthrone isomers and their mutagenic activities.

    PubMed

    Ostojić, Bojana D; Stanković, Branislav; Ðorđević, Dragana S

    2014-06-01

    The mutagenic activity of five mono-substituted nitrobenzanthrones (NBA) has been determined in the Ames assay (Takamura-Enya et al., 2006). In the present study, a theoretical investigation of the electronic properties of all mono-substituted NBA isomers and their relation to mutagenic activity are presented. Equilibrium geometries, vertical ionization potentials (VIP), vertical electron affinities (VEA), relative energies, dipole moments and electronic dipole polarizabilities, and the IR and Raman spectra of NBA isomers calculated by Density Functional Theory (DFT) methods are presented. The position of the nitro group affects the spectral features of the IR and Raman spectra of the NBA isomers. The results show that a good linear relationship exists between the summation of Raman activities (∑ARaman) over all the 3N-6 vibrational modes and the mutagenic activity of the NBA isomers in Salmonella typhimurium strains. The spectroscopic results suggest that the unknown mutagenic activities of 4-NBA, 5-NBA, 6-NBA, 8-NBA and 10-NBA are predicted to follow the order 4-NBA>10-NBA>5-NBA>8-NBA>6-NBA.

  20. 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.

  1. 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).

  2. 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.

  3. High Spin Isomers and Super Heavy Elements (SHE) Synthesis

    SciTech Connect

    Popescu, Domitian G.

    2010-04-30

    To get closer to the SHE-Island the new radioactive beams are proposed for future fusion reaction. We suggest something different: to use the advantage of High Spin Isomer States, by tacking into account the importance of the G (spin-isospin cupling) suggested by Ripka 1.

  4. 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...

  5. 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

  6. 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.

  7. 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.

  8. Theoretical Investigation of Intramolecular Hydrogen Shift Reactions in 3-Methyltetrahydrofuran (3-MTHF) Oxidation.

    PubMed

    Parab, Prajakta R; Sakade, Naoki; Sakai, Yasuyuki; Fernandes, Ravi; Heufer, K Alexander

    2015-11-05

    3-Methyltetrahydrofuran (3-MTHF) is proposed to be a promising fuel component among the cyclic oxygenated species. To have detailed insight of its combustion kinetics, intramolecular hydrogen shift reactions for the ROO to QOOH reaction class are studied for eight ROO isomers of 3-MTHF. Rate constants of all possible reaction paths that involve formation of cyclic transition states are computed by employing the CBS-QB3 composite method. A Pitzer-Gwinn-like approximation has been applied for the internal rotations in reactants, products, and transition states for the accurate treatment of hindered rotors. Calculated relative barrier heights highlight that the most favorable reaction channel proceeds via a six membered transition state, which is consistent with the computed rate constants. Comparing total rate constants in ROO isomers of 3-MTHF with the corresponding isomers of methylcyclopentane depicts faster kinetics in 3-MTHF than methylcyclopentane reflecting the effect of ring oxygen on the intramolecular hydrogen shift reactions.

  9. 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

  10. 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...

  11. 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...

  12. 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)

  13. Azaphthalocyanines with fused triazolo rings: formation of sterically stressed constitutional isomers.

    PubMed

    Novakova, Veronika; Roh, Jaroslav; Gela, Petr; Kuneš, Jiří; Zimcik, Petr

    2012-05-07

    The presented work deals with synthesis and isolation of constitutional isomers of triazolo-fused azaphthalocyanines. Distribution of the isomers did not follow the statistical calculations due to steric effects of the substituents preferring the least sterically stressed C(4h) isomer.

  14. 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... Exemptions From Tolerances § 180.1073 Isomate-M; exemption from the requirement of a tolerance. The oriental fruit moth pheromone (Isomate-M) (Z-8-dodecen-l-yl acetate, E-8-dodecen-l-yl acetate,...

  15. 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... Exemptions From Tolerances § 180.1073 Isomate-M; exemption from the requirement of a tolerance. The oriental fruit moth pheromone (Isomate-M) (Z-8-dodecen-l-yl acetate, E-8-dodecen-l-yl acetate,...

  16. Isomer selective ionization of chlorinated PAH's: Detection of impurities in technical 9-monochloroanthracene

    SciTech Connect

    Zimmermann, Ralf; Lermer, Christoph; Lenoir, Dieter; Boesl, Ulrich

    1995-04-01

    Two-color RIS of anthracene (A), of all of its monochloroisomers and one dichlorinated (DCA) isomer have been measured. The possibility of isomer selective resonance ionization of the monochloroanthracenes (MCA) is demonstrated. A technical sample of the 9-DCA isomer has been investigated; no impurities of monochroroisomers have been found but significant impurities of non-chlorinated A and 9, 10-DCA.

  17. 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...

  18. 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...

  19. 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...

  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.

  1. Racemization as a stereochemical measure of dynamics and robustness in shape-shifting organic molecules

    PubMed Central

    He, Maggie; Bode, Jeffrey W.

    2011-01-01

    Bullvalene is a structurally unique dynamic molecule thought to interconvert among 1.2 million degenerate isomers. The incorporation of different chemical substituents onto the bullvalene core should lead to a “shape-shifting” molecule that can interconvert among thousands of discrete structural isomers. Previous NMR spectroscopy and HPLC studies on substituted bullvalenes ascertained the fact that these compounds are dynamic, but they could not attest to whether the molecules are only interconverting among only a few isomers or if a multitude of structures are being accessed. Here we confirm the remarkable shape-shifting property of a tetrasubstituted bullvalene by means of a racemization experiment. We show that a single, though fleeting, chiral, enantioenriched tetrasubstituted bullvalene isomer can spontaneously equilibrate to a racemic population of dynamic compounds. Despite the fact that conversion from one enantiomer of a bullvalene isomer to the other may require dozens or even hundreds of rearrangements and involve many potential pathways, CD spectroscopy and HPLC analysis of different bullvalene populations showed that multiple pathways exist and result in the complete racemization of an initial enantioenriched chiral bullvalene. These oligosubstituted bullvalenes represent a very rare example of an entity that can spontaneously transform itself into different discrete structures using ambient thermal energy. The confirmation that these shape-shifting organic molecules are chemically robust yet structurally dynamic is an important step toward their further use as materials, sensors, and biologically active compounds. PMID:21873220

  2. Population and decay of a Kπ=8– two-quasineutron isomer in Pu244

    DOE PAGES

    Hota, S. S.; Tandel, S. K.; Chowdhury, P.; ...

    2016-08-22

    Here, the decay of a Kπ = 8– isomer in 244Pu and the collective band structures populating the isomer were studied using deep inelastic excitations with 47Ti and 208Pb beams, respectively. Precise measurements of M1/E2 branching ratios in the band confirm a 9/2–[734]νⓍ7/2+[624]ν configuration assignment for the isomer, validating the systematics of Kπ = 8–, two-quasineutron isomers observed in even-Z, N = 150 isotones. These isomers around the deformed shell gap at N = 152 provide critical benchmarks for theoretical predictions of single-particle energies in this gateway region to superheavy nuclei.

  3. Population and decay of a Kπ=8- two-quasineutron isomer in 244Pu

    NASA Astrophysics Data System (ADS)

    Hota, S. S.; Tandel, S. K.; Chowdhury, P.; Ahmad, I.; Carpenter, M. P.; Chiara, C. J.; Greene, J. P.; Hoffman, C. R.; Jackson, E. G.; Janssens, R. V. F.; Kay, B. P.; Khoo, T. L.; Kondev, F. G.; Lakshmi, S.; Lalkovski, S.; Lauritsen, T.; Lister, C. J.; McCutchan, E. A.; Moran, K.; Peterson, D.; Shirwadkar, U.; Seweryniak, D.; Stefanescu, I.; Toh, Y.; Zhu, S.

    2016-08-01

    The decay of a Kπ=8- isomer in 244Pu and the collective band structures populating the isomer were studied using deep inelastic excitations with 47Ti and 208Pb beams, respectively. Precise measurements of M 1 /E 2 branching ratios in the band confirm a 9 /2-[734] ν⊗7 /2+[624] ν configuration assignment for the isomer, validating the systematics of Kπ=8- , two-quasineutron isomers observed in even-Z , N =150 isotones. These isomers around the deformed shell gap at N =152 provide critical benchmarks for theoretical predictions of single-particle energies in this gateway region to superheavy nuclei.

  4. 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.

  5. [Beaded molecule imprinted polymer for stereo isomer separation].

    PubMed

    Meng, Z; Wang, J; Zhou, L; Wang, Q; Zhu, D

    1999-07-01

    Beaded molecule imprinted polymer (MIP) was made by suspension polymerization. Particles with the size of 50-70 microns in diameter were collected and evaluated in HPLC mode to separate stereo isomers. Stereo isomers cinchonine and cinchonidine were successfully discriminated with selectivity factor of 2.89 and resolution factor of 0.76. Stereo selectivity of the MIP was found to come from both the interaction between the analyte and carboxyl group on the MIP and the similarity between the stereo structure of imprinted molecule and the MIP. The thermal analysis results showed that the MIP had high thermal stability with initial thermal decomposition temperature of 320 degrees C. The pore volume of the MIP was 0.1849 mL/g, the specific surface area was 126.84 sqm/g and the average pore diameter was 5.8 nanometer. Scanning electron microscopy showed that MIP had perfect spherical morphology.

  6. Novel bioactive oxazolomycin isomers produced by Streptomyces albus JA3453.

    PubMed

    Kanzaki, H; Wada, K; Nitoda, T; Kawazu, K

    1998-03-01

    Two novel oxazolomycin isomers, oxazolomycins B (2) and C (3), were isolated from the fermentation broth of an oxazolomycin-producing strain, Streptomyces albus JA3453. Both compounds are geometrical isomers of oxazolomycin (1), the configurations of their triene moieties being (4'E, 6'E, 8'E) (2) and (4'Z, 6'E, 8'E) (3) while that of oxazolomycin (1) is (4'Z, 6'Z, 8'E). Compounds 2 and 3 exhibited potent inhibitory activity against crown gall formation with the same MIC (0.8 microgram/disk) as oxazolomycin. Compounds 2 and 3 showed no antibacterial activity against Agrobacterium tumefaciens, in contrast to oxazolomycin which has specific anti-A. tumefaciens activity.

  7. 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.

  8. A simple, rapid method for HPLC analysis of lycopene isomers.

    PubMed

    Ishida, B K; Ma, J; Chan, B

    2001-01-01

    A rapid method for the extraction, separation and quantification of the geometric isomers of lycopene and beta-carotene from tomato fruit is described. Carotenoids in tomato were separated and eluted using a reversed-phase HPLC with a C30 column and a mobile phase consisting of methyl-t-butyl ether, methanol and ethyl acetate. The system provided sharp resolution of cis- and trans-isomers of lycopene within approximately 23 min in contrast to the longer and more complex gradient procedures required by previously described methods. Experiments indicate that the stability of extracts of fresh tomato may be improved if stored at -20 degrees C, and that the presence of the antioxidant BHA has no apparent effect on stability.

  9. Positional isomer differentiation of synthetic cannabinoid JWH-081 by GC-MS/MS.

    PubMed

    Kusano, Maiko; Zaitsu, Kei; Nakayama, Hiroshi; Nakajima, Junichi; Hisatsune, Kazuaki; Moriyasu, Takako; Matsuta, Shuntaro; Katagi, Munehiro; Tsuchihashi, Hitoshi; Ishii, Akira

    2015-03-01

    Like many new designer drugs of abuse, synthetic cannabinoids (SC) have structural or positional isomers which may or may not all be regulated under law. Differences in acute toxicity may exist between isomers which impose further burden in the fields of forensic toxicology, medicine and legislation. Isomer differentiation therefore becomes crucial from these standpoints as new designer drugs continuously emerge with just minor positional modifications to their preexisting analogs. The aim of this study was to differentiate the positional isomers of JWH-081. Purchased standard compounds of JWH-081 and its positional isomers were analyzed by gas chromatography-electron ionization-mass spectrometry (GC-EI-MS) first in scan mode to investigate those isomers who could be differentiated by EI scan spectra. Isomers with identical or near-identical EI spectra were further subjected to GC-tandem mass spectrometry (MS/MS) analysis with appropriate precursor ions. EI scan was able to distinguish 3 of the 7 isomers: 2-methoxy, 7-methoxy and 8-methoxy. The remaining isomers exhibited near-identical spectra; hence, MS/MS was performed by selecting m/z 185 and 157 as precursor ions. 3-Methoxy and 5-methoxy isomers produced characteristic product ions that enabled the differentiation between them. Product ion spectrum of 6-methoxy isomer resembled that of JWH-081; however, the relative ion intensities were clearly different from one another. The combination of EI scan and MS/MS allowed for the regioisomeric differentiation of the targeted compounds in this study.

  10. Isomer-specific biodegradation of nonylphenol in river sediments and structure-biodegradability relationship.

    PubMed

    Lu, Zhijiang; Gan, Jay

    2014-01-21

    Nonylphenol (NP), a well-known environmental estrogen with numerous isomers, is frequently found in surface water and sediments. Recent studies showed that NP isomers exhibited different estrogenicity. However, at present little information is available on its isomer-specific degradation in the bed sediment, which is the primary sink of NP in surface aquatic systems. In this study, we investigated the biodegradability of 19 NP isomers in two river sediments under oxic and anoxic conditions. Under oxic conditions, the half-lives of NP isomers in an upper river sediment ranged from 0.9 to 13.2 d. Under reduced conditions, the persistence of NP isomers generally increased, with negligible dissipation under strongly reduced conditions. In the well-aerated sediment, NP isomers with short side chain and/or bulky α-substituents were found to be more recalcitrant to degradation. Moreover, when a total of 57 molecular descriptors were examined, the degree of branching as quantified by IDWbar was found to result in the best linear correlation with half-lives of NP isomers (R(2) = 0.88). These results indicated that the isomer-specificity of NP in environmental processes should be considered, and that simple molecular descriptors may be used to identify the more recalcitrant isomers, thus allowing prioritization in the evaluation of environmental fate and risks of NP isomers.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

  13. Determination of aminocresol isomers by high-speed liquid chromatography.

    PubMed

    Sakurai, H; Kito, M

    Aminocresol isomers (4-hydroxy-m-toluidine [II], 3-hydroxy-p-toluidine [II], 2-hydroxy-p-toluidine [III]) and p-aminophenol have been separated and determined by a high-speed liquid Chromatographie method. Since this method is applicable in aqueous media, it was used to investigate the suitability of a haemin-cysteine system as a model for the cytochrome P-450 mono-oxygenase system, by determination of the [I], [II], [III] and p-aminophenol formed.

  14. 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.

  15. Preignition and Autoignition Behavior of the Xylene Isomers

    DTIC Science & Technology

    2010-03-01

    for the addition of three additives – a fuel system icing inhibitor, a corrosion inhibitor, and a static dissipater additive. The consequences of...identified were p-tolualdehyde, toluene, and p- cresol . Of note, p- cresol was identified in this experiment but its ortho- and meta- isomers were not...methylbenzaldehyde (p-tolualdehyde) and hydrogen radical. Hydroxyl radical attack on p-tolualdehyde produces p- cresol and formyl radical. Another

  16. 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.

  17. Focal point analysis of torsional isomers of acrylic acid

    NASA Astrophysics Data System (ADS)

    Alev Çiftçioğlu, Gökçen; Trindle, Carl; Yavuz, Ilhan

    2010-10-01

    The thermochemistry of acrylic acid has presented challenges owing to its high reactivity, tendency to dimerize in the gas phase, and the existence of two very nearly equal energy conformational isomers. Well-tested thermochemical schemes including G2, G3, G4, and CBS-QB3 agree in the prediction that the s-cis syn structure is the most stable of the torsional isomers, with the s-cis anti form lying 3 kJ mol-1 or less higher in energy. Microwave spectra suggest a value of 0.63 kJ mol-1. The energy barrier between these forms is in the neighbourhood of 25 kJ mol-1 according to a MP2/cc-pVDZ calculation. We present estimates of the relative energies of all four torsional isomers and the rotational barrier based on a variant of the Focal Point Analysis developed by Császár and co-workers. These calculations, extending to the CCSD(T)/cc-pV5Z level, predict that the s-cis anti torsional isomer is the most stable form, in contrast to prior estimates. The s-cis syn form lies about 2.9 kJ mol-1 higher, while the s-trans syn and anti forms lie at about 21.7 and 23.3 kJ mol-1, respectively. We estimate the rotational barrier between the s-cis trans and s-cis anti structures to be about 23.9 kJ mol-1. Error ranges derived from the fit to extrapolation forms suggest that our estimates have an uncertainty of about 0.1 kJ mol-1.

  18. Biodegradation of Alpha TNT and Its Production Isomers

    DTIC Science & Technology

    1974-07-01

    1 ^*"* **».-._ BIODEGRADATION OF ALPHA TNT ANT) ITS PRODUCTION ISOMERS Annual Report-U by: Richard W. Traxler University of Rhode Island...associated with the burning process. If these nitrobodies are found to be biodegradable , they could be rendered ecologically safe by biological...molecules are biodegradable by some microbial form whereas the truly recalcitrant molecules are found in broad classes of the synthetic organic compounds

  19. A Rapid Compression Machine Modelling Study of the Heptane Isomers

    SciTech Connect

    Silke, E J; Curran, H J; Simmie, J M; Pitz, W J; Westbrook, C K

    2005-05-10

    Previously we have reported on the combustion behavior of all nine isomers of heptane in a rapid compression machine (RCM) with stoichiometric fuel and ''air'' mixtures at a compressed gas pressure of 15 atm. The dependence of autoignition delay times on molecular structure was illustrated. Here, we report some additional experimental work that was performed in order to address unusual results regarding significant differences in the ignition delay times recorded at the same fuel and oxygen composition, but with different fractions of nitrogen and argon diluent gases. Moreover, we have begun to simulate these experiments with detailed chemical kinetic mechanisms. These mechanisms are based on previous studies of other alkane molecules, in particular, n-heptane and iso-octane. We have focused our attention on n-heptane in order to systematically redevelop the chemistry and thermochemistry for this C{sub 7} isomer with the intention of extending our greater knowledge gained to the other eight isomers. The addition of new reaction types, that were not included previously, has had a significant impact on the simulations, particularly at low temperatures.

  20. Borromean halo, Tango halo, and halo isomers in atomic nuclei

    NASA Astrophysics Data System (ADS)

    Izosimov, Igor

    2016-01-01

    Structure of the ground and excited states in halo-like nuclei is discussed. Both the Borromean and tango halo types can be observed for n-p configurations of atomic nuclei.Structure of the halo may be different for the different levels and resonances in atomic nuclei. Isobar analog, double isobar analog, configuration, and double configuration states can simultaneously have n-n, n-p, and p-p halo components in their wave functions. When the halo structure of the excited state differs from that of the ground state, or the ground state has non-halo structure, the γ-transition from the excited state to the ground state can be essentially hindered, i.e. the formation of a specific type of isomers (halo isomers) becomes possible. B(Mγ) and B(Eγ) values for γ-transitions in 6,7,8Li, 8,9,10Be, 8,10,11B, 10,11,12,13,14C, 13,14,15,16,17N, 15,16,17,19O, and 17F are analyzed. Special attention is given to nuclei which ground state does not exhibit halo structure but the excited state (halo isomer) may have one.

  1. Three bilindione isomers: synthesis, characterization and reactivity of biliverdin analogs.

    PubMed

    Wang, Jun-Fei; Ma, Fang; Sun, Hao-Ling; Zhang, Jing; Zhang, Jun-Long

    2017-02-07

    Linear tetrapyrrole is the core structure of light-sensitive native cofactors such as phycocyanobilin, phytochromobilin and bile pigments, which attracts increasing attention in biomimetic chemistry, photochemistry and coordination chemistry. To decipher the relationship between structures and functions, in this work, we firstly reported the synthesis, isolation and characterization of three bilindione isomers (ZZZ, syn, syn, syn 1, EZE, syn, syn, anti 2 and EZE, anti, syn, anti 3) bearing meso-pentafluorophenyl groups. The structures were confirmed by X-ray diffraction and 2-D NMR spectroscopes. More importantly, the interconversion between three isomers under heating and light irradiation was investigated, and isomer 3 was found to be transformed to 1 and 2 more easily, which is in line with the results of DFT calculation. This work provides important insights for understanding the relationship between structures and functions and would be important to further construct metal complexes based on linear tetrapyrrole ligands, which are complementary to well-studied the cyclic analogs such as porphyrin and corroles.

  2. 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

  3. Electron attachment and detachment: Electron affinities of isomers of trifluoromethylbenzonitrile

    NASA Astrophysics Data System (ADS)

    Miller, Thomas M.; Viggiano, A. A.; Friedman, Jeffrey F.; Van Doren, Jane M.

    2004-11-01

    Rate constants for electron attachment to the three isomers of trifluoromethylbenzonitrile [(CF3)(CN)C6H4, or TFMBN] were measured over the temperature range of 303-463 K in a 133-Pa He buffer gas, using a flowing-afterglow Langmuir-probe apparatus. At 303 K, the measured attachment rate constants are 9.0×10-8 (o-TFMBN), 5.5×10-8 (m-TFMBN), and 8.9×10-8 cm3 s-1 (p-TFMBN), estimated accurate to ±25%. The attachment process formed only the parent anion in all three cases. Thermal electron detachment was observed for all three anion isomers, and rate constants for this reverse process were also measured. From the attachment and detachment results, the electron affinities of the three isomers of TFMBN were determined to be 0.70(o-TFMBN), 0.67(m-TFMBN), and 0.83 eV (p-TFMBN), all ±0.05 eV. G3(MP2) [Gaussian-3 calculations with reduced Møller-Plesset orders (MP2)] calculations were carried out for the neutrals and anions. Electron affinities derived from these calculations are in good agreement with the experimental values.

  4. Electron attachment and detachment: electron affinities of isomers of trifluoromethylbenzonitrile.

    PubMed

    Miller, Thomas M; Viggiano, A A; Friedman, Jeffrey F; Van Doren, Jane M

    2004-11-22

    Rate constants for electron attachment to the three isomers of trifluoromethylbenzonitrile [(CF(3))(CN)C(6)H(4), or TFMBN] were measured over the temperature range of 303-463 K in a 133-Pa He buffer gas, using a flowing-afterglow Langmuir-probe apparatus. At 303 K, the measured attachment rate constants are 9.0 x 10(-8) (o-TFMBN), 5.5 x 10(-8) (m-TFMBN), and 8.9 x 10(-8) cm(3) s(-1) (p-TFMBN), estimated accurate to +/-25%. The attachment process formed only the parent anion in all three cases. Thermal electron detachment was observed for all three anion isomers, and rate constants for this reverse process were also measured. From the attachment and detachment results, the electron affinities of the three isomers of TFMBN were determined to be 0.70(o-TFMBN), 0.67(m-TFMBN), and 0.83 eV (p-TFMBN), all +/-0.05 eV. G3(MP2) [Gaussian-3 calculations with reduced Møller-Plesset orders (MP2)] calculations were carried out for the neutrals and anions. Electron affinities derived from these calculations are in good agreement with the experimental values.

  5. Isomer-specific biodegradation of methylphenanthrenes by soil bacteria.

    PubMed

    Lamberts, Rasmus F; Christensen, Jan H; Mayer, Philipp; Andersen, Ole; Johnsen, Anders R

    2008-07-01

    It is assumed that bacteria generally degrade 2-methylphenanthrene (2MPhe) in preference to 1-methylphenanthrene (1MPhe), and that environmental biodegradation of methylated PAHs therefore can be described qualitatively by changes in relative concentrations of these isomers. Our objective was to investigate whether microbial phenanthrene degraders (Sphingomonas and Mycobacterium) show such isomer-specific PAH degradation. Eleven out of twenty-nine phenanthrene degraders could grow on methylphenanthrene. The mycobacteria grew only on 2MPhe, the sphingomonads grew mostly on 1MPhe, and one sphingomonad could utilize both substrates. Seven strains were tested in a two-phase system where 1MPhe and 2MPhe were supplied in heptamethylnonane. For these strains, a consistent description of biodegradation based on the 2MPhe/1MPhe diagnostic ratio would not be possible because three Mycobacterium and one Sphingomonas degraded 2MPhe faster than 1MPhe, another Sphingomonas degraded 1MPhe and 2MPhe at almost equal rates, and two Sphingomonas degraded 1MPhe faster than 2MPhe. Thus, environmental biodegradation of phenanthrenes may theoretically proceed with only minor changes in 2MPhe/1MPhe ratios if individual members of the degrader community have different isomer preferences. However, two soil microcosms polluted with bunker oil confirmed the general decline in 2MPhe/1MPhe ratio during oil biodegradation.

  6. Synthesis, structure of [H{sub 3} dien].(MF{sub 6}).H{sub 2}O (M=Cr, Fe) and {sup 57}Fe Moessbauer study of [H{sub 3} dien].(FeF{sub 6}).H{sub 2}O

    SciTech Connect

    Ben Ali, Amor Trang Dang, Minh; Greneche, Jean-Marc; Hemon-Ribaud, Annie; Leblanc, Marc; Maisonneuve, Vincent

    2007-06-15

    Single crystals of [H{sub 3} dien].(FeF{sub 6}).H{sub 2}O (I) and [H{sub 3} dien].(CrF{sub 6}).H{sub 2}O (II) are obtained by solvothermal synthesis under microwave heating. I is orthorhombic (Pna2{sub 1}) with a=11.530(2) A, b=6.6446(8) A, c=13.787(3) A, V=1056.3(2) A{sup 3} and Z=4. II is monoclinic (P2{sub 1} /c) with a=13.706(1) A, b=6.7606(6) A, c=11.3181(9) A, {beta}=99.38(1){sup o}, V=1034.7(1) A{sup 3} and Z=4. The structure determinations, performed from single crystal X-ray diffraction data, lead to the R {sub 1}/wR {sub 2} reliability factors 0.028/0.066 for I and 0.035/0.102 for II. The structures of I and II are built up from isolated FeF{sub 6} or CrF{sub 6} octahedra, water molecules and triprotonated amines. In both structures, each octahedron is connected by hydrogen bonds to six organic cations and two water molecules. The iron-based compound is also characterized by {sup 57}Fe Moessbauer spectrometry: the hyperfine structure confirms the presence of Fe{sup 3+} in octahedral coordination and reveals the existence of paramagnetic spin fluctuations. - Graphical abstract: Moessbauer spectra of [H{sub 3} dien].(FeF{sub 6}).H{sub 2}O.

