The etiology of pinhole and bubble defects in enteric and controlled-release film coatings

Film coatings are frequently applied to tablets or pellets in order to control or delay the release of medication from these dosage forms. Pinhole and bubble defects create weak points in the film through which fluid can penetrate relatively easily. It is postulated that bubble defects are continuously formed on the surfaces of tablets and pellets during the film coating operation because of foam produced by spray atomization of the coating solution. These bubbles are broken down rapidly during particle-to-particle collisions as the coating operation proceeds. Logos and very rough surfaces form protected areas free from abrasion which allow the bubbles to set or partially collapse to form pinholes.     

Stability of acyclic multiclass queueing networks

In this paper we study multiclass queueing networks with fluid arrival streams and service processes. Assuming that the arrival rate does not exceed the network capacity, we deduce stability of the network using the tools of ergodic theory. We show that the distributions of the process converge to a unique steady state value and that convergence takes place at a geometric rate under appropriate moment conditions     

Cooking in West Sumatra: Interfuel substitution and the choice of cooking method

The results of a survey on energy consumption in cooking in five villages in West Sumatra, Indonesia, are used to investigate the substitution of commercial fuels for non-commercial ones in a rural community. Land-use patterns, the availability of non-commercial fuelwood and the state of socio-economic development of the villages (affecting the average income, availability of commercial fuels and the expectations of the villagers) all influenced the types and quantities of fuel use. Within each village cooking energy consumption and the type of cooking method chosen varied considerably with income and household size, and with the individual preferences of each villager.     

Single-phase voltage regulators and three-phase systems

Voltage regulators are applied on distribution systems to control the voltage delivered to customers within acceptable industry standards. Concerns about the quality of electric power delivered to customers by electric utility companies have raised the level of awareness of high- and low-voltage conditions at customer facilities. Normally occurring voltage drops through lines and transformers vary with the load level on the system. Voltage regulators, when properly applied, can compensate for these voltage drops and keep customer voltage within proper limits. Single-phase voltage regulators can be applied on three-phase systems in a variety of ways, including grounded-wye, open-wye, closed-delta, and open-delta. The capabilities of the regulator systems are affected by the system design. In this article, the authors review the characteristics of the closed-delta and wye applications, and discuss the advantages and disadvantages of each application scheme. The impact of the regulator connection on overcurrent protection is also reviewed     

Dynamic scheduling for heterogeneous Desktop Grids

Desktop Grids have emerged as an important methodology to harness the idle cycles of millions of participant desktop PCs over the Internet. However, to effectively utilize the resources of a Desktop Grid, it is necessary to use scheduling policies suitable for such systems. In this paper, we analyze the performance of a policy which is shown to perform well in highly heterogeneous Desktop Grids. The policy utilizes the solution to a linear programming (LP) problem which maximizes system capacity. We suggest robust modifications to address several limitations of the policy.     

Household energy consumption in west Sumatra. Implications for policy makers

The results of a field survey on domestic energy consumption in West Sumatra are discussed within the context of Indonesian energy policy, particularly with regard to the problem of domestic kerosene subsidisation. Many energy planners believe that the heavy subsidies on kerosene are necessary to prevent deforestation and protect the poor. Inequalities in fuel consumption for different sectors of the population may vary for different uses. In formulating policies aimed at reducing inequalities it is helpful to consider the end uses of the fuels separately. Energy use in cooking and lighting and the villagers' attitudes towards different fuels are investigated to see what effect a removal of the kerosene subsidies would have. In the case of lighting, a removal or reduction in the subsidies would primarily affect the lowest income sector of the population, unless a system of loans or subsidies is established for the initial installation charges of electricity. For cooking the higher income group would primarily be affected, and reducing the subsidies would not cause considerable hardship to the villagers or adverse environmental effects as there are considerable underutilized forest resources in the region. However, unless suitable alternatives to kerosene are made available at reasonable prices, the villagers now using kerosene would consider it a retrogressive step in their standard of living to return to the use of smoky and inconvenient open wood fires.     

Operation of superconducting magnet with dilution refrigerator insert in zero boil-off regime

The combination of high magnetic field and ultra-low temperatures has proved to be indispensable for a broad range of condensed matter physics experiments. However problems with the global helium supply have raised significant concern about affordability of conventional cryogenic equipment. The latest developments in cryo-cooler technology offer a new generation of cryogenic systems in which the cryogen consumption can be significantly reduced and in some cases completely eliminated. We have demonstrated a new high magnetic field - ultra-low temperature neutron scattering sample environment system based on re-condensing technology. In our tests we have shown that the 9 T superconducting magnet, built for the ISIS facility, can be run with a dilution refrigerator insert in continuous zero boil-off regime without any additional cooling.     

Heuristics for allocation of reconfigurable resources in a serial line with reliability considerations

We consider the allocation of reconfigurable resources in a serial line with machine failures. Each station is equipped with non-idling dedicated servers while the whole system is equipped with a finite number of reconfigurable servers. The reconfigurable servers are available to be assigned to any station and all servers are allowed to collaborate on a single job. We provide conditions for a policy to achieve throughput optimality. We also show in the two-station case that transition monotone optimal policies exist. We discuss heuristics based on the two-server model that reduce average holding costs significantly. These heuristics are compared to several heuristics from the literature via a detailed numerical study.     

Radiation dose-fractionation and dose-rate relationships for long-term repopulating hemopoietic stem cells in a murine bone marrow transplant model

Fractionated and low-dose-rate total-body irradiation (TBI) were compared with single-dose high-dose-rate TBI for induction of long-term hemopoietic chimerism in a murine syngeneic bone marrow transplantation model. At 5 months after TBI and bone marrow transplantation, the degree of stable blood chimerism was determined from the proportion of stem cell-derived donor (B6-Gpi-1a) and host (B6-Gpi-1b) blood erythrocytes. This end point was used to construct radiation dose-response curves for long-term donor marrow engraftment corresponding to ablation of primitive bone marrow stem cells of the host. Increasing dose fractionation and decreasing dose rate had the effect of restoring host hemopoiesis and required higher TBI doses for equal donor engraftment. Most of the dose recovery occurred within the first 6 h between fractions, consistent with the kinetics of sublethal damage repair. The late chimerism data were fitted to the linear-quadratic model using indirect and direct analysis for a fixed threshold response. Both analyses gave relatively low alpha/beta ratios (below 2 Gy), within the range normally seen in late-responding tissues. The dose-rate data gave a repair half-time of 2 h as estimated by the incomplete-repair model. These estimates contrast with the much higher alpha/beta values and lower repair half-times derived from acute hemopoietic failure as indicated by LD50/30, with the implication that separate target cell populations with differing radiosensitivities are involved in these two bone marrow end points.