Melting,regelling, and remelting of poly(vinyl alcohol) hydrogels

The melting behaviors of hydrogels of syndiotacticity-rich poly(vinyl alcohol) (s-PVA), derived from vinyl trifluoroacetate, during heating at various rates of rising temperature were examined. For the hydrogels with the polymer concentrations above 5 g/dL chilled at the temperatures of 0 ∼ 40°C, the melting temperature increased with a decrease in the rate of rising temperature. During rising temperature at lower rates, the phase separation with spinodal decomposition progressed even in gels and the microcrystals, which play an important role as the junction points, propagated to thermally more stable size. The small, broad exothermic peaks during rising temperature of s-PVA hydrogels in DSC thermograms was found at the temperature ranges of 10 ∼ 30 and 45 ∼ 60°C. © 1996 John Wiley & Sons, Inc.     

A numerical simulation of pulverized coal combustion employing a tabulated-devolatilization-process model (TDP model)

A new coal devolatilization model employing a tabulated-devolatilization-process model (TDP model) is developed, and its validity is investigated by performing a numerical simulation of a pulverized coal combustion field formed by an industrial low-NO_x burner in a 100 kg-coal/h test furnace. The predicted characteristics of the pulverized coal combustion field obtained from the simulation employing the TDP model are compared with those employing the conventional devolatilization model, those employing the two competing reaction rate model, and the experiments. The results show that drastic differences in the gas flow patterns and coal particle behavior appear between simulations. In particular, the recirculation flow behavior is strongly affected by the difference in the coal devolatilization model because of the difference in the volatile matter evolution rate. The TDP model captures the observed behavior of the coal particles in the experiment better than the other models. Although it is considered that by adjusting the devolatilization parameters the prediction similar to the TDP model is also possible by the other models, appropriate devolatilization parameters are automatically set to particles depending on the particle heating rate without trial–error method by employing the TDP model.     

Amelioration of chronic inflammation by ingestion of elemental diet in a rat model of granulomatous enteritis

The beneficial effect of elemental diet (ED) in the treatment of Crohn's disease is reported, although the exact mechanism for this remains to be elucidated. In this study the effects of ED on intestinal inflammation were investigated in a rat model of granulomatous enteritis. Intestinal inflammation was induced by a single intramural injection of peptidoglycan-polysaccharide (PG-PS) from group A streptococci into rat ileal Peyer's patches. A single injection of PG-PS in combination with fibrinogen, which retains PG-PS at the injection site, induced severe granulomatous inflammation associated with mucosal ulceration. Immunohistochemical study and immunocytochemical analysis of the cell suspension from Peyer's patches showed accumulation of macrophages and an increase in interleukin-2 receptor (IL-2R)-positive T cells after PG-PS treatment. Chemiluminescence (ChL) activity and nitrite and nitrate (NOx) levels in the mesenteric venous blood as well as Ca(2+)-independent (inducible) nitric oxide synthase (NOS) activity in Peyer's patches were increased by PG-PS treatment. In rats fed with ED, both macroscopic and histologic damage scores were significantly decreased as compared with those in rats fed with the control diet. ED inhibited the increase in the numbers of macrophages and IL-2R-positive T cells in Peyer's patches. Increased ChL activity, NOx levels, and Ca(2+)-independent NOS activity were also reduced significantly by feeding with ED. These data suggest that ED reduces progression of PG-PS-induced chronic intestinal inflammation by modulating activation of T cells, production of nitric oxide, and generation of oxygen free radicals.     