  7. Psychopathology of Shift Work.

    ERIC Educational Resources Information Center

    Akinnawo, Ebenezer Olutope

    1989-01-01

    Examined incidence and nature of general psychopathology among Nigerian shift workers (N=320). Found shift workers more significantly psychopathological than non-shift workers (p<0.001). Prominent disorders among shift workers were intellectual, sleep, mood, and general somatic disorders. No significant difference could be attributed to gender…

  8. Structures and photoelectric properties of five benzotrithiophene isomers-based donor-acceptor copolymers

    NASA Astrophysics Data System (ADS)

    Cheng, Na; Ma, Yuchen; Liu, Yongjun; Zhang, Changqiao; Liu, Chengbu

    2016-04-01

    In this paper, we have investigated the structures, electronic and optical properties of five conjugated copolymers (BTT1-BTz, BTT2-BTz, BTT3-BTz, BTT4-BTz and BTT5-BTz) featuring benzotrithiophene (BTT) isomers as donor units and benzothiadiazole (BTz) as acceptor units, linked through thiophene spacers, employing many-body perturbation theory (MBPT). We have explored the isomer effects by configuration of the sulfur atoms in BTT units, aimed to get insight into how the structural modifications to the conjugated backbone can influence the molecular structures and electronic properties of conjugated polymers. Using the trimer as the computational model, the calculated low and high energy absorption bands (660 and 413 nm) for BTT1-BTz agree well with the experimental ones (645 and 430 nm) with a small offset of ~ 15 nm. On the basis of our calculations, it is found that the backbones of these polymers display different coplanarities, with the dihedral angles between the two neighboring rings varying from 12.3° to 79.0°. Importantly, both BTT1-BTz and BTT2-BTz exhibit intense adsorption around 660 and 623 nm, indicating their promising application in solar cells, whereas BTT3-BTz and BTT4-BTz display the intense adsorption at 569 and 551 nm, which are also usable in the tandem solar cells. BTT5-BTz has narrow and weak adsorption in the visible and infrared region, implying it is not conducive to the sunlight absorption. The blue shift of about 150 nm from BTT1-BTz to BTT5-BTz is suggested to be originated from the shorter effective conjugation lengths.

  9. Structures and photoelectric properties of five benzotrithiophene isomers-based donor-acceptor copolymers.

    PubMed

    Cheng, Na; Ma, Yuchen; Liu, Yongjun; Zhang, Changqiao; Liu, Chengbu

    2016-04-15

    In this paper, we have investigated the structures, electronic and optical properties of five conjugated copolymers (BTT1-BTz, BTT2-BTz, BTT3-BTz, BTT4-BTz and BTT5-BTz) featuring benzotrithiophene (BTT) isomers as donor units and benzothiadiazole (BTz) as acceptor units, linked through thiophene spacers, employing many-body perturbation theory (MBPT). We have explored the isomer effects by configuration of the sulfur atoms in BTT units, aimed to get insight into how the structural modifications to the conjugated backbone can influence the molecular structures and electronic properties of conjugated polymers. Using the trimer as the computational model, the calculated low and high energy absorption bands (660 and 413 nm) for BTT1-BTz agree well with the experimental ones (645 and 430 nm) with a small offset of ~15 nm. On the basis of our calculations, it is found that the backbones of these polymers display different coplanarities, with the dihedral angles between the two neighboring rings varying from 12.3° to 79.0°. Importantly, both BTT1-BTz and BTT2-BTz exhibit intense adsorption around 660 and 623 nm, indicating their promising application in solar cells, whereas BTT3-BTz and BTT4-BTz display the intense adsorption at 569 and 551 nm, which are also usable in the tandem solar cells. BTT5-BTz has narrow and weak adsorption in the visible and infrared region, implying it is not conducive to the sunlight absorption. The blue shift of about 150 nm from BTT1-BTz to BTT5-BTz is suggested to be originated from the shorter effective conjugation lengths.

  10. Gear shift control mechanism

    SciTech Connect

    Janson, D.A.

    1987-03-10

    A gear shift control mechanism is described comprising: multiple shift rods directed substantially parallel to one another, each rod carrying a shift fork for axial movement; a shift lever supported for pivotal movement about a first axis directed parallel to the axes of the shift rods and for pivotal movement about a second axis directed substantially perpendicular to the axes of the shift rods. The lever is moveable about the first axis and the second axis into engagement with a selected shift fork; interlock means located on each lateral side of the shift lever and mounted for pivotal movement about the first axis for blocking engagement with the shift forks; detent means for holding the shift lever in multiple predetermined angular positions about the second axis; and spring means located on a lateral side of the shift lever and mounted for pivotal movement about the first axis into interference contact with the shift forks for producing a force tending to resiliently bias the shift lever out of engagement with the selected shift fork.

  11. 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.

  12. 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.

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

    PubMed

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

    2010-12-02

    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.

  14. Formation of melatonin and its isomer during bread dough fermentation and effect of baking.

    PubMed

    Yılmaz, Cemile; Kocadağlı, Tolgahan; Gökmen, Vural

    2014-04-02

    Melatonin is produced mainly by the pineal gland in vertebrates. Also, melatonin and its isomer are found in foods. Investigating the formation of melatonin and its isomer is of importance during bread dough fermentation and its degradation during baking since bread is widely consumed in high amounts. Formation of melatonin was not significant during dough fermentation. The melatonin isomer content of nonfermented dough was found to be 4.02 ng/g and increased up to 16.71 ng/g during fermentation. Lower amounts of isomer in crumb and crust than dough showed that the thermal process caused a remarkable degree of degradation in melatonin isomer. At the end of the 180 min fermentation Trp decreased by 58%. The results revealed for the first time the formation of a melatonin isomer in bread dough during yeast fermentation.

  15. Isomers of broparoestrol and antiestrogen action: comparison with tamoxifen.

    PubMed

    Edery, M; Barnova, A; Drosdowsky, M; Guggiari, M; Vives, C; Rudali, G

    1985-01-01

    This study compares the relative biological potencies of a known antiestrogen tamoxifen to two triarylethylene compounds which have been shown previously to be potent inhibitors of rodent mammary tumorigenesis. Based on a) uterotrophic and anti-uterotrophic tests, b) indexes of cellularity, and c) protein content, these studies indicate that the trans, as well as the cis, isomers of bromotriphenylethylene are partial estrogen antagonists with no estrogenic effects in rat uteri and partial agonists in mouse uteri, whereas tamoxifen shows partial antiestrogenic/estrogenic effects in rats and is fully estrogenic in mice.

  16. Periodicity of monoisotopic mass isomers and isobars in proteomics.

    PubMed

    Yu, Long; Xiong, Yan-Mei; Polfer, Nick C

    2011-10-15

    We report trends in the theoretically derived number of compositionally distinct peptides (i.e., peptides made up of different amino acid residues) up to a nominal mass of 1000. A total of 21 amino acid residues commonly found in proteomics studies are included in this study, 19 natural, nonisomeric amino acid residues as well as oxidated methione and acetamidated cysteine. The number of possibilities is found to increase in an exponential fashion with increasing nominal mass, and the data show a periodic oscillation that starts at mass ~200 and continues throughout to 1000. Note that similar effects are reported in the companion article on fragment ions from electron capture/transfer dissociation (ECD/ETD) (Mao et al. Anal. Chem.2011, DOI: 10.1021/ac201619t). The spacing of this oscillation is ~15 mass units at lower masses and ~14 mass units at higher nominal masses. This correlates with the most common mass differences between the amino acid building blocks. In other words, some mass differences are more common than others, thus determining the periodicity in this data. From an analytical point of view, nominal masses with a larger number of compositionally distinct peptides include a substantial number of isomers, which cannot be separated based on mass. Consequently, even ultrahigh mass accuracy (i.e., 0.5 ppm) does not lead to a substantially enhanced rate of identification. Conversely, for adjacent nominal masses with a lower number of isomers, moderately accurate mass (i.e., 10 ppm) gives a higher degree of certainty in identification. These effects are limited to the mass range between 200 and 500 Da. At higher masses, the percentage of uniquely identified peptides drops off to close to zero, independent of nominal mass, due the inherently high number of isomers. While the exact number of isobars/isomers at each nominal mass depends on the amino acid building blocks that are considered, the periodicity in the data is found to be remarkably robust; for

  17. 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

  18. Facile and selective synthesis of oligothiophene-based sensitizer isomers: an approach toward efficient dye-sensitized solar cells.

    PubMed

    Feng, Quanyou; Zhang, Qian; Lu, Xuefeng; Wang, Hong; Zhou, Gang; Wang, Zhong-Sheng

    2013-09-25

    Two sets of isomeric organic dyes with n-hexyl (DH and AH) or 2-ethylhexyl (DEH and AEH) groups substituted at the spacer part have been designed and straightforwardly synthesized via a facile and selective synthetic route. The structure difference between the isomers stands at the position of the incorporated alkyl chains which are introduced into the terthiophene spacer close to the donor (D) or anchor (A) side. The relationship between the isomeric structures and the optoelectronic properties are systematically investigated. It is found that, in the D series dyes, the alkyl group is much closer to the aromatic donor moiety, which brings about strong steric hindrance and therefore causes a remarkable twist in the molecular skeleton. In contrast, a more planar chemical structure and more effective π-conjugation are realized in the A series dye isomers. Consequently, the A series isomeric dyes demonstrate bathochromically shifted absorption bands, resulting in the improved light-harvesting capability and enhanced photo-generated current. However, the D series isomeric dyes with more twisted molecular skeleton have suppressed the intermolecular interactions and retarded the charge recombination more efficiently, which induces higher open-circuit photovoltage. Combining the two effects on the performance of the fabricated dye-sensitized solar cells (DSSC), the influence from the short-circuit photocurrent plays a more significant role on the power conversion efficiency (η). As a result, isomer AEH-based DSSC with quasi-solid-state electrolyte displays the highest η of 7.10% which remained at 98% of the initial value after continuous light soaking for 1000 h. Promisingly, a η of 8.66% has been achieved for AEH-based DSSC with liquid electrolyte containing Co(II)/(III) redox couple. This work presents the crucial issue of molecular engineering and paves a way to design organic sensitizers for highly efficient and stable DSSCs.

  19. Identification of absolute geometries of cis and trans molecular isomers by Coulomb Explosion Imaging

    PubMed Central

    Ablikim, Utuq; Bomme, Cédric; Xiong, Hui; Savelyev, Evgeny; Obaid, Razib; Kaderiya, Balram; Augustin, Sven; Schnorr, Kirsten; Dumitriu, Ileana; Osipov, Timur; Bilodeau, René; Kilcoyne, David; Kumarappan, Vinod; Rudenko, Artem; Berrah, Nora; Rolles, Daniel

    2016-01-01

    An experimental route to identify and separate geometric isomers by means of coincident Coulomb explosion imaging is presented, allowing isomer-resolved photoionization studies on isomerically mixed samples. We demonstrate the technique on cis/trans 1,2-dibromoethene (C2H2Br2). The momentum correlation between the bromine ions in a three-body fragmentation process induced by bromine 3d inner-shell photoionization is used to identify the cis and trans structures of the isomers. The experimentally determined momentum correlations and the isomer-resolved fragment-ion kinetic energies are matched closely by a classical Coulomb explosion model. PMID:27910943

  20. Isomer-Specific Binding Affinity of Perfluorooctanesulfonate (PFOS) and Perfluorooctanoate (PFOA) to Serum Proteins.

    PubMed

    Beesoon, Sanjay; Martin, Jonathan W

    2015-05-05

    Perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) are among the most prominent contaminants in human serum, and these were historically manufactured as technical mixtures of linear and branched isomers. The isomers display unique pharmacokinetics in humans and in animal models, but molecular mechanisms underlying isomer-specific PFOS and PFOA disposition have not previously been studied. Here, ultrafiltration devices were used to examine (i) the dissociation constants (Kd) of individual PFOS and PFOA isomers with human serum albumin (HSA) and (ii) relative binding affinity of isomers in technical mixtures spiked to whole calf serum and human serum. Measurement of HSA Kd's demonstrated that linear PFOS (Kd=8(±4)×10(-8) M) was much more tightly bound than branched PFOS isomers (Kd range from 8(±1)×10(-5) M to 4(±2)×10(-4) M). Similarly, linear PFOA (Kd=1(±0.9)×10(-4) M) was more strongly bound to HSA compared to branched PFOA isomers (Kd range from 4(±2)×10(-4) M to 3(±2)×10(-4) M). The higher binding affinities of linear PFOS and PFOA to total serum protein were confirmed when both calf serum and human serum were spiked with technical mixtures. Overall, these data provide a mechanistic explanation for the longer biological half-life of PFOS in humans, compared to PFOA, and for the higher transplacental transfer efficiencies and renal clearance of branched PFOS and PFOA isomers, compared to the respective linear isomer.

  1. Identification of absolute geometries of cis and trans molecular isomers by Coulomb Explosion Imaging

    NASA Astrophysics Data System (ADS)

    Ablikim, Utuq; Bomme, Cédric; Xiong, Hui; Savelyev, Evgeny; Obaid, Razib; Kaderiya, Balram; Augustin, Sven; Schnorr, Kirsten; Dumitriu, Ileana; Osipov, Timur; Bilodeau, René; Kilcoyne, David; Kumarappan, Vinod; Rudenko, Artem; Berrah, Nora; Rolles, Daniel

    2016-12-01

    An experimental route to identify and separate geometric isomers by means of coincident Coulomb explosion imaging is presented, allowing isomer-resolved photoionization studies on isomerically mixed samples. We demonstrate the technique on cis/trans 1,2-dibromoethene (C2H2Br2). The momentum correlation between the bromine ions in a three-body fragmentation process induced by bromine 3d inner-shell photoionization is used to identify the cis and trans structures of the isomers. The experimentally determined momentum correlations and the isomer-resolved fragment-ion kinetic energies are matched closely by a classical Coulomb explosion model.

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

    PubMed

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

    2015-12-15

    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.

  3. Calculations of long-lived isomer production in neutron reactions

    SciTech Connect

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

    1991-01-01

    We have carried out theoretical calculations for the production of the long-lived isomers {sup 93m}Nb({1/2}{sup {minus}}, 16y), {sup 121m}Sn(11/2{minus}, 55 yr), {sup 166m}Ho(7-, 1200 yr), {sup 184m}Re(8+, 165 d), {sup 186m}Re(8+, 2{times}10{sup 5} yr), {sup 178m}Hf(16+, 31 yr), {sup 179m}Hf(25/2-, 25 d), {sup 192m}Ir(9+, 241 yr), all of which pose potential radiation activation problems in nuclear fusion reactors. We consider (n, 2n), (n,n{prime}), and (n, {gamma}) production modes and compare our results both with experimental data (where available) and systematic. We also investigate the dependence of the isomeric cross section ratio on incident neutron energy for the isomers under consideration. The statistical Hauser-Feshbach plus preequilibrium code GNASH was used for the calculations. Where discrete state experimental information was lacking, rotational band members above the isomeric state, which can be justified theoretically but have not been experimentally resolved, were reconstructed. 16 refs., 8 figs.

  4. 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)..

  5. 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.

  6. Development of an alternative eluent system for Ag+-HPLC analysis of conjugated linoleic acid isomers.

    PubMed

    Müller, André; Düsterloh, Kaja; Ringseis, Robert; Eder, Klaus; Steinhart, Hans

    2006-02-01

    In this study, 13 different eluent systems containing n-hexane, n-heptane and iso-octane as main solvents and ACN, propionitrile (PCN) and butyronitrile (BCN) in concentrations between 0.1 and 0.2% as modifiers were tested for their influence on retention time shifts (RTS) and resolution of conjugated linoleic acid (CLA) methyl esters using two ChromSpher 5 Lipids columns (250 mm x 4.6 mm, 5 microm) in series. The eluent system n-hexane/PCN 0.2% showed the highest stability with an obtained RTS of 0.26 min for the cis/trans-group after 14 consecutive injections of a CLA isomer mix compared to the reference system of n-hexane/ACN 0.15% (RTS of 2.35 min). This enhanced stability is due to better solubility of PCN in n-hexane compared to ACN. The enhanced stability coincided with a negligible loss in resolution for the cis,trans/trans,cis- and the cis,cis-groups. As shown for the analysis of human aortic endothelial cells spiked with t10c12-CLA, data from CLA-analysis by Ag+-HPLC-DAD must be judged very carefully, especially at low concentrations, as coeluting matrix compounds may give false-positive results. Therefore, results should be confirmed by GC-FID and GC-MS.

  7. The gamma-ray spectra of 5-carbon alkane isomers in the positron annihilation process

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoguang; Zhu, Yinghao; Liu, Yang

    2016-05-01

    The gamma-ray spectra of pentane (C5H12) and its two isomers, i.e., 2-Methylbutane (CH3C(CH3)HC2H5) and 2,2-Dimethylpropane (C(CH3)4) have been studied theoretically in the present work. The recent experimental gamma-ray spectra of these three molecules show that they have the same Doppler shifts, although their molecular structures are dramatically different. In order to reveal why the gamma-ray spectra of these molecules are less sensitive to the molecular structures, the one-dimensional gamma-ray spectra and spherically averaged momentum (SAM) distributions, the two-dimensional angular correlation of annihilation radiation (ACAR), and the three-dimensional momentum distributions of the positron-electron pair are studied. The one-centered momentum distributions of the electrons are found to play more important role than the multi-centered coordinate distributions. The present theoretical predictions have confirmed the experimental findings for the first time. The dominance of the inner valence electrons in the positron-electron annihilation process has also been suggested in the present work.

  8. 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.

  9. Theoretical Prediction of the Structures and Energies of Olympicene and its Isomers

    NASA Astrophysics Data System (ADS)

    Valentine, Andrew J. S.; Mazziotti, David A.

    2013-10-01

    Pentacene, a linear five-ringed polyaromatic hydrocarbon, has recently been used as an organic semiconductor in field-effect transistors. The recently synthesized olympicene molecule, so named because of its resemblance to the olympic rings, is a more compact five-ringed structure. This paper offers the first theoretical study of the kinetic stability of olympicene and its isomers. We use the parametric two-electron reduced density matrix (2-RDM) method, which takes the 2-RDM as the basic variable in lieu of the traditional wave function in calculations [ Mazziotti, D. A. Phys. Rev. Lett. 2008, 101, 253002 ]. Our calculations demonstrate that olympicene-s isomers may be separated into aromatic and diradical isomers, the latter of which require accurate treatment of strong electron correlation to detect multireference character. Albeit formally a single-reference method, the parametric 2-RDM captures the multireference correlation of the diradical isomers; relative to olympicene, the 2-RDM predicts five diradical isomers that are 16-22 kcal/mol lower in energy than those from coupled cluster with single and double excitations-a significant change that causes these isomers to be stable to dissociation by 2-20 kcal/mol. We characterize the transition states between olympicene-s isomers, observe differences in aromaticity among the different isomers, and compare the electronic properties of olympicene to those of pentacene. The olympicene molecule has the potential to complement pentacene as an organic semiconductor.

  10. 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.

  11. 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...

  12. Synthesis of the optical isomers of a new anticholinergic drug, penehyclidine hydrochloride (8018).

    PubMed

    Han, Xiang-Yu; Liu, He; Liu, Chun-He; Wu, Bo; Chen, Lan-Fu; Zhong, Bo-Hua; Liu, Ke-Liang

    2005-04-15

    A practical diastereoselective synthetic method for 8018 enantiopure isomers is described. The intramolecular asymmetric epoxidation of mono-sulfonate 4 was applied for the execution of the synthesis of the key chiral building block for the first time. The isomers were obtained with 70-76% yields in 99-100% ee.

  13. 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...

  14. 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...

  15. Enantiomers of a nonylphenol isomer: absolute configurations and estrogenic potencies.

    PubMed

    Zhang, Haifeng; Oppel, Iris M; Spiteller, Michael; Guenther, Klaus; Boehmler, Gabriele; Zuehlke, Sebastian

    2009-02-01

    Enantiomers of 4-(1,1,2-trimethylhexyl)phenol, a chiral isomer of the endocrine disrupting chemical nonylphenol, have been resolved and isolated by preparative chiral HPLC. The absolute configurations of the enantiomers were then determined by an X-ray crystallographic study of the (-)-camphanoyl derivative of the first eluted enantiomer NP(35)E1. The first enantiomer (NP(35)E1) and the second enantiomer (NP(35)E2) eluted were found to have the S and R absolute configurations, respectively. The estrogenic potencies of the S and R enantiomers were tested by the E-screen assay. A slight difference was observed in the relative proliferative effect between the S enantiomer and R enantiomer in the E-screen assay.

  16. Social isomers of picolines in a small space.

    PubMed

    Ajami, Dariush; Theodorakopoulos, Giannoula; Petsalakis, Ioannis D; Rebek, Julius

    2013-12-09

    Encapsulation complexes permit the observation of molecules under conditions of limited motion. Inside capsules, molecular encounters are prolonged, prearranged, and protected from the medium, in contrast to the short-lived and random encounters that occur in bulk solution. Herein, the interaction of α-, β-, and γ-picolines in a cylindrical capsule is described. Two picolines were taken up, and NMR spectra indicated dynamic combinations of various social isomers. The stabilities of the complexes are interpreted through computational methods. The shape of the space in the capsule allowed the alignment of molecules and revealed delicate, atom-to-atom interactions and attractive forces that elude observation in dilute solution. These weak forces were amplified in the isolated small space of the capsule.

  17. Theoretical study of structural patterns in CH₂OP₂ isomers.

    PubMed

    Septelean, Raluca; Petrar, Petronela Maria; Gabriela, Nemes; Escudié, Jean; Silaghi-Dumitrescu, Ioan

    2011-07-01

    DFT calculations have been performed on the derivatives of formula CH₂OP₂ to determine their total energy, the relative energy between the isomers and their geometry. Among compounds with a P-C-P linkage, the most stable one is the 2-hydroxy-1,2-diphosphirene II.1, a three-membered heterocycle with a P=C unsaturation. The phosphavinylidene(oxo)phosphorane HP=C=P(O)H IV.5 (which has the same skeleton as the experimentally obtained Mes*P=C=P(O)Mes*) lies 36.30 kcal mol⁻¹ above it. The least stable compounds are carbenes; the singlet carbenes are more stable than the triplet ones.

  18. Communication: "Position" does matter: The photofragmentation of the nitroimidazole isomers

    NASA Astrophysics Data System (ADS)

    Bolognesi, P.; Casavola, A. R.; Cartoni, A.; Richter, R.; Markus, P.; Borocci, S.; Chiarinelli, J.; Tošić, S.; Sa'adeh, H.; Masič, M.; Marinković, B. P.; Prince, K. C.; Avaldi, L.

    2016-11-01

    A combined experimental and theoretical approach has been used to disentangle the fundamental mechanisms of the fragmentation of the three isomers of nitroimidazole induced by vacuum ultra-violet (VUV) radiation, namely, 4-, 5-, and 2-nitroimidazole. The results of mass spectrometry as well as photoelectron-photoion coincidence spectroscopy display striking differences in the radiation-induced decomposition of the different nitroimidazole radical cations. Based on density functional theory (DFT) calculations, a model is proposed which fully explains such differences, and reveals the subtle fragmentation mechanisms leading to the release of neutral species like NO, CO, and HCN. Such species have a profound impact in biological media and may play a fundamental role in radiosensitising mechanisms during radiotherapy.

  19. Lifetime Measurement of the 229Th nuclear isomer

    NASA Astrophysics Data System (ADS)

    Seiferle, Benedict; von der Wense, Lars; Thirolf, Peter G.

    2017-01-01

    The first excited isomeric state of 229Th possesses the lowest energy among all known excited nuclear states. The expected energy is accessible with today's laser technology and in principle allows for a direct optical laser excitation of the nucleus. The isomer decays via three channels to its ground state (internal conversion, γ decay, and bound internal conversion), whose strengths depend on the charge state of Thm229 . We report on the measurement of the internal-conversion decay half-life of neutral Thm229 . A half-life of 7 ±1 μ s has been measured, which is in the range of theoretical predictions and, based on the theoretically expected lifetime of ≈1 04 s of the photonic decay channel, gives further support for an internal conversion coefficient of ≈1 09, thus constraining the strength of a radiative branch in the presence of internal conversion.

  20. Chiral recognition of pinacidil and its 3-pyridyl isomer by canine cardiac and smooth muscle: Antagonism by sulfonylureas

    SciTech Connect

    Steinberg, M.I.; Wiest, S.A.; Zimmerman, K.M.; Ertel, P.J.; Bemis, K.G.; Robertson, D.W. )

    1991-01-01

    Pinacidil, a potassium channel opener (PCO), relaxes vascular smooth muscle by increasing potassium ion membrane conductance, thereby causing membrane hyperpolarization. PCOs also act on cardiac muscle to decrease action potential duration (APD) selectively. To examine the enantiomeric selectivity of pinacidil, the stereoisomers of pinacidil (a 4-pyridylcyanoguanidine) and its 3-pyridyl isomer (LY222675) were synthesized and studied in canine Purkinje fibers and cephalic veins. The (-)-enantiomers of both pinacidil and LY222675 were more potent in relaxing phenylephrine-contracted cephalic veins and decreasing APD than were their corresponding (+)-enantiomers. The EC50 values for (-)-pinacidil and (-)-LY222675 in relaxing cephalic veins were 0.44 and 0.09 microM, respectively. In decreasing APD, the EC50 values were 3.2 microM for (-)-pinacidil and 0.43 microM for (-)-LY222675. The eudismic ratio was greater for the 3-pyridyl isomer than for pinacidil in both cardiac (71 vs. 22) and vascular (53 vs. 17) tissues. (-)-LY222675 and (-)-pinacidil (0.1-30 microM) also increased 86Rb efflux from cephalic veins to a greater extent than did their respective optical antipodes. The antidiabetic sulfonylurea, glyburide (1-30 microM), shifted the vascular concentration-response curve of (-)-pinacidil to the right by a similar extent at each inhibitor concentration. Glipizide also antagonized the response to (-)-pinacidil, but was about 1/10 as potent with a maximal shift occurring at 10 and 30 microM. Glyburide antagonized the vascular relaxant effects of 0.3 microM (-)-LY222675 (EC50, 2.3 microM) and reversed the decrease in APD caused by 3 microM (-)-LY222675 (EC50, 1.9 microM). Nitroprusside did not alter 86Rb efflux, and vascular relaxation induced by sodium nitroprusside was unaffected by sulfonylureas.

  1. Static and Dynamic Nanosheets from Selective Assembly of Geometric Macrocycle Isomers.

    PubMed

    Wang, Yanqiu; Kim, Yongju; Lee, Myongsoo

    2016-10-10

    In contrast to the significant advances that have been made in the construction of two-dimensional (2D) nanostructures, the rational modification from static to dynamic 2D sheets remains a great challenge. Static and dynamic sheets formed from selective self-assembly of geometric macrocycle isomers based on anthracene units are presented. The self-assembly of the cis isomer generates static planar sheets, whereas the trans isomer forms dynamic rolled sheets which are reversibly unrolled upon stimulation by a thermal signal. Furthermore, the mixed solution of the two isomers exhibits self-sorting behavior, generating the coexistence of the two independent self-assembled structures, the planar sheets and the folded scrolls. The self-sorted supramolecular objects with considerable shape and size differences are able to be readily separated, one isomer from the other.

