The effect of sodium chloride on the two-step kinetics of the nitrifying process.

Sodium chloride affects the transformation rate of several compounds in bioreactors. Most authors report a decrease in microorganism activity at increasing salt concentrations. In this work, a kinetic model that relates sodium chloride concentration with the rates of each step of the nitrification process is proposed; thus, the effect of sodium chloride concentration (0 to 60 g/L) on the nitritation and nitratation rates was separately studied. To carry out the independent study of each step, a combination of the respirometric method with sodium azide, an inhibitor of the nitratation step, was performed. The dot-blot hybridization technique with 16S rRNA-targeted probes was used to determine the ammonia-oxidizing and nitrite-oxidizing bacterial fraction, then it was possible to relate the culture's function with its biological composition. Rates of both steps were linearly reduced at increasing salt concentrations: the nitratation rate was more affected than the nitritation rate. Simulations carried out in a nitrifying sequencing batch reactor indicate that nitrite might accumulate at high salt concentrations. Sodium chloride exerts a reversible inhibition on ammonia oxidation and nitrite oxidation.     

Influence of daytime running lamps on visual reaction time of pedestrians when detecting turn indicators

Introduction

This article describes one experiment that studied the influence of Daytime Running Lamps (DRL) on pedestrian detection of turn indicators.

Method

An experimental device including one DRL and one turn indicator was used in order to determine Visual Reaction Times (VRT) of 148 observers in different situations involving turn indicator activation. Such situations were combinations of three main variables: color of DRL, separation between DRL and Turn Indicator, and observation angle.

Results

Significant changes in VRT were found depending on the configurations above, especially the observation angle and the color of DRL. This second result demonstrates that amber DRLs inhibit the detection of Turn Indicators.

Impact on industry

One of the main targets of this paper is to recommend that carmakers introduce only white DRLs on new vehicles. We also intend to advise regulatory bodies working on automotive regulation about the consequences of allowing amber DRLs and also about the danger of introducing constrains on the distance between DRL and Turn Indicator without further experimental evidences.