Activities of oxygen in liquid Bi-Pb and Bi-Sb alloys

The activity coefficient of oxygen, γ_o, in liquid Bi-Pb and Bi-Sb alloys at 1073 K has been measured over the entire composition range utilizing a modified coulometric titration method with the electrochemical cell: O in liquid Bi-Pb or Bi-Sb alloys/ZrO₂(+CaO)/Air, Pt. The measured In y0 values for both systems, plotted in terms of alloy composition, lie on upwardly concave curves. This behavior is significantly different from what is predicted by the quasi-chemical equations. The models of Wagner and of Blanderet al., which involve one adjustable parameter,h, give a satisfactory representation of the data. YOSHIKAZU KUROSE, formerly a Graduate Student, Osaka University, Osaka, 565, Japan     

Efficient rate-controlled bulk data transfer using multiple multicast Groups

Controlling the rate of bulk data multicast to a large number of receivers is difficult, due to the heterogeneity among the end systems' capabilities and their available network bandwidth. If the data transfer rate is too high, some receivers will lose data, and retransmissions will be required. If the data transfer rate is too slow, an inordinate amount of time will be required to transfer the data. In this paper, we examine an approach toward rate-controlled multicast of bulk data in which the sender uses multiple multicast groups to transmit data at different rates to different subgroups of receivers. We present simple algorithms for determining the transmission rate associated with each multicast channel, based on static resource constraints, e.g., network bandwidth bottlenecks. Transmission rates are chosen so as to minimize the average time needed to transfer data to all receivers. Analysis and simulation are used to show that our policies for rate selection perform well for large and diverse receiver groups and make efficient use of network bandwidth. Moreover, we find that only a small number of multicast groups are needed to reap most of the possible performance benefits.     

Asynchronous migration for parallel genetic programming on a computer cluster with multi-core processors

An island model is a typical implementation of genetic programming on parallel computers with distributed memory. The island model has a migration facility that sends/receives some individuals in an island to/from another island to maintain diversity. The island model requires synchronization to migrate same-generation individuals between islands, and this synchronization causes an increase in computation time. This article proposes a new parallel genetic programming implementation based on the island model with asynchronous migration. Most recent computers are equipped with one or more multi-core processors, and are suitable for multi-threading. Therefore we employ a communication thread for migration between islands. The communication thread on a processor communicates with the communication thread on another processor to migrate individuals at appropriate intervals. Since the migration and other genetic operations can be independently processed on each core, and since we allow the exchange of individuals of different generations, no synchronization is needed in our implementation. In addition, a fitness calculation is also executed in parallel by the remaining cores. Experimental results show that the proposed method can reduce the computation time to about 17% in serial GP by using 40 threads.     

Inhibition of nitric oxide production. Mechanisms of vascular albumin leakage

The mechanisms by which nitric oxide modulates microvascular albumin exchange were investigated by monitoring leukocyte-endothelial cell adhesion and fluorescein isothiocyanate-albumin leakage in rat mesenteric venules exposed to NG-nitro-L-arginine methyl ester (L-NAME). L-NAME elicited an initial rapid increase followed by a slower rate of albumin accumulation in the interstitial space. The initial phase of albumin leakage preceded the L-NAME-induced leukocyte adherence and emigration, whereas the magnitude of the albumin leakage observed in the later phase of L-NAME exposure was highly correlated with the number of adherent and emigrated leukocytes in the same segment of venule. Monoclonal antibodies (MAbs) directed against adhesion molecules CD11/CD18, ICAM-1, or P-selectin, but not a nonbinding MAb, attenuated the albumin leakage induced by L-NAME. WEB2086, a platelet activating factor antagonist, and 8-bromoguanosine 3',5'-cyclic monophosphate (8-br-cGMP) reduced the leukocyte adherence and emigration as well as the increased albumin leakage. Only 8-br-cGMP and the P-selectin MAb attenuated the platelet-leukocyte aggregation elicited by L-NAME. Phalloidin, which promotes endothelial junctional integrity, inhibited both the early and late phases of albumin leakage. Overall, these findings suggest that the increased albumin leakage observed in postcapillary venules after inhibition of nitric oxide production involves a mechanism that includes a role for cGMP, platelet activating factor, leukocyte-endothelial cell adhesion, and the endothelial cell cytoskeleton.