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The path integral methodology for computation of the equilibrium isotope effect is described and applied to three [1,5] sigmatropic hydrogen shift reactions. An efficient estimator for the derivative of the free energy is used, which shortens the computati ...
This thesis describes new methods for the detection of 14N nuclei by solid-state nuclear magnetic resonance. So far, the low natural abundance (0.4 %) 15N isotope has been widely used to study nitrogen-containing samples because of its spin-1/2 nature. The ...
This paper presents the results of an effort to label calcium carbonates formed by marine organisms with stable isotopes to obtain information about the biomineralization processes. The growing skeleton of the scleractinian coral Porites porites was labele ...
Mass transfer of organic contaminants from nonaqueous phase liquids to the aqueous phase can significantly modulate the observable carbon isotope fractionation behavior associated with contaminant transformation. We evaluated the effects of kinetic interph ...
The radioactive isotope Fe-60 (T-1/2 = 1.5 Myr) was present in the early solar system. It is unlikely that it was injected directly into the nascent solar system by a single, nearby supernova (SN). It is proposed instead that it was inherited during the mo ...
The application of stable Fe isotopes as a tracer of the biogeochemical Fe cycle necessitates a mechanistic knowledge of natural fractionation processes. We studied the equilibrium Fe isotope fractionation upon sorption of Fe(II) to aluminum oxide (gamma-A ...
Major breakthroughs have recently been reported that can help overcome two inherent drawbacks of NMR: the lack of sensitivity and the limited memory of longitudinal magnetization. Dynamic nuclear polarization (DNP) couples nuclear spins to the large reserv ...
We describe here a study of the spectroscopy of two peptides that we expect to be helical, Ac-Phe-(Ala)5-Lys-H+ and Ac-Phe-(Ala)10-Lys-H+, and one that we expect to be globular, Ac-Lys(H+)-Phe-(Ala)10, with the goal of identifying spectral features charact ...
Compound-specific isotope analysis was used to monitor the delta C-13 signature of chloroform produced upon the chlorination of model compounds representing natural organic matter functional groups (resorcinol, acetylacetone, acetophenone, phenol, and 2,4, ...
A field method called gas push–pull test (GPPT) was previously developed for in-situ quantification of methane (CH4) oxidation by soil microorganisms. We examined whether natural-abundance stable carbon-isotope analysis of CH4, a common approach used to me ...