Selecting job scheduling algorithms: beta distribution model for service times

Over a decade ago, Leonard Kleinrock developed a model for selecting best–performance scheduling algorithms for computer systems. The M/G/I queuing system used by Kleinrock requires that an estimate of the service–time probability distribution function (p.d.f.) be made in order to derive results. While methods of fitting service–time data to p.d.f.s are available, this paper argues that the use of a generalized beta distribution of the second type (GB2) in concert with the Kleinrock model reduces the need to estimate alternative models and avoids the consequences of arbitrarily imposing invalid assumptions on the data.     

Moving Boundary Electrophoresis of Food Stabilizers

SUMMARY— The electrophoretic characteristics of locust bean gum, guar gum, arabic gum, carboxymethylcellulose, K- and h-carrageenan, alginate and the non-dialyzable fraction of corn syrup solids were studied by moving boundary electrophoresis. The physical properties of these colloids require the use of modified techniques in order to eliminate boundary disturbances which otherwise might be interpreted as heterogeneity of composition.
A high degree of homogeneity was observed for carboxymethylcellulose, arabic gum, alginate and X-carrageenan. In contrast, K-carrageenan was composed of a mixture of migrating components. The colloidal fractions of guar gum, locust bean gum, and corn syrup solids did not migrate in the electrical field.
Mixtures of carboxymethylcellulose with guar gum or gum arabic could be separated at pH 7. Mixtures of carboxymethylcellulose with carrageenan could be effectively separated at pH 2. Electrophoretic separation at 23°C of different stabilizer mixtures was unsatisfactory and the patterns showed evidence of interactions.     

RADIO FREQUENCY PULSE APPLICATION FOR HEATING UNIFORMITY IN POSTHARVEST CODLING MOTH (LEPIDOPTERA: TORTRICIDAE) CONTROL OF FRESH APPLES (MALUS DOMESTICA BORKH.)

A radio frequency (RF) treatment, with a pulse mode to increase heating uniformity, was examined as a potential quarantine treatment against fifth instars of the codling moth, Cydia pomonella L. (Lepidoptera: Tortricidae), in apples, Malus sylvestris L. var. domestica (Borkh.) Mansf., intended for export to Japan. Apples were exposed in water baths to 27.12‐MHz RF energy at 12 kW with a pulse mode of 30 s‐on/30 s‐off for different durations. The temperature uniformity was determined by measurements at 12 sites evenly spaced at two depths in the fruit. The most promising exposure time was 29 min. The efficacy of the treatment with the pulse mode was examined against the codling moth larvae by using exposures between 27 and 30 min and up to 30 min of holding time in bath after treatment. The treatment that killed all larvae with the least amount of energy was the 29‐min exposure with 50‐min holding time. This treatment was appraised for fruit quality in “Delicious” apples. Some injury was observed when treated fruits were removed from 1C storage after 30 days. When these fruits were held at 25C for 1 week, all were too damaged to evaluate for fruit quality. Although pulse mode increased heating uniformity in the fruit, the thermal requirements to control codling moth larvae may exceed the injury threshold of the fruits.     

HOT WATER TO CONTROL CODLING MOTH IN SWEET CHERRIES: EFFICACY AND QUALITY

Quarantine regulations require domestic cherries exported to Japan be treated to control for codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae). The current procedure, methyl bromide fumigation, uses a restricted chemical, reduces fruit quality, and involves health, safety and environmental concerns. Single and double hot water dips were evaluated using fresh ‘Bing’ and ‘Sweetheart’ sweet cherries from Washington state as a potential replacement. The double dip procedure had a pretreatment bath at 40C for 5 min. For both procedures, submersions in heated water from 48 to 55C for 2–14 min were examined for treatment efficacy against third‐instar codling moth and fruit quality. Although a 100% mortality response was found for each temperature and procedure, the submersion durations significantly damaged fruit and stem parameters for both cultivars. Thus, hot water dips are not feasible for Pacific Northwest cherries at this time.     

OSCILLATORY PROBE RHEOMETRY AS A TOOL FOR DETERMINING THE RHEOLOGICAL PROPERTIES OF STARCH-WATER SYSTEMS 1

An oscillatory probe rheometer was effective at measuring the viscosity of starch pastes and the viscoelastic properties of starch gels. Because low shear strains were applied, the integrity of the gel was not disrupted during the testing. As the starch concentration of the systems increased, the complex modulus (G*) and storage modulus (G′) increased. At 20°C, the strength of the resulting gels, as measured by log G′, was a linear function of starch concentration. Loss tangent values (G″/G′) could be used to determine the approximate temperature at which the sol became a gel. As the starch concentration of the systems increased, the temperature of the sol to gel transformation increased from approximately 35°C (5% starch) to 60°C (10% starch).     

An automated and highly efficient method for counting and measuring fluorescent foci in rod‐shaped bacteria

Direct measurements of cells from photo micrographs are becoming increasingly used when investigating the position and/or distribution of chromosomal loci in bacteria. In general, these measurements have been done manually, and without clear definition of how they are made. Here we present a procedure for standardizing the measurement of cell properties from phase contrast images. Furthermore, we present a program using these standardized methods that can measure the intracellular positions of fluorescent foci in bacterial cells faster and with more precision than manual measurement.     

CHEMICAL AND SENSORY QUALITY OF BROCCOLI (BRASSICA OLERACEA L. VAR ITALICA)

Five cultivars of broccoli (Brassica oleracea L. var. italica) were analyzed for individual glucosinolates, S-methylcysteine sulfoxide (SMCSO), aroma volatiles and sensory quality. Total glucosinolate content ranged from 47 to 93 μmol μmol·g dry weight¹, and SMCSO ranged from 22 to 57 μmol μmol·g dry weight¹. A total of 11 glucosinolates were identified in the broccoli cultivars. The major glucosinolates were: progoitrin, glucoiberin, glucoraphanin, glucobrassicin and neo-glucobrassicin and they accounted for more than 95% of the total content. Glucoiberin was only found in appreciable amounts in purple-headed broccoli. Pentanol, pentanal, hexanal, heptanal and nonanal were the most abundant higher boiling volatiles isolated from cooked broccoli using dynamic headspace trapping on Porapak and solvent desorption with diethyl ether. Sensory analysis by a trained panel showed that scores for cooked vegetable odor (‘hay’ and ‘green peapod’) were significantly different between cultivars. In contrast, scores related to Brassica odor (‘cauliflower’ and ‘mustard’) were not significantly different. The content of individual glucosinolates, SMCSO and higher boiling volatiles in the cultivars is discussed in relation to the sensory quality of the cooked product.