Mitochondrial oxidative phosphorylation has a central role in eukaryotic metabolism, providing the energy (ATP) required for survival. Regulation of this important pathway is, however, still not understood, largely due to limitations in the ability to measure the essential metabolites, including oxygen (pO2, oxygen pressure), ADP, and AMP. In addition, neither the mechanism of oxygen reduction ...

Photosynthetic water oxidation by photosystem II is mediated by a Mn4 cluster, a cofactor X still chemically ill-defined, and a tyrosine, YZ (D1-Tyr161). Before the final reaction with water proceeds to yield O2 (transition S4-->S0), two oxidizing equivalents are stored on Mn4 (S0-->S1-->S2), a third on X (S2-->S3), and a forth on YZ(S3-->S4). It has been proposed that YZ functions as a pure el...

Combination of a partial nitritation process and an anaerobic ammonium oxidation process for the treatment of sludge reject water has some general cost-efficient advantages compared to nitrification-denitrification. The integrated process features two-stage autotrophic conversion of ammonium via nitrite to dinitrogen gas with lower demand for oxygen and no external carbon requirement. A nitrify...

Wind-driven surficial oxygen transfer into stationary water bodies has become increasingly important because the fate of many pollutants in these water bodies is strongly influenced by oxygen mass transfer. There are many existing correlations that can be used for predicting wind-driven surficial oxygen transfer; however, the actual prediction has been difficult because there are large variatio...

Hemoglobin in solution augments the rate of steady state diffusion of oxygen. The flux of oxygen exceeds the diffusive flux by an amount, the facilitated flux, which is constant for a given hemoglobin concentration and is invariant with changing oxygen tension. The facilitated flux is inversely proportional to the length of the diffusion path. Facilitation decreases with increasing molecular si...

background: recent reports have suggested that ultrasound-guided embryo transfer (ug-et) might improve pregnancy rates. objective: to determine whether transabdominal ug-et is a useful tool for increasing pregnancy and implantation rates in patients undergoing ivf or icsi. materials and methods: a prospective randomized clinical trial was conducted in 180 patients in order to compare embryo tra...