Now showing items 21-30 of 440
A Model for the Oceanic Mass Balance of Rhenium and Implications for the Extent of Proterozoic Ocean Anoxia
Emerging geochemical evidence suggests that the atmosphere-ocean system underwent a significant decrease in O2 content following the Great Oxidation Event (GOE), leading to a mid-Proterozoic ocean (ca. 2.0–0.8 Ga) with ...
Good Golly, Why Moly? THE STABLE ISOTOPE GEOCHEMISTRY OF MOLYBDENUM
(Mineralogical Society of America, 2017-01-01)
No abstract available.
Trace elements at the intersection of marine biological and geochemical evolution
Life requires a wide variety of bioessential trace elements to act as structural components and reactive centers in metalloenzymes. These requirements differ between organisms and have evolved over geological time, likely ...
Extensive marine anoxia during the terminal Ediacaran Period
(American Association for the Advancement of Science, 2018-06-20)
The terminal Ediacaran Period witnessed the decline of the Ediacara biota (which may have included many stemgroup animals). To test whether oceanic anoxia might have played a role in this evolutionary event, we measured U ...
New approaches to characterize polymeric oil additives in solution based on pyrene excimer fluorescence
Maleated polyolefins (MaPOs) such as maleated ethylene propylene copolymers or polyisobutylene terminated at one end with a succininic anhydride can be used as polymeric dispersants in engine oils after reaction with ...
Genesis of a giant Paleoproterozoic strata-bound magnesite deposit: Constraints from Mg isotopes
Giant strata-bound magnesite deposits are absent in modern and most Phanerozoic sedimentary environments but occur predominantly in Precambrian strata. These deposits may have formed directly through precipitation of evolved ...
The effect of hematocrit on solid-phase microextraction
Solid-phase microextraction (SPME) is an approach to sample preparation that has demonstrated its appropriateness for isolating/enriching analytes present in complex biofluids with minimum sample pre-treatment. Several ...
Using Pyrene Excimer Fluorescence To Probe Polymer Diffusion in Latex Films
(American Chemical Society, 2017-02-28)
This study introduces a simple technique that can be used to quantitatively probe interparticle polymer diffusion (IPD) between adjacent particles in a latex film using pyrene excimer fluorescence (PEF). To demonstrate the ...
Conformation of Pyrene-Labeled Amylose in DMSO Characterized with the Fluorescence Blob Model
(American Chemical Society, 2016-10-25)
Amylose and poly(methyl acrylate) were randomly labeled with pyrene to yield a series of Py-Amylose and Py-PMA constructs, and their ability to form excimer in DMSO was characterized quantitatively by steady-state and ...
Using Pyrene Excimer Fluorescence To Probe the Interactions between Viscosity Index Improvers and Waxes Present in Automotive Oil
(American Chemical Society, 2017-03-28)
A new methodology based on pyrene excimer fluorescence (PEF) was applied to quantitatively measure the actual level of intermolecular association between ethylene propylene (EP) copolymers in toluene in the presence of ...