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Atomic hydrogen reaction rates in aqueous solution via free-induction decay attenuation
This new pulsed EPR method is providing data on H-atom reaction rates in water, which are important in radiation chemistry of aqueous solutions, eg, corrosion in reactor cooling systems, H2 production in high-level radioactive waste, and spread of radioactive iodine following the Chernobyl accident. This AECL-Argonne collaborative effort was undertaken to investigate fundamental aqueous H-atom chemistry for the purpose of developing predictive models of iodine transport that will be used by the nuclear power industry to enhance plant safety. Reactions of (H){sub aq} with many representative organic and inorganicmolecules have already been investigated. Radiolysis of aqueous solns with 3-MeV electrons produces H atoms in high yield; in the free induction decay method, a powerful 30 ns microwave pulse is applied immediately following pulse radiolysis, creating a phase coherence of the H-atom electron spins that is detected in the pulsed EPR spectrometer as a damped cosine free induction decay (FID). Natural decay time of the spin coherence is many microseconds, but if a reaction partner for the H atoms is introduced, the FID becomes shorter, revealing the H reaction rate. Results of H atom reaction with benzene, methanol, periodate and periodic acid are discussed briefly
Isotope dependence and quantum effects on atomic hydrogen diffusion in liquid water
Relative diffusion coefficients were determined in water for the D, H, and
Mu isotopes of atomic hydrogen by measuring their diffusion-limited spin-exchange rate
constants with Ni2+ as a function of temperature. H and D atoms were generated by pulse
radiolysis of water and measured by time-resolved pulsed EPR. Mu atoms are detected by
muonium spin resonance. To isolate the atomic mass effect from solvent isotope effect,
we measured all three spin-exchange rates in 90% D2O. The diffusion depends on the
atomic mass, demonstrating breakdown of StokesâEinstein behavior. The diffusion can
be understood using a combination of water âcavity diffusionâ and âhoppingâ
mechanisms, as has been proposed in the literature. The H/D isotope effect agrees
with previous modeling using ring polymer molecular dynamics. The âquantum swellingâ
effect on muonium due to its larger de Broglie wavelength does not seem to slow its
âhoppingâ diffusion as much as predicted in previous work. Quantum effects of both the
atom mass and the water librations have been modeled using RPMD and a qTIP4P/f
quantized flexible water model. These results suggest that the muonium diffusion is very
sensitive to the Mu versus water potential used.Division of Chemical Sciences,Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy through award DE-FC02-04ER15533.http://pubs.acs.org/journal/jpcafh2016-12-30hb201
Tests of sunspot number sequences: 2. Using geomagnetic and auroral data
We compare four sunspot-number data sequences against geomagnetic and terrestrial auroral observations. The comparisons are made for the original SIDC (Solar Influences Data Center) composite of Wolf/ZĂŒrich/International sunspot number [RISNv1], the group sunspot number [RG] by Hoyt and Schatten (Solar Phys., 181, 491, 1998), the new âbackboneâ group sunspot number [RBB] by Svalgaard and Schatten (Solar Phys., doi: 10.1007/s11207-015-0815-8, 2016), and the âcorrectedâ sunspot number [RC] by Lockwood, Owens, and Barnard (J. Geophys. Res., 119, 5172, 2014). Each sunspot number is fitted with terrestrial observations, or parameters derived from terrestrial observations to be linearly proportional to sunspot number, over a 30-year calibration interval of 1982 - 2012. The fits are then used to compute test sequences, which extend further back in time and which are compared to RISNv1, RG, RBB, and RC. To study the long-term trends, comparisons are made using averages over whole solar cycles (minimum-to-minimum). The test variations are generated in four ways: i) using the IDV(1d) and IDV geomagnetic indices (for 1845 - 2013) fitted over the calibration interval using the various sunspot numbers and the phase of the solar cycle; ii) from the open solar flux (OSF) generated for 1845 - 2013 from four pairings of geomagnetic indices by Lockwood et al. (Ann. Geophys., 32, 383, 2014) and analysed using the OSF continuity model of Solanki, SchĂŒssler, and Fligge (Nature, 408, 445, 2000) which employs a constant fractional OSF loss rate; iii) the same OSF data analysed using the OSF continuity model of Owens and Lockwood (J. Geophys. Res., 117, A04102, 2012) in which the fractional loss rate varies with the tilt of the heliospheric current sheet and hence with the phase of the solar cycle; iv) the occurrence frequency of low-latitude aurora for 1780 - 1980 from the survey of Legrand and Simon (Ann. Geophys., 5, 161, 1987). For all cases, RBB exceeds the test terrestrial series by an amount that increases as one goes back in time
PCR-based identification of Neospora caninum in the umbilical cord of a newborn calf in Brazil
Managing the solvent water polarization to obtain improved NMR spectra of large molecular structures
Next-to-Leading Order QCD Analysis of Polarized Deep Inelastic Scattering Data
We present a Next-to-Leading order perturbative QCD analysis of world data on
the spin dependent structure functions , and , including
the new experimental information on the dependence of . Careful
attention is paid to the experimental and theoretical uncertainties. The data
constrain the first moments of the polarized valence quark distributions, but
only qualitatively constrain the polarized sea quark and gluon distributions.
The NLO results are used to determine the dependence of the ratio
and evolve the experimental data to a constant . We
determine the first moments of the polarized structure functions of the proton
and neutron and find agreement with the Bjorken sum rule.Comment: 21 pages, 4 figures; final version to be published in Phys. Lett. B.
References updated. Uses elsart.cls version 1996/04/22, 2e-1.4
CASA: An Efficient Automated Assignment of Protein Mainchain NMR Data Using an Ordered Tree Search Algorithm
Rapid analysis of protein structure, interaction, and dynamics requires fast and automated assignments of 3D protein backbone triple-resonance NMR spectra. We introduce a new depth-first ordered tree search method of automated assignment, CASA, which uses hand-edited peak-pick lists of a flexible number of triple resonance experiments. The computer program was tested on 13 artificially simulated peak lists for proteins up to 723 residues, as well as on the experimental data for four proteins. Under reasonable tolerances, it generated assignments that correspond to the ones reported in the literature within a few minutes of CPU time. The program was also tested on the proteins analyzed by other methods, with both simulated and experimental peaklists, and it could generate good assignments in all relevant cases. The robustness was further tested under various situations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43050/1/10858_2005_Article_4079.pd
Sq and EEJâA Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents
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