A forward speed effects study on jet noise from several suppressor nozzles in the NASA/Ames 40- by 80-foot wind tunnel

A test program was conducted in a 40 by 80 foot wind tunnel to evaluate the effect of relative velocity on the jet noise signature of a conical ejector, auxiliary inlet ejector, 32 spokes and 104 tube nozzle with and without an acoustically treated shroud. The freestream velocities in the wind tunnel were varied from 0 to 103.6 m/sec (300 ft/sec) for exhaust jet velocities of 259.1 m/sec (850 ft/sec) to 609.6 m/sec (2000 ft/sec). Reverberation corrections for the wind tunnel were developed and the procedure is explained. In conjunction with wind tunnel testing the nozzles were also evaluated on an outdoor test stand. The wind tunnel microphone arrays were duplicated during the outdoor testing. The data were then extrapolated for comparisons with data measured using a microphone array placed on a 30.5 meter (100 ft) arc. Using these data as a basis, farfield to nearfield arguments are presented with regards to the data measured in the wind tunnel. Finally, comparisons are presented between predictions made using existing methods and the measured data

Cyclobutanone Inhibitors of Diaminopimelate Desuccinylase (DapE) as Potential New Antibiotics

Based on our previous success in using cyclobutanone derivatives as enzyme inhibitors, we have designed and prepared a 37-member library of α-aminocyclobutanone amides and sulfonamides, screened for inhibition of the bacterial enzyme diaminopimelate desuccinylase (DapE), which is a promising antibiotic target, and identified several inhibitors with micromolar inhibitory potency. Molecular docking suggests binding of the deprotonated hydrate of the strained cyclobutanone, and thermal shift analysis with the most potent inhibitor (3y, IC50 = 23.1 µM) enabled determination of a Ki value of 10.2 +/− 0.26 µM and observed two separate Tm values for H. influenzae DapE (HiDapE)

Volume application rate adapted to the canopy size in greenhouse tomato crops

The application rate of plant-protection products is indicated as a concentration or amount of product per area. Greenhouse crops grow swiftly, and an application rate based on a fixed amount of product per hectare can result either in large losses and overdoses when the plants are small or to be insufficient when the plants are fully developed. To solve these problems, the application rates of plant-protection products need to be adapted to the plant mass present in the greenhouse when the spray is applied. Two models were developed to estimate the leaf area based on easily measured geometric data of the vegetation in a greenhouse tomato crop. The model based on the PRV (Plant Row Volume) had that best results. The calculation of the volume application rate from the PRV has resulted in a reduction of more than 30 % of the quantity of plant protection product sprayed, without decreasing yield. The PRV of a greenhouse tomato (Lycopersicon esculentum Mill.) is an easily measured parameter that enables the estimation of the leaf area index and the use of application strategies adapted to the changes in the plant canopy, saving major amounts of plant protection product used, compared to the conventional system

The kinetics of sorption by retarded diffusion into soil aggregate pores

This study investigates time-dependent sorption of pesticides in soil aggregates. We tested if the sorption kinetics of pesticides in soil aggregates can be described by modeling diffusion into aggregates for a range of soils and pesticides. Our hypothesis is that the rate of sorption is negatively related to sorption strength due to retardated diffusion. Natural aggregates of 3 - 5 mm diameter were separated from three soils: a clay, a silty clay loam, and a clay loam. The aggregates werestabilized with alginate gel, and adsorption of azoxystrobin, chlorotoluron, and atrazine was measured in batch experiments with eight equilibration times up to 28 days. Equilibrium sorption appeared to be reached within the 28-day period for each pesticide. An intra-aggregate diffusion model was employed to describe the increase of sorption with time. The model describes diffusion of the dissolved pesticides through the pore space inside the aggregates and sorption on internal surfaces. Sorption could be described by pore diffusion into the aggregates with diffusion coefficients between 0.5 × 10-10 and 1.5 × 10-10 m 2 s-1. The model fits support the theory that pore diffusion is the rate-limiting process for sorption of pesticides in aggregates, although the diffusion coefficients were a factor 3 - 10 smaller than the theoretical diffusion coefficient for diffusion in water. Comparing the results from the different pesticide - soil combinations showed that the extent of nonequilibrium increased with increasing sorption strength. This confirmed that sorption takes longer to reach equilibrium for pesticides and soils with stronger sorption. The differences between the different pesticides and soils were fully accounted for in the model by stronger retardation of the more strongly sorbed pesticides. The results imply that diffusion into aggregates may be the major time-limiting process for sorption of pesticides in structured soils. Commonly performed sorption experiments with sieved soil fail to account for this process. © 2009 American Chemical Society.Peer Reviewe

Reanalysis of experiments to quantify irreversibility of pesticide sorption-desorption in soil

