We analyze a comprehensive model for multi-class job scheduling accounting for user abandonment, with the objective of minimizing the total discounted or time-average sum of linear holding costs and abandonment penalties. We assume geometric service times and Bernoulli abandonment probabilities. We solve analytically the case in which there are 1 or 2 users in the system to obtain an optimal index rule. For the case with more users we use recent advances from the restless bandits literature to obtain a new simple index rule, denoted by AJN, which we propose to use also in the system with arrivals. In the problem without abandonment, the proposed rule recovers the cµ-rule which is well-known to be optimal both without and with arrivals. Under certain conditions, our rule is equivalent to the cµ/θ-rule, which was recently proposed and shown to be asymptotically optimal in a multi-server system with overload conditions. We present results of an extensive computational study that suggest that our rule is almost always superior or equivalent to other rules proposed in the literature, and is often optimal.
Summary The morbidity and mortality of the cardiovascular diseases is high in the developed countries. The lifestyle changes are capable to decrease it by 50%. The aim of the present study was to measure the parameters of some risk factors before and after a one-week NEW START rehabilitative retreat. 1,349 volunteers, 320 men, 1,029 woman, mean age 51±14.5 (SD) years participated in 30 rehabilitative retreats from 1999–2006 in the Czech Republic, using a low-fat, low-energy, lacto-ovo-vegetarian diet and exercise, in a stress-free environment. Body weight, height, BMI, blood pressure, heart rate, serum cholesterol and blood glucose were measured. Body weight decreased in 1,223 measured persons from 71.2±14.38 (SD) to 70.6±14.02 kg (p<0.0001), BMI (1,046 measured persons) from 25.1±4.60 (SD) to 24.8±4.49 (SD) kg/m2 (p<0.0001), systolic blood pressure (1,218 persons) from 129.8±23.02 (SD) to 123.8±21.52 (SD) mmHg (p<0.0001), diastolic blood pressure (1,210 persons) from 79.8±12.7 (SD) to 77.5±11.6 (SD) mmHg (p<0.0001), serum cholesterol (998 persons) from 4.86±0.95 (SD) to 4.32±0.77 (SD) mmol (p<0.0001), blood glucose (544 persons) from 4.31±1.59 (SD) to 3.88±1.33 (SD) mmol (p<0.0001). Heart rate was not significantly decreased. The parameters were lower in lacto-ovo vegetarians and Seventh-day Adventists than in controls who never observed the diet and avail the lifestyle programs. The parameters were nonsignificantly changed one year after finishing the retreat in the sample of 68 persons showing the positive effect of retreats. Our results showed, that the intake of a low-fat, low-energy diet, over the course of one week in a stress-free environment, had positive impact on the risk factors of cardiovascular diseases.
The thermal degradation of industrially manufactured polymers based on polyethylene, polypropylene and polystyrene was studied. The pyrolysis was carried out in a tubular quartz pyrolyzer at 510°C and the products were separated on capillary columns coated with squalane and OV-17 and were identified on the basis of their retention indices.
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