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S F Cox

Publications and source records attributed to S F Cox.

4 recordsLinked to original sources
PubMed2002

Effect of 2,4-dinitrophenol on the energy metabolism of cattle embryos produced by in vitro fertilization and culture.

In cattle embryos, the proportion of ATP produced by glycolysis increases following the major activation of the embryonic genome, and development to the blastocyst stage is improved in the presence of 10 microM 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation, from Day 5 to Day 7 of culture. In Experiment 1 of the present study, culture of cattle embryos in the presence of 10 microM DNP from Day 5 to Day 7 stimulated development to the blastocyst stage, but had no significant effects on oxygen, pyruvate or glucose uptake, or on lactate production. In Experiment 2, culture of cattle embryos in the presence of 10 microM DNP from Day 5 to Day 7, stimulated the metabolism of [2-14C]pyruvate (a measure of Krebs cycle activity) on all of Days 5, 6 and 7, and stimulated metabolism of [5-3H]glucose (a measure of glycolysis) on Day 7 only. The results show that 10 microM DNP stimulates oxidative and glycolytic metabolism in Day-5 to Day-7 cattle embryos, but this does not fully explain the observed increase in developmental competence. We propose that partial inhibition or uncoupling of oxidative phosphorylation may reduce the level of intracellular reactive oxygen species production, thereby facilitating development.

2,4-Dinitrophenol↗
PubMed2001

Experimental confirmation of the predicted shallow donor hydrogen state in zinc oxide.

We confirm the recent prediction that interstitial protium may act as a shallow donor in zinc oxide, by direct spectroscopic observation of its muonium counterpart. On implantation into ZnO, positive muons--chemically analogous to protons in this context--form paramagnetic centers below about 40 K. The muon-electron contact hyperfine interaction, as well as the temperature and activation energy for ionization, imply a shallow level. Similar results for the cadmium chalcogenides suggest that such shallow donor states are generic to the II-VI compounds. The donor level depths should serve as a guide for the electrical activity of interstitial hydrogen.

Journal Article↗
PubMed1998

Muon spin relaxation studies of interstitial and molecular motion.

The unusual methods of preparation and analysis of spin polarization in muSR spectroscopy, which exploit the unique properties of the positive muon, are introduced in this article. Following a summary overview of applications, particular attention is paid to the problem of spin-lattice relaxation for a muon experiencing a hyperfine interaction with a single unpaired electron. The specific cases considered are the interstitial diffusion of muonium--the 1-electron atom which may be considered as a light isotope of hydrogen-and the molecular dynamics of organic radicals labelled by muonium. Rate equations for the evolution of population in the hyperfine-coupled spin states are solved numerically for various relaxation mechanisms. The formalism is equally valid for conventional ESR studies of paramagnetic states but is pursued specifically to simulate T1-relaxation in muSR. The simulations are compared with literature data. Also treated is the case of intermittent hyperfine coupling, appropriate to electron capture and loss in semiconductors or soliton motion in polymers; for this, a Monte Carlo approach is used to simulate the muon response. (For low-dimensional motion, the relaxation function is not exponential, so that a unique value of T1 cannot be defined.) Finally, a proposal is made to implement muon-T1 measurements in the rotating frame; this is designed for the selective study of electronically diamagnetic muonium states (i.e., those without hyperfine coupling) in the presence of a paramagnetic muonium or radical fraction.

Carbon↗