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Now showing items 129 - 144 of 27133

  • D. H. Lawrence In Context || F. R. Leavis

    Harrison, Andrew  

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  • D. H. Lawrence In Context || The Cambridge Edition

    Harrison, Andrew  

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  • D/H fractionation during the sublimation of water ice

    Christophe Lécuyer   Aurélien Royer   François Fourel   Magali Seris   Laurent Simon   François Robert  

    Highlights • Sublimation of water ice was performed between −105 °C and −30 °C. • Sublimation produced isotopic fractionations in the range 0.969–1.123. • Below ≈ −50 °C the water vapour is D-depleted relative to the residual ice. • Such D/H fractionations have impacts on the water cycle of terrestrial planets. • Sublimation cannot explain the D/H differences amongst Earth's water and comets. Abstract Experiments of sublimation of pure water ice have been performed in the temperature range −105 °C to −30 °C and atmospheric partial pressures ranging from 10 −6 to 10 −1 mb. Sampling of both vapour and residual ice fractions has been performed with the use of a vacuum line designed for the extraction and purification of gases before the measurement of their D/H ratios. Sublimation was responsible for sizable isotopic fractionation factors in the range 0.969–1.123 for temperatures lying between −105 °C and −30 °C. The fractionation factor exhibits a cross-over at temperatures around −50 °C with the water vapour fraction being D-depleted relative to the residual ice fraction at T < −50 °C (α ice-vapour =  0.969–0.995). This cross-over has implications for the understanding of the atmospheric water cycle of some terrestrial planets such as the Earth or Mars. The magnitude of deuterium enrichment or depletion between ice and water vapour cannot explain the differences in the D/H ratios amongst Jupiter comets and long–period comets families nor those that have been documented between Earth's and cometary water.
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  • D. H. Lawrence In Context || Sex, Sexuality, Sexology

    Harrison, Andrew  

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  • D. H. Lawrence In Context || The Great War

    Harrison, Andrew  

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  • EPR Study of H and D Atoms in Quench-Condensed Solid D\\(_{2}\\)

    Dmitriev   Yu. A.  

    We present an experimental study of H and D atoms trapped in a solid D\(_{2}\) matrix. The samples were prepared by quench condensing gaseous \(n\)D\(_{2}\) with small (0.15 %) admixture of molecular \(n\)H\(_{2}\) on a substrate at 1.3–4.2 K. An EPR observation revealed two types of H and D atoms: with narrow- and broad-line spectra. In order to elucidate the origin of the centers we performed an analysis that included comparing the matrix shifts of the hyperfine structure constants, considering the saturation and spin-relaxation times, estimation of the superhyperfine broadening, and evaluation of an effect which the tunneling isotope exchange reaction has on the H and D atoms relative EPR intensities. As a result, the broad-line H and D spectra were attributed to atoms at the substitutional positions in the regular D\(_{2}\) lattice, while the narrow-line spectra were due to atoms trapped at the one-dimensional structure imperfections (like dislocations). These trapped atoms are capable of moving quickly along the defects with a diffusion coefficient \(D\approx 4\times 10^{-6}\) cm\(^{2}\)/s. The results were compared to earlier observations which allowed us to build a suggestion about the nature of previously found atomic centers in D\(_{2}\) not explained in the literature.
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  • Attorney General Robert H. Jackson and President Franklin D. Roosevelt

    BARRETT, JOHN Q.  

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  • Measuring the D/H Ratios of Exoplanets and Brown Dwarfs

    Morley, Caroline V.   Skemer, Andrew J.   Miles, Brittany E.   Line, Michael R.   Lopez, Eric D.   Brogi, Matteo   Freedman, Richard S.   Marley, Mark S.  

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  • Book Review: D. A. Shepherd and H. Patzelt, Entrepreneurial Cognition

    Jafary, Maziar  

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  • D/H fractionation during the sublimation of water ice

    Lécuyer, Christophe   Royer, Aurélien   Fourel, Fran?ois   Seris, Magali   Simon, Laurent   Robert, Fran?ois  

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  • Analytical Description of the H/D Exchange Kinetic of Macromolecule.

