This paper presents an analysis of National Airspace System (NAS) delay. An interacting set of models called the Airspace Concept Evaluation System (ACES) was used to simulate one day of NAS-wide air traffic. A total of 36 simulations were run. They included nine different airport capacity conditions across the NAS and four levels of NAS-wide demand. The analysis of delay results for these 36 simulations shows that delay increases quadratically with increased demand. The delay versus capacity curves have linear trends. However, nonlinearities within these curves expand with increased demand. These nonlinearities suggest that additional factors such as regional concentrations of airports in low capacity conditions due to regional weather do have a significant influence on the results. This analysis is an important first step in exploring and understanding the intricacies of the NAS so that further efforts can be made to improve it.
A rapid, quantitative, inexpensive, efficient method was developed to determine deoxynivalenol (DON) in wheat, barley, corn, wheat middlings, wheat flour, bran, malted barley, and oats. Samples are ground and extracted with acetonitrile-water (86 + 14). A portion of the extract is cleaned up by passage through a MycoSep No. 225 column, evaporated to dryness, and derivatized with zirconyl nitrate and ethylenediamine in methanol. The resulting fluorescent derivative of DON is identified and quantitated with a calibrated fluorometer containing a broad wavelength pulsed xenon light source. This method quantitated DON concentrations from 0.5 to 50 ppm without dilution and was linear when applied to samples of noncontaminated wheat spiked at 0.5, 5, 10, 25, and 50 μg DON/g. Correlation coefficients of the method with LC for multiple analyses (n ≥ 14 for each commodity) applied to wheat, corn, barley, wheat flour, and wheat middlings were 0.99, 0.99, 0.99, 0.93, and 0.98, respectively. Individual analyses were conducted in < 30 min, and 24 samples were analyzed in 2 h.
A rapid, quantitative, inexpensive, and efficient method was developed to determine aflatoxins in corn, corn meal, popcorn, rice, wheat, cottonseed, and peanuts. Samples are ground and extracted with methanol–water (80 + 20). A portion of the extract is cleaned up by passage through a solid-phase separatory column, 500 μL purified extract is derivatized with a bromine reagent, and fluorescence of the solution is immediately quantified with a calibrated fluorometer containing a broad wavelength pulsed xenon light source. This method can quantify aflatoxin from 5 to 5000 ppb without dilution and was linear when applied to samples of noncontaminated corn spiked at 0 to 5000 μg aflatoxin B1/g. Correlation coefficients of the method with LC for multiple analyses for corn (n = 34), cottonseed (n = 32), and peanuts (n = 11) were 0.999, 0.995, and 0.980, respectively. Individual analyses may be conducted in less than 5 min, and grouping of samples is unnecessary. The sensitivity of the method for corn is 5 ppb and the fluorometer, under the operating conditions, has a limit of detection of 0.6 ng aflatoxin B1.
The Holaday-Velasco method and a modified Holaday method have been compared. The former method combines the speed and simplicity of the Holaday extraction and cleanup with the sensitivity of the minicolumn originally described by Velasco. The combination method has been approved by the AOAC and the AACC for determining aflatoxin in corn. The Holaday method was modified by substituting toluene for benzene in the solvent partition, and methylene chloride for chloroform in the minicolumn development to eliminate use of hazardous solvents. The neutral alumina in the Holaday minicolumn was changed from activity V to activity III to provide a more stable column. At aflatoxin levels in raw peanuts of 13-20 ng/g, the presence of aflatoxin was missed by the modified Holaday method in 4 analyses (3 laboratories) of 42 reported. There were no misses in this contamination range by the Holaday-Velasco method. There were no misses by either method with samples containing >20 ng total anatoxins/g. Analysis of uncontaminated raw peanuts by the modified Holaday method resulted in 2 false positives of 14 reports; the Holaday-Velasco method produced no false positive reports from 15 analyses of uncontaminated peanuts. The Holaday-Velasco method was adopted official first action for peanuts.
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