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Endogenous peroxide levels in pear fruit (Pyrus communis) were measured using a titanium assay method, and were found to increase during senescence in both Bartlett and Bosc varieties. Application of glycolic acid or xanthine, serving as substrates for the formation of H202, increased the peroxide content of the tissue and accelerated the onset of ripening, as measured by increased softening and ethylene evolution. Application of ethylene also induced increased peroxide levels. Ripening processes were similarly promoted when peroxides were conserved by inhibiting the activity of catalase with hydroxylamine or potassium cyanide. By comparison, the inhibition of glycolate oxidase with alphahydroxy-2-pyridinemethanesulfonic add decreased the peroxide content of the tissue and delayed the onset of ripening. These results indicate that the onset of ripening correlates with the peroxide content of fruit tissues as occurring under normal conditions or as influenced by the treatments. Hydrogen peroxide may be involved in oxidative processes required in the initiation and the promotion of ripening.Fruit ripening is viewed as an oxidative phenomenon (3, 5), as indicated by results suggesting the decline in sulfhydryl gradients during ripening (7) and the acceleration of ripening processes by the application of high 02 tensions (2, 5, 10). We hypothesize that the effects of 02 reflect, in part, the utilization of 02 for the formation of peroxides for the following reasons.a. The free radical theory of aging proposes that progressive aging results from the random and cumulative attack by oxygen radicals (partially reduced oxygen forms) (16). However, the view of ripening as a regulated senescence phenomenon (13) requires a controlled turnover of radicals. Hydrogen peroxide is a stable partially reduced oxygen form (15), and its turnover is characteristically mediated by enzyme action. For that reason, we envision that H202 can be integrated into the regulated metabolic events occurring during senescence in fruit.b. The acceleration of ripening by high 02 tensions (6, 10) is consistent with the high Km(02) of some peroxide-forming enzyme systems (26).c. The onset of senescence in some systems is accompanied by an increase in the activity of peroxide-utilizing enzymes (4) and a decrease in peroxide-destroying enzymes (17).In the present work, we found that changes in peroxides, as The treated fruit were kept at 21 C at standard conditions and ventilated with air at a rate of 400 ml/min. Ethylene was scrubbed from the ventilating air with Purafil (H. E. Burrough and Assoc., Chamblee, Ga.).Fruits were sampled at intervals for measuring the rate of softening, ethylene evolution, and peroxide levels. Softening and peroxides were measured at 0, 2, 4, 6, and 8 days following infiltration. Ethylene evolution was measured daily for the duration of the experiment. Samples of 10 fruit were used for each of the above determinations. All determinations were run in duplicate. Ethylene was collected from the ventilating gases accor...

PERFORMANCE MEASURES FOR TRAFFIC SIGNAL SYSTEMS:AN OUTCOME-ORIENTED APPROACH This monograph is a synthesis of research carried out on traffic signal performance measures based on highresolution controller event data, assembled into a methodology for performance evaluation of traffic signal systems. High-resolution data consist of a log of discrete events such as changes in detector and signal phase states. A discussion is provided on the collection and management of the signal event data and on the necessary infrastructure to collect these data. A portfolio of performance measures is then presented, focusing on several different topics under the umbrella of traffic signal systems operation. System maintenance and asset management is one focus. Another focus is signal operations, considered from the perspectives of vehicle capacity allocation and vehicle progression. Performance measures are also presented for nonvehicle modes, including pedestrians, and modes that require signal preemption and priority features. Finally, the use of travel time data is demonstrated for evaluating system operations and assessing the impact of signal retiming activities.

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This work describes the in situ synthesis of oligonucleotide arrays on glass surfaces. These arrays are composed of features defined and separated by differential surface tension (surface tension arrays). Specifically, photolithographic methods were used to create a series of spatially addressable, circular features containing an amino-terminated organosilane coupled to the glass through a siloxane linkage. Each feature is bounded by a perfluorosilanated surface. The differences in surface energies between the features and surrounding zones allow for chemical reactions to be readily localized within a defined site. The aminosilanation process was analyzed using contact angle, X-ray photoelectron spectroscopy (XPS), and time-of-flight/secondary ion mass spectroscopy (TOF-SIMS). The efficiency of phosphoramidite-based oligonucleotide synthesis on these surface tension arrays was measured by two methods. One method, termed step-yields-by-hybridization, indicates an average synthesis efficiency for all four (A,G,C,T) bases of 99.9 +/- 1.1%. Step yields measured for the individual amidite bases showed efficiencies of 98.8% (dT), 98.0% (dA), 97.0% (dC), and 97.6% (dG). The second method for determining the amidite coupling efficiencies was by capillary electrophoresis (CE) analysis. Homopolymers of dT (40- and 60mer), dA (40mer), and dC (40mer) were synthesized on an NH(4)OH labile linkage. After cleavage, the products were analyzed by CE. Synthesis efficiencies were calculated by comparison of the full-length product peak with the failure peaks. The calculated coupling efficiencies were 98.8% (dT), 96.8% (dA), and 96.7% (dC).