  2. Structures of cage, prism, and book isomers of water hexamer from broadband rotational spectroscopy.

    PubMed

    Pérez, Cristóbal; Muckle, Matt T; Zaleski, Daniel P; Seifert, Nathan A; Temelso, Berhane; Shields, George C; Kisiel, Zbigniew; Pate, Brooks H

    2012-05-18

    Theory predicts the water hexamer to be the smallest water cluster with a three-dimensional hydrogen-bonding network as its minimum energy structure. There are several possible low-energy isomers, and calculations with different methods and basis sets assign them different relative stabilities. Previous experimental work has provided evidence for the cage, book, and cyclic isomers, but no experiment has identified multiple coexisting structures. Here, we report that broadband rotational spectroscopy in a pulsed supersonic expansion unambiguously identifies all three isomers; we determined their oxygen framework structures by means of oxygen-18-substituted water (H(2)(18)O). Relative isomer populations at different expansion conditions establish that the cage isomer is the minimum energy structure. Rotational spectra consistent with predicted heptamer and nonamer structures have also been identified.

  3. An inconvenient influence of iridium(III) isomer on OLED efficiency.

    PubMed

    Baranoff, Etienne; Bolink, Henk J; De Angelis, Filippo; Fantacci, Simona; Di Censo, Davide; Djellab, Karim; Grätzel, Michael; Nazeeruddin, Md Khaja

    2010-10-14

    The recently reported heteroleptic cyclometallated iridium(III) complex [Ir(2-phenylpyridine)(2)(2-carboxy-4-dimethylaminopyridine)] N984 and its isomer N984b have been studied more in detail. While photo- and electrochemical properties are very similar, DFT/TDDFT calculations show that the two isomers have different HOMO orbital characteristics. As a consequence, solution processed OLEDs made using a mixture of N984 and isomer N984b similar to vacuum processed devices show that the isomer has a dramatic detrimental effect on the performances of the device. In addition, commonly used thermogravimetric analysis is not suitable for showing the isomerization process. The isomer could impact performances of vacuum processed OLEDs using heteroleptic cyclometallated iridium(III) complexes as dopant.

  4. Lipid and Glycolipid Isomer Analyses Using Ultra-High Resolution Ion Mobility Spectrometry Separations

    SciTech Connect

    Wojcik, Roza; Webb, Ian; Deng, Liulin; Garimella, Sandilya; Prost, Spencer; Ibrahim, Yehia; Baker, Erin; Smith, Richard

    2017-01-01

    Understanding the biological mechanisms related to lipids and glycolipids is challenging due to the vast number of possible isomers. Mass spectrometry (MS) measurements are currently the dominant approach for studying and providing detailed information on lipid and glycolipid structures. However, difficulties in distinguishing many structural isomers (e.g. distinct acyl chain positions, double bond locations, as well as glycan isomers) inhibit the understanding of their biological roles. Here we utilized ultra-high resolution ion mobility spectrometry (IMS) separations based upon the use of traveling waves in a serpentine long path length multi-pass Structures for Lossless Manipulations (SLIM) to enhance isomer resolution. The multi-pass arrangement allowed separations ranging from ~16 m (1 pass) to ~470 m (32 passes) to be investigated for the distinction of lipids and glycolipids with extremely small structural differences. These ultra-high resolution SLIM IMS-MS analyses provide a foundation for exploring and better understanding isomer specific biological and disease processes.

  5. 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.

  6. 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.

  7. Gaussian and linear deconvolution of LC-MS/MS chromatograms of the eight aminobutyric acid isomers.

    PubMed

    Vemula, Harika; Kitase, Yukiko; Ayon, Navid J; Bonewald, Lynda; Gutheil, William G

    2017-01-01

    Isomeric molecules present a challenge for analytical resolution and quantification, even with MS-based detection. The eight aminobutyric acid (ABA) isomers are of interest for their various biological activities, particularly γ-aminobutyric acid (GABA) and the d- and l-isomers of β-aminoisobutyric acid (β-AIBA; BAIBA). This study aimed to investigate LC-MS/MS-based resolution of these ABA isomers as their Marfey's (Mar) reagent derivatives. HPLC was able to separate three Mar-ABA isomers l-β-ABA (l-BABA), and l- and d-α-ABA (AABA) completely, with three isomers (GABA, and d/l-BAIBA) in one chromatographic cluster, and two isomers (α-AIBA (AAIBA) and d-BABA) in a second cluster. Partially separated cluster components were deconvoluted using Gaussian peak fitting except for GABA and d-BAIBA. MS/MS detection of Marfey's derivatized ABA isomers provided six MS/MS fragments, with substantially different intensity profiles between structural isomers. This allowed linear deconvolution of ABA isomer peaks. Combining HPLC separation with linear and Gaussian deconvolution allowed resolution of all eight ABA isomers. Application to human serum found a substantial level of l-AABA (13 μM), an intermediate level of l-BAIBA (0.8 μM), and low but detectable levels (<0.2 μM) of GABA, l-BABA, AAIBA, d-BAIBA, and d-AABA. This approach should be useful for LC-MS/MS deconvolution of other challenging groups of isomeric molecules.

  8. Making Shifts toward Proficiency

    ERIC Educational Resources Information Center

    McGatha, Maggie B.; Bay-Williams, Jennifer M.

    2013-01-01

    The Leading for Mathematical Proficiency (LMP) Framework (Bay-Williams et al.) has three components: (1) The Standards for Mathematical Practice; (2) Shifts in classroom practice; and (3) Teaching skills. This article briefly describes each component of the LMP framework and then focuses more in depth on the second component, the shifts in…

  9. Examination of isomer specific bioaccumulation parameters and potential in vivo hepatic metabolites of syn- and anti-Dechlorane Plus isomers in juvenile rainbow trout (Oncorhynchus mykiss).

    PubMed

    Tomy, Gregg T; Thomas, Caden R; Zidane, Thane M; Murison, Kathryn E; Pleskach, Kerri; Hare, Jonathon; Arsenault, Gilles; Marvin, Chris H; Sverko, Ed

    2008-08-01

    Juvenile rainbow trout (Oncorhynchus mykiss) were exposed in the laboratory to elevated doses of syn- and anti-isomers of Dechlorane Plus (DP) via their diet for 49 days (uptake phase), followed by 112 days of untreated food (depuration phase) to examine bioaccumulation parameters and possible metabolic products. Three groups of 60 fish were used in the study. Two groups were exposed separately to food fortified with known concentrations of syn- (0.79 +/- 0.03 microg/g, lipid weight) and anti-DP (1.17 +/- 0.12 microg/g, lipid weight) while a third control group was fed unfortified food. Neither isomer reached steady-state after 49 days of exposure. Only the syn-isomer accumulated linearly in the fish (whole-body minus liver) during the dosing phase with a calculated uptake rate constant of 0.045 +/- 0.005 (arithmetic mean +/- 1 x standard error) nmoles per day. A similar uptake rate was also observed for this isomer in the liver. The elimination of both isomers from the whole fish (minus liver) obeyed first order depuration kinetics (syn-: r2 = 0.6427, p < 0.001, anti-: r2 = 0.5350, p < 0.005) with calculated half-lives (t1/2) of 53.3 +/- 13.1 (syn-) and 30.4 +/- 5.7 (anti-) days. Elimination of the isomers from the liver was difficult to interpret because of suspected enterohepatic circulation and redistribution of the isomers in the liver during clearance from other tissues. The biomagnification factor (BMF, determined in whole fish minus liver) of the syn-isomer (5.2) was greater than the anti-isomer (1.9) suggesting that the former isomer is more bioavailable. A suite of metabolites were screened for in the liver including dechlorinated, hydroxylated, methoxylated and methyl sulfone degradates. Even with the purposely high dose used in the uptake phase, none of these degradates could be detected in the extracts. This suggests that if metabolites of DP are detected in fish from aquatic food webs their presence is likely not from in vivo biotransformation of the

  10. Shifting scintillator neutron detector

    DOEpatents

    Clonts, Lloyd G; Cooper, Ronald G; Crow, Jr., Morris Lowell; Hannah, Bruce W; Hodges, Jason P; Richards, John D; Riedel, Richard A

    2014-03-04

    Provided are sensors and methods for detecting thermal neutrons. Provided is an apparatus having a scintillator for absorbing a neutron, the scintillator having a back side for discharging a scintillation light of a first wavelength in response to the absorbed neutron, an array of wavelength-shifting fibers proximate to the back side of the scintillator for shifting the scintillation light of the first wavelength to light of a second wavelength, the wavelength-shifting fibers being disposed in a two-dimensional pattern and defining a plurality of scattering plane pixels where the wavelength-shifting fibers overlap, a plurality of photomultiplier tubes, in coded optical communication with the wavelength-shifting fibers, for converting the light of the second wavelength to an electronic signal, and a processor for processing the electronic signal to identify one of the plurality of scattering plane pixels as indicative of a position within the scintillator where the neutron was absorbed.

  11. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Excitation of nuclear isomers by X rays from laser plasma

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

    The possibility of obtaining isomer nuclei is studied by the example of the molybdenum isomer 93Mo upon irradiation of a niobium 93Nb target by ~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.

  12. Matrix Isolation and Computational Study of [2C, 2N, x] (X=S, Se) Isomers

    NASA Astrophysics Data System (ADS)

    Voros, Tamas; Tarczay, Gyorgy

    2015-06-01

    The [2C, 2N, S] and the [2C, 2N, Se] systems were investigated by quantum chemical computations and matrix isolation IR spectroscopy. For both systems nine isomers were computationally investigated, for which harmonic and anharmonic vibrational wavenumbers and infrared (IR) intensities were calculated using the CCSD(T)/aug-cc-pVTZ level of theory. The results show that each of the isomers have two or more detectable bands in the mid IR region, which have one or two orders of magnitude larger intensity compared to the IR intensity of the most intense bands of the most stable NCSCN and NCSeCN isomers'. It follows that if the most stable isomers can be detected, then the other previously unobserved isomers generated from NCSCN or NCSeCN should also be detectable with IR spectroscopy. UV spectra were also computed for each isomer at the TD-DFT B3LYP/aug-cc-pVTZ level of theory. These computations showed that the most stable isomers (NCSCN and NCSeCN) can absorb the UV radiation around 250 nm, and the irradiation may promote photoisomerization. This means that if the initial isomers are irradiated by narrow-band UV radiation, new isomers may be generated, which likely decompose by irradiating broad-band UV radiation. The two most stable isomers, sulphur dicyanide (NCSCN) and selenium dicyanide (NCSeCN), were prepared following literature methods. The matrix isolation IR spectra of these molecules in Ar and Kr were measured for the first time. As a result of a selective 254 nm-irradiation of the deposited matrices some new bands appeared in the IR spectra, while the intensity of the bands of NCSCN or NCSeCN were decreased at the same time. Irradiation of the matrices with broad-band UV light decreased the intensity of the bands corresponding to the deposited isomers and some of the bands appeared on the 254 nm-irradiation. On the basis of the analysis of the formation rates of the different bands upon 254 nm photolysis and by comparison with the results of the quantum

  13. 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...

  14. 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...

  15. 40 CFR 180.449 - Avermectin B1 and its delta-8,9-isomer; tolerances for residues.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 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. Tolerances... delta-8,9-isomer in or on the following commodities: Commodity Parts per million Almond, hulls...

  16. Instantaneous phase shifting deflectometry.

    PubMed

    Trumper, Isaac; Choi, Heejoo; Kim, Dae Wook

    2016-11-28

    An instantaneous phase shifting deflectometry measurement method is presented and implemented by measuring a time varying deformable mirror with an iPhone ® 6. The instantaneous method is based on multiplexing phase shifted fringe patterns with color, and decomposing them in x and y using Fourier techniques. Along with experimental data showing the capabilities of the instantaneous deflectometry system, a quantitative comparison with the Fourier transform profilometry method, which is a distinct phase measuring method from the phase shifting approach, is presented. Sources of error, nonlinear color-multiplexing induced error correction, and hardware limitations are discussed.

  17. 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.

  18. 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.

  19. 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

  20. Gas-phase ion isomer analysis reveals the mechanism of peptide sequence scrambling.

    PubMed

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

    2014-03-18

    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 → (c)b) pathway is less energetically (or kinetically) favored.

  1. 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.

  2. 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.

  3. 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

  4. Isomers/enantiomers of perfluorocarboxylic acids: Method development and detection in environmental samples.

    PubMed

    Naile, Jonathan E; Garrison, A Wayne; Avants, Jimmy K; Washington, John W

    2016-02-01

    Perfluoroalkyl substances are globally distributed in both urban and remote settings, and routinely are detected in wildlife, humans, and the environment. One of the most prominent and routinely detected perfluoroalkyl substances is perfluorooctanoic acid (PFOA), which has been shown to be toxic to both humans and animals. PFOA exists as both linear and branched isomers; some of the branched isomers are chiral. A novel GC-NCI-MS method was developed to allow for isomer/enantiomer separation, which was achieved using two columns working in tandem; a 30-m DB-5MS column and a 30-m BGB-172 Analytik column. Samples were derivatized with diazomethane to form methyl esters of the PFOA isomers. In standards, at least eight PFOA isomers were detected, of which at least four were enantiomers of chiral isomers; one chiral isomer (P3) was sufficiently separated to allow for enantiomer-fraction calculations. Soil, sediment and plant samples from contaminated locations in Alabama and Georgia were analyzed. P3 was observed in most of these environmental samples, and was non-racemic in at least one sediment, suggesting the possibility of chirally selective generation from precursors or enantioselective sorption. In addition, the ratio of P3/linear PFOA was inversely related to distance from source, which we suggest might reflect a higher sorption affinity for the P3 over the linear isomer. This method focuses on PFOA, but preliminary results suggest that it should be broadly applicable to other chiral and achiral perfluorocarboxylic acids (PFCAs); e.g., we detected several other homologous PFCA isomers in our PFCA standards and some environmental samples.

  5. [Identification of Six Isomers of Dimethylbenzoic Acid by Using Terahertz Time-Domain Spectroscopy Technique].

    PubMed

    Liu, Jian-wei; Shen, Jing-ling; Zhang, Bo

    2015-11-01

    In this paper, the absorption spectra of 6 isomers of dimethylbenzoic acid, which were widely used in chemical and pharmaceutical production as intermediate substance, were measured by using the terahertz time-domain spectroscopy (THz-TDS) system in the range 0.2-2.2 THz at room temperature. The experimental results show that the six measured isomers present apparent different spectral response. However, the results of using infrared spectroscopy indicates that different isomers show high similarity in absorption spectra in the range 1450-1700 cm⁻¹. The vibrational frequencies are calculated by using the density functional theory (DFT), and identification of vibrational modes are given. It is clear that the absorption peaks of the 6 isomers in the range 1450-1700 cm⁻¹ come from the stretching vibration of benzene ring and C==O, while the absorption peaks in the terahertz range are caused by the relative wagging of benzene ring and all the chains out of plane, which lead to the different absorption characteristics of the 6 isomers in the range 0.2-2.2 THz. The results suggest that the difference and similarity of the absorption spectra observed in the two different frequency range are resulted from the difference and similarity of the molecular structures of the six isomers. By using the different absorption characteristics, we can identify the six isomers of dimethylbenzoic acid effectively. Our study indicates that it is feasible to distinguish the isomers by using terahertz and infrared spectroscopy technique. It provides an effective way to identify different isomers and test the purity of the intermediate substance in the process of production quickly and accurately.

  6. 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

  7. Isolation and spectral characterization of thermally generated multi-Z-isomers of lycopene and the theoretically preferred pathway to di-Z-isomers.

    PubMed

    Honda, Masaki; Kudo, Tatsuya; Kuwa, Takahiro; Higashiura, Takuma; Fukaya, Tetsuya; Inoue, Yoshinori; Kitamura, Chitoshi; Takehara, Munenori

    2017-02-01

    Lycopene has a large number of geometric isomers caused by E/Z isomerization at arbitrary sites within the 11 conjugated double bonds, offering varying characteristics related to features such as antioxidant capacity and bioavailability. However, the geometric structures of only a few lycopene Z-isomers have been thoroughly identified from natural sources. In this study, seven multi-Z-isomers of lycopene, (9Z,13'Z)-, (5Z,13Z,9'Z)-, (9Z,9'Z)-, (5Z,13'Z)-, (5Z,9'Z)-, (5Z,9Z,5'Z)-, and (5Z,9Z)-lycopene, were obtained from tomato samples by thermal isomerization, and then isolated by elaborate chromatography, and fully assigned using proton nuclear magnetic resonance. Moreover, the theoretically preferred pathway from (all-E)-lycopene to di-Z-isomers was examined with a computational approach using a Gaussian program. Fine-tuning of the HPLC separation conditions led to the discovery of novel multi-Z-isomers, and whose formation was supported by advanced theoretical calculations.

  8. 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.

  9. Improved feedback shift register

    NASA Technical Reports Server (NTRS)

    Perlman, M.

    1972-01-01

    Design of feedback shift register with three tap feedback decoding scheme is described. Application for obtaining sequence synchronization patterns is examined. Operation of the circuitry is described and drawings of the systems are included.

  10. Shape-Shifting Plastic

    SciTech Connect

    2015-05-20

    A new plastic developed by ORNL and Washington State University transforms from its original shape through a series of temporary shapes and returns to its initial form. The shape-shifting process is controlled through changes in temperature

  11. Our World: Fluid Shift

    NASA Video Gallery

    Learn about the circulatory system and how gravity aids blood flow in our bodies here on Earth. Find out how NASA flight surgeons help the astronauts deal with the fluid shift that happens during s...

  12. Shift Verification and Validation

    SciTech Connect

    Pandya, Tara M.; Evans, Thomas M.; Davidson, Gregory G; Johnson, Seth R.; Godfrey, Andrew T.

    2016-09-07

    This documentation outlines the verification and validation of Shift for the Consortium for Advanced Simulation of Light Water Reactors (CASL). Five main types of problems were used for validation: small criticality benchmark problems; full-core reactor benchmarks for light water reactors; fixed-source coupled neutron-photon dosimetry benchmarks; depletion/burnup benchmarks; and full-core reactor performance benchmarks. We compared Shift results to measured data and other simulated Monte Carlo radiation transport code results, and found very good agreement in a variety of comparison measures. These include prediction of critical eigenvalue, radial and axial pin power distributions, rod worth, leakage spectra, and nuclide inventories over a burn cycle. Based on this validation of Shift, we are confident in Shift to provide reference results for CASL benchmarking.

  13. Straddling a paradigm shift

    SciTech Connect

    Landgren, D.

    1995-05-01

    Paul Meagher made a big mistake when he asked me about my speech. I asked him what I should talk about. He reiterated the title of the conference {open_quotes}Forecasting and DSM: Organizing for Success,{close_quotes} and said that whatever issues I wanted to cover were fine with him. As a result I will cover those areas I`ve been thinking about recently. It is hard for me to extract either Forecasting or Demand-Side Management out from the broader issues unwinding in the industry today. I`ve been around long enough to be involved in two major shifts in the industry. I call these paradigm shifts because as a planner I tend to build models in my mind to represent business or regulatory structure. Since a paradigm is defined as a clear model of something, I tend to talk about structural shifts in the industry as paradigm shifts. The first paradigm shift was brought about by the rapid escalation of energy prices in the 1970s. The second paradigm shift, brought about in part because of the first and because of growing concerns about the environment, ushered in the era of utility conservation and load management programs (components of a broader DSM concept - unfortunately today many people limit DSM to only these two pieces). The third paradigm shift is just starting, driven by partial deregulation and the subsequent increase in competition. My talk today will focus on issues related to the second paradigm, particularly in terms of utility planners getting more organized to deal with the synergies in the fields of forecasting, demand-side planning, and evaluation. I will also reflect on two new issues within the existing paradigm that influence these functional areas, namely beneficial electrification and integration of DSM into T&D planning. Finally I will talk about what I see coming as we go through another paradigm shift, particularly as it impacts forecasting and DSM.

  14. Molecular Electronic Shift Registers

    NASA Technical Reports Server (NTRS)

    Beratan, David N.; Onuchic, Jose N.

    1990-01-01

    Molecular-scale shift registers eventually constructed as parts of high-density integrated memory circuits. In principle, variety of organic molecules makes possible large number of different configurations and modes of operation for such shift-register devices. Several classes of devices and implementations in some specific types of molecules proposed. All based on transfer of electrons or holes along chains of repeating molecular units.

  15. 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.

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

    DOE PAGES

    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=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.

  17. Identification of a new isomer from a reversible isomerization of ceftriaxone in aqueous solution.

    PubMed

    Tian, Ye; Lu, Li; Chang, Yan; Zhang, Dou-sheng; Li, Jin; Feng, Yan-Chun; Hu, Chang-Qin

    2015-01-01

    A reversible isomerization of ceftriaxone in aqueous solution was observed, and the structure of the isomer was determined by mass spectrometry and various 1D and 2D NMR techniques. The mechanism of isomerization was also discussed. Finally, molecular docking simulations were performed and the antimicrobial activities of the isomers were measured. This showed that the biological activity of ceftriaxone was stronger than that of its isomer. The results reported in this article may be important to quality control requirements and to the stability of ceftriaxone products.

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

    SciTech Connect

    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=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.

  19. 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.

  20. 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.

  1. Quantification of Triacylglycerol Positional Isomers in Rat Milk.

    PubMed

    Watanabe, Natsuko; Nagai, Toshiharu; Mizobe, Hoyo; Yoshinaga, Kazuaki; Yoshida, Akihiko; Kitamura, Yohei; Shimizu, Takashi; Beppu, Fumiaki; Gotoh, Naohiro

    2016-12-01

    The absolute amount of triacylglycerol (TAG) positional isomers was analyzed in rat milk fat, a representative of non-ruminant milk fat, using a HPLC-UV-atmospheric pressure chemical ionization-MS/MS system equipped with an octacosyl silylation column or polymeric ODS column. TAGs consisting of two oleic acids (O) and one palmitic acid (P) were the most abundant. In particular, β-OPO, a TAG binding P at the β-position (sn-2) and two Os at the α-positions (sn-1/3), was prominent. The β-OPO content decreased over time, while a TAG consisting of two Ps and one capric acid, a medium-chain fatty acid, increased. TAGs consisting of two Ps and one docosahexaenoic acid were present in small amounts and decreased with time. These results indicated that the recombination of fatty acids in TAGs in milk fat occurs in the mother, and is thought to depend on the infant's stage of growth, in response to their nutritional needs. It was also demonstrated that medium-chain fatty acids were mainly located at the α-position (sn-3), while Ps were mainly located at the β-position (sn-2). Therefore, the combination and binding positions of fatty acids of TAG are considered very important in infant nutrition.

  2. Actual ratio of triacylglycerol positional isomers in milk and cheese.

    PubMed

    Gotoh, Naohiro; Matsumoto, Yumiko; Nagai, Toshiharu; Mizobe, Hoyo; Yoshinaga, Kazuaki; Kojima, Koichi; Kuroda, Ikuma; Kitamura, Yohei; Shimizu, Takashi; Ishida, Hiroki; Wada, Shun

    2012-01-01

    Actual ratios of triacylglycerol (TAG) positional isomers in human, rat, and cow milk fat and cow, buffalo, goat, and sheep cheese fat were analyzed using HPLC-UV-atmospheric pressure chemical ionization-MS/MS system equipped with an octacosyl silylation column or polymeric ODS column. We substituted cheese fats for milk fats in parts of our study because milks from ruminants, with the exception of cows, are difficult to get in Japan. The actual ratio of β-PPC (the TAG consisting of two palmitic acids (P) and one capric acid (C), with the palmitic acid located at the β position) and β-PCP in human milk was different from those in ruminants, with more than half of the medium-chain fatty acids located at the β position even though other fats possessed it mainly at the α position. Palmitic acid was mainly located at the β position for human milk and rat milk; however, the location in ruminant cheese fat was mainly at the α position. The location of fatty acids is thought to be very important for infant nutrition. Particularly, the location of palmitic acid in case of human milk and of medium-chain fatty acids in case of ruminant milk was very characteristic and is considered to be very important to the fatty acids in milk fat.

  3. Electron and Positron Scattering from C3H6 Isomers

    NASA Astrophysics Data System (ADS)

    Makochekanwa, Casten; Sueoka, Osamu; Kimura, Mineo; Hoshino, Masamitsu; Tanaka, Takahiro; Kitajima, Masashi; Tanaka, Hiroshi

    2004-09-01

    Hydrocarbons play an important role in high temperature plasmas in Tokamak fusion devices in plasma processing and many other fields [1]. In this paper we report experiments for 0.4-1000 eV electron and 0.2-1000 eV positron total cross sections (TCS) measured using a linear time-of-flight apparatus [2], and electron differential cross sections (DCS) for elastic, vibrational and electronic excitations covering the ranges 1.5 to 100 eV and 15 deg to 130 deg, measured using the crossed beam and relative flow method [3]. The continuum multiple scattering (CMS) [4] calculations have also been performed for the theoretical analysis of the observed features in our cross sections. We observe the isomer effect in both electron and positron TCSs and DCSs. The presence of a dipole moment in propene molecules shows up in enhanced forward scattering in DCSs, leading to larger TCSs and integral cross sections compared to cyclopropane at energies less than 20 eV. However, both electron and positron TCSs for these two molecules nearly equal each other above 100 eV, i.e. the molecular size effect. [1] W. L. Moragn, Adv. At. Mol. Opt. Phys. 43, 79 (2000). [2] O. Sueoka, S. Mori and A. Hamada, J. Phys. B 27, 1453 (1994). [3] H. Tanaka, L. Boesten, D. Matsunaga and T. Kudo, J. Phys. B 21, 1255 (1988). [4] M. Kimura and H. Sato, Comments At. Mol. Phys. 26, 333 (1991).

  4. Search for superradiant emission states in nuclear isomer crystals

    SciTech Connect

    Rundberg, R.S.; Wilhelmy, J.B.; Taylor, R.D.; Solem, J.C.; Fowler, M.M.; Miller, G.G.; Baldwin, G.

    1998-01-01

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The objective was to verify the stimulated emission of gamma rays from {sup 125m}Te, as claimed by Russian scientists. The reported cross section for stimulated emission was sufficiently large to allow gain in a single-pass gamma-ray laser. The stimulated emission of gamma rays from a nuclear isomer is expected to result in collinear photons and, therefore, should be observable as a sum peak in the gamma-ray spectrum. Skorobogatov and Dzevitskii reported an increase of an order of magnitude in the sum peak (218.56 keV) when a sample of beryllium telluride containing {sup 125m}Te was cooled from room temperature to near-liquid-helium temperatures. The authors have repeated their experiment and have observed no increase in the sum peak above accidental summing. The upper limit for the stimulated-emission cross section based on the three-standard-deviation statistical error is 6.8 x 10 {sup {minus}21} cm{sup 2}. This result is one order of magnitude lower than the cross section reported by Skorobogatov and Dzevitskii. The cross section would not allow gain in a single-pass gamma-ray laser. Their results support the position of Baldwin and Solem rather than that of Kamenov.

  5. Effect of a Single Water Molecule on the Electronic Absorption by o- and p-Nitrophenolate: A Shift to the Red or to the Blue?

