Electromagnetic velocity transducer with optimal parameters

We show that the characteristic geometric parameters of a local velocity transducer for a flow with an internal magnetic-field source can be determined by analyzing an electromagnetic flow meter of conventional design by using the method of conformal mappings from the theory of functions of a complex variable. We show that this method can be used to obtain an electromagnetic transducer with optimal parameters for measurement of both speed and flowrates of liquids in large pipes and open channels. Translated from Izmeritel'naya Tekhnika, No. 9, pp. 17–24, September, 1998.     

Microstructure and Superconducting Properties of TaC-Doped Bi-2223 Ceramics

The microstructure, phase composition, and superconducting properties of Bi-2223 ceramics doped with 0.05–0.5 wt % TaC were investigated. The materials were heat-treated at 840°C in three steps (10 + 24 + 24 h). By optimizing the TaC content and heat-treatment conditions, the 77-K critical current density of the Bi-2223 ceramics in zero field was raised by a factor of 2.     

Functional stability of hippocampal slices after treatment with cyclooxygenase inhibitors

The influence of cyclooxygenase inhibitors on functional stability of hippocampal slices, determined by electrophysiological criteria of recovery after slicing and long-term maintainence of population activity, was studied. Transient (3 min) treatment of slices during slicing with indomethacin (45 microM) or aspirin (0.5 mM) allowed registration of the population responses from the second minute. The activity reached 100% after 15 min incubation and could be registrated for 3 days under conditions of overnight hypothermia. The presence of the same drugs for the entire incubation period had the same effect. The present findings suggest that slicing is a crucial point for triggering of pathological events mediated by cyclooxygenase products and that blockade of cyclooxygenase provides for the further high longterm functional stability of brain slices.     

Radiation Resistance and Hydrolytic Stability of Y0.95Gd0.05PO4-Based Ceramics with the Xenotime Structure

Inorganic Materials - The Y0.95Gd0.05PO4 phosphate with the xenotime structure has been synthesized in powder form and as ceramics. Ceramics with a relative density of ~99% have been produced by...     

Murine hepatitis virus strain 3 induces the macrophage prothrombinase fgl-2 through p38 mitogen-activated protein kinase activation

The clinical syndrome of acute liver failure produced by fulminant viral hepatitis can be reproduced in mice by infection with murine hepatitis virus strain 3 (MHV-3). Although it is clear that MHV-3-induced hepatitis depends upon macrophage activation and the expression of a specific prothrombinase, fgl-2, the signaling pathways involved in virally stimulated cell activation are unclear. Since we had previously found that MHV-3 induces the tyrosine phosphorylation of cellular proteins, we investigated the roles of the mitogen-activated protein kinase (MAPK) proteins. In a series of Western blots, immunoprecipitation and in vitro kinase assay studies, we found that both the extracellular signal-related kinase (ERK) and p38 MAPK proteins are tyrosine-phosphorylated and activated following exposure of murine peritoneal exudative macrophages (PEM) to MHV-3. Although p38 phosphorylation and activity are induced soon after MHV-3 exposure, peaking by 1-5 min, ERK phosphorylation and activity increase more gradually, peaking at 20-30 min and gradually fading thereafter. Interestingly, whereas selective p38 inhibition with SB203580 (1-20 microM) abolished the virally stimulated induction of fgl-2 mRNA, protein, and functional activity, selective ERK inhibition with PD98059 (1-50 microM) limited fgl-2 functional activity but had little to no effect on fgl-2 mRNA or protein levels. Moreover, whereas inhibition of ERK had no effect on p38 activity, p38 inhibition consistently increased MHV-3-induced ERK activity. To ensure that these pathways were relevant in vivo, MHV-3 was injected intraperitoneally, and peritoneal exudative macrophages were collected. Again, MHV-3 exposure led to increased p38 and ERK tyrosine phosphorylation. These data argue that MHV-3 induces tightly interconnected ERK and p38 MAPK cascades in the macrophage both in vitro and in vivo. Although the ERK and p38 MAPK proteins have discordant effects at the level of fgl-2 expression, both converge at the level of its activity, suggesting that targeted MAPK inhibition may ultimately be useful in the modulation of viral hepatitis.     

Relationship between microtubule dynamics and lamellipodium formation revealed by direct imaging of microtubules in cells treated with nocodazole or taxol

Microtubules (MTs) contribute to the directional locomotion of many cell types through an unknown mechanism. Previously, we showed that low concentrations (<200 nM) of nocodazole or taxol reduced the rate of locomotion of NRK fibroblasts over 60% without altering MT polymer level [Liao et al., 1995: J. Cell Sci. 108:3473-3483]. In this paper, we directly measured the dynamics of MTs in migrating NRK cells injected with rhodamine tubulin and treated with low concentrations of nocodazole or taxol. Both drug treatments caused statistically significant reductions (approx. twofold) in growth and shortening rates and less dramatic effects on rescue and catastrophe transition frequencies. The percent time MTs were inactive (i.e., paused) increased greater than twofold in nocodazole- and taxol-treated cells, while the percent time growing was substantially reduced. Three parameters of MT dynamics were linearly related to the rates of locomotion determined previously: rate of shortening, percent time pausing and percent time growing. The number of MTs that came within 1 microm of the leading edge was reduced in drug-treated cells, suggesting that reduced MT dynamics may affect actin arrays necessary for cell locomotion. We examined two such structures, lamellipodium and adhesion plaques, and found that lamellipodia area was coordinately reduced with MT dynamics. No effect was detected on adhesion plaque density or distribution. In time-lapse recordings, MTs did not penetrate into the lamellipodium of untreated cells, suggesting that MTs affect lamellipodia either through their interaction with factors at the base of the lamellipodium or by releasing factors that diffuse into the lamellipodia. In support of the latter hypothesis, when all MTs were rapidly depolymerized by 20 microM nocodazole, we detected the rapid formation of exaggerated protrusions from the leading edge of the cell. Our results show for the first time a linear relationship between MT dynamics and the formation of the lamellipodium and support the idea that MT dynamics may contribute to cell locomotion by regulating the size of the lamellipodium, perhaps through diffusable factors.     

Anomalous magnetic susceptibility in Nd<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>MnO<Subscript>3</Subscript> manganite single crystals

Chaotic oscillations of the low-frequency magnetic susceptibility χ in a Nd_0.5Sr_0.5MnO₃ (NSMO) manganite single crystal have been observed in the temperature interval of the coexistence of the ferro- and antiferromagnetic phases of the given composition. It is established that the amplitude of χ oscillations depends on the constant bias magnetic field. The appearance of susceptibility oscillations in NSMO single crystals is attributed to the formation of magnetic transition regions, which can exist at the boundaries between ferro- and antiferromagnetic phases.