6 pages, 4 figures, 2 tables, 19 references.Previously published research used an isotope-exchange technique to measure irreversibility of pesticide sorption-desorption in soil. Results indicated significant irreversibility (6-51%) in sorption in five pesticide-soil systems measured over 72 h. Here, we propose a three-site model to reanalyze the experimental data. The model adds a slow but reversible binding on nonequilibrium sorption sites in addition to instantaneously reversible sites and irreversible sites. The model was able to match experimental data very closely, but only if irreversible sorption was assumed to be absent. Observed asymmetry in the binding of 12C- and 14C-pesticide was explained on the basis of nonattainment of sorption equilibrium over the study period. Results suggest that irreversible sorption may be less significant than previously considered with important implications for understanding the fate of pesticides applied to soil.EPSRC and Syngenta Ltd are gratefully acknowledged for funding this research.Peer Reviewe

Pesticide sorption and diffusion in natural clay loam aggregates

Pesticide sorption in soils is controlled by time-dependent processes such as diffusion into soil aggregates and microscopic sorbent particles. This study examines the rate-controlling step for time-dependent sorption in clay loam aggregates. Aggregates (5 mm) were stabilized with alginate, and adsorption of azoxystrobin, chlorotoluron, and cyanazine was measured in batch systems equilibrated for periods between 1 h and 7 days. Stepwise desorption was measured at 1- or 3-day intervals following 1 or 7 days of adsorption. Time-dependent adsorption was also measured on dispersed soil. Results were interpreted using process-based modeling. Adsorption on dispersed soil was described by intraparticle sorption and diffusion. Adsorption in the aggregates was much less than in suspension, suggesting that part of the sorption capacity of the dispersed soil was not available within the aggregates (50%). Adsorption and desorption were reversible and could be described by pore diffusion into the aggregate with effective diffusion coefficients between 0.5 × 10-10 and 1 × 10-10 m2 s-1, a factor 3−6 slower than estimated theoretically. Intraparticle diffusion did not seem to contribute to sorption in the aggregates at this time scale. Apparent hysteresis was explained by nonattainment of equilibrium during the adsorption and desorption steps

Acceptability of inversely-modelled parameters for non-equilibrium sorption of pesticides in soil

Simulation of the increase of sorption in time is one of the options in higher tiers of pesticide regulatory leaching assessments to obtain more realistic leaching estimates. Therefore, accurate estimates of non-equilibrium sorption parameters are required as input for the pesticide leaching scenarios. Usually, non-equilibrium sorption is described with a two-site equilibrium/non-equilibrium model in which the non-equilibrium sorption is described with two parameters (i.e. the desorption rate coefficient of the non-equilibrium site and the Freundlich sorption coefficient of this site). Estimates of these parameters can be obtained with inverse modelling techniques. At the moment, there is little understanding about whether the confidence intervals provided by inverse modelling can be used as measure of the likely accuracy (i.e. how close the estimated value is to the true value) of these estimates. We set up a semi-global inverse modelling exercise for a large number of parameter sets (Le. different pesticides) using simulated datasets. Inverse modelling of non-equilibrium parameters demonstrated decreasing accuracy of the estimates for decreasing values of the non-equilibrium sorption parameters and the equilibrium sorption coefficient. Furthermore, we found a relationship between the accuracy of a parameter estimate and its CV (coefficient of variation) provided by the inverse modelling technique. Using this relationship we calculated the likelihood of rightly or wrongly accepting or rejecting a parameter estimate as a function of this CV. We recommend to use this likelihood as the basis of communication with decision makers on how to decide on accepting or rejecting parameter estimates. (C) 2013 Elsevier Ltd. All rights reserved

Acceptability of inversely-modelled parameters for non-equilibrium sorption of pesticides in soil

Simulation of the increase of sorption in time is one of the options in higher tiers of pesticide regulatory leaching assessments to obtain more realistic leaching estimates. Therefore, accurate estimates of non-equilibrium sorption parameters are required as input for the pesticide leaching scenarios. Usually, non-equilibrium sorption is described with a two-site equilibrium/non-equilibrium model in which the non-equilibrium sorption is described with two parameters (i.e. the desorption rate coefficient of the non-equilibrium site and the Freundlich sorption coefficient of this site). Estimates of these parameters can be obtained with inverse modelling techniques. At the moment, there is little understanding about whether the confidence intervals provided by inverse modelling can be used as measure of the likely accuracy (i.e. how close the estimated value is to the true value) of these estimates. We set up a semi-global inverse modelling exercise for a large number of parameter sets (Le. different pesticides) using simulated datasets. Inverse modelling of non-equilibrium parameters demonstrated decreasing accuracy of the estimates for decreasing values of the non-equilibrium sorption parameters and the equilibrium sorption coefficient. Furthermore, we found a relationship between the accuracy of a parameter estimate and its CV (coefficient of variation) provided by the inverse modelling technique. Using this relationship we calculated the likelihood of rightly or wrongly accepting or rejecting a parameter estimate as a function of this CV. We recommend to use this likelihood as the basis of communication with decision makers on how to decide on accepting or rejecting parameter estimates. (C) 2013 Elsevier Ltd. All rights reserved