    PubMed

    Houmøller, Jørgen; Wanko, Marius; Rubio, Angel; Nielsen, Steen Brøndsted

    2015-11-25

    Many photoactive biomolecules are anions and exhibit ππ* optical transitions but with a degree of charge transfer (CT) character determined by the local environment. The phenolate moiety is a common structural motif among biochromophores and luminophores, and nitrophenolates are good model systems because the nitro substituent allows for CT-like transitions. Here we report gas-phase absorption spectra of o- and p-nitrophenolate·H2O complexes to decipher the effect of just one H2O and compare them with ab initio calculations of vertical excitation energies. The experimental band maximum is at 3.01 and 3.00 eV for ortho and para isomers, respectively, and is red-shifted by 0.10 and 0.13 eV relative to the bare ions, respectively. These shifts indicate that the transition has become more CT-like because of localization of negative charge on the phenolate oxygen, i.e., diminished delocalization of the negative excess charge. However, the transition bears less CT than that of m-nitrophenolate·H2O because this complex absorbs further to the red (2.56 eV). Our work emphasizes the importance of local perturbations: one water causes a larger shift than experienced in bulk for para isomer and almost the full shift for ortho isomer. Predicting microenvironmental effects in the boundary between CT and non-CT with high accuracy is nontrivial. However, in agreement with experiment, our calculations show a competition between the effects of electronic delocalization and electrostatic interaction with the solvent molecule. As a result, the excitation energy of ortho and para isomers is less sensitive to hydration than that of the meta isomer because donor and acceptor orbitals are only weakly coupled in the meta isomer.

  6. AN ISOMER PREDICTION MODEL FOR PCNS, PCDD/FS, AND PCBS FROM MUNICIPAL WASTE INCINERATORS

    EPA Science Inventory

    Isomer patterns of polychlorinated naphthalenes (PCNs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated biphenyls (PCBs) from municipal waste incinerators (MWIs) were predicted by a model based on dechlorination kinetics from the most-chlorinated species. Successfu...

  7. Low-energy electron scattering from C{sub 4}H{sub 9}OH isomers

    SciTech Connect

    Bettega, M. H. F.; Winstead, C.; McKoy, V.

    2010-12-15

    We present differential, integral, and momentum-transfer cross sections for elastic scattering of low-energy electrons by three butanol isomers, isobutanol, t-butanol, and 2-butanol. Our results were calculated with the Schwinger multichannel method in the static-exchange plus polarization approximation for collision energies from 1 to 50 eV. The present results are compared with previous calculations and measurements for the remaining C{sub 4}H{sub 9}OH isomer, n-butanol [Khakoo et al., Phys. Rev. A 78, 062714 (2008)]. Distinctive behavior is observed in the differential cross sections at collision energies between 5 and 10 eV. In particular, whereas n-butanol exhibits an f-wave scattering pattern, the other isomers exhibit d-wave behavior. A similar pattern is found in the related alkanes when comparing straight-chain versus branched isomers. We discuss the possible connection of this behavior to shape resonances that influence the scattering.

  8. 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)

  9. 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)

  10. 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.

  11. 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.

  12. Differential adsorption of complex organic molecule isomers on interstellar ice surfaces

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    We present a combined theoretical and experimental study of the adsorption of two pairs of organic isomers, (i) acetic acid AA (CH3COOH) and methyl formate MF (HCOOCH3), and (ii) ethanol EtOH (CH3CH2OH) and dimethyl ether DME (CH3OCH3), onto crystalline water ice surfaces at low temperatures. Both approaches show that, for each pair, the most stable isomer from a thermodynamical point of view, i.e. AA and EtOH, is also the one which is the more tightly bound to the water ice surface compared to the less stable isomers (MF and DME). This finding, which can be explained by the ability of AA or EtOH to efficiently interact with the ice surface via hydrogen bondings, may have important consequences in an astrophysical context, since it could explain why the most stable isomer is not the most abundant observed in the interstellar gas phase.

  13. 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.

  14. New isomer in 96Y marking the onset of deformation at N = 57

    NASA Astrophysics Data System (ADS)

    Iskra, Ł. W.; Fornal, B.; Leoni, S.; Bocchi, G.; Petrovici, A.; Porzio, C.; Blanc, A.; De France, G.; Jentschel, M.; Köster, U.; Mutti, P.; Régis, J.-M.; Simpson, G.; Soldner, T.; Ur, C. A.; Urban, W.; Bazzacco, D.; Benzoni, G.; Bottoni, S.; Bruce, A.; Cieplicka-Oryńczak, N.; Crespi, F. C. L.; Fraile, L. M.; Korten, W.; Kröll, T.; Lalkovski, S.; Márginean, N.; Michelagnoli, C.; Melon, B.; Mengoni, D.; Million, B.; Nannini, A.; Napoli, D.; Podolyák, Zs.; Regan, P. H.; Szpak, B.

    2017-01-01

    The level scheme of 96Y was significantly extended and a new 201 ns isomer was located at 1655 keV excitation energy, with spin-parity assignment of 5± or 6‑. The isomer decays to spherical low-spin structure by transitions with large hindrance and is fed by a short cascade which resembles the beginning of a rotational band. This is in analogy with the feeding and decay pattern of the 4‑ isomer in 98Y, here confirmed, by lifetime analysis, as a bandhead of a rotational structure with sizable deformation. It is suggested that the new isomer in 96Y arises from a shape change between deformed and spherical configurations, which indicates the appearance of deformation already at N = 57 in the yttrium chain. The experimental findings for 96Y are strengthened by theoretical calculations based on the complex Excited Vampir model.

  15. Optical isomer separation of single-chirality carbon nanotubes using gel column chromatography.

    PubMed

    Liu, Huaping; Tanaka, Takeshi; Kataura, Hiromichi

    2014-11-12

    We report a gel column chromatography method for easily separating the optical isomers (i.e., left- and right-handed structures) of single-chirality carbon nanotubes. This method uses the difference in the interactions of the two isomers of a chiral single-wall carbon nanotube (SWCNT) with an allyl dextran-based gel, which result from the selective interaction of the chiral moieties of the gel with the isomers. Using this technique, we sorted optical isomers of nine distinct (n, m) single-chirality species from HiPco SWCNTs, which is the maximum number of isolable species of SWCNTs reported to date. Because of its advantages of technical simplicity, low cost, and high efficiency, gel column chromatography allows researchers to prepare macroscopic ensembles of single-structure SWCNTs and enables the complete discovery of intrinsic properties of SWCNTs and advances their application.

  16. Electronic and vibrational properties of stable isomers of (SiO)n((0,±)) (n = 2-7) clusters.

    PubMed

    Du, Hong-Bo; Huang, Shu-Ping; De Sarkar, Abir; Fan, Wen-Jie; Jia, Yu; Zhang, Rui-Qin

    2014-10-02

    First-principles calculations based on density functional theory have been performed to explore the stable configurations, electronic structures, and vibrational spectra of neutral and charged silicon monoxide clusters (SiO)n((0,±)) (n = 2-7), which could be used as precursors in the synthesis of silicon nanowires. Our theoretical calculations provide new results on characteristic electron affinity, ionization potential, and vibrational spectroscopy, guiding future experiments in the synthesis of high-quality silicon nanowires. Specifically, as the number of SiO units n increases, IR spectra of (SiO)n(±) and Raman spectra of (SiO)n(-) show an evident blue shift, and Raman spectra of (SiO)n demonstrate a red shift. Moreover, most of the neutral silicon monoxide clusters have strong IR intensities and weak Raman activities, while most of the anionic counterparts have relatively weak IR intensities and strong Raman activities. Some other energetically competitive isomers of some (SiO)n((0,±)) species were also studied for comparison.

  17. Isomers of OCS{sub 2}: IR absorption spectra of OSCS and O(CS{sub 2}) in solid Ar

    SciTech Connect

    Lo, W.-J.; Chen, H.-F.; Chou, P.-H.; Lee, Y.-P.

    2004-12-22

    Irradiation of an Ar matrix sample containing O{sub 3} and CS{sub 2} with a KrF excimer laser at 248 nm yielded new lines at 1402.1 (1404.7), 1056.2 (1052.7), and 622.3 (620.5) cm-1; numbers in parentheses correspond to species in a minor matrix site. Secondary photolysis at 308 nm diminished these lines and produced mainly OCS and SO{sub 2}. Annealing of this matrix to 30 K yielded a second set of new lines at 1824.7 and 617.8 cm-1. The first set of lines are assigned to C=S stretching, O-S stretching, and S-C stretching modes of carbon disulfide S-oxide, OSCS; and the second set of lines are assigned to C=O stretching and OCS bending modes of dithiiranone, O(CS{sub 2}), respectively, based on results of {sup 34}S- and {sup 18}O-isotopic experiments and quantum-chemical calculations. These calculations using density-functional theory (B3LYP/aug-cc-pVTZ) predict four stable isomers of OCS{sub 2}: O(CS{sub 2}), SSCO, OSCS, and SOCS, listed in order of increasing energy. According to calculations, O(CS{sub 2}) has a cyclic CS{sub 2} moiety and is the most stable isomer of OCS{sub 2}. OSCS is planar, with bond angles anguprOSC congruent with 111.9 deg. and anguprSCS congruent with 177.3 deg.; it is less stable than SSCO and O(CS{sub 2}) by {approx}102 and 154 kJ mol-1, respectively, and more stable than SOCS by {approx}26 kJ mol-1. Calculated vibrational wave numbers, IR intensities, {sup 34}S- and {sup 18}O-isotopic shifts for OSCS and O(CS{sub 2}) fit satisfactorily with experimental results.

  18. Isomer Tagging with a Dual Multi-Wire Proportional Counter and a Differential Plunger

    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.; Pakarinen, J.; Nieminen, P.

    2008-05-12

    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 large 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 144}Ho, {sup 142}Tb) the N = 82 shell gap were presented. These studies have charted the evolution of isomeric states across the neutron shell from K-Isomers at N = 74, to shape isomers at N = 77 and shell-model isomers at N = 82, 83. The excitation energies for some of the lowest-lying excited states in these isomeric nuclei show behaviour which is characteristic of an X(5) symmetry falling midway between the limits expected for pure vibrational and rotational behaviour. The future prospects for studies of these nuclei were discussed using an isomer-tagged differential-plunger setup. This technique will be capable of establishing the deformation of the states above the isomers and will aid in determining whether their behaviour is indeed well described by the X(5) symmetry limit.

  19. Isomer-specific biotransformation of perfluorooctane sulfonamide in Sprague-Dawley rats.

    PubMed

    Ross, Matthew S; Wong, Charles S; Martin, Jonathan W

    2012-03-20

    Great variability exists in perfluorooctane sulfonate (PFOS) isomer patterns in human and wildlife samples, including unexpectedly high percentages (e.g., >40%) of branched isomers in human sera. Previous in vitro tests showed that branched PFOS-precursors were biotransformed faster than the corresponding linear isomer. Thus, high percentages of branched PFOS may be a biomarker of PFOS-precursor exposure in humans. We evaluated this hypothesis by examining the isomer-specific fate of perfluorooctane sulfonamide (PFOSA), a known PFOS-precursor, in male Sprague-Dawley rats exposed to commercial PFOSA via food for 77 days (83.0 ± 20.4 ng kg(-1) day(-1)), followed by 27 days of depuration. Elimination half-lives of the two major branched PFOSA isomers (2.5 ± 1.0 days and 3.7 ± 1.2 days) were quicker than for linear PFOSA (5.9 ± 4.6 days), resulting in a depletion of branched PFOSA isomers in blood and tissues relative to the dose. A corresponding increase in the total branched isomer content of PFOS, the ultimate metabolite, in rat serum was not observed. However, a significant enrichment of 5m-PFOS and a significant depletion of 1m-PFOS were observed, relative to authentic electrochemical PFOS. The data cannot be directly extrapolated to humans, due to known differences in the toxicokinetics of PFOS in rodents and humans. However, the results confirm that in vivo exposure to commercially relevant PFOS-precursors can result in a distinct PFOS isomer profile that may be useful as a biomarker of exposure source.

  20. Energy spectrum of isomer no. 3 of C82 fullerene of C 2 symmetry

    NASA Astrophysics Data System (ADS)

    Kareev, I. E.; Bubnov, V. P.; Kotov, A. I.; Lobanov, B. V.; Murzashev, A. I.; Rumyantsev, I. A.

    2017-01-01

    The energy spectrum of C82 fullerene (isomer no. 3 of C 2 symmetry) is calculated within the Hubbard model in the approximation of static fluctuations. Based on the energy spectrum, optical absorption spectra of this isomer in neutral and anionic states with one, two, three, and four additional electrons are simulated. The calculated optical spectra in neutral and monoanionic states are compared with known experimental spectra.

  1. 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.

  2. Roles of the tyrosine isomers meta-tyrosine and ortho-tyrosine in oxidative stress.

    PubMed

    Ipson, Brett R; Fisher, Alfred L

    2016-05-01

    The damage to cellular components by reactive oxygen species, termed oxidative stress, both increases with age and likely contributes to age-related diseases including Alzheimer's disease, atherosclerosis, diabetes, and cataract formation. In the setting of oxidative stress, hydroxyl radicals can oxidize the benzyl ring of the amino acid phenylalanine, which then produces the abnormal tyrosine isomers meta-tyrosine or ortho-tyrosine. While elevations in m-tyrosine and o-tyrosine concentrations have been used as a biological marker of oxidative stress, there is emerging evidence from bacterial, plant, and mammalian studies demonstrating that these isomers, particularly m-tyrosine, directly produce adverse effects to cells and tissues. These new findings suggest that the abnormal tyrosine isomers could in fact represent mediators of the effects of oxidative stress. Consequently the accumulation of m- and o-tyrosine may disrupt cellular homeostasis and contribute to disease pathogenesis, and as result, effective defenses against oxidative stress can encompass not only the elimination of reactive oxygen species but also the metabolism and ultimately the removal of the abnormal tyrosine isomers from the cellular amino acid pool. Future research in this area is needed to clarify the biologic mechanisms by which the tyrosine isomers damage cells and disrupt the function of tissues and organs and to identify the metabolic pathways involved in removing the accumulated isomers after exposure to oxidative stress.

  3. Surfactant mediated enhanced biodegradation of hexachlorocyclohexane (HCH) isomers by Sphingomonas sp. NM05.

    PubMed

    Manickam, Natesan; Bajaj, Abhay; Saini, Harvinder S; Shanker, Rishi

    2012-09-01

    Environmental biodegradation of several chlorinated pesticides is limited by their low solubility and sorption to soil surfaces. To mitigate this problem we quantified the effect of three biosurfactant viz., rhamnolipid, sophorolipid and trehalose-containing lipid on the dissolution, bioavailability, and biodegradation of HCH-isomers in liquid culture and in contaminated soil. The effect of biosurfactants was evaluated through the critical micelle concentration (CMC) value as determined for each isomer. The surfactant increased the solubilization of HCH isomers by 3-9 folds with rhamnolipid and sophorolipid being more effective and showing maximum solubilization of HCH isomers at 40 μg/mL, compared to trehalose-containing lipid showing peak solubilization at 60 μg/mL. The degradation of HCH isomers by Sphingomonas sp. NM05 in surfactant-amended liquid mineral salts medium showed 30% enhancement in 2 days as compared to degradation in 10 days in the absence of surfactant. HCH-spiked soil slurry incubated with surfactant also showed around 30-50% enhanced degradation of HCH which was comparable to the corresponding batch culture experiments. Among the three surfactants, sophorolipid offered highest solubilization and enhanced degradation of HCH isomers both in liquid medium and soil culture. The results of this study suggest the effectiveness of surfactants in improving HCH degradation by increased bioaccessibility.

  4. 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

  5. Isotonic similarities in isotope shifts from Hg to Ra.

    NASA Astrophysics Data System (ADS)

    Stroke, H. H.

    2003-04-01

    Isotope shifts (IS) in atomic spectra of heavy elements reflect largely the variation in of the nuclear charge distribution. Our early systematic measurements of IS for an extended range of stable and radioactive isotopes and nuclear isomers in Tl and Hg^1 showed that by displaying the relative IS, normalized to a chosen pair of isotopes, there was a striking similarity for the IS of isotones. This essentially divides out the electronic factor in the IS and allows the comparison of Δ for neighboring Z as N is varied. Following our further studies on Pb and Bi^2 and those on Fr at ISOLDE by the Orsay spectroscopy group^3, we found that the isotonic similarity extended to these elements. Since then, many additional measurements were made, principally at ISOLDE^4, extending to Ra the elements studied. The isotonic shift similarities persist from Z=80 to 88. We noted that the relative isotope and isomer shifts can be used to investigate the polarization of the nucleus by the added neutrons, a model used in a calculation by Barrett.^5 . The new data may serve further in this direction. ^1W,J.Tomlinson, H.H. Stroke, Nucl.Phys. 60, 614 (1964). ^2M. Barboza-Flores et al., Z.Phys. A 321, 85 (1985), ^3S. Liberman et al., Phys .Rev. A 22, 2732 (1980). ^4E,g. M.R. Pearson et al., J.Phys. G 26, 1829 (2000). ^5R.C. Barrett, Nucl. Phys. 88, 128 (1966).

  6. Quantification of Structural Isomers via Mode-Selective Irmpd

    NASA Astrophysics Data System (ADS)

    Polfer, Nicolas C.

    2016-06-01

    Mixtures of structural isomers can pose a challenge for vibrational ion spectroscopy. In cases where particular structures display diagnostic vibrations, these structures can be selectively "burned away". In ion traps, the ion population can be subjected to multiple laser shots, in order to fully deplete a particular structure, in effect allowing a quantification of this structure. Protonated para-amino benzoic acid (PABA) serves as an illustrative example. PABA is known to preferentially exist in the N-protonated (N-prot) form in solution, but in the gas phase it is energetically favorable in the O-protonated (O-prot) form. As shown in Figure 1, the N-prot structure can be kinetically trapped in the gas phase when sprayed from non-protic solvent, whereas the O-prot structure is obtained when sprayed from protic solvents, analogous to results by others [1,2]. y parking the light source on the diagnostic 3440 wn mode, the percentage of the O-prot structure can be determined, and by default the remainder is assumed to adopt the N-prot structure. It will be shown that the relative percentages of O-prot vs N-prot are highly dependent on the solvent mixture, going from close to 0% O-prot in non-protic solvents, to 99% in protic solvents. Surprisingly, water behaves much more like a non-protic solvent than methanol. It is observed that the capillary temperature, which aids droplet desolvation by black-body radiation in the ESI source, is critical to promote the appearance of O-prot structures. These results are consistent with the picture that a protic bridge mechanism is at play to facilitate proton transfer, and thus allow conversion from N-prot to O-prot, but that this mechanism is subject to appreciable kinetic barriers on the timescale of solvent evaporation. 1. J. Phys. Chem. A 2011, 115, 7625. 2. Anal. Chem. 2012, 84, 7857.

  7. Trophic shift, not collapse

    USGS Publications Warehouse

    Madenjian, Charles P.; Rutherford, Edward S.; Stow, Craig A.; Roseman, Edward F.; He, Ji X.

    2013-01-01

    scientists who are closely monitoring Lake Huron’s food web, we believe that the ongoing changes are more accurately characterized as a trophic shift in which benthic pathways have become more prominent. While decreases in abundance have occurred for some species, others are experiencing improved reproduction resulting in the restoration of several important native species.

  8. Eluding catastrophic shifts.

    PubMed

    Villa Martín, Paula; Bonachela, Juan A; Levin, Simon A; Muñoz, Miguel A

    2015-04-14

    Transitions between regimes with radically different properties are ubiquitous in nature. Such transitions can occur either smoothly or in an abrupt and catastrophic fashion. Important examples of the latter can be found in ecology, climate sciences, and economics, to name a few, where regime shifts have catastrophic consequences that are mostly irreversible (e.g., desertification, coral reef collapses, and market crashes). Predicting and preventing these abrupt transitions remains a challenging and important task. Usually, simple deterministic equations are used to model and rationalize these complex situations. However, stochastic effects might have a profound effect. Here we use 1D and 2D spatially explicit models to show that intrinsic (demographic) stochasticity can alter deterministic predictions dramatically, especially in the presence of other realistic features such as limited mobility or spatial heterogeneity. In particular, these ingredients can alter the possibility of catastrophic shifts by giving rise to much smoother and easily reversible continuous ones. The ideas presented here can help further understand catastrophic shifts and contribute to the discussion about the possibility of preventing such shifts to minimize their disruptive ecological, economic, and societal consequences.

  9. Eluding catastrophic shifts

    PubMed Central

    Villa Martín, Paula; Bonachela, Juan A.; Levin, Simon A.; Muñoz, Miguel A.

    2015-01-01

    Transitions between regimes with radically different properties are ubiquitous in nature. Such transitions can occur either smoothly or in an abrupt and catastrophic fashion. Important examples of the latter can be found in ecology, climate sciences, and economics, to name a few, where regime shifts have catastrophic consequences that are mostly irreversible (e.g., desertification, coral reef collapses, and market crashes). Predicting and preventing these abrupt transitions remains a challenging and important task. Usually, simple deterministic equations are used to model and rationalize these complex situations. However, stochastic effects might have a profound effect. Here we use 1D and 2D spatially explicit models to show that intrinsic (demographic) stochasticity can alter deterministic predictions dramatically, especially in the presence of other realistic features such as limited mobility or spatial heterogeneity. In particular, these ingredients can alter the possibility of catastrophic shifts by giving rise to much smoother and easily reversible continuous ones. The ideas presented here can help further understand catastrophic shifts and contribute to the discussion about the possibility of preventing such shifts to minimize their disruptive ecological, economic, and societal consequences. PMID:25825772

  10. Understanding NMR Chemical Shifts

    NASA Astrophysics Data System (ADS)

    Jameson, Cynthia J.

    1996-10-01

    The NMR chemical shift serves as a paradigm for molecular electronic properties. We consider the factors that determine the general magnitudes of the shifts, the state of the art in theoretical calculations, the nature of the shielding tensor, and the multidimensional shielding surface that describes the variation of the shielding with nuclear positions. We also examine the nature of the intermolecular shielding surface as a general example of a supermolecule property surface. The observed chemical shift in the zero-pressure limit is determined not only by the value of the shielding at the equilibrium geometry, but the dynamic average over the multidimensional shielding surface during rotation and vibration of the molecule. In the gas, solution, or adsorbed phase it is an average of the intermolecular shielding surface over all the configurations of the molecule with its neighbors. The temperature dependence of the chemical shift in the isolated molecule, the changes upon isotopic substitution, the changes with environment, are well characterized experimentally so that quantum mechanical descriptions of electronic structure and theories related to dynamics averaging of any electronic property can be subjected to stringent test.

  11. Definition of "positional isomer" as it pertains to the control of schedule I controlled substances. Final rule.

    PubMed

    2007-12-03

    On May 25, 2006, DEA published a Notice of Proposed Rulemaking which proposed the addition of a specific definition for the term "positional isomer" to allow for the systematic determination of which isomers of schedule I substances would be considered to be "positional," and therefore, subject to schedule I control. This rulemaking finalizes that definition. The Controlled Substances Act (CSA) and its implementing regulations specify which hallucinogenic substances are considered schedule I controlled substances. The CSA states that all salts, isomers, and salts of isomers of these substances are also schedule I controlled substances. In non-technical terms, an isomer of a substance is a different compound, but a compound which has the same number and kind of atoms. The terms "optical isomer" and "geometric isomer" are specific scientific terms and it is easy to determine whether one substance is an optical or geometric isomer of another. The term "positional isomer," however, is subject to scientific interpretation. The addition of a definition for the term "positional isomer" will assist legitimate research[ers] and industry in determining the control status of materials that are "positional isomers" of schedule I hallucinogens. While the DEA will remain the authority for ultimately determining the control status of a given material, providing a specific definition for "positional isomer" will ensure consistent criteria are utilized in making these determinations. This rule does not change existing laws, regulations, policies, processes, and procedures regarding the determination of control status for schedule I hallucinogenic substances. This rule merely makes available to the public the longstanding definition of "positional isomer" which DEA has used when making these scheduling determinations. This rule is relevant only to specialized forensic or research chemists. Most of these individuals are existing DEA registrants who are authorized by the DEA to handle

  12. Feeding of Rh and Ag isomers in fast-neutron-induced reactions

    DOE PAGES

    Fotiades, Nikolaos; Devlin, Matthew James; Nelson, Ronald Owen; ...

    2016-10-17

    In (n,n') reactions on stable Ir and Au isotopes in the mass A=190 region, the experimentally established feeding of the isomers relative to the feeding of the corresponding ground states increases with increasing neutron energy, up to the neutron energy where the (n,2n) reaction channel opens up, and then decreases. In order to check for similar behavior in the mass A=100 region, the feeding of isomers and ground states in fast-neutron-induced reactions on stable isotopes in this mass region was studied. This is of especial interest for Rh which can be used as a radiochemical detector. Here, excited states weremore » studied using the (n,n'γ), (n,2nγ), and (n,3nγ) reactions on 103Rh and 109Ag. A germanium detector array for γ-ray detection and the broad-spectrum pulsed neutron source of the Los Alamos Neutron Science Center's Weapons Neutron Research facility were used for the measurement. The energy of the incident neutrons was determined using the time-of-flight technique. Absolute partial γ-ray cross sections were measured for 57 transitions feeding isomers and ground states in 101,102,103Rh and 107,108,109Ag. The feeding of the isomers was found to be very similar in the corresponding reaction channels and it is compared to the feeding determined for the ground states. In conclusion, the opening of reaction channels at higher neutron energies removes angular momentum from the residual nucleus and reduces the population of the higher-spin isomers relative to the feeding of the lower-spin ground states. Similar behavior was observed in the mass A=190 region in the feeding of higher-spin isomers, but the reverse behavior was observed in 176Lu with a lower-spin isomer and a higher-spin ground state.« less

  13. 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.

  14. Isomers of perfluorooctanesulfonate (PFOS) in cord serum and birth outcomes in China: Guangzhou Birth Cohort Study.

    PubMed

    Li, Meng; Zeng, Xiao-Wen; Qian, Zhengmin Min; Vaughn, Michael G; Sauvé, Sébastien; Paul, Gunther; Lin, Shao; Lu, Long; Hu, Li-Wen; Yang, Bo-Yi; Zhou, Yang; Qin, Xiao-Di; Xu, Shu-Li; Bao, Wen-Wen; Zhang, Ya-Zhi; Yuan, Ping; Wang, Jia; Zhang, Chuan; Tian, Yan-Peng; Nian, Min; Xiao, Xiang; Fu, Chuanxi; Dong, Guang-Hui

    2017-03-12

    Prior investigations on the associations of polyfluoroalkyl substances (PFASs) with fetal growth are mixed. Moreover, little research has accrued pertaining to the association between isomers of PFASs with gestational age and birth weight. To address this gap and present novel information, we conducted a study including 321 pairs of mothers and their infants recruited from Guangzhou, China. High performance liquid chromatography-mass spectrometry was utilized to analyze isomers of perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA) along with other PFAS levels in cord serum samples. Mothers' and infants' characteristics were gathered from medical records. The resulting data revealed that higher PFOS, PFOA and isomers of PFOS were associated with lower birth weight. Per ln-unit (ng/mL) increase in cord serum total branched PFOS isomers was associated with a 126.3g (95% CI: -195.9, -56.8) reduction in the weight of infants at birth, while an ln-unit (ng/mL) increase of serum linear PFOS isomers (n-PFOS) was associated with a 57.2g (95% CI: -103.1, -11.3) reduction in the weight of infants at birth upon the subsequent adjustment for potential confounding variables. Notably, the association between cord PFAS level and birth weight was more pronounced in male infants. Furthermore, a positive association among branched PFOS isomers (1m-PFOS and 3+4+5m-PFOS) and gestational age was found. No associations could be found among other PFASs in conjunction with gestational age or birth weight. In conclusion, this investigation suggests that higher PFAS concentrations are associated with lower birth weight, and branched PFOS isomers show greater impact on infant birth weight than linear PFOS.

