Videoconferencing on the Internet

Videoconferences are becoming increasingly frequent on the Internet and are generating much research interest. Readily available software tools enable real-time audio and video channels as well as shared whiteboards that allow groups to collaborate on distributed group work more quickly and easily than ever. The paper considers how the Internet infrastructure is beginning to support videoconferencing applications in several ways. It particularly focuses on some of the problems experienced in the virtual classroom     

Influence of oxidized low-density lipoprotein on vascular angiotensin II receptor expression

OBJECTIVES: To investigate the effect of oxidized low-density lipoprotein (LDL) on angiotensin type 1 (AT1) receptor expression and on angiotensin-induced mitogenesis in vascular smooth muscle cells. DESIGN: Since both LDL and the AT1 receptor are thought to be involved in the pathogenesis of chronic vascular disease, we studied possible interactions between these two biological systems in cultured rat vascular smooth muscle cells. Recent studies have demonstrated that native LDL profoundly increases the AT1 receptor gene expression in vascular smooth muscle cells. The present study was designed to show whether an oxidative modification of LDL, which has been implicated as a major participant in atherogenesis, has similar effects on vascular smooth muscle cells. MATERIALS AND METHODS: Vascular smooth muscle cells isolated from rat thoracic aorta were cultured with oxidized LDL and assessed for their ability to synthesize DNA, and messenger (m)RNA expression, using Northern blot technology. RESULTS: Oxidized LDL had no significant effect on AT1 receptor mRNA steady-state levels when incubated for 0-24 h. Moreover, oxidized LDL itself had no stimulatory effect on DNA synthesis in vascular smooth muscle cells, nor was the angiotensin II-induced increase in DNA synthesis influenced by oxidized LDL. CONCLUSIONS: These data show that in contrast to native LDL, oxidized LDL has no effect on AT1 receptor mRNA expression and no effect on angiotensin II-induced mitogenesis in vascular smooth muscle cells.     

Beta thalassemia in Germany: molecular genetics and clinical phenotype in immigrant and in the native population

Dentin dysplasia, type II (MIM*125420) is an autosomal dominant disorder of dentin development. Clinically the primary dentition appears opalescent, and radiographically the pulp chambers are obliterated, resembling dentinogenesis imperfecta. However, unlike dentinogenesis imperfecta, the permanent teeth in dentin dysplasia, type II are normal in color and, on radiographs, have a thistle-tube pulp chamber configuration with pulp stones. The similarity of the primary dentition phenotype suggested that the gene for dentin dysplasia, type II is allelic with the gene for dentinogenesis imperfecta, Shields type II (DGII; MIM*125490), which has been localized to chromosome 4q13-q21. Twenty-four members of a three generation family in which ten members are affected with dentin dysplasia, type II were genotyped for microsatellite alleles specific for the area of chromosome 4q linked to DGII. Linkage was assessed by using the LINKAGE computer program, assuming autosomal dominant inheritance, a disease allele frequency of 0.0001, and complete penetrance. The maximum two-point LOD score (Zmax = 4.2 at theta = 0.0) was obtained with SPPI and D4S2691. Multipoint analysis gave a maximum LOD score of 4.33. The candidate region for dentin dysplasia, type II is approximately 14.1 cM, includes SPPI, D4S2691, D4S2690, D4S451, and D4S2456, and overlaps the most likely location of the DGII locus. A candidate gene for DGII should also be considered a candidate gene for dentin dysplasia, type II.     

Molecular anatomy of the perivascular sheath in human placental stem villi: the contractile apparatus and its association to the extracellular matrix

In previous studies, we have shown that smooth muscle cells and myofibroblast subpopulations of the perivascular stem villous sheath of the human placenta contain focal adhesion plaques and talin immunoreactivity. The close association of these cells to elastic and collagen fibres have led to the assumption of a functional myofibroelastic unit within the perivascular stem villous sheath. Interactions between the extracellular matrix and smooth muscle cells depend on a variety of structural protein assemblies. In the present study, we examined, by immunocytochemistry, whether the molecular assembly of extracellular matrix proteins and molecules of focal adhesions, known to be essential for signal transduction in smooth muscle cells, are also found in smooth muscle cells of the perivascular stem villous sheath of the human placenta. Vascular and extravascular smooth muscle cells were immunoreactive for alpha-actinin, vinculin, paxillin and tensin, the integrin chains alpha1 and beta1, and the basement membrane components laminin and heparan/-chondroitin sulfate proteoglycan perlecan. pp125(FAK) did not react. In the extracellular matrix of blood vessel walls and the perivascular stem villous sheath, we found immunoreactivity of fibronectin and collagen types I, VI and undulin (collagen type XIV). From our data we conclude that within the perivascular stem villous sheath, there exists a system of signal transduction molecules, indicating a cross talk between the smooth muscle cells of this sheath and their surrounding extracellular matrix.     

Neuere Entwicklungen auf dem Gebiet der Vakuumbogenbeschichtung

Actually millions of tools and engine components are coated with hard coatings by cathodic vacuum arc deposition monthly. Most of the coatings are applied for abrasion protection. But also coatings for decoration or corrosionprotection are usual. The most important coating is TiN, but also a great number of different kinds of coatings are available for various applications. Recent developments are dedicated to fit the coat- substrat combination for the specific application or to coat materials with a low thermal load capacity. On the other hand the technology of the coating- devices are improved permanently. Coating chambers from a size of some ten centimetres to some metres with fully automatic process control are available.     

Electrosorption valency of mixed electrosorption reactions

The thermodynamic analysis given recently for single electrosorption reactions is extended to mixed electrosorption reactions. In the case of excess supporting electrolyte the potential dependence and the charge flow of the electrosorption of a substance S in the presence of a second electrosorbed substance X can be described again by the derivatives

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However, the additional condition, μ_x = const, must be maintained. The mixed valency, γ_s,mix, is the sum of the two single valencies γ_s,mix = γ_s + ργ_x, where

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is a coupling factor. ρ is positive in the case of coadsorption and negative in the case of competitive electrosorption. The derivatives

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correspond to the single valency, γ_s, of the isolated electrosorption process of S.The applicability of the thermodynamic relations is demonstrated by various examples, and the mixed valencies are analysed as far as possible. Examples are given for strong attraction (Hg/Cd²⁺, N⁻₃), weak attraction (Hg/pyridine, KCl), and competitive electrosorption (Ag/Pb²⁺, X⁻).     

Effect of pulsating flow on Coriolis mass flowmeters

The last ten years have seen an increasing use of Coriolis flowmeters in the measurement of small flows of liquids. The performance of Coriolis meters under pulsating flow conditions was not well known, however. This paper presents some investigations on such flowmeters in the presence of monofrequent and polyfrequent pulsating flows. The linearity of the flow characteristics is checked mathematically and the mechanical resonances of the measuring tubes are determined. Two U-tube type Coriolis meters are tested and the measuring error resulting from the pulsation of the flow is examined. The investigations are carried out with monofrequent pulsation by a special test rig flow and with geared and piston type pumps (polyfrequent excitation).