No abstract

A concrete-filled fiber-reinforced polymer-steel composite tube column consisting of inner concrete and an exterior fiber-reinforced polymer-steel tube was studied in this paper. A total of 22 specimens were tested under axial compression to investigate the performance of the circular concrete-filled fiber-reinforced polymer-steel composite tube columns. The main experimental parameters were the thickness of the steel tube, the number of fiber-reinforced polymer layers, the type of fiber-reinforced polymer, and the hybridization of fiber-reinforced polymer, in which basalt-fiber-reinforced polymer was used to manufacture concrete-filled fiber-reinforced polymer-steel composite tube columns and was compared with carbon fiber-reinforced polymer. The test results showed that local buckling of the steel tube can be suppressed and even prevented effectively with fiber-reinforced polymer strengthening, and the compressive strength of the concrete-filled fiber-reinforced polymer-steel composite tube specimens is enhanced by the external fiber-reinforced polymer confinement compared with that of the concrete-filled steel tube specimens. With the increase in the number of fiber-reinforced polymer layers or with a larger ultimate tensile strain in the fiberreinforced polymer, the peak axial strain corresponding to fiber-reinforced polymer fracture increases accordingly. A new model that considers composite action was developed for strength prediction of concrete-filled fiber-reinforced polymer-steel composite tube columns, and the analytical results agree well with the experimental results.

No abstract

No abstract

Fungal denitrification is claimed to produce nonnegligible amounts of N 2 O in soils, but few tested species have shown significant activity. We hypothesized that denitrifying fungi would be found among those with assimilatory nitrate reductase, and tested 20 such batch cultures for their respiratory metabolism, including two positive controls, Fusarium oxysporum and Fusarium lichenicola, throughout the transition from oxic to anoxic conditions in media supplemented with NO − 2 . Enzymatic reduction of NO − 2 (NIR) and NO (NOR) was assessed by correcting measured NO-and N 2 O-kinetics for abiotic NO-and N 2 O-production (sterile controls). Significant anaerobic respiration was only confirmed for the positive controls and for two of three Fusarium solani cultures. The NO kinetics in six cultures showed NIR but not NOR activity, observed through the accumulation of NO. Others had NOR but not NIR activity, thus reducing abiotically produced NO to N 2 O. The presence of candidate genes (nirK and p450nor) was confirmed in the positive controls, but not in some of the NO or N 2 O accumulating cultures. Based on our results, we conclude that only the Fusarium cultures were able to sustain anaerobic respiration and produced low amounts of N 2 O as a response to an abiotic NO production from the medium.