  15. Feeding of Rh and Ag isomers in fast-neutron-induced reactions

    NASA Astrophysics Data System (ADS)

    Fotiades, N.; Devlin, M.; Nelson, R. O.; Kawano, T.; Carroll, J. J.

    2016-10-01

    Background: In (n ,n' ) reactions on stable Ir and Au isotopes in the mass A =190 region, the experimentally established feeding of the isomers relative to the feeding of the corresponding ground states increases with increasing neutron energy, up to the neutron energy where the (n ,2 n ) reaction channel opens up, and then decreases. Purpose: In order to check for similar behavior in the mass A =100 region, the feeding of isomers and ground states in fast-neutron-induced reactions on stable isotopes in this mass region was studied. This is of especial interest for Rh which can be used as a radiochemical detector. Methods: Excited states were studied using the (n ,n'γ ), (n ,2 n γ ), and (n ,3 n γ ) reactions on 103Rh and 109Ag. A germanium detector array for γ -ray detection and the broad-spectrum pulsed neutron source of the Los Alamos Neutron Science Center's Weapons Neutron Research facility were used for the measurement. The energy of the incident neutrons was determined using the time-of-flight technique. Results: Absolute partial γ -ray cross sections were measured for 57 transitions feeding isomers and ground states in 101,102,103Rh and 107,108,109Ag. The feeding of the isomers was found to be very similar in the corresponding reaction channels and it is compared to the feeding determined for the ground states. Conclusions: The opening of reaction channels at higher neutron energies removes angular momentum from the residual nucleus and reduces the population of the higher-spin isomers relative to the feeding of the lower-spin ground states. Similar behavior was observed in the mass A =190 region in the feeding of higher-spin isomers, but the reverse behavior was observed in 176Lu with a lower-spin isomer and a higher-spin ground state.

  16. Feeding of Rh and Ag isomers in fast-neutron-induced reactions

    SciTech Connect

    Fotiades, Nikolaos; Devlin, Matthew James; Nelson, Ronald Owen; Kawano, T.; Carroll, J. J.

    2016-10-17

    In (n,n') reactions on stable Ir and Au isotopes in the mass A=190 region, the experimentally established feeding of the isomers relative to the feeding of the corresponding ground states increases with increasing neutron energy, up to the neutron energy where the (n,2n) reaction channel opens up, and then decreases. In order to check for similar behavior in the mass A=100 region, the feeding of isomers and ground states in fast-neutron-induced reactions on stable isotopes in this mass region was studied. This is of especial interest for Rh which can be used as a radiochemical detector. Here, excited states were studied using the (n,n'γ), (n,2nγ), and (n,3nγ) reactions on 103Rh and 109Ag. A germanium detector array for γ-ray detection and the broad-spectrum pulsed neutron source of the Los Alamos Neutron Science Center's Weapons Neutron Research facility were used for the measurement. The energy of the incident neutrons was determined using the time-of-flight technique. Absolute partial γ-ray cross sections were measured for 57 transitions feeding isomers and ground states in 101,102,103Rh and 107,108,109Ag. The feeding of the isomers was found to be very similar in the corresponding reaction channels and it is compared to the feeding determined for the ground states. In conclusion, the opening of reaction channels at higher neutron energies removes angular momentum from the residual nucleus and reduces the population of the higher-spin isomers relative to the feeding of the lower-spin ground states. Similar behavior was observed in the mass A=190 region in the feeding of higher-spin isomers, but the reverse behavior was observed in 176Lu with a lower-spin isomer and a higher-spin ground state.

  17. Maternal dietary Alpine butter intake affects human milk: fatty acids and conjugated linoleic acid isomers.

    PubMed

    Bertschi, Isabelle; Collomb, Marius; Rist, Lukas; Eberhard, Pius; Sieber, Robert; Bütikofer, Ulrich; Wechsler, Daniel; Folkers, Gerd; von Mandach, Ursula

    2005-06-01

    Consumption of CLA by lactating women affects the composition of their milk, but the pattern of the different CLA isomers is still unknown. We determined the effects of short maternal supplementation with CLA-rich Alpine butter on the occurrence of FA and CLA isomers in human milk. In an open randomized controlled study with a two-period cross-over design, milk FA and CLA isomer concentrations were measured on postpartum days > or = 20 in two parallel groups of lactating women before, during, and after consumption of defined quantities of Alpine butter or margarine with comparable fat content (10 d of butter followed by 10 d of margarine for one group, and vice versa in the other). In the 16 women who completed the study (8/group), Alpine butter supplementation increased the C16 and C18 FA, the sum of saturated FA, the 18:1 trans FA, and the trans FA with CLA. The CLA isomer 18:2 c9,t11 increased by 49.7%. Significant increases were also found for the isomers t9,t11, t7,c9, t11,c13, and t8,c10 18:2. The remaining nine of the total 14 detectable isomers showed no changes, and concentrations were <5 mg/100 g fat. A breastfeeding mother can therefore modulate the FA/CLA supply of her child by consuming Alpine butter. Further studies will show whether human milk containing this FA and CLA isomer pattern acts as a functional food for newborns.

  18. Accurate ab initio quartic force fields of cyclic and bent HC2N isomers.

    PubMed

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

    2011-12-28

    Highly correlated ab initio quartic force fields (QFFs) are used to calculate the equilibrium structures and predict the spectroscopic parameters of three HC(2)N 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 as 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 (PT) (with proper treatment of Fermi resonances) and variational methods to solve the nuclear Schrödinger 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 PT). On the other hand, this procedure (a QFF together with either PT or variational methods) leads to highly accurate fundamental vibrational frequencies and spectroscopic constants for the cyclic and bent singlet isomers of HC(2)N. All three isomers possess significant dipole moments, 3.05 D, 3.06 D, and 1.71 D, 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.

  19. Isomers of fluoroamphetamines detected in forensic cases in Denmark.

    PubMed

    Johansen, Sys Stybe; Hansen, Tina Maria

    2012-07-01

    A study was performed on the detection, separation and quantification of isomers from the new designer drugs named fluoroamphetamines (FAs) in forensic cases in eastern Denmark. The drugs were detected in whole blood extracts by ultraperformance liquid chromatography with time of flight mass spectrometer (UPLC-TOF-MS) and thereafter verified and quantified by UPLC tandem mass spectrometer (MS/MS). The quantitative method involved liquid–liquid extraction of FAs from whole blood, evaporation of organic solvent, and reconstitution with a mobile phase mixture. Identification of the FAs was achieved by the retention time, multiple reaction monitoring (MRM) traces [154 > 109 (quantifier); 154 > 137], and ion ratio of the two transitions. For all FAs, LOQ was 0.002 mg/kg with linear ranges from 0.002 to 1.0 mg/kg whole blood. Since 2008, a total of 15 forensic investigations, mainly driving under the influence of drugs (DUID) cases, involving 4-fluoroamphetamine (4-FA) have been observed with whole blood concentrations ranging from 0.006 to 0.58 mg/kg. One autopsy case involved 4-FA; however, it was determined to be a combined intoxication. In 2010, ortho-fluoroamphetamine (2-FA) was discovered in forensic samples by the same UPLC/MS/MS method and MRM functions because of variation in retention time and ion ratio. Up to now, three eastern Danish DUID cases have involved 2-FA. The whole blood concentrations of 2-FA were 0.028, 0.041 and 0.37 mg/kg, respectively. Thirteen cases with 4-FA and the three cases with 2-FA also contained amphetamine, but no correlation was observed between the amount of FA and amphetamine. So far, 3-FA has not been observed in any cases, and although it co-elutes with 4-FA, 3-FA will be identified by its variation in ion ratio. To our knowledge, this study has confirmed 2-FA in blood from DUID cases for the first time, and provides typical whole blood concentrations of FAs in forensic cases.

  20. New shifted hybrid inflation

    NASA Astrophysics Data System (ADS)

    Jeannerot, Rachel; Khalil, Shaaban; Lazarides, George

    2002-07-01

    A new shifted hybrid inflationary scenario is introduced which, in contrast to the older one, relies only on renormalizable superpotential terms. This scenario is automatically realized in a concrete extension of the `minimal' supersymmetric Pati-Salam model which naturally leads to a moderate violation of Yukawa unification so that, for μ>0, the predicted b-quark mass is acceptable even with universal boundary conditions. It is shown that this extended model possesses a classically flat `shifted' trajectory which acquires a slope via one-loop radiative corrections and can be used as inflationary path. The constraints from the cosmic background explorer can be met with natural values of the relevant parameters. Also, there is no disastrous production of magnetic monopoles after inflation since the Pati-Salam gauge group is already broken on the `shifted' path. The relevant part of inflation takes place at values of the inflaton field which are not much smaller than the `reduced' Planck scale and, thus, supergravity corrections could easily invalidate inflation. It is, however, shown that inflation can be kept intact provided that an extra gauge singlet with a superheavy vacuum expectation value, which originates from D-terms, is introduced and a specific form of the Kähler potential is used. Moreover, it is found that, although the supergravity corrections are sizable, the constraints from the cosmic background explorer can again be met by readjusting the values of the parameters which were obtained with global supersymmetry.

  1. 40 CFR 180.449 - Avermectin B1 and its delta-8,9-isomer; tolerances for residues.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 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. Tolerances... (5-O-demethyl-25-de(1-methylpropyl)-25-(1-methylethyl) avermectin A1) and its delta-8,9-isomer in...

  2. 40 CFR 180.449 - Avermectin B1 and its delta-8,9-isomer; tolerances for residues.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 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. Tolerances... (5-O-demethyl-25-de(1-methylpropyl)-25-(1-methylethyl) avermectin A1) and its delta-8,9-isomer in...

  3. 40 CFR 180.449 - Avermectin B1 and its delta-8,9-isomer; tolerances for residues.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 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. Tolerances... following table is to be determined by measuring only avermectin B1 and its delta-8,9-isomer in or on...

  4. 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.

  5. 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.

  6. Classification of polychlorinated biphenyl residues: isomers vs. homologue concentrations in modeling aroclors and polychlorinated biphenyl residues

    SciTech Connect

    Stalling, D.L.; Schwartz, T.R.; Dunn, W.J. III; Wold, S.

    1987-07-15

    SIMCA (soft independent modeling by class analogy), a principal components chemometric modeling program, was used to examine complex mixtures of polychlorinated biphenyl residues (PCBs) in fish and turtles. Individual PCB isomers were measured by electron capture capillary gas chromatography. The authors calculated PCB (Cl/sub 1-10/) congener concentrations by summing 105 isomer concentrations into homologue subgroups. Information theory was used to estimate the maximum information content of the two data sets. The authors compared the results from principal components modeling of samples and Aroclors by using both isomer and Cl/sub 1-10/ homologue concentrations. Modeling of normalized data from Aroclors or their mixtures gave similar sample score plots for both data sets. However, modeling environmental sample congener concentrations gave erroneous classification results when compared to results from modeling isomer data. Although the Cl/sub 1-10/ sums accurately reflect the concentration of PCBs in the sample, calculations to determine PCB profiles as Aroclor mixtures should be made by using individual PCB isomers.

  7. Incorporation profiles of conjugated linoleic acid isomers in cell membranes and their positional distribution in phospholipids

    PubMed Central

    Subbaiah, Papasani V.; Gould, Ian G.; Lal, Samanta; Aizezi, Buzulagu

    2010-01-01

    Although the conjugated linoleic acids (CLA) have several isomer-specific biological effects including anti-carcinogenic and anti-adipogenic effects, their mechanisms of action remain unclear. To determine their potential effects on membrane structure and function, we studied the incorporation profiles of four CLA isomers (trans-10 cis-12 (A), trans-9 trans-11 (B), cis-9 trans-11 (C), and cis-9 cis-11 (D)) in CHO and HepG2 cells. All four isomers were incorporated into cellular lipids as efficiently as linoleic acid (LA), with the majority of the incorporated CLA present in membrane rafts. Of the four isomers, only CLA-A increased the cholesterol content of the raft fraction. Over 50% of the incorporated CLAs were recovered in phosphatidylcholine of CHO cells, but in HepG2 the neutral lipids contained the majority of CLA. The desaturation index (18:1/18:0 and 16:1/16:0) was reduced by CLA-A, but increased by CLA-B, the effects being apparent mostly in raft lipids. The Δ9 desaturase activity was inhibited by CLAs A and C. Unlike LA, which was mostly found in the sn-2 position of phospholipids, most CLAs were also incorporated significantly into the sn-1 position in both cell types. These studies show that the incorporation profiles of CLA isomers differ significantly from that of LA, and this could lead to alterations in membrane function, especially in the raft-associated proteins. PMID:20920595

  8. Perfluorinated acid isomer profiling in water and quantitative assessment of manufacturing source.

    PubMed

    Benskin, Jonathan P; Yeung, Leo W Y; Yamashita, Nobuyoshi; Taniyasu, Sachi; Lam, Paul K S; Martin, Jonathan W

    2010-12-01

    A method for isomer profiling of perfluorinated compounds (PFCs) in water was developed and applied to quantitatively assess the contributions from electrochemical (ECF) and telomer manufacturing processes around source regions of North America, Asia, and Europe. With the exception of 3 sites in Japan, over 80% of total perfluorooctanoate (PFOA, C(7)F(15)COO(-)) was from ECF, with the balance attributable to strictly linear (presumably telomer) manufacturing source(s). Comparing PFOA isomer profiles in samples from China, with PFOA obtained from a local Chinese manufacturer, indicated <3% difference in overall branched isomer content; thus, exclusive contribution from local ECF production cannot be ruled out. In Tokyo Bay, ECF, linear-telomer, and isopropyl-telomer sources contributed to 33%, 53%, and 14% of total PFOA, respectively. Perfluorooctane sulfonate (PFOS, C(8)F(17)SO(3)(-)) isomer profiles were enriched in branched content (i.e., >50% branched) in the Mississippi River but in all other locations were similar or only slightly enriched in branched content relative to historical ECF PFOS. Isomer profiles of other PFCs are also reported. Overall, these data suggest that, with the exception of Tokyo Bay, ECF manufacturing has contributed to the bulk of contamination around these source regions, but other sources are significant, and remote sites should be monitored.

  9. Geometric isomerism in the OCS-CS2 complex: observation of a cross-shaped isomer.

    PubMed

    Norooz Oliaee, J; Mivehvar, F; Dehghany, M; Moazzen-Ahmadi, N

    2010-07-15

    Infrared spectra of the OCS-CS(2) van der Waals complex were studied in a pulsed supersonic slit-jet using a tunable diode laser probe. Spectra were recorded in the region of nu(1) fundamental of OCS. Two bands were observed and analyzed, one band corresponding to a previously observed planar isomer and another due to a new isomer which has a nonplanar cross-shaped structure. The intermolecular (center of mass) separation of the planar isomer is 3.87017(2) A. The structure of this isomer has been determined previously from its rotational spectrum. The cross-shaped isomer was observed here for the first time, and its structure was determined with the help of isotopic substitution. Two structural parameters, the intermolecular distance (R) and an angle (phi), are necessary to completely define the structure. These were determined to be R 3.5553(8) A and phi = 104.82(22) degrees which are in fair agreement with the theoretical predictions.

  10. Isomer profiles of perfluoroalkyl substances in water and soil surrounding a chinese fluorochemical manufacturing park.

    PubMed

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

    2015-04-21

    Despite that China is the largest global manufacturer of perfluoroalkyl substances (PFASs), the manufacturing methods and isomer purity of these chemicals are generally unknown. Here, sampling was conducted around a major fluorochemical manufacturing park in China in 2012, including soil and water collection inside the park, including from a wastewater treatment plant (WWTP), as well as in surrounding rivers and soil (∼15 km radius). Perfluoroalkyl sulfonates (PFSAs) were lower than perfluoroalkyl carboxylates (PFCAs) in all samples, and short-chain (C4-C6) PFCAs were predominant. Perfluoroalkyl phosphonates and phosphate diesters were occasionally detected, but at low detection frequency. Branched isomers of perfluorobutanesulfonate (PFBS) are reported for the first time, accounting for 15-27% of total PFBS in water. An enrichment of isopropyl-PFOA (28%) was found in WWTP influent, suggesting its manufacturing primarily by isopropyl telomerization. More numerous branched isomers were observed for the longer C9-C13 PFCAs (e.g., C12 PFCA had 16 branched isomers), including high proportions of one major branched isomer (likely isopropyl), possibly as impurities from isopropyl-PFOA manufacturing. Overall, short-chain perfluorinated acids were the predominant PFASs being released, but PFOA was still a major chemical in use at this site, primarily from isopropyl telomerization.

  11. Natural and bioremediated selective degradation of polycyclic aromatic alkyl isomers in oil-contaminated soils

    SciTech Connect

    Sauer, T.C.; McCarthy, K.; Uhler, A.; Porta, A.

    1995-12-31

    In studies where 2- to 6-ring polycyclic aromatic hydrocarbons (PAHs) are determined as part of characterizing released oil constituents in environmental samples, the changes in composition of PAHs from weathering (e.g., evaporation, dissolution) and biodegradation are most often represented by PAH alkyl homologue distributions. Concentrations of PAH alkyl groups are the sum of individual PAH isomers of similar carbon number; such as for C2-naphthalenes, the C2 alkyl group consists of dimethyl and ethyl substitutions on the parent naphthalene. In weathering and degradation studies, the changes in relative concentration of the individual isomers within an alkyl group are rarely reported. In a field study of oiled soils, the authors looked at the selective losses, for a period of a year, of individual PAH alkyl isomers that occur both naturally by weathering processes and through the use of bioremediation technology. Results showed that decreases in alkyl group concentrations were not always represented by similar losses of each isomer in the alkyl group, but were often due to the preferential or selective loss of certain isomers in the group.

  12. Identification of the isomer of methionine sulfoximine that extends the lifespan of the SOD1 G93A mouse.

    PubMed

    Brusilow, William S A

    2017-04-24

    In previous studies methionine sulfoximine (MSO) significantly extended the lifespan of the SOD1 G93A mouse model for ALS. Those studies used commercially available MSO, which is a racemic mixture of the LS and LR diastereomers, leaving unanswered the question of which isomer was responsible for the therapeutic effects. In this study we tested both purified isomers and showed that the LS isomer, a well-characterized inhibitor of glutamine synthetase, extends the lifespan of these mice, but the LR isomer, which has no known activity, does not.

  13. [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.

  14. 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.

  15. Isomer-specific accumulation of perfluorooctane sulfonate in the liver of chicken embryos exposed in ovo to a technical mixture.

    PubMed

    O'Brien, Jason M; Kennedy, Sean W; Chu, Shaogang; Letcher, Robert J

    2011-01-01

    Prior to its recent phaseout, perfluorooctane sulfonate (PFOS) was produced by electrochemical fluorination processes, which yielded technical mixtures composed of linear isomer (∼65-79%) and several branched isomers (∼21-35%). Because PFOS can biomagnify in wildlife, birds that occupy higher trophic levels are at increased risk of exposure. We hypothesized that the pharmacokinetic properties of PFOS are isomer-specific in developing chicken (Gallus gallus domesticus) embryos exposed to technical grade PFOS (T-PFOS). In the present study, T-PFOS was composed of 62.7% linear isomer (L-PFOS), and 37.3% branched isomer, including six mono(trifluoromethyl)-branched isomers and four bis(trifluoromethyl)-branched isomers. Concentrations of 0.1, 5, or 100 µg/g of T-PFOS were injected into the air cell of chicken eggs prior to incubation. After pipping, compared with T-PFOS, the PFOS isomer profile in embryonic liver tissue for the 0.1 µg/g dose group showed 21% enrichment in the proportion of L-PFOS with a corresponding decrease in the proportion of branched isomers. Not all branched isomers were discriminated against at equal rates. The proportion of two mono(trifluoromethyl)-branched isomers and three bis(trifluoromethyl)-branched isomers decreased to a greater degree than other branched isomers. In contrast, the mono-branched isomer, P6MHpS, was overrepresented in the low-dose group. In the higher dose groups, L-PFOS was still enriched but only by approximately 10%, which indicated a dose-dependent change in isomer composition relative to T-PFOS. These results show that accumulation of PFOS in chicken embryo livers is dependent on the presence and position of branches on the alkyl backbone. This supports the hypothesis that the pharmacokinetics of PFOS are isomer-specific in biota, and may help explain why wildlife PFOS burdens are dominated by L-PFOS relative to T-PFOS mixtures.

  16. Advances in research on cis-9, trans-11 conjugated linoleic acid: a major functional conjugated linoleic acid isomer.

    PubMed

    Wang, Tao; Lee, Hong Gu

    2015-01-01

    Conjugated linoleic acid (CLA) consists of a group of positional and geometric conjugated isomers of linoleic acid. Since the identification of CLA as a factor that can inhibit mutagenesis and carcinogenesis, thousands of studies have been conducted in the last several decades. Among the many isomers discovered, cis-9, trans-11 CLA is the most intensively studied because of its multiple, isomer-specific effects in humans and animals. This paper provides an overview of the available data on cis-9, trans-11 CLA, including its isomer-specific effects, biosynthesis, in vivo/in vitro research models, quantification, and the factors influencing its content in ruminant products.

  17. 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.

  18. Studies of multi-quasiparticle k-isomers in rare-earth and trans-fermium nuclei.

    SciTech Connect

    Kondev, F. G.; Dracoulis, G. D.; Khoo, T. L.; Lane, G. J.; Byrne, A. P.; Kibedi, T.; Ahmad, I.; Carpenter, M. P.; Janssens, R. V. F.; Lauritzen, T.; Lister, C. J.; Seweryniak, D.; Zhu, S.; Chowdhury, P.; Tandel, S. K.; Australian National Univ.; Univ. of Massachusetts Lowell

    2007-01-01

    Nuclear K-isomers play an important role in understanding the structure of deformed axially symmetric nuclei. Examples are presented of recent studies in the rare-earth region (A {approx} 180) using deep-inelastic and multi-nucleon transfer reactions, and in the trans-fermium region (A {approx} 250) using fusion-evaporation reactions. A specific two-level mixing scenario is invoked to explain the unusual decay of the K{sup {pi}} = 13{sup +} isomer in {sup 174}Lu. The identification of 2- and 4-quasiparticle isomers in {sup 254}No is discussed and predictions of similar isomers in neighboring No and Rf nuclei are presented.

  19. [GC-FTIR analysis of structural isomers from hydrogenation products of p-phenylphenol].

    PubMed

    Xin, Jun-Na; Xu, Qiang; Zhang, Hua; Yang, Xi-Chuan; Lü, Lian-Hai

    2008-04-01

    The hydrogenation of p-phenylphenol is a consecutive and parallel complex reaction. Owing to the difference in the hydrogenation ability of the two benzene rings in pphenylphenol, the hydrogenation products contained several structural isomers, which can not be identified by normal analytical method. However, the reaction mixture was effectively separated and identified by GC-FTIR technique. According to the characteristic wave numbers of benzene ring substituted at different positions, the main product was confirmed to be p-cyclohexylphenol, and the two typical by-products were p-phenylcyclohexanol and p-cyclohexylcyclohexanol, respectively. Each product has several stereo-isomers. GC-MS, melting point measurement and NMR proved the accuracy of GC-FTIR results, indicating that GC-IR is an useful and rapid method for analyzing structural isomers of organic compounds.

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

    PubMed

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

    2015-04-01

    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.

  1. Isomer discrimination of polycyclic aromatic hydrocarbons in the Murchison meteorite by resonant ionization.

    PubMed

    Callahan, Michael P; Abo-Riziq, Ali; Crews, Bridgit; Grace, Louis; de Vries, Mattanjah S

    2008-12-15

    We have used two-color resonant two-photon ionization (2C-R2PI) mass spectrometry to discriminate between isomers of polycyclic aromatic hydrocarbons in the Murchison meteorite. We measured the 2C-R2PI spectra of chrysene and triphenylene seeded in a supersonic jet by laser desorption. Since each isomer differs in its R2PI spectrum, we can distinguish between isomers using wavelength dependent ionization and mass spectrometry. We found both chrysene and triphenylene in sublimates from carbonaceous residue obtained by acid demineralization of the Murchison meteorite. Their R2PI mass spectra show only the molecular ion, even though these samples contain a complex inventory of organic molecules.

  2. Visualizing the Role of Molecular Orbitals in Charge Transport through Individual Diarylethene Isomers

    PubMed Central

    2016-01-01

    Diarylethene molecules are prototype molecular switches with their two isomeric forms exhibiting strikingly different conductance, while maintaining similar length. We employed low-temperature scanning tunneling microscopy (STM) to resolve the energy and the spatial extend of the molecular orbitals of the open and closed isomers when lying on a Au(111) surface. We find an intriguing difference in the extension of the respective HOMOs and a peculiar energy splitting of the formerly degenerate LUMO of the open isomer. We then lift the two isomers with the tip of the STM and measure the current through the individual molecules. By a simple analytical model of the transport, we show that the previously determined orbital characteristics are essential ingredients for the complete understanding of the transport properties. We also succeeded in switching the suspended molecules by the current, while switching the ones which are in direct contact to the surface occurs nonlocally with the help of the electric field of the tip. PMID:27775886

  3. Isomer Specific Microwave Spectrum of - and - Phenylvinylnitrile. Implementing a New Multi-Resonant Spectral Analysis Tool.

    NASA Astrophysics Data System (ADS)

    Hernandez-Castillo, Alicia O.; Hays, Brian M.; Abeysekera, Chamara; Zwier, Timothy S.

    2016-06-01

    There are many circumstances in modern microwave spectroscopy where the observed spectra contain contributions from many distinct sub-populations, creating a complicated spectrum with interleaved transitions due to its components making spectral assignment challenging. A new method, exploiting multi resonance effects with broadband CP-FTMW was developed and implemented to differentiate the structural isomers: (E)- and (Z)-phenylvinylnitrile. This method will output an exclusive set of isomer-specific transitions reducing the spectral assignment time. Details of the method implementation and structural analysis of the two-isomer mixture will be discussed. The application of the method to other circumstances where selective modulation of the transitions due to a single set of connected transitions is vital for complex spectral assignment, will also be considered.

