Adaptive response to oxidative stress in the filamentous fungus Aspergillus niger B1-D

In the present study, we used a recombinant filamentous fungus strain, Aspergillus niger B1-D, as a model system, and investigated the antioxidant defences in this organism. Our findings indicate that pretreatment with low concentrations of H2O2 completely prevents killing by this oxidant at high concentrations. It shows that A. niger adapts to exposure to H2O2 by reducing growth and inducing a number of antioxidant enzyme activities, including superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, of which the induction of catalase is the most pronounced. Moreover the decline of these antioxidant enzymes activities after H2O2 detoxification, coincides with recommencement of growth. Results from monitoring the extracellular H2O2 concentration clearly indicate a very rapid detoxification rate for H2O2 in adapted A. niger cultures. A mathematical model predicts only very low concentrations of intracellular H2O2 accumulating in such cultures. Our results also show that glutathione plays a role in the oxidative defence against H2O2 in A. niger. On addition of H2O2, the intracellular pool of glutathione increases while the redox state of glutathione becomes more oxidized

Economic Effects of Lifting the Spring Load Restriction Policy in Minnesota

Spring load restrictions (SLR) regulate the weight per axle carried by heavy trucks during the spring thaw period. This policy aims to reduce pavement damage caused by heavy vehicles and extend the useful life of roads, but it also imposes costs on the trucking industry due to detouring or increased number of truckloads. Although the policies have been implemented for many years, their resulting economic effect has been unclear. The Minnesota Local Road Research Board (LRRB) and the Minnesota Department of Transportation (Mn/DOT) sponsored a cost/benefit study of spring load restrictions in Minnesota. The study, based on the results of surveys of industry costs, a pavement performance model, and a freight demand model, concludes that the benefits of lifting the existing SLR policy outweigh the additional costs. Roadways operating at 5-tons require additional study; however, current analysis warrants repealing SLR and keeping roadways operating year-round at 9-tons. The cost of additional damage should be recovered from those who benefit from the change in policy.

Skeletal Rigidity of Phylogenetic Trees

Motivated by geometric origami and the straight skeleton construction, we outline a map between spaces of phylogenetic trees and spaces of planar polygons. The limitations of this map is studied through explicit examples, culminating in proving a structural rigidity result.Comment: 17 pages, 12 figure