SynopsisPropylene and ethylene polymerization in liquid and gas media are described by a multigrain particle model. Intraparticle heat and mass transfer effects are investigated for a range of catalyst activities. For slurry polymerization, intraparticle mass transfer effects may be significant at both the macroparticle and microparticle level; however, for normal gas phase polymerization, microparticle mass transfer effects appear more likely to be important. Intraparticle temperature gradients would appear to be negligible under most normal operating conditions.

Ca2+ handling in excitation-contraction coupling requires considerable O2 consumption (Vo 2) in cardiac contraction. We have developed an integrative method to quantify total Ca2+ handling in normal hearts. However, its direct application to failing hearts, where futile Ca2+ cycling via the Ca2+-leaky sarcoplasmic reticulum (SR) required an increased Ca2+handling Vo 2, was not legitimate. To quantify total Ca2+ handling even in such failing hearts, we combined futile Ca2+ cycling with Ca2+ handling Vo 2 and the internal Ca2+ recirculation fraction via the SR. We applied this method to the canine heart mechanoenergetics before and after intracoronary ryanodine at nanomolar concentrations. We found that total Ca2+ handling per beat was halved after the ryanodine treatment from ∼60 μmol/kg left ventricle before ryanodine. We also found that futile Ca2+ cycling via the SR increased to >1 cycle/beat after ryanodine from presumably zero before ryanodine. These results support the applicability of the present method to the failing hearts with futile Ca2+ cycling via the SR.

SynopsisPropylene and ethylene polymerization in liquid and gas media are described by a multigrain particle model. External boundary layer heat and mass transfer effects are investigated for various catalysts and operating conditions. For high-activity catalysts used in slurry, external film mass transfer effects may be significant. For gas-phase polymerization of propylene or ethylene, the model predicts significant particle overheating at short times, which may explain the particle sticking and agglomeration problems sometimes observed in industrial reactors.

The main objective of these experiments was to study the effect of three levels of N fertilizer on the quantity and quality of late‐summer and autumn‐produced ‘Kenblue’ Kentucky bluegrass, Poa pratensis L., and ‘Kentucky 31’ tall fescue, Festuca arundinacea Schreb., forage left standing in the field during fall and winter. Information is needed on the extent to which stockpiled pasturage can serve as a reliable cheap source of feed for beef brood cows, dry dairy cows, and growing stock. Factorial experiments were conducted for three successive years. The trials involved two grasses, three N levels, and six stockpiling periods. Nitrogen fertilizer was applied in mid‐August, and the standing stockpiled grass crops were harvested in early October, November, December, February, and March. Regrowth herbage was harvested in May, July, and mid‐August, after which the experiments were terminated. Production from 15 Aug. to I Dec. on plots receiving 0, 50, and 100 kg/ha of N was 800, 1,800, and 2,300 kg DM/ha for Kentucky bluegrass and 1,900; 3,100; and 4,400 for tall fescue, respectively. At the high level of N tall fescue continued to accumulate dry matter at a significant level (17.7 kg/ha per day) during November. From December to March accumulated dry matter of the standing crops decreased, apparently owing to unfavorable growing conditions, weathering, and leaf drop. Swards of both grasses were high enough in crude protein and P throughout the winter to meet the requirements of non‐lactating beef brood cows. Generally, tall fescue contained more total sugar in late autumn and early winter than did bluegrass. Sward sugars of both grasses declined sharply as the winter advanced. Phosphorus concentration was high in October, November, and early December, but declined markedly during late winter. Estimated nutritive value indices of the standing forage decreased as the autumn and winter advanced. Fall and winter harvesting of stockpiled forage resulted in little or no yield reduction of the spring crop.

We tested our hypothesis that the O2 wasting of Ca2+ handling in the excitation-contraction (E-C) coupling in ryanodine-treated failing hearts could be reflected by a decrease in the internal Ca2+ recirculation fraction (RF). We have reported, using canine excised cross-circulated hearts, that intracoronary ryanodine (40 nmol/l blood) halved left ventricular contractility without decreasing myocardial O2 consumption for the E-C coupling. We previously suspected this mechanoenergetic state to manifest energy wasting of Ca2+ handling due to ryanodine causing leakage of Ca2+ from the sarcoplasmic reticulum. To test this hypothesis, we analyzed all the sporadic spontaneous cases of postextrasystolic potentiation (PESP) obtained during the ryanodine experiments. We calculated RF from the beat constant of the exponential decay component of not only the monotonic type but also the transient alternans type of PESP. Results showed that ryanodine significantly decreased the beat constant in both types of PESP from about 2 to 1.5 beats and hence RF from 0.6 to 0.5 on the average, supporting the hypothesis. This organ-level systems approach to Ca2+ handling using transient alternans PESP as well as monotonic PESP may help obtain better insights into the mechanoenergetics of failing hearts.