    Kostyukevich, Yury   Kononikhin, Alexey   Popov, Igor   Nikolaev, Eugene  

    We present the accurate analytical solution obtained for the system of rate equations describing the isotope exchange process for molecules containing an arbitrary number of equivalent labile atoms. The exact solution was obtained using Mathematica 7.0 software, and this solution has the form of the time-dependent Gaussian distribution. For the case when forward exchange considerably overlaps the back exchange, it is possible to estimate the activation energy of the reaction by obtaining a temperature dependence of the reaction degree. Using a previously developed approach for performing H/D exchange directly in the ESI source, we have estimated the activation energies for ions with different functional groups and they were found to be in a range 0.04-0.3 eV. Since the value of the activation energy depends on the type of functional group, the developed approach can have potential analytical applications for determining types of functional groups in complex mixtures, such as petroleum, humic substances, bio-oil, and so on.=20
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  • H/D exchange pathways: Flip-flop and relay processes

    Zhixin Tiana   Dana R. Reedb   Steven R. Kassa  

    •H/D exchange mechanisms of 16 small rigid anions were examined.•Four deuterated reagents were used to probe relay and flip-flop processes.•Distortion energies were found to account for relay mechanism barriers.
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  • H/D exchange pathways: Flip-flop and relay processes

    Tian, Zhixin   Reed, Dana R.   Kass, Steven R.  

    •H/D exchange mechanisms of 16 small rigid anions were examined.•Four deuterated reagents were used to probe relay and flip-flop processes.•Distortion energies were found to account for relay mechanism barriers.
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  • Isotope identity experiments in JET-ILW with H and D L-mode plasmas

    Maggi, C.F.; Weisen, H.; Casson, F.J.; Auriemma, F.; Lorenzini, R.; Nordman, H.; Delabie, E.; Eriksson, F.; Flanagan, J.; Keeling, D.; King, D.; Horvath, L.; Menmuir, S.; Salmi, A.; Sips, G.; Tala, T.; Voitsekhovich, I.  

    NBI-heated L-mode plasmas have been obtained in JET with the Be/W ITER-like wall (JET-ILW) in H and D, with matched profiles of the dimensionless plasma parameters, rho*, nu*, beta and q in the plasma core confinement region and same T-i/T-e and Z(eff). The achieved isotope identity indicates that the confinement scale invariance principle is satisfied in the core confinement region of these plasmas, where the dominant instabilities are Ion Temperature Gradient (ITG) modes. The dimensionless thermal energy confinement time, Omega(i) tau(E,th), and the scaled core plasma heat diffusivity, A chi(eff)/B-T, are identical in H and D within error bars, indicating lack of isotope mass dependence of the dimensionless L-mode thermal energy confinement time in JET-ILW. Predictive flux driven simulations with JETTO-TGLF of the H and D identity pair is in very good agreement with experiment for both isotopes: the stiff core heat transport, typical of JET-ILW NBI heated L-modes, overcomes the local gyro-Bohm scaling of gradient-driven TGLF, explaining the lack of isotope mass dependence in the confinement region of these plasmas. The effect of E x B shearing on the predicted heat and particle transport channels is found to be negligible for these low beta and low momentum input plasmas.
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  • THz spectroscopy of D2H+

    S. Yu   J.C. Pearson   T. Amano   F. Matsushima  

    Graphical abstract Highlights • Five new THz lines have been observed and the accurate frequencies are obtained. • Improved set of rotational parameters has been determined. • More reliable predictions for more THz lines are given. Abstract We extended the measurements of the rotational transitions of D 2 H + up to 3 THz by using the JPL frequency multiplier chains and a TuFIR system at Toyama. D 2 H + was generated in an extended negative glow discharge cell cooled to liquid nitrogen temperature. We observed five new THz lines. All the available rotational transition frequencies together with the combination differences derived from the three fundamental bands were subject to least square analysis to determine the molecular constants. New THz measurements are definitely useful for better characterization of spectroscopic properties. The improved molecular constants provide better predictions of other unobserved rotational transitions.
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  • 'Mr. W. H.': Stationer William Holme (d. 1607)

    Caveney, G.  

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