Restrictions on components of variance for epistatic models

The putative role(s) of a mechanically gated (MG) cation channel in Xenopus oocyte growth, maturation, fertilization and embryogenesis has been examined. Using a pharmacological approach, we have tested the effects of the MG channel blockers, gadolinium, gentamicin and amiloride on the above developmental events. Our results indicate that oocyte maturation, fertilization and early embryogenesis (up to the free-swimming stage 45) can proceed normally in the presence of concentrations of agents that either completely abolish (i.e., > or = 10 microM Gd3+) or partially block (i.e., 1 mM gentamicin) single MG channel activity as measured by patch-clamp recording. However, we also find that higher concentrations of Gd3+ (> or = 50 microM) can lead to an increased percentage (> 20%) of axis-perturbed embryos compared with control (< 1%) and that amiloride (0.5 mM) reduces the success of fertilization (from 100% to < 50%) and increases mortality (by approximately 75%) in developing embryos. Furthermore, we find that all three agents inhibit oocyte growth in vitro. However, their order of effectiveness (amiloride > gentamicin > Gd3+) is opposite to their order for blocking MG channels (Gd3+ > gentamicin > amiloride). These discrepancies indicated that the drugs effects occur by mechanisms other than, or in addition to, MG channel block. Our results provide no compelling evidence for the idea that MG channel activity is critical for development in Xenopus. This could mean that there are other mechanisms in the oocyte that can compensate when MG channel activity is blocked or that the protein that forms the channel can undergo additional interactions that result in a function insensitive to MG channel blockers.     

On Effective viscosity models for gas-stirred ladle systems

Metallurgical and Materials Transactions B -     

Ternary Diffusion: Restrictions on the (2D) Matrix

An analysis has been made of ternary diffusing systems to determine the possibility that individual diagonal interdiffusion coefficient elements of the_k(²D) (k = 1,2,3) interdiffusion coefficient matrices can be negative. It is shown that in ternary diffusing systems, in which the concentration-penetration curves are monotonic, as many as three of the six diagonal coefficients can be negative. It is further shown that several ternary diffusing systems having a negative diagonal interdiffusion coefficient matrix element have already in fact been determined experimentally.     

Dislocation patterns from reaction-diffusion models

We addressed the formation of dislocation patterns by using a reaction-diffusion model (proposed some years ago) where well-known dislocation interaction mechanisms are represented by linear and non-linear terms. The non-linear analysis developed shows that it is possible to obtain a rich dynamical behaviour with spatial and/or temporal patterns, which one could be tempted to associate to those observed experimentally (e.g. persistent slip bands, rod-like structures or cell structures). However, the transformation of the reaction-diffusion model into its Ginzburg—Landau equation leads to unexpected results showing the limitation of the model.     

Immunoconjugates: lessons from animal models

Monoclonal antibody-mediated cancer therapy has evolved through a challenging chain of problems and solutions. The very limited therapeutic success obtained with unarmed monoclonal antibodies has increased the interest in different antibody-based targeting strategies, and numerous preclinical and even clinical studies with immunoconjugates have now been conducted. We comment here on the messages implicit in a recent report on a doxorubicin-anti-carcinoma antibody conjugate and from several other studies.     

Retrieval from temporally organized situation models

Time is an important part of establishing situations in the world. As such, temporal information should be reflected in the organization of information into situation models. This article reports 3 experiments that explore whether people will integrate sets of related facts into situation models in a time-based fashion. People memorized lists of facts and then took a speeded recognition test. A retrieval interference methodology was used to assess whether they had integrated the facts into situation models. The presence of interference indicated a lack of integration. In contrast, a marked reduction or an absence in interference indicated integration. In 2 experiments, time-based integration was observed when common time periods were referred to by either events (e.g., "when the camera flashed") or verb tense (i.e., past, present, and future). A 3rd experiment demonstrated that common time periods alone are not sufficient; the information must be allowed to occur potentially within the same situation.     

Optimizing the operation of straight-grate iron-ore pellet induration systems using process models

Mathematical models of straight-grate pellet induration processes have been developed and carefully validated by a number of workers over the past two decades. However, the subsequent exploitation of these models in process optimization is less clear, but obviously requires a sound understanding of how the key factors control the operation. In this article, we show how a thermokinetic model of pellet induration, validated against operating data from one of the Iron Ore Company of Canada (IOCC) lines in Canada, can be exploited in process optimization from the perspective of fuel efficiency, production rate, and product quality. Most existing processes are restricted in the options available for process optimization. Here, we review the role of each of the drying (D), preheating (PH), firing (F), after-firing (AF), and cooling (C) phases of the induration process. We then use the induration process model to evaluate whether the first drying zone is best to use on the up- or down-draft gas-flow stream, and we optimize the on-gas temperature profile in the hood of the PH, F, and AF zones, to reduce the burner fuel by at least 10 pct over the long term. Finally, we consider how efficient and flexible the process could be if some of the structural constraints were removed (i.e., addressed at the design stage). The analysis suggests it should be possible to reduce the burner fuel lead by 35 pct, easily increase production by 5+ pct, and improve pellet quality.