  4. Curcumin promotes fibril formation in F isomer of human serum albumin via amorphous aggregation.

    PubMed

    Mothi, Nivin; Muthu, Shivani A; Kale, Avinash; Ahmad, Basir

    2015-12-01

    We here describe the amyloid fibrils promoting behavior of curcumin, which ability to inhibit amyloid fibrillization of several globular proteins is well documented. Transmission electron microscopy (TEM), 90° light scattering (RLS), thioflavine T (ThT) and Congo red (CR) binding studies demonstrated that both F (pH3.4) and E (pH1.8) isomers of human serum albumin (HSA) in the absence and presence of curcumin initially converted into amorphous aggregates. Interestingly, only the sample containing F isomer preincubated with curcumin formed fibrils on incubation for longer period. We also found that curcumin strongly bind to the F isomer, alter its secondary, tertiary structures and thermal stability. We conclude that the conversion of intermediate states into amorphous aggregate to fibrils is dictated by its conformation. This study provides unique insights into ligand-controlled HSA aggregation pathway and should provide a useful model system to study both amorphous and the fibrillar aggregation of multidomain proteins.

  5. Effects of pentanol isomers on the phase behavior of phospholipid bilayer membranes.

    PubMed

    Griffin, Kathryn L; Cheng, Chih-Yin; Smith, Eric A; Dea, Phoebe K

    2010-11-01

    Differential scanning calorimetry (DSC) was used to analyze the thermotropic phase behavior of dipalmitoylphosphatidylcholine (DPPC) bilayers in the presence of pentanol isomers. The concentration of each pentanol isomer needed to induce the interdigitated phase was determined by the appearance of a biphasic effect in the main transition temperatures, the onset of a hysteresis associated with the main transition from the gel-to-liquid crystalline phase, and the disappearance of the pretransition. Lower threshold concentrations were found to correlate with isomers of greater alkyl chain length while branching of the alkyl chain was found to increase biphasic behavior. The addition of a methyl group to butanol systems drastically decreased threshold concentrations. However, as demonstrated in the DPPC/neopentanol system, branching of the alkyl chain away from the -OH group lowers the threshold concentration while maintaining a biphasic effect.

  6. On the nature of the 17 μs isomer of the 133Sb valence nucleus

    NASA Astrophysics Data System (ADS)

    Genevey, J.; Pinston, J. A.; Faust, H.; Foin, C.; Oberstedt, S.; Weiss, B.

    The decay of the 17 μs isomer of 133Sb was re-investigated experimentally. It was produced by thermal neutron induced fission of 241Pu. Its detection is based on time correlation between fission fragments selected by the LOHENGRIN spectrometer at ILL (Grenoble), and the γ-rays, and conversion electrons from the isomer. The interpretation of the level scheme is based on shell model calculations, where empirical two-body matrix elements were employed. The good agreement between theory and experiment suggests that the isomer is the 21/2+ member of the 2p-1h πg7/2ν(f7/2h11/2-1) configuration.

  7. Identification of μs-isomers produced in the fragmentation of a 112Sn beam

    NASA Astrophysics Data System (ADS)

    Grzywacz, R.; Anne, R.; Auger, G.; Bazin, D.; Borcea, C.; Borrel, V.; Corre, J. M.; Dörfler, T.; Fomichov, A.; Gaelens, M.; Guillemaud-Mueller, D.; Hue, R.; Huyse, M.; Janas, Z.; Keller, H.; Lewitowicz, M.; Lukyanov, S.; Mueller, A. C.; Penionzhkevich, Yu.; Pfützner, M.; Pougheon, F.; Rykaczewski, K.; Saint-Laurent, M. G.; Schmidt, K.; Schmidt-Ott, W.-D.; Sorlin, O.; Szerypo, J.; Tarasov, O.; Wauters, J.; Żylicz, J.

    1995-02-01

    Decays of over forty short-lived ( T {1}/{2} from ≈ 50 ns to 70 μs) isomeric states including a new isomer 66mAs produced in the fragmentation of a 112Sn beam (58 A·MeV, 63 A·MeV) on a natNi target were observed at the final focus of the LISE3 spectrometer at GANIL. Their detection, based on the slow (≈ 10 μs) time correlation of identified ions with the characteristic γ-radiation, represents a novel method to search for new isomers and can be used for unambiguous isotope identification for projectile fragment separator experiments. Isomeric yields and isomer-to-total production ratios were determined.

  8. Synthesis and isolation of one isomer of C{sub 60}H{sub 6}

    SciTech Connect

    Meier, M.S.; Weedon, B.R.; Spielmann, H.P.

    1996-11-20

    A reaction is reported that produces C{sub 60}H{sub 6} with essentially no contamination by adjacent oxidation states. The compound is formed as one dominant isomer and one minor isomer, and the assignment is reported of the structure of the major isomer through a comparison of its C-H coupled {sup 13}C NMR spectrum with that of 1, 2-C{sub 60}H{sub 2}. Isolation of the major C{sub 60}H{sub 6} band was accomplished by HPLC using a preparative Buckyclutcher column and an automated injector/fraction collector. Analysis of the fraction containing 1 (a cranberry-colored solution when concentrated) by Buckyclutcher and C{sub 18} HPCL in several different solvent systems has failed to produce evidence of more than one component. The typical isolated yield is 35%. 15 refs., 3 figs.

  9. 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

  10. 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.

  11. Experimental investigation of the low temperature oxidation of the five isomers of hexane.

    PubMed

    Wang, Zhandong; Herbinet, Olivier; Cheng, Zhanjun; Husson, Benoit; Fournet, René; Qi, Fei; Battin-Leclerc, Frédérique

    2014-07-31

    The low-temperature oxidation of the five hexane isomers (n-hexane, 2-methyl-pentane, 3-methyl-pentane, 2,2-dimethylbutane, and 2,3-dimethylbutane) was studied in a jet-stirred reactor (JSR) at atmospheric pressure under stoichiometric conditions between 550 and 1000 K. The evolution of reactant and product mole fraction profiles were recorded as a function of the temperature using two analytical methods: gas chromatography and synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Experimental data obtained with both methods were in good agreement for the five fuels. These data were used to compare the reactivity and the nature of the reaction products and their distribution. At low temperature (below 800 K), n-hexane was the most reactive isomer. The two methyl-pentane isomers have about the same reactivity, which was lower than that of n-hexane. 2,2-Dimethylbutane was less reactive than the two methyl-pentane isomers, and 2,3-dimethylbutane was the least reactive isomer. These observations are in good agreement with research octane numbers given in the literature. Cyclic ethers with rings including 3, 4, 5, and 6 atoms have been identified and quantified for the five fuels. While the cyclic ether distribution was notably more detailed than in other literature of JSR studies of branched alkane oxidation, some oxiranes were missing among the cyclic ethers expected from methyl-pentanes. Using SVUV-PIMS, the formation of C2-C3 monocarboxylic acids, ketohydroperoxides, and species with two carbonyl groups have also been observed, supporting their possible formation from branched reactants. This is in line with what was previously experimentally demonstrated from linear fuels. Possible structures and ways of decomposition of the most probable ketohydroperoxides were discussed. Above 800 K, all five isomers have about the same reactivity, with a larger formation from branched alkanes of some unsaturated species, such as allene and propyne, which

  12. Trophic magnification and isomer fractionation of perfluoroalkyl substances in the food web of Taihu Lake, China.

    PubMed

    Fang, Shuhong; Chen, Xinwei; Zhao, Shuyan; Zhang, Yifeng; Jiang, Weiwei; Yang, Liping; Zhu, Lingyan

    2014-02-18

    Biomagnification of perfluoroalkyl substances (PFASs) are well studied in marine food webs, but related information in fresh water ecosystem and knowledge on fractionation of their isomers along the food web are limited. The distribution, bioaccumulation, magnification, and isomer fractionation of PFASs were investigated in a food web of Taihu Lake, China. Perfluorooctanesulfonate (PFOS) and perfluorocarboxylates (PFCAs) with longer carbon chain lengths, such as perfluorodecanoate (PFDA) and perfluoroundecanoate (PFUnA), were predominant in organisms, while perfluorohexanoate (PFHxA) and perfluorooctanoate (∑PFOA) contributed more in the water phase. The consistent profile signature of PFOA isomers in water phase with 3M electrochemical fluorination (ECF) products suggests that ECF production of PFOA still exists in China. Linear proportions of PFOA, PFOS and perfluorooctane sulfonamide (PFOSA) in the biota were in the range of 91.9-100%, 78.6-95.5%, and 72.2-95.5%, respectively, indicating preferential bioaccumulation of linear isomers in biota. Trophic magnification factors (TMFs) were estimated for PFDA (2.43), perfluorododecanoate (PFDoA) (2.68) and PFOS (3.46) when all biota were included, suggesting that PFOS and long-chained PFCAs are biomagnified in the fresh water food web. The TMF of PFOS isomers descended in the order: n-PFOS (3.86) > 3+5m-PFOS (3.35) > 4m-PFOS (3.32) > 1m-PFOS (2.92) > m2-PFOS (2.67) > iso-PFOS (2.59), which is roughly identical to their elution order on a FluoroSep-RP Octyl column, suggesting that hydrophobicity may be an important contributor for isomer discrimination in biota.

  13. Terahertz Spectroscopy and Solid-State Density Functional Theory Calculations of Cyanobenzaldehyde Isomers.

    PubMed

    Dash, Jyotirmayee; Ray, Shaumik; Nallappan, Kathirvel; Kaware, Vaibhav; Basutkar, Nitin; Gonnade, Rajesh G; Ambade, Ashootosh V; Joshi, Kavita; Pesala, Bala

    2015-07-23

    Spectral signatures in the terahertz (THz) frequency region are mainly due to bulk vibrations of the molecules. These resonances are highly sensitive to the relative position of atoms in a molecule as well as the crystal packing arrangement. To understand the variation of THz resonances, THz spectra (2-10 THz) of three structural isomers: 2-, 3-, and 4-cyanobenzaldehyde have been studied. THz spectra obtained from Fourier transform infrared (FTIR) spectrometry of these isomers show that the resonances are distinctly different especially below 5 THz. For understanding the intermolecular interactions due to hydrogen bonds, four molecule cluster simulations of each of the isomers have been carried out using the B3LYP density functional with the 6-31G(d,p) basis set in Gaussian09 software and the compliance constants are obtained. However, to understand the exact reason behind the observed resonances, simulation of each isomer considering the full crystal structure is essential. The crystal structure of each isomer has been determined using X-ray diffraction (XRD) analysis for carrying out crystal structure simulations. Density functional theory (DFT) simulations using CRYSTAL14 software, utilizing the hybrid density functional B3LYP, have been carried out to understand the vibrational modes. The bond lengths and bond angles from the optimized structures are compared with the XRD results in terms of root-mean-square-deviation (RMSD) values. Very low RMSD values confirm the overall accuracy of the results. The simulations are able to predict most of the spectral features exhibited by the isomers. The results show that low frequency modes (<3 THz) are mediated through hydrogen bonds and are dominated by intermolecular vibrations.

  14. Transmission shift control assembly

    SciTech Connect

    Dzioba, D.L.

    1989-04-18

    This patent describes a transmission shift control assembly mounted on a steering column having a longitudinal axis comprising: bracket means secured to the steering column; transmission shift cable means having a portion secured to the bracket means and a portion linearly movable relative to the secured portion; mounting means on the bracket cable drive arm means having an axis and being rotatably mounted on the rotary axis on the mounting means oblique to the longitudinal axis and including a cable connecting portion secured to the movable portion of the cable means and lever mounting means adjacent the mounting means; operator control means including lever means, pin means for pivotally mounting the lever means on the lever mounting means on an axis substantially perpendicular to the rotary axis and positioning arm means formed on the lever means and extending from the pin means; and detent gate means disposed on the bracket means in position to abut the positioning arm means for limiting the extent of pivotal movement of the lever means.

  15. Quantitative Analysis of the Distribution of cis-Eicosenoic Acid Positional Isomers in Marine Fishes from the Indian Ocean.

    PubMed

    Senarath, Samanthika; Yoshinaga, Kazuaki; Nagai, Toshiharu; Yoshida, Akihiko; Beppu, Fumiaki; Jayasinghe, Chamila; Devadawson, Chandravathany; Gotoh, Naohiro

    2017-02-01

    This study investigated the occurrence and distribution of cis-eicosenoic acid (c-20:1) positional isomers in fishes from the Indian Ocean and compared to those from the Pacific and Atlantic Ocean. Lipids were extracted from the edible part of the fish and then methylated. The eicosenoic acid methyl ester fraction was separated from total fatty acid methyl esters by reversed-phase HPLC and quantitatively analyzed using a GC-FID fitted with the SLB-IL111 highly polar GC column. c14-20:1 was used as an internal standard. The results indicated that the highest levels of c-20:1 positional isomers were found in fishes from the Pacific Ocean (saury, 166.95±12.4 mg/g of oil), followed by the Atlantic Ocean (capelin, 162.7±3.5 mg/g of oil), and lastly in fishes from the Indian Ocean (goatfish, 34.39 mg/g of oil). With only a few exceptions, the most abundant 20:1 positional isomer found in fishes of the Indian and Atlantic Ocean was the c11-20:1 isomer (>50%) followed by the c13-20:1 isomer (<25%). Unusually, the c7-20:1 isomer was predominantly found in a few fishes such as the tooth ponyfish, longface emperor, and commerson's sole. The c9, c5, and c15-20:1 isomers were the least occurring in fishes from the Indian and Atlantic Ocean. In contrast, the c9-20:1 isomer was the principal isomer identified in fishes from the Pacific Ocean. The results revealed that the content and distribution of c-20:1 positional isomers varied among fishes in different oceans. The data presented in the current study are the first to report on the distribution of c-20:1 positional isomers in fishes from the Indian Ocean.

  16. NMR study on iridium(III) complexes for identifying disulfonate substituted bathophenanthroline regio-isomers.

    PubMed

    Liu, Chenchen; Yu, Linpo; Liu, Yang; Li, Fang; Zhou, Ming

    2011-12-01

    A series of novel biscyclometalated iridium (III) complexes with an ancillary disulfonated bathophenanthroline (DSBP(2-)) ligand, Ir(L)(2)DSBPNa, L = 2-phenylpyridine (ppy), 2,4-difluorophenylpyridine (fppy), and 1-phenylisoquinoline (piq) were found to have two isomeric forms. The chemical structures of the isomers were determined by the one- and two-dimensional (1)H and (13)C NMR studies. The isomeric state was proved to have originated from the disulfonate-related regio-isomer of the DSBP(2-) ligand.

  17. 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.

  18. 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

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    Henry, E. A.; Becker, J. A.; Bauer, R. W.; Gardner, D. G.; Decman, D. J.

    1988-01-01

    Nuclear isomerism plays a key role in current conceptual designs of a gamma-ray laser. Conversion electrons from the decay of low-lying levels of Np-237 have been measured to detect the population of these levels by gamma-ray decay of the Np-237 shape isomer. Analysis of the 208-keV transition L conversion-electron peak gives an upper limit of about 17 micro-b for the population of the 3/2(-) 267-keV level in Np-237 from the shape isomer decay. Model calculations are compared with the measured limit, and experimental improvements are suggested.

  2. Separation of cis and trans Isomers of Polyproline by FAIMS Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Creese, Andrew J.; Cooper, Helen J.

    2016-12-01

    High field asymmetric waveform ion mobility spectrometry (FAIMS) is well-established as a tool for separating peptide isomers (sequence inversions and post-translationally modified localization variants). Here, we demonstrate the FAIMS is able to differentiate cis and trans isomers of polyproline. Polyproline assumes an all- cis conformation—the PPI helix—in 1-propanol, and an all- trans conformation—the PPII helix—in aqueous solutions. Differentiation of these conformers may be achieved both through use of a cylindrical FAIMS device and a miniaturized ultrahigh field planar FAIMS device.

  3. Distribution, fate and formation of non-extractable residues of a nonylphenol isomer in soil with special emphasis on soil derived organo-clay complexes.

    PubMed

    Riefer, Patrick; Klausmeyer, Timm; Schäffer, Andreas; Schwarzbauer, Jan; Schmidt, Burkhard

    2011-01-01

    Anthropogenic contaminants like nonylphenols (NP) are added to soil, for instance if sewage-sludge is used as fertilizer in agriculture. A commercial mixture of NP consists of more than 20 isomers. For our study, we used one of the predominate isomers of NP mixtures, 4-(3,5-dimethylhept-3-yl)phenol, as a representative compound. The aim was to investigate the fate and distribution of the isomer within soil and soil derived organo-clay complexes. Therefore, (14)C- and (13)C-labeled NP was added to soil samples and incubated up to 180 days. Mineralization was measured and soil samples were fractionated into sand, silt and clay; the clay fraction was further separated in humic acids, fulvic acids and humin. The organo-clay complexes pre-incubated for 90 or 180 days were re-incubated with fresh soil for 180 days, to study the potential of re-mobilization of incorporated residues. The predominate incorporation sites of the nonylphenol isomer in soil were the organo-clay complexes. After 180 days of incubation, 22 % of the applied (14)C was mineralized. The bioavailable, water extractable portion was low (9 % of applied (14)C) and remained constant during the entire incubation period, which could be explained by an incorporation/release equilibrium. Separation of organo-clay complexes, after extraction with solvents to release weakly incorporated, bioaccessible portions, showed that non-extractable residues (NER) were preferentially located in the humic acid fraction, which was regarded as an effect of the chemical composition of this fraction. Generally, 27 % of applied (14)C was incorporated into organo-clay complexes as NER, whereas 9 % of applied (14)C was bioaccessible after 180 days of incubation. The re-mobilization experiments showed on the one hand, a decrease of the bioavailability of the nonylphenol residues due to stronger incorporation, when the pre-incubation period was increased from 90 to 180 days. On the other hand, a shift of these residues from the

  4. Laser-Induced Hydrogen Radical Removal in UV MALDI-MS Allows for the Differentiation of Flavonoid Monoglycoside Isomers

    NASA Astrophysics Data System (ADS)

    Yamagaki, Tohru; Watanabe, Takehiro; Tanaka, Masaki; Sugahara, Kohtaro

    2014-01-01

    Negative-ion matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectra and tandem mass spectra of flavonoid mono- O-glycosides showed the irregular signals that were 1 and/or 2 Da smaller than the parent deprotonated molecules ([M - H]-) and the sugar-unit lost fragment ions ([M - Sugar - H]-). The 1 and/or 2 Da mass shifts are generated with the removing of a neutral hydrogen radical (H*), and/or with the homolytic cleavage of the glycosidic bond, such as [M - H* - H]-, [M - Sugar - H* - H]-, and [M - Sugar - 2H* - H]-. It was revealed that the hydrogen radical removes from the phenolic hydroxy groups on the flavonoids, not from the sugar moiety, because the flavonoid backbones themselves absorb the laser. The glycosyl positions depend on the extent of the hydrogen radical removals and that of the homolytic cleavage of the glycosidic bonds. Flavonoid mono-glycoside isomers were distinguished according to their TOF MS and tandem mass spectra.

  5. Probing the Ag, Au, and Cu electrode/pyridine-α-hydroxymethyl biphenyl phosphine oxide isomer interface with SERS

    NASA Astrophysics Data System (ADS)

    Pięta, Ewa; Proniewicz, Edyta; Boduszek, Bogdan; Olszewski, Tomasz K.; Nattich-Rak, Małgorzata; Kim, Younkyoo

    2015-04-01

    The potential-dependent surface enhanced Raman scattering (SERS) and generalized two-dimensional correlation analysis (G2DCA) methods were used to characterize three pyridine-α-hydroxymethyl biphenyl phosphine oxide isomers: (diphenylphosphoryl)(pyridine-2-yl)methanol (α-Py), (diphenylphosphoryl)(pyridine-3-yl)methanol (β-Py), and (diphenylphosphoryl)(pyridine-4-yl)methanol (γ-Py). The aforementioned compounds were deposited onto Ag, Au, and Cu electrode surfaces under different applied electrode potentials in an aqueous solution at physiological pH. On the basis of the enhancement, broadening, and shift in wavenumbers of individual bands, the geometry of the investigated molecules and influence of substituent position on the adsorption mode (in the α-(2-), β-(3-), and γ-(4-) positions), electrode type, and applied electrode potential were examined. It was found that the SERS spectra are dominated by bands assigned to phenyl (Ph) and pyridine (Py) ring vibrations. However, some differences in the arrangement of the aforementioned fragments were observed with changes to the type of the metal surface and the applied electrode potential.

  6. A case of Z/E-isomers elution order inversion caused by cosolvent percentage change in supercritical fluid chromatography.

    PubMed

    Pokrovskiy, Oleg I; Ustinovich, Konstantin B; Usovich, Oleg I; Parenago, Olga O; Lunin, Valeriy V; Ovchinnikov, Denis V; Kosyakov, Dmitry S

    2017-01-06

    A case of elution order inversion caused by cosolvent percentage change in supercritical fluid chromatography was observed and investigated in some detail. Z- and E-isomers of phenylisobutylketone oxime experience an elution order reversal on most columns if the mobile phase consists of CO2 and alcohol. At lower percentages of alcohol Z-oxime is retained less, somewhere at 2-5% coelution occurs and at larger cosolvent volume elution order reverses - Z-oxime is eluted later than E-oxime. We suppose inversion with CO2-ROH phases happens due to a shift in balance between two main interactions governing retention. At low ROH percentages stationary phase surface is only slightly covered by ROH molecules so oximes primarily interact with adsorption sites via hydrogen bond formation. Due to intramolecular sterical hindrance Z-oxime is less able to form hydrogen bonds and consequently is eluted first. At higher percentages alcohols occupy most of strong hydrogen bonding sites on silica surface thus leaving non-specific electrostatic interactions predominantly responsible for Z/E selectivity. Z-oxime has a much larger dipole moment than E-oxime and at these conditions it is eluted later. Additional experimental data with CO2-CH3CN, hexane-iPrOH and CHF3-ROH mobile phases supporting this explanation are presented.

  7. Shift Work: Improving Daytime Sleep

    MedlinePlus

    Healthy Lifestyle Adult health I just started working the night shift, and I'm having trouble sleeping during ... as long as you work the shift. Make healthy lifestyle choices. Eat a healthy diet and include physical ...

  8. Phase shifting diffraction interferometer

    DOEpatents

    Sommargren, G.E.

    1996-08-29

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 8 figs.

  9. Phase shifting interferometer

    DOEpatents

    Sommargren, Gary E.

    1999-01-01

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

  10. Phase shifting diffraction interferometer

    DOEpatents

    Sommargren, Gary E.

    1996-01-01

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

  11. Phase shifting interferometer

    DOEpatents

    Sommargren, G.E.

    1999-08-03

    An interferometer is disclosed which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 11 figs.

  12. Highly enantioselective and anti-diastereoselective catalytic intermolecular glyoxylate-ene reactions: effect of the geometrical isomers of alkenes.

    PubMed

    Zhang, Xiang; Wang, Min; Ding, Ran; Xu, Yun-He; Loh, Teck-Peng

    2015-06-05

    An efficient method for the synthesis of homoallylic alcohols with high enantioselectivities and anti-diastereoselectivities via an In(III)-catalyzed intermolecular glyoxylate-ene reaction has been developed. The geometrical isomers of alkenes were shown to have different reactivities. Only the isomers of the alkenes having a proton β-cis to the substituent reacted in this catalytic system.

  13. SEPARATION OF ISOMERS OF NONYLPHENOL AND SELECT NONPHENYL POLYETHOXYLATES BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY ON A GRAPHITIC CARBON COLUMN

    EPA Science Inventory

    p-Nonylphenol (NP) is ubiquitous degradation product of nonylphenol polyethoxylate (NPE) surfactants and has been reported to be an endocrine disrupter. It is composed of numerous structural isomers resulting from ;the various branching patterns of the C-9 group. Twenty-two isome...

  14. Energetics of the S2 State Spin Isomers of the Oxygen-Evolving Complex of Photosystem II.

    PubMed

    Vinyard, David J; Khan, Sahr; Askerka, Mikhail; Batista, Victor S; Brudvig, Gary W

    2017-02-09

    The S2 redox intermediate of the oxygen-evolving complex in photosystem II is present as two spin isomers. The S = 1/2 isomer gives rise to a multiline electron paramagnetic resonance (EPR) signal at g = 2.0, whereas the S = 5/2 isomer exhibits a broad EPR signal at g = 4.1. The electronic structures of these isomers are known, but their role in the catalytic cycle of water oxidation remains unclear. We show that formation of the S = 1/2 state from the S = 5/2 state is exergonic at temperatures above 160 K. However, the S = 1/2 isomer decays to S1 more slowly than the S = 5/2 isomer. These differences support the hypotheses that the S3 state is formed via the S2 state S = 5/2 isomer and that the stabilized S2 state S = 1/2 isomer plays a role in minimizing S2QA(-) decay under light-limiting conditions.

  15. 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...

  16. 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...

  17. Energetics of the S2 state spin isomers of the oxygen-evolving complex of Photosystem II

    DOE PAGES

    Vinyard, David J.; Khan, Sahr; Askerka, Mikhail; ...

    2017-01-12

    Here, the S2 redox intermediate of the oxygen-evolving complex in Photosystem II is present as two spin isomers. The S = 1/2 isomer gives rise to a multiline EPR signal at g = 2, while the S = 5/2 isomer exhibits a broad EPR signal at g = 4.1. The electronic structures of these isomers are known, but their role in the catalytic cycle of water oxidation remains unclear. We show that formation of the S = 1/2 state from the S = 5/2 state is exergonic at temperatures above 160 K. However, the S = 1/2 isomer decays tomore » S1 more slowly than the S = 5/2 isomer. These differences support the hypotheses that the S3 state is formed via the S2 state S = 5/2 isomer and that the stabilized S2 state S = 1/2 isomer plays a role in minimizing S2QA- decay in light-limiting conditions.« less

  18. Structural, electronic, and magnetic properties of two isomers of C40 O10 with cage-like structure.

    PubMed

    Liu, Feng-Ling; Wang, Chen-Hui

    2008-02-01

    Bonding, vibrational and magnetic properties of two isomers of cage-like molecule C40 O10 are studied by using hybrid DFT calculations at the B3LYP/6-31G* level of theory. Infrared- and Raman-active vibrational frequencies of two isomers of C40 O10 are assigned. Three 13C and one 17O nuclear magnetic resonance (NMR) spectral signals of each isomer are characterized. Heat of formation of each isomer is estimated. Compared the stability of the two isomers of C40 O10 with that of C60, only from the thermodynamic points of view, they are more stable than C60. Thus, we believe that they have sufficient stability to allow their experimental preparation. We proposed their synthesized route in this paper.

  19. Mechanistic evaluation of polychlorinated dibenzo-p-dioxin, dibenzofuran and naphthalene isomer fingerprints in microwave pyrolysis of biomass.

    PubMed

    Gao, Qiuju; Cieplik, Mariusz K; Budarin, Vitaliy L; Gronnow, Mark; Jansson, Stina

    2016-05-01

    Isomer distribution patterns of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and naphthalenes (PCNs) were investigated in microwave-assisted pyrolysis (MAP) products of woody biomass. The feedstocks included bark and impregnated wood. The results indicated that isomer distributions in MAP are more selective compared to those reported from wood burning and waste incineration. Favored formation of 4-MoCDF and highly selective chlorine substitution at the 2,4-position observed during MAP suggested a preferred formation pathway of PCDFs involving (chloro)phenol precursors followed by subsequent chlorination. The PCDD distribution was dominated by isomers typically formed from chlorophenol condensation at relatively low temperature. The PCN isomer distributions showed a tendency for sequential chlorination from non-substituted naphthalene at successive positions. The presence of isomers such as 1-MoCDD, 4-MoCDF, 1,2,3-TriCN with low thermodynamic stability indicates that kinetic factors may be important in the MAP process.

