Solving applied general equilibrium models represented as a mixture of linearized and levels equations

General equilibrium moels are usually represented as a system of levels equations (e.g., in North America) or a system of linearized equations (e.g., in Australia). Either representation can be used to obtain accurate solutions. General-purpose software is available in both cases-GAMS or MPS/GE is typically used by levels modellers and GEMPACK by linearizers. Some equations (notably accounting identities) are naturally expressed in the levels while others (especially behavioural equations) are naturally expressed in a linearized form. This paper describes the new GEMPACK facility for solving models represented as a mixture of levels and linearized equations and discusses the advantages to modellers of using such a representation.     

Slow cellular dynamics in MDCK and R5 cells monitored by time-lapse atomic force microscopy

We have examined dynamic events that occur on a time scale of minutes in an epithelial monolayer of Madine-Darby Canine Kidney (MDCK) cells and in ras-transformed MDCK cells by atomic force microscopy (AFM). Cells were imaged under physiological conditions, and time-lapse movies representing approximately 60 s real time per frame were assembled. In normal MDCK cells, two types of protrusions in the apical plasma membrane exhibit dynamic behavior. First, smooth bulges formed transiently over the time scale of minutes to tens of minutes. Second, spike-like protrusions appear initially as bulges, extend well above the apical surface and, finally, seem to detach. R5, an oncogenic transformant derived from MDCK cells, grows very flat on glass. During AFM imaging, these cells sometimes round up and detach from the substrate. In light microscopic observations of parallel preparations, cells rarely detach, suggesting that this is an active response of these cells to irritation by the AFM tip. R5 cells often extend processes that are supported by actin stress fibers. During imaging with the AFM, these processes withdraw at a rate of 1-5 microns/min, similar to that observed by light microscopy. During the withdrawal, movement of the stress fibers can be clearly seen. In the flat periphery of these cells, the transport of intracellular particles along cytoskeletal elements was seen. In addition, we have observed two types of wave-like movements through the cell, which appear to be an organized rearrangement of cytoplasm. One type of wave moves radially out from center of the cell while the other moves circularly along the cell periphery.     

Marfan syndrome: diagnosis of cardiovascular manifestations]

BACKGROUND: Despite the availability of several different markers for Epstein--Barr virus (EBV) serology, the EBV status of some patients cannot be resolved from a single serum sample with routine testing. To avoid the requirement of follow-up samples, supplementary tests have to be used in these cases. OBJECTIVE: To evaluate the usefulness of avidity and immunoblot assays as supplementary tests for the diagnosis of acute EBV infections. STUDY DESIGN: Three groups of samples for which a definite diagnosis on the EBV status could not be obtained with the routine serological tests were further examined by an EBV IgG avidity assay, by an immunoblot based on a lysate of EBV infected cells, and by a second immunoblot based on recombinant EBV antigens. The three groups consisted of 38 samples with negative/borderline EB nuclear antigen 1 (EBNA-1) antibodies, negative/borderline EBV IgM and positive EBV IgG; 10 samples with indeterminate EBNA-1 and/or EBV IgM assays because of control antigen reactions; and 4 samples with positive EBV IgM results that were not plausible. RESULTS: The avidity assay differentiated between acute and past infections for all samples. In contrast, some cases remained unresolved with both the recombinant and the lysate immunoblot. Two samples were incorrectly classified with the lysate immunoblot. Interpretation of the lysate immunoblot banding patterns was complicated when anticellular antibodies were present. CONCLUSION: Avidity testing appears to be the confirmatory method of choice to differentiate between acute and past EBV infections.     

Hemispheric contributions to the integration of visual and auditory information in speech perception

Differential hemispheric contributions to the perceptual phenomenon known as the McGurk effect were examined in normal subjects, 1 callosotomy patient, and 4 patients with intractable epilepsy. Twenty-five right-handed subjects were more likely to demonstrate an influence of a mouthed word on identification of a dubbed acoustic word when the speaker's face was lateralized to the LVF as compared with the RVF. In contrast, display of printed response alternatives in the RVF elicited a greater percentage of McGurk responses than display in the LVF. Visual field differences were absent in a group of 15 left-handed subjects. These results suggest that in right-handers, the two hemispheres may make distinct contributions to the McGurk effect. The callosotomy patient demonstrated reliable McGurk effects, but at a lower rate than the normal subjects and the epileptic control subjects. These data support the view that both the right and left hemisphere can make significant contributions to the McGurk effect.     

VISCOMETRIC FLOWS OF NEUTRALLY BUOYANT SUSPENSIONS IN SECOND-ORDER FLUIDS

The local volume averages of the equations of motion as well as the appropriate boundary conditions for neutrally buoyant suspensions of spheres in second-order fluids (Li and Slattery, 1989a) are employed to analyze both the cone-plate viscometer and the parallel-plate viscometer. The predicted results are compared with measurements of apparent viscosity and of the primary normal stress difference. Predictions of measured apparent viscosities are in excellent agreement with the experimental data up to 20% solids by volume; the average error is no more than 5%. Predictions of apparent viscosities for the limiting case of a very dilute suspension are restricted to less than 10% solids by volume. The primary normal stress difference is predicted to be independent of the volume fraction of solids, in approximate agreement with previously reported data.

Both theory and experiment have demonstrated that a neutrally buoyant suspension of uniform spheres in an incompressible second-order fluid behaves like a single-phase second-order fluid in these two viscometers.     

Microstructure and creep behavior in AE42 magnesium die-casting alloy

The micro structural analysis of die-cast AE42 reveals a correlation between micro structure and creep strength. A lamellar-phase Al₁₁RE₃, which dominates the interdendritic microstructure of the alloy, partly decomposes above 150‡C into Al₂RE and Al (forming Mg₁₇Al₁₂). The increased solubility of aluminum in magnesium at higher temperatures may also promote the decomposition of Al₁₁RE₃. The creep strength decreases sharply with these phase changes. A mechanism for the decrease in creep strength of AE42 is proposed whereby the reduced presence of lamellar Al1₁₁RE₃ and/or the presence of Mg₁₇Al₁₂ contribute to the observed poor creep strength at higher temperatures.