Comparative study of ferredoxin-linked and oxygen-metabolizing enzymes of trichomonads

1. The activities of pyruvate:methyl viologen oxidoreductase (EC 1.2.7.1), hydrogenase (EC 1.18.99.1), NADH:methyl viologen oxidoreductase (EC 1.6.99.3), NADPH:methyl viologen oxidoreductase (EC 1.6.99.1), NADH oxidase (EC 1.6.99.3) and NADPH oxidase (EC 1.6.99.1) were determined for Trichomonas vaginalis, Tritrichomonas foetus and Trichomitus batrachorum. 2. The three trichomonad species were found to differ significantly, especially with respect to NADH oxidase and NADH:methyl viologen oxidoreductase activities. 3. The species differences in ferredoxin-linked and oxygen-metabolising enzymes may be related to the ways in which the trichomonads are adapted for growth in their respective hosts.     

PAFit: A Statistical Method for Measuring Preferential Attachment in Temporal Complex Networks

Preferential attachment is a stochastic process that has been proposed to explain certain topological features characteristic of complex networks from diverse domains. The systematic investigation of preferential attachment is an important area of research in network science, not only for the theoretical matter of verifying whether this hypothesized process is operative in real-world networks, but also for the practical insights that follow from knowledge of its functional form. Here we describe a maximum likelihood based estimation method for the measurement of preferential attachment in temporal complex networks. We call the method PAFit, and implement it in an R package of the same name. PAFit constitutes an advance over previous methods primarily because we based it on a nonparametric statistical framework that enables attachment kernel estimation free of any assumptions about its functional form. We show this results in PAFit outperforming the popular methods of Jeong and Newman in Monte Carlo simulations. What is more, we found that the application of PAFit to a publically available Flickr social network dataset yielded clear evidence for a deviation of the attachment kernel from the popularly assumed log-linear form. Independent of our main work, we provide a correction to a consequential error in Newman’s original method which had evidently gone unnoticed since its publication over a decade ago.