  20. Hydraulically actuated well shifting tool

    SciTech Connect

    Roth, B.A.

    1992-10-20

    This patent describes a hydraulically actuated shifting tool for actuating a sliding member in a well tool. It comprises: a housing having a hydraulic fluid bore therein; shifting dog means positioned on the housing for movement away and toward the housing; locking dog means positioned on the housing for movement away and toward the body; shifting dog hydraulic actuating means in fluid communication with the bore for causing engagement of the shifting dogs with the sliding member; locking dog hydraulic actuating means in communication with the bore for causing engagement of the locking dogs with the locking means; and hydraulic shifting means in communication with the bore for causing relative movement between the shifting dog means and the locking dog means for shifting the sliding sleeve.

  1. Configuration assignments to isomers in the neutron-rich 186Ta (Z =73 ) nucleus

    NASA Astrophysics Data System (ADS)

    Sood, P. C.; Gowrishankar, R.

    2014-12-01

    Though the neutron-rich odd-odd nucleus Ta18673113 was first produced in 1955, even after 60 years its ground state (g.s.) and both of its two other isomers remain undefined. We use the well-tested two-quasiparticle rotor model, which explicitly includes residual neutron-proton n -p interaction and other contributing factors, to evaluate the bandhead energies of the physically admissible low-lying two-particle structures in 186Ta with inputs from experimentally observed structures in neighboring isotopes and isotones to characterize these levels. Our analysis assigns Kπ = 5-{p :7 /2 [404 ]⊗n :3 /2 [512 ]} configuration to the 10.5 min 186Ta (g.s.) and the antiparallel-spin Kπ=2- of the same configuration to the 1.54 min isomer with Ex = 90(10) keV. We further assign Kπ=8-{p :7 /2 [404 ]⊗n :9 /2 [505 ]} configuration to the recently identified 3.0 min isomer with Ex=336 (20) keV. These assignments are shown to be consistent with all the available experimental data. Further, they are seen to fit nicely as another instance of highly hindered Δ I =3 isomeric transitions, and also of low-lying long-lived isomer triplets, frequently observed in numerous odd-odd Z =61 (2 )75 nuclides.

  2. Design Study of Triggered Isomer Heat Exchanger-Combustion Hybrid Jet Engine for High Altitude Flight

    DTIC Science & Technology

    2007-11-02

    Lift (lbf) l Nozzle length (ft) lbf Pounds force lbm Pounds mass LPC π Low pressure compressor pressure ratio Lu Lutetium M Mach number m0 Mass...sponsoring an international group of physicists to research an exciting new process for extracting energy from isomers of Lutetium (Lu), Hafnium (Hf), and

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

    PubMed Central

    Fan, Guoling; Yan, Dongpeng

    2014-01-01

    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. PMID:24816686

  4. Isomer production ratios and the angular momentum distribution of fission fragments

    NASA Astrophysics Data System (ADS)

    Stetcu, I.; Talou, P.; Kawano, T.; Jandel, M.

    2013-10-01

    Latest generation fission experiments provide an excellent testing ground for theoretical models. In this contribution we compare the measurements for 235U(nth,f), obtained with the Detector for Advanced Neutron Capture Experiments (DANCE) calorimeter at Los Alamos Neutron Science Center (LANSCE), with our full-scale simulation of the primary fragment de-excitation, using the recently developed cgmf code, based on a Monte Carlo implementation of the Hauser-Feshbach theoretical model. We compute the isomer ratios as a function of the initial angular momentum of the fission fragments, for which no direct information exists. Comparison with the available experimental data allows us to determine the initial spin distribution. We also study the dependence of the isomer ratio on the knowledge of the low-lying discrete spectrum input for nuclear fission reactions, finding a high degree of sensitivity. Finally, in the same Hauser-Feshbach approach, we calculate the isomer production ratio for thermal neutron capture on stable isotopes, where the initial conditions (spin, excitation energy, etc.) are well understood. We find that with the current parameters involved in Hauser-Feshbach calculations, we obtain up to a factor of 2 deviation from the measured isomer ratios.

  5. 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.

  6. 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.

  7. 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),...

  8. 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.

  9. 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…

  10. 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

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Prospects for measuring the (229)Th isomer energy using a metallic magnetic microcalorimeter.

    PubMed

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

    2014-01-21

    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.

  13. 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.

  14. Optical Spectroscopy of an Atomic Nucleus: Progress toward Direct Observation of the 229Th Isomer Transition

    DTIC Science & Technology

    2011-09-28

    3.1. Acquisition of 229Th Thorium is an actinide element , and the most abundant isotope is 232Th with a half life of 1.41010 years [1]. In contrast...isomer u·ansition Sb. GRANT NUMBER Sc. PROGRAM ELEMENT NUMBER 1D10BP 6. AUTHORS Sd. PROJECT NUMBER Wade G . Rellergett, Scott T . Sullivan, David

  15. 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.

  16. 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.

  17. 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.

  18. Magnetite-platinum nanoparticles-modified glassy carbon electrode as electrochemical detector for nitrophenol isomers.

    PubMed

    Gerent, Giles G; Spinelli, Almir

    2017-05-15

    A glassy carbon electrode was modified with magnetite and platinum nanoparticles stabilized with 3-n-propyl-4-picoline silsesquioxane chloride. This chemically-modified electrode is proposed for the first time for the individual or simultaneous electrochemical detection of nitrophenol isomers. Nanoparticles act as catalysts and also increase the surface area. The polymer stabilizes the particles and provides the electrochemical separation of isomers. Under optimized conditions, the reduction peak currents, obtained by differential-pulse voltammetry, of 2-, 3-, and 4-nitrophenol increased linearly with increases in their concentration in the range of 0.1-1.5μmolL(-1). In individual analysis, the detection limits were 33.7nmolL(-1), 45.3nmolL(-1) and 48.2nmolL(-1), respectively. Also, simultaneous analysis was possible for 2-, and 4-nitrophenol. In this case, the separation of the peak potentials was 0.138V and the detection limits were 69.6nmolL(-1) and 58.0nmolL(-1), respectively. These analytical figures of merit evidence the outstanding performance of the modified electrode, which was also successfully applied to the individual determination of isomers in environmental and biological samples. The magnetite and platinum nanoparticles modified glassy carbon electrode was able to detect nitrophenol isomers at the ppm level in rain water and human urine samples.

  19. Differentiation of hydroxyproline isomers and isobars in peptides by tandem mass spectrometry.

    PubMed

    Kassel, D B; Biemann, K

    1990-08-01

    The isomeric 3- and 4-hydroxyprolines are isobaric with the isomers leucine and isoleucine, and all four have, therefore, the same "residue mass" of 113. Secondary fragmentation processes were found that differentiate the hydroxyproline isomers from each other and from the leucines. Variants of synthetic bradykinin containing one or two hydroxyproline moieties were prepared by using manual Edman degradation and/or enzymatic methods. The tandem mass spectra of these peptides were recorded. The C-terminal wn fragment ions allow the differentiation of 4-hydroxyproline from the 3-isomer and isoleucine, while the N-terminal an ions containing 4-hydroxyproline undergo H2O elimination to differentiate this amino acid from the 3-isomer and leucine. Lys-C digestion of a mussel adhesive protein produced a set of decapeptides varying in the degree of hydroxylation of proline and tyrosine. Heterogeneity with respect to 3-hydroxyproline and 4-hydroxyproline at a certain position in these peptides was assessed by tandem mass spectrometry based on the wn ion series in the CID spectra of these Lys-C peptides. Some N-terminal ions further allow for the differentiation of these two isomeric species.

  20. Ultrafast time-resolved absorption spectroscopy of geometric isomers of xanthophylls

    NASA Astrophysics Data System (ADS)

    Niedzwiedzki, Dariusz M.; Enriquez, Miriam M.; LaFountain, Amy M.; Frank, Harry A.

    2010-07-01

    This paper presents an ultrafast optical spectroscopic investigation of the excited state energies, lifetimes and spectra of specific geometric isomers of neoxanthin, violaxanthin, lutein, and zeaxanthin. All- trans- and 15,15'- cis-β-carotene were also examined. The spectroscopy was done on molecules purified by HPLC frozen immediately to inhibit isomerization. The spectra were taken at 77 K to maintain the configurations and to provide better spectral resolution than seen at room temperature. The kinetics reveal that for all of the molecules except neoxanthin, the S 1 state lifetime of the cis isomers is shorter than that of the all- trans isomers. The S 1 excited state energies of all the isomers were determined by recording S 1 → S 2 transient absorption spectra. The results obtained in this manner at cryogenic temperatures provide an unprecedented level of precision in the measurement of the S 1 energies of these xanthophylls, which are critical components in light-harvesting pigment-protein complexes of green plants.

  1. Lactones 42. Stereoselective enzymatic/microbial synthesis of optically active isomers of whisky lactone.

    PubMed

    Boratyński, Filip; Smuga, Małgorzata; Wawrzeńczyk, Czesław

    2013-11-01

    Two different methods, enzyme-mediated reactions and biotrasformations with microorganisms, were applied to obtain optically pure cis- and trans-isomers of whisky lactone 4a and 4b. In the first method, eight alcohol dehydrogenases were investigated as biocatalysts to enantioselective oxidation of racemic erythro- and threo-3-methyloctane-1,4-diols (1a and 1b). Oxidation processes with three of them, alcohol dehydrogenases isolated from horse liver (HLADH) as well as recombinant from Escherichia coli and primary alcohol dehydrogenase (PADH I), were characterized by the highest degree of conversion with moderate enantioselectivity (ee=27-82%) of the reaction. In all enzymatic reactions enantiomerically enriched not naturally occurring isomers of trans-(-)-(4R,5S)-4b or cis-(+)-(4R,5R)-4a were formed preferentially. In the second strategy, based on microbial lactonization of γ-oxoacids, naturally occurring opposite isomers of whisky lactones were obtained. Trans-(+)-(4S,5R)-isomer (ee=99%) of whisky lactone 4b was stereoselectively formed as the only product of biotransformations of 3-methyl-4-oxooctanoic acid (5) catalyzed by Didimospheria igniaria KCH6651, Laetiporus sulphurens AM525, Chaetomium sp.1 KCH6670 and Saccharomyces cerevisiae AM464. Biotransformation of γ-oxoacid 5, in the culture of Beauveria bassiana AM278 and Pycnidiella resinae KCH50 afforded a mixtures of trans-(+)-(4S,5R)-4b with enantiomeric excess ee=99% and cis-(-)-(4S,5S)-4a with enantiomeric excesses ee=77% and ee=45% respectively.

  2. Lipid and Glycolipid Isomer Analyses Using Ultra-High Resolution Ion Mobility Spectrometry Separations

    PubMed Central

    Wojcik, Roza; Webb, Ian K.; Deng, Liulin; Garimella, Sandilya V. B.; Prost, Spencer A.; Ibrahim, Yehia M.; Baker, Erin S.; Smith, Richard D.

    2017-01-01

    Understanding the biological roles and mechanisms of lipids and glycolipids is challenging due to the vast number of possible isomers that may exist. Mass spectrometry (MS) measurements are currently the dominant approach for studying and providing detailed information on lipid and glycolipid presence and changes. However, difficulties in distinguishing the many structural isomers, due to the distinct lipid acyl chain positions, double bond locations or specific glycan types, inhibit the delineation and assignment of their biological roles. Here we utilized ultra-high resolution ion mobility spectrometry (IMS) separations by applying traveling waves in a serpentine multi-pass Structures for Lossless Ion Manipulations (SLIM) platform to enhance the separation of selected lipid and glycolipid isomers. The multi-pass arrangement allowed the investigation of paths ranging from ~16 m (one pass) to ~60 m (four passes) for the distinction of lipids and glycolipids with extremely small structural differences. These ultra-high resolution SLIM IMS-MS analyses provide a foundation for exploring and better understanding isomer-specific biological activities and disease processes. PMID:28106768

  3. Modeling nuclear field shift isotope fractionation in crystals

    NASA Astrophysics Data System (ADS)

    Schauble, E. A.

    2013-12-01

    In this study nuclear field shift fractionations in solids (and chemically similar liquids) are estimated using calibrated density functional theory calculations. The nuclear field shift effect is a potential driver of mass independent isotope fractionation(1,2), especially for elements with high atomic number such as Hg, Tl and U. This effect is caused by the different shapes and volumes of isotopic nuclei, and their interactions with electronic structures and energies. Nuclear field shift isotope fractionations can be estimated with first principles methods, but the calculations are computationally difficult, limiting most theoretical studies so far to small gas-phase molecules and molecular clusters. Many natural materials of interest are more complex, and it is important to develop ways to estimate field shift effects that can be applied to minerals, solutions, in biomolecules, and at mineral-solution interfaces. Plane-wave density functional theory, in combination with the projector augmented wave method (DFT-PAW), is much more readily adapted to complex materials than the relativistic all-electron calculations that have been the focus of most previous studies. DFT-PAW is a particularly effective tool for studying crystals with periodic boundary conditions, and may also be incorporated into molecular dynamics simulations of solutions and other disordered phases. Initial calibrations of DFT-PAW calculations against high-level all-electron models of field shift fractionation suggest that there may be broad applicability of this method to a variety of elements and types of materials. In addition, the close relationship between the isomer shift of Mössbauer spectroscopy and the nuclear field shift isotope effect makes it possible, at least in principle, to estimate the volume component of field shift fractionations in some species that are too complex even for DFT-PAW models, so long as there is a Mössbauer isotope for the element of interest. Initial results

  4. 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).

  5. Branched perfluorooctane sulfonate isomer quantification and characterization in blood serum samples by HPLC/ESI-MS(/MS).

    PubMed

    Riddell, Nicole; Arsenault, Gilles; Benskin, Jonathan P; Chittim, Brock; Martin, Jonathan W; McAlees, Alan; McCrindle, Robert

    2009-10-15

    Perfluorooctane sulfonate (PFOS) is a global contaminant and is currently among the most prominent contaminants in human blood and wildlife samples. Although "total PFOS" (SigmaPFOS) analytical methods continue to be the most commonly used for quantification, recent analytical method developments have made it possible to resolve the various isomers of PFOS by HPLC-MS/MS. Characterized technical PFOS standards (i.e., containing a mixture of PFOS isomers) are now available that enable isomer specific quantification of PFOS, however the advantages of such an analysis have notyet been examined systematically. Herein, PFOS isomers have been individually quantified for the first time in real samples and the results are compared to a traditional SigmaPFOS method; the influence of analytical standards and isomer specific electrospray and MS/ MS behavior were also investigated. The two human serum standard reference materials chosen for analysis contained dramaticallydifferent PFOS isomer profiles (approximately 30-50% total branched isomers) emphasizing that isomer patterns should not be ignored and may provide useful information on exposure sources (i.e., direct exposure to PFOS vs indirect exposure from PFOS-precursors). Depending on the sample and the particular MS/MS transition chosen for SigmaPFOS analysis (i.e., 499-->80 or 499-->99), SigmaPFOS concentrations may be over- or underestimated compared to the isomer specific analysis. Differences in the extent of in-source fragmentation and MS/MS dissociation contributed to the systematic analytical bias. It was also shown that SigmaPFOS data are prone to interlaboratory variation due to various choices of PFOS standards and instrumental conditions used. In the future, for either SigmaPFOS or isomer specific PFOS analyses, we suggest that accuracy can be maximized and interlaboratory discrepancies minimized by using a common chemically pure technical PFOS standard characterized by 19F NMR.

  6. 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...

  7. 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).

  8. 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.

  9. 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)).

  10. 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.

  11. Reactions of Atomic Carbon with Butene Isomers: Implications for Molecular Growth in Carbon-Rich Environments

    DOE PAGES

    Bourgalais, J.; Spencer, Michael; Osborn, David L.; ...

    2016-10-31

    We carried out the product detection studies of C(3P) atom reactions with butene (C4H8) isomers (but-1-ene, cis-but-2-ene, trans-but-2-ene) in a flow tube reactor at 353 K and 4 Torr under multiple collision conditions. Ground state carbon atoms are generated by 248 nm laser photolysis of tetrabromomethane, CBr4, in a buffer of helium. Thermalized reaction products are detected using synchrotron tunable VUV photoionization and time-of-flight mass spectrometry. The temporal profiles of the detected ions are used to discriminate products from side or secondary reactions. Furthermore, for the C(3P) + trans-but-2-ene and C(3P) + cis-but-2-ene reactions, various isomers of C4H5 and C5H7more » are identified as reaction products formed via CH3 and H elimination. Assuming equal ionization cross sections for all C4H5 and C5H7 isomers, C4H5:C5H7 branching ratios of 0.63:1 and 0.60:1 are derived for the C(3P) + trans-but-2-ene and the C(3P) + cis-but-2-ene reactions, respectively. For the C(3P) + but-1-ene reaction, two reaction channels are observed: the H-elimination channel, leading to the formation of the ethylpropargyl isomer, and the C3H3 + C2H5 channel. Assuming equal ionization cross sections for ethylpropargyl and C3H3 radicals, a branching ratio of 1:0.95 for the C3H3 + C2H5 and H + ethylpropargyl channels is derived. Finally, the experimental results are compared to previous H atom branching ratios and used to propose the most likely mechanisms for the reaction of ground state carbon atoms with butene isomers.« less

  12. Glass transition dynamics and boiling temperatures of molecular liquids and their isomers.

    PubMed

    Wang, Li-Min; Richert, Ranko

    2007-03-29

    The relation between a dynamic and a thermodynamic temperature, glass transition Tg and boiling point Tb, is investigated for various glass-forming liquids, with emphasis on monohydroxy alcohols. As is well known, Tb and Tg are positively correlated across a large variety of liquids. However, we found that the same quantities show a negative correlation within an isomeric series, i.e., Tb decreases with increasing Tg for different isomers of the same chemical formula. For the alcohol series, CnH2n+1OH with 3 < or = n < or = 10, a master curve of the negative Tg - Tb correlation is obtained if the temperatures are normalized to the respective values of the n-alkanols. This Tg - Tb dependence of isomeric liquids is linked to entropic effects and responsible for much of the scatter of the correlation observed for a large number of molecular organic glass-formers with 45 < Tg < 250 K. Dielectric relaxation is measured for three groups of isomers: (a) 3-methoxyl-1-butanol and 2-iso-propoxyethanol, (b) 1,4-, 1,2-, and 2,4-pentanediol, and (c) di-n- and di-iso-butyl phthalate. Two key parameters of the dynamics, fragility m and stretching exponent beta, are found to be indistinguishable within isomers of moderately different Tgs. Larger fragility differences are readily expected with pronounced structural change, but no systematic trend is observed within an isomer series. The results provide a useful tool for assessing Tg, m, and beta for marginal glass formers on the basis of their isomers.

  13. CYANOMETHANIMINE ISOMERS IN COLD INTERSTELLAR CLOUDS: INSIGHTS FROM ELECTRONIC STRUCTURE AND KINETIC CALCULATIONS

    SciTech Connect

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

    2015-09-10

    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 + CH{sub 2} = 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){sup 0.152} × e{sup (−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{sup −10} × (T/300){sup 0.153} × e{sup (−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 + CH{sub 2} = 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.

  14. Reactions of Atomic Carbon with Butene Isomers: Implications for Molecular Growth in Carbon-Rich Environments

    NASA Astrophysics Data System (ADS)

    Bourgalais, J.; Spencer, Michael; Osborn, David L.; Goulay, F.; Le Picard, S. D.

    2016-10-01

    Product detection studies of C(3P) atom reactions with butene (C4H8) isomers (but-1-ene, cis-but-2-ene, trans-but-2-ene) are carried out in a flow tube reactor at 353 K and 4 Torr under multiple collision conditions. Ground state carbon atoms are generated by 248 nm laser photolysis of tetrabromomethane, CBr4, in a buffer of helium. Thermalized reaction products are detected using synchrotron tunable VUV photoionization and time-of-flight mass spectrometry. The temporal profiles of the detected ions are used to discriminate products from side or secondary reactions. For the C(3P) + trans-but-2-ene and C(3P) + cis-but-2-ene reactions, various isomers of C4H5 and C5H7 are identified as reaction products formed via CH3 and H elimination. Assuming equal ionization cross sections for all C4H5 and C5H7 isomers, C4H5:C5H7 branching ratios of 0.63:1 and 0.60:1 are derived for the C(3P) + trans-but-2-ene and the C(3P) + cis-but-2-ene reactions, respectively. For the C(3P) + but-1ene reaction, two reaction channels are observed: the H-elimination channel, leading to the formation of the ethylpropargyl isomer, and the C3H3 + C2H5 channel. Assuming equal ionization cross sections for ethylpropargyl and C3H3 radicals, a branching ratio of 1:0.95 for the C3H3 + C2H5 and H + ethylpropargyl channels is derived. The experimental results are compared to previous H atom branching ratios and used to propose the most likely mechanisms for the reaction of ground state carbon atoms with butene isomers.

  15. 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.

  16. 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})

  17. 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.

  18. Antiretroviral therapy: Shifting sands

    PubMed Central

    Sashindran, V.K.; Chauhan, Rajeev

    2016-01-01

    HIV/AIDS has been an extremely difficult pandemic to control. However, with the advent of antiretroviral therapy (ART), HIV has now been transformed into a chronic illness in patients who have continued treatment access and excellent long-term adherence. Existing indications for ART initiation in asymptomatic patients were based on CD4 levels; however, recent evidence has broken the shackles of CD4 levels. Early initiation of ART in HIV patients irrespective of CD4 counts can have profound positive impact on morbidity and mortality. Early initiation of ART has been found not only beneficial for patients but also to community as it reduces the risk of transmission. There have been few financial concerns about providing ART to all HIV-positive people but various studies have proven that early initiation of ART not only proves to be cost-effective but also contributes to economic and social growth of community. A novel multidisciplinary approach with early initiation and availability of ART at its heart can turn the tide in our favor in future. Effective preexposure prophylaxis and postexposure prophylaxis can also lower transmission risk of HIV in community. New understanding of HIV pathogenesis is opening new vistas to cure and prevention. Various promising candidate vaccines and drugs are undergoing aggressive clinical trials, raising optimism for an ever-elusive cure for HIV. This review describes various facets of tectonic shift in management of HIV. PMID:26900224

  19. ArnHF van der Waals clusters revisited: II. Energetics and HF vibrational frequency shifts from diffusion Monte Carlo calculations on additive and nonadditive potential-energy surfaces for n =1-12

    NASA Astrophysics Data System (ADS)

    Jiang, Hao; Xu, Minzhong; Hutson, Jeremy M.; Bačić, Zlatko

    2005-08-01

    The ground-state energies and HF vibrational frequency shifts of ArnHF clusters have been calculated on the nonadditive potential-energy surfaces (PESs) for n =2-7 and on the pairwise-additive PESs for the clusters with n =1-12, using the diffusion Monte Carlo (DMC) method. For n >3, the calculations have been performed for the lowest-energy isomer and several higher-lying isomers which are the closest in energy. They provide information about the isomer dependence of the HF redshift, and enable direct comparison with the experimental data recently obtained in helium nanodroplets. The agreement between theory and experiment is excellent, in particular, for the nonadditive DMC redshifts. The relative, incremental redshifts are reproduced accurately even at the lower level of theory, i.e., the DMC and quantum five-dimensional (rigid Arn) calculations on the pairwise-additive PESs. The nonadditive interactions make a significant contribution to the frequency shift, on the order of 10%-12%, and have to be included in the PESs in order for the theory to yield accurate magnitude of the HF redshift. The energy gaps between the DMC ground states of the cluster isomers are very different from the energy separation of their respective minima on the PES, due to the considerable variations in the intermolecular zero-point energy of different ArnHF isomers.

  20. Phase-shift coherence holography.

    PubMed

    Naik, Dinesh N; Ezawa, Takahiro; Miyamoto, Yoko; Takeda, Mitsuo

    2010-05-15

    We propose and experimentally demonstrate a new reconstruction scheme for coherence holography using computer-generated phase-shift coherence holograms. A 3D object encoded into the spatial coherence function is reconstructed directly from a set of incoherently illuminated computer-generated holograms with numerically introduced phase shifts. Although a rotating ground glass is used to introduce spatially incoherent illumination, the phase-shifting portion of the system is simple and free from mechanically moving components.

  1. Zero-shifted accelerometer outputs

    NASA Astrophysics Data System (ADS)

    Galef, Arnold

    1986-08-01

    It is claimed that the commonly appearing zero-shift in pyroshock data is usually a symptom of a malfunctioning measurement system, so that the data can not be repaired (by high-pass filtering or equivalent) unless tests can be devised that permit the demonstration that the system is operating in a linear mode in all respects other than the shift. The likely cause of the zero-shift and its prevention are discussed.

  2. Detection, identification, and quantification of hydroxylated bis(2-ethylhexyl)-tetrabromophthalate isomers in house dust.

