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Notes: Viscoelastic solids with high viscosity were experimentally studied with the intention of having them deformed under uniform shear stress. A kind of sandwich method was developed for applying a constant shear stress to a specimen, and its deformation was observed optically using heterodyne interferometry with a sensitivity of 10 nm in displacement measurement. Time-dependent deformation data were analyzed on the basis of a mechanical model of anelasticity plus viscosity. Viscosity in the range of 108–1014 Pa⋅s could be determined at temperatures of 20–200 °C. Through a simulation using the finite element method together with an experiment visualizing the deformation, the specimen deformation was shown to be of an almost uniform shear mode. Experiments were performed to determine the temperature dependence of viscosity for several kinds of glasses near their glass transition Tg, and the determined viscosity values were about 107 Pa⋅s at Tg. The viscosity values measured by a rotation disk viscometer were in good agreement with the present data. The viscosity of some glasses was also measured by the beam bending and penetration methods, and values of 109–1012 Pa⋅s at Tg were obtained. The large discrepancy between the two kinds of data was considered. © 1996 American Institute of Physics.

Notes: The thermal diffusivity, and specific heat, of polyethylene (76% crystallinity) containing dispersed particles (1%–15% volume fraction) of SiO2 (diameter d=7,16,40 nm; 1,5,10 μm), Fe (d=27 nm), Cu (d=53 nm), and Ag (d=140 nm) have been measured using the laser flash method, and the thermal relaxation method, in the temperature range of 4.2–300 K, and the thermal conductivity was derived from the two quantities. The thermal conductivity was decreased by the addition of particles, and the decrease was more remarkable at lower temperatures for smaller particles. The boundary thermal resistance between the particles and the medium was derived from the change of conductivity due to the nm-diameter dispersed particles. The boundary resistance was independent of the size and the volume fraction of the particles, and was shown to be inversely proportional to the phonon specific heat of particle-dispersed medium in over a wide range of temperatures. The phonon Debye temperature and the strength of the boundary thermal resistance were determined by analyzing the data, and obtained results were quite reasonable. © 1996 American Institute of Physics.

Notes: The transient hot-wire method for simultaneously measuring the thermal conductivity and thermal diffusivity of materials has been modified to improve the accuracy of the measurements. In this new experimental method, called the multicurrent method, several constant current values are used for heating the hot wire in order to determine accurately the thermal transport quantities. The details of the multicurrent method are precisely described, and examples of experiments using the method with pure water, electrolytic solution, and ionic conducting glasses are given. It is shown that this method can be used both for liquid and solid materials; a relatively small amount of the specimen material is sufficient for each experiment; the material can be insulating as well as highly ionic-conductive; the accuracies of the determined thermal conductivity and the thermal diffusivity values are, respectively, around ±1% and ±5%.

Notes: The viscosities of metaphosphate, pyrophosphate, molybdate, and fluorophosphate glasses were measured under the shear deformation mode using a sandwich method from room temperature up to the glass transition temperature Tg. An optical method was used to measure the deformation under constant load as a function of time, and the results were analyzed using a mechanical model of anelasticity plus viscosity. In glasses containing long molecular chains, two relaxations appeared at lower and higher temperatures, while only one relaxation existed at higher temperatures in glasses without the chain. Both these relaxations were of the thermal activation type. A correlation between the frequency factor and the activation energy was found for the high temperature relaxation, and the values of the frequency factor were very large. Another apparatus, a rotation disk viscometer, was also used to measure the shear viscosity above Tg. The data obtained by the two experimental methods related to each other well, and the viscosity value at Tg was of the order of 108 Pa s. The viscosity was in the hydrodynamic regime at temperatures sufficiently above Tg, and in the hopping regime below a temperature near Tg. © 1998 American Institute of Physics.

Notes: Background: The IgA1 molecule, which is predominantly deposited in glomeruli of IgA nephropathy, has the characteristic O-glycan side chain in its hinge region. Several lines of evidence have demonstrated that underglycosylated IgA1 acquires self-aggregation1 and binding affinities to the extra-cellular matrix,1,2 resulting in deposition in the glomeruli.3,4 However, there is little information concerning actual biological activities of the underglycosylated IgA1 deposited in glomeruli, which lead to mesangial cell proliferation and/or matrix expansion.Aim: To clarify the influence of O-glycan side chain in the hinge of IgA1 on its biological activity in mesangial cells, we performed a comprehensive gene expression profiling analysis of human cultured mesangial cells stimulated by enzymatically underglycosylated IgA1 using cDNA array.Methods: IgA1 was purified by affinity chromatography using anti IgA column followed by Jacalin column. Asialo/agalacto IgA1 was obtained by enzyme digestion using sialidase and β-galactosidase. Heat aggregated IgA1 was obtained by incubation at 63°C for 150 min. Cultured human mesangial cells were stimulated for 3 h by non-treated IgA1, heat aggregated IgA1 or asialo/agalacto IgA1, respectively, and total RNA was obtained. Only the enzyme stimulation was performed as a negative control for asialo/agalacto IgA1. After DNase treatment, isotope labelled probes were prepared by reverse transcription and hybridized to the Atlas Human 1.2 Array (CLONTECH, Palo Alto, CA, USA) according to the manufacturer’s protocol. A total of 1176 arrayed genes were quantitatively evaluated using BAS.Results: Expression profiles of 1176 genes were obtained. In all experiments, none of the three negative controls on the cDNA array was detected. The expression profiles of mesangial cells by each IgA1 stimulation resembled one another, but they were widely different from that of mononuclear cells. On the whole, 10% of the genes expressed in the mesangial cells were up-regulated by asialo/agalacto IgA1 stimulation compared to that by enzyme stimulation. The results suggested that under-O-glycosylated IgA1 has a biological function in human mesangial cells in vitro. In good agreement with previous studies,5 heat aggregated IgA1 stimulation up-regulated IL-6 and TNF-α expressions in mesangial cells compared to by non-treated IgA1. Asialo/agalacto IgA1 stimulation also up-regulated these molecules, suggesting its pathogenetic role in IgA nephropathy. However, since a similar tendency was revealed by enzyme stimulation alone, further study may be necessary to establish these observations.Conclusion. In the present study, we investigated the comprehensive expression profiles of mesangial cells stimulated by various types of IgA1 using cDNA array. This approach may serve as a useful database not only to evaluate the biological activities of under-O-glycosylated IgA1 but also to elucidate the pathogenesis of IgA nephropathy.