    PubMed

    Peng, Hui; Saunders, David M V; Sun, Jianxian; Codling, Garry; Wiseman, Steve; Jones, Paul D; Giesy, John P

    2015-03-03

    Ultra-High Resolution LC/mass spectrometry (LC-UHRMS; Thermo Fisher Q-Exactive) was used to identify two novel isomers of hydroxylated bis(2-ethylhexyl)-tetrabromophthalate (OH-TBPH) which were unexpectedly observed in a commercial standard of TBPH. By combining ultra-high resolution (UHR) mass spectra (MS(1)), mass errors to theoretical [TBPH-Br+O](-) were 2.1 and 1.0 ppm for the two isomers, UHR-MS(2) spectra and NMR analysis; the structures of the two compounds were identified as hydroxylated TBPH with a hydroxyl group on the aromatic ring. Relatively great proportions of the two isomers of OH-TBPH were detected in two technical products, Firemaster 550 (FM-550; 0.1% and 6.2%, respectively) and Firemaster BZ 54 (BZ-54; 0.1% and 7.9%), compared to a commercial standard (0.4% and 0.9%). To simultaneously analyze OH-TBPH isomers and TBPH in samples of dust, a method based on LC-UHRMS was developed to quantify the two compounds, using negative and positive ion modes, respectively. The instrumental limit of detection for TBPH was 0.01 μg/L, which was 200-300 times better than traditional methods (2.5 μg/L) based on gas chromatography-mass spectrometry. The analytical method combined with a Florisil cleanup was successfully applied to analyze TBPH and OH-TBPH in 23 indoor dust samples from Saskatoon, Saskatchewan, Canada. Two OH-TBPH isomers, OH-TBPH1 and OH-TBPH2, were detected in 52% and 91% of dust samples, respectively. Concentrations of OH-TBPH2 (0.35 ± 1.0 ng/g) were 10-fold greater than those of OH-TBPH1 (0.04 ± 0.88 ng/g) in dust, which was similar to profiles in FM-550 and BZ-54. TBPH was also detected in 100% of dust samples with a mean concentration of 733 ± 0.87 ng/g. A significant (p < 0.001) log-linear relationship was observed between TBPH and OH-TBPH isomers, further supporting the hypothesis of a common source of emission. Relatively small proportions of OH-TBPH isomers were detected in dust (0.01% ± 0.67 OH-TBPH1 and 0.1% ± 0.60 OH-TBPH2

  3. Ultra-soft magnetic properties and correlated phase analysis by {sup 57}Fe Mössbauer spectroscopy of Fe{sub 74}Cu{sub 0.8}Nb{sub 2.7}Si{sub 15.5}B{sub 7} alloy

    SciTech Connect

    Manjura Hoque, S.; Liba, S. I.; Akhter, Shireen; Anirban, A.; Choudhury, Shamima

    2016-02-15

    A detailed study of magnetic softness has been performed on FINEMENT type of ribbons by investigating the BH loop with maximum applied field of 960 A/m. The ribbon with the composition of Fe{sub 74}Cu{sub 0.8}Nb{sub 2.7}Si{sub 15.5}B{sub 7} was synthesized by rapid solidification technique and the compositions volume fraction was controlled by changing the annealing condition. Detail phase analysis was performed through X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Vibrating sample magnetometer (VSM) and Mössbauer spectroscopy in order to correlate the ultrasoft magnetic properties with the volume fraction of amorphous and α-Fe(Si) soft nano composites. Bright (BF) and dark field (DF) image with selective area diffraction (SAD) patterns by the transmission electron microscopy (TEM) of the sample annealed for the optimized annealed condition at 853 K for 3 min reveals nanocrystals with an average size between 10-15 nm possessing the bcc structure which matches with the grain size revealed by the X-ray diffraction. Kinetics of crystallization of α-Fe(Si) phases has been determined by DSC curves. Extremely small coercivity of 30.9 A/m and core loss of 2.5 W/Kg for the sample annealed at 853 K for 3 min was found. Similar values for other crystalline conditions were determined by using BH loop tracer with a maximum applied field of around 960 A/m. Mössbauer spectroscopy was used to determine chemical shift, hyperfine field distribution (HFD), and peak width of different phases. The volume fractions of the relative amount of amorphous and crystalline phases are also determined by Mössbauer spectroscopy. High saturation magnetization along with ultrasoft magnetic properties exhibits very high potentials technological applications.

  4. Quantized beam shifts in graphene

    SciTech Connect

    de Melo Kort-Kamp, Wilton Junior; Sinitsyn, Nikolai; Dalvit, Diego Alejandro Roberto

    2015-10-08

    We predict the existence of quantized Imbert-Fedorov, Goos-Hanchen, and photonic spin Hall shifts for light beams impinging on a graphene-on-substrate system in an external magnetic field. In the quantum Hall regime the Imbert-Fedorov and photonic spin Hall shifts are quantized in integer multiples of the fine structure constant α, while the Goos-Hanchen ones in multiples of α2. We investigate the influence on these shifts of magnetic field, temperature, and material dispersion and dissipation. An experimental demonstration of quantized beam shifts could be achieved at terahertz frequencies for moderate values of the magnetic field.

  5. Thermochromic shifts in supercritical fluids

    SciTech Connect

    Yonker, C.R.; Smith, R.D. )

    1989-02-23

    Thermochromic shifts of organic solute molecules in supercritical CO{sub 2} under conditions of both constant pressure and density are compared to previous studies of solvatochromic shifts at isothermal conditions. Similar solvatochromic and thermochromic shifts are seen as a function of density for supercritical CO{sub 2}. At constant density a small thermochromic shift ({approx}400 cm{sup {minus}1}) for supercritical CO{sub 2} was seen for both 2-nitroanisole and 4-ethylnitrobenzene. The excited-state dipole moments for 2-nitroanisole, as calculated from the thermochromic and solvatochromic data, were in agreement.

  6. Trolox equivalent antioxidant capacity of different geometrical isomers of alpha-carotene, beta-carotene, lycopene, and zeaxanthin.

    PubMed

    Böhm, Volker; Puspitasari-Nienaber, Ni Luh; Ferruzzi, Mario G; Schwartz, Steven J

    2002-01-02

    Isomerization of carotenoids, which is often encountered in food processing under the influence of temperature and light, may play a role in the observed protective effects of this group of secondary plant products. Investigation of in vitro antioxidant activity of prominent carotenoid geometrical isomers was undertaken in light of recent reports illustrating a large percentage of carotenoid (Z)-isomers in biological fluids and tissues. Alpha-carotene, beta-carotene, lycopene, and zeaxanthin were isolated from foods or supplements and subsequently photoisomerized with iodine as a catalyst. Major Z-isomers of each carotenoid were fractionated by semipreparative C(30) HPLC. In vitro antioxidant activity of all isomers collected was measured photometrically using the Trolox equivalent antioxidant capacity (TEAC) assay. TEAC values of 17 geometrical isomers investigated ranged from 0.5 to 3.1 mmol/L. Three unidentified (Z)-isomers of lycopene showed the highest antioxidant activity, being significantly higher than the result for (all-E)-lycopene, which had approximately two times the activity of (all-E)-beta-carotene. On the other hand, (9Z)-zeaxanthin had a more than 80% lower TEAC value compared to that of (all-E)-lycopene. These results allow for the in vivo relevance of (Z)-isomers of carotenoids to be considered.

  7. Perfluorooctane sulfonate toxicity, isomer-specific accumulation, and maternal transfer in zebrafish (Danio rerio) and rainbow trout (Oncorhynchus mykiss).

    PubMed

    Sharpe, Rainie L; Benskin, Jonathan P; Laarman, Anne H; Macleod, Sherri L; Martin, Jonathan W; Wong, Charles S; Goss, Greg G

    2010-09-01

    Perfluorooctane sulfonate (PFOS; C(8)F(17)SO(3) (-)) bioaccumulation and toxicity have been demonstrated in both aquatic and terrestrial organisms. The majority of investigations have examined total PFOS concentrations in wildlife and in toxicity testing, but isomer-specific monitoring studies are less common, and no laboratory-based study of PFOS isomer accumulation in fish has been reported. The present study examined accumulation and maternal transfer of PFOS isomers in zebrafish and tissue-specific accumulation of PFOS isomers in trout parr. A median lethal dose (LC50) of 22.2 and 2.5 mg/L was calculated for adult zebrafish and trout parr, respectively. A two-week PFOS exposure resulted in tissue-specific PFOS accumulation in trout, with maximum concentrations identified in the liver tissue (>50 microg/g). Prior exposure to PFOS as alevin did not affect the accumulation of PFOS in tissues later in life. In both species, accumulation of branched PFOS isomers generally occurred to a lesser extent than linear PFOS, which may explain the relative deficiency of branched PFOS isomers in some aquatic species in the field. Analysis of exposed trout tissues indicated that isomer discrimination may occur at the level of elimination or uptake and elimination processes in the kidney or gill, respectively. When zebrafish underwent a reproductive cycle in the presence of PFOS, approximately 10% (wt) of the adult PFOS body burden was transferred to the developing embryos, resulting in a higher total PFOS concentration in eggs (116 +/- 13.3 microg/g) than in the parent fish (72.1 +/- 7.6 microg/g). The isomer profile in eggs was not significantly different from that of adults, suggesting that the maternal transfer of branched and linear PFOS isomers in fish is largely nonisomer specific.

  8. 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.

  9. Shifts in fisheries management: adapting to regime shifts

    PubMed Central

    King, Jacquelynne R.; McFarlane, Gordon A.; Punt, André E.

    2015-01-01

    For many years, fisheries management was based on optimizing yield and maintaining a target biomass, with little regard given to low-frequency environmental forcing. However, this policy was often unsuccessful. In the last two to three decades, fisheries science and management have undergone a shift towards balancing sustainable yield with conservation, with the goal of including ecosystem considerations in decision-making frameworks. Scientific understanding of low-frequency climate–ocean variability, which is manifested as ecosystem regime shifts and states, has led to attempts to incorporate these shifts and states into fisheries assessment and management. To date, operationalizing these attempts to provide tactical advice has met with limited success. We review efforts to incorporate regime shifts and states into the assessment and management of fisheries resources, propose directions for future investigation and outline a potential framework to include regime shifts and changes in ecosystem states into fisheries management.

  10. 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.

  11. 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

  12. Synthesis of the E and Z isomers of the antiestrogen tamoxifen and its metabolite, hydroxytamoxifen, in tritium-labeled form

    SciTech Connect

    Robertson, D.W.; Katzenellenbogen, J.A.

    1982-06-04

    Both isomers of the potent antiestrogen tamoxifen (1,2-diphenyl-1-(4-(2-(dimethylamino)ethoxy)phenyl)-1-butene: E isomer = ICI-47699; Z isomer = ICI-46474, Nolvadex) and its metabolite, hydroxytamoxifen (1-(4-(2-(dimethylamino)ethoxy)phenyl)-1-(4-hydroxyphenyl)-2-phenyl-1-butene), have been synthesized in a high specific activity, tritium-labeled form by catalytic tritium-halogen exchange performed on brominated precursors. The synthesis of another precursor to labeled tamoxifen which would enable the incorporation of three tritium atoms into the molecule by tritium-halogen exchange is reported.

  13. Metabolic impact of shift work.

    PubMed

    Zimberg, Ioná Zalcman; Fernandes Junior, Silvio A; Crispim, Cibele Aparecida; Tufik, Sergio; de Mello, Marco Tulio

    2012-01-01

    In developing countries, shift work represents a considerable contingent workforce. Recently, studies have shown that overweight and obesity are more prevalent in shift workers than day workers. In addition, shift work has been associated with a higher propensity for the development of many metabolic disorders, such as insulin resistance, diabetes, dislipidemias and metabolic syndrome. Recent data have pointed that decrease of the sleep time, desynchronization of circadian rhythm and alteration of environmental aspects are the main factors related to such problems. Shortened or disturbed sleep is among the most common health-related effects of shift work. The plausible physiological and biological mechanisms are related to the activation of the autonomic nervous system, inflammation, changes in lipid and glucose metabolism, and related changes in the risk for atherosclerosis, metabolic syndrome, and type II diabetes. The present review will discuss the impact of shift work on obesity and metabolic disorders and how disruption of sleep and circadian misalignment may contribute to these metabolic dysfunctions.

  14. Identification of (2-aminopropyl)benzofuran (APB) phenyl ring positional isomers in internet purchased products.

    PubMed

    Stanczuk, Andrzej; Morris, Noreen; Gardner, Elizabeth A; Kavanagh, Pierce

    2013-04-01

    5-(2-Aminopropyl)benzofuran (5-APB), a 'research chemical' that was first reported by UK authorities to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) in 2010, is anecdotally reported to produce a combination of stimulant and entactogenic effects. More recently, in 2011, 6-(2-aminopropyl)benzofuran (6-APB) was identified by Hungarian authorities. To confirm positional isomer identity in Internet purchased products, 4- 5- 6- and 7-APBs were synthesized and found to be separable by gas chromatography (as heptafluorobutyramide derivatives) and liquid chromatography. The analyses of products purchased from online vendors of 'research chemicals' identified the presence of 5- or 6-APBs. These findings were further confirmed by liquid chromatography-mass spectrometry and (1) H nuclear magnetic resonance spectroscopy. In products containing 6-APB, the 4- positional isomer was also identified and this may have arisen during the manufacturing process.

  15. Isomers of Pm Isotopes on the Neutron-Rich Frontier of the Deformed Z ~ 60 Region

    NASA Astrophysics Data System (ADS)

    Yokoyama, Rin; Ideguchi, Eiji; Simpson, Gary; Tanaka, Mana; Nishimura, Shunji; Doornnbal, Pieter; Söderström, Pär-Anders; Lorusso, Giuseppe; Xu, Zhengyu; Wu, Jin; Sumikama, Toshiyuki; Aoi, Nori; Baba, Hidetada; Bello, Frank; Browne, Frank; Daido, Rie; Fang, Yifan; Fukuda, Naoki; Gey, Guillaume; Go, Shintaro; Inabe, Naohiro; Isobe, Tadaaki; Kameda, Daisuke; Kobayashi, Kazuma; Kobayashi, Motoki; Komatsubara, Tetsuro; Kubo, Toshiyuki; Kuti, Istvan; Li, Zhihuan; Matsushita, Masafumi; Michimasa, Shin'ichiro; Moon, Chang-Bum; Nishibata, Hiroki; Nishizuka, Ippei; Odahara, Atsuko; Patel, Zena; Rice, Simon; Sahin, Eda; Sinclair, Laura; Suzuki, Hiroshi; Takeda, Hiroyuki; Taprogge, Jan; Vajta, Zsolt; Watanabe, Hiroshi; Yagi, Ayumi

    Neutron-rich Pm (Z = 61) isotopes were studied by delayed γ-ray spectroscopy at RIBF, Riken Nishina Center using the in-flight fission of 345 MeV/u 238U beam. An array of cluster-type Ge detectors, EURICA, was used to measure the delayed γ rays from stopped ions. Isomers were observed in 158Pm, 159Pm and 161Pm with half-lives of >16, 4.64(21), and 0.88(10) µs respectively. Preliminary level schemes for 159Pm and 161Pm were constructed in this study. They have ground-state bands similar to those of 153Pm and 155Pm. The isomeric state of 161Pm could be interpreted as a two quasi-particle excitation of neutrons with configuration of ν 7/2[633] otimes ν 1/2[521] as other Kπ = 4 - isomers observed systematically in other N = 100 isotones.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Electronic single-molecule identification of carbohydrate isomers by recognition tunnelling

    PubMed Central

    Im, JongOne; Biswas, Sovan; Liu, Hao; Zhao, Yanan; Sen, Suman; Biswas, Sudipta; Ashcroft, Brian; Borges, Chad; Wang, Xu; Lindsay, Stuart; Zhang, Peiming

    2016-01-01

    Carbohydrates are one of the four main building blocks of life, and are categorized as monosaccharides (sugars), oligosaccharides and polysaccharides. Each sugar can exist in two alternative anomers (in which a hydroxy group at C-1 takes different orientations) and each pair of sugars can form different epimers (isomers around the stereocentres connecting the sugars). This leads to a vast combinatorial complexity, intractable to mass spectrometry and requiring large amounts of sample for NMR characterization. Combining measurements of collision cross section with mass spectrometry (IM–MS) helps, but many isomers are still difficult to separate. Here, we show that recognition tunnelling (RT) can classify many anomers and epimers via the current fluctuations they produce when captured in a tunnel junction functionalized with recognition molecules. Most importantly, RT is a nanoscale technique utilizing sub-picomole quantities of analyte. If integrated into a nanopore, RT would provide a unique approach to sequencing linear polysaccharides. PMID:28000682

  1. New shape isomer in the self-conjugate nucleus 72Kr.

    PubMed

    Bouchez, E; Matea, I; Korten, W; Becker, F; Blank, B; Borcea, C; Buta, A; Emsallem, A; de France, G; Genevey, J; Hannachi, F; Hauschild, K; Hürstel, A; Le Coz, Y; Lewitowicz, M; Lucas, R; Negoita, F; de Oliveira Santos, F; Pantelica, D; Pinston, J; Rahkila, P; Rejmund, M; Stanoiu, M; Theisen, Ch

    2003-02-28

    A new isomeric 0(+) state was identified as the first excited state in the self-conjugate (N=Z) nucleus 72Kr. By combining for the first time conversion-electron and gamma-ray spectroscopy with the production of metastable states in high-energy fragmentation, the electric-monopole decay of the new isomer to the ground state was established. The new 0(+) state is understood as the band head of the known prolate rotational structure, which strongly supports the interpretation that 72Kr is one of the rare nuclei having an oblate-deformed ground state. This observation gives in fact the first evidence for a shape isomer in a N=Z nucleus.

  2. Electronic single-molecule identification of carbohydrate isomers by recognition tunnelling

    NASA Astrophysics Data System (ADS)

    Im, Jongone; Biswas, Sovan; Liu, Hao; Zhao, Yanan; Sen, Suman; Biswas, Sudipta; Ashcroft, Brian; Borges, Chad; Wang, Xu; Lindsay, Stuart; Zhang, Peiming

    2016-12-01

    Carbohydrates are one of the four main building blocks of life, and are categorized as monosaccharides (sugars), oligosaccharides and polysaccharides. Each sugar can exist in two alternative anomers (in which a hydroxy group at C-1 takes different orientations) and each pair of sugars can form different epimers (isomers around the stereocentres connecting the sugars). This leads to a vast combinatorial complexity, intractable to mass spectrometry and requiring large amounts of sample for NMR characterization. Combining measurements of collision cross section with mass spectrometry (IM-MS) helps, but many isomers are still difficult to separate. Here, we show that recognition tunnelling (RT) can classify many anomers and epimers via the current fluctuations they produce when captured in a tunnel junction functionalized with recognition molecules. Most importantly, RT is a nanoscale technique utilizing sub-picomole quantities of analyte. If integrated into a nanopore, RT would provide a unique approach to sequencing linear polysaccharides.

  3. 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

  4. Ab initio kinetics for isomerization reaction of normal-chain hexadiene isomers

    NASA Astrophysics Data System (ADS)

    Yang, Feiyu; Deng, Fuquan; Pan, Youshun; Tian, Zemin; Zhang, Yingjia; Huang, Zuohua

    2016-10-01

    The ground-state potential energy surface (PES) of isomerization philosophy of ten normal-chain hexadiene isomers is computed by density functional methods using the geometries optimized at B3LYP/6-311++G (d, p) level of theory. These detailed reaction pathways are used to calculate the rate constants for the unimolecular isomerization reactions by transition state theory (TST) in the temperature range of 500-2500 K. Difference of rate constant between each hexadiene isomer is interpreted through the PES and Ḣ atom transfer, and only 2,4-hexadiene readily fulfills cis-cis to trans-trans conformation conversion. All the conversions are kinetically interpreted from the PES and ST geometry.

  5. 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.

  6. 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.

  7. 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.

  8. Adsorptive process design for the separation of hexane isomers using zeolites.

    PubMed

    Luna-Triguero, A; Gómez-Álvarez, P; Calero, S

    2017-02-15

    The product of catalytic isomerization is a mixture of linear and branched hydrocarbons that are in thermodynamic equilibrium, and their separation becomes necessary in the petrochemical industry. Zeolite 5A is usually industrially used to sieve alkane isomers, but its pore size allows only the separation of linear alkanes from the monobranched and dibranched alkanes by a kinetic mechanism. A more efficient approach to improve the average research octane number would be to adsorptively separate the di-methyl alkanes as products and recycle both the linear and mono-methyl alkanes to the isomerization reactor. Since the microscopic processes of adsorbates in zeolites are generally difficult or impossible to determine by experiments, especially in the case of mixtures, molecular simulation represents an attractive alternative. In this computational study, we propose a conceptual separation process for hexane isomers consisting of several adsorptive steps. Different zeolite topologies were examined for their ability to conduct this separation based on adsorption equilibrium and kinetics.

  9. 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.

  10. Isomer-specific product formation in the proton transfer reaction of HOCO+ with CO

    NASA Astrophysics Data System (ADS)

    Carrascosa, Eduardo; Stei, Martin; Kainz, Martin A.; Wester, Roland

    2015-12-01

    The proton transfer reaction HOCO++CO → HCO+/HOC+ has been studied using crossed-beam velocity map imaging. Angular and energy differential cross sections were obtained for collision energies from 0.3 to 2.3 eV. Scattering in forward direction together with a prominent scattering angle-dependent internal excitation is found at all collision energies. The exothermic HCO+ product appears to be very dominant even at energies above the energy threshold for the formation of metastable HOC+ ion. To determine the HOC+ contribution for different angular ranges, a model has been developed. We obtain an upper limit for the HOC+ product isomer fraction of <2%. In theoretical calculations, we find the CO2-catalysed isomerisation channel to be energetically accessible. However, it may not have a strong impact on the isomer ratio. Chemical dynamics simulations are needed to shed more light on this question.

  11. 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.

  12. Determination of ortho-cresyl phosphate isomers of tricresyl phosphate used in aircraft turbine engine oils by gas chromatography and mass spectrometry.

    PubMed

    De Nola, G; Kibby, J; Mazurek, W

    2008-07-25

    Tricresyl phosphate (TCP) is used as an anti-wear additive in aircraft turbine engine oil. Concerns about its toxicity are largely based on the tri-o-cresyl phosphate isomer content. However, the presence of other and more toxic isomers has been previously suggested. In this work, the structural isomers of TCP have been determined by two methods (experimental and semi-theoretical). First, the TCP isomers were separated by gas chromatography (GC) and identified by mass spectrometry (MS). Second, after base cleavage of TCP, GC was used to quantify the cresol precursors. These results were used to calculate the TCP isomer distribution based on the assumption of a statistical distribution of the TCP isomers. The results from the two determinations showed reasonable agreement for three of the four oils studied. The o-cresyl isomers were found to be present almost exclusively as the more toxic mono-o-cresyl isomers in the concentration range 13-150 mg/L. The ability to analyse for the mono-o-cresyl isomers allows the toxicity of TCP to be based on the latter isomers rather than on the less toxic tri-o-cresyl phosphate isomer.

  13. Two new antioxidant malonated caffeoylquinic acid isomers in fruits of wild eggplant relatives.

    PubMed

    Ma, Chunhui; Dastmalchi, Keyvan; Whitaker, Bruce D; Kennelly, Edward J

    2011-09-14

    Fruits of the cultivated eggplant species Solanum melongena and its wild relative Solanum incanum have a high content of hydroxycinnamic acid conjugates, which are implicated in the human health benefits of various fruits and vegetables. Monocaffeoylquinic acid esters, in particular 5-O-(E)-caffeoylquinic acid, are usually predominant in solanaceous fruits and tubers. Two closely related caffeoylquinic acid derivatives with longer C(18) HPLC retention times than those of monocaffeoylquinic acids are minor constituents in cultivated eggplant fruit. In a prior study, the two compounds were tentatively identified as 3-O-acetyl- and 4-O-acetyl-5-O-(E)-caffeoylquinic acids and composed ≤2% of the total hydroxycinnamic acid conjugates in fruit of most S. melongena accessions. It was recently found that the pair of these caffeoylquinic acid derivatives can compose 15-25% of the total hydroxycinnamic acid conjugates in fruits of S. incanum and wild S. melongena. This facilitated C(18) HPLC isolation and structural elucidation using (1)H and (13)C NMR techniques and HR-ToF-MS. The isomeric compounds were identified as 3-O-malonyl-5-O-(E)-caffeoylquinic acid (isomer 1) and 4-O-(E)-caffeoyl-5-O-malonylquinic acid (isomer 2). Both exhibited free radical scavenging activity, albeit about 4-fold lower than that of the flavonol quercetin dihydrate. By contrast, the iron chelation activities of isomers 1 and 2, respectively, were about 3- and 6-fold greater than that of quercetin dihydrate. Reports of malonylhydroxycinnamoylquinic acids are rare, and only a few of these compounds have been structurally elucidated using both NMR and MS techniques. To the authors' knowledge, these two malonylcaffeoylquinic acid isomers have not previously been reported.

  14. 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.

  15. Optical isomers of a new 2-nitroimidazole nucleoside analog (PR-350 series): Radiosensitization efficiency and toxicity

    SciTech Connect

    Oya, Natsuo; Sasai, Keisuke; Shibata, Toru

    1995-08-30

    A new 2-nitroimidazole nucleoside radiosensitizer, PR-350 (1-[1{prime},3{prime},4{prime}-trihydroxy-2{prime}-butoxy]-methyl-2-nitroimidazole), has been reported to be as efficient as and less toxic than etanidazole. This compound is racemic, and it was recently optically resolved into two isomers, PR-68 (2{prime}R,3{prime}S type) and PR-69 (2{prime}S,3{prime}R type). The other two isomers, PR-28 (2{prime}S,3{prime}S type) and PR-44 (2{prime}R,3{prime}R type), were asymmetrically synthesized. In the present study, we investigated the properties, sensitizing activity, and toxicity of PR-350 and the four optical isomers in comparison with those of other 2-nitroimidazole hypoxic cell radiosensitizers, etanidazole, KU-2285, KIN-804, and RP-170. Because PR-350 and PR-28 can be industrially synthesized, we evaluated whether either of these two drugs are suitable for further investigation. In vivo radiosensitizing activity differed among the four optical isomers, which appeared to be due, at least in part, to differences in lipophilicity. Although PR-28 was the least toxic, its low sensitization efficiency does not warrant clinical trials. Among the PR compounds, PR-68 appears to be most efficient, but optical resolution of PR-68 from PR-350 is expensive, and asymmetrical synthesis of PR-68 is not established. Therefore, PR-350 seems to be most suitable for further investigation among the PR-350 series compounds, considering its higher efficiency compared with PR-28 and PR-44, and established synthesis. 28 refs., 7 figs., 1 tab.

  16. Half-life and excitation energy of the Iπ=13/2+ isomer in Ra209

    NASA Astrophysics Data System (ADS)

    Hauschild, K.; Lopez-Martens, A.; Yeremin, A. V.; Dorvaux, O.; Belozerov, A. V.; Chelnokov, M. L.; Chepigin, V. I.; Gall, B.; Gorshkov, V. A.; Guttormsen, M.; Jones, P.; Kabachenko, A. P.; Khouaja, A.; Larsen, A. C.; Malyshev, O. N.; Minkova, A.; Nyhus, H. T.; Oganessian, Yu. Ts.; Pantelica, D.; Popeko, A. G.; Rotaru, F.; Saro, S.; Shutov, A. V.; Siem, S.; Svirikhin, A. I.; Syed, N. U. H.

    2008-04-01

    An isomeric state in Ra209 has been observed for the first time, using the GABRIELA setup at the focal plane of VASSILISSA, to decay to the ground state of Ra209 via a cascade of 238-keV (M2) and 644-keV transitions. The half-life of the isomer has been measured to be 117(5)μs and from systematics is assigned as a neutron i13/2-1 excitation.

  17. Ignition of Isomers of Pentane: An Experimental and Kinetic Modeling Study

    DTIC Science & Technology

    2000-08-04

    diesel engines [26,27], and ignition under homogeneous charge compres- sion ignition ( HCCI ) conditions [26,28]. Kinetic modeling shows that the isomers of...Introduction Hydrocarbon ignition is important in many prac- tical combustion systems, including internal com- bustion engines , detonations, pulse combustors...tem- peratures are similar to those in automotive engines during diesel ignition and end-gas autoignition in spark-ignition engines . The RCM provides

  18. 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.

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

    PubMed

    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.

  20. Efficient algorithms to enumerate isomers and diamutamers with more than one type of substituent

    PubMed

    van Almsick M; Dolhaine; Honig

    2000-07-01

    In this paper we describe numeric as well as symbolic algorithms for the enumeration of substitutional isomers with an unlimited number of different achiral substituents. We consider three different scenarios: first, the enumeration of diamutamers with a given set of ligand types and ligand multiplicity, second, the enumeration of diamutamer libraries with a given ligand assortment pattern, and, third, the enumerations of libraries with diamutamers exhibiting a limited number of ligands.